diff --git a/.clang-format b/.clang-format
index 73eac7ef6fe..3067583e106 100644
--- a/.clang-format
+++ b/.clang-format
@@ -15,7 +15,7 @@ SpaceAfterCStyleCast: true
 SpaceAfterTemplateKeyword: false
 AccessModifierOffset: -4
 AlignAfterOpenBracket: AlwaysBreak
-AlignEscapedNewlines: DontAlign
+AlignEscapedNewlines: Left
 ColumnLimit: 120
 BreakStringLiterals: false
 BitFieldColonSpacing: None
@@ -30,3 +30,4 @@ BreakBeforeBinaryOperators: NonAssignment
 AlwaysBreakBeforeMultilineStrings: true
 IndentPPDirectives: AfterHash
 PPIndentWidth: 2
+BinPackArguments: false
diff --git a/.editorconfig b/.editorconfig
index 86360e6582d..e1c8bae3929 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -4,20 +4,20 @@
 # Top-most EditorConfig file
 root = true
 
-# Unix-style newlines with a newline ending every file, utf-8 charset
+# Unix-style newlines with a newline ending every file, UTF-8 charset
 [*]
 end_of_line = lf
 insert_final_newline = true
 trim_trailing_whitespace = true
 charset = utf-8
 
-# Match nix files, set indent to spaces with width of two
+# Match Nix files, set indent to spaces with width of two
 [*.nix]
 indent_style = space
 indent_size = 2
 
-# Match c++/shell/perl, set indent to spaces with width of four
-[*.{hpp,cc,hh,sh,pl,xs}]
+# Match C++/C/shell/Perl, set indent to spaces with width of four
+[*.{hpp,cc,hh,c,h,sh,pl,xs}]
 indent_style = space
 indent_size = 4
 
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 59db217d968..a9ca74c17cc 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -11,7 +11,16 @@
 .github/CODEOWNERS @edolstra
 
 # Documentation of built-in functions
-src/libexpr/primops.cc @roberth
+src/libexpr/primops.cc @roberth @fricklerhandwerk
+
+# Documentation of settings
+src/libexpr/eval-settings.hh @fricklerhandwerk
+src/libstore/globals.hh @fricklerhandwerk
+
+# Documentation
+doc/manual @fricklerhandwerk
+maintainers/*.md @fricklerhandwerk
+src/**/*.md @fricklerhandwerk
 
 # Libstore layer
-/src/libstore @thufschmitt @ericson2314
+/src/libstore @ericson2314
diff --git a/.github/labeler.yml b/.github/labeler.yml
index e036eb3c844..0e6fd3e2677 100644
--- a/.github/labeler.yml
+++ b/.github/labeler.yml
@@ -13,7 +13,7 @@
 
 "documentation":
   - changed-files:
-    - any-glob-to-any-file: "doc/manual/*"
+    - any-glob-to-any-file: "doc/manual/**/*"
     - any-glob-to-any-file: "src/nix/**/*.md"
 
 "store":
@@ -40,4 +40,4 @@
     - any-glob-to-any-file: "src/*/tests/**/*"
     # Functional and integration tests
     - any-glob-to-any-file: "tests/functional/**/*"
-    
+
diff --git a/.github/workflows/backport.yml b/.github/workflows/backport.yml
index 8f83b913c0b..dd110de6c2a 100644
--- a/.github/workflows/backport.yml
+++ b/.github/workflows/backport.yml
@@ -21,7 +21,7 @@ jobs:
           fetch-depth: 0
       - name: Create backport PRs
         # should be kept in sync with `version`
-        uses: zeebe-io/backport-action@v2.5.0
+        uses: zeebe-io/backport-action@v3.0.2
         with:
           # Config README: https://github.com/zeebe-io/backport-action#backport-action
           github_token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2b8eac49d52..ca94ff956f0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,19 +20,45 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v26
+    - uses: cachix/install-nix-action@V27
       with:
         # The sandbox would otherwise be disabled by default on Darwin
         extra_nix_config: "sandbox = true"
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/cachix-action@v14
+    - uses: cachix/cachix-action@v15
       if: needs.check_secrets.outputs.cachix == 'true'
       with:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+    - if: matrix.os == 'ubuntu-latest'
+      run: |
+        free -h
+        swapon --show
+        swap=$(swapon --show --noheadings | head -n 1 | awk '{print $1}')
+        echo "Found swap: $swap"
+        sudo swapoff $swap
+        # resize it (fallocate)
+        sudo fallocate -l 10G $swap
+        sudo mkswap $swap
+        sudo swapon $swap
+        free -h
+        (
+          while sleep 60; do
+            free -h
+          done
+        ) &
     - run: nix --experimental-features 'nix-command flakes' flake check -L
 
+  # Steps to test CI automation in your own fork.
+  # Cachix:
+  # 1. Sign-up for https://www.cachix.org/
+  # 2. Create a cache for $githubuser-nix-install-tests
+  # 3. Create a cachix auth token and save it in https://github.com/$githubuser/nix/settings/secrets/actions in "Repository secrets" as CACHIX_AUTH_TOKEN
+  # Dockerhub:
+  # 1. Sign-up for https://hub.docker.com/
+  # 2. Store your dockerhub username as DOCKERHUB_USERNAME in "Repository secrets" of your fork repository settings (https://github.com/$githubuser/nix/settings/secrets/actions)
+  # 3. Create an access token in https://hub.docker.com/settings/security and store it as DOCKERHUB_TOKEN in "Repository secrets" of your fork
   check_secrets:
     permissions:
       contents: none
@@ -62,14 +88,15 @@ jobs:
       with:
         fetch-depth: 0
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v26
+    - uses: cachix/install-nix-action@V27
       with:
         install_url: https://releases.nixos.org/nix/nix-2.20.3/install
-    - uses: cachix/cachix-action@v14
+    - uses: cachix/cachix-action@v15
       with:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+        cachixArgs: '-v'
     - id: prepare-installer
       run: scripts/prepare-installer-for-github-actions
 
@@ -84,7 +111,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v26
+    - uses: cachix/install-nix-action@V27
       with:
         install_url: '${{needs.installer.outputs.installerURL}}'
         install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"
@@ -114,12 +141,12 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - uses: cachix/install-nix-action@v26
+    - uses: cachix/install-nix-action@V27
       with:
         install_url: https://releases.nixos.org/nix/nix-2.20.3/install
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
     - run: echo NIX_VERSION="$(nix --experimental-features 'nix-command flakes' eval .\#default.version | tr -d \")" >> $GITHUB_ENV
-    - uses: cachix/cachix-action@v14
+    - uses: cachix/cachix-action@v15
       if: needs.check_secrets.outputs.cachix == 'true'
       with:
         name: '${{ env.CACHIX_NAME }}'
@@ -127,8 +154,8 @@ jobs:
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
     - run: nix --experimental-features 'nix-command flakes' build .#dockerImage -L
     - run: docker load -i ./result/image.tar.gz
-    - run: docker tag nix:$NIX_VERSION nixos/nix:$NIX_VERSION
-    - run: docker tag nix:$NIX_VERSION nixos/nix:master
+    - run: docker tag nix:$NIX_VERSION ${{ secrets.DOCKERHUB_USERNAME }}/nix:$NIX_VERSION
+    - run: docker tag nix:$NIX_VERSION ${{ secrets.DOCKERHUB_USERNAME }}/nix:master
     # We'll deploy the newly built image to both Docker Hub and Github Container Registry.
     #
     # Push to Docker Hub first
@@ -137,8 +164,8 @@ jobs:
       with:
         username: ${{ secrets.DOCKERHUB_USERNAME }}
         password: ${{ secrets.DOCKERHUB_TOKEN }}
-    - run: docker push nixos/nix:$NIX_VERSION
-    - run: docker push nixos/nix:master
+    - run: docker push ${{ secrets.DOCKERHUB_USERNAME }}/nix:$NIX_VERSION
+    - run: docker push ${{ secrets.DOCKERHUB_USERNAME }}/nix:master
     # Push to GitHub Container Registry as well
     - name: Login to GitHub Container Registry
       uses: docker/login-action@v3
@@ -166,4 +193,18 @@ jobs:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@main
       - uses: DeterminateSystems/magic-nix-cache-action@main
-      - run: nix build -L .#hydraJobs.tests.githubFlakes .#hydraJobs.tests.tarballFlakes
+      - run: nix build -L .#hydraJobs.tests.githubFlakes .#hydraJobs.tests.tarballFlakes .#hydraJobs.tests.functional_user
+
+  meson_build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      # Only meson packages that don't have a tests.run derivation.
+      # Those that have it are already built and tested as part of nix flake check.
+      - run: nix build -L .#hydraJobs.build.{nix-cmd,nix-main}.$(nix-instantiate --eval --expr builtins.currentSystem | sed -e 's/"//g')
diff --git a/.github/workflows/hydra_status.yml b/.github/workflows/hydra_status.yml
deleted file mode 100644
index 2a75747479f..00000000000
--- a/.github/workflows/hydra_status.yml
+++ /dev/null
@@ -1,20 +0,0 @@
-name: Hydra status
-
-permissions: read-all
-
-on:
-  schedule:
-    - cron: "12,42 * * * *"
-  workflow_dispatch:
-
-jobs:
-  check_hydra_status:
-    name: Check Hydra status
-    if: github.repository_owner == 'NixOS'
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-      with:
-        fetch-depth: 0
-    - run: bash scripts/check-hydra-status.sh
-
diff --git a/.gitignore b/.gitignore
index 6996ca484aa..a17b627f44a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,8 @@ perl/Makefile.config
 /svn-revision
 /libtool
 /config/config.*
+# Default meson build dir
+/build
 
 # /doc/manual/
 /doc/manual/*.1
@@ -52,6 +54,9 @@ perl/Makefile.config
 # /src/libfetchers
 /tests/unit/libfetchers/libnixfetchers-tests
 
+# /src/libflake
+/tests/unit/libflake/libnixflake-tests
+
 # /src/libstore/
 *.gen.*
 /src/libstore/tests
@@ -92,7 +97,7 @@ perl/Makefile.config
 
 # /tests/functional/
 /tests/functional/test-tmp
-/tests/functional/common/vars-and-functions.sh
+/tests/functional/common/subst-vars.sh
 /tests/functional/result*
 /tests/functional/restricted-innocent
 /tests/functional/shell
@@ -154,6 +159,8 @@ result-*
 .vscode/
 .idea/
 
+.pre-commit-config.yaml
+
 # clangd and possibly more
 .cache/
 
diff --git a/.shellcheckrc b/.shellcheckrc
new file mode 100644
index 00000000000..de98055f719
--- /dev/null
+++ b/.shellcheckrc
@@ -0,0 +1,4 @@
+external-sources=true
+source-path=SCRIPTDIR
+# Hack for scripts in e.g. tests/functional/ca
+source-path=SCRIPTDIR/..
diff --git a/.version b/.version
index f48f82fa2c4..ad2261920c0 100644
--- a/.version
+++ b/.version
@@ -1 +1 @@
-2.22.0
+2.24.0
diff --git a/CITATION.cff b/CITATION.cff
new file mode 100644
index 00000000000..0105fb82307
--- /dev/null
+++ b/CITATION.cff
@@ -0,0 +1,42 @@
+cff-version: 1.2.0
+title: Nix
+message: >-
+  If you use this software, please cite it using the
+  metadata from this file.
+type: software
+authors:
+  - given-names: Eelco
+    family-names: Dolstra
+    email: edolstra@gmail.com
+  - name: The Nix contributors
+    website: 'https://github.com/NixOS/nix'
+references:
+  - title: The Purely Functional Software Deployment Model
+    authors:
+    - family-names: Dolstra
+      given-names: Eelco
+    year: 2006
+    type: thesis
+    thesis-type: PhD thesis
+    isbn: 90-393-4130-3
+    url: https://dspace.library.uu.nl/handle/1874/7540
+    database-provider: Utrecht University Repository
+    institution:
+      name: Utrecht University
+    keywords:
+    - configuration management
+    - software deployment
+    - purely functional
+    - component-based software engineering
+repository-code: 'https://github.com/NixOS/nix'
+url: 'https://nixos.org/'
+abstract: >-
+  Nix, a purely functional package manager, is a powerful
+  package manager for Linux and other Unix systems that
+  makes package management reliable and reproducible.
+keywords:
+  - reproducibility
+  - open-source
+  - c++
+  - functional
+license: LGPL-2.1
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 887bd480273..38f5d43b710 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -27,6 +27,8 @@ Check out the [security policy](https://github.com/NixOS/nix/security/policy).
 1. Search for related issues that cover what you're going to work on.
    It could help to mention there that you will work on the issue.
 
+   We strongly recommend first-time contributors not to propose new features but rather fix tightly-scoped problems in order to build trust and a working relationship with maintainers.
+
    Issues labeled [good first issue](https://github.com/NixOS/nix/labels/good%20first%20issue) should be relatively easy to fix and are likely to get merged quickly.
    Pull requests addressing issues labeled [idea approved](https://github.com/NixOS/nix/labels/idea%20approved) or [RFC](https://github.com/NixOS/nix/labels/RFC) are especially welcomed by maintainers and will receive prioritised review.
 
diff --git a/Makefile b/Makefile
index ba5a6cd92f8..bb64a104e72 100644
--- a/Makefile
+++ b/Makefile
@@ -18,6 +18,7 @@ makefiles = \
   src/libfetchers/local.mk \
   src/libmain/local.mk \
   src/libexpr/local.mk \
+  src/libflake/local.mk \
   src/libcmd/local.mk \
   src/nix/local.mk \
   src/libutil-c/local.mk \
@@ -27,6 +28,7 @@ makefiles = \
 ifdef HOST_UNIX
 makefiles += \
   scripts/local.mk \
+  maintainers/local.mk \
   misc/bash/local.mk \
   misc/fish/local.mk \
   misc/zsh/local.mk \
@@ -44,7 +46,8 @@ makefiles += \
   tests/unit/libstore-support/local.mk \
   tests/unit/libfetchers/local.mk \
   tests/unit/libexpr/local.mk \
-  tests/unit/libexpr-support/local.mk
+  tests/unit/libexpr-support/local.mk \
+  tests/unit/libflake/local.mk
 endif
 
 ifeq ($(ENABLE_FUNCTIONAL_TESTS), yes)
@@ -67,14 +70,6 @@ ifeq ($(ENABLE_DOC_GEN), yes)
 makefiles-late += doc/manual/local.mk
 endif
 
-ifeq ($(ENABLE_INTERNAL_API_DOCS), yes)
-makefiles-late += doc/internal-api/local.mk
-endif
-
-ifeq ($(ENABLE_EXTERNAL_API_DOCS), yes)
-makefiles-late += doc/external-api/local.mk
-endif
-
 # Miscellaneous global Flags
 
 OPTIMIZE = 1
@@ -97,7 +92,7 @@ ifdef HOST_WINDOWS
   GLOBAL_LDFLAGS += -Wl,--export-all-symbols
 endif
 
-GLOBAL_CXXFLAGS += -g -Wall -Wimplicit-fallthrough -include $(buildprefix)config.h -std=c++2a -I src
+GLOBAL_CXXFLAGS += -g -Wall -Wdeprecated-copy -Wignored-qualifiers -Wimplicit-fallthrough -Werror=unused-result -include $(buildprefix)config.h -std=c++2a -I src
 
 # Include the main lib, causing rules to be defined
 
@@ -130,17 +125,3 @@ manual-html manpages:
 	@echo "Generated docs are disabled. Configure without '--disable-doc-gen', or avoid calling 'make manpages' and 'make manual-html'."
 	@exit 1
 endif
-
-ifneq ($(ENABLE_INTERNAL_API_DOCS), yes)
-.PHONY: internal-api-html
-internal-api-html:
-	@echo "Internal API docs are disabled. Configure with '--enable-internal-api-docs', or avoid calling 'make internal-api-html'."
-	@exit 1
-endif
-
-ifneq ($(ENABLE_EXTERNAL_API_DOCS), yes)
-.PHONY: external-api-html
-external-api-html:
-	@echo "External API docs are disabled. Configure with '--enable-external-api-docs', or avoid calling 'make external-api-html'."
-	@exit 1
-endif
diff --git a/Makefile.config.in b/Makefile.config.in
index 7f517898c14..3100d207365 100644
--- a/Makefile.config.in
+++ b/Makefile.config.in
@@ -11,8 +11,6 @@ EDITLINE_LIBS = @EDITLINE_LIBS@
 ENABLE_BUILD = @ENABLE_BUILD@
 ENABLE_DOC_GEN = @ENABLE_DOC_GEN@
 ENABLE_FUNCTIONAL_TESTS = @ENABLE_FUNCTIONAL_TESTS@
-ENABLE_INTERNAL_API_DOCS = @ENABLE_INTERNAL_API_DOCS@
-ENABLE_EXTERNAL_API_DOCS = @ENABLE_EXTERNAL_API_DOCS@
 ENABLE_S3 = @ENABLE_S3@
 ENABLE_UNIT_TESTS = @ENABLE_UNIT_TESTS@
 GTEST_LIBS = @GTEST_LIBS@
diff --git a/README.md b/README.md
index e1cace3b4d5..931a60bba2c 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ Visit [nix.dev](https://nix.dev) for [installation instructions](https://nix.dev
 
 Full reference documentation can be found in the [Nix manual](https://nixos.org/nix/manual).
 
-## Building And Developing
+## Building and developing
 
 See our [Hacking guide](https://nixos.org/manual/nix/unstable/contributing/hacking.html) in our manual for instruction on how to
  set up a development environment and build Nix from source.
@@ -22,12 +22,17 @@ See our [Hacking guide](https://nixos.org/manual/nix/unstable/contributing/hacki
 
 Check the [contributing guide](./CONTRIBUTING.md) if you want to get involved with developing Nix.
 
-## Additional Resources
+## Additional resources
 
-- [Nix manual](https://nixos.org/nix/manual)
-- [Nix jobsets on hydra.nixos.org](https://hydra.nixos.org/project/nix)
-- [NixOS Discourse](https://discourse.nixos.org/)
-- [Matrix - #nix:nixos.org](https://matrix.to/#/#nix:nixos.org)
+Nix was created by Eelco Dolstra and developed as the subject of his PhD thesis [The Purely Functional Software Deployment Model](https://edolstra.github.io/pubs/phd-thesis.pdf), published 2006.
+Today, a world-wide developer community contributes to Nix and the ecosystem that has grown around it.
+
+- [The Nix, Nixpkgs, NixOS Community on nixos.org](https://nixos.org/)
+- [Official documentation on nix.dev](https://nix.dev)
+- [Nixpkgs](https://github.com/NixOS/nixpkgs) is [the largest, most up-to-date free software repository in the world](https://repology.org/repositories/graphs)
+- [NixOS](https://github.com/NixOS/nixpkgs/tree/master/nixos) is a Linux distribution that can be configured fully declaratively
+- [Discourse](https://discourse.nixos.org/)
+- [Matrix](https://matrix.to/#/#nix:nixos.org)
 
 ## License
 
diff --git a/build-utils-meson/deps-lists/meson.build b/build-utils-meson/deps-lists/meson.build
new file mode 100644
index 00000000000..237eac5459a
--- /dev/null
+++ b/build-utils-meson/deps-lists/meson.build
@@ -0,0 +1,36 @@
+# These are private dependencies with pkg-config files. What private
+# means is that the dependencies are used by the library but they are
+# *not* used (e.g. `#include`-ed) in any installed header file, and only
+# in regular source code (`*.cc`) or private, uninstalled headers. They
+# are thus part of the *implementation* of the library, but not its
+# *interface*.
+#
+# See `man pkg-config` for some details.
+deps_private = [ ]
+
+# These are public dependencies with pkg-config files. Public is the
+# opposite of private: these dependencies are used in installed header
+# files. They are part of the interface (and implementation) of the
+# library.
+#
+# N.B. This concept is mostly unrelated to our own concept of a public
+# (stable) API, for consumption outside of the Nix repository.
+# `libnixutil` is an unstable C++ library, whose public interface is
+# likewise unstable. `libutilc` conversely is a hopefully-soon stable
+# C library, whose public interface --- including public but not private
+# dependencies --- will also likewise soon be stable.
+#
+# N.B. For distributions that care about "ABI" stability and not just
+# "API" stability, the private dependencies also matter as they can
+# potentially affect the public ABI.
+deps_public = [ ]
+
+# These are subproject deps (type == "internal"). They are other
+# packages in `/src` in this repo. The private vs public distinction is
+# the same as above.
+deps_private_subproject = [ ]
+deps_public_subproject = [ ]
+
+# These are dependencencies without pkg-config files. Ideally they are
+# just private, but they may also be public (e.g. boost).
+deps_other = [ ]
diff --git a/build-utils-meson/diagnostics/meson.build b/build-utils-meson/diagnostics/meson.build
new file mode 100644
index 00000000000..2b79f6566dc
--- /dev/null
+++ b/build-utils-meson/diagnostics/meson.build
@@ -0,0 +1,13 @@
+add_project_arguments(
+  '-Wno-deprecated-declarations',
+  '-Wimplicit-fallthrough',
+  '-Werror=switch',
+  '-Werror=switch-enum',
+  '-Werror=unused-result',
+  '-Wdeprecated-copy',
+  '-Wignored-qualifiers',
+  # Enable assertions in libstdc++ by default. Harmless on libc++. Benchmarked
+  # at ~1% overhead in `nix search`.
+  #
+  language : 'cpp',
+)
diff --git a/build-utils-meson/export-all-symbols/meson.build b/build-utils-meson/export-all-symbols/meson.build
new file mode 100644
index 00000000000..d7c086749fb
--- /dev/null
+++ b/build-utils-meson/export-all-symbols/meson.build
@@ -0,0 +1,11 @@
+if host_machine.system() == 'cygwin' or host_machine.system() == 'windows'
+  # Windows DLLs are stricter about symbol visibility than Unix shared
+  # objects --- see https://gcc.gnu.org/wiki/Visibility for details.
+  # This is a temporary sledgehammer to export everything like on Unix,
+  # and not detail with this yet.
+  #
+  # TODO do not do this, and instead do fine-grained export annotations.
+  linker_export_flags = ['-Wl,--export-all-symbols']
+else
+  linker_export_flags = []
+endif
diff --git a/build-utils-meson/export/meson.build b/build-utils-meson/export/meson.build
new file mode 100644
index 00000000000..40f6dcd59a0
--- /dev/null
+++ b/build-utils-meson/export/meson.build
@@ -0,0 +1,30 @@
+requires_private = []
+foreach dep : deps_private_subproject
+  requires_private  += dep.name()
+endforeach
+requires_private += deps_private
+
+requires_public  = []
+foreach dep : deps_public_subproject
+  requires_public  += dep.name()
+endforeach
+requires_public += deps_public
+
+import('pkgconfig').generate(
+  this_library,
+  filebase : meson.project_name(),
+  name : 'Nix',
+  description : 'Nix Package Manager',
+  subdirs : ['nix'],
+  extra_cflags : ['-std=c++2a'],
+  requires : requires_public,
+  requires_private : requires_private,
+  libraries_private : libraries_private,
+)
+
+meson.override_dependency(meson.project_name(), declare_dependency(
+  include_directories : include_dirs,
+  link_with : this_library,
+  compile_args : ['-std=c++2a'],
+  dependencies : deps_public_subproject + deps_public,
+))
diff --git a/build-utils-meson/generate-header/meson.build b/build-utils-meson/generate-header/meson.build
new file mode 100644
index 00000000000..dfbe1375f4f
--- /dev/null
+++ b/build-utils-meson/generate-header/meson.build
@@ -0,0 +1,7 @@
+bash = find_program('bash', native: true)
+
+gen_header = generator(
+  bash,
+  arguments : [ '-c', '{ echo \'R"__NIX_STR(\' && cat @INPUT@ && echo \')__NIX_STR"\'; } > "$1"', '_ignored_argv0', '@OUTPUT@' ],
+  output : '@PLAINNAME@.gen.hh',
+)
diff --git a/build-utils-meson/subprojects/meson.build b/build-utils-meson/subprojects/meson.build
new file mode 100644
index 00000000000..30a54ed913e
--- /dev/null
+++ b/build-utils-meson/subprojects/meson.build
@@ -0,0 +1,19 @@
+foreach maybe_subproject_dep : deps_private_maybe_subproject
+  if maybe_subproject_dep.type_name() == 'internal'
+    deps_private_subproject += maybe_subproject_dep
+    # subproject sadly no good for pkg-config module
+    deps_other += maybe_subproject_dep
+  else
+    deps_private += maybe_subproject_dep
+  endif
+endforeach
+
+foreach maybe_subproject_dep : deps_public_maybe_subproject
+  if maybe_subproject_dep.type_name() == 'internal'
+    deps_public_subproject += maybe_subproject_dep
+    # subproject sadly no good for pkg-config module
+    deps_other += maybe_subproject_dep
+  else
+    deps_public += maybe_subproject_dep
+  endif
+endforeach
diff --git a/build-utils-meson/threads/meson.build b/build-utils-meson/threads/meson.build
new file mode 100644
index 00000000000..294160de130
--- /dev/null
+++ b/build-utils-meson/threads/meson.build
@@ -0,0 +1,6 @@
+# This is only conditional to work around
+# https://github.com/mesonbuild/meson/issues/13293. It should be
+# unconditional.
+if not (host_machine.system() == 'windows' and cxx.get_id() == 'gcc')
+  deps_private += dependency('threads')
+endif
diff --git a/configure.ac b/configure.ac
index 1d327d51dfb..4f66a3efcf6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -63,7 +63,6 @@ AC_SYS_LARGEFILE
 
 
 # Solaris-specific stuff.
-AC_STRUCT_DIRENT_D_TYPE
 case "$host_os" in
   solaris*)
     # Solaris requires -lsocket -lnsl for network functions
@@ -150,11 +149,6 @@ AC_ARG_ENABLE(unit-tests, AS_HELP_STRING([--disable-unit-tests],[Do not build th
   ENABLE_UNIT_TESTS=$enableval, ENABLE_UNIT_TESTS=$ENABLE_BUILD)
 AC_SUBST(ENABLE_UNIT_TESTS)
 
-# Build external API docs by default
-AC_ARG_ENABLE(external_api_docs, AS_HELP_STRING([--enable-external-api-docs],[Build API docs for Nix's C interface]),
-  external_api_docs=$enableval, external_api_docs=yes)
-AC_SUBST(external_api_docs)
-
 AS_IF(
   [test "$ENABLE_BUILD" == "no" && test "$ENABLE_UNIT_TESTS" == "yes"],
   [AC_MSG_ERROR([Cannot enable unit tests when building overall is disabled. Please do not pass '--enable-unit-tests' or do not pass '--disable-build'.])])
@@ -172,15 +166,6 @@ AS_IF(
   [test "$ENABLE_BUILD" == "no" && test "$ENABLE_DOC_GEN" == "yes"],
   [AC_MSG_ERROR([Cannot enable generated docs when building overall is disabled. Please do not pass '--enable-doc-gen' or do not pass '--disable-build'.])])
 
-# Building without API docs is the default as Nix' C++ interfaces are internal and unstable.
-AC_ARG_ENABLE(internal-api-docs, AS_HELP_STRING([--enable-internal-api-docs],[Build API docs for Nix's internal unstable C++ interfaces]),
-  ENABLE_INTERNAL_API_DOCS=$enableval, ENABLE_INTERNAL_API_DOCS=no)
-AC_SUBST(ENABLE_INTERNAL_API_DOCS)
-
-AC_ARG_ENABLE(external-api-docs, AS_HELP_STRING([--enable-external-api-docs],[Build API docs for Nix's external unstable C interfaces]),
-  ENABLE_EXTERNAL_API_DOCS=$enableval, ENABLE_EXTERNAL_API_DOCS=no)
-AC_SUBST(ENABLE_EXTERNAL_API_DOCS)
-
 AS_IF(
   [test "$ENABLE_FUNCTIONAL_TESTS" == "yes" || test "$ENABLE_DOC_GEN" == "yes"],
   [NEED_PROG(jq, jq)])
@@ -314,9 +299,20 @@ case "$host_os" in
                                 ]))
     if test "x$enable_seccomp_sandboxing" != "xno"; then
       PKG_CHECK_MODULES([LIBSECCOMP], [libseccomp],
-                        [CXXFLAGS="$LIBSECCOMP_CFLAGS $CXXFLAGS"])
+                        [CXXFLAGS="$LIBSECCOMP_CFLAGS $CXXFLAGS" CFLAGS="$LIBSECCOMP_CFLAGS $CFLAGS"])
       have_seccomp=1
       AC_DEFINE([HAVE_SECCOMP], [1], [Whether seccomp is available and should be used for sandboxing.])
+      AC_COMPILE_IFELSE([
+        AC_LANG_SOURCE([[
+          #include <seccomp.h>
+          #ifndef __SNR_fchmodat2
+          # error "Missing support for fchmodat2"
+          #endif
+        ]])
+      ], [], [
+        echo "libseccomp is missing __SNR_fchmodat2. Please provide libseccomp 2.5.5 or later"
+        exit 1
+      ])
     else
       have_seccomp=
     fi
@@ -359,6 +355,14 @@ if test "$gc" = yes; then
   PKG_CHECK_MODULES([BDW_GC], [bdw-gc])
   CXXFLAGS="$BDW_GC_CFLAGS $CXXFLAGS"
   AC_DEFINE(HAVE_BOEHMGC, 1, [Whether to use the Boehm garbage collector.])
+
+  # See `fixupBoehmStackPointer`, for the integration between Boehm GC
+  # and Boost coroutines.
+  old_CFLAGS="$CFLAGS"
+  # Temporary set `-pthread` just for the next check
+  CFLAGS="$CFLAGS -pthread"
+  AC_CHECK_FUNCS([pthread_attr_get_np pthread_getattr_np])
+  CFLAGS="$old_CFLAGS"
 fi
 
 AS_IF([test "$ENABLE_UNIT_TESTS" == "yes"],[
@@ -396,6 +400,11 @@ AS_CASE(["$enable_markdown"],
 PKG_CHECK_MODULES([LIBGIT2], [libgit2])
 
 
+# Look for toml11, a required dependency.
+AC_LANG_PUSH(C++)
+AC_CHECK_HEADER([toml.hpp], [], [AC_MSG_ERROR([toml11 is not found.])])
+AC_LANG_POP(C++)
+
 # Setuid installations.
 AC_CHECK_FUNCS([setresuid setreuid lchown])
 
diff --git a/dep-patches/boehmgc-coroutine-sp-fallback.diff b/dep-patches/boehmgc-coroutine-sp-fallback.diff
deleted file mode 100644
index 2afbe96712b..00000000000
--- a/dep-patches/boehmgc-coroutine-sp-fallback.diff
+++ /dev/null
@@ -1,99 +0,0 @@
-diff --git a/darwin_stop_world.c b/darwin_stop_world.c
-index 0468aaec..b348d869 100644
---- a/darwin_stop_world.c
-+++ b/darwin_stop_world.c
-@@ -356,6 +356,7 @@ GC_INNER void GC_push_all_stacks(void)
-   int nthreads = 0;
-   word total_size = 0;
-   mach_msg_type_number_t listcount = (mach_msg_type_number_t)THREAD_TABLE_SZ;
-+  size_t stack_limit;
-   if (!EXPECT(GC_thr_initialized, TRUE))
-     GC_thr_init();
- 
-@@ -411,6 +412,19 @@ GC_INNER void GC_push_all_stacks(void)
-             GC_push_all_stack_sections(lo, hi, p->traced_stack_sect);
-           }
-           if (altstack_lo) {
-+            // When a thread goes into a coroutine, we lose its original sp until
-+            // control flow returns to the thread.
-+            // While in the coroutine, the sp points outside the thread stack,
-+            // so we can detect this and push the entire thread stack instead,
-+            // as an approximation.
-+            // We assume that the coroutine has similarly added its entire stack.
-+            // This could be made accurate by cooperating with the application
-+            // via new functions and/or callbacks.
-+            stack_limit = pthread_get_stacksize_np(p->id);
-+            if (altstack_lo >= altstack_hi || altstack_lo < altstack_hi - stack_limit) { // sp outside stack
-+              altstack_lo = altstack_hi - stack_limit;
-+            }
-+
-             total_size += altstack_hi - altstack_lo;
-             GC_push_all_stack(altstack_lo, altstack_hi);
-           }
-diff --git a/include/gc.h b/include/gc.h
-index edab6c22..f2c61282 100644
---- a/include/gc.h
-+++ b/include/gc.h
-@@ -2172,6 +2172,11 @@ GC_API void GC_CALL GC_win32_free_heap(void);
-         (*GC_amiga_allocwrapper_do)(a,GC_malloc_atomic_ignore_off_page)
- #endif /* _AMIGA && !GC_AMIGA_MAKINGLIB */
- 
-+#if !__APPLE__
-+/* Patch doesn't work on apple */
-+#define NIX_BOEHM_PATCH_VERSION 1
-+#endif
-+
- #ifdef __cplusplus
-   } /* extern "C" */
- #endif
-diff --git a/pthread_stop_world.c b/pthread_stop_world.c
-index b5d71e62..aed7b0bf 100644
---- a/pthread_stop_world.c
-+++ b/pthread_stop_world.c
-@@ -768,6 +768,8 @@ STATIC void GC_restart_handler(int sig)
- /* world is stopped.  Should not fail if it isn't.                      */
- GC_INNER void GC_push_all_stacks(void)
- {
-+    size_t stack_limit;
-+    pthread_attr_t pattr;
-     GC_bool found_me = FALSE;
-     size_t nthreads = 0;
-     int i;
-@@ -851,6 +853,37 @@ GC_INNER void GC_push_all_stacks(void)
-           hi = p->altstack + p->altstack_size;
-           /* FIXME: Need to scan the normal stack too, but how ? */
-           /* FIXME: Assume stack grows down */
-+        } else {
-+#ifdef HAVE_PTHREAD_ATTR_GET_NP
-+          if (!pthread_attr_init(&pattr)
-+              || !pthread_attr_get_np(p->id, &pattr))
-+#else /* HAVE_PTHREAD_GETATTR_NP */
-+          if (pthread_getattr_np(p->id, &pattr))
-+#endif
-+          {
-+            ABORT("GC_push_all_stacks: pthread_getattr_np failed!");
-+          }
-+          if (pthread_attr_getstacksize(&pattr, &stack_limit)) {
-+            ABORT("GC_push_all_stacks: pthread_attr_getstacksize failed!");
-+          }
-+          if (pthread_attr_destroy(&pattr)) {
-+            ABORT("GC_push_all_stacks: pthread_attr_destroy failed!");
-+          }
-+          // When a thread goes into a coroutine, we lose its original sp until
-+          // control flow returns to the thread.
-+          // While in the coroutine, the sp points outside the thread stack,
-+          // so we can detect this and push the entire thread stack instead,
-+          // as an approximation.
-+          // We assume that the coroutine has similarly added its entire stack.
-+          // This could be made accurate by cooperating with the application
-+          // via new functions and/or callbacks.
-+          #ifndef STACK_GROWS_UP
-+            if (lo >= hi || lo < hi - stack_limit) { // sp outside stack
-+              lo = hi - stack_limit;
-+            }
-+          #else
-+          #error "STACK_GROWS_UP not supported in boost_coroutine2 (as of june 2021), so we don't support it in Nix."
-+          #endif
-         }
-         GC_push_all_stack_sections(lo, hi, traced_stack_sect);
- #       ifdef STACK_GROWS_UP
diff --git a/dep-patches/boehmgc-traceable_allocator-public.diff b/dep-patches/boehmgc-traceable_allocator-public.diff
deleted file mode 100644
index 903c707a698..00000000000
--- a/dep-patches/boehmgc-traceable_allocator-public.diff
+++ /dev/null
@@ -1,12 +0,0 @@
-diff --git a/include/gc_allocator.h b/include/gc_allocator.h
-index 597c7f13..587286be 100644
---- a/include/gc_allocator.h
-+++ b/include/gc_allocator.h
-@@ -312,6 +312,7 @@ public:
- 
- template<>
- class traceable_allocator<void> {
-+public:
-   typedef size_t      size_type;
-   typedef ptrdiff_t   difference_type;
-   typedef void*       pointer;
diff --git a/doc/external-api/local.mk b/doc/external-api/local.mk
deleted file mode 100644
index c739bdaf0ef..00000000000
--- a/doc/external-api/local.mk
+++ /dev/null
@@ -1,7 +0,0 @@
-$(docdir)/external-api/html/index.html $(docdir)/external-api/latex: $(d)/doxygen.cfg
-	mkdir -p $(docdir)/external-api
-	{ cat $< ; echo "OUTPUT_DIRECTORY=$(docdir)/external-api" ; } | doxygen -
-
-# Generate the HTML API docs for Nix's unstable C bindings
-.PHONY: external-api-html
-external-api-html: $(docdir)/external-api/html/index.html
diff --git a/doc/internal-api/local.mk b/doc/internal-api/local.mk
deleted file mode 100644
index bf2c4dedea1..00000000000
--- a/doc/internal-api/local.mk
+++ /dev/null
@@ -1,7 +0,0 @@
-$(docdir)/internal-api/html/index.html $(docdir)/internal-api/latex: $(d)/doxygen.cfg
-	mkdir -p $(docdir)/internal-api
-	{ cat $< ; echo "OUTPUT_DIRECTORY=$(docdir)/internal-api" ; } | doxygen -
-
-# Generate the HTML API docs for Nix's unstable internal interfaces.
-.PHONY: internal-api-html
-internal-api-html: $(docdir)/internal-api/html/index.html
diff --git a/doc/manual/book.toml b/doc/manual/book.toml
index d524dbb1309..73fb7e75e24 100644
--- a/doc/manual/book.toml
+++ b/doc/manual/book.toml
@@ -6,8 +6,6 @@ additional-css = ["custom.css"]
 additional-js = ["redirects.js"]
 edit-url-template = "https://github.com/NixOS/nix/tree/master/doc/manual/{path}"
 git-repository-url = "https://github.com/NixOS/nix"
-fold.enable = true
-fold.level = 1
 
 [preprocessor.anchors]
 renderers = ["html"]
diff --git a/doc/manual/generate-builtin-constants.nix b/doc/manual/generate-builtin-constants.nix
deleted file mode 100644
index cccd1e279e6..00000000000
--- a/doc/manual/generate-builtin-constants.nix
+++ /dev/null
@@ -1,31 +0,0 @@
-let
-  inherit (builtins) concatStringsSep attrValues mapAttrs;
-  inherit (import <nix/utils.nix>) optionalString squash;
-in
-
-builtinsInfo:
-let
-  showBuiltin = name: { doc, type, impure-only }:
-    let
-      type' = optionalString (type != null) " (${type})";
-
-      impureNotice = optionalString impure-only ''
-        > **Note**
-        >
-        > Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
-      '';
-    in
-    squash ''
-      <dt id="builtins-${name}">
-        <a href="#builtins-${name}"><code>${name}</code></a>${type'}
-      </dt>
-      <dd>
-
-      ${doc}
-
-      ${impureNotice}
-
-      </dd>
-    '';
-in
-concatStringsSep "\n" (attrValues (mapAttrs showBuiltin builtinsInfo))
diff --git a/doc/manual/generate-builtins.nix b/doc/manual/generate-builtins.nix
index 007b698f1bf..13de6c3972c 100644
--- a/doc/manual/generate-builtins.nix
+++ b/doc/manual/generate-builtins.nix
@@ -5,8 +5,10 @@ in
 
 builtinsInfo:
 let
-  showBuiltin = name: { doc, args, arity, experimental-feature }:
+  showBuiltin = name: { doc, type ? null, args ? [ ], experimental-feature ? null, impure-only ? false }:
     let
+      type' = optionalString (type != null) " (${type})";
+
       experimentalNotice = optionalString (experimental-feature != null) ''
         > **Note**
         >
@@ -18,18 +20,26 @@ let
         > extra-experimental-features = ${experimental-feature}
         > ```
       '';
+
+      impureNotice = optionalString impure-only ''
+        > **Note**
+        >
+        > Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
+      '';
     in
     squash ''
       <dt id="builtins-${name}">
-        <a href="#builtins-${name}"><code>${name} ${listArgs args}</code></a>
+        <a href="#builtins-${name}"><code>${name}${listArgs args}</code></a>${type'}
       </dt>
       <dd>
 
       ${experimentalNotice}
 
       ${doc}
+
+      ${impureNotice}
       </dd>
     '';
-  listArgs = args: concatStringsSep " " (map (s: "<var>${s}</var>") args);
+  listArgs = args: concatStringsSep "" (map (s: " <var>${s}</var>") args);
 in
 concatStringsSep "\n" (attrValues (mapAttrs showBuiltin builtinsInfo))
diff --git a/doc/manual/local.mk b/doc/manual/local.mk
index 71ad5c8e640..0cec5288504 100644
--- a/doc/manual/local.mk
+++ b/doc/manual/local.mk
@@ -140,16 +140,10 @@ $(d)/xp-features.json: $(doc_nix)
 
 $(d)/src/language/builtins.md: $(d)/language.json $(d)/generate-builtins.nix $(d)/src/language/builtins-prefix.md $(doc_nix)
 	@cat doc/manual/src/language/builtins-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<)).builtins' >> $@.tmp;
+	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp;
 	@cat doc/manual/src/language/builtins-suffix.md >> $@.tmp
 	@mv $@.tmp $@
 
-$(d)/src/language/builtin-constants.md: $(d)/language.json $(d)/generate-builtin-constants.nix $(d)/src/language/builtin-constants-prefix.md $(doc_nix)
-	@cat doc/manual/src/language/builtin-constants-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtin-constants.nix (builtins.fromJSON (builtins.readFile $<)).constants' >> $@.tmp;
-	@cat doc/manual/src/language/builtin-constants-suffix.md >> $@.tmp
-	@mv $@.tmp $@
-
 $(d)/language.json: $(doc_nix)
 	$(trace-gen) $(dummy-env) $(doc_nix) __dump-language > $@.tmp
 	@mv $@.tmp $@
@@ -217,7 +211,7 @@ doc/manual/generated/man1/nix3-manpages: $(d)/src/command-ref/new-cli
 # `@docroot@` is to be preserved for documenting the mechanism
 # FIXME: maybe contributing guides should live right next to the code
 # instead of in the manual
-$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/store/types $(d)/src/command-ref/new-cli $(d)/src/contributing/experimental-feature-descriptions.md $(d)/src/command-ref/conf-file.md $(d)/src/language/builtins.md $(d)/src/language/builtin-constants.md $(d)/src/release-notes/rl-next.md $(d)/src/figures $(d)/src/favicon.png $(d)/src/favicon.svg
+$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/store/types $(d)/src/command-ref/new-cli $(d)/src/contributing/experimental-feature-descriptions.md $(d)/src/command-ref/conf-file.md $(d)/src/language/builtins.md $(d)/src/release-notes/rl-next.md $(d)/src/figures $(d)/src/favicon.png $(d)/src/favicon.svg
 	$(trace-gen) \
 		tmp="$$(mktemp -d)"; \
 		cp -r doc/manual "$$tmp"; \
diff --git a/doc/manual/redirects.js b/doc/manual/redirects.js
index 25648969d1c..0f9f91b037f 100644
--- a/doc/manual/redirects.js
+++ b/doc/manual/redirects.js
@@ -1,7 +1,7 @@
 // redirect rules for URL fragments (client-side) to prevent link rot.
 // this must be done on the client side, as web servers do not see the fragment part of the URL.
 // it will only work with JavaScript enabled in the browser, but this is the best we can do here.
-// see ./_redirects for path redirects (client-side)
+// see src/_redirects for path redirects (server-side)
 
 // redirects are declared as follows:
 // each entry has as its key a path matching the requested URL path, relative to the mdBook document root.
@@ -238,12 +238,12 @@ const redirects = {
     "attr-system": "language/derivations.html#attr-system",
     "ssec-derivation": "language/derivations.html",
     "ch-expression-language": "language/index.html",
-    "sec-constructs": "language/constructs.html",
-    "sect-let-language": "language/constructs.html#let-language",
-    "ss-functions": "language/constructs.html#functions",
+    "sec-constructs": "language/syntax.html",
+    "sect-let-language": "language/syntax.html#let-expressions",
+    "ss-functions": "language/syntax.html#functions",
     "sec-language-operators": "language/operators.html",
     "table-operators": "language/operators.html",
-    "ssec-values": "language/values.html",
+    "ssec-values": "language/types.html",
     "gloss-closure": "glossary.html#gloss-closure",
     "gloss-derivation": "glossary.html#gloss-derivation",
     "gloss-deriver": "glossary.html#gloss-deriver",
@@ -285,15 +285,15 @@ const redirects = {
     "ch-basic-package-mgmt": "package-management/basic-package-mgmt.html",
     "ssec-binary-cache-substituter": "package-management/binary-cache-substituter.html",
     "sec-channels": "command-ref/nix-channel.html",
-    "ssec-copy-closure": "package-management/copy-closure.html",
+    "ssec-copy-closure": "command-ref/nix-copy-closure.html",
     "sec-garbage-collection": "package-management/garbage-collection.html",
     "ssec-gc-roots": "package-management/garbage-collector-roots.html",
     "chap-package-management": "package-management/index.html",
     "sec-profiles": "package-management/profiles.html",
-    "ssec-s3-substituter": "package-management/s3-substituter.html",
-    "ssec-s3-substituter-anonymous-reads": "package-management/s3-substituter.html#anonymous-reads-to-your-s3-compatible-binary-cache",
-    "ssec-s3-substituter-authenticated-reads": "package-management/s3-substituter.html#authenticated-reads-to-your-s3-binary-cache",
-    "ssec-s3-substituter-authenticated-writes": "package-management/s3-substituter.html#authenticated-writes-to-your-s3-compatible-binary-cache",
+    "ssec-s3-substituter": "store/types/s3-substituter.html",
+    "ssec-s3-substituter-anonymous-reads": "store/types/s3-substituter.html#anonymous-reads-to-your-s3-compatible-binary-cache",
+    "ssec-s3-substituter-authenticated-reads": "store/types/s3-substituter.html#authenticated-reads-to-your-s3-binary-cache",
+    "ssec-s3-substituter-authenticated-writes": "store/types/s3-substituter.html#authenticated-writes-to-your-s3-compatible-binary-cache",
     "sec-sharing-packages": "package-management/sharing-packages.html",
     "ssec-ssh-substituter": "package-management/ssh-substituter.html",
     "chap-quick-start": "quick-start.html",
@@ -335,11 +335,15 @@ const redirects = {
     "ssec-relnotes-2.2": "release-notes/rl-2.2.html",
     "ssec-relnotes-2.3": "release-notes/rl-2.3.html",
   },
-  "language/values.html": {
+  "language/types.html": {
     "simple-values": "#primitives",
     "lists": "#list",
     "strings": "#string",
     "attribute-sets": "#attribute-set",
+    "type-number": "#type-int",
+  },
+  "language/syntax.html": {
+    "scoping-rules": "scoping.html",
   },
   "installation/installing-binary.html": {
     "linux": "uninstall.html#linux",
diff --git a/doc/manual/rl-next/drop-vendored-toml11.md b/doc/manual/rl-next/drop-vendored-toml11.md
new file mode 100644
index 00000000000..d1feeb7031a
--- /dev/null
+++ b/doc/manual/rl-next/drop-vendored-toml11.md
@@ -0,0 +1,6 @@
+---
+synopsis: Stop vendoring toml11
+---
+
+We don't apply any patches to it, and vendoring it locks users into
+bugs (it hasn't been updated since its introduction in late 2021).
diff --git a/doc/manual/rl-next/harden-user-sandboxing.md b/doc/manual/rl-next/harden-user-sandboxing.md
new file mode 100644
index 00000000000..a647acf2540
--- /dev/null
+++ b/doc/manual/rl-next/harden-user-sandboxing.md
@@ -0,0 +1,7 @@
+---
+synopsis: Harden the user sandboxing
+significance: significant
+issues:
+---
+
+The build directory has been hardened against interference with the outside world by nesting it inside another directory owned by (and only readable by) the daemon user.
diff --git a/doc/manual/rl-next/nix-eval-derivations.md b/doc/manual/rl-next/nix-eval-derivations.md
deleted file mode 100644
index ed0a7338464..00000000000
--- a/doc/manual/rl-next/nix-eval-derivations.md
+++ /dev/null
@@ -1,13 +0,0 @@
----
-synopsis: "`nix eval` prints derivations as `.drv` paths"
-prs: 10200
----
-
-`nix eval` will now print derivations as their `.drv` paths, rather than as
-attribute sets. This makes commands like `nix eval nixpkgs#bash` terminate
-instead of infinitely looping into recursive self-referential attributes:
-
-```ShellSession
-$ nix eval nixpkgs#bash
-«derivation /nix/store/m32cbgbd598f4w299g0hwyv7gbw6rqcg-bash-5.2p26.drv»
-```
diff --git a/doc/manual/rl-next/nix-shell-looks-for-shell-nix.md b/doc/manual/rl-next/nix-shell-looks-for-shell-nix.md
new file mode 100644
index 00000000000..99be4148bf1
--- /dev/null
+++ b/doc/manual/rl-next/nix-shell-looks-for-shell-nix.md
@@ -0,0 +1,28 @@
+---
+synopsis: "`nix-shell <directory>` looks for `shell.nix`"
+significance: significant
+issues:
+- 496
+- 2279
+- 4529
+- 5431
+- 11053
+prs:
+- 11057
+---
+
+`nix-shell $x` now looks for `$x/shell.nix` when `$x` resolves to a directory.
+
+Although this might be seen as a breaking change, its primarily interactive usage makes it a minor issue.
+This adjustment addresses a commonly reported problem.
+
+This also applies to `nix-shell` shebang scripts. Consider the following example:
+
+```shell
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash
+```
+
+This will now load `shell.nix` from the script's directory, if it exists; `default.nix` otherwise.
+
+The old behavior can be opted into by setting the option [`nix-shell-always-looks-for-shell-nix`](@docroot@/command-ref/conf-file.md#conf-nix-shell-always-looks-for-shell-nix) to `false`.
diff --git a/doc/manual/rl-next/remove-repl-flake.md b/doc/manual/rl-next/remove-repl-flake.md
deleted file mode 100644
index 23298e2edea..00000000000
--- a/doc/manual/rl-next/remove-repl-flake.md
+++ /dev/null
@@ -1,8 +0,0 @@
----
-synopsis: Remove experimental repl-flake
-significance: significant
-issues: 10103
-prs: 10299
----
-
-The `repl-flake` experimental feature has been removed. The `nix repl` command now works like the rest of the new CLI in that `nix repl {path}` now tries to load a flake at `{path}` (or fails if the `flakes` experimental feature isn't enabled).*
diff --git a/doc/manual/src/SUMMARY.md.in b/doc/manual/src/SUMMARY.md.in
index d9044fbdac6..a6a2101e9af 100644
--- a/doc/manual/src/SUMMARY.md.in
+++ b/doc/manual/src/SUMMARY.md.in
@@ -18,21 +18,24 @@
   - [Uninstalling Nix](installation/uninstall.md)
 - [Nix Store](store/index.md)
   - [File System Object](store/file-system-object.md)
+    - [Content-Addressing File System Objects](store/file-system-object/content-address.md)
   - [Store Object](store/store-object.md)
+    - [Content-Addressing Store Objects](store/store-object/content-address.md)
   - [Store Path](store/store-path.md)
   - [Store Types](store/types/index.md)
 {{#include ./store/types/SUMMARY.md}}
 - [Nix Language](language/index.md)
-  - [Data Types](language/values.md)
-  - [Language Constructs](language/constructs.md)
+  - [Data Types](language/types.md)
+    - [String context](language/string-context.md)
+  - [Syntax and semantics](language/syntax.md)
+    - [Scoping rules](language/scope.md)
     - [String interpolation](language/string-interpolation.md)
     - [Lookup path](language/constructs/lookup-path.md)
   - [Operators](language/operators.md)
-  - [Derivations](language/derivations.md)
-    - [Advanced Attributes](language/advanced-attributes.md)
-    - [Import From Derivation](language/import-from-derivation.md)
-  - [Built-in Constants](language/builtin-constants.md)
-  - [Built-in Functions](language/builtins.md)
+  - [Built-ins](language/builtins.md)
+    - [Derivations](language/derivations.md)
+      - [Advanced Attributes](language/advanced-attributes.md)
+      - [Import From Derivation](language/import-from-derivation.md)
 - [Package Management](package-management/index.md)
   - [Profiles](package-management/profiles.md)
   - [Garbage Collection](package-management/garbage-collection.md)
@@ -40,9 +43,7 @@
 - [Advanced Topics](advanced-topics/index.md)
   - [Sharing Packages Between Machines](package-management/sharing-packages.md)
     - [Serving a Nix store via HTTP](package-management/binary-cache-substituter.md)
-    - [Copying Closures via SSH](package-management/copy-closure.md)
     - [Serving a Nix store via SSH](package-management/ssh-substituter.md)
-    - [Serving a Nix store via S3](package-management/s3-substituter.md)
   - [Remote Builds](advanced-topics/distributed-builds.md)
   - [Tuning Cores and Jobs](advanced-topics/cores-vs-jobs.md)
   - [Verifying Build Reproducibility](advanced-topics/diff-hook.md)
@@ -112,6 +113,7 @@
   - [Store Path Specification](protocols/store-path.md)
   - [Nix Archive (NAR) Format](protocols/nix-archive.md)
   - [Derivation "ATerm" file format](protocols/derivation-aterm.md)
+- [C API](c-api.md)
 - [Glossary](glossary.md)
 - [Contributing](contributing/index.md)
   - [Hacking](contributing/hacking.md)
@@ -119,9 +121,12 @@
   - [Documentation](contributing/documentation.md)
   - [Experimental Features](contributing/experimental-features.md)
   - [CLI guideline](contributing/cli-guideline.md)
+  - [JSON guideline](contributing/json-guideline.md)
   - [C++ style guide](contributing/cxx.md)
 - [Releases](release-notes/index.md)
 {{#include ./SUMMARY-rl-next.md}}
+  - [Release 2.23 (2024-06-03)](release-notes/rl-2.23.md)
+  - [Release 2.22 (2024-04-23)](release-notes/rl-2.22.md)
   - [Release 2.21 (2024-03-11)](release-notes/rl-2.21.md)
   - [Release 2.20 (2024-01-29)](release-notes/rl-2.20.md)
   - [Release 2.19 (2023-11-17)](release-notes/rl-2.19.md)
diff --git a/doc/manual/src/_redirects b/doc/manual/src/_redirects
index 8bf0e854b26..578c48f06f1 100644
--- a/doc/manual/src/_redirects
+++ b/doc/manual/src/_redirects
@@ -1,5 +1,5 @@
 # redirect rules for paths (server-side) to prevent link rot.
-# see ./redirects.js for redirects based on URL fragments (client-side)
+# see ../redirects.js for redirects based on URL fragments (client-side)
 #
 # concrete user story this supports:
 # - user finds URL to the manual for Nix x.y
@@ -27,6 +27,9 @@
 /expressions/language-operators /language/operators 301!
 /expressions/language-values /language/values 301!
 /expressions/* /language/:splat 301!
+/language/values /language/types 301!
+/language/constructs /language/syntax 301!
+/language/builtin-constants /language/builtins 301!
 
 /installation/installation /installation 301!
 
@@ -39,3 +42,5 @@
 /json/* /protocols/json/:splat 301!
 
 /release-notes/release-notes /release-notes 301!
+
+/package-management/copy-closure /command-ref/nix-copy-closure 301!
diff --git a/doc/manual/src/advanced-topics/distributed-builds.md b/doc/manual/src/advanced-topics/distributed-builds.md
index 52acd039c10..ddabaeb4df1 100644
--- a/doc/manual/src/advanced-topics/distributed-builds.md
+++ b/doc/manual/src/advanced-topics/distributed-builds.md
@@ -12,14 +12,14 @@ machine is accessible via SSH and that it has Nix installed. You can
 test whether connecting to the remote Nix instance works, e.g.
 
 ```console
-$ nix store info --store ssh://mac
+$ nix store ping --store ssh://mac
 ```
 
 will try to connect to the machine named `mac`. It is possible to
 specify an SSH identity file as part of the remote store URI, e.g.
 
 ```console
-$ nix store info --store ssh://mac?ssh-key=/home/alice/my-key
+$ nix store ping --store ssh://mac?ssh-key=/home/alice/my-key
 ```
 
 Since builds should be non-interactive, the key should not have a
diff --git a/doc/manual/src/c-api.md b/doc/manual/src/c-api.md
new file mode 100644
index 00000000000..29df0b64419
--- /dev/null
+++ b/doc/manual/src/c-api.md
@@ -0,0 +1,16 @@
+# C API
+
+Nix provides a C API with the intent of [_becoming_](https://github.com/NixOS/nix/milestone/52) a stable API, which it is currently not.
+It is in development.
+
+See:
+- C API documentation for a recent build of master
+  - [Getting Started]
+  - [Index]
+- [Matrix Room *Nix Bindings*](https://matrix.to/#/#nix-bindings:nixos.org) for discussion and questions.
+- [Stabilisation Milestone](https://github.com/NixOS/nix/milestone/52)
+- [Other C API PRs and issues](https://github.com/NixOS/nix/labels/c%20api)
+- [Contributing C API Documentation](contributing/documentation.md#c-api-documentation), including how to build it locally.
+
+[Getting Started]: https://hydra.nixos.org/job/nix/master/external-api-docs/latest/download-by-type/doc/external-api-docs
+[Index]: https://hydra.nixos.org/job/nix/master/external-api-docs/latest/download-by-type/doc/external-api-docs/globals.html
diff --git a/doc/manual/src/command-ref/conf-file-prefix.md b/doc/manual/src/command-ref/conf-file-prefix.md
index 1e408597754..627806cfbda 100644
--- a/doc/manual/src/command-ref/conf-file-prefix.md
+++ b/doc/manual/src/command-ref/conf-file-prefix.md
@@ -66,5 +66,12 @@ Configuration options can be set on the command line, overriding the values set
 
 The `extra-` prefix is supported for settings that take a list of items (e.g. `--extra-trusted users alice` or `--option extra-trusted-users alice`).
 
+## Integer settings
+
+Settings that have an integer type support the suffixes `K`, `M`, `G`
+and `T`. These cause the specified value to be multiplied by 2^10,
+2^20, 2^30 and 2^40, respectively. For instance, `--min-free 1M` is
+equivalent to `--min-free 1048576`.
+
 # Available settings
 
diff --git a/doc/manual/src/command-ref/env-common.md b/doc/manual/src/command-ref/env-common.md
index 34e0dbfbd91..d3f5f9c1443 100644
--- a/doc/manual/src/command-ref/env-common.md
+++ b/doc/manual/src/command-ref/env-common.md
@@ -10,7 +10,7 @@ Most Nix commands interpret the following environment variables:
 - <span id="env-NIX_PATH">[`NIX_PATH`](#env-NIX_PATH)</span>
 
   A colon-separated list of directories used to look up the location of Nix
-  expressions using [paths](@docroot@/language/values.md#type-path)
+  expressions using [paths](@docroot@/language/types.md#type-path)
   enclosed in angle brackets (i.e., `<path>`),
   e.g. `/home/eelco/Dev:/etc/nixos`. It can be extended using the
   [`-I` option](@docroot@/command-ref/opt-common.md#opt-I).
diff --git a/doc/manual/src/command-ref/nix-build.md b/doc/manual/src/command-ref/nix-build.md
index e4223b54241..3bb59cbed12 100644
--- a/doc/manual/src/command-ref/nix-build.md
+++ b/doc/manual/src/command-ref/nix-build.md
@@ -55,20 +55,20 @@ All options not listed here are passed to
 [`nix-store --realise`](nix-store/realise.md),
 except for `--arg` and `--attr` / `-A` which are passed to [`nix-instantiate`](nix-instantiate.md).
 
-  - <span id="opt-no-out-link">[`--no-out-link`](#opt-no-out-link)<span>
+- <span id="opt-no-out-link">[`--no-out-link`](#opt-no-out-link)<span>
 
-    Do not create a symlink to the output path. Note that as a result
-    the output does not become a root of the garbage collector, and so
-    might be deleted by `nix-store --gc`.
+  Do not create a symlink to the output path. Note that as a result
+  the output does not become a root of the garbage collector, and so
+  might be deleted by `nix-store --gc`.
 
-  - <span id="opt-dry-run">[`--dry-run`](#opt-dry-run)</span>
+- <span id="opt-dry-run">[`--dry-run`](#opt-dry-run)</span>
 
-    Show what store paths would be built or downloaded.
+  Show what store paths would be built or downloaded.
 
-  - <span id="opt-out-link">[`--out-link`](#opt-out-link)</span> / `-o` *outlink*
+- <span id="opt-out-link">[`--out-link`](#opt-out-link)</span> / `-o` *outlink*
 
-    Change the name of the symlink to the output path created from
-    `result` to *outlink*.
+  Change the name of the symlink to the output path created from
+  `result` to *outlink*.
 
 {{#include ./status-build-failure.md}}
 
diff --git a/doc/manual/src/command-ref/nix-channel.md b/doc/manual/src/command-ref/nix-channel.md
index cebbc7b00d0..8b58392b7b5 100644
--- a/doc/manual/src/command-ref/nix-channel.md
+++ b/doc/manual/src/command-ref/nix-channel.md
@@ -27,40 +27,46 @@ The moving parts of channels are:
 
 This command has the following operations:
 
-  - `--add` *url* \[*name*\]\
-    Add a channel *name* located at *url* to the list of subscribed channels.
-    If *name* is omitted, default to the last component of *url*, with the suffixes `-stable` or `-unstable` removed.
+- `--add` *url* \[*name*\]
 
-    > **Note**
-    >
-    > `--add` does not automatically perform an update.
-    > Use `--update` explicitly.
+  Add a channel *name* located at *url* to the list of subscribed channels.
+  If *name* is omitted, default to the last component of *url*, with the suffixes `-stable` or `-unstable` removed.
 
-    A channel URL must point to a directory containing a file `nixexprs.tar.gz`.
-    At the top level, that tarball must contain a single directory with a `default.nix` file that serves as the channel’s entry point.
+  > **Note**
+  >
+  > `--add` does not automatically perform an update.
+  > Use `--update` explicitly.
 
-  - `--remove` *name*\
-    Remove the channel *name* from the list of subscribed channels.
+  A channel URL must point to a directory containing a file `nixexprs.tar.gz`.
+  At the top level, that tarball must contain a single directory with a `default.nix` file that serves as the channel’s entry point.
 
-  - `--list`\
-    Print the names and URLs of all subscribed channels on standard output.
+- `--remove` *name*
 
-  - `--update` \[*names*…\]\
-    Download the Nix expressions of subscribed channels and create a new generation.
-    Update all channels if none is specified, and only those included in *names* otherwise.
+  Remove the channel *name* from the list of subscribed channels.
 
-  - `--list-generations`\
-    Prints a list of all the current existing generations for the
-    channel profile.
+- `--list`
 
-    Works the same way as
-    ```
-    nix-env --profile /nix/var/nix/profiles/per-user/$USER/channels --list-generations
-    ```
+  Print the names and URLs of all subscribed channels on standard output.
 
-  - `--rollback` \[*generation*\]\
-    Revert channels to the state before the last call to `nix-channel --update`.
-    Optionally, you can specify a specific channel *generation* number to restore.
+- `--update` \[*names*…\]
+
+  Download the Nix expressions of subscribed channels and create a new generation.
+  Update all channels if none is specified, and only those included in *names* otherwise.
+
+- `--list-generations`
+
+  Prints a list of all the current existing generations for the
+  channel profile.
+
+  Works the same way as
+  ```
+  nix-env --profile /nix/var/nix/profiles/per-user/$USER/channels --list-generations
+  ```
+
+- `--rollback` \[*generation*\]
+
+  Revert channels to the state before the last call to `nix-channel --update`.
+  Optionally, you can specify a specific channel *generation* number to restore.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-collect-garbage.md b/doc/manual/src/command-ref/nix-collect-garbage.md
index 1bc88d85829..2136d28e929 100644
--- a/doc/manual/src/command-ref/nix-collect-garbage.md
+++ b/doc/manual/src/command-ref/nix-collect-garbage.md
@@ -48,12 +48,14 @@ Instead, it looks in a few locations, and acts on all profiles it finds there:
 
 These options are for deleting old [profiles] prior to deleting unreachable [store objects].
 
-- <span id="opt-delete-old">[`--delete-old`](#opt-delete-old)</span> / `-d`\
+- <span id="opt-delete-old">[`--delete-old`](#opt-delete-old)</span> / `-d`
+
   Delete all old generations of profiles.
 
   This is the equivalent of invoking [`nix-env --delete-generations old`](@docroot@/command-ref/nix-env/delete-generations.md#generations-old) on each found profile.
 
-- <span id="opt-delete-older-than">[`--delete-older-than`](#opt-delete-older-than)</span> *period*\
+- <span id="opt-delete-older-than">[`--delete-older-than`](#opt-delete-older-than)</span> *period*
+
   Delete all generations of profiles older than the specified amount (except for the generations that were active at that point in time).
   *period* is a value such as `30d`, which would mean 30 days.
 
@@ -74,4 +76,4 @@ $ nix-collect-garbage -d
 ```
 
 [profiles]: @docroot@/command-ref/files/profiles.md
-[store objects]: @docroot@/glossary.md#gloss-store-object
+[store objects]: @docroot@/store/store-object.md
diff --git a/doc/manual/src/command-ref/nix-copy-closure.md b/doc/manual/src/command-ref/nix-copy-closure.md
index eb1693e1e83..8cfd6ebad56 100644
--- a/doc/manual/src/command-ref/nix-copy-closure.md
+++ b/doc/manual/src/command-ref/nix-copy-closure.md
@@ -1,91 +1,91 @@
 # Name
 
-`nix-copy-closure` - copy a closure to or from a remote machine via SSH
+`nix-copy-closure` - copy store objects to or from a remote machine via SSH
 
 # Synopsis
 
 `nix-copy-closure`
-  [`--to` | `--from`]
+  [`--to` | `--from` ]
   [`--gzip`]
   [`--include-outputs`]
   [`--use-substitutes` | `-s`]
   [`-v`]
-  _user@machine_ _paths_
+  [_user_@]_machine_[:_port_] _paths_
 
 # Description
 
-`nix-copy-closure` gives you an easy and efficient way to exchange
-software between machines.  Given one or more Nix store _paths_ on the
-local machine, `nix-copy-closure` computes the closure of those paths
-(i.e. all their dependencies in the Nix store), and copies all paths
-in the closure to the remote machine via the `ssh` (Secure Shell)
-command.  With the `--from` option, the direction is reversed: the
-closure of _paths_ on a remote machine is copied to the Nix store on
-the local machine.
-
-This command is efficient because it only sends the store paths
-that are missing on the target machine.
-
-Since `nix-copy-closure` calls `ssh`, you may be asked to type in the
-appropriate password or passphrase.  In fact, you may be asked _twice_
-because `nix-copy-closure` currently connects twice to the remote
-machine, first to get the set of paths missing on the target machine,
-and second to send the dump of those paths.  When using public key
-authentication, you can avoid typing the passphrase with `ssh-agent`.
+Given _paths_ from one machine, `nix-copy-closure` computes the [closure](@docroot@/glossary.md#gloss-closure) of those paths (i.e. all their dependencies in the Nix store), and copies [store objects](@docroot@/glossary.md#gloss-store-object) in that closure to another machine via SSH.
+It doesn’t copy store objects that are already present on the other machine.
+
+> **Note**
+>
+> While the Nix store to use on the local machine can be specified on the command line with the [`--store`](@docroot@/command-ref/conf-file.md#conf-store) option, the Nix store to be accessed on the remote machine can only be [configured statically](@docroot@/command-ref/conf-file.md#configuration-file) on that remote machine.
+
+Since `nix-copy-closure` calls `ssh`, you may need to authenticate with the remote machine.
+In fact, you may be asked for authentication _twice_ because `nix-copy-closure` currently connects twice to the remote machine: first to get the set of paths missing on the target machine, and second to send the dump of those paths.
+When using public key authentication, you can avoid typing the passphrase with `ssh-agent`.
 
 # Options
 
-  - `--to`\
-    Copy the closure of _paths_ from the local Nix store to the Nix
-    store on _machine_. This is the default.
+- `--to`
+
+  Copy the closure of _paths_ from a Nix store accessible from the local machine to the Nix store on the remote _machine_.
+  This is the default behavior.
+
+- `--from`
+
+  Copy the closure of _paths_ from the Nix store on the remote _machine_ to the local machine's specified Nix store.
 
-  - `--from`\
-    Copy the closure of _paths_ from the Nix store on _machine_ to the
-    local Nix store.
+- `--gzip`
 
-  - `--gzip`\
-    Enable compression of the SSH connection.
+  Enable compression of the SSH connection.
 
-  - `--include-outputs`\
-    Also copy the outputs of [store derivation]s included in the closure.
+- `--include-outputs`
 
-    [store derivation]: @docroot@/glossary.md#gloss-store-derivation
+  Also copy the outputs of [store derivation]s included in the closure.
 
-  - `--use-substitutes` / `-s`\
-    Attempt to download missing paths on the target machine using Nix’s
-    substitute mechanism.  Any paths that cannot be substituted on the
-    target are still copied normally from the source.  This is useful,
-    for instance, if the connection between the source and target
-    machine is slow, but the connection between the target machine and
-    `nixos.org` (the default binary cache server) is
-    fast.
+  [store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
-  - `-v`\
-    Show verbose output.
+- `--use-substitutes` / `-s`
+
+  Attempt to download missing store objects on the target from [substituters](@docroot@/command-ref/conf-file.md#conf-substituters).
+  Any store objects that cannot be substituted on the target are still copied normally from the source.
+  This is useful, for instance, if the connection between the source and target machine is slow, but the connection between the target machine and `cache.nixos.org` (the default binary cache server) is fast.
 
 {{#include ./opt-common.md}}
 
 # Environment variables
 
-  - `NIX_SSHOPTS`\
-    Additional options to be passed to `ssh` on the command
-    line.
+- `NIX_SSHOPTS`
+
+  Additional options to be passed to `ssh` on the command line.
 
 {{#include ./env-common.md}}
 
 # Examples
 
-Copy Firefox with all its dependencies to a remote machine:
-
-```console
-$ nix-copy-closure --to alice@itchy.labs $(type -tP firefox)
-```
-
-Copy Subversion from a remote machine and then install it into a user
-environment:
-
-```console
-$ nix-copy-closure --from alice@itchy.labs \
-    /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
-$ nix-env --install /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
-```
+> **Example**
+>
+> Copy GNU Hello with all its dependencies to a remote machine:
+>
+> ```shell-session
+> $ storePath="$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)"
+> $ nix-copy-closure --to alice@itchy.example.org "$storePath"
+> copying 5 paths...
+> copying path '/nix/store/nrwkk6ak3rgkrxbqhsscb01jpzmslf2r-xgcc-13.2.0-libgcc' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/gm61h1y42pqyl6178g90x8zm22n6pyy5-libunistring-1.1' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/ddfzjdykw67s20c35i7a6624by3iz5jv-libidn2-2.3.7' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/apab5i73dqa09wx0q27b6fbhd1r18ihl-glibc-2.39-31' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/g1n2vryg06amvcc1avb2mcq36faly0mh-hello-2.12.1' to 'ssh://alice@itchy.example.org'...
+> ```
+
+> **Example**
+>
+> Copy GNU Hello from a remote machine using a known store path, and run it:
+>
+> ```shell-session
+> $ storePath="$(nix-instantiate --eval '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello.outPath | tr -d '"')"
+> $ nix-copy-closure --from alice@itchy.example.org "$storePath"
+> $ "$storePath"/bin/hello
+> Hello, world!
+> ```
diff --git a/doc/manual/src/command-ref/nix-env.md b/doc/manual/src/command-ref/nix-env.md
index 94172321609..c6f627365a5 100644
--- a/doc/manual/src/command-ref/nix-env.md
+++ b/doc/manual/src/command-ref/nix-env.md
@@ -47,39 +47,83 @@ These pages can be viewed offline:
 
   Example: `nix-env --help --install`
 
+# Package sources
+
+`nix-env` can obtain packages from multiple sources:
+
+- An attribute set of derivations from:
+  - The [default Nix expression](@docroot@/command-ref/files/default-nix-expression.md) (by default)
+  - A Nix file, specified via `--file`
+  - A [profile](@docroot@/command-ref/files/profiles.md), specified via `--from-profile`
+  - A Nix expression that is a function which takes default expression as argument, specified via `--from-expression`
+- A [store path](@docroot@/store/store-path.md)
+
 # Selectors
 
-Several commands, such as `nix-env --query ` and `nix-env --install `, take a list of
-arguments that specify the packages on which to operate. These are
-extended regular expressions that must match the entire name of the
-package. (For details on regular expressions, see **regex**(7).) The match is
-case-sensitive. The regular expression can optionally be followed by a
-dash and a version number; if omitted, any version of the package will
-match. Here are some examples:
-
-  - `firefox`\
-    Matches the package name `firefox` and any version.
-
-  - `firefox-32.0`\
-    Matches the package name `firefox` and version `32.0`.
-
-  - `gtk\\+`\
-    Matches the package name `gtk+`. The `+` character must be escaped
-    using a backslash to prevent it from being interpreted as a
-    quantifier, and the backslash must be escaped in turn with another
-    backslash to ensure that the shell passes it on.
-
-  - `.\*`\
-    Matches any package name. This is the default for most commands.
-
-  - `'.*zip.*'`\
-    Matches any package name containing the string `zip`. Note the dots:
-    `'*zip*'` does not work, because in a regular expression, the
-    character `*` is interpreted as a quantifier.
-
-  - `'.*(firefox|chromium).*'`\
-    Matches any package name containing the strings `firefox` or
-    `chromium`.
+Several operations, such as [`nix-env --query`](./nix-env/query.md) and [`nix-env --install`](./nix-env/install.md), take a list of *arguments* that specify the packages on which to operate.
+
+Packages are identified based on a `name` part and a `version` part of a [symbolic derivation name](@docroot@/language/derivations.md#attr-names):
+
+- `name`: Everything up to but not including the first dash (`-`) that is *not* followed by a letter.
+- `version`: The rest, excluding the separating dash.
+
+> **Example**
+>
+> `nix-env` parses the symbolic derivation name `apache-httpd-2.0.48` as:
+>
+> ```json
+> {
+>   "name": "apache-httpd",
+>   "version": "2.0.48"
+> }
+> ```
+
+> **Example**
+>
+> `nix-env` parses the symbolic derivation name `firefox.*` as:
+>
+> ```json
+> {
+>   "name": "firefox.*",
+>   "version": ""
+> }
+> ```
+
+The `name` parts of the *arguments* to `nix-env` are treated as extended regular expressions and matched against the `name` parts of derivation names in the package source.
+The match is case-sensitive.
+The regular expression can optionally be followed by a dash (`-`) and a version number; if omitted, any version of the package will match.
+For details on regular expressions, see [**regex**(7)](https://linux.die.net/man/7/regex).
+
+> **Example**
+>
+> Common patterns for finding package names with `nix-env`:
+>
+> - `firefox`
+>
+>   Matches the package name `firefox` and any version.
+>
+> - `firefox-32.0`
+>
+>   Matches the package name `firefox` and version `32.0`.
+>
+> - `gtk\\+`
+>
+>   Matches the package name `gtk+`.
+>   The `+` character must be escaped using a backslash (`\`) to prevent it from being interpreted as a quantifier, and the backslash must be escaped in turn with another backslash to ensure that the shell passes it on.
+>
+> - `.\*`
+>
+>   Matches any package name.
+>   This is the default for most commands.
+>
+> - `'.*zip.*'`
+>
+>   Matches any package name containing the string `zip`.
+>   Note the dots: `'*zip*'` does not work, because in a regular expression, the character `*` is interpreted as a quantifier.
+>
+> - `'.*(firefox|chromium).*'`
+>
+>   Matches any package name containing the strings `firefox` or `chromium`.
 
 # Files
 
diff --git a/doc/manual/src/command-ref/nix-env/delete-generations.md b/doc/manual/src/command-ref/nix-env/delete-generations.md
index 6b6ea798ead..b1ff0bb6941 100644
--- a/doc/manual/src/command-ref/nix-env/delete-generations.md
+++ b/doc/manual/src/command-ref/nix-env/delete-generations.md
@@ -12,7 +12,8 @@ This operation deletes the specified generations of the current profile.
 
 *generations* can be a one of the following:
 
-- <span id="generations-list">[`<number>...`](#generations-list)</span>:\
+- <span id="generations-list">[`<number>...`](#generations-list)</span>
+
   A list of generation numbers, each one a separate command-line argument.
 
   Delete exactly the profile generations given by their generation number.
@@ -30,7 +31,8 @@ This operation deletes the specified generations of the current profile.
   > Because one can roll back to a previous generation, it is possible to have generations newer than the current one.
   > They will also be deleted.
 
-- <span id="generations-time">[`<number>d`](#generations-time)</span>:\
+- <span id="generations-time">[`<number>d`](#generations-time)</span>
+
   The last *number* days
 
   *Example*: `30d`
@@ -38,7 +40,8 @@ This operation deletes the specified generations of the current profile.
   Delete all generations created more than *number* days ago, except the most recent one of them.
   This allows rolling back to generations that were available within the specified period.
 
-- <span id="generations-count">[`+<number>`](#generations-count)</span>:\
+- <span id="generations-count">[`+<number>`](#generations-count)</span>
+
   The last *number* generations up to the present
 
   *Example*: `+5`
@@ -49,7 +52,7 @@ Periodically deleting old generations is important to make garbage collection
 effective.
 The is because profiles are also garbage collection roots — any [store object] reachable from a profile is "alive" and ineligible for deletion.
 
-[store object]: @docroot@/glossary.md#gloss-store-object
+[store object]: @docroot@/store/store-object.md
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-env/env-common.md b/doc/manual/src/command-ref/nix-env/env-common.md
index 7358179592e..200da7219bd 100644
--- a/doc/manual/src/command-ref/nix-env/env-common.md
+++ b/doc/manual/src/command-ref/nix-env/env-common.md
@@ -1,6 +1,7 @@
 # Environment variables
 
-- `NIX_PROFILE`\
+- `NIX_PROFILE`
+
   Location of the Nix profile. Defaults to the target of the symlink
   `~/.nix-profile`, if it exists, or `/nix/var/nix/profiles/default`
   otherwise.
diff --git a/doc/manual/src/command-ref/nix-env/install.md b/doc/manual/src/command-ref/nix-env/install.md
index c1fff50e80f..748dd1e7a39 100644
--- a/doc/manual/src/command-ref/nix-env/install.md
+++ b/doc/manual/src/command-ref/nix-env/install.md
@@ -14,133 +14,132 @@
 
 # Description
 
-The install operation creates a new user environment.
+The `--install` operation creates a new user environment.
 It is based on the current generation of the active [profile](@docroot@/command-ref/files/profiles.md), to which a set of [store paths] described by *args* is added.
 
-[store paths]: @docroot@/glossary.md#gloss-store-path
+[store paths]: @docroot@/store/store-path.md
 
 The arguments *args* map to store paths in a number of possible ways:
 
-
-  - By default, *args* is a set of [derivation] names denoting derivations in the [default Nix expression].
-    These are [realised], and the resulting output paths are installed.
-    Currently installed derivations with a name equal to the name of a derivation being added are removed unless the option `--preserve-installed` is specified.
-
-    [derivation]: @docroot@/glossary.md#gloss-derivation
-    [default Nix expression]: @docroot@/command-ref/files/default-nix-expression.md
-    [realised]: @docroot@/glossary.md#gloss-realise
-
-    If there are multiple derivations matching a name in *args* that
-    have the same name (e.g., `gcc-3.3.6` and `gcc-4.1.1`), then the
-    derivation with the highest *priority* is used. A derivation can
-    define a priority by declaring the `meta.priority` attribute. This
-    attribute should be a number, with a higher value denoting a lower
-    priority. The default priority is `5`.
-
-    If there are multiple matching derivations with the same priority,
-    then the derivation with the highest version will be installed.
-
-    You can force the installation of multiple derivations with the same
-    name by being specific about the versions. For instance, `nix-env --install
-    gcc-3.3.6 gcc-4.1.1` will install both version of GCC (and will
-    probably cause a user environment conflict\!).
-
-  - If [`--attr`](#opt-attr) / `-A` is specified, the arguments are *attribute paths* that select attributes from the [default Nix expression].
-    This is faster than using derivation names and unambiguous.
-    Show the attribute paths of available packages with [`nix-env --query`](./query.md):
-
-    ```console
-    nix-env --query --available --attr-path`
-    ```
-
-  - If `--from-profile` *path* is given, *args* is a set of names
-    denoting installed [store paths] in the profile *path*. This is an
-    easy way to copy user environment elements from one profile to
-    another.
-
-  - If `--from-expression` is given, *args* are [Nix language functions](@docroot@/language/constructs.md#functions) that are called with the [default Nix expression] as their single argument.
-    The derivations returned by those function calls are installed.
-    This allows derivations to be specified in an unambiguous way, which is necessary if there are multiple derivations with the same name.
-
-  - If *args* are [store derivations](@docroot@/glossary.md#gloss-store-derivation), then these are [realised], and the resulting output paths are installed.
-
-  - If *args* are [store paths] that are not store derivations, then these are [realised] and installed.
-
-  - By default all [outputs](@docroot@/language/derivations.md#attr-outputs) are installed for each [derivation].
-    This can be overridden by adding a `meta.outputsToInstall` attribute on the derivation listing a subset of the output names.
-
-    Example:
-
-    The file `example.nix` defines a derivation with two outputs `foo` and `bar`, each containing a file.
-
-    ```nix
-    # example.nix
-    let
-      pkgs = import <nixpkgs> {};
-      command = ''
-        ${pkgs.coreutils}/bin/mkdir -p $foo $bar
-        echo foo > $foo/foo-file
-        echo bar > $bar/bar-file
-      '';
-    in
-    derivation {
-      name = "example";
-      builder = "${pkgs.bash}/bin/bash";
-      args = [ "-c" command ];
-      outputs = [ "foo" "bar" ];
-      system = builtins.currentSystem;
-    }
-    ```
-
-    Installing from this Nix expression will make files from both outputs appear in the current profile.
-
-    ```console
-    $ nix-env --install --file example.nix
-    installing 'example'
-    $ ls ~/.nix-profile
-    foo-file
-    bar-file
-    manifest.nix
-    ```
-
-    Adding `meta.outputsToInstall` to that derivation will make `nix-env` only install files from the specified outputs.
-
-    ```nix
-    # example-outputs.nix
-    import ./example.nix // { meta.outputsToInstall = [ "bar" ]; }
-    ```
-
-    ```console
-    $ nix-env --install --file example-outputs.nix
-    installing 'example'
-    $ ls ~/.nix-profile
-    bar-file
-    manifest.nix
-    ```
+- By default, *args* is a set of [derivation] names denoting derivations in the [default Nix expression].
+  These are [realised], and the resulting output paths are installed.
+  Currently installed derivations with a name equal to the name of a derivation being added are removed unless the option `--preserve-installed` is specified.
+
+  [derivation]: @docroot@/glossary.md#gloss-derivation
+  [default Nix expression]: @docroot@/command-ref/files/default-nix-expression.md
+  [realised]: @docroot@/glossary.md#gloss-realise
+
+  If there are multiple derivations matching a name in *args* that
+  have the same name (e.g., `gcc-3.3.6` and `gcc-4.1.1`), then the
+  derivation with the highest *priority* is used. A derivation can
+  define a priority by declaring the `meta.priority` attribute. This
+  attribute should be a number, with a higher value denoting a lower
+  priority. The default priority is `5`.
+
+  If there are multiple matching derivations with the same priority,
+  then the derivation with the highest version will be installed.
+
+  You can force the installation of multiple derivations with the same
+  name by being specific about the versions. For instance, `nix-env --install
+  gcc-3.3.6 gcc-4.1.1` will install both version of GCC (and will
+  probably cause a user environment conflict\!).
+
+- If [`--attr`](#opt-attr) / `-A` is specified, the arguments are *attribute paths* that select attributes from the [default Nix expression].
+  This is faster than using derivation names and unambiguous.
+  Show the attribute paths of available packages with [`nix-env --query`](./query.md):
+
+  ```console
+  nix-env --query --available --attr-path
+  ```
+
+- If `--from-profile` *path* is given, *args* is a set of names
+  denoting installed [store paths] in the profile *path*. This is an
+  easy way to copy user environment elements from one profile to
+  another.
+
+- If `--from-expression` is given, *args* are [Nix language functions](@docroot@/language/syntax.md#functions) that are called with the [default Nix expression] as their single argument.
+  The derivations returned by those function calls are installed.
+  This allows derivations to be specified in an unambiguous way, which is necessary if there are multiple derivations with the same name.
+
+- If *args* are [store derivations](@docroot@/glossary.md#gloss-store-derivation), then these are [realised], and the resulting output paths are installed.
+
+- If *args* are [store paths] that are not store derivations, then these are [realised] and installed.
+
+- By default all [outputs](@docroot@/language/derivations.md#attr-outputs) are installed for each [derivation].
+  This can be overridden by adding a `meta.outputsToInstall` attribute on the derivation listing a subset of the output names.
+
+  Example:
+
+  The file `example.nix` defines a derivation with two outputs `foo` and `bar`, each containing a file.
+
+  ```nix
+  # example.nix
+  let
+    pkgs = import <nixpkgs> {};
+    command = ''
+      ${pkgs.coreutils}/bin/mkdir -p $foo $bar
+      echo foo > $foo/foo-file
+      echo bar > $bar/bar-file
+    '';
+  in
+  derivation {
+    name = "example";
+    builder = "${pkgs.bash}/bin/bash";
+    args = [ "-c" command ];
+    outputs = [ "foo" "bar" ];
+    system = builtins.currentSystem;
+  }
+  ```
+
+  Installing from this Nix expression will make files from both outputs appear in the current profile.
+
+  ```console
+  $ nix-env --install --file example.nix
+  installing 'example'
+  $ ls ~/.nix-profile
+  foo-file
+  bar-file
+  manifest.nix
+  ```
+
+  Adding `meta.outputsToInstall` to that derivation will make `nix-env` only install files from the specified outputs.
+
+  ```nix
+  # example-outputs.nix
+  import ./example.nix // { meta.outputsToInstall = [ "bar" ]; }
+  ```
+
+  ```console
+  $ nix-env --install --file example-outputs.nix
+  installing 'example'
+  $ ls ~/.nix-profile
+  bar-file
+  manifest.nix
+  ```
 
 # Options
 
-  - `--prebuilt-only` / `-b`
+- `--prebuilt-only` / `-b`
 
-    Use only derivations for which a substitute is registered, i.e.,
-    there is a pre-built binary available that can be downloaded in lieu
-    of building the derivation. Thus, no packages will be built from
-    source.
+  Use only derivations for which a substitute is registered, i.e.,
+  there is a pre-built binary available that can be downloaded in lieu
+  of building the derivation. Thus, no packages will be built from
+  source.
 
-  - `--preserve-installed` / `-P`
+- `--preserve-installed` / `-P`
 
-    Do not remove derivations with a name matching one of the
-    derivations being installed. Usually, trying to have two versions of
-    the same package installed in the same generation of a profile will
-    lead to an error in building the generation, due to file name
-    clashes between the two versions. However, this is not the case for
-    all packages.
+  Do not remove derivations with a name matching one of the
+  derivations being installed. Usually, trying to have two versions of
+  the same package installed in the same generation of a profile will
+  lead to an error in building the generation, due to file name
+  clashes between the two versions. However, this is not the case for
+  all packages.
 
-  - `--remove-all` / `-r`
+- `--remove-all` / `-r`
 
-    Remove all previously installed packages first. This is equivalent
-    to running `nix-env --uninstall '.*'` first, except that everything happens
-    in a single transaction.
+  Remove all previously installed packages first. This is equivalent
+  to running `nix-env --uninstall '.*'` first, except that everything happens
+  in a single transaction.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-env/opt-common.md b/doc/manual/src/command-ref/nix-env/opt-common.md
index 636281b6d36..1479ca0bd47 100644
--- a/doc/manual/src/command-ref/nix-env/opt-common.md
+++ b/doc/manual/src/command-ref/nix-env/opt-common.md
@@ -2,34 +2,37 @@
 
 The following options are allowed for all `nix-env` operations, but may not always have an effect.
 
-  - `--file` / `-f` *path*\
-    Specifies the Nix expression (designated below as the *active Nix
-    expression*) used by the `--install`, `--upgrade`, and `--query
-    --available` operations to obtain derivations. The default is
-    `~/.nix-defexpr`.
-
-    If the argument starts with `http://` or `https://`, it is
-    interpreted as the URL of a tarball that will be downloaded and
-    unpacked to a temporary location. The tarball must include a single
-    top-level directory containing at least a file named `default.nix`.
-
-  - `--profile` / `-p` *path*\
-    Specifies the profile to be used by those operations that operate on
-    a profile (designated below as the *active profile*). A profile is a
-    sequence of user environments called *generations*, one of which is
-    the *current generation*.
-
-  - `--dry-run`\
-    For the `--install`, `--upgrade`, `--uninstall`,
-    `--switch-generation`, `--delete-generations` and `--rollback`
-    operations, this flag will cause `nix-env` to print what *would* be
-    done if this flag had not been specified, without actually doing it.
-
-    `--dry-run` also prints out which paths will be
-    [substituted](@docroot@/glossary.md) (i.e., downloaded) and which paths
-    will be built from source (because no substitute is available).
-
-  - `--system-filter` *system*\
-    By default, operations such as `--query
-                    --available` show derivations matching any platform. This option
-    allows you to use derivations for the specified platform *system*.
+- `--file` / `-f` *path*
+
+  Specifies the Nix expression (designated below as the *active Nix
+  expression*) used by the `--install`, `--upgrade`, and `--query
+  --available` operations to obtain derivations. The default is
+  `~/.nix-defexpr`.
+
+  If the argument starts with `http://` or `https://`, it is
+  interpreted as the URL of a tarball that will be downloaded and
+  unpacked to a temporary location. The tarball must include a single
+  top-level directory containing at least a file named `default.nix`.
+
+- `--profile` / `-p` *path*
+
+  Specifies the profile to be used by those operations that operate on
+  a profile (designated below as the *active profile*). A profile is a
+  sequence of user environments called *generations*, one of which is
+  the *current generation*.
+
+- `--dry-run`
+
+  For the `--install`, `--upgrade`, `--uninstall`,
+  `--switch-generation`, `--delete-generations` and `--rollback`
+  operations, this flag will cause `nix-env` to print what *would* be
+  done if this flag had not been specified, without actually doing it.
+
+  `--dry-run` also prints out which paths will be
+  [substituted](@docroot@/glossary.md) (i.e., downloaded) and which paths
+  will be built from source (because no substitute is available).
+
+- `--system-filter` *system*
+
+  By default, operations such as `--query --available` show derivations matching any platform. This option
+  allows you to use derivations for the specified platform *system*.
diff --git a/doc/manual/src/command-ref/nix-env/query.md b/doc/manual/src/command-ref/nix-env/query.md
index c9b4d851325..c67794ed58e 100644
--- a/doc/manual/src/command-ref/nix-env/query.md
+++ b/doc/manual/src/command-ref/nix-env/query.md
@@ -35,11 +35,13 @@ The derivations are sorted by their `name` attributes.
 The following flags specify the set of things on which the query
 operates.
 
-  - `--installed`\
+  - `--installed`
+
     The query operates on the store paths that are installed in the
     current generation of the active profile. This is the default.
 
-  - `--available`; `-a`\
+  - `--available` / `-a`
+
     The query operates on the derivations that are available in the
     active Nix expression.
 
@@ -50,24 +52,28 @@ selected derivations. Multiple flags may be specified, in which case the
 information is shown in the order given here. Note that the name of the
 derivation is shown unless `--no-name` is specified.
 
-  - `--xml`\
+  - `--xml`
+
     Print the result in an XML representation suitable for automatic
     processing by other tools. The root element is called `items`, which
     contains a `item` element for each available or installed
     derivation. The fields discussed below are all stored in attributes
     of the `item` elements.
 
-  - `--json`\
+  - `--json`
+
     Print the result in a JSON representation suitable for automatic
     processing by other tools.
 
-  - `--prebuilt-only` / `-b`\
+  - `--prebuilt-only` / `-b`
+
     Show only derivations for which a substitute is registered, i.e.,
     there is a pre-built binary available that can be downloaded in lieu
     of building the derivation. Thus, this shows all packages that
     probably can be installed quickly.
 
-  - `--status`; `-s`\
+  - `--status` / `-s`
+
     Print the *status* of the derivation. The status consists of three
     characters. The first is `I` or `-`, indicating whether the
     derivation is currently installed in the current generation of the
@@ -78,49 +84,61 @@ derivation is shown unless `--no-name` is specified.
     derivation to be built. The third is `S` or `-`, indicating whether
     a substitute is available for the derivation.
 
-  - `--attr-path`; `-P`\
+  - `--attr-path` / `-P`
+
     Print the *attribute path* of the derivation, which can be used to
     unambiguously select it using the `--attr` option available in
     commands that install derivations like `nix-env --install`. This
     option only works together with `--available`
 
-  - `--no-name`\
+  - `--no-name`
+
     Suppress printing of the `name` attribute of each derivation.
 
-  - `--compare-versions` / `-c`\
+  - `--compare-versions` / `-c`
+
     Compare installed versions to available versions, or vice versa (if
     `--available` is given). This is useful for quickly seeing whether
     upgrades for installed packages are available in a Nix expression. A
     column is added with the following meaning:
 
-      - `<` *version*\
+      - `<` *version*
+
         A newer version of the package is available or installed.
 
-      - `=` *version*\
+      - `=` *version*
+
         At most the same version of the package is available or
         installed.
 
-      - `>` *version*\
+      - `>` *version*
+
         Only older versions of the package are available or installed.
 
-      - `- ?`\
+      - `- ?`
+
         No version of the package is available or installed.
 
-  - `--system`\
+  - `--system`
+
     Print the `system` attribute of the derivation.
 
-  - `--drv-path`\
+  - `--drv-path`
+
     Print the path of the [store derivation](@docroot@/glossary.md#gloss-store-derivation).
 
-  - `--out-path`\
+  - `--out-path`
+
     Print the output path of the derivation.
 
-  - `--description`\
+  - `--description`
+
     Print a short (one-line) description of the derivation, if
     available. The description is taken from the `meta.description`
     attribute of the derivation.
 
-  - `--meta`\
+  - `--meta`
+
     Print all of the meta-attributes of the derivation. This option is
     only available with `--xml` or `--json`.
 
diff --git a/doc/manual/src/command-ref/nix-env/set-flag.md b/doc/manual/src/command-ref/nix-env/set-flag.md
index e04b22a918a..58a0248bba9 100644
--- a/doc/manual/src/command-ref/nix-env/set-flag.md
+++ b/doc/manual/src/command-ref/nix-env/set-flag.md
@@ -13,24 +13,24 @@ to be modified. There are several attributes that can be usefully
 modified, because they affect the behaviour of `nix-env` or the user
 environment build script:
 
-  - `priority` can be changed to resolve filename clashes. The user
-    environment build script uses the `meta.priority` attribute of
-    derivations to resolve filename collisions between packages. Lower
-    priority values denote a higher priority. For instance, the GCC
-    wrapper package and the Binutils package in Nixpkgs both have a file
-    `bin/ld`, so previously if you tried to install both you would get a
-    collision. Now, on the other hand, the GCC wrapper declares a higher
-    priority than Binutils, so the former’s `bin/ld` is symlinked in the
-    user environment.
-
-  - `keep` can be set to `true` to prevent the package from being
-    upgraded or replaced. This is useful if you want to hang on to an
-    older version of a package.
-
-  - `active` can be set to `false` to “disable” the package. That is, no
-    symlinks will be generated to the files of the package, but it
-    remains part of the profile (so it won’t be garbage-collected). It
-    can be set back to `true` to re-enable the package.
+- `priority` can be changed to resolve filename clashes. The user
+  environment build script uses the `meta.priority` attribute of
+  derivations to resolve filename collisions between packages. Lower
+  priority values denote a higher priority. For instance, the GCC
+  wrapper package and the Binutils package in Nixpkgs both have a file
+  `bin/ld`, so previously if you tried to install both you would get a
+  collision. Now, on the other hand, the GCC wrapper declares a higher
+  priority than Binutils, so the former’s `bin/ld` is symlinked in the
+  user environment.
+
+- `keep` can be set to `true` to prevent the package from being
+  upgraded or replaced. This is useful if you want to hang on to an
+  older version of a package.
+
+- `active` can be set to `false` to “disable” the package. That is, no
+  symlinks will be generated to the files of the package, but it
+  remains part of the profile (so it won’t be garbage-collected). It
+  can be set back to `true` to re-enable the package.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-env/upgrade.md b/doc/manual/src/command-ref/nix-env/upgrade.md
index 322dfbda22a..2779363c34a 100644
--- a/doc/manual/src/command-ref/nix-env/upgrade.md
+++ b/doc/manual/src/command-ref/nix-env/upgrade.md
@@ -28,42 +28,48 @@ version is installed.
 
 # Flags
 
-  - `--lt`\
-    Only upgrade a derivation to newer versions. This is the default.
-
-  - `--leq`\
-    In addition to upgrading to newer versions, also “upgrade” to
-    derivations that have the same version. Version are not a unique
-    identification of a derivation, so there may be many derivations
-    that have the same version. This flag may be useful to force
-    “synchronisation” between the installed and available derivations.
-
-  - `--eq`\
-    *Only* “upgrade” to derivations that have the same version. This may
-    not seem very useful, but it actually is, e.g., when there is a new
-    release of Nixpkgs and you want to replace installed applications
-    with the same versions built against newer dependencies (to reduce
-    the number of dependencies floating around on your system).
-
-  - `--always`\
-    In addition to upgrading to newer versions, also “upgrade” to
-    derivations that have the same or a lower version. I.e., derivations
-    may actually be downgraded depending on what is available in the
-    active Nix expression.
-
-  - `--prebuilt-only` / `-b`\
-    Use only derivations for which a substitute is registered, i.e.,
-    there is a pre-built binary available that can be downloaded in lieu
-    of building the derivation. Thus, no packages will be built from
-    source.
-
-  - `--preserve-installed` / `-P`\
-    Do not remove derivations with a name matching one of the
-    derivations being installed. Usually, trying to have two versions of
-    the same package installed in the same generation of a profile will
-    lead to an error in building the generation, due to file name
-    clashes between the two versions. However, this is not the case for
-    all packages.
+- `--lt`
+
+  Only upgrade a derivation to newer versions. This is the default.
+
+- `--leq`
+
+  In addition to upgrading to newer versions, also “upgrade” to
+  derivations that have the same version. Version are not a unique
+  identification of a derivation, so there may be many derivations
+  that have the same version. This flag may be useful to force
+  “synchronisation” between the installed and available derivations.
+
+- `--eq`
+
+  *Only* “upgrade” to derivations that have the same version. This may
+  not seem very useful, but it actually is, e.g., when there is a new
+  release of Nixpkgs and you want to replace installed applications
+  with the same versions built against newer dependencies (to reduce
+  the number of dependencies floating around on your system).
+
+- `--always`
+
+  In addition to upgrading to newer versions, also “upgrade” to
+  derivations that have the same or a lower version. I.e., derivations
+  may actually be downgraded depending on what is available in the
+  active Nix expression.
+
+- `--prebuilt-only` / `-b`
+
+  Use only derivations for which a substitute is registered, i.e.,
+  there is a pre-built binary available that can be downloaded in lieu
+  of building the derivation. Thus, no packages will be built from
+  source.
+
+- `--preserve-installed` / `-P`
+
+  Do not remove derivations with a name matching one of the
+  derivations being installed. Usually, trying to have two versions of
+  the same package installed in the same generation of a profile will
+  lead to an error in building the generation, due to file name
+  clashes between the two versions. However, this is not the case for
+  all packages.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-hash.md b/doc/manual/src/command-ref/nix-hash.md
index 37c8facecab..f249c2b84d6 100644
--- a/doc/manual/src/command-ref/nix-hash.md
+++ b/doc/manual/src/command-ref/nix-hash.md
@@ -20,58 +20,74 @@ an example.
 The hash is computed over a *serialisation* of each path: a dump of
 the file system tree rooted at the path. This allows directories and
 symlinks to be hashed as well as regular files. The dump is in the
-*NAR format* produced by [`nix-store
+*[Nix Archive (NAR)][Nix Archive] format* produced by [`nix-store
 --dump`](@docroot@/command-ref/nix-store/dump.md).  Thus, `nix-hash path`
 yields the same cryptographic hash as `nix-store --dump path |
 md5sum`.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+
 # Options
 
-  - `--flat`\
-    Print the cryptographic hash of the contents of each regular file
-    *path*. That is, do not compute the hash over the dump of *path*.
-    The result is identical to that produced by the GNU commands
-    `md5sum` and `sha1sum`.
+- `--flat`
+
+  Print the cryptographic hash of the contents of each regular file *path*.
+  That is, instead of computing
+  the hash of the [Nix Archive (NAR)](@docroot@/store/file-system-object/content-address.md#serial-nix-archive) of *path*,
+  just [directly hash]((@docroot@/store/file-system-object/content-address.md#serial-flat) *path* as is.
+  This requires *path* to resolve to a regular file rather than directory.
+  The result is identical to that produced by the GNU commands
+  `md5sum` and `sha1sum`.
+
+- `--base16`
+
+  Print the hash in a hexadecimal representation (default).
+
+- `--base32`
+
+  Print the hash in a base-32 representation rather than hexadecimal.
+  This base-32 representation is more compact and can be used in Nix
+  expressions (such as in calls to `fetchurl`).
+
+- `--base64`
+
+  Similar to --base32, but print the hash in a base-64 representation,
+  which is more compact than the base-32 one.
+
+- `--sri`
+
+  Print the hash in SRI format with base-64 encoding.
+  The type of hash algorithm will be prepended to the hash string,
+  followed by a hyphen (-) and the base-64 hash body.
+
+- `--truncate`
+
+  Truncate hashes longer than 160 bits (such as SHA-256) to 160 bits.
 
-  - `--base16`\
-    Print the hash in a hexadecimal representation (default).
+- `--type` *hashAlgo*
 
-  - `--base32`\
-    Print the hash in a base-32 representation rather than hexadecimal.
-    This base-32 representation is more compact and can be used in Nix
-    expressions (such as in calls to `fetchurl`).
+  Use the specified cryptographic hash algorithm, which can be one of
+  `md5`, `sha1`, `sha256`, and `sha512`.
 
-  - `--base64`\
-    Similar to --base32, but print the hash in a base-64 representation,
-    which is more compact than the base-32 one.
+- `--to-base16`
 
-  - `--sri`\
-    Print the hash in SRI format with base-64 encoding.
-    The type of hash algorithm will be prepended to the hash string,
-    followed by a hyphen (-) and the base-64 hash body.
+  Don’t hash anything, but convert the base-32 hash representation
+  *hash* to hexadecimal.
 
-  - `--truncate`\
-    Truncate hashes longer than 160 bits (such as SHA-256) to 160 bits.
+- `--to-base32`
 
-  - `--type` *hashAlgo*\
-    Use the specified cryptographic hash algorithm, which can be one of
-    `md5`, `sha1`, `sha256`, and `sha512`.
+  Don’t hash anything, but convert the hexadecimal hash representation
+  *hash* to base-32.
 
-  - `--to-base16`\
-    Don’t hash anything, but convert the base-32 hash representation
-    *hash* to hexadecimal.
+- `--to-base64`
 
-  - `--to-base32`\
-    Don’t hash anything, but convert the hexadecimal hash representation
-    *hash* to base-32.
+  Don’t hash anything, but convert the hexadecimal hash representation
+  *hash* to base-64.
 
-  - `--to-base64`\
-    Don’t hash anything, but convert the hexadecimal hash representation
-    *hash* to base-64.
+- `--to-sri`
 
-  - `--to-sri`\
-    Don’t hash anything, but convert the hexadecimal hash representation
-    *hash* to SRI.
+  Don’t hash anything, but convert the hexadecimal hash representation
+  *hash* to SRI.
 
 # Examples
 
diff --git a/doc/manual/src/command-ref/nix-instantiate.md b/doc/manual/src/command-ref/nix-instantiate.md
index dffbb2d70e1..6f6fcdc1f66 100644
--- a/doc/manual/src/command-ref/nix-instantiate.md
+++ b/doc/manual/src/command-ref/nix-instantiate.md
@@ -30,89 +30,97 @@ standard input.
 
 # Options
 
-  - `--add-root` *path*\
-    See the [corresponding option](nix-store.md) in `nix-store`.
-
-  - `--parse`\
-    Just parse the input files, and print their abstract syntax trees on
-    standard output as a Nix expression.
-
-  - `--eval`\
-    Just parse and evaluate the input files, and print the resulting
-    values on standard output. No instantiation of store derivations
-    takes place.
-
-    > **Warning**
-    >
-    > This option produces output which can be parsed as a Nix expression which
-    > will produce a different result than the input expression when evaluated.
-    > For example, these two Nix expressions print the same result despite
-    > having different meaning:
-    >
-    > ```console
-    > $ nix-instantiate --eval --expr '{ a = {}; }'
-    > { a = <CODE>; }
-    > $ nix-instantiate --eval --expr '{ a = <CODE>; }'
-    > { a = <CODE>; }
-    > ```
-    >
-    > For human-readable output, `nix eval` (experimental) is more informative:
-    >
-    > ```console
-    > $ nix-instantiate --eval --expr 'a: a'
-    > <LAMBDA>
-    > $ nix eval --expr 'a: a'
-    > «lambda @ «string»:1:1»
-    > ```
-    >
-    > For machine-readable output, the `--xml` option produces unambiguous
-    > output:
-    >
-    > ```console
-    > $ nix-instantiate --eval --xml --expr '{ foo = <CODE>; }'
-    > <?xml version='1.0' encoding='utf-8'?>
-    > <expr>
-    >   <attrs>
-    >     <attr column="3" line="1" name="foo">
-    >       <unevaluated />
-    >     </attr>
-    >   </attrs>
-    > </expr>
-    > ```
-
-  - `--find-file`\
-    Look up the given files in Nix’s search path (as specified by the
-    `NIX_PATH` environment variable). If found, print the corresponding
-    absolute paths on standard output. For instance, if `NIX_PATH` is
-    `nixpkgs=/home/alice/nixpkgs`, then `nix-instantiate --find-file
-    nixpkgs/default.nix` will print `/home/alice/nixpkgs/default.nix`.
-
-  - `--strict`\
-    When used with `--eval`, recursively evaluate list elements and
-    attributes. Normally, such sub-expressions are left unevaluated
-    (since the Nix language is lazy).
-
-    > **Warning**
-    >
-    > This option can cause non-termination, because lazy data
-    > structures can be infinitely large.
-
-  - `--json`\
-    When used with `--eval`, print the resulting value as an JSON
-    representation of the abstract syntax tree rather than as a Nix expression.
-
-  - `--xml`\
-    When used with `--eval`, print the resulting value as an XML
-    representation of the abstract syntax tree rather than as a Nix expression.
-    The schema is the same as that used by the [`toXML`
-    built-in](../language/builtins.md).
-
-  - `--read-write-mode`\
-    When used with `--eval`, perform evaluation in read/write mode so
-    nix language features that require it will still work (at the cost
-    of needing to do instantiation of every evaluated derivation). If
-    this option is not enabled, there may be uninstantiated store paths
-    in the final output.
+- `--add-root` *path*
+
+  See the [corresponding option](nix-store.md) in `nix-store`.
+
+- `--parse`
+
+  Just parse the input files, and print their abstract syntax trees on
+  standard output as a Nix expression.
+
+- `--eval`
+
+  Just parse and evaluate the input files, and print the resulting
+  values on standard output. No instantiation of store derivations
+  takes place.
+
+  > **Warning**
+  >
+  > This option produces output which can be parsed as a Nix expression which
+  > will produce a different result than the input expression when evaluated.
+  > For example, these two Nix expressions print the same result despite
+  > having different meaning:
+  >
+  > ```console
+  > $ nix-instantiate --eval --expr '{ a = {}; }'
+  > { a = <CODE>; }
+  > $ nix-instantiate --eval --expr '{ a = <CODE>; }'
+  > { a = <CODE>; }
+  > ```
+  >
+  > For human-readable output, `nix eval` (experimental) is more informative:
+  >
+  > ```console
+  > $ nix-instantiate --eval --expr 'a: a'
+  > <LAMBDA>
+  > $ nix eval --expr 'a: a'
+  > «lambda @ «string»:1:1»
+  > ```
+  >
+  > For machine-readable output, the `--xml` option produces unambiguous
+  > output:
+  >
+  > ```console
+  > $ nix-instantiate --eval --xml --expr '{ foo = <CODE>; }'
+  > <?xml version='1.0' encoding='utf-8'?>
+  > <expr>
+  >   <attrs>
+  >     <attr column="3" line="1" name="foo">
+  >       <unevaluated />
+  >     </attr>
+  >   </attrs>
+  > </expr>
+  > ```
+
+- `--find-file`
+
+  Look up the given files in Nix’s search path (as specified by the
+  `NIX_PATH` environment variable). If found, print the corresponding
+  absolute paths on standard output. For instance, if `NIX_PATH` is
+  `nixpkgs=/home/alice/nixpkgs`, then `nix-instantiate --find-file
+  nixpkgs/default.nix` will print `/home/alice/nixpkgs/default.nix`.
+
+- `--strict`
+
+  When used with `--eval`, recursively evaluate list elements and
+  attributes. Normally, such sub-expressions are left unevaluated
+  (since the Nix language is lazy).
+
+  > **Warning**
+  >
+  > This option can cause non-termination, because lazy data
+  > structures can be infinitely large.
+
+- `--json`
+
+  When used with `--eval`, print the resulting value as an JSON
+  representation of the abstract syntax tree rather than as a Nix expression.
+
+- `--xml`
+
+  When used with `--eval`, print the resulting value as an XML
+  representation of the abstract syntax tree rather than as a Nix expression.
+  The schema is the same as that used by the [`toXML`
+  built-in](../language/builtins.md).
+
+- `--read-write-mode`
+
+  When used with `--eval`, perform evaluation in read/write mode so
+  nix language features that require it will still work (at the cost
+  of needing to do instantiation of every evaluated derivation). If
+  this option is not enabled, there may be uninstantiated store paths
+  in the final output.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-prefetch-url.md b/doc/manual/src/command-ref/nix-prefetch-url.md
index 45ef01e02cc..ffab94b8afa 100644
--- a/doc/manual/src/command-ref/nix-prefetch-url.md
+++ b/doc/manual/src/command-ref/nix-prefetch-url.md
@@ -39,27 +39,32 @@ the path of the downloaded file in the Nix store is also printed.
 
 # Options
 
-  - `--type` *hashAlgo*\
-    Use the specified cryptographic hash algorithm,
-    which can be one of `md5`, `sha1`, `sha256`, and `sha512`.
-    The default is `sha256`.
-
-  - `--print-path`\
-    Print the store path of the downloaded file on standard output.
-
-  - `--unpack`\
-    Unpack the archive (which must be a tarball or zip file) and add the
-    result to the Nix store. The resulting hash can be used with
-    functions such as Nixpkgs’s `fetchzip` or `fetchFromGitHub`.
-
-  - `--executable`\
-    Set the executable bit on the downloaded file.
-
-  - `--name` *name*\
-    Override the name of the file in the Nix store. By default, this is
-    `hash-basename`, where *basename* is the last component of *url*.
-    Overriding the name is necessary when *basename* contains characters
-    that are not allowed in Nix store paths.
+- `--type` *hashAlgo*
+
+  Use the specified cryptographic hash algorithm,
+  which can be one of `md5`, `sha1`, `sha256`, and `sha512`.
+  The default is `sha256`.
+
+- `--print-path`
+
+  Print the store path of the downloaded file on standard output.
+
+- `--unpack`
+
+  Unpack the archive (which must be a tarball or zip file) and add the
+  result to the Nix store. The resulting hash can be used with
+  functions such as Nixpkgs’s `fetchzip` or `fetchFromGitHub`.
+
+- `--executable`
+
+  Set the executable bit on the downloaded file.
+
+- `--name` *name*
+
+  Override the name of the file in the Nix store. By default, this is
+  `hash-basename`, where *basename* is the last component of *url*.
+  Overriding the name is necessary when *basename* contains characters
+  that are not allowed in Nix store paths.
 
 # Examples
 
diff --git a/doc/manual/src/command-ref/nix-shell.md b/doc/manual/src/command-ref/nix-shell.md
index 1eaf3c36aa7..ddec30f5b3e 100644
--- a/doc/manual/src/command-ref/nix-shell.md
+++ b/doc/manual/src/command-ref/nix-shell.md
@@ -60,55 +60,63 @@ All options not listed here are passed to `nix-store
 --realise`, except for `--arg` and `--attr` / `-A` which are passed to
 `nix-instantiate`.
 
-  - `--command` *cmd*\
-    In the environment of the derivation, run the shell command *cmd*.
-    This command is executed in an interactive shell. (Use `--run` to
-    use a non-interactive shell instead.) However, a call to `exit` is
-    implicitly added to the command, so the shell will exit after
-    running the command. To prevent this, add `return` at the end;
-    e.g.  `--command "echo Hello; return"` will print `Hello` and then
-    drop you into the interactive shell. This can be useful for doing
-    any additional initialisation.
-
-  - `--run` *cmd*\
-    Like `--command`, but executes the command in a non-interactive
-    shell. This means (among other things) that if you hit Ctrl-C while
-    the command is running, the shell exits.
-
-  - `--exclude` *regexp*\
-    Do not build any dependencies whose store path matches the regular
-    expression *regexp*. This option may be specified multiple times.
-
-  - `--pure`\
-    If this flag is specified, the environment is almost entirely
-    cleared before the interactive shell is started, so you get an
-    environment that more closely corresponds to the “real” Nix build. A
-    few variables, in particular `HOME`, `USER` and `DISPLAY`, are
-    retained.
-
-  - `--packages` / `-p` *packages*…\
-    Set up an environment in which the specified packages are present.
-    The command line arguments are interpreted as attribute names inside
-    the Nix Packages collection. Thus, `nix-shell --packages libjpeg openjdk`
-    will start a shell in which the packages denoted by the attribute
-    names `libjpeg` and `openjdk` are present.
-
-  - `-i` *interpreter*\
-    The chained script interpreter to be invoked by `nix-shell`. Only
-    applicable in `#!`-scripts (described below).
-
-  - `--keep` *name*\
-    When a `--pure` shell is started, keep the listed environment
-    variables.
+- `--command` *cmd*
+
+  In the environment of the derivation, run the shell command *cmd*.
+  This command is executed in an interactive shell. (Use `--run` to
+  use a non-interactive shell instead.) However, a call to `exit` is
+  implicitly added to the command, so the shell will exit after
+  running the command. To prevent this, add `return` at the end;
+  e.g.  `--command "echo Hello; return"` will print `Hello` and then
+  drop you into the interactive shell. This can be useful for doing
+  any additional initialisation.
+
+- `--run` *cmd*
+
+  Like `--command`, but executes the command in a non-interactive
+  shell. This means (among other things) that if you hit Ctrl-C while
+  the command is running, the shell exits.
+
+- `--exclude` *regexp*
+
+  Do not build any dependencies whose store path matches the regular
+  expression *regexp*. This option may be specified multiple times.
+
+- `--pure`
+
+  If this flag is specified, the environment is almost entirely
+  cleared before the interactive shell is started, so you get an
+  environment that more closely corresponds to the “real” Nix build. A
+  few variables, in particular `HOME`, `USER` and `DISPLAY`, are
+  retained.
+
+- `--packages` / `-p` *packages*…
+
+  Set up an environment in which the specified packages are present.
+  The command line arguments are interpreted as attribute names inside
+  the Nix Packages collection. Thus, `nix-shell --packages libjpeg openjdk`
+  will start a shell in which the packages denoted by the attribute
+  names `libjpeg` and `openjdk` are present.
+
+- `-i` *interpreter*
+
+  The chained script interpreter to be invoked by `nix-shell`. Only
+  applicable in `#!`-scripts (described below).
+
+- `--keep` *name*
+
+  When a `--pure` shell is started, keep the listed environment
+  variables.
 
 {{#include ./opt-common.md}}
 
 # Environment variables
 
-  - `NIX_BUILD_SHELL`\
-    Shell used to start the interactive environment. Defaults to the
-    `bash` found in `<nixpkgs>`, falling back to the `bash` found in
-    `PATH` if not found.
+- `NIX_BUILD_SHELL`
+
+  Shell used to start the interactive environment. Defaults to the
+  `bash` found in `<nixpkgs>`, falling back to the `bash` found in
+  `PATH` if not found.
 
 {{#include ./env-common.md}}
 
@@ -202,14 +210,14 @@ For example, here is a Python script that depends on Python and the
 
 ```python
 #! /usr/bin/env nix-shell
-#! nix-shell -i python --packages python pythonPackages.prettytable
+#! nix-shell -i python3 --packages python3 python3Packages.prettytable
 
 import prettytable
 
 # Print a simple table.
 t = prettytable.PrettyTable(["N", "N^2"])
 for n in range(1, 10): t.add_row([n, n * n])
-print t
+print(t)
 ```
 
 Similarly, the following is a Perl script that specifies that it
diff --git a/doc/manual/src/command-ref/nix-store/add-fixed.md b/doc/manual/src/command-ref/nix-store/add-fixed.md
index d25db091ceb..bebf15026a6 100644
--- a/doc/manual/src/command-ref/nix-store/add-fixed.md
+++ b/doc/manual/src/command-ref/nix-store/add-fixed.md
@@ -16,9 +16,10 @@ public url or broke since the download expression was written.
 
 This operation has the following options:
 
-  - `--recursive`\
-    Use recursive instead of flat hashing mode, used when adding
-    directories to the store.
+- `--recursive`
+
+  Use recursive instead of flat hashing mode, used when adding
+  directories to the store.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-store/dump.md b/doc/manual/src/command-ref/nix-store/dump.md
index c2f3c42ef1f..3de0e27b07b 100644
--- a/doc/manual/src/command-ref/nix-store/dump.md
+++ b/doc/manual/src/command-ref/nix-store/dump.md
@@ -1,6 +1,6 @@
 # Name
 
-`nix-store --dump` - write a single path to a Nix Archive
+`nix-store --dump` - write a single path to a [Nix Archive]
 
 ## Synopsis
 
@@ -8,7 +8,7 @@
 
 ## Description
 
-The operation `--dump` produces a NAR (Nix ARchive) file containing the
+The operation `--dump` produces a [Nix archive](@docroot@/glossary.md#gloss-nar) (NAR) file containing the
 contents of the file system tree rooted at *path*. The archive is
 written to standard output.
 
@@ -30,8 +30,9 @@ NAR archives support filenames of unlimited length and 64-bit file
 sizes. They can contain regular files, directories, and symbolic links,
 but not other types of files (such as device nodes).
 
-A Nix archive can be unpacked using `nix-store
---restore`.
+A Nix archive can be unpacked using [`nix-store --restore`](@docroot@/command-ref/nix-store/restore.md).
+
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-store/export.md b/doc/manual/src/command-ref/nix-store/export.md
index 1bc46f53b50..ba772eb43c2 100644
--- a/doc/manual/src/command-ref/nix-store/export.md
+++ b/doc/manual/src/command-ref/nix-store/export.md
@@ -1,6 +1,6 @@
 # Name
 
-`nix-store --export` - export store paths to a Nix Archive
+`nix-store --export` - export store paths to a [Nix Archive]
 
 ## Synopsis
 
@@ -8,16 +8,22 @@
 
 ## Description
 
-The operation `--export` writes a serialisation of the specified store
-paths to standard output in a format that can be imported into another
-Nix store with `nix-store --import`. This is like `nix-store
---dump`, except that the NAR archive produced by that command doesn’t
-contain the necessary meta-information to allow it to be imported into
-another Nix store (namely, the set of references of the path).
+The operation `--export` writes a serialisation of the given [store objects](@docroot@/glossary.md#gloss-store-object) to standard output in a format that can be imported into another [Nix store](@docroot@/store/index.md) with [`nix-store --import`](./import.md).
 
-This command does not produce a *closure* of the specified paths, so if
-a store path references other store paths that are missing in the target
-Nix store, the import will fail.
+> **Warning**
+>
+> This command *does not* produce a [closure](@docroot@/glossary.md#gloss-closure) of the specified store paths.
+> Trying to import a store object that refers to store paths not available in the target Nix store will fail.
+>
+> Use [`nix-store --query`](@docroot@/command-ref/nix-store/query.md) to obtain the closure of a store path.
+
+This command is different from [`nix-store --dump`](./dump.md), which produces a [Nix archive](@docroot@/glossary.md#gloss-nar) that *does not* contain the set of [references](@docroot@/glossary.md#gloss-reference) of a given store path.
+
+> **Note**
+>
+> For efficient transfer of closures to remote machines over SSH, use [`nix-copy-closure`](@docroot@/command-ref/nix-copy-closure.md).
+
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 
 {{#include ./opt-common.md}}
 
@@ -27,15 +33,21 @@ Nix store, the import will fail.
 
 # Examples
 
-To copy a whole closure, do something
-like:
-
-```console
-$ nix-store --export $(nix-store --query --requisites paths) > out
-```
-
-To import the whole closure again, run:
-
-```console
-$ nix-store --import < out
-```
+> **Example**
+>
+> Deploy GNU Hello to an airgapped machine via USB stick.
+>
+> Write the closure to the block device on a machine with internet connection:
+>
+> ```shell-session
+> [alice@itchy]$ storePath=$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)
+> [alice@itchy]$ nix-store --export $(nix-store --query --requisites $storePath) | sudo dd of=/dev/usb
+> ```
+>
+> Read the closure from the block device on the machine without internet connection:
+>
+> ```shell-session
+> [bob@scratchy]$ hello=$(sudo dd if=/dev/usb | nix-store --import | tail -1)
+> [bob@scratchy]$ $hello/bin/hello
+> Hello, world!
+> ```
diff --git a/doc/manual/src/command-ref/nix-store/gc.md b/doc/manual/src/command-ref/nix-store/gc.md
index 7be0d559add..f432e00eb96 100644
--- a/doc/manual/src/command-ref/nix-store/gc.md
+++ b/doc/manual/src/command-ref/nix-store/gc.md
@@ -14,30 +14,34 @@ reachable via file system references from a set of “roots”, are deleted.
 
 The following suboperations may be specified:
 
-  - `--print-roots`\
-    This operation prints on standard output the set of roots used by
-    the garbage collector.
-
-  - `--print-live`\
-    This operation prints on standard output the set of “live” store
-    paths, which are all the store paths reachable from the roots. Live
-    paths should never be deleted, since that would break consistency —
-    it would become possible that applications are installed that
-    reference things that are no longer present in the store.
-
-  - `--print-dead`\
-    This operation prints out on standard output the set of “dead” store
-    paths, which is just the opposite of the set of live paths: any path
-    in the store that is not live (with respect to the roots) is dead.
+- `--print-roots`
+
+  This operation prints on standard output the set of roots used by
+  the garbage collector.
+
+- `--print-live`
+
+  This operation prints on standard output the set of “live” store
+  paths, which are all the store paths reachable from the roots. Live
+  paths should never be deleted, since that would break consistency —
+  it would become possible that applications are installed that
+  reference things that are no longer present in the store.
+
+- `--print-dead`
+
+  This operation prints out on standard output the set of “dead” store
+  paths, which is just the opposite of the set of live paths: any path
+  in the store that is not live (with respect to the roots) is dead.
 
 By default, all unreachable paths are deleted. The following options
 control what gets deleted and in what order:
 
-  - `--max-freed` *bytes*\
-    Keep deleting paths until at least *bytes* bytes have been deleted,
-    then stop. The argument *bytes* can be followed by the
-    multiplicative suffix `K`, `M`, `G` or `T`, denoting KiB, MiB, GiB
-    or TiB units.
+- `--max-freed` *bytes*
+
+  Keep deleting paths until at least *bytes* bytes have been deleted,
+  then stop. The argument *bytes* can be followed by the
+  multiplicative suffix `K`, `M`, `G` or `T`, denoting KiB, MiB, GiB
+  or TiB units.
 
 The behaviour of the collector is also influenced by the
 `keep-outputs` and `keep-derivations` settings in the Nix
diff --git a/doc/manual/src/command-ref/nix-store/import.md b/doc/manual/src/command-ref/nix-store/import.md
index 2711316a7d6..3f6b3d07610 100644
--- a/doc/manual/src/command-ref/nix-store/import.md
+++ b/doc/manual/src/command-ref/nix-store/import.md
@@ -1,6 +1,8 @@
 # Name
 
-`nix-store --import` - import Nix Archive into the store
+`nix-store --import` - import [Nix Archive] into the store
+
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 
 # Synopsis
 
@@ -8,14 +10,34 @@
 
 # Description
 
-The operation `--import` reads a serialisation of a set of store paths
-produced by `nix-store --export` from standard input and adds those
-store paths to the Nix store. Paths that already exist in the Nix store
-are ignored. If a path refers to another path that doesn’t exist in the
-Nix store, the import fails.
+The operation `--import` reads a serialisation of a set of [store objects](@docroot@/glossary.md#gloss-store-object) produced by [`nix-store --export`](./export.md) from standard input, and adds those store objects to the specified [Nix store](@docroot@/store/index.md).
+Paths that already exist in the target Nix store are ignored.
+If a path [refers](@docroot@/glossary.md#gloss-reference) to another path that doesn’t exist in the target Nix store, the import fails.
+
+> **Note**
+>
+> For efficient transfer of closures to remote machines over SSH, use [`nix-copy-closure`](@docroot@/command-ref/nix-copy-closure.md).
 
 {{#include ./opt-common.md}}
 
 {{#include ../opt-common.md}}
 
 {{#include ../env-common.md}}
+
+# Examples
+
+> **Example**
+>
+> Given a closure of GNU Hello as a file:
+>
+> ```shell-session
+> $ storePath="$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)"
+> $ nix-store --export $(nix-store --query --requisites $storePath) > hello.closure
+> ```
+>
+> Import the closure into a [remote SSH store](@docroot@/store/types/ssh-store.md) using the [`--store`](@docroot@/command-ref/conf-file.md#conf-store) option:
+>
+> ```console
+> $ nix-store --import --store ssh://alice@itchy.example.org < hello.closure
+> ```
+
diff --git a/doc/manual/src/command-ref/nix-store/optimise.md b/doc/manual/src/command-ref/nix-store/optimise.md
index dc392aeb8da..b257466b203 100644
--- a/doc/manual/src/command-ref/nix-store/optimise.md
+++ b/doc/manual/src/command-ref/nix-store/optimise.md
@@ -12,7 +12,7 @@ The operation `--optimise` reduces Nix store disk space usage by finding
 identical files in the store and hard-linking them to each other. It
 typically reduces the size of the store by something like 25-35%. Only
 regular files and symlinks are hard-linked in this manner. Files are
-considered identical when they have the same NAR archive serialisation:
+considered identical when they have the same [Nix Archive (NAR)][Nix Archive] serialisation:
 that is, regular files must have the same contents and permission
 (executable or non-executable), and symlinks must have the same
 contents.
@@ -38,3 +38,4 @@ hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
 there are 114486 files with equal contents out of 215894 files in total
 ```
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
diff --git a/doc/manual/src/command-ref/nix-store/query.md b/doc/manual/src/command-ref/nix-store/query.md
index 0bcacfe0cd7..b4efa734e78 100644
--- a/doc/manual/src/command-ref/nix-store/query.md
+++ b/doc/manual/src/command-ref/nix-store/query.md
@@ -24,122 +24,138 @@ symlink.
 
 # Common query options
 
-  - `--use-output`; `-u`\
-    For each argument to the query that is a [store derivation], apply the
-    query to the output path of the derivation instead.
+- `--use-output` / `-u`
 
-  - `--force-realise`; `-f`\
-    Realise each argument to the query first (see [`nix-store --realise`](./realise.md)).
+  For each argument to the query that is a [store derivation], apply the
+  query to the output path of the derivation instead.
+
+- `--force-realise` / `-f`
+
+  Realise each argument to the query first (see [`nix-store --realise`](./realise.md)).
 
 [store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
 # Queries
 
-  - `--outputs`\
-    Prints out the [output paths] of the store
-    derivations *paths*. These are the paths that will be produced when
-    the derivation is built.
-
-    [output paths]: @docroot@/glossary.md#gloss-output-path
-
-  - `--requisites`; `-R`\
-    Prints out the [closure] of the store path *paths*.
-
-    [closure]: @docroot@/glossary.md#gloss-closure
-
-    This query has one option:
-
-      - `--include-outputs`
-        Also include the existing output paths of [store derivation]s,
-        and their closures.
-
-    This query can be used to implement various kinds of deployment. A
-    *source deployment* is obtained by distributing the closure of a
-    store derivation. A *binary deployment* is obtained by distributing
-    the closure of an output path. A *cache deployment* (combined
-    source/binary deployment, including binaries of build-time-only
-    dependencies) is obtained by distributing the closure of a store
-    derivation and specifying the option `--include-outputs`.
-
-  - `--references`\
-    Prints the set of [references] of the store paths
-    *paths*, that is, their immediate dependencies. (For *all*
-    dependencies, use `--requisites`.)
-
-    [references]: @docroot@/glossary.md#gloss-reference
-
-  - `--referrers`\
-    Prints the set of *referrers* of the store paths *paths*, that is,
-    the store paths currently existing in the Nix store that refer to
-    one of *paths*. Note that contrary to the references, the set of
-    referrers is not constant; it can change as store paths are added or
-    removed.
-
-  - `--referrers-closure`\
-    Prints the closure of the set of store paths *paths* under the
-    referrers relation; that is, all store paths that directly or
-    indirectly refer to one of *paths*. These are all the path currently
-    in the Nix store that are dependent on *paths*.
-
-  - `--deriver`; `-d`\
-    Prints the [deriver] that was used to build the store paths *paths*. If
-    the path has no deriver (e.g., if it is a source file), or if the
-    deriver is not known (e.g., in the case of a binary-only
-    deployment), the string `unknown-deriver` is printed.
-    The returned deriver is not guaranteed to exist in the local store, for
-    example when *paths* were substituted from a binary cache.
-    Use `--valid-derivers` instead to obtain valid paths only.
-
-    [deriver]: @docroot@/glossary.md#gloss-deriver
-
-  - `--valid-derivers`\
-    Prints a set of derivation files (`.drv`) which are supposed produce
-    said paths when realized. Might print nothing, for example for source paths
-    or paths subsituted from a binary cache.
-
-  - `--graph`\
-    Prints the references graph of the store paths *paths* in the format
-    of the `dot` tool of AT\&T's [Graphviz
-    package](http://www.graphviz.org/). This can be used to visualise
-    dependency graphs. To obtain a build-time dependency graph, apply
-    this to a store derivation. To obtain a runtime dependency graph,
-    apply it to an output path.
-
-  - `--tree`\
-    Prints the references graph of the store paths *paths* as a nested
-    ASCII tree. References are ordered by descending closure size; this
-    tends to flatten the tree, making it more readable. The query only
-    recurses into a store path when it is first encountered; this
-    prevents a blowup of the tree representation of the graph.
-
-  - `--graphml`\
-    Prints the references graph of the store paths *paths* in the
-    [GraphML](http://graphml.graphdrawing.org/) file format. This can be
-    used to visualise dependency graphs. To obtain a build-time
-    dependency graph, apply this to a [store derivation]. To obtain a
-    runtime dependency graph, apply it to an output path.
-
-  - `--binding` *name*; `-b` *name*\
-    Prints the value of the attribute *name* (i.e., environment
-    variable) of the [store derivation]s *paths*. It is an error for a
-    derivation to not have the specified attribute.
-
-  - `--hash`\
-    Prints the SHA-256 hash of the contents of the store paths *paths*
-    (that is, the hash of the output of `nix-store --dump` on the given
-    paths). Since the hash is stored in the Nix database, this is a fast
-    operation.
-
-  - `--size`\
-    Prints the size in bytes of the contents of the store paths *paths*
-    — to be precise, the size of the output of `nix-store --dump` on
-    the given paths. Note that the actual disk space required by the
-    store paths may be higher, especially on filesystems with large
-    cluster sizes.
-
-  - `--roots`\
-    Prints the garbage collector roots that point, directly or
-    indirectly, at the store paths *paths*.
+- `--outputs`
+
+  Prints out the [output paths] of the store
+  derivations *paths*. These are the paths that will be produced when
+  the derivation is built.
+
+  [output paths]: @docroot@/glossary.md#gloss-output-path
+
+- `--requisites` / `-R`
+
+  Prints out the [closure] of the store path *paths*.
+
+  [closure]: @docroot@/glossary.md#gloss-closure
+
+  This query has one option:
+
+    - `--include-outputs`
+      Also include the existing output paths of [store derivation]s,
+      and their closures.
+
+  This query can be used to implement various kinds of deployment. A
+  *source deployment* is obtained by distributing the closure of a
+  store derivation. A *binary deployment* is obtained by distributing
+  the closure of an output path. A *cache deployment* (combined
+  source/binary deployment, including binaries of build-time-only
+  dependencies) is obtained by distributing the closure of a store
+  derivation and specifying the option `--include-outputs`.
+
+- `--references`
+
+  Prints the set of [references] of the store paths
+  *paths*, that is, their immediate dependencies. (For *all*
+  dependencies, use `--requisites`.)
+
+  [references]: @docroot@/glossary.md#gloss-reference
+
+- `--referrers`
+
+  Prints the set of *referrers* of the store paths *paths*, that is,
+  the store paths currently existing in the Nix store that refer to
+  one of *paths*. Note that contrary to the references, the set of
+  referrers is not constant; it can change as store paths are added or
+  removed.
+
+- `--referrers-closure`
+
+  Prints the closure of the set of store paths *paths* under the
+  referrers relation; that is, all store paths that directly or
+  indirectly refer to one of *paths*. These are all the path currently
+  in the Nix store that are dependent on *paths*.
+
+- `--deriver` / `-d`
+
+  Prints the [deriver] that was used to build the store paths *paths*. If
+  the path has no deriver (e.g., if it is a source file), or if the
+  deriver is not known (e.g., in the case of a binary-only
+  deployment), the string `unknown-deriver` is printed.
+  The returned deriver is not guaranteed to exist in the local store, for
+  example when *paths* were substituted from a binary cache.
+  Use `--valid-derivers` instead to obtain valid paths only.
+
+  [deriver]: @docroot@/glossary.md#gloss-deriver
+
+- `--valid-derivers`
+
+  Prints a set of derivation files (`.drv`) which are supposed produce
+  said paths when realized. Might print nothing, for example for source paths
+  or paths subsituted from a binary cache.
+
+- `--graph`
+
+  Prints the references graph of the store paths *paths* in the format
+  of the `dot` tool of AT\&T's [Graphviz
+  package](http://www.graphviz.org/). This can be used to visualise
+  dependency graphs. To obtain a build-time dependency graph, apply
+  this to a store derivation. To obtain a runtime dependency graph,
+  apply it to an output path.
+
+- `--tree`
+
+  Prints the references graph of the store paths *paths* as a nested
+  ASCII tree. References are ordered by descending closure size; this
+  tends to flatten the tree, making it more readable. The query only
+  recurses into a store path when it is first encountered; this
+  prevents a blowup of the tree representation of the graph.
+
+- `--graphml`
+
+  Prints the references graph of the store paths *paths* in the
+  [GraphML](http://graphml.graphdrawing.org/) file format. This can be
+  used to visualise dependency graphs. To obtain a build-time
+  dependency graph, apply this to a [store derivation]. To obtain a
+  runtime dependency graph, apply it to an output path.
+
+- `--binding` *name* / `-b` *name*
+
+  Prints the value of the attribute *name* (i.e., environment
+  variable) of the [store derivation]s *paths*. It is an error for a
+  derivation to not have the specified attribute.
+
+- `--hash`
+
+  Prints the SHA-256 hash of the contents of the store paths *paths*
+  (that is, the hash of the output of `nix-store --dump` on the given
+  paths). Since the hash is stored in the Nix database, this is a fast
+  operation.
+
+- `--size`
+
+  Prints the size in bytes of the contents of the store paths *paths*
+  — to be precise, the size of the output of `nix-store --dump` on
+  the given paths. Note that the actual disk space required by the
+  store paths may be higher, especially on filesystems with large
+  cluster sizes.
+
+- `--roots`
+
+  Prints the garbage collector roots that point, directly or
+  indirectly, at the store paths *paths*.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-store/realise.md b/doc/manual/src/command-ref/nix-store/realise.md
index 5428d57fa50..e30b351a416 100644
--- a/doc/manual/src/command-ref/nix-store/realise.md
+++ b/doc/manual/src/command-ref/nix-store/realise.md
@@ -25,11 +25,11 @@ Each of *paths* is processed as follows:
 
 If no substitutes are available and no store derivation is given, realisation fails.
 
-[store paths]: @docroot@/glossary.md#gloss-store-path
+[store paths]: @docroot@/store/store-path.md
 [valid]: @docroot@/glossary.md#gloss-validity
 [store derivation]: @docroot@/glossary.md#gloss-store-derivation
 [output paths]: @docroot@/glossary.md#gloss-output-path
-[store objects]: @docroot@/glossary.md#gloss-store-object
+[store objects]: @docroot@/store/store-object.md
 [closure]: @docroot@/glossary.md#gloss-closure
 [substituters]: @docroot@/command-ref/conf-file.md#conf-substituters
 [content-addressed derivations]: @docroot@/contributing/experimental-features.md#xp-feature-ca-derivations
@@ -42,23 +42,26 @@ For non-derivation arguments, the argument itself is printed.
 
 # Options
 
-  - `--dry-run`\
-    Print on standard error a description of what packages would be
-    built or downloaded, without actually performing the operation.
-
-  - `--ignore-unknown`\
-    If a non-derivation path does not have a substitute, then silently
-    ignore it.
-
-  - `--check`\
-    This option allows you to check whether a derivation is
-    deterministic. It rebuilds the specified derivation and checks
-    whether the result is bitwise-identical with the existing outputs,
-    printing an error if that’s not the case. The outputs of the
-    specified derivation must already exist. When used with `-K`, if an
-    output path is not identical to the corresponding output from the
-    previous build, the new output path is left in
-    `/nix/store/name.check.`
+- `--dry-run`
+
+  Print on standard error a description of what packages would be
+  built or downloaded, without actually performing the operation.
+
+- `--ignore-unknown`
+
+  If a non-derivation path does not have a substitute, then silently
+  ignore it.
+
+- `--check`
+
+  This option allows you to check whether a derivation is
+  deterministic. It rebuilds the specified derivation and checks
+  whether the result is bitwise-identical with the existing outputs,
+  printing an error if that’s not the case. The outputs of the
+  specified derivation must already exist. When used with `-K`, if an
+  output path is not identical to the corresponding output from the
+  previous build, the new output path is left in
+  `/nix/store/name.check.`
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-store/restore.md b/doc/manual/src/command-ref/nix-store/restore.md
index fcba43df4df..2d0aa3127be 100644
--- a/doc/manual/src/command-ref/nix-store/restore.md
+++ b/doc/manual/src/command-ref/nix-store/restore.md
@@ -8,9 +8,11 @@
 
 ## Description
 
-The operation `--restore` unpacks a NAR archive to *path*, which must
+The operation `--restore` unpacks a [Nix Archive (NAR)][Nix Archive] to *path*, which must
 not already exist. The archive is read from standard input.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+
 {{#include ./opt-common.md}}
 
 {{#include ../opt-common.md}}
diff --git a/doc/manual/src/command-ref/nix-store/serve.md b/doc/manual/src/command-ref/nix-store/serve.md
index 0f90f65aeae..9a4cf521620 100644
--- a/doc/manual/src/command-ref/nix-store/serve.md
+++ b/doc/manual/src/command-ref/nix-store/serve.md
@@ -14,10 +14,11 @@ access to a restricted ssh user.
 
 The following flags are available:
 
-  - `--write`\
-    Allow the connected client to request the realization of
-    derivations. In effect, this can be used to make the host act as a
-    remote builder.
+- `--write`
+
+  Allow the connected client to request the realization of
+  derivations. In effect, this can be used to make the host act as a
+  remote builder.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/nix-store/verify.md b/doc/manual/src/command-ref/nix-store/verify.md
index 2695b3361fa..40c9180dbc9 100644
--- a/doc/manual/src/command-ref/nix-store/verify.md
+++ b/doc/manual/src/command-ref/nix-store/verify.md
@@ -16,18 +16,20 @@ being modified by non-Nix tools, or of bugs in Nix itself.
 
 This operation has the following options:
 
-  - `--check-contents`\
-    Checks that the contents of every valid store path has not been
-    altered by computing a SHA-256 hash of the contents and comparing it
-    with the hash stored in the Nix database at build time. Paths that
-    have been modified are printed out. For large stores,
-    `--check-contents` is obviously quite slow.
-
-  - `--repair`\
-    If any valid path is missing from the store, or (if
-    `--check-contents` is given) the contents of a valid path has been
-    modified, then try to repair the path by redownloading it. See
-    `nix-store --repair-path` for details.
+- `--check-contents`
+
+  Checks that the contents of every valid store path has not been
+  altered by computing a SHA-256 hash of the contents and comparing it
+  with the hash stored in the Nix database at build time. Paths that
+  have been modified are printed out. For large stores,
+  `--check-contents` is obviously quite slow.
+
+- `--repair`
+
+  If any valid path is missing from the store, or (if
+  `--check-contents` is given) the contents of a valid path has been
+  modified, then try to repair the path by redownloading it. See
+  `nix-store --repair-path` for details.
 
 {{#include ./opt-common.md}}
 
diff --git a/doc/manual/src/command-ref/opt-common.md b/doc/manual/src/command-ref/opt-common.md
index 114b292f930..a42909e2d13 100644
--- a/doc/manual/src/command-ref/opt-common.md
+++ b/doc/manual/src/command-ref/opt-common.md
@@ -143,7 +143,7 @@ Most Nix commands accept the following command-line options:
 
   This option is accepted by `nix-env`, `nix-instantiate`, `nix-shell` and `nix-build`.
   When evaluating Nix expressions, the expression evaluator will automatically try to call functions that it encounters.
-  It can automatically call functions for which every argument has a [default value](@docroot@/language/constructs.md#functions) (e.g., `{ argName ?  defaultValue }: ...`).
+  It can automatically call functions for which every argument has a [default value](@docroot@/language/syntax.md#functions) (e.g., `{ argName ?  defaultValue }: ...`).
 
   With `--arg`, you can also call functions that have arguments without a default value (or override a default value).
   That is, if the evaluator encounters a function with an argument named *name*, it will call it with value *value*.
diff --git a/doc/manual/src/contributing/cli-guideline.md b/doc/manual/src/contributing/cli-guideline.md
index e90d6de8d99..23df844ec11 100644
--- a/doc/manual/src/contributing/cli-guideline.md
+++ b/doc/manual/src/contributing/cli-guideline.md
@@ -389,88 +389,6 @@ colors, no emojis and using ASCII instead of Unicode symbols). The same should
 happen when TTY is not detected on STDERR. We should not display progress /
 status section, but only print warnings and errors.
 
-## Returning future proof JSON
-
-The schema of JSON output should allow for backwards compatible extension. This section explains how to achieve this.
-
-Two definitions are helpful here, because while JSON only defines one "key-value"
-object type, we use it to cover two use cases:
-
- - **dictionary**: a map from names to value that all have the same type. In
-   C++ this would be a `std::map` with string keys.
- - **record**: a fixed set of attributes each with their own type. In C++, this
-   would be represented by a `struct`.
-
-It is best not to mix these use cases, as that may lead to incompatibilities when the schema changes. For example, adding a record field to a dictionary breaks consumers that assume all JSON object fields to have the same meaning and type.
-
-This leads to the following guidelines:
-
- - The top-level (root) value must be a record.
-
-   Otherwise, one can not change the structure of a command's output.
-
- - The value of a dictionary item must be a record.
-
-   Otherwise, the item type can not be extended.
-
- - List items should be records.
-
-   Otherwise, one can not change the structure of the list items.
-
-   If the order of the items does not matter, and each item has a unique key that is a string, consider representing the list as a dictionary instead. If the order of the items needs to be preserved, return a list of records.
-
- - Streaming JSON should return records.
-
-   An example of a streaming JSON format is [JSON lines](https://jsonlines.org/), where each line represents a JSON value. These JSON values can be considered top-level values or list items, and they must be records.
-
-### Examples
-
-
-This is bad, because all keys must be assumed to be store types:
-
-```json
-{
-  "local": { ... },
-  "remote": { ... },
-  "http": { ... }
-}
-```
-
-This is good, because the it is extensible at the root, and is somewhat self-documenting:
-
-```json
-{
-  "storeTypes": { "local": { ... }, ... },
-  "pluginSupport": true
-}
-```
-
-While the dictionary of store types seems like a very complete response at first, a use case may arise that warrants returning additional information.
-For example, the presence of plugin support may be crucial information for a client to proceed when their desired store type is missing.
-
-
-
-The following representation is bad because it is not extensible:
-
-```json
-{ "outputs": [ "out" "bin" ] }
-```
-
-However, simply converting everything to records is not enough, because the order of outputs must be preserved:
-
-```json
-{ "outputs": { "bin": {}, "out": {} } }
-```
-
-The first item is the default output. Deriving this information from the outputs ordering is not great, but this is how Nix currently happens to work.
-While it is possible for a JSON parser to preserve the order of fields, we can not rely on this capability to be present in all JSON libraries.
-
-This representation is extensible and preserves the ordering:
-
-```json
-{ "outputs": [ { "outputName": "out" }, { "outputName": "bin" } ] }
-```
-
 ## Dialog with the user
 
 CLIs don't always make it clear when an action has taken place. For every
diff --git a/doc/manual/src/contributing/documentation.md b/doc/manual/src/contributing/documentation.md
index e7f94ab8c35..a14ecedd6e6 100644
--- a/doc/manual/src/contributing/documentation.md
+++ b/doc/manual/src/contributing/documentation.md
@@ -147,7 +147,7 @@ Please observe these guidelines to ease reviews:
   ```
   A [store object] contains a [file system object] and [references] to other store objects.
 
-  [store object]: @docroot@/glossary.md#gloss-store-object
+  [store object]: @docroot@/store/store-object.md
   [file system object]: @docroot@/architecture/file-system-object.md
   [references]: @docroot@/glossary.md#gloss-reference
   ```
@@ -196,32 +196,35 @@ You can also build and view it yourself:
 [Doxygen API documentation]: https://hydra.nixos.org/job/nix/master/internal-api-docs/latest/download-by-type/doc/internal-api-docs
 
 ```console
-# nix build .#hydraJobs.internal-api-docs
-# xdg-open ./result/share/doc/nix/internal-api/html/index.html
+$ nix build .#hydraJobs.internal-api-docs
+$ xdg-open ./result/share/doc/nix/internal-api/html/index.html
 ```
 
 or inside `nix-shell` or `nix develop`:
 
-```
-# make internal-api-html
-# xdg-open ./outputs/doc/share/doc/nix/internal-api/html/index.html
+```console
+$ mesonConfigurePhase
+$ ninja src/internal-api-docs/html
+$ xdg-open src/internal-api-docs/html/index.html
 ```
 
-## C API documentation (experimental)
+## C API documentation
 
+Note that the C API is not yet stable.
 [C API documentation] is available online.
 You can also build and view it yourself:
 
 [C API documentation]: https://hydra.nixos.org/job/nix/master/external-api-docs/latest/download-by-type/doc/external-api-docs
 
 ```console
-# nix build .#hydraJobs.external-api-docs
-# xdg-open ./result/share/doc/nix/external-api/html/index.html
+$ nix build .#hydraJobs.external-api-docs
+$ xdg-open ./result/share/doc/nix/external-api/html/index.html
 ```
 
 or inside `nix-shell` or `nix develop`:
 
 ```
-# make external-api-html
-# xdg-open ./outputs/doc/share/doc/nix/external-api/html/index.html
+$ mesonConfigurePhase
+$ ninja src/external-api-docs/html
+$ xdg-open src/external-api-docs/html/index.html
 ```
diff --git a/doc/manual/src/contributing/hacking.md b/doc/manual/src/contributing/hacking.md
index d56ac29a46c..c128515e9ba 100644
--- a/doc/manual/src/contributing/hacking.md
+++ b/doc/manual/src/contributing/hacking.md
@@ -122,7 +122,6 @@ Run `make` with [`-e` / `--environment-overrides`](https://www.gnu.org/software/
 
   The docs can take a while to build, so you may want to disable this for local development.
 - `ENABLE_FUNCTIONAL_TESTS=yes` to enable building the functional tests.
-- `ENABLE_UNIT_TESTS=yes` to enable building the unit tests.
 - `OPTIMIZE=1` to enable optimizations.
 - `libraries=libutil programs=` to only build a specific library.
 
@@ -144,6 +143,7 @@ Nix can be built for various platforms, as specified in [`flake.nix`]:
 - `aarch64-darwin`
 - `armv6l-linux`
 - `armv7l-linux`
+- `riscv64-linux`
 
 In order to build Nix for a different platform than the one you're currently
 on, you need a way for your current Nix installation to build code for that
@@ -166,7 +166,10 @@ or for Nix with the [`flakes`] and [`nix-command`] experimental features enabled
 $ nix build .#packages.aarch64-linux.default
 ```
 
-Cross-compiled builds are available for ARMv6 (`armv6l-linux`) and ARMv7 (`armv7l-linux`).
+Cross-compiled builds are available for:
+- `armv6l-linux`
+- `armv7l-linux`
+- `riscv64-linux`
 Add more [system types](#system-type) to `crossSystems` in `flake.nix` to bootstrap Nix on unsupported platforms.
 
 ### Building for multiple platforms at once
@@ -269,6 +272,29 @@ Configure your editor to use the `clangd` from the `.#native-clangStdenvPackages
 > Some other editors (e.g. Emacs, Vim) need a plugin to support LSP servers in general (e.g. [lsp-mode](https://github.com/emacs-lsp/lsp-mode) for Emacs and [vim-lsp](https://github.com/prabirshrestha/vim-lsp) for vim).
 > Editor-specific setup is typically opinionated, so we will not cover it here in more detail.
 
+## Formatting and pre-commit hooks
+
+You may run the formatters as a one-off using:
+
+```console
+make format
+```
+
+If you'd like to run the formatters before every commit, install the hooks:
+
+```
+pre-commit-hooks-install
+```
+
+This installs [pre-commit](https://pre-commit.com) using [cachix/git-hooks.nix](https://github.com/cachix/git-hooks.nix).
+
+When making a commit, pay attention to the console output.
+If it fails, run `git add --patch` to approve the suggestions _and commit again_.
+
+To refresh pre-commit hook's config file, do the following:
+1. Exit the development shell and start it again by running `nix develop`.
+2. If you also use the pre-commit hook, also run `pre-commit-hooks-install` again.
+
 ## Add a release note
 
 `doc/manual/rl-next` contains release notes entries for all unreleased changes.
diff --git a/doc/manual/src/contributing/json-guideline.md b/doc/manual/src/contributing/json-guideline.md
new file mode 100644
index 00000000000..b4bc92af961
--- /dev/null
+++ b/doc/manual/src/contributing/json-guideline.md
@@ -0,0 +1,128 @@
+# JSON guideline
+
+Nix consumes and produces JSON in a variety of contexts.
+These guidelines ensure consistent practices for all our JSON interfaces, for ease of use, and so that experience in one part carries over to another.
+
+## Extensibility
+
+The schema of JSON input and output should allow for backwards compatible extension.
+This section explains how to achieve this.
+
+Two definitions are helpful here, because while JSON only defines one "key-value" object type, we use it to cover two use cases:
+
+ - **dictionary**: a map from names to value that all have the same type.
+   In C++ this would be a `std::map` with string keys.
+
+ - **record**: a fixed set of attributes each with their own type.
+   In C++, this would be represented by a `struct`.
+
+It is best not to mix these use cases, as that may lead to incompatibilities when the schema changes.
+For example, adding a record field to a dictionary breaks consumers that assume all JSON object fields to have the same meaning and type, and dictionary items with a colliding name can not be represented anymore.
+
+This leads to the following guidelines:
+
+ - The top-level (root) value must be a record.
+
+   Otherwise, one can not change the structure of a command's output.
+
+ - The value of a dictionary item must be a record.
+
+   Otherwise, the item type can not be extended.
+
+ - List items should be records.
+
+   Otherwise, one can not change the structure of the list items.
+
+   If the order of the items does not matter, and each item has a unique key that is a string, consider representing the list as a dictionary instead.
+   If the order of the items needs to be preserved, return a list of records.
+
+ - Streaming JSON should return records.
+
+   An example of a streaming JSON format is [JSON lines](https://jsonlines.org/), where each line represents a JSON value.
+   These JSON values can be considered top-level values or list items, and they must be records.
+
+### Examples
+
+This is bad, because all keys must be assumed to be store types:
+
+```json
+{
+  "local": { ... },
+  "remote": { ... },
+  "http": { ... }
+}
+```
+
+This is good, because the it is extensible at the root, and is somewhat self-documenting:
+
+```json
+{
+  "storeTypes": { "local": { ... }, ... },
+  "pluginSupport": true
+}
+```
+
+While the dictionary of store types seems like a very complete response at first, a use case may arise that warrants returning additional information.
+For example, the presence of plugin support may be crucial information for a client to proceed when their desired store type is missing.
+
+
+
+The following representation is bad because it is not extensible:
+
+```json
+{ "outputs": [ "out" "bin" ] }
+```
+
+However, simply converting everything to records is not enough, because the order of outputs must be preserved:
+
+```json
+{ "outputs": { "bin": {}, "out": {} } }
+```
+
+The first item is the default output. Deriving this information from the outputs ordering is not great, but this is how Nix currently happens to work.
+While it is possible for a JSON parser to preserve the order of fields, we can not rely on this capability to be present in all JSON libraries.
+
+This representation is extensible and preserves the ordering:
+
+```json
+{ "outputs": [ { "outputName": "out" }, { "outputName": "bin" } ] }
+```
+
+## Self-describing values
+
+As described in the previous section, it's crucial that schemas can be extended with with new fields without breaking compatibility.
+However, that should *not* mean we use the presence/absence of fields to indicate optional information *within* a version of the schema.
+Instead, always include the field, and use `null` to indicate the "nothing" case.
+
+### Examples
+
+Here are two JSON objects:
+
+```json
+{
+  "foo": {}
+}
+```
+```json
+{
+  "foo": {},
+  "bar": {}
+}
+```
+
+Since they differ in which fields they contain, they should *not* both be valid values of the same schema.
+At most, they can match two different schemas where the second (with `foo` and `bar`) is considered a newer version of the first (with just `foo`).
+Within each version, all fields are mandatory (always `foo`, and always `foo` and `bar`).
+Only *between* each version, `bar` gets added as a new mandatory field.
+
+Here are another two JSON objects:
+
+```json
+{ "foo": null }
+```
+```json
+{ "foo": { "bar": 1 } }
+```
+
+Since they both contain a `foo` field, they could be valid values of the same schema.
+The schema would have `foo` has an optional field, which is either `null` or an object where `bar` is an integer.
diff --git a/doc/manual/src/contributing/testing.md b/doc/manual/src/contributing/testing.md
index 31c39c16c09..a96ba997bed 100644
--- a/doc/manual/src/contributing/testing.md
+++ b/doc/manual/src/contributing/testing.md
@@ -59,15 +59,15 @@ The unit tests are defined using the [googletest] and [rapidcheck] frameworks.
 > …
 > ```
 
-The tests for each Nix library (`libnixexpr`, `libnixstore`, etc..) live inside a directory `tests/unit/${library_name_without-nix}`.
-Given a interface (header) and implementation pair in the original library, say, `src/libexpr/value/context.{hh,cc}`, we write tests for it in `tests/unit/libexpr/tests/value/context.cc`, and (possibly) declare/define additional interfaces for testing purposes in `tests/unit/libexpr-support/tests/value/context.{hh,cc}`.
+The tests for each Nix library (`libnixexpr`, `libnixstore`, etc..) live inside a directory `src/${library_name_without-nix}-test`.
+Given an interface (header) and implementation pair in the original library, say, `src/libexpr/value/context.{hh,cc}`, we write tests for it in `src/nix-expr-tests/value/context.cc`, and (possibly) declare/define additional interfaces for testing purposes in `src/nix-expr-test-support/tests/value/context.{hh,cc}`.
 
 Data for unit tests is stored in a `data` subdir of the directory for each unit test executable.
-For example, `libnixstore` code is in `src/libstore`, and its test data is in `tests/unit/libstore/data`.
-The path to the `tests/unit/data` directory is passed to the unit test executable with the environment variable `_NIX_TEST_UNIT_DATA`.
+For example, `libnixstore` code is in `src/libstore`, and its test data is in `src/nix-store-tests/data`.
+The path to the `src/${library_name_without-nix}-test/data` directory is passed to the unit test executable with the environment variable `_NIX_TEST_UNIT_DATA`.
 Note that each executable only gets the data for its tests.
 
-The unit test libraries are in `tests/unit/${library_name_without-nix}-lib`.
+The unit test libraries are in `src/${library_name_without-nix}-test-support`.
 All headers are in a `tests` subdirectory so they are included with `#include "tests/"`.
 
 The use of all these separate directories for the unit tests might seem inconvenient, as for example the tests are not "right next to" the part of the code they are testing.
@@ -76,8 +76,25 @@ there is no risk of any build-system wildcards for the library accidentally pick
 
 ### Running tests
 
-You can run the whole testsuite with `make check`, or the tests for a specific component with `make libfoo-tests_RUN`.
-Finer-grained filtering is also possible using the [--gtest_filter](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests) command-line option, or the `GTEST_FILTER` environment variable, e.g. `GTEST_FILTER='ErrorTraceTest.*' make check`.
+You can run the whole testsuite with `meson test` from the Meson build directory, or the tests for a specific component with `meson test nix-store-tests`.
+A environment variables that Google Test accepts are also worth knowing:
+
+1. [`GTEST_FILTER`](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests)
+
+   This is used for finer-grained filtering of which tests to run.
+
+
+2. [`GTEST_BRIEF`](https://google.github.io/googletest/advanced.html#suppressing-test-passes)
+
+   This is used to avoid logging passing tests.
+
+Putting the two together, one might run
+
+```bash
+GTEST_BREIF=1 GTEST_FILTER='ErrorTraceTest.*' meson test nix-expr-tests -v
+```
+
+for short but comprensive output.
 
 ### Characterisation testing { #characaterisation-testing-unit }
 
@@ -86,7 +103,7 @@ See [functional characterisation testing](#characterisation-testing-functional)
 Like with the functional characterisation, `_NIX_TEST_ACCEPT=1` is also used.
 For example:
 ```shell-session
-$ _NIX_TEST_ACCEPT=1 make libstore-tests_RUN
+$ _NIX_TEST_ACCEPT=1 meson test nix-store-tests -v
 ...
 [  SKIPPED ] WorkerProtoTest.string_read
 [  SKIPPED ] WorkerProtoTest.string_write
@@ -114,6 +131,8 @@ On other platforms they wouldn't be run at all.
 The functional tests reside under the `tests/functional` directory and are listed in `tests/functional/local.mk`.
 Each test is a bash script.
 
+Functional tests are run during `installCheck` in the `nix` package build, as well as separately from the build, in VM tests.
+
 ### Running the whole test suite
 
 The whole test suite can be run with:
@@ -162,14 +181,14 @@ ran test tests/functional/${testName}.sh... [PASS]
 or without `make`:
 
 ```shell-session
-$ ./mk/run-test.sh tests/functional/${testName}.sh tests/functional/init.sh
+$ ./mk/run-test.sh tests/functional/${testName}.sh
 ran test tests/functional/${testName}.sh... [PASS]
 ```
 
 To see the complete output, one can also run:
 
 ```shell-session
-$ ./mk/debug-test.sh tests/functional/${testName}.sh tests/functional/init.sh
+$ ./mk/debug-test.sh tests/functional/${testName}.sh
 +(${testName}.sh:1) foo
 output from foo
 +(${testName}.sh:2) bar
@@ -204,7 +223,7 @@ edit it like so:
 Then, running the test with `./mk/debug-test.sh` will drop you into GDB once the script reaches that point:
 
 ```shell-session
-$ ./mk/debug-test.sh tests/functional/${testName}.sh tests/functional/init.sh
+$ ./mk/debug-test.sh tests/functional/${testName}.sh
 ...
 + gdb blash blub
 GNU gdb (GDB) 12.1
@@ -252,13 +271,30 @@ Regressions are caught, and improvements always show up in code review.
 
 To ensure that characterisation testing doesn't make it harder to intentionally change these interfaces, there always must be an easy way to regenerate the expected output, as we do with `_NIX_TEST_ACCEPT=1`.
 
+### Running functional tests on NixOS
+
+We run the functional tests not just in the build, but also in VM tests.
+This helps us ensure that Nix works correctly on NixOS, and environments that have similar characteristics that are hard to reproduce in a build environment.
+
+The recommended way to run these tests during development is:
+
+```shell
+nix build .#hydraJobs.tests.functional_user.quickBuild
+```
+
+The `quickBuild` attribute configures the test to use a `nix` package that's built without integration tests, so that you can iterate on the tests without performing recompilations due to the changed sources for `installCheck`.
+
+Generally, this build is sufficient, but in nightly or CI we also test the attributes `functional_root` and `functional_trusted`, in which the test suite is run with different levels of authorization.
+
 ## Integration tests
 
 The integration tests are defined in the Nix flake under the `hydraJobs.tests` attribute.
 These tests include everything that needs to interact with external services or run Nix in a non-trivial distributed setup.
 Because these tests are expensive and require more than what the standard github-actions setup provides, they only run on the master branch (on <https://hydra.nixos.org/jobset/nix/master>).
 
-You can run them manually with `nix build .#hydraJobs.tests.{testName}` or `nix-build -A hydraJobs.tests.{testName}`
+You can run them manually with `nix build .#hydraJobs.tests.{testName}` or `nix-build -A hydraJobs.tests.{testName}`.
+
+If you are testing a build of `nix` that you haven't compiled yet, you may iterate faster by appending the `quickBuild` attribute: `nix build .#hydraJobs.tests.{testName}.quickBuild`.
 
 ## Installer tests
 
diff --git a/doc/manual/src/glossary.md b/doc/manual/src/glossary.md
index c4d9c2a524c..f65ada63a5c 100644
--- a/doc/manual/src/glossary.md
+++ b/doc/manual/src/glossary.md
@@ -1,5 +1,24 @@
 # Glossary
 
+- [content address]{#gloss-content-address}
+
+  A
+  [*content address*](https://en.wikipedia.org/wiki/Content-addressable_storage)
+  is a secure way to reference immutable data.
+  The reference is calculated directly from the content of the data being referenced, which means the reference is
+  [*tamper proof*](https://en.wikipedia.org/wiki/Tamperproofing)
+  --- variations of the data should always calculate to distinct content addresses.
+
+  For how Nix uses content addresses, see:
+
+    - [Content-Addressing File System Objects](@docroot@/store/file-system-object/content-address.md)
+    - [Content-Addressing Store Objects](@docroot@/store/store-object/content-address.md)
+    - [content-addressed derivation](#gloss-content-addressed-derivation)
+
+  Software Heritage's writing on [*Intrinsic and Extrinsic identifiers*](https://www.softwareheritage.org/2020/07/09/intrinsic-vs-extrinsic-identifiers) is also a good introduction to the value of content-addressing over other referencing schemes.
+
+  Besides content addressing, the Nix store also uses [input addressing](#gloss-input-addressed-store-object).
+
 - [derivation]{#gloss-derivation}
 
   A description of a build task. The result of a derivation is a
@@ -52,10 +71,9 @@
   [`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed)
   attribute set to `true`.
 
-- [fixed-output derivation]{#gloss-fixed-output-derivation}
+- [fixed-output derivation]{#gloss-fixed-output-derivation} (FOD)
 
-  A derivation which includes the
-  [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute.
+  A [derivation] where a cryptographic hash of the [output] is determined in advance using the [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute, and where the [`builder`](@docroot@/language/derivations.md#attr-builder) executable has access to the network.
 
 - [store]{#gloss-store}
 
@@ -118,9 +136,12 @@
 
 - [content-addressed store object]{#gloss-content-addressed-store-object}
 
-  A [store object] whose [store path] is determined by its contents.
+  A [store object] which is [content-addressed](#gloss-content-address),
+  i.e. whose [store path] is determined by its contents.
   This includes derivations, the outputs of [content-addressed derivations](#gloss-content-addressed-derivation), and the outputs of [fixed-output derivations](#gloss-fixed-output-derivation).
 
+  See [Content-Addressing Store Objects](@docroot@/store/store-object/content-address.md) for details.
+
 - [substitute]{#gloss-substitute}
 
   A substitute is a command invocation stored in the [Nix database] that
@@ -215,6 +236,20 @@
 
   [output path]: #gloss-output-path
 
+- [output closure]{#gloss-output-closure}\
+  The [closure] of an [output path]. It only contains what is [reachable] from the output.
+
+- [deriving path]{#gloss-deriving-path}
+
+  Deriving paths are a way to refer to [store objects][store object] that ar not yet [realised][realise].
+  This is necessary because, in general and particularly for [content-addressed derivations][content-addressed derivation], the [output path] of an [output] is not known in advance.
+  There are two forms:
+
+  - *constant*: just a [store path]
+    It can be made [valid][validity] by copying it into the store: from the evaluator, command line interface or another store.
+
+  - *output*: a pair of a [store path] to a [derivation] and an [output] name.
+
 - [deriver]{#gloss-deriver}
 
   The [store derivation] that produced an [output path].
@@ -252,13 +287,15 @@
 
   See [installables](./command-ref/new-cli/nix.md#installables) for [`nix` commands](./command-ref/new-cli/nix.md) (experimental) for details.
 
-- [NAR]{#gloss-nar}
+- [Nix Archive (NAR)]{#gloss-nar}
 
   A *N*ix *AR*chive. This is a serialisation of a path in the Nix
   store. It can contain regular files, directories and symbolic
   links.  NARs are generated and unpacked using `nix-store --dump`
   and `nix-store --restore`.
 
+  See [Nix Archive](store/file-system-object/content-address.html#serial-nix-archive) for details.
+
 - [`∅`]{#gloss-emtpy-set}
 
   The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile.
@@ -275,7 +312,7 @@
 
 - [package attribute set]{#package-attribute-set}
 
-  An [attribute set](@docroot@/language/values.md#attribute-set) containing the attribute `type = "derivation";` (derivation for historical reasons), as well as other attributes, such as
+  An [attribute set](@docroot@/language/types.md#attribute-set) containing the attribute `type = "derivation";` (derivation for historical reasons), as well as other attributes, such as
   - attributes that refer to the files of a [package], typically in the form of [derivation outputs](#output),
   - attributes that declare something about how the package is supposed to be installed or used,
   - other metadata or arbitrary attributes.
@@ -288,9 +325,28 @@
 
   See [String interpolation](./language/string-interpolation.md) for details.
 
-  [string]: ./language/values.md#type-string
-  [path]: ./language/values.md#type-path
-  [attribute name]: ./language/values.md#attribute-set
+  [string]: ./language/types.md#type-string
+  [path]: ./language/types.md#type-path
+  [attribute name]: ./language/types.md#attribute-set
+
+- [base directory]{#gloss-base-directory}
+
+  The location from which relative paths are resolved.
+
+  - For expressions in a file, the base directory is the directory containing that file.
+    This is analogous to the directory of a [base URL](https://datatracker.ietf.org/doc/html/rfc1808#section-3.3).
+    <!-- which is sufficient for resolving non-empty URLs -->
+
+  <!--
+    The wording here may look awkward, but it's for these reasons:
+      * "with --expr": it's a flag, and not an option with an accompanying value
+      * "written in": the expression itself must be written as an argument,
+        whereas the more natural "passed as an argument" allows an interpretation
+        where the expression could be passed by file name.
+    -->
+  - For expressions written in command line arguments with [`--expr`](@docroot@/command-ref/opt-common.html#opt-expr), the base directory is the current working directory.
+
+  [base directory]: #gloss-base-directory
 
 - [experimental feature]{#gloss-experimental-feature}
 
diff --git a/doc/manual/src/installation/env-variables.md b/doc/manual/src/installation/env-variables.md
index db98f52ff6e..0350904211a 100644
--- a/doc/manual/src/installation/env-variables.md
+++ b/doc/manual/src/installation/env-variables.md
@@ -53,7 +53,8 @@ ssl-cert-file = /etc/ssl/my-certificate-bundle.crt
 
 The Nix installer has special handling for these proxy-related
 environment variables: `http_proxy`, `https_proxy`, `ftp_proxy`,
-`no_proxy`, `HTTP_PROXY`, `HTTPS_PROXY`, `FTP_PROXY`, `NO_PROXY`.
+`all_proxy`, `no_proxy`, `HTTP_PROXY`, `HTTPS_PROXY`, `FTP_PROXY`,
+`ALL_PROXY`, `NO_PROXY`.
 
 If any of these variables are set when running the Nix installer, then
 the installer will create an override file at
diff --git a/doc/manual/src/installation/installing-binary.md b/doc/manual/src/installation/installing-binary.md
index 0dc9891598a..385008d8c16 100644
--- a/doc/manual/src/installation/installing-binary.md
+++ b/doc/manual/src/installation/installing-binary.md
@@ -50,7 +50,7 @@ Supported systems:
 To explicitly instruct the installer to perform a multi-user installation on your system:
 
 ```console
-$ curl -L https://nixos.org/nix/install | sh -s -- --daemon
+$ bash <(curl -L https://nixos.org/nix/install) --daemon
 ```
 
 You can run this under your usual user account or `root`.
@@ -61,7 +61,7 @@ The script will invoke `sudo` as needed.
 To explicitly select a single-user installation on your system:
 
 ```console
-$ curl -L https://nixos.org/nix/install | sh -s -- --no-daemon
+$ bash <(curl -L https://nixos.org/nix/install) --no-daemon
 ```
 
 In a single-user installation, `/nix` is owned by the invoking user.
diff --git a/doc/manual/src/installation/uninstall.md b/doc/manual/src/installation/uninstall.md
index 9ead5e53c5c..590327fea1b 100644
--- a/doc/manual/src/installation/uninstall.md
+++ b/doc/manual/src/installation/uninstall.md
@@ -1,16 +1,8 @@
 # Uninstalling Nix
 
-## Single User
-
-If you have a [single-user installation](./installing-binary.md#single-user-installation) of Nix, uninstall it by running:
-
-```console
-$ rm -rf /nix
-```
-
 ## Multi User
 
-Removing a [multi-user installation](./installing-binary.md#multi-user-installation) of Nix is more involved, and depends on the operating system.
+Removing a [multi-user installation](./installing-binary.md#multi-user-installation) depends on the operating system.
 
 ### Linux
 
@@ -51,7 +43,15 @@ which you may remove.
 
 ### macOS
 
-1. Edit `/etc/zshrc`, `/etc/bashrc`, and `/etc/bash.bashrc` to remove the lines sourcing `nix-daemon.sh`, which should look like this:
+1. If system-wide shell initialisation files haven't been altered since installing Nix, use the backups made by the installer:
+
+   ```console
+   sudo mv /etc/zshrc.backup-before-nix /etc/zshrc
+   sudo mv /etc/bashrc.backup-before-nix /etc/bashrc
+   sudo mv /etc/bash.bashrc.backup-before-nix /etc/bash.bashrc
+   ```
+
+   Otherwise, edit `/etc/zshrc`, `/etc/bashrc`, and `/etc/bash.bashrc` to remove the lines sourcing `nix-daemon.sh`, which should look like this:
 
    ```bash
    # Nix
@@ -61,18 +61,6 @@ which you may remove.
    # End Nix
    ```
 
-   If these files haven't been altered since installing Nix you can simply put
-   the backups back in place:
-
-   ```console
-   sudo mv /etc/zshrc.backup-before-nix /etc/zshrc
-   sudo mv /etc/bashrc.backup-before-nix /etc/bashrc
-   sudo mv /etc/bash.bashrc.backup-before-nix /etc/bash.bashrc
-   ```
-
-   This will stop shells from sourcing the file and bringing everything you
-   installed using Nix in scope.
-
 2. Stop and remove the Nix daemon services:
 
    ```console
@@ -82,8 +70,7 @@ which you may remove.
    sudo rm /Library/LaunchDaemons/org.nixos.darwin-store.plist
    ```
 
-   This stops the Nix daemon and prevents it from being started next time you
-   boot the system.
+   This stops the Nix daemon and prevents it from being started next time you boot the system.
 
 3. Remove the `nixbld` group and the `_nixbuildN` users:
 
@@ -94,25 +81,42 @@ which you may remove.
 
    This will remove all the build users that no longer serve a purpose.
 
-4. Edit fstab using `sudo vifs` to remove the line mounting the Nix Store
-   volume on `/nix`, which looks like
-   `UUID=<uuid> /nix apfs rw,noauto,nobrowse,suid,owners` or
-   `LABEL=Nix\040Store /nix apfs rw,nobrowse`. This will prevent automatic
-   mounting of the Nix Store volume.
+4. Edit fstab using `sudo vifs` to remove the line mounting the Nix Store volume on `/nix`, which looks like
+
+   ```
+   UUID=<uuid> /nix apfs rw,noauto,nobrowse,suid,owners
+   ```
+   or
+
+   ```
+   LABEL=Nix\040Store /nix apfs rw,nobrowse
+   ```
+
+   by setting the cursor on the respective line using the error keys, and pressing `dd`, and then `:wq` to save the file.
 
-5. Edit `/etc/synthetic.conf` to remove the `nix` line. If this is the only
-   line in the file you can remove it entirely, `sudo rm /etc/synthetic.conf`.
-   This will prevent the creation of the empty `/nix` directory to provide a
-   mountpoint for the Nix Store volume.
+   This will prevent automatic mounting of the Nix Store volume.
 
-6. Remove the files Nix added to your system:
+5. Edit `/etc/synthetic.conf` to remove the `nix` line.
+   If this is the only line in the file you can remove it entirely:
+
+   ```bash
+   if [ -f /etc/synthetic.conf ]; then
+     if [ "$(cat /etc/synthetic.conf)" = "nix" ]; then
+       sudo rm /etc/synthetic.conf
+     else
+       sudo vi /etc/synthetic.conf
+     fi
+   fi
+   ```
+
+   This will prevent the creation of the empty `/nix` directory.
+
+6. Remove the files Nix added to your system, except for the store:
 
    ```console
    sudo rm -rf /etc/nix /var/root/.nix-profile /var/root/.nix-defexpr /var/root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
    ```
 
-   This gets rid of any data Nix may have created except for the store which is
-   removed next.
 
 7. Remove the Nix Store volume:
 
@@ -120,29 +124,32 @@ which you may remove.
    sudo diskutil apfs deleteVolume /nix
    ```
 
-   This will remove the Nix Store volume and everything that was added to the
-   store.
+   This will remove the Nix Store volume and everything that was added to the store.
 
-   If the output indicates that the command couldn't remove the volume, you should
-   make sure you don't have an _unmounted_ Nix Store volume. Look for a
-   "Nix Store" volume in the output of the following command:
+   If the output indicates that the command couldn't remove the volume, you should make sure you don't have an _unmounted_ Nix Store volume.
+   Look for a "Nix Store" volume in the output of the following command:
 
    ```console
    diskutil list
    ```
 
-   If you _do_ see a "Nix Store" volume, delete it by re-running the diskutil
-   deleteVolume command, but replace `/nix` with the store volume's `diskXsY`
-   identifier.
+   If you _do_ find a "Nix Store" volume, delete it by running `diskutil deleteVolume` with the store volume's `diskXsY` identifier.
 
 > **Note**
 >
-> After you complete the steps here, you will still have an empty `/nix`
-> directory. This is an expected sign of a successful uninstall. The empty
-> `/nix` directory will disappear the next time you reboot.
+> After you complete the steps here, you will still have an empty `/nix` directory.
+> This is an expected sign of a successful uninstall.
+> The empty `/nix` directory will disappear the next time you reboot.
 >
-> You do not have to reboot to finish uninstalling Nix. The uninstall is
-> complete. macOS (Catalina+) directly controls root directories and its
-> read-only root will prevent you from manually deleting the empty `/nix`
-> mountpoint.
+> You do not have to reboot to finish uninstalling Nix.
+> The uninstall is complete.
+> macOS (Catalina+) directly controls root directories, and its read-only root will prevent you from manually deleting the empty `/nix` mountpoint.
 
+## Single User
+
+To remove a [single-user installation](./installing-binary.md#single-user-installation) of Nix, run:
+
+```console
+$ rm -rf /nix ~/.nix-channels ~/.nix-defexpr ~/.nix-profile
+```
+You might also want to manually remove references to Nix from your `~/.profile`.
diff --git a/doc/manual/src/language/advanced-attributes.md b/doc/manual/src/language/advanced-attributes.md
index 1fcc5a95ba2..e916c736040 100644
--- a/doc/manual/src/language/advanced-attributes.md
+++ b/doc/manual/src/language/advanced-attributes.md
@@ -120,12 +120,11 @@ Derivations can declare some infrequently used optional attributes.
     configuration setting.
 
   - [`outputHash`]{#adv-attr-outputHash}; [`outputHashAlgo`]{#adv-attr-outputHashAlgo}; [`outputHashMode`]{#adv-attr-outputHashMode}\
-    These attributes declare that the derivation is a so-called
-    *fixed-output derivation*, which means that a cryptographic hash of
-    the output is already known in advance. When the build of a
-    fixed-output derivation finishes, Nix computes the cryptographic
-    hash of the output and compares it to the hash declared with these
-    attributes. If there is a mismatch, the build fails.
+    These attributes declare that the derivation is a so-called *fixed-output derivation* (FOD), which means that a cryptographic hash of the output is already known in advance.
+
+    As opposed to regular derivations, the [`builder`] executable of a fixed-output derivation has access to the network.
+    Nix computes a cryptographic hash of its output and compares that to the hash declared with these attributes.
+    If there is a mismatch, the derivation fails.
 
     The rationale for fixed-output derivations is derivations such as
     those produced by the `fetchurl` function. This function downloads a
@@ -197,33 +196,40 @@ Derivations can declare some infrequently used optional attributes.
     `outputHashAlgo` can only be `null` when `outputHash` follows the SRI format.
 
     The `outputHashMode` attribute determines how the hash is computed.
-    It must be one of the following two values:
+    It must be one of the following values:
 
-      - `"flat"`\
-        The output must be a non-executable regular file. If it isn’t,
-        the build fails. The hash is simply computed over the contents
-        of that file (so it’s equal to what Unix commands like
-        `sha256sum` or `sha1sum` produce).
+      - [`"flat"`](@docroot@/store/store-object/content-address.md#method-flat)
 
         This is the default.
 
-      - `"recursive"` or `"nar"`\
-        The hash is computed over the [NAR archive](@docroot@/glossary.md#gloss-nar) dump of the output
-        (i.e., the result of [`nix-store --dump`](@docroot@/command-ref/nix-store/dump.md)). In
-        this case, the output can be anything, including a directory
-        tree.
+      - [`"recursive"` or `"nar"`](@docroot@/store/store-object/content-address.md#method-nix-archive)
+
+        > **Compatibility**
+        >
+        > `"recursive"` is the traditional way of indicating this,
+        > and is supported since 2005 (virtually the entire history of Nix).
+        > `"nar"` is more clear, and consistent with other parts of Nix (such as the CLI),
+        > however support for it is only added in Nix version 2.21.
+
+      - [`"text"`](@docroot@/store/store-object/content-address.md#method-text)
 
-    `"recursive"` is the traditional way of indicating this,
-    and is supported since 2005 (virtually the entire history of Nix).
-    `"nar"` is more clear, and consistent with other parts of Nix (such as the CLI),
-    however support for it is only added in Nix version 2.21.
+        > **Warning**
+        >
+        > The use of this method for derivation outputs is part of the [`dynamic-derivations`][xp-feature-dynamic-derivations] experimental feature.
+
+      - [`"git"`](@docroot@/store/store-object/content-address.md#method-git)
+
+        > **Warning**
+        >
+        > This method is part of the [`git-hashing`][xp-feature-git-hashing] experimental feature.
 
   - [`__contentAddressed`]{#adv-attr-__contentAddressed}
+
     > **Warning**
     > This attribute is part of an [experimental feature](@docroot@/contributing/experimental-features.md).
     >
     > To use this attribute, you must enable the
-    > [`ca-derivations`](@docroot@/contributing/experimental-features.md#xp-feature-ca-derivations) experimental feature.
+    > [`ca-derivations`][xp-feature-ca-derivations] experimental feature.
     > For example, in [nix.conf](../command-ref/conf-file.md) you could add:
     >
     > ```
@@ -272,7 +278,9 @@ Derivations can declare some infrequently used optional attributes.
 
     > **Note**
     >
-    > If set to `false`, the [`builder`](./derivations.md#attr-builder) should be able to run on the system type specified in the [`system` attribute](./derivations.md#attr-system), since the derivation cannot be substituted.
+    > If set to `false`, the [`builder`] should be able to run on the system type specified in the [`system` attribute](./derivations.md#attr-system), since the derivation cannot be substituted.
+
+    [`builder`]: ./derivations.md#attr-builder
 
   - [`__structuredAttrs`]{#adv-attr-structuredAttrs}\
     If the special attribute `__structuredAttrs` is set to `true`, the other derivation
@@ -294,6 +302,12 @@ Derivations can declare some infrequently used optional attributes.
     (associative) arrays. For example, the attribute `hardening.format = true`
     ends up as the Bash associative array element `${hardening[format]}`.
 
+    > **Warning**
+    >
+    > If set to `true`, other advanced attributes such as [`allowedReferences`](#adv-attr-allowedReferences), [`allowedReferences`](#adv-attr-allowedReferences), [`allowedRequisites`](#adv-attr-allowedRequisites),
+    [`disallowedReferences`](#adv-attr-disallowedReferences) and [`disallowedRequisites`](#adv-attr-disallowedRequisites), maxSize, and maxClosureSize.
+    will have no effect.
+
   - [`outputChecks`]{#adv-attr-outputChecks}\
     When using [structured attributes](#adv-attr-structuredAttrs), the `outputChecks`
     attribute allows defining checks per-output.
@@ -303,7 +317,7 @@ Derivations can declare some infrequently used optional attributes.
     [`disallowedReferences`](#adv-attr-disallowedReferences) and [`disallowedRequisites`](#adv-attr-disallowedRequisites),
     the following attributes are available:
 
-    - `maxSize` defines the maximum size of the resulting [store object](@docroot@/glossary.md#gloss-store-object).
+    - `maxSize` defines the maximum size of the resulting [store object](@docroot@/store/store-object.md).
     - `maxClosureSize` defines the maximum size of the output's closure.
     - `ignoreSelfRefs` controls whether self-references should be considered when
       checking for allowed references/requisites.
@@ -355,3 +369,7 @@ Derivations can declare some infrequently used optional attributes.
   ```
 
   ensures that the derivation can only be built on a machine with the `kvm` feature.
+
+[xp-feature-ca-derivations]: @docroot@/contributing/experimental-features.md#xp-feature-ca-derivations
+[xp-feature-dynamic-derivations]: @docroot@/contributing/experimental-features.md#xp-feature-dynamic-derivations
+[xp-feature-git-hashing]: @docroot@/contributing/experimental-features.md#xp-feature-git-hashing
diff --git a/doc/manual/src/language/builtin-constants-prefix.md b/doc/manual/src/language/builtin-constants-prefix.md
deleted file mode 100644
index 50f43006df4..00000000000
--- a/doc/manual/src/language/builtin-constants-prefix.md
+++ /dev/null
@@ -1,5 +0,0 @@
-# Built-in Constants
-
-These constants are built into the Nix language evaluator:
-
-<dl>
diff --git a/doc/manual/src/language/builtin-constants-suffix.md b/doc/manual/src/language/builtin-constants-suffix.md
deleted file mode 100644
index a74db28579e..00000000000
--- a/doc/manual/src/language/builtin-constants-suffix.md
+++ /dev/null
@@ -1 +0,0 @@
-</dl>
diff --git a/doc/manual/src/language/builtins-prefix.md b/doc/manual/src/language/builtins-prefix.md
index 7b2321466dd..fb983bb7f3c 100644
--- a/doc/manual/src/language/builtins-prefix.md
+++ b/doc/manual/src/language/builtins-prefix.md
@@ -1,9 +1,11 @@
-# Built-in Functions
+# Built-ins
 
-This section lists the functions built into the Nix language evaluator.
-All built-in functions are available through the global [`builtins`](./builtin-constants.md#builtins-builtins) constant.
+This section lists the values and functions built into the Nix language evaluator.
+All built-ins are available through the global [`builtins`](#builtins-builtins) constant.
 
-For convenience, some built-ins can be accessed directly:
+Some built-ins are also exposed directly in the global scope:
+
+<!-- TODO(@rhendric, #10970): this list is incomplete -->
 
 - [`derivation`](#builtins-derivation)
 - [`import`](#builtins-import)
diff --git a/doc/manual/src/language/constructs.md b/doc/manual/src/language/constructs.md
deleted file mode 100644
index a82ec5960a8..00000000000
--- a/doc/manual/src/language/constructs.md
+++ /dev/null
@@ -1,408 +0,0 @@
-# Language Constructs
-
-## Recursive sets
-
-Recursive sets are like normal [attribute sets](./values.md#attribute-set), but the attributes can refer to each other.
-
-> *rec-attrset* = `rec {` [ *name* `=` *expr* `;` `]`... `}`
-
-Example:
-
-```nix
-rec {
-  x = y;
-  y = 123;
-}.x
-```
-
-This evaluates to `123`.
-
-Note that without `rec` the binding `x = y;` would
-refer to the variable `y` in the surrounding scope, if one exists, and
-would be invalid if no such variable exists. That is, in a normal
-(non-recursive) set, attributes are not added to the lexical scope; in a
-recursive set, they are.
-
-Recursive sets of course introduce the danger of infinite recursion. For
-example, the expression
-
-```nix
-rec {
-  x = y;
-  y = x;
-}.x
-```
-
-will crash with an `infinite recursion encountered` error message.
-
-## Let-expressions
-
-A let-expression allows you to define local variables for an expression.
-
-> *let-in* = `let` [ *identifier* = *expr* ]... `in` *expr*
-
-Example:
-
-```nix
-let
-  x = "foo";
-  y = "bar";
-in x + y
-```
-
-This evaluates to `"foobar"`.
-
-## Inheriting attributes
-
-When defining an [attribute set](./values.md#attribute-set) or in a [let-expression](#let-expressions) it is often convenient to copy variables from the surrounding lexical scope (e.g., when you want to propagate attributes).
-This can be shortened using the `inherit` keyword.
-
-Example:
-
-```nix
-let x = 123; in
-{
-  inherit x;
-  y = 456;
-}
-```
-
-is equivalent to
-
-```nix
-let x = 123; in
-{
-  x = x;
-  y = 456;
-}
-```
-
-and both evaluate to `{ x = 123; y = 456; }`.
-
-> **Note**
->
-> This works because `x` is added to the lexical scope by the `let` construct.
-
-It is also possible to inherit attributes from another attribute set.
-
-Example:
-
-In this fragment from `all-packages.nix`,
-
-```nix
-graphviz = (import ../tools/graphics/graphviz) {
-  inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
-  inherit (xorg) libXaw;
-};
-
-xorg = {
-  libX11 = ...;
-  libXaw = ...;
-  ...
-}
-
-libpng = ...;
-libjpg = ...;
-...
-```
-
-the set used in the function call to the function defined in
-`../tools/graphics/graphviz` inherits a number of variables from the
-surrounding scope (`fetchurl` ... `yacc`), but also inherits `libXaw`
-(the X Athena Widgets) from the `xorg` set.
-
-Summarizing the fragment
-
-```nix
-...
-inherit x y z;
-inherit (src-set) a b c;
-...
-```
-
-is equivalent to
-
-```nix
-...
-x = x; y = y; z = z;
-a = src-set.a; b = src-set.b; c = src-set.c;
-...
-```
-
-when used while defining local variables in a let-expression or while
-defining a set.
-
-In a `let` expression, `inherit` can be used to selectively bring specific attributes of a set into scope. For example
-
-
-```nix
-let
-  x = { a = 1; b = 2; };
-  inherit (builtins) attrNames;
-in
-{
-  names = attrNames x;
-}
-```
-
-is equivalent to
-
-```nix
-let
-  x = { a = 1; b = 2; };
-in
-{
-  names = builtins.attrNames x;
-}
-```
-
-both evaluate to `{ names = [ "a" "b" ]; }`.
-
-## Functions
-
-Functions have the following form:
-
-```nix
-pattern: body
-```
-
-The pattern specifies what the argument of the function must look like,
-and binds variables in the body to (parts of) the argument. There are
-three kinds of patterns:
-
-  - If a pattern is a single identifier, then the function matches any
-    argument. Example:
-
-    ```nix
-    let negate = x: !x;
-        concat = x: y: x + y;
-    in if negate true then concat "foo" "bar" else ""
-    ```
-
-    Note that `concat` is a function that takes one argument and returns
-    a function that takes another argument. This allows partial
-    parameterisation (i.e., only filling some of the arguments of a
-    function); e.g.,
-
-    ```nix
-    map (concat "foo") [ "bar" "bla" "abc" ]
-    ```
-
-    evaluates to `[ "foobar" "foobla" "fooabc" ]`.
-
-  - A *set pattern* of the form `{ name1, name2, …, nameN }` matches a
-    set containing the listed attributes, and binds the values of those
-    attributes to variables in the function body. For example, the
-    function
-
-    ```nix
-    { x, y, z }: z + y + x
-    ```
-
-    can only be called with a set containing exactly the attributes `x`,
-    `y` and `z`. No other attributes are allowed. If you want to allow
-    additional arguments, you can use an ellipsis (`...`):
-
-    ```nix
-    { x, y, z, ... }: z + y + x
-    ```
-
-    This works on any set that contains at least the three named
-    attributes.
-
-    It is possible to provide *default values* for attributes, in
-    which case they are allowed to be missing. A default value is
-    specified by writing `name ?  e`, where *e* is an arbitrary
-    expression. For example,
-
-    ```nix
-    { x, y ? "foo", z ? "bar" }: z + y + x
-    ```
-
-    specifies a function that only requires an attribute named `x`, but
-    optionally accepts `y` and `z`.
-
-  - An `@`-pattern provides a means of referring to the whole value
-    being matched:
-
-    ```nix
-    args@{ x, y, z, ... }: z + y + x + args.a
-    ```
-
-    but can also be written as:
-
-    ```nix
-    { x, y, z, ... } @ args: z + y + x + args.a
-    ```
-
-    Here `args` is bound to the argument *as passed*, which is further
-    matched against the pattern `{ x, y, z, ... }`.
-    The `@`-pattern makes mainly sense with an ellipsis(`...`) as
-    you can access attribute names as `a`, using `args.a`, which was
-    given as an additional attribute to the function.
-
-    > **Warning**
-    >
-    > `args@` binds the name `args` to the attribute set that is passed to the function.
-    > In particular, `args` does *not* include any default values specified with `?` in the function's set pattern.
-    >
-    > For instance
-    >
-    > ```nix
-    > let
-    >   f = args@{ a ? 23, ... }: [ a args ];
-    > in
-    >   f {}
-    > ```
-    >
-    > is equivalent to
-    >
-    > ```nix
-    > let
-    >   f = args @ { ... }: [ (args.a or 23) args ];
-    > in
-    >   f {}
-    > ```
-    >
-    > and both expressions will evaluate to:
-    >
-    > ```nix
-    > [ 23 {} ]
-    > ```
-
-Note that functions do not have names. If you want to give them a name,
-you can bind them to an attribute, e.g.,
-
-```nix
-let concat = { x, y }: x + y;
-in concat { x = "foo"; y = "bar"; }
-```
-
-## Conditionals
-
-Conditionals look like this:
-
-```nix
-if e1 then e2 else e3
-```
-
-where *e1* is an expression that should evaluate to a Boolean value
-(`true` or `false`).
-
-## Assertions
-
-Assertions are generally used to check that certain requirements on or
-between features and dependencies hold. They look like this:
-
-```nix
-assert e1; e2
-```
-
-where *e1* is an expression that should evaluate to a Boolean value. If
-it evaluates to `true`, *e2* is returned; otherwise expression
-evaluation is aborted and a backtrace is printed.
-
-Here is a Nix expression for the Subversion package that shows how
-assertions can be used:.
-
-```nix
-{ localServer ? false
-, httpServer ? false
-, sslSupport ? false
-, pythonBindings ? false
-, javaSwigBindings ? false
-, javahlBindings ? false
-, stdenv, fetchurl
-, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null
-}:
-
-assert localServer -> db4 != null; ①
-assert httpServer -> httpd != null && httpd.expat == expat; ②
-assert sslSupport -> openssl != null && (httpServer -> httpd.openssl == openssl); ③
-assert pythonBindings -> swig != null && swig.pythonSupport;
-assert javaSwigBindings -> swig != null && swig.javaSupport;
-assert javahlBindings -> j2sdk != null;
-
-stdenv.mkDerivation {
-  name = "subversion-1.1.1";
-  ...
-  openssl = if sslSupport then openssl else null; ④
-  ...
-}
-```
-
-The points of interest are:
-
-1.  This assertion states that if Subversion is to have support for
-    local repositories, then Berkeley DB is needed. So if the Subversion
-    function is called with the `localServer` argument set to `true` but
-    the `db4` argument set to `null`, then the evaluation fails.
-
-    Note that `->` is the [logical
-    implication](https://en.wikipedia.org/wiki/Truth_table#Logical_implication)
-    Boolean operation.
-
-2.  This is a more subtle condition: if Subversion is built with Apache
-    (`httpServer`) support, then the Expat library (an XML library) used
-    by Subversion should be same as the one used by Apache. This is
-    because in this configuration Subversion code ends up being linked
-    with Apache code, and if the Expat libraries do not match, a build-
-    or runtime link error or incompatibility might occur.
-
-3.  This assertion says that in order for Subversion to have SSL support
-    (so that it can access `https` URLs), an OpenSSL library must be
-    passed. Additionally, it says that *if* Apache support is enabled,
-    then Apache's OpenSSL should match Subversion's. (Note that if
-    Apache support is not enabled, we don't care about Apache's
-    OpenSSL.)
-
-4.  The conditional here is not really related to assertions, but is
-    worth pointing out: it ensures that if SSL support is disabled, then
-    the Subversion derivation is not dependent on OpenSSL, even if a
-    non-`null` value was passed. This prevents an unnecessary rebuild of
-    Subversion if OpenSSL changes.
-
-## With-expressions
-
-A *with-expression*,
-
-```nix
-with e1; e2
-```
-
-introduces the set *e1* into the lexical scope of the expression *e2*.
-For instance,
-
-```nix
-let as = { x = "foo"; y = "bar"; };
-in with as; x + y
-```
-
-evaluates to `"foobar"` since the `with` adds the `x` and `y` attributes
-of `as` to the lexical scope in the expression `x + y`. The most common
-use of `with` is in conjunction with the `import` function. E.g.,
-
-```nix
-with (import ./definitions.nix); ...
-```
-
-makes all attributes defined in the file `definitions.nix` available as
-if they were defined locally in a `let`-expression.
-
-The bindings introduced by `with` do not shadow bindings introduced by
-other means, e.g.
-
-```nix
-let a = 3; in with { a = 1; }; let a = 4; in with { a = 2; }; ...
-```
-
-establishes the same scope as
-
-```nix
-let a = 1; in let a = 2; in let a = 3; in let a = 4; in ...
-```
-
-## Comments
-
-Comments can be single-line, started with a `#` character, or
-inline/multi-line, enclosed within `/* ... */`.
diff --git a/doc/manual/src/language/constructs/lookup-path.md b/doc/manual/src/language/constructs/lookup-path.md
index e87d2922bd3..11b9fe88c2a 100644
--- a/doc/manual/src/language/constructs/lookup-path.md
+++ b/doc/manual/src/language/constructs/lookup-path.md
@@ -4,9 +4,9 @@
 >
 > *lookup-path* = `<` *identifier* [ `/` *identifier* ]... `>`
 
-A lookup path is an identifier with an optional path suffix that resolves to a [path value](@docroot@/language/values.md#type-path) if the identifier matches a search path entry.
+A lookup path is an identifier with an optional path suffix that resolves to a [path value](@docroot@/language/types.md#type-path) if the identifier matches a search path entry.
 
-The value of a lookup path is determined by [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath).
+The value of a lookup path is determined by [`builtins.nixPath`](@docroot@/language/builtins.md#builtins-nixPath).
 
 See [`builtins.findFile`](@docroot@/language/builtins.md#builtins-findFile) for details on lookup path resolution.
 
diff --git a/doc/manual/src/language/derivations.md b/doc/manual/src/language/derivations.md
index 75f824a342b..8e3f0f79174 100644
--- a/doc/manual/src/language/derivations.md
+++ b/doc/manual/src/language/derivations.md
@@ -12,12 +12,12 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
 
 ### Required
 
-- [`name`]{#attr-name} ([String](@docroot@/language/values.md#type-string))
+- [`name`]{#attr-name} ([String](@docroot@/language/types.md#type-string))
 
   A symbolic name for the derivation.
   It is added to the [store path] of the corresponding [store derivation] as well as to its [output paths](@docroot@/glossary.md#gloss-output-path).
 
-  [store path]: @docroot@/glossary.md#gloss-store-path
+  [store path]: @docroot@/store/store-path.md
 
   > **Example**
   >
@@ -31,7 +31,7 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
   > The store derivation's path will be `/nix/store/<hash>-hello.drv`.
   > The [output](#attr-outputs) paths will be of the form `/nix/store/<hash>-hello[-<output>]`
 
-- [`system`]{#attr-system} ([String](@docroot@/language/values.md#type-string))
+- [`system`]{#attr-system} ([String](@docroot@/language/types.md#type-string))
 
   The system type on which the [`builder`](#attr-builder) executable is meant to be run.
 
@@ -64,9 +64,9 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
   > }
   > ```
   >
-  > [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem) has the value of the [`system` configuration option], and defaults to the system type of the current Nix installation.
+  > [`builtins.currentSystem`](@docroot@/language/builtins.md#builtins-currentSystem) has the value of the [`system` configuration option], and defaults to the system type of the current Nix installation.
 
-- [`builder`]{#attr-builder} ([Path](@docroot@/language/values.md#type-path) | [String](@docroot@/language/values.md#type-string))
+- [`builder`]{#attr-builder} ([Path](@docroot@/language/types.md#type-path) | [String](@docroot@/language/types.md#type-string))
 
   Path to an executable that will perform the build.
 
@@ -113,7 +113,7 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
 
 ### Optional
 
-- [`args`]{#attr-args} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string))
+- [`args`]{#attr-args} ([List](@docroot@/language/types.md#list) of [String](@docroot@/language/types.md#type-string))
 
   Default: `[ ]`
 
@@ -132,7 +132,7 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
   > };
   > ```
 
-- [`outputs`]{#attr-outputs} ([List](@docroot@/language/values.md#list) of [String](@docroot@/language/values.md#type-string))
+- [`outputs`]{#attr-outputs} ([List](@docroot@/language/types.md#list) of [String](@docroot@/language/types.md#type-string))
 
   Default: `[ "out" ]`
 
@@ -141,7 +141,7 @@ It outputs an attribute set, and produces a [store derivation] as a side effect
 
   By default, a derivation produces a single output called `out`.
   However, derivations can produce multiple outputs.
-  This allows the associated [store objects](@docroot@/glossary.md#gloss-store-object) and their [closures](@docroot@/glossary.md#gloss-closure) to be copied or garbage-collected separately.
+  This allows the associated [store objects](@docroot@/store/store-object.md) and their [closures](@docroot@/glossary.md#gloss-closure) to be copied or garbage-collected separately.
 
   > **Example**
   >
diff --git a/doc/manual/src/language/import-from-derivation.md b/doc/manual/src/language/import-from-derivation.md
index fb12ba51a8d..e901f5bcf5b 100644
--- a/doc/manual/src/language/import-from-derivation.md
+++ b/doc/manual/src/language/import-from-derivation.md
@@ -2,9 +2,9 @@
 
 The value of a Nix expression can depend on the contents of a [store object].
 
-[store object]: @docroot@/glossary.md#gloss-store-object
+[store object]: @docroot@/store/store-object.md
 
-Passing an expression `expr` that evaluates to a [store path](@docroot@/glossary.md#gloss-store-path) to any built-in function which reads from the filesystem constitutes Import From Derivation (IFD):
+Passing an expression `expr` that evaluates to a [store path](@docroot@/store/store-path.md) to any built-in function which reads from the filesystem constitutes Import From Derivation (IFD):
 
 - [`import`](./builtins.md#builtins-import)` expr`
 - [`builtins.readFile`](./builtins.md#builtins-readFile)` expr`
diff --git a/doc/manual/src/language/index.md b/doc/manual/src/language/index.md
index 650412f1b5d..2bfdbb8a0c6 100644
--- a/doc/manual/src/language/index.md
+++ b/doc/manual/src/language/index.md
@@ -53,7 +53,7 @@ This is an incomplete overview of language features, by example.
   <td>
 
 
-   *Basic values*
+   *Basic values ([primitives](@docroot@/language/types.md#primitives))*
 
 
   </td>
@@ -71,7 +71,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A string
+   A [string](@docroot@/language/types.md#type-string)
 
   </td>
  </tr>
@@ -94,6 +94,18 @@ This is an incomplete overview of language features, by example.
 
   </td>
  </tr>
+ <tr>
+  <td>
+
+   `# Explanation`
+
+  </td>
+  <td>
+
+   A [comment](@docroot@/language/syntax.md#comments).
+
+  </td>
+ </tr>
  <tr>
   <td>
 
@@ -106,7 +118,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   String interpolation (expands to `"hello world"`, `"1 2 3"`, `"/nix/store/<hash>-bash-<version>/bin/sh"`)
+   [String interpolation](@docroot@/language/string-interpolation.md) (expands to `"hello world"`, `"1 2 3"`, `"/nix/store/<hash>-bash-<version>/bin/sh"`)
 
   </td>
  </tr>
@@ -118,7 +130,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Booleans
+   [Booleans](@docroot@/language/types.md#type-boolean)
 
   </td>
  </tr>
@@ -130,7 +142,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Null value
+   [Null](@docroot@/language/types.md#type-null) value
 
   </td>
  </tr>
@@ -142,7 +154,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   An integer
+   An [integer](@docroot@/language/types.md#type-int)
 
   </td>
  </tr>
@@ -154,7 +166,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A floating point number
+   A [floating point number](@docroot@/language/types.md#type-float)
 
   </td>
  </tr>
@@ -166,7 +178,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   An absolute path
+   An absolute [path](@docroot@/language/types.md#type-path)
 
   </td>
  </tr>
@@ -178,7 +190,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A path relative to the file containing this Nix expression
+   A [path](@docroot@/language/types.md#type-path) relative to the file containing this Nix expression
 
   </td>
  </tr>
@@ -190,7 +202,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A home path. Evaluates to the `"<user's home directory>/.config"`.
+   A home [path](@docroot@/language/types.md#type-path). Evaluates to the `"<user's home directory>/.config"`.
 
   </td>
  </tr>
@@ -202,7 +214,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Search path for Nix files. Value determined by [`$NIX_PATH` environment variable](../command-ref/env-common.md#env-NIX_PATH).
+   A [lookup path](@docroot@/language/constructs/lookup-path.md) for Nix files. Value determined by [`$NIX_PATH` environment variable](../command-ref/env-common.md#env-NIX_PATH).
 
   </td>
  </tr>
@@ -226,7 +238,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A set with attributes named `x` and `y`
+   An [attribute set](@docroot@/language/types.md#attribute-set) with attributes named `x` and `y`
 
   </td>
  </tr>
@@ -250,7 +262,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A recursive set, equivalent to `{ x = "foo"; y = "foobar"; }`
+   A [recursive set](@docroot@/language/syntax.md#recursive-sets), equivalent to `{ x = "foo"; y = "foobar"; }`.
 
   </td>
  </tr>
@@ -266,7 +278,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Lists with three elements.
+   [Lists](@docroot@/language/types.md#list) with three elements.
 
   </td>
  </tr>
@@ -350,7 +362,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Attribute selection (evaluates to `1`)
+   [Attribute selection](@docroot@/language/types.md#attribute-set) (evaluates to `1`)
 
   </td>
  </tr>
@@ -362,7 +374,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Attribute selection with default (evaluates to `3`)
+   [Attribute selection](@docroot@/language/types.md#attribute-set) with default (evaluates to `3`)
 
   </td>
  </tr>
@@ -398,7 +410,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Conditional expression
+   [Conditional expression](@docroot@/language/syntax.md#conditionals).
 
   </td>
  </tr>
@@ -410,7 +422,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Assertion check (evaluates to `"yes!"`).
+   [Assertion](@docroot@/language/syntax.md#assertions) check (evaluates to `"yes!"`).
 
   </td>
  </tr>
@@ -422,7 +434,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Variable definition
+   Variable definition. See [`let`-expressions](@docroot@/language/syntax.md#let-expressions).
 
   </td>
  </tr>
@@ -434,7 +446,9 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Add all attributes from the given set to the scope (evaluates to `1`)
+   Add all attributes from the given set to the scope (evaluates to `1`).
+
+   See [`with`-expressions](@docroot@/language/syntax.md#with-expressions) for details and shadowing caveats.
 
   </td>
  </tr>
@@ -447,7 +461,8 @@ This is an incomplete overview of language features, by example.
   <td>
 
    Adds the variables to the current scope (attribute set or `let` binding).
-   Desugars to `pkgs = pkgs; src = src;`
+   Desugars to `pkgs = pkgs; src = src;`.
+   See [Inheriting attributes](@docroot@/language/syntax.md#inheriting-attributes).
 
   </td>
  </tr>
@@ -460,14 +475,15 @@ This is an incomplete overview of language features, by example.
   <td>
 
    Adds the attributes, from the attribute set in parentheses, to the current scope (attribute set or `let` binding).
-   Desugars to `lib = pkgs.lib; stdenv = pkgs.stdenv;`
+   Desugars to `lib = pkgs.lib; stdenv = pkgs.stdenv;`.
+   See [Inheriting attributes](@docroot@/language/syntax.md#inheriting-attributes).
 
   </td>
  </tr>
  <tr>
   <td>
 
-   *Functions (lambdas)*
+   *[Functions](@docroot@/language/syntax.md#functions) (lambdas)*
 
   </td>
   <td>
@@ -484,7 +500,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function that expects an integer and returns it increased by 1
+   A [function](@docroot@/language/syntax.md#functions) that expects an integer and returns it increased by 1.
 
   </td>
  </tr>
@@ -496,7 +512,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Curried function, equivalent to `x: (y: x + y)`. Can be used like a function that takes two arguments and returns their sum.
+   Curried [function](@docroot@/language/syntax.md#functions), equivalent to `x: (y: x + y)`. Can be used like a function that takes two arguments and returns their sum.
 
   </td>
  </tr>
@@ -508,7 +524,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function call (evaluates to 101)
+   A [function](@docroot@/language/syntax.md#functions) call (evaluates to 101)
 
   </td>
  </tr>
@@ -520,7 +536,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function bound to a variable and subsequently called by name (evaluates to 103)
+   A [function](@docroot@/language/syntax.md#functions) bound to a variable and subsequently called by name (evaluates to 103)
 
   </td>
  </tr>
@@ -532,7 +548,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function that expects a set with required attributes `x` and `y` and concatenates them
+   A [function](@docroot@/language/syntax.md#functions) that expects a set with required attributes `x` and `y` and concatenates them
 
   </td>
  </tr>
@@ -544,7 +560,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function that expects a set with required attribute `x` and optional `y`, using `"bar"` as default value for `y`
+   A [function](@docroot@/language/syntax.md#functions) that expects a set with required attribute `x` and optional `y`, using `"bar"` as default value for `y`
 
   </td>
  </tr>
@@ -556,7 +572,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function that expects a set with required attributes `x` and `y` and ignores any other attributes
+   A [function](@docroot@/language/syntax.md#functions) that expects a set with required attributes `x` and `y` and ignores any other attributes
 
   </td>
  </tr>
@@ -570,7 +586,7 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   A function that expects a set with required attributes `x` and `y`, and binds the whole set to `args`
+   A [function](@docroot@/language/syntax.md#functions) that expects a set with required attributes `x` and `y`, and binds the whole set to `args`
 
   </td>
  </tr>
@@ -594,7 +610,8 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Load and return Nix expression in given file
+   Load and return Nix expression in given file.
+   See [import](@docroot@/language/builtins.md#builtins-import).
 
   </td>
  </tr>
@@ -606,7 +623,8 @@ This is an incomplete overview of language features, by example.
   </td>
   <td>
 
-   Apply a function to every element of a list (evaluates to `[ 2 4 6 ]`)
+   Apply a function to every element of a list (evaluates to `[ 2 4 6 ]`).
+   See [`map`](@docroot@/language/builtins.md#builtins-map).
 
   </td>
  </tr>
diff --git a/doc/manual/src/language/operators.md b/doc/manual/src/language/operators.md
index 698fed47e0f..9660a764d92 100644
--- a/doc/manual/src/language/operators.md
+++ b/doc/manual/src/language/operators.md
@@ -27,11 +27,11 @@
 | Logical disjunction (`OR`)             | *bool* <code>\|\|</code> *bool*            | left          | 13         |
 | [Logical implication]                  | *bool* `->` *bool*                         | right         | 14         |
 
-[string]: ./values.md#type-string
-[path]: ./values.md#type-path
-[number]: ./values.md#type-number
-[list]: ./values.md#list
-[attribute set]: ./values.md#attribute-set
+[string]: ./types.md#type-string
+[path]: ./types.md#type-path
+[number]: ./types.md#type-float <!-- TODO(@rhendric, #10970): rationalize this -->
+[list]: ./types.md#list
+[attribute set]: ./types.md#attribute-set
 
 ## Attribute selection
 
@@ -42,7 +42,7 @@
 Select the attribute denoted by attribute path *attrpath* from [attribute set] *attrset*.
 If the attribute doesn’t exist, return the *expr* after `or` if provided, otherwise abort evaluation.
 
-An attribute path is a dot-separated list of [attribute names](./values.md#attribute-set).
+An attribute path is a dot-separated list of [attribute names](./types.md#attribute-set).
 
 > **Syntax**
 >
@@ -61,7 +61,7 @@ The result is a [Boolean] value.
 
 See also: [`builtins.hasAttr`](@docroot@/language/builtins.md#builtins-hasAttr)
 
-[Boolean]: ./values.md#type-boolean
+[Boolean]: ./types.md#type-boolean
 
 [Has attribute]: #has-attribute
 
@@ -128,7 +128,7 @@ The result is a string.
 > The file or directory at *path* must exist and is copied to the [store].
 > The path appears in the result as the corresponding [store path].
 
-[store path]: @docroot@/glossary.md#gloss-store-path
+[store path]: @docroot@/store/store-path.md
 [store]: @docroot@/glossary.md#gloss-store
 
 [String and path concatenation]: #string-and-path-concatenation
@@ -141,7 +141,7 @@ The result is a string.
 
 Update [attribute set] *attrset1* with names and values from *attrset2*.
 
-The returned attribute set will have of all the attributes in *attrset1* and *attrset2*.
+The returned attribute set will have all of the attributes in *attrset1* and *attrset2*.
 If an attribute name is present in both, the attribute value from the latter is taken.
 
 [Update]: #update
@@ -172,7 +172,7 @@ All comparison operators are implemented in terms of `<`, and the following equi
 - Numbers are type-compatible, see [arithmetic] operators.
 - Floating point numbers only differ up to a limited precision.
 
-[function]: ./constructs.md#functions
+[function]: ./syntax.md#functions
 
 [Equality]: #equality
 
diff --git a/doc/manual/src/language/scope.md b/doc/manual/src/language/scope.md
new file mode 100644
index 00000000000..5c6aed38d31
--- /dev/null
+++ b/doc/manual/src/language/scope.md
@@ -0,0 +1,14 @@
+# Scoping rules
+
+Nix is [statically scoped](https://en.wikipedia.org/wiki/Scope_(computer_science)#Lexical_scope), but with multiple scopes and shadowing rules.
+
+* primary scope: explicitly-bound variables
+  * [`let`](./syntax.md#let-expressions)
+  * [`inherit`](./syntax.md#inheriting-attributes)
+  * [function](./syntax.md#functions) arguments
+
+* secondary scope: implicitly-bound variables
+  * [`with`](./syntax.md#with-expressions)
+
+Primary scope takes precedence over secondary scope.
+See [`with`](./syntax.md#with-expressions) for a detailed example.
diff --git a/doc/manual/src/language/string-context.md b/doc/manual/src/language/string-context.md
new file mode 100644
index 00000000000..6a3482cfd95
--- /dev/null
+++ b/doc/manual/src/language/string-context.md
@@ -0,0 +1,134 @@
+# String context
+
+> **Note**
+>
+> This is an advanced topic.
+> The Nix language is designed to be used without the programmer consciously dealing with string contexts or even knowing what they are.
+
+A string in the Nix language is not just a sequence of characters like strings in other languages.
+It is actually a pair of a sequence of characters and a *string context*.
+The string context is an (unordered) set of *string context elements*.
+
+The purpose of string contexts is to collect non-string values attached to strings via
+[string concatenation](./operators.md#string-concatenation),
+[string interpolation](./string-interpolation.md),
+and similar operations.
+The idea is that a user can combine together values to create a build instructions for derivations without manually keeping track of where they come from.
+Then the Nix language implicitly does that bookkeeping to efficiently obtain the closure of derivation inputs.
+
+> **Note**
+>
+> String contexts are *not* explicitly manipulated in idiomatic Nix language code.
+
+String context elements come in different forms:
+
+- [deriving path]{#string-context-element-derived-path}
+
+  A string context element of this type is a [deriving path](@docroot@/glossary.md#gloss-deriving-path).
+  They can be either of type [constant](#string-context-constant) or [output](#string-context-output), which correspond to the types of deriving paths.
+
+  - [Constant string context elements]{#string-context-constant}
+
+    > **Example**
+    >
+    > [`builtins.storePath`] creates a string with a single constant string context element:
+    >
+    > ```nix
+    > builtins.getContext (builtins.storePath "/nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10")
+    > ```
+    > evaluates to
+    > ```nix
+    > {
+    >   "/nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10" = {
+    >     path = true;
+    >   };
+    > }
+    > ```
+
+    [deriving path]: @docroot@/glossary.md#gloss-deriving-path
+    [store path]: @docroot@/glossary.md#gloss-store-path
+    [`builtins.storePath`]: ./builtins.md#builtins-storePath
+
+  - [Output string context elements]{#string-context-output}
+
+    > **Example**
+    >
+    > The behavior of string contexts are best demonstrated with a built-in function that is still experimental: [`builtins.outputOf`].
+    > This example will *not* work with stable Nix!
+    >
+    > ```nix
+    > builtins.getContext
+    >   (builtins.outputOf
+    >     (builtins.storePath "/nix/store/fvchh9cvcr7kdla6n860hshchsba305w-hello-2.12.drv")
+    >     "out")
+    > ```
+    > evaluates to
+    > ```nix
+    > {
+    >   "/nix/store/fvchh9cvcr7kdla6n860hshchsba305w-hello-2.12.drv" = {
+    >     outputs = [ "out" ];
+    >   };
+    > }
+    > ```
+
+    [`builtins.outputOf`]: ./builtins.md#builtins-outputOf
+
+- [*derivation deep*]{#string-context-element-derivation-deep}
+
+  *derivation deep* is an advanced feature intended to be used with the
+  [`exportReferencesGraph` derivation attribute](./advanced-attributes.html#adv-attr-exportReferencesGraph).
+  A *derivation deep* string context element is a derivation path, and refers to both its outputs and the entire build closure of that derivation:
+  all its outputs, all the other derivations the given derivation depends on, and all the outputs of those.
+
+  > **Example**
+  >
+  > The best way to illustrate *derivation deep* string contexts is with [`builtins.addDrvOutputDependencies`].
+  > Take a regular constant string context element pointing to a derivation, and transform it into a "Derivation deep" string context element.
+  >
+  > ```nix
+  > builtins.getContext
+  >   (builtins.addDrvOutputDependencies
+  >     (builtins.storePath "/nix/store/fvchh9cvcr7kdla6n860hshchsba305w-hello-2.12.drv"))
+  > ```
+  > evaluates to
+  > ```nix
+  > {
+  >   "/nix/store/fvchh9cvcr7kdla6n860hshchsba305w-hello-2.12.drv" = {
+  >     allOutputs = true;
+  >   };
+  > }
+  > ```
+
+  [`builtins.addDrvOutputDependencies`]: ./builtins.md#builtins-addDrvOutputDependencies
+  [`builtins.unsafeDiscardOutputDependency`]: ./builtins.md#builtins-unsafeDiscardOutputDependency
+
+## Inspecting string contexts
+
+Most basically, [`builtins.hasContext`] will tell whether a string has a non-empty context.
+
+When more granular information is needed, [`builtins.getContext`] can be used.
+It creates an [attribute set] representing the string context, which can be inspected as usual.
+
+[`builtins.hasContext`]: ./builtins.md#builtins-hasContext
+[`builtins.getContext`]: ./builtins.md#builtins-getContext
+[attribute set]: ./types.md#attribute-set
+
+## Clearing string contexts
+
+[`buitins.unsafeDiscardStringContext`](./builtins.md#builtins-unsafeDiscardStringContext) will make a copy of a string, but with an empty string context.
+The returned string can be used in more ways, e.g. by operators that require the string context to be empty.
+The requirement to explicitly discard the string context in such use cases helps ensure that string context elements are not lost by mistake.
+The "unsafe" marker is only there to remind that Nix normally guarantees that dependencies are tracked, whereas the returned string has lost them.
+
+## Constructing string contexts
+
+[`builtins.appendContext`] will create a copy of a string, but with additional string context elements.
+The context is specified explicitly by an [attribute set] in the format that [`builtins.hasContext`] produces.
+A string with arbitrary contexts can be made like this:
+
+1. Create a string with the desired string context elements.
+   (The contents of the string do not matter.)
+2. Dump its context with [`builtins.getContext`].
+3. Combine it with a base string and repeated [`builtins.appendContext`] calls.
+
+[`builtins.appendContext`]: ./builtins.md#builtins-appendContext
diff --git a/doc/manual/src/language/string-interpolation.md b/doc/manual/src/language/string-interpolation.md
index 1f8fecca86b..1778bdfa06b 100644
--- a/doc/manual/src/language/string-interpolation.md
+++ b/doc/manual/src/language/string-interpolation.md
@@ -4,9 +4,9 @@ String interpolation is a language feature where a [string], [path], or [attribu
 
 Such a construct is called *interpolated string*, and the expression inside is an [interpolated expression](#interpolated-expression).
 
-[string]: ./values.md#type-string
-[path]: ./values.md#type-path
-[attribute set]: ./values.md#attribute-set
+[string]: ./types.md#type-string
+[path]: ./types.md#type-path
+[attribute set]: ./types.md#attribute-set
 
 ## Examples
 
@@ -43,6 +43,47 @@ configureFlags = "
 Note that Nix expressions and strings can be arbitrarily nested;
 in this case the outer string contains various interpolated expressions that themselves contain strings (e.g., `"-thread"`), some of which in turn contain interpolated expressions (e.g., `${mesa}`).
 
+To write a literal `${` in an regular string, escape it with a backslash (`\`).
+
+> **Example**
+>
+> ```nix
+> "echo \${PATH}"
+> ```
+>
+>     "echo ${PATH}"
+
+To write a literal `${` in an indented string, escape it with two single quotes (`''`).
+
+> **Example**
+>
+> ```nix
+> ''
+>   echo ''${PATH}
+> ''
+> ```
+>
+>     "echo ${PATH}\n"
+
+`$${` can be written literally in any string.
+
+> **Example**
+>
+> In Make, `$` in file names or recipes is represented as `$$`, see [GNU `make`: Basics of Variable Reference](https://www.gnu.org/software/make/manual/html_node/Reference.html#Basics-of-Variable-References).
+> This can be expressed directly in the Nix language strings:
+>
+> ```nix
+> ''
+>   MAKEVAR = Hello
+>   all:
+>   	@export BASHVAR=world; echo $(MAKEVAR) $${BASHVAR}
+> ''
+> ```
+>
+>     "MAKEVAR = Hello\nall:\n\t@export BASHVAR=world; echo $(MAKEVAR) $\${BASHVAR}\n"
+
+See the [documentation on strings][string] for details.
+
 ### Path
 
 Rather than writing
@@ -107,9 +148,9 @@ An expression that is interpolated must evaluate to one of the following:
 
 A string interpolates to itself.
 
-A path in an interpolated expression is first copied into the Nix store, and the resulting string is the [store path] of the newly created [store object](@docroot@/glossary.md#gloss-store-object).
+A path in an interpolated expression is first copied into the Nix store, and the resulting string is the [store path] of the newly created [store object](@docroot@/store/store-object.md).
 
-[store path]: @docroot@/glossary.md#gloss-store-path
+[store path]: @docroot@/store/store-path.md
 
 > **Example**
 >
diff --git a/doc/manual/src/language/syntax.md b/doc/manual/src/language/syntax.md
new file mode 100644
index 00000000000..238c502f979
--- /dev/null
+++ b/doc/manual/src/language/syntax.md
@@ -0,0 +1,841 @@
+# Language Constructs
+
+This section covers syntax and semantics of the Nix language.
+
+## Basic Literals
+
+### String {#string-literal}
+
+  *Strings* can be written in three ways.
+
+  The most common way is to enclose the string between double quotes, e.g., `"foo bar"`.
+  Strings can span multiple lines.
+  The results of other expressions can be included into a string by enclosing them in `${ }`, a feature known as [string interpolation].
+
+  [string interpolation]: ./string-interpolation.md
+
+  The following must be escaped to represent them within a string, by prefixing with a backslash (`\`):
+
+  - Double quote (`"`)
+
+    > **Example**
+    >
+    > ```nix
+    > "\""
+    > ```
+    >
+    >    "\""
+
+  - Backslash (`\`)
+
+    > **Example**
+    >
+    > ```nix
+    > "\\"
+    > ```
+    >
+    >    "\\"
+
+  - Dollar sign followed by an opening curly bracket (`${`) – "dollar-curly"
+
+    > **Example**
+    >
+    > ```nix
+    > "\${"
+    > ```
+    >
+    >    "\${"
+
+  The newline, carriage return, and tab characters can be written as `\n`, `\r` and `\t`, respectively.
+
+  A "double-dollar-curly" (`$${`) can be written literally.
+
+  > **Example**
+  >
+  > ```nix
+  > "$${"
+  > ```
+  >
+  >    "$\${"
+
+  String values are output on the terminal with Nix-specific escaping.
+  Strings written to files will contain the characters encoded by the escaping.
+
+  The second way to write string literals is as an *indented string*, which is enclosed between pairs of *double single-quotes* (`''`), like so:
+
+  ```nix
+  ''
+    This is the first line.
+    This is the second line.
+      This is the third line.
+  ''
+  ```
+
+  This kind of string literal intelligently strips indentation from
+  the start of each line. To be precise, it strips from each line a
+  number of spaces equal to the minimal indentation of the string as a
+  whole (disregarding the indentation of empty lines). For instance,
+  the first and second line are indented two spaces, while the third
+  line is indented four spaces. Thus, two spaces are stripped from
+  each line, so the resulting string is
+
+  ```nix
+  "This is the first line.\nThis is the second line.\n  This is the third line.\n"
+  ```
+
+  > **Note**
+  >
+  > Whitespace and newline following the opening `''` is ignored if there is no non-whitespace text on the initial line.
+
+  > **Warning**
+  >
+  > Prefixed tab characters are not stripped.
+  >
+  > > **Example**
+  > >
+  > > The following indented string is prefixed with tabs:
+  > >
+  > > ''
+  > > 	all:
+  > > 		@echo hello
+  > > ''
+  > >
+  > >     "\tall:\n\t\t@echo hello\n"
+
+  Indented strings support [string interpolation].
+
+  The following must be escaped to represent them in an indented string:
+
+  - `$` is escaped by prefixing it with two single quotes (`''`)
+
+    > **Example**
+    >
+    > ```nix
+    > ''
+    >   ''$
+    > ''
+    > ```
+    >
+    >     "$\n"
+
+  - `''` is escaped by prefixing it with one single quote (`'`)
+
+    > **Example**
+    >
+    > ```nix
+    > ''
+    >   '''
+    > ''
+    > ```
+    >
+    >     "''\n"
+
+  These special characters are escaped as follows:
+  - Linefeed (`\n`): `''\n`
+  - Carriage return (`\r`): `''\r`
+  - Tab (`\t`): `''\t`
+
+  `''\` escapes any other character.
+
+  A "double-dollar-curly" (`$${`) can be written literally.
+
+  > **Example**
+  >
+  > ```nix
+  > ''
+  >   $${
+  > ''
+  > ```
+  >
+  >     "$\${\n"
+
+  Indented strings are primarily useful in that they allow multi-line
+  string literals to follow the indentation of the enclosing Nix
+  expression, and that less escaping is typically necessary for
+  strings representing languages such as shell scripts and
+  configuration files because `''` is much less common than `"`.
+  Example:
+
+  ```nix
+  stdenv.mkDerivation {
+    ...
+    postInstall =
+      ''
+        mkdir $out/bin $out/etc
+        cp foo $out/bin
+        echo "Hello World" > $out/etc/foo.conf
+        ${if enableBar then "cp bar $out/bin" else ""}
+      '';
+    ...
+  }
+  ```
+
+  Finally, as a convenience, *URIs* as defined in appendix B of
+  [RFC 2396](http://www.ietf.org/rfc/rfc2396.txt) can be written *as
+  is*, without quotes. For instance, the string
+  `"http://example.org/foo.tar.bz2"` can also be written as
+  `http://example.org/foo.tar.bz2`.
+
+### Number {#number-literal}
+
+<!-- TODO(@rhendric, #10970): split this into int and float -->
+
+  Numbers, which can be *integers* (like `123`) or *floating point*
+  (like `123.43` or `.27e13`).
+
+  See [arithmetic] and [comparison] operators for semantics.
+
+  [arithmetic]: ./operators.md#arithmetic
+  [comparison]: ./operators.md#comparison
+
+### Path {#path-literal}
+
+  *Paths* are distinct from strings and can be expressed by path literals such as `./builder.sh`.
+
+  Paths are suitable for referring to local files, and are often preferable over strings.
+  - Path values do not contain trailing slashes, `.` and `..`, as they are resolved when evaluating a path literal.
+  - Path literals are automatically resolved relative to their [base directory](@docroot@/glossary.md#gloss-base-directory).
+  - The files referred to by path values are automatically copied into the Nix store when used in a string interpolation or concatenation.
+  - Tooling can recognize path literals and provide additional features, such as autocompletion, refactoring automation and jump-to-file.
+
+  A path literal must contain at least one slash to be recognised as such.
+  For instance, `builder.sh` is not a path:
+  it's parsed as an expression that selects the attribute `sh` from the variable `builder`.
+
+  Path literals may also refer to absolute paths by starting with a slash.
+
+  > **Note**
+  >
+  > Absolute paths make expressions less portable.
+  > In the case where a function translates a path literal into an absolute path string for a configuration file, it is recommended to write a string literal instead.
+  > This avoids some confusion about whether files at that location will be used during evaluation.
+  > It also avoids unintentional situations where some function might try to copy everything at the location into the store.
+
+  If the first component of a path is a `~`, it is interpreted such that the rest of the path were relative to the user's home directory.
+  For example, `~/foo` would be equivalent to `/home/edolstra/foo` for a user whose home directory is `/home/edolstra`.
+  Path literals that start with `~` are not allowed in [pure](@docroot@/command-ref/conf-file.md#conf-pure-eval) evaluation.
+
+  Paths can be used in [string interpolation] and string concatenation.
+  For instance, evaluating `"${./foo.txt}"` will cause `foo.txt` from the same directory to be copied into the Nix store and result in the string `"/nix/store/<hash>-foo.txt"`.
+
+  Note that the Nix language assumes that all input files will remain _unchanged_ while evaluating a Nix expression.
+  For example, assume you used a file path in an interpolated string during a `nix repl` session.
+  Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new [store path], since Nix might not re-read the file contents. Use `:r` to reset the repl as needed.
+
+  [store path]: @docroot@/store/store-path.md
+
+  Path literals can also include [string interpolation], besides being [interpolated into other expressions].
+
+  [interpolated into other expressions]: ./string-interpolation.md#interpolated-expressions
+
+  At least one slash (`/`) must appear *before* any interpolated expression for the result to be recognized as a path.
+
+  `a.${foo}/b.${bar}` is a syntactically valid number division operation.
+  `./a.${foo}/b.${bar}` is a path.
+
+  [Lookup path](./constructs/lookup-path.md) literals such as `<nixpkgs>` also resolve to path values.
+
+## List {#list-literal}
+
+Lists are formed by enclosing a whitespace-separated list of values
+between square brackets. For example,
+
+```nix
+[ 123 ./foo.nix "abc" (f { x = y; }) ]
+```
+
+defines a list of four elements, the last being the result of a call to
+the function `f`. Note that function calls have to be enclosed in
+parentheses. If they had been omitted, e.g.,
+
+```nix
+[ 123 ./foo.nix "abc" f { x = y; } ]
+```
+
+the result would be a list of five elements, the fourth one being a
+function and the fifth being a set.
+
+Note that lists are only lazy in values, and they are strict in length.
+
+Elements in a list can be accessed using [`builtins.elemAt`](./builtins.md#builtins-elemAt).
+
+## Attribute Set {#attrs-literal}
+
+An attribute set is a collection of name-value-pairs (called *attributes*) enclosed in curly brackets (`{ }`).
+
+An attribute name can be an identifier or a [string](#string).
+An identifier must start with a letter (`a-z`, `A-Z`) or underscore (`_`), and can otherwise contain letters (`a-z`, `A-Z`), numbers (`0-9`), underscores (`_`), apostrophes (`'`), or dashes (`-`).
+
+> **Syntax**
+>
+> *name* = *identifier* | *string* \
+> *identifier* ~ `[a-zA-Z_][a-zA-Z0-9_'-]*`
+
+Names and values are separated by an equal sign (`=`).
+Each value is an arbitrary expression terminated by a semicolon (`;`).
+
+> **Syntax**
+>
+> *attrset* = `{` [ *name* `=` *expr* `;` ]... `}`
+
+Attributes can appear in any order.
+An attribute name may only occur once.
+
+Example:
+
+```nix
+{
+  x = 123;
+  text = "Hello";
+  y = f { bla = 456; };
+}
+```
+
+This defines a set with attributes named `x`, `text`, `y`.
+
+Attributes can be accessed with the [`.` operator](./operators.md#attribute-selection).
+
+Example:
+
+```nix
+{ a = "Foo"; b = "Bar"; }.a
+```
+
+This evaluates to `"Foo"`.
+
+It is possible to provide a default value in an attribute selection using the `or` keyword.
+
+Example:
+
+```nix
+{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"
+```
+
+```nix
+{ a = "Foo"; b = "Bar"; }.c.d.e.f.g or "Xyzzy"
+```
+
+will both evaluate to `"Xyzzy"` because there is no `c` attribute in the set.
+
+You can use arbitrary double-quoted strings as attribute names:
+
+```nix
+{ "$!@#?" = 123; }."$!@#?"
+```
+
+```nix
+let bar = "bar"; in
+{ "foo ${bar}" = 123; }."foo ${bar}"
+```
+
+Both will evaluate to `123`.
+
+Attribute names support [string interpolation]:
+
+```nix
+let bar = "foo"; in
+{ foo = 123; }.${bar}
+```
+
+```nix
+let bar = "foo"; in
+{ ${bar} = 123; }.foo
+```
+
+Both will evaluate to `123`.
+
+In the special case where an attribute name inside of a set declaration
+evaluates to `null` (which is normally an error, as `null` cannot be coerced to
+a string), that attribute is simply not added to the set:
+
+```nix
+{ ${if foo then "bar" else null} = true; }
+```
+
+This will evaluate to `{}` if `foo` evaluates to `false`.
+
+A set that has a `__functor` attribute whose value is callable (i.e. is
+itself a function or a set with a `__functor` attribute whose value is
+callable) can be applied as if it were a function, with the set itself
+passed in first , e.g.,
+
+```nix
+let add = { __functor = self: x: x + self.x; };
+    inc = add // { x = 1; };
+in inc 1
+```
+
+evaluates to `2`. This can be used to attach metadata to a function
+without the caller needing to treat it specially, or to implement a form
+of object-oriented programming, for example.
+
+## Recursive sets
+
+Recursive sets are like normal [attribute sets](./types.md#attribute-set), but the attributes can refer to each other.
+
+> *rec-attrset* = `rec {` [ *name* `=` *expr* `;` `]`... `}`
+
+Example:
+
+```nix
+rec {
+  x = y;
+  y = 123;
+}.x
+```
+
+This evaluates to `123`.
+
+Note that without `rec` the binding `x = y;` would
+refer to the variable `y` in the surrounding scope, if one exists, and
+would be invalid if no such variable exists. That is, in a normal
+(non-recursive) set, attributes are not added to the lexical scope; in a
+recursive set, they are.
+
+Recursive sets of course introduce the danger of infinite recursion. For
+example, the expression
+
+```nix
+rec {
+  x = y;
+  y = x;
+}.x
+```
+
+will crash with an `infinite recursion encountered` error message.
+
+## Let-expressions
+
+A let-expression allows you to define local variables for an expression.
+
+> *let-in* = `let` [ *identifier* = *expr* ]... `in` *expr*
+
+Example:
+
+```nix
+let
+  x = "foo";
+  y = "bar";
+in x + y
+```
+
+This evaluates to `"foobar"`.
+
+## Inheriting attributes
+
+When defining an [attribute set](./types.md#attribute-set) or in a [let-expression](#let-expressions) it is often convenient to copy variables from the surrounding lexical scope (e.g., when you want to propagate attributes).
+This can be shortened using the `inherit` keyword.
+
+Example:
+
+```nix
+let x = 123; in
+{
+  inherit x;
+  y = 456;
+}
+```
+
+is equivalent to
+
+```nix
+let x = 123; in
+{
+  x = x;
+  y = 456;
+}
+```
+
+and both evaluate to `{ x = 123; y = 456; }`.
+
+> **Note**
+>
+> This works because `x` is added to the lexical scope by the `let` construct.
+
+It is also possible to inherit attributes from another attribute set.
+
+Example:
+
+In this fragment from `all-packages.nix`,
+
+```nix
+graphviz = (import ../tools/graphics/graphviz) {
+  inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
+  inherit (xorg) libXaw;
+};
+
+xorg = {
+  libX11 = ...;
+  libXaw = ...;
+  ...
+}
+
+libpng = ...;
+libjpg = ...;
+...
+```
+
+the set used in the function call to the function defined in
+`../tools/graphics/graphviz` inherits a number of variables from the
+surrounding scope (`fetchurl` ... `yacc`), but also inherits `libXaw`
+(the X Athena Widgets) from the `xorg` set.
+
+Summarizing the fragment
+
+```nix
+...
+inherit x y z;
+inherit (src-set) a b c;
+...
+```
+
+is equivalent to
+
+```nix
+...
+x = x; y = y; z = z;
+a = src-set.a; b = src-set.b; c = src-set.c;
+...
+```
+
+when used while defining local variables in a let-expression or while
+defining a set.
+
+In a `let` expression, `inherit` can be used to selectively bring specific attributes of a set into scope. For example
+
+
+```nix
+let
+  x = { a = 1; b = 2; };
+  inherit (builtins) attrNames;
+in
+{
+  names = attrNames x;
+}
+```
+
+is equivalent to
+
+```nix
+let
+  x = { a = 1; b = 2; };
+in
+{
+  names = builtins.attrNames x;
+}
+```
+
+both evaluate to `{ names = [ "a" "b" ]; }`.
+
+## Functions
+
+Functions have the following form:
+
+```nix
+pattern: body
+```
+
+The pattern specifies what the argument of the function must look like,
+and binds variables in the body to (parts of) the argument. There are
+three kinds of patterns:
+
+  - If a pattern is a single identifier, then the function matches any
+    argument. Example:
+
+    ```nix
+    let negate = x: !x;
+        concat = x: y: x + y;
+    in if negate true then concat "foo" "bar" else ""
+    ```
+
+    Note that `concat` is a function that takes one argument and returns
+    a function that takes another argument. This allows partial
+    parameterisation (i.e., only filling some of the arguments of a
+    function); e.g.,
+
+    ```nix
+    map (concat "foo") [ "bar" "bla" "abc" ]
+    ```
+
+    evaluates to `[ "foobar" "foobla" "fooabc" ]`.
+
+  - A *set pattern* of the form `{ name1, name2, …, nameN }` matches a
+    set containing the listed attributes, and binds the values of those
+    attributes to variables in the function body. For example, the
+    function
+
+    ```nix
+    { x, y, z }: z + y + x
+    ```
+
+    can only be called with a set containing exactly the attributes `x`,
+    `y` and `z`. No other attributes are allowed. If you want to allow
+    additional arguments, you can use an ellipsis (`...`):
+
+    ```nix
+    { x, y, z, ... }: z + y + x
+    ```
+
+    This works on any set that contains at least the three named
+    attributes.
+
+    It is possible to provide *default values* for attributes, in
+    which case they are allowed to be missing. A default value is
+    specified by writing `name ?  e`, where *e* is an arbitrary
+    expression. For example,
+
+    ```nix
+    { x, y ? "foo", z ? "bar" }: z + y + x
+    ```
+
+    specifies a function that only requires an attribute named `x`, but
+    optionally accepts `y` and `z`.
+
+  - An `@`-pattern provides a means of referring to the whole value
+    being matched:
+
+    ```nix
+    args@{ x, y, z, ... }: z + y + x + args.a
+    ```
+
+    but can also be written as:
+
+    ```nix
+    { x, y, z, ... } @ args: z + y + x + args.a
+    ```
+
+    Here `args` is bound to the argument *as passed*, which is further
+    matched against the pattern `{ x, y, z, ... }`.
+    The `@`-pattern makes mainly sense with an ellipsis(`...`) as
+    you can access attribute names as `a`, using `args.a`, which was
+    given as an additional attribute to the function.
+
+    > **Warning**
+    >
+    > `args@` binds the name `args` to the attribute set that is passed to the function.
+    > In particular, `args` does *not* include any default values specified with `?` in the function's set pattern.
+    >
+    > For instance
+    >
+    > ```nix
+    > let
+    >   f = args@{ a ? 23, ... }: [ a args ];
+    > in
+    >   f {}
+    > ```
+    >
+    > is equivalent to
+    >
+    > ```nix
+    > let
+    >   f = args @ { ... }: [ (args.a or 23) args ];
+    > in
+    >   f {}
+    > ```
+    >
+    > and both expressions will evaluate to:
+    >
+    > ```nix
+    > [ 23 {} ]
+    > ```
+
+Note that functions do not have names. If you want to give them a name,
+you can bind them to an attribute, e.g.,
+
+```nix
+let concat = { x, y }: x + y;
+in concat { x = "foo"; y = "bar"; }
+```
+
+## Conditionals
+
+Conditionals look like this:
+
+```nix
+if e1 then e2 else e3
+```
+
+where *e1* is an expression that should evaluate to a Boolean value
+(`true` or `false`).
+
+## Assertions
+
+Assertions are generally used to check that certain requirements on or
+between features and dependencies hold. They look like this:
+
+```nix
+assert e1; e2
+```
+
+where *e1* is an expression that should evaluate to a Boolean value. If
+it evaluates to `true`, *e2* is returned; otherwise expression
+evaluation is aborted and a backtrace is printed.
+
+Here is a Nix expression for the Subversion package that shows how
+assertions can be used:.
+
+```nix
+{ localServer ? false
+, httpServer ? false
+, sslSupport ? false
+, pythonBindings ? false
+, javaSwigBindings ? false
+, javahlBindings ? false
+, stdenv, fetchurl
+, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null
+}:
+
+assert localServer -> db4 != null; ①
+assert httpServer -> httpd != null && httpd.expat == expat; ②
+assert sslSupport -> openssl != null && (httpServer -> httpd.openssl == openssl); ③
+assert pythonBindings -> swig != null && swig.pythonSupport;
+assert javaSwigBindings -> swig != null && swig.javaSupport;
+assert javahlBindings -> j2sdk != null;
+
+stdenv.mkDerivation {
+  name = "subversion-1.1.1";
+  ...
+  openssl = if sslSupport then openssl else null; ④
+  ...
+}
+```
+
+The points of interest are:
+
+1.  This assertion states that if Subversion is to have support for
+    local repositories, then Berkeley DB is needed. So if the Subversion
+    function is called with the `localServer` argument set to `true` but
+    the `db4` argument set to `null`, then the evaluation fails.
+
+    Note that `->` is the [logical
+    implication](https://en.wikipedia.org/wiki/Truth_table#Logical_implication)
+    Boolean operation.
+
+2.  This is a more subtle condition: if Subversion is built with Apache
+    (`httpServer`) support, then the Expat library (an XML library) used
+    by Subversion should be same as the one used by Apache. This is
+    because in this configuration Subversion code ends up being linked
+    with Apache code, and if the Expat libraries do not match, a build-
+    or runtime link error or incompatibility might occur.
+
+3.  This assertion says that in order for Subversion to have SSL support
+    (so that it can access `https` URLs), an OpenSSL library must be
+    passed. Additionally, it says that *if* Apache support is enabled,
+    then Apache's OpenSSL should match Subversion's. (Note that if
+    Apache support is not enabled, we don't care about Apache's
+    OpenSSL.)
+
+4.  The conditional here is not really related to assertions, but is
+    worth pointing out: it ensures that if SSL support is disabled, then
+    the Subversion derivation is not dependent on OpenSSL, even if a
+    non-`null` value was passed. This prevents an unnecessary rebuild of
+    Subversion if OpenSSL changes.
+
+## With-expressions
+
+A *with-expression*,
+
+```nix
+with e1; e2
+```
+
+introduces the set *e1* into the lexical scope of the expression *e2*.
+For instance,
+
+```nix
+let as = { x = "foo"; y = "bar"; };
+in with as; x + y
+```
+
+evaluates to `"foobar"` since the `with` adds the `x` and `y` attributes
+of `as` to the lexical scope in the expression `x + y`. The most common
+use of `with` is in conjunction with the `import` function. E.g.,
+
+```nix
+with (import ./definitions.nix); ...
+```
+
+makes all attributes defined in the file `definitions.nix` available as
+if they were defined locally in a `let`-expression.
+
+The bindings introduced by `with` do not shadow bindings introduced by
+other means, e.g.
+
+```nix
+let a = 3; in with { a = 1; }; let a = 4; in with { a = 2; }; ...
+```
+
+establishes the same scope as
+
+```nix
+let a = 1; in let a = 2; in let a = 3; in let a = 4; in ...
+```
+
+Variables coming from outer `with` expressions *are* shadowed:
+
+```nix
+with { a = "outer"; };
+with { a = "inner"; };
+a
+```
+
+Does evaluate to `"inner"`.
+
+## Comments
+
+- Inline comments start with `#` and run until the end of the line.
+
+  > **Example**
+  >
+  > ```nix
+  > # A number
+  > 2 # Equals 1 + 1
+  > ```
+  >
+  > ```console
+  > 2
+  > ```
+
+- Block comments start with `/*` and run until the next occurrence of `*/`.
+
+  > **Example**
+  >
+  > ```nix
+  > /*
+  > Block comments
+  > can span multiple lines.
+  > */ "hello"
+  > ```
+  >
+  > ```console
+  > "hello"
+  > ```
+
+  This means that block comments cannot be nested.
+
+  > **Example**
+  >
+  > ```nix
+  > /* /* nope */ */ 1
+  > ```
+  >
+  > ```console
+  > error: syntax error, unexpected '*'
+  >
+  >        at «string»:1:15:
+  >
+  >             1| /* /* nope */ *
+  >              |               ^
+  > ```
+
+  Consider escaping nested comments and unescaping them in post-processing.
+
+  > **Example**
+  >
+  > ```nix
+  > /* /* nested *\/ */ 1
+  > ```
+  >
+  > ```console
+  > 1
+  > ```
diff --git a/doc/manual/src/language/types.md b/doc/manual/src/language/types.md
new file mode 100644
index 00000000000..c6cfb3c6909
--- /dev/null
+++ b/doc/manual/src/language/types.md
@@ -0,0 +1,91 @@
+# Data Types
+
+Every value in the Nix language has one of the following types:
+
+* [Integer](#type-int)
+* [Float](#type-float)
+* [Boolean](#type-bool)
+* [String](#type-string)
+* [Path](#type-path)
+* [Null](#type-null)
+* [Attribute set](#type-attrs)
+* [List](#type-list)
+* [Function](#type-function)
+* [External](#type-external)
+
+## Primitives
+
+### Integer {#type-int}
+
+An _integer_ in the Nix language is a signed 64-bit integer.
+
+Non-negative integers can be expressed as [integer literals](syntax.md#number-literal).
+Negative integers are created with the [arithmetic negation operator](./operators.md#arithmetic).
+The function [`builtins.isInt`](builtins.md#builtins-isInt) can be used to determine if a value is an integer.
+
+### Float {#type-float}
+
+A _float_ in the Nix language is a 64-bit [IEEE 754](https://en.wikipedia.org/wiki/IEEE_754) floating-point number.
+
+Most non-negative floats can be expressed as [float literals](syntax.md#number-literal).
+Negative floats are created with the [arithmetic negation operator](./operators.md#arithmetic).
+The function [`builtins.isFloat`](builtins.md#builtins-isFloat) can be used to determine if a value is a float.
+
+### Boolean {#type-bool}
+
+A _boolean_ in the Nix language is one of _true_ or _false_.
+
+<!-- TODO: mention the top-level environment -->
+
+These values are available as attributes of [`builtins`](builtins.md#builtins-builtins) as [`builtins.true`](builtins.md#builtins-true) and [`builtins.false`](builtins.md#builtins-false).
+The function [`builtins.isBool`](builtins.md#builtins-isBool) can be used to determine if a value is a boolean.
+
+### String {#type-string}
+
+A _string_ in the Nix language is an immutable, finite-length sequence of bytes, along with a [string context](string-context.md).
+Nix does not assume or support working natively with character encodings.
+
+String values without string context can be expressed as [string literals](syntax.md#string-literal).
+The function [`builtins.isString`](builtins.md#builtins-isString) can be used to determine if a value is a string.
+
+### Path {#type-path}
+
+<!-- TODO(@rhendric, #10970): Incorporate content from syntax.md#path-literal -->
+
+The function [`builtins.isPath`](builtins.md#builtins-isPath) can be used to determine if a value is a path.
+
+### Null {#type-null}
+
+There is a single value of type _null_ in the Nix language.
+
+<!-- TODO: mention the top-level environment -->
+
+This value is available as an attribute on the [`builtins`](builtins.md#builtins-builtins) attribute set as [`builtins.null`](builtins.md#builtins-null).
+
+## Compound values
+
+### Attribute set {#type-attrs}
+
+<!-- TODO(@rhendric, #10970): fill this out -->
+
+An attribute set can be constructed with an [attribute set literal](syntax.md#attrs-literal).
+The function [`builtins.isAttrs`](builtins.md#builtins-isAttrs) can be used to determine if a value is an attribute set.
+
+### List {#type-list}
+
+<!-- TODO(@rhendric, #10970): fill this out -->
+
+A list can be constructed with a [list literal](syntax.md#list-literal).
+The function [`builtins.isList`](builtins.md#builtins-isList) can be used to determine if a value is a list.
+
+## Function {#type-function}
+
+<!-- TODO(@rhendric, #10970): fill this out -->
+
+A function can be constructed with a [function expression](syntax.md#functions).
+The function [`builtins.isFunction`](builtins.md#builtins-isFunction) can be used to determine if a value is a function.
+
+## External {#type-external}
+
+An _external_ value is an opaque value created by a Nix [plugin](../command-ref/conf-file.md#conf-plugin-files).
+Such a value can be substituted in Nix expressions but only created and used by plugin code.
diff --git a/doc/manual/src/language/values.md b/doc/manual/src/language/values.md
deleted file mode 100644
index 568542c0bcc..00000000000
--- a/doc/manual/src/language/values.md
+++ /dev/null
@@ -1,269 +0,0 @@
-# Data Types
-
-## Primitives
-
-- <a id="type-string" href="#type-string">String</a>
-
-  *Strings* can be written in three ways.
-
-  The most common way is to enclose the string between double quotes,
-  e.g., `"foo bar"`. Strings can span multiple lines. The special
-  characters `"` and `\` and the character sequence `${` must be
-  escaped by prefixing them with a backslash (`\`). Newlines, carriage
-  returns and tabs can be written as `\n`, `\r` and `\t`,
-  respectively.
-
-  You can include the results of other expressions into a string by enclosing them in `${ }`, a feature known as [string interpolation].
-
-  [string interpolation]: ./string-interpolation.md
-
-  The second way to write string literals is as an *indented string*,
-  which is enclosed between pairs of *double single-quotes*, like so:
-
-  ```nix
-  ''
-    This is the first line.
-    This is the second line.
-      This is the third line.
-  ''
-  ```
-
-  This kind of string literal intelligently strips indentation from
-  the start of each line. To be precise, it strips from each line a
-  number of spaces equal to the minimal indentation of the string as a
-  whole (disregarding the indentation of empty lines). For instance,
-  the first and second line are indented two spaces, while the third
-  line is indented four spaces. Thus, two spaces are stripped from
-  each line, so the resulting string is
-
-  ```nix
-  "This is the first line.\nThis is the second line.\n  This is the third line.\n"
-  ```
-
-  Note that the whitespace and newline following the opening `''` is
-  ignored if there is no non-whitespace text on the initial line.
-
-  Indented strings support [string interpolation].
-
-  Since `${` and `''` have special meaning in indented strings, you
-  need a way to quote them. `$` can be escaped by prefixing it with
-  `''` (that is, two single quotes), i.e., `''$`. `''` can be escaped
-  by prefixing it with `'`, i.e., `'''`. `$` removes any special
-  meaning from the following `$`. Linefeed, carriage-return and tab
-  characters can be written as `''\n`, `''\r`, `''\t`, and `''\`
-  escapes any other character.
-
-  Indented strings are primarily useful in that they allow multi-line
-  string literals to follow the indentation of the enclosing Nix
-  expression, and that less escaping is typically necessary for
-  strings representing languages such as shell scripts and
-  configuration files because `''` is much less common than `"`.
-  Example:
-
-  ```nix
-  stdenv.mkDerivation {
-    ...
-    postInstall =
-      ''
-        mkdir $out/bin $out/etc
-        cp foo $out/bin
-        echo "Hello World" > $out/etc/foo.conf
-        ${if enableBar then "cp bar $out/bin" else ""}
-      '';
-    ...
-  }
-  ```
-
-  Finally, as a convenience, *URIs* as defined in appendix B of
-  [RFC 2396](http://www.ietf.org/rfc/rfc2396.txt) can be written *as
-  is*, without quotes. For instance, the string
-  `"http://example.org/foo.tar.bz2"` can also be written as
-  `http://example.org/foo.tar.bz2`.
-
-- <a id="type-number" href="#type-number">Number</a>
-
-  Numbers, which can be *integers* (like `123`) or *floating point*
-  (like `123.43` or `.27e13`).
-
-  See [arithmetic] and [comparison] operators for semantics.
-
-  [arithmetic]: ./operators.md#arithmetic
-  [comparison]: ./operators.md#comparison
-
-- <a id="type-path" href="#type-path">Path</a>
-
-  *Paths*, e.g., `/bin/sh` or `./builder.sh`. A path must contain at
-  least one slash to be recognised as such. For instance, `builder.sh`
-  is not a path: it's parsed as an expression that selects the
-  attribute `sh` from the variable `builder`. If the file name is
-  relative, i.e., if it does not begin with a slash, it is made
-  absolute at parse time relative to the directory of the Nix
-  expression that contained it. For instance, if a Nix expression in
-  `/foo/bar/bla.nix` refers to `../xyzzy/fnord.nix`, the absolute path
-  is `/foo/xyzzy/fnord.nix`.
-
-  If the first component of a path is a `~`, it is interpreted as if
-  the rest of the path were relative to the user's home directory.
-  e.g. `~/foo` would be equivalent to `/home/edolstra/foo` for a user
-  whose home directory is `/home/edolstra`.
-
-  For instance, evaluating `"${./foo.txt}"` will cause `foo.txt` in the current directory to be copied into the Nix store and result in the string `"/nix/store/<hash>-foo.txt"`.
-
-  Note that the Nix language assumes that all input files will remain _unchanged_ while  evaluating a Nix expression.
-  For example, assume you used a file path in an interpolated string during a `nix repl` session.
-  Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new [store path], since Nix might not re-read the file contents.
-
-  [store path]: @docroot@/glossary.md#gloss-store-path
-
-  Paths can include [string interpolation] and can themselves be [interpolated in other expressions].
-
-  [interpolated in other expressions]: ./string-interpolation.md#interpolated-expressions
-
-  At least one slash (`/`) must appear *before* any interpolated expression for the result to be recognized as a path.
-
-  `a.${foo}/b.${bar}` is a syntactically valid division operation.
-  `./a.${foo}/b.${bar}` is a path.
-
-  [Lookup paths](./constructs/lookup-path.md) such as `<nixpkgs>` resolve to path values.
-
-- <a id="type-boolean" href="#type-boolean">Boolean</a>
-
-  *Booleans* with values `true` and `false`.
-
-- <a id="type-null" href="#type-null">Null</a>
-
-  The null value, denoted as `null`.
-
-## List
-
-Lists are formed by enclosing a whitespace-separated list of values
-between square brackets. For example,
-
-```nix
-[ 123 ./foo.nix "abc" (f { x = y; }) ]
-```
-
-defines a list of four elements, the last being the result of a call to
-the function `f`. Note that function calls have to be enclosed in
-parentheses. If they had been omitted, e.g.,
-
-```nix
-[ 123 ./foo.nix "abc" f { x = y; } ]
-```
-
-the result would be a list of five elements, the fourth one being a
-function and the fifth being a set.
-
-Note that lists are only lazy in values, and they are strict in length.
-
-Elements in a list can be accessed using [`builtins.elemAt`](./builtins.md#builtins-elemAt). 
-
-## Attribute Set
-
-An attribute set is a collection of name-value-pairs (called *attributes*) enclosed in curly brackets (`{ }`).
-
-An attribute name can be an identifier or a [string](#string).
-An identifier must start with a letter (`a-z`, `A-Z`) or underscore (`_`), and can otherwise contain letters (`a-z`, `A-Z`), numbers (`0-9`), underscores (`_`), apostrophes (`'`), or dashes (`-`).
-
-> **Syntax**
->
-> *name* = *identifier* | *string* \
-> *identifier* ~ `[a-zA-Z_][a-zA-Z0-9_'-]*`
-
-Names and values are separated by an equal sign (`=`).
-Each value is an arbitrary expression terminated by a semicolon (`;`).
-
-> **Syntax**
->
-> *attrset* = `{` [ *name* `=` *expr* `;` ]... `}`
-
-Attributes can appear in any order.
-An attribute name may only occur once.
-
-Example:
-
-```nix
-{
-  x = 123;
-  text = "Hello";
-  y = f { bla = 456; };
-}
-```
-
-This defines a set with attributes named `x`, `text`, `y`.
-
-Attributes can be accessed with the [`.` operator](./operators.md#attribute-selection).
-
-Example:
-
-```nix
-{ a = "Foo"; b = "Bar"; }.a
-```
-
-This evaluates to `"Foo"`.
-
-It is possible to provide a default value in an attribute selection using the `or` keyword.
-
-Example:
-
-```nix
-{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"
-```
-
-```nix
-{ a = "Foo"; b = "Bar"; }.c.d.e.f.g or "Xyzzy"
-```
-
-will both evaluate to `"Xyzzy"` because there is no `c` attribute in the set.
-
-You can use arbitrary double-quoted strings as attribute names:
-
-```nix
-{ "$!@#?" = 123; }."$!@#?"
-```
-
-```nix
-let bar = "bar"; in
-{ "foo ${bar}" = 123; }."foo ${bar}"
-```
-
-Both will evaluate to `123`.
-
-Attribute names support [string interpolation]:
-
-```nix
-let bar = "foo"; in
-{ foo = 123; }.${bar}
-```
-
-```nix
-let bar = "foo"; in
-{ ${bar} = 123; }.foo
-```
-
-Both will evaluate to `123`.
-
-In the special case where an attribute name inside of a set declaration
-evaluates to `null` (which is normally an error, as `null` cannot be coerced to
-a string), that attribute is simply not added to the set:
-
-```nix
-{ ${if foo then "bar" else null} = true; }
-```
-
-This will evaluate to `{}` if `foo` evaluates to `false`.
-
-A set that has a `__functor` attribute whose value is callable (i.e. is
-itself a function or a set with a `__functor` attribute whose value is
-callable) can be applied as if it were a function, with the set itself
-passed in first , e.g.,
-
-```nix
-let add = { __functor = self: x: x + self.x; };
-    inc = add // { x = 1; };
-in inc 1
-```
-
-evaluates to `2`. This can be used to attach metadata to a function
-without the caller needing to treat it specially, or to implement a form
-of object-oriented programming, for example.
diff --git a/doc/manual/src/package-management/copy-closure.md b/doc/manual/src/package-management/copy-closure.md
deleted file mode 100644
index 14326298bea..00000000000
--- a/doc/manual/src/package-management/copy-closure.md
+++ /dev/null
@@ -1,34 +0,0 @@
-# Copying Closures via SSH
-
-The command `nix-copy-closure` copies a Nix store path along with all
-its dependencies to or from another machine via the SSH protocol. It
-doesn’t copy store paths that are already present on the target machine.
-For example, the following command copies Firefox with all its
-dependencies:
-
-    $ nix-copy-closure --to alice@itchy.example.org $(type -p firefox)
-
-See the [manpage for `nix-copy-closure`](../command-ref/nix-copy-closure.md) for details.
-
-With `nix-store
---export` and `nix-store --import` you can write the closure of a store
-path (that is, the path and all its dependencies) to a file, and then
-unpack that file into another Nix store. For example,
-
-    $ nix-store --export $(nix-store --query --requisites $(type -p firefox)) > firefox.closure
-
-writes the closure of Firefox to a file. You can then copy this file to
-another machine and install the closure:
-
-    $ nix-store --import < firefox.closure
-
-Any store paths in the closure that are already present in the target
-store are ignored. It is also possible to pipe the export into another
-command, e.g. to copy and install a closure directly to/on another
-machine:
-
-    $ nix-store --export $(nix-store --query --requisites $(type -p firefox)) | bzip2 | \
-        ssh alice@itchy.example.org "bunzip2 | nix-store --import"
-
-However, `nix-copy-closure` is generally more efficient because it only
-copies paths that are not already present in the target Nix store.
diff --git a/doc/manual/src/protocols/json/derivation.md b/doc/manual/src/protocols/json/derivation.md
index 649d543ccf3..f881dd70381 100644
--- a/doc/manual/src/protocols/json/derivation.md
+++ b/doc/manual/src/protocols/json/derivation.md
@@ -18,10 +18,30 @@ is a JSON object with the following fields:
   Information about the output paths of the derivation.
   This is a JSON object with one member per output, where the key is the output name and the value is a JSON object with these fields:
 
-  * `path`: The output path.
+  * `path`:
+    The output path, if it is known in advanced.
+    Otherwise, `null`.
+
+
+  * `method`:
+    For an output which will be [content addresed], a string representing the [method](@docroot@/store/store-object/content-address.md) of content addressing that is chosen.
+    Valid method strings are:
+
+    - [`flat`](@docroot@/store/store-object/content-address.md#method-flat)
+    - [`nar`](@docroot@/store/store-object/content-address.md#method-nix-archive)
+    - [`text`](@docroot@/store/store-object/content-address.md#method-text)
+    - [`git`](@docroot@/store/store-object/content-address.md#method-git)
+
+    Otherwise, `null`.
 
   * `hashAlgo`:
-    For fixed-output derivations, the hashing algorithm (e.g. `sha256`), optionally prefixed by `r:` if `hash` denotes a NAR hash rather than a flat file hash.
+    For an output which will be [content addresed], the name of the hash algorithm used.
+    Valid algorithm strings are:
+
+    - `md5`
+    - `sha1`
+    - `sha256`
+    - `sha512`
 
   * `hash`:
     For fixed-output derivations, the expected content hash in base-16.
@@ -32,7 +52,8 @@ is a JSON object with the following fields:
   > "outputs": {
   >   "out": {
   >     "path": "/nix/store/2543j7c6jn75blc3drf4g5vhb1rhdq29-source",
-  >     "hashAlgo": "r:sha256",
+  >     "method": "nar",
+  >     "hashAlgo": "sha256",
   >     "hash": "6fc80dcc62179dbc12fc0b5881275898f93444833d21b89dfe5f7fbcbb1d0d62"
   >   }
   > }
diff --git a/doc/manual/src/protocols/json/store-object-info.md b/doc/manual/src/protocols/json/store-object-info.md
index 179cafbb44a..9f647a96c24 100644
--- a/doc/manual/src/protocols/json/store-object-info.md
+++ b/doc/manual/src/protocols/json/store-object-info.md
@@ -24,41 +24,45 @@ Info about a [store object].
 
   An array of [store paths][store path], possibly including this one.
 
-* `ca` (optional):
+* `ca`:
 
-  Content address of this store object's file system object, used to compute its store path.
+  If the store object is [content-addressed],
+  this is the content address of this store object's file system object, used to compute its store path.
+  Otherwise (i.e. if it is [input-addressed]), this is `null`.
 
-[store path]: @docroot@/glossary.md#gloss-store-path
+[store path]: @docroot@/store/store-path.md
 [file system object]: @docroot@/store/file-system-object.md
-[Nix Archive]: @docroot@/glossary.md#gloss-nar
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 
 ## Impure fields
 
 These are not intrinsic properties of the store object.
 In other words, the same store object residing in different store could have different values for these properties.
 
-* `deriver` (optional):
+* `deriver`:
 
-  The path to the [derivation] from which this store object is produced.
+  If known, the path to the [derivation] from which this store object was produced.
+  Otherwise `null`.
 
   [derivation]: @docroot@/glossary.md#gloss-store-derivation
 
 * `registrationTime` (optional):
 
-  When this derivation was added to the store.
+  If known, when this derivation was added to the store.
+  Otherwise `null`.
 
-* `ultimate` (optional):
+* `ultimate`:
 
   Whether this store object is trusted because we built it ourselves, rather than substituted a build product from elsewhere.
 
-* `signatures` (optional):
+* `signatures`:
 
   Signatures claiming that this store object is what it claims to be.
   Not relevant for [content-addressed] store objects,
   but useful for [input-addressed] store objects.
 
-  [content-addressed]: @docroot@/glossary.md#gloss-content-addressed-store-object
-  [input-addressed]: @docroot@/glossary.md#gloss-input-addressed-store-object
+[content-addressed]: @docroot@/store/store-object/content-address.md
+[input-addressed]: @docroot@/glossary.md#gloss-input-addressed-store-object
 
 ### `.narinfo` extra fields
 
diff --git a/doc/manual/src/protocols/nix-archive.md b/doc/manual/src/protocols/nix-archive.md
index 4fb6282eeeb..640b527f10e 100644
--- a/doc/manual/src/protocols/nix-archive.md
+++ b/doc/manual/src/protocols/nix-archive.md
@@ -1,9 +1,10 @@
 # Nix Archive (NAR) format
 
-This is the complete specification of the Nix Archive format.
+This is the complete specification of the [Nix Archive] format.
 The Nix Archive format closely follows the abstract specification of a [file system object] tree,
 because it is designed to serialize exactly that data structure.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#nix-archive
 [file system object]: @docroot@/store/file-system-object.md
 
 The format of this specification is close to [Extended Backus–Naur form](https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form), with the exception of the `str(..)` function / parameterized rule, which length-prefixes and pads strings.
@@ -28,7 +29,7 @@ regular = [ str("executable"), str("") ], str("contents"), str(contents);
 symlink = str("target"), str(target);
 
 (* side condition: directory entries must be ordered by their names *)
-directory = str("type"), str("directory") { directory-entry };
+directory = { directory-entry };
 
 directory-entry = str("entry"), str("("), str("name"), str(name), str("node"), nar-obj, str(")");
 ```
diff --git a/doc/manual/src/protocols/store-path.md b/doc/manual/src/protocols/store-path.md
index 565c4fa7505..52352d358a1 100644
--- a/doc/manual/src/protocols/store-path.md
+++ b/doc/manual/src/protocols/store-path.md
@@ -1,12 +1,14 @@
 # Complete Store Path Calculation
 
-This is the complete specification for how store paths are calculated.
+This is the complete specification for how [store path]s are calculated.
 
 The format of this specification is close to [Extended Backus–Naur form](https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form), but must deviate for a few things such as hash functions which we treat as bidirectional for specification purposes.
 
 Regular users do *not* need to know this information --- store paths can be treated as black boxes computed from the properties of the store objects they refer to.
 But for those interested in exactly how Nix works, e.g. if they are reimplementing it, this information can be useful.
 
+[store path](@docroot@/store/store-path.md)
+
 ## Store path proper
 
 ```ebnf
@@ -34,18 +36,23 @@ where
 - `type` = one of:
 
   - ```ebnf
-    | "text" ( ":" store-path )*
+    | "text" { ":" store-path }
     ```
 
-    for encoded derivations written to the store.
+    This is for the
+    ["Text"](@docroot@/store/store-object/content-address.md#method-text)
+    method of content addressing store objects.
     The optional trailing store paths are the references of the store object.
 
   - ```ebnf
-    | "source" ( ":" store-path )*
+    | "source" { ":" store-path } [ ":self" ]
     ```
 
-    For paths copied to the store and hashed via a [Nix Archive (NAR)] and [SHA-256][sha-256].
-    Just like in the text case, we can have the store objects referenced by their paths.
+    This is for the
+    ["Nix Archive"](@docroot@/store/store-object/content-address.md#method-nix-archive)
+    method of content addressing store objects,
+    if the hash algorithm is [SHA-256].
+    Just like in the "Text" case, we can have the store objects referenced by their paths.
     Additionally, we can have an optional `:self` label to denote self reference.
 
   - ```ebnf
@@ -53,8 +60,12 @@ where
     ```
 
     For either the outputs built from derivations,
-    paths copied to the store hashed that area single file hashed directly, or the via a hash algorithm other than [SHA-256][sha-256].
-    (in that case "source" is used; this is only necessary for compatibility).
+    or content-addressed store objects that are not using one of the two above cases.
+    To be explicit about the latter, that is currently these methods:
+
+    - ["Flat"](@docroot@/store/store-object/content-address.md#method-flat)
+    - ["Git"](@docroot@/store/store-object/content-address.md#method-git)
+    - ["Nix Archive"](@docroot@/store/store-object/content-address.md#method-nix-archive) if the hash algorithm is not [SHA-256].
 
     `id` is the name of the output (usually, "out").
     For content-addressed store objects, `id`, is always "out".
@@ -113,8 +124,8 @@ where
       Note that `id` = `"out"`, regardless of the name part of the store path.
       Also note that NAR + SHA-256 must not use this case, and instead must use the `type` = `"source:" ...` case.
 
-[Nix Archive (NAR)]: @docroot@/glossary.md#gloss-NAR
-[sha-256]: https://en.m.wikipedia.org/wiki/SHA-256
+[Nix Archive (NAR)]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+[SHA-256]: https://en.m.wikipedia.org/wiki/SHA-256
 
 ### Historical Note
 
diff --git a/doc/manual/src/protocols/tarball-fetcher.md b/doc/manual/src/protocols/tarball-fetcher.md
index 274fa6d63c8..24ec7ae14aa 100644
--- a/doc/manual/src/protocols/tarball-fetcher.md
+++ b/doc/manual/src/protocols/tarball-fetcher.md
@@ -22,7 +22,7 @@ Link: <flakeref>; rel="immutable"
 
 *flakeref* must be a tarball flakeref. It can contain the tarball flake attributes
 `narHash`, `rev`, `revCount` and `lastModified`. If `narHash` is included, its
-value must be the NAR hash of the unpacked tarball (as computed via
+value must be the [NAR hash][Nix Archive] of the unpacked tarball (as computed via
 `nix hash path`). Nix checks the contents of the returned tarball
 against the `narHash` attribute. The `rev` and `revCount` attributes
 are useful when the tarball flake is a mirror of a fetcher type that
@@ -40,3 +40,5 @@ Link: <https://example.org/hello/442793d9ec0584f6a6e82fa253850c8085bb150a.tar.gz
 
 For tarball flakes, the value of the `lastModified` flake attribute is
 defined as the timestamp of the newest file inside the tarball.
+
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
diff --git a/doc/manual/src/release-notes/rl-2.22.md b/doc/manual/src/release-notes/rl-2.22.md
new file mode 100644
index 00000000000..c78d3d692af
--- /dev/null
+++ b/doc/manual/src/release-notes/rl-2.22.md
@@ -0,0 +1,21 @@
+# Release 2.22.0 (2024-04-23)
+
+### Significant changes
+
+- Remove experimental repl-flake [#10103](https://github.com/NixOS/nix/issues/10103) [#10299](https://github.com/NixOS/nix/pull/10299)
+
+  The `repl-flake` experimental feature has been removed. The `nix repl` command now works like the rest of the new CLI in that `nix repl {path}` now tries to load a flake at `{path}` (or fails if the `flakes` experimental feature isn't enabled).
+
+### Other changes
+
+- `nix eval` prints derivations as `.drv` paths [#10200](https://github.com/NixOS/nix/pull/10200)
+
+  `nix eval` will now print derivations as their `.drv` paths, rather than as
+  attribute sets. This makes commands like `nix eval nixpkgs#bash` terminate
+  instead of infinitely looping into recursive self-referential attributes:
+
+  ```ShellSession
+  $ nix eval nixpkgs#bash
+  «derivation /nix/store/m32cbgbd598f4w299g0hwyv7gbw6rqcg-bash-5.2p26.drv»
+  ```
+
diff --git a/doc/manual/src/release-notes/rl-2.23.md b/doc/manual/src/release-notes/rl-2.23.md
new file mode 100644
index 00000000000..3c59b85838f
--- /dev/null
+++ b/doc/manual/src/release-notes/rl-2.23.md
@@ -0,0 +1,102 @@
+# Release 2.23.0 (2024-06-03)
+
+- New builtin: `builtins.warn` [#306026](https://github.com/NixOS/nix/issues/306026) [#10592](https://github.com/NixOS/nix/pull/10592)
+
+  `builtins.warn` behaves like `builtins.trace "warning: ${msg}"`, has an accurate log level, and is controlled by the options
+  [`debugger-on-trace`](@docroot@/command-ref/conf-file.md#conf-debugger-on-trace),
+  [`debugger-on-warn`](@docroot@/command-ref/conf-file.md#conf-debugger-on-warn) and
+  [`abort-on-warn`](@docroot@/command-ref/conf-file.md#conf-abort-on-warn).
+
+- Make `nix build --keep-going` consistent with `nix-build --keep-going`
+
+  This means that if e.g. multiple fixed-output derivations fail to
+  build, all hash mismatches are displayed.
+
+- Modify `nix derivation {add,show}` JSON format [#9866](https://github.com/NixOS/nix/issues/9866) [#10722](https://github.com/NixOS/nix/pull/10722)
+
+  The JSON format for derivations has been slightly revised to better conform to our [JSON guidelines](@docroot@/contributing/cli-guideline.md#returning-future-proof-json).
+  In particular, the hash algorithm and content addressing method of content-addresed derivation outputs are now separated into two fields `hashAlgo` and `method`,
+  rather than one field with an arcane `:`-separated format.
+
+  This JSON format is only used by the experimental `nix derivation` family of commands, at this time.
+  Future revisions are expected as the JSON format is still not entirely in compliance even after these changes.
+
+- Warn on unknown settings anywhere in the command line [#10701](https://github.com/NixOS/nix/pull/10701)
+
+  All `nix` commands will now properly warn when an unknown option is specified anywhere in the command line.
+
+  Before:
+
+  ```console
+  $ nix-instantiate --option foobar baz --expr '{}'
+  warning: unknown setting 'foobar'
+  $ nix-instantiate '{}' --option foobar baz --expr
+  $ nix eval --expr '{}' --option foobar baz
+  { }
+  ```
+
+  After:
+
+  ```console
+  $ nix-instantiate --option foobar baz --expr '{}'
+  warning: unknown setting 'foobar'
+  $ nix-instantiate '{}' --option foobar baz --expr
+  warning: unknown setting 'foobar'
+  $ nix eval --expr '{}' --option foobar baz
+  warning: unknown setting 'foobar'
+  { }
+  ```
+
+- `nix env shell` is the new `nix shell`, and `nix shell` remains an accepted alias [#10504](https://github.com/NixOS/nix/issues/10504) [#10807](https://github.com/NixOS/nix/pull/10807)
+
+  This is part of an effort to bring more structure to the CLI subcommands.
+
+  `nix env` will be about the process environment.
+  Future commands may include `nix env run` and `nix env print-env`.
+
+  It is also somewhat analogous to the [planned](https://github.com/NixOS/nix/issues/10504) `nix dev shell` (currently `nix develop`), which is less about environment variables, and more about running a development shell, which is a more powerful command, but also requires more setup.
+
+- Flake operations that expect derivations now print the failing value and its type [#10778](https://github.com/NixOS/nix/pull/10778)
+
+  In errors like `flake output attribute 'nixosConfigurations.yuki.config' is not a derivation or path`, the message now includes the failing value and type.
+
+  Before:
+
+  ```
+  error: flake output attribute 'nixosConfigurations.yuki.config' is not a derivation or path
+  ````
+
+  After:
+
+  ```
+  error: expected flake output attribute 'nixosConfigurations.yuki.config' to be a derivation or path but found a set: { appstream = «thunk»; assertions = «thunk»; boot = { bcache = «thunk»; binfmt = «thunk»; binfmtMiscRegistrations = «thunk»; blacklistedKernelModules = «thunk»; bootMount = «thunk»; bootspec = «thunk»; cleanTmpDir = «thunk»; consoleLogLevel = «thunk»; «43 attributes elided» }; «48 attributes elided» }
+  ```
+
+- `fetchTree` now fetches Git repositories shallowly by default [#10028](https://github.com/NixOS/nix/pull/10028)
+
+  `builtins.fetchTree` now clones Git repositories shallowly by default, which reduces network traffic and disk usage significantly in many cases.
+
+  Previously, the default behavior was to clone the full history of a specific tag or branch (e.g. `ref`) and only afterwards extract the files of one specific revision.
+
+  From now on, the `ref` and `allRefs` arguments will be ignored, except if shallow cloning is disabled by setting `shallow = false`.
+
+  The defaults for `builtins.fetchGit` remain unchanged. Here, shallow cloning has to be enabled manually by passing `shallow = true`.
+
+- Store object info JSON format now uses `null` rather than omitting fields [#9995](https://github.com/NixOS/nix/pull/9995)
+
+  The [store object info JSON format](@docroot@/protocols/json/store-object-info.md), used for e.g. `nix path-info`, no longer omits fields to indicate absent information, but instead includes the fields with a `null` value.
+  For example, `"ca": null` is used to to indicate a store object that isn't content-addressed rather than omitting the `ca` field entirely.
+  This makes records of this sort more self-describing, and easier to consume programmatically.
+
+  We will follow this design principle going forward;
+  the [JSON guidelines](@docroot@/contributing/json-guideline.md) in the contributing section have been updated accordingly.
+
+- Large path warnings [#10661](https://github.com/NixOS/nix/pull/10661)
+
+  Nix can now warn when evaluation of a Nix expression causes a large
+  path to be copied to the Nix store. The threshold for this warning can
+  be configured using [the `warn-large-path-threshold`
+  setting](@docroot@/command-ref/conf-file.md#warn-large-path-threshold),
+  e.g. `--warn-large-path-threshold 100M` will warn about paths larger
+  than 100 MiB.
+
diff --git a/doc/manual/src/store/file-system-object/content-address.md b/doc/manual/src/store/file-system-object/content-address.md
new file mode 100644
index 00000000000..1c63c52ebda
--- /dev/null
+++ b/doc/manual/src/store/file-system-object/content-address.md
@@ -0,0 +1,85 @@
+# Content-Addressing File System Objects
+
+For many operations, Nix needs to calculate [a content addresses](@docroot@/glossary.md#gloss-content-address) of [a file system object][file system object].
+Usually this is needed as part of
+[content addressing store objects](../store-object/content-address.md),
+since store objects always have a root file system object.
+But some command-line utilities also just work on "raw" file system objects, not part of any store object.
+
+Every content addressing scheme Nix uses ultimately involves feeding data into a [hash function](https://en.wikipedia.org/wiki/Hash_function), and getting back an opaque fixed-size digest which is deemed a content address.
+The various *methods* of content addressing thus differ in how abstract data (in this case, a file system object and its descendents) are fed into the hash function.
+
+## Serialising File System Objects { #serial }
+
+The simplest method is to serialise the entire file system object tree into a single binary string, and then hash that binary string, yielding the content address.
+In this section we describe the currently-supported methods of serialising file system objects.
+
+### Flat { #serial-flat }
+
+A single file object can just be hashed by its contents.
+This is not enough information to encode the fact that the file system object is a file,
+but if we *already* know that the FSO is a single non-executable file by other means, it is sufficient.
+
+Because the hashed data is just the raw file, as is, this choice is good for compatibility with other systems.
+For example, Unix commands like `sha256sum` or `sha1sum` will produce hashes for single files that match this.
+
+### Nix Archive (NAR) { #serial-nix-archive }
+
+For the other cases of [file system objects][file system object], especially directories with arbitrary descendents, we need a more complex serialisation format.
+Examples of such serialisations are the ZIP and TAR file formats.
+However, for our purposes these formats have two problems:
+
+- They do not have a canonical serialisation, meaning that given an FSO, there can
+be many different serialisations.
+  For instance, TAR files can have variable amounts of padding between archive members;
+  and some archive formats leave the order of directory entries undefined.
+  This would be bad because we use serialisation to compute cryptographic hashes over file system objects, and for those hashes to be useful as a content address or for integrity checking, uniqueness is crucial.
+  Otherwise, correct hashes would report false mismatches, and the store would fail to find the content.
+
+- They store more information than we have in our notion of FSOs, such as time stamps.
+  This can cause FSOs that Nix should consider equal to hash to different values on different machines, just because the dates differ.
+
+- As a practical consideration, the TAR format is the only truly universal format in the Unix environment.
+  It has many problems, such as an inability to deal with long file names and files larger than 2^33 bytes.
+  Current implementations such as GNU Tar work around these limitations in various ways.
+
+For these reasons, Nix has its very own archive format—the Nix Archive (NAR) format,
+which is carefully designed to avoid the problems described above.
+
+The exact specification of the Nix Archive format is in `protocols/nix-archive.md`
+
+## Content addressing File System Objects beyond a single serialisation pass
+
+Serialising the entire tree and then hashing that binary string is not the only option for content addressing, however.
+Another technique is that of a [Merkle graph](https://en.wikipedia.org/wiki/Merkle_tree), where previously computed hashes are included in subsequent byte strings to be hashed.
+
+In particular, the Merkle graphs can match the original graph structure of file system objects:
+we can first hash (serialised) child file system objects, and then hash parent objects using the hashes of their children in the serialisation (to be hashed) of the parent file system objects.
+
+Currently, there is one such Merkle DAG content addressing method supported.
+
+### Git ([experimental][xp-feature-git-hashing]) { #git }
+
+> **Warning**
+>
+> This method is part of the [`git-hashing`][xp-feature-git-hashing] experimental feature.
+
+Git's file system model is very close to Nix's, and so Git's content addressing method is a pretty good fit.
+Just as with regular Git, files and symlinks are hashed as git "blobs", and directories are hashed as git "trees".
+
+However, one difference between Nix's and Git's file system model needs special treatment.
+Plain files, executable files, and symlinks are not differentiated as distinctly addressable objects, but by their context: by the directory entry that refers to them.
+That means so long as the root object is a directory, there is no problem:
+every non-directory object is owned by a parent directory, and the entry that refers to it provides the missing information.
+However, if the root object is not a directory, then we have no way of knowing which one of an executable file, non-executable file, or symlink it is supposed to be.
+
+In response to this, we have decided to treat a bare file as non-executable file.
+This is similar to do what we do with [flat serialisation](#serial-flat), which also lacks this information.
+To avoid an address collision, attempts to hash a bare executable file or symlink will result in an error (just as would happen for flat serialisation also).
+Thus, Git can encode some, but not all of Nix's "File System Objects", and this sort of content-addressing is likewise partial.
+
+In the future, we may support a Git-like hash for such file system objects, or we may adopt another Merkle DAG format which is capable of representing all Nix file system objects.
+
+[file system object]: ../file-system-object.md
+[store object]: ../store-object.md
+[xp-feature-git-hashing]: @docroot@/contributing/experimental-features.md#xp-feature-git-hashing
diff --git a/doc/manual/src/store/store-object/content-address.md b/doc/manual/src/store/store-object/content-address.md
new file mode 100644
index 00000000000..f6f982035ef
--- /dev/null
+++ b/doc/manual/src/store/store-object/content-address.md
@@ -0,0 +1,95 @@
+# Content-Addressing Store Objects
+
+Just [like][fso-ca] [File System Objects][File System Object],
+[Store Objects][Store Object] can also be [content-addressed](@docroot@/glossary.md#gloss-content-addressed),
+unless they are [input-addressed](@docroot@/glossary.md#gloss-input-addressed-store-object).
+
+For store objects, the content address we produce will take the form of a [Store Path] rather than regular hash.
+In particular, the content-addressing scheme will ensure that the digest of the store path is solely computed from the
+
+- file system object graph (the root one and its children, if it has any)
+- references
+- [store directory](../store-path.md#store-directory)
+- name
+
+of the store object, and not any other information, which would not be an intrinsic property of that store object.
+
+For the full specification of the algorithms involved, see the [specification of store path digests][sp-spec].
+
+[File System Object]: ../file-system-object.md
+[Store Object]: ../store-object.md
+[Store Path]: ../store-path.md
+
+## Content addressing each part of a store object
+
+### File System Objects
+
+With all currently supported store object content addressing methods, the file system object is always [content-addressed][fso-ca] first, and then that hash is incorporated into content address computation for the store object.
+
+### References
+
+With all currently supported store object content addressing methods,
+other objects are referred to by their regular (string-encoded-) [store paths][Store Path].
+
+Self-references however cannot be referred to by their path, because we are in the midst of describing how to compute that path!
+
+> The alternative would require finding as hash function fixed point, i.e. the solution to an equation in the form
+> ```
+> digest = hash(..... || digest || ....)
+> ```
+> which is computationally infeasible.
+> As far as we know, this is equivalent to finding a hash collision.
+
+Instead we just have a "has self reference" boolean, which will end up affecting the digest.
+
+### Name and Store Directory
+
+These two items affect the digest in a way that is standard for store path digest computations and not specific to content-addressing.
+Consult the [specification of store path digests][sp-spec] for further details.
+
+## Content addressing Methods
+
+For historical reasons, we don't support all features in all combinations.
+Each currently supported method of content addressing chooses a single method of file system object hashing, and may offer some restrictions on references.
+The names and store directories are unrestricted however.
+
+### Flat { #method-flat }
+
+This uses the corresponding [Flat](../file-system-object/content-address.md#serial-flat) method of file system object content addressing.
+
+References are not supported: store objects with flat hashing *and* references can not be created.
+
+### Text { #method-text }
+
+This also uses the corresponding [Flat](../file-system-object/content-address.md#serial-flat) method of file system object content addressing.
+
+References to other store objects are supported, but self references are not.
+
+This is the only store-object content-addressing method that is not named identically with a corresponding file system object method.
+It is somewhat obscure, mainly used for "drv files"
+(derivations serialized as store objects in their ["ATerm" file format](@docroot@/protocols/derivation-aterm.md)).
+Prefer another method if possible.
+
+### Nix Archive { #method-nix-archive }
+
+This uses the corresponding [Nix Archive](../file-system-object/content-address.md#serial-nix-archive) method of file system object content addressing.
+
+References (to other store objects and self references alike) are supported so long as the hash algorithm is SHA-256, but not (neither kind) otherwise.
+
+### Git { #method-git }
+
+> **Warning**
+>
+> This method is part of the [`git-hashing`][xp-feature-git-hashing] experimental feature.
+
+This uses the corresponding [Git](../file-system-object/content-address.md#serial-git) method of file system object content addressing.
+
+References are not supported.
+
+Only SHA-1 is supported at this time.
+If [SHA-256-based Git](https://git-scm.com/docs/hash-function-transition)
+becomes more widespread, this restriction will be revisited.
+
+[fso-ca]: ../file-system-object/content-address.md
+[sp-spec]: @docroot@/protocols/store-path.md
+[xp-feature-git-hashing]: @docroot@/contributing/experimental-features.md#xp-feature-git-hashing
diff --git a/doc/manual/src/store/store-path.md b/doc/manual/src/store/store-path.md
index 085aead5163..beec2389b1c 100644
--- a/doc/manual/src/store/store-path.md
+++ b/doc/manual/src/store/store-path.md
@@ -1,5 +1,11 @@
 # Store Path
 
+> **Example**
+>
+> `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1`
+>
+> A rendered store path
+
 Nix implements references to [store objects](./index.md#store-object) as *store paths*.
 
 Think of a store path as an [opaque], [unique identifier]:
@@ -37,6 +43,10 @@ A store path is rendered to a file system path as the concatenation of
 > store directory            digest                 name
 > ```
 
+Exactly how the digest is calculated depends on the type of store path.
+Store path digests are *supposed* to be opaque, and so for most operations, it is not necessary to know the details.
+That said, the manual has a full [specification of store path digests](@docroot@/protocols/store-path.md).
+
 ## Store Directory
 
 Every [Nix store](./index.md) has a store directory.
diff --git a/flake.lock b/flake.lock
index bb2e400c0a9..f64e3ea3712 100644
--- a/flake.lock
+++ b/flake.lock
@@ -16,6 +16,41 @@
         "type": "github"
       }
     },
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1712014858,
+        "narHash": "sha256-sB4SWl2lX95bExY2gMFG5HIzvva5AVMJd4Igm+GpZNw=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "9126214d0a59633752a136528f5f3b9aa8565b7d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1667395993,
+        "narHash": "sha256-nuEHfE/LcWyuSWnS8t12N1wc105Qtau+/OdUAjtQ0rA=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "5aed5285a952e0b949eb3ba02c12fa4fcfef535f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
     "libgit2": {
       "flake": false,
       "locked": {
@@ -34,17 +69,33 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1709083642,
-        "narHash": "sha256-7kkJQd4rZ+vFrzWu8sTRtta5D1kBG0LSRYAfhtmMlSo=",
+        "lastModified": 1717432640,
+        "narHash": "sha256-+f9c4/ZX5MWDOuB1rKoWj+lBNm0z0rs4CK47HBLxy1o=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "88269ab3044128b7c2f4c7d68448b2fb50456870",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "release-24.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-23-11": {
+      "locked": {
+        "lastModified": 1717159533,
+        "narHash": "sha256-oamiKNfr2MS6yH64rUn99mIZjc45nGJlj9eGth/3Xuw=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "b550fe4b4776908ac2a861124307045f8e717c8e",
+        "rev": "a62e6edd6d5e1fa0329b8653c801147986f8d446",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "release-23.11",
         "repo": "nixpkgs",
+        "rev": "a62e6edd6d5e1fa0329b8653c801147986f8d446",
         "type": "github"
       }
     },
@@ -64,12 +115,41 @@
         "type": "github"
       }
     },
+    "pre-commit-hooks": {
+      "inputs": {
+        "flake-compat": [],
+        "flake-utils": "flake-utils",
+        "gitignore": [],
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "nixpkgs-stable": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1712897695,
+        "narHash": "sha256-nMirxrGteNAl9sWiOhoN5tIHyjBbVi5e2tgZUgZlK3Y=",
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "40e6053ecb65fcbf12863338a6dcefb3f55f1bf8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "flake-compat": "flake-compat",
+        "flake-parts": "flake-parts",
         "libgit2": "libgit2",
         "nixpkgs": "nixpkgs",
-        "nixpkgs-regression": "nixpkgs-regression"
+        "nixpkgs-23-11": "nixpkgs-23-11",
+        "nixpkgs-regression": "nixpkgs-regression",
+        "pre-commit-hooks": "pre-commit-hooks"
       }
     }
   },
diff --git a/flake.nix b/flake.nix
index 8ee46101be6..d83c2ecad36 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,16 +3,28 @@
 
   # TODO switch to nixos-23.11-small
   #      https://nixpk.gs/pr-tracker.html?pr=291954
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/release-23.11";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/release-24.05";
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
+  inputs.nixpkgs-23-11.url = "github:NixOS/nixpkgs/a62e6edd6d5e1fa0329b8653c801147986f8d446";
   inputs.flake-compat = { url = "github:edolstra/flake-compat"; flake = false; };
   inputs.libgit2 = { url = "github:libgit2/libgit2"; flake = false; };
 
-  outputs = { self, nixpkgs, nixpkgs-regression, libgit2, ... }:
+  # dev tooling
+  inputs.flake-parts.url = "github:hercules-ci/flake-parts";
+  inputs.pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
+  # work around https://github.com/NixOS/nix/issues/7730
+  inputs.flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
+  inputs.pre-commit-hooks.inputs.nixpkgs.follows = "nixpkgs";
+  inputs.pre-commit-hooks.inputs.nixpkgs-stable.follows = "nixpkgs";
+  # work around 7730 and https://github.com/NixOS/nix/issues/7807
+  inputs.pre-commit-hooks.inputs.flake-compat.follows = "";
+  inputs.pre-commit-hooks.inputs.gitignore.follows = "";
+
+  outputs = inputs@{ self, nixpkgs, nixpkgs-regression, libgit2, ... }:
+
 
     let
       inherit (nixpkgs) lib;
-      inherit (lib) fileset;
 
       officialRelease = false;
 
@@ -31,7 +43,9 @@
       crossSystems = [
         "armv6l-unknown-linux-gnueabihf"
         "armv7l-unknown-linux-gnueabihf"
+        "riscv64-unknown-linux-gnu"
         "x86_64-unknown-netbsd"
+        "x86_64-unknown-freebsd"
         "x86_64-w64-mingw32"
       ];
 
@@ -43,6 +57,18 @@
         "stdenv"
       ];
 
+      /**
+        `flatMapAttrs attrs f` applies `f` to each attribute in `attrs` and
+        merges the results into a single attribute set.
+
+        This can be nested to form a build matrix where all the attributes
+        generated by the innermost `f` are returned as is.
+        (Provided that the names are unique.)
+
+        See https://nixos.org/manual/nixpkgs/stable/index.html#function-library-lib.attrsets.concatMapAttrs
+       */
+      flatMapAttrs = attrs: f: lib.concatMapAttrs f attrs;
+
       forAllSystems = lib.genAttrs systems;
 
       forAllCrossSystems = lib.genAttrs crossSystems;
@@ -56,6 +82,17 @@
             })
             stdenvs);
 
+
+      # We don't apply flake-parts to the whole flake so that non-development attributes
+      # load without fetching any development inputs.
+      devFlake = inputs.flake-parts.lib.mkFlake { inherit inputs; } {
+        imports = [ ./maintainers/flake-module.nix ];
+        systems = lib.subtractLists crossSystems systems;
+        perSystem = { system, ... }: {
+          _module.args.pkgs = nixpkgsFor.${system}.native;
+        };
+      };
+
       # Memoize nixpkgs for different platforms for efficiency.
       nixpkgsFor = forAllSystems
         (system: let
@@ -80,28 +117,6 @@
           cross = forAllCrossSystems (crossSystem: make-pkgs crossSystem "stdenv");
         });
 
-      installScriptFor = tarballs:
-        nixpkgsFor.x86_64-linux.native.callPackage ./scripts/installer.nix {
-          inherit tarballs;
-        };
-
-      testNixVersions = pkgs: client: daemon:
-        pkgs.callPackage ./package.nix {
-          pname =
-            "nix-tests"
-            + lib.optionalString
-              (lib.versionAtLeast daemon.version "2.4pre20211005" &&
-               lib.versionAtLeast client.version "2.4pre20211005")
-              "-${client.version}-against-${daemon.version}";
-
-          inherit fileset;
-
-          test-client = client;
-          test-daemon = daemon;
-
-          doBuild = false;
-        };
-
       binaryTarball = nix: pkgs: pkgs.callPackage ./scripts/binary-tarball.nix {
         inherit nix;
       };
@@ -113,233 +128,50 @@
         {
           nixStable = prev.nix;
 
-          default-busybox-sandbox-shell = final.busybox.override {
-            useMusl = true;
-            enableStatic = true;
-            enableMinimal = true;
-            extraConfig = ''
-              CONFIG_FEATURE_FANCY_ECHO y
-              CONFIG_FEATURE_SH_MATH y
-              CONFIG_FEATURE_SH_MATH_64 y
-
-              CONFIG_ASH y
-              CONFIG_ASH_OPTIMIZE_FOR_SIZE y
-
-              CONFIG_ASH_ALIAS y
-              CONFIG_ASH_BASH_COMPAT y
-              CONFIG_ASH_CMDCMD y
-              CONFIG_ASH_ECHO y
-              CONFIG_ASH_GETOPTS y
-              CONFIG_ASH_INTERNAL_GLOB y
-              CONFIG_ASH_JOB_CONTROL y
-              CONFIG_ASH_PRINTF y
-              CONFIG_ASH_TEST y
-            '';
-          };
-
-          libgit2-nix = final.libgit2.overrideAttrs (attrs: {
-            src = libgit2;
-            version = libgit2.lastModifiedDate;
-            cmakeFlags = attrs.cmakeFlags or []
-              ++ [ "-DUSE_SSH=exec" ];
+          # A new scope, so that we can use `callPackage` to inject our own interdependencies
+          # without "polluting" the top level "`pkgs`" attrset.
+          # This also has the benefit of providing us with a distinct set of packages
+          # we can iterate over.
+          nixComponents = lib.makeScope final.nixDependencies.newScope (import ./packaging/components.nix);
+
+          # The dependencies are in their own scope, so that they don't have to be
+          # in Nixpkgs top level `pkgs` or `nixComponents`.
+          nixDependencies = lib.makeScope final.newScope (import ./packaging/dependencies.nix {
+            inherit inputs stdenv versionSuffix;
+            pkgs = final;
           });
 
-          boehmgc-nix = (final.boehmgc.override {
-            enableLargeConfig = true;
-          }).overrideAttrs(o: {
-            patches = (o.patches or []) ++ [
-              ./dep-patches/boehmgc-coroutine-sp-fallback.diff
+          nix = final.nixComponents.nix;
 
-              # https://github.com/ivmai/bdwgc/pull/586
-              ./dep-patches/boehmgc-traceable_allocator-public.diff
-            ];
-          });
-
-          changelog-d-nix = final.buildPackages.callPackage ./misc/changelog-d.nix { };
-
-          nix =
-            let
-              officialRelease = false;
-              versionSuffix =
-                if officialRelease
-                then ""
-                else "pre${builtins.substring 0 8 (self.lastModifiedDate or self.lastModified or "19700101")}_${self.shortRev or "dirty"}";
-
-            in final.callPackage ./package.nix {
-              inherit
-                fileset
-                stdenv
-                versionSuffix
-                ;
-              officialRelease = false;
-              boehmgc = final.boehmgc-nix;
-              libgit2 = final.libgit2-nix;
-              busybox-sandbox-shell = final.busybox-sandbox-shell or final.default-busybox-sandbox-shell;
-            } // {
-              # this is a proper separate downstream package, but put
-              # here also for back compat reasons.
-              perl-bindings = final.nix-perl-bindings;
-            };
-
-          nix-perl-bindings = final.callPackage ./perl {
-            inherit fileset stdenv;
+          nix_noTests = final.nix.override {
+            doInstallCheck = false;
           };
 
+          # See https://github.com/NixOS/nixpkgs/pull/214409
+          # Remove when fixed in this flake's nixpkgs
+          pre-commit =
+            if prev.stdenv.hostPlatform.system == "i686-linux"
+            then (prev.pre-commit.override (o: { dotnet-sdk = ""; })).overridePythonAttrs (o: { doCheck = false; })
+            else prev.pre-commit;
+
         };
 
     in {
       # A Nixpkgs overlay that overrides the 'nix' and
-      # 'nix.perl-bindings' packages.
+      # 'nix-perl-bindings' packages.
       overlays.default = overlayFor (p: p.stdenv);
 
-      hydraJobs = {
-
-        # Binary package for various platforms.
-        build = forAllSystems (system: self.packages.${system}.nix);
-
-        shellInputs = forAllSystems (system: self.devShells.${system}.default.inputDerivation);
-
-        buildStatic = lib.genAttrs linux64BitSystems (system: self.packages.${system}.nix-static);
-
-        buildCross = forAllCrossSystems (crossSystem:
-          lib.genAttrs ["x86_64-linux"] (system: self.packages.${system}."nix-${crossSystem}"));
-
-        buildNoGc = forAllSystems (system:
-          self.packages.${system}.nix.override { enableGC = false; }
-        );
-
-        buildNoTests = forAllSystems (system:
-          self.packages.${system}.nix.override {
-            doCheck = false;
-            doInstallCheck = false;
-            installUnitTests = false;
-          }
-        );
-
-        # Toggles some settings for better coverage. Windows needs these
-        # library combinations, and Debian build Nix with GNU readline too.
-        buildReadlineNoMarkdown = forAllSystems (system:
-          self.packages.${system}.nix.override {
-            enableMarkdown = false;
-            readlineFlavor = "readline";
-          }
-        );
-
-        # Perl bindings for various platforms.
-        perlBindings = forAllSystems (system: nixpkgsFor.${system}.native.nix.perl-bindings);
-
-        # Binary tarball for various platforms, containing a Nix store
-        # with the closure of 'nix' package, and the second half of
-        # the installation script.
-        binaryTarball = forAllSystems (system: binaryTarball nixpkgsFor.${system}.native.nix nixpkgsFor.${system}.native);
-
-        binaryTarballCross = lib.genAttrs ["x86_64-linux"] (system:
-          forAllCrossSystems (crossSystem:
-            binaryTarball
-              self.packages.${system}."nix-${crossSystem}"
-              nixpkgsFor.${system}.cross.${crossSystem}));
-
-        # The first half of the installation script. This is uploaded
-        # to https://nixos.org/nix/install. It downloads the binary
-        # tarball for the user's system and calls the second half of the
-        # installation script.
-        installerScript = installScriptFor [
-          # Native
-          self.hydraJobs.binaryTarball."x86_64-linux"
-          self.hydraJobs.binaryTarball."i686-linux"
-          self.hydraJobs.binaryTarball."aarch64-linux"
-          self.hydraJobs.binaryTarball."x86_64-darwin"
-          self.hydraJobs.binaryTarball."aarch64-darwin"
-          # Cross
-          self.hydraJobs.binaryTarballCross."x86_64-linux"."armv6l-unknown-linux-gnueabihf"
-          self.hydraJobs.binaryTarballCross."x86_64-linux"."armv7l-unknown-linux-gnueabihf"
-        ];
-        installerScriptForGHA = installScriptFor [
-          # Native
-          self.hydraJobs.binaryTarball."x86_64-linux"
-          self.hydraJobs.binaryTarball."x86_64-darwin"
-          # Cross
-          self.hydraJobs.binaryTarballCross."x86_64-linux"."armv6l-unknown-linux-gnueabihf"
-          self.hydraJobs.binaryTarballCross."x86_64-linux"."armv7l-unknown-linux-gnueabihf"
-        ];
-
-        # docker image with Nix inside
-        dockerImage = lib.genAttrs linux64BitSystems (system: self.packages.${system}.dockerImage);
-
-        # Line coverage analysis.
-        coverage = nixpkgsFor.x86_64-linux.native.nix.override {
-          pname = "nix-coverage";
-          withCoverageChecks = true;
-        };
-
-        # API docs for Nix's unstable internal C++ interfaces.
-        internal-api-docs = nixpkgsFor.x86_64-linux.native.callPackage ./package.nix {
-          inherit fileset;
-          doBuild = false;
-          enableInternalAPIDocs = true;
-        };
-
-        # API docs for Nix's C bindings.
-        external-api-docs = nixpkgsFor.x86_64-linux.native.callPackage ./package.nix {
-          inherit fileset;
-          doBuild = false;
-          enableExternalAPIDocs = true;
-        };
-
-        # System tests.
-        tests = import ./tests/nixos { inherit lib nixpkgs nixpkgsFor; } // {
-
-          # Make sure that nix-env still produces the exact same result
-          # on a particular version of Nixpkgs.
-          evalNixpkgs =
-            let
-              inherit (nixpkgsFor.x86_64-linux.native) runCommand nix;
-            in
-            runCommand "eval-nixos" { buildInputs = [ nix ]; }
-              ''
-                type -p nix-env
-                # Note: we're filtering out nixos-install-tools because https://github.com/NixOS/nixpkgs/pull/153594#issuecomment-1020530593.
-                (
-                  set -x
-                  time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
-                  [[ $(sha1sum < packages | cut -c1-40) = e01b031fc9785a572a38be6bc473957e3b6faad7 ]]
-                )
-                mkdir $out
-              '';
-
-          nixpkgsLibTests =
-            forAllSystems (system:
-              import (nixpkgs + "/lib/tests/release.nix")
-                { pkgs = nixpkgsFor.${system}.native;
-                  nixVersions = [ self.packages.${system}.nix ];
-                }
-            );
-        };
-
-        metrics.nixpkgs = import "${nixpkgs-regression}/pkgs/top-level/metrics.nix" {
-          pkgs = nixpkgsFor.x86_64-linux.native;
-          nixpkgs = nixpkgs-regression;
-        };
-
-        installTests = forAllSystems (system:
-          let pkgs = nixpkgsFor.${system}.native; in
-          pkgs.runCommand "install-tests" {
-            againstSelf = testNixVersions pkgs pkgs.nix pkgs.pkgs.nix;
-            againstCurrentUnstable =
-              # FIXME: temporarily disable this on macOS because of #3605.
-              if system == "x86_64-linux"
-              then testNixVersions pkgs pkgs.nix pkgs.nixUnstable
-              else null;
-            # Disabled because the latest stable version doesn't handle
-            # `NIX_DAEMON_SOCKET_PATH` which is required for the tests to work
-            # againstLatestStable = testNixVersions pkgs pkgs.nix pkgs.nixStable;
-          } "touch $out");
-
-        installerTests = import ./tests/installer {
-          binaryTarballs = self.hydraJobs.binaryTarball;
-          inherit nixpkgsFor;
-        };
-
+      hydraJobs = import ./packaging/hydra.nix {
+        inherit
+          inputs
+          binaryTarball
+          forAllCrossSystems
+          forAllSystems
+          lib
+          linux64BitSystems
+          nixpkgsFor
+          self
+          ;
       };
 
       checks = forAllSystems (system: {
@@ -349,22 +181,76 @@
         rl-next =
           let pkgs = nixpkgsFor.${system}.native;
           in pkgs.buildPackages.runCommand "test-rl-next-release-notes" { } ''
-          LANG=C.UTF-8 ${pkgs.changelog-d-nix}/bin/changelog-d ${./doc/manual/rl-next} >$out
+          LANG=C.UTF-8 ${pkgs.changelog-d}/bin/changelog-d ${./doc/manual/rl-next} >$out
         '';
+        repl-completion = nixpkgsFor.${system}.native.callPackage ./tests/repl-completion.nix { };
       } // (lib.optionalAttrs (builtins.elem system linux64BitSystems)) {
         dockerImage = self.hydraJobs.dockerImage.${system};
       } // (lib.optionalAttrs (!(builtins.elem system linux32BitSystems))) {
         # Some perl dependencies are broken on i686-linux.
         # Since the support is only best-effort there, disable the perl
         # bindings
-        perlBindings = self.hydraJobs.perlBindings.${system};
-      });
 
-      packages = forAllSystems (system: rec {
-        inherit (nixpkgsFor.${system}.native) nix changelog-d-nix;
-        default = nix;
-      } // (lib.optionalAttrs (builtins.elem system linux64BitSystems) {
-        nix-static = nixpkgsFor.${system}.static.nix;
+        # Temporarily disabled because GitHub Actions OOM issues. Once
+        # the old build system is gone and we are back to one build
+        # system, we should reenable this.
+        #perlBindings = self.hydraJobs.perlBindings.${system};
+      }
+      # Add "passthru" tests
+      // flatMapAttrs ({
+          "" = nixpkgsFor.${system}.native;
+        } // lib.optionalAttrs (! nixpkgsFor.${system}.native.stdenv.hostPlatform.isDarwin) {
+          # TODO: enable static builds for darwin, blocked on:
+          #       https://github.com/NixOS/nixpkgs/issues/320448
+          "static-" = nixpkgsFor.${system}.static;
+        })
+        (nixpkgsPrefix: nixpkgs:
+          flatMapAttrs nixpkgs.nixComponents
+            (pkgName: pkg:
+              flatMapAttrs pkg.tests or {}
+              (testName: test: {
+                "${nixpkgsPrefix}${pkgName}-${testName}" = test;
+              })
+            )
+        )
+      // devFlake.checks.${system} or {}
+      );
+
+      packages = forAllSystems (system:
+        { # Here we put attributes that map 1:1 into packages.<system>, ie
+          # for which we don't apply the full build matrix such as cross or static.
+          inherit (nixpkgsFor.${system}.native)
+            changelog-d;
+          default = self.packages.${system}.nix;
+          nix-internal-api-docs = nixpkgsFor.${system}.native.nixComponents.nix-internal-api-docs;
+          nix-external-api-docs = nixpkgsFor.${system}.native.nixComponents.nix-external-api-docs;
+        }
+        # We need to flatten recursive attribute sets of derivations to pass `flake check`.
+        // flatMapAttrs
+          { # Components we'll iterate over in the upcoming lambda
+            "nix" = { };
+            # Temporarily disabled because GitHub Actions OOM issues. Once
+            # the old build system is gone and we are back to one build
+            # system, we should reenable these.
+            #"nix-util" = { };
+            #"nix-store" = { };
+            #"nix-fetchers" = { };
+          }
+          (pkgName: {}: {
+              # These attributes go right into `packages.<system>`.
+              "${pkgName}" = nixpkgsFor.${system}.native.nixComponents.${pkgName};
+              "${pkgName}-static" = nixpkgsFor.${system}.static.nixComponents.${pkgName};
+            }
+            // flatMapAttrs (lib.genAttrs crossSystems (_: { })) (crossSystem: {}: {
+              # These attributes go right into `packages.<system>`.
+              "${pkgName}-${crossSystem}" = nixpkgsFor.${system}.cross.${crossSystem}.nixComponents.${pkgName};
+            })
+            // flatMapAttrs (lib.genAttrs stdenvs (_: { })) (stdenvName: {}: {
+              # These attributes go right into `packages.<system>`.
+              "${pkgName}-${stdenvName}" = nixpkgsFor.${system}.stdenvs."${stdenvName}Packages".nixComponents.${pkgName};
+            })
+          )
+        // lib.optionalAttrs (builtins.elem system linux64BitSystems) {
         dockerImage =
           let
             pkgs = nixpkgsFor.${system}.native;
@@ -379,21 +265,26 @@
               ln -s ${image} $image
               echo "file binary-dist $image" >> $out/nix-support/hydra-build-products
             '';
-      } // builtins.listToAttrs (map
-          (crossSystem: {
-            name = "nix-${crossSystem}";
-            value = nixpkgsFor.${system}.cross.${crossSystem}.nix;
-          })
-          crossSystems)
-        // builtins.listToAttrs (map
-          (stdenvName: {
-            name = "nix-${stdenvName}";
-            value = nixpkgsFor.${system}.stdenvs."${stdenvName}Packages".nix;
-          })
-          stdenvs)));
+      });
 
       devShells = let
-        makeShell = pkgs: stdenv: (pkgs.nix.override { inherit stdenv; forDevShell = true; }).overrideAttrs (attrs: {
+        makeShell = pkgs: stdenv: (pkgs.nix.override { inherit stdenv; forDevShell = true; }).overrideAttrs (attrs:
+        let
+          modular = devFlake.getSystem stdenv.buildPlatform.system;
+          transformFlag = prefix: flag:
+            assert builtins.isString flag;
+            let
+              rest = builtins.substring 2 (builtins.stringLength flag) flag;
+            in
+              "-D${prefix}:${rest}";
+          havePerl = stdenv.buildPlatform == stdenv.hostPlatform && stdenv.hostPlatform.isUnix;
+        in {
+          pname = "shell-for-" + attrs.pname;
+
+          # Remove the version suffix to avoid unnecessary attempts to substitute in nix develop
+          version = lib.fileContents ./.version;
+          name = attrs.pname;
+
           installFlags = "sysconfdir=$(out)/etc";
           shellHook = ''
             PATH=$prefix/bin:$PATH
@@ -404,11 +295,51 @@
             XDG_DATA_DIRS+=:$out/share
           '';
 
+          # We use this shell with the local checkout, not unpackPhase.
+          src = null;
+
+          env = {
+            # Needed for Meson to find Boost.
+            # https://github.com/NixOS/nixpkgs/issues/86131.
+            BOOST_INCLUDEDIR = "${lib.getDev pkgs.nixDependencies.boost}/include";
+            BOOST_LIBRARYDIR = "${lib.getLib pkgs.nixDependencies.boost}/lib";
+            # For `make format`, to work without installing pre-commit
+            _NIX_PRE_COMMIT_HOOKS_CONFIG =
+              "${(pkgs.formats.yaml { }).generate "pre-commit-config.yaml" modular.pre-commit.settings.rawConfig}";
+          };
+
+          mesonFlags =
+            map (transformFlag "libutil") pkgs.nixComponents.nix-util.mesonFlags
+            ++ map (transformFlag "libstore") pkgs.nixComponents.nix-store.mesonFlags
+            ++ map (transformFlag "libfetchers") pkgs.nixComponents.nix-fetchers.mesonFlags
+            ++ lib.optionals havePerl (map (transformFlag "perl") pkgs.nixComponents.nix-perl-bindings.mesonFlags)
+            ;
+
           nativeBuildInputs = attrs.nativeBuildInputs or []
+            ++ pkgs.nixComponents.nix-util.nativeBuildInputs
+            ++ pkgs.nixComponents.nix-store.nativeBuildInputs
+            ++ pkgs.nixComponents.nix-fetchers.nativeBuildInputs
+            ++ lib.optionals havePerl pkgs.nixComponents.nix-perl-bindings.nativeBuildInputs
+            ++ pkgs.nixComponents.nix-internal-api-docs.nativeBuildInputs
+            ++ pkgs.nixComponents.nix-external-api-docs.nativeBuildInputs
+            ++ [
+              pkgs.buildPackages.cmake
+              modular.pre-commit.settings.package
+              (pkgs.writeScriptBin "pre-commit-hooks-install"
+                modular.pre-commit.settings.installationScript)
+            ]
             # TODO: Remove the darwin check once
             # https://github.com/NixOS/nixpkgs/pull/291814 is available
             ++ lib.optional (stdenv.cc.isClang && !stdenv.buildPlatform.isDarwin) pkgs.buildPackages.bear
             ++ lib.optional (stdenv.cc.isClang && stdenv.hostPlatform == stdenv.buildPlatform) pkgs.buildPackages.clang-tools;
+
+          buildInputs = attrs.buildInputs or []
+            ++ [
+              pkgs.gtest
+              pkgs.rapidcheck
+            ]
+            ++ lib.optional havePerl pkgs.perl
+            ;
         });
         in
         forAllSystems (system:
diff --git a/maintainers/README.md b/maintainers/README.md
index fa321c7c09f..2a718e283a2 100644
--- a/maintainers/README.md
+++ b/maintainers/README.md
@@ -30,17 +30,18 @@ We aim to achieve this by improving the contributor experience and attracting mo
 ## Members
 
 - Eelco Dolstra (@edolstra) – Team lead
-- Théophane Hufschmitt (@thufschmitt)
 - Valentin Gagarin (@fricklerhandwerk)
 - Thomas Bereknyei (@tomberek)
 - Robert Hensing (@roberth)
 - John Ericson (@Ericson2314)
 
+The team is on Github as [@NixOS/nix-team](https://github.com/orgs/NixOS/teams/nix-team).
+
 ## Meeting protocol
 
-The team meets twice a week:
+The team meets twice a week (times are denoted in the [Europe/Amsterdam](https://en.m.wikipedia.org/wiki/Time_in_the_Netherlands) time zone):
 
-- Discussion meeting: [Fridays 13:00-14:00 CET](https://calendar.google.com/calendar/event?eid=MHNtOGVuNWtrZXNpZHR2bW1sM3QyN2ZjaGNfMjAyMjExMjVUMTIwMDAwWiBiOW81MmZvYnFqYWs4b3E4bGZraGczdDBxZ0Bn)
+- Discussion meeting: [Wednesday 21:00-22:00 Europe/Amsterdam](https://www.google.com/calendar/event?eid=ZG5rZzNyajRjajducGV2NGY5aGkzYWIwdnJfMjAyNDA1MDhUMTkwMDAwWiBiOW81MmZvYnFqYWs4b3E4bGZraGczdDBxZ0Bn)
 
   1. Triage issues and pull requests from the [No Status](#no-status) column (30 min)
   2. Discuss issues and pull requests from the [To discuss](#to-discuss) column (30 min).
@@ -49,15 +50,19 @@ The team meets twice a week:
        - mark it as draft if it is blocked on the contributor
        - escalate it back to the team by moving it to To discuss, and leaving a comment as to why the issue needs to be discussed again.
 
-- Work meeting: [Mondays 13:00-15:00 CET](https://calendar.google.com/calendar/event?eid=NTM1MG1wNGJnOGpmOTZhYms3bTB1bnY5cWxfMjAyMjExMjFUMTIwMDAwWiBiOW81MmZvYnFqYWs4b3E4bGZraGczdDBxZ0Bn)
+- Work meeting: [Mondays 13:00-15:00 Europe/Amsterdam](https://www.google.com/calendar/event?eid=Ym52NDdzYnRic2NzcDcybjZiNDhpNzhpa3NfMjAyNDA1MTNUMTIwMDAwWiBiOW81MmZvYnFqYWs4b3E4bGZraGczdDBxZ0Bn)
 
   1. Code review on pull requests from [In review](#in-review).
   2. Other chores and tasks.
 
 Meeting notes are collected on a [collaborative scratchpad](https://pad.lassul.us/Cv7FpYx-Ri-4VjUykQOLAw).
-Notes on issues and pull requests are posted as comments and linked from the meeting notes, so they are easy to find from both places.
+Notes on issues and pull requests are posted as comments and linked from the meeting notes, so they are can be found from both places.
 [All meeting notes](https://discourse.nixos.org/search?expanded=true&q=Nix%20team%20meeting%20minutes%20%23%20%23dev%3Anix%20in%3Atitle%20order%3Alatest_topic) are published on Discourse under the [Nix category](https://discourse.nixos.org/c/dev/nix/50).
 
+Team meetings are generally open to anyone interested.
+We can make exceptions to discuss sensitive issues, such as security incidents or people matters.
+Contact any team member to get a calendar invite for reminders and updates.
+
 ## Project board protocol
 
 The team uses a [GitHub project board](https://github.com/orgs/NixOS/projects/19/views/1) for tracking its work.
diff --git a/maintainers/flake-module.nix b/maintainers/flake-module.nix
new file mode 100644
index 00000000000..46b3e136324
--- /dev/null
+++ b/maintainers/flake-module.nix
@@ -0,0 +1,678 @@
+{ lib, getSystem, inputs, ... }:
+
+{
+  imports = [
+    inputs.pre-commit-hooks.flakeModule
+  ];
+
+  perSystem = { config, pkgs, ... }: {
+
+    # https://flake.parts/options/pre-commit-hooks-nix.html#options
+    pre-commit.settings = {
+      hooks = {
+        clang-format = {
+          enable = true;
+          excludes = [
+            # We don't want to format test data
+            # ''tests/(?!nixos/).*\.nix''
+            ''^tests/unit/[^/]*/data/.*$''
+
+            # Don't format vendored code
+            ''^doc/manual/redirects\.js$''
+            ''^doc/manual/theme/highlight\.js$''
+
+            # We haven't applied formatting to these files yet
+            ''^doc/manual/redirects\.js$''
+            ''^doc/manual/theme/highlight\.js$''
+            ''^precompiled-headers\.h$''
+            ''^src/build-remote/build-remote\.cc$''
+            ''^src/libcmd/built-path\.cc$''
+            ''^src/libcmd/built-path\.hh$''
+            ''^src/libcmd/command\.cc$''
+            ''^src/libcmd/command\.hh$''
+            ''^src/libcmd/common-eval-args\.cc$''
+            ''^src/libcmd/common-eval-args\.hh$''
+            ''^src/libcmd/editor-for\.cc$''
+            ''^src/libcmd/installable-attr-path\.cc$''
+            ''^src/libcmd/installable-attr-path\.hh$''
+            ''^src/libcmd/installable-derived-path\.cc$''
+            ''^src/libcmd/installable-derived-path\.hh$''
+            ''^src/libcmd/installable-flake\.cc$''
+            ''^src/libcmd/installable-flake\.hh$''
+            ''^src/libcmd/installable-value\.cc$''
+            ''^src/libcmd/installable-value\.hh$''
+            ''^src/libcmd/installables\.cc$''
+            ''^src/libcmd/installables\.hh$''
+            ''^src/libcmd/legacy\.hh$''
+            ''^src/libcmd/markdown\.cc$''
+            ''^src/libcmd/misc-store-flags\.cc$''
+            ''^src/libcmd/repl-interacter\.cc$''
+            ''^src/libcmd/repl-interacter\.hh$''
+            ''^src/libcmd/repl\.cc$''
+            ''^src/libcmd/repl\.hh$''
+            ''^src/libexpr-c/nix_api_expr\.cc$''
+            ''^src/libexpr-c/nix_api_external\.cc$''
+            ''^src/libexpr/attr-path\.cc$''
+            ''^src/libexpr/attr-path\.hh$''
+            ''^src/libexpr/attr-set\.cc$''
+            ''^src/libexpr/attr-set\.hh$''
+            ''^src/libexpr/eval-cache\.cc$''
+            ''^src/libexpr/eval-cache\.hh$''
+            ''^src/libexpr/eval-error\.cc$''
+            ''^src/libexpr/eval-inline\.hh$''
+            ''^src/libexpr/eval-settings\.cc$''
+            ''^src/libexpr/eval-settings\.hh$''
+            ''^src/libexpr/eval\.cc$''
+            ''^src/libexpr/eval\.hh$''
+            ''^src/libexpr/function-trace\.cc$''
+            ''^src/libexpr/gc-small-vector\.hh$''
+            ''^src/libexpr/get-drvs\.cc$''
+            ''^src/libexpr/get-drvs\.hh$''
+            ''^src/libexpr/json-to-value\.cc$''
+            ''^src/libexpr/nixexpr\.cc$''
+            ''^src/libexpr/nixexpr\.hh$''
+            ''^src/libexpr/parser-state\.hh$''
+            ''^src/libexpr/pos-table\.hh$''
+            ''^src/libexpr/primops\.cc$''
+            ''^src/libexpr/primops\.hh$''
+            ''^src/libexpr/primops/context\.cc$''
+            ''^src/libexpr/primops/fetchClosure\.cc$''
+            ''^src/libexpr/primops/fetchMercurial\.cc$''
+            ''^src/libexpr/primops/fetchTree\.cc$''
+            ''^src/libexpr/primops/fromTOML\.cc$''
+            ''^src/libexpr/print-ambiguous\.cc$''
+            ''^src/libexpr/print-ambiguous\.hh$''
+            ''^src/libexpr/print-options\.hh$''
+            ''^src/libexpr/print\.cc$''
+            ''^src/libexpr/print\.hh$''
+            ''^src/libexpr/search-path\.cc$''
+            ''^src/libexpr/symbol-table\.hh$''
+            ''^src/libexpr/value-to-json\.cc$''
+            ''^src/libexpr/value-to-json\.hh$''
+            ''^src/libexpr/value-to-xml\.cc$''
+            ''^src/libexpr/value-to-xml\.hh$''
+            ''^src/libexpr/value\.hh$''
+            ''^src/libexpr/value/context\.cc$''
+            ''^src/libexpr/value/context\.hh$''
+            ''^src/libfetchers/attrs\.cc$''
+            ''^src/libfetchers/cache\.cc$''
+            ''^src/libfetchers/cache\.hh$''
+            ''^src/libfetchers/fetch-settings\.cc$''
+            ''^src/libfetchers/fetch-settings\.hh$''
+            ''^src/libfetchers/fetch-to-store\.cc$''
+            ''^src/libfetchers/fetchers\.cc$''
+            ''^src/libfetchers/fetchers\.hh$''
+            ''^src/libfetchers/filtering-source-accessor\.cc$''
+            ''^src/libfetchers/filtering-source-accessor\.hh$''
+            ''^src/libfetchers/fs-source-accessor\.cc$''
+            ''^src/libfetchers/fs-source-accessor\.hh$''
+            ''^src/libfetchers/git-utils\.cc$''
+            ''^src/libfetchers/git-utils\.hh$''
+            ''^src/libfetchers/github\.cc$''
+            ''^src/libfetchers/indirect\.cc$''
+            ''^src/libfetchers/memory-source-accessor\.cc$''
+            ''^src/libfetchers/path\.cc$''
+            ''^src/libfetchers/registry\.cc$''
+            ''^src/libfetchers/registry\.hh$''
+            ''^src/libfetchers/tarball\.cc$''
+            ''^src/libfetchers/tarball\.hh$''
+            ''^src/libfetchers/git\.cc$''
+            ''^src/libfetchers/mercurial\.cc$''
+            ''^src/libflake/flake/config\.cc$''
+            ''^src/libflake/flake/flake\.cc$''
+            ''^src/libflake/flake/flake\.hh$''
+            ''^src/libflake/flake/flakeref\.cc$''
+            ''^src/libflake/flake/flakeref\.hh$''
+            ''^src/libflake/flake/lockfile\.cc$''
+            ''^src/libflake/flake/lockfile\.hh$''
+            ''^src/libflake/flake/url-name\.cc$''
+            ''^src/libmain/common-args\.cc$''
+            ''^src/libmain/common-args\.hh$''
+            ''^src/libmain/loggers\.cc$''
+            ''^src/libmain/loggers\.hh$''
+            ''^src/libmain/progress-bar\.cc$''
+            ''^src/libmain/shared\.cc$''
+            ''^src/libmain/shared\.hh$''
+            ''^src/libmain/unix/stack\.cc$''
+            ''^src/libstore/binary-cache-store\.cc$''
+            ''^src/libstore/binary-cache-store\.hh$''
+            ''^src/libstore/build-result\.hh$''
+            ''^src/libstore/builtins\.hh$''
+            ''^src/libstore/builtins/buildenv\.cc$''
+            ''^src/libstore/builtins/buildenv\.hh$''
+            ''^src/libstore/common-protocol-impl\.hh$''
+            ''^src/libstore/common-protocol\.cc$''
+            ''^src/libstore/common-protocol\.hh$''
+            ''^src/libstore/content-address\.cc$''
+            ''^src/libstore/content-address\.hh$''
+            ''^src/libstore/daemon\.cc$''
+            ''^src/libstore/daemon\.hh$''
+            ''^src/libstore/derivations\.cc$''
+            ''^src/libstore/derivations\.hh$''
+            ''^src/libstore/derived-path-map\.cc$''
+            ''^src/libstore/derived-path-map\.hh$''
+            ''^src/libstore/derived-path\.cc$''
+            ''^src/libstore/derived-path\.hh$''
+            ''^src/libstore/downstream-placeholder\.cc$''
+            ''^src/libstore/downstream-placeholder\.hh$''
+            ''^src/libstore/dummy-store\.cc$''
+            ''^src/libstore/export-import\.cc$''
+            ''^src/libstore/filetransfer\.cc$''
+            ''^src/libstore/filetransfer\.hh$''
+            ''^src/libstore/gc-store\.hh$''
+            ''^src/libstore/globals\.cc$''
+            ''^src/libstore/globals\.hh$''
+            ''^src/libstore/http-binary-cache-store\.cc$''
+            ''^src/libstore/legacy-ssh-store\.cc$''
+            ''^src/libstore/legacy-ssh-store\.hh$''
+            ''^src/libstore/length-prefixed-protocol-helper\.hh$''
+            ''^src/libstore/linux/personality\.cc$''
+            ''^src/libstore/linux/personality\.hh$''
+            ''^src/libstore/local-binary-cache-store\.cc$''
+            ''^src/libstore/local-fs-store\.cc$''
+            ''^src/libstore/local-fs-store\.hh$''
+            ''^src/libstore/log-store\.cc$''
+            ''^src/libstore/log-store\.hh$''
+            ''^src/libstore/machines\.cc$''
+            ''^src/libstore/machines\.hh$''
+            ''^src/libstore/make-content-addressed\.cc$''
+            ''^src/libstore/make-content-addressed\.hh$''
+            ''^src/libstore/misc\.cc$''
+            ''^src/libstore/names\.cc$''
+            ''^src/libstore/names\.hh$''
+            ''^src/libstore/nar-accessor\.cc$''
+            ''^src/libstore/nar-accessor\.hh$''
+            ''^src/libstore/nar-info-disk-cache\.cc$''
+            ''^src/libstore/nar-info-disk-cache\.hh$''
+            ''^src/libstore/nar-info\.cc$''
+            ''^src/libstore/nar-info\.hh$''
+            ''^src/libstore/outputs-spec\.cc$''
+            ''^src/libstore/outputs-spec\.hh$''
+            ''^src/libstore/parsed-derivations\.cc$''
+            ''^src/libstore/path-info\.cc$''
+            ''^src/libstore/path-info\.hh$''
+            ''^src/libstore/path-references\.cc$''
+            ''^src/libstore/path-regex\.hh$''
+            ''^src/libstore/path-with-outputs\.cc$''
+            ''^src/libstore/path\.cc$''
+            ''^src/libstore/path\.hh$''
+            ''^src/libstore/pathlocks\.cc$''
+            ''^src/libstore/pathlocks\.hh$''
+            ''^src/libstore/profiles\.cc$''
+            ''^src/libstore/profiles\.hh$''
+            ''^src/libstore/realisation\.cc$''
+            ''^src/libstore/realisation\.hh$''
+            ''^src/libstore/remote-fs-accessor\.cc$''
+            ''^src/libstore/remote-fs-accessor\.hh$''
+            ''^src/libstore/remote-store-connection\.hh$''
+            ''^src/libstore/remote-store\.cc$''
+            ''^src/libstore/remote-store\.hh$''
+            ''^src/libstore/s3-binary-cache-store\.cc$''
+            ''^src/libstore/s3\.hh$''
+            ''^src/libstore/serve-protocol-impl\.cc$''
+            ''^src/libstore/serve-protocol-impl\.hh$''
+            ''^src/libstore/serve-protocol\.cc$''
+            ''^src/libstore/serve-protocol\.hh$''
+            ''^src/libstore/sqlite\.cc$''
+            ''^src/libstore/sqlite\.hh$''
+            ''^src/libstore/ssh-store-config\.hh$''
+            ''^src/libstore/ssh-store\.cc$''
+            ''^src/libstore/ssh\.cc$''
+            ''^src/libstore/ssh\.hh$''
+            ''^src/libstore/store-api\.cc$''
+            ''^src/libstore/store-api\.hh$''
+            ''^src/libstore/store-dir-config\.hh$''
+            ''^src/libstore/build/derivation-goal\.cc$''
+            ''^src/libstore/build/derivation-goal\.hh$''
+            ''^src/libstore/build/drv-output-substitution-goal\.cc$''
+            ''^src/libstore/build/drv-output-substitution-goal\.hh$''
+            ''^src/libstore/build/entry-points\.cc$''
+            ''^src/libstore/build/goal\.cc$''
+            ''^src/libstore/build/goal\.hh$''
+            ''^src/libstore/unix/build/hook-instance\.cc$''
+            ''^src/libstore/unix/build/local-derivation-goal\.cc$''
+            ''^src/libstore/unix/build/local-derivation-goal\.hh$''
+            ''^src/libstore/build/substitution-goal\.cc$''
+            ''^src/libstore/build/substitution-goal\.hh$''
+            ''^src/libstore/build/worker\.cc$''
+            ''^src/libstore/build/worker\.hh$''
+            ''^src/libstore/builtins/fetchurl\.cc$''
+            ''^src/libstore/builtins/unpack-channel\.cc$''
+            ''^src/libstore/gc\.cc$''
+            ''^src/libstore/local-overlay-store\.cc$''
+            ''^src/libstore/local-overlay-store\.hh$''
+            ''^src/libstore/local-store\.cc$''
+            ''^src/libstore/local-store\.hh$''
+            ''^src/libstore/unix/user-lock\.cc$''
+            ''^src/libstore/unix/user-lock\.hh$''
+            ''^src/libstore/optimise-store\.cc$''
+            ''^src/libstore/unix/pathlocks\.cc$''
+            ''^src/libstore/posix-fs-canonicalise\.cc$''
+            ''^src/libstore/posix-fs-canonicalise\.hh$''
+            ''^src/libstore/uds-remote-store\.cc$''
+            ''^src/libstore/uds-remote-store\.hh$''
+            ''^src/libstore/windows/build\.cc$''
+            ''^src/libstore/worker-protocol-impl\.hh$''
+            ''^src/libstore/worker-protocol\.cc$''
+            ''^src/libstore/worker-protocol\.hh$''
+            ''^src/libutil-c/nix_api_util_internal\.h$''
+            ''^src/libutil/archive\.cc$''
+            ''^src/libutil/archive\.hh$''
+            ''^src/libutil/args\.cc$''
+            ''^src/libutil/args\.hh$''
+            ''^src/libutil/args/root\.hh$''
+            ''^src/libutil/callback\.hh$''
+            ''^src/libutil/canon-path\.cc$''
+            ''^src/libutil/canon-path\.hh$''
+            ''^src/libutil/chunked-vector\.hh$''
+            ''^src/libutil/closure\.hh$''
+            ''^src/libutil/comparator\.hh$''
+            ''^src/libutil/compute-levels\.cc$''
+            ''^src/libutil/config-impl\.hh$''
+            ''^src/libutil/config\.cc$''
+            ''^src/libutil/config\.hh$''
+            ''^src/libutil/current-process\.cc$''
+            ''^src/libutil/current-process\.hh$''
+            ''^src/libutil/english\.cc$''
+            ''^src/libutil/english\.hh$''
+            ''^src/libutil/environment-variables\.cc$''
+            ''^src/libutil/error\.cc$''
+            ''^src/libutil/error\.hh$''
+            ''^src/libutil/exit\.hh$''
+            ''^src/libutil/experimental-features\.cc$''
+            ''^src/libutil/experimental-features\.hh$''
+            ''^src/libutil/file-content-address\.cc$''
+            ''^src/libutil/file-content-address\.hh$''
+            ''^src/libutil/file-descriptor\.cc$''
+            ''^src/libutil/file-descriptor\.hh$''
+            ''^src/libutil/file-path-impl\.hh$''
+            ''^src/libutil/file-path\.hh$''
+            ''^src/libutil/file-system\.cc$''
+            ''^src/libutil/file-system\.hh$''
+            ''^src/libutil/finally\.hh$''
+            ''^src/libutil/fmt\.hh$''
+            ''^src/libutil/fs-sink\.cc$''
+            ''^src/libutil/fs-sink\.hh$''
+            ''^src/libutil/git\.cc$''
+            ''^src/libutil/git\.hh$''
+            ''^src/libutil/hash\.cc$''
+            ''^src/libutil/hash\.hh$''
+            ''^src/libutil/hilite\.cc$''
+            ''^src/libutil/hilite\.hh$''
+            ''^src/libutil/source-accessor\.hh$''
+            ''^src/libutil/json-impls\.hh$''
+            ''^src/libutil/json-utils\.cc$''
+            ''^src/libutil/json-utils\.hh$''
+            ''^src/libutil/linux/cgroup\.cc$''
+            ''^src/libutil/linux/namespaces\.cc$''
+            ''^src/libutil/logging\.cc$''
+            ''^src/libutil/logging\.hh$''
+            ''^src/libutil/lru-cache\.hh$''
+            ''^src/libutil/memory-source-accessor\.cc$''
+            ''^src/libutil/memory-source-accessor\.hh$''
+            ''^src/libutil/pool\.hh$''
+            ''^src/libutil/position\.cc$''
+            ''^src/libutil/position\.hh$''
+            ''^src/libutil/posix-source-accessor\.cc$''
+            ''^src/libutil/posix-source-accessor\.hh$''
+            ''^src/libutil/processes\.hh$''
+            ''^src/libutil/ref\.hh$''
+            ''^src/libutil/references\.cc$''
+            ''^src/libutil/references\.hh$''
+            ''^src/libutil/regex-combinators\.hh$''
+            ''^src/libutil/serialise\.cc$''
+            ''^src/libutil/serialise\.hh$''
+            ''^src/libutil/signals\.hh$''
+            ''^src/libutil/signature/local-keys\.cc$''
+            ''^src/libutil/signature/local-keys\.hh$''
+            ''^src/libutil/signature/signer\.cc$''
+            ''^src/libutil/signature/signer\.hh$''
+            ''^src/libutil/source-accessor\.cc$''
+            ''^src/libutil/source-accessor\.hh$''
+            ''^src/libutil/source-path\.cc$''
+            ''^src/libutil/source-path\.hh$''
+            ''^src/libutil/split\.hh$''
+            ''^src/libutil/suggestions\.cc$''
+            ''^src/libutil/suggestions\.hh$''
+            ''^src/libutil/sync\.hh$''
+            ''^src/libutil/terminal\.cc$''
+            ''^src/libutil/terminal\.hh$''
+            ''^src/libutil/thread-pool\.cc$''
+            ''^src/libutil/thread-pool\.hh$''
+            ''^src/libutil/topo-sort\.hh$''
+            ''^src/libutil/types\.hh$''
+            ''^src/libutil/unix/file-descriptor\.cc$''
+            ''^src/libutil/unix/file-path\.cc$''
+            ''^src/libutil/unix/monitor-fd\.hh$''
+            ''^src/libutil/unix/processes\.cc$''
+            ''^src/libutil/unix/signals-impl\.hh$''
+            ''^src/libutil/unix/signals\.cc$''
+            ''^src/libutil/unix-domain-socket\.cc$''
+            ''^src/libutil/unix/users\.cc$''
+            ''^src/libutil/url-parts\.hh$''
+            ''^src/libutil/url\.cc$''
+            ''^src/libutil/url\.hh$''
+            ''^src/libutil/users\.cc$''
+            ''^src/libutil/users\.hh$''
+            ''^src/libutil/util\.cc$''
+            ''^src/libutil/util\.hh$''
+            ''^src/libutil/variant-wrapper\.hh$''
+            ''^src/libutil/windows/environment-variables\.cc$''
+            ''^src/libutil/windows/file-descriptor\.cc$''
+            ''^src/libutil/windows/file-path\.cc$''
+            ''^src/libutil/windows/processes\.cc$''
+            ''^src/libutil/windows/users\.cc$''
+            ''^src/libutil/windows/windows-error\.cc$''
+            ''^src/libutil/windows/windows-error\.hh$''
+            ''^src/libutil/xml-writer\.cc$''
+            ''^src/libutil/xml-writer\.hh$''
+            ''^src/nix-build/nix-build\.cc$''
+            ''^src/nix-channel/nix-channel\.cc$''
+            ''^src/nix-collect-garbage/nix-collect-garbage\.cc$''
+            ''^src/nix-env/buildenv.nix$''
+            ''^src/nix-env/nix-env\.cc$''
+            ''^src/nix-env/user-env\.cc$''
+            ''^src/nix-env/user-env\.hh$''
+            ''^src/nix-instantiate/nix-instantiate\.cc$''
+            ''^src/nix-store/dotgraph\.cc$''
+            ''^src/nix-store/graphml\.cc$''
+            ''^src/nix-store/nix-store\.cc$''
+            ''^src/nix/add-to-store\.cc$''
+            ''^src/nix/app\.cc$''
+            ''^src/nix/build\.cc$''
+            ''^src/nix/bundle\.cc$''
+            ''^src/nix/cat\.cc$''
+            ''^src/nix/config-check\.cc$''
+            ''^src/nix/config\.cc$''
+            ''^src/nix/copy\.cc$''
+            ''^src/nix/derivation-add\.cc$''
+            ''^src/nix/derivation-show\.cc$''
+            ''^src/nix/derivation\.cc$''
+            ''^src/nix/develop\.cc$''
+            ''^src/nix/diff-closures\.cc$''
+            ''^src/nix/dump-path\.cc$''
+            ''^src/nix/edit\.cc$''
+            ''^src/nix/eval\.cc$''
+            ''^src/nix/flake\.cc$''
+            ''^src/nix/fmt\.cc$''
+            ''^src/nix/hash\.cc$''
+            ''^src/nix/log\.cc$''
+            ''^src/nix/ls\.cc$''
+            ''^src/nix/main\.cc$''
+            ''^src/nix/make-content-addressed\.cc$''
+            ''^src/nix/nar\.cc$''
+            ''^src/nix/optimise-store\.cc$''
+            ''^src/nix/path-from-hash-part\.cc$''
+            ''^src/nix/path-info\.cc$''
+            ''^src/nix/prefetch\.cc$''
+            ''^src/nix/profile\.cc$''
+            ''^src/nix/realisation\.cc$''
+            ''^src/nix/registry\.cc$''
+            ''^src/nix/repl\.cc$''
+            ''^src/nix/run\.cc$''
+            ''^src/nix/run\.hh$''
+            ''^src/nix/search\.cc$''
+            ''^src/nix/sigs\.cc$''
+            ''^src/nix/store-copy-log\.cc$''
+            ''^src/nix/store-delete\.cc$''
+            ''^src/nix/store-gc\.cc$''
+            ''^src/nix/store-info\.cc$''
+            ''^src/nix/store-repair\.cc$''
+            ''^src/nix/store\.cc$''
+            ''^src/nix/unix/daemon\.cc$''
+            ''^src/nix/upgrade-nix\.cc$''
+            ''^src/nix/verify\.cc$''
+            ''^src/nix/why-depends\.cc$''
+
+            ''^tests/functional/plugins/plugintest\.cc''
+            ''^tests/functional/test-libstoreconsumer/main\.cc''
+            ''^tests/nixos/ca-fd-leak/sender\.c''
+            ''^tests/nixos/ca-fd-leak/smuggler\.c''
+            ''^tests/nixos/user-sandboxing/attacker\.c''
+            ''^tests/unit/libexpr-support/tests/libexpr\.hh''
+            ''^tests/unit/libexpr-support/tests/value/context\.cc''
+            ''^tests/unit/libexpr-support/tests/value/context\.hh''
+            ''^tests/unit/libexpr/derived-path\.cc''
+            ''^tests/unit/libexpr/error_traces\.cc''
+            ''^tests/unit/libexpr/eval\.cc''
+            ''^tests/unit/libexpr/json\.cc''
+            ''^tests/unit/libexpr/main\.cc''
+            ''^tests/unit/libexpr/primops\.cc''
+            ''^tests/unit/libexpr/search-path\.cc''
+            ''^tests/unit/libexpr/trivial\.cc''
+            ''^tests/unit/libexpr/value/context\.cc''
+            ''^tests/unit/libexpr/value/print\.cc''
+            ''^tests/unit/libfetchers/public-key\.cc''
+            ''^tests/unit/libflake/flakeref\.cc''
+            ''^tests/unit/libflake/url-name\.cc''
+            ''^tests/unit/libstore-support/tests/derived-path\.cc''
+            ''^tests/unit/libstore-support/tests/derived-path\.hh''
+            ''^tests/unit/libstore-support/tests/nix_api_store\.hh''
+            ''^tests/unit/libstore-support/tests/outputs-spec\.cc''
+            ''^tests/unit/libstore-support/tests/outputs-spec\.hh''
+            ''^tests/unit/libstore-support/tests/path\.cc''
+            ''^tests/unit/libstore-support/tests/path\.hh''
+            ''^tests/unit/libstore-support/tests/protocol\.hh''
+            ''^tests/unit/libstore/common-protocol\.cc''
+            ''^tests/unit/libstore/content-address\.cc''
+            ''^tests/unit/libstore/derivation\.cc''
+            ''^tests/unit/libstore/derived-path\.cc''
+            ''^tests/unit/libstore/downstream-placeholder\.cc''
+            ''^tests/unit/libstore/machines\.cc''
+            ''^tests/unit/libstore/nar-info-disk-cache\.cc''
+            ''^tests/unit/libstore/nar-info\.cc''
+            ''^tests/unit/libstore/outputs-spec\.cc''
+            ''^tests/unit/libstore/path-info\.cc''
+            ''^tests/unit/libstore/path\.cc''
+            ''^tests/unit/libstore/serve-protocol\.cc''
+            ''^tests/unit/libstore/worker-protocol\.cc''
+            ''^tests/unit/libutil-support/tests/characterization\.hh''
+            ''^tests/unit/libutil-support/tests/hash\.cc''
+            ''^tests/unit/libutil-support/tests/hash\.hh''
+            ''^tests/unit/libutil/args\.cc''
+            ''^tests/unit/libutil/canon-path\.cc''
+            ''^tests/unit/libutil/chunked-vector\.cc''
+            ''^tests/unit/libutil/closure\.cc''
+            ''^tests/unit/libutil/compression\.cc''
+            ''^tests/unit/libutil/config\.cc''
+            ''^tests/unit/libutil/file-content-address\.cc''
+            ''^tests/unit/libutil/git\.cc''
+            ''^tests/unit/libutil/hash\.cc''
+            ''^tests/unit/libutil/hilite\.cc''
+            ''^tests/unit/libutil/json-utils\.cc''
+            ''^tests/unit/libutil/logging\.cc''
+            ''^tests/unit/libutil/lru-cache\.cc''
+            ''^tests/unit/libutil/pool\.cc''
+            ''^tests/unit/libutil/references\.cc''
+            ''^tests/unit/libutil/suggestions\.cc''
+            ''^tests/unit/libutil/tests\.cc''
+            ''^tests/unit/libutil/url\.cc''
+            ''^tests/unit/libutil/xml-writer\.cc''
+          ];
+        };
+        shellcheck = {
+          enable = true;
+          excludes = [
+            # We haven't linted these files yet
+            ''^config/install-sh$''
+            ''^misc/systemv/nix-daemon$''
+            ''^misc/bash/completion\.sh$''
+            ''^misc/fish/completion\.fish$''
+            ''^misc/zsh/completion\.zsh$''
+            ''^scripts/create-darwin-volume\.sh$''
+            ''^scripts/install-darwin-multi-user\.sh$''
+            ''^scripts/install-multi-user\.sh$''
+            ''^scripts/install-nix-from-closure\.sh$''
+            ''^scripts/install-systemd-multi-user\.sh$''
+            ''^src/nix/get-env\.sh$''
+            ''^tests/functional/build\.sh$''
+            ''^tests/functional/ca/build-dry\.sh$''
+            ''^tests/functional/ca/build-with-garbage-path\.sh$''
+            ''^tests/functional/ca/common\.sh$''
+            ''^tests/functional/ca/concurrent-builds\.sh$''
+            ''^tests/functional/ca/eval-store\.sh$''
+            ''^tests/functional/ca/gc\.sh$''
+            ''^tests/functional/ca/import-derivation\.sh$''
+            ''^tests/functional/ca/new-build-cmd\.sh$''
+            ''^tests/functional/ca/nix-shell\.sh$''
+            ''^tests/functional/ca/post-hook\.sh$''
+            ''^tests/functional/ca/recursive\.sh$''
+            ''^tests/functional/ca/repl\.sh$''
+            ''^tests/functional/ca/selfref-gc\.sh$''
+            ''^tests/functional/ca/why-depends\.sh$''
+            ''^tests/functional/characterisation-test-infra\.sh$''
+            ''^tests/functional/check\.sh$''
+            ''^tests/functional/common/vars-and-functions\.sh$''
+            ''^tests/functional/completions\.sh$''
+            ''^tests/functional/compute-levels\.sh$''
+            ''^tests/functional/config\.sh$''
+            ''^tests/functional/db-migration\.sh$''
+            ''^tests/functional/debugger\.sh$''
+            ''^tests/functional/dependencies\.builder0\.sh$''
+            ''^tests/functional/dependencies\.sh$''
+            ''^tests/functional/dump-db\.sh$''
+            ''^tests/functional/dyn-drv/build-built-drv\.sh$''
+            ''^tests/functional/dyn-drv/common\.sh$''
+            ''^tests/functional/dyn-drv/dep-built-drv\.sh$''
+            ''^tests/functional/dyn-drv/eval-outputOf\.sh$''
+            ''^tests/functional/dyn-drv/old-daemon-error-hack\.sh$''
+            ''^tests/functional/dyn-drv/recursive-mod-json\.sh$''
+            ''^tests/functional/eval-store\.sh$''
+            ''^tests/functional/eval\.sh$''
+            ''^tests/functional/export-graph\.sh$''
+            ''^tests/functional/export\.sh$''
+            ''^tests/functional/extra-sandbox-profile\.sh$''
+            ''^tests/functional/fetchClosure\.sh$''
+            ''^tests/functional/fetchGit\.sh$''
+            ''^tests/functional/fetchGitRefs\.sh$''
+            ''^tests/functional/fetchGitSubmodules\.sh$''
+            ''^tests/functional/fetchGitVerification\.sh$''
+            ''^tests/functional/fetchMercurial\.sh$''
+            ''^tests/functional/fetchurl\.sh$''
+            ''^tests/functional/fixed\.builder1\.sh$''
+            ''^tests/functional/fixed\.builder2\.sh$''
+            ''^tests/functional/fixed\.sh$''
+            ''^tests/functional/flakes/absolute-paths\.sh$''
+            ''^tests/functional/flakes/check\.sh$''
+            ''^tests/functional/flakes/common\.sh$''
+            ''^tests/functional/flakes/config\.sh$''
+            ''^tests/functional/flakes/develop\.sh$''
+            ''^tests/functional/flakes/flakes\.sh$''
+            ''^tests/functional/flakes/follow-paths\.sh$''
+            ''^tests/functional/flakes/prefetch\.sh$''
+            ''^tests/functional/flakes/run\.sh$''
+            ''^tests/functional/flakes/show\.sh$''
+            ''^tests/functional/fmt\.sh$''
+            ''^tests/functional/fmt\.simple\.sh$''
+            ''^tests/functional/gc-auto\.sh$''
+            ''^tests/functional/gc-concurrent\.builder\.sh$''
+            ''^tests/functional/gc-concurrent\.sh$''
+            ''^tests/functional/gc-concurrent2\.builder\.sh$''
+            ''^tests/functional/gc-non-blocking\.sh$''
+            ''^tests/functional/gc\.sh$''
+            ''^tests/functional/git-hashing/common\.sh$''
+            ''^tests/functional/git-hashing/simple\.sh$''
+            ''^tests/functional/hash-convert\.sh$''
+            ''^tests/functional/help\.sh$''
+            ''^tests/functional/impure-derivations\.sh$''
+            ''^tests/functional/impure-env\.sh$''
+            ''^tests/functional/impure-eval\.sh$''
+            ''^tests/functional/install-darwin\.sh$''
+            ''^tests/functional/lang\.sh$''
+            ''^tests/functional/legacy-ssh-store\.sh$''
+            ''^tests/functional/linux-sandbox\.sh$''
+            ''^tests/functional/local-overlay-store/add-lower-inner\.sh$''
+            ''^tests/functional/local-overlay-store/add-lower\.sh$''
+            ''^tests/functional/local-overlay-store/bad-uris\.sh$''
+            ''^tests/functional/local-overlay-store/build-inner\.sh$''
+            ''^tests/functional/local-overlay-store/build\.sh$''
+            ''^tests/functional/local-overlay-store/check-post-init-inner\.sh$''
+            ''^tests/functional/local-overlay-store/check-post-init\.sh$''
+            ''^tests/functional/local-overlay-store/common\.sh$''
+            ''^tests/functional/local-overlay-store/delete-duplicate-inner\.sh$''
+            ''^tests/functional/local-overlay-store/delete-duplicate\.sh$''
+            ''^tests/functional/local-overlay-store/delete-refs-inner\.sh$''
+            ''^tests/functional/local-overlay-store/delete-refs\.sh$''
+            ''^tests/functional/local-overlay-store/gc-inner\.sh$''
+            ''^tests/functional/local-overlay-store/gc\.sh$''
+            ''^tests/functional/local-overlay-store/optimise-inner\.sh$''
+            ''^tests/functional/local-overlay-store/optimise\.sh$''
+            ''^tests/functional/local-overlay-store/redundant-add-inner\.sh$''
+            ''^tests/functional/local-overlay-store/redundant-add\.sh$''
+            ''^tests/functional/local-overlay-store/remount\.sh$''
+            ''^tests/functional/local-overlay-store/stale-file-handle-inner\.sh$''
+            ''^tests/functional/local-overlay-store/stale-file-handle\.sh$''
+            ''^tests/functional/local-overlay-store/verify-inner\.sh$''
+            ''^tests/functional/local-overlay-store/verify\.sh$''
+            ''^tests/functional/logging\.sh$''
+            ''^tests/functional/misc\.sh$''
+            ''^tests/functional/multiple-outputs\.sh$''
+            ''^tests/functional/nar-access\.sh$''
+            ''^tests/functional/nested-sandboxing\.sh$''
+            ''^tests/functional/nested-sandboxing/command\.sh$''
+            ''^tests/functional/nix-build\.sh$''
+            ''^tests/functional/nix-channel\.sh$''
+            ''^tests/functional/nix-collect-garbage-d\.sh$''
+            ''^tests/functional/nix-copy-ssh-common\.sh$''
+            ''^tests/functional/nix-copy-ssh-ng\.sh$''
+            ''^tests/functional/nix-copy-ssh\.sh$''
+            ''^tests/functional/nix-daemon-untrusting\.sh$''
+            ''^tests/functional/nix-profile\.sh$''
+            ''^tests/functional/nix-shell\.sh$''
+            ''^tests/functional/nix_path\.sh$''
+            ''^tests/functional/optimise-store\.sh$''
+            ''^tests/functional/output-normalization\.sh$''
+            ''^tests/functional/parallel\.builder\.sh$''
+            ''^tests/functional/parallel\.sh$''
+            ''^tests/functional/pass-as-file\.sh$''
+            ''^tests/functional/path-from-hash-part\.sh$''
+            ''^tests/functional/path-info\.sh$''
+            ''^tests/functional/placeholders\.sh$''
+            ''^tests/functional/plugins\.sh$''
+            ''^tests/functional/post-hook\.sh$''
+            ''^tests/functional/pure-eval\.sh$''
+            ''^tests/functional/push-to-store-old\.sh$''
+            ''^tests/functional/push-to-store\.sh$''
+            ''^tests/functional/read-only-store\.sh$''
+            ''^tests/functional/readfile-context\.sh$''
+            ''^tests/functional/recursive\.sh$''
+            ''^tests/functional/referrers\.sh$''
+            ''^tests/functional/remote-store\.sh$''
+            ''^tests/functional/repair\.sh$''
+            ''^tests/functional/restricted\.sh$''
+            ''^tests/functional/search\.sh$''
+            ''^tests/functional/secure-drv-outputs\.sh$''
+            ''^tests/functional/selfref-gc\.sh$''
+            ''^tests/functional/shell\.sh$''
+            ''^tests/functional/shell\.shebang\.sh$''
+            ''^tests/functional/signing\.sh$''
+            ''^tests/functional/simple\.builder\.sh$''
+            ''^tests/functional/simple\.sh$''
+            ''^tests/functional/ssh-relay\.sh$''
+            ''^tests/functional/store-info\.sh$''
+            ''^tests/functional/structured-attrs\.sh$''
+            ''^tests/functional/substitute-with-invalid-ca\.sh$''
+            ''^tests/functional/suggestions\.sh$''
+            ''^tests/functional/supplementary-groups\.sh$''
+            ''^tests/functional/tarball\.sh$''
+            ''^tests/functional/test-infra\.sh$''
+            ''^tests/functional/test-libstoreconsumer\.sh$''
+            ''^tests/functional/timeout\.sh$''
+            ''^tests/functional/toString-path\.sh$''
+            ''^tests/functional/user-envs-migration\.sh$''
+            ''^tests/functional/user-envs-test-case\.sh$''
+            ''^tests/functional/user-envs\.builder\.sh$''
+            ''^tests/functional/user-envs\.sh$''
+            ''^tests/functional/why-depends\.sh$''
+            ''^tests/functional/zstd\.sh$''
+            ''^tests/unit/libutil/data/git/check-data\.sh$''
+          ];
+        };
+        # TODO: nixfmt, https://github.com/NixOS/nixfmt/issues/153
+      };
+    };
+  };
+
+  # We'll be pulling from this in the main flake
+  flake.getSystem = getSystem;
+}
diff --git a/maintainers/local.mk b/maintainers/local.mk
new file mode 100644
index 00000000000..88d594d67d8
--- /dev/null
+++ b/maintainers/local.mk
@@ -0,0 +1,15 @@
+
+.PHONY: format
+print-top-help += echo '  format: Format source code'
+
+# This uses the cached .pre-commit-hooks.yaml file
+format:
+	@if ! type -p pre-commit &>/dev/null; then \
+	  echo "make format: pre-commit not found. Please use \`nix develop\`."; \
+	  exit 1; \
+	fi; \
+	if test -z "$$_NIX_PRE_COMMIT_HOOKS_CONFIG"; then \
+	  echo "make format: _NIX_PRE_COMMIT_HOOKS_CONFIG not set. Please use \`nix develop\`."; \
+	  exit 1; \
+	fi; \
+	pre-commit run --config $$_NIX_PRE_COMMIT_HOOKS_CONFIG --all-files
diff --git a/maintainers/release-notes b/maintainers/release-notes
index 2d84485c173..0fca5abf27e 100755
--- a/maintainers/release-notes
+++ b/maintainers/release-notes
@@ -1,5 +1,5 @@
 #!/usr/bin/env nix
-#!nix shell .#changelog-d-nix --command bash
+#!nix shell .#changelog-d --command bash
 
 # --- CONFIGURATION ---
 
diff --git a/maintainers/upload-release.pl b/maintainers/upload-release.pl
index f2830a3af15..4c4e2bd6f5e 100755
--- a/maintainers/upload-release.pl
+++ b/maintainers/upload-release.pl
@@ -171,6 +171,10 @@ sub downloadFile {
     downloadFile("binaryTarballCross.x86_64-linux.armv7l-unknown-linux-gnueabihf", "1");
 };
 warn "$@" if $@;
+eval {
+    downloadFile("binaryTarballCross.x86_64-linux.riscv64-unknown-linux-gnu", "1");
+};
+warn "$@" if $@;
 downloadFile("installerScript", "1");
 
 # Upload docker images to dockerhub.
@@ -185,10 +189,7 @@ sub downloadFile {
     eval {
         downloadFile("dockerImage.$system", "1", $fn);
     };
-    if ($@) {
-        warn "$@" if $@;
-        next;
-    }
+    die "$@" if $@;
     $haveDocker = 1;
 
     print STDERR "loading docker image for $dockerPlatform...\n";
@@ -242,6 +243,7 @@ sub downloadFile {
     "  x86_64-linux = \"" . getStorePath("build.x86_64-linux") . "\";\n" .
     "  i686-linux = \"" . getStorePath("build.i686-linux") . "\";\n" .
     "  aarch64-linux = \"" . getStorePath("build.aarch64-linux") . "\";\n" .
+    "  riscv64-linux = \"" . getStorePath("buildCross.riscv64-unknown-linux-gnu.x86_64-linux") . "\";\n" .
     "  x86_64-darwin = \"" . getStorePath("build.x86_64-darwin") . "\";\n" .
     "  aarch64-darwin = \"" . getStorePath("build.aarch64-darwin") . "\";\n" .
     "}\n");
diff --git a/meson.build b/meson.build
new file mode 100644
index 00000000000..e6bdc2eac30
--- /dev/null
+++ b/meson.build
@@ -0,0 +1,41 @@
+# This is just a stub project to include all the others as subprojects
+# for development shell purposes
+
+project('nix-dev-shell', 'cpp',
+  version : files('.version'),
+  subproject_dir : 'src',
+)
+
+# Internal Libraries
+subproject('libutil')
+subproject('libstore')
+subproject('libfetchers')
+subproject('libexpr')
+subproject('libflake')
+subproject('libmain')
+subproject('libcmd')
+
+# Executables
+subproject('nix')
+
+# Docs
+subproject('internal-api-docs')
+subproject('external-api-docs')
+
+# External C wrapper libraries
+subproject('libutil-c')
+subproject('libstore-c')
+subproject('libexpr-c')
+
+# Language Bindings
+subproject('perl')
+
+# Testing
+subproject('nix-util-test-support')
+subproject('nix-util-tests')
+subproject('nix-store-test-support')
+subproject('nix-store-tests')
+subproject('nix-fetchers-tests')
+subproject('nix-expr-test-support')
+subproject('nix-expr-tests')
+subproject('nix-flake-tests')
diff --git a/misc/changelog-d.cabal.nix b/misc/changelog-d.cabal.nix
deleted file mode 100644
index 76f9353cd5d..00000000000
--- a/misc/changelog-d.cabal.nix
+++ /dev/null
@@ -1,31 +0,0 @@
-{ mkDerivation, aeson, base, bytestring, cabal-install-parsers
-, Cabal-syntax, containers, directory, filepath, frontmatter
-, generic-lens-lite, lib, mtl, optparse-applicative, parsec, pretty
-, regex-applicative, text, pkgs
-}:
-let rev = "f30f6969e9cd8b56242309639d58acea21c99d06";
-in
-mkDerivation {
-  pname = "changelog-d";
-  version = "0.1";
-  src = pkgs.fetchurl {
-    name = "changelog-d-${rev}.tar.gz";
-    url = "https://codeberg.org/roberth/changelog-d/archive/${rev}.tar.gz";
-    hash = "sha256-8a2+i5u7YoszAgd5OIEW0eYUcP8yfhtoOIhLJkylYJ4=";
-  } // { inherit rev; };
-  isLibrary = false;
-  isExecutable = true;
-  libraryHaskellDepends = [
-    aeson base bytestring cabal-install-parsers Cabal-syntax containers
-    directory filepath frontmatter generic-lens-lite mtl parsec pretty
-    regex-applicative text
-  ];
-  executableHaskellDepends = [
-    base bytestring Cabal-syntax directory filepath
-    optparse-applicative
-  ];
-  doHaddock = false;
-  description = "Concatenate changelog entries into a single one";
-  license = lib.licenses.gpl3Plus;
-  mainProgram = "changelog-d";
-}
diff --git a/misc/changelog-d.nix b/misc/changelog-d.nix
deleted file mode 100644
index 1b20f4596f6..00000000000
--- a/misc/changelog-d.nix
+++ /dev/null
@@ -1,31 +0,0 @@
-# Taken temporarily from <nixpkgs/pkgs/by-name/ch/changelog-d/package.nix>
-{
-  callPackage,
-  lib,
-  haskell,
-  haskellPackages,
-}:
-
-let
-  hsPkg = haskellPackages.callPackage ./changelog-d.cabal.nix { };
-
-  addCompletions = haskellPackages.generateOptparseApplicativeCompletions ["changelog-d"];
-
-  haskellModifications =
-    lib.flip lib.pipe [
-      addCompletions
-      haskell.lib.justStaticExecutables
-    ];
-
-  mkDerivationOverrides = finalAttrs: oldAttrs: {
-
-    version = oldAttrs.version + "-git-${lib.strings.substring 0 7 oldAttrs.src.rev}";
-
-    meta = oldAttrs.meta // {
-      homepage = "https://codeberg.org/roberth/changelog-d";
-      maintainers = [ lib.maintainers.roberth ];
-    };
-
-  };
-in
-  (haskellModifications hsPkg).overrideAttrs mkDerivationOverrides
diff --git a/mk/common-test.sh b/mk/common-test.sh
index 2783d293bc4..817422c402d 100644
--- a/mk/common-test.sh
+++ b/mk/common-test.sh
@@ -1,27 +1,23 @@
+# shellcheck shell=bash
+
 # Remove overall test dir (at most one of the two should match) and
 # remove file extension.
-test_name=$(echo -n "$test" | sed \
-    -e "s|^tests/unit/[^/]*/data/||" \
+
+test_name=$(echo -n "${test?must be defined by caller (test runner)}" | sed \
+    -e "s|^src/[^/]*-test/data/||" \
     -e "s|^tests/functional/||" \
     -e "s|\.sh$||" \
     )
 
+# shellcheck disable=SC2016
 TESTS_ENVIRONMENT=(
     "TEST_NAME=$test_name"
     'NIX_REMOTE='
     'PS4=+(${BASH_SOURCE[0]-$0}:$LINENO) '
 )
 
-: ${BASH:=/usr/bin/env bash}
+read -r -a bash <<< "${BASH:-/usr/bin/env bash}"
 
 run () {
-   cd "$(dirname $1)" && env "${TESTS_ENVIRONMENT[@]}" $BASH -x -e -u -o pipefail $(basename $1)
-}
-
-init_test () {
-   run "$init" 2>/dev/null > /dev/null
-}
-
-run_test_proper () {
-   run "$test"
+   cd "$(dirname "$1")" && env "${TESTS_ENVIRONMENT[@]}" "${bash[@]}" -x -e -u -o pipefail "$(basename "$1")"
 }
diff --git a/mk/debug-test.sh b/mk/debug-test.sh
index 52482c01e47..0dd4406c38e 100755
--- a/mk/debug-test.sh
+++ b/mk/debug-test.sh
@@ -3,12 +3,8 @@
 set -eu -o pipefail
 
 test=$1
-init=${2-}
 
 dir="$(dirname "${BASH_SOURCE[0]}")"
 source "$dir/common-test.sh"
 
-if [ -n "$init" ]; then
-    (init_test)
-fi
-run_test_proper
+run "$test"
diff --git a/mk/lib.mk b/mk/lib.mk
index a002d823fe3..1e7af6ad556 100644
--- a/mk/lib.mk
+++ b/mk/lib.mk
@@ -87,15 +87,14 @@ $(foreach script, $(bin-scripts), $(eval $(call install-program-in,$(script),$(b
 $(foreach script, $(bin-scripts), $(eval programs-list += $(script)))
 $(foreach script, $(noinst-scripts), $(eval programs-list += $(script)))
 $(foreach template, $(template-files), $(eval $(call instantiate-template,$(template))))
-install_test_init=tests/functional/init.sh
 $(foreach test, $(install-tests), \
-  $(eval $(call run-test,$(test),$(install_test_init))) \
+  $(eval $(call run-test,$(test))) \
   $(eval installcheck: $(test).test))
 $(foreach test-group, $(install-tests-groups), \
-  $(eval $(call run-test-group,$(test-group),$(install_test_init))) \
+  $(eval $(call run-test-group,$(test-group))) \
   $(eval installcheck: $(test-group).test-group) \
   $(foreach test, $($(test-group)-tests), \
-    $(eval $(call run-test,$(test),$(install_test_init))) \
+    $(eval $(call run-test,$(test))) \
     $(eval $(test-group).test-group: $(test).test)))
 
 # Compilation database.
diff --git a/mk/precompiled-headers.mk b/mk/precompiled-headers.mk
index cdd3daecd2b..f2803eb79eb 100644
--- a/mk/precompiled-headers.mk
+++ b/mk/precompiled-headers.mk
@@ -8,7 +8,7 @@ GCH = $(buildprefix)precompiled-headers.h.gch
 $(GCH): precompiled-headers.h
 	@rm -f $@
 	@mkdir -p "$(dir $@)"
-	$(trace-gen) $(CXX) -x c++-header -o $@ $< $(GLOBAL_CXXFLAGS) $(GCH_CXXFLAGS)
+	$(trace-gen) $(CXX) -c -x c++-header -o $@ $< $(GLOBAL_CXXFLAGS) $(GCH_CXXFLAGS)
 
 clean-files += $(GCH)
 
diff --git a/mk/run-test.sh b/mk/run-test.sh
index da9c5a473b4..543c845e122 100755
--- a/mk/run-test.sh
+++ b/mk/run-test.sh
@@ -8,7 +8,6 @@ yellow=""
 normal=""
 
 test=$1
-init=${2-}
 
 dir="$(dirname "${BASH_SOURCE[0]}")"
 source "$dir/common-test.sh"
@@ -22,20 +21,18 @@ if [ -t 1 ]; then
 fi
 
 run_test () {
-    if [ -n "$init" ]; then
-        (init_test 2>/dev/null > /dev/null)
-    fi
-    log="$(run_test_proper 2>&1)" && status=0 || status=$?
+    log="$(run "$test" 2>&1)" && status=0 || status=$?
 }
 
 run_test
 
-if [ $status -eq 0 ]; then
+if [[ "$status" = 0 ]]; then
   echo "$post_run_msg [${green}PASS$normal]"
-elif [ $status -eq 99 ]; then
+elif [[ "$status" = 99 ]]; then
   echo "$post_run_msg [${yellow}SKIP$normal]"
 else
   echo "$post_run_msg [${red}FAIL$normal]"
+  # shellcheck disable=SC2001
   echo "$log" | sed 's/^/    /'
   exit "$status"
 fi
diff --git a/mk/tests.mk b/mk/tests.mk
index bac9b704ad1..0a10f6d3bfd 100644
--- a/mk/tests.mk
+++ b/mk/tests.mk
@@ -12,8 +12,8 @@ endef
 
 define run-test
 
-  $(eval $(call run-bash,$1.test,$1 $(test-deps),mk/run-test.sh $1 $2))
-  $(eval $(call run-bash,$1.test-debug,$1 $(test-deps),mk/debug-test.sh $1 $2))
+  $(eval $(call run-bash,$1.test,$1 $(test-deps),mk/run-test.sh $1))
+  $(eval $(call run-bash,$1.test-debug,$1 $(test-deps),mk/debug-test.sh $1))
 
 endef
 
diff --git a/package.nix b/package.nix
index 1e5b9e449b3..c3e565399e8 100644
--- a/package.nix
+++ b/package.nix
@@ -5,7 +5,6 @@
 , autoreconfHook
 , aws-sdk-cpp
 , boehmgc
-, buildPackages
 , nlohmann_json
 , bison
 , boost
@@ -14,12 +13,10 @@
 , curl
 , editline
 , readline
-, fileset
 , flex
 , git
 , gtest
 , jq
-, doxygen
 , libarchive
 , libcpuid
 , libgit2
@@ -35,7 +32,8 @@
 , pkg-config
 , rapidcheck
 , sqlite
-, util-linux
+, toml11
+, unixtools
 , xz
 
 , busybox-sandbox-shell ? null
@@ -50,10 +48,8 @@
 , pname ? "nix"
 
 , versionSuffix ? ""
-, officialRelease ? false
 
-# Whether to build Nix. Useful to skip for tasks like (a) just
-# generating API docs or (b) testing existing pre-built versions of Nix
+# Whether to build Nix. Useful to skip for tasks like testing existing pre-built versions of Nix
 , doBuild ? true
 
 # Run the unit tests as part of the build. See `installUnitTests` for an
@@ -92,11 +88,6 @@
 # - readline
 , readlineFlavor ? if stdenv.hostPlatform.isWindows then "readline" else "editline"
 
-# Whether to build the internal/external API docs, can be done separately from
-# everything else.
-, enableInternalAPIDocs ? forDevShell
-, enableExternalAPIDocs ? forDevShell
-
 # Whether to install unit tests. This is useful when cross compiling
 # since we cannot run them natively during the build, but can do so
 # later.
@@ -119,6 +110,8 @@
 }:
 
 let
+  inherit (lib) fileset;
+
   version = lib.fileContents ./.version + versionSuffix;
 
   # selected attributes with defaults, will be used to define some
@@ -167,6 +160,8 @@ in {
           ./m4
           # TODO: do we really need README.md? It doesn't seem used in the build.
           ./README.md
+          # This could be put behind a conditional
+          ./maintainers/local.mk
           # For make, regardless of what we are building
           ./local.mk
           ./Makefile
@@ -177,20 +172,11 @@ in {
           ./doc
           ./misc
           ./precompiled-headers.h
-          ./src
+          (fileset.difference ./src ./src/perl)
           ./COPYING
           ./scripts/local.mk
-        ] ++ lib.optionals buildUnitTests [
+        ] ++ lib.optionals enableManual [
           ./doc/manual
-        ] ++ lib.optionals enableInternalAPIDocs [
-          ./doc/internal-api
-        ] ++ lib.optionals enableExternalAPIDocs [
-          ./doc/external-api
-        ] ++ lib.optionals (enableInternalAPIDocs || enableExternalAPIDocs) [
-          # Source might not be compiled, but still must be available
-          # for Doxygen to gather comments.
-          ./src
-          ./tests/unit
         ] ++ lib.optionals buildUnitTests [
           ./tests/unit
         ] ++ lib.optionals doInstallCheck [
@@ -204,8 +190,10 @@ in {
     ++ lib.optional doBuild "dev"
     # If we are doing just build or just docs, the one thing will use
     # "out". We only need additional outputs if we are doing both.
-    ++ lib.optional (doBuild && (enableManual || enableInternalAPIDocs || enableExternalAPIDocs)) "doc"
-    ++ lib.optional installUnitTests "check";
+    ++ lib.optional (doBuild && enableManual) "doc"
+    ++ lib.optional installUnitTests "check"
+    ++ lib.optional doCheck "testresults"
+    ;
 
   nativeBuildInputs = [
     autoconf-archive
@@ -225,12 +213,10 @@ in {
     man # for testing `nix-* --help`
   ] ++ lib.optionals (doInstallCheck || enableManual) [
     jq # Also for custom mdBook preprocessor.
-  ] ++ lib.optional stdenv.hostPlatform.isLinux util-linux
-    ++ lib.optional (enableInternalAPIDocs || enableExternalAPIDocs) doxygen
+  ] ++ lib.optional stdenv.hostPlatform.isStatic unixtools.hexdump
   ;
 
   buildInputs = lib.optionals doBuild [
-    boost
     brotli
     bzip2
     curl
@@ -239,6 +225,7 @@ in {
     libsodium
     openssl
     sqlite
+    toml11
     xz
     ({ inherit readline editline; }.${readlineFlavor})
   ] ++ lib.optionals enableMarkdown [
@@ -257,40 +244,17 @@ in {
   ;
 
   propagatedBuildInputs = [
+    boost
     nlohmann_json
   ] ++ lib.optional enableGC boehmgc;
 
   dontBuild = !attrs.doBuild;
   doCheck = attrs.doCheck;
 
-  disallowedReferences = [ boost ];
-
-  preConfigure = lib.optionalString (doBuild && ! stdenv.hostPlatform.isStatic) (
-    ''
-      # Copy libboost_context so we don't get all of Boost in our closure.
-      # https://github.com/NixOS/nixpkgs/issues/45462
-      mkdir -p $out/lib
-      cp -pd ${boost}/lib/{libboost_context*,libboost_thread*,libboost_system*} $out/lib
-      rm -f $out/lib/*.a
-    '' + lib.optionalString stdenv.hostPlatform.isLinux ''
-      chmod u+w $out/lib/*.so.*
-      patchelf --set-rpath $out/lib:${stdenv.cc.cc.lib}/lib $out/lib/libboost_thread.so.*
-    '' + lib.optionalString stdenv.hostPlatform.isDarwin ''
-      for LIB in $out/lib/*.dylib; do
-        chmod u+w $LIB
-        install_name_tool -id $LIB $LIB
-        install_name_tool -delete_rpath ${boost}/lib/ $LIB || true
-      done
-      install_name_tool -change ${boost}/lib/libboost_system.dylib $out/lib/libboost_system.dylib $out/lib/libboost_thread.dylib
-    ''
-  );
-
   configureFlags = [
     (lib.enableFeature doBuild "build")
     (lib.enableFeature buildUnitTests "unit-tests")
     (lib.enableFeature doInstallCheck "functional-tests")
-    (lib.enableFeature enableInternalAPIDocs "internal-api-docs")
-    (lib.enableFeature enableExternalAPIDocs "external-api-docs")
     (lib.enableFeature enableManual "doc-gen")
     (lib.enableFeature enableGC "gc")
     (lib.enableFeature enableMarkdown "markdown")
@@ -314,9 +278,11 @@ in {
 
   makeFlags = "profiledir=$(out)/etc/profile.d PRECOMPILE_HEADERS=1";
 
-  installTargets = lib.optional doBuild "install"
-    ++ lib.optional enableInternalAPIDocs "internal-api-html"
-    ++ lib.optional enableExternalAPIDocs "external-api-html";
+  preCheck = ''
+    mkdir $testresults
+  '';
+
+  installTargets = lib.optional doBuild "install";
 
   installFlags = "sysconfdir=$(out)/etc";
 
@@ -331,22 +297,10 @@ in {
     lib.optionalString stdenv.hostPlatform.isStatic ''
       mkdir -p $out/nix-support
       echo "file binary-dist $out/bin/nix" >> $out/nix-support/hydra-build-products
-    '' + lib.optionalString stdenv.isDarwin ''
-      install_name_tool \
-      -change ${boost}/lib/libboost_context.dylib \
-      $out/lib/libboost_context.dylib \
-      $out/lib/libnixutil.dylib
     ''
   ) + lib.optionalString enableManual ''
     mkdir -p ''${!outputDoc}/nix-support
     echo "doc manual ''${!outputDoc}/share/doc/nix/manual" >> ''${!outputDoc}/nix-support/hydra-build-products
-  '' + lib.optionalString enableInternalAPIDocs ''
-    mkdir -p ''${!outputDoc}/nix-support
-    echo "doc internal-api-docs $out/share/doc/nix/internal-api/html" >> ''${!outputDoc}/nix-support/hydra-build-products
-  ''
-    + lib.optionalString enableExternalAPIDocs ''
-    mkdir -p ''${!outputDoc}/nix-support
-    echo "doc external-api-docs $out/share/doc/nix/external-api/html" >> ''${!outputDoc}/nix-support/hydra-build-products
   '';
 
   # So the check output gets links for DLLs in the out output.
@@ -382,8 +336,7 @@ in {
 
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
-  # TODO `releaseTools.coverageAnalysis` in Nixpkgs needs to be updated
-  # to work with `strictDeps`.
+  # TODO Always true after https://github.com/NixOS/nixpkgs/issues/318564
   strictDeps = !withCoverageChecks;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
diff --git a/packaging/components.nix b/packaging/components.nix
new file mode 100644
index 00000000000..0e369a055cd
--- /dev/null
+++ b/packaging/components.nix
@@ -0,0 +1,42 @@
+scope:
+let
+  inherit (scope) callPackage;
+in
+
+# This becomes the pkgs.nixComponents attribute set
+{
+  nix = callPackage ../package.nix { };
+
+  nix-util = callPackage ../src/libutil/package.nix { };
+  nix-util-c = callPackage ../src/libutil-c/package.nix { };
+  nix-util-test-support = callPackage ../tests/unit/libutil-support/package.nix { };
+  nix-util-tests = callPackage ../tests/unit/libutil/package.nix { };
+
+  nix-store = callPackage ../src/libstore/package.nix { };
+  nix-store-c = callPackage ../src/libstore-c/package.nix { };
+  nix-store-test-support = callPackage ../tests/unit/libstore-support/package.nix { };
+  nix-store-tests = callPackage ../tests/unit/libstore/package.nix { };
+
+  nix-fetchers = callPackage ../src/libfetchers/package.nix { };
+  nix-fetchers-tests = callPackage ../tests/unit/libfetchers/package.nix { };
+
+  nix-expr = callPackage ../src/libexpr/package.nix { };
+  nix-expr-c = callPackage ../src/libexpr-c/package.nix { };
+  nix-expr-test-support = callPackage ../tests/unit/libexpr-support/package.nix { };
+  nix-expr-tests = callPackage ../tests/unit/libexpr/package.nix { };
+
+  nix-flake = callPackage ../src/libflake/package.nix { };
+  nix-flake-tests = callPackage ../tests/unit/libflake/package.nix { };
+
+  nix-main = callPackage ../src/libmain/package.nix { };
+
+  nix-cmd = callPackage ../src/libcmd/package.nix { };
+
+  # Will replace `nix` once the old build system is gone.
+  nix-ng = callPackage ../src/nix/package.nix { };
+
+  nix-internal-api-docs = callPackage ../src/internal-api-docs/package.nix { };
+  nix-external-api-docs = callPackage ../src/external-api-docs/package.nix { };
+
+  nix-perl-bindings = callPackage ../src/perl/package.nix { };
+}
diff --git a/packaging/dependencies.nix b/packaging/dependencies.nix
new file mode 100644
index 00000000000..34b3449718d
--- /dev/null
+++ b/packaging/dependencies.nix
@@ -0,0 +1,117 @@
+# These overrides are applied to the dependencies of the Nix components.
+
+{
+  # Flake inputs; used for sources
+  inputs,
+
+  # The raw Nixpkgs, not affected by this scope
+  pkgs,
+
+  stdenv,
+  versionSuffix,
+}:
+
+let
+  inherit (pkgs) lib;
+
+  root = ../.;
+
+  # Nixpkgs implements this by returning a subpath into the fetched Nix sources.
+  resolvePath = p: p;
+
+  # Indirection for Nixpkgs to override when package.nix files are vendored
+  filesetToSource = lib.fileset.toSource;
+
+  localSourceLayer = finalAttrs: prevAttrs:
+    let
+      workDirPath =
+        # Ideally we'd pick finalAttrs.workDir, but for now `mkDerivation` has
+        # the requirement that everything except passthru and meta must be
+        # serialized by mkDerivation, which doesn't work for this.
+        prevAttrs.workDir;
+
+      workDirSubpath = lib.path.removePrefix root workDirPath;
+      sources = assert prevAttrs.fileset._type == "fileset"; prevAttrs.fileset;
+      src = lib.fileset.toSource { fileset = sources; inherit root; };
+
+    in
+    {
+      sourceRoot = "${src.name}/" + workDirSubpath;
+      inherit src;
+
+      # Clear what `derivation` can't/shouldn't serialize; see prevAttrs.workDir.
+      fileset = null;
+      workDir = null;
+    };
+
+in
+scope: {
+  inherit stdenv versionSuffix;
+  version = lib.fileContents ../.version + versionSuffix;
+
+  libseccomp = pkgs.libseccomp.overrideAttrs (_: rec {
+    version = "2.5.5";
+    src = pkgs.fetchurl {
+      url = "https://github.com/seccomp/libseccomp/releases/download/v${version}/libseccomp-${version}.tar.gz";
+      hash = "sha256-JIosik2bmFiqa69ScSw0r+/PnJ6Ut23OAsHJqiX7M3U=";
+    };
+  });
+
+  boehmgc = pkgs.boehmgc.override {
+    enableLargeConfig = true;
+  };
+
+  # TODO Hack until https://github.com/NixOS/nixpkgs/issues/45462 is fixed.
+  boost = (pkgs.boost.override {
+    extraB2Args = [
+      "--with-container"
+      "--with-context"
+      "--with-coroutine"
+    ];
+  }).overrideAttrs (old: {
+    # Need to remove `--with-*` to use `--with-libraries=...`
+    buildPhase = lib.replaceStrings [ "--without-python" ] [ "" ] old.buildPhase;
+    installPhase = lib.replaceStrings [ "--without-python" ] [ "" ] old.installPhase;
+  });
+
+  libgit2 = pkgs.libgit2.overrideAttrs (attrs: {
+    src = inputs.libgit2;
+    version = inputs.libgit2.lastModifiedDate;
+    cmakeFlags = attrs.cmakeFlags or []
+      ++ [ "-DUSE_SSH=exec" ];
+  });
+
+  busybox-sandbox-shell = pkgs.busybox-sandbox-shell or (pkgs.busybox.override {
+    useMusl = true;
+    enableStatic = true;
+    enableMinimal = true;
+    extraConfig = ''
+      CONFIG_FEATURE_FANCY_ECHO y
+      CONFIG_FEATURE_SH_MATH y
+      CONFIG_FEATURE_SH_MATH_64 y
+
+      CONFIG_ASH y
+      CONFIG_ASH_OPTIMIZE_FOR_SIZE y
+
+      CONFIG_ASH_ALIAS y
+      CONFIG_ASH_BASH_COMPAT y
+      CONFIG_ASH_CMDCMD y
+      CONFIG_ASH_ECHO y
+      CONFIG_ASH_GETOPTS y
+      CONFIG_ASH_INTERNAL_GLOB y
+      CONFIG_ASH_JOB_CONTROL y
+      CONFIG_ASH_PRINTF y
+      CONFIG_ASH_TEST y
+    '';
+  });
+
+  # TODO change in Nixpkgs, Windows works fine. First commit of
+  # https://github.com/NixOS/nixpkgs/pull/322977 backported will fix.
+  toml11 = pkgs.toml11.overrideAttrs (old: {
+    meta.platforms = lib.platforms.all;
+  });
+
+  inherit resolvePath filesetToSource;
+
+  mkMesonDerivation = f: stdenv.mkDerivation (lib.extends localSourceLayer f);
+}
diff --git a/packaging/hydra.nix b/packaging/hydra.nix
new file mode 100644
index 00000000000..4dfaf9bbfaa
--- /dev/null
+++ b/packaging/hydra.nix
@@ -0,0 +1,199 @@
+{ inputs
+, binaryTarball
+, forAllCrossSystems
+, forAllSystems
+, lib
+, linux64BitSystems
+, nixpkgsFor
+, self
+}:
+let
+  inherit (inputs) nixpkgs nixpkgs-regression;
+
+  installScriptFor = tarballs:
+    nixpkgsFor.x86_64-linux.native.callPackage ../scripts/installer.nix {
+      inherit tarballs;
+    };
+
+  testNixVersions = pkgs: client: daemon:
+    pkgs.callPackage ../package.nix {
+      pname =
+        "nix-tests"
+        + lib.optionalString
+          (lib.versionAtLeast daemon.version "2.4pre20211005" &&
+           lib.versionAtLeast client.version "2.4pre20211005")
+          "-${client.version}-against-${daemon.version}";
+
+      test-client = client;
+      test-daemon = daemon;
+
+      doBuild = false;
+    };
+
+  # Technically we could just return `pkgs.nixComponents`, but for Hydra it's
+  # convention to transpose it, and to transpose it efficiently, we need to
+  # enumerate them manually, so that we don't evaluate unnecessary package sets.
+  forAllPackages = lib.genAttrs [
+    "nix"
+    "nix-util"
+    "nix-util-c"
+    "nix-util-test-support"
+    "nix-util-tests"
+    "nix-store"
+    "nix-store-c"
+    "nix-store-test-support"
+    "nix-store-tests"
+    "nix-fetchers"
+    "nix-fetchers-tests"
+    "nix-expr"
+    "nix-expr-c"
+    "nix-expr-test-support"
+    "nix-expr-tests"
+    "nix-flake"
+    "nix-flake-tests"
+    "nix-main"
+    "nix-cmd"
+    "nix-ng"
+  ];
+in
+{
+  # Binary package for various platforms.
+  build = forAllPackages (pkgName:
+    forAllSystems (system: nixpkgsFor.${system}.native.nixComponents.${pkgName}));
+
+  shellInputs = forAllSystems (system: self.devShells.${system}.default.inputDerivation);
+
+  buildStatic = forAllPackages (pkgName:
+    lib.genAttrs linux64BitSystems (system: nixpkgsFor.${system}.static.nixComponents.${pkgName}));
+
+  buildCross = forAllPackages (pkgName:
+    forAllCrossSystems (crossSystem:
+      lib.genAttrs [ "x86_64-linux" ] (system: nixpkgsFor.${system}.cross.${crossSystem}.nixComponents.${pkgName})));
+
+  buildNoGc = forAllSystems (system:
+    self.packages.${system}.nix.override { enableGC = false; }
+  );
+
+  buildNoTests = forAllSystems (system: nixpkgsFor.${system}.native.nix_noTests);
+
+  # Toggles some settings for better coverage. Windows needs these
+  # library combinations, and Debian build Nix with GNU readline too.
+  buildReadlineNoMarkdown = forAllSystems (system:
+    self.packages.${system}.nix.override {
+      enableMarkdown = false;
+      readlineFlavor = "readline";
+    }
+  );
+
+  # Perl bindings for various platforms.
+  perlBindings = forAllSystems (system: nixpkgsFor.${system}.native.nixComponents.nix-perl-bindings);
+
+  # Binary tarball for various platforms, containing a Nix store
+  # with the closure of 'nix' package, and the second half of
+  # the installation script.
+  binaryTarball = forAllSystems (system: binaryTarball nixpkgsFor.${system}.native.nix nixpkgsFor.${system}.native);
+
+  binaryTarballCross = lib.genAttrs [ "x86_64-linux" ] (system:
+    forAllCrossSystems (crossSystem:
+      binaryTarball
+        nixpkgsFor.${system}.cross.${crossSystem}.nix
+        nixpkgsFor.${system}.cross.${crossSystem}));
+
+  # The first half of the installation script. This is uploaded
+  # to https://nixos.org/nix/install. It downloads the binary
+  # tarball for the user's system and calls the second half of the
+  # installation script.
+  installerScript = installScriptFor [
+    # Native
+    self.hydraJobs.binaryTarball."x86_64-linux"
+    self.hydraJobs.binaryTarball."i686-linux"
+    self.hydraJobs.binaryTarball."aarch64-linux"
+    self.hydraJobs.binaryTarball."x86_64-darwin"
+    self.hydraJobs.binaryTarball."aarch64-darwin"
+    # Cross
+    self.hydraJobs.binaryTarballCross."x86_64-linux"."armv6l-unknown-linux-gnueabihf"
+    self.hydraJobs.binaryTarballCross."x86_64-linux"."armv7l-unknown-linux-gnueabihf"
+    self.hydraJobs.binaryTarballCross."x86_64-linux"."riscv64-unknown-linux-gnu"
+  ];
+  installerScriptForGHA = installScriptFor [
+    # Native
+    self.hydraJobs.binaryTarball."x86_64-linux"
+    self.hydraJobs.binaryTarball."aarch64-darwin"
+    # Cross
+    self.hydraJobs.binaryTarballCross."x86_64-linux"."armv6l-unknown-linux-gnueabihf"
+    self.hydraJobs.binaryTarballCross."x86_64-linux"."armv7l-unknown-linux-gnueabihf"
+    self.hydraJobs.binaryTarballCross."x86_64-linux"."riscv64-unknown-linux-gnu"
+  ];
+
+  # docker image with Nix inside
+  dockerImage = lib.genAttrs linux64BitSystems (system: self.packages.${system}.dockerImage);
+
+  # Line coverage analysis.
+  coverage = nixpkgsFor.x86_64-linux.native.nix.override {
+    pname = "nix-coverage";
+    withCoverageChecks = true;
+  };
+
+  # API docs for Nix's unstable internal C++ interfaces.
+  internal-api-docs = nixpkgsFor.x86_64-linux.native.nixComponents.nix-internal-api-docs;
+
+  # API docs for Nix's C bindings.
+  external-api-docs = nixpkgsFor.x86_64-linux.native.nixComponents.nix-external-api-docs;
+
+  # System tests.
+  tests = import ../tests/nixos { inherit lib nixpkgs nixpkgsFor self; } // {
+
+    # Make sure that nix-env still produces the exact same result
+    # on a particular version of Nixpkgs.
+    evalNixpkgs =
+      let
+        inherit (nixpkgsFor.x86_64-linux.native) runCommand nix;
+      in
+      runCommand "eval-nixos" { buildInputs = [ nix ]; }
+        ''
+          type -p nix-env
+          # Note: we're filtering out nixos-install-tools because https://github.com/NixOS/nixpkgs/pull/153594#issuecomment-1020530593.
+          (
+            set -x
+            time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
+            [[ $(sha1sum < packages | cut -c1-40) = e01b031fc9785a572a38be6bc473957e3b6faad7 ]]
+          )
+          mkdir $out
+        '';
+
+    nixpkgsLibTests =
+      forAllSystems (system:
+        import (nixpkgs + "/lib/tests/test-with-nix.nix")
+          {
+            lib = nixpkgsFor.${system}.native.lib;
+            nix = self.packages.${system}.nix;
+            pkgs = nixpkgsFor.${system}.native;
+          }
+      );
+  };
+
+  metrics.nixpkgs = import "${nixpkgs-regression}/pkgs/top-level/metrics.nix" {
+    pkgs = nixpkgsFor.x86_64-linux.native;
+    nixpkgs = nixpkgs-regression;
+  };
+
+  installTests = forAllSystems (system:
+    let pkgs = nixpkgsFor.${system}.native; in
+    pkgs.runCommand "install-tests"
+      {
+        againstSelf = testNixVersions pkgs pkgs.nix pkgs.pkgs.nix;
+        againstCurrentLatest =
+          # FIXME: temporarily disable this on macOS because of #3605.
+          if system == "x86_64-linux"
+          then testNixVersions pkgs pkgs.nix pkgs.nixVersions.latest
+          else null;
+        # Disabled because the latest stable version doesn't handle
+        # `NIX_DAEMON_SOCKET_PATH` which is required for the tests to work
+        # againstLatestStable = testNixVersions pkgs pkgs.nix pkgs.nixStable;
+      } "touch $out");
+
+  installerTests = import ../tests/installer {
+    binaryTarballs = self.hydraJobs.binaryTarball;
+    inherit nixpkgsFor;
+  };
+}
diff --git a/perl/.yath.rc b/perl/.yath.rc
deleted file mode 100644
index 118bf80c821..00000000000
--- a/perl/.yath.rc
+++ /dev/null
@@ -1,2 +0,0 @@
-[test]
--I=rel(lib/Nix)
diff --git a/perl/Makefile b/perl/Makefile
deleted file mode 100644
index 832668dd155..00000000000
--- a/perl/Makefile
+++ /dev/null
@@ -1,21 +0,0 @@
-makefiles = local.mk
-
-GLOBAL_CXXFLAGS += -g -Wall -std=c++2a
-
-# A convenience for concurrent development of Nix and its Perl bindings.
-# Not needed in a standalone build of the Perl bindings.
-ifneq ("$(wildcard ../src)", "")
-  GLOBAL_CXXFLAGS += -I ../src
-endif
-
--include Makefile.config
-
-OPTIMIZE = 1
-
-ifeq ($(OPTIMIZE), 1)
-  GLOBAL_CXXFLAGS += -O3
-else
-  GLOBAL_CXXFLAGS += -O0
-endif
-
-include mk/lib.mk
diff --git a/perl/Makefile.config.in b/perl/Makefile.config.in
deleted file mode 100644
index d856de3ada8..00000000000
--- a/perl/Makefile.config.in
+++ /dev/null
@@ -1,18 +0,0 @@
-HOST_OS = @host_os@
-CC = @CC@
-CFLAGS = @CFLAGS@
-CXX = @CXX@
-CXXFLAGS = @CXXFLAGS@
-PACKAGE_NAME = @PACKAGE_NAME@
-PACKAGE_VERSION = @PACKAGE_VERSION@
-SODIUM_LIBS = @SODIUM_LIBS@
-NIX_CFLAGS = @NIX_CFLAGS@
-NIX_LIBS = @NIX_LIBS@
-nixbindir = @nixbindir@
-curl = @curl@
-nixlibexecdir = @nixlibexecdir@
-nixlocalstatedir = @nixlocalstatedir@
-perl = @perl@
-perllibdir = @perllibdir@
-nixstoredir = @nixstoredir@
-nixsysconfdir = @nixsysconfdir@
diff --git a/perl/configure.ac b/perl/configure.ac
deleted file mode 100644
index a02cb06c9ed..00000000000
--- a/perl/configure.ac
+++ /dev/null
@@ -1,84 +0,0 @@
-AC_INIT(nix-perl, m4_esyscmd([bash -c "echo -n $(cat ../.version)$VERSION_SUFFIX"]))
-AC_CONFIG_SRCDIR(MANIFEST)
-AC_CONFIG_AUX_DIR(../config)
-
-CFLAGS=
-CXXFLAGS=
-AC_PROG_CC
-AC_PROG_CXX
-
-AC_CANONICAL_HOST
-
-# Use 64-bit file system calls so that we can support files > 2 GiB.
-AC_SYS_LARGEFILE
-
-AC_DEFUN([NEED_PROG],
-[
-AC_PATH_PROG($1, $2)
-if test -z "$$1"; then
-    AC_MSG_ERROR([$2 is required])
-fi
-])
-
-NEED_PROG(perl, perl)
-NEED_PROG(curl, curl)
-NEED_PROG(bzip2, bzip2)
-NEED_PROG(xz, xz)
-
-# Test that Perl has the open/fork feature (Perl 5.8.0 and beyond).
-AC_MSG_CHECKING([whether Perl is recent enough])
-if ! $perl -e 'open(FOO, "-|", "true"); while (<FOO>) { print; }; close FOO or die;'; then
-    AC_MSG_RESULT(no)
-    AC_MSG_ERROR([Your Perl version is too old.  Nix requires Perl 5.8.0 or newer.])
-fi
-AC_MSG_RESULT(yes)
-
-
-# Figure out where to install Perl modules.
-AC_MSG_CHECKING([for the Perl installation prefix])
-perlversion=$($perl -e 'use Config; print $Config{version};')
-perlarchname=$($perl -e 'use Config; print $Config{archname};')
-AC_SUBST(perllibdir, [${libdir}/perl5/site_perl/$perlversion/$perlarchname])
-AC_MSG_RESULT($perllibdir)
-
-# Look for libsodium.
-PKG_CHECK_MODULES([SODIUM], [libsodium], [CXXFLAGS="$SODIUM_CFLAGS $CXXFLAGS"])
-
-# Check for the required Perl dependencies (DBI and DBD::SQLite).
-perlFlags="-I$perllibdir"
-
-AC_ARG_WITH(dbi, AC_HELP_STRING([--with-dbi=PATH],
-  [prefix of the Perl DBI library]),
-  perlFlags="$perlFlags -I$withval")
-
-AC_ARG_WITH(dbd-sqlite, AC_HELP_STRING([--with-dbd-sqlite=PATH],
-  [prefix of the Perl DBD::SQLite library]),
-  perlFlags="$perlFlags -I$withval")
-
-AC_MSG_CHECKING([whether DBD::SQLite works])
-if ! $perl $perlFlags -e 'use DBI; use DBD::SQLite;' 2>&5; then
-    AC_MSG_RESULT(no)
-    AC_MSG_FAILURE([The Perl modules DBI and/or DBD::SQLite are missing.])
-fi
-AC_MSG_RESULT(yes)
-
-AC_SUBST(perlFlags)
-
-PKG_CHECK_MODULES([NIX], [nix-store])
-
-NEED_PROG([NIX], [nix])
-
-# Expand all variables in config.status.
-test "$prefix" = NONE && prefix=$ac_default_prefix
-test "$exec_prefix" = NONE && exec_prefix='${prefix}'
-for name in $ac_subst_vars; do
-    declare $name="$(eval echo "${!name}")"
-    declare $name="$(eval echo "${!name}")"
-    declare $name="$(eval echo "${!name}")"
-done
-
-rm -f Makefile.config
-ln -sfn ../mk mk
-
-AC_CONFIG_FILES([])
-AC_OUTPUT
diff --git a/perl/default.nix b/perl/default.nix
deleted file mode 100644
index 7103574c9a9..00000000000
--- a/perl/default.nix
+++ /dev/null
@@ -1,61 +0,0 @@
-{ lib, fileset
-, stdenv
-, perl, perlPackages
-, autoconf-archive, autoreconfHook, pkg-config
-, nix, curl, bzip2, xz, boost, libsodium, darwin
-}:
-
-perl.pkgs.toPerlModule (stdenv.mkDerivation (finalAttrs: {
-  name = "nix-perl-${nix.version}";
-
-  src = fileset.toSource {
-    root = ../.;
-    fileset = fileset.unions ([
-      ../.version
-      ../m4
-      ../mk
-      ./MANIFEST
-      ./Makefile
-      ./Makefile.config.in
-      ./configure.ac
-      ./lib
-      ./local.mk
-    ] ++ lib.optionals finalAttrs.doCheck [
-      ./.yath.rc
-      ./t
-    ]);
-  };
-
-  nativeBuildInputs =
-    [ autoconf-archive
-      autoreconfHook
-      pkg-config
-    ];
-
-  buildInputs =
-    [ nix
-      curl
-      bzip2
-      xz
-      perl
-      boost
-    ]
-    ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
-    ++ lib.optional stdenv.isDarwin darwin.apple_sdk.frameworks.Security;
-
-  # `perlPackages.Test2Harness` is marked broken for Darwin
-  doCheck = !stdenv.isDarwin;
-
-  nativeCheckInputs = [
-    perlPackages.Test2Harness
-  ];
-
-  configureFlags = [
-    "--with-dbi=${perlPackages.DBI}/${perl.libPrefix}"
-    "--with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}"
-  ];
-
-  enableParallelBuilding = true;
-
-  postUnpack = "sourceRoot=$sourceRoot/perl";
-}))
diff --git a/perl/local.mk b/perl/local.mk
deleted file mode 100644
index ed4764eb96b..00000000000
--- a/perl/local.mk
+++ /dev/null
@@ -1,46 +0,0 @@
-nix_perl_sources := \
-  lib/Nix/Store.pm \
-  lib/Nix/Manifest.pm \
-  lib/Nix/SSH.pm \
-  lib/Nix/CopyClosure.pm \
-  lib/Nix/Config.pm.in \
-  lib/Nix/Utils.pm
-
-nix_perl_modules := $(nix_perl_sources:.in=)
-
-$(foreach x, $(nix_perl_modules), $(eval $(call install-data-in, $(x), $(perllibdir)/Nix)))
-
-lib/Nix/Store.cc: lib/Nix/Store.xs
-	$(trace-gen) xsubpp $^ -output $@
-
-libraries += Store
-
-Store_DIR := lib/Nix
-
-Store_SOURCES := $(Store_DIR)/Store.cc
-
-Store_CXXFLAGS = \
-  $(NIX_CFLAGS) \
-  -I$(shell perl -e 'use Config; print $$Config{archlibexp};')/CORE \
-  -D_FILE_OFFSET_BITS=64 \
-  -Wno-unknown-warning-option -Wno-unused-variable -Wno-literal-suffix \
-  -Wno-reserved-user-defined-literal -Wno-duplicate-decl-specifier -Wno-pointer-bool-conversion
-
-Store_LDFLAGS := $(SODIUM_LIBS) $(NIX_LIBS)
-
-ifdef HOST_CYGWIN
-  archlib = $(shell perl -E 'use Config; print $$Config{archlib};')
-  libperl = $(shell perl -E 'use Config; print $$Config{libperl};')
-  Store_LDFLAGS += $(shell find ${archlib} -name ${libperl})
-endif
-
-Store_ALLOW_UNDEFINED = 1
-
-Store_FORCE_INSTALL = 1
-
-Store_INSTALL_DIR = $(perllibdir)/auto/Nix/Store
-
-clean-files += lib/Nix/Config.pm lib/Nix/Store.cc Makefile.config
-
-check: all
-	yath test
diff --git a/scripts/bigsur-nixbld-user-migration.sh b/scripts/bigsur-nixbld-user-migration.sh
index f1619fd56d3..0eb312e07cd 100755
--- a/scripts/bigsur-nixbld-user-migration.sh
+++ b/scripts/bigsur-nixbld-user-migration.sh
@@ -3,7 +3,7 @@
 ((NEW_NIX_FIRST_BUILD_UID=301))
 
 id_available(){
-	dscl . list /Users UniqueID | grep -E '\b'$1'\b' >/dev/null
+	dscl . list /Users UniqueID | grep -E '\b'"$1"'\b' >/dev/null
 }
 
 change_nixbld_names_and_ids(){
@@ -26,18 +26,18 @@ change_nixbld_names_and_ids(){
 			fi
 		done
 
-		if [[ $name == _* ]]; then
+		if [[ "$name" == _* ]]; then
 			echo "      It looks like $name has already been renamed--skipping."
 		else
 			# first 3 are cleanup, it's OK if they aren't here
-			sudo dscl . delete /Users/$name dsAttrTypeNative:_writers_passwd &>/dev/null || true
-			sudo dscl . change /Users/$name NFSHomeDirectory "/private/var/empty 1" "/var/empty" &>/dev/null || true
+			sudo dscl . delete "/Users/$name" dsAttrTypeNative:_writers_passwd &>/dev/null || true
+			sudo dscl . change "/Users/$name" NFSHomeDirectory "/private/var/empty 1" "/var/empty" &>/dev/null || true
 			# remove existing user from group
-			sudo dseditgroup -o edit -t user -d $name nixbld || true
-			sudo dscl . change /Users/$name UniqueID $uid $next_id
-			sudo dscl . change /Users/$name RecordName $name _$name
+			sudo dseditgroup -o edit -t user -d "$name" nixbld || true
+			sudo dscl . change "/Users/$name" UniqueID "$uid" "$next_id"
+			sudo dscl . change "/Users/$name" RecordName "$name" "_$name"
 			# add renamed user to group
-			sudo dseditgroup -o edit -t user -a _$name nixbld
+			sudo dseditgroup -o edit -t user -a "_$name" nixbld
 			echo "      $name migrated to _$name (uid: $next_id)"
 		fi
 	done < <(dscl . list /Users UniqueID | grep nixbld | sort -n -k2)
diff --git a/scripts/check-hydra-status.sh b/scripts/check-hydra-status.sh
deleted file mode 100644
index e62705e9498..00000000000
--- a/scripts/check-hydra-status.sh
+++ /dev/null
@@ -1,33 +0,0 @@
-#!/usr/bin/env bash
-
-set -euo pipefail
-# set -x
-
-
-# mapfile BUILDS_FOR_LATEST_EVAL < <(
-# curl -H 'Accept: application/json' https://hydra.nixos.org/jobset/nix/master/evals | \
-#   jq -r '.evals[0].builds[] | @sh')
-BUILDS_FOR_LATEST_EVAL=$(
-curl -sS -H 'Accept: application/json' https://hydra.nixos.org/jobset/nix/master/evals | \
-  jq -r '.evals[0].builds[]')
-
-someBuildFailed=0
-
-for buildId in $BUILDS_FOR_LATEST_EVAL; do
-  buildInfo=$(curl --fail -sS -H 'Accept: application/json' "https://hydra.nixos.org/build/$buildId")
-
-  finished=$(echo "$buildInfo" | jq -r '.finished')
-
-  if [[ $finished = 0 ]]; then
-    continue
-  fi
-
-  buildStatus=$(echo "$buildInfo" | jq -r '.buildstatus')
-
-  if [[ $buildStatus != 0 ]]; then
-    someBuildFailed=1
-    echo "Job “$(echo "$buildInfo" | jq -r '.job')” failed on hydra: $buildInfo"
-  fi
-done
-
-exit "$someBuildFailed"
diff --git a/scripts/install-multi-user.sh b/scripts/install-multi-user.sh
index ad3ee888138..6aee073e3f9 100644
--- a/scripts/install-multi-user.sh
+++ b/scripts/install-multi-user.sh
@@ -754,7 +754,7 @@ I will:
    (if it does, I will tell you how to clean them up.)
  - create local users (see the list above for the users I'll make)
  - create a local group ($NIX_BUILD_GROUP_NAME)
- - install Nix in to $NIX_ROOT
+ - install Nix in $NIX_ROOT
  - create a configuration file in /etc/nix
  - set up the "default profile" by creating some Nix-related files in
    $ROOT_HOME
diff --git a/scripts/install-systemd-multi-user.sh b/scripts/install-systemd-multi-user.sh
index 202a9bb548b..a62ed7e3aa4 100755
--- a/scripts/install-systemd-multi-user.sh
+++ b/scripts/install-systemd-multi-user.sh
@@ -35,7 +35,7 @@ escape_systemd_env() {
 
 # Gather all non-empty proxy environment variables into a string
 create_systemd_proxy_env() {
-    vars="http_proxy https_proxy ftp_proxy no_proxy HTTP_PROXY HTTPS_PROXY FTP_PROXY NO_PROXY"
+    vars="http_proxy https_proxy ftp_proxy all_proxy no_proxy HTTP_PROXY HTTPS_PROXY FTP_PROXY ALL_PROXY NO_PROXY"
     for v in $vars; do
         if [ "x${!v:-}" != "x" ]; then
             echo "Environment=${v}=$(escape_systemd_env ${!v})"
diff --git a/scripts/install.in b/scripts/install.in
index 7d2e52b2637..b4e808d8e94 100755
--- a/scripts/install.in
+++ b/scripts/install.in
@@ -50,6 +50,11 @@ case "$(uname -s).$(uname -m)" in
         path=@tarballPath_armv7l-linux@
         system=armv7l-linux
         ;;
+    Linux.riscv64)
+        hash=@tarballHash_riscv64-linux@
+        path=@tarballPath_riscv64-linux@
+        system=riscv64-linux
+        ;;
     Darwin.x86_64)
         hash=@tarballHash_x86_64-darwin@
         path=@tarballPath_x86_64-darwin@
diff --git a/scripts/nix-profile-daemon.sh.in b/scripts/nix-profile-daemon.sh.in
index 0ec72e79742..eb124c0b5c0 100644
--- a/scripts/nix-profile-daemon.sh.in
+++ b/scripts/nix-profile-daemon.sh.in
@@ -1,4 +1,5 @@
 # Only execute this file once per shell.
+# This file is tested by tests/installer/default.nix.
 if [ -n "${__ETC_PROFILE_NIX_SOURCED:-}" ]; then return; fi
 __ETC_PROFILE_NIX_SOURCED=1
 
@@ -9,11 +10,9 @@ else
     NIX_LINK_NEW=$HOME/.local/state/nix/profile
 fi
 if [ -e "$NIX_LINK_NEW" ]; then
-    NIX_LINK="$NIX_LINK_NEW"
-else
-    if [ -t 2 ] && [ -e "$NIX_LINK_NEW" ]; then
+    if [ -t 2 ] && [ -e "$NIX_LINK" ]; then
         warning="\033[1;35mwarning:\033[0m"
-        printf "$warning Both %s and legacy %s exist; using the latter.\n" "$NIX_LINK_NEW" "$NIX_LINK" 1>&2
+        printf "$warning Both %s and legacy %s exist; using the former.\n" "$NIX_LINK_NEW" "$NIX_LINK" 1>&2
         if [ "$(realpath "$NIX_LINK")" = "$(realpath "$NIX_LINK_NEW")" ]; then
             printf "         Since the profiles match, you can safely delete either of them.\n" 1>&2
         else
@@ -26,6 +25,7 @@ else
             printf "$warning Profiles do not match. You should manually migrate from %s to %s.\n" "$NIX_LINK" "$NIX_LINK_NEW" 1>&2
         fi
     fi
+    NIX_LINK="$NIX_LINK_NEW"
 fi
 
 export NIX_PROFILES="@localstatedir@/nix/profiles/default $NIX_LINK"
diff --git a/scripts/nix-profile.sh.in b/scripts/nix-profile.sh.in
index 44bc96e894b..e868399b143 100644
--- a/scripts/nix-profile.sh.in
+++ b/scripts/nix-profile.sh.in
@@ -1,3 +1,4 @@
+# This file is tested by tests/installer/default.nix.
 if [ -n "$HOME" ] && [ -n "$USER" ]; then
 
     # Set up the per-user profile.
@@ -9,11 +10,9 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
         NIX_LINK_NEW="$HOME/.local/state/nix/profile"
     fi
     if [ -e "$NIX_LINK_NEW" ]; then
-        NIX_LINK="$NIX_LINK_NEW"
-    else
-        if [ -t 2 ] && [ -e "$NIX_LINK_NEW" ]; then
+        if [ -t 2 ] && [ -e "$NIX_LINK" ]; then
             warning="\033[1;35mwarning:\033[0m"
-            printf "$warning Both %s and legacy %s exist; using the latter.\n" "$NIX_LINK_NEW" "$NIX_LINK" 1>&2
+            printf "$warning Both %s and legacy %s exist; using the former.\n" "$NIX_LINK_NEW" "$NIX_LINK" 1>&2
             if [ "$(realpath "$NIX_LINK")" = "$(realpath "$NIX_LINK_NEW")" ]; then
                 printf "         Since the profiles match, you can safely delete either of them.\n" 1>&2
             else
@@ -26,6 +25,7 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
                 printf "$warning Profiles do not match. You should manually migrate from %s to %s.\n" "$NIX_LINK" "$NIX_LINK_NEW" 1>&2
             fi
         fi
+        NIX_LINK="$NIX_LINK_NEW"
     fi
 
     # Set up environment.
diff --git a/src/build-remote/build-remote.cc b/src/build-remote/build-remote.cc
index 2a4723643f8..582e6d623d0 100644
--- a/src/build-remote/build-remote.cc
+++ b/src/build-remote/build-remote.cc
@@ -22,7 +22,6 @@
 #include "experimental-features.hh"
 
 using namespace nix;
-using namespace nix::unix;
 using std::cin;
 
 static void handleAlarm(int sig) {
@@ -38,7 +37,7 @@ static std::string currentLoad;
 
 static AutoCloseFD openSlotLock(const Machine & m, uint64_t slot)
 {
-    return openLockFile(fmt("%s/%s-%d", currentLoad, escapeUri(m.storeUri), slot), true);
+    return openLockFile(fmt("%s/%s-%d", currentLoad, escapeUri(m.storeUri.render()), slot), true);
 }
 
 static bool allSupportedLocally(Store & store, const std::set<std::string>& requiredFeatures) {
@@ -100,7 +99,7 @@ static int main_build_remote(int argc, char * * argv)
         }
 
         std::optional<StorePath> drvPath;
-        std::string storeUri;
+        StoreReference storeUri;
 
         while (true) {
 
@@ -136,7 +135,7 @@ static int main_build_remote(int argc, char * * argv)
                 Machine * bestMachine = nullptr;
                 uint64_t bestLoad = 0;
                 for (auto & m : machines) {
-                    debug("considering building on remote machine '%s'", m.storeUri);
+                    debug("considering building on remote machine '%s'", m.storeUri.render());
 
                     if (m.enabled &&
                         m.systemSupported(neededSystem) &&
@@ -234,7 +233,7 @@ static int main_build_remote(int argc, char * * argv)
 
                 try {
 
-                    Activity act(*logger, lvlTalkative, actUnknown, fmt("connecting to '%s'", bestMachine->storeUri));
+                    Activity act(*logger, lvlTalkative, actUnknown, fmt("connecting to '%s'", bestMachine->storeUri.render()));
 
                     sshStore = bestMachine->openStore();
                     sshStore->connect();
@@ -243,7 +242,7 @@ static int main_build_remote(int argc, char * * argv)
                 } catch (std::exception & e) {
                     auto msg = chomp(drainFD(5, false));
                     printError("cannot build on '%s': %s%s",
-                        bestMachine->storeUri, e.what(),
+                        bestMachine->storeUri.render(), e.what(),
                         msg.empty() ? "" : ": " + msg);
                     bestMachine->enabled = false;
                     continue;
@@ -258,15 +257,15 @@ static int main_build_remote(int argc, char * * argv)
 
         assert(sshStore);
 
-        std::cerr << "# accept\n" << storeUri << "\n";
+        std::cerr << "# accept\n" << storeUri.render() << "\n";
 
         auto inputs = readStrings<PathSet>(source);
         auto wantedOutputs = readStrings<StringSet>(source);
 
-        AutoCloseFD uploadLock = openLockFile(currentLoad + "/" + escapeUri(storeUri) + ".upload-lock", true);
+        AutoCloseFD uploadLock = openLockFile(currentLoad + "/" + escapeUri(storeUri.render()) + ".upload-lock", true);
 
         {
-            Activity act(*logger, lvlTalkative, actUnknown, fmt("waiting for the upload lock to '%s'", storeUri));
+            Activity act(*logger, lvlTalkative, actUnknown, fmt("waiting for the upload lock to '%s'", storeUri.render()));
 
             auto old = signal(SIGALRM, handleAlarm);
             alarm(15 * 60);
@@ -279,7 +278,7 @@ static int main_build_remote(int argc, char * * argv)
         auto substitute = settings.buildersUseSubstitutes ? Substitute : NoSubstitute;
 
         {
-            Activity act(*logger, lvlTalkative, actUnknown, fmt("copying dependencies to '%s'", storeUri));
+            Activity act(*logger, lvlTalkative, actUnknown, fmt("copying dependencies to '%s'", storeUri.render()));
             copyPaths(*store, *sshStore, store->parseStorePathSet(inputs), NoRepair, NoCheckSigs, substitute);
         }
 
@@ -317,7 +316,7 @@ static int main_build_remote(int argc, char * * argv)
             optResult = sshStore->buildDerivation(*drvPath, (const BasicDerivation &) drv);
             auto & result = *optResult;
             if (!result.success())
-                throw Error("build of '%s' on '%s' failed: %s", store->printStorePath(*drvPath), storeUri, result.errorMsg);
+                throw Error("build of '%s' on '%s' failed: %s", store->printStorePath(*drvPath), storeUri.render(), result.errorMsg);
         } else {
             copyClosure(*store, *sshStore, StorePathSet {*drvPath}, NoRepair, NoCheckSigs, substitute);
             auto res = sshStore->buildPathsWithResults({
@@ -360,7 +359,7 @@ static int main_build_remote(int argc, char * * argv)
         }
 
         if (!missingPaths.empty()) {
-            Activity act(*logger, lvlTalkative, actUnknown, fmt("copying outputs from '%s'", storeUri));
+            Activity act(*logger, lvlTalkative, actUnknown, fmt("copying outputs from '%s'", storeUri.render()));
             if (auto localStore = store.dynamic_pointer_cast<LocalStore>())
                 for (auto & path : missingPaths)
                     localStore->locksHeld.insert(store->printStorePath(path)); /* FIXME: ugly */
diff --git a/doc/external-api/.gitignore b/src/external-api-docs/.gitignore
similarity index 100%
rename from doc/external-api/.gitignore
rename to src/external-api-docs/.gitignore
diff --git a/src/external-api-docs/.version b/src/external-api-docs/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/external-api-docs/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/doc/external-api/README.md b/src/external-api-docs/README.md
similarity index 93%
rename from doc/external-api/README.md
rename to src/external-api-docs/README.md
index 167c021994e..8760ac88b4c 100644
--- a/doc/external-api/README.md
+++ b/src/external-api-docs/README.md
@@ -27,7 +27,7 @@ appreciated.
 The following examples, for simplicity, don't include error handling. See the
 [Handling errors](@ref errors) section for more information.
 
-# Embedding the Nix Evaluator
+# Embedding the Nix Evaluator{#nix_evaluator_example}
 
 In this example we programmatically start the Nix language evaluator with a
 dummy store (that has no store paths and cannot be written to), and evaluate the
@@ -46,9 +46,9 @@ Nix expression `builtins.nixVersion`.
 // NOTE: This example lacks all error handling. Production code must check for
 // errors, as some return values will be undefined.
 
-void my_get_string_cb(const char * start, unsigned int n, char ** user_data)
+void my_get_string_cb(const char * start, unsigned int n, void * user_data)
 {
-    *user_data = strdup(start);
+    *((char **) user_data) = strdup(start);
 }
 
 int main()
@@ -63,7 +63,7 @@ int main()
     nix_value_force(NULL, state, value);
 
     char * version;
-    nix_get_string(NULL, value, my_get_string_cb, version);
+    nix_get_string(NULL, value, my_get_string_cb, &version);
     printf("Nix version: %s\n", version);
 
     free(version);
diff --git a/doc/external-api/doxygen.cfg.in b/src/external-api-docs/doxygen.cfg.in
similarity index 91%
rename from doc/external-api/doxygen.cfg.in
rename to src/external-api-docs/doxygen.cfg.in
index cd8b4989bab..1be71d895e2 100644
--- a/doc/external-api/doxygen.cfg.in
+++ b/src/external-api-docs/doxygen.cfg.in
@@ -12,7 +12,9 @@ PROJECT_NAME           = "Nix"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = @PACKAGE_VERSION@
+PROJECT_NUMBER         = @PROJECT_NUMBER@
+
+OUTPUT_DIRECTORY       = @OUTPUT_DIRECTORY@
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
@@ -36,10 +38,10 @@ GENERATE_LATEX         = NO
 # so they can expand variables despite configure variables.
 
 INPUT                  = \
-  src/libutil-c \
-  src/libexpr-c \
-  src/libstore-c \
-  doc/external-api/README.md
+  @src@/src/libutil-c \
+  @src@/src/libexpr-c \
+  @src@/src/libstore-c \
+  @src@/doc/external-api/README.md
 
 FILE_PATTERNS = nix_api_*.h *.md
 
@@ -49,7 +51,6 @@ FILE_PATTERNS = nix_api_*.h *.md
 # RECURSIVE has no effect here.
 # This tag requires that the tag SEARCH_INCLUDES is set to YES.
 
-INCLUDE_PATH           = @RAPIDCHECK_HEADERS@
 EXCLUDE_PATTERNS = *_internal.h
 GENERATE_TREEVIEW = YES
 OPTIMIZE_OUTPUT_FOR_C  = YES
diff --git a/src/external-api-docs/meson.build b/src/external-api-docs/meson.build
new file mode 100644
index 00000000000..62474ffe401
--- /dev/null
+++ b/src/external-api-docs/meson.build
@@ -0,0 +1,31 @@
+project('nix-external-api-docs',
+  version : files('.version'),
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+fs = import('fs')
+
+doxygen_cfg = configure_file(
+  input : 'doxygen.cfg.in',
+  output : 'doxygen.cfg',
+  configuration : {
+    'PROJECT_NUMBER': meson.project_version(),
+    'OUTPUT_DIRECTORY' : meson.current_build_dir(),
+    'src' : fs.parent(fs.parent(meson.project_source_root())),
+  },
+)
+
+doxygen = find_program('doxygen', native : true, required : true)
+
+custom_target(
+  'external-api-docs',
+  command : [ doxygen , doxygen_cfg ],
+  input : [
+    doxygen_cfg,
+  ],
+  output : 'html',
+  install : true,
+  install_dir : get_option('datadir') / 'doc/nix/external-api',
+  build_always_stale : true,
+)
diff --git a/src/external-api-docs/package.nix b/src/external-api-docs/package.nix
new file mode 100644
index 00000000000..da136bbe1fc
--- /dev/null
+++ b/src/external-api-docs/package.nix
@@ -0,0 +1,63 @@
+{ lib
+, mkMesonDerivation
+
+, meson
+, ninja
+, doxygen
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-external-api-docs";
+  inherit version;
+
+  workDir = ./.;
+  fileset =
+    let
+      cpp = fileset.fileFilter (file: file.hasExt "cc" || file.hasExt "h");
+    in
+    fileset.unions [
+      ./.version
+      ../../.version
+      ./meson.build
+      ./doxygen.cfg.in
+      ./README.md
+      # Source is not compiled, but still must be available for Doxygen
+      # to gather comments.
+      (cpp ../libexpr-c)
+      (cpp ../libstore-c)
+      (cpp ../libutil-c)
+    ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    doxygen
+  ];
+
+  preConfigure =
+    ''
+      chmod u+w ./.version
+      echo ${finalAttrs.version} > ./.version
+    '';
+
+  postInstall = ''
+    mkdir -p ''${!outputDoc}/nix-support
+    echo "doc external-api-docs $out/share/doc/nix/external-api/html" >> ''${!outputDoc}/nix-support/hydra-build-products
+  '';
+
+  enableParallelBuilding = true;
+
+  strictDeps = true;
+
+  meta = {
+    platforms = lib.platforms.all;
+  };
+})
diff --git a/doc/internal-api/.gitignore b/src/internal-api-docs/.gitignore
similarity index 100%
rename from doc/internal-api/.gitignore
rename to src/internal-api-docs/.gitignore
diff --git a/src/internal-api-docs/.version b/src/internal-api-docs/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/internal-api-docs/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/doc/internal-api/doxygen.cfg.in b/src/internal-api-docs/doxygen.cfg.in
similarity index 84%
rename from doc/internal-api/doxygen.cfg.in
rename to src/internal-api-docs/doxygen.cfg.in
index 6c6c325bdc9..f1ef75b380d 100644
--- a/doc/internal-api/doxygen.cfg.in
+++ b/src/internal-api-docs/doxygen.cfg.in
@@ -12,7 +12,9 @@ PROJECT_NAME           = "Nix"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = @PACKAGE_VERSION@
+PROJECT_NUMBER         = @PROJECT_NUMBER@
+
+OUTPUT_DIRECTORY       = @OUTPUT_DIRECTORY@
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
@@ -36,27 +38,27 @@ GENERATE_LATEX         = NO
 # so they can expand variables despite configure variables.
 
 INPUT                  = \
-  src/libcmd \
-  src/libexpr \
-  src/libexpr/flake \
-  tests/unit/libexpr \
-  tests/unit/libexpr/value \
-  tests/unit/libexpr/test \
-  tests/unit/libexpr/test/value \
-  src/libexpr/value \
-  src/libfetchers \
-  src/libmain \
-  src/libstore \
-  src/libstore/build \
-  src/libstore/builtins \
-  tests/unit/libstore \
-  tests/unit/libstore/test \
-  src/libutil \
-  tests/unit/libutil \
-  tests/unit/libutil/test \
-  src/nix \
-  src/nix-env \
-  src/nix-store
+  @src@/libcmd \
+  @src@/libexpr \
+  @src@/libexpr/flake \
+  @src@/nix-expr-tests \
+  @src@/nix-expr-tests/value \
+  @src@/nix-expr-test-support/test \
+  @src@/nix-expr-test-support/test/value \
+  @src@/libexpr/value \
+  @src@/libfetchers \
+  @src@/libmain \
+  @src@/libstore \
+  @src@/libstore/build \
+  @src@/libstore/builtins \
+  @src@/nix-store-tests \
+  @src@/nix-store-test-support/test \
+  @src@/libutil \
+  @src@/nix-util-tests \
+  @src@/nix-util-test-support/test \
+  @src@/nix \
+  @src@/nix-env \
+  @src@/nix-store
 
 # If the MACRO_EXPANSION tag is set to YES, doxygen will expand all macro names
 # in the source code. If set to NO, only conditional compilation will be
diff --git a/src/internal-api-docs/meson.build b/src/internal-api-docs/meson.build
new file mode 100644
index 00000000000..54eb7e5dd47
--- /dev/null
+++ b/src/internal-api-docs/meson.build
@@ -0,0 +1,31 @@
+project('nix-internal-api-docs',
+  version : files('.version'),
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+fs = import('fs')
+
+doxygen_cfg = configure_file(
+  input : 'doxygen.cfg.in',
+  output : 'doxygen.cfg',
+  configuration : {
+    'PROJECT_NUMBER': meson.project_version(),
+    'OUTPUT_DIRECTORY' : meson.current_build_dir(),
+    'src' : fs.parent(fs.parent(meson.project_source_root())) / 'src',
+  },
+)
+
+doxygen = find_program('doxygen', native : true, required : true)
+
+custom_target(
+  'internal-api-docs',
+  command : [ doxygen , doxygen_cfg ],
+  input : [
+    doxygen_cfg,
+  ],
+  output : 'html',
+  install : true,
+  install_dir : get_option('datadir') / 'doc/nix/internal-api',
+  build_always_stale : true,
+)
diff --git a/src/internal-api-docs/package.nix b/src/internal-api-docs/package.nix
new file mode 100644
index 00000000000..f2077dcafa4
--- /dev/null
+++ b/src/internal-api-docs/package.nix
@@ -0,0 +1,58 @@
+{ lib
+, mkMesonDerivation
+
+, meson
+, ninja
+, doxygen
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-internal-api-docs";
+  inherit version;
+
+  workDir = ./.;
+  fileset = let
+    cpp = fileset.fileFilter (file: file.hasExt "cc" || file.hasExt "hh");
+  in fileset.unions [
+    ./.version
+    ../../.version
+    ./meson.build
+    ./doxygen.cfg.in
+    # Source is not compiled, but still must be available for Doxygen
+    # to gather comments.
+    (cpp ../.)
+  ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    doxygen
+  ];
+
+  preConfigure =
+    ''
+      chmod u+w ./.version
+      echo ${finalAttrs.version} > ./.version
+    '';
+
+  postInstall = ''
+    mkdir -p ''${!outputDoc}/nix-support
+    echo "doc internal-api-docs $out/share/doc/nix/internal-api/html" >> ''${!outputDoc}/nix-support/hydra-build-products
+  '';
+
+  enableParallelBuilding = true;
+
+  strictDeps = true;
+
+  meta = {
+    platforms = lib.platforms.all;
+  };
+})
diff --git a/src/libcmd/.version b/src/libcmd/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libcmd/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libcmd/build-utils-meson b/src/libcmd/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libcmd/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 220a90cf686..74d146c66c5 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -127,12 +127,12 @@ ref<EvalState> EvalCommand::getEvalState()
     if (!evalState) {
         evalState =
             #if HAVE_BOEHMGC
-            std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
-                searchPath, getEvalStore(), getStore())
+            std::allocate_shared<EvalState>(
+                traceable_allocator<EvalState>(),
             #else
             std::make_shared<EvalState>(
-                searchPath, getEvalStore(), getStore())
             #endif
+                lookupPath, getEvalStore(), evalSettings, getStore())
             ;
 
         evalState->repair = repair;
diff --git a/src/libcmd/common-eval-args.cc b/src/libcmd/common-eval-args.cc
index c6ee0d0b259..62745b6815f 100644
--- a/src/libcmd/common-eval-args.cc
+++ b/src/libcmd/common-eval-args.cc
@@ -1,6 +1,7 @@
 #include "eval-settings.hh"
 #include "common-eval-args.hh"
 #include "shared.hh"
+#include "config-global.hh"
 #include "filetransfer.hh"
 #include "eval.hh"
 #include "fetchers.hh"
@@ -10,9 +11,35 @@
 #include "command.hh"
 #include "tarball.hh"
 #include "fetch-to-store.hh"
+#include "compatibility-settings.hh"
+#include "eval-settings.hh"
 
 namespace nix {
 
+EvalSettings evalSettings {
+    settings.readOnlyMode,
+    {
+        {
+            "flake",
+            [](ref<Store> store, std::string_view rest) {
+                experimentalFeatureSettings.require(Xp::Flakes);
+                // FIXME `parseFlakeRef` should take a `std::string_view`.
+                auto flakeRef = parseFlakeRef(std::string { rest }, {}, true, false);
+                debug("fetching flake search path element '%s''", rest);
+                auto storePath = flakeRef.resolve(store).fetchTree(store).first;
+                return store->toRealPath(storePath);
+            },
+        },
+    },
+};
+
+static GlobalConfig::Register rEvalSettings(&evalSettings);
+
+CompatibilitySettings compatibilitySettings {};
+
+static GlobalConfig::Register rCompatibilitySettings(&compatibilitySettings);
+
+
 MixEvalArgs::MixEvalArgs()
 {
     addFlag({
@@ -20,7 +47,7 @@ MixEvalArgs::MixEvalArgs()
         .description = "Pass the value *expr* as the argument *name* to Nix functions.",
         .category = category,
         .labels = {"name", "expr"},
-        .handler = {[&](std::string name, std::string expr) { autoArgs.insert_or_assign(name, AutoArg{AutoArgExpr(expr)}); }}
+        .handler = {[&](std::string name, std::string expr) { autoArgs.insert_or_assign(name, AutoArg{AutoArgExpr{expr}}); }}
     });
 
     addFlag({
@@ -28,7 +55,7 @@ MixEvalArgs::MixEvalArgs()
         .description = "Pass the string *string* as the argument *name* to Nix functions.",
         .category = category,
         .labels = {"name", "string"},
-        .handler = {[&](std::string name, std::string s) { autoArgs.insert_or_assign(name, AutoArg{AutoArgString(s)}); }},
+        .handler = {[&](std::string name, std::string s) { autoArgs.insert_or_assign(name, AutoArg{AutoArgString{s}}); }},
     });
 
     addFlag({
@@ -36,7 +63,7 @@ MixEvalArgs::MixEvalArgs()
         .description = "Pass the contents of file *path* as the argument *name* to Nix functions.",
         .category = category,
         .labels = {"name", "path"},
-        .handler = {[&](std::string name, std::string path) { autoArgs.insert_or_assign(name, AutoArg{AutoArgFile(path)}); }},
+        .handler = {[&](std::string name, std::string path) { autoArgs.insert_or_assign(name, AutoArg{AutoArgFile{path}}); }},
         .completer = completePath
     });
 
@@ -54,7 +81,7 @@ MixEvalArgs::MixEvalArgs()
         .description = R"(
   Add *path* to the Nix search path. The Nix search path is
   initialized from the colon-separated [`NIX_PATH`](@docroot@/command-ref/env-common.md#env-NIX_PATH) environment
-  variable, and is used to look up the location of Nix expressions using [paths](@docroot@/language/values.md#type-path) enclosed in angle
+  variable, and is used to look up the location of Nix expressions using [paths](@docroot@/language/types.md#type-path) enclosed in angle
   brackets (i.e., `<nixpkgs>`).
 
   For instance, passing
@@ -125,7 +152,7 @@ MixEvalArgs::MixEvalArgs()
         .category = category,
         .labels = {"path"},
         .handler = {[&](std::string s) {
-            searchPath.elements.emplace_back(SearchPath::Elem::parse(s));
+            lookupPath.elements.emplace_back(LookupPath::Elem::parse(s));
         }}
     });
 
diff --git a/src/libcmd/common-eval-args.hh b/src/libcmd/common-eval-args.hh
index 25ce5b9dada..8d303ee7c13 100644
--- a/src/libcmd/common-eval-args.hh
+++ b/src/libcmd/common-eval-args.hh
@@ -12,9 +12,21 @@ namespace nix {
 
 class Store;
 class EvalState;
+struct EvalSettings;
+struct CompatibilitySettings;
 class Bindings;
 struct SourcePath;
 
+/**
+ * @todo Get rid of global setttings variables
+ */
+extern EvalSettings evalSettings;
+
+/**
+ * Settings that control behaviors that have changed since Nix 2.3.
+ */
+extern CompatibilitySettings compatibilitySettings;
+
 struct MixEvalArgs : virtual Args, virtual MixRepair
 {
     static constexpr auto category = "Common evaluation options";
@@ -23,7 +35,7 @@ struct MixEvalArgs : virtual Args, virtual MixRepair
 
     Bindings * getAutoArgs(EvalState & state);
 
-    SearchPath searchPath;
+    LookupPath lookupPath;
 
     std::optional<std::string> evalStoreUrl;
 
@@ -38,6 +50,9 @@ private:
     std::map<std::string, AutoArg> autoArgs;
 };
 
+/**
+ * @param baseDir Optional [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory)
+ */
 SourcePath lookupFileArg(EvalState & state, std::string_view s, const Path * baseDir = nullptr);
 
 }
diff --git a/src/libcmd/compatibility-settings.hh b/src/libcmd/compatibility-settings.hh
new file mode 100644
index 00000000000..5dc0eaf2b38
--- /dev/null
+++ b/src/libcmd/compatibility-settings.hh
@@ -0,0 +1,19 @@
+#pragma once
+#include "config.hh"
+
+namespace nix {
+struct CompatibilitySettings : public Config
+{
+
+    CompatibilitySettings() = default;
+
+    Setting<bool> nixShellAlwaysLooksForShellNix{this, true, "nix-shell-always-looks-for-shell-nix", R"(
+        Before Nix 2.24, [`nix-shell`](@docroot@/command-ref/nix-shell.md) would only look at `shell.nix` if it was in the working directory - when no file was specified.
+
+        Since Nix 2.24, `nix-shell` always looks for a `shell.nix`, whether that's in the working directory, or in a directory that was passed as an argument.
+
+        You may set this to `false` to revert to the Nix 2.3 behavior.
+    )"};
+};
+
+};
diff --git a/src/libcmd/installable-attr-path.cc b/src/libcmd/installable-attr-path.cc
index 3ec1c161477..8917e7a018a 100644
--- a/src/libcmd/installable-attr-path.cc
+++ b/src/libcmd/installable-attr-path.cc
@@ -75,6 +75,8 @@ DerivedPathsWithInfo InstallableAttrPath::toDerivedPaths()
                 std::set<std::string> outputsToInstall;
                 for (auto & output : packageInfo.queryOutputs(false, true))
                     outputsToInstall.insert(output.first);
+                if (outputsToInstall.empty())
+                    outputsToInstall.insert("out");
                 return OutputsSpec::Names { std::move(outputsToInstall) };
             },
             [&](const ExtendedOutputsSpec::Explicit & e) -> OutputsSpec {
diff --git a/src/libcmd/installable-flake.cc b/src/libcmd/installable-flake.cc
index 6ff837ddc4b..d42fa7aaccc 100644
--- a/src/libcmd/installable-flake.cc
+++ b/src/libcmd/installable-flake.cc
@@ -106,9 +106,14 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
             fmt("while evaluating the flake output attribute '%s'", attrPath)))
         {
             return { *derivedPathWithInfo };
+        } else {
+            throw Error(
+                "expected flake output attribute '%s' to be a derivation or path but found %s: %s",
+                attrPath,
+                showType(v),
+                ValuePrinter(*this->state, v, errorPrintOptions)
+            );
         }
-        else
-            throw Error("flake output attribute '%s' is not a derivation or path", attrPath);
     }
 
     auto drvPath = attr->forceDerivation();
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index ed67723778f..6835c512c1c 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -21,7 +21,6 @@
 #include "url.hh"
 #include "registry.hh"
 #include "build-result.hh"
-#include "fs-input-accessor.hh"
 
 #include <regex>
 #include <queue>
@@ -147,7 +146,7 @@ MixFlakeOptions::MixFlakeOptions()
         .category = category,
         .labels = {"flake-lock-path"},
         .handler = {[&](std::string lockFilePath) {
-            lockFlags.referenceLockFilePath = getUnfilteredRootPath(CanonPath(absPath(lockFilePath)));
+            lockFlags.referenceLockFilePath = {getFSSourceAccessor(), CanonPath(absPath(lockFilePath))};
         }},
         .completer = completePath
     });
@@ -443,13 +442,10 @@ ref<eval_cache::EvalCache> openEvalCache(
     EvalState & state,
     std::shared_ptr<flake::LockedFlake> lockedFlake)
 {
-    auto fingerprint = lockedFlake->getFingerprint(state.store);
-    return make_ref<nix::eval_cache::EvalCache>(
-        evalSettings.useEvalCache && evalSettings.pureEval
-            ? fingerprint
-            : std::nullopt,
-        state,
-        [&state, lockedFlake]()
+    auto fingerprint = evalSettings.useEvalCache && evalSettings.pureEval
+        ? lockedFlake->getFingerprint(state.store)
+        : std::nullopt;
+    auto rootLoader = [&state, lockedFlake]()
         {
             /* For testing whether the evaluation cache is
                complete. */
@@ -465,7 +461,17 @@ ref<eval_cache::EvalCache> openEvalCache(
             assert(aOutputs);
 
             return aOutputs->value;
-        });
+        };
+
+    if (fingerprint) {
+        auto search = state.evalCaches.find(fingerprint.value());
+        if (search == state.evalCaches.end()) {
+            search = state.evalCaches.emplace(fingerprint.value(), make_ref<nix::eval_cache::EvalCache>(fingerprint, state, rootLoader)).first;
+        }
+        return search->second;
+    } else {
+        return make_ref<nix::eval_cache::EvalCache>(std::nullopt, state, rootLoader);
+    }
 }
 
 Installables SourceExprCommand::parseInstallables(
@@ -595,6 +601,37 @@ std::vector<BuiltPathWithResult> Installable::build(
     return res;
 }
 
+static void throwBuildErrors(
+    std::vector<KeyedBuildResult> & buildResults,
+    const Store & store)
+{
+    std::vector<KeyedBuildResult> failed;
+    for (auto & buildResult : buildResults) {
+        if (!buildResult.success()) {
+            failed.push_back(buildResult);
+        }
+    }
+
+    auto failedResult = failed.begin();
+    if (failedResult != failed.end()) {
+        if (failed.size() == 1) {
+            failedResult->rethrow();
+        } else {
+            StringSet failedPaths;
+            for (; failedResult != failed.end(); failedResult++) {
+                if (!failedResult->errorMsg.empty()) {
+                    logError(ErrorInfo{
+                        .level = lvlError,
+                        .msg = failedResult->errorMsg,
+                    });
+                }
+                failedPaths.insert(failedResult->path.to_string(store));
+            }
+            throw Error("build of %s failed", concatStringsSep(", ", quoteStrings(failedPaths)));
+        }
+    }
+}
+
 std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build2(
     ref<Store> evalStore,
     ref<Store> store,
@@ -656,10 +693,9 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
         if (settings.printMissing)
             printMissing(store, pathsToBuild, lvlInfo);
 
-        for (auto & buildResult : store->buildPathsWithResults(pathsToBuild, bMode, evalStore)) {
-            if (!buildResult.success())
-                buildResult.rethrow();
-
+        auto buildResults = store->buildPathsWithResults(pathsToBuild, bMode, evalStore);
+        throwBuildErrors(buildResults, *store);
+        for (auto & buildResult : buildResults) {
             for (auto & aux : backmap[buildResult.path]) {
                 std::visit(overloaded {
                     [&](const DerivedPath::Built & bfd) {
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index 9aa33a9d3c2..a270333f451 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -6,10 +6,10 @@ libcmd_DIR := $(d)
 
 libcmd_SOURCES := $(wildcard $(d)/*.cc)
 
-libcmd_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) $(INCLUDE_libmain)
+libcmd_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) $(INCLUDE_libflake) $(INCLUDE_libmain)
 
 libcmd_LDFLAGS = $(EDITLINE_LIBS) $(LOWDOWN_LIBS) $(THREAD_LDFLAGS)
 
-libcmd_LIBS = libstore libutil libexpr libmain libfetchers
+libcmd_LIBS = libutil libstore libfetchers libflake libexpr libmain
 
 $(eval $(call install-file-in, $(buildprefix)$(d)/nix-cmd.pc, $(libdir)/pkgconfig, 0644))
diff --git a/src/libcmd/meson.build b/src/libcmd/meson.build
new file mode 100644
index 00000000000..687b37aacbd
--- /dev/null
+++ b/src/libcmd/meson.build
@@ -0,0 +1,128 @@
+project('nix-cmd', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+  dependency('nix-fetchers'),
+  dependency('nix-expr'),
+  dependency('nix-flake'),
+  dependency('nix-main'),
+]
+subdir('build-utils-meson/subprojects')
+
+nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
+deps_public += nlohmann_json
+
+lowdown = dependency('lowdown', version : '>= 0.9.0', required : get_option('markdown'))
+deps_private += lowdown
+configdata.set('HAVE_LOWDOWN', lowdown.found().to_int())
+
+readline_flavor = get_option('readline-flavor')
+if readline_flavor == 'editline'
+  editline = dependency('libeditline', 'editline', version : '>=1.14')
+  deps_private += editline
+elif readline_flavor == 'readline'
+  readline = dependency('readline')
+  deps_private += readline
+  configdata.set(
+    'USE_READLINE',
+    1,
+    description: 'Use readline instead of editline',
+  )
+else
+  error('illegal editline flavor', readline_flavor)
+endif
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-cmd.hh',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  # '-include', 'config-fetchers.h',
+  '-include', 'config-expr.hh',
+  '-include', 'config-main.hh',
+  '-include', 'config-cmd.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'built-path.cc',
+  'command-installable-value.cc',
+  'command.cc',
+  'common-eval-args.cc',
+  'editor-for.cc',
+  'installable-attr-path.cc',
+  'installable-derived-path.cc',
+  'installable-flake.cc',
+  'installable-value.cc',
+  'installables.cc',
+  'legacy.cc',
+  'markdown.cc',
+  'misc-store-flags.cc',
+  'network-proxy.cc',
+  'repl-interacter.cc',
+  'repl.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'built-path.hh',
+  'command-installable-value.hh',
+  'command.hh',
+  'common-eval-args.hh',
+  'compatibility-settings.hh',
+  'editor-for.hh',
+  'installable-attr-path.hh',
+  'installable-derived-path.hh',
+  'installable-flake.hh',
+  'installable-value.hh',
+  'installables.hh',
+  'legacy.hh',
+  'markdown.hh',
+  'misc-store-flags.hh',
+  'network-proxy.hh',
+  'repl-interacter.hh',
+  'repl.hh',
+)
+
+this_library = library(
+  'nixcmd',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libcmd/meson.options b/src/libcmd/meson.options
new file mode 100644
index 00000000000..79ae4fa5519
--- /dev/null
+++ b/src/libcmd/meson.options
@@ -0,0 +1,15 @@
+# vim: filetype=meson
+
+option(
+  'markdown',
+  type: 'feature',
+  description: 'Enable Markdown rendering in the Nix binary (requires lowdown)',
+)
+
+option(
+  'readline-flavor',
+  type : 'combo',
+  choices : ['editline', 'readline'],
+  value : 'editline',
+  description : 'Which library to use for nice line editing with the Nix language REPL',
+)
diff --git a/src/libcmd/misc-store-flags.cc b/src/libcmd/misc-store-flags.cc
index e66d3f63b1c..06552c03223 100644
--- a/src/libcmd/misc-store-flags.cc
+++ b/src/libcmd/misc-store-flags.cc
@@ -81,9 +81,15 @@ Args::Flag fileIngestionMethod(FileIngestionMethod * method)
     How to compute the hash of the input.
     One of:
 
-    - `nar` (the default): Serialises the input as an archive (following the [_Nix Archive Format_](https://edolstra.github.io/pubs/phd-thesis.pdf#page=101)) and passes that to the hash function.
+    - `nar` (the default):
+      Serialises the input as a
+      [Nix Archive](@docroot@/store/file-system-object/content-address.md#serial-nix-archive)
+      and passes that to the hash function.
 
-    - `flat`: Assumes that the input is a single file and directly passes it to the hash function;
+    - `flat`:
+      Assumes that the input is a single file and
+      [directly passes](@docroot@/store/file-system-object/content-address.md#serial-flat)
+      it to the hash function.
         )",
         .labels = {"file-ingestion-method"},
         .handler = {[method](std::string s) {
@@ -101,15 +107,23 @@ Args::Flag contentAddressMethod(ContentAddressMethod * method)
     How to compute the content-address of the store object.
     One of:
 
-    - `nar` (the default): Serialises the input as an archive (following the [_Nix Archive Format_](https://edolstra.github.io/pubs/phd-thesis.pdf#page=101)) and passes that to the hash function.
+    - [`nar`](@docroot@/store/store-object/content-address.md#method-nix-archive)
+      (the default):
+      Serialises the input as a
+      [Nix Archive](@docroot@/store/file-system-object/content-address.md#serial-nix-archive)
+      and passes that to the hash function.
 
-    - `flat`: Assumes that the input is a single file and directly passes it to the hash function;
+    - [`flat`](@docroot@/store/store-object/content-address.md#method-flat):
+      Assumes that the input is a single file and
+      [directly passes](@docroot@/store/file-system-object/content-address.md#serial-flat)
+      it to the hash function.
 
-    - `text`: Like `flat`, but used for
-      [derivations](@docroot@/glossary.md#store-derivation) serialized in store object and 
+    - [`text`](@docroot@/store/store-object/content-address.md#method-text):
+      Like `flat`, but used for
+      [derivations](@docroot@/glossary.md#store-derivation) serialized in store object and
       [`builtins.toFile`](@docroot@/language/builtins.html#builtins-toFile).
       For advanced use-cases only;
-      for regular usage prefer `nar` and `flat.
+      for regular usage prefer `nar` and `flat`.
         )",
         .labels = {"content-address-method"},
         .handler = {[method](std::string s) {
diff --git a/src/libcmd/network-proxy.cc b/src/libcmd/network-proxy.cc
new file mode 100644
index 00000000000..738bf614729
--- /dev/null
+++ b/src/libcmd/network-proxy.cc
@@ -0,0 +1,50 @@
+#include "network-proxy.hh"
+
+#include <algorithm>
+
+#include "environment-variables.hh"
+
+namespace nix {
+
+static const StringSet lowercaseVariables{"http_proxy", "https_proxy", "ftp_proxy", "all_proxy", "no_proxy"};
+
+static StringSet getAllVariables()
+{
+    StringSet variables = lowercaseVariables;
+    for (const auto & variable : lowercaseVariables) {
+        std::string upperVariable;
+        std::transform(
+            variable.begin(), variable.end(), upperVariable.begin(), [](unsigned char c) { return std::toupper(c); });
+        variables.insert(std::move(upperVariable));
+    }
+    return variables;
+}
+
+const StringSet networkProxyVariables = getAllVariables();
+
+static StringSet getExcludingNoProxyVariables()
+{
+    static const StringSet excludeVariables{"no_proxy", "NO_PROXY"};
+    StringSet variables;
+    std::set_difference(
+        networkProxyVariables.begin(),
+        networkProxyVariables.end(),
+        excludeVariables.begin(),
+        excludeVariables.end(),
+        std::inserter(variables, variables.begin()));
+    return variables;
+}
+
+static const StringSet excludingNoProxyVariables = getExcludingNoProxyVariables();
+
+bool haveNetworkProxyConnection()
+{
+    for (const auto & variable : excludingNoProxyVariables) {
+        if (getEnv(variable).has_value()) {
+            return true;
+        }
+    }
+    return false;
+}
+
+}
diff --git a/src/libcmd/network-proxy.hh b/src/libcmd/network-proxy.hh
new file mode 100644
index 00000000000..0b6856acbf4
--- /dev/null
+++ b/src/libcmd/network-proxy.hh
@@ -0,0 +1,22 @@
+#pragma once
+///@file
+
+#include "types.hh"
+
+namespace nix {
+
+/**
+ * Environment variables relating to network proxying. These are used by
+ * a few misc commands.
+ *
+ * See the Environment section of https://curl.se/docs/manpage.html for details.
+ */
+extern const StringSet networkProxyVariables;
+
+/**
+ * Heuristically check if there is a proxy connection by checking for defined
+ * proxy variables.
+ */
+bool haveNetworkProxyConnection();
+
+}
diff --git a/src/libcmd/package.nix b/src/libcmd/package.nix
new file mode 100644
index 00000000000..ec3aa46600d
--- /dev/null
+++ b/src/libcmd/package.nix
@@ -0,0 +1,110 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+, nix-store
+, nix-fetchers
+, nix-expr
+, nix-flake
+, nix-main
+, editline
+, readline
+, lowdown
+, nlohmann_json
+
+# Configuration Options
+
+, version
+
+# Whether to enable Markdown rendering in the Nix binary.
+, enableMarkdown ? !stdenv.hostPlatform.isWindows
+
+# Which interactive line editor library to use for Nix's repl.
+#
+# Currently supported choices are:
+#
+# - editline (default)
+# - readline
+, readlineFlavor ? if stdenv.hostPlatform.isWindows then "readline" else "editline"
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-cmd";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    ({ inherit editline readline; }.${readlineFlavor})
+  ] ++ lib.optional enableMarkdown lowdown;
+
+  propagatedBuildInputs = [
+    nix-util
+    nix-store
+    nix-fetchers
+    nix-expr
+    nix-flake
+    nix-main
+    nlohmann_json
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+    (lib.mesonEnable "markdown" enableMarkdown)
+    (lib.mesonOption "readline-flavor" readlineFlavor)
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  # TODO `releaseTools.coverageAnalysis` in Nixpkgs needs to be updated
+  # to work with `strictDeps`.
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libcmd/repl-interacter.cc b/src/libcmd/repl-interacter.cc
index eb4361e2562..420cce1db89 100644
--- a/src/libcmd/repl-interacter.cc
+++ b/src/libcmd/repl-interacter.cc
@@ -18,7 +18,7 @@ extern "C" {
 #include "finally.hh"
 #include "repl-interacter.hh"
 #include "file-system.hh"
-#include "libcmd/repl.hh"
+#include "repl.hh"
 
 namespace nix {
 
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index ffbb43a698c..ce1c5af6997 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -3,11 +3,12 @@
 #include <cstring>
 #include <climits>
 
-#include "libcmd/repl-interacter.hh"
+#include "repl-interacter.hh"
 #include "repl.hh"
 
 #include "ansicolor.hh"
 #include "shared.hh"
+#include "config-global.hh"
 #include "eval.hh"
 #include "eval-cache.hh"
 #include "eval-inline.hh"
@@ -77,7 +78,7 @@ struct NixRepl
 
     std::unique_ptr<ReplInteracter> interacter;
 
-    NixRepl(const SearchPath & searchPath, nix::ref<Store> store,ref<EvalState> state,
+    NixRepl(const LookupPath & lookupPath, nix::ref<Store> store,ref<EvalState> state,
             std::function<AnnotatedValues()> getValues);
     virtual ~NixRepl() = default;
 
@@ -122,7 +123,7 @@ std::string removeWhitespace(std::string s)
 }
 
 
-NixRepl::NixRepl(const SearchPath & searchPath, nix::ref<Store> store, ref<EvalState> state,
+NixRepl::NixRepl(const LookupPath & lookupPath, nix::ref<Store> store, ref<EvalState> state,
             std::function<NixRepl::AnnotatedValues()> getValues)
     : AbstractNixRepl(state)
     , debugTraceIndex(0)
@@ -137,12 +138,13 @@ void runNix(Path program, const Strings & args,
 {
     auto subprocessEnv = getEnv();
     subprocessEnv["NIX_CONFIG"] = globalConfig.toKeyValue();
-
+    //isInteractive avoid grabling interactive commands
     runProgram2(RunOptions {
         .program = settings.nixBinDir+ "/" + program,
         .args = args,
         .environment = subprocessEnv,
         .input = input,
+        .isInteractive = true,
     });
 
     return;
@@ -259,11 +261,14 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
         try {
             auto dir = std::string(cur, 0, slash);
             auto prefix2 = std::string(cur, slash + 1);
-            for (auto & entry : readDirectory(dir == "" ? "/" : dir)) {
-                if (entry.name[0] != '.' && hasPrefix(entry.name, prefix2))
-                    completions.insert(prev + dir + "/" + entry.name);
+            for (auto & entry : std::filesystem::directory_iterator{dir == "" ? "/" : dir}) {
+                checkInterrupt();
+                auto name = entry.path().filename().string();
+                if (name[0] != '.' && hasPrefix(name, prefix2))
+                    completions.insert(prev + entry.path().string());
             }
         } catch (Error &) {
+        } catch (std::filesystem::filesystem_error &) {
         }
     } else if ((dot = cur.rfind('.')) == std::string::npos) {
         /* This is a variable name; look it up in the current scope. */
@@ -302,6 +307,8 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
             // Quietly ignore evaluation errors.
         } catch (BadURL & e) {
             // Quietly ignore BadURL flake-related errors.
+        } catch (FileNotFound & e) {
+            // Quietly ignore non-existent file beeing `import`-ed.
         }
     }
 
@@ -508,7 +515,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
 
         // runProgram redirects stdout to a StringSink,
         // using runProgram2 to allow editors to display their UI
-        runProgram2(RunOptions { .program = editor, .searchPath = true, .args = args });
+        runProgram2(RunOptions { .program = editor, .lookupPath = true, .args = args , .isInteractive = true });
 
         // Reload right after exiting the editor
         state->resetFileCache();
@@ -784,11 +791,11 @@ void NixRepl::evalString(std::string s, Value & v)
 
 
 std::unique_ptr<AbstractNixRepl> AbstractNixRepl::create(
-   const SearchPath & searchPath, nix::ref<Store> store, ref<EvalState> state,
+   const LookupPath & lookupPath, nix::ref<Store> store, ref<EvalState> state,
    std::function<AnnotatedValues()> getValues)
 {
     return std::make_unique<NixRepl>(
-        searchPath,
+        lookupPath,
         openStore(),
         state,
         getValues
@@ -804,9 +811,9 @@ ReplExitStatus AbstractNixRepl::runSimple(
         NixRepl::AnnotatedValues values;
         return values;
     };
-    SearchPath searchPath = {};
+    LookupPath lookupPath = {};
     auto repl = std::make_unique<NixRepl>(
-            searchPath,
+            lookupPath,
             openStore(),
             evalState,
             getValues
diff --git a/src/libcmd/repl.hh b/src/libcmd/repl.hh
index aac79ec7404..3fd4b2c391a 100644
--- a/src/libcmd/repl.hh
+++ b/src/libcmd/repl.hh
@@ -20,7 +20,7 @@ struct AbstractNixRepl
     typedef std::vector<std::pair<Value*,std::string>> AnnotatedValues;
 
     static std::unique_ptr<AbstractNixRepl> create(
-        const SearchPath & searchPath, nix::ref<Store> store, ref<EvalState> state,
+        const LookupPath & lookupPath, nix::ref<Store> store, ref<EvalState> state,
         std::function<AnnotatedValues()> getValues);
 
     static ReplExitStatus runSimple(
diff --git a/src/libexpr-c/.version b/src/libexpr-c/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libexpr-c/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libexpr-c/build-utils-meson b/src/libexpr-c/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libexpr-c/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libexpr-c/meson.build b/src/libexpr-c/meson.build
new file mode 100644
index 00000000000..2a2669b3e5e
--- /dev/null
+++ b/src/libexpr-c/meson.build
@@ -0,0 +1,91 @@
+project('nix-expr-c', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+  dependency('nix-expr'),
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util-c'),
+  dependency('nix-store-c'),
+]
+subdir('build-utils-meson/subprojects')
+
+# TODO rename, because it will conflict with downstream projects
+configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-expr.h',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+
+  # From C++ libraries, only for internals
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-expr.hh',
+
+  # From C libraries, for our public, installed headers too
+  '-include', 'config-util.h',
+  '-include', 'config-store.h',
+  '-include', 'config-expr.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'nix_api_expr.cc',
+  'nix_api_external.cc',
+  'nix_api_value.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'nix_api_expr.h',
+  'nix_api_external.h',
+  'nix_api_value.h',
+)
+
+# TODO move this header to libexpr, maybe don't use it in tests?
+headers += files('nix_api_expr_internal.h')
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nixexprc',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libexpr-c/nix_api_expr.cc b/src/libexpr-c/nix_api_expr.cc
index a5c03d5aace..13e0f5f3a9f 100644
--- a/src/libexpr-c/nix_api_expr.cc
+++ b/src/libexpr-c/nix_api_expr.cc
@@ -7,6 +7,7 @@
 #include "eval.hh"
 #include "globals.hh"
 #include "util.hh"
+#include "eval-settings.hh"
 
 #include "nix_api_expr.h"
 #include "nix_api_expr_internal.h"
@@ -42,60 +43,85 @@ nix_err nix_libexpr_init(nix_c_context * context)
 }
 
 nix_err nix_expr_eval_from_string(
-    nix_c_context * context, EvalState * state, const char * expr, const char * path, Value * value)
+    nix_c_context * context, EvalState * state, const char * expr, const char * path, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
         nix::Expr * parsedExpr = state->state.parseExprFromString(expr, state->state.rootPath(nix::CanonPath(path)));
-        state->state.eval(parsedExpr, *(nix::Value *) value);
-        state->state.forceValue(*(nix::Value *) value, nix::noPos);
+        state->state.eval(parsedExpr, value->value);
+        state->state.forceValue(value->value, nix::noPos);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_value_call(nix_c_context * context, EvalState * state, Value * fn, Value * arg, Value * value)
+nix_err nix_value_call(nix_c_context * context, EvalState * state, Value * fn, nix_value * arg, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        state->state.callFunction(*(nix::Value *) fn, *(nix::Value *) arg, *(nix::Value *) value, nix::noPos);
-        state->state.forceValue(*(nix::Value *) value, nix::noPos);
+        state->state.callFunction(fn->value, arg->value, value->value, nix::noPos);
+        state->state.forceValue(value->value, nix::noPos);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_value_force(nix_c_context * context, EvalState * state, Value * value)
+nix_err nix_value_call_multi(nix_c_context * context, EvalState * state, nix_value * fn, size_t nargs, nix_value ** args, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        state->state.forceValue(*(nix::Value *) value, nix::noPos);
+        state->state.callFunction(fn->value, nargs, (nix::Value * *)args, value->value, nix::noPos);
+        state->state.forceValue(value->value, nix::noPos);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_value_force_deep(nix_c_context * context, EvalState * state, Value * value)
+nix_err nix_value_force(nix_c_context * context, EvalState * state, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        state->state.forceValueDeep(*(nix::Value *) value);
+        state->state.forceValue(value->value, nix::noPos);
     }
     NIXC_CATCH_ERRS
 }
 
-EvalState * nix_state_create(nix_c_context * context, const char ** searchPath_c, Store * store)
+nix_err nix_value_force_deep(nix_c_context * context, EvalState * state, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        nix::Strings searchPath;
-        if (searchPath_c != nullptr)
-            for (size_t i = 0; searchPath_c[i] != nullptr; i++)
-                searchPath.push_back(searchPath_c[i]);
+        state->state.forceValueDeep(value->value);
+    }
+    NIXC_CATCH_ERRS
+}
 
-        return new EvalState{nix::EvalState(nix::SearchPath::parse(searchPath), store->ptr)};
+EvalState * nix_state_create(nix_c_context * context, const char ** lookupPath_c, Store * store)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        nix::Strings lookupPath;
+        if (lookupPath_c != nullptr)
+            for (size_t i = 0; lookupPath_c[i] != nullptr; i++)
+                lookupPath.push_back(lookupPath_c[i]);
+
+        void * p = ::operator new(
+            sizeof(EvalState),
+            static_cast<std::align_val_t>(alignof(EvalState)));
+        auto * p2 = static_cast<EvalState *>(p);
+        new (p) EvalState {
+            .settings = nix::EvalSettings{
+                nix::settings.readOnlyMode,
+            },
+            .state = nix::EvalState(
+                nix::LookupPath::parse(lookupPath),
+                store->ptr,
+                p2->settings),
+        };
+        loadConfFile(p2->settings);
+        return p2;
     }
     NIXC_CATCH_ERRS_NULL
 }
@@ -170,6 +196,15 @@ nix_err nix_gc_decref(nix_c_context * context, const void *)
 void nix_gc_now() {}
 #endif
 
+nix_err nix_value_incref(nix_c_context * context, nix_value *x)
+{
+    return nix_gc_incref(context, (const void *) x);
+}
+nix_err nix_value_decref(nix_c_context * context, nix_value *x)
+{
+    return nix_gc_decref(context, (const void *) x);
+}
+
 void nix_gc_register_finalizer(void * obj, void * cd, void (*finalizer)(void * obj, void * cd))
 {
 #ifdef HAVE_BOEHMGC
diff --git a/src/libexpr-c/nix_api_expr.h b/src/libexpr-c/nix_api_expr.h
index 7504b5d7adc..adf8b65b1a3 100644
--- a/src/libexpr-c/nix_api_expr.h
+++ b/src/libexpr-c/nix_api_expr.h
@@ -3,25 +3,7 @@
 /** @defgroup libexpr libexpr
  * @brief Bindings to the Nix language evaluator
  *
- * Example (without error handling):
- * @code{.c}
- * int main() {
- *    nix_libexpr_init(NULL);
- *
- *    Store* store = nix_store_open(NULL, "dummy", NULL);
- *    EvalState* state = nix_state_create(NULL, NULL, store); // empty nix path
- *    Value *value = nix_alloc_value(NULL, state);
- *
- *    nix_expr_eval_from_string(NULL, state, "builtins.nixVersion", ".", value);
- *    nix_value_force(NULL, state, value);
- *    printf("nix version: %s\n", nix_get_string(NULL, value));
- *
- *    nix_gc_decref(NULL, value);
- *    nix_state_free(state);
- *    nix_store_free(store);
- *    return 0;
- *    }
- * @endcode
+ * See *[Embedding the Nix Evaluator](@ref nix_evaluator_example)* for an example.
  * @{
  */
 /** @file
@@ -30,6 +12,7 @@
 
 #include "nix_api_store.h"
 #include "nix_api_util.h"
+#include <stddef.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -46,14 +29,23 @@ extern "C" {
  * @see nix_state_create
  */
 typedef struct EvalState EvalState; // nix::EvalState
-/**
- * @brief Represents a value in the Nix language.
+
+/** @brief A Nix language value, or thunk that may evaluate to a value.
+ *
+ * Values are the primary objects manipulated in the Nix language.
+ * They are considered to be immutable from a user's perspective, but the process of evaluating a value changes its
+ * ValueType if it was a thunk. After a value has been evaluated, its ValueType does not change.
+ *
+ * Evaluation in this context refers to the process of evaluating a single value object, also called "forcing" the
+ * value; see `nix_value_force`.
+ *
+ * The evaluator manages its own memory, but your use of the C API must follow the reference counting rules.
  *
- * Owned by the garbage collector.
- * @struct Value
  * @see value_manip
+ * @see nix_value_incref, nix_value_decref
  */
-typedef void Value; // nix::Value
+typedef struct nix_value nix_value;
+[[deprecated("use nix_value instead")]] typedef nix_value Value;
 
 // Function prototypes
 /**
@@ -82,7 +74,7 @@ nix_err nix_libexpr_init(nix_c_context * context);
  * @return NIX_OK if the evaluation was successful, an error code otherwise.
  */
 nix_err nix_expr_eval_from_string(
-    nix_c_context * context, EvalState * state, const char * expr, const char * path, Value * value);
+    nix_c_context * context, EvalState * state, const char * expr, const char * path, nix_value * value);
 
 /**
  * @brief Calls a Nix function with an argument.
@@ -93,21 +85,58 @@ nix_err nix_expr_eval_from_string(
  * @param[in] arg The argument to pass to the function.
  * @param[out] value The result of the function call.
  * @return NIX_OK if the function call was successful, an error code otherwise.
+ * @see nix_init_apply() for a similar function that does not performs the call immediately, but stores it as a thunk.
+ *      Note the different argument order.
  */
-nix_err nix_value_call(nix_c_context * context, EvalState * state, Value * fn, Value * arg, Value * value);
+nix_err nix_value_call(nix_c_context * context, EvalState * state, nix_value * fn, nix_value * arg, nix_value * value);
+
+/**
+ * @brief Calls a Nix function with multiple arguments.
+ *
+ * Technically these are functions that return functions. It is common for Nix
+ * functions to be curried, so this function is useful for calling them.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] state The state of the evaluation.
+ * @param[in] fn The Nix function to call.
+ * @param[in] nargs The number of arguments.
+ * @param[in] args The arguments to pass to the function.
+ * @param[out] value The result of the function call.
+ *
+ * @see nix_value_call     For the single argument primitive.
+ * @see NIX_VALUE_CALL           For a macro that wraps this function for convenience.
+ */
+nix_err nix_value_call_multi(
+    nix_c_context * context, EvalState * state, nix_value * fn, size_t nargs, nix_value ** args, nix_value * value);
+
+/**
+ * @brief Calls a Nix function with multiple arguments.
+ *
+ * Technically these are functions that return functions. It is common for Nix
+ * functions to be curried, so this function is useful for calling them.
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] state The state of the evaluation.
+ * @param[out] value The result of the function call.
+ * @param[in] fn The Nix function to call.
+ * @param[in] args The arguments to pass to the function.
+ *
+ * @see nix_value_call_multi
+ */
+#define NIX_VALUE_CALL(context, state, value, fn, ...)                      \
+    do {                                                                    \
+        nix_value * args_array[] = {__VA_ARGS__};                           \
+        size_t nargs = sizeof(args_array) / sizeof(args_array[0]);          \
+        nix_value_call_multi(context, state, fn, nargs, args_array, value); \
+    } while (0)
 
 /**
  * @brief Forces the evaluation of a Nix value.
  *
- * The Nix interpreter is lazy, and not-yet-evaluated Values can be
+ * The Nix interpreter is lazy, and not-yet-evaluated values can be
  * of type NIX_TYPE_THUNK instead of their actual value.
  *
- * This function converts these Values into their final type.
- *
- * @note You don't need this function for basic API usage, since all functions
- * that return a value call it for you. The only place you will see a
- * NIX_TYPE_THUNK is in the arguments that are passed to a PrimOp function
- * you supplied to nix_alloc_primop.
+ * This function mutates such a `nix_value`, so that, if successful, it has its final type.
  *
  * @param[out] context Optional, stores error information
  * @param[in] state The state of the evaluation.
@@ -116,7 +145,7 @@ nix_err nix_value_call(nix_c_context * context, EvalState * state, Value * fn, V
  * @return NIX_OK if the force operation was successful, an error code
  * otherwise.
  */
-nix_err nix_value_force(nix_c_context * context, EvalState * state, Value * value);
+nix_err nix_value_force(nix_c_context * context, EvalState * state, nix_value * value);
 
 /**
  * @brief Forces the deep evaluation of a Nix value.
@@ -132,17 +161,17 @@ nix_err nix_value_force(nix_c_context * context, EvalState * state, Value * valu
  * @return NIX_OK if the deep force operation was successful, an error code
  * otherwise.
  */
-nix_err nix_value_force_deep(nix_c_context * context, EvalState * state, Value * value);
+nix_err nix_value_force_deep(nix_c_context * context, EvalState * state, nix_value * value);
 
 /**
  * @brief Create a new Nix language evaluator state.
  *
  * @param[out] context Optional, stores error information
- * @param[in] searchPath Array of strings corresponding to entries in NIX_PATH.
+ * @param[in] lookupPath Null-terminated array of strings corresponding to entries in NIX_PATH.
  * @param[in] store The Nix store to use.
  * @return A new Nix state or NULL on failure.
  */
-EvalState * nix_state_create(nix_c_context * context, const char ** searchPath, Store * store);
+EvalState * nix_state_create(nix_c_context * context, const char ** lookupPath, Store * store);
 
 /**
  * @brief Frees a Nix state.
@@ -166,6 +195,11 @@ void nix_state_free(EvalState * state);
  * you're done with a value returned by the evaluator.
  * @{
  */
+
+// TODO: Deprecate nix_gc_incref in favor of the type-specific reference counting functions?
+//       e.g. nix_value_incref.
+//       It gives implementors more flexibility, and adds safety, so that generated
+//       bindings can be used without fighting the host type system (where applicable).
 /**
  * @brief Increment the garbage collector reference counter for the given object.
  *
diff --git a/src/libexpr-c/nix_api_expr_internal.h b/src/libexpr-c/nix_api_expr_internal.h
index 7743849fdb8..d4ccffd29d6 100644
--- a/src/libexpr-c/nix_api_expr_internal.h
+++ b/src/libexpr-c/nix_api_expr_internal.h
@@ -2,11 +2,13 @@
 #define NIX_API_EXPR_INTERNAL_H
 
 #include "eval.hh"
+#include "eval-settings.hh"
 #include "attr-set.hh"
 #include "nix_api_value.h"
 
 struct EvalState
 {
+    nix::EvalSettings settings;
     nix::EvalState state;
 };
 
@@ -20,6 +22,11 @@ struct ListBuilder
     nix::ListBuilder builder;
 };
 
+struct nix_value
+{
+    nix::Value value;
+};
+
 struct nix_string_return
 {
     std::string str;
diff --git a/src/libexpr-c/nix_api_external.h b/src/libexpr-c/nix_api_external.h
index 12ea004074c..6c524b9755d 100644
--- a/src/libexpr-c/nix_api_external.h
+++ b/src/libexpr-c/nix_api_external.h
@@ -48,7 +48,7 @@ void nix_set_string_return(nix_string_return * str, const char * c);
  * Print to the nix_printer
  *
  * @param[out] context Optional, stores error information
- * @param printer The nix_printer to print to
+ * @param[out] printer The nix_printer to print to
  * @param[in] str The string to print
  * @returns NIX_OK if everything worked
  */
@@ -136,7 +136,7 @@ typedef struct NixCExternalValueDesc
      * or setting it to the empty string, will make the conversion throw an error.
      */
     void (*printValueAsJSON)(
-        void * self, EvalState *, bool strict, nix_string_context * c, bool copyToStore, nix_string_return * res);
+        void * self, EvalState * state, bool strict, nix_string_context * c, bool copyToStore, nix_string_return * res);
     /**
      * @brief Convert the external value to XML
      *
@@ -155,7 +155,7 @@ typedef struct NixCExternalValueDesc
      */
     void (*printValueAsXML)(
         void * self,
-        EvalState *,
+        EvalState * state,
         int strict,
         int location,
         void * doc,
diff --git a/src/libexpr-c/nix_api_value.cc b/src/libexpr-c/nix_api_value.cc
index 79e62a1d238..2f2f99617e2 100644
--- a/src/libexpr-c/nix_api_value.cc
+++ b/src/libexpr-c/nix_api_value.cc
@@ -20,21 +20,53 @@
 #  include "gc_cpp.h"
 #endif
 
-// Helper function to throw an exception if value is null
-static const nix::Value & check_value_not_null(const Value * value)
+// Internal helper functions to check [in] and [out] `Value *` parameters
+static const nix::Value & check_value_not_null(const nix_value * value)
 {
     if (!value) {
-        throw std::runtime_error("Value is null");
+        throw std::runtime_error("nix_value is null");
     }
     return *((const nix::Value *) value);
 }
 
-static nix::Value & check_value_not_null(Value * value)
+static nix::Value & check_value_not_null(nix_value * value)
 {
     if (!value) {
-        throw std::runtime_error("Value is null");
+        throw std::runtime_error("nix_value is null");
     }
-    return *((nix::Value *) value);
+    return value->value;
+}
+
+static const nix::Value & check_value_in(const nix_value * value)
+{
+    auto & v = check_value_not_null(value);
+    if (!v.isValid()) {
+        throw std::runtime_error("Uninitialized nix_value");
+    }
+    return v;
+}
+
+static nix::Value & check_value_in(nix_value * value)
+{
+    auto & v = check_value_not_null(value);
+    if (!v.isValid()) {
+        throw std::runtime_error("Uninitialized nix_value");
+    }
+    return v;
+}
+
+static nix::Value & check_value_out(nix_value * value)
+{
+    auto & v = check_value_not_null(value);
+    if (v.isValid()) {
+        throw std::runtime_error("nix_value already initialized. Variables are immutable");
+    }
+    return v;
+}
+
+static inline nix_value * as_nix_value_ptr(nix::Value * v)
+{
+    return reinterpret_cast<nix_value *>(v);
 }
 
 /**
@@ -46,10 +78,43 @@ static void nix_c_primop_wrapper(
     PrimOpFun f, void * userdata, nix::EvalState & state, const nix::PosIdx pos, nix::Value ** args, nix::Value & v)
 {
     nix_c_context ctx;
-    f(userdata, &ctx, (EvalState *) &state, (Value **) args, (Value *) &v);
-    /* TODO: In the future, this should throw different errors depending on the error code */
-    if (ctx.last_err_code != NIX_OK)
-        state.error<nix::EvalError>("Error from builtin function: %s", *ctx.last_err).atPos(pos).debugThrow();
+
+    // v currently has a thunk, but the C API initializers require an uninitialized value.
+    //
+    // We can't destroy the thunk, because that makes it impossible to retry,
+    // which is needed for tryEval and for evaluation drivers that evaluate more
+    // than one value (e.g. an attrset with two derivations, both of which
+    // reference v).
+    //
+    // Instead we create a temporary value, and then assign the result to v.
+    // This does not give the primop definition access to the thunk, but that's
+    // ok because we don't see a need for this yet (e.g. inspecting thunks,
+    // or maybe something to make blackholes work better; we don't know).
+    nix::Value vTmp;
+
+    f(userdata, &ctx, (EvalState *) &state, (nix_value **) args, (nix_value *) &vTmp);
+
+    if (ctx.last_err_code != NIX_OK) {
+        /* TODO: Throw different errors depending on the error code */
+        state.error<nix::EvalError>("Error from custom function: %s", *ctx.last_err).atPos(pos).debugThrow();
+    }
+
+    if (!vTmp.isValid()) {
+        state.error<nix::EvalError>("Implementation error in custom function: return value was not initialized")
+            .atPos(pos)
+            .debugThrow();
+    }
+
+    if (vTmp.type() == nix::nThunk) {
+        // We might allow this in the future if it makes sense for the evaluator
+        // e.g. implementing tail recursion by returning a thunk to the next
+        // "iteration". Until then, this is most likely a mistake or misunderstanding.
+        state.error<nix::EvalError>("Implementation error in custom function: return value must not be a thunk")
+            .atPos(pos)
+            .debugThrow();
+    }
+
+    v = vTmp;
 }
 
 PrimOp * nix_alloc_primop(
@@ -94,24 +159,24 @@ nix_err nix_register_primop(nix_c_context * context, PrimOp * primOp)
     NIXC_CATCH_ERRS
 }
 
-Value * nix_alloc_value(nix_c_context * context, EvalState * state)
+nix_value * nix_alloc_value(nix_c_context * context, EvalState * state)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        Value * res = state->state.allocValue();
+        nix_value * res = as_nix_value_ptr(state->state.allocValue());
         nix_gc_incref(nullptr, res);
         return res;
     }
     NIXC_CATCH_ERRS_NULL
 }
 
-ValueType nix_get_type(nix_c_context * context, const Value * value)
+ValueType nix_get_type(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         using namespace nix;
         switch (v.type()) {
         case nThunk:
@@ -142,48 +207,49 @@ ValueType nix_get_type(nix_c_context * context, const Value * value)
     NIXC_CATCH_ERRS_RES(NIX_TYPE_NULL);
 }
 
-const char * nix_get_typename(nix_c_context * context, const Value * value)
+const char * nix_get_typename(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         auto s = nix::showType(v);
         return strdup(s.c_str());
     }
     NIXC_CATCH_ERRS_NULL
 }
 
-bool nix_get_bool(nix_c_context * context, const Value * value)
+bool nix_get_bool(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nBool);
         return v.boolean();
     }
     NIXC_CATCH_ERRS_RES(false);
 }
 
-nix_err nix_get_string(nix_c_context * context, const Value * value, nix_get_string_callback callback, void * user_data)
+nix_err
+nix_get_string(nix_c_context * context, const nix_value * value, nix_get_string_callback callback, void * user_data)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nString);
         call_nix_get_string_callback(v.c_str(), callback, user_data);
     }
     NIXC_CATCH_ERRS
 }
 
-const char * nix_get_path_string(nix_c_context * context, const Value * value)
+const char * nix_get_path_string(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nPath);
         // NOTE (from @yorickvP)
         // v._path.path should work but may not be how Eelco intended it.
@@ -197,95 +263,95 @@ const char * nix_get_path_string(nix_c_context * context, const Value * value)
     NIXC_CATCH_ERRS_NULL
 }
 
-unsigned int nix_get_list_size(nix_c_context * context, const Value * value)
+unsigned int nix_get_list_size(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nList);
         return v.listSize();
     }
     NIXC_CATCH_ERRS_RES(0);
 }
 
-unsigned int nix_get_attrs_size(nix_c_context * context, const Value * value)
+unsigned int nix_get_attrs_size(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nAttrs);
         return v.attrs()->size();
     }
     NIXC_CATCH_ERRS_RES(0);
 }
 
-double nix_get_float(nix_c_context * context, const Value * value)
+double nix_get_float(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nFloat);
         return v.fpoint();
     }
     NIXC_CATCH_ERRS_RES(0.0);
 }
 
-int64_t nix_get_int(nix_c_context * context, const Value * value)
+int64_t nix_get_int(nix_c_context * context, const nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nInt);
         return v.integer();
     }
     NIXC_CATCH_ERRS_RES(0);
 }
 
-ExternalValue * nix_get_external(nix_c_context * context, Value * value)
+ExternalValue * nix_get_external(nix_c_context * context, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         assert(v.type() == nix::nExternal);
         return (ExternalValue *) v.external();
     }
     NIXC_CATCH_ERRS_NULL;
 }
 
-Value * nix_get_list_byidx(nix_c_context * context, const Value * value, EvalState * state, unsigned int ix)
+nix_value * nix_get_list_byidx(nix_c_context * context, const nix_value * value, EvalState * state, unsigned int ix)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nList);
         auto * p = v.listElems()[ix];
         nix_gc_incref(nullptr, p);
         if (p != nullptr)
             state->state.forceValue(*p, nix::noPos);
-        return (Value *) p;
+        return as_nix_value_ptr(p);
     }
     NIXC_CATCH_ERRS_NULL
 }
 
-Value * nix_get_attr_byname(nix_c_context * context, const Value * value, EvalState * state, const char * name)
+nix_value * nix_get_attr_byname(nix_c_context * context, const nix_value * value, EvalState * state, const char * name)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nAttrs);
         nix::Symbol s = state->state.symbols.create(name);
         auto attr = v.attrs()->get(s);
         if (attr) {
             nix_gc_incref(nullptr, attr->value);
             state->state.forceValue(*attr->value, nix::noPos);
-            return attr->value;
+            return as_nix_value_ptr(attr->value);
         }
         nix_set_err_msg(context, NIX_ERR_KEY, "missing attribute");
         return nullptr;
@@ -293,12 +359,12 @@ Value * nix_get_attr_byname(nix_c_context * context, const Value * value, EvalSt
     NIXC_CATCH_ERRS_NULL
 }
 
-bool nix_has_attr_byname(nix_c_context * context, const Value * value, EvalState * state, const char * name)
+bool nix_has_attr_byname(nix_c_context * context, const nix_value * value, EvalState * state, const char * name)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         assert(v.type() == nix::nAttrs);
         nix::Symbol s = state->state.symbols.create(name);
         auto attr = v.attrs()->get(s);
@@ -309,107 +375,121 @@ bool nix_has_attr_byname(nix_c_context * context, const Value * value, EvalState
     NIXC_CATCH_ERRS_RES(false);
 }
 
-Value *
-nix_get_attr_byidx(nix_c_context * context, const Value * value, EvalState * state, unsigned int i, const char ** name)
+nix_value * nix_get_attr_byidx(
+    nix_c_context * context, const nix_value * value, EvalState * state, unsigned int i, const char ** name)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         const nix::Attr & a = (*v.attrs())[i];
         *name = ((const std::string &) (state->state.symbols[a.name])).c_str();
         nix_gc_incref(nullptr, a.value);
         state->state.forceValue(*a.value, nix::noPos);
-        return a.value;
+        return as_nix_value_ptr(a.value);
     }
     NIXC_CATCH_ERRS_NULL
 }
 
-const char * nix_get_attr_name_byidx(nix_c_context * context, const Value * value, EvalState * state, unsigned int i)
+const char *
+nix_get_attr_name_byidx(nix_c_context * context, const nix_value * value, EvalState * state, unsigned int i)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         const nix::Attr & a = (*v.attrs())[i];
         return ((const std::string &) (state->state.symbols[a.name])).c_str();
     }
     NIXC_CATCH_ERRS_NULL
 }
 
-nix_err nix_init_bool(nix_c_context * context, Value * value, bool b)
+nix_err nix_init_bool(nix_c_context * context, nix_value * value, bool b)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkBool(b);
     }
     NIXC_CATCH_ERRS
 }
 
 // todo string context
-nix_err nix_init_string(nix_c_context * context, Value * value, const char * str)
+nix_err nix_init_string(nix_c_context * context, nix_value * value, const char * str)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkString(std::string_view(str));
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_init_path_string(nix_c_context * context, EvalState * s, Value * value, const char * str)
+nix_err nix_init_path_string(nix_c_context * context, EvalState * s, nix_value * value, const char * str)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkPath(s->state.rootPath(nix::CanonPath(str)));
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_init_float(nix_c_context * context, Value * value, double d)
+nix_err nix_init_float(nix_c_context * context, nix_value * value, double d)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkFloat(d);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_init_int(nix_c_context * context, Value * value, int64_t i)
+nix_err nix_init_int(nix_c_context * context, nix_value * value, int64_t i)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkInt(i);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_init_null(nix_c_context * context, Value * value)
+nix_err nix_init_null(nix_c_context * context, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkNull();
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_init_external(nix_c_context * context, Value * value, ExternalValue * val)
+nix_err nix_init_apply(nix_c_context * context, nix_value * value, nix_value * fn, nix_value * arg)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
         auto & v = check_value_not_null(value);
+        auto & f = check_value_not_null(fn);
+        auto & a = check_value_not_null(arg);
+        v.mkApp(&f, &a);
+    }
+    NIXC_CATCH_ERRS
+}
+
+nix_err nix_init_external(nix_c_context * context, nix_value * value, ExternalValue * val)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        auto & v = check_value_out(value);
         auto r = (nix::ExternalValueBase *) val;
         v.mkExternal(r);
     }
@@ -431,7 +511,8 @@ ListBuilder * nix_make_list_builder(nix_c_context * context, EvalState * state,
     NIXC_CATCH_ERRS_NULL
 }
 
-nix_err nix_list_builder_insert(nix_c_context * context, ListBuilder * list_builder, unsigned int index, Value * value)
+nix_err
+nix_list_builder_insert(nix_c_context * context, ListBuilder * list_builder, unsigned int index, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -451,46 +532,46 @@ void nix_list_builder_free(ListBuilder * list_builder)
 #endif
 }
 
-nix_err nix_make_list(nix_c_context * context, ListBuilder * list_builder, Value * value)
+nix_err nix_make_list(nix_c_context * context, ListBuilder * list_builder, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkList(list_builder->builder);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_init_primop(nix_c_context * context, Value * value, PrimOp * p)
+nix_err nix_init_primop(nix_c_context * context, nix_value * value, PrimOp * p)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkPrimOp((nix::PrimOp *) p);
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_copy_value(nix_c_context * context, Value * value, Value * source)
+nix_err nix_copy_value(nix_c_context * context, nix_value * value, const nix_value * source)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
-        auto & s = check_value_not_null(source);
+        auto & v = check_value_out(value);
+        auto & s = check_value_in(source);
         v = s;
     }
     NIXC_CATCH_ERRS
 }
 
-nix_err nix_make_attrs(nix_c_context * context, Value * value, BindingsBuilder * b)
+nix_err nix_make_attrs(nix_c_context * context, nix_value * value, BindingsBuilder * b)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_out(value);
         v.mkAttrs(b->builder);
     }
     NIXC_CATCH_ERRS
@@ -511,7 +592,7 @@ BindingsBuilder * nix_make_bindings_builder(nix_c_context * context, EvalState *
     NIXC_CATCH_ERRS_NULL
 }
 
-nix_err nix_bindings_builder_insert(nix_c_context * context, BindingsBuilder * bb, const char * name, Value * value)
+nix_err nix_bindings_builder_insert(nix_c_context * context, BindingsBuilder * bb, const char * name, nix_value * value)
 {
     if (context)
         context->last_err_code = NIX_OK;
@@ -532,12 +613,12 @@ void nix_bindings_builder_free(BindingsBuilder * bb)
 #endif
 }
 
-nix_realised_string * nix_string_realise(nix_c_context * context, EvalState * state, Value * value, bool isIFD)
+nix_realised_string * nix_string_realise(nix_c_context * context, EvalState * state, nix_value * value, bool isIFD)
 {
     if (context)
         context->last_err_code = NIX_OK;
     try {
-        auto & v = check_value_not_null(value);
+        auto & v = check_value_in(value);
         nix::NixStringContext stringContext;
         auto rawStr = state->state.coerceToString(nix::noPos, v, stringContext, "while realising a string").toOwned();
         nix::StorePathSet storePaths;
diff --git a/src/libexpr-c/nix_api_value.h b/src/libexpr-c/nix_api_value.h
index e6744e6101e..044f68c9e79 100644
--- a/src/libexpr-c/nix_api_value.h
+++ b/src/libexpr-c/nix_api_value.h
@@ -35,8 +35,11 @@ typedef enum {
 } ValueType;
 
 // forward declarations
-typedef void Value;
+typedef struct nix_value nix_value;
 typedef struct EvalState EvalState;
+
+[[deprecated("use nix_value instead")]] typedef nix_value Value;
+
 // type defs
 /** @brief Stores an under-construction set of bindings
  * @ingroup value_manip
@@ -79,6 +82,7 @@ typedef struct nix_realised_string nix_realised_string;
  * @{
  */
 /** @brief Function pointer for primops
+ *
  * When you want to return an error, call nix_set_err_msg(context, NIX_ERR_UNKNOWN, "your error message here").
  *
  * @param[in] user_data Arbitrary data that was initially supplied to nix_alloc_primop
@@ -89,7 +93,8 @@ typedef struct nix_realised_string nix_realised_string;
  * @param[out] ret return value
  * @see nix_alloc_primop, nix_init_primop
  */
-typedef void (*PrimOpFun)(void * user_data, nix_c_context * context, EvalState * state, Value ** args, Value * ret);
+typedef void (*PrimOpFun)(
+    void * user_data, nix_c_context * context, EvalState * state, nix_value ** args, nix_value * ret);
 
 /** @brief Allocate a PrimOp
  *
@@ -141,13 +146,33 @@ nix_err nix_register_primop(nix_c_context * context, PrimOp * primOp);
  * @return value, or null in case of errors
  *
  */
-Value * nix_alloc_value(nix_c_context * context, EvalState * state);
+nix_value * nix_alloc_value(nix_c_context * context, EvalState * state);
+
+/**
+ * @brief Increment the garbage collector reference counter for the given `nix_value`.
+ *
+ * The Nix language evaluator C API keeps track of alive objects by reference counting.
+ * When you're done with a refcounted pointer, call nix_value_decref().
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] value The object to keep alive
+ */
+nix_err nix_value_incref(nix_c_context * context, nix_value * value);
+
+/**
+ * @brief Decrement the garbage collector reference counter for the given object
+ *
+ * @param[out] context Optional, stores error information
+ * @param[in] value The object to stop referencing
+ */
+nix_err nix_value_decref(nix_c_context * context, nix_value * value);
 
 /** @addtogroup value_manip Manipulating values
- * @brief Functions to inspect and change Nix language values, represented by Value.
+ * @brief Functions to inspect and change Nix language values, represented by nix_value.
  * @{
  */
-/** @name Getters
+/** @anchor getters
+ * @name Getters
  */
 /**@{*/
 /** @brief Get value type
@@ -155,7 +180,7 @@ Value * nix_alloc_value(nix_c_context * context, EvalState * state);
  * @param[in] value Nix value to inspect
  * @return type of nix value
  */
-ValueType nix_get_type(nix_c_context * context, const Value * value);
+ValueType nix_get_type(nix_c_context * context, const nix_value * value);
 
 /** @brief Get type name of value as defined in the evaluator
  * @param[out] context Optional, stores error information
@@ -163,14 +188,14 @@ ValueType nix_get_type(nix_c_context * context, const Value * value);
  * @return type name, owned string
  * @todo way to free the result
  */
-const char * nix_get_typename(nix_c_context * context, const Value * value);
+const char * nix_get_typename(nix_c_context * context, const nix_value * value);
 
 /** @brief Get boolean value
  * @param[out] context Optional, stores error information
  * @param[in] value Nix value to inspect
  * @return true or false, error info via context
  */
-bool nix_get_bool(nix_c_context * context, const Value * value);
+bool nix_get_bool(nix_c_context * context, const nix_value * value);
 
 /** @brief Get the raw string
  *
@@ -184,7 +209,7 @@ bool nix_get_bool(nix_c_context * context, const Value * value);
  * @return error code, NIX_OK on success.
  */
 nix_err
-nix_get_string(nix_c_context * context, const Value * value, nix_get_string_callback callback, void * user_data);
+nix_get_string(nix_c_context * context, const nix_value * value, nix_get_string_callback callback, void * user_data);
 
 /** @brief Get path as string
  * @param[out] context Optional, stores error information
@@ -192,42 +217,42 @@ nix_get_string(nix_c_context * context, const Value * value, nix_get_string_call
  * @return string
  * @return NULL in case of error.
  */
-const char * nix_get_path_string(nix_c_context * context, const Value * value);
+const char * nix_get_path_string(nix_c_context * context, const nix_value * value);
 
 /** @brief Get the length of a list
  * @param[out] context Optional, stores error information
  * @param[in] value Nix value to inspect
  * @return length of list, error info via context
  */
-unsigned int nix_get_list_size(nix_c_context * context, const Value * value);
+unsigned int nix_get_list_size(nix_c_context * context, const nix_value * value);
 
 /** @brief Get the element count of an attrset
  * @param[out] context Optional, stores error information
  * @param[in] value Nix value to inspect
  * @return attrset element count, error info via context
  */
-unsigned int nix_get_attrs_size(nix_c_context * context, const Value * value);
+unsigned int nix_get_attrs_size(nix_c_context * context, const nix_value * value);
 
 /** @brief Get float value in 64 bits
  * @param[out] context Optional, stores error information
  * @param[in] value Nix value to inspect
  * @return float contents, error info via context
  */
-double nix_get_float(nix_c_context * context, const Value * value);
+double nix_get_float(nix_c_context * context, const nix_value * value);
 
 /** @brief Get int value
  * @param[out] context Optional, stores error information
  * @param[in] value Nix value to inspect
  * @return int contents, error info via context
  */
-int64_t nix_get_int(nix_c_context * context, const Value * value);
+int64_t nix_get_int(nix_c_context * context, const nix_value * value);
 
 /** @brief Get external reference
  * @param[out] context Optional, stores error information
  * @param[in] value Nix value to inspect
  * @return reference to external, NULL in case of error
  */
-ExternalValue * nix_get_external(nix_c_context * context, Value *);
+ExternalValue * nix_get_external(nix_c_context * context, nix_value *);
 
 /** @brief Get the ix'th element of a list
  *
@@ -238,7 +263,7 @@ ExternalValue * nix_get_external(nix_c_context * context, Value *);
  * @param[in] ix list element to get
  * @return value, NULL in case of errors
  */
-Value * nix_get_list_byidx(nix_c_context * context, const Value * value, EvalState * state, unsigned int ix);
+nix_value * nix_get_list_byidx(nix_c_context * context, const nix_value * value, EvalState * state, unsigned int ix);
 
 /** @brief Get an attr by name
  *
@@ -249,7 +274,7 @@ Value * nix_get_list_byidx(nix_c_context * context, const Value * value, EvalSta
  * @param[in] name attribute name
  * @return value, NULL in case of errors
  */
-Value * nix_get_attr_byname(nix_c_context * context, const Value * value, EvalState * state, const char * name);
+nix_value * nix_get_attr_byname(nix_c_context * context, const nix_value * value, EvalState * state, const char * name);
 
 /** @brief Check if an attribute name exists on a value
  * @param[out] context Optional, stores error information
@@ -258,7 +283,7 @@ Value * nix_get_attr_byname(nix_c_context * context, const Value * value, EvalSt
  * @param[in] name attribute name
  * @return value, error info via context
  */
-bool nix_has_attr_byname(nix_c_context * context, const Value * value, EvalState * state, const char * name);
+bool nix_has_attr_byname(nix_c_context * context, const nix_value * value, EvalState * state, const char * name);
 
 /** @brief Get an attribute by index in the sorted bindings
  *
@@ -272,8 +297,8 @@ bool nix_has_attr_byname(nix_c_context * context, const Value * value, EvalState
  * @param[out] name will store a pointer to the attribute name
  * @return value, NULL in case of errors
  */
-Value *
-nix_get_attr_byidx(nix_c_context * context, const Value * value, EvalState * state, unsigned int i, const char ** name);
+nix_value * nix_get_attr_byidx(
+    nix_c_context * context, const nix_value * value, EvalState * state, unsigned int i, const char ** name);
 
 /** @brief Get an attribute name by index in the sorted bindings
  *
@@ -286,7 +311,8 @@ nix_get_attr_byidx(nix_c_context * context, const Value * value, EvalState * sta
  * @param[in] i attribute index
  * @return name, NULL in case of errors
  */
-const char * nix_get_attr_name_byidx(nix_c_context * context, const Value * value, EvalState * state, unsigned int i);
+const char *
+nix_get_attr_name_byidx(nix_c_context * context, const nix_value * value, EvalState * state, unsigned int i);
 
 /**@}*/
 /** @name Initializers
@@ -303,7 +329,7 @@ const char * nix_get_attr_name_byidx(nix_c_context * context, const Value * valu
  * @param[in] b the boolean value
  * @return error code, NIX_OK on success.
  */
-nix_err nix_init_bool(nix_c_context * context, Value * value, bool b);
+nix_err nix_init_bool(nix_c_context * context, nix_value * value, bool b);
 
 /** @brief Set a string
  * @param[out] context Optional, stores error information
@@ -311,7 +337,7 @@ nix_err nix_init_bool(nix_c_context * context, Value * value, bool b);
  * @param[in] str the string, copied
  * @return error code, NIX_OK on success.
  */
-nix_err nix_init_string(nix_c_context * context, Value * value, const char * str);
+nix_err nix_init_string(nix_c_context * context, nix_value * value, const char * str);
 
 /** @brief Set a path
  * @param[out] context Optional, stores error information
@@ -319,7 +345,7 @@ nix_err nix_init_string(nix_c_context * context, Value * value, const char * str
  * @param[in] str the path string, copied
  * @return error code, NIX_OK on success.
  */
-nix_err nix_init_path_string(nix_c_context * context, EvalState * s, Value * value, const char * str);
+nix_err nix_init_path_string(nix_c_context * context, EvalState * s, nix_value * value, const char * str);
 
 /** @brief Set a float
  * @param[out] context Optional, stores error information
@@ -327,7 +353,7 @@ nix_err nix_init_path_string(nix_c_context * context, EvalState * s, Value * val
  * @param[in] d the float, 64-bits
  * @return error code, NIX_OK on success.
  */
-nix_err nix_init_float(nix_c_context * context, Value * value, double d);
+nix_err nix_init_float(nix_c_context * context, nix_value * value, double d);
 
 /** @brief Set an int
  * @param[out] context Optional, stores error information
@@ -336,21 +362,37 @@ nix_err nix_init_float(nix_c_context * context, Value * value, double d);
  * @return error code, NIX_OK on success.
  */
 
-nix_err nix_init_int(nix_c_context * context, Value * value, int64_t i);
+nix_err nix_init_int(nix_c_context * context, nix_value * value, int64_t i);
 /** @brief Set null
  * @param[out] context Optional, stores error information
  * @param[out] value Nix value to modify
  * @return error code, NIX_OK on success.
  */
+nix_err nix_init_null(nix_c_context * context, nix_value * value);
+
+/** @brief Set the value to a thunk that will perform a function application when needed.
+ *
+ * Thunks may be put into attribute sets and lists to perform some computation lazily; on demand.
+ * However, note that in some places, a thunk must not be returned, such as in the return value of a PrimOp.
+ * In such cases, you may use nix_value_call() instead (but note the different argument order).
+ *
+ * @param[out] context Optional, stores error information
+ * @param[out] value Nix value to modify
+ * @param[in] fn function to call
+ * @param[in] arg argument to pass
+ * @return error code, NIX_OK on successful initialization.
+ * @see nix_value_call() for a similar function that performs the call immediately and only stores the return value.
+ *      Note the different argument order.
+ */
+nix_err nix_init_apply(nix_c_context * context, nix_value * value, nix_value * fn, nix_value * arg);
 
-nix_err nix_init_null(nix_c_context * context, Value * value);
 /** @brief Set an external value
  * @param[out] context Optional, stores error information
  * @param[out] value Nix value to modify
  * @param[in] val the external value to set. Will be GC-referenced by the value.
  * @return error code, NIX_OK on success.
  */
-nix_err nix_init_external(nix_c_context * context, Value * value, ExternalValue * val);
+nix_err nix_init_external(nix_c_context * context, nix_value * value, ExternalValue * val);
 
 /** @brief Create a list from a list builder
  * @param[out] context Optional, stores error information
@@ -358,7 +400,7 @@ nix_err nix_init_external(nix_c_context * context, Value * value, ExternalValue
  * @param[out] value Nix value to modify
  * @return error code, NIX_OK on success.
  */
-nix_err nix_make_list(nix_c_context * context, ListBuilder * list_builder, Value * value);
+nix_err nix_make_list(nix_c_context * context, ListBuilder * list_builder, nix_value * value);
 
 /** @brief Create a list builder
  * @param[out] context Optional, stores error information
@@ -375,7 +417,8 @@ ListBuilder * nix_make_list_builder(nix_c_context * context, EvalState * state,
  * @param[in] value value to insert
  * @return error code, NIX_OK on success.
  */
-nix_err nix_list_builder_insert(nix_c_context * context, ListBuilder * list_builder, unsigned int index, Value * value);
+nix_err
+nix_list_builder_insert(nix_c_context * context, ListBuilder * list_builder, unsigned int index, nix_value * value);
 
 /** @brief Free a list builder
  *
@@ -390,7 +433,7 @@ void nix_list_builder_free(ListBuilder * list_builder);
  * @param[in] b bindings builder to use. Make sure to unref this afterwards.
  * @return error code, NIX_OK on success.
  */
-nix_err nix_make_attrs(nix_c_context * context, Value * value, BindingsBuilder * b);
+nix_err nix_make_attrs(nix_c_context * context, nix_value * value, BindingsBuilder * b);
 
 /** @brief Set primop
  * @param[out] context Optional, stores error information
@@ -399,14 +442,14 @@ nix_err nix_make_attrs(nix_c_context * context, Value * value, BindingsBuilder *
  * @see nix_alloc_primop
  * @return error code, NIX_OK on success.
  */
-nix_err nix_init_primop(nix_c_context * context, Value * value, PrimOp * op);
+nix_err nix_init_primop(nix_c_context * context, nix_value * value, PrimOp * op);
 /** @brief Copy from another value
  * @param[out] context Optional, stores error information
  * @param[out] value Nix value to modify
  * @param[in] source value to copy from
  * @return error code, NIX_OK on success.
  */
-nix_err nix_copy_value(nix_c_context * context, Value * value, Value * source);
+nix_err nix_copy_value(nix_c_context * context, nix_value * value, const nix_value * source);
 /**@}*/
 
 /** @brief Create a bindings builder
@@ -421,12 +464,12 @@ BindingsBuilder * nix_make_bindings_builder(nix_c_context * context, EvalState *
 /** @brief Insert bindings into a builder
  * @param[out] context Optional, stores error information
  * @param[in] builder BindingsBuilder to insert into
- * @param[in] name attribute name, copied into the symbol store
+ * @param[in] name attribute name, only used for the duration of the call.
  * @param[in] value value to give the binding
  * @return error code, NIX_OK on success.
  */
 nix_err
-nix_bindings_builder_insert(nix_c_context * context, BindingsBuilder * builder, const char * name, Value * value);
+nix_bindings_builder_insert(nix_c_context * context, BindingsBuilder * builder, const char * name, nix_value * value);
 
 /** @brief Free a bindings builder
  *
@@ -453,7 +496,7 @@ void nix_bindings_builder_free(BindingsBuilder * builder);
                     You should set this to false when building for your application's purpose.
  * @return NULL if failed, are a new nix_realised_string, which must be freed with nix_realised_string_free
  */
-nix_realised_string * nix_string_realise(nix_c_context * context, EvalState * state, Value * value, bool isIFD);
+nix_realised_string * nix_string_realise(nix_c_context * context, EvalState * state, nix_value * value, bool isIFD);
 
 /** @brief Start of the string
  * @param[in] realised_string
diff --git a/src/libexpr-c/package.nix b/src/libexpr-c/package.nix
new file mode 100644
index 00000000000..0b895437b6a
--- /dev/null
+++ b/src/libexpr-c/package.nix
@@ -0,0 +1,78 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+
+, meson
+, ninja
+, pkg-config
+
+, nix-store-c
+, nix-expr
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-expr-c";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    (fileset.fileFilter (file: file.hasExt "h") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-store-c
+    nix-expr
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libexpr/.version b/src/libexpr/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libexpr/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libexpr/build-utils-meson b/src/libexpr/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libexpr/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libexpr/flake/call-flake.nix b/src/libexpr/call-flake.nix
similarity index 97%
rename from src/libexpr/flake/call-flake.nix
rename to src/libexpr/call-flake.nix
index d0ccb1e37b7..a411564df5b 100644
--- a/src/libexpr/flake/call-flake.nix
+++ b/src/libexpr/call-flake.nix
@@ -4,7 +4,7 @@
 lockFileStr:
 
 # A mapping of lock file node IDs to { sourceInfo, subdir } attrsets,
-# with sourceInfo.outPath providing an InputAccessor to a previously
+# with sourceInfo.outPath providing an SourceAccessor to a previously
 # fetched tree. This is necessary for possibly unlocked inputs, in
 # particular the root input, but also --override-inputs pointing to
 # unlocked trees.
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index d60967a14a7..2630c34d563 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -7,6 +7,25 @@
 
 namespace nix::eval_cache {
 
+CachedEvalError::CachedEvalError(ref<AttrCursor> cursor, Symbol attr)
+    : EvalError(cursor->root->state, "cached failure of attribute '%s'", cursor->getAttrPathStr(attr))
+    , cursor(cursor), attr(attr)
+{ }
+
+void CachedEvalError::force()
+{
+    auto & v = cursor->forceValue();
+
+    if (v.type() == nAttrs) {
+        auto a = v.attrs()->get(this->attr);
+
+        state.forceValue(*a->value, a->pos);
+    }
+
+    // Shouldn't happen.
+    throw EvalError(state, "evaluation of cached failed attribute '%s' unexpectedly succeeded", cursor->getAttrPathStr(attr));
+}
+
 static const char * schema = R"sql(
 create table if not exists Attributes (
     parent      integer not null,
@@ -470,7 +489,7 @@ Suggestions AttrCursor::getSuggestionsForAttr(Symbol name)
     return Suggestions::bestMatches(strAttrNames, root->state.symbols[name]);
 }
 
-std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name, bool forceErrors)
+std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name)
 {
     if (root->db) {
         if (!cachedValue)
@@ -487,12 +506,9 @@ std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name, bool forceErro
                 if (attr) {
                     if (std::get_if<missing_t>(&attr->second))
                         return nullptr;
-                    else if (std::get_if<failed_t>(&attr->second)) {
-                        if (forceErrors)
-                            debug("reevaluating failed cached attribute '%s'", getAttrPathStr(name));
-                        else
-                            throw CachedEvalError(root->state, "cached failure of attribute '%s'", getAttrPathStr(name));
-                    } else
+                    else if (std::get_if<failed_t>(&attr->second))
+                        throw CachedEvalError(ref(shared_from_this()), name);
+                    else
                         return std::make_shared<AttrCursor>(root,
                             std::make_pair(shared_from_this(), name), nullptr, std::move(attr));
                 }
@@ -537,9 +553,9 @@ std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(std::string_view name)
     return maybeGetAttr(root->state.symbols.create(name));
 }
 
-ref<AttrCursor> AttrCursor::getAttr(Symbol name, bool forceErrors)
+ref<AttrCursor> AttrCursor::getAttr(Symbol name)
 {
-    auto p = maybeGetAttr(name, forceErrors);
+    auto p = maybeGetAttr(name);
     if (!p)
         throw Error("attribute '%s' does not exist", getAttrPathStr(name));
     return ref(p);
@@ -550,11 +566,11 @@ ref<AttrCursor> AttrCursor::getAttr(std::string_view name)
     return getAttr(root->state.symbols.create(name));
 }
 
-OrSuggestions<ref<AttrCursor>> AttrCursor::findAlongAttrPath(const std::vector<Symbol> & attrPath, bool force)
+OrSuggestions<ref<AttrCursor>> AttrCursor::findAlongAttrPath(const std::vector<Symbol> & attrPath)
 {
     auto res = shared_from_this();
     for (auto & attr : attrPath) {
-        auto child = res->maybeGetAttr(attr, force);
+        auto child = res->maybeGetAttr(attr);
         if (!child) {
             auto suggestions = res->getSuggestionsForAttr(attr);
             return OrSuggestions<ref<AttrCursor>>::failed(suggestions);
@@ -751,8 +767,9 @@ bool AttrCursor::isDerivation()
 
 StorePath AttrCursor::forceDerivation()
 {
-    auto aDrvPath = getAttr(root->state.sDrvPath, true);
+    auto aDrvPath = getAttr(root->state.sDrvPath);
     auto drvPath = root->state.store->parseStorePath(aDrvPath->getString());
+    drvPath.requireDerivation();
     if (!root->state.store->isValidPath(drvPath) && !settings.readOnlyMode) {
         /* The eval cache contains 'drvPath', but the actual path has
            been garbage-collected. So force it to be regenerated. */
diff --git a/src/libexpr/eval-cache.hh b/src/libexpr/eval-cache.hh
index 46c4999c84c..b1911e3a4f7 100644
--- a/src/libexpr/eval-cache.hh
+++ b/src/libexpr/eval-cache.hh
@@ -10,14 +10,28 @@
 
 namespace nix::eval_cache {
 
-MakeError(CachedEvalError, EvalError);
-
 struct AttrDb;
 class AttrCursor;
 
+struct CachedEvalError : EvalError
+{
+    const ref<AttrCursor> cursor;
+    const Symbol attr;
+
+    CachedEvalError(ref<AttrCursor> cursor, Symbol attr);
+
+    /**
+     * Evaluate this attribute, which should result in a regular
+     * `EvalError` exception being thrown.
+     */
+    [[noreturn]]
+    void force();
+};
+
 class EvalCache : public std::enable_shared_from_this<EvalCache>
 {
     friend class AttrCursor;
+    friend struct CachedEvalError;
 
     std::shared_ptr<AttrDb> db;
     EvalState & state;
@@ -73,6 +87,7 @@ typedef std::variant<
 class AttrCursor : public std::enable_shared_from_this<AttrCursor>
 {
     friend class EvalCache;
+    friend struct CachedEvalError;
 
     ref<EvalCache> root;
     typedef std::optional<std::pair<std::shared_ptr<AttrCursor>, Symbol>> Parent;
@@ -102,11 +117,11 @@ public:
 
     Suggestions getSuggestionsForAttr(Symbol name);
 
-    std::shared_ptr<AttrCursor> maybeGetAttr(Symbol name, bool forceErrors = false);
+    std::shared_ptr<AttrCursor> maybeGetAttr(Symbol name);
 
     std::shared_ptr<AttrCursor> maybeGetAttr(std::string_view name);
 
-    ref<AttrCursor> getAttr(Symbol name, bool forceErrors = false);
+    ref<AttrCursor> getAttr(Symbol name);
 
     ref<AttrCursor> getAttr(std::string_view name);
 
@@ -114,7 +129,7 @@ public:
      * Get an attribute along a chain of attrsets. Note that this does
      * not auto-call functors or functions.
      */
-    OrSuggestions<ref<AttrCursor>> findAlongAttrPath(const std::vector<Symbol> & attrPath, bool force = false);
+    OrSuggestions<ref<AttrCursor>> findAlongAttrPath(const std::vector<Symbol> & attrPath);
 
     std::string getString();
 
diff --git a/src/libexpr/eval-error.cc b/src/libexpr/eval-error.cc
index 8db03610b14..bd84e0428a3 100644
--- a/src/libexpr/eval-error.cc
+++ b/src/libexpr/eval-error.cc
@@ -27,8 +27,7 @@ EvalErrorBuilder<T> & EvalErrorBuilder<T>::atPos(Value & value, PosIdx fallback)
 template<class T>
 EvalErrorBuilder<T> & EvalErrorBuilder<T>::withTrace(PosIdx pos, const std::string_view text)
 {
-    error.err.traces.push_front(
-        Trace{.pos = error.state.positions[pos], .hint = HintFmt(std::string(text))});
+    error.addTrace(error.state.positions[pos], text);
     return *this;
 }
 
@@ -71,15 +70,17 @@ EvalErrorBuilder<T>::addTrace(PosIdx pos, std::string_view formatString, const A
     return *this;
 }
 
+template<class T>
+EvalErrorBuilder<T> & EvalErrorBuilder<T>::setIsFromExpr()
+{
+    error.err.isFromExpr = true;
+    return *this;
+}
+
 template<class T>
 void EvalErrorBuilder<T>::debugThrow()
 {
-    if (error.state.debugRepl && !error.state.debugTraces.empty()) {
-        const DebugTrace & last = error.state.debugTraces.front();
-        const Env * env = &last.env;
-        const Expr * expr = &last.expr;
-        error.state.runDebugRepl(&error, *env, *expr);
-    }
+    error.state.runDebugRepl(&error);
 
     // `EvalState` is the only class that can construct an `EvalErrorBuilder`,
     // and it does so in dynamic storage. This is the final method called on
@@ -91,6 +92,7 @@ void EvalErrorBuilder<T>::debugThrow()
     throw error;
 }
 
+template class EvalErrorBuilder<EvalBaseError>;
 template class EvalErrorBuilder<EvalError>;
 template class EvalErrorBuilder<AssertionError>;
 template class EvalErrorBuilder<ThrownError>;
@@ -99,7 +101,6 @@ template class EvalErrorBuilder<TypeError>;
 template class EvalErrorBuilder<UndefinedVarError>;
 template class EvalErrorBuilder<MissingArgumentError>;
 template class EvalErrorBuilder<InfiniteRecursionError>;
-template class EvalErrorBuilder<CachedEvalError>;
 template class EvalErrorBuilder<InvalidPathError>;
 
 }
diff --git a/src/libexpr/eval-error.hh b/src/libexpr/eval-error.hh
index 7e0cbe982ec..fe48e054bf2 100644
--- a/src/libexpr/eval-error.hh
+++ b/src/libexpr/eval-error.hh
@@ -15,27 +15,39 @@ class EvalState;
 template<class T>
 class EvalErrorBuilder;
 
-class EvalError : public Error
+/**
+ * Base class for all errors that occur during evaluation.
+ *
+ * Most subclasses should inherit from `EvalError` instead of this class.
+ */
+class EvalBaseError : public Error
 {
     template<class T>
     friend class EvalErrorBuilder;
 public:
     EvalState & state;
 
-    EvalError(EvalState & state, ErrorInfo && errorInfo)
+    EvalBaseError(EvalState & state, ErrorInfo && errorInfo)
         : Error(errorInfo)
         , state(state)
     {
     }
 
     template<typename... Args>
-    explicit EvalError(EvalState & state, const std::string & formatString, const Args &... formatArgs)
+    explicit EvalBaseError(EvalState & state, const std::string & formatString, const Args &... formatArgs)
         : Error(formatString, formatArgs...)
         , state(state)
     {
     }
 };
 
+/**
+ * `EvalError` is the base class for almost all errors that occur during evaluation.
+ *
+ * All instances of `EvalError` should show a degree of purity that allows them to be
+ * cached in pure mode. This means that they should not depend on the configuration or the overall environment.
+ */
+MakeError(EvalError, EvalBaseError);
 MakeError(ParseError, Error);
 MakeError(AssertionError, EvalError);
 MakeError(ThrownError, AssertionError);
@@ -43,7 +55,6 @@ MakeError(Abort, EvalError);
 MakeError(TypeError, EvalError);
 MakeError(UndefinedVarError, EvalError);
 MakeError(MissingArgumentError, EvalError);
-MakeError(CachedEvalError, EvalError);
 MakeError(InfiniteRecursionError, EvalError);
 
 struct InvalidPathError : public EvalError
@@ -91,6 +102,8 @@ public:
 
     [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> & addTrace(PosIdx pos, HintFmt hint);
 
+    [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> & setIsFromExpr();
+
     template<typename... Args>
     [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> &
     addTrace(PosIdx pos, std::string_view formatString, const Args &... formatArgs);
diff --git a/src/libexpr/eval-gc.cc b/src/libexpr/eval-gc.cc
new file mode 100644
index 00000000000..baf9df3324a
--- /dev/null
+++ b/src/libexpr/eval-gc.cc
@@ -0,0 +1,226 @@
+#include "error.hh"
+#include "environment-variables.hh"
+#include "serialise.hh"
+#include "eval-gc.hh"
+
+#if HAVE_BOEHMGC
+
+#  include <pthread.h>
+#  if __FreeBSD__
+#    include <pthread_np.h>
+#  endif
+
+#  include <gc/gc.h>
+#  include <gc/gc_cpp.h>
+#  include <gc/gc_allocator.h>
+
+#  include <boost/coroutine2/coroutine.hpp>
+#  include <boost/coroutine2/protected_fixedsize_stack.hpp>
+#  include <boost/context/stack_context.hpp>
+
+#endif
+
+namespace nix {
+
+#if HAVE_BOEHMGC
+/* Called when the Boehm GC runs out of memory. */
+static void * oomHandler(size_t requested)
+{
+    /* Convert this to a proper C++ exception. */
+    throw std::bad_alloc();
+}
+
+class BoehmGCStackAllocator : public StackAllocator
+{
+    boost::coroutines2::protected_fixedsize_stack stack{
+        // We allocate 8 MB, the default max stack size on NixOS.
+        // A smaller stack might be quicker to allocate but reduces the stack
+        // depth available for source filter expressions etc.
+        std::max(boost::context::stack_traits::default_size(), static_cast<std::size_t>(8 * 1024 * 1024))};
+
+    // This is specific to boost::coroutines2::protected_fixedsize_stack.
+    // The stack protection page is included in sctx.size, so we have to
+    // subtract one page size from the stack size.
+    std::size_t pfss_usable_stack_size(boost::context::stack_context & sctx)
+    {
+        return sctx.size - boost::context::stack_traits::page_size();
+    }
+
+public:
+    boost::context::stack_context allocate() override
+    {
+        auto sctx = stack.allocate();
+
+        // Stacks generally start at a high address and grow to lower addresses.
+        // Architectures that do the opposite are rare; in fact so rare that
+        // boost_routine does not implement it.
+        // So we subtract the stack size.
+        GC_add_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
+        return sctx;
+    }
+
+    void deallocate(boost::context::stack_context sctx) override
+    {
+        GC_remove_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
+        stack.deallocate(sctx);
+    }
+};
+
+static BoehmGCStackAllocator boehmGCStackAllocator;
+
+/**
+ * When a thread goes into a coroutine, we lose its original sp until
+ * control flow returns to the thread.
+ * While in the coroutine, the sp points outside the thread stack,
+ * so we can detect this and push the entire thread stack instead,
+ * as an approximation.
+ * The coroutine's stack is covered by `BoehmGCStackAllocator`.
+ * This is not an optimal solution, because the garbage is scanned when a
+ * coroutine is active, for both the coroutine and the original thread stack.
+ * However, the implementation is quite lean, and usually we don't have active
+ * coroutines during evaluation, so this is acceptable.
+ */
+void fixupBoehmStackPointer(void ** sp_ptr, void * _pthread_id)
+{
+    void *& sp = *sp_ptr;
+    auto pthread_id = reinterpret_cast<pthread_t>(_pthread_id);
+    pthread_attr_t pattr;
+    size_t osStackSize;
+    void * osStackLow;
+    void * osStackBase;
+
+#  ifdef __APPLE__
+    osStackSize = pthread_get_stacksize_np(pthread_id);
+    osStackLow = pthread_get_stackaddr_np(pthread_id);
+#  else
+    if (pthread_attr_init(&pattr)) {
+        throw Error("fixupBoehmStackPointer: pthread_attr_init failed");
+    }
+#    ifdef HAVE_PTHREAD_GETATTR_NP
+    if (pthread_getattr_np(pthread_id, &pattr)) {
+        throw Error("fixupBoehmStackPointer: pthread_getattr_np failed");
+    }
+#    elif HAVE_PTHREAD_ATTR_GET_NP
+    if (!pthread_attr_init(&pattr)) {
+        throw Error("fixupBoehmStackPointer: pthread_attr_init failed");
+    }
+    if (!pthread_attr_get_np(pthread_id, &pattr)) {
+        throw Error("fixupBoehmStackPointer: pthread_attr_get_np failed");
+    }
+#    else
+#      error "Need one of `pthread_attr_get_np` or `pthread_getattr_np`"
+#    endif
+    if (pthread_attr_getstack(&pattr, &osStackLow, &osStackSize)) {
+        throw Error("fixupBoehmStackPointer: pthread_attr_getstack failed");
+    }
+    if (pthread_attr_destroy(&pattr)) {
+        throw Error("fixupBoehmStackPointer: pthread_attr_destroy failed");
+    }
+#  endif
+    osStackBase = (char *) osStackLow + osStackSize;
+    // NOTE: We assume the stack grows down, as it does on all architectures we support.
+    //       Architectures that grow the stack up are rare.
+    if (sp >= osStackBase || sp < osStackLow) { // lo is outside the os stack
+        sp = osStackBase;
+    }
+}
+
+/* Disable GC while this object lives. Used by CoroutineContext.
+ *
+ * Boehm keeps a count of GC_disable() and GC_enable() calls,
+ * and only enables GC when the count matches.
+ */
+class BoehmDisableGC
+{
+public:
+    BoehmDisableGC()
+    {
+        GC_disable();
+    };
+    ~BoehmDisableGC()
+    {
+        GC_enable();
+    };
+};
+
+static inline void initGCReal()
+{
+    /* Initialise the Boehm garbage collector. */
+
+    /* Don't look for interior pointers. This reduces the odds of
+       misdetection a bit. */
+    GC_set_all_interior_pointers(0);
+
+    /* We don't have any roots in data segments, so don't scan from
+       there. */
+    GC_set_no_dls(1);
+
+    GC_INIT();
+
+    GC_set_oom_fn(oomHandler);
+
+    StackAllocator::defaultAllocator = &boehmGCStackAllocator;
+
+// TODO: Remove __APPLE__ condition.
+//       Comment suggests an implementation that works on darwin and windows
+//       https://github.com/ivmai/bdwgc/issues/362#issuecomment-1936672196
+#  if GC_VERSION_MAJOR >= 8 && GC_VERSION_MINOR >= 2 && GC_VERSION_MICRO >= 4 && !defined(__APPLE__)
+    GC_set_sp_corrector(&fixupBoehmStackPointer);
+
+    if (!GC_get_sp_corrector()) {
+        printTalkative("BoehmGC on this platform does not support sp_corrector; will disable GC inside coroutines");
+        /* Used to disable GC when entering coroutines on macOS */
+        create_coro_gc_hook = []() -> std::shared_ptr<void> { return std::make_shared<BoehmDisableGC>(); };
+    }
+#  else
+#    warning \
+        "BoehmGC version does not support GC while coroutine exists. GC will be disabled inside coroutines. Consider updating bdw-gc to 8.2.4 or later."
+#  endif
+
+    /* Set the initial heap size to something fairly big (25% of
+       physical RAM, up to a maximum of 384 MiB) so that in most cases
+       we don't need to garbage collect at all.  (Collection has a
+       fairly significant overhead.)  The heap size can be overridden
+       through libgc's GC_INITIAL_HEAP_SIZE environment variable.  We
+       should probably also provide a nix.conf setting for this.  Note
+       that GC_expand_hp() causes a lot of virtual, but not physical
+       (resident) memory to be allocated.  This might be a problem on
+       systems that don't overcommit. */
+    if (!getEnv("GC_INITIAL_HEAP_SIZE")) {
+        size_t size = 32 * 1024 * 1024;
+#  if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES)
+        size_t maxSize = 384 * 1024 * 1024;
+        long pageSize = sysconf(_SC_PAGESIZE);
+        long pages = sysconf(_SC_PHYS_PAGES);
+        if (pageSize != -1)
+            size = (pageSize * pages) / 4; // 25% of RAM
+        if (size > maxSize)
+            size = maxSize;
+#  endif
+        debug("setting initial heap size to %1% bytes", size);
+        GC_expand_hp(size);
+    }
+}
+
+#endif
+
+static bool gcInitialised = false;
+
+void initGC()
+{
+    if (gcInitialised)
+        return;
+
+#if HAVE_BOEHMGC
+    initGCReal();
+#endif
+
+    gcInitialised = true;
+}
+
+void assertGCInitialized()
+{
+    assert(gcInitialised);
+}
+
+}
diff --git a/src/libexpr/eval-gc.hh b/src/libexpr/eval-gc.hh
new file mode 100644
index 00000000000..cd4ea914d9f
--- /dev/null
+++ b/src/libexpr/eval-gc.hh
@@ -0,0 +1,16 @@
+#pragma once
+///@file
+
+namespace nix {
+
+/**
+ * Initialise the Boehm GC, if applicable.
+ */
+void initGC();
+
+/**
+ * Make sure `initGC` has already been called.
+ */
+void assertGCInitialized();
+
+}
diff --git a/src/libexpr/eval-settings.cc b/src/libexpr/eval-settings.cc
index 2ccbe327fad..6b7b52cef32 100644
--- a/src/libexpr/eval-settings.cc
+++ b/src/libexpr/eval-settings.cc
@@ -1,4 +1,5 @@
 #include "users.hh"
+#include "config-global.hh"
 #include "globals.hh"
 #include "profiles.hh"
 #include "eval.hh"
@@ -44,13 +45,19 @@ static Strings parseNixPath(const std::string & s)
     return res;
 }
 
-EvalSettings::EvalSettings()
+EvalSettings::EvalSettings(bool & readOnlyMode, EvalSettings::LookupPathHooks lookupPathHooks)
+    : readOnlyMode{readOnlyMode}
+    , lookupPathHooks{lookupPathHooks}
 {
     auto var = getEnv("NIX_PATH");
     if (var) nixPath = parseNixPath(*var);
+
+    var = getEnv("NIX_ABORT_ON_WARN");
+    if (var && (var == "1" || var == "yes" || var == "true"))
+        builtinsAbortOnWarn = true;
 }
 
-Strings EvalSettings::getDefaultNixPath()
+Strings EvalSettings::getDefaultNixPath() const
 {
     Strings res;
     auto add = [&](const Path & p, const std::string & s = std::string()) {
@@ -63,7 +70,7 @@ Strings EvalSettings::getDefaultNixPath()
         }
     };
 
-    if (!evalSettings.restrictEval && !evalSettings.pureEval) {
+    if (!restrictEval && !pureEval) {
         add(getNixDefExpr() + "/channels");
         add(rootChannelsDir() + "/nixpkgs", "nixpkgs");
         add(rootChannelsDir());
@@ -89,16 +96,12 @@ std::string EvalSettings::resolvePseudoUrl(std::string_view url)
         return std::string(url);
 }
 
-const std::string & EvalSettings::getCurrentSystem()
+const std::string & EvalSettings::getCurrentSystem() const
 {
     const auto & evalSystem = currentSystem.get();
     return evalSystem != "" ? evalSystem : settings.thisSystem.get();
 }
 
-EvalSettings evalSettings;
-
-static GlobalConfig::Register rEvalSettings(&evalSettings);
-
 Path getNixDefExpr()
 {
     return settings.useXDGBaseDirectories
diff --git a/src/libexpr/eval-settings.hh b/src/libexpr/eval-settings.hh
index 60d3a6f25dd..191dde21aa9 100644
--- a/src/libexpr/eval-settings.hh
+++ b/src/libexpr/eval-settings.hh
@@ -5,25 +5,76 @@
 
 namespace nix {
 
+class Store;
+
 struct EvalSettings : Config
 {
-    EvalSettings();
+    /**
+     * Function used to interpet look path entries of a given scheme.
+     *
+     * The argument is the non-scheme part of the lookup path entry (see
+     * `LookupPathHooks` below).
+     *
+     * The return value is (a) whether the entry was valid, and, if so,
+     * what does it map to.
+     *
+     * @todo Return (`std::optional` of) `SourceAccssor` or something
+     * more structured instead of mere `std::string`?
+     */
+    using LookupPathHook = std::optional<std::string>(ref<Store> store, std::string_view);
+
+    /**
+     * Map from "scheme" to a `LookupPathHook`.
+     *
+     * Given a lookup path value (i.e. either the whole thing, or after
+     * the `<key>=`) in the form of:
+     *
+     * ```
+     * <scheme>:<arbitrary string>
+     * ```
+     *
+     * if `<scheme>` is a key in this map, then `<arbitrary string>` is
+     * passed to the hook that is the value in this map.
+     */
+    using LookupPathHooks = std::map<std::string, std::function<LookupPathHook>>;
+
+    EvalSettings(bool & readOnlyMode, LookupPathHooks lookupPathHooks = {});
+
+    bool & readOnlyMode;
 
-    static Strings getDefaultNixPath();
+    Strings getDefaultNixPath() const;
 
     static bool isPseudoUrl(std::string_view s);
 
     static std::string resolvePseudoUrl(std::string_view url);
 
-    Setting<bool> enableNativeCode{this, false, "allow-unsafe-native-code-during-evaluation",
-        "Whether builtin functions that allow executing native code should be enabled."};
+    LookupPathHooks lookupPathHooks;
+
+    Setting<bool> enableNativeCode{this, false, "allow-unsafe-native-code-during-evaluation", R"(
+        Enable built-in functions that allow executing native code.
+
+        In particular, this adds:
+        - `builtins.importNative` *path* *symbol*
+
+          Opens dynamic shared object (DSO) at *path*, loads the function with the symbol name *symbol* from it and runs it.
+          The loaded function must have the following signature:
+          ```cpp
+          extern "C" typedef void (*ValueInitialiser) (EvalState & state, Value & v);
+          ```
+
+          The [Nix C++ API documentation](@docroot@/contributing/documentation.md#api-documentation) has more details on evaluator internals.
+
+        - `builtins.exec` *arguments*
+
+          Execute a program, where *arguments* are specified as a list of strings, and parse its output as a Nix expression.
+    )"};
 
     Setting<Strings> nixPath{
         this, getDefaultNixPath(), "nix-path",
         R"(
           List of search paths to use for [lookup path](@docroot@/language/constructs/lookup-path.md) resolution.
           This setting determines the value of
-          [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath) and can be used with [`builtins.findFile`](@docroot@/language/builtin-constants.md#builtins-findFile).
+          [`builtins.nixPath`](@docroot@/language/builtins.md#builtins-nixPath) and can be used with [`builtins.findFile`](@docroot@/language/builtins.md#builtins-findFile).
 
           The default value is
 
@@ -44,7 +95,7 @@ struct EvalSettings : Config
         this, "", "eval-system",
         R"(
           This option defines
-          [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem)
+          [`builtins.currentSystem`](@docroot@/language/builtins.md#builtins-currentSystem)
           in the Nix language if it is set as a non-empty string.
           Otherwise, if it is defined as the empty string (the default), the value of the
           [`system` ](#conf-system)
@@ -58,14 +109,14 @@ struct EvalSettings : Config
      * Implements the `eval-system` vs `system` defaulting logic
      * described for `eval-system`.
      */
-    const std::string & getCurrentSystem();
+    const std::string & getCurrentSystem() const;
 
     Setting<bool> restrictEval{
         this, false, "restrict-eval",
         R"(
           If set to `true`, the Nix evaluator will not allow access to any
           files outside of
-          [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath),
+          [`builtins.nixPath`](@docroot@/language/builtins.md#builtins-nixPath),
           or to URIs outside of
           [`allowed-uris`](@docroot@/command-ref/conf-file.md#conf-allowed-uris).
         )"};
@@ -76,10 +127,10 @@ struct EvalSettings : Config
 
           - Restrict file system and network access to files specified by cryptographic hash
           - Disable impure constants:
-            - [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem)
-            - [`builtins.currentTime`](@docroot@/language/builtin-constants.md#builtins-currentTime)
-            - [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath)
-            - [`builtins.storePath`](@docroot@/language/builtin-constants.md#builtins-storePath)
+            - [`builtins.currentSystem`](@docroot@/language/builtins.md#builtins-currentSystem)
+            - [`builtins.currentTime`](@docroot@/language/builtins.md#builtins-currentTime)
+            - [`builtins.nixPath`](@docroot@/language/builtins.md#builtins-nixPath)
+            - [`builtins.storePath`](@docroot@/language/builtins.md#builtins-storePath)
         )"
         };
 
@@ -142,16 +193,40 @@ struct EvalSettings : Config
 
     Setting<bool> builtinsTraceDebugger{this, false, "debugger-on-trace",
         R"(
-          If set to true and the `--debugger` flag is given,
-          [`builtins.trace`](@docroot@/language/builtins.md#builtins-trace) will
-          enter the debugger like
-          [`builtins.break`](@docroot@/language/builtins.md#builtins-break).
+          If set to true and the `--debugger` flag is given, the following functions
+          will enter the debugger like [`builtins.break`](@docroot@/language/builtins.md#builtins-break).
+
+          * [`builtins.trace`](@docroot@/language/builtins.md#builtins-trace)
+          * [`builtins.traceVerbose`](@docroot@/language/builtins.md#builtins-traceVerbose)
+            if [`trace-verbose`](#conf-trace-verbose) is set to true.
+          * [`builtins.warn`](@docroot@/language/builtins.md#builtins-warn)
 
           This is useful for debugging warnings in third-party Nix code.
         )"};
-};
 
-extern EvalSettings evalSettings;
+    Setting<bool> builtinsDebuggerOnWarn{this, false, "debugger-on-warn",
+        R"(
+          If set to true and the `--debugger` flag is given, [`builtins.warn`](@docroot@/language/builtins.md#builtins-warn)
+          will enter the debugger like [`builtins.break`](@docroot@/language/builtins.md#builtins-break).
+
+          This is useful for debugging warnings in third-party Nix code.
+
+          Use [`debugger-on-trace`](#conf-debugger-on-trace) to also enter the debugger on legacy warnings that are logged with [`builtins.trace`](@docroot@/language/builtins.md#builtins-trace).
+        )"};
+
+    Setting<bool> builtinsAbortOnWarn{this, false, "abort-on-warn",
+        R"(
+          If set to true, [`builtins.warn`](@docroot@/language/builtins.md#builtins-warn) will throw an error when logging a warning.
+
+          This will give you a stack trace that leads to the location of the warning.
+
+          This is useful for finding information about warnings in third-party Nix code when you can not start the interactive debugger, such as when Nix is called from a non-interactive script. See [`debugger-on-warn`](#conf-debugger-on-warn).
+
+          Currently, a stack trace can only be produced when the debugger is enabled, or when evaluation is aborted.
+
+          This option can be enabled by setting `NIX_ABORT_ON_WARN=1` in the environment.
+        )"};
+};
 
 /**
  * Conventionally part of the default nix path in impure mode.
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 72da1c46577..2a08621231f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -3,57 +3,51 @@
 #include "hash.hh"
 #include "primops.hh"
 #include "print-options.hh"
-#include "shared.hh"
+#include "exit.hh"
 #include "types.hh"
 #include "util.hh"
 #include "store-api.hh"
 #include "derivations.hh"
 #include "downstream-placeholder.hh"
-#include "globals.hh"
 #include "eval-inline.hh"
 #include "filetransfer.hh"
 #include "function-trace.hh"
 #include "profiles.hh"
 #include "print.hh"
-#include "fs-input-accessor.hh"
-#include "filtering-input-accessor.hh"
-#include "memory-input-accessor.hh"
+#include "filtering-source-accessor.hh"
+#include "memory-source-accessor.hh"
 #include "signals.hh"
 #include "gc-small-vector.hh"
 #include "url.hh"
 #include "fetch-to-store.hh"
 #include "tarball.hh"
-#include "flake/flakeref.hh"
 #include "parser-tab.hh"
 
 #include <algorithm>
 #include <chrono>
 #include <iostream>
+#include <sstream>
 #include <cstring>
 #include <optional>
 #include <unistd.h>
 #include <sys/time.h>
 #include <fstream>
 #include <functional>
-#include <iostream>
 
 #include <nlohmann/json.hpp>
 #include <boost/container/small_vector.hpp>
 
 #ifndef _WIN32 // TODO use portable implementation
-# include <sys/resource.h>
+#  include <sys/resource.h>
 #endif
 
 #if HAVE_BOEHMGC
 
-#define GC_INCLUDE_NEW
-
-#include <gc/gc.h>
-#include <gc/gc_cpp.h>
+#  define GC_INCLUDE_NEW
 
-#include <boost/coroutine2/coroutine.hpp>
-#include <boost/coroutine2/protected_fixedsize_stack.hpp>
-#include <boost/context/stack_context.hpp>
+#  include <gc/gc.h>
+#  include <gc/gc_cpp.h>
+#  include <gc/gc_allocator.h>
 
 #endif
 
@@ -206,53 +200,6 @@ bool Value::isTrivial() const
 }
 
 
-#if HAVE_BOEHMGC
-/* Called when the Boehm GC runs out of memory. */
-static void * oomHandler(size_t requested)
-{
-    /* Convert this to a proper C++ exception. */
-    throw std::bad_alloc();
-}
-
-class BoehmGCStackAllocator : public StackAllocator {
-    boost::coroutines2::protected_fixedsize_stack stack {
-        // We allocate 8 MB, the default max stack size on NixOS.
-        // A smaller stack might be quicker to allocate but reduces the stack
-        // depth available for source filter expressions etc.
-        std::max(boost::context::stack_traits::default_size(), static_cast<std::size_t>(8 * 1024 * 1024))
-    };
-
-    // This is specific to boost::coroutines2::protected_fixedsize_stack.
-    // The stack protection page is included in sctx.size, so we have to
-    // subtract one page size from the stack size.
-    std::size_t pfss_usable_stack_size(boost::context::stack_context &sctx) {
-        return sctx.size - boost::context::stack_traits::page_size();
-    }
-
-  public:
-    boost::context::stack_context allocate() override {
-        auto sctx = stack.allocate();
-
-        // Stacks generally start at a high address and grow to lower addresses.
-        // Architectures that do the opposite are rare; in fact so rare that
-        // boost_routine does not implement it.
-        // So we subtract the stack size.
-        GC_add_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
-        return sctx;
-    }
-
-    void deallocate(boost::context::stack_context sctx) override {
-        GC_remove_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
-        stack.deallocate(sctx);
-    }
-
-};
-
-static BoehmGCStackAllocator boehmGCStackAllocator;
-
-#endif
-
-
 static Symbol getName(const AttrName & name, EvalState & state, Env & env)
 {
     if (name.symbol) {
@@ -265,88 +212,15 @@ static Symbol getName(const AttrName & name, EvalState & state, Env & env)
     }
 }
 
-#if HAVE_BOEHMGC
-/* Disable GC while this object lives. Used by CoroutineContext.
- *
- * Boehm keeps a count of GC_disable() and GC_enable() calls,
- * and only enables GC when the count matches.
- */
-class BoehmDisableGC {
-public:
-    BoehmDisableGC() {
-        GC_disable();
-    };
-    ~BoehmDisableGC() {
-        GC_enable();
-    };
-};
-#endif
-
-static bool gcInitialised = false;
-
-void initGC()
-{
-    if (gcInitialised) return;
-
-#if HAVE_BOEHMGC
-    /* Initialise the Boehm garbage collector. */
-
-    /* Don't look for interior pointers. This reduces the odds of
-       misdetection a bit. */
-    GC_set_all_interior_pointers(0);
-
-    /* We don't have any roots in data segments, so don't scan from
-       there. */
-    GC_set_no_dls(1);
-
-    GC_INIT();
-
-    GC_set_oom_fn(oomHandler);
-
-    StackAllocator::defaultAllocator = &boehmGCStackAllocator;
-
-
-#if NIX_BOEHM_PATCH_VERSION != 1
-    printTalkative("Unpatched BoehmGC, disabling GC inside coroutines");
-    /* Used to disable GC when entering coroutines on macOS */
-    create_coro_gc_hook = []() -> std::shared_ptr<void> {
-        return std::make_shared<BoehmDisableGC>();
-    };
-#endif
-
-    /* Set the initial heap size to something fairly big (25% of
-       physical RAM, up to a maximum of 384 MiB) so that in most cases
-       we don't need to garbage collect at all.  (Collection has a
-       fairly significant overhead.)  The heap size can be overridden
-       through libgc's GC_INITIAL_HEAP_SIZE environment variable.  We
-       should probably also provide a nix.conf setting for this.  Note
-       that GC_expand_hp() causes a lot of virtual, but not physical
-       (resident) memory to be allocated.  This might be a problem on
-       systems that don't overcommit. */
-    if (!getEnv("GC_INITIAL_HEAP_SIZE")) {
-        size_t size = 32 * 1024 * 1024;
-#if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES)
-        size_t maxSize = 384 * 1024 * 1024;
-        long pageSize = sysconf(_SC_PAGESIZE);
-        long pages = sysconf(_SC_PHYS_PAGES);
-        if (pageSize != -1)
-            size = (pageSize * pages) / 4; // 25% of RAM
-        if (size > maxSize) size = maxSize;
-#endif
-        debug("setting initial heap size to %1% bytes", size);
-        GC_expand_hp(size);
-    }
-
-#endif
-
-    gcInitialised = true;
-}
+static constexpr size_t BASE_ENV_SIZE = 128;
 
 EvalState::EvalState(
-    const SearchPath & _searchPath,
+    const LookupPath & _lookupPath,
     ref<Store> store,
+    const EvalSettings & settings,
     std::shared_ptr<Store> buildStore)
-    : sWith(symbols.create("<with>"))
+    : settings{settings}
+    , sWith(symbols.create("<with>"))
     , sOutPath(symbols.create("outPath"))
     , sDrvPath(symbols.create("drvPath"))
     , sType(symbols.create("type"))
@@ -366,6 +240,12 @@ EvalState::EvalState(
     , sRight(symbols.create("right"))
     , sWrong(symbols.create("wrong"))
     , sStructuredAttrs(symbols.create("__structuredAttrs"))
+    , sAllowedReferences(symbols.create("allowedReferences"))
+    , sAllowedRequisites(symbols.create("allowedRequisites"))
+    , sDisallowedReferences(symbols.create("disallowedReferences"))
+    , sDisallowedRequisites(symbols.create("disallowedRequisites"))
+    , sMaxSize(symbols.create("maxSize"))
+    , sMaxClosureSize(symbols.create("maxClosureSize"))
     , sBuilder(symbols.create("builder"))
     , sArgs(symbols.create("args"))
     , sContentAddressed(symbols.create("__contentAddressed"))
@@ -396,24 +276,24 @@ EvalState::EvalState(
     , repair(NoRepair)
     , emptyBindings(0)
     , rootFS(
-        evalSettings.restrictEval || evalSettings.pureEval
-        ? ref<InputAccessor>(AllowListInputAccessor::create(makeFSInputAccessor(), {},
-            [](const CanonPath & path) -> RestrictedPathError {
-                auto modeInformation = evalSettings.pureEval
+        settings.restrictEval || settings.pureEval
+        ? ref<SourceAccessor>(AllowListSourceAccessor::create(getFSSourceAccessor(), {},
+            [&settings](const CanonPath & path) -> RestrictedPathError {
+                auto modeInformation = settings.pureEval
                     ? "in pure evaluation mode (use '--impure' to override)"
                     : "in restricted mode";
                 throw RestrictedPathError("access to absolute path '%1%' is forbidden %2%", path, modeInformation);
             }))
-        : makeFSInputAccessor())
-    , corepkgsFS(makeMemoryInputAccessor())
-    , internalFS(makeMemoryInputAccessor())
+        : getFSSourceAccessor())
+    , corepkgsFS(make_ref<MemorySourceAccessor>())
+    , internalFS(make_ref<MemorySourceAccessor>())
     , derivationInternal{corepkgsFS->addFile(
         CanonPath("derivation-internal.nix"),
         #include "primops/derivation.nix.gen.hh"
     )}
     , callFlakeInternal{internalFS->addFile(
         CanonPath("call-flake.nix"),
-        #include "flake/call-flake.nix.gen.hh"
+        #include "call-flake.nix.gen.hh"
     )}
     , store(store)
     , buildStore(buildStore ? buildStore : store)
@@ -424,8 +304,11 @@ EvalState::EvalState(
 #if HAVE_BOEHMGC
     , valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
     , env1AllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
+    , baseEnvP(std::allocate_shared<Env *>(traceable_allocator<Env *>(), &allocEnv(BASE_ENV_SIZE)))
+    , baseEnv(**baseEnvP)
+#else
+    , baseEnv(allocEnv(BASE_ENV_SIZE))
 #endif
-    , baseEnv(allocEnv(128))
     , staticBaseEnv{std::make_shared<StaticEnv>(nullptr, nullptr)}
 {
     corepkgsFS->setPathDisplay("<nix", ">");
@@ -433,7 +316,7 @@ EvalState::EvalState(
 
     countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
 
-    assert(gcInitialised);
+    assertGCInitialized();
 
     static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
 
@@ -447,17 +330,17 @@ EvalState::EvalState(
     vStringUnknown.mkString("unknown");
 
     /* Initialise the Nix expression search path. */
-    if (!evalSettings.pureEval) {
-        for (auto & i : _searchPath.elements)
-            searchPath.elements.emplace_back(SearchPath::Elem {i});
-        for (auto & i : evalSettings.nixPath.get())
-            searchPath.elements.emplace_back(SearchPath::Elem::parse(i));
+    if (!settings.pureEval) {
+        for (auto & i : _lookupPath.elements)
+            lookupPath.elements.emplace_back(LookupPath::Elem {i});
+        for (auto & i : settings.nixPath.get())
+            lookupPath.elements.emplace_back(LookupPath::Elem::parse(i));
     }
 
     /* Allow access to all paths in the search path. */
-    if (rootFS.dynamic_pointer_cast<AllowListInputAccessor>())
-        for (auto & i : searchPath.elements)
-            resolveSearchPathPath(i.path, true);
+    if (rootFS.dynamic_pointer_cast<AllowListSourceAccessor>())
+        for (auto & i : lookupPath.elements)
+            resolveLookupPathPath(i.path, true);
 
     corepkgsFS->addFile(
         CanonPath("fetchurl.nix"),
@@ -475,13 +358,13 @@ EvalState::~EvalState()
 
 void EvalState::allowPath(const Path & path)
 {
-    if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListInputAccessor>())
+    if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListSourceAccessor>())
         rootFS2->allowPrefix(CanonPath(path));
 }
 
 void EvalState::allowPath(const StorePath & storePath)
 {
-    if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListInputAccessor>())
+    if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListSourceAccessor>())
         rootFS2->allowPrefix(CanonPath(store->toRealPath(storePath)));
 }
 
@@ -528,20 +411,20 @@ bool isAllowedURI(std::string_view uri, const Strings & allowedUris)
 
 void EvalState::checkURI(const std::string & uri)
 {
-    if (!evalSettings.restrictEval) return;
+    if (!settings.restrictEval) return;
 
-    if (isAllowedURI(uri, evalSettings.allowedUris.get())) return;
+    if (isAllowedURI(uri, settings.allowedUris.get())) return;
 
     /* If the URI is a path, then check it against allowedPaths as
        well. */
     if (hasPrefix(uri, "/")) {
-        if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListInputAccessor>())
+        if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListSourceAccessor>())
             rootFS2->checkAccess(CanonPath(uri));
         return;
     }
 
     if (hasPrefix(uri, "file://")) {
-        if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListInputAccessor>())
+        if (auto rootFS2 = rootFS.dynamic_pointer_cast<AllowListSourceAccessor>())
             rootFS2->checkAccess(CanonPath(uri.substr(7)));
         return;
     }
@@ -575,7 +458,7 @@ void EvalState::addConstant(const std::string & name, Value * v, Constant info)
 
     constantInfos.push_back({name2, info});
 
-    if (!(evalSettings.pureEval && info.impureOnly)) {
+    if (!(settings.pureEval && info.impureOnly)) {
         /* Check the type, if possible.
 
            We might know the type of a thunk in advance, so be allowed
@@ -780,6 +663,24 @@ class DebuggerGuard {
     }
 };
 
+bool EvalState::canDebug()
+{
+    return debugRepl && !debugTraces.empty();
+}
+
+void EvalState::runDebugRepl(const Error * error)
+{
+    if (!canDebug())
+        return;
+
+    assert(!debugTraces.empty());
+    const DebugTrace & last = debugTraces.front();
+    const Env & env = last.env;
+    const Expr & expr = last.expr;
+
+    runDebugRepl(error, env, expr);
+}
+
 void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr & expr)
 {
     // Make sure we have a debugger to run and we're not already in a debugger.
@@ -1512,11 +1413,11 @@ class CallDepth {
 
 void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value & vRes, const PosIdx pos)
 {
-    if (callDepth > evalSettings.maxCallDepth)
+    if (callDepth > settings.maxCallDepth)
         error<EvalError>("stack overflow; max-call-depth exceeded").atPos(pos).debugThrow();
     CallDepth _level(callDepth);
 
-    auto trace = evalSettings.traceFunctionCalls
+    auto trace = settings.traceFunctionCalls
         ? std::make_unique<FunctionCallTrace>(positions[pos])
         : nullptr;
 
@@ -2392,21 +2293,21 @@ StorePath EvalState::copyPathToStore(NixStringContext & context, const SourcePat
     if (nix::isDerivation(path.path.abs()))
         error<EvalError>("file names are not allowed to end in '%1%'", drvExtension).debugThrow();
 
-    auto i = srcToStore.find(path);
+    auto dstPathCached = get(*srcToStore.lock(), path);
 
-    auto dstPath = i != srcToStore.end()
-        ? i->second
+    auto dstPath = dstPathCached
+        ? *dstPathCached
         : [&]() {
             auto dstPath = fetchToStore(
                 *store,
                 path.resolveSymlinks(),
                 settings.readOnlyMode ? FetchMode::DryRun : FetchMode::Copy,
                 path.baseName(),
-                FileIngestionMethod::Recursive,
+                ContentAddressMethod::Raw::NixArchive,
                 nullptr,
                 repair);
             allowPath(dstPath);
-            srcToStore.insert_or_assign(path, dstPath);
+            srcToStore.lock()->try_emplace(path, dstPath);
             printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, store->printStorePath(dstPath));
             return dstPath;
         }();
@@ -2749,7 +2650,7 @@ void EvalState::printStatistics()
 }
 
 
-SourcePath resolveExprPath(SourcePath path)
+SourcePath resolveExprPath(SourcePath path, bool addDefaultNix)
 {
     unsigned int followCount = 0, maxFollow = 1024;
 
@@ -2760,12 +2661,12 @@ SourcePath resolveExprPath(SourcePath path)
         if (++followCount >= maxFollow)
             throw Error("too many symbolic links encountered while traversing the path '%s'", path);
         auto p = path.parent().resolveSymlinks() / path.baseName();
-        if (p.lstat().type != InputAccessor::tSymlink) break;
+        if (p.lstat().type != SourceAccessor::tSymlink) break;
         path = {path.accessor, CanonPath(p.readLink(), path.path.parent().value_or(CanonPath::root))};
     }
 
     /* If `path' refers to a directory, append `/default.nix'. */
-    if (path.resolveSymlinks().lstat().type == InputAccessor::tDirectory)
+    if (addDefaultNix && path.resolveSymlinks().lstat().type == SourceAccessor::tDirectory)
         return path / "default.nix";
 
     return path;
@@ -2820,19 +2721,19 @@ Expr * EvalState::parseStdin()
 
 SourcePath EvalState::findFile(const std::string_view path)
 {
-    return findFile(searchPath, path);
+    return findFile(lookupPath, path);
 }
 
 
-SourcePath EvalState::findFile(const SearchPath & searchPath, const std::string_view path, const PosIdx pos)
+SourcePath EvalState::findFile(const LookupPath & lookupPath, const std::string_view path, const PosIdx pos)
 {
-    for (auto & i : searchPath.elements) {
+    for (auto & i : lookupPath.elements) {
         auto suffixOpt = i.prefix.suffixIfPotentialMatch(path);
 
         if (!suffixOpt) continue;
         auto suffix = *suffixOpt;
 
-        auto rOpt = resolveSearchPathPath(i.path);
+        auto rOpt = resolveLookupPathPath(i.path);
         if (!rOpt) continue;
         auto r = *rOpt;
 
@@ -2844,7 +2745,7 @@ SourcePath EvalState::findFile(const SearchPath & searchPath, const std::string_
         return {corepkgsFS, CanonPath(path.substr(3))};
 
     error<ThrownError>(
-        evalSettings.pureEval
+        settings.pureEval
             ? "cannot look up '<%s>' in pure evaluation mode (use '--impure' to override)"
             : "file '%s' was not found in the Nix search path (add it using $NIX_PATH or -I)",
         path
@@ -2852,20 +2753,24 @@ SourcePath EvalState::findFile(const SearchPath & searchPath, const std::string_
 }
 
 
-std::optional<std::string> EvalState::resolveSearchPathPath(const SearchPath::Path & value0, bool initAccessControl)
+std::optional<std::string> EvalState::resolveLookupPathPath(const LookupPath::Path & value0, bool initAccessControl)
 {
     auto & value = value0.s;
-    auto i = searchPathResolved.find(value);
-    if (i != searchPathResolved.end()) return i->second;
+    auto i = lookupPathResolved.find(value);
+    if (i != lookupPathResolved.end()) return i->second;
 
-    std::optional<std::string> res;
+    auto finish = [&](std::string res) {
+        debug("resolved search path element '%s' to '%s'", value, res);
+        lookupPathResolved.emplace(value, res);
+        return res;
+    };
 
     if (EvalSettings::isPseudoUrl(value)) {
         try {
             auto accessor = fetchers::downloadTarball(
                 EvalSettings::resolvePseudoUrl(value)).accessor;
             auto storePath = fetchToStore(*store, SourcePath(accessor), FetchMode::Copy);
-            res = { store->toRealPath(storePath) };
+            return finish(store->toRealPath(storePath));
         } catch (Error & e) {
             logWarning({
                 .msg = HintFmt("Nix search path entry '%1%' cannot be downloaded, ignoring", value)
@@ -2873,15 +2778,17 @@ std::optional<std::string> EvalState::resolveSearchPathPath(const SearchPath::Pa
         }
     }
 
-    else if (hasPrefix(value, "flake:")) {
-        experimentalFeatureSettings.require(Xp::Flakes);
-        auto flakeRef = parseFlakeRef(value.substr(6), {}, true, false);
-        debug("fetching flake search path element '%s''", value);
-        auto storePath = flakeRef.resolve(store).fetchTree(store).first;
-        res = { store->toRealPath(storePath) };
+    if (auto colPos = value.find(':'); colPos != value.npos) {
+        auto scheme = value.substr(0, colPos);
+        auto rest = value.substr(colPos + 1);
+        if (auto * hook = get(settings.lookupPathHooks, scheme)) {
+            auto res = (*hook)(store, rest);
+            if (res)
+                return finish(std::move(*res));
+        }
     }
 
-    else {
+    {
         auto path = absPath(value);
 
         /* Allow access to paths in the search path. */
@@ -2898,22 +2805,17 @@ std::optional<std::string> EvalState::resolveSearchPathPath(const SearchPath::Pa
         }
 
         if (pathExists(path))
-            res = { path };
+            return finish(std::move(path));
         else {
             logWarning({
                 .msg = HintFmt("Nix search path entry '%1%' does not exist, ignoring", value)
             });
-            res = std::nullopt;
         }
     }
 
-    if (res)
-        debug("resolved search path element '%s' to '%s'", value, *res);
-    else
-        debug("failed to resolve search path element '%s'", value);
+    debug("failed to resolve search path element '%s'", value);
+    return std::nullopt;
 
-    searchPathResolved.emplace(value, res);
-    return res;
 }
 
 
@@ -2924,7 +2826,7 @@ Expr * EvalState::parse(
     const SourcePath & basePath,
     std::shared_ptr<StaticEnv> & staticEnv)
 {
-    auto result = parseExprFromBuf(text, length, origin, basePath, symbols, positions, rootFS, exprSymbols);
+    auto result = parseExprFromBuf(text, length, origin, basePath, symbols, settings, positions, rootFS, exprSymbols);
 
     result->bindVars(*this, staticEnv);
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index af65fdcbaa3..e45358055ed 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -3,13 +3,14 @@
 
 #include "attr-set.hh"
 #include "eval-error.hh"
+#include "eval-gc.hh"
 #include "types.hh"
 #include "value.hh"
 #include "nixexpr.hh"
 #include "symbol-table.hh"
 #include "config.hh"
 #include "experimental-features.hh"
-#include "input-accessor.hh"
+#include "source-accessor.hh"
 #include "search-path.hh"
 #include "repl-exit-status.hh"
 
@@ -29,12 +30,15 @@ namespace nix {
 constexpr size_t maxPrimOpArity = 8;
 
 class Store;
+struct EvalSettings;
 class EvalState;
 class StorePath;
 struct SingleDerivedPath;
 enum RepairFlag : bool;
-struct MemoryInputAccessor;
-
+struct MemorySourceAccessor;
+namespace eval_cache {
+    class EvalCache;
+}
 
 /**
  * Function that implements a primop.
@@ -143,12 +147,6 @@ std::string printValue(EvalState & state, Value & v);
 std::ostream & operator << (std::ostream & os, const ValueType t);
 
 
-/**
- * Initialise the Boehm GC, if applicable.
- */
-void initGC();
-
-
 struct RegexCache;
 
 std::shared_ptr<RegexCache> makeRegexCache();
@@ -161,19 +159,20 @@ struct DebugTrace {
     bool isError;
 };
 
-// Don't want Windows function
-#undef SearchPath
-
 class EvalState : public std::enable_shared_from_this<EvalState>
 {
 public:
+    const EvalSettings & settings;
     SymbolTable symbols;
     PosTable positions;
 
     const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName, sValue,
         sSystem, sOverrides, sOutputs, sOutputName, sIgnoreNulls,
         sFile, sLine, sColumn, sFunctor, sToString,
-        sRight, sWrong, sStructuredAttrs, sBuilder, sArgs,
+        sRight, sWrong, sStructuredAttrs,
+        sAllowedReferences, sAllowedRequisites, sDisallowedReferences, sDisallowedRequisites,
+        sMaxSize, sMaxClosureSize,
+        sBuilder, sArgs,
         sContentAddressed, sImpure,
         sOutputHash, sOutputHashAlgo, sOutputHashMode,
         sRecurseForDerivations,
@@ -229,18 +228,18 @@ public:
     /**
      * The accessor for the root filesystem.
      */
-    const ref<InputAccessor> rootFS;
+    const ref<SourceAccessor> rootFS;
 
     /**
      * The in-memory filesystem for <nix/...> paths.
      */
-    const ref<MemoryInputAccessor> corepkgsFS;
+    const ref<MemorySourceAccessor> corepkgsFS;
 
     /**
      * In-memory filesystem for internal, non-user-callable Nix
      * expressions like call-flake.nix.
      */
-    const ref<MemoryInputAccessor> internalFS;
+    const ref<MemorySourceAccessor> internalFS;
 
     const SourcePath derivationInternal;
 
@@ -276,6 +275,18 @@ public:
             return std::shared_ptr<const StaticEnv>();;
     }
 
+    /** Whether a debug repl can be started. If `false`, `runDebugRepl(error)` will return without starting a repl. */
+    bool canDebug();
+
+    /** Use front of `debugTraces`; see `runDebugRepl(error,env,expr)` */
+    void runDebugRepl(const Error * error);
+
+    /**
+     * Run a debug repl with the given error, environment and expression.
+     * @param error The error to debug, may be nullptr.
+     * @param env The environment to debug, matching the expression.
+     * @param expr The expression to debug, matching the environment.
+     */
     void runDebugRepl(const Error * error, const Env & env, const Expr & expr);
 
     template<class T, typename... Args>
@@ -285,11 +296,16 @@ public:
         return *new EvalErrorBuilder<T>(*this, args...);
     }
 
+    /**
+     * A cache for evaluation caches, so as to reuse the same root value if possible
+     */
+    std::map<const Hash, ref<eval_cache::EvalCache>> evalCaches;
+
 private:
 
     /* Cache for calls to addToStore(); maps source paths to the store
        paths. */
-    std::map<SourcePath, StorePath> srcToStore;
+    Sync<std::map<SourcePath, StorePath>> srcToStore;
 
     /**
      * A cache from path names to parse trees.
@@ -311,9 +327,9 @@ private:
 #endif
     FileEvalCache fileEvalCache;
 
-    SearchPath searchPath;
+    LookupPath lookupPath;
 
-    std::map<std::string, std::optional<std::string>> searchPathResolved;
+    std::map<std::string, std::optional<std::string>> lookupPathResolved;
 
     /**
      * Cache used by prim_match().
@@ -335,12 +351,13 @@ private:
 public:
 
     EvalState(
-        const SearchPath & _searchPath,
+        const LookupPath & _lookupPath,
         ref<Store> store,
+        const EvalSettings & settings,
         std::shared_ptr<Store> buildStore = nullptr);
     ~EvalState();
 
-    SearchPath getSearchPath() { return searchPath; }
+    LookupPath getLookupPath() { return lookupPath; }
 
     /**
      * Return a `SourcePath` that refers to `path` in the root
@@ -409,7 +426,7 @@ public:
      * Look up a file in the search path.
      */
     SourcePath findFile(const std::string_view path);
-    SourcePath findFile(const SearchPath & searchPath, const std::string_view path, const PosIdx pos = noPos);
+    SourcePath findFile(const LookupPath & lookupPath, const std::string_view path, const PosIdx pos = noPos);
 
     /**
      * Try to resolve a search path value (not the optional key part).
@@ -418,8 +435,8 @@ public:
      *
      * If it is not found, return `std::nullopt`
      */
-    std::optional<std::string> resolveSearchPathPath(
-        const SearchPath::Path & elem,
+    std::optional<std::string> resolveLookupPathPath(
+        const LookupPath::Path & elem,
         bool initAccessControl = false);
 
     /**
@@ -542,6 +559,11 @@ public:
      */
     SingleDerivedPath coerceToSingleDerivedPath(const PosIdx pos, Value & v, std::string_view errorCtx);
 
+#if HAVE_BOEHMGC
+    /** A GC root for the baseEnv reference. */
+    std::shared_ptr<Env *> baseEnvP;
+#endif
+
 public:
 
     /**
@@ -828,8 +850,10 @@ std::string showType(const Value & v);
 
 /**
  * If `path` refers to a directory, then append "/default.nix".
+ *
+ * @param addDefaultNix Whether to append "/default.nix" after resolving symlinks.
  */
-SourcePath resolveExprPath(SourcePath path);
+SourcePath resolveExprPath(SourcePath path, bool addDefaultNix = true);
 
 /**
  * Whether a URI is allowed, assuming restrictEval is enabled
diff --git a/src/libexpr/fetchurl.nix b/src/libexpr/fetchurl.nix
index 9d1b61d7fef..85a01d16179 100644
--- a/src/libexpr/fetchurl.nix
+++ b/src/libexpr/fetchurl.nix
@@ -28,11 +28,8 @@ derivation ({
   # No need to double the amount of network traffic
   preferLocalBuild = true;
 
+  # This attribute does nothing; it's here to avoid changing evaluation results.
   impureEnvVars = [
-    # We borrow these environment variables from the caller to allow
-    # easy proxy configuration.  This is impure, but a fixed-output
-    # derivation like fetchurl is allowed to do so since its result is
-    # by definition pure.
     "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
   ];
 
diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index cf10ed84ac9..8967334237a 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -69,10 +69,17 @@ std::string PackageInfo::querySystem() const
 std::optional<StorePath> PackageInfo::queryDrvPath() const
 {
     if (!drvPath && attrs) {
-        NixStringContext context;
-        if (auto i = attrs->get(state->sDrvPath))
-            drvPath = {state->coerceToStorePath(i->pos, *i->value, context, "while evaluating the 'drvPath' attribute of a derivation")};
-        else
+        if (auto i = attrs->get(state->sDrvPath)) {
+            NixStringContext context;
+            auto found = state->coerceToStorePath(i->pos, *i->value, context, "while evaluating the 'drvPath' attribute of a derivation");
+            try {
+                found.requireDerivation();
+            } catch (Error & e) {
+                e.addTrace(state->positions[i->pos], "while evaluating the 'drvPath' attribute of a derivation");
+                throw;
+            }
+            drvPath = {std::move(found)};
+        } else
             drvPath = {std::nullopt};
     }
     return drvPath.value_or(std::nullopt);
@@ -367,21 +374,26 @@ static void getDerivations(EvalState & state, Value & vIn,
            bound to the attribute with the "lower" name should take
            precedence). */
         for (auto & i : v.attrs()->lexicographicOrder(state.symbols)) {
-            debug("evaluating attribute '%1%'", state.symbols[i->name]);
-            if (!std::regex_match(std::string(state.symbols[i->name]), attrRegex))
-                continue;
-            std::string pathPrefix2 = addToPath(pathPrefix, state.symbols[i->name]);
-            if (combineChannels)
-                getDerivations(state, *i->value, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
-            else if (getDerivation(state, *i->value, pathPrefix2, drvs, done, ignoreAssertionFailures)) {
-                /* If the value of this attribute is itself a set,
-                   should we recurse into it?  => Only if it has a
-                   `recurseForDerivations = true' attribute. */
-                if (i->value->type() == nAttrs) {
-                    auto j = i->value->attrs()->get(state.sRecurseForDerivations);
-                    if (j && state.forceBool(*j->value, j->pos, "while evaluating the attribute `recurseForDerivations`"))
-                        getDerivations(state, *i->value, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
+            try {
+                debug("evaluating attribute '%1%'", state.symbols[i->name]);
+                if (!std::regex_match(std::string(state.symbols[i->name]), attrRegex))
+                    continue;
+                std::string pathPrefix2 = addToPath(pathPrefix, state.symbols[i->name]);
+                if (combineChannels)
+                    getDerivations(state, *i->value, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
+                else if (getDerivation(state, *i->value, pathPrefix2, drvs, done, ignoreAssertionFailures)) {
+                    /* If the value of this attribute is itself a set,
+                    should we recurse into it?  => Only if it has a
+                    `recurseForDerivations = true' attribute. */
+                    if (i->value->type() == nAttrs) {
+                        auto j = i->value->attrs()->get(state.sRecurseForDerivations);
+                        if (j && state.forceBool(*j->value, j->pos, "while evaluating the attribute `recurseForDerivations`"))
+                            getDerivations(state, *i->value, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
+                    }
                 }
+            } catch (Error & e) {
+                e.addTrace(state.positions[i->pos], "while evaluating the attribute '%s'", state.symbols[i->name]);
+                throw;
             }
         }
     }
diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index ee2b6b80790..8c0f9d1f2f7 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -20,8 +20,6 @@
 #pragma clang diagnostic ignored "-Wunneeded-internal-declaration"
 #endif
 
-#include <boost/lexical_cast.hpp>
-
 #include "nixexpr.hh"
 #include "parser-tab.hh"
 
@@ -129,9 +127,10 @@ or          { return OR_KW; }
 
 {ID}        { yylval->id = {yytext, (size_t) yyleng}; return ID; }
 {INT}       { errno = 0;
-              try {
-                  yylval->n = boost::lexical_cast<int64_t>(yytext);
-              } catch (const boost::bad_lexical_cast &) {
+              std::optional<int64_t> numMay = string2Int<int64_t>(yytext);
+              if (numMay.has_value()) {
+                  yylval->n = *numMay;
+              } else {
                   throw ParseError(ErrorInfo{
                       .msg = HintFmt("invalid integer '%1%'", yytext),
                       .pos = state->positions[CUR_POS],
diff --git a/src/libexpr/local.mk b/src/libexpr/local.mk
index ecadc5e5d53..68518e184b5 100644
--- a/src/libexpr/local.mk
+++ b/src/libexpr/local.mk
@@ -8,14 +8,15 @@ libexpr_SOURCES := \
   $(wildcard $(d)/*.cc) \
   $(wildcard $(d)/value/*.cc) \
   $(wildcard $(d)/primops/*.cc) \
-  $(wildcard $(d)/flake/*.cc) \
   $(d)/lexer-tab.cc \
   $(d)/parser-tab.cc
 # Not just for this library itself, but also for downstream libraries using this library
 
 INCLUDE_libexpr := -I $(d)
 
-libexpr_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libmain) $(INCLUDE_libexpr)
+libexpr_CXXFLAGS += \
+	$(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) \
+	-DGC_THREADS
 
 libexpr_LIBS = libutil libstore libfetchers
 
@@ -43,11 +44,7 @@ $(eval $(call install-file-in, $(buildprefix)$(d)/nix-expr.pc, $(libdir)/pkgconf
 
 $(foreach i, $(wildcard src/libexpr/value/*.hh), \
   $(eval $(call install-file-in, $(i), $(includedir)/nix/value, 0644)))
-$(foreach i, $(wildcard src/libexpr/flake/*.hh), \
-  $(eval $(call install-file-in, $(i), $(includedir)/nix/flake, 0644)))
 
 $(d)/primops.cc: $(d)/imported-drv-to-derivation.nix.gen.hh
 
-$(d)/eval.cc: $(d)/primops/derivation.nix.gen.hh $(d)/fetchurl.nix.gen.hh $(d)/flake/call-flake.nix.gen.hh
-
-$(buildprefix)src/libexpr/primops/fromTOML.o:	ERROR_SWITCH_ENUM =
+$(d)/eval.cc: $(d)/primops/derivation.nix.gen.hh $(d)/fetchurl.nix.gen.hh $(d)/call-flake.nix.gen.hh
diff --git a/src/libexpr/meson.build b/src/libexpr/meson.build
new file mode 100644
index 00000000000..e65cf545f2d
--- /dev/null
+++ b/src/libexpr/meson.build
@@ -0,0 +1,202 @@
+project('nix-expr', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+  dependency('nix-fetchers'),
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/threads')
+
+boost = dependency(
+  'boost',
+  modules : ['container', 'context'],
+)
+# boost is a public dependency, but not a pkg-config dependency unfortunately, so we
+# put in `deps_other`.
+deps_other += boost
+
+nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
+deps_public += nlohmann_json
+
+bdw_gc = dependency('bdw-gc', required : get_option('gc'))
+if bdw_gc.found()
+  deps_public += bdw_gc
+  foreach funcspec : [
+    'pthread_attr_get_np',
+    'pthread_getattr_np',
+  ]
+    define_name = 'HAVE_' + funcspec.underscorify().to_upper()
+    define_value = cxx.has_function(funcspec).to_int()
+    configdata.set(define_name, define_value)
+  endforeach
+  configdata.set('GC_THREADS', 1)
+endif
+configdata.set('HAVE_BOEHMGC', bdw_gc.found().to_int())
+
+toml11 = dependency('toml11', version : '>=3.7.0', method : 'cmake')
+deps_other += toml11
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-expr.hh',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  # '-include', 'config-fetchers.h',
+  '-include', 'config-expr.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+parser_tab = custom_target(
+  input : 'parser.y',
+  output : [
+    'parser-tab.cc',
+    'parser-tab.hh',
+  ],
+  command : [
+    'bison',
+    '-v',
+    '-o',
+    '@OUTPUT0@',
+    '@INPUT@',
+    '-d',
+  ],
+  # NOTE(Qyriad): Meson doesn't support installing only part of a custom target, so we add
+  # an install script below which removes parser-tab.cc.
+  install : true,
+  install_dir : get_option('includedir') / 'nix',
+)
+
+lexer_tab = custom_target(
+  input : [
+    'lexer.l',
+    parser_tab,
+  ],
+  output : [
+    'lexer-tab.cc',
+    'lexer-tab.hh',
+  ],
+  command : [
+    'flex',
+    '--outfile',
+    '@OUTPUT0@',
+    '--header-file=' + '@OUTPUT1@',
+    '@INPUT0@',
+  ],
+  # NOTE(Qyriad): Meson doesn't support installing only part of a custom target, so we add
+  # an install script below which removes lexer-tab.cc.
+  install : true,
+  install_dir : get_option('includedir') / 'nix',
+)
+
+subdir('build-utils-meson/generate-header')
+
+generated_headers = []
+foreach header : [
+  'imported-drv-to-derivation.nix',
+  'fetchurl.nix',
+  'call-flake.nix',
+]
+  generated_headers += gen_header.process(header)
+endforeach
+
+sources = files(
+  'attr-path.cc',
+  'attr-set.cc',
+  'eval-cache.cc',
+  'eval-error.cc',
+  'eval-gc.cc',
+  'eval-settings.cc',
+  'eval.cc',
+  'function-trace.cc',
+  'get-drvs.cc',
+  'json-to-value.cc',
+  'nixexpr.cc',
+  'paths.cc',
+  'primops.cc',
+  'print-ambiguous.cc',
+  'print.cc',
+  'search-path.cc',
+  'value-to-json.cc',
+  'value-to-xml.cc',
+  'value/context.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'attr-path.hh',
+  'attr-set.hh',
+  'eval-cache.hh',
+  'eval-error.hh',
+  'eval-gc.hh',
+  'eval-inline.hh',
+  'eval-settings.hh',
+  'eval.hh',
+  'function-trace.hh',
+  'gc-small-vector.hh',
+  'get-drvs.hh',
+  'json-to-value.hh',
+  'nixexpr.hh',
+  'parser-state.hh',
+  'pos-idx.hh',
+  'pos-table.hh',
+  'primops.hh',
+  'print-ambiguous.hh',
+  'print-options.hh',
+  'print.hh',
+  'repl-exit-status.hh',
+  'search-path.hh',
+  'symbol-table.hh',
+  'value-to-json.hh',
+  'value-to-xml.hh',
+  'value.hh',
+  'value/context.hh',
+)
+
+subdir('primops')
+
+this_library = library(
+  'nixexpr',
+  sources,
+  parser_tab,
+  lexer_tab,
+  generated_headers,
+  dependencies : deps_public + deps_private + deps_other,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libexpr/meson.options b/src/libexpr/meson.options
new file mode 100644
index 00000000000..242d30ea785
--- /dev/null
+++ b/src/libexpr/meson.options
@@ -0,0 +1,3 @@
+option('gc', type : 'feature',
+  description : 'enable garbage collection in the Nix expression evaluator (requires Boehm GC)',
+)
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index c1e2b044882..44198a25238 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -6,6 +6,7 @@
 #include "print.hh"
 
 #include <cstdlib>
+#include <sstream>
 
 namespace nix {
 
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index e3cae8385cf..e37e3bdd153 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -92,10 +92,10 @@ struct ExprString : Expr
 
 struct ExprPath : Expr
 {
-    ref<InputAccessor> accessor;
+    ref<SourceAccessor> accessor;
     std::string s;
     Value v;
-    ExprPath(ref<InputAccessor> accessor, std::string s) : accessor(accessor), s(std::move(s))
+    ExprPath(ref<SourceAccessor> accessor, std::string s) : accessor(accessor), s(std::move(s))
     {
         v.mkPath(&*accessor, this->s.c_str());
     }
diff --git a/src/libexpr/package.nix b/src/libexpr/package.nix
new file mode 100644
index 00000000000..704456c96cd
--- /dev/null
+++ b/src/libexpr/package.nix
@@ -0,0 +1,117 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+, bison
+, flex
+, cmake # for resolving toml11 dep
+
+, nix-util
+, nix-store
+, nix-fetchers
+, boost
+, boehmgc
+, nlohmann_json
+, toml11
+
+# Configuration Options
+
+, version
+
+# Whether to use garbage collection for the Nix language evaluator.
+#
+# If it is disabled, we just leak memory, but this is not as bad as it
+# sounds so long as evaluation just takes places within short-lived
+# processes. (When the process exits, the memory is reclaimed; it is
+# only leaked *within* the process.)
+#
+# Temporarily disabled on Windows because the `GC_throw_bad_alloc`
+# symbol is missing during linking.
+, enableGC ? !stdenv.hostPlatform.isWindows
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-expr";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    ./meson.options
+    ./primops/meson.build
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    ./lexer.l
+    ./parser.y
+    (fileset.fileFilter (file: file.hasExt "nix") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+    bison
+    flex
+    cmake
+  ];
+
+  buildInputs = [
+    toml11
+  ];
+
+  propagatedBuildInputs = [
+    nix-util
+    nix-store
+    nix-fetchers
+    boost
+    nlohmann_json
+  ] ++ lib.optional enableGC boehmgc;
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+    (lib.mesonEnable "gc" enableGC)
+  ];
+
+  env = {
+    # Needed for Meson to find Boost.
+    # https://github.com/NixOS/nixpkgs/issues/86131.
+    BOOST_INCLUDEDIR = "${lib.getDev boost}/include";
+    BOOST_LIBRARYDIR = "${lib.getLib boost}/lib";
+  } // lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libexpr/parser-state.hh b/src/libexpr/parser-state.hh
index 024e79c432e..cff6282faa0 100644
--- a/src/libexpr/parser-state.hh
+++ b/src/libexpr/parser-state.hh
@@ -44,8 +44,9 @@ struct ParserState
     Expr * result;
     SourcePath basePath;
     PosTable::Origin origin;
-    const ref<InputAccessor> rootFS;
+    const ref<SourceAccessor> rootFS;
     const Expr::AstSymbols & s;
+    const EvalSettings & settings;
 
     void dupAttr(const AttrPath & attrPath, const PosIdx pos, const PosIdx prevPos);
     void dupAttr(Symbol attr, const PosIdx pos, const PosIdx prevPos);
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index bff0661703d..709a4532a85 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -25,7 +25,6 @@
 #include "nixexpr.hh"
 #include "eval.hh"
 #include "eval-settings.hh"
-#include "globals.hh"
 #include "parser-state.hh"
 
 #define YYLTYPE ::nix::ParserLocation
@@ -40,8 +39,9 @@ Expr * parseExprFromBuf(
     Pos::Origin origin,
     const SourcePath & basePath,
     SymbolTable & symbols,
+    const EvalSettings & settings,
     PosTable & positions,
-    const ref<InputAccessor> rootFS,
+    const ref<SourceAccessor> rootFS,
     const Expr::AstSymbols & astSymbols);
 
 }
@@ -291,17 +291,17 @@ path_start
     /* add back in the trailing '/' to the first segment */
     if ($1.p[$1.l-1] == '/' && $1.l > 1)
       path += "/";
-    $$ = new ExprPath(ref<InputAccessor>(state->rootFS), std::move(path));
+    $$ = new ExprPath(ref<SourceAccessor>(state->rootFS), std::move(path));
   }
   | HPATH {
-    if (evalSettings.pureEval) {
+    if (state->settings.pureEval) {
         throw Error(
             "the path '%s' can not be resolved in pure mode",
             std::string_view($1.p, $1.l)
         );
     }
     Path path(getHome() + std::string($1.p + 1, $1.l - 1));
-    $$ = new ExprPath(ref<InputAccessor>(state->rootFS), std::move(path));
+    $$ = new ExprPath(ref<SourceAccessor>(state->rootFS), std::move(path));
   }
   ;
 
@@ -429,8 +429,9 @@ Expr * parseExprFromBuf(
     Pos::Origin origin,
     const SourcePath & basePath,
     SymbolTable & symbols,
+    const EvalSettings & settings,
     PosTable & positions,
-    const ref<InputAccessor> rootFS,
+    const ref<SourceAccessor> rootFS,
     const Expr::AstSymbols & astSymbols)
 {
     yyscan_t scanner;
@@ -441,6 +442,7 @@ Expr * parseExprFromBuf(
         .origin = positions.addOrigin(origin, length),
         .rootFS = rootFS,
         .s = astSymbols,
+        .settings = settings,
     };
 
     yylex_init(&scanner);
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index f03acc2daab..134363e1ab2 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -5,7 +5,6 @@
 #include "eval.hh"
 #include "eval-settings.hh"
 #include "gc-small-vector.hh"
-#include "globals.hh"
 #include "json-to-value.hh"
 #include "names.hh"
 #include "path-references.hh"
@@ -15,7 +14,6 @@
 #include "value-to-json.hh"
 #include "value-to-xml.hh"
 #include "primops.hh"
-#include "fs-input-accessor.hh"
 #include "fetch-to-store.hh"
 
 #include <boost/container/small_vector.hpp>
@@ -27,6 +25,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <sstream>
 #include <regex>
 
 #ifndef _WIN32
@@ -78,8 +77,8 @@ StringMap EvalState::realiseContext(const NixStringContext & context, StorePathS
 
     if (drvs.empty()) return {};
 
-    if (isIFD && !evalSettings.enableImportFromDerivation)
-        error<EvalError>(
+    if (isIFD && !settings.enableImportFromDerivation)
+        error<EvalBaseError>(
             "cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
             drvs.begin()->to_string(*store)
         ).debugThrow();
@@ -733,11 +732,12 @@ static RegisterPrimOp primop_genericClosure(PrimOp {
       Each attribute set in the list `startSet` and the list returned by `operator` must have an attribute `key`, which must support equality comparison.
       The value of `key` can be one of the following types:
 
-      - [Number](@docroot@/language/values.md#type-number)
-      - [Boolean](@docroot@/language/values.md#type-boolean)
-      - [String](@docroot@/language/values.md#type-string)
-      - [Path](@docroot@/language/values.md#type-path)
-      - [List](@docroot@/language/values.md#list)
+      - [Int](@docroot@/language/types.md#type-int)
+      - [Float](@docroot@/language/types.md#type-float)
+      - [Boolean](@docroot@/language/types.md#type-boolean)
+      - [String](@docroot@/language/types.md#type-string)
+      - [Path](@docroot@/language/types.md#type-path)
+      - [List](@docroot@/language/types.md#list)
 
       The result is produced by calling the `operator` on each `item` that has not been called yet, including newly added items, until no new items are added.
       Items are compared by their `key` attribute.
@@ -780,15 +780,14 @@ static RegisterPrimOp primop_break({
     )",
     .fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
     {
-        if (state.debugRepl && !state.debugTraces.empty()) {
+        if (state.canDebug()) {
             auto error = Error(ErrorInfo {
                 .level = lvlInfo,
                 .msg = HintFmt("breakpoint reached"),
                 .pos = state.positions[pos],
             });
 
-            auto & dt = state.debugTraces.front();
-            state.runDebugRepl(&error, dt.env, dt.expr);
+            state.runDebugRepl(&error);
         }
 
         // Return the value we were passed.
@@ -807,7 +806,7 @@ static RegisterPrimOp primop_abort({
         NixStringContext context;
         auto s = state.coerceToString(pos, *args[0], context,
                 "while evaluating the error message passed to builtins.abort").toOwned();
-        state.error<Abort>("evaluation aborted with the following error message: '%1%'", s).debugThrow();
+        state.error<Abort>("evaluation aborted with the following error message: '%1%'", s).setIsFromExpr().debugThrow();
     }
 });
 
@@ -826,7 +825,7 @@ static RegisterPrimOp primop_throw({
       NixStringContext context;
       auto s = state.coerceToString(pos, *args[0], context,
               "while evaluating the error message passed to builtin.throw").toOwned();
-      state.error<ThrownError>(s).debugThrow();
+      state.error<ThrownError>(s).setIsFromExpr().debugThrow();
     }
 });
 
@@ -902,7 +901,7 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
     MaintainCount trylevel(state.trylevel);
 
     ReplExitStatus (* savedDebugRepl)(ref<EvalState> es, const ValMap & extraEnv) = nullptr;
-    if (state.debugRepl && evalSettings.ignoreExceptionsDuringTry)
+    if (state.debugRepl && state.settings.ignoreExceptionsDuringTry)
     {
         /* to prevent starting the repl from exceptions withing a tryEval, null it. */
         savedDebugRepl = state.debugRepl;
@@ -951,7 +950,7 @@ static RegisterPrimOp primop_tryEval({
 static void prim_getEnv(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
     std::string name(state.forceStringNoCtx(*args[0], pos, "while evaluating the first argument passed to builtins.getEnv"));
-    v.mkString(evalSettings.restrictEval || evalSettings.pureEval ? "" : getEnv(name).value_or(""));
+    v.mkString(state.settings.restrictEval || state.settings.pureEval ? "" : getEnv(name).value_or(""));
 }
 
 static RegisterPrimOp primop_getEnv({
@@ -1018,9 +1017,8 @@ static void prim_trace(EvalState & state, const PosIdx pos, Value * * args, Valu
         printError("trace: %1%", args[0]->string_view());
     else
         printError("trace: %1%", ValuePrinter(state, *args[0]));
-    if (evalSettings.builtinsTraceDebugger && state.debugRepl && !state.debugTraces.empty()) {
-        const DebugTrace & last = state.debugTraces.front();
-        state.runDebugRepl(nullptr, last.env, last.expr);
+    if (state.settings.builtinsTraceDebugger) {
+        state.runDebugRepl(nullptr);
     }
     state.forceValue(*args[1], pos);
     v = *args[1];
@@ -1043,6 +1041,55 @@ static RegisterPrimOp primop_trace({
     .fun = prim_trace,
 });
 
+static void prim_warn(EvalState & state, const PosIdx pos, Value * * args, Value & v)
+{
+    // We only accept a string argument for now. The use case for pretty printing a value is covered by `trace`.
+    // By rejecting non-strings we allow future versions to add more features without breaking existing code.
+    auto msgStr = state.forceString(*args[0], pos, "while evaluating the first argument; the message passed to builtins.warn");
+
+    {
+        BaseError msg(std::string{msgStr});
+        msg.atPos(state.positions[pos]);
+        auto info = msg.info();
+        info.level = lvlWarn;
+        info.isFromExpr = true;
+        logWarning(info);
+    }
+
+    if (state.settings.builtinsAbortOnWarn) {
+        // Not an EvalError or subclass, which would cause the error to be stored in the eval cache.
+        state.error<EvalBaseError>("aborting to reveal stack trace of warning, as abort-on-warn is set").setIsFromExpr().debugThrow();
+    }
+    if (state.settings.builtinsTraceDebugger || state.settings.builtinsDebuggerOnWarn) {
+        state.runDebugRepl(nullptr);
+    }
+    state.forceValue(*args[1], pos);
+    v = *args[1];
+}
+
+static RegisterPrimOp primop_warn({
+    .name = "__warn",
+    .args = {"e1", "e2"},
+    .doc = R"(
+      Evaluate *e1*, which must be a string and print iton standard error as a warning.
+      Then return *e2*.
+      This function is useful for non-critical situations where attention is advisable.
+
+      If the
+      [`debugger-on-trace`](@docroot@/command-ref/conf-file.md#conf-debugger-on-trace)
+      or [`debugger-on-warn`](@docroot@/command-ref/conf-file.md#conf-debugger-on-warn)
+      option is set to `true` and the `--debugger` flag is given, the
+      interactive debugger will be started when `warn` is called (like
+      [`break`](@docroot@/language/builtins.md#builtins-break)).
+
+      If the
+      [`abort-on-warn`](@docroot@/command-ref/conf-file.md#conf-abort-on-warn)
+      option is set, the evaluation will be aborted after the warning is printed.
+      This is useful to reveal the stack trace of the warning, when the context is non-interactive and a debugger can not be launched.
+    )",
+    .fun = prim_warn,
+});
+
 
 /* Takes two arguments and evaluates to the second one. Used as the
  * builtins.traceVerbose implementation when --trace-verbose is not enabled
@@ -1116,12 +1163,34 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
     }
 }
 
+/**
+ * Early validation for the derivation name, for better error message.
+ * It is checked again when constructing store paths.
+ *
+ * @todo Check that the `.drv` suffix also fits.
+ */
+static void checkDerivationName(EvalState & state, std::string_view drvName)
+{
+    try {
+        checkName(drvName);
+    } catch (BadStorePathName & e) {
+        // "Please pass a different name": Users may not be aware that they can
+        //     pass a different one, in functions like `fetchurl` where the name
+        //     is optional.
+        // Note that Nixpkgs generally won't trigger this, because `mkDerivation`
+        // sanitizes the name.
+        state.error<EvalError>("invalid derivation name: %s. Please pass a different '%s'.", Uncolored(e.message()), "name").debugThrow();
+    }
+}
+
 static void derivationStrictInternal(
     EvalState & state,
     const std::string & drvName,
     const Bindings * attrs,
     Value & v)
 {
+    checkDerivationName(state, drvName);
+
     /* Check whether attributes should be passed as a JSON file. */
     using nlohmann::json;
     std::optional<json> jsonObject;
@@ -1162,7 +1231,7 @@ static void derivationStrictInternal(
         auto handleHashMode = [&](const std::string_view s) {
             if (s == "recursive") {
                 // back compat, new name is "nar"
-                ingestionMethod = FileIngestionMethod::Recursive;
+                ingestionMethod = ContentAddressMethod::Raw::NixArchive;
             } else try {
                 ingestionMethod = ContentAddressMethod::parse(s);
             } catch (UsageError &) {
@@ -1170,9 +1239,9 @@ static void derivationStrictInternal(
                     "invalid value '%s' for 'outputHashMode' attribute", s
                 ).atPos(v).debugThrow();
             }
-            if (ingestionMethod == TextIngestionMethod {})
+            if (ingestionMethod == ContentAddressMethod::Raw::Text)
                 experimentalFeatureSettings.require(Xp::DynamicDerivations);
-            if (ingestionMethod == FileIngestionMethod::Git)
+            if (ingestionMethod == ContentAddressMethod::Raw::Git)
                 experimentalFeatureSettings.require(Xp::GitHashing);
         };
 
@@ -1185,11 +1254,11 @@ static void derivationStrictInternal(
                         .debugThrow();
                 /* !!! Check whether j is a valid attribute
                    name. */
-                /* Derivations cannot be named ‘drv’, because
-                   then we'd have an attribute ‘drvPath’ in
-                   the resulting set. */
-                if (j == "drv")
-                    state.error<EvalError>("invalid derivation output name 'drv'")
+                /* Derivations cannot be named ‘drvPath’, because
+                   we already have an attribute ‘drvPath’ in
+                   the resulting set (see state.sDrvPath). */
+                if (j == "drvPath")
+                    state.error<EvalError>("invalid derivation output name 'drvPath'")
                         .atPos(v)
                         .debugThrow();
                 outputs.insert(j);
@@ -1261,6 +1330,20 @@ static void derivationStrictInternal(
                         handleOutputs(ss);
                     }
 
+                    if (i->name == state.sAllowedReferences)
+                        warn("In a derivation named '%s', 'structuredAttrs' disables the effect of the derivation attribute 'allowedReferences'; use 'outputChecks.<output>.allowedReferences' instead", drvName);
+                    if (i->name == state.sAllowedRequisites)
+                        warn("In a derivation named '%s', 'structuredAttrs' disables the effect of the derivation attribute 'allowedRequisites'; use 'outputChecks.<output>.allowedRequisites' instead", drvName);
+                    if (i->name == state.sDisallowedReferences)
+                        warn("In a derivation named '%s', 'structuredAttrs' disables the effect of the derivation attribute 'disallowedReferences'; use 'outputChecks.<output>.disallowedReferences' instead", drvName);
+                    if (i->name == state.sDisallowedRequisites)
+                        warn("In a derivation named '%s', 'structuredAttrs' disables the effect of the derivation attribute 'disallowedRequisites'; use 'outputChecks.<output>.disallowedRequisites' instead", drvName);
+                    if (i->name == state.sMaxSize)
+                        warn("In a derivation named '%s', 'structuredAttrs' disables the effect of the derivation attribute 'maxSize'; use 'outputChecks.<output>.maxSize' instead", drvName);
+                    if (i->name == state.sMaxClosureSize)
+                        warn("In a derivation named '%s', 'structuredAttrs' disables the effect of the derivation attribute 'maxClosureSize'; use 'outputChecks.<output>.maxClosureSize' instead", drvName);
+
+
                 } else {
                     auto s = state.coerceToString(pos, *i->value, context, context_below, true).toOwned();
                     drv.env.emplace(key, s);
@@ -1330,7 +1413,7 @@ static void derivationStrictInternal(
 
     /* Check whether the derivation name is valid. */
     if (isDerivation(drvName) &&
-        !(ingestionMethod == ContentAddressMethod { TextIngestionMethod { } } &&
+        !(ingestionMethod == ContentAddressMethod::Raw::Text &&
           outputs.size() == 1 &&
           *(outputs.begin()) == "out"))
     {
@@ -1352,7 +1435,7 @@ static void derivationStrictInternal(
 
         auto h = newHashAllowEmpty(*outputHash, outputHashAlgo);
 
-        auto method = ingestionMethod.value_or(FileIngestionMethod::Flat);
+        auto method = ingestionMethod.value_or(ContentAddressMethod::Raw::Flat);
 
         DerivationOutput::CAFixed dof {
             .ca = ContentAddress {
@@ -1371,7 +1454,7 @@ static void derivationStrictInternal(
                 .atPos(v).debugThrow();
 
         auto ha = outputHashAlgo.value_or(HashAlgorithm::SHA256);
-        auto method = ingestionMethod.value_or(FileIngestionMethod::Recursive);
+        auto method = ingestionMethod.value_or(ContentAddressMethod::Raw::NixArchive);
 
         for (auto & i : outputs) {
             drv.env[i] = hashPlaceholder(i);
@@ -1517,7 +1600,7 @@ static RegisterPrimOp primop_toPath({
    corner cases. */
 static void prim_storePath(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
-    if (evalSettings.pureEval)
+    if (state.settings.pureEval)
         state.error<EvalError>(
             "'%s' is not allowed in pure evaluation mode",
             "builtins.storePath"
@@ -1627,7 +1710,7 @@ static RegisterPrimOp primop_baseNameOf({
     .name = "baseNameOf",
     .args = {"x"},
     .doc = R"(
-      Return the *base name* of either a [path value](@docroot@/language/values.md#type-path) *x* or a string *x*, depending on which type is passed, and according to the following rules.
+      Return the *base name* of either a [path value](@docroot@/language/types.md#type-path) *x* or a string *x*, depending on which type is passed, and according to the following rules.
 
       For a path value, the *base name* is considered to be the part of the path after the last directory separator, including any file extensions.
       This is the simple case, as path values don't have trailing slashes.
@@ -1716,7 +1799,7 @@ static void prim_findFile(EvalState & state, const PosIdx pos, Value * * args, V
 {
     state.forceList(*args[0], pos, "while evaluating the first argument passed to builtins.findFile");
 
-    SearchPath searchPath;
+    LookupPath lookupPath;
 
     for (auto v2 : args[0]->listItems()) {
         state.forceAttrs(*v2, pos, "while evaluating an element of the list passed to builtins.findFile");
@@ -1744,15 +1827,15 @@ static void prim_findFile(EvalState & state, const PosIdx pos, Value * * args, V
             ).atPos(pos).debugThrow();
         }
 
-        searchPath.elements.emplace_back(SearchPath::Elem {
-            .prefix = SearchPath::Prefix { .s = prefix },
-            .path = SearchPath::Path { .s = path },
+        lookupPath.elements.emplace_back(LookupPath::Elem {
+            .prefix = LookupPath::Prefix { .s = prefix },
+            .path = LookupPath::Path { .s = path },
         });
     }
 
     auto path = state.forceStringNoCtx(*args[1], pos, "while evaluating the second argument passed to builtins.findFile");
 
-    v.mkPath(state.findFile(searchPath, path, pos));
+    v.mkPath(state.findFile(lookupPath, path, pos));
 }
 
 static RegisterPrimOp primop_findFile(PrimOp {
@@ -1761,7 +1844,7 @@ static RegisterPrimOp primop_findFile(PrimOp {
     .doc = R"(
       Find *lookup-path* in *search-path*.
 
-      A search path is represented list of [attribute sets](./values.md#attribute-set) with two attributes:
+      A search path is represented list of [attribute sets](./types.md#attribute-set) with two attributes:
       - `prefix` is a relative path.
       - `path` denotes a file system location
       The exact syntax depends on the command line interface.
@@ -1782,14 +1865,14 @@ static RegisterPrimOp primop_findFile(PrimOp {
         }
         ```
 
-      The lookup algorithm checks each entry until a match is found, returning a [path value](@docroot@/language/values.html#type-path) of the match:
+      The lookup algorithm checks each entry until a match is found, returning a [path value](@docroot@/language/types.md#type-path) of the match:
 
       - If *lookup-path* matches `prefix`, then the remainder of *lookup-path* (the "suffix") is searched for within the directory denoted by `path`.
         Note that the `path` may need to be downloaded at this point to look inside.
       - If the suffix is found inside that directory, then the entry is a match.
         The combined absolute path of the directory (now downloaded if need be) and the suffix is returned.
 
-      [Lookup path](@docroot@/language/constructs/lookup-path.md) expressions are [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath):
+      [Lookup path](@docroot@/language/constructs/lookup-path.md) expressions are [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and [`builtins.nixPath`](#builtins-nixPath):
 
       ```nix
       <nixpkgs>
@@ -1828,12 +1911,12 @@ static RegisterPrimOp primop_hashFile({
     .fun = prim_hashFile,
 });
 
-static Value * fileTypeToString(EvalState & state, InputAccessor::Type type)
+static Value * fileTypeToString(EvalState & state, SourceAccessor::Type type)
 {
     return
-        type == InputAccessor::Type::tRegular ? &state.vStringRegular :
-        type == InputAccessor::Type::tDirectory ? &state.vStringDirectory :
-        type == InputAccessor::Type::tSymlink ? &state.vStringSymlink :
+        type == SourceAccessor::Type::tRegular ? &state.vStringRegular :
+        type == SourceAccessor::Type::tDirectory ? &state.vStringDirectory :
+        type == SourceAccessor::Type::tSymlink ? &state.vStringSymlink :
         &state.vStringUnknown;
 }
 
@@ -2147,7 +2230,7 @@ static void prim_toFile(EvalState & state, const PosIdx pos, Value * * args, Val
         })
         : ({
             StringSource s { contents };
-            state.store->addToStoreFromDump(s, name, FileSerialisationMethod::Flat, TextIngestionMethod {}, HashAlgorithm::SHA256, refs, state.repair);
+            state.store->addToStoreFromDump(s, name, FileSerialisationMethod::Flat, ContentAddressMethod::Raw::Text, HashAlgorithm::SHA256, refs, state.repair);
         });
 
     /* Note: we don't need to add `context' to the context of the
@@ -2210,7 +2293,7 @@ static RegisterPrimOp primop_toFile({
       ```
 
       Note that `${configFile}` is a
-      [string interpolation](@docroot@/language/values.md#type-string), so the result of the
+      [string interpolation](@docroot@/language/types.md#type-string), so the result of the
       expression `configFile`
       (i.e., a path like `/nix/store/m7p7jfny445k...-foo.conf`) will be
       spliced into the resulting string.
@@ -2262,7 +2345,7 @@ static void addPath(
     std::string_view name,
     SourcePath path,
     Value * filterFun,
-    FileIngestionMethod method,
+    ContentAddressMethod method,
     const std::optional<Hash> expectedHash,
     Value & v,
     const NixStringContext & context)
@@ -2294,11 +2377,10 @@ static void addPath(
 
         std::optional<StorePath> expectedStorePath;
         if (expectedHash)
-            expectedStorePath = state.store->makeFixedOutputPath(name, FixedOutputInfo {
-                .method = method,
-                .hash = *expectedHash,
-                .references = {},
-            });
+            expectedStorePath = state.store->makeFixedOutputPathFromCA(name, ContentAddressWithReferences::fromParts(
+                method,
+                *expectedHash,
+                {}));
 
         if (!expectedHash || !state.store->isValidPath(*expectedStorePath)) {
             auto dstPath = fetchToStore(
@@ -2331,7 +2413,7 @@ static void prim_filterSource(EvalState & state, const PosIdx pos, Value * * arg
         "while evaluating the second argument (the path to filter) passed to 'builtins.filterSource'");
     state.forceFunction(*args[0], pos, "while evaluating the first argument passed to builtins.filterSource");
 
-    addPath(state, pos, path.baseName(), path, args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
+    addPath(state, pos, path.baseName(), path, args[0], ContentAddressMethod::Raw::NixArchive, std::nullopt, v, context);
 }
 
 static RegisterPrimOp primop_filterSource({
@@ -2394,7 +2476,7 @@ static void prim_path(EvalState & state, const PosIdx pos, Value * * args, Value
     std::optional<SourcePath> path;
     std::string name;
     Value * filterFun = nullptr;
-    auto method = FileIngestionMethod::Recursive;
+    auto method = ContentAddressMethod::Raw::NixArchive;
     std::optional<Hash> expectedHash;
     NixStringContext context;
 
@@ -2409,7 +2491,9 @@ static void prim_path(EvalState & state, const PosIdx pos, Value * * args, Value
         else if (n == "filter")
             state.forceFunction(*(filterFun = attr.value), attr.pos, "while evaluating the `filter` parameter passed to builtins.path");
         else if (n == "recursive")
-            method = FileIngestionMethod { state.forceBool(*attr.value, attr.pos, "while evaluating the `recursive` attribute passed to builtins.path") };
+            method = state.forceBool(*attr.value, attr.pos, "while evaluating the `recursive` attribute passed to builtins.path")
+                ? ContentAddressMethod::Raw::NixArchive
+                : ContentAddressMethod::Raw::Flat;
         else if (n == "sha256")
             expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the `sha256` attribute passed to builtins.path"), HashAlgorithm::SHA256);
         else
@@ -4014,17 +4098,23 @@ static RegisterPrimOp primop_convertHash({
 
 struct RegexCache
 {
-    // TODO use C++20 transparent comparison when available
-    std::unordered_map<std::string_view, std::regex> cache;
-    std::list<std::string> keys;
+    struct State
+    {
+        // TODO use C++20 transparent comparison when available
+        std::unordered_map<std::string_view, std::regex> cache;
+        std::list<std::string> keys;
+    };
+
+    Sync<State> state_;
 
     std::regex get(std::string_view re)
     {
-        auto it = cache.find(re);
-        if (it != cache.end())
+        auto state(state_.lock());
+        auto it = state->cache.find(re);
+        if (it != state->cache.end())
             return it->second;
-        keys.emplace_back(re);
-        return cache.emplace(keys.back(), std::regex(keys.back(), std::regex::extended)).first->second;
+        state->keys.emplace_back(re);
+        return state->cache.emplace(state->keys.back(), std::regex(state->keys.back(), std::regex::extended)).first->second;
     }
 };
 
@@ -4429,7 +4519,7 @@ void EvalState::createBaseEnv()
     addConstant("builtins", v, {
         .type = nAttrs,
         .doc = R"(
-          Contains all the [built-in functions](@docroot@/language/builtins.md) and values.
+          Contains all the built-in functions and values.
 
           Since built-in functions were added over time, [testing for attributes](./operators.md#has-attribute) in `builtins` can be used for graceful fallback on older Nix installations:
 
@@ -4449,7 +4539,7 @@ void EvalState::createBaseEnv()
           It can be returned by
           [comparison operators](@docroot@/language/operators.md#Comparison)
           and used in
-          [conditional expressions](@docroot@/language/constructs.md#Conditionals).
+          [conditional expressions](@docroot@/language/syntax.md#Conditionals).
 
           The name `true` is not special, and can be shadowed:
 
@@ -4469,7 +4559,7 @@ void EvalState::createBaseEnv()
           It can be returned by
           [comparison operators](@docroot@/language/operators.md#Comparison)
           and used in
-          [conditional expressions](@docroot@/language/constructs.md#Conditionals).
+          [conditional expressions](@docroot@/language/syntax.md#Conditionals).
 
           The name `false` is not special, and can be shadowed:
 
@@ -4494,7 +4584,7 @@ void EvalState::createBaseEnv()
         )",
     });
 
-    if (!evalSettings.pureEval) {
+    if (!settings.pureEval) {
         v.mkInt(time(0));
     }
     addConstant("__currentTime", v, {
@@ -4516,13 +4606,13 @@ void EvalState::createBaseEnv()
           1683705525
           ```
 
-          The [store path](@docroot@/glossary.md#gloss-store-path) of a derivation depending on `currentTime` will differ for each evaluation, unless both evaluate `builtins.currentTime` in the same second.
+          The [store path](@docroot@/store/store-path.md) of a derivation depending on `currentTime` will differ for each evaluation, unless both evaluate `builtins.currentTime` in the same second.
         )",
         .impureOnly = true,
     });
 
-    if (!evalSettings.pureEval)
-        v.mkString(evalSettings.getCurrentSystem());
+    if (!settings.pureEval)
+        v.mkString(settings.getCurrentSystem());
     addConstant("__currentSystem", v, {
         .type = nString,
         .doc = R"(
@@ -4602,7 +4692,7 @@ void EvalState::createBaseEnv()
 
 #ifndef _WIN32 // TODO implement on Windows
     // Miscellaneous
-    if (evalSettings.enableNativeCode) {
+    if (settings.enableNativeCode) {
         addPrimOp({
             .name = "__importNative",
             .arity = 2,
@@ -4625,12 +4715,12 @@ void EvalState::createBaseEnv()
           error if `--trace-verbose` is enabled. Then return *e2*. This function
           is useful for debugging.
         )",
-        .fun = evalSettings.traceVerbose ? prim_trace : prim_second,
+        .fun = settings.traceVerbose ? prim_trace : prim_second,
     });
 
     /* Add a value containing the current Nix expression search path. */
-    auto list = buildList(searchPath.elements.size());
-    for (const auto & [n, i] : enumerate(searchPath.elements)) {
+    auto list = buildList(lookupPath.elements.size());
+    for (const auto & [n, i] : enumerate(lookupPath.elements)) {
         auto attrs = buildBindings(2);
         attrs.alloc("path").mkString(i.path.s);
         attrs.alloc("prefix").mkString(i.prefix.s);
diff --git a/src/libexpr/primops/context.cc b/src/libexpr/primops/context.cc
index 2d3013132f7..8c3f1b4e8b0 100644
--- a/src/libexpr/primops/context.cc
+++ b/src/libexpr/primops/context.cc
@@ -14,8 +14,11 @@ static void prim_unsafeDiscardStringContext(EvalState & state, const PosIdx pos,
 
 static RegisterPrimOp primop_unsafeDiscardStringContext({
     .name = "__unsafeDiscardStringContext",
-    .arity = 1,
-    .fun = prim_unsafeDiscardStringContext
+    .args = {"s"},
+    .doc = R"(
+        Discard the [string context](@docroot@/language/string-context.md) from a value that can be coerced to a string.
+    )",
+    .fun = prim_unsafeDiscardStringContext,
 });
 
 
@@ -75,7 +78,11 @@ static RegisterPrimOp primop_unsafeDiscardOutputDependency({
     .name = "__unsafeDiscardOutputDependency",
     .args = {"s"},
     .doc = R"(
-      Create a copy of the given string where every "derivation deep" string context element is turned into a constant string context element.
+      Create a copy of the given string where every
+      [derivation deep](@docroot@/language/string-context.md#string-context-element-derivation-deep)
+      string context element is turned into a
+      [constant](@docroot@/language/string-context.md#string-context-element-constant)
+      string context element.
 
       This is the opposite of [`builtins.addDrvOutputDependencies`](#builtins-addDrvOutputDependencies).
 
@@ -137,7 +144,11 @@ static RegisterPrimOp primop_addDrvOutputDependencies({
     .name = "__addDrvOutputDependencies",
     .args = {"s"},
     .doc = R"(
-      Create a copy of the given string where a single constant string context element is turned into a "derivation deep" string context element.
+      Create a copy of the given string where a single
+      [constant](@docroot@/language/string-context.md#string-context-element-constant)
+      string context element is turned into a
+      [derivation deep](@docroot@/language/string-context.md#string-context-element-derivation-deep)
+      string context element.
 
       The store path that is the constant string context element should point to a valid derivation, and end in `.drv`.
 
diff --git a/src/libexpr/primops/fetchMercurial.cc b/src/libexpr/primops/fetchMercurial.cc
index d9ba6aa97d8..7b5f4193a23 100644
--- a/src/libexpr/primops/fetchMercurial.cc
+++ b/src/libexpr/primops/fetchMercurial.cc
@@ -53,7 +53,7 @@ static void prim_fetchMercurial(EvalState & state, const PosIdx pos, Value * * a
     // whitelist. Ah well.
     state.checkURI(url);
 
-    if (evalSettings.pureEval && !rev)
+    if (state.settings.pureEval && !rev)
         throw Error("in pure evaluation mode, 'fetchMercurial' requires a Mercurial revision");
 
     fetchers::Attrs attrs;
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index e27f30512b8..567b73f9a1b 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -1,4 +1,4 @@
-#include "libfetchers/attrs.hh"
+#include "attrs.hh"
 #include "primops.hh"
 #include "eval-inline.hh"
 #include "eval-settings.hh"
@@ -137,6 +137,11 @@ static void fetchTree(
             attrs.emplace("exportIgnore", Explicit<bool>{true});
         }
 
+        // fetchTree should fetch git repos with shallow = true by default
+        if (type == "git" && !params.isFetchGit && !attrs.contains("shallow")) {
+            attrs.emplace("shallow", Explicit<bool>{true});
+        }
+
         if (!params.allowNameArgument)
             if (auto nameIter = attrs.find("name"); nameIter != attrs.end())
                 state.error<EvalError>(
@@ -166,10 +171,10 @@ static void fetchTree(
         }
     }
 
-    if (!evalSettings.pureEval && !input.isDirect() && experimentalFeatureSettings.isEnabled(Xp::Flakes))
+    if (!state.settings.pureEval && !input.isDirect() && experimentalFeatureSettings.isEnabled(Xp::Flakes))
         input = lookupInRegistries(state.store, input).first;
 
-    if (evalSettings.pureEval && !input.isLocked()) {
+    if (state.settings.pureEval && !input.isLocked()) {
         auto fetcher = "fetchTree";
         if (params.isFetchGit)
             fetcher = "fetchGit";
@@ -200,8 +205,8 @@ static RegisterPrimOp primop_fetchTree({
     .doc = R"(
       Fetch a file system tree or a plain file using one of the supported backends and return an attribute set with:
 
-      - the resulting fixed-output [store path](@docroot@/glossary.md#gloss-store-path)
-      - the corresponding [NAR](@docroot@/glossary.md#gloss-nar) hash
+      - the resulting fixed-output [store path](@docroot@/store/store-path.md)
+      - the corresponding [NAR](@docroot@/store/file-system-object/content-address.md#serial-nix-archive) hash
       - backend-specific metadata (currently not documented). <!-- TODO: document output attributes -->
 
       *input* must be an attribute set with the following attributes:
@@ -320,6 +325,8 @@ static RegisterPrimOp primop_fetchTree({
 
         - `ref` (String, optional)
 
+          By default, this has no effect. This becomes relevant only once `shallow` cloning is disabled.
+
           A [Git reference](https://git-scm.com/book/en/v2/Git-Internals-Git-References), such as a branch or tag name.
 
           Default: `"HEAD"`
@@ -333,8 +340,9 @@ static RegisterPrimOp primop_fetchTree({
         - `shallow` (Bool, optional)
 
           Make a shallow clone when fetching the Git tree.
+          When this is enabled, the options `ref` and `allRefs` have no effect anymore.
 
-          Default: `false`
+          Default: `true`
 
         - `submodules` (Bool, optional)
 
@@ -344,8 +352,11 @@ static RegisterPrimOp primop_fetchTree({
 
         - `allRefs` (Bool, optional)
 
-          If set to `true`, always fetch the entire repository, even if the latest commit is still in the cache.
-          Otherwise, only the latest commit is fetched if it is not already cached.
+          By default, this has no effect. This becomes relevant only once `shallow` cloning is disabled.
+
+          Whether to fetch all references (eg. branches and tags) of the repository.
+          With this argument being true, it's possible to load a `rev` from *any* `ref`.
+          (Without setting this option, only `rev`s from the specified `ref` are supported).
 
           Default: `false`
 
@@ -420,7 +431,10 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
 
     state.forceValue(*args[0], pos);
 
-    if (args[0]->type() == nAttrs) {
+    bool isArgAttrs = args[0]->type() == nAttrs;
+    bool nameAttrPassed = false;
+
+    if (isArgAttrs) {
 
         for (auto & attr : *args[0]->attrs()) {
             std::string_view n(state.symbols[attr.name]);
@@ -428,8 +442,10 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
                 url = state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the url we should fetch");
             else if (n == "sha256")
                 expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the sha256 of the content we should fetch"), HashAlgorithm::SHA256);
-            else if (n == "name")
+            else if (n == "name") {
+                nameAttrPassed = true;
                 name = state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the name of the content we should fetch");
+            }
             else
                 state.error<EvalError>("unsupported argument '%s' to '%s'", n, who)
                 .atPos(pos).debugThrow();
@@ -442,14 +458,27 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
         url = state.forceStringNoCtx(*args[0], pos, "while evaluating the url we should fetch");
 
     if (who == "fetchTarball")
-        url = evalSettings.resolvePseudoUrl(*url);
+        url = state.settings.resolvePseudoUrl(*url);
 
     state.checkURI(*url);
 
     if (name == "")
         name = baseNameOf(*url);
 
-    if (evalSettings.pureEval && !expectedHash)
+    try {
+        checkName(name);
+    } catch (BadStorePathName & e) {
+        auto resolution =
+            nameAttrPassed ? HintFmt("Please change the value for the 'name' attribute passed to '%s', so that it can create a valid store path.", who) :
+            isArgAttrs ? HintFmt("Please add a valid 'name' attribute to the argument for '%s', so that it can create a valid store path.", who) :
+            HintFmt("Please pass an attribute set with 'url' and 'name' attributes to '%s',  so that it can create a valid store path.", who);
+
+        state.error<EvalError>(
+            std::string("invalid store path name when fetching URL '%s': %s. %s"), *url, Uncolored(e.message()), Uncolored(resolution.str()))
+        .atPos(pos).debugThrow();
+    }
+
+    if (state.settings.pureEval && !expectedHash)
         state.error<EvalError>("in pure evaluation mode, '%s' requires a 'sha256' argument", who).atPos(pos).debugThrow();
 
     // early exit if pinned and already in the store
@@ -457,7 +486,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
         auto expectedPath = state.store->makeFixedOutputPath(
             name,
             FixedOutputInfo {
-                .method = unpack ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat,
+                .method = unpack ? FileIngestionMethod::NixArchive : FileIngestionMethod::Flat,
                 .hash = *expectedHash,
                 .references = {}
             });
@@ -599,6 +628,8 @@ static RegisterPrimOp primop_fetchGit({
 
         [Git reference]: https://git-scm.com/book/en/v2/Git-Internals-Git-References
 
+        This option has no effect once `shallow` cloning is enabled.
+
         By default, the `ref` value is prefixed with `refs/heads/`.
         As of 2.3.0, Nix will not prefix `refs/heads/` if `ref` starts with `refs/`.
 
@@ -616,13 +647,15 @@ static RegisterPrimOp primop_fetchGit({
       - `shallow` (default: `false`)
 
         Make a shallow clone when fetching the Git tree.
-
+        When this is enabled, the options `ref` and `allRefs` have no effect anymore.
       - `allRefs`
 
-        Whether to fetch all references of the repository.
-        With this argument being true, it's possible to load a `rev` from *any* `ref`
+        Whether to fetch all references (eg. branches and tags) of the repository.
+        With this argument being true, it's possible to load a `rev` from *any* `ref`.
         (by default only `rev`s from the specified `ref` are supported).
 
+        This option has no effect once `shallow` cloning is enabled.
+
       - `verifyCommit` (default: `true` if `publicKey` or `publicKeys` are provided, otherwise `false`)
 
         Whether to check `rev` for a signature matching `publicKey` or `publicKeys`.
diff --git a/src/libexpr/primops/fromTOML.cc b/src/libexpr/primops/fromTOML.cc
index 9bee8ca3864..6c7d303e85a 100644
--- a/src/libexpr/primops/fromTOML.cc
+++ b/src/libexpr/primops/fromTOML.cc
@@ -1,9 +1,8 @@
 #include "primops.hh"
 #include "eval-inline.hh"
 
-#include "../../toml11/toml.hpp"
-
 #include <sstream>
+#include <toml.hpp>
 
 namespace nix {
 
diff --git a/src/libexpr/primops/meson.build b/src/libexpr/primops/meson.build
new file mode 100644
index 00000000000..f910fe23768
--- /dev/null
+++ b/src/libexpr/primops/meson.build
@@ -0,0 +1,12 @@
+generated_headers += gen_header.process(
+  'derivation.nix',
+  preserve_path_from: meson.project_source_root(),
+)
+
+sources += files(
+  'context.cc',
+  'fetchClosure.cc',
+  'fetchMercurial.cc',
+  'fetchTree.cc',
+  'fromTOML.cc',
+)
diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index 7799a0bbebf..2f377e5886e 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -1,5 +1,6 @@
 #include <limits>
 #include <unordered_set>
+#include <sstream>
 
 #include "print.hh"
 #include "ansicolor.hh"
@@ -162,8 +163,8 @@ class Printer
     EvalState & state;
     PrintOptions options;
     std::optional<ValuesSeen> seen;
-    size_t attrsPrinted = 0;
-    size_t listItemsPrinted = 0;
+    size_t totalAttrsPrinted = 0;
+    size_t totalListItemsPrinted = 0;
     std::string indent;
 
     void increaseIndent()
@@ -271,16 +272,27 @@ class Printer
 
     void printDerivation(Value & v)
     {
-        NixStringContext context;
-        std::string storePath;
-        if (auto i = v.attrs()->get(state.sDrvPath))
-            storePath = state.store->printStorePath(state.coerceToStorePath(i->pos, *i->value, context, "while evaluating the drvPath of a derivation"));
+        std::optional<StorePath> storePath;
+        if (auto i = v.attrs()->get(state.sDrvPath)) {
+            NixStringContext context;
+            storePath = state.coerceToStorePath(i->pos, *i->value, context, "while evaluating the drvPath of a derivation");
+        }
+
+        /* This unfortunately breaks printing nested values because of
+           how the pretty printer is used (when pretting printing and warning
+           to same terminal / std stream). */
+#if 0
+        if (storePath && !storePath->isDerivation())
+            warn(
+                "drvPath attribute '%s' is not a valid store path to a derivation, this value not work properly",
+                state.store->printStorePath(*storePath));
+#endif
 
         if (options.ansiColors)
             output << ANSI_GREEN;
         output << "«derivation";
-        if (!storePath.empty()) {
-            output << " " << storePath;
+        if (storePath) {
+            output << " " << state.store->printStorePath(*storePath);
         }
         output << "»";
         if (options.ansiColors)
@@ -333,11 +345,13 @@ class Printer
 
             auto prettyPrint = shouldPrettyPrintAttrs(sorted);
 
+            size_t currentAttrsPrinted = 0;
+
             for (auto & i : sorted) {
                 printSpace(prettyPrint);
 
-                if (attrsPrinted >= options.maxAttrs) {
-                    printElided(sorted.size() - attrsPrinted, "attribute", "attributes");
+                if (totalAttrsPrinted >= options.maxAttrs) {
+                    printElided(sorted.size() - currentAttrsPrinted, "attribute", "attributes");
                     break;
                 }
 
@@ -345,7 +359,8 @@ class Printer
                 output << " = ";
                 print(*i.second, depth + 1);
                 output << ";";
-                attrsPrinted++;
+                totalAttrsPrinted++;
+                currentAttrsPrinted++;
             }
 
             decreaseIndent();
@@ -390,11 +405,14 @@ class Printer
             output << "[";
             auto listItems = v.listItems();
             auto prettyPrint = shouldPrettyPrintList(listItems);
+
+            size_t currentListItemsPrinted = 0;
+
             for (auto elem : listItems) {
                 printSpace(prettyPrint);
 
-                if (listItemsPrinted >= options.maxListItems) {
-                    printElided(listItems.size() - listItemsPrinted, "item", "items");
+                if (totalListItemsPrinted >= options.maxListItems) {
+                    printElided(listItems.size() - currentListItemsPrinted, "item", "items");
                     break;
                 }
 
@@ -403,7 +421,8 @@ class Printer
                 } else {
                     printNullptr();
                 }
-                listItemsPrinted++;
+                totalListItemsPrinted++;
+                currentListItemsPrinted++;
             }
 
             decreaseIndent();
@@ -576,8 +595,8 @@ class Printer
 
     void print(Value & v)
     {
-        attrsPrinted = 0;
-        listItemsPrinted = 0;
+        totalAttrsPrinted = 0;
+        totalListItemsPrinted = 0;
         indent.clear();
 
         if (options.trackRepeated) {
diff --git a/src/libexpr/search-path.cc b/src/libexpr/search-path.cc
index e2c3e050ae0..657744e745c 100644
--- a/src/libexpr/search-path.cc
+++ b/src/libexpr/search-path.cc
@@ -2,7 +2,7 @@
 
 namespace nix {
 
-std::optional<std::string_view> SearchPath::Prefix::suffixIfPotentialMatch(
+std::optional<std::string_view> LookupPath::Prefix::suffixIfPotentialMatch(
     std::string_view path) const
 {
     auto n = s.size();
@@ -27,11 +27,11 @@ std::optional<std::string_view> SearchPath::Prefix::suffixIfPotentialMatch(
 }
 
 
-SearchPath::Elem SearchPath::Elem::parse(std::string_view rawElem)
+LookupPath::Elem LookupPath::Elem::parse(std::string_view rawElem)
 {
     size_t pos = rawElem.find('=');
 
-    return SearchPath::Elem {
+    return LookupPath::Elem {
         .prefix = Prefix {
             .s = pos == std::string::npos
                 ? std::string { "" }
@@ -44,11 +44,11 @@ SearchPath::Elem SearchPath::Elem::parse(std::string_view rawElem)
 }
 
 
-SearchPath SearchPath::parse(const Strings & rawElems)
+LookupPath LookupPath::parse(const Strings & rawElems)
 {
-    SearchPath res;
+    LookupPath res;
     for (auto & rawElem : rawElems)
-        res.elements.emplace_back(SearchPath::Elem::parse(rawElem));
+        res.elements.emplace_back(LookupPath::Elem::parse(rawElem));
     return res;
 }
 
diff --git a/src/libexpr/search-path.hh b/src/libexpr/search-path.hh
index 231752ea66c..acd84363853 100644
--- a/src/libexpr/search-path.hh
+++ b/src/libexpr/search-path.hh
@@ -8,17 +8,14 @@
 
 namespace nix {
 
-// Do not want the windows macro (alias to `SearchPathA`)
-#undef SearchPath
-
 /**
  * A "search path" is a list of ways look for something, used with
  * `builtins.findFile` and `< >` lookup expressions.
  */
-struct SearchPath
+struct LookupPath
 {
     /**
-     * A single element of a `SearchPath`.
+     * A single element of a `LookupPath`.
      *
      * Each element is tried in succession when looking up a path. The first
      * element to completely match wins.
@@ -26,16 +23,16 @@ struct SearchPath
     struct Elem;
 
     /**
-     * The first part of a `SearchPath::Elem` pair.
+     * The first part of a `LookupPath::Elem` pair.
      *
      * Called a "prefix" because it takes the form of a prefix of a file
      * path (first `n` path components). When looking up a path, to use
-     * a `SearchPath::Elem`, its `Prefix` must match the path.
+     * a `LookupPath::Elem`, its `Prefix` must match the path.
      */
     struct Prefix;
 
     /**
-     * The second part of a `SearchPath::Elem` pair.
+     * The second part of a `LookupPath::Elem` pair.
      *
      * It is either a path or a URL (with certain restrictions / extra
      * structure).
@@ -43,7 +40,7 @@ struct SearchPath
      * If the prefix of the path we are looking up matches, we then
      * check if the rest of the path points to something that exists
      * within the directory denoted by this. If so, the
-     * `SearchPath::Elem` as a whole matches, and that *something* being
+     * `LookupPath::Elem` as a whole matches, and that *something* being
      * pointed to by the rest of the path we are looking up is the
      * result.
      */
@@ -54,24 +51,24 @@ struct SearchPath
      * when looking up. (The actual lookup entry point is in `EvalState`
      * not in this class.)
      */
-    std::list<SearchPath::Elem> elements;
+    std::list<LookupPath::Elem> elements;
 
     /**
-     * Parse a string into a `SearchPath`
+     * Parse a string into a `LookupPath`
      */
-    static SearchPath parse(const Strings & rawElems);
+    static LookupPath parse(const Strings & rawElems);
 };
 
-struct SearchPath::Prefix
+struct LookupPath::Prefix
 {
     /**
      * Underlying string
      *
-     * @todo Should we normalize this when constructing a `SearchPath::Prefix`?
+     * @todo Should we normalize this when constructing a `LookupPath::Prefix`?
      */
     std::string s;
 
-    GENERATE_CMP(SearchPath::Prefix, me->s);
+    GENERATE_CMP(LookupPath::Prefix, me->s);
 
     /**
      * If the path possibly matches this search path element, return the
@@ -82,7 +79,7 @@ struct SearchPath::Prefix
     std::optional<std::string_view> suffixIfPotentialMatch(std::string_view path) const;
 };
 
-struct SearchPath::Path
+struct LookupPath::Path
 {
     /**
      * The location of a search path item, as a path or URL.
@@ -91,21 +88,21 @@ struct SearchPath::Path
      */
     std::string s;
 
-    GENERATE_CMP(SearchPath::Path, me->s);
+    GENERATE_CMP(LookupPath::Path, me->s);
 };
 
-struct SearchPath::Elem
+struct LookupPath::Elem
 {
 
     Prefix prefix;
     Path path;
 
-    GENERATE_CMP(SearchPath::Elem, me->prefix, me->path);
+    GENERATE_CMP(LookupPath::Elem, me->prefix, me->path);
 
     /**
-     * Parse a string into a `SearchPath::Elem`
+     * Parse a string into a `LookupPath::Elem`
      */
-    static SearchPath::Elem parse(std::string_view rawElem);
+    static LookupPath::Elem parse(std::string_view rawElem);
 };
 
 }
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index 7ed3fa5a9ff..208cab21d60 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -7,7 +7,6 @@
 
 #include "symbol-table.hh"
 #include "value/context.hh"
-#include "input-accessor.hh"
 #include "source-path.hh"
 #include "print-options.hh"
 
@@ -23,6 +22,7 @@ class BindingsBuilder;
 
 
 typedef enum {
+    tUninitialized = 0,
     tInt = 1,
     tBool,
     tString,
@@ -166,7 +166,7 @@ public:
 struct Value
 {
 private:
-    InternalType internalType;
+    InternalType internalType = tUninitialized;
 
     friend std::string showType(const Value & v);
 
@@ -216,7 +216,7 @@ public:
     };
 
     struct Path {
-        InputAccessor * accessor;
+        SourceAccessor * accessor;
         const char * path;
     };
 
@@ -270,6 +270,7 @@ public:
     inline ValueType type(bool invalidIsThunk = false) const
     {
         switch (internalType) {
+            case tUninitialized: break;
             case tInt: return nInt;
             case tBool: return nBool;
             case tString: return nString;
@@ -294,6 +295,16 @@ public:
         internalType = newType;
     }
 
+    /**
+     * A value becomes valid when it is initialized. We don't use this
+     * in the evaluator; only in the bindings, where the slight extra
+     * cost is warranted because of inexperienced callers.
+     */
+    inline bool isValid() const
+    {
+        return internalType != tUninitialized;
+    }
+
     inline void mkInt(NixInt n)
     {
         finishValue(tInt, { .integer = n });
@@ -323,7 +334,7 @@ public:
     void mkPath(const SourcePath & path);
     void mkPath(std::string_view path);
 
-    inline void mkPath(InputAccessor * accessor, const char * path)
+    inline void mkPath(SourceAccessor * accessor, const char * path)
     {
         finishValue(tPath, { .path = { .accessor = accessor, .path = path } });
     }
@@ -438,7 +449,7 @@ public:
         return std::string_view(payload.string.c_str);
     }
 
-    const char * const c_str() const
+    const char * c_str() const
     {
         assert(internalType == tString);
         return payload.string.c_str;
diff --git a/src/libfetchers/.version b/src/libfetchers/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libfetchers/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libfetchers/build-utils-meson b/src/libfetchers/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libfetchers/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libfetchers/cache.cc b/src/libfetchers/cache.cc
index e071b4717b4..7019b0325d7 100644
--- a/src/libfetchers/cache.cc
+++ b/src/libfetchers/cache.cc
@@ -11,12 +11,11 @@ namespace nix::fetchers {
 static const char * schema = R"sql(
 
 create table if not exists Cache (
-    input     text not null,
-    info      text not null,
-    path      text not null,
-    immutable integer not null,
+    domain    text not null,
+    key       text not null,
+    value     text not null,
     timestamp integer not null,
-    primary key (input)
+    primary key (domain, key)
 );
 )sql";
 
@@ -28,7 +27,7 @@ struct CacheImpl : Cache
     struct State
     {
         SQLite db;
-        SQLiteStmt add, lookup;
+        SQLiteStmt upsert, lookup;
     };
 
     Sync<State> _state;
@@ -37,136 +36,129 @@ struct CacheImpl : Cache
     {
         auto state(_state.lock());
 
-        auto dbPath = getCacheDir() + "/nix/fetcher-cache-v1.sqlite";
+        auto dbPath = getCacheDir() + "/nix/fetcher-cache-v2.sqlite";
         createDirs(dirOf(dbPath));
 
         state->db = SQLite(dbPath);
         state->db.isCache();
         state->db.exec(schema);
 
-        state->add.create(state->db,
-            "insert or replace into Cache(input, info, path, immutable, timestamp) values (?, ?, ?, ?, ?)");
+        state->upsert.create(state->db,
+            "insert or replace into Cache(domain, key, value, timestamp) values (?, ?, ?, ?)");
 
         state->lookup.create(state->db,
-            "select info, path, immutable, timestamp from Cache where input = ?");
+            "select value, timestamp from Cache where domain = ? and key = ?");
     }
 
     void upsert(
-        const Attrs & inAttrs,
-        const Attrs & infoAttrs) override
+        const Key & key,
+        const Attrs & value) override
     {
-        _state.lock()->add.use()
-            (attrsToJSON(inAttrs).dump())
-            (attrsToJSON(infoAttrs).dump())
-            ("") // no path
-            (false)
+        _state.lock()->upsert.use()
+            (key.first)
+            (attrsToJSON(key.second).dump())
+            (attrsToJSON(value).dump())
             (time(0)).exec();
     }
 
-    std::optional<Attrs> lookup(const Attrs & inAttrs) override
+    std::optional<Attrs> lookup(
+        const Key & key) override
     {
-        if (auto res = lookupExpired(inAttrs))
-            return std::move(res->infoAttrs);
+        if (auto res = lookupExpired(key))
+            return std::move(res->value);
         return {};
     }
 
-    std::optional<Attrs> lookupWithTTL(const Attrs & inAttrs) override
+    std::optional<Attrs> lookupWithTTL(
+        const Key & key) override
     {
-        if (auto res = lookupExpired(inAttrs)) {
+        if (auto res = lookupExpired(key)) {
             if (!res->expired)
-                return std::move(res->infoAttrs);
-            debug("ignoring expired cache entry '%s'",
-                attrsToJSON(inAttrs).dump());
+                return std::move(res->value);
+            debug("ignoring expired cache entry '%s:%s'",
+                key.first, attrsToJSON(key.second).dump());
         }
         return {};
     }
 
-    std::optional<Result2> lookupExpired(const Attrs & inAttrs) override
+    std::optional<Result> lookupExpired(
+        const Key & key) override
     {
         auto state(_state.lock());
 
-        auto inAttrsJSON = attrsToJSON(inAttrs).dump();
+        auto keyJSON = attrsToJSON(key.second).dump();
 
-        auto stmt(state->lookup.use()(inAttrsJSON));
+        auto stmt(state->lookup.use()(key.first)(keyJSON));
         if (!stmt.next()) {
-            debug("did not find cache entry for '%s'", inAttrsJSON);
+            debug("did not find cache entry for '%s:%s'", key.first, keyJSON);
             return {};
         }
 
-        auto infoJSON = stmt.getStr(0);
-        auto locked = stmt.getInt(2) != 0;
-        auto timestamp = stmt.getInt(3);
+        auto valueJSON = stmt.getStr(0);
+        auto timestamp = stmt.getInt(1);
 
-        debug("using cache entry '%s' -> '%s'", inAttrsJSON, infoJSON);
+        debug("using cache entry '%s:%s' -> '%s'", key.first, keyJSON, valueJSON);
 
-        return Result2 {
-            .expired = !locked && (settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0)),
-            .infoAttrs = jsonToAttrs(nlohmann::json::parse(infoJSON)),
+        return Result {
+            .expired = settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0),
+            .value = jsonToAttrs(nlohmann::json::parse(valueJSON)),
         };
     }
 
-    void add(
+    void upsert(
+        Key key,
         Store & store,
-        const Attrs & inAttrs,
-        const Attrs & infoAttrs,
-        const StorePath & storePath,
-        bool locked) override
+        Attrs value,
+        const StorePath & storePath) override
     {
-        _state.lock()->add.use()
-            (attrsToJSON(inAttrs).dump())
-            (attrsToJSON(infoAttrs).dump())
-            (store.printStorePath(storePath))
-            (locked)
-            (time(0)).exec();
-    }
+        /* Add the store prefix to the cache key to handle multiple
+           store prefixes. */
+        key.second.insert_or_assign("store", store.storeDir);
 
-    std::optional<std::pair<Attrs, StorePath>> lookup(
-        Store & store,
-        const Attrs & inAttrs) override
-    {
-        if (auto res = lookupExpired(store, inAttrs)) {
-            if (!res->expired)
-                return std::make_pair(std::move(res->infoAttrs), std::move(res->storePath));
-            debug("ignoring expired cache entry '%s'",
-                attrsToJSON(inAttrs).dump());
-        }
-        return {};
+        value.insert_or_assign("storePath", (std::string) storePath.to_string());
+
+        upsert(key, value);
     }
 
-    std::optional<Result> lookupExpired(
-        Store & store,
-        const Attrs & inAttrs) override
+    std::optional<ResultWithStorePath> lookupStorePath(
+        Key key,
+        Store & store) override
     {
-        auto state(_state.lock());
+        key.second.insert_or_assign("store", store.storeDir);
 
-        auto inAttrsJSON = attrsToJSON(inAttrs).dump();
+        auto res = lookupExpired(key);
+        if (!res) return std::nullopt;
 
-        auto stmt(state->lookup.use()(inAttrsJSON));
-        if (!stmt.next()) {
-            debug("did not find cache entry for '%s'", inAttrsJSON);
-            return {};
-        }
+        auto storePathS = getStrAttr(res->value, "storePath");
+        res->value.erase("storePath");
 
-        auto infoJSON = stmt.getStr(0);
-        auto storePath = store.parseStorePath(stmt.getStr(1));
-        auto locked = stmt.getInt(2) != 0;
-        auto timestamp = stmt.getInt(3);
+        ResultWithStorePath res2(*res, StorePath(storePathS));
 
-        store.addTempRoot(storePath);
-        if (!store.isValidPath(storePath)) {
+        store.addTempRoot(res2.storePath);
+        if (!store.isValidPath(res2.storePath)) {
             // FIXME: we could try to substitute 'storePath'.
-            debug("ignoring disappeared cache entry '%s'", inAttrsJSON);
-            return {};
+            debug("ignoring disappeared cache entry '%s:%s' -> '%s'",
+                key.first,
+                attrsToJSON(key.second).dump(),
+                store.printStorePath(res2.storePath));
+            return std::nullopt;
         }
 
-        debug("using cache entry '%s' -> '%s', '%s'",
-            inAttrsJSON, infoJSON, store.printStorePath(storePath));
+        debug("using cache entry '%s:%s' -> '%s', '%s'",
+            key.first,
+            attrsToJSON(key.second).dump(),
+            attrsToJSON(res2.value).dump(),
+            store.printStorePath(res2.storePath));
 
-        return Result {
-            .expired = !locked && (settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0)),
-            .infoAttrs = jsonToAttrs(nlohmann::json::parse(infoJSON)),
-            .storePath = std::move(storePath)
-        };
+        return res2;
+    }
+
+    std::optional<ResultWithStorePath> lookupStorePathWithTTL(
+        Key key,
+        Store & store) override
+    {
+        auto res = lookupStorePath(std::move(key), store);
+        return res && !res->expired ? res : std::nullopt;
     }
 };
 
diff --git a/src/libfetchers/cache.hh b/src/libfetchers/cache.hh
index 791d77025aa..4d834fe0ca3 100644
--- a/src/libfetchers/cache.hh
+++ b/src/libfetchers/cache.hh
@@ -15,61 +15,80 @@ struct Cache
     virtual ~Cache() { }
 
     /**
-     * Add a value to the cache. The cache is an arbitrary mapping of
-     * Attrs to Attrs.
+     * A domain is a partition of the key/value cache for a particular
+     * purpose, e.g. git revision to revcount.
+     */
+    using Domain = std::string_view;
+
+    /**
+     * A cache key is a domain and an arbitrary set of attributes.
+     */
+    using Key = std::pair<Domain, Attrs>;
+
+    /**
+     * Add a key/value pair to the cache.
      */
     virtual void upsert(
-        const Attrs & inAttrs,
-        const Attrs & infoAttrs) = 0;
+        const Key & key,
+        const Attrs & value) = 0;
 
     /**
      * Look up a key with infinite TTL.
      */
     virtual std::optional<Attrs> lookup(
-        const Attrs & inAttrs) = 0;
+        const Key & key) = 0;
 
     /**
      * Look up a key. Return nothing if its TTL has exceeded
      * `settings.tarballTTL`.
      */
     virtual std::optional<Attrs> lookupWithTTL(
-        const Attrs & inAttrs) = 0;
+        const Key & key) = 0;
 
-    struct Result2
+    struct Result
     {
         bool expired = false;
-        Attrs infoAttrs;
+        Attrs value;
     };
 
     /**
      * Look up a key. Return a bool denoting whether its TTL has
      * exceeded `settings.tarballTTL`.
      */
-    virtual std::optional<Result2> lookupExpired(
-        const Attrs & inAttrs) = 0;
-
-    /* Old cache for things that have a store path. */
-    virtual void add(
-        Store & store,
-        const Attrs & inAttrs,
-        const Attrs & infoAttrs,
-        const StorePath & storePath,
-        bool locked) = 0;
+    virtual std::optional<Result> lookupExpired(
+        const Key & key) = 0;
 
-    virtual std::optional<std::pair<Attrs, StorePath>> lookup(
+    /**
+     * Insert a cache entry that has a store path associated with
+     * it. Such cache entries are always considered stale if the
+     * associated store path is invalid.
+     */
+    virtual void upsert(
+        Key key,
         Store & store,
-        const Attrs & inAttrs) = 0;
+        Attrs value,
+        const StorePath & storePath) = 0;
 
-    struct Result
+    struct ResultWithStorePath : Result
     {
-        bool expired = false;
-        Attrs infoAttrs;
         StorePath storePath;
     };
 
-    virtual std::optional<Result> lookupExpired(
-        Store & store,
-        const Attrs & inAttrs) = 0;
+    /**
+     * Look up a store path in the cache. The returned store path will
+     * be valid, but it may be expired.
+     */
+    virtual std::optional<ResultWithStorePath> lookupStorePath(
+        Key key,
+        Store & store) = 0;
+
+    /**
+     * Look up a store path in the cache. Return nothing if its TTL
+     * has exceeded `settings.tarballTTL`.
+     */
+    virtual std::optional<ResultWithStorePath> lookupStorePathWithTTL(
+        Key key,
+        Store & store) = 0;
 };
 
 ref<Cache> getCache();
diff --git a/src/libfetchers/fetch-settings.cc b/src/libfetchers/fetch-settings.cc
index e7d5244dc2c..21c42567cb5 100644
--- a/src/libfetchers/fetch-settings.cc
+++ b/src/libfetchers/fetch-settings.cc
@@ -1,4 +1,5 @@
 #include "fetch-settings.hh"
+#include "config-global.hh"
 
 namespace nix {
 
diff --git a/src/libfetchers/fetch-settings.hh b/src/libfetchers/fetch-settings.hh
index d085f0d8277..629967697da 100644
--- a/src/libfetchers/fetch-settings.hh
+++ b/src/libfetchers/fetch-settings.hh
@@ -70,30 +70,6 @@ struct FetchSettings : public Config
     Setting<bool> warnDirty{this, true, "warn-dirty",
         "Whether to warn about dirty Git/Mercurial trees."};
 
-    Setting<std::string> flakeRegistry{this, "https://channels.nixos.org/flake-registry.json", "flake-registry",
-        R"(
-          Path or URI of the global flake registry.
-
-          When empty, disables the global flake registry.
-        )",
-        {}, true, Xp::Flakes};
-
-    Setting<bool> useRegistries{this, true, "use-registries",
-        "Whether to use flake registries to resolve flake references.",
-        {}, true, Xp::Flakes};
-
-    Setting<bool> acceptFlakeConfig{this, false, "accept-flake-config",
-        "Whether to accept nix configuration from a flake without prompting.",
-        {}, true, Xp::Flakes};
-
-    Setting<std::string> commitLockFileSummary{
-        this, "", "commit-lockfile-summary",
-        R"(
-          The commit summary to use when committing changed flake lock files. If
-          empty, the summary is generated based on the action performed.
-        )",
-        {}, true, Xp::Flakes};
-
     Setting<bool> trustTarballsFromGitForges{
         this, true, "trust-tarballs-from-git-forges",
         R"(
@@ -108,7 +84,6 @@ struct FetchSettings : public Config
           `narHash` attribute is specified,
           e.g. `github:NixOS/patchelf/7c2f768bf9601268a4e71c2ebe91e2011918a70f?narHash=sha256-PPXqKY2hJng4DBVE0I4xshv/vGLUskL7jl53roB8UdU%3D`.
         )"};
-
 };
 
 // FIXME: don't use a global variable.
diff --git a/src/libfetchers/fetch-to-store.cc b/src/libfetchers/fetch-to-store.cc
index 398286065e6..65aa72a6c36 100644
--- a/src/libfetchers/fetch-to-store.cc
+++ b/src/libfetchers/fetch-to-store.cc
@@ -14,22 +14,20 @@ StorePath fetchToStore(
     RepairFlag repair)
 {
     // FIXME: add an optimisation for the case where the accessor is
-    // an FSInputAccessor pointing to a store path.
+    // a `PosixSourceAccessor` pointing to a store path.
 
-    std::optional<fetchers::Attrs> cacheKey;
+    std::optional<fetchers::Cache::Key> cacheKey;
 
     if (!filter && path.accessor->fingerprint) {
-        cacheKey = fetchers::Attrs{
-            {"_what", "fetchToStore"},
-            {"store", store.storeDir},
+        cacheKey = fetchers::Cache::Key{"fetchToStore", {
             {"name", std::string{name}},
             {"fingerprint", *path.accessor->fingerprint},
             {"method", std::string{method.render()}},
             {"path", path.path.abs()}
-        };
-        if (auto res = fetchers::getCache()->lookup(store, *cacheKey)) {
+        }};
+        if (auto res = fetchers::getCache()->lookupStorePath(*cacheKey, store)) {
             debug("store path cache hit for '%s'", path);
-            return res->second;
+            return res->storePath;
         }
     } else
         debug("source path '%s' is uncacheable", path);
@@ -42,15 +40,14 @@ StorePath fetchToStore(
     auto storePath =
         mode == FetchMode::DryRun
         ? store.computeStorePath(
-            name, *path.accessor, path.path, method, HashAlgorithm::SHA256, {}, filter2).first
+            name, path, method, HashAlgorithm::SHA256, {}, filter2).first
         : store.addToStore(
-            name, *path.accessor, path.path, method, HashAlgorithm::SHA256, {}, filter2, repair);
+            name, path, method, HashAlgorithm::SHA256, {}, filter2, repair);
 
     if (cacheKey && mode == FetchMode::Copy)
-        fetchers::getCache()->add(store, *cacheKey, {}, storePath, true);
+        fetchers::getCache()->upsert(*cacheKey, store, {}, storePath);
 
     return storePath;
 }
 
-
 }
diff --git a/src/libfetchers/fetch-to-store.hh b/src/libfetchers/fetch-to-store.hh
index 81af1e24019..c762629f3cb 100644
--- a/src/libfetchers/fetch-to-store.hh
+++ b/src/libfetchers/fetch-to-store.hh
@@ -18,7 +18,7 @@ StorePath fetchToStore(
     const SourcePath & path,
     FetchMode mode,
     std::string_view name = "source",
-    ContentAddressMethod method = FileIngestionMethod::Recursive,
+    ContentAddressMethod method = ContentAddressMethod::Raw::NixArchive,
     PathFilter * filter = nullptr,
     RepairFlag repair = NoRepair);
 
diff --git a/src/libfetchers/fetchers.cc b/src/libfetchers/fetchers.cc
index a06d931db6c..29496067832 100644
--- a/src/libfetchers/fetchers.cc
+++ b/src/libfetchers/fetchers.cc
@@ -1,6 +1,5 @@
 #include "fetchers.hh"
 #include "store-api.hh"
-#include "input-accessor.hh"
 #include "source-path.hh"
 #include "fetch-to-store.hh"
 #include "json-utils.hh"
@@ -238,7 +237,7 @@ void InputScheme::checkLocks(const Input & specified, const Input & final) const
     }
 }
 
-std::pair<ref<InputAccessor>, Input> Input::getAccessor(ref<Store> store) const
+std::pair<ref<SourceAccessor>, Input> Input::getAccessor(ref<Store> store) const
 {
     try {
         auto [accessor, final] = getAccessorUnchecked(store);
@@ -252,7 +251,7 @@ std::pair<ref<InputAccessor>, Input> Input::getAccessor(ref<Store> store) const
     }
 }
 
-std::pair<ref<InputAccessor>, Input> Input::getAccessorUnchecked(ref<Store> store) const
+std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(ref<Store> store) const
 {
     // FIXME: cache the accessor
 
@@ -261,6 +260,7 @@ std::pair<ref<InputAccessor>, Input> Input::getAccessorUnchecked(ref<Store> stor
 
     auto [accessor, final] = scheme->getAccessor(store, *this);
 
+    assert(!accessor->fingerprint);
     accessor->fingerprint = scheme->getFingerprint(store, final);
 
     return {accessor, std::move(final)};
@@ -306,7 +306,7 @@ StorePath Input::computeStorePath(Store & store) const
     if (!narHash)
         throw Error("cannot compute store path for unlocked input '%s'", to_string());
     return store.makeFixedOutputPath(getName(), FixedOutputInfo {
-        .method = FileIngestionMethod::Recursive,
+        .method = FileIngestionMethod::NixArchive,
         .hash = *narHash,
         .references = {},
     });
@@ -419,9 +419,13 @@ namespace nlohmann {
 using namespace nix;
 
 fetchers::PublicKey adl_serializer<fetchers::PublicKey>::from_json(const json & json) {
-    auto type = optionalValueAt(json, "type").value_or("ssh-ed25519");
-    auto key = valueAt(json, "key");
-    return fetchers::PublicKey { getString(type), getString(key) };
+    fetchers::PublicKey res = { };
+    if (auto type = optionalValueAt(json, "type"))
+        res.type = getString(*type);
+
+    res.key = getString(valueAt(json, "key"));
+
+    return res;
 }
 
 void adl_serializer<fetchers::PublicKey>::to_json(json & json, fetchers::PublicKey p) {
diff --git a/src/libfetchers/fetchers.hh b/src/libfetchers/fetchers.hh
index bb21c68cc83..551be9a1f9a 100644
--- a/src/libfetchers/fetchers.hh
+++ b/src/libfetchers/fetchers.hh
@@ -11,7 +11,7 @@
 #include <memory>
 #include <nlohmann/json_fwd.hpp>
 
-namespace nix { class Store; class StorePath; struct InputAccessor; }
+namespace nix { class Store; class StorePath; struct SourceAccessor; }
 
 namespace nix::fetchers {
 
@@ -84,15 +84,15 @@ public:
     std::pair<StorePath, Input> fetchToStore(ref<Store> store) const;
 
     /**
-     * Return an InputAccessor that allows access to files in the
+     * Return a `SourceAccessor` that allows access to files in the
      * input without copying it to the store. Also return a possibly
      * unlocked input.
      */
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store) const;
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store) const;
 
 private:
 
-    std::pair<ref<InputAccessor>, Input> getAccessorUnchecked(ref<Store> store) const;
+    std::pair<ref<SourceAccessor>, Input> getAccessorUnchecked(ref<Store> store) const;
 
 public:
 
@@ -185,7 +185,7 @@ struct InputScheme
         std::string_view contents,
         std::optional<std::string> commitMsg) const;
 
-    virtual std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const = 0;
+    virtual std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const = 0;
 
     /**
      * Is this `InputScheme` part of an experimental feature?
@@ -230,6 +230,8 @@ struct PublicKey
 {
     std::string type = "ssh-ed25519";
     std::string key;
+
+    auto operator <=>(const PublicKey &) const = default;
 };
 
 std::string publicKeys_to_string(const std::vector<PublicKey>&);
diff --git a/src/libfetchers/filtering-input-accessor.cc b/src/libfetchers/filtering-source-accessor.cc
similarity index 55%
rename from src/libfetchers/filtering-input-accessor.cc
rename to src/libfetchers/filtering-source-accessor.cc
index e0cbfd905c7..d4557b6d4dd 100644
--- a/src/libfetchers/filtering-input-accessor.cc
+++ b/src/libfetchers/filtering-source-accessor.cc
@@ -1,25 +1,31 @@
-#include "filtering-input-accessor.hh"
+#include "filtering-source-accessor.hh"
 
 namespace nix {
 
-std::string FilteringInputAccessor::readFile(const CanonPath & path)
+std::optional<std::filesystem::path> FilteringSourceAccessor::getPhysicalPath(const CanonPath & path)
+{
+    checkAccess(path);
+    return next->getPhysicalPath(prefix / path);
+}
+
+std::string FilteringSourceAccessor::readFile(const CanonPath & path)
 {
     checkAccess(path);
     return next->readFile(prefix / path);
 }
 
-bool FilteringInputAccessor::pathExists(const CanonPath & path)
+bool FilteringSourceAccessor::pathExists(const CanonPath & path)
 {
     return isAllowed(path) && next->pathExists(prefix / path);
 }
 
-std::optional<InputAccessor::Stat> FilteringInputAccessor::maybeLstat(const CanonPath & path)
+std::optional<SourceAccessor::Stat> FilteringSourceAccessor::maybeLstat(const CanonPath & path)
 {
     checkAccess(path);
     return next->maybeLstat(prefix / path);
 }
 
-InputAccessor::DirEntries FilteringInputAccessor::readDirectory(const CanonPath & path)
+SourceAccessor::DirEntries FilteringSourceAccessor::readDirectory(const CanonPath & path)
 {
     checkAccess(path);
     DirEntries entries;
@@ -30,18 +36,18 @@ InputAccessor::DirEntries FilteringInputAccessor::readDirectory(const CanonPath
     return entries;
 }
 
-std::string FilteringInputAccessor::readLink(const CanonPath & path)
+std::string FilteringSourceAccessor::readLink(const CanonPath & path)
 {
     checkAccess(path);
     return next->readLink(prefix / path);
 }
 
-std::string FilteringInputAccessor::showPath(const CanonPath & path)
+std::string FilteringSourceAccessor::showPath(const CanonPath & path)
 {
     return displayPrefix + next->showPath(prefix / path) + displaySuffix;
 }
 
-void FilteringInputAccessor::checkAccess(const CanonPath & path)
+void FilteringSourceAccessor::checkAccess(const CanonPath & path)
 {
     if (!isAllowed(path))
         throw makeNotAllowedError
@@ -49,15 +55,15 @@ void FilteringInputAccessor::checkAccess(const CanonPath & path)
             : RestrictedPathError("access to path '%s' is forbidden", showPath(path));
 }
 
-struct AllowListInputAccessorImpl : AllowListInputAccessor
+struct AllowListSourceAccessorImpl : AllowListSourceAccessor
 {
     std::set<CanonPath> allowedPrefixes;
 
-    AllowListInputAccessorImpl(
-        ref<InputAccessor> next,
+    AllowListSourceAccessorImpl(
+        ref<SourceAccessor> next,
         std::set<CanonPath> && allowedPrefixes,
         MakeNotAllowedError && makeNotAllowedError)
-        : AllowListInputAccessor(SourcePath(next), std::move(makeNotAllowedError))
+        : AllowListSourceAccessor(SourcePath(next), std::move(makeNotAllowedError))
         , allowedPrefixes(std::move(allowedPrefixes))
     { }
 
@@ -72,15 +78,15 @@ struct AllowListInputAccessorImpl : AllowListInputAccessor
     }
 };
 
-ref<AllowListInputAccessor> AllowListInputAccessor::create(
-    ref<InputAccessor> next,
+ref<AllowListSourceAccessor> AllowListSourceAccessor::create(
+    ref<SourceAccessor> next,
     std::set<CanonPath> && allowedPrefixes,
     MakeNotAllowedError && makeNotAllowedError)
 {
-    return make_ref<AllowListInputAccessorImpl>(next, std::move(allowedPrefixes), std::move(makeNotAllowedError));
+    return make_ref<AllowListSourceAccessorImpl>(next, std::move(allowedPrefixes), std::move(makeNotAllowedError));
 }
 
-bool CachingFilteringInputAccessor::isAllowed(const CanonPath & path)
+bool CachingFilteringSourceAccessor::isAllowed(const CanonPath & path)
 {
     auto i = cache.find(path);
     if (i != cache.end()) return i->second;
diff --git a/src/libfetchers/filtering-input-accessor.hh b/src/libfetchers/filtering-source-accessor.hh
similarity index 68%
rename from src/libfetchers/filtering-input-accessor.hh
rename to src/libfetchers/filtering-source-accessor.hh
index 133a6cee3d0..1f8d84e531e 100644
--- a/src/libfetchers/filtering-input-accessor.hh
+++ b/src/libfetchers/filtering-source-accessor.hh
@@ -1,6 +1,5 @@
 #pragma once
 
-#include "input-accessor.hh"
 #include "source-path.hh"
 
 namespace nix {
@@ -13,17 +12,17 @@ namespace nix {
 typedef std::function<RestrictedPathError(const CanonPath & path)> MakeNotAllowedError;
 
 /**
- * An abstract wrapping `InputAccessor` that performs access
+ * An abstract wrapping `SourceAccessor` that performs access
  * control. Subclasses should override `isAllowed()` to implement an
  * access control policy. The error message is customized at construction.
  */
-struct FilteringInputAccessor : InputAccessor
+struct FilteringSourceAccessor : SourceAccessor
 {
-    ref<InputAccessor> next;
+    ref<SourceAccessor> next;
     CanonPath prefix;
     MakeNotAllowedError makeNotAllowedError;
 
-    FilteringInputAccessor(const SourcePath & src, MakeNotAllowedError && makeNotAllowedError)
+    FilteringSourceAccessor(const SourcePath & src, MakeNotAllowedError && makeNotAllowedError)
         : next(src.accessor)
         , prefix(src.path)
         , makeNotAllowedError(std::move(makeNotAllowedError))
@@ -31,6 +30,8 @@ struct FilteringInputAccessor : InputAccessor
         displayPrefix.clear();
     }
 
+    std::optional<std::filesystem::path> getPhysicalPath(const CanonPath & path) override;
+
     std::string readFile(const CanonPath & path) override;
 
     bool pathExists(const CanonPath & path) override;
@@ -56,32 +57,32 @@ struct FilteringInputAccessor : InputAccessor
 };
 
 /**
- * A wrapping `InputAccessor` that checks paths against a set of
+ * A wrapping `SourceAccessor` that checks paths against a set of
  * allowed prefixes.
  */
-struct AllowListInputAccessor : public FilteringInputAccessor
+struct AllowListSourceAccessor : public FilteringSourceAccessor
 {
     /**
      * Grant access to the specified prefix.
      */
     virtual void allowPrefix(CanonPath prefix) = 0;
 
-    static ref<AllowListInputAccessor> create(
-        ref<InputAccessor> next,
+    static ref<AllowListSourceAccessor> create(
+        ref<SourceAccessor> next,
         std::set<CanonPath> && allowedPrefixes,
         MakeNotAllowedError && makeNotAllowedError);
 
-    using FilteringInputAccessor::FilteringInputAccessor;
+    using FilteringSourceAccessor::FilteringSourceAccessor;
 };
 
 /**
- * A wrapping `InputAccessor` mix-in where `isAllowed()` caches the result of virtual `isAllowedUncached()`.
+ * A wrapping `SourceAccessor` mix-in where `isAllowed()` caches the result of virtual `isAllowedUncached()`.
  */
-struct CachingFilteringInputAccessor : FilteringInputAccessor
+struct CachingFilteringSourceAccessor : FilteringSourceAccessor
 {
     std::map<CanonPath, bool> cache;
 
-    using FilteringInputAccessor::FilteringInputAccessor;
+    using FilteringSourceAccessor::FilteringSourceAccessor;
 
     bool isAllowed(const CanonPath & path) override;
 
diff --git a/src/libfetchers/fs-input-accessor.cc b/src/libfetchers/fs-input-accessor.cc
deleted file mode 100644
index 2bbe53e11bd..00000000000
--- a/src/libfetchers/fs-input-accessor.cc
+++ /dev/null
@@ -1,39 +0,0 @@
-#include "fs-input-accessor.hh"
-#include "posix-source-accessor.hh"
-#include "store-api.hh"
-
-namespace nix {
-
-struct FSInputAccessor : InputAccessor, PosixSourceAccessor
-{
-    using PosixSourceAccessor::PosixSourceAccessor;
-};
-
-ref<InputAccessor> makeFSInputAccessor()
-{
-    return make_ref<FSInputAccessor>();
-}
-
-ref<InputAccessor> makeFSInputAccessor(std::filesystem::path root)
-{
-    return make_ref<FSInputAccessor>(std::move(root));
-}
-
-ref<InputAccessor> makeStorePathAccessor(
-    ref<Store> store,
-    const StorePath & storePath)
-{
-    // FIXME: should use `store->getFSAccessor()`
-    auto root = std::filesystem::path { store->toRealPath(storePath) };
-    auto accessor = makeFSInputAccessor(root);
-    accessor->setPathDisplay(root.string());
-    return accessor;
-}
-
-SourcePath getUnfilteredRootPath(CanonPath path)
-{
-    static auto rootFS = makeFSInputAccessor();
-    return {rootFS, path};
-}
-
-}
diff --git a/src/libfetchers/fs-input-accessor.hh b/src/libfetchers/fs-input-accessor.hh
deleted file mode 100644
index e60906bd827..00000000000
--- a/src/libfetchers/fs-input-accessor.hh
+++ /dev/null
@@ -1,21 +0,0 @@
-#pragma once
-
-#include "input-accessor.hh"
-#include "source-path.hh"
-
-namespace nix {
-
-class StorePath;
-class Store;
-
-ref<InputAccessor> makeFSInputAccessor();
-
-ref<InputAccessor> makeFSInputAccessor(std::filesystem::path root);
-
-ref<InputAccessor> makeStorePathAccessor(
-    ref<Store> store,
-    const StorePath & storePath);
-
-SourcePath getUnfilteredRootPath(CanonPath path);
-
-}
diff --git a/src/libfetchers/git-utils.cc b/src/libfetchers/git-utils.cc
index a4a00374c19..500064ceedc 100644
--- a/src/libfetchers/git-utils.cc
+++ b/src/libfetchers/git-utils.cc
@@ -1,8 +1,4 @@
 #include "git-utils.hh"
-#include "fs-input-accessor.hh"
-#include "input-accessor.hh"
-#include "filtering-input-accessor.hh"
-#include "memory-input-accessor.hh"
 #include "cache.hh"
 #include "finally.hh"
 #include "processes.hh"
@@ -57,7 +53,7 @@ bool operator == (const git_oid & oid1, const git_oid & oid2)
 
 namespace nix {
 
-struct GitInputAccessor;
+struct GitSourceAccessor;
 
 // Some wrapper types that ensure that the git_*_free functions get called.
 template<auto del>
@@ -334,13 +330,13 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
     }
 
     /**
-     * A 'GitInputAccessor' with no regard for export-ignore or any other transformations.
+     * A 'GitSourceAccessor' with no regard for export-ignore or any other transformations.
      */
-    ref<GitInputAccessor> getRawAccessor(const Hash & rev);
+    ref<GitSourceAccessor> getRawAccessor(const Hash & rev);
 
-    ref<InputAccessor> getAccessor(const Hash & rev, bool exportIgnore) override;
+    ref<SourceAccessor> getAccessor(const Hash & rev, bool exportIgnore) override;
 
-    ref<InputAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError e) override;
+    ref<SourceAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError e) override;
 
     ref<GitFileSystemObjectSink> getFileSystemObjectSink() override;
 
@@ -385,7 +381,7 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
 
         runProgram(RunOptions {
             .program = "git",
-            .searchPath = true,
+            .lookupPath = true,
             // FIXME: git stderr messes up our progress indicator, so
             // we're using --quiet for now. Should process its stderr.
             .args = gitArgs,
@@ -456,7 +452,7 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
     {
         auto accessor = getAccessor(treeHash, false);
 
-        fetchers::Attrs cacheKey({{"_what", "treeHashToNarHash"}, {"treeHash", treeHash.gitRev()}});
+        fetchers::Cache::Key cacheKey{"treeHashToNarHash", {{"treeHash", treeHash.gitRev()}}};
 
         if (auto res = fetchers::getCache()->lookup(cacheKey))
             return Hash::parseAny(fetchers::getStrAttr(*res, "narHash"), HashAlgorithm::SHA256);
@@ -477,12 +473,12 @@ ref<GitRepo> GitRepo::openRepo(const std::filesystem::path & path, bool create,
 /**
  * Raw git tree input accessor.
  */
-struct GitInputAccessor : InputAccessor
+struct GitSourceAccessor : SourceAccessor
 {
     ref<GitRepoImpl> repo;
     Tree root;
 
-    GitInputAccessor(ref<GitRepoImpl> repo_, const Hash & rev)
+    GitSourceAccessor(ref<GitRepoImpl> repo_, const Hash & rev)
         : repo(repo_)
         , root(peelObject<Tree>(*repo, lookupObject(*repo, hashToOID(rev)).get(), GIT_OBJECT_TREE))
     {
@@ -706,12 +702,12 @@ struct GitInputAccessor : InputAccessor
     }
 };
 
-struct GitExportIgnoreInputAccessor : CachingFilteringInputAccessor {
+struct GitExportIgnoreSourceAccessor : CachingFilteringSourceAccessor {
     ref<GitRepoImpl> repo;
     std::optional<Hash> rev;
 
-    GitExportIgnoreInputAccessor(ref<GitRepoImpl> repo, ref<InputAccessor> next, std::optional<Hash> rev)
-        : CachingFilteringInputAccessor(next, [&](const CanonPath & path) {
+    GitExportIgnoreSourceAccessor(ref<GitRepoImpl> repo, ref<SourceAccessor> next, std::optional<Hash> rev)
+        : CachingFilteringSourceAccessor(next, [&](const CanonPath & path) {
             return RestrictedPathError(fmt("'%s' does not exist because it was fetched with exportIgnore enabled", path));
         })
         , repo(repo)
@@ -855,10 +851,10 @@ struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
     }
 
     void createRegularFile(
-        const Path & path,
+        const CanonPath & path,
         std::function<void(CreateRegularFileSink &)> func) override
     {
-        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path.rel(), "/");
         if (!prepareDirs(pathComponents, false)) return;
 
         git_writestream * stream = nullptr;
@@ -866,11 +862,11 @@ struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
             throw Error("creating a blob stream object: %s", git_error_last()->message);
 
         struct CRF : CreateRegularFileSink {
-            const Path & path;
+            const CanonPath & path;
             GitFileSystemObjectSinkImpl & back;
             git_writestream * stream;
             bool executable = false;
-            CRF(const Path & path, GitFileSystemObjectSinkImpl & back, git_writestream * stream)
+            CRF(const CanonPath & path, GitFileSystemObjectSinkImpl & back, git_writestream * stream)
                 : path(path), back(back), stream(stream)
             {}
             void operator () (std::string_view data) override
@@ -895,15 +891,15 @@ struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
             : GIT_FILEMODE_BLOB);
     }
 
-    void createDirectory(const Path & path) override
+    void createDirectory(const CanonPath & path) override
     {
-        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path.rel(), "/");
         (void) prepareDirs(pathComponents, true);
     }
 
-    void createSymlink(const Path & path, const std::string & target) override
+    void createSymlink(const CanonPath & path, const std::string & target) override
     {
-        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path.rel(), "/");
         if (!prepareDirs(pathComponents, false)) return;
 
         git_oid oid;
@@ -922,40 +918,40 @@ struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
     }
 };
 
-ref<GitInputAccessor> GitRepoImpl::getRawAccessor(const Hash & rev)
+ref<GitSourceAccessor> GitRepoImpl::getRawAccessor(const Hash & rev)
 {
     auto self = ref<GitRepoImpl>(shared_from_this());
-    return make_ref<GitInputAccessor>(self, rev);
+    return make_ref<GitSourceAccessor>(self, rev);
 }
 
-ref<InputAccessor> GitRepoImpl::getAccessor(const Hash & rev, bool exportIgnore)
+ref<SourceAccessor> GitRepoImpl::getAccessor(const Hash & rev, bool exportIgnore)
 {
     auto self = ref<GitRepoImpl>(shared_from_this());
-    ref<GitInputAccessor> rawGitAccessor = getRawAccessor(rev);
+    ref<GitSourceAccessor> rawGitAccessor = getRawAccessor(rev);
     if (exportIgnore) {
-        return make_ref<GitExportIgnoreInputAccessor>(self, rawGitAccessor, rev);
+        return make_ref<GitExportIgnoreSourceAccessor>(self, rawGitAccessor, rev);
     }
     else {
         return rawGitAccessor;
     }
 }
 
-ref<InputAccessor> GitRepoImpl::getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError)
+ref<SourceAccessor> GitRepoImpl::getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError)
 {
     auto self = ref<GitRepoImpl>(shared_from_this());
     /* In case of an empty workdir, return an empty in-memory tree. We
-       cannot use AllowListInputAccessor because it would return an
+       cannot use AllowListSourceAccessor because it would return an
        error for the root (and we can't add the root to the allow-list
        since that would allow access to all its children). */
-    ref<InputAccessor> fileAccessor =
+    ref<SourceAccessor> fileAccessor =
         wd.files.empty()
-        ? makeEmptyInputAccessor()
-        : AllowListInputAccessor::create(
-            makeFSInputAccessor(path),
+        ? makeEmptySourceAccessor()
+        : AllowListSourceAccessor::create(
+            makeFSSourceAccessor(path),
             std::set<CanonPath> { wd.files },
-            std::move(makeNotAllowedError)).cast<InputAccessor>();
+            std::move(makeNotAllowedError)).cast<SourceAccessor>();
     if (exportIgnore)
-        return make_ref<GitExportIgnoreInputAccessor>(self, fileAccessor, std::nullopt);
+        return make_ref<GitExportIgnoreSourceAccessor>(self, fileAccessor, std::nullopt);
     else
         return fileAccessor;
 }
diff --git a/src/libfetchers/git-utils.hh b/src/libfetchers/git-utils.hh
index 600a42da064..29d79955480 100644
--- a/src/libfetchers/git-utils.hh
+++ b/src/libfetchers/git-utils.hh
@@ -1,7 +1,6 @@
 #pragma once
 
-#include "filtering-input-accessor.hh"
-#include "input-accessor.hh"
+#include "filtering-source-accessor.hh"
 #include "fs-sink.hh"
 
 namespace nix {
@@ -75,9 +74,9 @@ struct GitRepo
 
     virtual bool hasObject(const Hash & oid) = 0;
 
-    virtual ref<InputAccessor> getAccessor(const Hash & rev, bool exportIgnore) = 0;
+    virtual ref<SourceAccessor> getAccessor(const Hash & rev, bool exportIgnore) = 0;
 
-    virtual ref<InputAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError) = 0;
+    virtual ref<SourceAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError) = 0;
 
     virtual ref<GitFileSystemObjectSink> getFileSystemObjectSink() = 0;
 
diff --git a/src/libfetchers/unix/git.cc b/src/libfetchers/git.cc
similarity index 93%
rename from src/libfetchers/unix/git.cc
rename to src/libfetchers/git.cc
index 18915c0a7a0..184c1383e58 100644
--- a/src/libfetchers/unix/git.cc
+++ b/src/libfetchers/git.cc
@@ -9,8 +9,7 @@
 #include "pathlocks.hh"
 #include "processes.hh"
 #include "git.hh"
-#include "fs-input-accessor.hh"
-#include "mounted-input-accessor.hh"
+#include "mounted-source-accessor.hh"
 #include "git-utils.hh"
 #include "logging.hh"
 #include "finally.hh"
@@ -20,7 +19,10 @@
 #include <regex>
 #include <string.h>
 #include <sys/time.h>
-#include <sys/wait.h>
+
+#ifndef _WIN32
+#  include <sys/wait.h>
+#endif
 
 using namespace std::string_literals;
 
@@ -39,17 +41,6 @@ bool isCacheFileWithinTtl(time_t now, const struct stat & st)
     return st.st_mtime + settings.tarballTtl > now;
 }
 
-bool touchCacheFile(const Path & path, time_t touch_time)
-{
-    struct timeval times[2];
-    times[0].tv_sec = touch_time;
-    times[0].tv_usec = 0;
-    times[1].tv_sec = touch_time;
-    times[1].tv_usec = 0;
-
-    return lutimes(path.c_str(), times) == 0;
-}
-
 Path getCachePath(std::string_view key, bool shallow)
 {
     return getCacheDir()
@@ -99,7 +90,15 @@ bool storeCachedHead(const std::string & actualUrl, const std::string & headRef)
     try {
         runProgram("git", true, { "-C", cacheDir, "--git-dir", ".", "symbolic-ref", "--", "HEAD", headRef });
     } catch (ExecError &e) {
-        if (!WIFEXITED(e.status)) throw;
+        if (
+#ifndef WIN32 // TODO abstract over exit status handling on Windows
+            !WIFEXITED(e.status)
+#else
+            e.status != 0
+#endif
+            )
+            throw;
+
         return false;
     }
     /* No need to touch refs/HEAD, because `git symbolic-ref` updates the mtime. */
@@ -330,7 +329,13 @@ struct GitInputScheme : InputScheme
             .program = "git",
             .args = {"-C", repoInfo.url, "--git-dir", repoInfo.gitDir, "check-ignore", "--quiet", std::string(path.rel())},
         });
-        auto exitCode = WEXITSTATUS(result.first);
+        auto exitCode =
+#ifndef WIN32 // TODO abstract over exit status handling on Windows
+            WEXITSTATUS(result.first)
+#else
+            result.first
+#endif
+            ;
 
         if (exitCode != 0) {
             // The path is not `.gitignore`d, we can add the file.
@@ -343,7 +348,8 @@ struct GitInputScheme : InputScheme
                 logger->pause();
                 Finally restoreLogger([]() { logger->resume(); });
                 runProgram("git", true,
-                    { "-C", repoInfo.url, "--git-dir", repoInfo.gitDir, "commit", std::string(path.rel()), "-m", *commitMsg });
+                    { "-C", repoInfo.url, "--git-dir", repoInfo.gitDir, "commit", std::string(path.rel()), "-F", "-" },
+                    *commitMsg);
             }
         }
     }
@@ -427,7 +433,7 @@ struct GitInputScheme : InputScheme
 
     uint64_t getLastModified(const RepoInfo & repoInfo, const std::string & repoDir, const Hash & rev) const
     {
-        Attrs key{{"_what", "gitLastModified"}, {"rev", rev.gitRev()}};
+        Cache::Key key{"gitLastModified", {{"rev", rev.gitRev()}}};
 
         auto cache = getCache();
 
@@ -436,14 +442,14 @@ struct GitInputScheme : InputScheme
 
         auto lastModified = GitRepo::openRepo(repoDir)->getLastModified(rev);
 
-        cache->upsert(key, Attrs{{"lastModified", lastModified}});
+        cache->upsert(key, {{"lastModified", lastModified}});
 
         return lastModified;
     }
 
     uint64_t getRevCount(const RepoInfo & repoInfo, const std::string & repoDir, const Hash & rev) const
     {
-        Attrs key{{"_what", "gitRevCount"}, {"rev", rev.gitRev()}};
+        Cache::Key key{"gitRevCount", {{"rev", rev.gitRev()}}};
 
         auto cache = getCache();
 
@@ -495,7 +501,7 @@ struct GitInputScheme : InputScheme
         }
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessorFromCommit(
+    std::pair<ref<SourceAccessor>, Input> getAccessorFromCommit(
         ref<Store> store,
         RepoInfo & repoInfo,
         Input && input) const
@@ -573,8 +579,11 @@ struct GitInputScheme : InputScheme
                     warn("could not update local clone of Git repository '%s'; continuing with the most recent version", repoInfo.url);
                 }
 
-                if (!touchCacheFile(localRefFile, now))
-                    warn("could not update mtime for file '%s': %s", localRefFile, strerror(errno));
+                try {
+                    setWriteTime(localRefFile, now, now);
+                } catch (Error & e) {
+                    warn("could not update mtime for file '%s': %s", localRefFile, e.msg());
+                }
                 if (!originalRef && !storeCachedHead(repoInfo.url, ref))
                     warn("could not update cached head '%s' for '%s'", ref, repoInfo.url);
             }
@@ -629,7 +638,7 @@ struct GitInputScheme : InputScheme
            input accessor consisting of the accessor for the top-level
            repo and the accessors for the submodules. */
         if (getSubmodulesAttr(input)) {
-            std::map<CanonPath, nix::ref<InputAccessor>> mounts;
+            std::map<CanonPath, nix::ref<SourceAccessor>> mounts;
 
             for (auto & [submodule, submoduleRev] : repo->getSubmodules(rev, exportIgnore)) {
                 auto resolved = repo->resolveSubmoduleUrl(submodule.url);
@@ -642,6 +651,8 @@ struct GitInputScheme : InputScheme
                     attrs.insert_or_assign("ref", submodule.branch);
                 attrs.insert_or_assign("rev", submoduleRev.gitRev());
                 attrs.insert_or_assign("exportIgnore", Explicit<bool>{ exportIgnore });
+                attrs.insert_or_assign("submodules", Explicit<bool>{ true });
+                attrs.insert_or_assign("allRefs", Explicit<bool>{ true });
                 auto submoduleInput = fetchers::Input::fromAttrs(std::move(attrs));
                 auto [submoduleAccessor, submoduleInput2] =
                     submoduleInput.getAccessor(store);
@@ -651,7 +662,7 @@ struct GitInputScheme : InputScheme
 
             if (!mounts.empty()) {
                 mounts.insert_or_assign(CanonPath::root, accessor);
-                accessor = makeMountedInputAccessor(std::move(mounts));
+                accessor = makeMountedSourceAccessor(std::move(mounts));
             }
         }
 
@@ -663,7 +674,7 @@ struct GitInputScheme : InputScheme
         return {accessor, std::move(input)};
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessorFromWorkdir(
+    std::pair<ref<SourceAccessor>, Input> getAccessorFromWorkdir(
         ref<Store> store,
         RepoInfo & repoInfo,
         Input && input) const
@@ -677,7 +688,7 @@ struct GitInputScheme : InputScheme
 
         auto exportIgnore = getExportIgnoreAttr(input);
 
-        ref<InputAccessor> accessor =
+        ref<SourceAccessor> accessor =
             repo->getAccessor(repoInfo.workdirInfo,
                 exportIgnore,
                 makeNotAllowedError(repoInfo.url));
@@ -688,7 +699,7 @@ struct GitInputScheme : InputScheme
            consisting of the accessor for the top-level repo and the
            accessors for the submodule workdirs. */
         if (getSubmodulesAttr(input) && !repoInfo.workdirInfo.submodules.empty()) {
-            std::map<CanonPath, nix::ref<InputAccessor>> mounts;
+            std::map<CanonPath, nix::ref<SourceAccessor>> mounts;
 
             for (auto & submodule : repoInfo.workdirInfo.submodules) {
                 auto submodulePath = CanonPath(repoInfo.url) / submodule.path;
@@ -696,6 +707,9 @@ struct GitInputScheme : InputScheme
                 attrs.insert_or_assign("type", "git");
                 attrs.insert_or_assign("url", submodulePath.abs());
                 attrs.insert_or_assign("exportIgnore", Explicit<bool>{ exportIgnore });
+                attrs.insert_or_assign("submodules", Explicit<bool>{ true });
+                // TODO: fall back to getAccessorFromCommit-like fetch when submodules aren't checked out
+                // attrs.insert_or_assign("allRefs", Explicit<bool>{ true });
 
                 auto submoduleInput = fetchers::Input::fromAttrs(std::move(attrs));
                 auto [submoduleAccessor, submoduleInput2] =
@@ -711,7 +725,7 @@ struct GitInputScheme : InputScheme
             }
 
             mounts.insert_or_assign(CanonPath::root, accessor);
-            accessor = makeMountedInputAccessor(std::move(mounts));
+            accessor = makeMountedSourceAccessor(std::move(mounts));
         }
 
         if (!repoInfo.workdirInfo.isDirty) {
@@ -750,7 +764,7 @@ struct GitInputScheme : InputScheme
         return {accessor, std::move(input)};
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
 
diff --git a/src/libfetchers/github.cc b/src/libfetchers/github.cc
index 985f2e47991..ddb41e63f9f 100644
--- a/src/libfetchers/github.cc
+++ b/src/libfetchers/github.cc
@@ -225,8 +225,8 @@ struct GitArchiveInputScheme : InputScheme
 
         auto cache = getCache();
 
-        Attrs treeHashKey{{"_what", "gitRevToTreeHash"}, {"rev", rev->gitRev()}};
-        Attrs lastModifiedKey{{"_what", "gitRevToLastModified"}, {"rev", rev->gitRev()}};
+        Cache::Key treeHashKey{"gitRevToTreeHash", {{"rev", rev->gitRev()}}};
+        Cache::Key lastModifiedKey{"gitRevToLastModified", {{"rev", rev->gitRev()}}};
 
         if (auto treeHashAttrs = cache->lookup(treeHashKey)) {
             if (auto lastModifiedAttrs = cache->lookup(lastModifiedKey)) {
@@ -272,7 +272,7 @@ struct GitArchiveInputScheme : InputScheme
         return {std::move(input), tarballInfo};
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         auto [input, tarballInfo] = downloadArchive(store, _input);
 
@@ -433,9 +433,15 @@ struct GitLabInputScheme : GitArchiveInputScheme
                 store->toRealPath(
                     downloadFile(store, url, "source", headers).storePath)));
 
-        return RefInfo {
-            .rev = Hash::parseAny(std::string(json[0]["id"]), HashAlgorithm::SHA1)
-        };
+        if (json.is_array() && json.size() >= 1 && json[0]["id"] != nullptr) {
+          return RefInfo {
+              .rev = Hash::parseAny(std::string(json[0]["id"]), HashAlgorithm::SHA1)
+          };
+        } if (json.is_array() && json.size() == 0) {
+            throw Error("No commits returned by GitLab API -- does the git ref really exist?");
+        } else {
+            throw Error("Unexpected response received from GitLab: %s", json);
+        }
     }
 
     DownloadUrl getDownloadUrl(const Input & input) const override
diff --git a/src/libfetchers/indirect.cc b/src/libfetchers/indirect.cc
index 3f21445e101..ba507863138 100644
--- a/src/libfetchers/indirect.cc
+++ b/src/libfetchers/indirect.cc
@@ -97,7 +97,7 @@ struct IndirectInputScheme : InputScheme
         return input;
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const override
     {
         throw Error("indirect input '%s' cannot be fetched directly", input.to_string());
     }
diff --git a/src/libfetchers/local.mk b/src/libfetchers/local.mk
index 0fef1466b1c..e229a099353 100644
--- a/src/libfetchers/local.mk
+++ b/src/libfetchers/local.mk
@@ -5,16 +5,10 @@ libfetchers_NAME = libnixfetchers
 libfetchers_DIR := $(d)
 
 libfetchers_SOURCES := $(wildcard $(d)/*.cc)
-ifdef HOST_UNIX
-  libfetchers_SOURCES += $(wildcard $(d)/unix/*.cc)
-endif
 
 # Not just for this library itself, but also for downstream libraries using this library
 
 INCLUDE_libfetchers := -I $(d)
-ifdef HOST_UNIX
-  INCLUDE_libfetchers += -I $(d)/unix
-endif
 
 libfetchers_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers)
 
diff --git a/src/libfetchers/memory-input-accessor.cc b/src/libfetchers/memory-input-accessor.cc
deleted file mode 100644
index 34a801f671c..00000000000
--- a/src/libfetchers/memory-input-accessor.cc
+++ /dev/null
@@ -1,29 +0,0 @@
-#include "memory-input-accessor.hh"
-#include "memory-source-accessor.hh"
-#include "source-path.hh"
-
-namespace nix {
-
-struct MemoryInputAccessorImpl : MemoryInputAccessor, MemorySourceAccessor
-{
-    SourcePath addFile(CanonPath path, std::string && contents) override
-    {
-        return {
-            ref(shared_from_this()),
-            MemorySourceAccessor::addFile(path, std::move(contents))
-        };
-    }
-};
-
-ref<MemoryInputAccessor> makeMemoryInputAccessor()
-{
-    return make_ref<MemoryInputAccessorImpl>();
-}
-
-ref<InputAccessor> makeEmptyInputAccessor()
-{
-    static auto empty = makeMemoryInputAccessor().cast<InputAccessor>();
-    return empty;
-}
-
-}
diff --git a/src/libfetchers/memory-input-accessor.hh b/src/libfetchers/memory-input-accessor.hh
deleted file mode 100644
index 63afadd2af5..00000000000
--- a/src/libfetchers/memory-input-accessor.hh
+++ /dev/null
@@ -1,18 +0,0 @@
-#include "input-accessor.hh"
-#include "source-path.hh"
-
-namespace nix {
-
-/**
- * An input accessor for an in-memory file system.
- */
-struct MemoryInputAccessor : InputAccessor
-{
-    virtual SourcePath addFile(CanonPath path, std::string && contents) = 0;
-};
-
-ref<MemoryInputAccessor> makeMemoryInputAccessor();
-
-ref<InputAccessor> makeEmptyInputAccessor();
-
-}
diff --git a/src/libfetchers/unix/mercurial.cc b/src/libfetchers/mercurial.cc
similarity index 79%
rename from src/libfetchers/unix/mercurial.cc
rename to src/libfetchers/mercurial.cc
index 4e0b26274fe..198795caa23 100644
--- a/src/libfetchers/unix/mercurial.cc
+++ b/src/libfetchers/mercurial.cc
@@ -6,8 +6,7 @@
 #include "tarfile.hh"
 #include "store-api.hh"
 #include "url-parts.hh"
-#include "fs-input-accessor.hh"
-#include "posix-source-accessor.hh"
+#include "store-path-accessor.hh"
 #include "fetch-settings.hh"
 
 #include <sys/time.h>
@@ -24,7 +23,7 @@ static RunOptions hgOptions(const Strings & args)
 
     return {
         .program = "hg",
-        .searchPath = true,
+        .lookupPath = true,
         .args = args,
         .environment = env
     };
@@ -211,11 +210,10 @@ struct MercurialInputScheme : InputScheme
                     return files.count(file);
                 };
 
-                PosixSourceAccessor accessor;
                 auto storePath = store->addToStore(
                     input.getName(),
-                    accessor, CanonPath { actualPath },
-                    FileIngestionMethod::Recursive, HashAlgorithm::SHA256, {},
+                    {getFSSourceAccessor(), CanonPath(actualPath)},
+                    ContentAddressMethod::Raw::NixArchive, HashAlgorithm::SHA256, {},
                     filter);
 
                 return storePath;
@@ -224,22 +222,16 @@ struct MercurialInputScheme : InputScheme
 
         if (!input.getRef()) input.attrs.insert_or_assign("ref", "default");
 
-        auto checkHashAlgorithm = [&](const std::optional<Hash> & hash)
+        auto revInfoKey = [&](const Hash & rev)
         {
-            if (hash.has_value() && hash->algo != HashAlgorithm::SHA1)
-                throw Error("Hash '%s' is not supported by Mercurial. Only sha1 is supported.", hash->to_string(HashFormat::Base16, true));
-        };
-
-
-        auto getLockedAttrs = [&]()
-        {
-            checkHashAlgorithm(input.getRev());
+            if (rev.algo != HashAlgorithm::SHA1)
+                throw Error("Hash '%s' is not supported by Mercurial. Only sha1 is supported.", rev.to_string(HashFormat::Base16, true));
 
-            return Attrs({
-                {"type", "hg"},
+            return Cache::Key{"hgRev", {
+                {"store", store->storeDir},
                 {"name", name},
-                {"rev", input.getRev()->gitRev()},
-            });
+                {"rev", input.getRev()->gitRev()}
+            }};
         };
 
         auto makeResult = [&](const Attrs & infoAttrs, const StorePath & storePath) -> StorePath
@@ -250,26 +242,21 @@ struct MercurialInputScheme : InputScheme
             return storePath;
         };
 
-        if (input.getRev()) {
-            if (auto res = getCache()->lookup(*store, getLockedAttrs()))
-                return makeResult(res->first, std::move(res->second));
-        }
-
-        auto revOrRef = input.getRev() ? input.getRev()->gitRev() : *input.getRef();
-
-        Attrs unlockedAttrs({
-            {"type", "hg"},
-            {"name", name},
+        /* Check the cache for the most recent rev for this URL/ref. */
+        Cache::Key refToRevKey{"hgRefToRev", {
             {"url", actualUrl},
-            {"ref", *input.getRef()},
-        });
+            {"ref", *input.getRef()}
+        }};
 
-        if (auto res = getCache()->lookup(*store, unlockedAttrs)) {
-            auto rev2 = Hash::parseAny(getStrAttr(res->first, "rev"), HashAlgorithm::SHA1);
-            if (!input.getRev() || input.getRev() == rev2) {
-                input.attrs.insert_or_assign("rev", rev2.gitRev());
-                return makeResult(res->first, std::move(res->second));
-            }
+        if (!input.getRev()) {
+            if (auto res = getCache()->lookupWithTTL(refToRevKey))
+                input.attrs.insert_or_assign("rev", getRevAttr(*res, "rev").gitRev());
+        }
+
+        /* If we have a rev, check if we have a cached store path. */
+        if (auto rev = input.getRev()) {
+            if (auto res = getCache()->lookupStorePath(revInfoKey(*rev), *store))
+                return makeResult(res->value, res->storePath);
         }
 
         Path cacheDir = fmt("%s/nix/hg/%s", getCacheDir(), hashString(HashAlgorithm::SHA256, actualUrl).to_string(HashFormat::Nix32, false));
@@ -302,51 +289,47 @@ struct MercurialInputScheme : InputScheme
             }
         }
 
+        /* Fetch the remote rev or ref. */
         auto tokens = tokenizeString<std::vector<std::string>>(
-            runHg({ "log", "-R", cacheDir, "-r", revOrRef, "--template", "{node} {rev} {branch}" }));
+            runHg({
+                "log", "-R", cacheDir,
+                "-r", input.getRev() ? input.getRev()->gitRev() : *input.getRef(),
+                "--template", "{node} {rev} {branch}"
+            }));
         assert(tokens.size() == 3);
 
-        input.attrs.insert_or_assign("rev", Hash::parseAny(tokens[0], HashAlgorithm::SHA1).gitRev());
+        auto rev = Hash::parseAny(tokens[0], HashAlgorithm::SHA1);
+        input.attrs.insert_or_assign("rev", rev.gitRev());
         auto revCount = std::stoull(tokens[1]);
         input.attrs.insert_or_assign("ref", tokens[2]);
 
-        if (auto res = getCache()->lookup(*store, getLockedAttrs()))
-            return makeResult(res->first, std::move(res->second));
+        /* Now that we have the rev, check the cache again for a
+           cached store path. */
+        if (auto res = getCache()->lookupStorePath(revInfoKey(rev), *store))
+            return makeResult(res->value, res->storePath);
 
         Path tmpDir = createTempDir();
         AutoDelete delTmpDir(tmpDir, true);
 
-        runHg({ "archive", "-R", cacheDir, "-r", input.getRev()->gitRev(), tmpDir });
+        runHg({ "archive", "-R", cacheDir, "-r", rev.gitRev(), tmpDir });
 
         deletePath(tmpDir + "/.hg_archival.txt");
 
-        PosixSourceAccessor accessor;
-        auto storePath = store->addToStore(name, accessor, CanonPath { tmpDir });
+        auto storePath = store->addToStore(name, {getFSSourceAccessor(), CanonPath(tmpDir)});
 
         Attrs infoAttrs({
-            {"rev", input.getRev()->gitRev()},
             {"revCount", (uint64_t) revCount},
         });
 
         if (!origRev)
-            getCache()->add(
-                *store,
-                unlockedAttrs,
-                infoAttrs,
-                storePath,
-                false);
-
-        getCache()->add(
-            *store,
-            getLockedAttrs(),
-            infoAttrs,
-            storePath,
-            true);
+            getCache()->upsert(refToRevKey, {{"rev", rev.gitRev()}});
+
+        getCache()->upsert(revInfoKey(rev), *store, infoAttrs, storePath);
 
         return makeResult(infoAttrs, std::move(storePath));
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
 
diff --git a/src/libfetchers/meson.build b/src/libfetchers/meson.build
new file mode 100644
index 00000000000..c39fe99f316
--- /dev/null
+++ b/src/libfetchers/meson.build
@@ -0,0 +1,93 @@
+project('nix-fetchers', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+]
+subdir('build-utils-meson/subprojects')
+
+nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
+deps_public += nlohmann_json
+
+libgit2 = dependency('libgit2')
+deps_private += libgit2
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  # '-include', 'config-fetchers.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'attrs.cc',
+  'cache.cc',
+  'fetch-settings.cc',
+  'fetch-to-store.cc',
+  'fetchers.cc',
+  'filtering-source-accessor.cc',
+  'git.cc',
+  'git-utils.cc',
+  'github.cc',
+  'indirect.cc',
+  'mercurial.cc',
+  'mounted-source-accessor.cc',
+  'path.cc',
+  'store-path-accessor.cc',
+  'registry.cc',
+  'tarball.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = files(
+  'attrs.hh',
+  'cache.hh',
+  'fetch-settings.hh',
+  'fetch-to-store.hh',
+  'filtering-source-accessor.hh',
+  'git-utils.hh',
+  'mounted-source-accessor.hh',
+  'fetchers.hh',
+  'registry.hh',
+  'store-path-accessor.hh',
+  'tarball.hh',
+)
+
+this_library = library(
+  'nixfetchers',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libfetchers/mounted-input-accessor.hh b/src/libfetchers/mounted-input-accessor.hh
deleted file mode 100644
index b557c5dad7f..00000000000
--- a/src/libfetchers/mounted-input-accessor.hh
+++ /dev/null
@@ -1,9 +0,0 @@
-#pragma once
-
-#include "input-accessor.hh"
-
-namespace nix {
-
-ref<InputAccessor> makeMountedInputAccessor(std::map<CanonPath, ref<InputAccessor>> mounts);
-
-}
diff --git a/src/libfetchers/mounted-input-accessor.cc b/src/libfetchers/mounted-source-accessor.cc
similarity index 80%
rename from src/libfetchers/mounted-input-accessor.cc
rename to src/libfetchers/mounted-source-accessor.cc
index b1eeaa97dbf..68f3a546b57 100644
--- a/src/libfetchers/mounted-input-accessor.cc
+++ b/src/libfetchers/mounted-source-accessor.cc
@@ -1,12 +1,12 @@
-#include "mounted-input-accessor.hh"
+#include "mounted-source-accessor.hh"
 
 namespace nix {
 
-struct MountedInputAccessor : InputAccessor
+struct MountedSourceAccessor : SourceAccessor
 {
-    std::map<CanonPath, ref<InputAccessor>> mounts;
+    std::map<CanonPath, ref<SourceAccessor>> mounts;
 
-    MountedInputAccessor(std::map<CanonPath, ref<InputAccessor>> _mounts)
+    MountedSourceAccessor(std::map<CanonPath, ref<SourceAccessor>> _mounts)
         : mounts(std::move(_mounts))
     {
         displayPrefix.clear();
@@ -53,7 +53,7 @@ struct MountedInputAccessor : InputAccessor
         return displayPrefix + accessor->showPath(subpath) + displaySuffix;
     }
 
-    std::pair<ref<InputAccessor>, CanonPath> resolve(CanonPath path)
+    std::pair<ref<SourceAccessor>, CanonPath> resolve(CanonPath path)
     {
         // Find the nearest parent of `path` that is a mount point.
         std::vector<std::string> subpath;
@@ -71,9 +71,9 @@ struct MountedInputAccessor : InputAccessor
     }
 };
 
-ref<InputAccessor> makeMountedInputAccessor(std::map<CanonPath, ref<InputAccessor>> mounts)
+ref<SourceAccessor> makeMountedSourceAccessor(std::map<CanonPath, ref<SourceAccessor>> mounts)
 {
-    return make_ref<MountedInputAccessor>(std::move(mounts));
+    return make_ref<MountedSourceAccessor>(std::move(mounts));
 }
 
 }
diff --git a/src/libfetchers/mounted-source-accessor.hh b/src/libfetchers/mounted-source-accessor.hh
new file mode 100644
index 00000000000..45cbcb09a24
--- /dev/null
+++ b/src/libfetchers/mounted-source-accessor.hh
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "source-accessor.hh"
+
+namespace nix {
+
+ref<SourceAccessor> makeMountedSourceAccessor(std::map<CanonPath, ref<SourceAccessor>> mounts);
+
+}
diff --git a/src/libfetchers/package.nix b/src/libfetchers/package.nix
new file mode 100644
index 00000000000..b4abb144b50
--- /dev/null
+++ b/src/libfetchers/package.nix
@@ -0,0 +1,84 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+, nix-store
+, nlohmann_json
+, libgit2
+, man
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-fetchers";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    libgit2
+  ];
+
+  propagatedBuildInputs = [
+    nix-store
+    nix-util
+    nlohmann_json
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  # TODO `releaseTools.coverageAnalysis` in Nixpkgs needs to be updated
+  # to work with `strictDeps`.
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libfetchers/path.cc b/src/libfetchers/path.cc
index 0af1bad7381..68958d55971 100644
--- a/src/libfetchers/path.cc
+++ b/src/libfetchers/path.cc
@@ -1,8 +1,7 @@
 #include "fetchers.hh"
 #include "store-api.hh"
 #include "archive.hh"
-#include "fs-input-accessor.hh"
-#include "posix-source-accessor.hh"
+#include "store-path-accessor.hh"
 
 namespace nix::fetchers {
 
@@ -54,6 +53,7 @@ struct PathInputScheme : InputScheme
             "narHash",
         };
     }
+
     std::optional<Input> inputFromAttrs(const Attrs & attrs) const override
     {
         getStrAttr(attrs, "path");
@@ -113,7 +113,7 @@ struct PathInputScheme : InputScheme
         throw Error("cannot fetch input '%s' because it uses a relative path", input.to_string());
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         Input input(_input);
         std::string absPath;
diff --git a/src/libfetchers/registry.cc b/src/libfetchers/registry.cc
index e00b9de46a8..52cbac5e0a0 100644
--- a/src/libfetchers/registry.cc
+++ b/src/libfetchers/registry.cc
@@ -1,12 +1,11 @@
 #include "registry.hh"
 #include "tarball.hh"
 #include "users.hh"
+#include "config-global.hh"
 #include "globals.hh"
 #include "store-api.hh"
 #include "local-fs-store.hh"
 
-#include "fetch-settings.hh"
-
 #include <nlohmann/json.hpp>
 
 namespace nix::fetchers {
@@ -149,10 +148,25 @@ void overrideRegistry(
     flagRegistry->add(from, to, extraAttrs);
 }
 
+struct RegistrySettings : Config
+{
+    Setting<std::string> flakeRegistry{this, "https://channels.nixos.org/flake-registry.json", "flake-registry",
+        R"(
+          Path or URI of the global flake registry.
+
+          When empty, disables the global flake registry.
+        )",
+        {}, true, Xp::Flakes};
+};
+
+RegistrySettings registrySettings;
+
+static GlobalConfig::Register rRegistrySettings(&registrySettings);
+
 static std::shared_ptr<Registry> getGlobalRegistry(ref<Store> store)
 {
     static auto reg = [&]() {
-        auto path = fetchSettings.flakeRegistry.get();
+        auto path = registrySettings.flakeRegistry.get();
         if (path == "") {
             return std::make_shared<Registry>(Registry::Global); // empty registry
         }
diff --git a/src/libfetchers/store-path-accessor.cc b/src/libfetchers/store-path-accessor.cc
new file mode 100644
index 00000000000..528bf2a4f51
--- /dev/null
+++ b/src/libfetchers/store-path-accessor.cc
@@ -0,0 +1,15 @@
+#include "store-path-accessor.hh"
+#include "store-api.hh"
+
+namespace nix {
+
+ref<SourceAccessor> makeStorePathAccessor(ref<Store> store, const StorePath & storePath)
+{
+    // FIXME: should use `store->getFSAccessor()`
+    auto root = std::filesystem::path{store->toRealPath(storePath)};
+    auto accessor = makeFSSourceAccessor(root);
+    accessor->setPathDisplay(root.string());
+    return accessor;
+}
+
+}
diff --git a/src/libfetchers/store-path-accessor.hh b/src/libfetchers/store-path-accessor.hh
new file mode 100644
index 00000000000..989cf3fa29c
--- /dev/null
+++ b/src/libfetchers/store-path-accessor.hh
@@ -0,0 +1,14 @@
+#pragma once
+
+#include "source-path.hh"
+
+namespace nix {
+
+class StorePath;
+class Store;
+
+ref<SourceAccessor> makeStorePathAccessor(ref<Store> store, const StorePath & storePath);
+
+SourcePath getUnfilteredRootPath(CanonPath path);
+
+}
diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index a1f934c35df..aa8ff652f07 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -8,8 +8,7 @@
 #include "tarfile.hh"
 #include "types.hh"
 #include "split.hh"
-#include "posix-source-accessor.hh"
-#include "fs-input-accessor.hh"
+#include "store-path-accessor.hh"
 #include "store-api.hh"
 #include "git-utils.hh"
 
@@ -23,21 +22,20 @@ DownloadFileResult downloadFile(
 {
     // FIXME: check store
 
-    Attrs inAttrs({
-        {"type", "file"},
+    Cache::Key key{"file", {{
         {"url", url},
         {"name", name},
-    });
+    }}};
 
-    auto cached = getCache()->lookupExpired(*store, inAttrs);
+    auto cached = getCache()->lookupStorePath(key, *store);
 
     auto useCached = [&]() -> DownloadFileResult
     {
         return {
             .storePath = std::move(cached->storePath),
-            .etag = getStrAttr(cached->infoAttrs, "etag"),
-            .effectiveUrl = getStrAttr(cached->infoAttrs, "url"),
-            .immutableUrl = maybeGetStrAttr(cached->infoAttrs, "immutableUrl"),
+            .etag = getStrAttr(cached->value, "etag"),
+            .effectiveUrl = getStrAttr(cached->value, "url"),
+            .immutableUrl = maybeGetStrAttr(cached->value, "immutableUrl"),
         };
     };
 
@@ -47,7 +45,7 @@ DownloadFileResult downloadFile(
     FileTransferRequest request(url);
     request.headers = headers;
     if (cached)
-        request.expectedETag = getStrAttr(cached->infoAttrs, "etag");
+        request.expectedETag = getStrAttr(cached->value, "etag");
     FileTransferResult res;
     try {
         res = getFileTransfer()->download(request);
@@ -93,14 +91,9 @@ DownloadFileResult downloadFile(
 
     /* Cache metadata for all URLs in the redirect chain. */
     for (auto & url : res.urls) {
-        inAttrs.insert_or_assign("url", url);
+        key.second.insert_or_assign("url", url);
         infoAttrs.insert_or_assign("url", *res.urls.rbegin());
-        getCache()->add(
-            *store,
-            inAttrs,
-            infoAttrs,
-            *storePath,
-            false);
+        getCache()->upsert(key, *store, infoAttrs, *storePath);
     }
 
     return {
@@ -115,12 +108,9 @@ DownloadTarballResult downloadTarball(
     const std::string & url,
     const Headers & headers)
 {
-    Attrs inAttrs({
-        {"_what", "tarballCache"},
-        {"url", url},
-    });
+    Cache::Key cacheKey{"tarball", {{"url", url}}};
 
-    auto cached = getCache()->lookupExpired(inAttrs);
+    auto cached = getCache()->lookupExpired(cacheKey);
 
     auto attrsToResult = [&](const Attrs & infoAttrs)
     {
@@ -133,19 +123,19 @@ DownloadTarballResult downloadTarball(
         };
     };
 
-    if (cached && !getTarballCache()->hasObject(getRevAttr(cached->infoAttrs, "treeHash")))
+    if (cached && !getTarballCache()->hasObject(getRevAttr(cached->value, "treeHash")))
         cached.reset();
 
     if (cached && !cached->expired)
         /* We previously downloaded this tarball and it's younger than
            `tarballTtl`, so no need to check the server. */
-        return attrsToResult(cached->infoAttrs);
+        return attrsToResult(cached->value);
 
     auto _res = std::make_shared<Sync<FileTransferResult>>();
 
     auto source = sinkToSource([&](Sink & sink) {
         FileTransferRequest req(url);
-        req.expectedETag = cached ? getStrAttr(cached->infoAttrs, "etag") : "";
+        req.expectedETag = cached ? getStrAttr(cached->value, "etag") : "";
         getFileTransfer()->download(std::move(req), sink,
             [_res](FileTransferResult r)
             {
@@ -155,9 +145,27 @@ DownloadTarballResult downloadTarball(
 
     // TODO: fall back to cached value if download fails.
 
+    AutoDelete cleanupTemp;
+
     /* Note: if the download is cached, `importTarball()` will receive
        no data, which causes it to import an empty tarball. */
-    TarArchive archive { *source };
+    auto archive =
+        hasSuffix(toLower(parseURL(url).path), ".zip")
+        ? ({
+                /* In streaming mode, libarchive doesn't handle
+                   symlinks in zip files correctly (#10649). So write
+                   the entire file to disk so libarchive can access it
+                   in random-access mode. */
+                auto [fdTemp, path] = createTempFile("nix-zipfile");
+                cleanupTemp.reset(path);
+                debug("downloading '%s' into '%s'...", url, path);
+                {
+                    FdSink sink(fdTemp.get());
+                    source->drainInto(sink);
+                }
+                TarArchive{path};
+          })
+        : TarArchive{*source};
     auto parseSink = getTarballCache()->getFileSystemObjectSink();
     auto lastModified = unpackTarfileToSink(archive, *parseSink);
 
@@ -168,7 +176,7 @@ DownloadTarballResult downloadTarball(
     if (res->cached) {
         /* The server says that the previously downloaded version is
            still current. */
-        infoAttrs = cached->infoAttrs;
+        infoAttrs = cached->value;
     } else {
         infoAttrs.insert_or_assign("etag", res->etag);
         infoAttrs.insert_or_assign("treeHash", parseSink->sync().gitRev());
@@ -179,8 +187,8 @@ DownloadTarballResult downloadTarball(
 
     /* Insert a cache entry for every URL in the redirect chain. */
     for (auto & url : res->urls) {
-        inAttrs.insert_or_assign("url", url);
-        getCache()->upsert(inAttrs, infoAttrs);
+        cacheKey.second.insert_or_assign("url", url);
+        getCache()->upsert(cacheKey, infoAttrs);
     }
 
     // FIXME: add a cache entry for immutableUrl? That could allow
@@ -194,7 +202,7 @@ struct CurlInputScheme : InputScheme
 {
     const std::set<std::string> transportUrlSchemes = {"file", "http", "https"};
 
-    const bool hasTarballExtension(std::string_view path) const
+    bool hasTarballExtension(std::string_view path) const
     {
         return hasSuffix(path, ".zip") || hasSuffix(path, ".tar")
             || hasSuffix(path, ".tgz") || hasSuffix(path, ".tar.gz")
@@ -297,7 +305,7 @@ struct FileInputScheme : CurlInputScheme
                 : (!requireTree && !hasTarballExtension(url.path)));
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         auto input(_input);
 
@@ -332,7 +340,7 @@ struct TarballInputScheme : CurlInputScheme
                 : (requireTree || hasTarballExtension(url.path)));
     }
 
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    std::pair<ref<SourceAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
     {
         auto input(_input);
 
@@ -357,6 +365,16 @@ struct TarballInputScheme : CurlInputScheme
 
         return {result.accessor, input};
     }
+
+    std::optional<std::string> getFingerprint(ref<Store> store, const Input & input) const override
+    {
+        if (auto narHash = input.getNarHash())
+            return narHash->to_string(HashFormat::SRI, true);
+        else if (auto rev = input.getRev())
+            return rev->gitRev();
+        else
+            return std::nullopt;
+    }
 };
 
 static auto rTarballInputScheme = OnStartup([] { registerInputScheme(std::make_unique<TarballInputScheme>()); });
diff --git a/src/libfetchers/tarball.hh b/src/libfetchers/tarball.hh
index bcb5dcc5ecf..ba0dfd6230a 100644
--- a/src/libfetchers/tarball.hh
+++ b/src/libfetchers/tarball.hh
@@ -8,7 +8,7 @@
 
 namespace nix {
 class Store;
-struct InputAccessor;
+struct SourceAccessor;
 }
 
 namespace nix::fetchers {
@@ -32,7 +32,7 @@ struct DownloadTarballResult
     Hash treeHash;
     time_t lastModified;
     std::optional<std::string> immutableUrl;
-    ref<InputAccessor> accessor;
+    ref<SourceAccessor> accessor;
 };
 
 /**
diff --git a/src/libflake/.version b/src/libflake/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libflake/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libflake/build-utils-meson b/src/libflake/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libflake/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libflake/flake-settings.cc b/src/libflake/flake-settings.cc
new file mode 100644
index 00000000000..ba97e0ce723
--- /dev/null
+++ b/src/libflake/flake-settings.cc
@@ -0,0 +1,12 @@
+#include "flake-settings.hh"
+#include "config-global.hh"
+
+namespace nix {
+
+FlakeSettings::FlakeSettings() {}
+
+FlakeSettings flakeSettings;
+
+static GlobalConfig::Register rFlakeSettings(&flakeSettings);
+
+}
diff --git a/src/libflake/flake-settings.hh b/src/libflake/flake-settings.hh
new file mode 100644
index 00000000000..f97c175e8a3
--- /dev/null
+++ b/src/libflake/flake-settings.hh
@@ -0,0 +1,53 @@
+#pragma once
+///@file
+
+#include "types.hh"
+#include "config.hh"
+#include "util.hh"
+
+#include <map>
+#include <limits>
+
+#include <sys/types.h>
+
+namespace nix {
+
+struct FlakeSettings : public Config
+{
+    FlakeSettings();
+
+    Setting<bool> useRegistries{
+        this,
+        true,
+        "use-registries",
+        "Whether to use flake registries to resolve flake references.",
+        {},
+        true,
+        Xp::Flakes};
+
+    Setting<bool> acceptFlakeConfig{
+        this,
+        false,
+        "accept-flake-config",
+        "Whether to accept nix configuration from a flake without prompting.",
+        {},
+        true,
+        Xp::Flakes};
+
+    Setting<std::string> commitLockFileSummary{
+        this,
+        "",
+        "commit-lock-file-summary",
+        R"(
+          The commit summary to use when committing changed flake lock files. If
+          empty, the summary is generated based on the action performed.
+        )",
+        {"commit-lockfile-summary"},
+        true,
+        Xp::Flakes};
+};
+
+// TODO: don't use a global variable.
+extern FlakeSettings flakeSettings;
+
+}
diff --git a/src/libexpr/flake/config.cc b/src/libflake/flake/config.cc
similarity index 92%
rename from src/libexpr/flake/config.cc
rename to src/libflake/flake/config.cc
index 3c7ed5d8a5b..49859535939 100644
--- a/src/libexpr/flake/config.cc
+++ b/src/libflake/flake/config.cc
@@ -1,6 +1,6 @@
 #include "users.hh"
-#include "globals.hh"
-#include "fetch-settings.hh"
+#include "config-global.hh"
+#include "flake-settings.hh"
 #include "flake.hh"
 
 #include <nlohmann/json.hpp>
@@ -32,7 +32,7 @@ static void writeTrustedList(const TrustedList & trustedList)
 
 void ConfigFile::apply()
 {
-    std::set<std::string> whitelist{"bash-prompt", "bash-prompt-prefix", "bash-prompt-suffix", "flake-registry", "commit-lockfile-summary"};
+    std::set<std::string> whitelist{"bash-prompt", "bash-prompt-prefix", "bash-prompt-suffix", "flake-registry", "commit-lock-file-summary", "commit-lockfile-summary"};
 
     for (auto & [name, value] : settings) {
 
@@ -51,7 +51,7 @@ void ConfigFile::apply()
         else
             assert(false);
 
-        if (!whitelist.count(baseName) && !nix::fetchSettings.acceptFlakeConfig) {
+        if (!whitelist.count(baseName) && !nix::flakeSettings.acceptFlakeConfig) {
             bool trusted = false;
             auto trustedList = readTrustedList();
             auto tlname = get(trustedList, name);
diff --git a/src/libexpr/flake/flake.cc b/src/libflake/flake/flake.cc
similarity index 97%
rename from src/libexpr/flake/flake.cc
rename to src/libflake/flake/flake.cc
index 3af9ef14ee3..6f47b599229 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libflake/flake/flake.cc
@@ -9,6 +9,7 @@
 #include "fetchers.hh"
 #include "finally.hh"
 #include "fetch-settings.hh"
+#include "flake-settings.hh"
 #include "value-to-json.hh"
 #include "local-fs-store.hh"
 
@@ -346,7 +347,7 @@ LockedFlake lockFlake(
 
     FlakeCache flakeCache;
 
-    auto useRegistries = lockFlags.useRegistries.value_or(fetchSettings.useRegistries);
+    auto useRegistries = lockFlags.useRegistries.value_or(flakeSettings.useRegistries);
 
     auto flake = getFlake(state, topRef, useRegistries, flakeCache);
 
@@ -691,7 +692,7 @@ LockedFlake lockFlake(
                             if (lockFlags.commitLockFile) {
                                 std::string cm;
 
-                                cm = fetchSettings.commitLockFileSummary.get();
+                                cm = flakeSettings.commitLockFileSummary.get();
 
                                 if (cm == "") {
                                     cm = fmt("%s: %s", relPath, lockFileExists ? "Update" : "Add");
@@ -803,7 +804,7 @@ static void prim_getFlake(EvalState & state, const PosIdx pos, Value * * args, V
 {
     std::string flakeRefS(state.forceStringNoCtx(*args[0], pos, "while evaluating the argument passed to builtins.getFlake"));
     auto flakeRef = parseFlakeRef(flakeRefS, {}, true);
-    if (evalSettings.pureEval && !flakeRef.input.isLocked())
+    if (state.settings.pureEval && !flakeRef.input.isLocked())
         throw Error("cannot call 'getFlake' on unlocked flake reference '%s', at %s (use --impure to override)", flakeRefS, state.positions[pos]);
 
     callFlake(state,
@@ -811,8 +812,8 @@ static void prim_getFlake(EvalState & state, const PosIdx pos, Value * * args, V
             LockFlags {
                 .updateLockFile = false,
                 .writeLockFile = false,
-                .useRegistries = !evalSettings.pureEval && fetchSettings.useRegistries,
-                .allowUnlocked = !evalSettings.pureEval,
+                .useRegistries = !state.settings.pureEval && flakeSettings.useRegistries,
+                .allowUnlocked = !state.settings.pureEval,
             }),
         v);
 }
@@ -949,10 +950,20 @@ std::optional<Fingerprint> LockedFlake::getFingerprint(ref<Store> store) const
     auto fingerprint = flake.lockedRef.input.getFingerprint(store);
     if (!fingerprint) return std::nullopt;
 
+    *fingerprint += fmt(";%s;%s", flake.lockedRef.subdir, lockFile);
+
+    /* Include revCount and lastModified because they're not
+       necessarily implied by the content fingerprint (e.g. for
+       tarball flakes) but can influence the evaluation result. */
+    if (auto revCount = flake.lockedRef.input.getRevCount())
+        *fingerprint += fmt(";revCount=%d", *revCount);
+    if (auto lastModified = flake.lockedRef.input.getLastModified())
+        *fingerprint += fmt(";lastModified=%d", *lastModified);
+
     // FIXME: as an optimization, if the flake contains a lock file
     // and we haven't changed it, then it's sufficient to use
     // flake.sourceInfo.storePath for the fingerprint.
-    return hashString(HashAlgorithm::SHA256, fmt("%s;%s;%s", *fingerprint, flake.lockedRef.subdir, lockFile));
+    return hashString(HashAlgorithm::SHA256, *fingerprint);
 }
 
 Flake::~Flake() { }
diff --git a/src/libexpr/flake/flake.hh b/src/libflake/flake/flake.hh
similarity index 100%
rename from src/libexpr/flake/flake.hh
rename to src/libflake/flake/flake.hh
diff --git a/src/libexpr/flake/flakeref.cc b/src/libflake/flake/flakeref.cc
similarity index 100%
rename from src/libexpr/flake/flakeref.cc
rename to src/libflake/flake/flakeref.cc
diff --git a/src/libexpr/flake/flakeref.hh b/src/libflake/flake/flakeref.hh
similarity index 82%
rename from src/libexpr/flake/flakeref.hh
rename to src/libflake/flake/flakeref.hh
index 5d78f49b683..04c812ed099 100644
--- a/src/libexpr/flake/flakeref.hh
+++ b/src/libflake/flake/flakeref.hh
@@ -68,24 +68,39 @@ struct FlakeRef
 
 std::ostream & operator << (std::ostream & str, const FlakeRef & flakeRef);
 
+/**
+ * @param baseDir Optional [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory)
+ */
 FlakeRef parseFlakeRef(
     const std::string & url,
     const std::optional<Path> & baseDir = {},
     bool allowMissing = false,
     bool isFlake = true);
 
+/**
+ * @param baseDir Optional [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory)
+ */
 std::optional<FlakeRef> maybeParseFlake(
     const std::string & url, const std::optional<Path> & baseDir = {});
 
+/**
+ * @param baseDir Optional [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory)
+ */
 std::pair<FlakeRef, std::string> parseFlakeRefWithFragment(
     const std::string & url,
     const std::optional<Path> & baseDir = {},
     bool allowMissing = false,
     bool isFlake = true);
 
+/**
+ * @param baseDir Optional [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory)
+ */
 std::optional<std::pair<FlakeRef, std::string>> maybeParseFlakeRefWithFragment(
     const std::string & url, const std::optional<Path> & baseDir = {});
 
+/**
+ * @param baseDir Optional [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory)
+ */
 std::tuple<FlakeRef, std::string, ExtendedOutputsSpec> parseFlakeRefWithFragmentAndExtendedOutputsSpec(
     const std::string & url,
     const std::optional<Path> & baseDir = {},
diff --git a/src/libexpr/flake/lockfile.cc b/src/libflake/flake/lockfile.cc
similarity index 100%
rename from src/libexpr/flake/lockfile.cc
rename to src/libflake/flake/lockfile.cc
diff --git a/src/libexpr/flake/lockfile.hh b/src/libflake/flake/lockfile.hh
similarity index 100%
rename from src/libexpr/flake/lockfile.hh
rename to src/libflake/flake/lockfile.hh
diff --git a/src/libexpr/flake/url-name.cc b/src/libflake/flake/url-name.cc
similarity index 100%
rename from src/libexpr/flake/url-name.cc
rename to src/libflake/flake/url-name.cc
diff --git a/src/libexpr/flake/url-name.hh b/src/libflake/flake/url-name.hh
similarity index 100%
rename from src/libexpr/flake/url-name.hh
rename to src/libflake/flake/url-name.hh
diff --git a/src/libflake/local.mk b/src/libflake/local.mk
new file mode 100644
index 00000000000..2cceda2bf25
--- /dev/null
+++ b/src/libflake/local.mk
@@ -0,0 +1,17 @@
+libraries += libflake
+
+libflake_NAME = libnixflake
+
+libflake_DIR := $(d)
+
+libflake_SOURCES := $(wildcard $(d)/*.cc $(d)/flake/*.cc)
+
+# Not just for this library itself, but also for downstream libraries using this library
+
+INCLUDE_libflake := -I $(d)
+
+libflake_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) $(INCLUDE_libflake)
+
+libflake_LDFLAGS += $(THREAD_LDFLAGS)
+
+libflake_LIBS = libutil libstore libfetchers libexpr
diff --git a/src/libflake/meson.build b/src/libflake/meson.build
new file mode 100644
index 00000000000..d3c3d3079cf
--- /dev/null
+++ b/src/libflake/meson.build
@@ -0,0 +1,75 @@
+project('nix-flake', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+  dependency('nix-fetchers'),
+  dependency('nix-expr'),
+]
+subdir('build-utils-meson/subprojects')
+
+nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
+deps_public += nlohmann_json
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  # '-include', 'config-fetchers.h',
+  '-include', 'config-expr.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'flake-settings.cc',
+  'flake/config.cc',
+  'flake/flake.cc',
+  'flake/flakeref.cc',
+  'flake/url-name.cc',
+  'flake/lockfile.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = files(
+  'flake-settings.hh',
+  'flake/flake.hh',
+  'flake/flakeref.hh',
+  'flake/lockfile.hh',
+  'flake/url-name.hh',
+)
+
+this_library = library(
+  'nixflake',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libflake/package.nix b/src/libflake/package.nix
new file mode 100644
index 00000000000..af6f5da9416
--- /dev/null
+++ b/src/libflake/package.nix
@@ -0,0 +1,84 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+, nix-store
+, nix-fetchers
+, nix-expr
+, nlohmann_json
+, libgit2
+, man
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-flake";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-store
+    nix-util
+    nix-fetchers
+    nix-expr
+    nlohmann_json
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  # TODO `releaseTools.coverageAnalysis` in Nixpkgs needs to be updated
+  # to work with `strictDeps`.
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libmain/.version b/src/libmain/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libmain/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libmain/build-utils-meson b/src/libmain/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libmain/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libmain/common-args.cc b/src/libmain/common-args.cc
index 5b49aaabcef..a94845ab8f3 100644
--- a/src/libmain/common-args.cc
+++ b/src/libmain/common-args.cc
@@ -1,5 +1,6 @@
 #include "common-args.hh"
 #include "args/root.hh"
+#include "config-global.hh"
 #include "globals.hh"
 #include "logging.hh"
 #include "loggers.hh"
diff --git a/src/libmain/meson.build b/src/libmain/meson.build
new file mode 100644
index 00000000000..859ce22f8ba
--- /dev/null
+++ b/src/libmain/meson.build
@@ -0,0 +1,98 @@
+project('nix-main', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+]
+subdir('build-utils-meson/subprojects')
+
+
+pubsetbuf_test = '''
+#include <iostream>
+
+using namespace std;
+
+char buf[1024];
+
+int main() {
+  cerr.rdbuf()->pubsetbuf(buf, sizeof(buf));
+}
+'''
+
+configdata.set(
+  'HAVE_PUBSETBUF',
+  cxx.compiles(pubsetbuf_test).to_int(),
+  description: 'Optionally used for buffering on standard error'
+)
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-main.hh',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-main.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'common-args.cc',
+  'loggers.cc',
+  'progress-bar.cc',
+  'shared.cc',
+)
+
+if host_machine.system() != 'windows'
+  sources += files(
+    'unix/stack.cc',
+  )
+endif
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'common-args.hh',
+  'loggers.hh',
+  'progress-bar.hh',
+  'shared.hh',
+)
+
+this_library = library(
+  'nixmain',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libmain/package.nix b/src/libmain/package.nix
new file mode 100644
index 00000000000..bbd97ec3e58
--- /dev/null
+++ b/src/libmain/package.nix
@@ -0,0 +1,79 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, openssl
+
+, nix-util
+, nix-store
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-main";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-util
+    nix-store
+    openssl
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  # TODO `releaseTools.coverageAnalysis` in Nixpkgs needs to be updated
+  # to work with `strictDeps`.
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libmain/progress-bar.cc b/src/libmain/progress-bar.cc
index ce45eae2ba1..bb4c52ef7ea 100644
--- a/src/libmain/progress-bar.cc
+++ b/src/libmain/progress-bar.cc
@@ -7,6 +7,7 @@
 #include <atomic>
 #include <map>
 #include <thread>
+#include <sstream>
 #include <iostream>
 #include <chrono>
 
diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index a43a00f1647..fc55fe3f1b2 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -113,7 +113,7 @@ static void sigHandler(int signo) { }
 #endif
 
 
-void initNix()
+void initNix(bool loadConfig)
 {
     /* Turn on buffering for cerr. */
 #if HAVE_PUBSETBUF
@@ -121,7 +121,7 @@ void initNix()
     std::cerr.rdbuf()->pubsetbuf(buf, sizeof(buf));
 #endif
 
-    initLibStore();
+    initLibStore(loadConfig);
 
 #ifndef _WIN32
     unix::startSignalHandlerThread();
@@ -173,12 +173,13 @@ void initNix()
        everybody. */
     umask(0022);
 
-#ifndef _WIN32
     /* Initialise the PRNG. */
     struct timeval tv;
     gettimeofday(&tv, 0);
+#ifndef _WIN32
     srandom(tv.tv_usec);
 #endif
+    srand(tv.tv_usec);
 
 
 }
@@ -319,6 +320,10 @@ void showManPage(const std::string & name)
     restoreProcessContext();
     setEnv("MANPATH", settings.nixManDir.c_str());
     execlp("man", "man", name.c_str(), nullptr);
+    if (errno == ENOENT) {
+        // Not SysError because we don't want to suffix the errno, aka No such file or directory.
+        throw Error("The '%1%' command was not found, but it is needed for '%2%' and some other '%3%' commands' help text. Perhaps you could install the '%1%' command?", "man", name.c_str(), "nix-*");
+    }
     throw SysError("command 'man %1%' failed", name.c_str());
 }
 
diff --git a/src/libmain/shared.hh b/src/libmain/shared.hh
index 3c657d2b7b7..aa44e1321fa 100644
--- a/src/libmain/shared.hh
+++ b/src/libmain/shared.hh
@@ -21,8 +21,9 @@ int handleExceptions(const std::string & programName, std::function<void()> fun)
 
 /**
  * Don't forget to call initPlugins() after settings are initialized!
+ * @param loadConfig Whether to load configuration from `nix.conf`, `NIX_CONFIG`, etc. May be disabled for unit tests.
  */
-void initNix();
+void initNix(bool loadConfig = true);
 
 void parseCmdLine(int argc, char * * argv,
     std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg);
diff --git a/src/libstore-c/.version b/src/libstore-c/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libstore-c/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libstore-c/build-utils-meson b/src/libstore-c/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libstore-c/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libstore-c/meson.build b/src/libstore-c/meson.build
new file mode 100644
index 00000000000..917de4cda51
--- /dev/null
+++ b/src/libstore-c/meson.build
@@ -0,0 +1,83 @@
+project('nix-store-c', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util-c'),
+]
+subdir('build-utils-meson/subprojects')
+
+# TODO rename, because it will conflict with downstream projects
+configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-store.h',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+
+  # From C++ libraries, only for internals
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+
+  # From C libraries, for our public, installed headers too
+  '-include', 'config-util.h',
+  '-include', 'config-store.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'nix_api_store.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'nix_api_store.h',
+)
+
+# TODO don't install this once tests don't use it and/or move the header into `libstore`, non-`c`
+headers += files('nix_api_store_internal.h')
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nixstorec',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libstore-c/nix_api_store.cc b/src/libstore-c/nix_api_store.cc
index 6ce4d01bbdf..4fe25c7d4ee 100644
--- a/src/libstore-c/nix_api_store.cc
+++ b/src/libstore-c/nix_api_store.cc
@@ -19,6 +19,16 @@ nix_err nix_libstore_init(nix_c_context * context)
     NIXC_CATCH_ERRS
 }
 
+nix_err nix_libstore_init_no_load_config(nix_c_context * context)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        nix::initLibStore(false);
+    }
+    NIXC_CATCH_ERRS
+}
+
 nix_err nix_init_plugins(nix_c_context * context)
 {
     if (context)
diff --git a/src/libstore-c/nix_api_store.h b/src/libstore-c/nix_api_store.h
index c83aca3f797..d3cb8fab84e 100644
--- a/src/libstore-c/nix_api_store.h
+++ b/src/libstore-c/nix_api_store.h
@@ -35,6 +35,13 @@ typedef struct StorePath StorePath;
  */
 nix_err nix_libstore_init(nix_c_context * context);
 
+/**
+ * @brief Like nix_libstore_init, but does not load the Nix configuration.
+ *
+ * This is useful when external configuration is not desired, such as when running unit tests.
+ */
+nix_err nix_libstore_init_no_load_config(nix_c_context * context);
+
 /**
  * @brief Loads the plugins specified in Nix's plugin-files setting.
  *
@@ -47,16 +54,20 @@ nix_err nix_libstore_init(nix_c_context * context);
 nix_err nix_init_plugins(nix_c_context * context);
 
 /**
- * @brief Open a nix store
+ * @brief Open a nix store.
+ *
  * Store instances may share state and resources behind the scenes.
+ *
  * @param[out] context Optional, stores error information
- * @param[in] uri URI of the nix store, copied
- * @param[in] params optional, array of key-value pairs, {{"endpoint",
- * "https://s3.local"}}
+ * @param[in] uri URI of the Nix store, copied. See [*Store URL format* in the Nix Reference
+ * Manual](https://nixos.org/manual/nix/stable/store/types/#store-url-format).
+ * @param[in] params optional, null-terminated array of key-value pairs, e.g. {{"endpoint",
+ * "https://s3.local"}}. See [*Store Types* in the Nix Reference
+ * Manual](https://nixos.org/manual/nix/stable/store/types).
  * @return a Store pointer, NULL in case of errors
  * @see nix_store_free
  */
-Store * nix_store_open(nix_c_context *, const char * uri, const char *** params);
+Store * nix_store_open(nix_c_context * context, const char * uri, const char *** params);
 
 /**
  * @brief Deallocate a nix store and free any resources if not also held by other Store instances.
@@ -148,7 +159,9 @@ nix_err nix_store_realise(
 
 /**
  * @brief get the version of a nix store.
+ *
  * If the store doesn't have a version (like the dummy store), returns an empty string.
+ *
  * @param[out] context Optional, stores error information
  * @param[in] store nix store reference
  * @param[in] callback Called with the version.
diff --git a/src/libstore-c/package.nix b/src/libstore-c/package.nix
new file mode 100644
index 00000000000..fc34c1bda72
--- /dev/null
+++ b/src/libstore-c/package.nix
@@ -0,0 +1,79 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util-c
+, nix-store
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-store-c";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    (fileset.fileFilter (file: file.hasExt "h") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-util-c
+    nix-store
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libstore/.version b/src/libstore/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libstore/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 97b6ec0529a..e8c8892b337 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -18,6 +18,7 @@
 #include <future>
 #include <regex>
 #include <fstream>
+#include <sstream>
 
 #include <nlohmann/json.hpp>
 
@@ -321,7 +322,7 @@ StorePath BinaryCacheStore::addToStoreFromDump(
         if (static_cast<FileIngestionMethod>(dumpMethod) == hashMethod.getFileIngestionMethod())
             caHash = hashString(HashAlgorithm::SHA256, dump2.s);
         switch (dumpMethod) {
-        case FileSerialisationMethod::Recursive:
+        case FileSerialisationMethod::NixArchive:
             // The dump is already NAR in this case, just use it.
             nar = dump2.s;
             break;
@@ -338,7 +339,7 @@ StorePath BinaryCacheStore::addToStoreFromDump(
     } else {
         // Otherwise, we have to do th same hashing as NAR so our single
         // hash will suffice for both purposes.
-        if (dumpMethod != FileSerialisationMethod::Recursive || hashAlgo != HashAlgorithm::SHA256)
+        if (dumpMethod != FileSerialisationMethod::NixArchive || hashAlgo != HashAlgorithm::SHA256)
             unsupported("addToStoreFromDump");
     }
     StringSource narDump { nar };
@@ -442,8 +443,7 @@ void BinaryCacheStore::queryPathInfoUncached(const StorePath & storePath,
 
 StorePath BinaryCacheStore::addToStore(
     std::string_view name,
-    SourceAccessor & accessor,
-    const CanonPath & path,
+    const SourcePath & path,
     ContentAddressMethod method,
     HashAlgorithm hashAlgo,
     const StorePathSet & references,
@@ -454,10 +454,10 @@ StorePath BinaryCacheStore::addToStore(
        non-recursive+sha256 so we can just use the default
        implementation of this method in terms of addToStoreFromDump. */
 
-    auto h = hashPath(accessor, path, method.getFileIngestionMethod(), hashAlgo, filter);
+    auto h = hashPath(path, method.getFileIngestionMethod(), hashAlgo, filter).first;
 
     auto source = sinkToSource([&](Sink & sink) {
-        accessor.dumpPath(path, sink, filter);
+        path.dumpPath(sink, filter);
     });
     return addToStoreCommon(*source, repair, CheckSigs, [&](HashResult nar) {
         ValidPathInfo info {
diff --git a/src/libstore/binary-cache-store.hh b/src/libstore/binary-cache-store.hh
index 7c282830933..695bc925277 100644
--- a/src/libstore/binary-cache-store.hh
+++ b/src/libstore/binary-cache-store.hh
@@ -133,8 +133,7 @@ public:
 
     StorePath addToStore(
         std::string_view name,
-        SourceAccessor & accessor,
-        const CanonPath & srcPath,
+        const SourcePath & path,
         ContentAddressMethod method,
         HashAlgorithm hashAlgo,
         const StorePathSet & references,
diff --git a/src/libstore/build-utils-meson b/src/libstore/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libstore/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libstore/unix/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
similarity index 97%
rename from src/libstore/unix/build/derivation-goal.cc
rename to src/libstore/build/derivation-goal.cc
index 4d43429965d..64b8495e1bb 100644
--- a/src/libstore/unix/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -1,5 +1,9 @@
 #include "derivation-goal.hh"
-#include "hook-instance.hh"
+#ifndef _WIN32 // TODO enable build hook on Windows
+#  include "hook-instance.hh"
+#endif
+#include "processes.hh"
+#include "config-global.hh"
 #include "worker.hh"
 #include "builtins.hh"
 #include "builtins/buildenv.hh"
@@ -19,46 +23,13 @@
 
 #include <fstream>
 #include <sys/types.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <sys/wait.h>
-#include <netdb.h>
 #include <fcntl.h>
-#include <termios.h>
 #include <unistd.h>
-#include <sys/mman.h>
-#include <sys/utsname.h>
-#include <sys/resource.h>
-
-#if HAVE_STATVFS
-#include <sys/statvfs.h>
-#endif
-
-/* Includes required for chroot support. */
-#if __linux__
-#include <sys/socket.h>
-#include <sys/ioctl.h>
-#include <net/if.h>
-#include <netinet/ip.h>
-#include <sys/mman.h>
-#include <sched.h>
-#include <sys/param.h>
-#include <sys/mount.h>
-#include <sys/syscall.h>
-#if HAVE_SECCOMP
-#include <seccomp.h>
-#endif
-#define pivot_root(new_root, put_old) (syscall(SYS_pivot_root, new_root, put_old))
-#endif
 
-#if __APPLE__
-#include <spawn.h>
-#include <sys/sysctl.h>
+#ifndef _WIN32 // TODO abstract over proc exit status
+#  include <sys/wait.h>
 #endif
 
-#include <pwd.h>
-#include <grp.h>
-
 #include <nlohmann/json.hpp>
 
 namespace nix {
@@ -127,7 +98,9 @@ std::string DerivationGoal::key()
 
 void DerivationGoal::killChild()
 {
+#ifndef _WIN32 // TODO enable build hook on Windows
     hook.reset();
+#endif
 }
 
 
@@ -667,9 +640,17 @@ void DerivationGoal::started()
         buildMode == bmCheck ? "checking outputs of '%s'" :
         "building '%s'", worker.store.printStorePath(drvPath));
     fmt("building '%s'", worker.store.printStorePath(drvPath));
+#ifndef _WIN32 // TODO enable build hook on Windows
     if (hook) msg += fmt(" on '%s'", machineName);
+#endif
     act = std::make_unique<Activity>(*logger, lvlInfo, actBuild, msg,
-        Logger::Fields{worker.store.printStorePath(drvPath), hook ? machineName : "", 1, 1});
+        Logger::Fields{worker.store.printStorePath(drvPath),
+#ifndef _WIN32 // TODO enable build hook on Windows
+        hook ? machineName :
+#endif
+            "",
+        1,
+        1});
     mcRunningBuilds = std::make_unique<MaintainCount<uint64_t>>(worker.runningBuilds);
     worker.updateProgress();
 }
@@ -804,12 +785,18 @@ static void movePath(const Path & src, const Path & dst)
 {
     auto st = lstat(src);
 
-    bool changePerm = (geteuid() && S_ISDIR(st.st_mode) && !(st.st_mode & S_IWUSR));
+    bool changePerm = (
+#ifndef _WIN32
+        geteuid()
+#else
+        !isRootUser()
+#endif
+        && S_ISDIR(st.st_mode) && !(st.st_mode & S_IWUSR));
 
     if (changePerm)
         chmod_(src, st.st_mode | S_IWUSR);
 
-    renameFile(src, dst);
+    std::filesystem::rename(src, dst);
 
     if (changePerm)
         chmod_(dst, st.st_mode);
@@ -822,7 +809,7 @@ void replaceValidPath(const Path & storePath, const Path & tmpPath)
        tmpPath (the replacement), so we have to move it out of the
        way first.  We'd better not be interrupted here, because if
        we're repairing (say) Glibc, we end up with a broken system. */
-    Path oldPath = fmt("%1%.old-%2%-%3%", storePath, getpid(), random());
+    Path oldPath = fmt("%1%.old-%2%-%3%", storePath, getpid(), rand());
     if (pathExists(storePath))
         movePath(storePath, oldPath);
 
@@ -844,14 +831,20 @@ void replaceValidPath(const Path & storePath, const Path & tmpPath)
 
 int DerivationGoal::getChildStatus()
 {
+#ifndef _WIN32 // TODO enable build hook on Windows
     return hook->pid.kill();
+#else
+    return 0;
+#endif
 }
 
 
 void DerivationGoal::closeReadPipes()
 {
-    hook->builderOut.readSide = -1;
-    hook->fromHook.readSide = -1;
+#ifndef _WIN32 // TODO enable build hook on Windows
+    hook->builderOut.readSide.close();
+    hook->fromHook.readSide.close();
+#endif
 }
 
 
@@ -1045,13 +1038,16 @@ void DerivationGoal::buildDone()
 
         BuildResult::Status st = BuildResult::MiscFailure;
 
+#ifndef _WIN32 // TODO abstract over proc exit status
         if (hook && WIFEXITED(status) && WEXITSTATUS(status) == 101)
             st = BuildResult::TimedOut;
 
         else if (hook && (!WIFEXITED(status) || WEXITSTATUS(status) != 100)) {
         }
 
-        else {
+        else
+#endif
+        {
             assert(derivationType);
             st =
                 dynamic_cast<NotDeterministic*>(&e) ? BuildResult::NotDeterministic :
@@ -1138,6 +1134,9 @@ void DerivationGoal::resolvedFinished()
 
 HookReply DerivationGoal::tryBuildHook()
 {
+#ifdef _WIN32 // TODO enable build hook on Windows
+    return rpDecline;
+#else
     if (settings.buildHook.get().empty() || !worker.tryBuildHook || !useDerivation) return rpDecline;
 
     if (!worker.hook)
@@ -1231,17 +1230,18 @@ HookReply DerivationGoal::tryBuildHook()
     }
 
     hook->sink = FdSink();
-    hook->toHook.writeSide = -1;
+    hook->toHook.writeSide.close();
 
     /* Create the log file and pipe. */
     Path logFile = openLogFile();
 
-    std::set<int> fds;
+    std::set<MuxablePipePollState::CommChannel> fds;
     fds.insert(hook->fromHook.readSide.get());
     fds.insert(hook->builderOut.readSide.get());
     worker.childStarted(shared_from_this(), fds, false, false);
 
     return rpAccept;
+#endif
 }
 
 
@@ -1277,7 +1277,11 @@ Path DerivationGoal::openLogFile()
     Path logFileName = fmt("%s/%s%s", dir, baseName.substr(2),
         settings.compressLog ? ".bz2" : "");
 
-    fdLogFile = open(logFileName.c_str(), O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC, 0666);
+    fdLogFile = toDescriptor(open(logFileName.c_str(), O_CREAT | O_WRONLY | O_TRUNC
+#ifndef _WIN32
+        | O_CLOEXEC
+#endif
+        , 0666));
     if (!fdLogFile) throw SysError("creating log file '%1%'", logFileName);
 
     logFileSink = std::make_shared<FdSink>(fdLogFile.get());
@@ -1297,16 +1301,20 @@ void DerivationGoal::closeLogFile()
     if (logSink2) logSink2->finish();
     if (logFileSink) logFileSink->flush();
     logSink = logFileSink = 0;
-    fdLogFile = -1;
+    fdLogFile.close();
 }
 
 
-bool DerivationGoal::isReadDesc(int fd)
+bool DerivationGoal::isReadDesc(Descriptor fd)
 {
+#ifdef _WIN32 // TODO enable build hook on Windows
+    return false;
+#else
     return fd == hook->builderOut.readSide.get();
+#endif
 }
 
-void DerivationGoal::handleChildOutput(int fd, std::string_view data)
+void DerivationGoal::handleChildOutput(Descriptor fd, std::string_view data)
 {
     // local & `ssh://`-builds are dealt with here.
     auto isWrittenToLog = isReadDesc(fd);
@@ -1336,6 +1344,7 @@ void DerivationGoal::handleChildOutput(int fd, std::string_view data)
         if (logSink) (*logSink)(data);
     }
 
+#ifndef _WIN32 // TODO enable build hook on Windows
     if (hook && fd == hook->fromHook.readSide.get()) {
         for (auto c : data)
             if (c == '\n') {
@@ -1370,10 +1379,11 @@ void DerivationGoal::handleChildOutput(int fd, std::string_view data)
             } else
                 currentHookLine += c;
     }
+#endif
 }
 
 
-void DerivationGoal::handleEOF(int fd)
+void DerivationGoal::handleEOF(Descriptor fd)
 {
     if (!currentLogLine.empty()) flushLine();
     worker.wakeUp(shared_from_this());
diff --git a/src/libstore/unix/build/derivation-goal.hh b/src/libstore/build/derivation-goal.hh
similarity index 96%
rename from src/libstore/unix/build/derivation-goal.hh
rename to src/libstore/build/derivation-goal.hh
index ddb5ee1e34a..04f13aedd17 100644
--- a/src/libstore/unix/build/derivation-goal.hh
+++ b/src/libstore/build/derivation-goal.hh
@@ -2,7 +2,9 @@
 ///@file
 
 #include "parsed-derivations.hh"
-#include "lock.hh"
+#ifndef _WIN32
+#  include "user-lock.hh"
+#endif
 #include "outputs-spec.hh"
 #include "store-api.hh"
 #include "pathlocks.hh"
@@ -12,7 +14,9 @@ namespace nix {
 
 using std::map;
 
+#ifndef _WIN32 // TODO enable build hook on Windows
 struct HookInstance;
+#endif
 
 typedef enum {rpAccept, rpDecline, rpPostpone} HookReply;
 
@@ -178,10 +182,12 @@ struct DerivationGoal : public Goal
 
     std::string currentHookLine;
 
+#ifndef _WIN32 // TODO enable build hook on Windows
     /**
      * The build hook.
      */
     std::unique_ptr<HookInstance> hook;
+#endif
 
     /**
      * The sort of derivation we are building.
@@ -287,13 +293,13 @@ struct DerivationGoal : public Goal
     virtual void cleanupPostOutputsRegisteredModeCheck();
     virtual void cleanupPostOutputsRegisteredModeNonCheck();
 
-    virtual bool isReadDesc(int fd);
+    virtual bool isReadDesc(Descriptor fd);
 
     /**
      * Callback used by the worker to write to the log.
      */
-    void handleChildOutput(int fd, std::string_view data) override;
-    void handleEOF(int fd) override;
+    void handleChildOutput(Descriptor fd, std::string_view data) override;
+    void handleEOF(Descriptor fd) override;
     void flushLine();
 
     /**
diff --git a/src/libstore/unix/build/drv-output-substitution-goal.cc b/src/libstore/build/drv-output-substitution-goal.cc
similarity index 93%
rename from src/libstore/unix/build/drv-output-substitution-goal.cc
rename to src/libstore/build/drv-output-substitution-goal.cc
index b30957c8417..13a07e4ea38 100644
--- a/src/libstore/unix/build/drv-output-substitution-goal.cc
+++ b/src/libstore/build/drv-output-substitution-goal.cc
@@ -66,7 +66,11 @@ void DrvOutputSubstitutionGoal::tryNext()
        some other error occurs), so it must not touch `this`. So put
        the shared state in a separate refcounted object. */
     downloadState = std::make_shared<DownloadState>();
+#ifndef _WIN32
     downloadState->outPipe.create();
+#else
+    downloadState->outPipe.createAsyncPipe(worker.ioport.get());
+#endif
 
     sub->queryRealisation(
         id,
@@ -79,7 +83,13 @@ void DrvOutputSubstitutionGoal::tryNext()
             }
         } });
 
-    worker.childStarted(shared_from_this(), {downloadState->outPipe.readSide.get()}, true, false);
+    worker.childStarted(shared_from_this(), {
+#ifndef _WIN32
+        downloadState->outPipe.readSide.get()
+#else
+        &downloadState->outPipe
+#endif
+    }, true, false);
 
     state = &DrvOutputSubstitutionGoal::realisationFetched;
 }
@@ -158,7 +168,7 @@ void DrvOutputSubstitutionGoal::work()
     (this->*state)();
 }
 
-void DrvOutputSubstitutionGoal::handleEOF(int fd)
+void DrvOutputSubstitutionGoal::handleEOF(Descriptor fd)
 {
     if (fd == downloadState->outPipe.readSide.get()) worker.wakeUp(shared_from_this());
 }
diff --git a/src/libstore/unix/build/drv-output-substitution-goal.hh b/src/libstore/build/drv-output-substitution-goal.hh
similarity index 94%
rename from src/libstore/unix/build/drv-output-substitution-goal.hh
rename to src/libstore/build/drv-output-substitution-goal.hh
index da2426e5e86..6967ca84ff8 100644
--- a/src/libstore/unix/build/drv-output-substitution-goal.hh
+++ b/src/libstore/build/drv-output-substitution-goal.hh
@@ -1,11 +1,13 @@
 #pragma once
 ///@file
 
+#include <thread>
+#include <future>
+
 #include "store-api.hh"
 #include "goal.hh"
 #include "realisation.hh"
-#include <thread>
-#include <future>
+#include "muxable-pipe.hh"
 
 namespace nix {
 
@@ -43,7 +45,7 @@ class DrvOutputSubstitutionGoal : public Goal {
 
     struct DownloadState
     {
-        Pipe outPipe;
+        MuxablePipe outPipe;
         std::promise<std::shared_ptr<const Realisation>> promise;
     };
 
@@ -71,7 +73,7 @@ public:
     std::string key() override;
 
     void work() override;
-    void handleEOF(int fd) override;
+    void handleEOF(Descriptor fd) override;
 
     JobCategory jobCategory() const override {
         return JobCategory::Substitution;
diff --git a/src/libstore/unix/build/entry-points.cc b/src/libstore/build/entry-points.cc
similarity index 90%
rename from src/libstore/unix/build/entry-points.cc
rename to src/libstore/build/entry-points.cc
index d4bead28edf..784f618c1a0 100644
--- a/src/libstore/unix/build/entry-points.cc
+++ b/src/libstore/build/entry-points.cc
@@ -1,6 +1,8 @@
 #include "worker.hh"
 #include "substitution-goal.hh"
-#include "derivation-goal.hh"
+#ifndef _WIN32 // TODO Enable building on Windows
+#  include "derivation-goal.hh"
+#endif
 #include "local-store.hh"
 
 namespace nix {
@@ -25,9 +27,12 @@ void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMod
                 ex = std::move(i->ex);
         }
         if (i->exitCode != Goal::ecSuccess) {
+#ifndef _WIN32 // TODO Enable building on Windows
             if (auto i2 = dynamic_cast<DerivationGoal *>(i.get()))
                 failed.insert(printStorePath(i2->drvPath));
-            else if (auto i2 = dynamic_cast<PathSubstitutionGoal *>(i.get()))
+            else
+#endif
+            if (auto i2 = dynamic_cast<PathSubstitutionGoal *>(i.get()))
                 failed.insert(printStorePath(i2->storePath));
         }
     }
@@ -74,7 +79,12 @@ BuildResult Store::buildDerivation(const StorePath & drvPath, const BasicDerivat
     BuildMode buildMode)
 {
     Worker worker(*this, *this);
+#ifndef _WIN32 // TODO Enable building on Windows
     auto goal = worker.makeBasicDerivationGoal(drvPath, drv, OutputsSpec::All {}, buildMode);
+#else
+    std::shared_ptr<Goal> goal;
+    throw UnimplementedError("Building derivations not yet implemented on windows.");
+#endif
 
     try {
         worker.run(Goals{goal});
diff --git a/src/libstore/unix/build/goal.cc b/src/libstore/build/goal.cc
similarity index 100%
rename from src/libstore/unix/build/goal.cc
rename to src/libstore/build/goal.cc
diff --git a/src/libstore/unix/build/goal.hh b/src/libstore/build/goal.hh
similarity index 97%
rename from src/libstore/unix/build/goal.hh
rename to src/libstore/build/goal.hh
index 9af083230ee..0d9b828e1d6 100644
--- a/src/libstore/unix/build/goal.hh
+++ b/src/libstore/build/goal.hh
@@ -138,12 +138,12 @@ public:
 
     virtual void waiteeDone(GoalPtr waitee, ExitCode result);
 
-    virtual void handleChildOutput(int fd, std::string_view data)
+    virtual void handleChildOutput(Descriptor fd, std::string_view data)
     {
         abort();
     }
 
-    virtual void handleEOF(int fd)
+    virtual void handleEOF(Descriptor fd)
     {
         abort();
     }
diff --git a/src/libstore/unix/build/substitution-goal.cc b/src/libstore/build/substitution-goal.cc
similarity index 96%
rename from src/libstore/unix/build/substitution-goal.cc
rename to src/libstore/build/substitution-goal.cc
index c7e8e282508..0be3d1e8d98 100644
--- a/src/libstore/unix/build/substitution-goal.cc
+++ b/src/libstore/build/substitution-goal.cc
@@ -212,7 +212,11 @@ void PathSubstitutionGoal::tryToRun()
     maintainRunningSubstitutions = std::make_unique<MaintainCount<uint64_t>>(worker.runningSubstitutions);
     worker.updateProgress();
 
+#ifndef _WIN32
     outPipe.create();
+#else
+    outPipe.createAsyncPipe(worker.ioport.get());
+#endif
 
     promise = std::promise<void>();
 
@@ -235,7 +239,13 @@ void PathSubstitutionGoal::tryToRun()
         }
     });
 
-    worker.childStarted(shared_from_this(), {outPipe.readSide.get()}, true, false);
+    worker.childStarted(shared_from_this(), {
+#ifndef _WIN32
+        outPipe.readSide.get()
+#else
+        &outPipe
+#endif
+    }, true, false);
 
     state = &PathSubstitutionGoal::finished;
 }
@@ -294,12 +304,12 @@ void PathSubstitutionGoal::finished()
 }
 
 
-void PathSubstitutionGoal::handleChildOutput(int fd, std::string_view data)
+void PathSubstitutionGoal::handleChildOutput(Descriptor fd, std::string_view data)
 {
 }
 
 
-void PathSubstitutionGoal::handleEOF(int fd)
+void PathSubstitutionGoal::handleEOF(Descriptor fd)
 {
     if (fd == outPipe.readSide.get()) worker.wakeUp(shared_from_this());
 }
diff --git a/src/libstore/unix/build/substitution-goal.hh b/src/libstore/build/substitution-goal.hh
similarity index 93%
rename from src/libstore/unix/build/substitution-goal.hh
rename to src/libstore/build/substitution-goal.hh
index 1d389d328ff..1a051fc1fd5 100644
--- a/src/libstore/unix/build/substitution-goal.hh
+++ b/src/libstore/build/substitution-goal.hh
@@ -1,9 +1,9 @@
 #pragma once
 ///@file
 
-#include "lock.hh"
 #include "store-api.hh"
 #include "goal.hh"
+#include "muxable-pipe.hh"
 
 namespace nix {
 
@@ -45,7 +45,7 @@ struct PathSubstitutionGoal : public Goal
     /**
      * Pipe for the substituter's standard output.
      */
-    Pipe outPipe;
+    MuxablePipe outPipe;
 
     /**
      * The substituter thread.
@@ -111,8 +111,8 @@ public:
     /**
      * Callback used by the worker to write to the log.
      */
-    void handleChildOutput(int fd, std::string_view data) override;
-    void handleEOF(int fd) override;
+    void handleChildOutput(Descriptor fd, std::string_view data) override;
+    void handleEOF(Descriptor fd) override;
 
     /* Called by destructor, can't be overridden */
     void cleanup() override final;
diff --git a/src/libstore/unix/build/worker.cc b/src/libstore/build/worker.cc
similarity index 85%
rename from src/libstore/unix/build/worker.cc
rename to src/libstore/build/worker.cc
index 815ded3d5b0..8a5d6de725f 100644
--- a/src/libstore/unix/build/worker.cc
+++ b/src/libstore/build/worker.cc
@@ -1,13 +1,15 @@
+#include "local-store.hh"
 #include "machines.hh"
 #include "worker.hh"
 #include "substitution-goal.hh"
 #include "drv-output-substitution-goal.hh"
-#include "local-derivation-goal.hh"
-#include "hook-instance.hh"
+#include "derivation-goal.hh"
+#ifndef _WIN32 // TODO Enable building on Windows
+#  include "local-derivation-goal.hh"
+#  include "hook-instance.hh"
+#endif
 #include "signals.hh"
 
-#include <poll.h>
-
 namespace nix {
 
 Worker::Worker(Store & store, Store & evalStore)
@@ -17,7 +19,6 @@ Worker::Worker(Store & store, Store & evalStore)
     , store(store)
     , evalStore(evalStore)
 {
-    /* Debugging: prevent recursive workers. */
     nrLocalBuilds = 0;
     nrSubstitutions = 0;
     lastWokenUp = steady_time_point::min();
@@ -64,20 +65,27 @@ std::shared_ptr<DerivationGoal> Worker::makeDerivationGoal(const StorePath & drv
     const OutputsSpec & wantedOutputs, BuildMode buildMode)
 {
     return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
-        return !dynamic_cast<LocalStore *>(&store)
-            ? std::make_shared</* */DerivationGoal>(drvPath, wantedOutputs, *this, buildMode)
-            : std::make_shared<LocalDerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
+        return
+#ifndef _WIN32 // TODO Enable building on Windows
+            dynamic_cast<LocalStore *>(&store)
+            ? std::make_shared<LocalDerivationGoal>(drvPath, wantedOutputs, *this, buildMode)
+            :
+#endif
+            std::make_shared</* */DerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
     });
 }
 
-
 std::shared_ptr<DerivationGoal> Worker::makeBasicDerivationGoal(const StorePath & drvPath,
     const BasicDerivation & drv, const OutputsSpec & wantedOutputs, BuildMode buildMode)
 {
     return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
-        return !dynamic_cast<LocalStore *>(&store)
-            ? std::make_shared</* */DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode)
-            : std::make_shared<LocalDerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
+        return
+#ifndef _WIN32 // TODO Enable building on Windows
+            dynamic_cast<LocalStore *>(&store)
+            ? std::make_shared<LocalDerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode)
+            :
+#endif
+            std::make_shared</* */DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
     });
 }
 
@@ -143,7 +151,8 @@ void Worker::removeGoal(GoalPtr goal)
 {
     if (auto drvGoal = std::dynamic_pointer_cast<DerivationGoal>(goal))
         nix::removeGoal(drvGoal, derivationGoals);
-    else if (auto subGoal = std::dynamic_pointer_cast<PathSubstitutionGoal>(goal))
+    else
+    if (auto subGoal = std::dynamic_pointer_cast<PathSubstitutionGoal>(goal))
         nix::removeGoal(subGoal, substitutionGoals);
     else if (auto subGoal = std::dynamic_pointer_cast<DrvOutputSubstitutionGoal>(goal))
         nix::removeGoal(subGoal, drvOutputSubstitutionGoals);
@@ -187,13 +196,13 @@ unsigned Worker::getNrSubstitutions()
 }
 
 
-void Worker::childStarted(GoalPtr goal, const std::set<int> & fds,
+void Worker::childStarted(GoalPtr goal, const std::set<MuxablePipePollState::CommChannel> & channels,
     bool inBuildSlot, bool respectTimeouts)
 {
     Child child;
     child.goal = goal;
     child.goal2 = goal.get();
-    child.fds = fds;
+    child.channels = channels;
     child.timeStarted = child.lastOutput = steady_time_point::clock::now();
     child.inBuildSlot = inBuildSlot;
     child.respectTimeouts = respectTimeouts;
@@ -286,7 +295,8 @@ void Worker::run(const Goals & _topGoals)
                 .drvPath = makeConstantStorePathRef(goal->drvPath),
                 .outputs = goal->wantedOutputs,
             });
-        } else if (auto goal = dynamic_cast<PathSubstitutionGoal *>(i.get())) {
+        } else
+        if (auto goal = dynamic_cast<PathSubstitutionGoal *>(i.get())) {
             topPaths.push_back(DerivedPath::Opaque{goal->storePath});
         }
     }
@@ -408,23 +418,25 @@ void Worker::waitForInput()
     if (useTimeout)
         vomit("sleeping %d seconds", timeout);
 
+    MuxablePipePollState state;
+
+#ifndef _WIN32
     /* Use select() to wait for the input side of any logger pipe to
        become `available'.  Note that `available' (i.e., non-blocking)
        includes EOF. */
-    std::vector<struct pollfd> pollStatus;
-    std::map<int, size_t> fdToPollStatus;
     for (auto & i : children) {
-        for (auto & j : i.fds) {
-            pollStatus.push_back((struct pollfd) { .fd = j, .events = POLLIN });
-            fdToPollStatus[j] = pollStatus.size() - 1;
+        for (auto & j : i.channels) {
+            state.pollStatus.push_back((struct pollfd) { .fd = j, .events = POLLIN });
+            state.fdToPollStatus[j] = state.pollStatus.size() - 1;
         }
     }
+#endif
 
-    if (poll(pollStatus.data(), pollStatus.size(),
-            useTimeout ? timeout * 1000 : -1) == -1) {
-        if (errno == EINTR) return;
-        throw SysError("waiting for input");
-    }
+    state.poll(
+#ifdef _WIN32
+        ioport.get(),
+#endif
+        useTimeout ? (std::optional { timeout * 1000 }) : std::nullopt);
 
     auto after = steady_time_point::clock::now();
 
@@ -439,32 +451,18 @@ void Worker::waitForInput()
         GoalPtr goal = j->goal.lock();
         assert(goal);
 
-        std::set<int> fds2(j->fds);
-        std::vector<unsigned char> buffer(4096);
-        for (auto & k : fds2) {
-            const auto fdPollStatusId = get(fdToPollStatus, k);
-            assert(fdPollStatusId);
-            assert(*fdPollStatusId < pollStatus.size());
-            if (pollStatus.at(*fdPollStatusId).revents) {
-                ssize_t rd = ::read(k, buffer.data(), buffer.size());
-                // FIXME: is there a cleaner way to handle pt close
-                // than EIO? Is this even standard?
-                if (rd == 0 || (rd == -1 && errno == EIO)) {
-                    debug("%1%: got EOF", goal->getName());
-                    goal->handleEOF(k);
-                    j->fds.erase(k);
-                } else if (rd == -1) {
-                    if (errno != EINTR)
-                        throw SysError("%s: read failed", goal->getName());
-                } else {
-                    printMsg(lvlVomit, "%1%: read %2% bytes",
-                        goal->getName(), rd);
-                    std::string_view data((char *) buffer.data(), rd);
-                    j->lastOutput = after;
-                    goal->handleChildOutput(k, data);
-                }
-            }
-        }
+        state.iterate(
+            j->channels,
+            [&](Descriptor k, std::string_view data) {
+                printMsg(lvlVomit, "%1%: read %2% bytes",
+                    goal->getName(), data.size());
+                j->lastOutput = after;
+                goal->handleChildOutput(k, data);
+            },
+            [&](Descriptor k) {
+                debug("%1%: got EOF", goal->getName());
+                goal->handleEOF(k);
+            });
 
         if (goal->exitCode == Goal::ecBusy &&
             0 != settings.maxSilentTime &&
@@ -529,9 +527,9 @@ bool Worker::pathContentsGood(const StorePath & path)
     if (!pathExists(store.printStorePath(path)))
         res = false;
     else {
-        Hash current = hashPath(
-            *store.getFSAccessor(), CanonPath { store.printStorePath(path) },
-            FileIngestionMethod::Recursive, info->narHash.algo);
+        auto current = hashPath(
+            {store.getFSAccessor(), CanonPath(store.printStorePath(path))},
+            FileIngestionMethod::NixArchive, info->narHash.algo).first;
         Hash nullHash(HashAlgorithm::SHA256);
         res = info->narHash == nullHash || info->narHash == current;
     }
diff --git a/src/libstore/unix/build/worker.hh b/src/libstore/build/worker.hh
similarity index 94%
rename from src/libstore/unix/build/worker.hh
rename to src/libstore/build/worker.hh
index ced013ddd84..33a7bf01517 100644
--- a/src/libstore/unix/build/worker.hh
+++ b/src/libstore/build/worker.hh
@@ -2,10 +2,10 @@
 ///@file
 
 #include "types.hh"
-#include "lock.hh"
 #include "store-api.hh"
 #include "goal.hh"
 #include "realisation.hh"
+#include "muxable-pipe.hh"
 
 #include <future>
 #include <thread>
@@ -36,14 +36,14 @@ typedef std::chrono::time_point<std::chrono::steady_clock> steady_time_point;
 
 /**
  * A mapping used to remember for each child process to what goal it
- * belongs, and file descriptors for receiving log data and output
+ * belongs, and comm channels for receiving log data and output
  * path creation commands.
  */
 struct Child
 {
     WeakGoalPtr goal;
     Goal * goal2; // ugly hackery
-    std::set<int> fds;
+    std::set<MuxablePipePollState::CommChannel> channels;
     bool respectTimeouts;
     bool inBuildSlot;
     /**
@@ -53,11 +53,13 @@ struct Child
     steady_time_point timeStarted;
 };
 
+#ifndef _WIN32 // TODO Enable building on Windows
 /* Forward definition. */
 struct HookInstance;
+#endif
 
 /**
- * The worker class.
+ * Coordinates one or more realisations and their interdependencies.
  */
 class Worker
 {
@@ -152,10 +154,16 @@ public:
      */
     bool checkMismatch;
 
+#ifdef _WIN32
+    AutoCloseFD ioport;
+#endif
+
     Store & store;
     Store & evalStore;
 
+#ifndef _WIN32 // TODO Enable building on Windows
     std::unique_ptr<HookInstance> hook;
+#endif
 
     uint64_t expectedBuilds = 0;
     uint64_t doneBuilds = 0;
@@ -238,7 +246,7 @@ public:
      * Registers a running child process.  `inBuildSlot` means that
      * the process counts towards the jobs limit.
      */
-    void childStarted(GoalPtr goal, const std::set<int> & fds,
+    void childStarted(GoalPtr goal, const std::set<MuxablePipePollState::CommChannel> & channels,
         bool inBuildSlot, bool respectTimeouts);
 
     /**
diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
index e009f5b9dbf..0f7bcd99b1c 100644
--- a/src/libstore/builtins/buildenv.cc
+++ b/src/libstore/builtins/buildenv.cc
@@ -1,5 +1,6 @@
 #include "buildenv.hh"
 #include "derivations.hh"
+#include "signals.hh"
 
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -17,12 +18,12 @@ struct State
 /* For each activated package, create symlinks */
 static void createLinks(State & state, const Path & srcDir, const Path & dstDir, int priority)
 {
-    DirEntries srcFiles;
+    std::filesystem::directory_iterator srcFiles;
 
     try {
-        srcFiles = readDirectory(srcDir);
-    } catch (SysError & e) {
-        if (e.errNo == ENOTDIR) {
+        srcFiles = std::filesystem::directory_iterator{srcDir};
+    } catch (std::filesystem::filesystem_error & e) {
+        if (e.code() == std::errc::not_a_directory) {
             warn("not including '%s' in the user environment because it's not a directory", srcDir);
             return;
         }
@@ -30,11 +31,13 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
     }
 
     for (const auto & ent : srcFiles) {
-        if (ent.name[0] == '.')
+        checkInterrupt();
+        auto name = ent.path().filename();
+        if (name.string()[0] == '.')
             /* not matched by glob */
             continue;
-        auto srcFile = srcDir + "/" + ent.name;
-        auto dstFile = dstDir + "/" + ent.name;
+        auto srcFile = (std::filesystem::path{srcDir} / name).string();
+        auto dstFile = (std::filesystem::path{dstDir} / name).string();
 
         struct stat srcSt;
         try {
diff --git a/src/libstore/unix/builtins/fetchurl.cc b/src/libstore/builtins/fetchurl.cc
similarity index 100%
rename from src/libstore/unix/builtins/fetchurl.cc
rename to src/libstore/builtins/fetchurl.cc
diff --git a/src/libstore/unix/builtins/unpack-channel.cc b/src/libstore/builtins/unpack-channel.cc
similarity index 67%
rename from src/libstore/unix/builtins/unpack-channel.cc
rename to src/libstore/builtins/unpack-channel.cc
index 6f68d4c0bc7..a5f2b8e3adf 100644
--- a/src/libstore/unix/builtins/unpack-channel.cc
+++ b/src/libstore/builtins/unpack-channel.cc
@@ -21,10 +21,13 @@ void builtinUnpackChannel(
 
     unpackTarfile(src, out);
 
-    auto entries = readDirectory(out);
-    if (entries.size() != 1)
+    auto entries = std::filesystem::directory_iterator{out};
+    auto fileName = entries->path().string();
+    auto fileCount = std::distance(std::filesystem::begin(entries), std::filesystem::end(entries));
+
+    if (fileCount != 1)
         throw Error("channel tarball '%s' contains more than one file", src);
-    renameFile((out + "/" + entries[0].name), (out + "/" + channelName));
+    std::filesystem::rename(fileName, (out + "/" + channelName));
 }
 
 }
diff --git a/src/libstore/unix/ca-specific-schema.sql b/src/libstore/ca-specific-schema.sql
similarity index 100%
rename from src/libstore/unix/ca-specific-schema.sql
rename to src/libstore/ca-specific-schema.sql
diff --git a/src/libstore/content-address.cc b/src/libstore/content-address.cc
index 4ed4f2de561..e1cdfece6e9 100644
--- a/src/libstore/content-address.cc
+++ b/src/libstore/content-address.cc
@@ -8,98 +8,136 @@ std::string_view makeFileIngestionPrefix(FileIngestionMethod m)
 {
     switch (m) {
     case FileIngestionMethod::Flat:
+        // Not prefixed for back compat
         return "";
-    case FileIngestionMethod::Recursive:
+    case FileIngestionMethod::NixArchive:
         return "r:";
     case FileIngestionMethod::Git:
         experimentalFeatureSettings.require(Xp::GitHashing);
         return "git:";
     default:
-        throw Error("impossible, caught both cases");
+        assert(false);
     }
 }
 
 std::string_view ContentAddressMethod::render() const
 {
-    return std::visit(overloaded {
-        [](TextIngestionMethod) -> std::string_view { return "text"; },
-        [](FileIngestionMethod m2) {
-             /* Not prefixed for back compat with things that couldn't produce text before. */
-            return renderFileIngestionMethod(m2);
-        },
-    }, raw);
+    switch (raw) {
+    case ContentAddressMethod::Raw::Text:
+        return "text";
+    case ContentAddressMethod::Raw::Flat:
+    case ContentAddressMethod::Raw::NixArchive:
+    case ContentAddressMethod::Raw::Git:
+        return renderFileIngestionMethod(getFileIngestionMethod());
+    default:
+        assert(false);
+    }
+}
+
+/**
+ * **Not surjective**
+ *
+ * This is not exposed because `FileIngestionMethod::Flat` maps to
+ * `ContentAddressMethod::Raw::Flat` and
+ * `ContentAddressMethod::Raw::Text` alike. We can thus only safely use
+ * this when the latter is ruled out (e.g. because it is already
+ * handled).
+ */
+static ContentAddressMethod fileIngestionMethodToContentAddressMethod(FileIngestionMethod m)
+{
+    switch (m) {
+    case FileIngestionMethod::Flat:
+        return ContentAddressMethod::Raw::Flat;
+    case FileIngestionMethod::NixArchive:
+        return ContentAddressMethod::Raw::NixArchive;
+    case FileIngestionMethod::Git:
+        return ContentAddressMethod::Raw::Git;
+    default:
+        assert(false);
+    }
 }
 
 ContentAddressMethod ContentAddressMethod::parse(std::string_view m)
 {
     if (m == "text")
-        return TextIngestionMethod {};
+        return ContentAddressMethod::Raw::Text;
     else
-        return parseFileIngestionMethod(m);
+        return fileIngestionMethodToContentAddressMethod(
+            parseFileIngestionMethod(m));
 }
 
 std::string_view ContentAddressMethod::renderPrefix() const
 {
-    return std::visit(overloaded {
-        [](TextIngestionMethod) -> std::string_view { return "text:"; },
-        [](FileIngestionMethod m2) {
-             /* Not prefixed for back compat with things that couldn't produce text before. */
-            return makeFileIngestionPrefix(m2);
-        },
-    }, raw);
+    switch (raw) {
+    case ContentAddressMethod::Raw::Text:
+        return "text:";
+    case ContentAddressMethod::Raw::Flat:
+    case ContentAddressMethod::Raw::NixArchive:
+    case ContentAddressMethod::Raw::Git:
+        return makeFileIngestionPrefix(getFileIngestionMethod());
+    default:
+        assert(false);
+    }
 }
 
 ContentAddressMethod ContentAddressMethod::parsePrefix(std::string_view & m)
 {
     if (splitPrefix(m, "r:")) {
-        return FileIngestionMethod::Recursive;
+        return ContentAddressMethod::Raw::NixArchive;
     }
     else if (splitPrefix(m, "git:")) {
         experimentalFeatureSettings.require(Xp::GitHashing);
-        return FileIngestionMethod::Git;
+        return ContentAddressMethod::Raw::Git;
     }
     else if (splitPrefix(m, "text:")) {
-        return TextIngestionMethod {};
+        return ContentAddressMethod::Raw::Text;
+    }
+    return ContentAddressMethod::Raw::Flat;
+}
+
+/**
+ * This is slightly more mindful of forward compat in that it uses `fixed:`
+ * rather than just doing a raw empty prefix or `r:`, which doesn't "save room"
+ * for future changes very well.
+ */
+static std::string renderPrefixModern(const ContentAddressMethod & ca)
+{
+    switch (ca.raw) {
+    case ContentAddressMethod::Raw::Text:
+        return "text:";
+    case ContentAddressMethod::Raw::Flat:
+    case ContentAddressMethod::Raw::NixArchive:
+    case ContentAddressMethod::Raw::Git:
+        return "fixed:" + makeFileIngestionPrefix(ca.getFileIngestionMethod());
+    default:
+        assert(false);
     }
-    return FileIngestionMethod::Flat;
 }
 
 std::string ContentAddressMethod::renderWithAlgo(HashAlgorithm ha) const
 {
-    return std::visit(overloaded {
-        [&](const TextIngestionMethod & th) {
-            return std::string{"text:"} + printHashAlgo(ha);
-        },
-        [&](const FileIngestionMethod & fim) {
-            return "fixed:" + makeFileIngestionPrefix(fim) + printHashAlgo(ha);
-        }
-    }, raw);
+    return renderPrefixModern(*this) + printHashAlgo(ha);
 }
 
 FileIngestionMethod ContentAddressMethod::getFileIngestionMethod() const
 {
-    return std::visit(overloaded {
-        [&](const TextIngestionMethod & th) {
-            return FileIngestionMethod::Flat;
-        },
-        [&](const FileIngestionMethod & fim) {
-            return fim;
-        }
-    }, raw);
+    switch (raw) {
+    case ContentAddressMethod::Raw::Flat:
+        return FileIngestionMethod::Flat;
+    case ContentAddressMethod::Raw::NixArchive:
+        return FileIngestionMethod::NixArchive;
+    case ContentAddressMethod::Raw::Git:
+        return FileIngestionMethod::Git;
+    case ContentAddressMethod::Raw::Text:
+        return FileIngestionMethod::Flat;
+    default:
+        assert(false);
+    }
 }
 
 std::string ContentAddress::render() const
 {
-    return std::visit(overloaded {
-        [](const TextIngestionMethod &) -> std::string {
-            return "text:";
-        },
-        [](const FileIngestionMethod & method) {
-            return "fixed:"
-                + makeFileIngestionPrefix(method);
-        },
-    }, method.raw)
-        + this->hash.to_string(HashFormat::Nix32, true);
+    return renderPrefixModern(method) + this->hash.to_string(HashFormat::Nix32, true);
 }
 
 /**
@@ -130,17 +168,17 @@ static std::pair<ContentAddressMethod, HashAlgorithm> parseContentAddressMethodP
         // No parsing of the ingestion method, "text" only support flat.
         HashAlgorithm hashAlgo = parseHashAlgorithm_();
         return {
-            TextIngestionMethod {},
+            ContentAddressMethod::Raw::Text,
             std::move(hashAlgo),
         };
     } else if (prefix == "fixed") {
         // Parse method
-        auto method = FileIngestionMethod::Flat;
+        auto method = ContentAddressMethod::Raw::Flat;
         if (splitPrefix(rest, "r:"))
-            method = FileIngestionMethod::Recursive;
+            method = ContentAddressMethod::Raw::NixArchive;
         else if (splitPrefix(rest, "git:")) {
             experimentalFeatureSettings.require(Xp::GitHashing);
-            method = FileIngestionMethod::Git;
+            method = ContentAddressMethod::Raw::Git;
         }
         HashAlgorithm hashAlgo = parseHashAlgorithm_();
         return {
@@ -201,57 +239,58 @@ size_t StoreReferences::size() const
 
 ContentAddressWithReferences ContentAddressWithReferences::withoutRefs(const ContentAddress & ca) noexcept
 {
-    return std::visit(overloaded {
-        [&](const TextIngestionMethod &) -> ContentAddressWithReferences {
-            return TextInfo {
-                .hash = ca.hash,
-                .references = {},
-            };
-        },
-        [&](const FileIngestionMethod & method) -> ContentAddressWithReferences {
-            return FixedOutputInfo {
-                .method = method,
-                .hash = ca.hash,
-                .references = {},
-            };
-        },
-    }, ca.method.raw);
+    switch (ca.method.raw) {
+    case ContentAddressMethod::Raw::Text:
+        return TextInfo {
+            .hash = ca.hash,
+            .references = {},
+        };
+    case ContentAddressMethod::Raw::Flat:
+    case ContentAddressMethod::Raw::NixArchive:
+    case ContentAddressMethod::Raw::Git:
+        return FixedOutputInfo {
+            .method = ca.method.getFileIngestionMethod(),
+            .hash = ca.hash,
+            .references = {},
+        };
+    default:
+        assert(false);
+    }
 }
 
 ContentAddressWithReferences ContentAddressWithReferences::fromParts(
     ContentAddressMethod method, Hash hash, StoreReferences refs)
 {
-    return std::visit(overloaded {
-        [&](TextIngestionMethod _) -> ContentAddressWithReferences {
-            if (refs.self)
-                throw Error("self-reference not allowed with text hashing");
-            return ContentAddressWithReferences {
-                TextInfo {
-                    .hash = std::move(hash),
-                    .references = std::move(refs.others),
-                }
-            };
-        },
-        [&](FileIngestionMethod m2) -> ContentAddressWithReferences {
-            return ContentAddressWithReferences {
-                FixedOutputInfo {
-                    .method = m2,
-                    .hash = std::move(hash),
-                    .references = std::move(refs),
-                }
-            };
-        },
-    }, method.raw);
+    switch (method.raw) {
+    case ContentAddressMethod::Raw::Text:
+        if (refs.self)
+            throw Error("self-reference not allowed with text hashing");
+        return TextInfo {
+            .hash = std::move(hash),
+            .references = std::move(refs.others),
+        };
+    case ContentAddressMethod::Raw::Flat:
+    case ContentAddressMethod::Raw::NixArchive:
+    case ContentAddressMethod::Raw::Git:
+        return FixedOutputInfo {
+            .method = method.getFileIngestionMethod(),
+            .hash = std::move(hash),
+            .references = std::move(refs),
+        };
+    default:
+        assert(false);
+    }
 }
 
 ContentAddressMethod ContentAddressWithReferences::getMethod() const
 {
     return std::visit(overloaded {
         [](const TextInfo & th) -> ContentAddressMethod {
-            return TextIngestionMethod {};
+            return ContentAddressMethod::Raw::Text;
         },
         [](const FixedOutputInfo & fsh) -> ContentAddressMethod {
-            return fsh.method;
+            return fileIngestionMethodToContentAddressMethod(
+                fsh.method);
         },
     }, raw);
 }
diff --git a/src/libstore/content-address.hh b/src/libstore/content-address.hh
index 5925f8e01a2..6cc3b7cd9e7 100644
--- a/src/libstore/content-address.hh
+++ b/src/libstore/content-address.hh
@@ -5,7 +5,6 @@
 #include "hash.hh"
 #include "path.hh"
 #include "file-content-address.hh"
-#include "comparator.hh"
 #include "variant-wrapper.hh"
 
 namespace nix {
@@ -14,24 +13,6 @@ namespace nix {
  * Content addressing method
  */
 
-/* We only have one way to hash text with references, so this is a single-value
-   type, mainly useful with std::variant.
-*/
-
-/**
- * The single way we can serialize "text" file system objects.
- *
- * Somewhat obscure, used by \ref Derivation derivations and
- * `builtins.toFile` currently.
- *
- * TextIngestionMethod is identical to FileIngestionMethod::Fixed except that
- * the former may not have self-references and is tagged `text:${algo}:${hash}`
- * rather than `fixed:${algo}:${hash}`.  The contents of the store path are
- * ingested and hashed identically, aside from the slightly different tag and
- * restriction on self-references.
- */
-struct TextIngestionMethod : std::monostate { };
-
 /**
  * Compute the prefix to the hash algorithm which indicates how the
  * files were ingested.
@@ -48,14 +29,51 @@ std::string_view makeFileIngestionPrefix(FileIngestionMethod m);
  */
 struct ContentAddressMethod
 {
-    typedef std::variant<
-        TextIngestionMethod,
-        FileIngestionMethod
-    > Raw;
+    enum struct Raw {
+        /**
+         * Calculate a store path using the `FileIngestionMethod::Flat`
+         * hash of the file system objects, and references.
+         *
+         * See `store-object/content-address.md#method-flat` in the
+         * manual.
+         */
+        Flat,
+
+        /**
+         * Calculate a store path using the
+         * `FileIngestionMethod::NixArchive` hash of the file system
+         * objects, and references.
+         *
+         * See `store-object/content-address.md#method-flat` in the
+         * manual.
+         */
+        NixArchive,
+
+        /**
+         * Calculate a store path using the `FileIngestionMethod::Git`
+         * hash of the file system objects, and references.
+         *
+         * Part of `ExperimentalFeature::GitHashing`.
+         *
+         * See `store-object/content-address.md#method-git` in the
+         * manual.
+         */
+        Git,
+
+        /**
+         * Calculate a store path using the `FileIngestionMethod::Flat`
+         * hash of the file system objects, and references, but in a
+         * different way than `ContentAddressMethod::Raw::Flat`.
+         *
+         * See `store-object/content-address.md#method-text` in the
+         * manual.
+         */
+        Text,
+    };
 
     Raw raw;
 
-    GENERATE_CMP(ContentAddressMethod, me->raw);
+    auto operator <=>(const ContentAddressMethod &) const = default;
 
     MAKE_WRAPPER_CONSTRUCTOR(ContentAddressMethod);
 
@@ -141,7 +159,7 @@ struct ContentAddress
      */
     Hash hash;
 
-    GENERATE_CMP(ContentAddress, me->method, me->hash);
+    auto operator <=>(const ContentAddress &) const = default;
 
     /**
      * Compute the content-addressability assertion
@@ -200,7 +218,7 @@ struct StoreReferences
      */
     size_t size() const;
 
-    GENERATE_CMP(StoreReferences, me->self, me->others);
+    auto operator <=>(const StoreReferences &) const = default;
 };
 
 // This matches the additional info that we need for makeTextPath
@@ -217,7 +235,7 @@ struct TextInfo
      */
     StorePathSet references;
 
-    GENERATE_CMP(TextInfo, me->hash, me->references);
+    auto operator <=>(const TextInfo &) const = default;
 };
 
 struct FixedOutputInfo
@@ -237,7 +255,7 @@ struct FixedOutputInfo
      */
     StoreReferences references;
 
-    GENERATE_CMP(FixedOutputInfo, me->hash, me->references);
+    auto operator <=>(const FixedOutputInfo &) const = default;
 };
 
 /**
@@ -254,7 +272,7 @@ struct ContentAddressWithReferences
 
     Raw raw;
 
-    GENERATE_CMP(ContentAddressWithReferences, me->raw);
+    auto operator <=>(const ContentAddressWithReferences &) const = default;
 
     MAKE_WRAPPER_CONSTRUCTOR(ContentAddressWithReferences);
 
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index e22e2fefb9b..a2e1ae4f10d 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -1,6 +1,7 @@
 #include "daemon.hh"
 #include "signals.hh"
 #include "worker-protocol.hh"
+#include "worker-protocol-connection.hh"
 #include "worker-protocol-impl.hh"
 #include "build-result.hh"
 #include "store-api.hh"
@@ -23,6 +24,8 @@
 # include "monitor-fd.hh"
 #endif
 
+#include <sstream>
+
 namespace nix::daemon {
 
 Sink & operator << (Sink & sink, const Logger::Fields & fields)
@@ -416,12 +419,12 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
                 case FileIngestionMethod::Flat:
                     dumpMethod = FileSerialisationMethod::Flat;
                     break;
-                case FileIngestionMethod::Recursive:
-                    dumpMethod = FileSerialisationMethod::Recursive;
+                case FileIngestionMethod::NixArchive:
+                    dumpMethod = FileSerialisationMethod::NixArchive;
                     break;
                 case FileIngestionMethod::Git:
                     // Use NAR; Git is not a serialization method
-                    dumpMethod = FileSerialisationMethod::Recursive;
+                    dumpMethod = FileSerialisationMethod::NixArchive;
                     break;
                 default:
                     assert(false);
@@ -436,19 +439,21 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         } else {
             HashAlgorithm hashAlgo;
             std::string baseName;
-            FileIngestionMethod method;
+            ContentAddressMethod method;
             {
                 bool fixed;
                 uint8_t recursive;
                 std::string hashAlgoRaw;
                 from >> baseName >> fixed /* obsolete */ >> recursive >> hashAlgoRaw;
-                if (recursive > (uint8_t) FileIngestionMethod::Recursive)
+                if (recursive > true)
                     throw Error("unsupported FileIngestionMethod with value of %i; you may need to upgrade nix-daemon", recursive);
-                method = FileIngestionMethod { recursive };
+                method = recursive
+                    ? ContentAddressMethod::Raw::NixArchive
+                    : ContentAddressMethod::Raw::Flat;
                 /* Compatibility hack. */
                 if (!fixed) {
                     hashAlgoRaw = "sha256";
-                    method = FileIngestionMethod::Recursive;
+                    method = ContentAddressMethod::Raw::NixArchive;
                 }
                 hashAlgo = parseHashAlgo(hashAlgoRaw);
             }
@@ -469,7 +474,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
             });
             logger->startWork();
             auto path = store->addToStoreFromDump(
-                *dumpSource, baseName, FileSerialisationMethod::Recursive, method, hashAlgo);
+                *dumpSource, baseName, FileSerialisationMethod::NixArchive, method, hashAlgo);
             logger->stopWork();
 
             to << store->printStorePath(path);
@@ -501,7 +506,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         logger->startWork();
         auto path = ({
             StringSource source { s };
-            store->addToStoreFromDump(source, suffix, FileSerialisationMethod::Flat, TextIngestionMethod {}, HashAlgorithm::SHA256, refs, NoRepair);
+            store->addToStoreFromDump(source, suffix, FileSerialisationMethod::Flat, ContentAddressMethod::Raw::Text, HashAlgorithm::SHA256, refs, NoRepair);
         });
         logger->stopWork();
         to << store->printStorePath(path);
@@ -535,7 +540,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         auto drvs = WorkerProto::Serialise<DerivedPaths>::read(*store, rconn);
         BuildMode mode = bmNormal;
         if (GET_PROTOCOL_MINOR(clientVersion) >= 15) {
-            mode = (BuildMode) readInt(from);
+            mode = WorkerProto::Serialise<BuildMode>::read(*store, rconn);
 
             /* Repairing is not atomic, so disallowed for "untrusted"
                clients.
@@ -559,7 +564,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     case WorkerProto::Op::BuildPathsWithResults: {
         auto drvs = WorkerProto::Serialise<DerivedPaths>::read(*store, rconn);
         BuildMode mode = bmNormal;
-        mode = (BuildMode) readInt(from);
+        mode = WorkerProto::Serialise<BuildMode>::read(*store, rconn);
 
         /* Repairing is not atomic, so disallowed for "untrusted"
            clients.
@@ -590,7 +595,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
          * correctly.
          */
         readDerivation(from, *store, drv, Derivation::nameFromPath(drvPath));
-        BuildMode buildMode = (BuildMode) readInt(from);
+        auto buildMode = WorkerProto::Serialise<BuildMode>::read(*store, rconn);
         logger->startWork();
 
         auto drvType = drv.type();
@@ -1067,11 +1072,9 @@ void processConnection(
 #endif
 
     /* Exchange the greeting. */
-    unsigned int magic = readInt(from);
-    if (magic != WORKER_MAGIC_1) throw Error("protocol mismatch");
-    to << WORKER_MAGIC_2 << PROTOCOL_VERSION;
-    to.flush();
-    WorkerProto::Version clientVersion = readInt(from);
+    WorkerProto::Version clientVersion =
+        WorkerProto::BasicServerConnection::handshake(
+            to, from, PROTOCOL_VERSION);
 
     if (clientVersion < 0x10a)
         throw Error("the Nix client version is too old");
@@ -1089,29 +1092,20 @@ void processConnection(
         printMsgUsing(prevLogger, lvlDebug, "%d operations", opCount);
     });
 
-    if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from)) {
-        // Obsolete CPU affinity.
-        readInt(from);
-    }
-
-    if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
-        readInt(from); // obsolete reserveSpace
-
-    if (GET_PROTOCOL_MINOR(clientVersion) >= 33)
-        to << nixVersion;
+    WorkerProto::BasicServerConnection conn {
+        .to = to,
+        .from = from,
+        .clientVersion = clientVersion,
+    };
 
-    if (GET_PROTOCOL_MINOR(clientVersion) >= 35) {
+    conn.postHandshake(*store, {
+        .daemonNixVersion = nixVersion,
         // We and the underlying store both need to trust the client for
         // it to be trusted.
-        auto temp = trusted
+        .remoteTrustsUs = trusted
             ? store->isTrustedClient()
-            : std::optional { NotTrusted };
-        WorkerProto::WriteConn wconn {
-            .to = to,
-            .version = clientVersion,
-        };
-        WorkerProto::write(*store, wconn, temp);
-    }
+            : std::optional { NotTrusted },
+    });
 
     /* Send startup error messages to the client. */
     tunnelLogger->startWork();
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index fcf813a37d4..6dfcc408c33 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -150,7 +150,7 @@ StorePath writeDerivation(Store & store,
         })
         : ({
             StringSource s { contents };
-            store.addToStoreFromDump(s, suffix, FileSerialisationMethod::Flat, TextIngestionMethod {}, HashAlgorithm::SHA256, references, repair);
+            store.addToStoreFromDump(s, suffix, FileSerialisationMethod::Flat, ContentAddressMethod::Raw::Text, HashAlgorithm::SHA256, references, repair);
         });
 }
 
@@ -274,7 +274,7 @@ static DerivationOutput parseDerivationOutput(
 {
     if (hashAlgoStr != "") {
         ContentAddressMethod method = ContentAddressMethod::parsePrefix(hashAlgoStr);
-        if (method == TextIngestionMethod {})
+        if (method == ContentAddressMethod::Raw::Text)
             xpSettings.require(Xp::DynamicDerivations);
         const auto hashAlgo = parseHashAlgo(hashAlgoStr);
         if (hashS == "impure") {
@@ -930,10 +930,9 @@ DerivationOutputsAndOptPaths BasicDerivation::outputsAndOptPaths(const StoreDirC
 
 std::string_view BasicDerivation::nameFromPath(const StorePath & drvPath)
 {
+    drvPath.requireDerivation();
     auto nameWithSuffix = drvPath.name();
-    constexpr std::string_view extension = ".drv";
-    assert(hasSuffix(nameWithSuffix, extension));
-    nameWithSuffix.remove_suffix(extension.size());
+    nameWithSuffix.remove_suffix(drvExtension.size());
     return nameWithSuffix;
 }
 
@@ -1216,16 +1215,19 @@ nlohmann::json DerivationOutput::toJSON(
         },
         [&](const DerivationOutput::CAFixed & dof) {
             res["path"] = store.printStorePath(dof.path(store, drvName, outputName));
-            res["hashAlgo"] = dof.ca.printMethodAlgo();
+            res["method"] = std::string { dof.ca.method.render() };
+            res["hashAlgo"] = printHashAlgo(dof.ca.hash.algo);
             res["hash"] = dof.ca.hash.to_string(HashFormat::Base16, false);
             // FIXME print refs?
         },
         [&](const DerivationOutput::CAFloating & dof) {
-            res["hashAlgo"] = std::string { dof.method.renderPrefix() } + printHashAlgo(dof.hashAlgo);
+            res["method"] = std::string { dof.method.render() };
+            res["hashAlgo"] = printHashAlgo(dof.hashAlgo);
         },
         [&](const DerivationOutput::Deferred &) {},
         [&](const DerivationOutput::Impure & doi) {
-            res["hashAlgo"] = std::string { doi.method.renderPrefix() } + printHashAlgo(doi.hashAlgo);
+            res["method"] = std::string { doi.method.render() };
+            res["hashAlgo"] = printHashAlgo(doi.hashAlgo);
             res["impure"] = true;
         },
     }, raw);
@@ -1245,12 +1247,13 @@ DerivationOutput DerivationOutput::fromJSON(
         keys.insert(key);
 
     auto methodAlgo = [&]() -> std::pair<ContentAddressMethod, HashAlgorithm> {
-        auto & str = getString(valueAt(json, "hashAlgo"));
-        std::string_view s = str;
-        ContentAddressMethod method = ContentAddressMethod::parsePrefix(s);
-        if (method == TextIngestionMethod {})
+        auto & method_ = getString(valueAt(json, "method"));
+        ContentAddressMethod method = ContentAddressMethod::parse(method_);
+        if (method == ContentAddressMethod::Raw::Text)
             xpSettings.require(Xp::DynamicDerivations);
-        auto hashAlgo = parseHashAlgo(s);
+
+        auto & hashAlgo_ = getString(valueAt(json, "hashAlgo"));
+        auto hashAlgo = parseHashAlgo(hashAlgo_);
         return { std::move(method), std::move(hashAlgo) };
     };
 
@@ -1260,7 +1263,7 @@ DerivationOutput DerivationOutput::fromJSON(
         };
     }
 
-    else if (keys == (std::set<std::string_view> { "path", "hashAlgo", "hash" })) {
+    else if (keys == (std::set<std::string_view> { "path", "method", "hashAlgo", "hash" })) {
         auto [method, hashAlgo] = methodAlgo();
         auto dof = DerivationOutput::CAFixed {
             .ca = ContentAddress {
@@ -1273,7 +1276,7 @@ DerivationOutput DerivationOutput::fromJSON(
         return dof;
     }
 
-    else if (keys == (std::set<std::string_view> { "hashAlgo" })) {
+    else if (keys == (std::set<std::string_view> { "method", "hashAlgo" })) {
         xpSettings.require(Xp::CaDerivations);
         auto [method, hashAlgo] = methodAlgo();
         return DerivationOutput::CAFloating {
@@ -1286,7 +1289,7 @@ DerivationOutput DerivationOutput::fromJSON(
         return DerivationOutput::Deferred {};
     }
 
-    else if (keys == (std::set<std::string_view> { "hashAlgo", "impure" })) {
+    else if (keys == (std::set<std::string_view> { "method", "hashAlgo", "impure" })) {
         xpSettings.require(Xp::ImpureDerivations);
         auto [method, hashAlgo] = methodAlgo();
         return DerivationOutput::Impure {
diff --git a/src/libstore/dummy-store.cc b/src/libstore/dummy-store.cc
index 30f23cff91a..17ebaace6a8 100644
--- a/src/libstore/dummy-store.cc
+++ b/src/libstore/dummy-store.cc
@@ -18,9 +18,12 @@ struct DummyStoreConfig : virtual StoreConfig {
 
 struct DummyStore : public virtual DummyStoreConfig, public virtual Store
 {
-    DummyStore(const std::string scheme, const std::string uri, const Params & params)
+    DummyStore(std::string_view scheme, std::string_view authority, const Params & params)
         : DummyStore(params)
-    { }
+    {
+        if (!authority.empty())
+            throw UsageError("`%s` store URIs must not contain an authority part %s", scheme, authority);
+    }
 
     DummyStore(const Params & params)
         : StoreConfig(params)
@@ -61,8 +64,8 @@ struct DummyStore : public virtual DummyStoreConfig, public virtual Store
     virtual StorePath addToStoreFromDump(
         Source & dump,
         std::string_view name,
-        FileSerialisationMethod dumpMethod = FileSerialisationMethod::Recursive,
-        ContentAddressMethod hashMethod = FileIngestionMethod::Recursive,
+        FileSerialisationMethod dumpMethod = FileSerialisationMethod::NixArchive,
+        ContentAddressMethod hashMethod = FileIngestionMethod::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = StorePathSet(),
         RepairFlag repair = NoRepair) override
diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index 4620a03da60..4e068a82c33 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -1,5 +1,6 @@
 #include "filetransfer.hh"
 #include "globals.hh"
+#include "config-global.hh"
 #include "store-api.hh"
 #include "s3.hh"
 #include "compression.hh"
@@ -616,7 +617,12 @@ struct curlFileTransfer : public FileTransfer
         #endif
 
         #if __linux__
-        unshareFilesystem();
+        try {
+            tryUnshareFilesystem();
+        } catch (nix::Error & e) {
+            e.addTrace({}, "in download thread");
+            throw;
+        }
         #endif
 
         std::map<CURL *, std::shared_ptr<TransferItem>> items;
diff --git a/src/libstore/unix/gc.cc b/src/libstore/gc.cc
similarity index 89%
rename from src/libstore/unix/gc.cc
rename to src/libstore/gc.cc
index 9b2e6d525cd..54e09cb1639 100644
--- a/src/libstore/unix/gc.cc
+++ b/src/libstore/gc.cc
@@ -7,7 +7,7 @@
 
 #if !defined(__linux__)
 // For shelling out to lsof
-# include "processes.hh"
+#  include "processes.hh"
 #endif
 
 #include <functional>
@@ -19,36 +19,24 @@
 #include <climits>
 #include <errno.h>
 #include <fcntl.h>
-#include <poll.h>
-#include <sys/socket.h>
 #include <sys/stat.h>
-#include <sys/statvfs.h>
+#if HAVE_STATVFS
+#  include <sys/statvfs.h>
+#endif
+#ifndef _WIN32
+#  include <poll.h>
+#  include <sys/socket.h>
+#  include <sys/un.h>
+#endif
 #include <sys/types.h>
-#include <sys/un.h>
 #include <unistd.h>
 
 namespace nix {
 
-using namespace nix::unix;
-
 static std::string gcSocketPath = "/gc-socket/socket";
 static std::string gcRootsDir = "gcroots";
 
 
-static void makeSymlink(const Path & link, const Path & target)
-{
-    /* Create directories up to `gcRoot'. */
-    createDirs(dirOf(link));
-
-    /* Create the new symlink. */
-    Path tempLink = fmt("%1%.tmp-%2%-%3%", link, getpid(), random());
-    createSymlink(target, tempLink);
-
-    /* Atomically replace the old one. */
-    renameFile(tempLink, link);
-}
-
-
 void LocalStore::addIndirectRoot(const Path & path)
 {
     std::string hash = hashString(HashAlgorithm::SHA1, path).to_string(HashFormat::Nix32, false);
@@ -57,32 +45,6 @@ void LocalStore::addIndirectRoot(const Path & path)
 }
 
 
-Path IndirectRootStore::addPermRoot(const StorePath & storePath, const Path & _gcRoot)
-{
-    Path gcRoot(canonPath(_gcRoot));
-
-    if (isInStore(gcRoot))
-        throw Error(
-                "creating a garbage collector root (%1%) in the Nix store is forbidden "
-                "(are you running nix-build inside the store?)", gcRoot);
-
-    /* Register this root with the garbage collector, if it's
-       running. This should be superfluous since the caller should
-       have registered this root yet, but let's be on the safe
-       side. */
-    addTempRoot(storePath);
-
-    /* Don't clobber the link if it already exists and doesn't
-       point to the Nix store. */
-    if (pathExists(gcRoot) && (!isLink(gcRoot) || !isInStore(readLink(gcRoot))))
-        throw Error("cannot create symlink '%1%'; already exists", gcRoot);
-    makeSymlink(gcRoot, printStorePath(storePath));
-    addIndirectRoot(gcRoot);
-
-    return gcRoot;
-}
-
-
 void LocalStore::createTempRootsFile()
 {
     auto fdTempRoots(_fdTempRoots.lock());
@@ -104,7 +66,7 @@ void LocalStore::createTempRootsFile()
         /* Check whether the garbage collector didn't get in our
            way. */
         struct stat st;
-        if (fstat(fdTempRoots->get(), &st) == -1)
+        if (fstat(fromDescriptorReadOnly(fdTempRoots->get()), &st) == -1)
             throw SysError("statting '%1%'", fnTempRoots);
         if (st.st_size == 0) break;
 
@@ -148,7 +110,7 @@ void LocalStore::addTempRoot(const StorePath & path)
             debug("connecting to '%s'", socketPath);
             *fdRootsSocket = createUnixDomainSocket();
             try {
-                nix::connect(fdRootsSocket->get(), socketPath);
+                nix::connect(toSocket(fdRootsSocket->get()), socketPath);
             } catch (SysError & e) {
                 /* The garbage collector may have exited or not
                    created the socket yet, so we need to restart. */
@@ -199,18 +161,24 @@ void LocalStore::findTempRoots(Roots & tempRoots, bool censor)
 {
     /* Read the `temproots' directory for per-process temporary root
        files. */
-    for (auto & i : readDirectory(tempRootsDir)) {
-        if (i.name[0] == '.') {
+    for (auto & i : std::filesystem::directory_iterator{tempRootsDir}) {
+        checkInterrupt();
+        auto name = i.path().filename().string();
+        if (name[0] == '.') {
             // Ignore hidden files. Some package managers (notably portage) create
             // those to keep the directory alive.
             continue;
         }
-        Path path = tempRootsDir + "/" + i.name;
+        Path path = i.path().string();
 
-        pid_t pid = std::stoi(i.name);
+        pid_t pid = std::stoi(name);
 
         debug("reading temporary root file '%1%'", path);
-        AutoCloseFD fd(open(path.c_str(), O_CLOEXEC | O_RDWR, 0666));
+        AutoCloseFD fd(toDescriptor(open(path.c_str(),
+#ifndef _WIN32
+            O_CLOEXEC |
+#endif
+            O_RDWR, 0666)));
         if (!fd) {
             /* It's okay if the file has disappeared. */
             if (errno == ENOENT) continue;
@@ -243,7 +211,7 @@ void LocalStore::findTempRoots(Roots & tempRoots, bool censor)
 }
 
 
-void LocalStore::findRoots(const Path & path, unsigned char type, Roots & roots)
+void LocalStore::findRoots(const Path & path, std::filesystem::file_type type, Roots & roots)
 {
     auto foundRoot = [&](const Path & path, const Path & target) {
         try {
@@ -257,15 +225,17 @@ void LocalStore::findRoots(const Path & path, unsigned char type, Roots & roots)
 
     try {
 
-        if (type == DT_UNKNOWN)
-            type = getFileType(path);
+        if (type == std::filesystem::file_type::unknown)
+            type = std::filesystem::symlink_status(path).type();
 
-        if (type == DT_DIR) {
-            for (auto & i : readDirectory(path))
-                findRoots(path + "/" + i.name, i.type, roots);
+        if (type == std::filesystem::file_type::directory) {
+            for (auto & i : std::filesystem::directory_iterator{path}) {
+                checkInterrupt();
+                findRoots(i.path().string(), i.symlink_status().type(), roots);
+            }
         }
 
-        else if (type == DT_LNK) {
+        else if (type == std::filesystem::file_type::symlink) {
             Path target = readLink(path);
             if (isInStore(target))
                 foundRoot(path, target);
@@ -279,15 +249,14 @@ void LocalStore::findRoots(const Path & path, unsigned char type, Roots & roots)
                         unlink(path.c_str());
                     }
                 } else {
-                    struct stat st2 = lstat(target);
-                    if (!S_ISLNK(st2.st_mode)) return;
+                    if (!std::filesystem::is_symlink(target)) return;
                     Path target2 = readLink(target);
                     if (isInStore(target2)) foundRoot(target, target2);
                 }
             }
         }
 
-        else if (type == DT_REG) {
+        else if (type == std::filesystem::file_type::regular) {
             auto storePath = maybeParseStorePath(storeDir + "/" + std::string(baseNameOf(path)));
             if (storePath && isValidPath(*storePath))
                 roots[std::move(*storePath)].emplace(path);
@@ -295,6 +264,14 @@ void LocalStore::findRoots(const Path & path, unsigned char type, Roots & roots)
 
     }
 
+    catch (std::filesystem::filesystem_error & e) {
+        /* We only ignore permanent failures. */
+        if (e.code() == std::errc::permission_denied || e.code() == std::errc::no_such_file_or_directory || e.code() == std::errc::not_a_directory)
+            printInfo("cannot read potential root '%1%'", path);
+        else
+            throw;
+    }
+
     catch (SysError & e) {
         /* We only ignore permanent failures. */
         if (e.errNo == EACCES || e.errNo == ENOENT || e.errNo == ENOTDIR)
@@ -308,8 +285,8 @@ void LocalStore::findRoots(const Path & path, unsigned char type, Roots & roots)
 void LocalStore::findRootsNoTemp(Roots & roots, bool censor)
 {
     /* Process direct roots in {gcroots,profiles}. */
-    findRoots(stateDir + "/" + gcRootsDir, DT_UNKNOWN, roots);
-    findRoots(stateDir + "/profiles", DT_UNKNOWN, roots);
+    findRoots(stateDir + "/" + gcRootsDir, std::filesystem::file_type::unknown, roots);
+    findRoots(stateDir + "/profiles", std::filesystem::file_type::unknown, roots);
 
     /* Add additional roots returned by different platforms-specific
        heuristics.  This is typically used to add running programs to
@@ -328,24 +305,25 @@ Roots LocalStore::findRoots(bool censor)
     return roots;
 }
 
-typedef std::unordered_map<Path, std::unordered_set<std::string>> UncheckedRoots;
+/**
+ * Key is a mere string because cannot has path with macOS's libc++
+ */
+typedef std::unordered_map<std::string, std::unordered_set<std::string>> UncheckedRoots;
 
-static void readProcLink(const std::string & file, UncheckedRoots & roots)
+static void readProcLink(const std::filesystem::path & file, UncheckedRoots & roots)
 {
-    constexpr auto bufsiz = PATH_MAX;
-    char buf[bufsiz];
-    auto res = readlink(file.c_str(), buf, bufsiz);
-    if (res == -1) {
-        if (errno == ENOENT || errno == EACCES || errno == ESRCH)
+    std::filesystem::path buf;
+    try {
+        buf = std::filesystem::read_symlink(file);
+    } catch (std::filesystem::filesystem_error & e) {
+        if (e.code() == std::errc::no_such_file_or_directory
+                || e.code() == std::errc::permission_denied
+                || e.code() == std::errc::no_such_process)
             return;
-        throw SysError("reading symlink");
+        throw;
     }
-    if (res == bufsiz) {
-        throw Error("overly long symlink starting with '%1%'", std::string_view(buf, bufsiz));
-    }
-    if (res > 0 && buf[0] == '/')
-        roots[std::string(static_cast<char *>(buf), res)]
-            .emplace(file);
+    if (buf.is_absolute())
+        roots[buf.string()].emplace(file.string());
 }
 
 static std::string quoteRegexChars(const std::string & raw)
@@ -402,12 +380,12 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
                     }
                     fdDir.reset();
 
-                    auto mapFile = fmt("/proc/%s/maps", ent->d_name);
-                    auto mapLines = tokenizeString<std::vector<std::string>>(readFile(mapFile), "\n");
+                    std::filesystem::path mapFile = fmt("/proc/%s/maps", ent->d_name);
+                    auto mapLines = tokenizeString<std::vector<std::string>>(readFile(mapFile.string()), "\n");
                     for (const auto & line : mapLines) {
                         auto match = std::smatch{};
                         if (std::regex_match(line, match, mapRegex))
-                            unchecked[match[1]].emplace(mapFile);
+                            unchecked[match[1]].emplace(mapFile.string());
                     }
 
                     auto envFile = fmt("/proc/%s/environ", ent->d_name);
@@ -438,7 +416,7 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
             for (const auto & line : lsofLines) {
                 std::smatch match;
                 if (std::regex_match(line, match, lsofRegex))
-                    unchecked[match[1]].emplace("{lsof}");
+                    unchecked[match[1].str()].emplace("{lsof}");
             }
         } catch (ExecError & e) {
             /* lsof not installed, lsof failed */
@@ -521,6 +499,10 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
     createDirs(dirOf(socketPath));
     auto fdServer = createUnixDomainSocket(socketPath, 0666);
 
+    // TODO nonblocking socket on windows?
+#ifdef _WIN32
+    throw UnimplementedError("External GC client not implemented yet");
+#else
     if (fcntl(fdServer.get(), F_SETFL, fcntl(fdServer.get(), F_GETFL) | O_NONBLOCK) == -1)
         throw SysError("making socket '%1%' non-blocking", socketPath);
 
@@ -621,6 +603,8 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
         if (serverThread.joinable()) serverThread.join();
     });
 
+#endif
+
     /* Find the roots.  Since we've grabbed the GC lock, the set of
        permanent roots cannot increase now. */
     printInfo("finding garbage collector roots...");
@@ -654,8 +638,8 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
            by another process. We need to be sure that we can acquire an
            exclusive lock before deleting them. */
         if (baseName.find("tmp-", 0) == 0) {
-            AutoCloseFD tmpDirFd = open(realPath.c_str(), O_RDONLY | O_DIRECTORY);
-            if (tmpDirFd.get() == -1 || !lockFile(tmpDirFd.get(), ltWrite, false)) {
+            AutoCloseFD tmpDirFd = openDirectory(realPath);
+            if (!tmpDirFd || !lockFile(tmpDirFd.get(), ltWrite, false)) {
                 debug("skipping locked tempdir '%s'", realPath);
                 return;
             }
@@ -800,7 +784,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
                 throw Error(
                     "Cannot delete path '%1%' since it is still alive. "
                     "To find out why, use: "
-                    "nix-store --query --roots",
+                    "nix-store --query --roots and nix-store --query --referrers",
                     printStorePath(i));
         }
 
@@ -888,7 +872,13 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
         struct stat st;
         if (stat(linksDir.c_str(), &st) == -1)
             throw SysError("statting '%1%'", linksDir);
-        int64_t overhead = st.st_blocks * 512ULL;
+        int64_t overhead =
+#ifdef _WIN32
+            0
+#else
+            st.st_blocks * 512ULL
+#endif
+            ;
 
         printInfo("note: currently hard linking saves %.2f MiB",
             ((unsharedSize - actualSize - overhead) / (1024.0 * 1024.0)));
@@ -901,6 +891,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
 
 void LocalStore::autoGC(bool sync)
 {
+#ifdef HAVE_STATVFS
     static auto fakeFreeSpaceFile = getEnv("_NIX_TEST_FREE_SPACE_FILE");
 
     auto getAvail = [this]() -> uint64_t {
@@ -977,6 +968,7 @@ void LocalStore::autoGC(bool sync)
  sync:
     // Wait for the future outside of the state lock.
     if (sync) future.get();
+#endif
 }
 
 
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 83e54e008f1..7e1d7ea6d67 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -1,9 +1,11 @@
 #include "globals.hh"
+#include "config-global.hh"
 #include "current-process.hh"
 #include "archive.hh"
 #include "args.hh"
 #include "abstract-setting-to-json.hh"
 #include "compute-levels.hh"
+#include "signals.hh"
 
 #include <algorithm>
 #include <map>
@@ -122,12 +124,12 @@ Settings::Settings()
     };
 }
 
-void loadConfFile()
+void loadConfFile(AbstractConfig & config)
 {
     auto applyConfigFile = [&](const Path & path) {
         try {
             std::string contents = readFile(path);
-            globalConfig.applyConfig(contents, path);
+            config.applyConfig(contents, path);
         } catch (SystemError &) { }
     };
 
@@ -135,7 +137,7 @@ void loadConfFile()
 
     /* We only want to send overrides to the daemon, i.e. stuff from
        ~/.nix/nix.conf or the command line. */
-    globalConfig.resetOverridden();
+    config.resetOverridden();
 
     auto files = settings.nixUserConfFiles;
     for (auto file = files.rbegin(); file != files.rend(); file++) {
@@ -144,7 +146,7 @@ void loadConfFile()
 
     auto nixConfEnv = getEnv("NIX_CONFIG");
     if (nixConfEnv.has_value()) {
-        globalConfig.applyConfig(nixConfEnv.value(), "NIX_CONFIG");
+        config.applyConfig(nixConfEnv.value(), "NIX_CONFIG");
     }
 
 }
@@ -343,17 +345,20 @@ void initPlugins()
 {
     assert(!settings.pluginFiles.pluginsLoaded);
     for (const auto & pluginFile : settings.pluginFiles.get()) {
-        Paths pluginFiles;
+        std::vector<std::filesystem::path> pluginFiles;
         try {
-            auto ents = readDirectory(pluginFile);
-            for (const auto & ent : ents)
-                pluginFiles.emplace_back(pluginFile + "/" + ent.name);
-        } catch (SysError & e) {
-            if (e.errNo != ENOTDIR)
+            auto ents = std::filesystem::directory_iterator{pluginFile};
+            for (const auto & ent : ents) {
+                checkInterrupt();
+                pluginFiles.emplace_back(ent.path());
+            }
+        } catch (std::filesystem::filesystem_error & e) {
+            if (e.code() != std::errc::not_a_directory)
                 throw;
             pluginFiles.emplace_back(pluginFile);
         }
         for (const auto & file : pluginFiles) {
+            checkInterrupt();
             /* handle is purposefully leaked as there may be state in the
                DSO needed by the action of the plugin. */
 #ifndef _WIN32 // TODO implement via DLL loading on Windows
@@ -427,12 +432,13 @@ void assertLibStoreInitialized() {
     };
 }
 
-void initLibStore() {
+void initLibStore(bool loadConfig) {
     if (initLibStoreDone) return;
 
     initLibUtil();
 
-    loadConfFile();
+    if (loadConfig)
+        loadConfFile(globalConfig);
 
     preloadNSS();
 
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 8f1788a4c74..b927f0479e6 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -228,7 +228,7 @@ public:
           While you can force Nix to run a Darwin-specific `builder` executable on a Linux machine, the result would obviously be wrong.
 
           This value is available in the Nix language as
-          [`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem)
+          [`builtins.currentSystem`](@docroot@/language/builtins.md#builtins-currentSystem)
           if the
           [`eval-system`](#conf-eval-system)
           configuration option is set as the empty string.
@@ -424,8 +424,10 @@ public:
     Setting<bool> useSQLiteWAL{this, !isWSL1(), "use-sqlite-wal",
         "Whether SQLite should use WAL mode."};
 
+#ifndef _WIN32
     Setting<bool> syncBeforeRegistering{this, false, "sync-before-registering",
         "Whether to call `sync()` before registering a path as valid."};
+#endif
 
     Setting<bool> useSubstitutes{
         this, true, "substitute",
@@ -782,6 +784,7 @@ public:
 
           - the store object has been signed using a key in the trusted keys list
           - the [`require-sigs`](#conf-require-sigs) option has been set to `false`
+          - the store URL is configured with `trusted=true`
           - the store object is [content-addressed](@docroot@/glossary.md#gloss-content-addressed-store-object)
         )",
         {"binary-cache-public-keys"}};
@@ -907,7 +910,7 @@ public:
         "substituters",
         R"(
           A list of [URLs of Nix stores](@docroot@/store/types/index.md#store-url-format) to be used as substituters, separated by whitespace.
-          A substituter is an additional [store](@docroot@/glossary.md#gloss-store) from which Nix can obtain [store objects](@docroot@/glossary.md#gloss-store-object) instead of building them.
+          A substituter is an additional [store](@docroot@/glossary.md#gloss-store) from which Nix can obtain [store objects](@docroot@/store/store-object.md) instead of building them.
 
           Substituters are tried based on their priority value, which each substituter can set independently.
           Lower value means higher priority.
@@ -1234,6 +1237,16 @@ public:
           store paths of the latest Nix release.
         )"
     };
+
+    Setting<uint64_t> warnLargePathThreshold{
+        this,
+        std::numeric_limits<uint64_t>::max(),
+        "warn-large-path-threshold",
+        R"(
+          Warn when copying a path larger than this number of bytes to the Nix store
+          (as determined by its NAR serialisation).
+        )"
+    };
 };
 
 
@@ -1246,7 +1259,13 @@ extern Settings settings;
  */
 void initPlugins();
 
-void loadConfFile();
+/**
+ * Load the configuration (from `nix.conf`, `NIX_CONFIG`, etc.) into the
+ * given configuration object.
+ *
+ * Usually called with `globalConfig`.
+ */
+void loadConfFile(AbstractConfig & config);
 
 // Used by the Settings constructor
 std::vector<Path> getUserConfigFiles();
@@ -1254,9 +1273,10 @@ std::vector<Path> getUserConfigFiles();
 extern const std::string nixVersion;
 
 /**
- * NB: This is not sufficient. You need to call initNix()
+ * @param loadConfig Whether to load configuration from `nix.conf`, `NIX_CONFIG`, etc. May be disabled for unit tests.
+ * @note When using libexpr, and/or libmain, This is not sufficient. See initNix().
  */
-void initLibStore();
+void initLibStore(bool loadConfig = true);
 
 /**
  * It's important to initialize before doing _anything_, which is why we
diff --git a/src/libstore/http-binary-cache-store.cc b/src/libstore/http-binary-cache-store.cc
index 10828041668..04e0d524bd0 100644
--- a/src/libstore/http-binary-cache-store.cc
+++ b/src/libstore/http-binary-cache-store.cc
@@ -42,15 +42,20 @@ class HttpBinaryCacheStore : public virtual HttpBinaryCacheStoreConfig, public v
 public:
 
     HttpBinaryCacheStore(
-        const std::string & scheme,
-        const Path & _cacheUri,
+        std::string_view scheme,
+        PathView _cacheUri,
         const Params & params)
         : StoreConfig(params)
         , BinaryCacheStoreConfig(params)
         , HttpBinaryCacheStoreConfig(params)
         , Store(params)
         , BinaryCacheStore(params)
-        , cacheUri(scheme + "://" + _cacheUri)
+        , cacheUri(
+            std::string { scheme }
+            + "://"
+            + (!_cacheUri.empty()
+                ? _cacheUri
+                : throw UsageError("`%s` Store requires a non-empty authority in Store URL", scheme)))
     {
         while (!cacheUri.empty() && cacheUri.back() == '/')
             cacheUri.pop_back();
diff --git a/src/libstore/indirect-root-store.cc b/src/libstore/indirect-root-store.cc
new file mode 100644
index 00000000000..844d0d6edad
--- /dev/null
+++ b/src/libstore/indirect-root-store.cc
@@ -0,0 +1,45 @@
+#include "indirect-root-store.hh"
+
+namespace nix {
+
+void IndirectRootStore::makeSymlink(const Path & link, const Path & target)
+{
+    /* Create directories up to `gcRoot'. */
+    createDirs(dirOf(link));
+
+    /* Create the new symlink. */
+    Path tempLink = fmt("%1%.tmp-%2%-%3%", link, getpid(), rand());
+    createSymlink(target, tempLink);
+
+    /* Atomically replace the old one. */
+    std::filesystem::rename(tempLink, link);
+}
+
+Path IndirectRootStore::addPermRoot(const StorePath & storePath, const Path & _gcRoot)
+{
+    Path gcRoot(canonPath(_gcRoot));
+
+    if (isInStore(gcRoot))
+        throw Error(
+            "creating a garbage collector root (%1%) in the Nix store is forbidden "
+            "(are you running nix-build inside the store?)",
+            gcRoot);
+
+    /* Register this root with the garbage collector, if it's
+       running. This should be superfluous since the caller should
+       have registered this root yet, but let's be on the safe
+       side. */
+    addTempRoot(storePath);
+
+    /* Don't clobber the link if it already exists and doesn't
+       point to the Nix store. */
+    if (pathExists(gcRoot) && (!std::filesystem::is_symlink(gcRoot) || !isInStore(readLink(gcRoot))))
+        throw Error("cannot create symlink '%1%'; already exists", gcRoot);
+
+    makeSymlink(gcRoot, printStorePath(storePath));
+    addIndirectRoot(gcRoot);
+
+    return gcRoot;
+}
+
+}
diff --git a/src/libstore/indirect-root-store.hh b/src/libstore/indirect-root-store.hh
index c11679fe8b8..b74ebc1eed4 100644
--- a/src/libstore/indirect-root-store.hh
+++ b/src/libstore/indirect-root-store.hh
@@ -67,6 +67,9 @@ struct IndirectRootStore : public virtual LocalFSStore
      * The form this weak-reference takes is implementation-specific.
      */
     virtual void addIndirectRoot(const Path & path) = 0;
+
+protected:
+    void makeSymlink(const Path & link, const Path & target);
 };
 
 }
diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index e422adeec85..9664b126edc 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -4,6 +4,7 @@
 #include "pool.hh"
 #include "remote-store.hh"
 #include "serve-protocol.hh"
+#include "serve-protocol-connection.hh"
 #include "serve-protocol-impl.hh"
 #include "build-result.hh"
 #include "store-api.hh"
@@ -28,26 +29,23 @@ struct LegacySSHStore::Connection : public ServeProto::BasicClientConnection
     bool good = true;
 };
 
-
-LegacySSHStore::LegacySSHStore(const std::string & scheme, const std::string & host, const Params & params)
+LegacySSHStore::LegacySSHStore(
+    std::string_view scheme,
+    std::string_view host,
+    const Params & params)
     : StoreConfig(params)
-    , CommonSSHStoreConfig(params)
+    , CommonSSHStoreConfig(scheme, host, params)
     , LegacySSHStoreConfig(params)
     , Store(params)
-    , host(host)
     , connections(make_ref<Pool<Connection>>(
         std::max(1, (int) maxConnections),
         [this]() { return openConnection(); },
         [](const ref<Connection> & r) { return r->good; }
         ))
-    , master(
-        host,
-        sshKey,
-        sshPublicHostKey,
+    , master(createSSHMaster(
         // Use SSH master only if using more than 1 connection.
         connections->capacity() > 1,
-        compress,
-        logFD)
+        logFD))
 {
 }
 
@@ -76,7 +74,7 @@ ref<LegacySSHStore::Connection> LegacySSHStore::openConnection()
         conn->sshConn->in.close();
         {
             NullSink nullSink;
-            conn->from.drainInto(nullSink);
+            tee.drainInto(nullSink);
         }
         throw Error("'nix-store --serve' protocol mismatch from '%s', got '%s'",
             host, chomp(saved.s));
@@ -105,24 +103,26 @@ void LegacySSHStore::queryPathInfoUncached(const StorePath & path,
 
         debug("querying remote host '%s' for info on '%s'", host, printStorePath(path));
 
-        conn->to << ServeProto::Command::QueryPathInfos << PathSet{printStorePath(path)};
-        conn->to.flush();
-
-        auto p = readString(conn->from);
-        if (p.empty()) return callback(nullptr);
-        auto path2 = parseStorePath(p);
-        assert(path == path2);
-        auto info = std::make_shared<ValidPathInfo>(
-            path,
-            ServeProto::Serialise<UnkeyedValidPathInfo>::read(*this, *conn));
+        auto infos = conn->queryPathInfos(*this, {path});
 
-        if (info->narHash == Hash::dummy)
-            throw Error("NAR hash is now mandatory");
+        switch (infos.size()) {
+        case 0:
+            return callback(nullptr);
+        case 1: {
+            auto & [path2, info] = *infos.begin();
 
-        auto s = readString(conn->from);
-        assert(s == "");
+            if (info.narHash == Hash::dummy)
+                throw Error("NAR hash is now mandatory");
 
-        callback(std::move(info));
+            assert(path == path2);
+            return callback(std::make_shared<ValidPathInfo>(
+                std::move(path),
+                std::move(info)
+            ));
+        }
+        default:
+            throw Error("More path infos returned than queried");
+        }
     } catch (...) { callback.rethrow(); }
 }
 
@@ -156,41 +156,38 @@ void LegacySSHStore::addToStore(const ValidPathInfo & info, Source & source,
         }
         conn->to.flush();
 
+        if (readInt(conn->from) != 1)
+            throw Error("failed to add path '%s' to remote host '%s'", printStorePath(info.path), host);
+
     } else {
 
-        conn->to
-            << ServeProto::Command::ImportPaths
-            << 1;
-        try {
-            copyNAR(source, conn->to);
-        } catch (...) {
-            conn->good = false;
-            throw;
-        }
-        conn->to
-            << exportMagic
-            << printStorePath(info.path);
-        ServeProto::write(*this, *conn, info.references);
-        conn->to
-            << (info.deriver ? printStorePath(*info.deriver) : "")
-            << 0
-            << 0;
-        conn->to.flush();
+        conn->importPaths(*this, [&](Sink & sink) {
+            try {
+                copyNAR(source, sink);
+            } catch (...) {
+                conn->good = false;
+                throw;
+            }
+            sink
+                << exportMagic
+                << printStorePath(info.path);
+            ServeProto::write(*this, *conn, info.references);
+            sink
+                << (info.deriver ? printStorePath(*info.deriver) : "")
+                << 0
+                << 0;
+        });
 
     }
-
-    if (readInt(conn->from) != 1)
-        throw Error("failed to add path '%s' to remote host '%s'", printStorePath(info.path), host);
 }
 
 
 void LegacySSHStore::narFromPath(const StorePath & path, Sink & sink)
 {
     auto conn(connections->get());
-
-    conn->to << ServeProto::Command::DumpStorePath << printStorePath(path);
-    conn->to.flush();
-    copyNAR(conn->from, sink);
+    conn->narFromPath(*this, path, [&](auto & source) {
+        copyNAR(source, sink);
+    });
 }
 
 
@@ -214,7 +211,7 @@ BuildResult LegacySSHStore::buildDerivation(const StorePath & drvPath, const Bas
 
     conn->putBuildDerivationRequest(*this, drvPath, drv, buildSettings());
 
-    return ServeProto::Serialise<BuildResult>::read(*this, *conn);
+    return conn->getBuildDerivationResponse(*this);
 }
 
 
diff --git a/src/libstore/legacy-ssh-store.hh b/src/libstore/legacy-ssh-store.hh
index ca2f115d25e..db49188ec9d 100644
--- a/src/libstore/legacy-ssh-store.hh
+++ b/src/libstore/legacy-ssh-store.hh
@@ -26,22 +26,27 @@ struct LegacySSHStoreConfig : virtual CommonSSHStoreConfig
 
 struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Store
 {
+#ifndef _WIN32
     // Hack for getting remote build log output.
     // Intentionally not in `LegacySSHStoreConfig` so that it doesn't appear in
     // the documentation
-    const Setting<int> logFD{this, -1, "log-fd", "file descriptor to which SSH's stderr is connected"};
+    const Setting<int> logFD{this, INVALID_DESCRIPTOR, "log-fd", "file descriptor to which SSH's stderr is connected"};
+#else
+    Descriptor logFD = INVALID_DESCRIPTOR;
+#endif
 
     struct Connection;
 
-    std::string host;
-
     ref<Pool<Connection>> connections;
 
     SSHMaster master;
 
     static std::set<std::string> uriSchemes() { return {"ssh"}; }
 
-    LegacySSHStore(const std::string & scheme, const std::string & host, const Params & params);
+    LegacySSHStore(
+        std::string_view scheme,
+        std::string_view host,
+        const Params & params);
 
     ref<Connection> openConnection();
 
@@ -60,8 +65,7 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
 
     StorePath addToStore(
         std::string_view name,
-        SourceAccessor & accessor,
-        const CanonPath & srcPath,
+        const SourcePath & path,
         ContentAddressMethod method,
         HashAlgorithm hashAlgo,
         const StorePathSet & references,
@@ -72,8 +76,8 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
     virtual StorePath addToStoreFromDump(
         Source & dump,
         std::string_view name,
-        FileSerialisationMethod dumpMethod = FileSerialisationMethod::Recursive,
-        ContentAddressMethod hashMethod = FileIngestionMethod::Recursive,
+        FileSerialisationMethod dumpMethod = FileSerialisationMethod::NixArchive,
+        ContentAddressMethod hashMethod = FileIngestionMethod::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = StorePathSet(),
         RepairFlag repair = NoRepair) override
diff --git a/src/libstore/linux/fchmodat2-compat.hh b/src/libstore/linux/fchmodat2-compat.hh
new file mode 100644
index 00000000000..fd03b9ed5aa
--- /dev/null
+++ b/src/libstore/linux/fchmodat2-compat.hh
@@ -0,0 +1,34 @@
+/*
+ * Determine the syscall number for `fchmodat2`.
+ *
+ * On most platforms this is 452. Exceptions can be found on
+ * a glibc git checkout via `rg --pcre2 'define __NR_fchmodat2 (?!452)'`.
+ *
+ * The problem is that glibc 2.39 and libseccomp 2.5.5 are needed to
+ * get the syscall number. However, a Nix built against nixpkgs 23.11
+ * (glibc 2.38) should still have the issue fixed without depending
+ * on the build environment.
+ *
+ * To achieve that, the macros below try to determine the platform and
+ * set the syscall number which is platform-specific, but
+ * in most cases 452.
+ *
+ * TODO: remove this when 23.11 is EOL and the entire (supported) ecosystem
+ * is on glibc 2.39.
+ */
+
+#if HAVE_SECCOMP
+#  if defined(__alpha__)
+#    define NIX_SYSCALL_FCHMODAT2 562
+#  elif defined(__x86_64__) && SIZE_MAX == 0xFFFFFFFF // x32
+#    define NIX_SYSCALL_FCHMODAT2 1073742276
+#  elif defined(__mips__) && defined(__mips64) && defined(_ABIN64) // mips64/n64
+#    define NIX_SYSCALL_FCHMODAT2 5452
+#  elif defined(__mips__) && defined(__mips64) && defined(_ABIN32) // mips64/n32
+#    define NIX_SYSCALL_FCHMODAT2 6452
+#  elif defined(__mips__) && defined(_ABIO32) // mips32
+#    define NIX_SYSCALL_FCHMODAT2 4452
+#  else
+#    define NIX_SYSCALL_FCHMODAT2 452
+#  endif
+#endif // HAVE_SECCOMP
diff --git a/src/libstore/linux/meson.build b/src/libstore/linux/meson.build
new file mode 100644
index 00000000000..0c494b5d62e
--- /dev/null
+++ b/src/libstore/linux/meson.build
@@ -0,0 +1,10 @@
+sources += files(
+  'personality.cc',
+)
+
+include_dirs += include_directories('.')
+
+headers += files(
+  'fchmodat2-compat.hh',
+  'personality.hh',
+)
diff --git a/src/libstore/unix/build/personality.cc b/src/libstore/linux/personality.cc
similarity index 95%
rename from src/libstore/unix/build/personality.cc
rename to src/libstore/linux/personality.cc
index 1a620175844..255d174a6cc 100644
--- a/src/libstore/unix/build/personality.cc
+++ b/src/libstore/linux/personality.cc
@@ -1,18 +1,15 @@
 #include "personality.hh"
 #include "globals.hh"
 
-#if __linux__
 #include <sys/utsname.h>
 #include <sys/personality.h>
-#endif
 
 #include <cstring>
 
-namespace nix {
+namespace nix::linux {
 
 void setPersonality(std::string_view system)
 {
-#if __linux__
         /* Change the personality to 32-bit if we're doing an
            i686-linux build on an x86_64-linux machine. */
         struct utsname utsbuf;
@@ -39,7 +36,6 @@ void setPersonality(std::string_view system)
            determinism. */
         int cur = personality(0xffffffff);
         if (cur != -1) personality(cur | ADDR_NO_RANDOMIZE);
-#endif
 }
 
 }
diff --git a/src/libstore/unix/build/personality.hh b/src/libstore/linux/personality.hh
similarity index 80%
rename from src/libstore/unix/build/personality.hh
rename to src/libstore/linux/personality.hh
index 91b730fab41..6a6376f8ff5 100644
--- a/src/libstore/unix/build/personality.hh
+++ b/src/libstore/linux/personality.hh
@@ -3,7 +3,7 @@
 
 #include <string>
 
-namespace nix {
+namespace nix::linux {
 
 void setPersonality(std::string_view system);
 
diff --git a/src/libstore/local-binary-cache-store.cc b/src/libstore/local-binary-cache-store.cc
index 5481dd762e2..aa2efdb8fb6 100644
--- a/src/libstore/local-binary-cache-store.cc
+++ b/src/libstore/local-binary-cache-store.cc
@@ -1,6 +1,7 @@
 #include "binary-cache-store.hh"
 #include "globals.hh"
 #include "nar-info-disk-cache.hh"
+#include "signals.hh"
 
 #include <atomic>
 
@@ -28,9 +29,13 @@ class LocalBinaryCacheStore : public virtual LocalBinaryCacheStoreConfig, public
 
 public:
 
+    /**
+     * @param binaryCacheDir `file://` is a short-hand for `file:///`
+     * for now.
+     */
     LocalBinaryCacheStore(
-        const std::string scheme,
-        const Path & binaryCacheDir,
+        std::string_view scheme,
+        PathView binaryCacheDir,
         const Params & params)
         : StoreConfig(params)
         , BinaryCacheStoreConfig(params)
@@ -64,7 +69,7 @@ class LocalBinaryCacheStore : public virtual LocalBinaryCacheStoreConfig, public
         AutoDelete del(tmp, false);
         StreamToSourceAdapter source(istream);
         writeFile(tmp, source);
-        renameFile(tmp, path2);
+        std::filesystem::rename(tmp, path2);
         del.cancel();
     }
 
@@ -83,12 +88,14 @@ class LocalBinaryCacheStore : public virtual LocalBinaryCacheStoreConfig, public
     {
         StorePathSet paths;
 
-        for (auto & entry : readDirectory(binaryCacheDir)) {
-            if (entry.name.size() != 40 ||
-                !hasSuffix(entry.name, ".narinfo"))
+        for (auto & entry : std::filesystem::directory_iterator{binaryCacheDir}) {
+            checkInterrupt();
+            auto name = entry.path().filename().string();
+            if (name.size() != 40 ||
+                !hasSuffix(name, ".narinfo"))
                 continue;
             paths.insert(parseStorePath(
-                    storeDir + "/" + entry.name.substr(0, entry.name.size() - 8)
+                    storeDir + "/" + name.substr(0, name.size() - 8)
                     + "-" + MissingName));
         }
 
diff --git a/src/libstore/unix/local-overlay-store.cc b/src/libstore/local-overlay-store.cc
similarity index 100%
rename from src/libstore/unix/local-overlay-store.cc
rename to src/libstore/local-overlay-store.cc
diff --git a/src/libstore/unix/local-overlay-store.hh b/src/libstore/local-overlay-store.hh
similarity index 98%
rename from src/libstore/unix/local-overlay-store.hh
rename to src/libstore/local-overlay-store.hh
index 2c24285dd47..35a30101391 100644
--- a/src/libstore/unix/local-overlay-store.hh
+++ b/src/libstore/local-overlay-store.hh
@@ -92,7 +92,7 @@ class LocalOverlayStore : public virtual LocalOverlayStoreConfig, public virtual
 public:
     LocalOverlayStore(const Params & params);
 
-    LocalOverlayStore(std::string scheme, std::string path, const Params & params)
+    LocalOverlayStore(std::string_view scheme, PathView path, const Params & params)
         : LocalOverlayStore(params)
     {
         if (!path.empty())
diff --git a/src/libstore/unix/local-overlay-store.md b/src/libstore/local-overlay-store.md
similarity index 86%
rename from src/libstore/unix/local-overlay-store.md
rename to src/libstore/local-overlay-store.md
index cc310bc7f17..1e1a3d26c7b 100644
--- a/src/libstore/unix/local-overlay-store.md
+++ b/src/libstore/local-overlay-store.md
@@ -16,6 +16,8 @@ The parts of a local overlay store are as follows:
 
 - **Lower store**:
 
+  > Specified with the [`lower-store`](#store-experimental-local-overlay-store-lower-store) setting.
+
   This is any store implementation that includes a store directory as part of the native operating system filesystem.
   For example, this could be a [local store], [local daemon store], or even another local overlay store.
 
@@ -28,13 +30,11 @@ The parts of a local overlay store are as follows:
   The lower store must not change while it is mounted as part of an overlay store.
   To ensure it does not, you might want to mount the store directory read-only (which then requires the [read-only] parameter to be set to `true`).
 
-  Specified with the [`lower-store`](#store-experimental-local-overlay-store-lower-store) setting.
-
   - **Lower store directory**:
 
-    This is the directory used/exposed by the lower store.
+    > Specified with `lower-store.real` setting.
 
-    Specified with `lower-store.real` setting.
+    This is the directory used/exposed by the lower store.
 
     As specified above, Nix requires the local store can only grow not change in other ways.
     Linux's OverlayFS in addition imposes the further requirement that this directory cannot change at all.
@@ -42,6 +42,9 @@ The parts of a local overlay store are as follows:
 
   - **Lower metadata source**:
 
+    > Not directly specified.
+    > A consequence of the `lower-store` setting, depending on the type of lower store chosen.
+
     This is abstract, just some way to read the metadata of lower store [store objects][store object].
     For example it could be a SQLite database (for the [local store]), or a socket connection (for the [local daemon store]).
 
@@ -51,36 +54,41 @@ The parts of a local overlay store are as follows:
 
 - **Upper almost-store**:
 
+  > Not directly specified.
+  > Instead the constituent parts are independently specified as described below.
+
   This is almost but not quite just a [local store].
   That is because taken in isolation, not as part of a local overlay store, by itself, it would appear corrupted.
   But combined with everything else as part of an overlay local store, it is valid.
 
   - **Upper layer directory**:
 
+    > Specified with [`upper-layer`](#store-experimental-local-overlay-store-upper-layer) setting.
+
     This contains additional [store objects][store object]
     (or, strictly speaking, their [file system objects][file system object] that the local overlay store will extend the lower store with).
 
-    Specified with [`upper-layer`](#store-experimental-local-overlay-store-upper-layer) setting.
-
   - **Upper store directory**:
 
+    > Specified with the [`real`](#store-experimental-local-overlay-store-real) setting.
+    > This the same as the base local store setting, and can also be indirectly specified with the [`root`](#store-experimental-local-overlay-store-root) setting.
+
     This contains all the store objects from each of the two directories.
 
     The lower store directory and upper layer directory are combined via OverlayFS to create this directory.
     Nix doesn't do this itself, because it typically wouldn't have the permissions to do so, so it is the responsibility of the user to set this up first.
     Nix can, however, optionally check that that the OverlayFS mount settings appear as expected, matching Nix's own settings.
 
-    Specified with the [`real`](#store-experimental-local-overlay-store-real) setting.
-
   - **Upper SQLite database**:
 
+    > Not directly specified.
+    > The location of the database instead depends on the [`state`](#store-experimental-local-overlay-store-state) setting.
+    > It is is always `${state}/db`.
+
     This contains the metadata of all of the upper layer [store objects][store object] (everything beyond their file system objects), and also duplicate copies of some lower layer store object's metadta.
     The duplication is so the metadata for the [closure](@docroot@/glossary.md#gloss-closure) of upper layer [store objects][store object] can be found entirely within the upper layer.
     (This allows us to use the same SQL Schema as the [local store]'s SQLite database, as foreign keys in that schema enforce closure metadata to be self-contained in this way.)
 
-    The location of the database is directly specified, but depends on the [`state`](#store-experimental-local-overlay-store-state) setting.
-    It is is always `${state}/db`.
-
 [file system object]: @docroot@/store/file-system-object.md
 [store object]: @docroot@/store/store-object.md
 
diff --git a/src/libstore/unix/local-store.cc b/src/libstore/local-store.cc
similarity index 94%
rename from src/libstore/unix/local-store.cc
rename to src/libstore/local-store.cc
index 1593affd608..2b4e01eb3ba 100644
--- a/src/libstore/unix/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -26,7 +26,6 @@
 #include <new>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/select.h>
 #include <sys/time.h>
 #include <unistd.h>
 #include <utime.h>
@@ -34,17 +33,20 @@
 #include <errno.h>
 #include <stdio.h>
 #include <time.h>
-#include <grp.h>
+
+#ifndef _WIN32
+# include <grp.h>
+#endif
 
 #if __linux__
-#include <sched.h>
-#include <sys/statvfs.h>
-#include <sys/mount.h>
-#include <sys/ioctl.h>
+# include <sched.h>
+# include <sys/statvfs.h>
+# include <sys/mount.h>
+# include <sys/ioctl.h>
 #endif
 
 #ifdef __CYGWIN__
-#include <windows.h>
+# include <windows.h>
 #endif
 
 #include <sqlite3.h>
@@ -52,8 +54,6 @@
 
 namespace nix {
 
-using namespace nix::unix;
-
 std::string LocalStoreConfig::doc()
 {
     return
@@ -224,6 +224,7 @@ LocalStore::LocalStore(const Params & params)
         }
     }
 
+#ifndef _WIN32
     /* Optionally, create directories and set permissions for a
        multi-user install. */
     if (isRootUser() && settings.buildUsersGroup != "") {
@@ -232,7 +233,7 @@ LocalStore::LocalStore(const Params & params)
         struct group * gr = getgrnam(settings.buildUsersGroup.get().c_str());
         if (!gr)
             printError("warning: the group '%1%' specified in 'build-users-group' does not exist", settings.buildUsersGroup);
-        else {
+        else if (!readOnly) {
             struct stat st;
             if (stat(realStoreDir.get().c_str(), &st))
                 throw SysError("getting attributes of path '%1%'", realStoreDir);
@@ -245,6 +246,7 @@ LocalStore::LocalStore(const Params & params)
             }
         }
     }
+#endif
 
     /* Ensure that the store and its parents are not symlinks. */
     if (!settings.allowSymlinkedStore) {
@@ -270,14 +272,25 @@ LocalStore::LocalStore(const Params & params)
         if (stat(reservedPath.c_str(), &st) == -1 ||
             st.st_size != settings.reservedSize)
         {
-            AutoCloseFD fd = open(reservedPath.c_str(), O_WRONLY | O_CREAT | O_CLOEXEC, 0600);
+            AutoCloseFD fd = toDescriptor(open(reservedPath.c_str(), O_WRONLY | O_CREAT
+#ifndef _WIN32
+                | O_CLOEXEC
+#endif
+                , 0600));
             int res = -1;
 #if HAVE_POSIX_FALLOCATE
             res = posix_fallocate(fd.get(), 0, settings.reservedSize);
 #endif
             if (res == -1) {
                 writeFull(fd.get(), std::string(settings.reservedSize, 'X'));
-                [[gnu::unused]] auto res2 = ftruncate(fd.get(), settings.reservedSize);
+                [[gnu::unused]] auto res2 =
+
+#ifdef _WIN32
+                    SetEndOfFile(fd.get())
+#else
+                    ftruncate(fd.get(), settings.reservedSize)
+#endif
+                    ;
             }
         }
     } catch (SystemError & e) { /* don't care about errors */
@@ -450,20 +463,34 @@ LocalStore::LocalStore(const Params & params)
 }
 
 
-LocalStore::LocalStore(std::string scheme, std::string path, const Params & params)
-    : LocalStore(params)
+LocalStore::LocalStore(
+    std::string_view scheme,
+    PathView path,
+    const Params & _params)
+    : LocalStore([&]{
+        // Default `?root` from `path` if non set
+        if (!path.empty() && _params.count("root") == 0) {
+            auto params = _params;
+            params.insert_or_assign("root", std::string { path });
+            return params;
+        }
+        return _params;
+    }())
 {
-    throw UnimplementedError("LocalStore");
 }
 
 
 AutoCloseFD LocalStore::openGCLock()
 {
     Path fnGCLock = stateDir + "/gc.lock";
-    auto fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
+    auto fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT
+#ifndef _WIN32
+        | O_CLOEXEC
+#endif
+        , 0600);
     if (!fdGCLock)
         throw SysError("opening global GC lock '%1%'", fnGCLock);
-    return fdGCLock;
+    return toDescriptor(fdGCLock);
 }
 
 
@@ -491,7 +518,7 @@ LocalStore::~LocalStore()
     try {
         auto fdTempRoots(_fdTempRoots.lock());
         if (*fdTempRoots) {
-            *fdTempRoots = -1;
+            fdTempRoots->close();
             unlink(fnTempRoots.c_str());
         }
     } catch (...) {
@@ -969,11 +996,13 @@ void LocalStore::registerValidPath(const ValidPathInfo & info)
 
 void LocalStore::registerValidPaths(const ValidPathInfos & infos)
 {
+#ifndef _WIN32
     /* SQLite will fsync by default, but the new valid paths may not
        be fsync-ed.  So some may want to fsync them before registering
        the validity, at the expense of some speed of the path
        registering operation. */
     if (settings.syncBeforeRegistering) sync();
+#endif
 
     return retrySQLite<void>([&]() {
         auto state(_state.lock());
@@ -1126,18 +1155,18 @@ void LocalStore::addToStore(const ValidPathInfo & info, Source & source,
                     auto fim = specified.method.getFileIngestionMethod();
                     switch (fim) {
                     case FileIngestionMethod::Flat:
-                    case FileIngestionMethod::Recursive:
+                    case FileIngestionMethod::NixArchive:
                     {
                         HashModuloSink caSink {
                             specified.hash.algo,
                             std::string { info.path.hashPart() },
                         };
-                        dumpPath(*accessor, path, caSink, (FileSerialisationMethod) fim);
+                        dumpPath({accessor, path}, caSink, (FileSerialisationMethod) fim);
                         h = caSink.finish().first;
                         break;
                     }
                     case FileIngestionMethod::Git:
-                        h = git::dumpHash(specified.hash.algo, *accessor, path).hash;
+                        h = git::dumpHash(specified.hash.algo, {accessor, path}).hash;
                         break;
                     }
                     ContentAddress {
@@ -1155,7 +1184,7 @@ void LocalStore::addToStore(const ValidPathInfo & info, Source & source,
 
             autoGC();
 
-            canonicalisePathMetaData(realPath, {});
+            canonicalisePathMetaData(realPath);
 
             optimisePath(realPath, repair); // FIXME: combine with hashPath()
 
@@ -1220,11 +1249,11 @@ StorePath LocalStore::addToStoreFromDump(
     }
 
     std::unique_ptr<AutoDelete> delTempDir;
-    Path tempPath;
-    Path tempDir;
+    std::filesystem::path tempPath;
+    std::filesystem::path tempDir;
     AutoCloseFD tempDirFd;
 
-    bool methodsMatch = ContentAddressMethod(FileIngestionMethod(dumpMethod)) == hashMethod;
+    bool methodsMatch = static_cast<FileIngestionMethod>(dumpMethod) == hashMethod.getFileIngestionMethod();
 
     /* If the methods don't match, our streaming hash of the dump is the
        wrong sort, and we need to rehash. */
@@ -1237,9 +1266,9 @@ StorePath LocalStore::addToStoreFromDump(
 
         std::tie(tempDir, tempDirFd) = createTempDirInStore();
         delTempDir = std::make_unique<AutoDelete>(tempDir);
-        tempPath = tempDir + "/x";
+        tempPath = tempDir / "x";
 
-        restorePath(tempPath, bothSource, dumpMethod);
+        restorePath(tempPath.string(), bothSource, dumpMethod);
 
         dumpBuffer.reset();
         dump = {};
@@ -1247,15 +1276,13 @@ StorePath LocalStore::addToStoreFromDump(
 
     auto [dumpHash, size] = hashSink->finish();
 
-    PosixSourceAccessor accessor;
-
     auto desc = ContentAddressWithReferences::fromParts(
         hashMethod,
         methodsMatch
             ? dumpHash
             : hashPath(
-                accessor, CanonPath { tempPath },
-                hashMethod.getFileIngestionMethod(), hashAlgo),
+                PosixSourceAccessor::createAtRoot(tempPath),
+                hashMethod.getFileIngestionMethod(), hashAlgo).first,
         {
             .others = references,
             // caller is not capable of creating a self-reference, because this is content-addressed without modulus
@@ -1287,7 +1314,7 @@ StorePath LocalStore::addToStoreFromDump(
                 auto fim = hashMethod.getFileIngestionMethod();
                 switch (fim) {
                 case FileIngestionMethod::Flat:
-                case FileIngestionMethod::Recursive:
+                case FileIngestionMethod::NixArchive:
                     restorePath(realPath, dumpSource, (FileSerialisationMethod) fim);
                     break;
                 case FileIngestionMethod::Git:
@@ -1297,19 +1324,19 @@ StorePath LocalStore::addToStoreFromDump(
                 }
             } else {
                 /* Move the temporary path we restored above. */
-                moveFile(tempPath, realPath);
+                moveFile(tempPath.string(), realPath);
             }
 
             /* For computing the nar hash. In recursive SHA-256 mode, this
                is the same as the store hash, so no need to do it again. */
             auto narHash = std::pair { dumpHash, size };
-            if (dumpMethod != FileSerialisationMethod::Recursive || hashAlgo != HashAlgorithm::SHA256) {
+            if (dumpMethod != FileSerialisationMethod::NixArchive || hashAlgo != HashAlgorithm::SHA256) {
                 HashSink narSink { HashAlgorithm::SHA256 };
                 dumpPath(realPath, narSink);
                 narHash = narSink.finish();
             }
 
-            canonicalisePathMetaData(realPath, {}); // FIXME: merge into restorePath
+            canonicalisePathMetaData(realPath); // FIXME: merge into restorePath
 
             optimisePath(realPath, repair);
 
@@ -1332,9 +1359,9 @@ StorePath LocalStore::addToStoreFromDump(
 
 /* Create a temporary directory in the store that won't be
    garbage-collected until the returned FD is closed. */
-std::pair<Path, AutoCloseFD> LocalStore::createTempDirInStore()
+std::pair<std::filesystem::path, AutoCloseFD> LocalStore::createTempDirInStore()
 {
-    Path tmpDirFn;
+    std::filesystem::path tmpDirFn;
     AutoCloseFD tmpDirFd;
     bool lockedByUs = false;
     do {
@@ -1342,12 +1369,12 @@ std::pair<Path, AutoCloseFD> LocalStore::createTempDirInStore()
            the GC between createTempDir() and when we acquire a lock on it.
            We'll repeat until 'tmpDir' exists and we've locked it. */
         tmpDirFn = createTempDir(realStoreDir, "tmp");
-        tmpDirFd = open(tmpDirFn.c_str(), O_RDONLY | O_DIRECTORY);
-        if (tmpDirFd.get() < 0) {
+        tmpDirFd = openDirectory(tmpDirFn);
+        if (!tmpDirFd) {
             continue;
         }
         lockedByUs = lockFile(tmpDirFd.get(), ltWrite, true);
-    } while (!pathExists(tmpDirFn) || !lockedByUs);
+    } while (!pathExists(tmpDirFn.string()) || !lockedByUs);
     return {tmpDirFn, std::move(tmpDirFd)};
 }
 
@@ -1389,21 +1416,20 @@ bool LocalStore::verifyStore(bool checkContents, RepairFlag repair)
 
         printInfo("checking link hashes...");
 
-        for (auto & link : readDirectory(linksDir)) {
-            printMsg(lvlTalkative, "checking contents of '%s'", link.name);
-            Path linkPath = linksDir + "/" + link.name;
+        for (auto & link : std::filesystem::directory_iterator{linksDir}) {
+            checkInterrupt();
+            auto name = link.path().filename();
+            printMsg(lvlTalkative, "checking contents of '%s'", name);
             PosixSourceAccessor accessor;
             std::string hash = hashPath(
-                accessor, CanonPath { linkPath },
-                FileIngestionMethod::Recursive, HashAlgorithm::SHA256).to_string(HashFormat::Nix32, false);
-            if (hash != link.name) {
+                PosixSourceAccessor::createAtRoot(link.path()),
+                FileIngestionMethod::NixArchive, HashAlgorithm::SHA256).first.to_string(HashFormat::Nix32, false);
+            if (hash != name.string()) {
                 printError("link '%s' was modified! expected hash '%s', got '%s'",
-                    linkPath, link.name, hash);
+                    link.path(), name, hash);
                 if (repair) {
-                    if (unlink(linkPath.c_str()) == 0)
-                        printInfo("removed link '%s'", linkPath);
-                    else
-                        throw SysError("removing corrupt link '%s'", linkPath);
+                    std::filesystem::remove(link.path());
+                    printInfo("removed link '%s'", link.path());
                 } else {
                     errors = true;
                 }
@@ -1483,9 +1509,10 @@ LocalStore::VerificationResult LocalStore::verifyAllValidPaths(RepairFlag repair
        database and the filesystem) in the loop below, in order to catch
        invalid states.
      */
-    for (auto & i : readDirectory(realStoreDir)) {
+    for (auto & i : std::filesystem::directory_iterator{realStoreDir.to_string()}) {
+        checkInterrupt();
         try {
-            storePathsInStoreDir.insert({i.name});
+            storePathsInStoreDir.insert({i.path().filename().string()});
         } catch (BadStorePath &) { }
     }
 
@@ -1584,8 +1611,12 @@ static void makeMutable(const Path & path)
     /* The O_NOFOLLOW is important to prevent us from changing the
        mutable bit on the target of a symlink (which would be a
        security hole). */
-    AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
-    if (fd == -1) {
+    AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW
+#ifndef _WIN32
+        | O_CLOEXEC
+#endif
+        );
+    if (fd == INVALID_DESCRIPTOR) {
         if (errno == ELOOP) return; // it's a symlink
         throw SysError("opening file '%1%'", path);
     }
@@ -1760,7 +1791,7 @@ void LocalStore::addBuildLog(const StorePath & drvPath, std::string_view log)
 
     writeFile(tmpFile, compress("bzip2", log));
 
-    renameFile(tmpFile, logPath);
+    std::filesystem::rename(tmpFile, logPath);
 }
 
 std::optional<std::string> LocalStore::getVersion()
diff --git a/src/libstore/unix/local-store.hh b/src/libstore/local-store.hh
similarity index 97%
rename from src/libstore/unix/local-store.hh
rename to src/libstore/local-store.hh
index 47d3c04bc78..b0a0def9aae 100644
--- a/src/libstore/unix/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -32,7 +32,6 @@ struct OptimiseStats
 {
     unsigned long filesLinked = 0;
     uint64_t bytesFreed = 0;
-    uint64_t blocksFreed = 0;
 };
 
 struct LocalStoreConfig : virtual LocalFSStoreConfig
@@ -138,12 +137,15 @@ public:
      * necessary.
      */
     LocalStore(const Params & params);
-    LocalStore(std::string scheme, std::string path, const Params & params);
+    LocalStore(
+        std::string_view scheme,
+        PathView path,
+        const Params & params);
 
     ~LocalStore();
 
     static std::set<std::string> uriSchemes()
-    { return {}; }
+    { return {"local"}; }
 
     /**
      * Implementations of abstract store API methods.
@@ -371,13 +373,13 @@ private:
     PathSet queryValidPathsOld();
     ValidPathInfo queryPathInfoOld(const Path & path);
 
-    void findRoots(const Path & path, unsigned char type, Roots & roots);
+    void findRoots(const Path & path, std::filesystem::file_type type, Roots & roots);
 
     void findRootsNoTemp(Roots & roots, bool censor);
 
     void findRuntimeRoots(Roots & roots, bool censor);
 
-    std::pair<Path, AutoCloseFD> createTempDirInStore();
+    std::pair<std::filesystem::path, AutoCloseFD> createTempDirInStore();
 
     typedef std::unordered_set<ino_t> InodeHash;
 
diff --git a/src/libstore/unix/local-store.md b/src/libstore/local-store.md
similarity index 100%
rename from src/libstore/unix/local-store.md
rename to src/libstore/local-store.md
diff --git a/src/libstore/local.mk b/src/libstore/local.mk
index 6be748581a3..5dc8f3370bc 100644
--- a/src/libstore/local.mk
+++ b/src/libstore/local.mk
@@ -4,9 +4,12 @@ libstore_NAME = libnixstore
 
 libstore_DIR := $(d)
 
-libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc)
+libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc $(d)/build/*.cc)
 ifdef HOST_UNIX
-  libstore_SOURCES += $(wildcard $(d)/unix/*.cc $(d)/unix/builtins/*.cc $(d)/unix/build/*.cc)
+  libstore_SOURCES += $(wildcard $(d)/unix/*.cc $(d)/unix/build/*.cc)
+endif
+ifdef HOST_LINUX
+  libstore_SOURCES += $(wildcard $(d)/linux/*.cc)
 endif
 ifdef HOST_WINDOWS
   libstore_SOURCES += $(wildcard $(d)/windows/*.cc)
@@ -18,6 +21,9 @@ libstore_LDFLAGS += $(SQLITE3_LIBS) $(LIBCURL_LIBS) $(THREAD_LDFLAGS)
 ifdef HOST_LINUX
   libstore_LDFLAGS += -ldl
 endif
+ifdef HOST_WINDOWS
+  libstore_LDFLAGS += -lws2_32
+endif
 
 $(foreach file,$(libstore_FILES),$(eval $(call install-data-in,$(d)/$(file),$(datadir)/nix/sandbox)))
 
@@ -37,7 +43,10 @@ endif
 
 INCLUDE_libstore := -I $(d) -I $(d)/build
 ifdef HOST_UNIX
-  INCLUDE_libstore += -I $(d)/unix
+  INCLUDE_libstore += -I $(d)/unix -I $(d)/unix/build
+endif
+ifdef HOST_LINUX
+  INCLUDE_libstore += -I $(d)/linux
 endif
 ifdef HOST_WINDOWS
   INCLUDE_libstore += -I $(d)/windows
@@ -80,11 +89,11 @@ else
   endif
 endif
 
-$(d)/unix/local-store.cc: $(d)/unix/schema.sql.gen.hh $(d)/unix/ca-specific-schema.sql.gen.hh
+$(d)/local-store.cc: $(d)/schema.sql.gen.hh $(d)/ca-specific-schema.sql.gen.hh
 
 $(d)/unix/build.cc:
 
-clean-files += $(d)/unix/schema.sql.gen.hh $(d)/unix/ca-specific-schema.sql.gen.hh
+clean-files += $(d)/schema.sql.gen.hh $(d)/ca-specific-schema.sql.gen.hh
 
 $(eval $(call install-file-in, $(buildprefix)$(d)/nix-store.pc, $(libdir)/pkgconfig, 0644))
 
diff --git a/src/libstore/machines.cc b/src/libstore/machines.cc
index 2d461c63afb..256cf918892 100644
--- a/src/libstore/machines.cc
+++ b/src/libstore/machines.cc
@@ -6,7 +6,8 @@
 
 namespace nix {
 
-Machine::Machine(decltype(storeUri) storeUri,
+Machine::Machine(
+    const std::string & storeUri,
     decltype(systemTypes) systemTypes,
     decltype(sshKey) sshKey,
     decltype(maxJobs) maxJobs,
@@ -14,7 +15,7 @@ Machine::Machine(decltype(storeUri) storeUri,
     decltype(supportedFeatures) supportedFeatures,
     decltype(mandatoryFeatures) mandatoryFeatures,
     decltype(sshPublicHostKey) sshPublicHostKey) :
-    storeUri(
+    storeUri(StoreReference::parse(
         // Backwards compatibility: if the URI is schemeless, is not a path,
         // and is not one of the special store connection words, prepend
         // ssh://.
@@ -28,7 +29,7 @@ Machine::Machine(decltype(storeUri) storeUri,
         || hasPrefix(storeUri, "local?")
         || hasPrefix(storeUri, "?")
         ? storeUri
-        : "ssh://" + storeUri),
+        : "ssh://" + storeUri)),
     systemTypes(systemTypes),
     sshKey(sshKey),
     maxJobs(maxJobs),
@@ -63,23 +64,26 @@ bool Machine::mandatoryMet(const std::set<std::string> & features) const
         });
 }
 
-ref<Store> Machine::openStore() const
+StoreReference Machine::completeStoreReference() const
 {
-    Store::Params storeParams;
-    if (hasPrefix(storeUri, "ssh://")) {
-        storeParams["max-connections"] = "1";
-        storeParams["log-fd"] = "4";
+    auto storeUri = this->storeUri;
+
+    auto * generic = std::get_if<StoreReference::Specified>(&storeUri.variant);
+
+    if (generic && generic->scheme == "ssh") {
+        storeUri.params["max-connections"] = "1";
+        storeUri.params["log-fd"] = "4";
     }
 
-    if (hasPrefix(storeUri, "ssh://") || hasPrefix(storeUri, "ssh-ng://")) {
+    if (generic && (generic->scheme == "ssh" || generic->scheme == "ssh-ng")) {
         if (sshKey != "")
-            storeParams["ssh-key"] = sshKey;
+            storeUri.params["ssh-key"] = sshKey;
         if (sshPublicHostKey != "")
-            storeParams["base64-ssh-public-host-key"] = sshPublicHostKey;
+            storeUri.params["base64-ssh-public-host-key"] = sshPublicHostKey;
     }
 
     {
-        auto & fs = storeParams["system-features"];
+        auto & fs = storeUri.params["system-features"];
         auto append = [&](auto feats) {
             for (auto & f : feats) {
                 if (fs.size() > 0) fs += ' ';
@@ -90,7 +94,12 @@ ref<Store> Machine::openStore() const
         append(mandatoryFeatures);
     }
 
-    return nix::openStore(storeUri, storeParams);
+    return storeUri;
+}
+
+ref<Store> Machine::openStore() const
+{
+    return nix::openStore(completeStoreReference());
 }
 
 static std::vector<std::string> expandBuilderLines(const std::string & builders)
@@ -122,7 +131,7 @@ static std::vector<std::string> expandBuilderLines(const std::string & builders)
     return result;
 }
 
-static Machine parseBuilderLine(const std::string & line)
+static Machine parseBuilderLine(const std::set<std::string> & defaultSystems, const std::string & line)
 {
     const auto tokens = tokenizeString<std::vector<std::string>>(line);
 
@@ -139,7 +148,7 @@ static Machine parseBuilderLine(const std::string & line)
     };
 
     auto parseFloatField = [&](size_t fieldIndex) {
-        const auto result = string2Int<float>(tokens[fieldIndex]);
+        const auto result = string2Float<float>(tokens[fieldIndex]);
         if (!result) {
             throw FormatError("bad machine specification: failed to convert column #%lu in a row: '%s' to 'float'", fieldIndex, line);
         }
@@ -159,29 +168,46 @@ static Machine parseBuilderLine(const std::string & line)
     if (!isSet(0))
         throw FormatError("bad machine specification: store URL was not found at the first column of a row: '%s'", line);
 
+    // TODO use designated initializers, once C++ supports those with
+    // custom constructors.
     return {
+        // `storeUri`
         tokens[0],
-        isSet(1) ? tokenizeString<std::set<std::string>>(tokens[1], ",") : std::set<std::string>{settings.thisSystem},
+        // `systemTypes`
+        isSet(1) ? tokenizeString<std::set<std::string>>(tokens[1], ",") : defaultSystems,
+        // `sshKey`
         isSet(2) ? tokens[2] : "",
+        // `maxJobs`
         isSet(3) ? parseUnsignedIntField(3) : 1U,
+        // `speedFactor`
         isSet(4) ? parseFloatField(4) : 1.0f,
+        // `supportedFeatures`
         isSet(5) ? tokenizeString<std::set<std::string>>(tokens[5], ",") : std::set<std::string>{},
+        // `mandatoryFeatures`
         isSet(6) ? tokenizeString<std::set<std::string>>(tokens[6], ",") : std::set<std::string>{},
+        // `sshPublicHostKey`
         isSet(7) ? ensureBase64(7) : ""
     };
 }
 
-static Machines parseBuilderLines(const std::vector<std::string> & builders)
+static Machines parseBuilderLines(const std::set<std::string> & defaultSystems, const std::vector<std::string> & builders)
 {
     Machines result;
-    std::transform(builders.begin(), builders.end(), std::back_inserter(result), parseBuilderLine);
+    std::transform(
+        builders.begin(), builders.end(), std::back_inserter(result),
+        [&](auto && line) { return parseBuilderLine(defaultSystems, line); });
     return result;
 }
 
+Machines Machine::parseConfig(const std::set<std::string> & defaultSystems, const std::string & s)
+{
+    const auto builderLines = expandBuilderLines(s);
+    return parseBuilderLines(defaultSystems, builderLines);
+}
+
 Machines getMachines()
 {
-    const auto builderLines = expandBuilderLines(settings.builders);
-    return parseBuilderLines(builderLines);
+    return Machine::parseConfig({settings.thisSystem}, settings.builders);
 }
 
 }
diff --git a/src/libstore/machines.hh b/src/libstore/machines.hh
index 8516409d48a..2a55c445667 100644
--- a/src/libstore/machines.hh
+++ b/src/libstore/machines.hh
@@ -2,14 +2,19 @@
 ///@file
 
 #include "types.hh"
+#include "store-reference.hh"
 
 namespace nix {
 
 class Store;
 
+struct Machine;
+
+typedef std::vector<Machine> Machines;
+
 struct Machine {
 
-    const std::string storeUri;
+    const StoreReference storeUri;
     const std::set<std::string> systemTypes;
     const std::string sshKey;
     const unsigned int maxJobs;
@@ -36,7 +41,8 @@ struct Machine {
      */
     bool mandatoryMet(const std::set<std::string> & features) const;
 
-    Machine(decltype(storeUri) storeUri,
+    Machine(
+        const std::string & storeUri,
         decltype(systemTypes) systemTypes,
         decltype(sshKey) sshKey,
         decltype(maxJobs) maxJobs,
@@ -45,13 +51,38 @@ struct Machine {
         decltype(mandatoryFeatures) mandatoryFeatures,
         decltype(sshPublicHostKey) sshPublicHostKey);
 
-    ref<Store> openStore() const;
-};
+    /**
+     * Elaborate `storeUri` into a complete store reference,
+     * incorporating information from the other fields of the `Machine`
+     * as applicable.
+     */
+    StoreReference completeStoreReference() const;
 
-typedef std::vector<Machine> Machines;
+    /**
+     * Open a `Store` for this machine.
+     *
+     * Just a simple function composition:
+     * ```c++
+     * nix::openStore(completeStoreReference())
+     * ```
+     */
+    ref<Store> openStore() const;
 
-void parseMachines(const std::string & s, Machines & machines);
+    /**
+     * Parse a machine configuration.
+     *
+     * Every machine is specified on its own line, and lines beginning
+     * with `@` are interpreted as paths to other configuration files in
+     * the same format.
+     */
+    static Machines parseConfig(const std::set<std::string> & defaultSystems, const std::string & config);
+};
 
+/**
+ * Parse machines from the global config
+ *
+ * @todo Remove, globals are bad.
+ */
 Machines getMachines();
 
 }
diff --git a/src/libstore/make-content-addressed.cc b/src/libstore/make-content-addressed.cc
index 170fe67b92b..a3130d7cc02 100644
--- a/src/libstore/make-content-addressed.cc
+++ b/src/libstore/make-content-addressed.cc
@@ -52,7 +52,7 @@ std::map<StorePath, StorePath> makeContentAddressed(
             dstStore,
             path.name(),
             FixedOutputInfo {
-                .method = FileIngestionMethod::Recursive,
+                .method = FileIngestionMethod::NixArchive,
                 .hash = narModuloHash,
                 .references = std::move(refs),
             },
diff --git a/src/libstore/meson.build b/src/libstore/meson.build
new file mode 100644
index 00000000000..5324b2a1fd7
--- /dev/null
+++ b/src/libstore/meson.build
@@ -0,0 +1,404 @@
+project('nix-store', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+# TODO rename, because it will conflict with downstream projects
+configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+configdata.set_quoted('SYSTEM', host_machine.system())
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+]
+subdir('build-utils-meson/subprojects')
+
+run_command('ln', '-s',
+  meson.project_build_root() / '__nothing_link_target',
+  meson.project_build_root() / '__nothing_symlink',
+  check : true,
+)
+can_link_symlink = run_command('ln',
+  meson.project_build_root() / '__nothing_symlink',
+  meson.project_build_root() / '__nothing_hardlink',
+  check : false,
+).returncode() == 0
+run_command('rm', '-f',
+  meson.project_build_root() / '__nothing_symlink',
+  meson.project_build_root() / '__nothing_hardlink',
+  check : true,
+)
+summary('can hardlink to symlink', can_link_symlink, bool_yn : true)
+configdata.set('CAN_LINK_SYMLINK', can_link_symlink.to_int())
+
+# Check for each of these functions, and create a define like `#define HAVE_LCHOWN 1`.
+#
+# Only need to do functions that deps (like `libnixutil`) didn't already
+# check for.
+check_funcs = [
+  # Optionally used for canonicalising files from the build
+  'lchown',
+]
+foreach funcspec : check_funcs
+  define_name = 'HAVE_' + funcspec.underscorify().to_upper()
+  define_value = cxx.has_function(funcspec).to_int()
+  configdata.set(define_name, define_value)
+endforeach
+
+has_acl_support = cxx.has_header('sys/xattr.h') \
+  and cxx.has_function('llistxattr') \
+  and cxx.has_function('lremovexattr')
+configdata.set('HAVE_ACL_SUPPORT', has_acl_support.to_int())
+
+subdir('build-utils-meson/threads')
+
+boost = dependency(
+  'boost',
+  modules : ['container'],
+)
+# boost is a public dependency, but not a pkg-config dependency unfortunately, so we
+# put in `deps_other`.
+deps_other += boost
+
+curl = dependency('libcurl', 'curl')
+deps_private += curl
+
+# seccomp only makes sense on Linux
+is_linux = host_machine.system() == 'linux'
+seccomp_required = get_option('seccomp-sandboxing')
+if not is_linux and seccomp_required.enabled()
+  warning('Force-enabling seccomp on non-Linux does not make sense')
+endif
+seccomp = dependency('libseccomp', 'seccomp', required : seccomp_required, version : '>=2.5.5')
+if is_linux and not seccomp.found()
+  warning('Sandbox security is reduced because libseccomp has not been found! Please provide libseccomp if it supports your CPU architecture.')
+endif
+configdata.set('HAVE_SECCOMP', seccomp.found().to_int())
+deps_private += seccomp
+
+nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
+deps_public += nlohmann_json
+
+sqlite = dependency('sqlite3', 'sqlite', version : '>=3.6.19')
+deps_private += sqlite
+
+subdir('build-utils-meson/generate-header')
+
+generated_headers = []
+foreach header : [
+  'schema.sql',
+  'ca-specific-schema.sql',
+]
+  generated_headers += gen_header.process(header)
+endforeach
+
+busybox = find_program(get_option('sandbox-shell'), required : false)
+
+if get_option('embedded-sandbox-shell')
+  # This one goes in config.h
+  # The path to busybox is passed as a -D flag when compiling this_library.
+  # This solution is inherited from the old make buildsystem
+  # TODO: do this differently?
+  configdata.set('HAVE_EMBEDDED_SANDBOX_SHELL', 1)
+  hexdump = find_program('hexdump', native : true)
+  embedded_sandbox_shell_gen = custom_target(
+    'embedded-sandbox-shell.gen.hh',
+    command : [
+      hexdump,
+      '-v',
+      '-e',
+      '1/1 "0x%x," "\n"'
+    ],
+    input : busybox.full_path(),
+    output : 'embedded-sandbox-shell.gen.hh',
+    capture : true,
+    feed : true,
+  )
+  generated_headers += embedded_sandbox_shell_gen
+endif
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-store.hh',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'binary-cache-store.cc',
+  'build-result.cc',
+  'build/derivation-goal.cc',
+  'build/drv-output-substitution-goal.cc',
+  'build/entry-points.cc',
+  'build/goal.cc',
+  'build/substitution-goal.cc',
+  'build/worker.cc',
+  'builtins/buildenv.cc',
+  'builtins/fetchurl.cc',
+  'builtins/unpack-channel.cc',
+  'common-protocol.cc',
+  'content-address.cc',
+  'daemon.cc',
+  'derivations.cc',
+  'derived-path-map.cc',
+  'derived-path.cc',
+  'downstream-placeholder.cc',
+  'dummy-store.cc',
+  'export-import.cc',
+  'filetransfer.cc',
+  'gc.cc',
+  'globals.cc',
+  'http-binary-cache-store.cc',
+  'indirect-root-store.cc',
+  'keys.cc',
+  'legacy-ssh-store.cc',
+  'local-binary-cache-store.cc',
+  'local-fs-store.cc',
+  'local-overlay-store.cc',
+  'local-store.cc',
+  'log-store.cc',
+  'machines.cc',
+  'make-content-addressed.cc',
+  'misc.cc',
+  'names.cc',
+  'nar-accessor.cc',
+  'nar-info-disk-cache.cc',
+  'nar-info.cc',
+  'optimise-store.cc',
+  'outputs-spec.cc',
+  'parsed-derivations.cc',
+  'path-info.cc',
+  'path-references.cc',
+  'path-with-outputs.cc',
+  'path.cc',
+  'pathlocks.cc',
+  'posix-fs-canonicalise.cc',
+  'profiles.cc',
+  'realisation.cc',
+  'remote-fs-accessor.cc',
+  'remote-store.cc',
+  's3-binary-cache-store.cc',
+  'serve-protocol-connection.cc',
+  'serve-protocol.cc',
+  'sqlite.cc',
+  'ssh-store-config.cc',
+  'ssh-store.cc',
+  'ssh.cc',
+  'store-api.cc',
+  'store-reference.cc',
+  'uds-remote-store.cc',
+  'worker-protocol-connection.cc',
+  'worker-protocol.cc',
+)
+
+include_dirs = [
+  include_directories('.'),
+  include_directories('build'),
+]
+
+headers = [config_h] + files(
+  'binary-cache-store.hh',
+  'build-result.hh',
+  'build/derivation-goal.hh',
+  'build/drv-output-substitution-goal.hh',
+  'build/goal.hh',
+  'build/substitution-goal.hh',
+  'build/worker.hh',
+  'builtins.hh',
+  'builtins/buildenv.hh',
+  'common-protocol-impl.hh',
+  'common-protocol.hh',
+  'content-address.hh',
+  'daemon.hh',
+  'derivations.hh',
+  'derived-path-map.hh',
+  'derived-path.hh',
+  'downstream-placeholder.hh',
+  'filetransfer.hh',
+  'gc-store.hh',
+  'globals.hh',
+  'indirect-root-store.hh',
+  'keys.hh',
+  'legacy-ssh-store.hh',
+  'length-prefixed-protocol-helper.hh',
+  'local-fs-store.hh',
+  'local-overlay-store.hh',
+  'local-store.hh',
+  'log-store.hh',
+  'machines.hh',
+  'make-content-addressed.hh',
+  'names.hh',
+  'nar-accessor.hh',
+  'nar-info-disk-cache.hh',
+  'nar-info.hh',
+  'outputs-spec.hh',
+  'parsed-derivations.hh',
+  'path-info.hh',
+  'path-references.hh',
+  'path-regex.hh',
+  'path-with-outputs.hh',
+  'path.hh',
+  'pathlocks.hh',
+  'posix-fs-canonicalise.hh',
+  'profiles.hh',
+  'realisation.hh',
+  'remote-fs-accessor.hh',
+  'remote-store-connection.hh',
+  'remote-store.hh',
+  's3-binary-cache-store.hh',
+  's3.hh',
+  'serve-protocol-connection.hh',
+  'serve-protocol-impl.hh',
+  'serve-protocol.hh',
+  'sqlite.hh',
+  'ssh-store-config.hh',
+  'ssh.hh',
+  'store-api.hh',
+  'store-cast.hh',
+  'store-dir-config.hh',
+  'store-reference.hh',
+  'uds-remote-store.hh',
+  'worker-protocol-connection.hh',
+  'worker-protocol-impl.hh',
+  'worker-protocol.hh',
+)
+
+if host_machine.system() == 'linux'
+  subdir('linux')
+endif
+
+if host_machine.system() == 'windows'
+  subdir('windows')
+else
+  subdir('unix')
+endif
+
+fs = import('fs')
+
+prefix = get_option('prefix')
+# For each of these paths, assume that it is relative to the prefix unless
+# it is already an absolute path (which is the default for store-dir, state-dir, and log-dir).
+path_opts = [
+  # Meson built-ins.
+  'datadir',
+  'bindir',
+  'mandir',
+  'libdir',
+  'includedir',
+  'libexecdir',
+  # Homecooked Nix directories.
+  'store-dir',
+  'state-dir',
+  'log-dir',
+]
+# For your grepping pleasure, this loop sets the following variables that aren't mentioned
+# literally above:
+# store_dir
+# state_dir
+# log_dir
+# profile_dir
+foreach optname : path_opts
+  varname = optname.replace('-', '_')
+  path = get_option(optname)
+  if fs.is_absolute(path)
+    set_variable(varname, path)
+  else
+    set_variable(varname, prefix / path)
+  endif
+endforeach
+
+# sysconfdir doesn't get anything installed to directly, and is only used to
+# tell Nix where to look for nix.conf, so it doesn't get appended to prefix.
+sysconfdir = get_option('sysconfdir')
+if not fs.is_absolute(sysconfdir)
+  sysconfdir = '/' / sysconfdir
+endif
+
+lsof = find_program('lsof', required : false)
+
+# Aside from prefix itself, each of these was made into an absolute path
+# by joining it with prefix, unless it was already an absolute path
+# (which is the default for store-dir, state-dir, and log-dir).
+cpp_str_defines = {
+  'NIX_PREFIX':    prefix,
+  'NIX_STORE_DIR': store_dir,
+  'NIX_DATA_DIR':  datadir,
+  'NIX_STATE_DIR': state_dir / 'nix',
+  'NIX_LOG_DIR':   log_dir,
+  'NIX_CONF_DIR':  sysconfdir / 'nix',
+  'NIX_BIN_DIR':   bindir,
+  'NIX_MAN_DIR':   mandir,
+}
+
+if lsof.found()
+  lsof_path = lsof.full_path()
+else
+  # Just look up on the PATH
+  lsof_path = 'lsof'
+endif
+cpp_str_defines += {
+  'LSOF': lsof_path
+}
+
+if get_option('embedded-sandbox-shell')
+  cpp_str_defines += {
+    'SANDBOX_SHELL': '__embedded_sandbox_shell__'
+  }
+elif busybox.found()
+  cpp_str_defines += {
+    'SANDBOX_SHELL': busybox.full_path()
+  }
+endif
+
+cpp_args = []
+
+foreach name, value : cpp_str_defines
+  cpp_args += [
+    '-D' + name + '=' + '"' + value + '"'
+  ]
+endforeach
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nixstore',
+  generated_headers,
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  cpp_args : cpp_args,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libstore/meson.options b/src/libstore/meson.options
new file mode 100644
index 00000000000..723a8e020fd
--- /dev/null
+++ b/src/libstore/meson.options
@@ -0,0 +1,25 @@
+# vim: filetype=meson
+
+option('embedded-sandbox-shell', type : 'boolean', value : false,
+  description : 'include the sandbox shell in the Nix binary',
+)
+
+option('seccomp-sandboxing', type : 'feature',
+  description : 'build support for seccomp sandboxing (recommended unless your arch doesn\'t support libseccomp, only relevant on Linux)',
+)
+
+option('sandbox-shell', type : 'string', value : 'busybox',
+  description : 'path to a statically-linked shell to use as /bin/sh in sandboxes (usually busybox)',
+)
+
+option('store-dir', type : 'string', value : '/nix/store',
+  description : 'path of the Nix store',
+)
+
+option('state-dir', type : 'string', value : '/nix/var',
+  description : 'path to store state in for Nix',
+)
+
+option('log-dir', type : 'string', value : '/nix/var/log/nix',
+  description : 'path to store logs in for Nix',
+)
diff --git a/src/libstore/nar-accessor.cc b/src/libstore/nar-accessor.cc
index cecf8148f45..b1079b027d6 100644
--- a/src/libstore/nar-accessor.cc
+++ b/src/libstore/nar-accessor.cc
@@ -71,9 +71,11 @@ struct NarAccessor : public SourceAccessor
             : acc(acc), source(source)
         { }
 
-        NarMember & createMember(const Path & path, NarMember member)
+        NarMember & createMember(const CanonPath & path, NarMember member)
         {
-            size_t level = std::count(path.begin(), path.end(), '/');
+            size_t level = 0;
+            for (auto _ : path) ++level;
+
             while (parents.size() > level) parents.pop();
 
             if (parents.empty()) {
@@ -83,14 +85,14 @@ struct NarAccessor : public SourceAccessor
             } else {
                 if (parents.top()->stat.type != Type::tDirectory)
                     throw Error("NAR file missing parent directory of path '%s'", path);
-                auto result = parents.top()->children.emplace(baseNameOf(path), std::move(member));
+                auto result = parents.top()->children.emplace(*path.baseName(), std::move(member));
                 auto & ref = result.first->second;
                 parents.push(&ref);
                 return ref;
             }
         }
 
-        void createDirectory(const Path & path) override
+        void createDirectory(const CanonPath & path) override
         {
             createMember(path, NarMember{ .stat = {
                 .type = Type::tDirectory,
@@ -100,7 +102,7 @@ struct NarAccessor : public SourceAccessor
             } });
         }
 
-        void createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func) override
+        void createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func) override
         {
             auto & nm = createMember(path, NarMember{ .stat = {
                 .type = Type::tRegular,
@@ -112,7 +114,7 @@ struct NarAccessor : public SourceAccessor
             func(nmc);
         }
 
-        void createSymlink(const Path & path, const std::string & target) override
+        void createSymlink(const CanonPath & path, const std::string & target) override
         {
             createMember(path,
                 NarMember{
diff --git a/src/libstore/nix-store.pc.in b/src/libstore/nix-store.pc.in
index dc42d0bca2a..cd3f2b8dad2 100644
--- a/src/libstore/nix-store.pc.in
+++ b/src/libstore/nix-store.pc.in
@@ -5,5 +5,6 @@ includedir=@includedir@
 Name: Nix
 Description: Nix Package Manager
 Version: @PACKAGE_VERSION@
-Libs: -L${libdir} -lnixstore -lnixutil
+Requires: nix-util
+Libs: -L${libdir} -lnixstore
 Cflags: -I${includedir}/nix -std=c++2a
diff --git a/src/libstore/unix/optimise-store.cc b/src/libstore/optimise-store.cc
similarity index 75%
rename from src/libstore/unix/optimise-store.cc
rename to src/libstore/optimise-store.cc
index daaaaf0733e..9d903f21869 100644
--- a/src/libstore/unix/optimise-store.cc
+++ b/src/libstore/optimise-store.cc
@@ -98,9 +98,10 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
 
 #if __APPLE__
     /* HFS/macOS has some undocumented security feature disabling hardlinking for
-       special files within .app dirs. *.app/Contents/PkgInfo and
-       *.app/Contents/Resources/\*.lproj seem to be the only paths affected. See
-       https://github.com/NixOS/nix/issues/1443 for more discussion. */
+       special files within .app dirs. Known affected paths include
+       *.app/Contents/{PkgInfo,Resources/\*.lproj,_CodeSignature} and .DS_Store.
+       See https://github.com/NixOS/nix/issues/1443 and 
+       https://github.com/NixOS/nix/pull/2230 for more discussion. */
 
     if (std::regex_search(path, std::regex("\\.app/Contents/.+$")))
     {
@@ -148,64 +149,60 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
        contents of the symlink (i.e. the result of readlink()), not
        the contents of the target (which may not even exist). */
     Hash hash = ({
-        PosixSourceAccessor accessor;
         hashPath(
-            accessor, CanonPath { path },
-            FileSerialisationMethod::Recursive, HashAlgorithm::SHA256).first;
+            {make_ref<PosixSourceAccessor>(), CanonPath(path)},
+            FileSerialisationMethod::NixArchive, HashAlgorithm::SHA256).first;
     });
     debug("'%1%' has hash '%2%'", path, hash.to_string(HashFormat::Nix32, true));
 
     /* Check if this is a known hash. */
-    Path linkPath = linksDir + "/" + hash.to_string(HashFormat::Nix32, false);
+    std::filesystem::path linkPath = std::filesystem::path{linksDir} / hash.to_string(HashFormat::Nix32, false);
 
     /* Maybe delete the link, if it has been corrupted. */
-    if (pathExists(linkPath)) {
-        auto stLink = lstat(linkPath);
+    if (std::filesystem::exists(std::filesystem::symlink_status(linkPath))) {
+        auto stLink = lstat(linkPath.string());
         if (st.st_size != stLink.st_size
             || (repair && hash != ({
-                PosixSourceAccessor accessor;
                 hashPath(
-                    accessor, CanonPath { linkPath },
-                    FileSerialisationMethod::Recursive, HashAlgorithm::SHA256).first;
+                    PosixSourceAccessor::createAtRoot(linkPath),
+                    FileSerialisationMethod::NixArchive, HashAlgorithm::SHA256).first;
            })))
         {
             // XXX: Consider overwriting linkPath with our valid version.
-            warn("removing corrupted link '%s'", linkPath);
+            warn("removing corrupted link %s", linkPath);
             warn("There may be more corrupted paths."
                  "\nYou should run `nix-store --verify --check-contents --repair` to fix them all");
-            unlink(linkPath.c_str());
+            std::filesystem::remove(linkPath);
         }
     }
 
-    if (!pathExists(linkPath)) {
+    if (!std::filesystem::exists(std::filesystem::symlink_status(linkPath))) {
         /* Nope, create a hard link in the links directory. */
-        if (link(path.c_str(), linkPath.c_str()) == 0) {
+        try {
+            std::filesystem::create_hard_link(path, linkPath);
             inodeHash.insert(st.st_ino);
-            return;
-        }
-
-        switch (errno) {
-        case EEXIST:
-            /* Fall through if another process created ‘linkPath’ before
-               we did. */
-            break;
-
-        case ENOSPC:
-            /* On ext4, that probably means the directory index is
-               full.  When that happens, it's fine to ignore it: we
-               just effectively disable deduplication of this
-               file.  */
-            printInfo("cannot link '%s' to '%s': %s", linkPath, path, strerror(errno));
-            return;
-
-        default:
-            throw SysError("cannot link '%1%' to '%2%'", linkPath, path);
+        } catch (std::filesystem::filesystem_error & e) {
+            if (e.code() == std::errc::file_exists) {
+                /* Fall through if another process created ‘linkPath’ before
+                   we did. */
+            }
+
+            else if (e.code() == std::errc::no_space_on_device) {
+                /* On ext4, that probably means the directory index is
+                   full.  When that happens, it's fine to ignore it: we
+                   just effectively disable deduplication of this
+                   file.  */
+                printInfo("cannot link '%s' to '%s': %s", linkPath, path, strerror(errno));
+                return;
+            }
+
+            else throw;
         }
     }
 
     /* Yes!  We've seen a file with the same contents.  Replace the
        current file with a hard link to that file. */
-    auto stLink = lstat(linkPath);
+    auto stLink = lstat(linkPath.string());
 
     if (st.st_ino == stLink.st_ino) {
         debug("'%1%' is already linked to '%2%'", path, linkPath);
@@ -225,10 +222,13 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
        its timestamp back to 0. */
     MakeReadOnly makeReadOnly(mustToggle ? dirOfPath : "");
 
-    Path tempLink = fmt("%1%/.tmp-link-%2%-%3%", realStoreDir, getpid(), random());
+    std::filesystem::path tempLink = fmt("%1%/.tmp-link-%2%-%3%", realStoreDir, getpid(), rand());
 
-    if (link(linkPath.c_str(), tempLink.c_str()) == -1) {
-        if (errno == EMLINK) {
+    try {
+        std::filesystem::create_hard_link(linkPath, tempLink);
+        inodeHash.insert(st.st_ino);
+    } catch (std::filesystem::filesystem_error & e) {
+        if (e.code() == std::errc::too_many_links) {
             /* Too many links to the same file (>= 32000 on most file
                systems).  This is likely to happen with empty files.
                Just shrug and ignore. */
@@ -236,16 +236,16 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
                 printInfo("'%1%' has maximum number of links", linkPath);
             return;
         }
-        throw SysError("cannot link '%1%' to '%2%'", tempLink, linkPath);
+        throw;
     }
 
     /* Atomically replace the old file with the new hard link. */
     try {
-        renameFile(tempLink, path);
-    } catch (SystemError & e) {
-        if (unlink(tempLink.c_str()) == -1)
+        std::filesystem::rename(tempLink, path);
+    } catch (std::filesystem::filesystem_error & e) {
+        std::filesystem::remove(tempLink);
             printError("unable to unlink '%1%'", tempLink);
-        if (errno == EMLINK) {
+        if (e.code() == std::errc::too_many_links) {
             /* Some filesystems generate too many links on the rename,
                rather than on the original link.  (Probably it
                temporarily increases the st_nlink field before
@@ -258,10 +258,13 @@ void LocalStore::optimisePath_(Activity * act, OptimiseStats & stats,
 
     stats.filesLinked++;
     stats.bytesFreed += st.st_size;
-    stats.blocksFreed += st.st_blocks;
 
     if (act)
-        act->result(resFileLinked, st.st_size, st.st_blocks);
+        act->result(resFileLinked, st.st_size
+#ifndef _WIN32
+            , st.st_blocks
+#endif
+            );
 }
 
 
diff --git a/src/libstore/package.nix b/src/libstore/package.nix
new file mode 100644
index 00000000000..0a2ace91e40
--- /dev/null
+++ b/src/libstore/package.nix
@@ -0,0 +1,116 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+, unixtools
+
+, nix-util
+, boost
+, curl
+, aws-sdk-cpp
+, libseccomp
+, nlohmann_json
+, sqlite
+
+, busybox-sandbox-shell ? null
+
+# Configuration Options
+
+, version
+
+, embeddedSandboxShell ? stdenv.hostPlatform.isStatic
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-store";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    ./meson.options
+    ./linux/meson.build
+    ./unix/meson.build
+    ./windows/meson.build
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    (fileset.fileFilter (file: file.hasExt "sb") ./.)
+    (fileset.fileFilter (file: file.hasExt "md") ./.)
+    (fileset.fileFilter (file: file.hasExt "sql") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ] ++ lib.optional embeddedSandboxShell unixtools.hexdump;
+
+  buildInputs = [
+    boost
+    curl
+    sqlite
+  ] ++ lib.optional stdenv.hostPlatform.isLinux libseccomp
+    # There have been issues building these dependencies
+    ++ lib.optional (stdenv.hostPlatform == stdenv.buildPlatform && (stdenv.isLinux || stdenv.isDarwin))
+      (aws-sdk-cpp.override {
+        apis = ["s3" "transfer"];
+        customMemoryManagement = false;
+      })
+  ;
+
+  propagatedBuildInputs = [
+    nix-util
+    nlohmann_json
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+    (lib.mesonEnable "seccomp-sandboxing" stdenv.hostPlatform.isLinux)
+    (lib.mesonBool "embedded-sandbox-shell" embeddedSandboxShell)
+  ] ++ lib.optionals stdenv.hostPlatform.isLinux [
+    (lib.mesonOption "sandbox-shell" "${busybox-sandbox-shell}/bin/busybox")
+  ];
+
+  env = {
+    # Needed for Meson to find Boost.
+    # https://github.com/NixOS/nixpkgs/issues/86131.
+    BOOST_INCLUDEDIR = "${lib.getDev boost}/include";
+    BOOST_LIBRARYDIR = "${lib.getLib boost}/lib";
+  } // lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libstore/parsed-derivations.cc b/src/libstore/parsed-derivations.cc
index 72f45143d4a..d8459d4d71c 100644
--- a/src/libstore/parsed-derivations.cc
+++ b/src/libstore/parsed-derivations.cc
@@ -135,18 +135,37 @@ static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
 /**
  * Write a JSON representation of store object metadata, such as the
  * hash and the references.
+ *
+ * @note Do *not* use `ValidPathInfo::toJSON` because this function is
+ * subject to stronger stability requirements since it is used to
+ * prepare build environments. Perhaps someday we'll have a versionining
+ * mechanism to allow this to evolve again and get back in sync, but for
+ * now we must not change - not even extend - the behavior.
  */
 static nlohmann::json pathInfoToJSON(
     Store & store,
     const StorePathSet & storePaths)
 {
-    nlohmann::json::array_t jsonList = nlohmann::json::array();
+    using nlohmann::json;
+
+    nlohmann::json::array_t jsonList = json::array();
 
     for (auto & storePath : storePaths) {
         auto info = store.queryPathInfo(storePath);
 
-        auto & jsonPath = jsonList.emplace_back(
-            info->toJSON(store, false, HashFormat::Nix32));
+        auto & jsonPath = jsonList.emplace_back(json::object());
+
+        jsonPath["narHash"] = info->narHash.to_string(HashFormat::Nix32, true);
+        jsonPath["narSize"] = info->narSize;
+
+        {
+            auto & jsonRefs = jsonPath["references"] = json::array();
+            for (auto & ref : info->references)
+                jsonRefs.emplace_back(store.printStorePath(ref));
+        }
+
+        if (info->ca)
+            jsonPath["ca"] = renderContentAddress(info->ca);
 
         // Add the path to the object whose metadata we are including.
         jsonPath["path"] = store.printStorePath(storePath);
@@ -186,7 +205,7 @@ std::optional<nlohmann::json> ParsedDerivation::prepareStructuredAttrs(Store & s
         for (auto i = e->begin(); i != e->end(); ++i) {
             StorePathSet storePaths;
             for (auto & p : *i)
-                storePaths.insert(store.parseStorePath(p.get<std::string>()));
+                storePaths.insert(store.toStorePath(p.get<std::string>()).first);
             json[i.key()] = pathInfoToJSON(store,
                 store.exportReferences(storePaths, inputPaths));
         }
diff --git a/src/libstore/path-info.cc b/src/libstore/path-info.cc
index 6523cb4258a..5c27182b720 100644
--- a/src/libstore/path-info.cc
+++ b/src/libstore/path-info.cc
@@ -48,15 +48,21 @@ std::optional<ContentAddressWithReferences> ValidPathInfo::contentAddressWithRef
     if (! ca)
         return std::nullopt;
 
-    return std::visit(overloaded {
-        [&](const TextIngestionMethod &) -> ContentAddressWithReferences {
+    switch (ca->method.raw) {
+        case ContentAddressMethod::Raw::Text:
+        {
             assert(references.count(path) == 0);
             return TextInfo {
                 .hash = ca->hash,
                 .references = references,
             };
-        },
-        [&](const FileIngestionMethod & m2) -> ContentAddressWithReferences {
+        }
+
+        case ContentAddressMethod::Raw::Flat:
+        case ContentAddressMethod::Raw::NixArchive:
+        case ContentAddressMethod::Raw::Git:
+        default:
+        {
             auto refs = references;
             bool hasSelfReference = false;
             if (refs.count(path)) {
@@ -64,15 +70,15 @@ std::optional<ContentAddressWithReferences> ValidPathInfo::contentAddressWithRef
                 refs.erase(path);
             }
             return FixedOutputInfo {
-                .method = m2,
+                .method = ca->method.getFileIngestionMethod(),
                 .hash = ca->hash,
                 .references = {
                     .others = std::move(refs),
                     .self = hasSelfReference,
                 },
             };
-        },
-    }, ca->method.raw);
+        }
+    }
 }
 
 bool ValidPathInfo::isContentAddressed(const Store & store) const
@@ -127,22 +133,18 @@ ValidPathInfo::ValidPathInfo(
       : UnkeyedValidPathInfo(narHash)
       , path(store.makeFixedOutputPathFromCA(name, ca))
 {
+    this->ca = ContentAddress {
+        .method = ca.getMethod(),
+        .hash = ca.getHash(),
+    };
     std::visit(overloaded {
         [this](TextInfo && ti) {
             this->references = std::move(ti.references);
-            this->ca = ContentAddress {
-                .method = TextIngestionMethod {},
-                .hash = std::move(ti.hash),
-            };
         },
         [this](FixedOutputInfo && foi) {
             this->references = std::move(foi.references.others);
             if (foi.references.self)
                 this->references.insert(path);
-            this->ca = ContentAddress {
-                .method = std::move(foi.method),
-                .hash = std::move(foi.hash),
-            };
         },
     }, std::move(ca).raw);
 }
@@ -161,28 +163,23 @@ nlohmann::json UnkeyedValidPathInfo::toJSON(
     jsonObject["narSize"] = narSize;
 
     {
-        auto& jsonRefs = (jsonObject["references"] = json::array());
+        auto & jsonRefs = jsonObject["references"] = json::array();
         for (auto & ref : references)
             jsonRefs.emplace_back(store.printStorePath(ref));
     }
 
-    if (ca)
-        jsonObject["ca"] = renderContentAddress(ca);
+    jsonObject["ca"] = ca ? (std::optional { renderContentAddress(*ca) }) : std::nullopt;
 
     if (includeImpureInfo) {
-        if (deriver)
-            jsonObject["deriver"] = store.printStorePath(*deriver);
+        jsonObject["deriver"] = deriver ? (std::optional { store.printStorePath(*deriver) }) : std::nullopt;
 
-        if (registrationTime)
-            jsonObject["registrationTime"] = registrationTime;
+        jsonObject["registrationTime"] = registrationTime ? (std::optional { registrationTime }) : std::nullopt;
 
-        if (ultimate)
-            jsonObject["ultimate"] = ultimate;
+        jsonObject["ultimate"] = ultimate;
 
-        if (!sigs.empty()) {
-            for (auto & sig : sigs)
-                jsonObject["signatures"].push_back(sig);
-        }
+        auto & sigsObj = jsonObject["signatures"] = json::array();
+        for (auto & sig : sigs)
+            sigsObj.push_back(sig);
     }
 
     return jsonObject;
@@ -210,20 +207,25 @@ UnkeyedValidPathInfo UnkeyedValidPathInfo::fromJSON(
         throw;
     }
 
+    // New format as this as nullable but mandatory field; handling
+    // missing is for back-compat.
     if (json.contains("ca"))
-        res.ca = ContentAddress::parse(getString(valueAt(json, "ca")));
+        if (auto * rawCa = getNullable(valueAt(json, "ca")))
+            res.ca = ContentAddress::parse(getString(*rawCa));
 
     if (json.contains("deriver"))
-        res.deriver = store.parseStorePath(getString(valueAt(json, "deriver")));
+        if (auto * rawDeriver = getNullable(valueAt(json, "deriver")))
+            res.deriver = store.parseStorePath(getString(*rawDeriver));
 
     if (json.contains("registrationTime"))
-        res.registrationTime = getInteger(valueAt(json, "registrationTime"));
+        if (auto * rawRegistrationTime = getNullable(valueAt(json, "registrationTime")))
+            res.registrationTime = getInteger(*rawRegistrationTime);
 
     if (json.contains("ultimate"))
         res.ultimate = getBoolean(valueAt(json, "ultimate"));
 
     if (json.contains("signatures"))
-        res.sigs = valueAt(json, "signatures");
+        res.sigs = getStringSet(valueAt(json, "signatures"));
 
     return res;
 }
diff --git a/src/libstore/path.cc b/src/libstore/path.cc
index 4b806e4084e..3e9d054778c 100644
--- a/src/libstore/path.cc
+++ b/src/libstore/path.cc
@@ -2,25 +2,24 @@
 
 namespace nix {
 
-static void checkName(std::string_view path, std::string_view name)
+void checkName(std::string_view name)
 {
     if (name.empty())
-        throw BadStorePath("store path '%s' has an empty name", path);
+        throw BadStorePathName("name must not be empty");
     if (name.size() > StorePath::MaxPathLen)
-        throw BadStorePath("store path '%s' has a name longer than %d characters",
-            path, StorePath::MaxPathLen);
+        throw BadStorePathName("name '%s' must be no longer than %d characters", name, StorePath::MaxPathLen);
     // See nameRegexStr for the definition
     if (name[0] == '.') {
         // check against "." and "..", followed by end or dash
         if (name.size() == 1)
-            throw BadStorePath("store path '%s' has invalid name '%s'", path, name);
+            throw BadStorePathName("name '%s' is not valid", name);
         if (name[1] == '-')
-            throw BadStorePath("store path '%s' has invalid name '%s': first dash-separated component must not be '%s'", path, name, ".");
+            throw BadStorePathName("name '%s' is not valid: first dash-separated component must not be '%s'", name, ".");
         if (name[1] == '.') {
             if (name.size() == 2)
-                throw BadStorePath("store path '%s' has invalid name '%s'", path, name);
+                throw BadStorePathName("name '%s' is not valid", name);
             if (name[2] == '-')
-                throw BadStorePath("store path '%s' has invalid name '%s': first dash-separated component must not be '%s'", path, name, "..");
+                throw BadStorePathName("name '%s' is not valid: first dash-separated component must not be '%s'", name, "..");
         }
     }
     for (auto c : name)
@@ -28,7 +27,16 @@ static void checkName(std::string_view path, std::string_view name)
                 || (c >= 'a' && c <= 'z')
                 || (c >= 'A' && c <= 'Z')
                 || c == '+' || c == '-' || c == '.' || c == '_' || c == '?' || c == '='))
-            throw BadStorePath("store path '%s' contains illegal character '%s'", path, c);
+            throw BadStorePathName("name '%s' contains illegal character '%s'", name, c);
+}
+
+static void checkPathName(std::string_view path, std::string_view name)
+{
+    try {
+        checkName(name);
+    } catch (BadStorePathName & e) {
+        throw BadStorePath("path '%s' is not a valid store path: %s", path, Uncolored(e.message()));
+    }
 }
 
 StorePath::StorePath(std::string_view _baseName)
@@ -40,20 +48,26 @@ StorePath::StorePath(std::string_view _baseName)
         if (c == 'e' || c == 'o' || c == 'u' || c == 't'
             || !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'z')))
             throw BadStorePath("store path '%s' contains illegal base-32 character '%s'", baseName, c);
-    checkName(baseName, name());
+    checkPathName(baseName, name());
 }
 
 StorePath::StorePath(const Hash & hash, std::string_view _name)
     : baseName((hash.to_string(HashFormat::Nix32, false) + "-").append(std::string(_name)))
 {
-    checkName(baseName, name());
+    checkPathName(baseName, name());
 }
 
-bool StorePath::isDerivation() const
+bool StorePath::isDerivation() const noexcept
 {
     return hasSuffix(name(), drvExtension);
 }
 
+void StorePath::requireDerivation() const
+{
+    if (!isDerivation())
+        throw FormatError("store path '%s' is not a valid derivation path", to_string());
+}
+
 StorePath StorePath::dummy("ffffffffffffffffffffffffffffffff-x");
 
 StorePath StorePath::random(std::string_view name)
diff --git a/src/libstore/path.hh b/src/libstore/path.hh
index 4ca6747b3b3..2380dc6a27a 100644
--- a/src/libstore/path.hh
+++ b/src/libstore/path.hh
@@ -9,11 +9,18 @@ namespace nix {
 
 struct Hash;
 
+/**
+ * Check whether a name is a valid store path name.
+ *
+ * @throws BadStorePathName if the name is invalid. The message is of the format "name %s is not valid, for this specific reason".
+ */
+void checkName(std::string_view name);
+
 /**
  * \ref StorePath "Store path" is the fundamental reference type of Nix.
  * A store paths refers to a Store object.
  *
- * See glossary.html#gloss-store-path for more information on a
+ * See store/store-path.html for more information on a
  * conceptual level.
  */
 class StorePath
@@ -31,34 +38,29 @@ public:
 
     StorePath() = delete;
 
+    /** @throws BadStorePath */
     StorePath(std::string_view baseName);
 
+    /** @throws BadStorePath */
     StorePath(const Hash & hash, std::string_view name);
 
-    std::string_view to_string() const
+    std::string_view to_string() const noexcept
     {
         return baseName;
     }
 
-    bool operator < (const StorePath & other) const
-    {
-        return baseName < other.baseName;
-    }
-
-    bool operator == (const StorePath & other) const
-    {
-        return baseName == other.baseName;
-    }
-
-    bool operator != (const StorePath & other) const
-    {
-        return baseName != other.baseName;
-    }
+    bool operator == (const StorePath & other) const noexcept = default;
+    auto operator <=> (const StorePath & other) const noexcept = default;
 
     /**
      * Check whether a file name ends with the extension for derivations.
      */
-    bool isDerivation() const;
+    bool isDerivation() const noexcept;
+
+    /**
+     * Throw an exception if `isDerivation` is false.
+     */
+    void requireDerivation() const;
 
     std::string_view name() const
     {
@@ -82,7 +84,7 @@ typedef std::vector<StorePath> StorePaths;
  * The file extension of \ref Derivation derivations when serialized
  * into store objects.
  */
-const std::string drvExtension = ".drv";
+constexpr std::string_view drvExtension = ".drv";
 
 }
 
diff --git a/src/libstore/pathlocks.hh b/src/libstore/pathlocks.hh
index b97fbecb923..42a84a1a37b 100644
--- a/src/libstore/pathlocks.hh
+++ b/src/libstore/pathlocks.hh
@@ -5,10 +5,26 @@
 
 namespace nix {
 
+/**
+ * Open (possibly create) a lock file and return the file descriptor.
+ * -1 is returned if create is false and the lock could not be opened
+ * because it doesn't exist.  Any other error throws an exception.
+ */
+AutoCloseFD openLockFile(const Path & path, bool create);
+
+/**
+ * Delete an open lock file.
+ */
+void deleteLockFile(const Path & path, Descriptor desc);
+
+enum LockType { ltRead, ltWrite, ltNone };
+
+bool lockFile(Descriptor desc, LockType lockType, bool wait);
+
 class PathLocks
 {
 private:
-    typedef std::pair<int, Path> FDPair;
+    typedef std::pair<Descriptor, Path> FDPair;
     std::list<FDPair> fds;
     bool deletePaths;
 
@@ -24,6 +40,18 @@ public:
     void setDeletion(bool deletePaths);
 };
 
-}
+struct FdLock
+{
+    Descriptor desc;
+    bool acquired = false;
+
+    FdLock(Descriptor desc, LockType lockType, bool wait, std::string_view waitMsg);
 
-#include "pathlocks-impl.hh"
+    ~FdLock()
+    {
+        if (acquired)
+            lockFile(desc, ltNone, false);
+    }
+};
+
+}
diff --git a/src/libstore/unix/posix-fs-canonicalise.cc b/src/libstore/posix-fs-canonicalise.cc
similarity index 84%
rename from src/libstore/unix/posix-fs-canonicalise.cc
rename to src/libstore/posix-fs-canonicalise.cc
index 8b29e90d48f..46a78cc86aa 100644
--- a/src/libstore/unix/posix-fs-canonicalise.cc
+++ b/src/libstore/posix-fs-canonicalise.cc
@@ -31,21 +31,13 @@ static void canonicaliseTimestampAndPermissions(const Path & path, const struct
 
     }
 
+#ifndef _WIN32 // TODO implement
     if (st.st_mtime != mtimeStore) {
-        struct timeval times[2];
-        times[0].tv_sec = st.st_atime;
-        times[0].tv_usec = 0;
-        times[1].tv_sec = mtimeStore;
-        times[1].tv_usec = 0;
-#if HAVE_LUTIMES
-        if (lutimes(path.c_str(), times) == -1)
-            if (errno != ENOSYS ||
-                (!S_ISLNK(st.st_mode) && utimes(path.c_str(), times) == -1))
-#else
-        if (!S_ISLNK(st.st_mode) && utimes(path.c_str(), times) == -1)
-#endif
-            throw SysError("changing modification time of '%1%'", path);
+        struct stat st2 = st;
+        st2.st_mtime = mtimeStore,
+        setWriteTime(path, st2);
     }
+#endif
 }
 
 
@@ -57,7 +49,9 @@ void canonicaliseTimestampAndPermissions(const Path & path)
 
 static void canonicalisePathMetaData_(
     const Path & path,
+#ifndef _WIN32
     std::optional<std::pair<uid_t, uid_t>> uidRange,
+#endif
     InodesSeen & inodesSeen)
 {
     checkInterrupt();
@@ -99,6 +93,7 @@ static void canonicalisePathMetaData_(
      }
 #endif
 
+#ifndef _WIN32
     /* Fail if the file is not owned by the build user.  This prevents
        us from messing up the ownership/permissions of files
        hard-linked into the output (e.g. "ln /etc/shadow $out/foo").
@@ -112,11 +107,13 @@ static void canonicalisePathMetaData_(
         assert(S_ISLNK(st.st_mode) || (st.st_uid == geteuid() && (mode == 0444 || mode == 0555) && st.st_mtime == mtimeStore));
         return;
     }
+#endif
 
     inodesSeen.insert(Inode(st.st_dev, st.st_ino));
 
     canonicaliseTimestampAndPermissions(path, st);
 
+#ifndef _WIN32
     /* Change ownership to the current uid.  If it's a symlink, use
        lchown if available, otherwise don't bother.  Wrong ownership
        of a symlink doesn't matter, since the owning user can't change
@@ -134,22 +131,37 @@ static void canonicalisePathMetaData_(
             throw SysError("changing owner of '%1%' to %2%",
                 path, geteuid());
     }
+#endif
 
     if (S_ISDIR(st.st_mode)) {
-        DirEntries entries = readDirectory(path);
-        for (auto & i : entries)
-            canonicalisePathMetaData_(path + "/" + i.name, uidRange, inodesSeen);
+        for (auto & i : std::filesystem::directory_iterator{path}) {
+            checkInterrupt();
+            canonicalisePathMetaData_(
+                i.path().string(),
+#ifndef _WIN32
+                uidRange,
+#endif
+                inodesSeen);
+        }
     }
 }
 
 
 void canonicalisePathMetaData(
     const Path & path,
+#ifndef _WIN32
     std::optional<std::pair<uid_t, uid_t>> uidRange,
+#endif
     InodesSeen & inodesSeen)
 {
-    canonicalisePathMetaData_(path, uidRange, inodesSeen);
+    canonicalisePathMetaData_(
+        path,
+#ifndef _WIN32
+        uidRange,
+#endif
+        inodesSeen);
 
+#ifndef _WIN32
     /* On platforms that don't have lchown(), the top-level path can't
        be a symlink, since we can't change its ownership. */
     auto st = lstat(path);
@@ -158,14 +170,23 @@ void canonicalisePathMetaData(
         assert(S_ISLNK(st.st_mode));
         throw Error("wrong ownership of top-level store path '%1%'", path);
     }
+#endif
 }
 
 
-void canonicalisePathMetaData(const Path & path,
-    std::optional<std::pair<uid_t, uid_t>> uidRange)
+void canonicalisePathMetaData(const Path & path
+#ifndef _WIN32
+    , std::optional<std::pair<uid_t, uid_t>> uidRange
+#endif
+    )
 {
     InodesSeen inodesSeen;
-    canonicalisePathMetaData(path, uidRange, inodesSeen);
+    canonicalisePathMetaData_(
+        path,
+#ifndef _WIN32
+        uidRange,
+#endif
+        inodesSeen);
 }
 
 }
diff --git a/src/libstore/unix/posix-fs-canonicalise.hh b/src/libstore/posix-fs-canonicalise.hh
similarity index 85%
rename from src/libstore/unix/posix-fs-canonicalise.hh
rename to src/libstore/posix-fs-canonicalise.hh
index 35644af125f..45a4f3f2069 100644
--- a/src/libstore/unix/posix-fs-canonicalise.hh
+++ b/src/libstore/posix-fs-canonicalise.hh
@@ -24,7 +24,7 @@ typedef std::set<Inode> InodesSeen;
  *   without execute permission; setuid bits etc. are cleared)
  *
  * - the owner and group are set to the Nix user and group, if we're
- *   running as root.
+ *   running as root. (Unix only.)
  *
  * If uidRange is not empty, this function will throw an error if it
  * encounters files owned by a user outside of the closed interval
@@ -32,11 +32,17 @@ typedef std::set<Inode> InodesSeen;
  */
 void canonicalisePathMetaData(
     const Path & path,
+#ifndef _WIN32
     std::optional<std::pair<uid_t, uid_t>> uidRange,
+#endif
     InodesSeen & inodesSeen);
+
 void canonicalisePathMetaData(
-    const Path & path,
-    std::optional<std::pair<uid_t, uid_t>> uidRange);
+    const Path & path
+#ifndef _WIN32
+    , std::optional<std::pair<uid_t, uid_t>> uidRange = std::nullopt
+#endif
+    );
 
 void canonicaliseTimestampAndPermissions(const Path & path);
 
diff --git a/src/libstore/profiles.cc b/src/libstore/profiles.cc
index 73d3976f43a..46efedfe327 100644
--- a/src/libstore/profiles.cc
+++ b/src/libstore/profiles.cc
@@ -1,4 +1,5 @@
 #include "profiles.hh"
+#include "signals.hh"
 #include "store-api.hh"
 #include "local-fs-store.hh"
 #include "users.hh"
@@ -34,12 +35,13 @@ std::pair<Generations, std::optional<GenerationNumber>> findGenerations(Path pro
 {
     Generations gens;
 
-    Path profileDir = dirOf(profile);
+    std::filesystem::path profileDir = dirOf(profile);
     auto profileName = std::string(baseNameOf(profile));
 
-    for (auto & i : readDirectory(profileDir)) {
-        if (auto n = parseName(profileName, i.name)) {
-            auto path = profileDir + "/" + i.name;
+    for (auto & i : std::filesystem::directory_iterator{profileDir}) {
+        checkInterrupt();
+        if (auto n = parseName(profileName, i.path().filename().string())) {
+            auto path = i.path().string();
             gens.push_back({
                 .number = *n,
                 .path = path,
@@ -338,6 +340,8 @@ Path getDefaultProfile()
         return absPath(readLink(profileLink), dirOf(profileLink));
     } catch (Error &) {
         return profileLink;
+    } catch (std::filesystem::filesystem_error &) {
+        return profileLink;
     }
 }
 
diff --git a/src/libstore/remote-store-connection.hh b/src/libstore/remote-store-connection.hh
index 44328b06b55..405120ee926 100644
--- a/src/libstore/remote-store-connection.hh
+++ b/src/libstore/remote-store-connection.hh
@@ -3,6 +3,7 @@
 
 #include "remote-store.hh"
 #include "worker-protocol.hh"
+#include "worker-protocol-connection.hh"
 #include "pool.hh"
 
 namespace nix {
@@ -14,90 +15,13 @@ namespace nix {
  * Contains `Source` and `Sink` for actual communication, along with
  * other information learned when negotiating the connection.
  */
-struct RemoteStore::Connection
+struct RemoteStore::Connection : WorkerProto::BasicClientConnection,
+  WorkerProto::ClientHandshakeInfo
 {
-    /**
-     * Send with this.
-     */
-    FdSink to;
-
-    /**
-     * Receive with this.
-     */
-    FdSource from;
-
-    /**
-     * Worker protocol version used for the connection.
-     *
-     * Despite its name, I think it is actually the maximum version both
-     * sides support. (If the maximum doesn't exist, we would fail to
-     * establish a connection and produce a value of this type.)
-     */
-    WorkerProto::Version daemonVersion;
-
-    /**
-     * Whether the remote side trusts us or not.
-     *
-     * 3 values: "yes", "no", or `std::nullopt` for "unknown".
-     *
-     * Note that the "remote side" might not be just the end daemon, but
-     * also an intermediary forwarder that can make its own trusting
-     * decisions. This would be the intersection of all their trust
-     * decisions, since it takes only one link in the chain to start
-     * denying operations.
-     */
-    std::optional<TrustedFlag> remoteTrustsUs;
-
-    /**
-     * The version of the Nix daemon that is processing our requests.
-     *
-     * Do note, it may or may not communicating with another daemon,
-     * rather than being an "end" `LocalStore` or similar.
-     */
-    std::optional<std::string> daemonNixVersion;
-
     /**
      * Time this connection was established.
      */
     std::chrono::time_point<std::chrono::steady_clock> startTime;
-
-    /**
-     * Coercion to `WorkerProto::ReadConn`. This makes it easy to use the
-     * factored out worker protocol searlizers with a
-     * `RemoteStore::Connection`.
-     *
-     * The worker protocol connection types are unidirectional, unlike
-     * this type.
-     */
-    operator WorkerProto::ReadConn ()
-    {
-        return WorkerProto::ReadConn {
-            .from = from,
-            .version = daemonVersion,
-        };
-    }
-
-    /**
-     * Coercion to `WorkerProto::WriteConn`. This makes it easy to use the
-     * factored out worker protocol searlizers with a
-     * `RemoteStore::Connection`.
-     *
-     * The worker protocol connection types are unidirectional, unlike
-     * this type.
-     */
-    operator WorkerProto::WriteConn ()
-    {
-        return WorkerProto::WriteConn {
-            .to = to,
-            .version = daemonVersion,
-        };
-    }
-
-    virtual ~Connection();
-
-    virtual void closeWrite() = 0;
-
-    std::exception_ptr processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
 };
 
 /**
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 09196481bb9..d749ccd0a35 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -69,50 +69,26 @@ void RemoteStore::initConnection(Connection & conn)
     /* Send the magic greeting, check for the reply. */
     try {
         conn.from.endOfFileError = "Nix daemon disconnected unexpectedly (maybe it crashed?)";
-        conn.to << WORKER_MAGIC_1;
-        conn.to.flush();
+
         StringSink saved;
+        TeeSource tee(conn.from, saved);
         try {
-            TeeSource tee(conn.from, saved);
-            unsigned int magic = readInt(tee);
-            if (magic != WORKER_MAGIC_2)
-                throw Error("protocol mismatch");
+            conn.daemonVersion = WorkerProto::BasicClientConnection::handshake(
+                conn.to, tee, PROTOCOL_VERSION);
         } catch (SerialisationError & e) {
             /* In case the other side is waiting for our input, close
                it. */
             conn.closeWrite();
-            auto msg = conn.from.drain();
-            throw Error("protocol mismatch, got '%s'", chomp(saved.s + msg));
-        }
-
-        conn.from >> conn.daemonVersion;
-        if (GET_PROTOCOL_MAJOR(conn.daemonVersion) != GET_PROTOCOL_MAJOR(PROTOCOL_VERSION))
-            throw Error("Nix daemon protocol version not supported");
-        if (GET_PROTOCOL_MINOR(conn.daemonVersion) < 10)
-            throw Error("the Nix daemon version is too old");
-        conn.to << PROTOCOL_VERSION;
-
-        if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 14) {
-            // Obsolete CPU affinity.
-            conn.to << 0;
+            {
+                NullSink nullSink;
+                tee.drainInto(nullSink);
+            }
+            throw Error("protocol mismatch, got '%s'", chomp(saved.s));
         }
 
-        if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 11)
-            conn.to << false; // obsolete reserveSpace
-
-        if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 33) {
-            conn.to.flush();
-            conn.daemonNixVersion = readString(conn.from);
-        }
+        static_cast<WorkerProto::ClientHandshakeInfo &>(conn) = conn.postHandshake(*this);
 
-        if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 35) {
-            conn.remoteTrustsUs = WorkerProto::Serialise<std::optional<TrustedFlag>>::read(*this, conn);
-        } else {
-            // We don't know the answer; protocol to old.
-            conn.remoteTrustsUs = std::nullopt;
-        }
-
-        auto ex = conn.processStderr();
+        auto ex = conn.processStderrReturn();
         if (ex) std::rethrow_exception(ex);
     }
     catch (Error & e) {
@@ -158,7 +134,7 @@ void RemoteStore::setOptions(Connection & conn)
             conn.to << i.first << i.second.value;
     }
 
-    auto ex = conn.processStderr();
+    auto ex = conn.processStderrReturn();
     if (ex) std::rethrow_exception(ex);
 }
 
@@ -173,28 +149,7 @@ RemoteStore::ConnectionHandle::~ConnectionHandle()
 
 void RemoteStore::ConnectionHandle::processStderr(Sink * sink, Source * source, bool flush)
 {
-    auto ex = handle->processStderr(sink, source, flush);
-    if (ex) {
-        daemonException = true;
-        try {
-            std::rethrow_exception(ex);
-        } catch (const Error & e) {
-            // Nix versions before #4628 did not have an adequate behavior for reporting that the derivation format was upgraded.
-            // To avoid having to add compatibility logic in many places, we expect to catch almost all occurrences of the
-            // old incomprehensible error here, so that we can explain to users what's going on when their daemon is
-            // older than #4628 (2023).
-            if (experimentalFeatureSettings.isEnabled(Xp::DynamicDerivations) &&
-                GET_PROTOCOL_MINOR(handle->daemonVersion) <= 35)
-            {
-                auto m = e.msg();
-                if (m.find("parsing derivation") != std::string::npos &&
-                    m.find("expected string") != std::string::npos &&
-                    m.find("Derive([") != std::string::npos)
-                    throw Error("%s, this might be because the daemon is too old to understand dependencies on dynamic derivations. Check to see if the raw derivation is in the form '%s'", std::move(m), "DrvWithVersion(..)");
-            }
-            throw;
-        }
-    }
+    handle->processStderr(&daemonException, sink, source, flush);
 }
 
 
@@ -226,13 +181,7 @@ StorePathSet RemoteStore::queryValidPaths(const StorePathSet & paths, Substitute
             if (isValidPath(i)) res.insert(i);
         return res;
     } else {
-        conn->to << WorkerProto::Op::QueryValidPaths;
-        WorkerProto::write(*this, *conn, paths);
-        if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 27) {
-            conn->to << maybeSubstitute;
-        }
-        conn.processStderr();
-        return WorkerProto::Serialise<StorePathSet>::read(*this, *conn);
+        return conn->queryValidPaths(*this, &conn.daemonException, paths, maybeSubstitute);
     }
 }
 
@@ -322,22 +271,10 @@ void RemoteStore::queryPathInfoUncached(const StorePath & path,
         std::shared_ptr<const ValidPathInfo> info;
         {
             auto conn(getConnection());
-            conn->to << WorkerProto::Op::QueryPathInfo << printStorePath(path);
-            try {
-                conn.processStderr();
-            } catch (Error & e) {
-                // Ugly backwards compatibility hack.
-                if (e.msg().find("is not valid") != std::string::npos)
-                    throw InvalidPath(std::move(e.info()));
-                throw;
-            }
-            if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 17) {
-                bool valid; conn->from >> valid;
-                if (!valid) throw InvalidPath("path '%s' is not valid", printStorePath(path));
-            }
             info = std::make_shared<ValidPathInfo>(
                 StorePath{path},
-                WorkerProto::Serialise<UnkeyedValidPathInfo>::read(*this, *conn));
+                conn->queryPathInfo(*this, &conn.daemonException, path));
+
         }
         callback(std::move(info));
     } catch (...) { callback.rethrow(); }
@@ -455,8 +392,9 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
     else {
         if (repair) throw Error("repairing is not supported when building through the Nix daemon protocol < 1.25");
 
-        std::visit(overloaded {
-            [&](const TextIngestionMethod & thm) -> void {
+        switch (caMethod.raw) {
+            case ContentAddressMethod::Raw::Text:
+            {
                 if (hashAlgo != HashAlgorithm::SHA256)
                     throw UnimplementedError("When adding text-hashed data called '%s', only SHA-256 is supported but '%s' was given",
                         name, printHashAlgo(hashAlgo));
@@ -464,13 +402,19 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
                 conn->to << WorkerProto::Op::AddTextToStore << name << s;
                 WorkerProto::write(*this, *conn, references);
                 conn.processStderr();
-            },
-            [&](const FileIngestionMethod & fim) -> void {
+                break;
+            }
+            case ContentAddressMethod::Raw::Flat:
+            case ContentAddressMethod::Raw::NixArchive:
+            case ContentAddressMethod::Raw::Git:
+            default:
+            {
+                auto fim = caMethod.getFileIngestionMethod();
                 conn->to
                     << WorkerProto::Op::AddToStore
                     << name
-                    << ((hashAlgo == HashAlgorithm::SHA256 && fim == FileIngestionMethod::Recursive) ? 0 : 1) /* backwards compatibility hack */
-                    << (fim == FileIngestionMethod::Recursive ? 1 : 0)
+                    << ((hashAlgo == HashAlgorithm::SHA256 && fim == FileIngestionMethod::NixArchive) ? 0 : 1) /* backwards compatibility hack */
+                    << (fim == FileIngestionMethod::NixArchive ? 1 : 0)
                     << printHashAlgo(hashAlgo);
 
                 try {
@@ -478,7 +422,7 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
                     connections->incCapacity();
                     {
                         Finally cleanup([&]() { connections->decCapacity(); });
-                        if (fim == FileIngestionMethod::Recursive) {
+                        if (fim == FileIngestionMethod::NixArchive) {
                             dump.drainInto(conn->to);
                         } else {
                             std::string contents = dump.drain();
@@ -495,9 +439,9 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
                         } catch (EndOfFile & e) { }
                     throw;
                 }
-
+                break;
             }
-        }, caMethod.raw);
+        }
         auto path = parseStorePath(readString(conn->from));
         // Release our connection to prevent a deadlock in queryPathInfo().
         conn_.reset();
@@ -520,12 +464,12 @@ StorePath RemoteStore::addToStoreFromDump(
     case FileIngestionMethod::Flat:
         fsm = FileSerialisationMethod::Flat;
         break;
-    case FileIngestionMethod::Recursive:
-        fsm = FileSerialisationMethod::Recursive;
+    case FileIngestionMethod::NixArchive:
+        fsm = FileSerialisationMethod::NixArchive;
         break;
     case FileIngestionMethod::Git:
         // Use NAR; Git is not a serialization method
-        fsm = FileSerialisationMethod::Recursive;
+        fsm = FileSerialisationMethod::NixArchive;
         break;
     default:
         assert(false);
@@ -542,8 +486,6 @@ void RemoteStore::addToStore(const ValidPathInfo & info, Source & source,
     auto conn(getConnection());
 
     if (GET_PROTOCOL_MINOR(conn->daemonVersion) < 18) {
-        conn->to << WorkerProto::Op::ImportPaths;
-
         auto source2 = sinkToSource([&](Sink & sink) {
             sink << 1 // == path follows
                 ;
@@ -558,11 +500,7 @@ void RemoteStore::addToStore(const ValidPathInfo & info, Source & source,
                 << 0 // == no path follows
                 ;
         });
-
-        conn.processStderr(0, source2.get());
-
-        auto importedPaths = WorkerProto::Serialise<StorePathSet>::read(*this, *conn);
-        assert(importedPaths.size() <= 1);
+        conn->importPaths(*this, &conn.daemonException, *source2);
     }
 
     else {
@@ -807,9 +745,7 @@ BuildResult RemoteStore::buildDerivation(const StorePath & drvPath, const BasicD
     BuildMode buildMode)
 {
     auto conn(getConnection());
-    conn->to << WorkerProto::Op::BuildDerivation << printStorePath(drvPath);
-    writeDerivation(conn->to, *this, drv);
-    conn->to << buildMode;
+    conn->putBuildDerivationRequest(*this, &conn.daemonException, drvPath, drv, buildMode);
     conn.processStderr();
     return WorkerProto::Serialise<BuildResult>::read(*this, *conn);
 }
@@ -827,9 +763,7 @@ void RemoteStore::ensurePath(const StorePath & path)
 void RemoteStore::addTempRoot(const StorePath & path)
 {
     auto conn(getConnection());
-    conn->to << WorkerProto::Op::AddTempRoot << printStorePath(path);
-    conn.processStderr();
-    readInt(conn->from);
+    conn->addTempRoot(*this, &conn.daemonException, path);
 }
 
 
@@ -969,22 +903,12 @@ void RemoteStore::flushBadConnections()
     connections->flushBad();
 }
 
-
-RemoteStore::Connection::~Connection()
-{
-    try {
-        to.flush();
-    } catch (...) {
-        ignoreException();
-    }
-}
-
 void RemoteStore::narFromPath(const StorePath & path, Sink & sink)
 {
-    auto conn(connections->get());
-    conn->to << WorkerProto::Op::NarFromPath << printStorePath(path);
-    conn->processStderr();
-    copyNAR(conn->from, sink);
+    auto conn(getConnection());
+    conn->narFromPath(*this, &conn.daemonException, path, [&](Source & source) {
+        copyNAR(conn->from, sink);
+    });
 }
 
 ref<SourceAccessor> RemoteStore::getFSAccessor(bool requireValidPath)
@@ -992,91 +916,6 @@ ref<SourceAccessor> RemoteStore::getFSAccessor(bool requireValidPath)
     return make_ref<RemoteFSAccessor>(ref<Store>(shared_from_this()));
 }
 
-static Logger::Fields readFields(Source & from)
-{
-    Logger::Fields fields;
-    size_t size = readInt(from);
-    for (size_t n = 0; n < size; n++) {
-        auto type = (decltype(Logger::Field::type)) readInt(from);
-        if (type == Logger::Field::tInt)
-            fields.push_back(readNum<uint64_t>(from));
-        else if (type == Logger::Field::tString)
-            fields.push_back(readString(from));
-        else
-            throw Error("got unsupported field type %x from Nix daemon", (int) type);
-    }
-    return fields;
-}
-
-
-std::exception_ptr RemoteStore::Connection::processStderr(Sink * sink, Source * source, bool flush)
-{
-    if (flush)
-        to.flush();
-
-    while (true) {
-
-        auto msg = readNum<uint64_t>(from);
-
-        if (msg == STDERR_WRITE) {
-            auto s = readString(from);
-            if (!sink) throw Error("no sink");
-            (*sink)(s);
-        }
-
-        else if (msg == STDERR_READ) {
-            if (!source) throw Error("no source");
-            size_t len = readNum<size_t>(from);
-            auto buf = std::make_unique<char[]>(len);
-            writeString({(const char *) buf.get(), source->read(buf.get(), len)}, to);
-            to.flush();
-        }
-
-        else if (msg == STDERR_ERROR) {
-            if (GET_PROTOCOL_MINOR(daemonVersion) >= 26) {
-                return std::make_exception_ptr(readError(from));
-            } else {
-                auto error = readString(from);
-                unsigned int status = readInt(from);
-                return std::make_exception_ptr(Error(status, error));
-            }
-        }
-
-        else if (msg == STDERR_NEXT)
-            printError(chomp(readString(from)));
-
-        else if (msg == STDERR_START_ACTIVITY) {
-            auto act = readNum<ActivityId>(from);
-            auto lvl = (Verbosity) readInt(from);
-            auto type = (ActivityType) readInt(from);
-            auto s = readString(from);
-            auto fields = readFields(from);
-            auto parent = readNum<ActivityId>(from);
-            logger->startActivity(act, lvl, type, s, fields, parent);
-        }
-
-        else if (msg == STDERR_STOP_ACTIVITY) {
-            auto act = readNum<ActivityId>(from);
-            logger->stopActivity(act);
-        }
-
-        else if (msg == STDERR_RESULT) {
-            auto act = readNum<ActivityId>(from);
-            auto type = (ResultType) readInt(from);
-            auto fields = readFields(from);
-            logger->result(act, type, fields);
-        }
-
-        else if (msg == STDERR_LAST)
-            break;
-
-        else
-            throw Error("got unknown message type %x from Nix daemon", msg);
-    }
-
-    return nullptr;
-}
-
 void RemoteStore::ConnectionHandle::withFramedSink(std::function<void(Sink & sink)> fun)
 {
     (*this)->to.flush();
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index 85ce2b73477..7d96232f43a 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -87,8 +87,8 @@ public:
     StorePath addToStoreFromDump(
         Source & dump,
         std::string_view name,
-        FileSerialisationMethod dumpMethod = FileSerialisationMethod::Recursive,
-        ContentAddressMethod hashMethod = FileIngestionMethod::Recursive,
+        FileSerialisationMethod dumpMethod = FileSerialisationMethod::NixArchive,
+        ContentAddressMethod hashMethod = FileIngestionMethod::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = StorePathSet(),
         RepairFlag repair = NoRepair) override;
diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index 1a62d92d44a..27013c0f17a 100644
--- a/src/libstore/s3-binary-cache-store.cc
+++ b/src/libstore/s3-binary-cache-store.cc
@@ -132,6 +132,7 @@ ref<Aws::Client::ClientConfiguration> S3Helper::makeConfig(
 {
     initAWS();
     auto res = make_ref<Aws::Client::ClientConfiguration>();
+    res->allowSystemProxy = true;
     res->region = region;
     if (!scheme.empty()) {
         res->scheme = Aws::Http::SchemeMapper::FromString(scheme.c_str());
@@ -213,7 +214,7 @@ struct S3BinaryCacheStoreConfig : virtual BinaryCacheStoreConfig
           support it.
 
           > **Note**
-          > 
+          >
           > HTTPS should be used if the cache might contain sensitive
           > information.
         )"};
@@ -224,7 +225,7 @@ struct S3BinaryCacheStoreConfig : virtual BinaryCacheStoreConfig
           Do not specify this setting if you're using Amazon S3.
 
           > **Note**
-          > 
+          >
           > This endpoint must support HTTPS and will use path-based
           > addressing instead of virtual host based addressing.
         )"};
@@ -269,8 +270,8 @@ struct S3BinaryCacheStoreImpl : virtual S3BinaryCacheStoreConfig, public virtual
     S3Helper s3Helper;
 
     S3BinaryCacheStoreImpl(
-        const std::string & uriScheme,
-        const std::string & bucketName,
+        std::string_view uriScheme,
+        std::string_view bucketName,
         const Params & params)
         : StoreConfig(params)
         , BinaryCacheStoreConfig(params)
@@ -281,6 +282,8 @@ struct S3BinaryCacheStoreImpl : virtual S3BinaryCacheStoreConfig, public virtual
         , bucketName(bucketName)
         , s3Helper(profile, region, scheme, endpoint)
     {
+        if (bucketName.empty())
+            throw UsageError("`%s` store requires a bucket name in its Store URI", uriScheme);
         diskCache = getNarInfoDiskCache();
     }
 
diff --git a/src/libstore/unix/schema.sql b/src/libstore/schema.sql
similarity index 100%
rename from src/libstore/unix/schema.sql
rename to src/libstore/schema.sql
diff --git a/src/libstore/serve-protocol-connection.cc b/src/libstore/serve-protocol-connection.cc
new file mode 100644
index 00000000000..07379999b4b
--- /dev/null
+++ b/src/libstore/serve-protocol-connection.cc
@@ -0,0 +1,106 @@
+#include "serve-protocol-connection.hh"
+#include "serve-protocol-impl.hh"
+#include "build-result.hh"
+#include "derivations.hh"
+
+namespace nix {
+
+ServeProto::Version ServeProto::BasicClientConnection::handshake(
+    BufferedSink & to, Source & from, ServeProto::Version localVersion, std::string_view host)
+{
+    to << SERVE_MAGIC_1 << localVersion;
+    to.flush();
+
+    unsigned int magic = readInt(from);
+    if (magic != SERVE_MAGIC_2)
+        throw Error("'nix-store --serve' protocol mismatch from '%s'", host);
+    auto remoteVersion = readInt(from);
+    if (GET_PROTOCOL_MAJOR(remoteVersion) != 0x200)
+        throw Error("unsupported 'nix-store --serve' protocol version on '%s'", host);
+    return std::min(remoteVersion, localVersion);
+}
+
+ServeProto::Version
+ServeProto::BasicServerConnection::handshake(BufferedSink & to, Source & from, ServeProto::Version localVersion)
+{
+    unsigned int magic = readInt(from);
+    if (magic != SERVE_MAGIC_1)
+        throw Error("protocol mismatch");
+    to << SERVE_MAGIC_2 << localVersion;
+    to.flush();
+    auto remoteVersion = readInt(from);
+    return std::min(remoteVersion, localVersion);
+}
+
+StorePathSet ServeProto::BasicClientConnection::queryValidPaths(
+    const StoreDirConfig & store, bool lock, const StorePathSet & paths, SubstituteFlag maybeSubstitute)
+{
+    to << ServeProto::Command::QueryValidPaths << lock << maybeSubstitute;
+    write(store, *this, paths);
+    to.flush();
+
+    return Serialise<StorePathSet>::read(store, *this);
+}
+
+std::map<StorePath, UnkeyedValidPathInfo>
+ServeProto::BasicClientConnection::queryPathInfos(const StoreDirConfig & store, const StorePathSet & paths)
+{
+    std::map<StorePath, UnkeyedValidPathInfo> infos;
+
+    to << ServeProto::Command::QueryPathInfos;
+    ServeProto::write(store, *this, paths);
+    to.flush();
+
+    while (true) {
+        auto storePathS = readString(from);
+        if (storePathS == "")
+            break;
+
+        auto storePath = store.parseStorePath(storePathS);
+        assert(paths.count(storePath) == 1);
+        auto info = ServeProto::Serialise<UnkeyedValidPathInfo>::read(store, *this);
+        infos.insert_or_assign(std::move(storePath), std::move(info));
+    }
+
+    return infos;
+}
+
+void ServeProto::BasicClientConnection::putBuildDerivationRequest(
+    const StoreDirConfig & store,
+    const StorePath & drvPath,
+    const BasicDerivation & drv,
+    const ServeProto::BuildOptions & options)
+{
+    to << ServeProto::Command::BuildDerivation << store.printStorePath(drvPath);
+    writeDerivation(to, store, drv);
+
+    ServeProto::write(store, *this, options);
+
+    to.flush();
+}
+
+BuildResult ServeProto::BasicClientConnection::getBuildDerivationResponse(const StoreDirConfig & store)
+{
+    return ServeProto::Serialise<BuildResult>::read(store, *this);
+}
+
+void ServeProto::BasicClientConnection::narFromPath(
+    const StoreDirConfig & store, const StorePath & path, std::function<void(Source &)> fun)
+{
+    to << ServeProto::Command::DumpStorePath << store.printStorePath(path);
+    to.flush();
+
+    fun(from);
+}
+
+void ServeProto::BasicClientConnection::importPaths(const StoreDirConfig & store, std::function<void(Sink &)> fun)
+{
+    to << ServeProto::Command::ImportPaths;
+    fun(to);
+    to.flush();
+
+    if (readInt(from) != 1)
+        throw Error("remote machine failed to import closure");
+}
+
+}
diff --git a/src/libstore/serve-protocol-connection.hh b/src/libstore/serve-protocol-connection.hh
new file mode 100644
index 00000000000..73bf714439e
--- /dev/null
+++ b/src/libstore/serve-protocol-connection.hh
@@ -0,0 +1,108 @@
+#pragma once
+///@file
+
+#include "serve-protocol.hh"
+#include "store-api.hh"
+
+namespace nix {
+
+struct ServeProto::BasicClientConnection
+{
+    FdSink to;
+    FdSource from;
+    ServeProto::Version remoteVersion;
+
+    /**
+     * Establishes connection, negotiating version.
+     *
+     * @return the version provided by the other side of the
+     * connection.
+     *
+     * @param to Taken by reference to allow for various error handling
+     * mechanisms.
+     *
+     * @param from Taken by reference to allow for various error
+     * handling mechanisms.
+     *
+     * @param localVersion Our version which is sent over
+     *
+     * @param host Just used to add context to thrown exceptions.
+     */
+    static ServeProto::Version
+    handshake(BufferedSink & to, Source & from, ServeProto::Version localVersion, std::string_view host);
+
+    /**
+     * Coercion to `ServeProto::ReadConn`. This makes it easy to use the
+     * factored out serve protocol serializers with a
+     * `LegacySSHStore::Connection`.
+     *
+     * The serve protocol connection types are unidirectional, unlike
+     * this type.
+     */
+    operator ServeProto::ReadConn()
+    {
+        return ServeProto::ReadConn{
+            .from = from,
+            .version = remoteVersion,
+        };
+    }
+
+    /**
+     * Coercion to `ServeProto::WriteConn`. This makes it easy to use the
+     * factored out serve protocol serializers with a
+     * `LegacySSHStore::Connection`.
+     *
+     * The serve protocol connection types are unidirectional, unlike
+     * this type.
+     */
+    operator ServeProto::WriteConn()
+    {
+        return ServeProto::WriteConn{
+            .to = to,
+            .version = remoteVersion,
+        };
+    }
+
+    StorePathSet queryValidPaths(
+        const StoreDirConfig & remoteStore, bool lock, const StorePathSet & paths, SubstituteFlag maybeSubstitute);
+
+    std::map<StorePath, UnkeyedValidPathInfo> queryPathInfos(const StoreDirConfig & store, const StorePathSet & paths);
+    ;
+
+    void putBuildDerivationRequest(
+        const StoreDirConfig & store,
+        const StorePath & drvPath,
+        const BasicDerivation & drv,
+        const ServeProto::BuildOptions & options);
+
+    /**
+     * Get the response, must be paired with
+     * `putBuildDerivationRequest`.
+     */
+    BuildResult getBuildDerivationResponse(const StoreDirConfig & store);
+
+    void narFromPath(const StoreDirConfig & store, const StorePath & path, std::function<void(Source &)> fun);
+
+    void importPaths(const StoreDirConfig & store, std::function<void(Sink &)> fun);
+};
+
+struct ServeProto::BasicServerConnection
+{
+    /**
+     * Establishes connection, negotiating version.
+     *
+     * @return the version provided by the other side of the
+     * connection.
+     *
+     * @param to Taken by reference to allow for various error handling
+     * mechanisms.
+     *
+     * @param from Taken by reference to allow for various error
+     * handling mechanisms.
+     *
+     * @param localVersion Our version which is sent over
+     */
+    static ServeProto::Version handshake(BufferedSink & to, Source & from, ServeProto::Version localVersion);
+};
+
+}
diff --git a/src/libstore/serve-protocol-impl.cc b/src/libstore/serve-protocol-impl.cc
deleted file mode 100644
index b39212884cd..00000000000
--- a/src/libstore/serve-protocol-impl.cc
+++ /dev/null
@@ -1,69 +0,0 @@
-#include "serve-protocol-impl.hh"
-#include "build-result.hh"
-#include "derivations.hh"
-
-namespace nix {
-
-ServeProto::Version ServeProto::BasicClientConnection::handshake(
-    BufferedSink & to,
-    Source & from,
-    ServeProto::Version localVersion,
-    std::string_view host)
-{
-    to << SERVE_MAGIC_1 << localVersion;
-    to.flush();
-
-    unsigned int magic = readInt(from);
-    if (magic != SERVE_MAGIC_2)
-        throw Error("'nix-store --serve' protocol mismatch from '%s'", host);
-    auto remoteVersion = readInt(from);
-    if (GET_PROTOCOL_MAJOR(remoteVersion) != 0x200)
-        throw Error("unsupported 'nix-store --serve' protocol version on '%s'", host);
-    return remoteVersion;
-}
-
-ServeProto::Version ServeProto::BasicServerConnection::handshake(
-    BufferedSink & to,
-    Source & from,
-    ServeProto::Version localVersion)
-{
-    unsigned int magic = readInt(from);
-    if (magic != SERVE_MAGIC_1) throw Error("protocol mismatch");
-    to << SERVE_MAGIC_2 << localVersion;
-    to.flush();
-    return readInt(from);
-}
-
-
-StorePathSet ServeProto::BasicClientConnection::queryValidPaths(
-    const Store & store,
-    bool lock, const StorePathSet & paths,
-    SubstituteFlag maybeSubstitute)
-{
-    to
-        << ServeProto::Command::QueryValidPaths
-        << lock
-        << maybeSubstitute;
-    write(store, *this, paths);
-    to.flush();
-
-    return Serialise<StorePathSet>::read(store, *this);
-}
-
-
-void ServeProto::BasicClientConnection::putBuildDerivationRequest(
-    const Store & store,
-    const StorePath & drvPath, const BasicDerivation & drv,
-    const ServeProto::BuildOptions & options)
-{
-    to
-        << ServeProto::Command::BuildDerivation
-        << store.printStorePath(drvPath);
-    writeDerivation(to, store, drv);
-
-    ServeProto::write(store, *this, options);
-
-    to.flush();
-}
-
-}
diff --git a/src/libstore/serve-protocol-impl.hh b/src/libstore/serve-protocol-impl.hh
index fd8d946970e..67bc5dc6eed 100644
--- a/src/libstore/serve-protocol-impl.hh
+++ b/src/libstore/serve-protocol-impl.hh
@@ -57,101 +57,4 @@ struct ServeProto::Serialise
 
 /* protocol-specific templates */
 
-struct ServeProto::BasicClientConnection
-{
-    FdSink to;
-    FdSource from;
-    ServeProto::Version remoteVersion;
-
-    /**
-     * Establishes connection, negotiating version.
-     *
-     * @return the version provided by the other side of the
-     * connection.
-     *
-     * @param to Taken by reference to allow for various error handling
-     * mechanisms.
-     *
-     * @param from Taken by reference to allow for various error
-     * handling mechanisms.
-     *
-     * @param localVersion Our version which is sent over
-     *
-     * @param host Just used to add context to thrown exceptions.
-     */
-    static ServeProto::Version handshake(
-        BufferedSink & to,
-        Source & from,
-        ServeProto::Version localVersion,
-        std::string_view host);
-
-    /**
-     * Coercion to `ServeProto::ReadConn`. This makes it easy to use the
-     * factored out serve protocol serializers with a
-     * `LegacySSHStore::Connection`.
-     *
-     * The serve protocol connection types are unidirectional, unlike
-     * this type.
-     */
-    operator ServeProto::ReadConn ()
-    {
-        return ServeProto::ReadConn {
-            .from = from,
-            .version = remoteVersion,
-        };
-    }
-
-    /**
-     * Coercion to `ServeProto::WriteConn`. This makes it easy to use the
-     * factored out serve protocol serializers with a
-     * `LegacySSHStore::Connection`.
-     *
-     * The serve protocol connection types are unidirectional, unlike
-     * this type.
-     */
-    operator ServeProto::WriteConn ()
-    {
-        return ServeProto::WriteConn {
-            .to = to,
-            .version = remoteVersion,
-        };
-    }
-
-    StorePathSet queryValidPaths(
-        const Store & remoteStore,
-        bool lock, const StorePathSet & paths,
-        SubstituteFlag maybeSubstitute);
-
-    /**
-     * Just the request half, because Hydra may do other things between
-     * issuing the request and reading the `BuildResult` response.
-     */
-    void putBuildDerivationRequest(
-        const Store & store,
-        const StorePath & drvPath, const BasicDerivation & drv,
-        const ServeProto::BuildOptions & options);
-};
-
-struct ServeProto::BasicServerConnection
-{
-    /**
-     * Establishes connection, negotiating version.
-     *
-     * @return the version provided by the other side of the
-     * connection.
-     *
-     * @param to Taken by reference to allow for various error handling
-     * mechanisms.
-     *
-     * @param from Taken by reference to allow for various error
-     * handling mechanisms.
-     *
-     * @param localVersion Our version which is sent over
-     */
-    static ServeProto::Version handshake(
-        BufferedSink & to,
-        Source & from,
-        ServeProto::Version localVersion);
-};
-
 }
diff --git a/src/libstore/ssh-store-config.cc b/src/libstore/ssh-store-config.cc
new file mode 100644
index 00000000000..e81a9487449
--- /dev/null
+++ b/src/libstore/ssh-store-config.cc
@@ -0,0 +1,43 @@
+#include <regex>
+
+#include "ssh-store-config.hh"
+#include "ssh.hh"
+
+namespace nix {
+
+static std::string extractConnStr(std::string_view scheme, std::string_view _connStr)
+{
+    if (_connStr.empty())
+        throw UsageError("`%s` store requires a valid SSH host as the authority part in Store URI", scheme);
+
+    std::string connStr{_connStr};
+
+    std::smatch result;
+    static std::regex v6AddrRegex("^((.*)@)?\\[(.*)\\]$");
+
+    if (std::regex_match(connStr, result, v6AddrRegex)) {
+        connStr = result[1].matched ? result.str(1) + result.str(3) : result.str(3);
+    }
+
+    return connStr;
+}
+
+CommonSSHStoreConfig::CommonSSHStoreConfig(std::string_view scheme, std::string_view host, const Params & params)
+    : StoreConfig(params)
+    , host(extractConnStr(scheme, host))
+{
+}
+
+SSHMaster CommonSSHStoreConfig::createSSHMaster(bool useMaster, Descriptor logFD)
+{
+    return {
+        host,
+        sshKey.get(),
+        sshPublicHostKey.get(),
+        useMaster,
+        compress,
+        logFD,
+    };
+}
+
+}
diff --git a/src/libstore/ssh-store-config.hh b/src/libstore/ssh-store-config.hh
index 4ce4ffc4ca1..5deb6f4c9e9 100644
--- a/src/libstore/ssh-store-config.hh
+++ b/src/libstore/ssh-store-config.hh
@@ -5,10 +5,14 @@
 
 namespace nix {
 
+class SSHMaster;
+
 struct CommonSSHStoreConfig : virtual StoreConfig
 {
     using StoreConfig::StoreConfig;
 
+    CommonSSHStoreConfig(std::string_view scheme, std::string_view host, const Params & params);
+
     const Setting<Path> sshKey{this, "", "ssh-key",
         "Path to the SSH private key used to authenticate to the remote machine."};
 
@@ -24,6 +28,35 @@ struct CommonSSHStoreConfig : virtual StoreConfig
           to be used on the remote machine. The default is `auto`
           (i.e. use the Nix daemon or `/nix/store` directly).
         )"};
+
+    /**
+     * The `parseURL` function supports both IPv6 URIs as defined in
+     * RFC2732, but also pure addresses. The latter one is needed here to
+     * connect to a remote store via SSH (it's possible to do e.g. `ssh root@::1`).
+     *
+     * When initialized, the following adjustments are made:
+     *
+     * - If the URL looks like `root@[::1]` (which is allowed by the URL parser and probably
+     *   needed to pass further flags), it
+     *   will be transformed into `root@::1` for SSH (same for `[::1]` -> `::1`).
+     *
+     * - If the URL looks like `root@::1` it will be left as-is.
+     *
+     * - In any other case, the string will be left as-is.
+     *
+     * Will throw an error if `connStr` is empty too.
+     */
+    std::string host;
+
+    /**
+     * Small wrapper around `SSHMaster::SSHMaster` that gets most
+     * arguments from this configuration.
+     *
+     * See that constructor for details on the remaining two arguments.
+     */
+    SSHMaster createSSHMaster(
+        bool useMaster,
+        Descriptor logFD = INVALID_DESCRIPTOR);
 };
 
 }
diff --git a/src/libstore/ssh-store.cc b/src/libstore/ssh-store.cc
index 0cf92b114c7..7ad934b738b 100644
--- a/src/libstore/ssh-store.cc
+++ b/src/libstore/ssh-store.cc
@@ -34,21 +34,19 @@ class SSHStore : public virtual SSHStoreConfig, public virtual RemoteStore
 {
 public:
 
-    SSHStore(const std::string & scheme, const std::string & host, const Params & params)
+    SSHStore(
+        std::string_view scheme,
+        std::string_view host,
+        const Params & params)
         : StoreConfig(params)
         , RemoteStoreConfig(params)
-        , CommonSSHStoreConfig(params)
+        , CommonSSHStoreConfig(scheme, host, params)
         , SSHStoreConfig(params)
         , Store(params)
         , RemoteStore(params)
-        , host(host)
-        , master(
-            host,
-            sshKey,
-            sshPublicHostKey,
+        , master(createSSHMaster(
             // Use SSH master only if using more than 1 connection.
-            connections->capacity() > 1,
-            compress)
+            connections->capacity() > 1))
     {
     }
 
@@ -108,7 +106,16 @@ struct MountedSSHStoreConfig : virtual SSHStoreConfig, virtual LocalFSStoreConfi
     {
     }
 
-    const std::string name() override { return "Experimental SSH Store with filesytem mounted"; }
+    MountedSSHStoreConfig(std::string_view scheme, std::string_view host, StringMap params)
+        : StoreConfig(params)
+        , RemoteStoreConfig(params)
+        , CommonSSHStoreConfig(scheme, host, params)
+        , SSHStoreConfig(params)
+        , LocalFSStoreConfig(params)
+    {
+    }
+
+    const std::string name() override { return "Experimental SSH Store with filesystem mounted"; }
 
     std::string doc() override
     {
@@ -141,10 +148,13 @@ class MountedSSHStore : public virtual MountedSSHStoreConfig, public virtual SSH
 {
 public:
 
-    MountedSSHStore(const std::string & scheme, const std::string & host, const Params & params)
+    MountedSSHStore(
+        std::string_view scheme,
+        std::string_view host,
+        const Params & params)
         : StoreConfig(params)
         , RemoteStoreConfig(params)
-        , CommonSSHStoreConfig(params)
+        , CommonSSHStoreConfig(scheme, host, params)
         , SSHStoreConfig(params)
         , LocalFSStoreConfig(params)
         , MountedSSHStoreConfig(params)
diff --git a/src/libstore/ssh.cc b/src/libstore/ssh.cc
index 04f45827943..e5d623adf3a 100644
--- a/src/libstore/ssh.cc
+++ b/src/libstore/ssh.cc
@@ -6,7 +6,11 @@
 
 namespace nix {
 
-SSHMaster::SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD)
+SSHMaster::SSHMaster(
+    std::string_view host,
+    std::string_view keyFile,
+    std::string_view sshPublicHostKey,
+    bool useMaster, bool compress, Descriptor logFD)
     : host(host)
     , fakeSSH(host == "localhost")
     , keyFile(keyFile)
@@ -31,11 +35,11 @@ void SSHMaster::addCommonSSHOpts(Strings & args)
     if (!keyFile.empty())
         args.insert(args.end(), {"-i", keyFile});
     if (!sshPublicHostKey.empty()) {
-        Path fileName = (Path) *state->tmpDir + "/host-key";
+        std::filesystem::path fileName = state->tmpDir->path() / "host-key";
         auto p = host.rfind("@");
         std::string thost = p != std::string::npos ? std::string(host, p + 1) : host;
-        writeFile(fileName, thost + " " + base64Decode(sshPublicHostKey) + "\n");
-        args.insert(args.end(), {"-oUserKnownHostsFile=" + fileName});
+        writeFile(fileName.string(), thost + " " + base64Decode(sshPublicHostKey) + "\n");
+        args.insert(args.end(), {"-oUserKnownHostsFile=" + fileName.string()});
     }
     if (compress)
         args.push_back("-C");
diff --git a/src/libstore/ssh.hh b/src/libstore/ssh.hh
index 3b1a0827a65..19b30e8838f 100644
--- a/src/libstore/ssh.hh
+++ b/src/libstore/ssh.hh
@@ -17,7 +17,7 @@ private:
     const std::string sshPublicHostKey;
     const bool useMaster;
     const bool compress;
-    const int logFD;
+    const Descriptor logFD;
 
     struct State
     {
@@ -39,7 +39,11 @@ private:
 
 public:
 
-    SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD = -1);
+    SSHMaster(
+        std::string_view host,
+        std::string_view keyFile,
+        std::string_view sshPublicHostKey,
+        bool useMaster, bool compress, Descriptor logFD = INVALID_DESCRIPTOR);
 
     struct Connection
     {
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 839311b9ad2..8e630ea5071 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -8,7 +8,6 @@
 #include "util.hh"
 #include "nar-info-disk-cache.hh"
 #include "thread-pool.hh"
-#include "url.hh"
 #include "references.hh"
 #include "archive.hh"
 #include "callback.hh"
@@ -20,12 +19,8 @@
 #include "signals.hh"
 #include "users.hh"
 
-#ifndef _WIN32
-# include "remote-store.hh"
-#endif
-
+#include <filesystem>
 #include <nlohmann/json.hpp>
-#include <regex>
 
 using json = nlohmann::json;
 
@@ -54,7 +49,7 @@ Path Store::followLinksToStore(std::string_view _path) const
 {
     Path path = absPath(std::string(_path));
     while (!isInStore(path)) {
-        if (!isLink(path)) break;
+        if (!std::filesystem::is_symlink(path)) break;
         auto target = readLink(path);
         path = absPath(target, dirOf(path));
     }
@@ -127,7 +122,7 @@ StorePath StoreDirConfig::makeFixedOutputPath(std::string_view name, const Fixed
     if (info.method == FileIngestionMethod::Git && info.hash.algo != HashAlgorithm::SHA1)
         throw Error("Git file ingestion must use SHA-1 hash");
 
-    if (info.hash.algo == HashAlgorithm::SHA256 && info.method == FileIngestionMethod::Recursive) {
+    if (info.hash.algo == HashAlgorithm::SHA256 && info.method == FileIngestionMethod::NixArchive) {
         return makeStorePath(makeType(*this, "source", info.references), info.hash, name);
     } else {
         if (!info.references.empty()) {
@@ -167,14 +162,15 @@ StorePath StoreDirConfig::makeFixedOutputPathFromCA(std::string_view name, const
 
 std::pair<StorePath, Hash> StoreDirConfig::computeStorePath(
     std::string_view name,
-    SourceAccessor & accessor,
-    const CanonPath & path,
+    const SourcePath & path,
     ContentAddressMethod method,
     HashAlgorithm hashAlgo,
     const StorePathSet & references,
     PathFilter & filter) const
 {
-    auto h = hashPath(accessor, path, method.getFileIngestionMethod(), hashAlgo, filter);
+    auto [h, size] = hashPath(path, method.getFileIngestionMethod(), hashAlgo, filter);
+    if (size && *size >= settings.warnLargePathThreshold)
+        warn("hashed large path '%s' (%s)", path, renderSize(*size));
     return {
         makeFixedOutputPathFromCA(
             name,
@@ -192,8 +188,7 @@ std::pair<StorePath, Hash> StoreDirConfig::computeStorePath(
 
 StorePath Store::addToStore(
     std::string_view name,
-    SourceAccessor & accessor,
-    const CanonPath & path,
+    const SourcePath & path,
     ContentAddressMethod method,
     HashAlgorithm hashAlgo,
     const StorePathSet & references,
@@ -205,18 +200,22 @@ StorePath Store::addToStore(
     case FileIngestionMethod::Flat:
         fsm = FileSerialisationMethod::Flat;
         break;
-    case FileIngestionMethod::Recursive:
-        fsm = FileSerialisationMethod::Recursive;
+    case FileIngestionMethod::NixArchive:
+        fsm = FileSerialisationMethod::NixArchive;
         break;
     case FileIngestionMethod::Git:
         // Use NAR; Git is not a serialization method
-        fsm = FileSerialisationMethod::Recursive;
+        fsm = FileSerialisationMethod::NixArchive;
         break;
     }
     auto source = sinkToSource([&](Sink & sink) {
-        dumpPath(accessor, path, sink, fsm, filter);
+        dumpPath(path, sink, fsm, filter);
     });
-    return addToStoreFromDump(*source, name, fsm, method, hashAlgo, references, repair);
+    LengthSource lengthSource(*source);
+    auto storePath = addToStoreFromDump(lengthSource, name, fsm, method, hashAlgo, references, repair);
+    if (lengthSource.total >= settings.warnLargePathThreshold)
+        warn("copied large path '%s' to the store (%s)", path, renderSize(lengthSource.total));
+    return storePath;
 }
 
 void Store::addMultipleToStore(
@@ -343,8 +342,7 @@ digraph graphname {
 */
 ValidPathInfo Store::addToStoreSlow(
     std::string_view name,
-    SourceAccessor & accessor,
-    const CanonPath & srcPath,
+    const SourcePath & srcPath,
     ContentAddressMethod method, HashAlgorithm hashAlgo,
     const StorePathSet & references,
     std::optional<Hash> expectedCAHash)
@@ -358,7 +356,7 @@ ValidPathInfo Store::addToStoreSlow(
     RegularFileSink fileSink { caHashSink };
     TeeSink unusualHashTee { narHashSink, caHashSink };
 
-    auto & narSink = method == FileIngestionMethod::Recursive && hashAlgo != HashAlgorithm::SHA256
+    auto & narSink = method == ContentAddressMethod::Raw::NixArchive && hashAlgo != HashAlgorithm::SHA256
         ? static_cast<Sink &>(unusualHashTee)
         : narHashSink;
 
@@ -366,7 +364,7 @@ ValidPathInfo Store::addToStoreSlow(
        srcPath. The fact that we use scratchpadSink as a temporary buffer here
        is an implementation detail. */
     auto fileSource = sinkToSource([&](Sink & scratchpadSink) {
-        accessor.dumpPath(srcPath, scratchpadSink);
+        srcPath.dumpPath(scratchpadSink);
     });
 
     /* tapped provides the same data as fileSource, but we also write all the
@@ -386,16 +384,15 @@ ValidPathInfo Store::addToStoreSlow(
        finish. */
     auto [narHash, narSize] = narHashSink.finish();
 
-    auto hash = method == FileIngestionMethod::Recursive && hashAlgo == HashAlgorithm::SHA256
+    auto hash = method == ContentAddressMethod::Raw::NixArchive && hashAlgo == HashAlgorithm::SHA256
         ? narHash
-        : method == FileIngestionMethod::Git
-        ? git::dumpHash(hashAlgo, accessor, srcPath).hash
+        : method == ContentAddressMethod::Raw::Git
+        ? git::dumpHash(hashAlgo, srcPath).hash
         : caHashSink.finish().first;
 
     if (expectedCAHash && expectedCAHash != hash)
         throw Error("hash mismatch for '%s'", srcPath);
 
-
     ValidPathInfo info {
         *this,
         name,
@@ -412,7 +409,7 @@ ValidPathInfo Store::addToStoreSlow(
 
     if (!isValidPath(info.path)) {
         auto source = sinkToSource([&](Sink & scratchpadSink) {
-            accessor.dumpPath(srcPath, scratchpadSink);
+            srcPath.dumpPath(scratchpadSink);
         });
         addToStore(info, *source);
     }
@@ -1269,159 +1266,70 @@ Derivation Store::readInvalidDerivation(const StorePath & drvPath)
 
 }
 
-#ifndef _WIN32
-# include "local-store.hh"
-# include "uds-remote-store.hh"
-#endif
 
+#include "local-store.hh"
+#include "uds-remote-store.hh"
 
-namespace nix {
 
-/* Split URI into protocol+hierarchy part and its parameter set. */
-std::pair<std::string, Store::Params> splitUriAndParams(const std::string & uri_)
-{
-    auto uri(uri_);
-    Store::Params params;
-    auto q = uri.find('?');
-    if (q != std::string::npos) {
-        params = decodeQuery(uri.substr(q + 1));
-        uri = uri_.substr(0, q);
-    }
-    return {uri, params};
-}
-
-#ifdef _WIN32 // Unused on Windows because the next `#ifndef`
-[[maybe_unused]]
-#endif
-static bool isNonUriPath(const std::string & spec)
-{
-    return
-        // is not a URL
-        spec.find("://") == std::string::npos
-        // Has at least one path separator, and so isn't a single word that
-        // might be special like "auto"
-        && spec.find("/") != std::string::npos;
-}
+namespace nix {
 
-std::shared_ptr<Store> openFromNonUri(const std::string & uri, const Store::Params & params)
+ref<Store> openStore(const std::string & uri,
+    const Store::Params & extraParams)
 {
-    // TODO reenable on Windows once we have `LocalStore` and
-    // `UDSRemoteStore`.
-    #ifndef _WIN32
-    if (uri == "" || uri == "auto") {
-        auto stateDir = getOr(params, "state", settings.nixStateDir);
-        if (access(stateDir.c_str(), R_OK | W_OK) == 0)
-            return std::make_shared<LocalStore>(params);
-        else if (pathExists(settings.nixDaemonSocketFile))
-            return std::make_shared<UDSRemoteStore>(params);
-        #if __linux__
-        else if (!pathExists(stateDir)
-            && params.empty()
-            && !isRootUser()
-            && !getEnv("NIX_STORE_DIR").has_value()
-            && !getEnv("NIX_STATE_DIR").has_value())
-        {
-            /* If /nix doesn't exist, there is no daemon socket, and
-               we're not root, then automatically set up a chroot
-               store in ~/.local/share/nix/root. */
-            auto chrootStore = getDataDir() + "/nix/root";
-            if (!pathExists(chrootStore)) {
-                try {
-                    createDirs(chrootStore);
-                } catch (Error & e) {
-                    return std::make_shared<LocalStore>(params);
-                }
-                warn("'%s' does not exist, so Nix will use '%s' as a chroot store", stateDir, chrootStore);
-            } else
-                debug("'%s' does not exist, so Nix will use '%s' as a chroot store", stateDir, chrootStore);
-            Store::Params params2;
-            params2["root"] = chrootStore;
-            return std::make_shared<LocalStore>(params2);
-        }
-        #endif
-        else
-            return std::make_shared<LocalStore>(params);
-    } else if (uri == "daemon") {
-        return std::make_shared<UDSRemoteStore>(params);
-    } else if (uri == "local") {
-        return std::make_shared<LocalStore>(params);
-    } else if (isNonUriPath(uri)) {
-        Store::Params params2 = params;
-        params2["root"] = absPath(uri);
-        return std::make_shared<LocalStore>(params2);
-    } else {
-        return nullptr;
-    }
-    #else
-    return nullptr;
-    #endif
+    return openStore(StoreReference::parse(uri, extraParams));
 }
 
-// The `parseURL` function supports both IPv6 URIs as defined in
-// RFC2732, but also pure addresses. The latter one is needed here to
-// connect to a remote store via SSH (it's possible to do e.g. `ssh root@::1`).
-//
-// This function now ensures that a usable connection string is available:
-// * If the store to be opened is not an SSH store, nothing will be done.
-// * If the URL looks like `root@[::1]` (which is allowed by the URL parser and probably
-//   needed to pass further flags), it
-//   will be transformed into `root@::1` for SSH (same for `[::1]` -> `::1`).
-// * If the URL looks like `root@::1` it will be left as-is.
-// * In any other case, the string will be left as-is.
-static std::string extractConnStr(const std::string &proto, const std::string &connStr)
+ref<Store> openStore(StoreReference && storeURI)
 {
-    if (proto.rfind("ssh") != std::string::npos) {
-        std::smatch result;
-        std::regex v6AddrRegex("^((.*)@)?\\[(.*)\\]$");
-
-        if (std::regex_match(connStr, result, v6AddrRegex)) {
-            if (result[1].matched) {
-                return result.str(1) + result.str(3);
+    auto & params = storeURI.params;
+
+    auto store = std::visit(overloaded {
+        [&](const StoreReference::Auto &) -> std::shared_ptr<Store> {
+            auto stateDir = getOr(params, "state", settings.nixStateDir);
+            if (access(stateDir.c_str(), R_OK | W_OK) == 0)
+                return std::make_shared<LocalStore>(params);
+            else if (pathExists(settings.nixDaemonSocketFile))
+                return std::make_shared<UDSRemoteStore>(params);
+            #if __linux__
+            else if (!pathExists(stateDir)
+                && params.empty()
+                && !isRootUser()
+                && !getEnv("NIX_STORE_DIR").has_value()
+                && !getEnv("NIX_STATE_DIR").has_value())
+            {
+                /* If /nix doesn't exist, there is no daemon socket, and
+                   we're not root, then automatically set up a chroot
+                   store in ~/.local/share/nix/root. */
+                auto chrootStore = getDataDir() + "/nix/root";
+                if (!pathExists(chrootStore)) {
+                    try {
+                        createDirs(chrootStore);
+                    } catch (SystemError & e) {
+                        return std::make_shared<LocalStore>(params);
+                    }
+                    warn("'%s' does not exist, so Nix will use '%s' as a chroot store", stateDir, chrootStore);
+                } else
+                    debug("'%s' does not exist, so Nix will use '%s' as a chroot store", stateDir, chrootStore);
+                return std::make_shared<LocalStore>("local", chrootStore, params);
             }
-            return result.str(3);
-        }
-    }
+            #endif
+            else
+                return std::make_shared<LocalStore>(params);
+        },
+        [&](const StoreReference::Specified & g) {
+            for (auto implem : *Implementations::registered)
+                if (implem.uriSchemes.count(g.scheme))
+                    return implem.create(g.scheme, g.authority, params);
 
-    return connStr;
-}
+            throw Error("don't know how to open Nix store with scheme '%s'", g.scheme);
+        },
+    }, storeURI.variant);
 
-ref<Store> openStore(const std::string & uri_,
-    const Store::Params & extraParams)
-{
-    auto params = extraParams;
-    try {
-        auto parsedUri = parseURL(uri_);
-        params.insert(parsedUri.query.begin(), parsedUri.query.end());
-
-        auto baseURI = extractConnStr(
-            parsedUri.scheme,
-            parsedUri.authority.value_or("") + parsedUri.path
-        );
-
-        for (auto implem : *Implementations::registered) {
-            if (implem.uriSchemes.count(parsedUri.scheme)) {
-                auto store = implem.create(parsedUri.scheme, baseURI, params);
-                if (store) {
-                    experimentalFeatureSettings.require(store->experimentalFeature());
-                    store->init();
-                    store->warnUnknownSettings();
-                    return ref<Store>(store);
-                }
-            }
-        }
-    }
-    catch (BadURL &) {
-        auto [uri, uriParams] = splitUriAndParams(uri_);
-        params.insert(uriParams.begin(), uriParams.end());
-
-        if (auto store = openFromNonUri(uri, params)) {
-            experimentalFeatureSettings.require(store->experimentalFeature());
-            store->warnUnknownSettings();
-            return ref<Store>(store);
-        }
-    }
+    experimentalFeatureSettings.require(store->experimentalFeature());
+    store->warnUnknownSettings();
+    store->init();
 
-    throw Error("don't know how to open Nix store '%s'", uri_);
+    return ref<Store> { store };
 }
 
 std::list<ref<Store>> getDefaultSubstituters()
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 5f683a21139..a5effb4c131 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -13,6 +13,7 @@
 #include "path-info.hh"
 #include "repair-flag.hh"
 #include "store-dir-config.hh"
+#include "store-reference.hh"
 #include "source-path.hh"
 
 #include <nlohmann/json_fwd.hpp>
@@ -65,7 +66,7 @@ MakeError(Unsupported, Error);
 MakeError(SubstituteGone, Error);
 MakeError(SubstituterDisabled, Error);
 
-MakeError(InvalidStoreURI, Error);
+MakeError(InvalidStoreReference, Error);
 
 struct Realisation;
 struct RealisedPath;
@@ -91,7 +92,7 @@ enum SubstituteFlag : bool { NoSubstitute = false, Substitute = true };
 const uint32_t exportMagic = 0x4558494e;
 
 
-enum BuildMode { bmNormal, bmRepair, bmCheck };
+enum BuildMode : uint8_t { bmNormal, bmRepair, bmCheck };
 enum TrustedFlag : bool { NotTrusted = false, Trusted = true };
 
 struct BuildResult;
@@ -102,7 +103,7 @@ typedef std::map<StorePath, std::optional<ContentAddress>> StorePathCAMap;
 
 struct StoreConfig : public StoreDirConfig
 {
-    typedef std::map<std::string, std::string> Params;
+    using Params = StoreReference::Params;
 
     using StoreDirConfig::StoreDirConfig;
 
@@ -439,9 +440,8 @@ public:
      */
     virtual StorePath addToStore(
         std::string_view name,
-        SourceAccessor & accessor,
-        const CanonPath & path,
-        ContentAddressMethod method = FileIngestionMethod::Recursive,
+        const SourcePath & path,
+        ContentAddressMethod method = ContentAddressMethod::Raw::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = StorePathSet(),
         PathFilter & filter = defaultPathFilter,
@@ -454,9 +454,8 @@ public:
      */
     ValidPathInfo addToStoreSlow(
         std::string_view name,
-        SourceAccessor & accessor,
-        const CanonPath & path,
-        ContentAddressMethod method = FileIngestionMethod::Recursive,
+        const SourcePath & path,
+        ContentAddressMethod method = ContentAddressMethod::Raw::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = StorePathSet(),
         std::optional<Hash> expectedCAHash = {});
@@ -471,7 +470,7 @@ public:
      *
      * @param dumpMethod What serialisation format is `dump`, i.e. how
      * to deserialize it. Must either match hashMethod or be
-     * `FileSerialisationMethod::Recursive`.
+     * `FileSerialisationMethod::NixArchive`.
      *
      * @param hashMethod How content addressing? Need not match be the
      * same as `dumpMethod`.
@@ -481,8 +480,8 @@ public:
     virtual StorePath addToStoreFromDump(
         Source & dump,
         std::string_view name,
-        FileSerialisationMethod dumpMethod = FileSerialisationMethod::Recursive,
-        ContentAddressMethod hashMethod = FileIngestionMethod::Recursive,
+        FileSerialisationMethod dumpMethod = FileSerialisationMethod::NixArchive,
+        ContentAddressMethod hashMethod = ContentAddressMethod::Raw::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = StorePathSet(),
         RepairFlag repair = NoRepair) = 0;
@@ -861,34 +860,13 @@ OutputPathMap resolveDerivedPath(Store &, const DerivedPath::Built &, Store * ev
 /**
  * @return a Store object to access the Nix store denoted by
  * ‘uri’ (slight misnomer...).
- *
- * @param uri Supported values are:
- *
- * - ‘local’: The Nix store in /nix/store and database in
- *   /nix/var/nix/db, accessed directly.
- *
- * - ‘daemon’: The Nix store accessed via a Unix domain socket
- *   connection to nix-daemon.
- *
- * - ‘unix://<path>’: The Nix store accessed via a Unix domain socket
- *   connection to nix-daemon, with the socket located at <path>.
- *
- * - ‘auto’ or ‘’: Equivalent to ‘local’ or ‘daemon’ depending on
- *   whether the user has write access to the local Nix
- *   store/database.
- *
- * - ‘file://<path>’: A binary cache stored in <path>.
- *
- * - ‘https://<path>’: A binary cache accessed via HTTP.
- *
- * - ‘s3://<path>’: A writable binary cache stored on Amazon's Simple
- *   Storage Service.
- *
- * - ‘ssh://[user@]<host>’: A remote Nix store accessed by running
- *   ‘nix-store --serve’ via SSH.
- *
- * You can pass parameters to the store type by appending
- * ‘?key=value&key=value&...’ to the URI.
+ */
+ref<Store> openStore(StoreReference && storeURI);
+
+
+/**
+ * Opens the store at `uri`, where `uri` is in the format expected by `StoreReference::parse`
+
  */
 ref<Store> openStore(const std::string & uri = settings.storeUri.get(),
     const Store::Params & extraParams = Store::Params());
@@ -903,7 +881,14 @@ std::list<ref<Store>> getDefaultSubstituters();
 struct StoreFactory
 {
     std::set<std::string> uriSchemes;
-    std::function<std::shared_ptr<Store> (const std::string & scheme, const std::string & uri, const Store::Params & params)> create;
+    /**
+     * The `authorityPath` parameter is `<authority>/<path>`, or really
+     * whatever comes after `<scheme>://` and before `?<query-params>`.
+     */
+    std::function<std::shared_ptr<Store> (
+        std::string_view scheme,
+        std::string_view authorityPath,
+        const Store::Params & params)> create;
     std::function<std::shared_ptr<StoreConfig> ()> getConfig;
 };
 
@@ -918,7 +903,7 @@ struct Implementations
         StoreFactory factory{
             .uriSchemes = T::uriSchemes(),
             .create =
-                ([](const std::string & scheme, const std::string & uri, const Store::Params & params)
+                ([](auto scheme, auto uri, auto & params)
                  -> std::shared_ptr<Store>
                  { return std::make_shared<T>(scheme, uri, params); }),
             .getConfig =
@@ -952,11 +937,6 @@ std::optional<ValidPathInfo> decodeValidPathInfo(
     std::istream & str,
     std::optional<HashResult> hashGiven = std::nullopt);
 
-/**
- * Split URI into protocol+hierarchy part and its parameter set.
- */
-std::pair<std::string, Store::Params> splitUriAndParams(const std::string & uri);
-
 const ContentAddress * getDerivationCA(const BasicDerivation & drv);
 
 std::map<DrvOutput, StorePath> drvOutputReferences(
diff --git a/src/libstore/store-dir-config.hh b/src/libstore/store-dir-config.hh
index 7ca8c2665c3..64c0dd8b70b 100644
--- a/src/libstore/store-dir-config.hh
+++ b/src/libstore/store-dir-config.hh
@@ -13,7 +13,10 @@
 
 namespace nix {
 
+struct SourcePath;
+
 MakeError(BadStorePath, Error);
+MakeError(BadStorePathName, BadStorePath);
 
 struct StoreDirConfig : public Config
 {
@@ -94,9 +97,8 @@ struct StoreDirConfig : public Config
      */
     std::pair<StorePath, Hash> computeStorePath(
         std::string_view name,
-        SourceAccessor & accessor,
-        const CanonPath & path,
-        ContentAddressMethod method = FileIngestionMethod::Recursive,
+        const SourcePath & path,
+        ContentAddressMethod method = FileIngestionMethod::NixArchive,
         HashAlgorithm hashAlgo = HashAlgorithm::SHA256,
         const StorePathSet & references = {},
         PathFilter & filter = defaultPathFilter) const;
diff --git a/src/libstore/store-reference.cc b/src/libstore/store-reference.cc
new file mode 100644
index 00000000000..b4968dfadbd
--- /dev/null
+++ b/src/libstore/store-reference.cc
@@ -0,0 +1,116 @@
+#include <regex>
+
+#include "error.hh"
+#include "url.hh"
+#include "store-reference.hh"
+#include "file-system.hh"
+#include "util.hh"
+
+namespace nix {
+
+static bool isNonUriPath(const std::string & spec)
+{
+    return
+        // is not a URL
+        spec.find("://") == std::string::npos
+        // Has at least one path separator, and so isn't a single word that
+        // might be special like "auto"
+        && spec.find("/") != std::string::npos;
+}
+
+std::string StoreReference::render() const
+{
+    std::string res;
+
+    std::visit(
+        overloaded{
+            [&](const StoreReference::Auto &) { res = "auto"; },
+            [&](const StoreReference::Specified & g) {
+                res = g.scheme;
+                res += "://";
+                res += g.authority;
+            },
+        },
+        variant);
+
+    if (!params.empty()) {
+        res += "?";
+        res += encodeQuery(params);
+    }
+
+    return res;
+}
+
+StoreReference StoreReference::parse(const std::string & uri, const StoreReference::Params & extraParams)
+{
+    auto params = extraParams;
+    try {
+        auto parsedUri = parseURL(uri);
+        params.insert(parsedUri.query.begin(), parsedUri.query.end());
+
+        auto baseURI = parsedUri.authority.value_or("") + parsedUri.path;
+
+        return {
+            .variant =
+                Specified{
+                    .scheme = std::move(parsedUri.scheme),
+                    .authority = std::move(baseURI),
+                },
+            .params = std::move(params),
+        };
+    } catch (BadURL &) {
+        auto [baseURI, uriParams] = splitUriAndParams(uri);
+        params.insert(uriParams.begin(), uriParams.end());
+
+        if (baseURI == "" || baseURI == "auto") {
+            return {
+                .variant = Auto{},
+                .params = std::move(params),
+            };
+        } else if (baseURI == "daemon") {
+            return {
+                .variant =
+                    Specified{
+                        .scheme = "unix",
+                        .authority = "",
+                    },
+                .params = std::move(params),
+            };
+        } else if (baseURI == "local") {
+            return {
+                .variant =
+                    Specified{
+                        .scheme = "local",
+                        .authority = "",
+                    },
+                .params = std::move(params),
+            };
+        } else if (isNonUriPath(baseURI)) {
+            return {
+                .variant =
+                    Specified{
+                        .scheme = "local",
+                        .authority = absPath(baseURI),
+                    },
+                .params = std::move(params),
+            };
+        }
+    }
+
+    throw UsageError("Cannot parse Nix store '%s'", uri);
+}
+
+/* Split URI into protocol+hierarchy part and its parameter set. */
+std::pair<std::string, StoreReference::Params> splitUriAndParams(const std::string & uri_)
+{
+    auto uri(uri_);
+    StoreReference::Params params;
+    auto q = uri.find('?');
+    if (q != std::string::npos) {
+        params = decodeQuery(uri.substr(q + 1));
+        uri = uri_.substr(0, q);
+    }
+    return {uri, params};
+}
+
+}
diff --git a/src/libstore/store-reference.hh b/src/libstore/store-reference.hh
new file mode 100644
index 00000000000..e99335c0d57
--- /dev/null
+++ b/src/libstore/store-reference.hh
@@ -0,0 +1,92 @@
+#pragma once
+///@file
+
+#include <variant>
+
+#include "types.hh"
+
+namespace nix {
+
+/**
+ * A parsed Store URI (URI is a slight misnomer...), parsed but not yet
+ * resolved to a specific instance and query parms validated.
+ *
+ * Supported values are:
+ *
+ * - ‘local’: The Nix store in /nix/store and database in
+ *   /nix/var/nix/db, accessed directly.
+ *
+ * - ‘daemon’: The Nix store accessed via a Unix domain socket
+ *   connection to nix-daemon.
+ *
+ * - ‘unix://<path>’: The Nix store accessed via a Unix domain socket
+ *   connection to nix-daemon, with the socket located at <path>.
+ *
+ * - ‘auto’ or ‘’: Equivalent to ‘local’ or ‘daemon’ depending on
+ *   whether the user has write access to the local Nix
+ *   store/database.
+ *
+ * - ‘file://<path>’: A binary cache stored in <path>.
+ *
+ * - ‘https://<path>’: A binary cache accessed via HTTP.
+ *
+ * - ‘s3://<path>’: A writable binary cache stored on Amazon's Simple
+ *   Storage Service.
+ *
+ * - ‘ssh://[user@]<host>’: A remote Nix store accessed by running
+ *   ‘nix-store --serve’ via SSH.
+ *
+ * You can pass parameters to the store type by appending
+ * ‘?key=value&key=value&...’ to the URI.
+ */
+struct StoreReference
+{
+    using Params = std::map<std::string, std::string>;
+
+    /**
+     * Special store reference `""` or `"auto"`
+     */
+    struct Auto
+    {
+        inline bool operator==(const Auto & rhs) const = default;
+        inline auto operator<=>(const Auto & rhs) const = default;
+    };
+
+    /**
+     * General case, a regular `scheme://authority` URL.
+     */
+    struct Specified
+    {
+        std::string scheme;
+        std::string authority = "";
+
+        bool operator==(const Specified & rhs) const = default;
+        auto operator<=>(const Specified & rhs) const = default;
+    };
+
+    typedef std::variant<Auto, Specified> Variant;
+
+    Variant variant;
+
+    Params params;
+
+    bool operator==(const StoreReference & rhs) const = default;
+    auto operator<=>(const StoreReference & rhs) const = default;
+
+    /**
+     * Render the whole store reference as a URI, including parameters.
+     */
+    std::string render() const;
+
+    /**
+     * Parse a URI into a store reference.
+     */
+    static StoreReference parse(const std::string & uri, const Params & extraParams = Params{});
+};
+
+/**
+ * Split URI into protocol+hierarchy part and its parameter set.
+ */
+std::pair<std::string, StoreReference::Params> splitUriAndParams(const std::string & uri);
+
+}
diff --git a/src/libstore/unix/uds-remote-store.cc b/src/libstore/uds-remote-store.cc
similarity index 87%
rename from src/libstore/unix/uds-remote-store.cc
rename to src/libstore/uds-remote-store.cc
index 01f48114467..231faa9271d 100644
--- a/src/libstore/unix/uds-remote-store.cc
+++ b/src/libstore/uds-remote-store.cc
@@ -5,16 +5,20 @@
 #include "auth.hh"
 #include "auth-tunnel.hh"
 
+#include <cstring>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/socket.h>
-#include <sys/un.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <unistd.h>
 
-#include <cstring>
-
+#ifdef _WIN32
+# include <winsock2.h>
+# include <afunix.h>
+#else
+# include <sys/socket.h>
+# include <sys/un.h>
+#endif
 
 namespace nix {
 
@@ -39,12 +43,13 @@ UDSRemoteStore::UDSRemoteStore(const Params & params)
 
 
 UDSRemoteStore::UDSRemoteStore(
-    const std::string scheme,
-    std::string socket_path,
+    std::string_view scheme,
+    PathView socket_path,
     const Params & params)
     : UDSRemoteStore(params)
 {
-    path.emplace(socket_path);
+    if (!socket_path.empty())
+        path.emplace(socket_path);
 }
 
 
@@ -53,6 +58,7 @@ std::string UDSRemoteStore::getUri()
     if (path) {
         return std::string("unix://") + *path;
     } else {
+        // unix:// with no path also works. Change what we return?
         return "daemon";
     }
 }
@@ -60,7 +66,7 @@ std::string UDSRemoteStore::getUri()
 
 void UDSRemoteStore::Connection::closeWrite()
 {
-    shutdown(fd.get(), SHUT_WR);
+    shutdown(toSocket(fd.get()), SHUT_WR);
 }
 
 
@@ -71,7 +77,7 @@ ref<RemoteStore::Connection> UDSRemoteStore::openConnection()
     /* Connect to a daemon that does the privileged work for us. */
     conn->fd = createUnixDomainSocket();
 
-    nix::connect(conn->fd.get(), path ? *path : settings.nixDaemonSocketFile);
+    nix::connect(toSocket(conn->fd.get()), path ? *path : settings.nixDaemonSocketFile);
 
     conn->from.fd = conn->fd.get();
     conn->to.fd = conn->fd.get();
@@ -127,7 +133,7 @@ void UDSRemoteStore::initConnection(RemoteStore::Connection & _conn)
         if (sendmsg(conn.fd.get(), &msg, 0) < 0)
             throw SysError("sending callback socket to the daemon");
 
-        conn.processStderr();
+        conn.processStderrReturn();
         readInt(conn.from);
     }
 }
diff --git a/src/libstore/unix/uds-remote-store.hh b/src/libstore/uds-remote-store.hh
similarity index 94%
rename from src/libstore/unix/uds-remote-store.hh
rename to src/libstore/uds-remote-store.hh
index 2a9dac59932..5b7bb7bc219 100644
--- a/src/libstore/unix/uds-remote-store.hh
+++ b/src/libstore/uds-remote-store.hh
@@ -30,7 +30,10 @@ class UDSRemoteStore : public virtual UDSRemoteStoreConfig
 public:
 
     UDSRemoteStore(const Params & params);
-    UDSRemoteStore(const std::string scheme, std::string path, const Params & params);
+    UDSRemoteStore(
+        std::string_view scheme,
+        PathView path,
+        const Params & params);
 
     std::string getUri() override;
 
diff --git a/src/libstore/unix/uds-remote-store.md b/src/libstore/uds-remote-store.md
similarity index 100%
rename from src/libstore/unix/uds-remote-store.md
rename to src/libstore/uds-remote-store.md
diff --git a/src/libstore/unix/build/hook-instance.cc b/src/libstore/unix/build/hook-instance.cc
index 5d045ec3d07..dfc20879881 100644
--- a/src/libstore/unix/build/hook-instance.cc
+++ b/src/libstore/unix/build/hook-instance.cc
@@ -1,4 +1,5 @@
 #include "globals.hh"
+#include "config-global.hh"
 #include "hook-instance.hh"
 #include "file-system.hh"
 #include "child.hh"
diff --git a/src/libstore/unix/build/local-derivation-goal.cc b/src/libstore/unix/build/local-derivation-goal.cc
index 3704eba2352..aafd7663f00 100644
--- a/src/libstore/unix/build/local-derivation-goal.cc
+++ b/src/libstore/unix/build/local-derivation-goal.cc
@@ -14,7 +14,6 @@
 #include "topo-sort.hh"
 #include "callback.hh"
 #include "json-utils.hh"
-#include "personality.hh"
 #include "current-process.hh"
 #include "child.hh"
 #include "unix-domain-socket.hh"
@@ -40,6 +39,7 @@
 
 /* Includes required for chroot support. */
 #if __linux__
+# include "fchmodat2-compat.hh"
 # include <sys/ioctl.h>
 # include <net/if.h>
 # include <netinet/ip.h>
@@ -54,6 +54,7 @@
 # endif
 # define pivot_root(new_root, put_old) (syscall(SYS_pivot_root, new_root, put_old))
 # include "cgroup.hh"
+# include "personality.hh"
 #endif
 
 #if __APPLE__
@@ -78,7 +79,7 @@ void handleDiffHook(
         try {
             auto diffRes = runProgram(RunOptions {
                 .program = diffHook,
-                .searchPath = true,
+                .lookupPath = true,
                 .args = {tryA, tryB, drvPath, tmpDir},
                 .uid = uid,
                 .gid = gid,
@@ -178,6 +179,10 @@ void LocalDerivationGoal::killSandbox(bool getStats)
 
 void LocalDerivationGoal::tryLocalBuild()
 {
+#if __APPLE__
+    additionalSandboxProfile = parsedDrv->getStringAttr("__sandboxProfile").value_or("");
+#endif
+
     unsigned int curBuilds = worker.getNrLocalBuilds();
     if (curBuilds >= settings.maxBuildJobs) {
         state = &DerivationGoal::tryToBuild;
@@ -282,7 +287,7 @@ static void movePath(const Path & src, const Path & dst)
     if (changePerm)
         chmod_(src, st.st_mode | S_IWUSR);
 
-    renameFile(src, dst);
+    std::filesystem::rename(src, dst);
 
     if (changePerm)
         chmod_(dst, st.st_mode);
@@ -369,7 +374,7 @@ bool LocalDerivationGoal::cleanupDecideWhetherDiskFull()
             if (buildMode != bmCheck && status.known->isValid()) continue;
             auto p = worker.store.toRealPath(status.known->path);
             if (pathExists(chrootRootDir + p))
-                renameFile((chrootRootDir + p), p);
+                std::filesystem::rename((chrootRootDir + p), p);
         }
 
     return diskFull;
@@ -418,7 +423,9 @@ static void doBind(const Path & source, const Path & target, bool optional = fal
     } else if (S_ISLNK(st.st_mode)) {
         // Symlinks can (apparently) not be bind-mounted, so just copy it
         createDirs(dirOf(target));
-        copyFile(source, target, /* andDelete */ false);
+        copyFile(
+            std::filesystem::path(source),
+            std::filesystem::path(target), false);
     } else {
         createDirs(dirOf(target));
         writeFile(target, "");
@@ -496,14 +503,26 @@ void LocalDerivationGoal::startBuilder()
             settings.thisSystem,
             concatStringsSep<StringSet>(", ", worker.store.systemFeatures));
 
-#if __APPLE__
-    additionalSandboxProfile = parsedDrv->getStringAttr("__sandboxProfile").value_or("");
-#endif
-
     /* Create a temporary directory where the build will take
        place. */
-    tmpDir = createTempDir(settings.buildDir.get().value_or(""), "nix-build-" + std::string(drvPath.name()), false, false, 0700);
-
+    topTmpDir = createTempDir(settings.buildDir.get().value_or(""), "nix-build-" + std::string(drvPath.name()), false, false, 0700);
+#if __APPLE__
+    if (false) {
+#else
+    if (useChroot) {
+#endif
+        /* If sandboxing is enabled, put the actual TMPDIR underneath
+           an inaccessible root-owned directory, to prevent outside
+           access.
+
+           On macOS, we don't use an actual chroot, so this isn't
+           possible. Any mitigation along these lines would have to be
+           done directly in the sandbox profile. */
+        tmpDir = topTmpDir + "/build";
+        createDir(tmpDir, 0700);
+    } else {
+        tmpDir = topTmpDir;
+    }
     chownToBuilder(tmpDir);
 
     for (auto & [outputName, status] : initialOutputs) {
@@ -671,15 +690,19 @@ void LocalDerivationGoal::startBuilder()
            environment using bind-mounts.  We put it in the Nix store
            so that the build outputs can be moved efficiently from the
            chroot to their final location. */
-        chrootRootDir = worker.store.Store::toRealPath(drvPath) + ".chroot";
-        deletePath(chrootRootDir);
+        chrootParentDir = worker.store.Store::toRealPath(drvPath) + ".chroot";
+        deletePath(chrootParentDir);
 
         /* Clean up the chroot directory automatically. */
-        autoDelChroot = std::make_shared<AutoDelete>(chrootRootDir);
+        autoDelChroot = std::make_shared<AutoDelete>(chrootParentDir);
 
-        printMsg(lvlChatty, "setting up chroot environment in '%1%'", chrootRootDir);
+        printMsg(lvlChatty, "setting up chroot environment in '%1%'", chrootParentDir);
+
+        if (mkdir(chrootParentDir.c_str(), 0700) == -1)
+            throw SysError("cannot create '%s'", chrootRootDir);
+
+        chrootRootDir = chrootParentDir + "/root";
 
-        // FIXME: make this 0700
         if (mkdir(chrootRootDir.c_str(), buildUser && buildUser->getUIDCount() != 1 ? 0755 : 0750) == -1)
             throw SysError("cannot create '%1%'", chrootRootDir);
 
@@ -1313,8 +1336,7 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual In
 
     StorePath addToStore(
         std::string_view name,
-        SourceAccessor & accessor,
-        const CanonPath & srcPath,
+        const SourcePath & srcPath,
         ContentAddressMethod method,
         HashAlgorithm hashAlgo,
         const StorePathSet & references,
@@ -1506,7 +1528,7 @@ void LocalDerivationGoal::startDaemon()
                 throw SysError("accepting connection");
             }
 
-            closeOnExec(remote.get());
+            unix::closeOnExec(remote.get());
 
             debug("received daemon connection");
 
@@ -1680,6 +1702,10 @@ void setupSeccomp()
         if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(fchmodat), 1,
                 SCMP_A2(SCMP_CMP_MASKED_EQ, (scmp_datum_t) perm, (scmp_datum_t) perm)) != 0)
             throw SysError("unable to add seccomp rule");
+
+        if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), NIX_SYSCALL_FCHMODAT2, 1,
+                SCMP_A2(SCMP_CMP_MASKED_EQ, (scmp_datum_t) perm, (scmp_datum_t) perm)) != 0)
+            throw SysError("unable to add seccomp rule");
     }
 
     /* Prevent builders from creating EAs or ACLs. Not all filesystems
@@ -1958,9 +1984,11 @@ void LocalDerivationGoal::runChild()
         std::set<int> fdsToKeep{STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO};
         if (authTunnel)
             fdsToKeep.insert(authTunnel->clientFd.get());
-        closeMostFDs(fdsToKeep);
+        unix::closeMostFDs(fdsToKeep);
 
-        setPersonality(drv->platform);
+#if __linux__
+        linux::setPersonality(drv->platform);
+#endif
 
         /* Disable core dumps by default. */
         struct rlimit limit = { 0, RLIM_INFINITY };
@@ -2488,24 +2516,23 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             /* FIXME optimize and deduplicate with addToStore */
             std::string oldHashPart { scratchPath->hashPart() };
             auto got = [&]{
-                PosixSourceAccessor accessor;
                 auto fim = outputHash.method.getFileIngestionMethod();
                 switch (fim) {
                 case FileIngestionMethod::Flat:
-                case FileIngestionMethod::Recursive:
+                case FileIngestionMethod::NixArchive:
                 {
                     HashModuloSink caSink { outputHash.hashAlgo, oldHashPart };
                     auto fim = outputHash.method.getFileIngestionMethod();
                     dumpPath(
-                        accessor, CanonPath { actualPath },
+                        {getFSSourceAccessor(), CanonPath(actualPath)},
                         caSink,
                         (FileSerialisationMethod) fim);
                     return caSink.finish().first;
                 }
                 case FileIngestionMethod::Git: {
                     return git::dumpHash(
-                        outputHash.hashAlgo, accessor,
-                        CanonPath { tmpDir + "/tmp" }).hash;
+                        outputHash.hashAlgo,
+                        {getFSSourceAccessor(), CanonPath(tmpDir + "/tmp")}).hash;
                 }
                 }
                 assert(false);
@@ -2532,10 +2559,9 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             }
 
             {
-                PosixSourceAccessor accessor;
                 HashResult narHashAndSize = hashPath(
-                    accessor, CanonPath { actualPath },
-                    FileSerialisationMethod::Recursive, HashAlgorithm::SHA256);
+                    {getFSSourceAccessor(), CanonPath(actualPath)},
+                    FileSerialisationMethod::NixArchive, HashAlgorithm::SHA256);
                 newInfo0.narHash = narHashAndSize.first;
                 newInfo0.narSize = narHashAndSize.second;
             }
@@ -2556,10 +2582,9 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
                         std::string { scratchPath->hashPart() },
                         std::string { requiredFinalPath.hashPart() });
                 rewriteOutput(outputRewrites);
-                PosixSourceAccessor accessor;
                 HashResult narHashAndSize = hashPath(
-                    accessor, CanonPath { actualPath },
-                    FileSerialisationMethod::Recursive, HashAlgorithm::SHA256);
+                    {getFSSourceAccessor(), CanonPath(actualPath)},
+                    FileSerialisationMethod::NixArchive, HashAlgorithm::SHA256);
                 ValidPathInfo newInfo0 { requiredFinalPath, narHashAndSize.first };
                 newInfo0.narSize = narHashAndSize.second;
                 auto refs = rewriteRefs();
@@ -2575,8 +2600,11 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
                 // Replace the output by a fresh copy of itself to make sure
                 // that there's no stale file descriptor pointing to it
                 Path tmpOutput = actualPath + ".tmp";
-                copyFile(actualPath, tmpOutput, true);
-                renameFile(tmpOutput, actualPath);
+                copyFile(
+                    std::filesystem::path(actualPath),
+                    std::filesystem::path(tmpOutput), true);
+
+                std::filesystem::rename(tmpOutput, actualPath);
 
                 auto newInfo0 = newInfoFromCA(DerivationOutput::CAFloating {
                     .method = dof.ca.method,
@@ -2906,6 +2934,24 @@ void LocalDerivationGoal::checkOutputs(const std::map<std::string, ValidPathInfo
         };
 
         if (auto structuredAttrs = parsedDrv->getStructuredAttrs()) {
+            if (get(*structuredAttrs, "allowedReferences")){
+                warn("'structuredAttrs' disables the effect of the top-level attribute 'allowedReferences'; use 'outputChecks' instead");
+            }
+            if (get(*structuredAttrs, "allowedRequisites")){
+                warn("'structuredAttrs' disables the effect of the top-level attribute 'allowedRequisites'; use 'outputChecks' instead");
+            }
+            if (get(*structuredAttrs, "disallowedRequisites")){
+                warn("'structuredAttrs' disables the effect of the top-level attribute 'disallowedRequisites'; use 'outputChecks' instead");
+            }
+            if (get(*structuredAttrs, "disallowedReferences")){
+                warn("'structuredAttrs' disables the effect of the top-level attribute 'disallowedReferences'; use 'outputChecks' instead");
+            }
+            if (get(*structuredAttrs, "maxSize")){
+                warn("'structuredAttrs' disables the effect of the top-level attribute 'maxSize'; use 'outputChecks' instead");
+            }
+            if (get(*structuredAttrs, "maxClosureSize")){
+                warn("'structuredAttrs' disables the effect of the top-level attribute 'maxClosureSize'; use 'outputChecks' instead");
+            }
             if (auto outputChecks = get(*structuredAttrs, "outputChecks")) {
                 if (auto output = get(*outputChecks, outputName)) {
                     Checks checks;
@@ -2954,7 +3000,7 @@ void LocalDerivationGoal::checkOutputs(const std::map<std::string, ValidPathInfo
 
 void LocalDerivationGoal::deleteTmpDir(bool force)
 {
-    if (tmpDir != "") {
+    if (topTmpDir != "") {
         /* Don't keep temporary directories for builtins because they
            might have privileged stuff. */
         if (settings.keepFailed && !force && !drv->isBuiltin()) {
@@ -2962,7 +3008,8 @@ void LocalDerivationGoal::deleteTmpDir(bool force)
             chmod(tmpDir.c_str(), 0755);
         }
         else
-            deletePath(tmpDir);
+            deletePath(topTmpDir);
+        topTmpDir = "";
         tmpDir = "";
     }
 }
diff --git a/src/libstore/unix/build/local-derivation-goal.hh b/src/libstore/unix/build/local-derivation-goal.hh
index 07bc3cd70ec..523e633148f 100644
--- a/src/libstore/unix/build/local-derivation-goal.hh
+++ b/src/libstore/unix/build/local-derivation-goal.hh
@@ -29,10 +29,16 @@ struct LocalDerivationGoal : public DerivationGoal
     std::optional<Path> cgroup;
 
     /**
-     * The temporary directory.
+     * The temporary directory used for the build.
      */
     Path tmpDir;
 
+    /**
+     * The top-level temporary directory. `tmpDir` is either equal to
+     * or a child of this directory.
+     */
+    Path topTmpDir;
+
     /**
      * The path of the temporary directory in the sandbox.
      */
@@ -67,6 +73,16 @@ struct LocalDerivationGoal : public DerivationGoal
      */
     bool useChroot = false;
 
+    /**
+     * The parent directory of `chrootRootDir`. It has permission 700
+     * and is owned by root to ensure other users cannot mess with
+     * `chrootRootDir`.
+     */
+    Path chrootParentDir;
+
+    /**
+     * The root of the chroot environment.
+     */
     Path chrootRootDir;
 
     /**
diff --git a/src/libstore/unix/build/sandbox-defaults.sb b/src/libstore/unix/build/sandbox-defaults.sb
index 2ad5fb616fd..6da01b7356b 100644
--- a/src/libstore/unix/build/sandbox-defaults.sb
+++ b/src/libstore/unix/build/sandbox-defaults.sb
@@ -17,6 +17,9 @@ R""(
 ; Allow POSIX semaphores and shared memory.
 (allow ipc-posix*)
 
+; Allow SYSV semaphores and shared memory.
+(allow ipc-sysv*)
+
 ; Allow socket creation.
 (allow system-socket)
 
diff --git a/src/libstore/unix/meson.build b/src/libstore/unix/meson.build
new file mode 100644
index 00000000000..d9d19013107
--- /dev/null
+++ b/src/libstore/unix/meson.build
@@ -0,0 +1,19 @@
+sources += files(
+  'build/child.cc',
+  'build/hook-instance.cc',
+  'build/local-derivation-goal.cc',
+  'pathlocks.cc',
+  'user-lock.cc',
+)
+
+include_dirs += include_directories(
+  '.',
+  'build',
+)
+
+headers += files(
+  'build/child.hh',
+  'build/hook-instance.hh',
+  'build/local-derivation-goal.hh',
+  'user-lock.hh',
+)
diff --git a/src/libstore/unix/pathlocks-impl.hh b/src/libstore/unix/pathlocks-impl.hh
deleted file mode 100644
index 31fe968bbb1..00000000000
--- a/src/libstore/unix/pathlocks-impl.hh
+++ /dev/null
@@ -1,38 +0,0 @@
-#pragma once
-///@file
-
-#include "file-descriptor.hh"
-
-namespace nix::unix {
-
-/**
- * Open (possibly create) a lock file and return the file descriptor.
- * -1 is returned if create is false and the lock could not be opened
- * because it doesn't exist.  Any other error throws an exception.
- */
-AutoCloseFD openLockFile(const Path & path, bool create);
-
-/**
- * Delete an open lock file.
- */
-void deleteLockFile(const Path & path, int fd);
-
-enum LockType { ltRead, ltWrite, ltNone };
-
-bool lockFile(int fd, LockType lockType, bool wait);
-
-struct FdLock
-{
-    int fd;
-    bool acquired = false;
-
-    FdLock(int fd, LockType lockType, bool wait, std::string_view waitMsg);
-
-    ~FdLock()
-    {
-        if (acquired)
-            lockFile(fd, ltNone, false);
-    }
-};
-
-}
diff --git a/src/libstore/unix/pathlocks.cc b/src/libstore/unix/pathlocks.cc
index 32c1b9ff44a..af21319a758 100644
--- a/src/libstore/unix/pathlocks.cc
+++ b/src/libstore/unix/pathlocks.cc
@@ -14,9 +14,7 @@
 
 namespace nix {
 
-using namespace nix::unix;
-
-AutoCloseFD unix::openLockFile(const Path & path, bool create)
+AutoCloseFD openLockFile(const Path & path, bool create)
 {
     AutoCloseFD fd;
 
@@ -28,20 +26,20 @@ AutoCloseFD unix::openLockFile(const Path & path, bool create)
 }
 
 
-void unix::deleteLockFile(const Path & path, int fd)
+void deleteLockFile(const Path & path, Descriptor desc)
 {
     /* Get rid of the lock file.  Have to be careful not to introduce
        races.  Write a (meaningless) token to the file to indicate to
        other processes waiting on this lock that the lock is stale
        (deleted). */
     unlink(path.c_str());
-    writeFull(fd, "d");
+    writeFull(desc, "d");
     /* Note that the result of unlink() is ignored; removing the lock
        file is an optimisation, not a necessity. */
 }
 
 
-bool unix::lockFile(int fd, LockType lockType, bool wait)
+bool lockFile(Descriptor desc, LockType lockType, bool wait)
 {
     int type;
     if (lockType == ltRead) type = LOCK_SH;
@@ -50,7 +48,7 @@ bool unix::lockFile(int fd, LockType lockType, bool wait)
     else abort();
 
     if (wait) {
-        while (flock(fd, type) != 0) {
+        while (flock(desc, type) != 0) {
             checkInterrupt();
             if (errno != EINTR)
                 throw SysError("acquiring/releasing lock");
@@ -58,7 +56,7 @@ bool unix::lockFile(int fd, LockType lockType, bool wait)
                 return false;
         }
     } else {
-        while (flock(fd, type | LOCK_NB) != 0) {
+        while (flock(desc, type | LOCK_NB) != 0) {
             checkInterrupt();
             if (errno == EWOULDBLOCK) return false;
             if (errno != EINTR)
@@ -149,16 +147,16 @@ void PathLocks::unlock()
 }
 
 
-FdLock::FdLock(int fd, LockType lockType, bool wait, std::string_view waitMsg)
-    : fd(fd)
+FdLock::FdLock(Descriptor desc, LockType lockType, bool wait, std::string_view waitMsg)
+    : desc(desc)
 {
     if (wait) {
-        if (!lockFile(fd, lockType, false)) {
+        if (!lockFile(desc, lockType, false)) {
             printInfo("%s", waitMsg);
-            acquired = lockFile(fd, lockType, true);
+            acquired = lockFile(desc, lockType, true);
         }
     } else
-        acquired = lockFile(fd, lockType, false);
+        acquired = lockFile(desc, lockType, false);
 }
 
 
diff --git a/src/libstore/unix/lock.cc b/src/libstore/unix/user-lock.cc
similarity index 99%
rename from src/libstore/unix/lock.cc
rename to src/libstore/unix/user-lock.cc
index fd7af171fca..8057aa13e1b 100644
--- a/src/libstore/unix/lock.cc
+++ b/src/libstore/unix/user-lock.cc
@@ -1,4 +1,4 @@
-#include "lock.hh"
+#include "user-lock.hh"
 #include "file-system.hh"
 #include "globals.hh"
 #include "pathlocks.hh"
@@ -9,8 +9,6 @@
 
 namespace nix {
 
-using namespace nix::unix;
-
 #if __linux__
 
 static std::vector<gid_t> get_group_list(const char *username, gid_t group_id)
diff --git a/src/libstore/unix/lock.hh b/src/libstore/unix/user-lock.hh
similarity index 100%
rename from src/libstore/unix/lock.hh
rename to src/libstore/unix/user-lock.hh
diff --git a/src/libstore/windows/build.cc b/src/libstore/windows/build.cc
deleted file mode 100644
index 3eadc5bdaf3..00000000000
--- a/src/libstore/windows/build.cc
+++ /dev/null
@@ -1,37 +0,0 @@
-#include "store-api.hh"
-#include "build-result.hh"
-
-namespace nix {
-
-void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMode, std::shared_ptr<Store> evalStore)
-{
-    unsupported("buildPaths");
-}
-
-std::vector<KeyedBuildResult> Store::buildPathsWithResults(
-    const std::vector<DerivedPath> & reqs,
-    BuildMode buildMode,
-    std::shared_ptr<Store> evalStore)
-{
-    unsupported("buildPathsWithResults");
-}
-
-BuildResult Store::buildDerivation(const StorePath & drvPath, const BasicDerivation & drv,
-    BuildMode buildMode)
-{
-    unsupported("buildDerivation");
-}
-
-
-void Store::ensurePath(const StorePath & path)
-{
-    unsupported("ensurePath");
-}
-
-
-void Store::repairPath(const StorePath & path)
-{
-    unsupported("repairPath");
-}
-
-}
diff --git a/src/libstore/windows/meson.build b/src/libstore/windows/meson.build
new file mode 100644
index 00000000000..b81c5b2afa7
--- /dev/null
+++ b/src/libstore/windows/meson.build
@@ -0,0 +1,11 @@
+sources += files(
+  'pathlocks.cc',
+)
+
+include_dirs += include_directories(
+  '.',
+  #'build',
+)
+
+headers += files(
+)
diff --git a/src/libstore/windows/pathlocks-impl.hh b/src/libstore/windows/pathlocks-impl.hh
deleted file mode 100644
index ba3ad28d948..00000000000
--- a/src/libstore/windows/pathlocks-impl.hh
+++ /dev/null
@@ -1,2 +0,0 @@
-#pragma once
-///@file Needed because Unix-specific counterpart
diff --git a/src/libstore/windows/pathlocks.cc b/src/libstore/windows/pathlocks.cc
index ab4294c2ab0..00761a8c33c 100644
--- a/src/libstore/windows/pathlocks.cc
+++ b/src/libstore/windows/pathlocks.cc
@@ -1,16 +1,156 @@
 #include "logging.hh"
 #include "pathlocks.hh"
+#include "signals.hh"
+#include "util.hh"
+#include <errhandlingapi.h>
+#include <fileapi.h>
+#include <windows.h>
+#include "windows-error.hh"
 
 namespace nix {
 
-bool PathLocks::lockPaths(const PathSet & _paths, const std::string & waitMsg, bool wait)
+using namespace nix::windows;
+
+void deleteLockFile(const Path & path, Descriptor desc)
 {
-    return true;
+
+    int exit = DeleteFileA(path.c_str());
+    if (exit == 0)
+        warn("%s: &s", path, std::to_string(GetLastError()));
 }
 
 void PathLocks::unlock()
 {
-    warn("PathLocks::unlock: not yet implemented");
+    for (auto & i : fds) {
+        if (deletePaths)
+            deleteLockFile(i.second, i.first);
+
+        if (CloseHandle(i.first) == -1)
+            printError("error (ignored): cannot close lock file on '%1%'", i.second);
+
+        debug("lock released on '%1%'", i.second);
+    }
+
+    fds.clear();
+}
+
+AutoCloseFD openLockFile(const Path & path, bool create)
+{
+    AutoCloseFD desc = CreateFileA(
+        path.c_str(),
+        GENERIC_READ | GENERIC_WRITE,
+        FILE_SHARE_READ | FILE_SHARE_WRITE,
+        NULL,
+        create ? OPEN_ALWAYS : OPEN_EXISTING,
+        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_POSIX_SEMANTICS,
+        NULL);
+    if (desc.get() == INVALID_HANDLE_VALUE)
+        warn("%s: %s", path, std::to_string(GetLastError()));
+
+    return desc;
+}
+
+bool lockFile(Descriptor desc, LockType lockType, bool wait)
+{
+    switch (lockType) {
+    case ltNone: {
+        OVERLAPPED ov = {0};
+        if (!UnlockFileEx(desc, 0, 2, 0, &ov)) {
+            WinError winError("Failed to unlock file desc %s", desc);
+            throw winError;
+        }
+        return true;
+    }
+    case ltRead: {
+        OVERLAPPED ov = {0};
+        if (!LockFileEx(desc, wait ? 0 : LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &ov)) {
+            WinError winError("Failed to lock file desc %s", desc);
+            if (winError.lastError == ERROR_LOCK_VIOLATION)
+                return false;
+            throw winError;
+        }
+
+        ov.Offset = 1;
+        if (!UnlockFileEx(desc, 0, 1, 0, &ov)) {
+            WinError winError("Failed to unlock file desc %s", desc);
+            if (winError.lastError != ERROR_NOT_LOCKED)
+                throw winError;
+        }
+        return true;
+    }
+    case ltWrite: {
+        OVERLAPPED ov = {0};
+        ov.Offset = 1;
+        if (!LockFileEx(desc, LOCKFILE_EXCLUSIVE_LOCK | (wait ? 0 : LOCKFILE_FAIL_IMMEDIATELY), 0, 1, 0, &ov)) {
+            WinError winError("Failed to lock file desc %s", desc);
+            if (winError.lastError == ERROR_LOCK_VIOLATION)
+                return false;
+            throw winError;
+        }
+
+        ov.Offset = 0;
+        if (!UnlockFileEx(desc, 0, 1, 0, &ov)) {
+            WinError winError("Failed to unlock file desc %s", desc);
+            if (winError.lastError != ERROR_NOT_LOCKED)
+                throw winError;
+        }
+        return true;
+    }
+    default:
+        assert(false);
+    }
+}
+
+bool PathLocks::lockPaths(const PathSet & paths, const std::string & waitMsg, bool wait)
+{
+    assert(fds.empty());
+
+    for (auto & path : paths) {
+        checkInterrupt();
+        Path lockPath = path + ".lock";
+        debug("locking path '%1%'", path);
+
+        AutoCloseFD fd;
+
+        while (1) {
+            fd = openLockFile(lockPath, true);
+            if (!lockFile(fd.get(), ltWrite, false)) {
+                if (wait) {
+                    if (waitMsg != "")
+                        printError(waitMsg);
+                    lockFile(fd.get(), ltWrite, true);
+                } else {
+                    unlock();
+                    return false;
+                }
+            }
+
+            debug("lock aquired on '%1%'", lockPath);
+
+            struct _stat st;
+            if (_fstat(fromDescriptorReadOnly(fd.get()), &st) == -1)
+                throw SysError("statting lock file '%1%'", lockPath);
+            if (st.st_size != 0)
+                debug("open lock file '%1%' has become stale", lockPath);
+            else
+                break;
+        }
+
+        fds.push_back(FDPair(fd.release(), lockPath));
+    }
+    return true;
+}
+
+FdLock::FdLock(Descriptor desc, LockType lockType, bool wait, std::string_view waitMsg)
+    : desc(desc)
+{
+    if (wait) {
+        if (!lockFile(desc, lockType, false)) {
+            printInfo("%s", waitMsg);
+            acquired = lockFile(desc, lockType, true);
+        }
+    } else
+        acquired = lockFile(desc, lockType, false);
 }
 
 }
diff --git a/src/libstore/worker-protocol-connection.cc b/src/libstore/worker-protocol-connection.cc
new file mode 100644
index 00000000000..072bae8da82
--- /dev/null
+++ b/src/libstore/worker-protocol-connection.cc
@@ -0,0 +1,280 @@
+#include "worker-protocol-connection.hh"
+#include "worker-protocol-impl.hh"
+#include "build-result.hh"
+#include "derivations.hh"
+
+namespace nix {
+
+WorkerProto::BasicClientConnection::~BasicClientConnection()
+{
+    try {
+        to.flush();
+    } catch (...) {
+        ignoreException();
+    }
+}
+
+static Logger::Fields readFields(Source & from)
+{
+    Logger::Fields fields;
+    size_t size = readInt(from);
+    for (size_t n = 0; n < size; n++) {
+        auto type = (decltype(Logger::Field::type)) readInt(from);
+        if (type == Logger::Field::tInt)
+            fields.push_back(readNum<uint64_t>(from));
+        else if (type == Logger::Field::tString)
+            fields.push_back(readString(from));
+        else
+            throw Error("got unsupported field type %x from Nix daemon", (int) type);
+    }
+    return fields;
+}
+
+std::exception_ptr WorkerProto::BasicClientConnection::processStderrReturn(Sink * sink, Source * source, bool flush)
+{
+    if (flush)
+        to.flush();
+
+    std::exception_ptr ex;
+
+    while (true) {
+
+        auto msg = readNum<uint64_t>(from);
+
+        if (msg == STDERR_WRITE) {
+            auto s = readString(from);
+            if (!sink)
+                throw Error("no sink");
+            (*sink)(s);
+        }
+
+        else if (msg == STDERR_READ) {
+            if (!source)
+                throw Error("no source");
+            size_t len = readNum<size_t>(from);
+            auto buf = std::make_unique<char[]>(len);
+            writeString({(const char *) buf.get(), source->read(buf.get(), len)}, to);
+            to.flush();
+        }
+
+        else if (msg == STDERR_ERROR) {
+            if (GET_PROTOCOL_MINOR(daemonVersion) >= 26) {
+                ex = std::make_exception_ptr(readError(from));
+            } else {
+                auto error = readString(from);
+                unsigned int status = readInt(from);
+                ex = std::make_exception_ptr(Error(status, error));
+            }
+            break;
+        }
+
+        else if (msg == STDERR_NEXT)
+            printError(chomp(readString(from)));
+
+        else if (msg == STDERR_START_ACTIVITY) {
+            auto act = readNum<ActivityId>(from);
+            auto lvl = (Verbosity) readInt(from);
+            auto type = (ActivityType) readInt(from);
+            auto s = readString(from);
+            auto fields = readFields(from);
+            auto parent = readNum<ActivityId>(from);
+            logger->startActivity(act, lvl, type, s, fields, parent);
+        }
+
+        else if (msg == STDERR_STOP_ACTIVITY) {
+            auto act = readNum<ActivityId>(from);
+            logger->stopActivity(act);
+        }
+
+        else if (msg == STDERR_RESULT) {
+            auto act = readNum<ActivityId>(from);
+            auto type = (ResultType) readInt(from);
+            auto fields = readFields(from);
+            logger->result(act, type, fields);
+        }
+
+        else if (msg == STDERR_LAST)
+            break;
+
+        else
+            throw Error("got unknown message type %x from Nix daemon", msg);
+    }
+
+    if (!ex) {
+        return ex;
+    } else {
+        try {
+            std::rethrow_exception(ex);
+        } catch (const Error & e) {
+            // Nix versions before #4628 did not have an adequate
+            // behavior for reporting that the derivation format was
+            // upgraded. To avoid having to add compatibility logic in
+            // many places, we expect to catch almost all occurrences of
+            // the old incomprehensible error here, so that we can
+            // explain to users what's going on when their daemon is
+            // older than #4628 (2023).
+            if (experimentalFeatureSettings.isEnabled(Xp::DynamicDerivations)
+                && GET_PROTOCOL_MINOR(daemonVersion) <= 35) {
+                auto m = e.msg();
+                if (m.find("parsing derivation") != std::string::npos && m.find("expected string") != std::string::npos
+                    && m.find("Derive([") != std::string::npos)
+                    return std::make_exception_ptr(Error(
+                        "%s, this might be because the daemon is too old to understand dependencies on dynamic derivations. Check to see if the raw derivation is in the form '%s'",
+                        std::move(m),
+                        "Drv WithVersion(..)"));
+            }
+            return std::current_exception();
+        }
+    }
+}
+
+void WorkerProto::BasicClientConnection::processStderr(bool * daemonException, Sink * sink, Source * source, bool flush)
+{
+    auto ex = processStderrReturn(sink, source, flush);
+    if (ex) {
+        *daemonException = true;
+        std::rethrow_exception(ex);
+    }
+}
+
+WorkerProto::Version
+WorkerProto::BasicClientConnection::handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion)
+{
+    to << WORKER_MAGIC_1 << localVersion;
+    to.flush();
+
+    unsigned int magic = readInt(from);
+    if (magic != WORKER_MAGIC_2)
+        throw Error("nix-daemon protocol mismatch from");
+    auto daemonVersion = readInt(from);
+
+    if (GET_PROTOCOL_MAJOR(daemonVersion) != GET_PROTOCOL_MAJOR(PROTOCOL_VERSION))
+        throw Error("Nix daemon protocol version not supported");
+    if (GET_PROTOCOL_MINOR(daemonVersion) < 10)
+        throw Error("the Nix daemon version is too old");
+    to << localVersion;
+
+    return std::min(daemonVersion, localVersion);
+}
+
+WorkerProto::Version
+WorkerProto::BasicServerConnection::handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion)
+{
+    unsigned int magic = readInt(from);
+    if (magic != WORKER_MAGIC_1)
+        throw Error("protocol mismatch");
+    to << WORKER_MAGIC_2 << localVersion;
+    to.flush();
+    auto clientVersion = readInt(from);
+    return std::min(clientVersion, localVersion);
+}
+
+WorkerProto::ClientHandshakeInfo WorkerProto::BasicClientConnection::postHandshake(const StoreDirConfig & store)
+{
+    WorkerProto::ClientHandshakeInfo res;
+
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 14) {
+        // Obsolete CPU affinity.
+        to << 0;
+    }
+
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 11)
+        to << false; // obsolete reserveSpace
+
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 33)
+        to.flush();
+
+    return WorkerProto::Serialise<ClientHandshakeInfo>::read(store, *this);
+}
+
+void WorkerProto::BasicServerConnection::postHandshake(const StoreDirConfig & store, const ClientHandshakeInfo & info)
+{
+    if (GET_PROTOCOL_MINOR(clientVersion) >= 14 && readInt(from)) {
+        // Obsolete CPU affinity.
+        readInt(from);
+    }
+
+    if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
+        readInt(from); // obsolete reserveSpace
+
+    WorkerProto::write(store, *this, info);
+}
+
+UnkeyedValidPathInfo WorkerProto::BasicClientConnection::queryPathInfo(
+    const StoreDirConfig & store, bool * daemonException, const StorePath & path)
+{
+    to << WorkerProto::Op::QueryPathInfo << store.printStorePath(path);
+    try {
+        processStderr(daemonException);
+    } catch (Error & e) {
+        // Ugly backwards compatibility hack.
+        if (e.msg().find("is not valid") != std::string::npos)
+            throw InvalidPath(std::move(e.info()));
+        throw;
+    }
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 17) {
+        bool valid;
+        from >> valid;
+        if (!valid)
+            throw InvalidPath("path '%s' is not valid", store.printStorePath(path));
+    }
+    return WorkerProto::Serialise<UnkeyedValidPathInfo>::read(store, *this);
+}
+
+StorePathSet WorkerProto::BasicClientConnection::queryValidPaths(
+    const StoreDirConfig & store, bool * daemonException, const StorePathSet & paths, SubstituteFlag maybeSubstitute)
+{
+    assert(GET_PROTOCOL_MINOR(daemonVersion) >= 12);
+    to << WorkerProto::Op::QueryValidPaths;
+    WorkerProto::write(store, *this, paths);
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 27) {
+        to << maybeSubstitute;
+    }
+    processStderr(daemonException);
+    return WorkerProto::Serialise<StorePathSet>::read(store, *this);
+}
+
+void WorkerProto::BasicClientConnection::addTempRoot(
+    const StoreDirConfig & store, bool * daemonException, const StorePath & path)
+{
+    to << WorkerProto::Op::AddTempRoot << store.printStorePath(path);
+    processStderr(daemonException);
+    readInt(from);
+}
+
+void WorkerProto::BasicClientConnection::putBuildDerivationRequest(
+    const StoreDirConfig & store,
+    bool * daemonException,
+    const StorePath & drvPath,
+    const BasicDerivation & drv,
+    BuildMode buildMode)
+{
+    to << WorkerProto::Op::BuildDerivation << store.printStorePath(drvPath);
+    writeDerivation(to, store, drv);
+    to << buildMode;
+}
+
+BuildResult
+WorkerProto::BasicClientConnection::getBuildDerivationResponse(const StoreDirConfig & store, bool * daemonException)
+{
+    return WorkerProto::Serialise<BuildResult>::read(store, *this);
+}
+
+void WorkerProto::BasicClientConnection::narFromPath(
+    const StoreDirConfig & store, bool * daemonException, const StorePath & path, std::function<void(Source &)> fun)
+{
+    to << WorkerProto::Op::NarFromPath << store.printStorePath(path);
+    processStderr(daemonException);
+
+    fun(from);
+}
+
+void WorkerProto::BasicClientConnection::importPaths(
+    const StoreDirConfig & store, bool * daemonException, Source & source)
+{
+    to << WorkerProto::Op::ImportPaths;
+    processStderr(daemonException, 0, &source);
+    auto importedPaths = WorkerProto::Serialise<StorePathSet>::read(store, *this);
+    assert(importedPaths.size() <= importedPaths.size());
+}
+}
diff --git a/src/libstore/worker-protocol-connection.hh b/src/libstore/worker-protocol-connection.hh
new file mode 100644
index 00000000000..9dd723fd089
--- /dev/null
+++ b/src/libstore/worker-protocol-connection.hh
@@ -0,0 +1,187 @@
+#pragma once
+///@file
+
+#include "worker-protocol.hh"
+#include "store-api.hh"
+
+namespace nix {
+
+struct WorkerProto::BasicClientConnection
+{
+    /**
+     * Send with this.
+     */
+    FdSink to;
+
+    /**
+     * Receive with this.
+     */
+    FdSource from;
+
+    /**
+     * Worker protocol version used for the connection.
+     *
+     * Despite its name, it is actually the maximum version both
+     * sides support. (If the maximum doesn't exist, we would fail to
+     * establish a connection and produce a value of this type.)
+     */
+    WorkerProto::Version daemonVersion;
+
+    /**
+     * Flush to direction
+     */
+    virtual ~BasicClientConnection();
+
+    virtual void closeWrite() = 0;
+
+    std::exception_ptr processStderrReturn(Sink * sink = 0, Source * source = 0, bool flush = true);
+
+    void processStderr(bool * daemonException, Sink * sink = 0, Source * source = 0, bool flush = true);
+
+    /**
+     * Establishes connection, negotiating version.
+     *
+     * @return the version provided by the other side of the
+     * connection.
+     *
+     * @param to Taken by reference to allow for various error handling
+     * mechanisms.
+     *
+     * @param from Taken by reference to allow for various error
+     * handling mechanisms.
+     *
+     * @param localVersion Our version which is sent over
+     */
+    static Version handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion);
+
+    /**
+     * After calling handshake, must call this to exchange some basic
+     * information abou the connection.
+     */
+    ClientHandshakeInfo postHandshake(const StoreDirConfig & store);
+
+    /**
+     * Coercion to `WorkerProto::ReadConn`. This makes it easy to use the
+     * factored out serve protocol serializers with a
+     * `LegacySSHStore::Connection`.
+     *
+     * The serve protocol connection types are unidirectional, unlike
+     * this type.
+     */
+    operator WorkerProto::ReadConn()
+    {
+        return WorkerProto::ReadConn{
+            .from = from,
+            .version = daemonVersion,
+        };
+    }
+
+    /**
+     * Coercion to `WorkerProto::WriteConn`. This makes it easy to use the
+     * factored out serve protocol serializers with a
+     * `LegacySSHStore::Connection`.
+     *
+     * The serve protocol connection types are unidirectional, unlike
+     * this type.
+     */
+    operator WorkerProto::WriteConn()
+    {
+        return WorkerProto::WriteConn{
+            .to = to,
+            .version = daemonVersion,
+        };
+    }
+
+    void addTempRoot(const StoreDirConfig & remoteStore, bool * daemonException, const StorePath & path);
+
+    StorePathSet queryValidPaths(
+        const StoreDirConfig & remoteStore,
+        bool * daemonException,
+        const StorePathSet & paths,
+        SubstituteFlag maybeSubstitute);
+
+    UnkeyedValidPathInfo queryPathInfo(const StoreDirConfig & store, bool * daemonException, const StorePath & path);
+
+    void putBuildDerivationRequest(
+        const StoreDirConfig & store,
+        bool * daemonException,
+        const StorePath & drvPath,
+        const BasicDerivation & drv,
+        BuildMode buildMode);
+
+    /**
+     * Get the response, must be paired with
+     * `putBuildDerivationRequest`.
+     */
+    BuildResult getBuildDerivationResponse(const StoreDirConfig & store, bool * daemonException);
+
+    void narFromPath(
+        const StoreDirConfig & store,
+        bool * daemonException,
+        const StorePath & path,
+        std::function<void(Source &)> fun);
+
+    void importPaths(const StoreDirConfig & store, bool * daemonException, Source & source);
+};
+
+struct WorkerProto::BasicServerConnection
+{
+    /**
+     * Send with this.
+     */
+    FdSink & to;
+
+    /**
+     * Receive with this.
+     */
+    FdSource & from;
+
+    /**
+     * Worker protocol version used for the connection.
+     *
+     * Despite its name, it is actually the maximum version both
+     * sides support. (If the maximum doesn't exist, we would fail to
+     * establish a connection and produce a value of this type.)
+     */
+    WorkerProto::Version clientVersion;
+
+    operator WorkerProto::ReadConn()
+    {
+        return WorkerProto::ReadConn{
+            .from = from,
+            .version = clientVersion,
+        };
+    }
+
+    operator WorkerProto::WriteConn()
+    {
+        return WorkerProto::WriteConn{
+            .to = to,
+            .version = clientVersion,
+        };
+    }
+
+    /**
+     * Establishes connection, negotiating version.
+     *
+     * @return the version provided by the other side of the
+     * connection.
+     *
+     * @param to Taken by reference to allow for various error handling
+     * mechanisms.
+     *
+     * @param from Taken by reference to allow for various error
+     * handling mechanisms.
+     *
+     * @param localVersion Our version which is sent over
+     */
+    static WorkerProto::Version handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion);
+
+    /**
+     * After calling handshake, must call this to exchange some basic
+     * information abou the connection.
+     */
+    void postHandshake(const StoreDirConfig & store, const ClientHandshakeInfo & info);
+};
+
+}
diff --git a/src/libstore/worker-protocol.cc b/src/libstore/worker-protocol.cc
index 03b471baa51..af0eec159d5 100644
--- a/src/libstore/worker-protocol.cc
+++ b/src/libstore/worker-protocol.cc
@@ -43,6 +43,34 @@ void writeOptional(const StoreDirConfig & store, WorkerProto::WriteConn conn, co
 
 /* protocol-specific definitions */
 
+BuildMode WorkerProto::Serialise<BuildMode>::read(const StoreDirConfig & store, WorkerProto::ReadConn conn)
+{
+    auto temp = readNum<uint8_t>(conn.from);
+    switch (temp) {
+    case 0: return bmNormal;
+    case 1: return bmRepair;
+    case 2: return bmCheck;
+    default: throw Error("Invalid build mode");
+    }
+}
+
+void WorkerProto::Serialise<BuildMode>::write(const StoreDirConfig & store, WorkerProto::WriteConn conn, const BuildMode & buildMode)
+{
+    switch (buildMode) {
+    case bmNormal:
+        conn.to << uint8_t{0};
+        break;
+    case bmRepair:
+        conn.to << uint8_t{1};
+        break;
+    case bmCheck:
+        conn.to << uint8_t{2};
+        break;
+    default:
+        assert(false);
+    };
+}
+
 std::optional<TrustedFlag> WorkerProto::Serialise<std::optional<TrustedFlag>>::read(const StoreDirConfig & store, WorkerProto::ReadConn conn)
 {
     auto temp = readNum<uint8_t>(conn.from);
@@ -251,6 +279,35 @@ void WorkerProto::Serialise<UnkeyedValidPathInfo>::write(const StoreDirConfig &
     }
 }
 
+WorkerProto::ClientHandshakeInfo WorkerProto::Serialise<WorkerProto::ClientHandshakeInfo>::read(const StoreDirConfig & store, ReadConn conn)
+{
+    WorkerProto::ClientHandshakeInfo res;
+
+    if (GET_PROTOCOL_MINOR(conn.version) >= 33) {
+        res.daemonNixVersion = readString(conn.from);
+    }
+
+    if (GET_PROTOCOL_MINOR(conn.version) >= 35) {
+        res.remoteTrustsUs = WorkerProto::Serialise<std::optional<    TrustedFlag>>::read(store, conn);
+    } else {
+        // We don't know the answer; protocol to old.
+        res.remoteTrustsUs = std::nullopt;
+    }
+
+    return res;
+}
+
+void WorkerProto::Serialise<WorkerProto::ClientHandshakeInfo>::write(const StoreDirConfig & store, WriteConn conn, const WorkerProto::ClientHandshakeInfo & info)
+{
+    if (GET_PROTOCOL_MINOR(conn.version) >= 33) {
+        assert(info.daemonNixVersion);
+        conn.to << *info.daemonNixVersion;
+    }
+
+    if (GET_PROTOCOL_MINOR(conn.version) >= 35) {
+        WorkerProto::write(store, conn, info.remoteTrustsUs);
+    }
+}
 
 auth::AuthData WorkerProto::Serialise<auth::AuthData>::read(const StoreDirConfig & store, ReadConn conn)
 {
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index 7ab3362da6c..e56a1a56ed5 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -35,8 +35,9 @@ struct BuildResult;
 struct KeyedBuildResult;
 struct ValidPathInfo;
 struct UnkeyedValidPathInfo;
-namespace auth { struct AuthData; }
+enum BuildMode : uint8_t;
 enum TrustedFlag : bool;
+namespace auth { struct AuthData; }
 
 
 /**
@@ -82,6 +83,19 @@ struct WorkerProto
         Version version;
     };
 
+    /**
+     * Stripped down serialization logic suitable for sharing with Hydra.
+     *
+     * @todo remove once Hydra uses Store abstraction consistently.
+     */
+    struct BasicClientConnection;
+    struct BasicServerConnection;
+
+    /**
+     * Extra information provided as part of protocol negotation.
+     */
+    struct ClientHandshakeInfo;
+
     /**
      * Data type for canonical pairs of serialisers for the worker protocol.
      *
@@ -173,6 +187,33 @@ enum struct WorkerProto::Op : uint64_t
     InitCallback = 48,
 };
 
+struct WorkerProto::ClientHandshakeInfo
+{
+    /**
+     * The version of the Nix daemon that is processing our requests
+.
+     *
+     * Do note, it may or may not communicating with another daemon,
+     * rather than being an "end" `LocalStore` or similar.
+     */
+    std::optional<std::string> daemonNixVersion;
+
+    /**
+     * Whether the remote side trusts us or not.
+     *
+     * 3 values: "yes", "no", or `std::nullopt` for "unknown".
+     *
+     * Note that the "remote side" might not be just the end daemon, but
+     * also an intermediary forwarder that can make its own trusting
+     * decisions. This would be the intersection of all their trust
+     * decisions, since it takes only one link in the chain to start
+     * denying operations.
+     */
+    std::optional<TrustedFlag> remoteTrustsUs;
+
+    bool operator == (const ClientHandshakeInfo &) const = default;
+};
+
 /**
  * Convenience for sending operation codes.
  *
@@ -228,10 +269,14 @@ DECLARE_WORKER_SERIALISER(ValidPathInfo);
 template<>
 DECLARE_WORKER_SERIALISER(UnkeyedValidPathInfo);
 template<>
+DECLARE_WORKER_SERIALISER(BuildMode);
+template<>
 DECLARE_WORKER_SERIALISER(std::optional<TrustedFlag>);
 template<>
 DECLARE_WORKER_SERIALISER(std::optional<std::chrono::microseconds>);
 template<>
+DECLARE_WORKER_SERIALISER(WorkerProto::ClientHandshakeInfo);
+template<>
 DECLARE_WORKER_SERIALISER(auth::AuthData);
 template<>
 DECLARE_WORKER_SERIALISER(std::optional<auth::AuthData>);
diff --git a/src/libutil-c/.version b/src/libutil-c/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libutil-c/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libutil-c/build-utils-meson b/src/libutil-c/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libutil-c/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libutil-c/meson.build b/src/libutil-c/meson.build
new file mode 100644
index 00000000000..3f0d9628201
--- /dev/null
+++ b/src/libutil-c/meson.build
@@ -0,0 +1,79 @@
+project('nix-util-c', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+# TODO rename, because it will conflict with downstream projects
+configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-util.h',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+
+  # From C++ libraries, only for internals
+  '-include', 'config-util.hh',
+
+  # From C libraries, for our public, installed headers too
+  '-include', 'config-util.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'nix_api_util.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'nix_api_util.h',
+)
+
+# TODO don't install this once tests don't use it.
+headers += files('nix_api_util_internal.h')
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nixutilc',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/src/libutil-c/meson.options b/src/libutil-c/meson.options
new file mode 100644
index 00000000000..04422feaf18
--- /dev/null
+++ b/src/libutil-c/meson.options
@@ -0,0 +1 @@
+# vim: filetype=meson
diff --git a/src/libutil-c/nix-util-c.pc.in b/src/libutil-c/nix-util-c.pc.in
new file mode 100644
index 00000000000..0ccae3f8a14
--- /dev/null
+++ b/src/libutil-c/nix-util-c.pc.in
@@ -0,0 +1,9 @@
+prefix=@prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: Nix libutil C API
+Description: Common functions for the Nix C API, such as error handling
+Version: @PACKAGE_VERSION@
+Libs: -L${libdir} -lnixutil
+Cflags: -I${includedir}/nix -std=c++2a
diff --git a/src/libutil-c/nix_api_util.cc b/src/libutil-c/nix_api_util.cc
index 0a9b493459c..4f65a4c122c 100644
--- a/src/libutil-c/nix_api_util.cc
+++ b/src/libutil-c/nix_api_util.cc
@@ -1,5 +1,5 @@
 #include "nix_api_util.h"
-#include "config.hh"
+#include "config-global.hh"
 #include "error.hh"
 #include "nix_api_util_internal.h"
 #include "util.hh"
diff --git a/src/libutil-c/package.nix b/src/libutil-c/package.nix
new file mode 100644
index 00000000000..53451998dca
--- /dev/null
+++ b/src/libutil-c/package.nix
@@ -0,0 +1,77 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util-c";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    (fileset.fileFilter (file: file.hasExt "h") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-util
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libutil/.version b/src/libutil/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/libutil/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/libutil/archive.cc b/src/libutil/archive.cc
index 351ee094b88..e2ebcda0c57 100644
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -6,8 +6,9 @@
 #include <strings.h> // for strcasecmp
 
 #include "archive.hh"
-#include "config.hh"
+#include "config-global.hh"
 #include "posix-source-accessor.hh"
+#include "source-path.hh"
 #include "file-system.hh"
 #include "signals.hh"
 
@@ -110,9 +111,9 @@ void SourceAccessor::dumpPath(
 
 time_t dumpPathAndGetMtime(const Path & path, Sink & sink, PathFilter & filter)
 {
-    auto [accessor, canonPath] = PosixSourceAccessor::createAtRoot(path);
-    accessor.dumpPath(canonPath, sink, filter);
-    return accessor.mtime;
+    auto path2 = PosixSourceAccessor::createAtRoot(path);
+    path2.dumpPath(sink, filter);
+    return path2.accessor.dynamic_pointer_cast<PosixSourceAccessor>()->mtime;
 }
 
 void dumpPath(const Path & path, Sink & sink, PathFilter & filter)
@@ -164,7 +165,7 @@ struct CaseInsensitiveCompare
 };
 
 
-static void parse(FileSystemObjectSink & sink, Source & source, const Path & path)
+static void parse(FileSystemObjectSink & sink, Source & source, const CanonPath & path)
 {
     std::string s;
 
@@ -245,7 +246,7 @@ static void parse(FileSystemObjectSink & sink, Source & source, const Path & pat
                                 }
                             } else if (s == "node") {
                                 if (name.empty()) throw badArchive("entry name missing");
-                                parse(sink, source, path + "/" + name);
+                                parse(sink, source, path / name);
                             } else
                                 throw badArchive("unknown field " + s);
                         }
@@ -289,11 +290,11 @@ void parseDump(FileSystemObjectSink & sink, Source & source)
     }
     if (version != narVersionMagic1)
         throw badArchive("input doesn't look like a Nix archive");
-    parse(sink, source, "");
+    parse(sink, source, CanonPath::root);
 }
 
 
-void restorePath(const Path & path, Source & source)
+void restorePath(const std::filesystem::path & path, Source & source)
 {
     RestoreSink sink;
     sink.dstPath = path;
@@ -314,13 +315,4 @@ void copyNAR(Source & source, Sink & sink)
 }
 
 
-void copyPath(const Path & from, const Path & to)
-{
-    auto source = sinkToSource([&](Sink & sink) {
-        dumpPath(from, sink);
-    });
-    restorePath(to, *source);
-}
-
-
 }
diff --git a/src/libutil/archive.hh b/src/libutil/archive.hh
index 28c63bb8550..2da8f0cb185 100644
--- a/src/libutil/archive.hh
+++ b/src/libutil/archive.hh
@@ -75,15 +75,13 @@ void dumpString(std::string_view s, Sink & sink);
 
 void parseDump(FileSystemObjectSink & sink, Source & source);
 
-void restorePath(const Path & path, Source & source);
+void restorePath(const std::filesystem::path & path, Source & source);
 
 /**
  * Read a NAR from 'source' and write it to 'sink'.
  */
 void copyNAR(Source & source, Sink & sink);
 
-void copyPath(const Path & from, const Path & to);
-
 
 inline constexpr std::string_view narVersionMagic1 = "nix-archive-1";
 
diff --git a/src/libutil/args.cc b/src/libutil/args.cc
index 243e3a5a620..c202facdfea 100644
--- a/src/libutil/args.cc
+++ b/src/libutil/args.cc
@@ -268,8 +268,6 @@ void RootArgs::parseCmdline(const Strings & _cmdline, bool allowShebang)
         verbosity = lvlError;
     }
 
-    bool argsSeen = false;
-
     // Heuristic to see if we're invoked as a shebang script, namely,
     // if we have at least one argument, it's the name of an
     // executable file, and it starts with "#!".
@@ -336,10 +334,6 @@ void RootArgs::parseCmdline(const Strings & _cmdline, bool allowShebang)
                 throw UsageError("unrecognised flag '%1%'", arg);
         }
         else {
-            if (!argsSeen) {
-                argsSeen = true;
-                initialFlagsProcessed();
-            }
             pos = rewriteArgs(cmdline, pos);
             pendingArgs.push_back(*pos++);
             if (processArgs(pendingArgs, false))
@@ -349,8 +343,7 @@ void RootArgs::parseCmdline(const Strings & _cmdline, bool allowShebang)
 
     processArgs(pendingArgs, true);
 
-    if (!argsSeen)
-        initialFlagsProcessed();
+    initialFlagsProcessed();
 
     /* Now that we are done parsing, make sure that any experimental
      * feature required by the flags is enabled */
diff --git a/src/libutil/args.hh b/src/libutil/args.hh
index 4b2e1d96055..7759b74a93c 100644
--- a/src/libutil/args.hh
+++ b/src/libutil/args.hh
@@ -41,7 +41,7 @@ public:
     virtual std::string doc() { return ""; }
 
     /**
-     * @brief Get the base directory for the command.
+     * @brief Get the [base directory](https://nixos.org/manual/nix/unstable/glossary#gloss-base-directory) for the command.
      *
      * @return Generally the working directory, but in case of a shebang
      *         interpreter, returns the directory of the script.
diff --git a/src/libutil/auth.cc b/src/libutil/auth.cc
index 0c43d98a5c4..b7cfb77c4f1 100644
--- a/src/libutil/auth.cc
+++ b/src/libutil/auth.cc
@@ -4,6 +4,7 @@
 #include "util.hh"
 #include "processes.hh"
 #include "environment-variables.hh"
+#include "config-global.hh"
 #include "config-impl.hh"
 #include "abstract-setting-to-json.hh"
 
@@ -131,9 +132,9 @@ struct NixAuthSource : AuthSource
         : authDir(std::filesystem::path(getDataDir()) / "nix" / "auth")
     {
         if (pathExists(authDir))
-            for (auto & file : readDirectory(authDir)) {
-                if (hasSuffix(file.name, "~")) continue;
-                auto path = authDir / file.name;
+            for (auto & file : std::filesystem::directory_iterator{authDir}) {
+                if (hasSuffix(file.path().filename().string(), "~")) continue;
+                auto path = authDir / file.path().filename();
                 auto authData = AuthData::parseGitAuthData(readFile(path));
                 if (!authData.password)
                     warn("authentication file '%s' does not contain a password, skipping", path);
diff --git a/src/libutil/build-utils-meson b/src/libutil/build-utils-meson
new file mode 120000
index 00000000000..5fff21bab55
--- /dev/null
+++ b/src/libutil/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson
\ No newline at end of file
diff --git a/src/libutil/compression.cc b/src/libutil/compression.cc
index d17401f278b..d2702856591 100644
--- a/src/libutil/compression.cc
+++ b/src/libutil/compression.cc
@@ -263,8 +263,13 @@ struct BrotliCompressionSink : ChunkedCompressionSink
             checkInterrupt();
 
             if (!BrotliEncoderCompressStream(
-                    state, data.data() ? BROTLI_OPERATION_PROCESS : BROTLI_OPERATION_FINISH, &avail_in, &next_in,
-                    &avail_out, &next_out, nullptr))
+                    state,
+                    data.data() ? BROTLI_OPERATION_PROCESS : BROTLI_OPERATION_FINISH,
+                    &avail_in,
+                    &next_in,
+                    &avail_out,
+                    &next_out,
+                    nullptr))
                 throw CompressionError("error while compressing brotli compression");
 
             if (avail_out < sizeof(outbuf) || avail_in == 0) {
@@ -280,8 +285,8 @@ struct BrotliCompressionSink : ChunkedCompressionSink
 
 ref<CompressionSink> makeCompressionSink(const std::string & method, Sink & nextSink, const bool parallel, int level)
 {
-    std::vector<std::string> la_supports = {"bzip2", "compress", "grzip", "gzip", "lrzip", "lz4",
-                                            "lzip",  "lzma",     "lzop",  "xz",   "zstd"};
+    std::vector<std::string> la_supports = {
+        "bzip2", "compress", "grzip", "gzip", "lrzip", "lz4", "lzip", "lzma", "lzop", "xz", "zstd"};
     if (std::find(la_supports.begin(), la_supports.end(), method) != la_supports.end()) {
         return make_ref<ArchiveCompressionSink>(nextSink, method, parallel, level);
     }
diff --git a/src/libutil/config-global.cc b/src/libutil/config-global.cc
new file mode 100644
index 00000000000..4c08898a40c
--- /dev/null
+++ b/src/libutil/config-global.cc
@@ -0,0 +1,67 @@
+#include "config-global.hh"
+
+namespace nix {
+
+bool GlobalConfig::set(const std::string & name, const std::string & value)
+{
+    for (auto & config : *configRegistrations)
+        if (config->set(name, value))
+            return true;
+
+    unknownSettings.emplace(name, value);
+
+    return false;
+}
+
+void GlobalConfig::getSettings(std::map<std::string, SettingInfo> & res, bool overriddenOnly)
+{
+    for (auto & config : *configRegistrations)
+        config->getSettings(res, overriddenOnly);
+}
+
+void GlobalConfig::resetOverridden()
+{
+    for (auto & config : *configRegistrations)
+        config->resetOverridden();
+}
+
+nlohmann::json GlobalConfig::toJSON()
+{
+    auto res = nlohmann::json::object();
+    for (const auto & config : *configRegistrations)
+        res.update(config->toJSON());
+    return res;
+}
+
+std::string GlobalConfig::toKeyValue()
+{
+    std::string res;
+    std::map<std::string, Config::SettingInfo> settings;
+    globalConfig.getSettings(settings);
+    for (const auto & s : settings)
+        res += fmt("%s = %s\n", s.first, s.second.value);
+    return res;
+}
+
+void GlobalConfig::convertToArgs(Args & args, const std::string & category)
+{
+    for (auto & config : *configRegistrations)
+        config->convertToArgs(args, category);
+}
+
+GlobalConfig globalConfig;
+
+GlobalConfig::ConfigRegistrations * GlobalConfig::configRegistrations;
+
+GlobalConfig::Register::Register(Config * config)
+{
+    if (!configRegistrations)
+        configRegistrations = new ConfigRegistrations;
+    configRegistrations->emplace_back(config);
+}
+
+ExperimentalFeatureSettings experimentalFeatureSettings;
+
+static GlobalConfig::Register rSettings(&experimentalFeatureSettings);
+
+}
diff --git a/src/libutil/config-global.hh b/src/libutil/config-global.hh
new file mode 100644
index 00000000000..2caf515240d
--- /dev/null
+++ b/src/libutil/config-global.hh
@@ -0,0 +1,33 @@
+#pragma once
+///@file
+
+#include "config.hh"
+
+namespace nix {
+
+struct GlobalConfig : public AbstractConfig
+{
+    typedef std::vector<Config *> ConfigRegistrations;
+    static ConfigRegistrations * configRegistrations;
+
+    bool set(const std::string & name, const std::string & value) override;
+
+    void getSettings(std::map<std::string, SettingInfo> & res, bool overriddenOnly = false) override;
+
+    void resetOverridden() override;
+
+    nlohmann::json toJSON() override;
+
+    std::string toKeyValue() override;
+
+    void convertToArgs(Args & args, const std::string & category) override;
+
+    struct Register
+    {
+        Register(Config * config);
+    };
+};
+
+extern GlobalConfig globalConfig;
+
+}
diff --git a/src/libutil/config-impl.hh b/src/libutil/config-impl.hh
index c4df352b3c0..debdc3776ed 100644
--- a/src/libutil/config-impl.hh
+++ b/src/libutil/config-impl.hh
@@ -117,10 +117,11 @@ T BaseSetting<T>::parse(const std::string & str) const
 {
     static_assert(std::is_integral<T>::value, "Integer required.");
 
-    if (auto n = string2Int<T>(str))
-        return *n;
-    else
+    try {
+        return string2IntWithUnitPrefix<T>(str);
+    } catch (...) {
         throw UsageError("setting '%s' has invalid value '%s'", name, str);
+    }
 }
 
 template<typename T>
diff --git a/src/libutil/config.cc b/src/libutil/config.cc
index efde8591b80..907ca7fc149 100644
--- a/src/libutil/config.cc
+++ b/src/libutil/config.cc
@@ -91,7 +91,14 @@ void Config::getSettings(std::map<std::string, SettingInfo> & res, bool overridd
 }
 
 
-static void applyConfigInner(const std::string & contents, const std::string & path, std::vector<std::pair<std::string, std::string>> & parsedContents) {
+/**
+ * Parse configuration in `contents`, and also the configuration files included from there, with their location specified relative to `path`.
+ *
+ * `contents` and `path` represent the file that is being parsed.
+ * The result is only an intermediate list of key-value pairs of strings.
+ * More parsing according to the settings-specific semantics is being done by `loadConfFile` in `libstore/globals.cc`.
+*/
+static void parseConfigFiles(const std::string & contents, const std::string & path, std::vector<std::pair<std::string, std::string>> & parsedContents) {
     unsigned int pos = 0;
 
     while (pos < contents.size()) {
@@ -125,7 +132,7 @@ static void applyConfigInner(const std::string & contents, const std::string & p
             if (pathExists(p)) {
                 try {
                     std::string includedContents = readFile(p);
-                    applyConfigInner(includedContents, p, parsedContents);
+                    parseConfigFiles(includedContents, p, parsedContents);
                 } catch (SystemError &) {
                     // TODO: Do we actually want to ignore this? Or is it better to fail?
                 }
@@ -153,7 +160,7 @@ static void applyConfigInner(const std::string & contents, const std::string & p
 void AbstractConfig::applyConfig(const std::string & contents, const std::string & path) {
     std::vector<std::pair<std::string, std::string>> parsedContents;
 
-    applyConfigInner(contents, path, parsedContents);
+    parseConfigFiles(contents, path, parsedContents);
 
     // First apply experimental-feature related settings
     for (const auto & [name, value] : parsedContents)
@@ -443,67 +450,6 @@ void OptionalPathSetting::operator =(const std::optional<Path> & v)
     this->assign(v);
 }
 
-bool GlobalConfig::set(const std::string & name, const std::string & value)
-{
-    for (auto & config : *configRegistrations)
-        if (config->set(name, value)) return true;
-
-    unknownSettings.emplace(name, value);
-
-    return false;
-}
-
-void GlobalConfig::getSettings(std::map<std::string, SettingInfo> & res, bool overriddenOnly)
-{
-    for (auto & config : *configRegistrations)
-        config->getSettings(res, overriddenOnly);
-}
-
-void GlobalConfig::resetOverridden()
-{
-    for (auto & config : *configRegistrations)
-        config->resetOverridden();
-}
-
-nlohmann::json GlobalConfig::toJSON()
-{
-    auto res = nlohmann::json::object();
-    for (const auto & config : *configRegistrations)
-        res.update(config->toJSON());
-    return res;
-}
-
-std::string GlobalConfig::toKeyValue()
-{
-    std::string res;
-    std::map<std::string, Config::SettingInfo> settings;
-    globalConfig.getSettings(settings);
-    for (const auto & s : settings)
-        res += fmt("%s = %s\n", s.first, s.second.value);
-    return res;
-}
-
-void GlobalConfig::convertToArgs(Args & args, const std::string & category)
-{
-    for (auto & config : *configRegistrations)
-        config->convertToArgs(args, category);
-}
-
-GlobalConfig globalConfig;
-
-GlobalConfig::ConfigRegistrations * GlobalConfig::configRegistrations;
-
-GlobalConfig::Register::Register(Config * config)
-{
-    if (!configRegistrations)
-        configRegistrations = new ConfigRegistrations;
-    configRegistrations->emplace_back(config);
-}
-
-ExperimentalFeatureSettings experimentalFeatureSettings;
-
-static GlobalConfig::Register rSettings(&experimentalFeatureSettings);
-
 bool ExperimentalFeatureSettings::isEnabled(const ExperimentalFeature & feature) const
 {
     auto & f = experimentalFeatures.get();
diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index 07322b60d7a..1952ba1b8d7 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -375,31 +375,6 @@ public:
     void operator =(const std::optional<Path> & v);
 };
 
-struct GlobalConfig : public AbstractConfig
-{
-    typedef std::vector<Config*> ConfigRegistrations;
-    static ConfigRegistrations * configRegistrations;
-
-    bool set(const std::string & name, const std::string & value) override;
-
-    void getSettings(std::map<std::string, SettingInfo> & res, bool overriddenOnly = false) override;
-
-    void resetOverridden() override;
-
-    nlohmann::json toJSON() override;
-
-    std::string toKeyValue() override;
-
-    void convertToArgs(Args & args, const std::string & category) override;
-
-    struct Register
-    {
-        Register(Config * config);
-    };
-};
-
-extern GlobalConfig globalConfig;
-
 
 struct ExperimentalFeatureSettings : Config {
 
diff --git a/src/libutil/current-process.cc b/src/libutil/current-process.cc
index c88013b3c42..6ca48220d21 100644
--- a/src/libutil/current-process.cc
+++ b/src/libutil/current-process.cc
@@ -7,6 +7,7 @@
 #include "file-system.hh"
 #include "processes.hh"
 #include "signals.hh"
+#include <math.h>
 
 #ifdef __APPLE__
 # include <mach-o/dyld.h>
@@ -59,15 +60,15 @@ unsigned int getMaxCPU()
 //////////////////////////////////////////////////////////////////////
 
 
-#ifndef _WIN32
-rlim_t savedStackSize = 0;
+size_t savedStackSize = 0;
 
-void setStackSize(rlim_t stackSize)
+void setStackSize(size_t stackSize)
 {
+    #ifndef _WIN32
     struct rlimit limit;
     if (getrlimit(RLIMIT_STACK, &limit) == 0 && limit.rlim_cur < stackSize) {
         savedStackSize = limit.rlim_cur;
-        limit.rlim_cur = std::min(stackSize, limit.rlim_max);
+        limit.rlim_cur = std::min(static_cast<rlim_t>(stackSize), limit.rlim_max);
         if (setrlimit(RLIMIT_STACK, &limit) != 0) {
             logger->log(
                 lvlError,
@@ -81,8 +82,31 @@ void setStackSize(rlim_t stackSize)
             );
         }
     }
+    #else
+    ULONG_PTR stackLow, stackHigh;
+    GetCurrentThreadStackLimits(&stackLow, &stackHigh);
+    ULONG maxStackSize = stackHigh - stackLow;
+    ULONG currStackSize = 0;
+    // This retrieves the current promised stack size
+    SetThreadStackGuarantee(&currStackSize);
+    if (currStackSize < stackSize) {
+        savedStackSize = currStackSize;
+        ULONG newStackSize = std::min(static_cast<ULONG>(stackSize), maxStackSize);
+        if (SetThreadStackGuarantee(&newStackSize) == 0) {
+            logger->log(
+                lvlError,
+                HintFmt(
+                    "Failed to increase stack size from %1% to %2% (maximum allowed stack size: %3%): %4%",
+                    savedStackSize,
+                    stackSize,
+                    maxStackSize,
+                    std::to_string(GetLastError())
+                ).str()
+            );
+        }
+    }
+    #endif
 }
-#endif
 
 void restoreProcessContext(bool restoreMounts)
 {
diff --git a/src/libutil/current-process.hh b/src/libutil/current-process.hh
index a5adb70cfd5..8286bf89d66 100644
--- a/src/libutil/current-process.hh
+++ b/src/libutil/current-process.hh
@@ -17,12 +17,10 @@ namespace nix {
  */
 unsigned int getMaxCPU();
 
-#ifndef _WIN32 // TODO implement on Windows, if needed.
 /**
  * Change the stack size.
  */
-void setStackSize(rlim_t stackSize);
-#endif
+void setStackSize(size_t stackSize);
 
 /**
  * Restore the original inherited Unix process context (such as signal
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index fd4f4efd187..e01f064484c 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -240,7 +240,10 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
             break;
         }
         case Verbosity::lvlWarn: {
-            prefix = ANSI_WARNING "warning";
+            if (einfo.isFromExpr)
+                prefix = ANSI_WARNING "evaluation warning";
+            else
+                prefix = ANSI_WARNING "warning";
             break;
         }
         case Verbosity::lvlInfo: {
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 0419f36d634..4b08a045e32 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -89,6 +89,11 @@ struct ErrorInfo {
     HintFmt msg;
     std::shared_ptr<Pos> pos;
     std::list<Trace> traces;
+    /**
+     * Some messages are generated directly by expressions; notably `builtins.warn`, `abort`, `throw`.
+     * These may be rendered differently, so that users can distinguish them.
+     */
+    bool isFromExpr = false;
 
     /**
      * Exit status.
@@ -150,6 +155,7 @@ public:
         : err(e)
     { }
 
+    /** The error message without "error: " prefixed to it. */
     std::string message() {
         return err.msg.str();
     }
@@ -206,11 +212,11 @@ MakeError(SystemError, Error);
  *
  * Throw this, but prefer not to catch this, and catch `SystemError`
  * instead. This allows implementations to freely switch between this
- * and `WinError` without breaking catch blocks.
+ * and `windows::WinError` without breaking catch blocks.
  *
  * However, it is permissible to catch this and rethrow so long as
  * certain conditions are not met (e.g. to catch only if `errNo =
- * EFooBar`). In that case, try to also catch the equivalent `WinError`
+ * EFooBar`). In that case, try to also catch the equivalent `windows::WinError`
  * code.
  *
  * @todo Rename this to `PosixError` or similar. At this point Windows
@@ -248,7 +254,9 @@ public:
 };
 
 #ifdef _WIN32
-class WinError;
+namespace windows {
+    class WinError;
+}
 #endif
 
 /**
@@ -258,7 +266,7 @@ class WinError;
  */
 using NativeSysError =
 #ifdef _WIN32
-    WinError
+    windows::WinError
 #else
     SysError
 #endif
diff --git a/src/libutil/experimental-features.cc b/src/libutil/experimental-features.cc
index fa118c647a5..b5ed6c6f4f5 100644
--- a/src/libutil/experimental-features.cc
+++ b/src/libutil/experimental-features.cc
@@ -66,7 +66,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
             an impure derivation cannot also be
             [content-addressed](#xp-feature-ca-derivations).
 
-            This is a more explicit alternative to using [`builtins.currentTime`](@docroot@/language/builtin-constants.md#builtins-currentTime).
+            This is a more explicit alternative to using [`builtins.currentTime`](@docroot@/language/builtins.md#builtins-currentTime).
         )",
         .trackingUrl = "https://github.com/NixOS/nix/milestone/42",
     },
@@ -282,7 +282,7 @@ constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails
         .tag = Xp::MountedSSHStore,
         .name = "mounted-ssh-store",
         .description = R"(
-            Allow the use of the [`mounted SSH store`](@docroot@/command-ref/new-cli/nix3-help-stores.html#experimental-ssh-store-with-filesytem-mounted).
+            Allow the use of the [`mounted SSH store`](@docroot@/command-ref/new-cli/nix3-help-stores.html#experimental-ssh-store-with-filesystem-mounted).
         )",
         .trackingUrl = "https://github.com/NixOS/nix/milestone/43",
     },
diff --git a/src/libutil/file-content-address.cc b/src/libutil/file-content-address.cc
index 570247b9e7b..438dac7daa6 100644
--- a/src/libutil/file-content-address.cc
+++ b/src/libutil/file-content-address.cc
@@ -1,6 +1,7 @@
 #include "file-content-address.hh"
 #include "archive.hh"
 #include "git.hh"
+#include "source-path.hh"
 
 namespace nix {
 
@@ -9,7 +10,7 @@ static std::optional<FileSerialisationMethod> parseFileSerialisationMethodOpt(st
     if (input == "flat") {
         return FileSerialisationMethod::Flat;
     } else if (input == "nar") {
-        return FileSerialisationMethod::Recursive;
+        return FileSerialisationMethod::NixArchive;
     } else {
         return std::nullopt;
     }
@@ -44,7 +45,7 @@ std::string_view renderFileSerialisationMethod(FileSerialisationMethod method)
     switch (method) {
     case FileSerialisationMethod::Flat:
         return "flat";
-    case FileSerialisationMethod::Recursive:
+    case FileSerialisationMethod::NixArchive:
         return "nar";
     default:
         assert(false);
@@ -56,7 +57,7 @@ std::string_view renderFileIngestionMethod(FileIngestionMethod method)
 {
     switch (method) {
     case FileIngestionMethod::Flat:
-    case FileIngestionMethod::Recursive:
+    case FileIngestionMethod::NixArchive:
         return renderFileSerialisationMethod(
             static_cast<FileSerialisationMethod>(method));
     case FileIngestionMethod::Git:
@@ -68,17 +69,17 @@ std::string_view renderFileIngestionMethod(FileIngestionMethod method)
 
 
 void dumpPath(
-    SourceAccessor & accessor, const CanonPath & path,
+    const SourcePath & path,
     Sink & sink,
     FileSerialisationMethod method,
     PathFilter & filter)
 {
     switch (method) {
     case FileSerialisationMethod::Flat:
-        accessor.readFile(path, sink);
+        path.readFile(sink);
         break;
-    case FileSerialisationMethod::Recursive:
-        accessor.dumpPath(path, sink, filter);
+    case FileSerialisationMethod::NixArchive:
+        path.dumpPath(sink, filter);
         break;
     }
 }
@@ -93,7 +94,7 @@ void restorePath(
     case FileSerialisationMethod::Flat:
         writeFile(path, source);
         break;
-    case FileSerialisationMethod::Recursive:
+    case FileSerialisationMethod::NixArchive:
         restorePath(path, source);
         break;
     }
@@ -101,27 +102,29 @@ void restorePath(
 
 
 HashResult hashPath(
-    SourceAccessor & accessor, const CanonPath & path,
+    const SourcePath & path,
     FileSerialisationMethod method, HashAlgorithm ha,
     PathFilter & filter)
 {
     HashSink sink { ha };
-    dumpPath(accessor, path, sink, method, filter);
+    dumpPath(path, sink, method, filter);
     return sink.finish();
 }
 
 
-Hash hashPath(
-    SourceAccessor & accessor, const CanonPath & path,
+std::pair<Hash, std::optional<uint64_t>> hashPath(
+    const SourcePath & path,
     FileIngestionMethod method, HashAlgorithm ht,
     PathFilter & filter)
 {
     switch (method) {
     case FileIngestionMethod::Flat:
-    case FileIngestionMethod::Recursive:
-        return hashPath(accessor, path, (FileSerialisationMethod) method, ht, filter).first;
+    case FileIngestionMethod::NixArchive: {
+        auto res = hashPath(path, (FileSerialisationMethod) method, ht, filter);
+        return {res.first, {res.second}};
+    }
     case FileIngestionMethod::Git:
-        return git::dumpHash(ht, accessor, path, filter).hash;
+        return {git::dumpHash(ht, path, filter).hash, std::nullopt};
     }
     assert(false);
 }
diff --git a/src/libutil/file-content-address.hh b/src/libutil/file-content-address.hh
index b361ab243f6..4c7218f1941 100644
--- a/src/libutil/file-content-address.hh
+++ b/src/libutil/file-content-address.hh
@@ -7,28 +7,42 @@
 
 namespace nix {
 
+struct SourcePath;
+
 /**
  * An enumeration of the ways we can serialize file system
  * objects.
+ *
+ * See `file-system-object/content-address.md#serial` in the manual for
+ * a user-facing description of this concept, but note that this type is also
+ * used for storing or sending copies; not just for addressing.
+ * Note also that there are other content addressing methods that don't
+ * correspond to a serialisation method.
  */
 enum struct FileSerialisationMethod : uint8_t {
     /**
      * Flat-file. The contents of a single file exactly.
+     *
+     * See `file-system-object/content-address.md#serial-flat` in the
+     * manual.
      */
     Flat,
 
     /**
      * Nix Archive. Serializes the file-system object in
      * Nix Archive format.
+     *
+     * See `file-system-object/content-address.md#serial-nix-archive` in
+     * the manual.
      */
-    Recursive,
+    NixArchive,
 };
 
 /**
  * Parse a `FileSerialisationMethod` by name. Choice of:
  *
  *  - `flat`: `FileSerialisationMethod::Flat`
- *  - `nar`: `FileSerialisationMethod::Recursive`
+ *  - `nar`: `FileSerialisationMethod::NixArchive`
  *
  * Opposite of `renderFileSerialisationMethod`.
  */
@@ -45,7 +59,7 @@ std::string_view renderFileSerialisationMethod(FileSerialisationMethod method);
  * Dump a serialization of the given file system object.
  */
 void dumpPath(
-    SourceAccessor & accessor, const CanonPath & path,
+    const SourcePath & path,
     Sink & sink,
     FileSerialisationMethod method,
     PathFilter & filter = defaultPathFilter);
@@ -72,40 +86,41 @@ void restorePath(
  * ```
  */
 HashResult hashPath(
-    SourceAccessor & accessor, const CanonPath & path,
+    const SourcePath & path,
     FileSerialisationMethod method, HashAlgorithm ha,
     PathFilter & filter = defaultPathFilter);
 
 /**
  * An enumeration of the ways we can ingest file system
  * objects, producing a hash or digest.
+ *
+ * See `file-system-object/content-address.md` in the manual for a
+ * user-facing description of this concept.
  */
 enum struct FileIngestionMethod : uint8_t {
     /**
      * Hash `FileSerialisationMethod::Flat` serialisation.
+     *
+     * See `file-system-object/content-address.md#serial-flat` in the
+     * manual.
      */
     Flat,
 
     /**
-     * Hash `FileSerialisationMethod::Git` serialisation.
+     * Hash `FileSerialisationMethod::NixArchive` serialisation.
+     *
+     * See `file-system-object/content-address.md#serial-flat` in the
+     * manual.
      */
-    Recursive,
+    NixArchive,
 
     /**
-     * Git hashing. In particular files are hashed as git "blobs", and
-     * directories are hashed as git "trees".
+     * Git hashing.
      *
-     * Unlike `Flat` and `Recursive`, this is not a hash of a single
-     * serialisation but a [Merkle
-     * DAG](https://en.wikipedia.org/wiki/Merkle_tree) of multiple
-     * rounds of serialisation and hashing.
+     * Part of `ExperimentalFeature::GitHashing`.
      *
-     * @note Git's data model is slightly different, in that a plain
-     * file doesn't have an executable bit, directory entries do
-     * instead. We decide treat a bare file as non-executable by fiat,
-     * as we do with `FileIngestionMethod::Flat` which also lacks this
-     * information. Thus, Git can encode some but all of Nix's "File
-     * System Objects", and this sort of hashing is likewise partial.
+     * See `file-system-object/content-address.md#serial-git` in the
+     * manual.
      */
     Git,
 };
@@ -114,7 +129,7 @@ enum struct FileIngestionMethod : uint8_t {
  * Parse a `FileIngestionMethod` by name. Choice of:
  *
  *  - `flat`: `FileIngestionMethod::Flat`
- *  - `nar`: `FileIngestionMethod::Recursive`
+ *  - `nar`: `FileIngestionMethod::NixArchive`
  *  - `git`: `FileIngestionMethod::Git`
  *
  * Opposite of `renderFileIngestionMethod`.
@@ -130,15 +145,16 @@ std::string_view renderFileIngestionMethod(FileIngestionMethod method);
 
 /**
  * Compute the hash of the given file system object according to the
- * given method.
+ * given method, and for some ingestion methods, the size of the
+ * serialisation.
  *
  * Unlike the other `hashPath`, this works on an arbitrary
  * `FileIngestionMethod` instead of `FileSerialisationMethod`, but
- * doesn't return the size as this is this is not a both simple and
+ * may not return the size as this is this is not a both simple and
  * useful defined for a merkle format.
  */
-Hash hashPath(
-    SourceAccessor & accessor, const CanonPath & path,
+std::pair<Hash, std::optional<uint64_t>> hashPath(
+    const SourcePath & path,
     FileIngestionMethod method, HashAlgorithm ha,
     PathFilter & filter = defaultPathFilter);
 
diff --git a/src/libutil/file-descriptor.hh b/src/libutil/file-descriptor.hh
index 50201d8465e..be61375f64f 100644
--- a/src/libutil/file-descriptor.hh
+++ b/src/libutil/file-descriptor.hh
@@ -17,13 +17,13 @@ struct Source;
 /**
  * Operating System capability
  */
-typedef
+using Descriptor =
 #if _WIN32
     HANDLE
 #else
     int
 #endif
-    Descriptor;
+    ;
 
 const Descriptor INVALID_DESCRIPTOR =
 #if _WIN32
@@ -41,7 +41,7 @@ const Descriptor INVALID_DESCRIPTOR =
 static inline Descriptor toDescriptor(int fd)
 {
 #ifdef _WIN32
-    return (HANDLE) _get_osfhandle(fd);
+    return reinterpret_cast<HANDLE>(_get_osfhandle(fd));
 #else
     return fd;
 #endif
@@ -56,7 +56,7 @@ static inline Descriptor toDescriptor(int fd)
 static inline int fromDescriptorReadOnly(Descriptor fd)
 {
 #ifdef _WIN32
-    return _open_osfhandle((intptr_t) fd, _O_RDONLY);
+    return _open_osfhandle(reinterpret_cast<intptr_t>(fd), _O_RDONLY);
 #else
     return fd;
 #endif
@@ -140,6 +140,7 @@ public:
 };
 
 #ifndef _WIN32 // Not needed on Windows, where we don't fork
+namespace unix {
 
 /**
  * Close all file descriptors except those listed in the given set.
@@ -152,13 +153,16 @@ void closeMostFDs(const std::set<Descriptor> & exceptions);
  */
 void closeOnExec(Descriptor fd);
 
+} // namespace unix
 #endif
 
-#ifdef _WIN32
-# if _WIN32_WINNT >= 0x0600
+#if defined(_WIN32) && _WIN32_WINNT >= 0x0600
+namespace windows {
+
 Path handleToPath(Descriptor handle);
 std::wstring handleToFileName(Descriptor handle);
-# endif
+
+} // namespace windows
 #endif
 
 MakeError(EndOfFile, Error);
diff --git a/src/libutil/file-path.hh b/src/libutil/file-path.hh
index 6fb1001250b..6589c4060bb 100644
--- a/src/libutil/file-path.hh
+++ b/src/libutil/file-path.hh
@@ -13,9 +13,8 @@ namespace nix {
  *
  * @todo drop `NG` suffix and replace the ones in `types.hh`.
  */
-typedef std::filesystem::path PathNG;
-typedef std::list<Path> PathsNG;
-typedef std::set<Path> PathSetNG;
+typedef std::list<std::filesystem::path> PathsNG;
+typedef std::set<std::filesystem::path> PathSetNG;
 
 /**
  * Stop gap until `std::filesystem::path_view` from P1030R6 exists in a
@@ -23,18 +22,18 @@ typedef std::set<Path> PathSetNG;
  *
  * @todo drop `NG` suffix and replace the one in `types.hh`.
  */
-struct PathViewNG : std::basic_string_view<PathNG::value_type>
+struct PathViewNG : std::basic_string_view<std::filesystem::path::value_type>
 {
-    using string_view = std::basic_string_view<PathNG::value_type>;
+    using string_view = std::basic_string_view<std::filesystem::path::value_type>;
 
     using string_view::string_view;
 
-    PathViewNG(const PathNG & path)
-        : std::basic_string_view<PathNG::value_type>(path.native())
+    PathViewNG(const std::filesystem::path & path)
+        : std::basic_string_view<std::filesystem::path::value_type>(path.native())
     { }
 
-    PathViewNG(const PathNG::string_type & path)
-        : std::basic_string_view<PathNG::value_type>(path)
+    PathViewNG(const std::filesystem::path::string_type & path)
+        : std::basic_string_view<std::filesystem::path::value_type>(path)
     { }
 
     const string_view & native() const { return *this; }
@@ -43,10 +42,19 @@ struct PathViewNG : std::basic_string_view<PathNG::value_type>
 
 std::string os_string_to_string(PathViewNG::string_view path);
 
-PathNG::string_type string_to_os_string(std::string_view s);
+std::filesystem::path::string_type string_to_os_string(std::string_view s);
 
-std::optional<PathNG> maybePathNG(PathView path);
+std::optional<std::filesystem::path> maybePath(PathView path);
 
-PathNG pathNG(PathView path);
+std::filesystem::path pathNG(PathView path);
+
+/**
+ * Create string literals with the native character width of paths
+ */
+#ifndef _WIN32
+# define PATHNG_LITERAL(s) s
+#else
+# define PATHNG_LITERAL(s) L ## s
+#endif
 
 }
diff --git a/src/libutil/file-system.cc b/src/libutil/file-system.cc
index b03bb767b6f..f75851bbd58 100644
--- a/src/libutil/file-system.cc
+++ b/src/libutil/file-system.cc
@@ -94,7 +94,7 @@ Path canonPath(PathView path, bool resolveSymlinks)
         path,
         [&followCount, &temp, maxFollow, resolveSymlinks]
         (std::string & result, std::string_view & remaining) {
-            if (resolveSymlinks && isLink(result)) {
+            if (resolveSymlinks && fs::is_symlink(result)) {
                 if (++followCount >= maxFollow)
                     throw Error("infinite symlink recursion in path '%0%'", remaining);
                 remaining = (temp = concatStrings(readLink(result), remaining));
@@ -120,10 +120,10 @@ Path canonPath(PathView path, bool resolveSymlinks)
 
 Path dirOf(const PathView path)
 {
-    Path::size_type pos = path.rfind('/');
+    Path::size_type pos = NativePathTrait::rfindPathSep(path);
     if (pos == path.npos)
         return ".";
-    return pos == 0 ? "/" : Path(path, 0, pos);
+    return fs::path{path}.parent_path().string();
 }
 
 
@@ -217,72 +217,8 @@ bool pathAccessible(const Path & path)
 
 Path readLink(const Path & path)
 {
-#ifndef _WIN32
     checkInterrupt();
-    std::vector<char> buf;
-    for (ssize_t bufSize = PATH_MAX/4; true; bufSize += bufSize/2) {
-        buf.resize(bufSize);
-        ssize_t rlSize = readlink(path.c_str(), buf.data(), bufSize);
-        if (rlSize == -1)
-            if (errno == EINVAL)
-                throw Error("'%1%' is not a symlink", path);
-            else
-                throw SysError("reading symbolic link '%1%'", path);
-        else if (rlSize < bufSize)
-            return std::string(buf.data(), rlSize);
-    }
-#else
-    // TODO modern Windows does in fact support symlinks
-    throw UnimplementedError("reading symbolic link '%1%'", path);
-#endif
-}
-
-
-bool isLink(const Path & path)
-{
-    return getFileType(path) == DT_LNK;
-}
-
-
-DirEntries readDirectory(DIR *dir, const Path & path)
-{
-    DirEntries entries;
-    entries.reserve(64);
-
-    struct dirent * dirent;
-    while (errno = 0, dirent = readdir(dir)) { /* sic */
-        checkInterrupt();
-        std::string name = dirent->d_name;
-        if (name == "." || name == "..") continue;
-        entries.emplace_back(name, dirent->d_ino,
-#ifdef HAVE_STRUCT_DIRENT_D_TYPE
-            dirent->d_type
-#else
-            DT_UNKNOWN
-#endif
-        );
-    }
-    if (errno) throw SysError("reading directory '%1%'", path);
-
-    return entries;
-}
-
-DirEntries readDirectory(const Path & path)
-{
-    AutoCloseDir dir(opendir(path.c_str()));
-    if (!dir) throw SysError("opening directory '%1%'", path);
-
-    return readDirectory(dir.get(), path);
-}
-
-
-unsigned char getFileType(const Path & path)
-{
-    struct stat st = lstat(path);
-    if (S_ISDIR(st.st_mode)) return DT_DIR;
-    if (S_ISLNK(st.st_mode)) return DT_LNK;
-    if (S_ISREG(st.st_mode)) return DT_REG;
-    return DT_UNKNOWN;
+    return fs::read_symlink(path).string();
 }
 
 
@@ -380,12 +316,12 @@ void syncParent(const Path & path)
 }
 
 
-static void _deletePath(Descriptor parentfd, const Path & path, uint64_t & bytesFreed)
+static void _deletePath(Descriptor parentfd, const fs::path & path, uint64_t & bytesFreed)
 {
 #ifndef _WIN32
     checkInterrupt();
 
-    std::string name(baseNameOf(path));
+    std::string name(baseNameOf(path.native()));
 
     struct stat st;
     if (fstatat(parentfd, name.c_str(), &st,
@@ -432,8 +368,15 @@ static void _deletePath(Descriptor parentfd, const Path & path, uint64_t & bytes
         AutoCloseDir dir(fdopendir(fd));
         if (!dir)
             throw SysError("opening directory '%1%'", path);
-        for (auto & i : readDirectory(dir.get(), path))
-            _deletePath(dirfd(dir.get()), path + "/" + i.name, bytesFreed);
+
+        struct dirent * dirent;
+        while (errno = 0, dirent = readdir(dir.get())) { /* sic */
+            checkInterrupt();
+            std::string childName = dirent->d_name;
+            if (childName == "." || childName == "..") continue;
+            _deletePath(dirfd(dir.get()), path + "/" + childName, bytesFreed);
+        }
+        if (errno) throw SysError("reading directory '%1%'", path);
     }
 
     int flags = S_ISDIR(st.st_mode) ? AT_REMOVEDIR : 0;
@@ -447,9 +390,9 @@ static void _deletePath(Descriptor parentfd, const Path & path, uint64_t & bytes
 #endif
 }
 
-static void _deletePath(const Path & path, uint64_t & bytesFreed)
+static void _deletePath(const fs::path & path, uint64_t & bytesFreed)
 {
-    Path dir = dirOf(path);
+    Path dir = dirOf(path.string());
     if (dir == "")
         dir = "/";
 
@@ -463,41 +406,29 @@ static void _deletePath(const Path & path, uint64_t & bytesFreed)
 }
 
 
-void deletePath(const Path & path)
+void deletePath(const fs::path & path)
 {
     uint64_t dummy;
     deletePath(path, dummy);
 }
 
-
-Paths createDirs(const Path & path)
+void createDir(const Path & path, mode_t mode)
 {
-    Paths created;
-    if (path == "/") return created;
+    if (mkdir(path.c_str(), mode) == -1)
+        throw SysError("creating directory '%1%'", path);
+}
 
-    struct stat st;
-    if (STAT(path.c_str(), &st) == -1) {
-        created = createDirs(dirOf(path));
-        if (mkdir(path.c_str()
-#ifndef _WIN32 // TODO abstract mkdir perms for Windows
-            , 0777
-#endif
-            ) == -1 && errno != EEXIST)
-            throw SysError("creating directory '%1%'", path);
-        st = STAT(path);
-        created.push_back(path);
+void createDirs(const Path & path)
+{
+    try {
+        fs::create_directories(path);
+    } catch (fs::filesystem_error & e) {
+        throw SysError("creating directory '%1%'", path);
     }
-
-    if (S_ISLNK(st.st_mode) && stat(path.c_str(), &st) == -1)
-        throw SysError("statting symlink '%1%'", path);
-
-    if (!S_ISDIR(st.st_mode)) throw Error("'%1%' is not a directory", path);
-
-    return created;
 }
 
 
-void deletePath(const Path & path, uint64_t & bytesFreed)
+void deletePath(const fs::path & path, uint64_t & bytesFreed)
 {
     //Activity act(*logger, lvlDebug, "recursively deleting path '%1%'", path);
     bytesFreed = 0;
@@ -509,7 +440,7 @@ void deletePath(const Path & path, uint64_t & bytesFreed)
 
 AutoDelete::AutoDelete() : del{false} {}
 
-AutoDelete::AutoDelete(const std::string & p, bool recursive) : path(p)
+AutoDelete::AutoDelete(const fs::path & p, bool recursive) : _path(p)
 {
     del = true;
     this->recursive = recursive;
@@ -520,10 +451,9 @@ AutoDelete::~AutoDelete()
     try {
         if (del) {
             if (recursive)
-                deletePath(path);
+                deletePath(_path);
             else {
-                if (remove(path.c_str()) == -1)
-                    throw SysError("cannot unlink '%1%'", path);
+                fs::remove(_path);
             }
         }
     } catch (...) {
@@ -536,8 +466,8 @@ void AutoDelete::cancel()
     del = false;
 }
 
-void AutoDelete::reset(const Path & p, bool recursive) {
-    path = p;
+void AutoDelete::reset(const fs::path & p, bool recursive) {
+    _path = p;
     this->recursive = recursive;
     del = true;
 }
@@ -604,20 +534,14 @@ std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix)
     if (!fd)
         throw SysError("creating temporary file '%s'", tmpl);
 #ifndef _WIN32
-    closeOnExec(fd.get());
+    unix::closeOnExec(fd.get());
 #endif
     return {std::move(fd), tmpl};
 }
 
 void createSymlink(const Path & target, const Path & link)
 {
-#ifndef _WIN32
-    if (symlink(target.c_str(), link.c_str()))
-        throw SysError("creating symlink from '%1%' to '%2%'", link, target);
-#else
-    // TODO modern Windows does in fact support symlinks
-    throw UnimplementedError("createSymlink");
-#endif
+    fs::create_symlink(target, link);
 }
 
 void replaceSymlink(const Path & target, const Path & link)
@@ -627,83 +551,111 @@ void replaceSymlink(const Path & target, const Path & link)
 
         try {
             createSymlink(target, tmp);
-        } catch (SysError & e) {
-            if (e.errNo == EEXIST) continue;
+        } catch (fs::filesystem_error & e) {
+            if (e.code() == std::errc::file_exists) continue;
             throw;
         }
 
-        renameFile(tmp, link);
+        std::filesystem::rename(tmp, link);
 
         break;
     }
 }
 
-#ifndef _WIN32
-static void setWriteTime(const fs::path & p, const struct stat & st)
+void setWriteTime(
+    const std::filesystem::path & path,
+    time_t accessedTime,
+    time_t modificationTime,
+    std::optional<bool> optIsSymlink)
 {
-    struct timeval times[2];
-    times[0] = {
-        .tv_sec = st.st_atime,
-        .tv_usec = 0,
+#ifndef _WIN32
+    struct timeval times[2] = {
+        {
+            .tv_sec = accessedTime,
+            .tv_usec = 0,
+        },
+        {
+            .tv_sec = modificationTime,
+            .tv_usec = 0,
+        },
     };
-    times[1] = {
-        .tv_sec = st.st_mtime,
-        .tv_usec = 0,
+#endif
+
+    auto nonSymlink = [&]{
+        bool isSymlink = optIsSymlink
+            ? *optIsSymlink
+            : fs::is_symlink(path);
+
+        if (!isSymlink) {
+#ifdef _WIN32
+            // FIXME use `fs::last_write_time`.
+            //
+            // Would be nice to use std::filesystem unconditionally, but
+            // doesn't support access time just modification time.
+            //
+            // System clock vs File clock issues also make that annoying.
+            warn("Changing file times is not yet implemented on Windows, path is '%s'", path);
+#else
+            if (utimes(path.c_str(), times) == -1) {
+
+                throw SysError("changing modification time of '%s' (not a symlink)", path);
+            }
+#endif
+        } else {
+            throw Error("Cannot modification time of symlink '%s'", path);
+        }
     };
-    if (lutimes(p.c_str(), times) != 0)
-        throw SysError("changing modification time of '%s'", p);
-}
+
+#if HAVE_LUTIMES
+    if (lutimes(path.c_str(), times) == -1) {
+        if (errno == ENOSYS)
+            nonSymlink();
+        else
+            throw SysError("changing modification time of '%s'", path);
+    }
+#else
+    nonSymlink();
 #endif
+}
 
-void copy(const fs::directory_entry & from, const fs::path & to, bool andDelete)
+void setWriteTime(const fs::path & path, const struct stat & st)
 {
-#ifndef _WIN32
-    // TODO: Rewrite the `is_*` to use `symlink_status()`
-    auto statOfFrom = lstat(from.path().c_str());
-#endif
-    auto fromStatus = from.symlink_status();
+    setWriteTime(path, st.st_atime, st.st_mtime, S_ISLNK(st.st_mode));
+}
+
+void copyFile(const fs::path & from, const fs::path & to, bool andDelete)
+{
+    auto fromStatus = fs::symlink_status(from);
 
     // Mark the directory as writable so that we can delete its children
     if (andDelete && fs::is_directory(fromStatus)) {
-        fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
+        fs::permissions(from, fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
     }
 
 
     if (fs::is_symlink(fromStatus) || fs::is_regular_file(fromStatus)) {
-        fs::copy(from.path(), to, fs::copy_options::copy_symlinks | fs::copy_options::overwrite_existing);
+        fs::copy(from, to, fs::copy_options::copy_symlinks | fs::copy_options::overwrite_existing);
     } else if (fs::is_directory(fromStatus)) {
         fs::create_directory(to);
-        for (auto & entry : fs::directory_iterator(from.path())) {
-            copy(entry, to / entry.path().filename(), andDelete);
+        for (auto & entry : fs::directory_iterator(from)) {
+            copyFile(entry, to / entry.path().filename(), andDelete);
         }
     } else {
-        throw Error("file '%s' has an unsupported type", from.path());
+        throw Error("file '%s' has an unsupported type", from);
     }
 
-#ifndef _WIN32
-    setWriteTime(to, statOfFrom);
-#endif
+    setWriteTime(to, lstat(from.string().c_str()));
     if (andDelete) {
         if (!fs::is_symlink(fromStatus))
-            fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
-        fs::remove(from.path());
+            fs::permissions(from, fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow);
+        fs::remove(from);
     }
 }
 
-void copyFile(const Path & oldPath, const Path & newPath, bool andDelete)
-{
-    return copy(fs::directory_entry(fs::path(oldPath)), fs::path(newPath), andDelete);
-}
-
-void renameFile(const Path & oldName, const Path & newName)
-{
-    fs::rename(oldName, newName);
-}
-
 void moveFile(const Path & oldName, const Path & newName)
 {
     try {
-        renameFile(oldName, newName);
+        std::filesystem::rename(oldName, newName);
     } catch (fs::filesystem_error & e) {
         auto oldPath = fs::path(oldName);
         auto newPath = fs::path(newName);
@@ -717,8 +669,8 @@ void moveFile(const Path & oldName, const Path & newName)
         if (e.code().value() == EXDEV) {
             fs::remove(newPath);
             warn("Can’t rename %s as %s, copying instead", oldName, newName);
-            copy(fs::directory_entry(oldPath), tempCopyTarget, true);
-            renameFile(
+            copyFile(oldPath, tempCopyTarget, true);
+            std::filesystem::rename(
                 os_string_to_string(PathViewNG { tempCopyTarget }),
                 os_string_to_string(PathViewNG { newPath }));
         }
diff --git a/src/libutil/file-system.hh b/src/libutil/file-system.hh
index 0c4e7cfdd48..4b215162de6 100644
--- a/src/libutil/file-system.hh
+++ b/src/libutil/file-system.hh
@@ -9,6 +9,7 @@
 #include "error.hh"
 #include "logging.hh"
 #include "file-descriptor.hh"
+#include "file-path.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -19,21 +20,12 @@
 #endif
 #include <signal.h>
 
-#include <boost/lexical_cast.hpp>
-
 #include <atomic>
 #include <functional>
 #include <map>
 #include <sstream>
 #include <optional>
 
-#ifndef HAVE_STRUCT_DIRENT_D_TYPE
-#define DT_UNKNOWN 0
-#define DT_REG 1
-#define DT_LNK 2
-#define DT_DIR 3
-#endif
-
 /**
  * Polyfill for MinGW
  *
@@ -123,29 +115,10 @@ bool pathAccessible(const Path & path);
  */
 Path readLink(const Path & path);
 
-bool isLink(const Path & path);
-
 /**
- * Read the contents of a directory.  The entries `.` and `..` are
- * removed.
+ * Open a `Descriptor` with read-only access to the given directory.
  */
-struct DirEntry
-{
-    std::string name;
-    ino_t ino;
-    /**
-     * one of DT_*
-     */
-    unsigned char type;
-    DirEntry(std::string name, ino_t ino, unsigned char type)
-        : name(std::move(name)), ino(ino), type(type) { }
-};
-
-typedef std::vector<DirEntry> DirEntries;
-
-DirEntries readDirectory(const Path & path);
-
-unsigned char getFileType(const Path & path);
+Descriptor openDirectory(const std::filesystem::path & path);
 
 /**
  * Read the contents of a file into a string.
@@ -170,20 +143,48 @@ void syncParent(const Path & path);
  * recursively. It's not an error if the path does not exist. The
  * second variant returns the number of bytes and blocks freed.
  */
-void deletePath(const Path & path);
+void deletePath(const std::filesystem::path & path);
 
-void deletePath(const Path & path, uint64_t & bytesFreed);
+void deletePath(const std::filesystem::path & path, uint64_t & bytesFreed);
 
 /**
- * Create a directory and all its parents, if necessary.  Returns the
- * list of created directories, in order of creation.
+ * Create a directory and all its parents, if necessary.
  */
-Paths createDirs(const Path & path);
-inline Paths createDirs(PathView path)
+void createDirs(const Path & path);
+inline void createDirs(PathView path)
 {
     return createDirs(Path(path));
 }
 
+/**
+ * Create a single directory.
+ */
+void createDir(const Path & path, mode_t mode = 0755);
+
+/**
+ * Set the access and modification times of the given path, not
+ * following symlinks.
+ *
+ * @param accessTime Specified in seconds.
+ *
+ * @param modificationTime Specified in seconds.
+ *
+ * @param isSymlink Whether the file in question is a symlink. Used for
+ * fallback code where we don't have `lutimes` or similar. if
+ * `std::optional` is passed, the information will be recomputed if it
+ * is needed. Race conditions are possible so be careful!
+ */
+void setWriteTime(
+    const std::filesystem::path & path,
+    time_t accessedTime,
+    time_t modificationTime,
+    std::optional<bool> isSymlink = std::nullopt);
+
+/**
+ * Convenience wrapper that takes all arguments from the `struct stat`.
+ */
+void setWriteTime(const std::filesystem::path & path, const struct stat & st);
+
 /**
  * Create a symlink.
  */
@@ -194,8 +195,6 @@ void createSymlink(const Path & target, const Path & link);
  */
 void replaceSymlink(const Path & target, const Path & link);
 
-void renameFile(const Path & src, const Path & dst);
-
 /**
  * Similar to 'renameFile', but fallback to a copy+remove if `src` and `dst`
  * are on a different filesystem.
@@ -211,24 +210,30 @@ void moveFile(const Path & src, const Path & dst);
  * with the guaranty that the destination will be “fresh”, with no stale inode
  * or file descriptor pointing to it).
  */
-void copyFile(const Path & oldPath, const Path & newPath, bool andDelete);
+void copyFile(const std::filesystem::path & from, const std::filesystem::path & to, bool andDelete);
 
 /**
  * Automatic cleanup of resources.
  */
 class AutoDelete
 {
-    Path path;
+    std::filesystem::path _path;
     bool del;
     bool recursive;
 public:
     AutoDelete();
-    AutoDelete(const Path & p, bool recursive = true);
+    AutoDelete(const std::filesystem::path & p, bool recursive = true);
     ~AutoDelete();
+
     void cancel();
-    void reset(const Path & p, bool recursive = true);
-    operator Path() const { return path; }
-    operator PathView() const { return path; }
+
+    void reset(const std::filesystem::path & p, bool recursive = true);
+
+    const std::filesystem::path & path() const { return _path; }
+    PathViewNG view() const { return _path; }
+
+    operator const std::filesystem::path & () const { return _path; }
+    operator PathViewNG () const { return _path; }
 };
 
 
diff --git a/src/libutil/finally.hh b/src/libutil/finally.hh
index f9f0195a155..bda4227e6e9 100644
--- a/src/libutil/finally.hh
+++ b/src/libutil/finally.hh
@@ -2,6 +2,8 @@
 ///@file
 
 #include <utility>
+#include <cassert>
+#include <exception>
 
 /**
  * A trivial class to run a function at the end of a scope.
@@ -21,5 +23,25 @@ public:
     Finally(Finally &&other) : fun(std::move(other.fun)) {
         other.movedFrom = true;
     }
-    ~Finally() { if (!movedFrom) fun(); }
+    ~Finally() noexcept(false)
+    {
+        try {
+            if (!movedFrom)
+                fun();
+        } catch (...) {
+            // finally may only throw an exception if exception handling is not already
+            // in progress. if handling *is* in progress we have to return cleanly here
+            // but are still prohibited from doing so since eating the exception would,
+            // in almost all cases, mess up error handling even more. the only good way
+            // to handle this is to abort entirely and leave a message, so we'll assert
+            // (and rethrow anyway, just as a defense against possible NASSERT builds.)
+            if (std::uncaught_exceptions()) {
+                assert(false &&
+                    "Finally function threw an exception during exception handling. "
+                    "this is not what you want, please use some other methods (like "
+                    "std::promise or async) instead.");
+            }
+            throw;
+        }
+    }
 };
diff --git a/src/libutil/fmt.hh b/src/libutil/fmt.hh
index c178257d416..850b7162d87 100644
--- a/src/libutil/fmt.hh
+++ b/src/libutil/fmt.hh
@@ -111,6 +111,8 @@ std::ostream & operator<<(std::ostream & out, const Magenta<T> & y)
 /**
  * Values wrapped in this class are printed without coloring.
  *
+ * Specifically, the color is reset to normal before printing the value.
+ *
  * By default, arguments to `HintFmt` are printed in magenta (see `Magenta`).
  */
 template <class T>
@@ -182,6 +184,8 @@ public:
         return *this;
     }
 
+    HintFmt & operator=(HintFmt const & rhs) = default;
+
     std::string str() const
     {
         return fmt.str();
diff --git a/src/libutil/fs-sink.cc b/src/libutil/fs-sink.cc
index 91070ea89a9..194e86fdd6b 100644
--- a/src/libutil/fs-sink.cc
+++ b/src/libutil/fs-sink.cc
@@ -1,7 +1,7 @@
 #include <fcntl.h>
 
 #include "error.hh"
-#include "config.hh"
+#include "config-global.hh"
 #include "fs-sink.hh"
 
 #if _WIN32
@@ -14,7 +14,7 @@ namespace nix {
 
 void copyRecursive(
     SourceAccessor & accessor, const CanonPath & from,
-    FileSystemObjectSink & sink, const Path & to)
+    FileSystemObjectSink & sink, const CanonPath & to)
 {
     auto stat = accessor.lstat(from);
 
@@ -43,7 +43,7 @@ void copyRecursive(
         for (auto & [name, _] : accessor.readDirectory(from)) {
             copyRecursive(
                 accessor, from / name,
-                sink, to + "/" + name);
+                sink, to / name);
             break;
         }
         break;
@@ -69,17 +69,9 @@ static RestoreSinkSettings restoreSinkSettings;
 static GlobalConfig::Register r1(&restoreSinkSettings);
 
 
-void RestoreSink::createDirectory(const Path & path)
+void RestoreSink::createDirectory(const CanonPath & path)
 {
-    Path p = dstPath + path;
-    if (
-#ifndef _WIN32 // TODO abstract mkdir perms for Windows
-        mkdir(p.c_str(), 0777) == -1
-#else
-        !CreateDirectoryW(pathNG(p).c_str(), NULL)
-#endif
-        )
-        throw NativeSysError("creating directory '%1%'", p);
+    std::filesystem::create_directory(dstPath / path.rel());
 };
 
 struct RestoreRegularFile : CreateRegularFileSink {
@@ -90,13 +82,22 @@ struct RestoreRegularFile : CreateRegularFileSink {
     void preallocateContents(uint64_t size) override;
 };
 
-void RestoreSink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
+static std::filesystem::path append(const std::filesystem::path & src, const CanonPath & path)
+{
+    auto dst = src;
+    if (!path.rel().empty())
+        dst /= path.rel();
+    return dst;
+}
+
+void RestoreSink::createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func)
 {
-    Path p = dstPath + path;
+    auto p = append(dstPath, path);
+
     RestoreRegularFile crf;
     crf.fd =
 #ifdef _WIN32
-        CreateFileW(pathNG(path).c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL)
+        CreateFileW(path.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL)
 #else
         open(p.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, 0666)
 #endif
@@ -141,14 +142,14 @@ void RestoreRegularFile::operator () (std::string_view data)
     writeFull(fd.get(), data);
 }
 
-void RestoreSink::createSymlink(const Path & path, const std::string & target)
+void RestoreSink::createSymlink(const CanonPath & path, const std::string & target)
 {
-    Path p = dstPath + path;
+    auto p = append(dstPath, path);
     nix::createSymlink(target, p);
 }
 
 
-void RegularFileSink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
+void RegularFileSink::createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func)
 {
     struct CRF : CreateRegularFileSink {
         RegularFileSink & back;
@@ -163,7 +164,7 @@ void RegularFileSink::createRegularFile(const Path & path, std::function<void(Cr
 }
 
 
-void NullFileSystemObjectSink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
+void NullFileSystemObjectSink::createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func)
 {
     struct : CreateRegularFileSink {
         void operator () (std::string_view data) override {}
diff --git a/src/libutil/fs-sink.hh b/src/libutil/fs-sink.hh
index ae577819a25..cf7d34d2273 100644
--- a/src/libutil/fs-sink.hh
+++ b/src/libutil/fs-sink.hh
@@ -28,17 +28,17 @@ struct FileSystemObjectSink
 {
     virtual ~FileSystemObjectSink() = default;
 
-    virtual void createDirectory(const Path & path) = 0;
+    virtual void createDirectory(const CanonPath & path) = 0;
 
     /**
      * This function in general is no re-entrant. Only one file can be
      * written at a time.
      */
     virtual void createRegularFile(
-        const Path & path,
+        const CanonPath & path,
         std::function<void(CreateRegularFileSink &)>) = 0;
 
-    virtual void createSymlink(const Path & path, const std::string & target) = 0;
+    virtual void createSymlink(const CanonPath & path, const std::string & target) = 0;
 };
 
 /**
@@ -46,17 +46,17 @@ struct FileSystemObjectSink
  */
 void copyRecursive(
     SourceAccessor & accessor, const CanonPath & sourcePath,
-    FileSystemObjectSink & sink, const Path & destPath);
+    FileSystemObjectSink & sink, const CanonPath & destPath);
 
 /**
  * Ignore everything and do nothing
  */
 struct NullFileSystemObjectSink : FileSystemObjectSink
 {
-    void createDirectory(const Path & path) override { }
-    void createSymlink(const Path & path, const std::string & target) override { }
+    void createDirectory(const CanonPath & path) override { }
+    void createSymlink(const CanonPath & path, const std::string & target) override { }
     void createRegularFile(
-        const Path & path,
+        const CanonPath & path,
         std::function<void(CreateRegularFileSink &)>) override;
 };
 
@@ -65,15 +65,15 @@ struct NullFileSystemObjectSink : FileSystemObjectSink
  */
 struct RestoreSink : FileSystemObjectSink
 {
-    Path dstPath;
+    std::filesystem::path dstPath;
 
-    void createDirectory(const Path & path) override;
+    void createDirectory(const CanonPath & path) override;
 
     void createRegularFile(
-        const Path & path,
+        const CanonPath & path,
         std::function<void(CreateRegularFileSink &)>) override;
 
-    void createSymlink(const Path & path, const std::string & target) override;
+    void createSymlink(const CanonPath & path, const std::string & target) override;
 };
 
 /**
@@ -88,18 +88,18 @@ struct RegularFileSink : FileSystemObjectSink
 
     RegularFileSink(Sink & sink) : sink(sink) { }
 
-    void createDirectory(const Path & path) override
+    void createDirectory(const CanonPath & path) override
     {
         regular = false;
     }
 
-    void createSymlink(const Path & path, const std::string & target) override
+    void createSymlink(const CanonPath & path, const std::string & target) override
     {
         regular = false;
     }
 
     void createRegularFile(
-        const Path & path,
+        const CanonPath & path,
         std::function<void(CreateRegularFileSink &)>) override;
 };
 
diff --git a/src/libutil/git.cc b/src/libutil/git.cc
index a60589baa17..a6968a43eed 100644
--- a/src/libutil/git.cc
+++ b/src/libutil/git.cc
@@ -8,7 +8,6 @@
 #include "signals.hh"
 #include "config.hh"
 #include "hash.hh"
-#include "posix-source-accessor.hh"
 
 #include "git.hh"
 #include "serialise.hh"
@@ -54,7 +53,7 @@ static std::string getString(Source & source, int n)
 
 void parseBlob(
     FileSystemObjectSink & sink,
-    const Path & sinkPath,
+    const CanonPath & sinkPath,
     Source & source,
     BlobMode blobMode,
     const ExperimentalFeatureSettings & xpSettings)
@@ -117,7 +116,7 @@ void parseBlob(
 
 void parseTree(
     FileSystemObjectSink & sink,
-    const Path & sinkPath,
+    const CanonPath & sinkPath,
     Source & source,
     std::function<SinkHook> hook,
     const ExperimentalFeatureSettings & xpSettings)
@@ -148,7 +147,7 @@ void parseTree(
         Hash hash(HashAlgorithm::SHA1);
         std::copy(hashs.begin(), hashs.end(), hash.hash);
 
-        hook(name, TreeEntry {
+        hook(CanonPath{name}, TreeEntry {
             .mode = mode,
             .hash = hash,
         });
@@ -172,7 +171,7 @@ ObjectType parseObjectType(
 
 void parse(
     FileSystemObjectSink & sink,
-    const Path & sinkPath,
+    const CanonPath & sinkPath,
     Source & source,
     BlobMode rootModeIfBlob,
     std::function<SinkHook> hook,
@@ -209,7 +208,7 @@ std::optional<Mode> convertMode(SourceAccessor::Type type)
 
 void restore(FileSystemObjectSink & sink, Source & source, std::function<RestoreHook> hook)
 {
-    parse(sink, "", source, BlobMode::Regular, [&](Path name, TreeEntry entry) {
+    parse(sink, CanonPath::root, source, BlobMode::Regular, [&](CanonPath name, TreeEntry entry) {
         auto [accessor, from] = hook(entry.hash);
         auto stat = accessor->lstat(from);
         auto gotOpt = convertMode(stat.type);
@@ -269,18 +268,18 @@ void dumpTree(const Tree & entries, Sink & sink,
 
 
 Mode dump(
-    SourceAccessor & accessor, const CanonPath & path,
+    const SourcePath & path,
     Sink & sink,
     std::function<DumpHook> hook,
     PathFilter & filter,
     const ExperimentalFeatureSettings & xpSettings)
 {
-    auto st = accessor.lstat(path);
+    auto st = path.lstat();
 
     switch (st.type) {
     case SourceAccessor::tRegular:
     {
-        accessor.readFile(path, sink, [&](uint64_t size) {
+        path.readFile(sink, [&](uint64_t size) {
             dumpBlobPrefix(size, sink, xpSettings);
         });
         return st.isExecutable
@@ -291,9 +290,9 @@ Mode dump(
     case SourceAccessor::tDirectory:
     {
         Tree entries;
-        for (auto & [name, _] : accessor.readDirectory(path)) {
+        for (auto & [name, _] : path.readDirectory()) {
             auto child = path / name;
-            if (!filter(child.abs())) continue;
+            if (!filter(child.path.abs())) continue;
 
             auto entry = hook(child);
 
@@ -309,7 +308,7 @@ Mode dump(
 
     case SourceAccessor::tSymlink:
     {
-        auto target = accessor.readLink(path);
+        auto target = path.readLink();
         dumpBlobPrefix(target.size(), sink, xpSettings);
         sink(target);
         return Mode::Symlink;
@@ -323,13 +322,14 @@ Mode dump(
 
 
 TreeEntry dumpHash(
-        HashAlgorithm ha,
-        SourceAccessor & accessor, const CanonPath & path, PathFilter & filter)
+    HashAlgorithm ha,
+    const SourcePath & path,
+    PathFilter & filter)
 {
     std::function<DumpHook> hook;
-    hook = [&](const CanonPath & path) -> TreeEntry {
+    hook = [&](const SourcePath & path) -> TreeEntry {
         auto hashSink = HashSink(ha);
-        auto mode = dump(accessor, path, hashSink, hook, filter);
+        auto mode = dump(path, hashSink, hook, filter);
         auto hash = hashSink.finish().first;
         return {
             .mode = mode,
diff --git a/src/libutil/git.hh b/src/libutil/git.hh
index cfea48fbe2d..2190cc5509c 100644
--- a/src/libutil/git.hh
+++ b/src/libutil/git.hh
@@ -8,7 +8,7 @@
 #include "types.hh"
 #include "serialise.hh"
 #include "hash.hh"
-#include "source-accessor.hh"
+#include "source-path.hh"
 #include "fs-sink.hh"
 
 namespace nix::git {
@@ -64,7 +64,7 @@ using Tree = std::map<std::string, TreeEntry>;
  * Implementations may seek to memoize resources (bandwidth, storage,
  * etc.) for the same Git hash.
  */
-using SinkHook = void(const Path & name, TreeEntry entry);
+using SinkHook = void(const CanonPath & name, TreeEntry entry);
 
 /**
  * Parse the "blob " or "tree " prefix.
@@ -89,13 +89,13 @@ enum struct BlobMode : RawMode
 };
 
 void parseBlob(
-    FileSystemObjectSink & sink, const Path & sinkPath,
+    FileSystemObjectSink & sink, const CanonPath & sinkPath,
     Source & source,
     BlobMode blobMode,
     const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
 void parseTree(
-    FileSystemObjectSink & sink, const Path & sinkPath,
+    FileSystemObjectSink & sink, const CanonPath & sinkPath,
     Source & source,
     std::function<SinkHook> hook,
     const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
@@ -108,7 +108,7 @@ void parseTree(
  * a blob, this is ignored.
  */
 void parse(
-    FileSystemObjectSink & sink, const Path & sinkPath,
+    FileSystemObjectSink & sink, const CanonPath & sinkPath,
     Source & source,
     BlobMode rootModeIfBlob,
     std::function<SinkHook> hook,
@@ -125,7 +125,7 @@ std::optional<Mode> convertMode(SourceAccessor::Type type);
  * Given a `Hash`, return a `SourceAccessor` and `CanonPath` pointing to
  * the file system object with that path.
  */
-using RestoreHook = std::pair<SourceAccessor *, CanonPath>(Hash);
+using RestoreHook = SourcePath(Hash);
 
 /**
  * Wrapper around `parse` and `RestoreSink`
@@ -157,10 +157,10 @@ void dumpTree(
  * Note that if the child is a directory, its child in must also be so
  * processed in order to compute this information.
  */
-using DumpHook = TreeEntry(const CanonPath & path);
+using DumpHook = TreeEntry(const SourcePath & path);
 
 Mode dump(
-    SourceAccessor & accessor, const CanonPath & path,
+    const SourcePath & path,
     Sink & sink,
     std::function<DumpHook> hook,
     PathFilter & filter = defaultPathFilter,
@@ -172,9 +172,9 @@ Mode dump(
  * A smaller wrapper around `dump`.
  */
 TreeEntry dumpHash(
-            HashAlgorithm ha,
-            SourceAccessor & accessor, const CanonPath & path,
-            PathFilter & filter = defaultPathFilter);
+    HashAlgorithm ha,
+    const SourcePath & path,
+    PathFilter & filter = defaultPathFilter);
 
 /**
  * A line from the output of `git ls-remote --symref`.
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index d4c9d65337b..7064e96e61c 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -50,21 +50,14 @@ bool Hash::operator == (const Hash & h2) const
 }
 
 
-bool Hash::operator != (const Hash & h2) const
+std::strong_ordering Hash::operator <=> (const Hash & h) const
 {
-    return !(*this == h2);
-}
-
-
-bool Hash::operator < (const Hash & h) const
-{
-    if (hashSize < h.hashSize) return true;
-    if (hashSize > h.hashSize) return false;
+    if (auto cmp = hashSize <=> h.hashSize; cmp != 0) return cmp;
     for (unsigned int i = 0; i < hashSize; i++) {
-        if (hash[i] < h.hash[i]) return true;
-        if (hash[i] > h.hash[i]) return false;
+        if (auto cmp = hash[i] <=> h.hash[i]; cmp != 0) return cmp;
     }
-    return false;
+    if (auto cmp = algo <=> h.algo; cmp != 0) return cmp;
+    return std::strong_ordering::equivalent;
 }
 
 
diff --git a/src/libutil/hash.hh b/src/libutil/hash.hh
index e14aae43c08..ef96d08c978 100644
--- a/src/libutil/hash.hh
+++ b/src/libutil/hash.hh
@@ -86,19 +86,14 @@ private:
 
 public:
     /**
-     * Check whether two hash are equal.
+     * Check whether two hashes are equal.
      */
     bool operator == (const Hash & h2) const;
 
     /**
-     * Check whether two hash are not equal.
+     * Compare how two hashes are ordered.
      */
-    bool operator != (const Hash & h2) const;
-
-    /**
-     * For sorting.
-     */
-    bool operator < (const Hash & h) const;
+    std::strong_ordering operator <=> (const Hash & h2) const;
 
     /**
      * Returns the length of a base-16 representation of this hash.
diff --git a/src/libutil/input-accessor.hh b/src/libutil/input-accessor.hh
deleted file mode 100644
index 55b7c2f2f84..00000000000
--- a/src/libutil/input-accessor.hh
+++ /dev/null
@@ -1,27 +0,0 @@
-#pragma once
-///@file
-
-#include "source-accessor.hh"
-#include "ref.hh"
-#include "repair-flag.hh"
-
-namespace nix {
-
-MakeError(RestrictedPathError, Error);
-
-struct InputAccessor : virtual SourceAccessor, std::enable_shared_from_this<InputAccessor>
-{
-    std::optional<std::string> fingerprint;
-
-    /**
-     * Return the maximum last-modified time of the files in this
-     * tree, if available.
-     */
-    virtual std::optional<time_t> getLastModified()
-    {
-        return std::nullopt;
-    }
-
-};
-
-}
diff --git a/src/libutil/json-utils.cc b/src/libutil/json-utils.cc
index 1b911bf75eb..dff068e07c5 100644
--- a/src/libutil/json-utils.cc
+++ b/src/libutil/json-utils.cc
@@ -39,12 +39,9 @@ std::optional<nlohmann::json> optionalValueAt(const nlohmann::json::object_t & m
 }
 
 
-std::optional<nlohmann::json> getNullable(const nlohmann::json & value)
+const nlohmann::json * getNullable(const nlohmann::json & value)
 {
-    if (value.is_null())
-        return std::nullopt;
-
-    return value.get<nlohmann::json>();
+    return value.is_null() ? nullptr : &value;
 }
 
 /**
diff --git a/src/libutil/json-utils.hh b/src/libutil/json-utils.hh
index 08c98cc8c0d..fe7a406cf91 100644
--- a/src/libutil/json-utils.hh
+++ b/src/libutil/json-utils.hh
@@ -29,7 +29,7 @@ std::optional<nlohmann::json> optionalValueAt(const nlohmann::json::object_t & v
  * Downcast the json object, failing with a nice error if the conversion fails.
  * See https://json.nlohmann.me/features/types/
  */
-std::optional<nlohmann::json> getNullable(const nlohmann::json & value);
+const nlohmann::json * getNullable(const nlohmann::json & value);
 const nlohmann::json::object_t & getObject(const nlohmann::json & value);
 const nlohmann::json::array_t & getArray(const nlohmann::json & value);
 const nlohmann::json::string_t & getString(const nlohmann::json & value);
diff --git a/src/libutil/linux/cgroup.cc b/src/libutil/linux/cgroup.cc
index 8b8942643e3..140ff45668a 100644
--- a/src/libutil/linux/cgroup.cc
+++ b/src/libutil/linux/cgroup.cc
@@ -1,4 +1,5 @@
 #include "cgroup.hh"
+#include "signals.hh"
 #include "util.hh"
 #include "file-system.hh"
 #include "finally.hh"
@@ -47,26 +48,27 @@ std::map<std::string, std::string> getCgroups(const Path & cgroupFile)
     return cgroups;
 }
 
-static CgroupStats destroyCgroup(const Path & cgroup, bool returnStats)
+static CgroupStats destroyCgroup(const std::filesystem::path & cgroup, bool returnStats)
 {
     if (!pathExists(cgroup)) return {};
 
-    auto procsFile = cgroup + "/cgroup.procs";
+    auto procsFile = cgroup / "cgroup.procs";
 
     if (!pathExists(procsFile))
         throw Error("'%s' is not a cgroup", cgroup);
 
     /* Use the fast way to kill every process in a cgroup, if
        available. */
-    auto killFile = cgroup + "/cgroup.kill";
+    auto killFile = cgroup / "cgroup.kill";
     if (pathExists(killFile))
         writeFile(killFile, "1");
 
     /* Otherwise, manually kill every process in the subcgroups and
        this cgroup. */
-    for (auto & entry : readDirectory(cgroup)) {
-        if (entry.type != DT_DIR) continue;
-        destroyCgroup(cgroup + "/" + entry.name, false);
+    for (auto & entry : std::filesystem::directory_iterator{cgroup}) {
+        checkInterrupt();
+        if (entry.symlink_status().type() != std::filesystem::file_type::directory) continue;
+        destroyCgroup(cgroup / entry.path().filename(), false);
     }
 
     int round = 1;
@@ -111,7 +113,7 @@ static CgroupStats destroyCgroup(const Path & cgroup, bool returnStats)
     CgroupStats stats;
 
     if (returnStats) {
-        auto cpustatPath = cgroup + "/cpu.stat";
+        auto cpustatPath = cgroup / "cpu.stat";
 
         if (pathExists(cpustatPath)) {
             for (auto & line : tokenizeString<std::vector<std::string>>(readFile(cpustatPath), "\n")) {
diff --git a/src/libutil/linux/meson.build b/src/libutil/linux/meson.build
new file mode 100644
index 00000000000..a1ded76ca16
--- /dev/null
+++ b/src/libutil/linux/meson.build
@@ -0,0 +1,11 @@
+sources += files(
+  'cgroup.cc',
+  'namespaces.cc',
+)
+
+include_dirs += include_directories('.')
+
+headers += files(
+  'cgroup.hh',
+  'namespaces.hh',
+)
diff --git a/src/libutil/linux/namespaces.cc b/src/libutil/linux/namespaces.cc
index f8289ef39c4..d4766cbba91 100644
--- a/src/libutil/linux/namespaces.cc
+++ b/src/libutil/linux/namespaces.cc
@@ -137,10 +137,10 @@ void restoreMountNamespace()
     }
 }
 
-void unshareFilesystem()
+void tryUnshareFilesystem()
 {
-    if (unshare(CLONE_FS) != 0 && errno != EPERM)
-        throw SysError("unsharing filesystem state in download thread");
+    if (unshare(CLONE_FS) != 0 && errno != EPERM && errno != ENOSYS)
+        throw SysError("unsharing filesystem state");
 }
 
 }
diff --git a/src/libutil/linux/namespaces.hh b/src/libutil/linux/namespaces.hh
index ef3c9123fbe..208920b80b1 100644
--- a/src/libutil/linux/namespaces.hh
+++ b/src/libutil/linux/namespaces.hh
@@ -20,11 +20,13 @@ void saveMountNamespace();
 void restoreMountNamespace();
 
 /**
- * Cause this thread to not share any FS attributes with the main
+ * Cause this thread to try to not share any FS attributes with the main
  * thread, because this causes setns() in restoreMountNamespace() to
  * fail.
+ *
+ * This is best effort -- EPERM and ENOSYS failures are just ignored.
  */
-void unshareFilesystem();
+void tryUnshareFilesystem();
 
 bool userNamespacesSupported();
 
diff --git a/src/libutil/local.mk b/src/libutil/local.mk
index 5cd8d4ac8d8..e9b498e65ad 100644
--- a/src/libutil/local.mk
+++ b/src/libutil/local.mk
@@ -40,3 +40,5 @@ $(foreach i, $(wildcard $(d)/signature/*.hh), \
 ifeq ($(HAVE_LIBCPUID), 1)
   libutil_LDFLAGS += -lcpuid
 endif
+
+$(eval $(call install-file-in, $(buildprefix)$(d)/nix-util.pc, $(libdir)/pkgconfig, 0644))
diff --git a/src/libutil/logging.cc b/src/libutil/logging.cc
index 2511c88499f..55751b4cf0d 100644
--- a/src/libutil/logging.cc
+++ b/src/libutil/logging.cc
@@ -3,11 +3,12 @@
 #include "environment-variables.hh"
 #include "terminal.hh"
 #include "util.hh"
-#include "config.hh"
+#include "config-global.hh"
 #include "source-path.hh"
 #include "position.hh"
 
 #include <atomic>
+#include <sstream>
 #include <nlohmann/json.hpp>
 #include <iostream>
 
diff --git a/src/libutil/memory-source-accessor.cc b/src/libutil/memory-source-accessor.cc
index 880fa61b7f8..c4eee1031cf 100644
--- a/src/libutil/memory-source-accessor.cc
+++ b/src/libutil/memory-source-accessor.cc
@@ -108,7 +108,7 @@ std::string MemorySourceAccessor::readLink(const CanonPath & path)
         throw Error("file '%s' is not a symbolic link", path);
 }
 
-CanonPath MemorySourceAccessor::addFile(CanonPath path, std::string && contents)
+SourcePath MemorySourceAccessor::addFile(CanonPath path, std::string && contents)
 {
     auto * f = open(path, File { File::Regular {} });
     if (!f)
@@ -118,15 +118,15 @@ CanonPath MemorySourceAccessor::addFile(CanonPath path, std::string && contents)
     else
         throw Error("file '%s' is not a regular file", path);
 
-    return path;
+    return SourcePath{ref(shared_from_this()), path};
 }
 
 
 using File = MemorySourceAccessor::File;
 
-void MemorySink::createDirectory(const Path & path)
+void MemorySink::createDirectory(const CanonPath & path)
 {
-    auto * f = dst.open(CanonPath{path}, File { File::Directory { } });
+    auto * f = dst.open(path, File { File::Directory { } });
     if (!f)
         throw Error("file '%s' cannot be made because some parent file is not a directory", path);
 
@@ -146,9 +146,9 @@ struct CreateMemoryRegularFile : CreateRegularFileSink {
     void preallocateContents(uint64_t size) override;
 };
 
-void MemorySink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
+void MemorySink::createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func)
 {
-    auto * f = dst.open(CanonPath{path}, File { File::Regular {} });
+    auto * f = dst.open(path, File { File::Regular {} });
     if (!f)
         throw Error("file '%s' cannot be made because some parent file is not a directory", path);
     if (auto * rp = std::get_if<File::Regular>(&f->raw)) {
@@ -173,9 +173,9 @@ void CreateMemoryRegularFile::operator () (std::string_view data)
     regularFile.contents += data;
 }
 
-void MemorySink::createSymlink(const Path & path, const std::string & target)
+void MemorySink::createSymlink(const CanonPath & path, const std::string & target)
 {
-    auto * f = dst.open(CanonPath{path}, File { File::Symlink { } });
+    auto * f = dst.open(path, File { File::Symlink { } });
     if (!f)
         throw Error("file '%s' cannot be made because some parent file is not a directory", path);
     if (auto * s = std::get_if<File::Symlink>(&f->raw))
@@ -184,4 +184,10 @@ void MemorySink::createSymlink(const Path & path, const std::string & target)
         throw Error("file '%s' is not a symbolic link", path);
 }
 
+ref<SourceAccessor> makeEmptySourceAccessor()
+{
+    static auto empty = make_ref<MemorySourceAccessor>().cast<SourceAccessor>();
+    return empty;
+}
+
 }
diff --git a/src/libutil/memory-source-accessor.hh b/src/libutil/memory-source-accessor.hh
index 7a1990d2f72..cd5146c8913 100644
--- a/src/libutil/memory-source-accessor.hh
+++ b/src/libutil/memory-source-accessor.hh
@@ -1,4 +1,4 @@
-#include "source-accessor.hh"
+#include "source-path.hh"
 #include "fs-sink.hh"
 #include "variant-wrapper.hh"
 
@@ -69,7 +69,7 @@ struct MemorySourceAccessor : virtual SourceAccessor
      */
     File * open(const CanonPath & path, std::optional<File> create);
 
-    CanonPath addFile(CanonPath path, std::string && contents);
+    SourcePath addFile(CanonPath path, std::string && contents);
 };
 
 /**
@@ -81,13 +81,13 @@ struct MemorySink : FileSystemObjectSink
 
     MemorySink(MemorySourceAccessor & dst) : dst(dst) { }
 
-    void createDirectory(const Path & path) override;
+    void createDirectory(const CanonPath & path) override;
 
     void createRegularFile(
-        const Path & path,
+        const CanonPath & path,
         std::function<void(CreateRegularFileSink &)>) override;
 
-    void createSymlink(const Path & path, const std::string & target) override;
+    void createSymlink(const CanonPath & path, const std::string & target) override;
 };
 
 }
diff --git a/src/libutil/meson.build b/src/libutil/meson.build
new file mode 100644
index 00000000000..ac2b8353674
--- /dev/null
+++ b/src/libutil/meson.build
@@ -0,0 +1,265 @@
+project('nix-util', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+# Check for each of these functions, and create a define like `#define
+# HAVE_LUTIMES 1`. The `#define` is unconditional, 0 for not found and 1
+# for found. One therefore uses it with `#if` not `#ifdef`.
+check_funcs = [
+  # Optionally used for changing the mtime of symlinks.
+  'lutimes',
+  # Optionally used for creating pipes on Unix
+  'pipe2',
+  # Optionally used to preallocate files to be large enough before
+  # writing to them.
+  'posix_fallocate',
+  # Optionally used to get more information about processes failing due
+  # to a signal on Unix.
+  'strsignal',
+  # Optionally used to try to close more file descriptors (e.g. before
+  # forking) on Unix.
+  'sysconf',
+]
+foreach funcspec : check_funcs
+  define_name = 'HAVE_' + funcspec.underscorify().to_upper()
+  define_value = cxx.has_function(funcspec).to_int()
+  configdata.set(define_name, define_value)
+endforeach
+
+subdir('build-utils-meson/threads')
+
+if host_machine.system() == 'windows'
+  socket = cxx.find_library('ws2_32')
+  deps_other += socket
+elif host_machine.system() == 'sunos'
+  socket = cxx.find_library('socket')
+  network_service_library = cxx.find_library('nsl')
+  deps_other += [socket, network_service_library]
+endif
+
+boost = dependency(
+  'boost',
+  modules : ['context', 'coroutine'],
+)
+# boost is a public dependency, but not a pkg-config dependency unfortunately, so we
+# put in `deps_other`.
+deps_other += boost
+
+openssl = dependency(
+  'libcrypto',
+  'openssl',
+  version : '>= 1.1.1',
+)
+deps_private += openssl
+
+libarchive = dependency('libarchive', version : '>= 3.1.2')
+deps_public += libarchive
+if get_option('default_library') == 'static'
+  # Workaround until https://github.com/libarchive/libarchive/issues/1446 is fixed
+  add_project_arguments('-lz', language : 'cpp')
+endif
+
+sodium = dependency('libsodium', 'sodium')
+deps_private += sodium
+
+brotli = [
+  dependency('libbrotlicommon'),
+  dependency('libbrotlidec'),
+  dependency('libbrotlienc'),
+]
+deps_private += brotli
+
+cpuid_required = get_option('cpuid')
+if host_machine.cpu_family() != 'x86_64' and cpuid_required.enabled()
+  warning('Force-enabling seccomp on non-x86_64 does not make sense')
+endif
+cpuid = dependency('libcpuid', 'cpuid', required : cpuid_required)
+configdata.set('HAVE_LIBCPUID', cpuid.found().to_int())
+deps_private += cpuid
+
+nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
+deps_public += nlohmann_json
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-util.hh',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'archive.cc',
+  'args.cc',
+  'canon-path.cc',
+  'compression.cc',
+  'compute-levels.cc',
+  'config.cc',
+  'config-global.cc',
+  'current-process.cc',
+  'english.cc',
+  'environment-variables.cc',
+  'error.cc',
+  'exit.cc',
+  'experimental-features.cc',
+  'file-content-address.cc',
+  'file-descriptor.cc',
+  'file-system.cc',
+  'fs-sink.cc',
+  'git.cc',
+  'hash.cc',
+  'hilite.cc',
+  'json-utils.cc',
+  'logging.cc',
+  'memory-source-accessor.cc',
+  'position.cc',
+  'posix-source-accessor.cc',
+  'references.cc',
+  'serialise.cc',
+  'signature/local-keys.cc',
+  'signature/signer.cc',
+  'source-accessor.cc',
+  'source-path.cc',
+  'suggestions.cc',
+  'tarfile.cc',
+  'terminal.cc',
+  'thread-pool.cc',
+  'unix-domain-socket.cc',
+  'url.cc',
+  'users.cc',
+  'util.cc',
+  'xml-writer.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'abstract-setting-to-json.hh',
+  'ansicolor.hh',
+  'archive.hh',
+  'args.hh',
+  'args/root.hh',
+  'callback.hh',
+  'canon-path.hh',
+  'chunked-vector.hh',
+  'closure.hh',
+  'comparator.hh',
+  'compression.hh',
+  'compute-levels.hh',
+  'config-global.hh',
+  'config-impl.hh',
+  'config.hh',
+  'current-process.hh',
+  'english.hh',
+  'environment-variables.hh',
+  'error.hh',
+  'exit.hh',
+  'experimental-features.hh',
+  'file-content-address.hh',
+  'file-descriptor.hh',
+  'file-path-impl.hh',
+  'file-path.hh',
+  'file-system.hh',
+  'finally.hh',
+  'fmt.hh',
+  'fs-sink.hh',
+  'git.hh',
+  'hash.hh',
+  'hilite.hh',
+  'json-impls.hh',
+  'json-utils.hh',
+  'logging.hh',
+  'lru-cache.hh',
+  'memory-source-accessor.hh',
+  'muxable-pipe.hh',
+  'pool.hh',
+  'position.hh',
+  'posix-source-accessor.hh',
+  'processes.hh',
+  'ref.hh',
+  'references.hh',
+  'regex-combinators.hh',
+  'repair-flag.hh',
+  'serialise.hh',
+  'signals.hh',
+  'signature/local-keys.hh',
+  'signature/signer.hh',
+  'source-accessor.hh',
+  'source-path.hh',
+  'split.hh',
+  'suggestions.hh',
+  'sync.hh',
+  'tarfile.hh',
+  'terminal.hh',
+  'thread-pool.hh',
+  'topo-sort.hh',
+  'types.hh',
+  'unix-domain-socket.hh',
+  'url-parts.hh',
+  'url.hh',
+  'users.hh',
+  'util.hh',
+  'variant-wrapper.hh',
+  'xml-writer.hh',
+)
+
+if host_machine.system() == 'linux'
+  subdir('linux')
+endif
+
+if host_machine.system() == 'windows'
+  subdir('windows')
+else
+  subdir('unix')
+endif
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nixutil',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+if host_machine.system() == 'windows'
+  # `libraries_private` cannot contain ad-hoc dependencies (from
+  # `find_library), so we need to do this manually
+  libraries_private += ['-lws2_32']
+endif
+
+subdir('build-utils-meson/export')
diff --git a/src/libutil/meson.options b/src/libutil/meson.options
new file mode 100644
index 00000000000..21883af0145
--- /dev/null
+++ b/src/libutil/meson.options
@@ -0,0 +1,5 @@
+# vim: filetype=meson
+
+option('cpuid', type : 'feature',
+  description : 'determine microarchitecture levels with libcpuid (only relevant on x86_64)',
+)
diff --git a/src/libutil/muxable-pipe.hh b/src/libutil/muxable-pipe.hh
new file mode 100644
index 00000000000..53ac39170f1
--- /dev/null
+++ b/src/libutil/muxable-pipe.hh
@@ -0,0 +1,82 @@
+#pragma once
+///@file
+
+#include "file-descriptor.hh"
+#ifdef _WIN32
+#  include "windows-async-pipe.hh"
+#endif
+
+#ifndef _WIN32
+#  include <poll.h>
+#else
+#  include <ioapiset.h>
+#  include "windows-error.hh"
+#endif
+
+namespace nix {
+
+/**
+ * An "muxable pipe" is a type of pipe supporting endpoints that wait
+ * for events on multiple pipes at once.
+ *
+ * On Unix, this is just a regular anonymous pipe. On Windows, this has
+ * to be a named pipe because we need I/O Completion Ports to wait on
+ * multiple pipes.
+ */
+using MuxablePipe =
+#ifndef _WIN32
+    Pipe
+#else
+    windows::AsyncPipe
+#endif
+    ;
+
+/**
+ * Use pool() (Unix) / I/O Completion Ports (Windows) to wait for the
+ * input side of any logger pipe to become `available'.  Note that
+ * `available' (i.e., non-blocking) includes EOF.
+ */
+struct MuxablePipePollState
+{
+#ifndef _WIN32
+    std::vector<struct pollfd> pollStatus;
+    std::map<int, size_t> fdToPollStatus;
+#else
+    OVERLAPPED_ENTRY oentries[0x20] = {0};
+    ULONG removed;
+    bool gotEOF = false;
+
+#endif
+
+    /**
+     * Check for ready (Unix) / completed (Windows) operations
+     */
+    void poll(
+#ifdef _WIN32
+        HANDLE ioport,
+#endif
+        std::optional<unsigned int> timeout);
+
+    using CommChannel =
+#ifndef _WIN32
+        Descriptor
+#else
+        windows::AsyncPipe *
+#endif
+        ;
+
+    /**
+     * Process for ready (Unix) / completed (Windows) operations,
+     * calling the callbacks as needed.
+     *
+     * @param handleRead callback to be passed read data.
+     *
+     * @param handleEOF callback for when the `MuxablePipe` has closed.
+     */
+    void iterate(
+        std::set<CommChannel> & channels,
+        std::function<void(Descriptor fd, std::string_view data)> handleRead,
+        std::function<void(Descriptor fd)> handleEOF);
+};
+
+}
diff --git a/src/libutil/nix-util.pc.in b/src/libutil/nix-util.pc.in
new file mode 100644
index 00000000000..85bb1e70eba
--- /dev/null
+++ b/src/libutil/nix-util.pc.in
@@ -0,0 +1,9 @@
+prefix=@prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: Nix
+Description: Nix Package Manager
+Version: @PACKAGE_VERSION@
+Libs: -L${libdir} -lnixutil
+Cflags: -I${includedir}/nix -std=c++2a
diff --git a/src/libutil/package.nix b/src/libutil/package.nix
new file mode 100644
index 00000000000..28d7d8f0edb
--- /dev/null
+++ b/src/libutil/package.nix
@@ -0,0 +1,103 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, boost
+, brotli
+, libarchive
+, libcpuid
+, libsodium
+, nlohmann_json
+, openssl
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    ./meson.options
+    ./linux/meson.build
+    ./unix/meson.build
+    ./windows/meson.build
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    brotli
+    libsodium
+    openssl
+  ] ++ lib.optional stdenv.hostPlatform.isx86_64 libcpuid
+  ;
+
+  propagatedBuildInputs = [
+    boost
+    libarchive
+    nlohmann_json
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    #
+    # TODO: change release process to add `pre` in `.version`, remove it
+    # before tagging, and restore after.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+    (lib.mesonEnable "cpuid" stdenv.hostPlatform.isx86_64)
+  ];
+
+  env = {
+    # Needed for Meson to find Boost.
+    # https://github.com/NixOS/nixpkgs/issues/86131.
+    BOOST_INCLUDEDIR = "${lib.getDev boost}/include";
+    BOOST_LIBRARYDIR = "${lib.getLib boost}/lib";
+  } // lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/libutil/posix-source-accessor.cc b/src/libutil/posix-source-accessor.cc
index a589bfd3d12..35047f89eb8 100644
--- a/src/libutil/posix-source-accessor.cc
+++ b/src/libutil/posix-source-accessor.cc
@@ -1,4 +1,5 @@
 #include "posix-source-accessor.hh"
+#include "source-path.hh"
 #include "signals.hh"
 #include "sync.hh"
 
@@ -17,11 +18,11 @@ PosixSourceAccessor::PosixSourceAccessor()
     : PosixSourceAccessor(std::filesystem::path {})
 { }
 
-std::pair<PosixSourceAccessor, CanonPath> PosixSourceAccessor::createAtRoot(const std::filesystem::path & path)
+SourcePath PosixSourceAccessor::createAtRoot(const std::filesystem::path & path)
 {
     std::filesystem::path path2 = absPath(path.string());
     return {
-        PosixSourceAccessor { path2.root_path() },
+        make_ref<PosixSourceAccessor>(path2.root_path()),
         CanonPath { path2.relative_path().string() },
     };
 }
@@ -89,14 +90,14 @@ bool PosixSourceAccessor::pathExists(const CanonPath & path)
 
 std::optional<struct stat> PosixSourceAccessor::cachedLstat(const CanonPath & path)
 {
-    static Sync<std::unordered_map<Path, std::optional<struct stat>>> _cache;
+    static SharedSync<std::unordered_map<Path, std::optional<struct stat>>> _cache;
 
     // Note: we convert std::filesystem::path to Path because the
     // former is not hashable on libc++.
     Path absPath = makeAbsPath(path).string();
 
     {
-        auto cache(_cache.lock());
+        auto cache(_cache.read());
         auto i = cache->find(absPath);
         if (i != cache->end()) return i->second;
     }
@@ -131,16 +132,34 @@ SourceAccessor::DirEntries PosixSourceAccessor::readDirectory(const CanonPath &
 {
     assertNoSymlinks(path);
     DirEntries res;
-    for (auto & entry : nix::readDirectory(makeAbsPath(path).string())) {
-        std::optional<Type> type;
-        switch (entry.type) {
-        case DT_REG: type = Type::tRegular; break;
-    #ifndef _WIN32
-        case DT_LNK: type = Type::tSymlink; break;
-    #endif
-        case DT_DIR: type = Type::tDirectory; break;
-        }
-        res.emplace(entry.name, type);
+    for (auto & entry : std::filesystem::directory_iterator{makeAbsPath(path)}) {
+        checkInterrupt();
+        auto type = [&]() -> std::optional<Type> {
+            std::filesystem::file_type nativeType;
+            try {
+                nativeType = entry.symlink_status().type();
+            } catch (std::filesystem::filesystem_error & e) {
+                // We cannot always stat the child. (Ideally there is no
+                // stat because the native directory entry has the type
+                // already, but this isn't always the case.)
+                if (e.code() == std::errc::permission_denied || e.code() == std::errc::operation_not_permitted)
+                    return std::nullopt;
+                else throw;
+            }
+
+            // cannot exhaustively enumerate because implementation-specific
+            // additional file types are allowed.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wswitch-enum"
+            switch (nativeType) {
+            case std::filesystem::file_type::regular: return Type::tRegular; break;
+            case std::filesystem::file_type::symlink: return Type::tSymlink; break;
+            case std::filesystem::file_type::directory: return Type::tDirectory; break;
+            default: return tMisc;
+            }
+#pragma GCC diagnostic pop
+        }();
+        res.emplace(entry.path().filename().string(), type);
     }
     return res;
 }
@@ -166,4 +185,14 @@ void PosixSourceAccessor::assertNoSymlinks(CanonPath path)
     }
 }
 
+ref<SourceAccessor> getFSSourceAccessor()
+{
+    static auto rootFS = make_ref<PosixSourceAccessor>();
+    return rootFS;
+}
+
+ref<SourceAccessor> makeFSSourceAccessor(std::filesystem::path root)
+{
+    return make_ref<PosixSourceAccessor>(std::move(root));
+}
 }
diff --git a/src/libutil/posix-source-accessor.hh b/src/libutil/posix-source-accessor.hh
index 717c8f01779..40f60bb54b8 100644
--- a/src/libutil/posix-source-accessor.hh
+++ b/src/libutil/posix-source-accessor.hh
@@ -4,6 +4,8 @@
 
 namespace nix {
 
+struct SourcePath;
+
 /**
  * A source accessor that uses the Unix filesystem.
  */
@@ -53,7 +55,7 @@ struct PosixSourceAccessor : virtual SourceAccessor
      * and
      * [`std::filesystem::path::relative_path`](https://en.cppreference.com/w/cpp/filesystem/path/relative_path).
      */
-    static std::pair<PosixSourceAccessor, CanonPath> createAtRoot(const std::filesystem::path & path);
+    static SourcePath createAtRoot(const std::filesystem::path & path);
 
 private:
 
diff --git a/src/libutil/processes.hh b/src/libutil/processes.hh
index a7e85b5beec..bbbe7dcabd3 100644
--- a/src/libutil/processes.hh
+++ b/src/libutil/processes.hh
@@ -3,6 +3,7 @@
 
 #include "types.hh"
 #include "error.hh"
+#include "file-descriptor.hh"
 #include "logging.hh"
 #include "ansicolor.hh"
 
@@ -12,8 +13,6 @@
 #include <unistd.h>
 #include <signal.h>
 
-#include <boost/lexical_cast.hpp>
-
 #include <atomic>
 #include <functional>
 #include <map>
@@ -25,26 +24,36 @@ namespace nix {
 struct Sink;
 struct Source;
 
-#ifndef _WIN32
 class Pid
 {
+#ifndef _WIN32
     pid_t pid = -1;
     bool separatePG = false;
     int killSignal = SIGKILL;
+#else
+    AutoCloseFD pid = INVALID_DESCRIPTOR;
+#endif
 public:
     Pid();
+#ifndef _WIN32
     Pid(pid_t pid);
-    ~Pid();
     void operator =(pid_t pid);
     operator pid_t();
+#else
+    Pid(AutoCloseFD pid);
+    void operator =(AutoCloseFD pid);
+#endif
+    ~Pid();
     int kill();
     int wait();
 
+    // TODO: Implement for Windows
+#ifndef _WIN32
     void setSeparatePG(bool separatePG);
     void setKillSignal(int signal);
     pid_t release();
-};
 #endif
+};
 
 
 #ifndef _WIN32
@@ -80,14 +89,14 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options = P
  * Run a program and return its stdout in a string (i.e., like the
  * shell backtick operator).
  */
-std::string runProgram(Path program, bool searchPath = false,
+std::string runProgram(Path program, bool lookupPath = false,
     const Strings & args = Strings(),
     const std::optional<std::string> & input = {}, bool isInteractive = false);
 
 struct RunOptions
 {
     Path program;
-    bool searchPath = true;
+    bool lookupPath = true;
     Strings args;
 #ifndef _WIN32
     std::optional<uid_t> uid;
@@ -118,8 +127,6 @@ public:
     { }
 };
 
-#ifndef _WIN32
-
 /**
  * Convert the exit status of a child as returned by wait() into an
  * error string.
@@ -128,6 +135,4 @@ std::string statusToString(int status);
 
 bool statusOk(int status);
 
-#endif
-
 }
diff --git a/src/libutil/ref.hh b/src/libutil/ref.hh
index 5d0c3696dbd..03aa642739c 100644
--- a/src/libutil/ref.hh
+++ b/src/libutil/ref.hh
@@ -77,6 +77,8 @@ public:
         return ref<T2>((std::shared_ptr<T2>) p);
     }
 
+    ref<T> & operator=(ref<T> const & rhs) = default;
+
     bool operator == (const ref<T> & other) const
     {
         return p == other.p;
diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 5ea27ccbed8..36b99905aab 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -136,7 +136,7 @@ size_t FdSource::readUnbuffered(char * data, size_t len)
     checkInterrupt();
     if (!::ReadFile(fd, data, len, &n, NULL)) {
         _good = false;
-        throw WinError("ReadFile when FdSource::readUnbuffered");
+        throw windows::WinError("ReadFile when FdSource::readUnbuffered");
     }
 #else
     ssize_t n;
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index 332bb5679ab..ea5d8f087c9 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -283,6 +283,26 @@ struct LengthSink : Sink
     }
 };
 
+/**
+ * A wrapper source that counts the number of bytes read from it.
+ */
+struct LengthSource : Source
+{
+    Source & next;
+
+    LengthSource(Source & next) : next(next)
+    { }
+
+    uint64_t total = 0;
+
+    size_t read(char * data, size_t len) override
+    {
+        auto n = next.read(data, len);
+        total += n;
+        return n;
+    }
+};
+
 /**
  * Convert a function into a sink.
  */
diff --git a/src/libutil/source-accessor.cc b/src/libutil/source-accessor.cc
index 66093d2ccb0..e797951c76e 100644
--- a/src/libutil/source-accessor.cc
+++ b/src/libutil/source-accessor.cc
@@ -53,7 +53,7 @@ SourceAccessor::Stat SourceAccessor::lstat(const CanonPath & path)
     if (auto st = maybeLstat(path))
         return *st;
     else
-        throw Error("path '%s' does not exist", showPath(path));
+        throw FileNotFound("path '%s' does not exist", showPath(path));
 }
 
 void SourceAccessor::setPathDisplay(std::string displayPrefix, std::string displaySuffix)
diff --git a/src/libutil/source-accessor.hh b/src/libutil/source-accessor.hh
index 1f272327f81..cc8db01f59c 100644
--- a/src/libutil/source-accessor.hh
+++ b/src/libutil/source-accessor.hh
@@ -29,13 +29,15 @@ enum class SymlinkResolution {
     Full,
 };
 
+MakeError(FileNotFound, Error);
+
 /**
  * A read-only filesystem abstraction. This is used by the Nix
  * evaluator and elsewhere for accessing sources in various
  * filesystem-like entities (such as the real filesystem, tarballs or
  * Git repositories).
  */
-struct SourceAccessor
+struct SourceAccessor : std::enable_shared_from_this<SourceAccessor>
 {
     const size_t number;
 
@@ -168,6 +170,43 @@ struct SourceAccessor
     CanonPath resolveSymlinks(
         const CanonPath & path,
         SymlinkResolution mode = SymlinkResolution::Full);
+
+    /**
+     * A string that uniquely represents the contents of this
+     * accessor. This is used for caching lookups (see `fetchToStore()`).
+     */
+    std::optional<std::string> fingerprint;
+
+    /**
+     * Return the maximum last-modified time of the files in this
+     * tree, if available.
+     */
+    virtual std::optional<time_t> getLastModified()
+    { return std::nullopt; }
 };
 
+/**
+ * Return a source accessor that contains only an empty root directory.
+ */
+ref<SourceAccessor> makeEmptySourceAccessor();
+
+/**
+ * Exception thrown when accessing a filtered path (see
+ * `FilteringSourceAccessor`).
+ */
+MakeError(RestrictedPathError, Error);
+
+/**
+ * Return an accessor for the root filesystem.
+ */
+ref<SourceAccessor> getFSSourceAccessor();
+
+/**
+ * Construct an accessor for the filesystem rooted at `root`. Note
+ * that it is not possible to escape `root` by appending `..` path
+ * elements, and that absolute symlinks are resolved relative to
+ * `root`.
+ */
+ref<SourceAccessor> makeFSSourceAccessor(std::filesystem::path root);
+
 }
diff --git a/src/libutil/source-path.cc b/src/libutil/source-path.cc
index 2a5b2085828..023b5ed4b91 100644
--- a/src/libutil/source-path.cc
+++ b/src/libutil/source-path.cc
@@ -18,13 +18,13 @@ std::string SourcePath::readFile() const
 bool SourcePath::pathExists() const
 { return accessor->pathExists(path); }
 
-InputAccessor::Stat SourcePath::lstat() const
+SourceAccessor::Stat SourcePath::lstat() const
 { return accessor->lstat(path); }
 
-std::optional<InputAccessor::Stat> SourcePath::maybeLstat() const
+std::optional<SourceAccessor::Stat> SourcePath::maybeLstat() const
 { return accessor->maybeLstat(path); }
 
-InputAccessor::DirEntries SourcePath::readDirectory() const
+SourceAccessor::DirEntries SourcePath::readDirectory() const
 { return accessor->readDirectory(path); }
 
 std::string SourcePath::readLink() const
diff --git a/src/libutil/source-path.hh b/src/libutil/source-path.hh
index b8f69af126a..83ec6295de1 100644
--- a/src/libutil/source-path.hh
+++ b/src/libutil/source-path.hh
@@ -7,7 +7,7 @@
 
 #include "ref.hh"
 #include "canon-path.hh"
-#include "input-accessor.hh"
+#include "source-accessor.hh"
 
 namespace nix {
 
@@ -19,10 +19,10 @@ namespace nix {
  */
 struct SourcePath
 {
-    ref<InputAccessor> accessor;
+    ref<SourceAccessor> accessor;
     CanonPath path;
 
-    SourcePath(ref<InputAccessor> accessor, CanonPath path = CanonPath::root)
+    SourcePath(ref<SourceAccessor> accessor, CanonPath path = CanonPath::root)
         : accessor(std::move(accessor))
         , path(std::move(path))
     { }
@@ -41,6 +41,11 @@ struct SourcePath
      */
     std::string readFile() const;
 
+    void readFile(
+        Sink & sink,
+        std::function<void(uint64_t)> sizeCallback = [](uint64_t size){}) const
+    { return accessor->readFile(path, sink, sizeCallback); }
+
     /**
      * Return whether this `SourcePath` denotes a file (of any type)
      * that exists
@@ -51,19 +56,19 @@ struct SourcePath
      * Return stats about this `SourcePath`, or throw an exception if
      * it doesn't exist.
      */
-    InputAccessor::Stat lstat() const;
+    SourceAccessor::Stat lstat() const;
 
     /**
      * Return stats about this `SourcePath`, or std::nullopt if it
      * doesn't exist.
      */
-    std::optional<InputAccessor::Stat> maybeLstat() const;
+    std::optional<SourceAccessor::Stat> maybeLstat() const;
 
     /**
      * If this `SourcePath` denotes a directory (not a symlink),
      * return its directory entries; otherwise throw an error.
      */
-    InputAccessor::DirEntries readDirectory() const;
+    SourceAccessor::DirEntries readDirectory() const;
 
     /**
      * If this `SourcePath` denotes a symlink, return its target;
diff --git a/src/libutil/sync.hh b/src/libutil/sync.hh
index a1163940891..4c37ea37b3a 100644
--- a/src/libutil/sync.hh
+++ b/src/libutil/sync.hh
@@ -3,6 +3,7 @@
 
 #include <cstdlib>
 #include <mutex>
+#include <shared_mutex>
 #include <condition_variable>
 #include <cassert>
 
@@ -24,8 +25,8 @@ namespace nix {
  * Here, "data" is automatically unlocked when "data_" goes out of
  * scope.
  */
-template<class T, class M = std::mutex>
-class Sync
+template<class T, class M, class WL, class RL>
+class SyncBase
 {
 private:
     M mutex;
@@ -33,26 +34,25 @@ private:
 
 public:
 
-    Sync() { }
-    Sync(const T & data) : data(data) { }
-    Sync(T && data) noexcept : data(std::move(data)) { }
+    SyncBase() { }
+    SyncBase(const T & data) : data(data) { }
+    SyncBase(T && data) noexcept : data(std::move(data)) { }
 
-    template< class... Args>
-    Sync(Args &&... args) : data(std::forward<decltype(args)>(args)...) { }
+    template<class... Args>
+    SyncBase(Args &&... args) : data(std::forward<decltype(args)>(args)...) { }
 
+    template<class L>
     class Lock
     {
-    private:
-        Sync * s;
-        std::unique_lock<M> lk;
-        friend Sync;
-        Lock(Sync * s) : s(s), lk(s->mutex) { }
+    protected:
+        SyncBase * s;
+        L lk;
+        friend SyncBase;
+        Lock(SyncBase * s) : s(s), lk(s->mutex) { }
     public:
         Lock(Lock && l) : s(l.s) { abort(); }
         Lock(const Lock & l) = delete;
         ~Lock() { }
-        T * operator -> () { return &s->data; }
-        T & operator * () { return s->data; }
 
         void wait(std::condition_variable & cv)
         {
@@ -86,7 +86,34 @@ public:
         }
     };
 
-    Lock lock() { return Lock(this); }
+    struct WriteLock : Lock<WL>
+    {
+        T * operator -> () { return &WriteLock::s->data; }
+        T & operator * () { return WriteLock::s->data; }
+    };
+
+    /**
+     * Acquire write (exclusive) access to the inner value.
+     */
+    WriteLock lock() { return WriteLock(this); }
+
+    struct ReadLock : Lock<RL>
+    {
+        const T * operator -> () { return &ReadLock::s->data; }
+        const T & operator * () { return ReadLock::s->data; }
+    };
+
+    /**
+     * Acquire read access to the inner value. When using
+     * `std::shared_mutex`, this will use a shared lock.
+     */
+    ReadLock read() const { return ReadLock(const_cast<SyncBase *>(this)); }
 };
 
+template<class T>
+using Sync = SyncBase<T, std::mutex, std::unique_lock<std::mutex>, std::unique_lock<std::mutex>>;
+
+template<class T>
+using SharedSync = SyncBase<T, std::shared_mutex, std::unique_lock<std::shared_mutex>, std::shared_lock<std::shared_mutex>>;
+
 }
diff --git a/src/libutil/tarfile.cc b/src/libutil/tarfile.cc
index 6bb2bd2f32b..f0df527b378 100644
--- a/src/libutil/tarfile.cc
+++ b/src/libutil/tarfile.cc
@@ -67,6 +67,17 @@ int getArchiveFilterCodeByName(const std::string & method)
     return code;
 }
 
+static void enableSupportedFormats(struct archive * archive)
+{
+    archive_read_support_format_tar(archive);
+    archive_read_support_format_zip(archive);
+
+    /* Enable support for empty files so we don't throw an exception
+       for empty HTTP 304 "Not modified" responses. See
+       downloadTarball(). */
+    archive_read_support_format_empty(archive);
+}
+
 TarArchive::TarArchive(Source & source, bool raw, std::optional<std::string> compression_method)
     : archive{archive_read_new()}
     , source{&source}
@@ -78,9 +89,9 @@ TarArchive::TarArchive(Source & source, bool raw, std::optional<std::string> com
         archive_read_support_filter_by_code(archive, getArchiveFilterCodeByName(*compression_method));
     }
 
-    if (!raw) {
-        archive_read_support_format_all(archive);
-    } else {
+    if (!raw)
+        enableSupportedFormats(archive);
+    else {
         archive_read_support_format_raw(archive);
         archive_read_support_format_empty(archive);
     }
@@ -96,7 +107,7 @@ TarArchive::TarArchive(const Path & path)
     , buffer(defaultBufferSize)
 {
     archive_read_support_filter_all(archive);
-    archive_read_support_format_all(archive);
+    enableSupportedFormats(archive);
     archive_read_set_option(archive, NULL, "mac-ext", NULL);
     check(archive_read_open_filename(archive, path.c_str(), 16384), "failed to open archive: %s");
 }
@@ -176,6 +187,7 @@ time_t unpackTarfileToSink(TarArchive & archive, FileSystemObjectSink & parseSin
         auto path = archive_entry_pathname(entry);
         if (!path)
             throw Error("cannot get archive member name: %s", archive_error_string(archive.archive));
+        auto cpath = CanonPath{path};
         if (r == ARCHIVE_WARN)
             warn(archive_error_string(archive.archive));
         else
@@ -186,11 +198,11 @@ time_t unpackTarfileToSink(TarArchive & archive, FileSystemObjectSink & parseSin
         switch (archive_entry_filetype(entry)) {
 
         case AE_IFDIR:
-            parseSink.createDirectory(path);
+            parseSink.createDirectory(cpath);
             break;
 
         case AE_IFREG: {
-            parseSink.createRegularFile(path, [&](auto & crf) {
+            parseSink.createRegularFile(cpath, [&](auto & crf) {
                 if (archive_entry_mode(entry) & S_IXUSR)
                     crf.isExecutable();
 
@@ -214,7 +226,7 @@ time_t unpackTarfileToSink(TarArchive & archive, FileSystemObjectSink & parseSin
         case AE_IFLNK: {
             auto target = archive_entry_symlink(entry);
 
-            parseSink.createSymlink(path, target);
+            parseSink.createSymlink(cpath, target);
 
             break;
         }
diff --git a/src/libutil/terminal.cc b/src/libutil/terminal.cc
index 4dc280f8c04..5d5ff7dcb63 100644
--- a/src/libutil/terminal.cc
+++ b/src/libutil/terminal.cc
@@ -4,6 +4,8 @@
 
 #if _WIN32
 # include <io.h>
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
 # define isatty _isatty
 #else
 # include <sys/ioctl.h>
@@ -97,17 +99,26 @@ std::string filterANSIEscapes(std::string_view s, bool filterAll, unsigned int w
 static Sync<std::pair<unsigned short, unsigned short>> windowSize{{0, 0}};
 
 
-#ifndef _WIN32
 void updateWindowSize()
 {
+    #ifndef _WIN32
     struct winsize ws;
     if (ioctl(2, TIOCGWINSZ, &ws) == 0) {
         auto windowSize_(windowSize.lock());
         windowSize_->first = ws.ws_row;
         windowSize_->second = ws.ws_col;
     }
+    #else
+    CONSOLE_SCREEN_BUFFER_INFO info;
+    // From https://stackoverflow.com/a/12642749
+    if (GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE), &info) != 0) {
+        auto windowSize_(windowSize.lock());
+        // From https://github.com/libuv/libuv/blob/v1.48.0/src/win/tty.c#L1130
+        windowSize_->first = info.srWindow.Bottom - info.srWindow.Top + 1;
+        windowSize_->second = info.dwSize.X;
+    }
+    #endif
 }
-#endif
 
 
 std::pair<unsigned short, unsigned short> getWindowSize()
diff --git a/src/libutil/terminal.hh b/src/libutil/terminal.hh
index 628833283d4..902e759456d 100644
--- a/src/libutil/terminal.hh
+++ b/src/libutil/terminal.hh
@@ -21,16 +21,13 @@ std::string filterANSIEscapes(std::string_view s,
     bool filterAll = false,
     unsigned int width = std::numeric_limits<unsigned int>::max());
 
-#ifndef _WIN32
-
 /**
- * Recalculate the window size, updating a global variable. Used in the
- * `SIGWINCH` signal handler.
+ * Recalculate the window size, updating a global variable.
+ *
+ * Used in the `SIGWINCH` signal handler on Unix, for example.
  */
 void updateWindowSize();
 
-#endif
-
 /**
  * @return the number of rows and columns of the terminal.
  *
diff --git a/src/libutil/unix/unix-domain-socket.cc b/src/libutil/unix-domain-socket.cc
similarity index 82%
rename from src/libutil/unix/unix-domain-socket.cc
rename to src/libutil/unix-domain-socket.cc
index b19917f0c06..f81d97f3be6 100644
--- a/src/libutil/unix/unix-domain-socket.cc
+++ b/src/libutil/unix-domain-socket.cc
@@ -1,10 +1,15 @@
 #include "file-system.hh"
-#include "processes.hh"
 #include "unix-domain-socket.hh"
 #include "util.hh"
 
-#include <sys/socket.h>
-#include <sys/un.h>
+#ifdef _WIN32
+# include <winsock2.h>
+# include <afunix.h>
+#else
+# include <sys/socket.h>
+# include <sys/un.h>
+# include "processes.hh"
+#endif
 #include <unistd.h>
 
 namespace nix {
@@ -17,10 +22,12 @@ namespace nix {
 
 AutoCloseFD createUnixDomainSocket()
 {
-    AutoCloseFD fdSocket = socket(PF_UNIX, SOCK_STREAM | MAYBE_SOCK_CLOEXEC, 0);
+    AutoCloseFD fdSocket = toDescriptor(socket(PF_UNIX, SOCK_STREAM | MAYBE_SOCK_CLOEXEC, 0));
     if (!fdSocket)
         throw SysError("cannot create Unix domain socket");
-    closeOnExec(fdSocket.get());
+#ifndef _WIN32
+    unix::closeOnExec(fdSocket.get());
+#endif
     return fdSocket;
 }
 
@@ -34,16 +41,15 @@ AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
     if (chmod(path.c_str(), mode) == -1)
         throw SysError("changing permissions on '%1%'", path);
 
-    if (listen(fdSocket.get(), 100) == -1)
+    if (listen(toSocket(fdSocket.get()), 100) == -1)
         throw SysError("cannot listen on socket '%1%'", path);
 
     return fdSocket;
 }
 
-
 static void bindConnectProcHelper(
     std::string_view operationName, auto && operation,
-    int fd, const std::string & path)
+    Socket fd, const std::string & path)
 {
     struct sockaddr_un addr;
     addr.sun_family = AF_UNIX;
@@ -56,6 +62,9 @@ static void bindConnectProcHelper(
     auto * psaddr = reinterpret_cast<struct sockaddr *>(&addr);
 
     if (path.size() + 1 >= sizeof(addr.sun_path)) {
+#ifdef _WIN32
+        throw Error("cannot %s to socket at '%s': path is too long", operationName, path);
+#else
         Pipe pipe;
         pipe.create();
         Pid pid = startProcess([&] {
@@ -85,6 +94,7 @@ static void bindConnectProcHelper(
             errno = *errNo;
             throw SysError("cannot %s to socket at '%s'", operationName, path);
         }
+#endif
     } else {
         memcpy(addr.sun_path, path.c_str(), path.size() + 1);
         if (operation(fd, psaddr, sizeof(addr)) == -1)
@@ -93,7 +103,7 @@ static void bindConnectProcHelper(
 }
 
 
-void bind(int fd, const std::string & path)
+void bind(Socket fd, const std::string & path)
 {
     unlink(path.c_str());
 
@@ -101,7 +111,7 @@ void bind(int fd, const std::string & path)
 }
 
 
-void connect(int fd, const std::string & path)
+void connect(Socket fd, const std::string & path)
 {
     bindConnectProcHelper("connect", ::connect, fd, path);
 }
@@ -111,8 +121,8 @@ std::pair<AutoCloseFD, AutoCloseFD> socketPair()
     int sockets[2];
     if (socketpair(PF_UNIX, SOCK_STREAM | MAYBE_SOCK_CLOEXEC, 0, sockets))
         throw SysError("creating a socket pair");
-    closeOnExec(sockets[0]);
-    closeOnExec(sockets[1]);
+    unix::closeOnExec(sockets[0]);
+    unix::closeOnExec(sockets[1]);
     return {AutoCloseFD(sockets[0]), AutoCloseFD(sockets[1])};
 }
 
diff --git a/src/libutil/unix-domain-socket.hh b/src/libutil/unix-domain-socket.hh
new file mode 100644
index 00000000000..b6b23a4f42c
--- /dev/null
+++ b/src/libutil/unix-domain-socket.hh
@@ -0,0 +1,88 @@
+#pragma once
+///@file
+
+#include "types.hh"
+#include "file-descriptor.hh"
+
+#ifdef _WIN32
+#  include <winsock2.h>
+#endif
+#include <unistd.h>
+
+namespace nix {
+
+/**
+ * Create a Unix domain socket.
+ */
+AutoCloseFD createUnixDomainSocket();
+
+/**
+ * Create a Unix domain socket in listen mode.
+ */
+AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
+
+/**
+ * Often we want to use `Descriptor`, but Windows makes a slightly
+ * stronger file descriptor vs socket distinction, at least at the level
+ * of C types.
+ */
+using Socket =
+#ifdef _WIN32
+    SOCKET
+#else
+    int
+#endif
+    ;
+
+#ifdef _WIN32
+/**
+ * Windows gives this a different name
+ */
+#  define SHUT_WR SD_SEND
+#  define SHUT_RDWR SD_BOTH
+#endif
+
+/**
+ * Convert a `Socket` to a `Descriptor`
+ *
+ * This is a no-op except on Windows.
+ */
+static inline Socket toSocket(Descriptor fd)
+{
+#ifdef _WIN32
+    return reinterpret_cast<Socket>(fd);
+#else
+    return fd;
+#endif
+}
+
+/**
+ * Convert a `Socket` to a `Descriptor`
+ *
+ * This is a no-op except on Windows.
+ */
+static inline Descriptor fromSocket(Socket fd)
+{
+#ifdef _WIN32
+    return reinterpret_cast<Descriptor>(fd);
+#else
+    return fd;
+#endif
+}
+
+/**
+ * Bind a Unix domain socket to a path.
+ */
+void bind(Socket fd, const std::string & path);
+
+/**
+ * Connect to a Unix domain socket.
+ */
+void connect(Socket fd, const std::string & path);
+
+/**
+ * Create an unnamed pair of connected sockets.
+ */
+std::pair<AutoCloseFD, AutoCloseFD> socketPair();
+
+}
diff --git a/src/libutil/unix/file-descriptor.cc b/src/libutil/unix/file-descriptor.cc
index 27c8d821b5d..a3af1623fc9 100644
--- a/src/libutil/unix/file-descriptor.cc
+++ b/src/libutil/unix/file-descriptor.cc
@@ -110,8 +110,8 @@ void Pipe::create()
     if (pipe2(fds, O_CLOEXEC) != 0) throw SysError("creating pipe");
 #else
     if (pipe(fds) != 0) throw SysError("creating pipe");
-    closeOnExec(fds[0]);
-    closeOnExec(fds[1]);
+    unix::closeOnExec(fds[0]);
+    unix::closeOnExec(fds[1]);
 #endif
     readSide = fds[0];
     writeSide = fds[1];
@@ -120,12 +120,13 @@ void Pipe::create()
 
 //////////////////////////////////////////////////////////////////////
 
-void closeMostFDs(const std::set<int> & exceptions)
+void unix::closeMostFDs(const std::set<int> & exceptions)
 {
 #if __linux__
     try {
-        for (auto & s : readDirectory("/proc/self/fd")) {
-            auto fd = std::stoi(s.name);
+        for (auto & s : std::filesystem::directory_iterator{"/proc/self/fd"}) {
+            checkInterrupt();
+            auto fd = std::stoi(s.path().filename());
             if (!exceptions.count(fd)) {
                 debug("closing leaked FD %d", fd);
                 close(fd);
@@ -133,18 +134,21 @@ void closeMostFDs(const std::set<int> & exceptions)
         }
         return;
     } catch (SysError &) {
+    } catch (std::filesystem::filesystem_error &) {
     }
 #endif
 
     int maxFD = 0;
+#if HAVE_SYSCONF
     maxFD = sysconf(_SC_OPEN_MAX);
+#endif
     for (int fd = 0; fd < maxFD; ++fd)
         if (!exceptions.count(fd))
             close(fd); /* ignore result */
 }
 
 
-void closeOnExec(int fd)
+void unix::closeOnExec(int fd)
 {
     int prev;
     if ((prev = fcntl(fd, F_GETFD, 0)) == -1 ||
diff --git a/src/libutil/unix/file-path.cc b/src/libutil/unix/file-path.cc
index 54a1cc278d4..294048a2f8f 100644
--- a/src/libutil/unix/file-path.cc
+++ b/src/libutil/unix/file-path.cc
@@ -13,17 +13,17 @@ std::string os_string_to_string(PathViewNG::string_view path)
     return std::string { path };
 }
 
-PathNG::string_type string_to_os_string(std::string_view s)
+std::filesystem::path::string_type string_to_os_string(std::string_view s)
 {
     return std::string { s };
 }
 
-std::optional<PathNG> maybePathNG(PathView path)
+std::optional<std::filesystem::path> maybePath(PathView path)
 {
     return { path };
 }
 
-PathNG pathNG(PathView path)
+std::filesystem::path pathNG(PathView path)
 {
     return path;
 }
diff --git a/src/libutil/unix/file-system.cc b/src/libutil/unix/file-system.cc
new file mode 100644
index 00000000000..bbbbfa5597c
--- /dev/null
+++ b/src/libutil/unix/file-system.cc
@@ -0,0 +1,10 @@
+#include "file-system.hh"
+
+namespace nix {
+
+Descriptor openDirectory(const std::filesystem::path & path)
+{
+    return open(path.c_str(), O_RDONLY | O_DIRECTORY);
+}
+
+}
diff --git a/src/libutil/unix/meson.build b/src/libutil/unix/meson.build
new file mode 100644
index 00000000000..38e5cd3aa47
--- /dev/null
+++ b/src/libutil/unix/meson.build
@@ -0,0 +1,17 @@
+sources += files(
+  'environment-variables.cc',
+  'file-descriptor.cc',
+  'file-path.cc',
+  'file-system.cc',
+  'muxable-pipe.cc',
+  'processes.cc',
+  'signals.cc',
+  'users.cc',
+)
+
+include_dirs += include_directories('.')
+
+headers += files(
+  'monitor-fd.hh',
+  'signals-impl.hh',
+)
diff --git a/src/libutil/unix/muxable-pipe.cc b/src/libutil/unix/muxable-pipe.cc
new file mode 100644
index 00000000000..0104663c3bf
--- /dev/null
+++ b/src/libutil/unix/muxable-pipe.cc
@@ -0,0 +1,47 @@
+#include <poll.h>
+
+#include "logging.hh"
+#include "util.hh"
+#include "muxable-pipe.hh"
+
+namespace nix {
+
+void MuxablePipePollState::poll(std::optional<unsigned int> timeout)
+{
+    if (::poll(pollStatus.data(), pollStatus.size(), timeout ? *timeout : -1) == -1) {
+        if (errno == EINTR)
+            return;
+        throw SysError("waiting for input");
+    }
+}
+
+void MuxablePipePollState::iterate(
+    std::set<MuxablePipePollState::CommChannel> & channels,
+    std::function<void(Descriptor fd, std::string_view data)> handleRead,
+    std::function<void(Descriptor fd)> handleEOF)
+{
+    std::set<Descriptor> fds2(channels);
+    std::vector<unsigned char> buffer(4096);
+    for (auto & k : fds2) {
+        const auto fdPollStatusId = get(fdToPollStatus, k);
+        assert(fdPollStatusId);
+        assert(*fdPollStatusId < pollStatus.size());
+        if (pollStatus.at(*fdPollStatusId).revents) {
+            ssize_t rd = ::read(fromDescriptorReadOnly(k), buffer.data(), buffer.size());
+            // FIXME: is there a cleaner way to handle pt close
+            // than EIO? Is this even standard?
+            if (rd == 0 || (rd == -1 && errno == EIO)) {
+                handleEOF(k);
+                channels.erase(k);
+            } else if (rd == -1) {
+                if (errno != EINTR)
+                    throw SysError("read failed");
+            } else {
+                std::string_view data((char *) buffer.data(), rd);
+                handleRead(k, data);
+            }
+        }
+    }
+}
+
+}
diff --git a/src/libutil/unix/processes.cc b/src/libutil/unix/processes.cc
index f5d584330ab..1af559a21b9 100644
--- a/src/libutil/unix/processes.cc
+++ b/src/libutil/unix/processes.cc
@@ -245,10 +245,10 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options)
 }
 
 
-std::string runProgram(Path program, bool searchPath, const Strings & args,
+std::string runProgram(Path program, bool lookupPath, const Strings & args,
     const std::optional<std::string> & input, bool isInteractive)
 {
-    auto res = runProgram(RunOptions {.program = program, .searchPath = searchPath, .args = args, .input = input, .isInteractive = isInteractive});
+    auto res = runProgram(RunOptions {.program = program, .lookupPath = lookupPath, .args = args, .input = input, .isInteractive = isInteractive});
 
     if (!statusOk(res.first))
         throw ExecError(res.first, "program '%1%' %2%", program, statusToString(res.first));
@@ -335,7 +335,7 @@ void runProgram2(const RunOptions & options)
 
         restoreProcessContext();
 
-        if (options.searchPath)
+        if (options.lookupPath)
             execvp(options.program.c_str(), stringsToCharPtrs(args_).data());
             // This allows you to refer to a program with a pathname relative
             // to the PATH variable.
diff --git a/src/libutil/unix/unix-domain-socket.hh b/src/libutil/unix/unix-domain-socket.hh
deleted file mode 100644
index 829ef02c22c..00000000000
--- a/src/libutil/unix/unix-domain-socket.hh
+++ /dev/null
@@ -1,36 +0,0 @@
-#pragma once
-///@file
-
-#include "types.hh"
-#include "file-descriptor.hh"
-
-#include <unistd.h>
-
-namespace nix {
-
-/**
- * Create a Unix domain socket.
- */
-AutoCloseFD createUnixDomainSocket();
-
-/**
- * Create a Unix domain socket in listen mode.
- */
-AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
-
-/**
- * Bind a Unix domain socket to a path.
- */
-void bind(int fd, const std::string & path);
-
-/**
- * Connect to a Unix domain socket.
- */
-void connect(int fd, const std::string & path);
-
-/**
- * Create an unnamed pair of connected sockets.
- */
-std::pair<AutoCloseFD, AutoCloseFD> socketPair();
-
-}
diff --git a/src/libutil/url.cc b/src/libutil/url.cc
index c6561441d93..f4178f87fd9 100644
--- a/src/libutil/url.cc
+++ b/src/libutil/url.cc
@@ -171,16 +171,16 @@ std::string fixGitURL(const std::string & url)
     std::regex scpRegex("([^/]*)@(.*):(.*)");
     if (!hasPrefix(url, "/") && std::regex_match(url, scpRegex))
         return std::regex_replace(url, scpRegex, "ssh://$1@$2/$3");
-    else {
-        if (url.find("://") == std::string::npos) {
-            return (ParsedURL {
-                .scheme = "file",
-                .authority = "",
-                .path = url
-            }).to_string();
-        } else
-            return url;
+    if (hasPrefix(url, "file:"))
+        return url;
+    if (url.find("://") == std::string::npos) {
+        return (ParsedURL {
+            .scheme = "file",
+            .authority = "",
+            .path = url
+        }).to_string();
     }
+    return url;
 }
 
 // https://www.rfc-editor.org/rfc/rfc3986#section-3.1
diff --git a/src/libutil/url.hh b/src/libutil/url.hh
index 24806bbff81..6cd06e53d17 100644
--- a/src/libutil/url.hh
+++ b/src/libutil/url.hh
@@ -33,6 +33,8 @@ std::string percentEncode(std::string_view s, std::string_view keep="");
 
 std::map<std::string, std::string> decodeQuery(const std::string & query);
 
+std::string encodeQuery(const std::map<std::string, std::string> & query);
+
 ParsedURL parseURL(const std::string & url);
 
 /**
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 103ce4232b3..698e181a1d1 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -7,6 +7,8 @@
 #include <regex>
 
 #include <sodium.h>
+#include <boost/lexical_cast.hpp>
+#include <stdint.h>
 
 #ifdef NDEBUG
 #error "Nix may not be built with assertions disabled (i.e. with -DNDEBUG)."
@@ -111,6 +113,58 @@ std::string rewriteStrings(std::string s, const StringMap & rewrites)
     return s;
 }
 
+template<class N>
+std::optional<N> string2Int(const std::string_view s)
+{
+    if (s.substr(0, 1) == "-" && !std::numeric_limits<N>::is_signed)
+        return std::nullopt;
+    try {
+        return boost::lexical_cast<N>(s.data(), s.size());
+    } catch (const boost::bad_lexical_cast &) {
+        return std::nullopt;
+    }
+}
+
+// Explicitly instantiated in one place for faster compilation
+template std::optional<unsigned char>  string2Int<unsigned char>(const std::string_view s);
+template std::optional<unsigned short> string2Int<unsigned short>(const std::string_view s);
+template std::optional<unsigned int> string2Int<unsigned int>(const std::string_view s);
+template std::optional<unsigned long> string2Int<unsigned long>(const std::string_view s);
+template std::optional<unsigned long long> string2Int<unsigned long long>(const std::string_view s);
+template std::optional<signed char> string2Int<signed char>(const std::string_view s);
+template std::optional<signed short> string2Int<signed short>(const std::string_view s);
+template std::optional<signed int> string2Int<signed int>(const std::string_view s);
+template std::optional<signed long> string2Int<signed long>(const std::string_view s);
+template std::optional<signed long long> string2Int<signed long long>(const std::string_view s);
+
+template<class N>
+std::optional<N> string2Float(const std::string_view s)
+{
+    try {
+        return boost::lexical_cast<N>(s.data(), s.size());
+    } catch (const boost::bad_lexical_cast &) {
+        return std::nullopt;
+    }
+}
+
+template std::optional<double> string2Float<double>(const std::string_view s);
+template std::optional<float> string2Float<float>(const std::string_view s);
+
+
+std::string renderSize(uint64_t value, bool align)
+{
+    static const std::array<char, 9> prefixes{{
+        'K', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'
+    }};
+    size_t power = 0;
+    double res = value;
+    while (res > 1024 && power < prefixes.size()) {
+        ++power;
+        res /= 1024;
+    }
+    return fmt(align ? "%6.1f %ciB" : "%.1f %ciB", power == 0 ? res / 1024 : res, prefixes.at(power));
+}
+
 
 bool hasPrefix(std::string_view s, std::string_view prefix)
 {
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 11a0431da89..23682ff7ca5 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -5,7 +5,6 @@
 #include "error.hh"
 #include "logging.hh"
 
-#include <boost/lexical_cast.hpp>
 
 #include <functional>
 #include <map>
@@ -102,16 +101,7 @@ std::string rewriteStrings(std::string s, const StringMap & rewrites);
  * Parse a string into an integer.
  */
 template<class N>
-std::optional<N> string2Int(const std::string_view s)
-{
-    if (s.substr(0, 1) == "-" && !std::numeric_limits<N>::is_signed)
-        return std::nullopt;
-    try {
-        return boost::lexical_cast<N>(s.data(), s.size());
-    } catch (const boost::bad_lexical_cast &) {
-        return std::nullopt;
-    }
-}
+std::optional<N> string2Int(const std::string_view s);
 
 /**
  * Like string2Int(), but support an optional suffix 'K', 'M', 'G' or
@@ -120,7 +110,7 @@ std::optional<N> string2Int(const std::string_view s)
 template<class N>
 N string2IntWithUnitPrefix(std::string_view s)
 {
-    N multiplier = 1;
+    uint64_t multiplier = 1;
     if (!s.empty()) {
         char u = std::toupper(*s.rbegin());
         if (std::isalpha(u)) {
@@ -137,18 +127,18 @@ N string2IntWithUnitPrefix(std::string_view s)
     throw UsageError("'%s' is not an integer", s);
 }
 
+/**
+ * Pretty-print a byte value, e.g. 12433615056 is rendered as `11.6
+ * GiB`. If `align` is set, the number will be right-justified by
+ * padding with spaces on the left.
+ */
+std::string renderSize(uint64_t value, bool align = false);
+
 /**
  * Parse a string into a float.
  */
 template<class N>
-std::optional<N> string2Float(const std::string_view s)
-{
-    try {
-        return boost::lexical_cast<N>(s.data(), s.size());
-    } catch (const boost::bad_lexical_cast &) {
-        return std::nullopt;
-    }
-}
+std::optional<N> string2Float(const std::string_view s);
 
 
 /**
diff --git a/src/libutil/windows/file-descriptor.cc b/src/libutil/windows/file-descriptor.cc
index 26f769b6650..16773e3eae6 100644
--- a/src/libutil/windows/file-descriptor.cc
+++ b/src/libutil/windows/file-descriptor.cc
@@ -14,6 +14,8 @@
 
 namespace nix {
 
+using namespace nix::windows;
+
 std::string readFile(HANDLE handle)
 {
     LARGE_INTEGER li;
@@ -120,7 +122,7 @@ void Pipe::create()
 
 #if _WIN32_WINNT >= 0x0600
 
-std::wstring handleToFileName(HANDLE handle) {
+std::wstring windows::handleToFileName(HANDLE handle) {
     std::vector<wchar_t> buf(0x100);
     DWORD dw = GetFinalPathNameByHandleW(handle, buf.data(), buf.size(), FILE_NAME_OPENED);
     if (dw == 0) {
@@ -139,7 +141,7 @@ std::wstring handleToFileName(HANDLE handle) {
 }
 
 
-Path handleToPath(HANDLE handle) {
+Path windows::handleToPath(HANDLE handle) {
     return os_string_to_string(handleToFileName(handle));
 }
 
diff --git a/src/libutil/windows/file-path.cc b/src/libutil/windows/file-path.cc
index d2f385f50d0..3114ac4dfa7 100644
--- a/src/libutil/windows/file-path.cc
+++ b/src/libutil/windows/file-path.cc
@@ -12,35 +12,35 @@ namespace nix {
 std::string os_string_to_string(PathViewNG::string_view path)
 {
     std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> converter;
-    return converter.to_bytes(PathNG::string_type { path });
+    return converter.to_bytes(std::filesystem::path::string_type { path });
 }
 
-PathNG::string_type string_to_os_string(std::string_view s)
+std::filesystem::path::string_type string_to_os_string(std::string_view s)
 {
     std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> converter;
     return converter.from_bytes(std::string { s });
 }
 
-std::optional<PathNG> maybePathNG(PathView path)
+std::optional<std::filesystem::path> maybePath(PathView path)
 {
     if (path.length() >= 3 && (('A' <= path[0] && path[0] <= 'Z') || ('a' <= path[0] && path[0] <= 'z')) && path[1] == ':' && WindowsPathTrait<char>::isPathSep(path[2])) {
-        PathNG::string_type sw = string_to_os_string(
+        std::filesystem::path::string_type sw = string_to_os_string(
             std::string { "\\\\?\\" } + path);
         std::replace(sw.begin(), sw.end(), '/', '\\');
         return sw;
     }
     if (path.length() >= 7 && path[0] == '\\' && path[1] == '\\' && (path[2] == '.' || path[2] == '?') && path[3] == '\\' &&
                ('A' <= path[4] && path[4] <= 'Z') && path[5] == ':' && WindowsPathTrait<char>::isPathSep(path[6])) {
-        PathNG::string_type sw = string_to_os_string(path);
+        std::filesystem::path::string_type sw = string_to_os_string(path);
         std::replace(sw.begin(), sw.end(), '/', '\\');
         return sw;
     }
-    return std::optional<PathNG::string_type>();
+    return std::optional<std::filesystem::path::string_type>();
 }
 
-PathNG pathNG(PathView path)
+std::filesystem::path pathNG(PathView path)
 {
-    std::optional<PathNG::string_type> sw = maybePathNG(path);
+    std::optional<std::filesystem::path::string_type> sw = maybePath(path);
     if (!sw) {
         // FIXME why are we not using the regular error handling?
         std::cerr << "invalid path for WinAPI call ["<<path<<"]"<<std::endl;
diff --git a/src/libutil/windows/file-system.cc b/src/libutil/windows/file-system.cc
new file mode 100644
index 00000000000..b15355efe88
--- /dev/null
+++ b/src/libutil/windows/file-system.cc
@@ -0,0 +1,17 @@
+#include "file-system.hh"
+
+namespace nix {
+
+Descriptor openDirectory(const std::filesystem::path & path)
+{
+    return CreateFileW(
+        path.c_str(),
+        GENERIC_READ,
+        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+        NULL,
+        OPEN_EXISTING,
+        FILE_FLAG_BACKUP_SEMANTICS,
+        NULL);
+}
+
+}
diff --git a/src/libutil/windows/meson.build b/src/libutil/windows/meson.build
new file mode 100644
index 00000000000..00320877ff9
--- /dev/null
+++ b/src/libutil/windows/meson.build
@@ -0,0 +1,19 @@
+sources += files(
+  'environment-variables.cc',
+  'file-descriptor.cc',
+  'file-path.cc',
+  'file-system.cc',
+  'muxable-pipe.cc',
+  'processes.cc',
+  'users.cc',
+  'windows-async-pipe.cc',
+  'windows-error.cc',
+)
+
+include_dirs += include_directories('.')
+
+headers += files(
+  'signals-impl.hh',
+  'windows-async-pipe.hh',
+  'windows-error.hh',
+)
diff --git a/src/libutil/windows/muxable-pipe.cc b/src/libutil/windows/muxable-pipe.cc
new file mode 100644
index 00000000000..91a321f7cfa
--- /dev/null
+++ b/src/libutil/windows/muxable-pipe.cc
@@ -0,0 +1,70 @@
+#include <ioapiset.h>
+#include "windows-error.hh"
+
+#include "logging.hh"
+#include "util.hh"
+#include "muxable-pipe.hh"
+
+namespace nix {
+
+void MuxablePipePollState::poll(HANDLE ioport, std::optional<unsigned int> timeout)
+{
+    /* We are on at least Windows Vista / Server 2008 and can get many
+       (countof(oentries)) statuses in one API call. */
+    if (!GetQueuedCompletionStatusEx(
+            ioport, oentries, sizeof(oentries) / sizeof(*oentries), &removed, timeout ? *timeout : INFINITE, false)) {
+        windows::WinError winError("GetQueuedCompletionStatusEx");
+        if (winError.lastError != WAIT_TIMEOUT)
+            throw winError;
+        assert(removed == 0);
+    } else {
+        assert(0 < removed && removed <= sizeof(oentries) / sizeof(*oentries));
+    }
+}
+
+void MuxablePipePollState::iterate(
+    std::set<MuxablePipePollState::CommChannel> & channels,
+    std::function<void(Descriptor fd, std::string_view data)> handleRead,
+    std::function<void(Descriptor fd)> handleEOF)
+{
+    auto p = channels.begin();
+    while (p != channels.end()) {
+        decltype(p) nextp = p;
+        ++nextp;
+        for (ULONG i = 0; i < removed; i++) {
+            if (oentries[i].lpCompletionKey == ((ULONG_PTR) ((*p)->readSide.get()) ^ 0x5555)) {
+                printMsg(lvlVomit, "read %s bytes", oentries[i].dwNumberOfBytesTransferred);
+                if (oentries[i].dwNumberOfBytesTransferred > 0) {
+                    std::string data{
+                        (char *) (*p)->buffer.data(),
+                        oentries[i].dwNumberOfBytesTransferred,
+                    };
+                    handleRead((*p)->readSide.get(), data);
+                }
+
+                if (gotEOF) {
+                    handleEOF((*p)->readSide.get());
+                    nextp = channels.erase(p); // no need to maintain `channels`?
+                } else {
+                    BOOL rc = ReadFile(
+                        (*p)->readSide.get(), (*p)->buffer.data(), (*p)->buffer.size(), &(*p)->got, &(*p)->overlapped);
+                    if (rc) {
+                        // here is possible (but not obligatory) to call
+                        // `handleRead` and repeat ReadFile immediately
+                    } else {
+                        windows::WinError winError("ReadFile(%s, ..)", (*p)->readSide.get());
+                        if (winError.lastError == ERROR_BROKEN_PIPE) {
+                            handleEOF((*p)->readSide.get());
+                            nextp = channels.erase(p); // no need to maintain `channels` ?
+                        } else if (winError.lastError != ERROR_IO_PENDING)
+                            throw winError;
+                    }
+                }
+                break;
+            }
+        }
+        p = nextp;
+    }
+}
+
+}
diff --git a/src/libutil/windows/processes.cc b/src/libutil/windows/processes.cc
index 2a5377f3ffa..9cd714f8419 100644
--- a/src/libutil/windows/processes.cc
+++ b/src/libutil/windows/processes.cc
@@ -1,9 +1,15 @@
 #include "current-process.hh"
 #include "environment-variables.hh"
+#include "error.hh"
+#include "file-descriptor.hh"
+#include "file-path.hh"
 #include "signals.hh"
 #include "processes.hh"
 #include "finally.hh"
 #include "serialise.hh"
+#include "file-system.hh"
+#include "util.hh"
+#include "windows-error.hh"
 
 #include <cerrno>
 #include <cstdlib>
@@ -16,33 +22,359 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#ifdef __APPLE__
-# include <sys/syscall.h>
-#endif
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
 
-#ifdef __linux__
-# include <sys/prctl.h>
-# include <sys/mman.h>
-#endif
+namespace nix {
 
+using namespace nix::windows;
 
-namespace nix {
+Pid::Pid() {}
+
+Pid::Pid(AutoCloseFD pid)
+    : pid(std::move(pid))
+{
+}
+
+Pid::~Pid()
+{
+    if (pid.get() != INVALID_DESCRIPTOR)
+        kill();
+}
+
+void Pid::operator=(AutoCloseFD pid)
+{
+    if (this->pid.get() != INVALID_DESCRIPTOR && this->pid.get() != pid.get())
+        kill();
+    this->pid = std::move(pid);
+}
+
+// TODO: Implement (not needed for process spawning yet)
+int Pid::kill()
+{
+    assert(pid.get() != INVALID_DESCRIPTOR);
+
+    debug("killing process %1%", pid.get());
+
+    throw UnimplementedError("Pid::kill unimplemented");
+}
+
+int Pid::wait()
+{
+    // https://github.com/nix-windows/nix/blob/windows-meson/src/libutil/util.cc#L1938
+    assert(pid.get() != INVALID_DESCRIPTOR);
+    DWORD status = WaitForSingleObject(pid.get(), INFINITE);
+    if (status != WAIT_OBJECT_0) {
+        debug("WaitForSingleObject returned %1%", status);
+    }
 
-std::string runProgram(Path program, bool searchPath, const Strings & args,
-    const std::optional<std::string> & input, bool isInteractive)
+    DWORD exitCode = 0;
+    if (GetExitCodeProcess(pid.get(), &exitCode) == FALSE) {
+        debug("GetExitCodeProcess failed on pid %1%", pid.get());
+    }
+
+    pid.close();
+    return exitCode;
+}
+
+// TODO: Merge this with Unix's runProgram since it's identical logic.
+std::string runProgram(
+    Path program, bool lookupPath, const Strings & args, const std::optional<std::string> & input, bool isInteractive)
+{
+    auto res = runProgram(RunOptions{
+        .program = program, .lookupPath = lookupPath, .args = args, .input = input, .isInteractive = isInteractive});
+
+    if (!statusOk(res.first))
+        throw ExecError(res.first, "program '%1%' %2%", program, statusToString(res.first));
+
+    return res.second;
+}
+
+std::optional<Path> getProgramInterpreter(const Path & program)
+{
+    // These extensions are automatically handled by Windows and don't require an interpreter.
+    static constexpr const char * exts[] = {".exe", ".cmd", ".bat"};
+    for (const auto ext : exts) {
+        if (hasSuffix(program, ext)) {
+            return {};
+        }
+    }
+    // TODO: Open file and read the shebang
+    throw UnimplementedError("getProgramInterpreter unimplemented");
+}
+
+// TODO: Not sure if this is needed in the unix version but it might be useful as a member func
+void setFDInheritable(AutoCloseFD & fd, bool inherit)
+{
+    if (fd.get() != INVALID_DESCRIPTOR) {
+        if (!SetHandleInformation(fd.get(), HANDLE_FLAG_INHERIT, inherit ? HANDLE_FLAG_INHERIT : 0)) {
+            throw WinError("Couldn't disable inheriting of handle");
+        }
+    }
+}
+
+AutoCloseFD nullFD()
 {
-    throw UnimplementedError("Cannot shell out to git on Windows yet");
+    // Create null handle to discard reads / writes
+    // https://stackoverflow.com/a/25609668
+    // https://github.com/nix-windows/nix/blob/windows-meson/src/libutil/util.cc#L2228
+    AutoCloseFD nul = CreateFileW(
+        L"NUL",
+        GENERIC_READ | GENERIC_WRITE,
+        // We don't care who reads / writes / deletes this file since it's NUL anyways
+        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+        NULL,
+        OPEN_EXISTING,
+        0,
+        NULL);
+    if (!nul.get()) {
+        throw WinError("Couldn't open NUL device");
+    }
+    // Let this handle be inheritable by child processes
+    setFDInheritable(nul, true);
+    return nul;
 }
 
+// Adapted from
+// https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/
+std::string windowsEscape(const std::string & str, bool cmd)
+{
+    // TODO: This doesn't handle cmd.exe escaping.
+    if (cmd) {
+        throw UnimplementedError("cmd.exe escaping is not implemented");
+    }
+
+    if (str.find_first_of(" \t\n\v\"") == str.npos && !str.empty()) {
+        // No need to escape this one, the nonempty contents don't have a special character
+        return str;
+    }
+    std::string buffer;
+    // Add the opening quote
+    buffer += '"';
+    for (auto iter = str.begin();; ++iter) {
+        size_t backslashes = 0;
+        while (iter != str.end() && *iter == '\\') {
+            ++iter;
+            ++backslashes;
+        }
+
+        // We only escape backslashes if:
+        // - They come immediately before the closing quote
+        // - They come immediately before a quote in the middle of the string
+        // Both of these cases break the escaping if not handled. Otherwise backslashes are fine as-is
+        if (iter == str.end()) {
+            // Need to escape each backslash
+            buffer.append(backslashes * 2, '\\');
+            // Exit since we've reached the end of the string
+            break;
+        } else if (*iter == '"') {
+            // Need to escape each backslash and the intermediate quote character
+            buffer.append(backslashes * 2, '\\');
+            buffer += "\\\"";
+        } else {
+            // Don't escape the backslashes since they won't break the delimiter
+            buffer.append(backslashes, '\\');
+            buffer += *iter;
+        }
+    }
+    // Add the closing quote
+    return buffer + '"';
+}
+
+Pid spawnProcess(const Path & realProgram, const RunOptions & options, Pipe & out, Pipe & in)
+{
+    // Setup pipes.
+    if (options.standardOut) {
+        // Don't inherit the read end of the output pipe
+        setFDInheritable(out.readSide, false);
+    } else {
+        out.writeSide = nullFD();
+    }
+    if (options.standardIn) {
+        // Don't inherit the write end of the input pipe
+        setFDInheritable(in.writeSide, false);
+    } else {
+        in.readSide = nullFD();
+    }
+
+    STARTUPINFOW startInfo = {0};
+    startInfo.cb = sizeof(startInfo);
+    startInfo.dwFlags = STARTF_USESTDHANDLES;
+    startInfo.hStdInput = in.readSide.get();
+    startInfo.hStdOutput = out.writeSide.get();
+    startInfo.hStdError = out.writeSide.get();
+
+    std::string envline;
+    // Retain the current processes' environment variables.
+    for (const auto & envVar : getEnv()) {
+        envline += (envVar.first + '=' + envVar.second + '\0');
+    }
+    // Also add new ones specified in options.
+    if (options.environment) {
+        for (const auto & envVar : *options.environment) {
+            envline += (envVar.first + '=' + envVar.second + '\0');
+        }
+    }
+
+    std::string cmdline = windowsEscape(realProgram, false);
+    for (const auto & arg : options.args) {
+        // TODO: This isn't the right way to escape windows command
+        // See https://learn.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-commandlinetoargvw
+        cmdline += ' ' + windowsEscape(arg, false);
+    }
+
+    PROCESS_INFORMATION procInfo = {0};
+    if (CreateProcessW(
+            // EXE path is provided in the cmdline
+            NULL,
+            string_to_os_string(cmdline).data(),
+            NULL,
+            NULL,
+            TRUE,
+            CREATE_UNICODE_ENVIRONMENT | CREATE_SUSPENDED,
+            string_to_os_string(envline).data(),
+            options.chdir.has_value() ? string_to_os_string(*options.chdir).data() : NULL,
+            &startInfo,
+            &procInfo)
+        == 0) {
+        throw WinError("CreateProcessW failed (%1%)", cmdline);
+    }
+
+    // Convert these to use RAII
+    AutoCloseFD process = procInfo.hProcess;
+    AutoCloseFD thread = procInfo.hThread;
+
+    // Add current process and child to job object so child terminates when parent terminates
+    // TODO: This spawns one job per child process. We can probably keep this as a global, and
+    // add children a single job so we don't use so many jobs at once.
+    Descriptor job = CreateJobObjectW(NULL, NULL);
+    if (job == NULL) {
+        TerminateProcess(procInfo.hProcess, 0);
+        throw WinError("Couldn't create job object for child process");
+    }
+    if (AssignProcessToJobObject(job, procInfo.hProcess) == FALSE) {
+        TerminateProcess(procInfo.hProcess, 0);
+        throw WinError("Couldn't assign child process to job object");
+    }
+    if (ResumeThread(procInfo.hThread) == (DWORD) -1) {
+        TerminateProcess(procInfo.hProcess, 0);
+        throw WinError("Couldn't resume child process thread");
+    }
+
+    return process;
+}
+
+// TODO: Merge this with Unix's runProgram since it's identical logic.
 // Output = error code + "standard out" output stream
 std::pair<int, std::string> runProgram(RunOptions && options)
 {
-    throw UnimplementedError("Cannot shell out to git on Windows yet");
+    StringSink sink;
+    options.standardOut = &sink;
+
+    int status = 0;
+
+    try {
+        runProgram2(options);
+    } catch (ExecError & e) {
+        status = e.status;
+    }
+
+    return {status, std::move(sink.s)};
 }
 
 void runProgram2(const RunOptions & options)
 {
-    throw UnimplementedError("Cannot shell out to git on Windows yet");
+    checkInterrupt();
+
+    assert(!(options.standardIn && options.input));
+
+    std::unique_ptr<Source> source_;
+    Source * source = options.standardIn;
+
+    if (options.input) {
+        source_ = std::make_unique<StringSource>(*options.input);
+        source = source_.get();
+    }
+
+    /* Create a pipe. */
+    Pipe out, in;
+    // TODO: I copied this from unix but this is handled again in spawnProcess, so might be weird to split it up like
+    // this
+    if (options.standardOut)
+        out.create();
+    if (source)
+        in.create();
+
+    Path realProgram = options.program;
+    // TODO: Implement shebang / program interpreter lookup on Windows
+    auto interpreter = getProgramInterpreter(realProgram);
+
+    std::optional<Finally<std::function<void()>>> resumeLoggerDefer;
+    if (options.isInteractive) {
+        logger->pause();
+        resumeLoggerDefer.emplace([]() { logger->resume(); });
+    }
+
+    Pid pid = spawnProcess(interpreter.has_value() ? *interpreter : realProgram, options, out, in);
+
+    // TODO: This is identical to unix, deduplicate?
+    out.writeSide.close();
+
+    std::thread writerThread;
+
+    std::promise<void> promise;
+
+    Finally doJoin([&] {
+        if (writerThread.joinable())
+            writerThread.join();
+    });
+
+    if (source) {
+        in.readSide.close();
+        writerThread = std::thread([&] {
+            try {
+                std::vector<char> buf(8 * 1024);
+                while (true) {
+                    size_t n;
+                    try {
+                        n = source->read(buf.data(), buf.size());
+                    } catch (EndOfFile &) {
+                        break;
+                    }
+                    writeFull(in.writeSide.get(), {buf.data(), n});
+                }
+                promise.set_value();
+            } catch (...) {
+                promise.set_exception(std::current_exception());
+            }
+            in.writeSide.close();
+        });
+    }
+
+    if (options.standardOut)
+        drainFD(out.readSide.get(), *options.standardOut);
+
+    /* Wait for the child to finish. */
+    int status = pid.wait();
+
+    /* Wait for the writer thread to finish. */
+    if (source)
+        promise.get_future().get();
+
+    if (status)
+        throw ExecError(status, "program '%1%' %2%", options.program, statusToString(status));
+}
+
+std::string statusToString(int status)
+{
+    if (status != 0)
+        return fmt("with exit code %d", status);
+    else
+        return "succeeded";
 }
 
+bool statusOk(int status)
+{
+    return status == 0;
+}
 }
diff --git a/src/libutil/windows/users.cc b/src/libutil/windows/users.cc
index 1792ff1a111..db6c42df381 100644
--- a/src/libutil/windows/users.cc
+++ b/src/libutil/windows/users.cc
@@ -9,6 +9,8 @@
 
 namespace nix {
 
+using namespace nix::windows;
+
 std::string getUserName()
 {
     // Get the required buffer size
diff --git a/src/libutil/windows/windows-async-pipe.cc b/src/libutil/windows/windows-async-pipe.cc
new file mode 100644
index 00000000000..4fa57ca3672
--- /dev/null
+++ b/src/libutil/windows/windows-async-pipe.cc
@@ -0,0 +1,49 @@
+#include "windows-async-pipe.hh"
+#include "windows-error.hh"
+
+namespace nix::windows {
+
+void AsyncPipe::createAsyncPipe(HANDLE iocp)
+{
+    // std::cerr << (format("-----AsyncPipe::createAsyncPipe(%x)") % iocp) << std::endl;
+
+    buffer.resize(0x1000);
+    memset(&overlapped, 0, sizeof(overlapped));
+
+    std::string pipeName = fmt("\\\\.\\pipe\\nix-%d-%p", GetCurrentProcessId(), (void *) this);
+
+    readSide = CreateNamedPipeA(
+        pipeName.c_str(),
+        PIPE_ACCESS_INBOUND | FILE_FLAG_OVERLAPPED,
+        PIPE_TYPE_BYTE,
+        PIPE_UNLIMITED_INSTANCES,
+        0,
+        0,
+        INFINITE,
+        NULL);
+    if (!readSide)
+        throw WinError("CreateNamedPipeA(%s)", pipeName);
+
+    HANDLE hIocp = CreateIoCompletionPort(readSide.get(), iocp, (ULONG_PTR) (readSide.get()) ^ 0x5555, 0);
+    if (hIocp != iocp)
+        throw WinError("CreateIoCompletionPort(%x[%s], %x, ...) returned %x", readSide.get(), pipeName, iocp, hIocp);
+
+    if (!ConnectNamedPipe(readSide.get(), &overlapped) && GetLastError() != ERROR_IO_PENDING)
+        throw WinError("ConnectNamedPipe(%s)", pipeName);
+
+    SECURITY_ATTRIBUTES psa2 = {0};
+    psa2.nLength = sizeof(SECURITY_ATTRIBUTES);
+    psa2.bInheritHandle = TRUE;
+
+    writeSide = CreateFileA(pipeName.c_str(), GENERIC_WRITE, 0, &psa2, OPEN_EXISTING, 0, NULL);
+    if (!readSide)
+        throw WinError("CreateFileA(%s)", pipeName);
+}
+
+void AsyncPipe::close()
+{
+    readSide.close();
+    writeSide.close();
+}
+
+}
diff --git a/src/libutil/windows/windows-async-pipe.hh b/src/libutil/windows/windows-async-pipe.hh
new file mode 100644
index 00000000000..8f554e403f3
--- /dev/null
+++ b/src/libutil/windows/windows-async-pipe.hh
@@ -0,0 +1,27 @@
+#pragma once
+///@file
+
+#include "file-descriptor.hh"
+
+namespace nix::windows {
+
+/***
+ * An "async pipe" is a pipe that supports I/O Completion Ports so
+ * multiple pipes can be listened too.
+ *
+ * Unfortunately, only named pipes support that on windows, so we use
+ * those with randomized temp file names.
+ */
+class AsyncPipe
+{
+public:
+    AutoCloseFD writeSide, readSide;
+    OVERLAPPED overlapped;
+    DWORD got;
+    std::vector<unsigned char> buffer;
+
+    void createAsyncPipe(HANDLE iocp);
+    void close();
+};
+
+}
diff --git a/src/libutil/windows/windows-error.cc b/src/libutil/windows/windows-error.cc
index 26faaae6d21..aead4af2378 100644
--- a/src/libutil/windows/windows-error.cc
+++ b/src/libutil/windows/windows-error.cc
@@ -4,7 +4,7 @@
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
-namespace nix {
+namespace nix::windows {
 
 std::string WinError::renderError(DWORD lastError)
 {
diff --git a/src/libutil/windows/windows-error.hh b/src/libutil/windows/windows-error.hh
index fdfd0f52c58..624b4c4cb0b 100644
--- a/src/libutil/windows/windows-error.hh
+++ b/src/libutil/windows/windows-error.hh
@@ -5,7 +5,7 @@
 
 #include "error.hh"
 
-namespace nix {
+namespace nix::windows {
 
 /**
  * Windows Error type.
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 198e9cda013..d37b16bdca0 100644
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -25,6 +25,8 @@
 #include "attr-path.hh"
 #include "legacy.hh"
 #include "users.hh"
+#include "network-proxy.hh"
+#include "compatibility-settings.hh"
 
 using namespace nix;
 using namespace std::string_literals;
@@ -89,24 +91,50 @@ static std::vector<std::string> shellwords(const std::string & s)
     return res;
 }
 
+/**
+ * Like `resolveExprPath`, but prefers `shell.nix` instead of `default.nix`,
+ * and if `path` was a directory, it checks eagerly whether `shell.nix` or
+ * `default.nix` exist, throwing an error if they don't.
+ */
+static SourcePath resolveShellExprPath(SourcePath path)
+{
+    auto resolvedOrDir = resolveExprPath(path, false);
+    if (resolvedOrDir.resolveSymlinks().lstat().type == SourceAccessor::tDirectory) {
+        if ((resolvedOrDir / "shell.nix").pathExists()) {
+            if (compatibilitySettings.nixShellAlwaysLooksForShellNix) {
+                return resolvedOrDir / "shell.nix";
+            } else {
+                warn("Skipping '%1%', because the setting '%2%' is disabled. This is a deprecated behavior. Consider enabling '%2%'.",
+                    resolvedOrDir / "shell.nix",
+                    "nix-shell-always-looks-for-shell-nix");
+            }
+        }
+        if ((resolvedOrDir / "default.nix").pathExists()) {
+            return resolvedOrDir / "default.nix";
+        }
+        throw Error("neither '%s' nor '%s' found in '%s'", "shell.nix", "default.nix", resolvedOrDir);
+    }
+    return resolvedOrDir;
+}
+
 static void main_nix_build(int argc, char * * argv)
 {
     auto dryRun = false;
-    auto runEnv = std::regex_search(argv[0], std::regex("nix-shell$"));
+    auto isNixShell = std::regex_search(argv[0], std::regex("nix-shell$"));
     auto pure = false;
     auto fromArgs = false;
     auto packages = false;
     // Same condition as bash uses for interactive shells
     auto interactive = isatty(STDIN_FILENO) && isatty(STDERR_FILENO);
     Strings attrPaths;
-    Strings left;
+    Strings remainingArgs;
     BuildMode buildMode = bmNormal;
     bool readStdin = false;
 
     std::string envCommand; // interactive shell
     Strings envExclude;
 
-    auto myName = runEnv ? "nix-shell" : "nix-build";
+    auto myName = isNixShell ? "nix-shell" : "nix-build";
 
     auto inShebang = false;
     std::string script;
@@ -121,8 +149,8 @@ static void main_nix_build(int argc, char * * argv)
         "HOME", "XDG_RUNTIME_DIR", "USER", "LOGNAME", "DISPLAY",
         "WAYLAND_DISPLAY", "WAYLAND_SOCKET", "PATH", "TERM", "IN_NIX_SHELL",
         "NIX_SHELL_PRESERVE_PROMPT", "TZ", "PAGER", "NIX_BUILD_SHELL", "SHLVL",
-        "http_proxy", "https_proxy", "ftp_proxy", "all_proxy", "no_proxy"
     };
+    keepVars.insert(networkProxyVariables.begin(), networkProxyVariables.end());
 
     Strings args;
     for (int i = 1; i < argc; ++i)
@@ -131,7 +159,7 @@ static void main_nix_build(int argc, char * * argv)
     // Heuristic to see if we're invoked as a shebang script, namely,
     // if we have at least one argument, it's the name of an
     // executable file, and it starts with "#!".
-    if (runEnv && argc > 1) {
+    if (isNixShell && argc > 1) {
         script = argv[1];
         try {
             auto lines = tokenizeString<Strings>(readFile(script), "\n");
@@ -170,7 +198,7 @@ static void main_nix_build(int argc, char * * argv)
             ; // obsolete
 
         else if (*arg == "--no-out-link" || *arg == "--no-link")
-            outLink = (Path) tmpDir + "/result";
+            outLink = (tmpDir.path() / "result").string();
 
         else if (*arg == "--attr" || *arg == "-A")
             attrPaths.push_back(getArg(*arg, arg, end));
@@ -185,9 +213,9 @@ static void main_nix_build(int argc, char * * argv)
             dryRun = true;
 
         else if (*arg == "--run-env") // obsolete
-            runEnv = true;
+            isNixShell = true;
 
-        else if (runEnv && (*arg == "--command" || *arg == "--run")) {
+        else if (isNixShell && (*arg == "--command" || *arg == "--run")) {
             if (*arg == "--run")
                 interactive = false;
             envCommand = getArg(*arg, arg, end) + "\nexit";
@@ -205,7 +233,7 @@ static void main_nix_build(int argc, char * * argv)
         else if (*arg == "--pure") pure = true;
         else if (*arg == "--impure") pure = false;
 
-        else if (runEnv && (*arg == "--packages" || *arg == "-p"))
+        else if (isNixShell && (*arg == "--packages" || *arg == "-p"))
             packages = true;
 
         else if (inShebang && *arg == "-i") {
@@ -245,7 +273,7 @@ static void main_nix_build(int argc, char * * argv)
             return false;
 
         else
-            left.push_back(*arg);
+            remainingArgs.push_back(*arg);
 
         return true;
     });
@@ -258,14 +286,14 @@ static void main_nix_build(int argc, char * * argv)
     auto store = openStore();
     auto evalStore = myArgs.evalStoreUrl ? openStore(*myArgs.evalStoreUrl) : store;
 
-    auto state = std::make_unique<EvalState>(myArgs.searchPath, evalStore, store);
+    auto state = std::make_unique<EvalState>(myArgs.lookupPath, evalStore, evalSettings, store);
     state->repair = myArgs.repair;
     if (myArgs.repair) buildMode = bmRepair;
 
     auto autoArgs = myArgs.getAutoArgs(*state);
 
     auto autoArgsWithInNixShell = autoArgs;
-    if (runEnv) {
+    if (isNixShell) {
         auto newArgs = state->buildBindings(autoArgsWithInNixShell->size() + 1);
         newArgs.alloc("inNixShell").mkBool(true);
         for (auto & i : *autoArgs) newArgs.insert(i);
@@ -275,19 +303,26 @@ static void main_nix_build(int argc, char * * argv)
     if (packages) {
         std::ostringstream joined;
         joined << "{...}@args: with import <nixpkgs> args; (pkgs.runCommandCC or pkgs.runCommand) \"shell\" { buildInputs = [ ";
-        for (const auto & i : left)
+        for (const auto & i : remainingArgs)
             joined << '(' << i << ") ";
         joined << "]; } \"\"";
         fromArgs = true;
-        left = {joined.str()};
-    } else if (!fromArgs) {
-        if (left.empty() && runEnv && pathExists("shell.nix"))
-            left = {"shell.nix"};
-        if (left.empty())
-            left = {"default.nix"};
+        remainingArgs = {joined.str()};
+    } else if (!fromArgs && remainingArgs.empty()) {
+        if (isNixShell && !compatibilitySettings.nixShellAlwaysLooksForShellNix && std::filesystem::exists("shell.nix")) {
+            // If we're in 2.3 compatibility mode, we need to look for shell.nix
+            // now, because it won't be done later.
+            remainingArgs = {"shell.nix"};
+        } else {
+            remainingArgs = {"."};
+
+            // Instead of letting it throw later, we throw here to give a more relevant error message
+            if (isNixShell && !std::filesystem::exists("shell.nix") && !std::filesystem::exists("default.nix"))
+                throw Error("no argument specified and no '%s' or '%s' file found in the working directory", "shell.nix", "default.nix");
+        }
     }
 
-    if (runEnv)
+    if (isNixShell)
         setEnv("IN_NIX_SHELL", pure ? "pure" : "impure");
 
     PackageInfos drvs;
@@ -298,7 +333,7 @@ static void main_nix_build(int argc, char * * argv)
     if (readStdin)
         exprs = {state->parseStdin()};
     else
-        for (auto i : left) {
+        for (auto i : remainingArgs) {
             if (fromArgs)
                 exprs.push_back(state->parseExprFromString(std::move(i), state->rootPath(".")));
             else {
@@ -309,14 +344,18 @@ static void main_nix_build(int argc, char * * argv)
                 auto [path, outputNames] = parsePathWithOutputs(absolute);
                 if (evalStore->isStorePath(path) && hasSuffix(path, ".drv"))
                     drvs.push_back(PackageInfo(*state, evalStore, absolute));
-                else
+                else {
                     /* If we're in a #! script, interpret filenames
                        relative to the script. */
-                    exprs.push_back(
-                        state->parseExprFromFile(
-                            resolveExprPath(
-                                lookupFileArg(*state,
-                                    inShebang && !packages ? absPath(i, absPath(dirOf(script))) : i))));
+                    auto baseDir = inShebang && !packages ? absPath(i, absPath(dirOf(script))) : i;
+
+                    auto sourcePath = lookupFileArg(*state,
+                                    baseDir);
+                    auto resolvedPath =
+                        isNixShell ? resolveShellExprPath(sourcePath) : resolveExprPath(sourcePath);
+
+                    exprs.push_back(state->parseExprFromFile(resolvedPath));
+                }
             }
         }
 
@@ -329,7 +368,7 @@ static void main_nix_build(int argc, char * * argv)
 
         std::function<bool(const Value & v)> takesNixShellAttr;
         takesNixShellAttr = [&](const Value & v) {
-            if (!runEnv) {
+            if (!isNixShell) {
                 return false;
             }
             bool add = false;
@@ -380,7 +419,7 @@ static void main_nix_build(int argc, char * * argv)
             store->buildPaths(paths, buildMode, evalStore);
     };
 
-    if (runEnv) {
+    if (isNixShell) {
         if (drvs.size() != 1)
             throw UsageError("nix-shell requires a single derivation");
 
@@ -476,9 +515,7 @@ static void main_nix_build(int argc, char * * argv)
         // Set the environment.
         auto env = getEnv();
 
-        auto tmp = getEnvNonEmpty("TMPDIR");
-        if (!tmp)
-            tmp = getEnvNonEmpty("XDG_RUNTIME_DIR").value_or("/tmp");
+        auto tmp = getEnvNonEmpty("TMPDIR").value_or("/tmp");
 
         if (pure) {
             decltype(env) newEnv;
@@ -490,7 +527,7 @@ static void main_nix_build(int argc, char * * argv)
             env["__ETC_PROFILE_SOURCED"] = "1";
         }
 
-        env["NIX_BUILD_TOP"] = env["TMPDIR"] = env["TEMPDIR"] = env["TMP"] = env["TEMP"] = *tmp;
+        env["NIX_BUILD_TOP"] = env["TMPDIR"] = env["TEMPDIR"] = env["TMP"] = env["TEMP"] = tmp;
         env["NIX_STORE"] = store->storeDir;
         env["NIX_BUILD_CORES"] = std::to_string(settings.buildCores);
 
@@ -503,7 +540,7 @@ static void main_nix_build(int argc, char * * argv)
             if (passAsFile.count(var.first)) {
                 keepTmp = true;
                 auto fn = ".attr-" + std::to_string(fileNr++);
-                Path p = (Path) tmpDir + "/" + fn;
+                Path p = (tmpDir.path() / fn).string();
                 writeFile(p, var.second);
                 env[var.first + "Path"] = p;
             } else
@@ -535,10 +572,10 @@ static void main_nix_build(int argc, char * * argv)
                 auto json = structAttrs.value();
                 structuredAttrsRC = writeStructuredAttrsShell(json);
 
-                auto attrsJSON = (Path) tmpDir + "/.attrs.json";
+                auto attrsJSON = (tmpDir.path() / ".attrs.json").string();
                 writeFile(attrsJSON, json.dump());
 
-                auto attrsSH = (Path) tmpDir + "/.attrs.sh";
+                auto attrsSH = (tmpDir.path() / ".attrs.sh").string();
                 writeFile(attrsSH, structuredAttrsRC);
 
                 env["NIX_ATTRS_SH_FILE"] = attrsSH;
@@ -551,7 +588,7 @@ static void main_nix_build(int argc, char * * argv)
            convenience, source $stdenv/setup to setup additional
            environment variables and shell functions.  Also don't
            lose the current $PATH directories. */
-        auto rcfile = (Path) tmpDir + "/rc";
+        auto rcfile = (tmpDir.path() / "rc").string();
         std::string rc = fmt(
                 R"(_nix_shell_clean_tmpdir() { command rm -rf %1%; }; )"s +
                 (keepTmp ?
@@ -582,7 +619,7 @@ static void main_nix_build(int argc, char * * argv)
                 "unset TZ; %6%"
                 "shopt -s execfail;"
                 "%7%",
-                shellEscape(tmpDir),
+                shellEscape(tmpDir.path().string()),
                 (pure ? "" : "p=$PATH; "),
                 (pure ? "" : "PATH=$PATH:$p; unset p; "),
                 shellEscape(dirOf(*shell)),
diff --git a/src/nix-collect-garbage/nix-collect-garbage.cc b/src/nix-collect-garbage/nix-collect-garbage.cc
index bb3f1bc6add..91209c97898 100644
--- a/src/nix-collect-garbage/nix-collect-garbage.cc
+++ b/src/nix-collect-garbage/nix-collect-garbage.cc
@@ -27,18 +27,18 @@ void removeOldGenerations(std::string dir)
 
     bool canWrite = access(dir.c_str(), W_OK) == 0;
 
-    for (auto & i : readDirectory(dir)) {
+    for (auto & i : std::filesystem::directory_iterator{dir}) {
         checkInterrupt();
 
-        auto path = dir + "/" + i.name;
-        auto type = i.type == DT_UNKNOWN ? getFileType(path) : i.type;
+        auto path = i.path().string();
+        auto type = i.symlink_status().type();
 
-        if (type == DT_LNK && canWrite) {
+        if (type == std::filesystem::file_type::symlink && canWrite) {
             std::string link;
             try {
                 link = readLink(path);
-            } catch (SysError & e) {
-                if (e.errNo == ENOENT) continue;
+            } catch (std::filesystem::filesystem_error & e) {
+                if (e.code() == std::errc::no_such_file_or_directory) continue;
                 throw;
             }
             if (link.find("link") != std::string::npos) {
@@ -49,7 +49,7 @@ void removeOldGenerations(std::string dir)
                 } else
                     deleteOldGenerations(path, dryRun);
             }
-        } else if (type == DT_DIR) {
+        } else if (type == std::filesystem::file_type::directory) {
             removeOldGenerations(path);
         }
     }
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index eeca01833b2..c72378cd5f4 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -94,11 +94,11 @@ static bool parseInstallSourceOptions(Globals & globals,
 }
 
 
-static bool isNixExpr(const SourcePath & path, struct InputAccessor::Stat & st)
+static bool isNixExpr(const SourcePath & path, struct SourceAccessor::Stat & st)
 {
     return
-        st.type == InputAccessor::tRegular
-        || (st.type == InputAccessor::tDirectory && (path / "default.nix").resolveSymlinks().pathExists());
+        st.type == SourceAccessor::tRegular
+        || (st.type == SourceAccessor::tDirectory && (path / "default.nix").resolveSymlinks().pathExists());
 }
 
 
@@ -119,14 +119,14 @@ static void getAllExprs(EvalState & state,
 
         auto path2 = (path / i).resolveSymlinks();
 
-        InputAccessor::Stat st;
+        SourceAccessor::Stat st;
         try {
             st = path2.lstat();
         } catch (Error &) {
             continue; // ignore dangling symlinks in ~/.nix-defexpr
         }
 
-        if (isNixExpr(path2, st) && (st.type != InputAccessor::tRegular || hasSuffix(path2.baseName(), ".nix"))) {
+        if (isNixExpr(path2, st) && (st.type != SourceAccessor::tRegular || hasSuffix(path2.baseName(), ".nix"))) {
             /* Strip off the `.nix' filename suffix (if applicable),
                otherwise the attribute cannot be selected with the
                `-A' option.  Useful if you want to stick a Nix
@@ -149,7 +149,7 @@ static void getAllExprs(EvalState & state,
                 throw Error("too many Nix expressions in directory '%1%'", path);
             attrs.alloc(attrName).mkApp(&state.getBuiltin("import"), vArg);
         }
-        else if (st.type == InputAccessor::tDirectory)
+        else if (st.type == SourceAccessor::tDirectory)
             /* `path2' is a directory (with no default.nix in it);
                recurse into it. */
             getAllExprs(state, path2, seen, attrs);
@@ -171,7 +171,7 @@ static void loadSourceExpr(EvalState & state, const SourcePath & path, Value & v
        set flat, not nested, to make it easier for a user to have a
        ~/.nix-defexpr directory that includes some system-wide
        directory). */
-    else if (st.type == InputAccessor::tDirectory) {
+    else if (st.type == SourceAccessor::tDirectory) {
         auto attrs = state.buildBindings(maxAttrs);
         attrs.insert(state.symbols.create("_combineChannels"), &state.vEmptyList);
         StringSet seen;
@@ -1525,7 +1525,7 @@ static int main_nix_env(int argc, char * * argv)
 
         auto store = openStore();
 
-        globals.state = std::shared_ptr<EvalState>(new EvalState(myArgs.searchPath, store));
+        globals.state = std::shared_ptr<EvalState>(new EvalState(myArgs.lookupPath, store, evalSettings));
         globals.state->repair = myArgs.repair;
 
         globals.instSource.nixExprPath = std::make_shared<SourcePath>(
diff --git a/src/nix-env/user-env.cc b/src/nix-env/user-env.cc
index 6cbbacb1522..a24dd11d6d1 100644
--- a/src/nix-env/user-env.cc
+++ b/src/nix-env/user-env.cc
@@ -9,8 +9,9 @@
 #include "eval-inline.hh"
 #include "profiles.hh"
 #include "print-ambiguous.hh"
-#include <limits>
 
+#include <limits>
+#include <sstream>
 
 namespace nix {
 
@@ -114,7 +115,7 @@ bool createUserEnv(EvalState & state, PackageInfos & elems,
         std::string str2 = str.str();
         StringSource source { str2 };
         state.store->addToStoreFromDump(
-            source, "env-manifest.nix", FileSerialisationMethod::Flat, TextIngestionMethod {}, HashAlgorithm::SHA256, references);
+            source, "env-manifest.nix", FileSerialisationMethod::Flat, ContentAddressMethod::Raw::Text, HashAlgorithm::SHA256, references);
     });
 
     /* Get the environment builder expression. */
@@ -140,6 +141,7 @@ bool createUserEnv(EvalState & state, PackageInfos & elems,
     NixStringContext context;
     auto & aDrvPath(*topLevel.attrs()->find(state.sDrvPath));
     auto topLevelDrv = state.coerceToStorePath(aDrvPath.pos, *aDrvPath.value, context, "");
+    topLevelDrv.requireDerivation();
     auto & aOutPath(*topLevel.attrs()->find(state.sOutPath));
     auto topLevelOut = state.coerceToStorePath(aOutPath.pos, *aOutPath.value, context, "");
 
diff --git a/src/nix-expr-test-support b/src/nix-expr-test-support
new file mode 120000
index 00000000000..427b80dff0b
--- /dev/null
+++ b/src/nix-expr-test-support
@@ -0,0 +1 @@
+../tests/unit/libexpr-support
\ No newline at end of file
diff --git a/src/nix-expr-tests b/src/nix-expr-tests
new file mode 120000
index 00000000000..3af7110d36d
--- /dev/null
+++ b/src/nix-expr-tests
@@ -0,0 +1 @@
+../tests/unit/libexpr
\ No newline at end of file
diff --git a/src/nix-fetchers-tests b/src/nix-fetchers-tests
new file mode 120000
index 00000000000..80e4b68ae5e
--- /dev/null
+++ b/src/nix-fetchers-tests
@@ -0,0 +1 @@
+../tests/unit/libfetchers
\ No newline at end of file
diff --git a/src/nix-flake-tests b/src/nix-flake-tests
new file mode 120000
index 00000000000..bb2d49400f9
--- /dev/null
+++ b/src/nix-flake-tests
@@ -0,0 +1 @@
+../tests/unit/libflake
\ No newline at end of file
diff --git a/src/nix-instantiate/nix-instantiate.cc b/src/nix-instantiate/nix-instantiate.cc
index 1e17282254f..a4bfeebbbdb 100644
--- a/src/nix-instantiate/nix-instantiate.cc
+++ b/src/nix-instantiate/nix-instantiate.cc
@@ -157,7 +157,7 @@ static int main_nix_instantiate(int argc, char * * argv)
         auto store = openStore();
         auto evalStore = myArgs.evalStoreUrl ? openStore(*myArgs.evalStoreUrl) : store;
 
-        auto state = std::make_unique<EvalState>(myArgs.searchPath, evalStore, store);
+        auto state = std::make_unique<EvalState>(myArgs.lookupPath, evalStore, evalSettings, store);
         state->repair = myArgs.repair;
 
         Bindings & autoArgs = *myArgs.getAutoArgs(*state);
diff --git a/src/nix-store-test-support b/src/nix-store-test-support
new file mode 120000
index 00000000000..af4befd90d8
--- /dev/null
+++ b/src/nix-store-test-support
@@ -0,0 +1 @@
+../tests/unit/libstore-support
\ No newline at end of file
diff --git a/src/nix-store-tests b/src/nix-store-tests
new file mode 120000
index 00000000000..fc9b910afe3
--- /dev/null
+++ b/src/nix-store-tests
@@ -0,0 +1 @@
+../tests/unit/libstore
\ No newline at end of file
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 719675cba2e..d0840a02e5e 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -7,6 +7,7 @@
 #include "local-fs-store.hh"
 #include "log-store.hh"
 #include "serve-protocol.hh"
+#include "serve-protocol-connection.hh"
 #include "serve-protocol-impl.hh"
 #include "shared.hh"
 #include "graphml.hh"
@@ -184,7 +185,7 @@ static void opAdd(Strings opFlags, Strings opArgs)
     for (auto & i : opArgs) {
         auto [accessor, canonPath] = PosixSourceAccessor::createAtRoot(i);
         cout << fmt("%s\n", store->printStorePath(store->addToStore(
-            std::string(baseNameOf(i)), accessor, canonPath)));
+            std::string(baseNameOf(i)), {accessor, canonPath})));
     }
 }
 
@@ -193,10 +194,10 @@ static void opAdd(Strings opFlags, Strings opArgs)
    store. */
 static void opAddFixed(Strings opFlags, Strings opArgs)
 {
-    auto method = FileIngestionMethod::Flat;
+    ContentAddressMethod method = ContentAddressMethod::Raw::Flat;
 
     for (auto & i : opFlags)
-        if (i == "--recursive") method = FileIngestionMethod::Recursive;
+        if (i == "--recursive") method = ContentAddressMethod::Raw::NixArchive;
         else throw UsageError("unknown flag '%1%'", i);
 
     if (opArgs.empty())
@@ -209,8 +210,7 @@ static void opAddFixed(Strings opFlags, Strings opArgs)
         auto [accessor, canonPath] = PosixSourceAccessor::createAtRoot(i);
         std::cout << fmt("%s\n", store->printStorePath(store->addToStoreSlow(
             baseNameOf(i),
-            accessor,
-            canonPath,
+            {accessor, canonPath},
             method,
             hashAlgo).path));
     }
@@ -223,7 +223,7 @@ static void opPrintFixedPath(Strings opFlags, Strings opArgs)
     auto method = FileIngestionMethod::Flat;
 
     for (auto i : opFlags)
-        if (i == "--recursive") method = FileIngestionMethod::Recursive;
+        if (i == "--recursive") method = FileIngestionMethod::NixArchive;
         else throw UsageError("unknown flag '%1%'", i);
 
     if (opArgs.size() != 3)
@@ -562,9 +562,8 @@ static void registerValidity(bool reregister, bool hashGiven, bool canonicalise)
 #endif
             if (!hashGiven) {
                 HashResult hash = hashPath(
-                    *store->getFSAccessor(false), CanonPath { store->printStorePath(info->path) },
-
-                    FileSerialisationMethod::Recursive, HashAlgorithm::SHA256);
+                    {store->getFSAccessor(false), CanonPath { store->printStorePath(info->path) }},
+                    FileSerialisationMethod::NixArchive, HashAlgorithm::SHA256);
                 info->narHash = hash.first;
                 info->narSize = hash.second;
             }
diff --git a/src/nix-util-test-support b/src/nix-util-test-support
new file mode 120000
index 00000000000..4b25930eb70
--- /dev/null
+++ b/src/nix-util-test-support
@@ -0,0 +1 @@
+../tests/unit/libutil-support
\ No newline at end of file
diff --git a/src/nix-util-tests b/src/nix-util-tests
new file mode 120000
index 00000000000..e1138411a6e
--- /dev/null
+++ b/src/nix-util-tests
@@ -0,0 +1 @@
+../tests/unit/libutil
\ No newline at end of file
diff --git a/src/nix/.version b/src/nix/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/nix/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/nix/add-to-store.cc b/src/nix/add-to-store.cc
index 02154715f81..5c08f761662 100644
--- a/src/nix/add-to-store.cc
+++ b/src/nix/add-to-store.cc
@@ -12,7 +12,7 @@ struct CmdAddToStore : MixDryRun, StoreCommand
 {
     Path path;
     std::optional<std::string> namePart;
-    ContentAddressMethod caMethod = FileIngestionMethod::Recursive;
+    ContentAddressMethod caMethod = ContentAddressMethod::Raw::NixArchive;
     HashAlgorithm hashAlgo = HashAlgorithm::SHA256;
 
     CmdAddToStore()
@@ -41,9 +41,9 @@ struct CmdAddToStore : MixDryRun, StoreCommand
 
         auto storePath = dryRun
             ? store->computeStorePath(
-                *namePart, accessor, path2, caMethod, hashAlgo, {}).first
+                *namePart, {accessor, path2}, caMethod, hashAlgo, {}).first
             : store->addToStoreSlow(
-                *namePart, accessor, path2, caMethod, hashAlgo, {}).path;
+                *namePart, {accessor, path2}, caMethod, hashAlgo, {}).path;
 
         logger->cout("%s", store->printStorePath(storePath));
     }
@@ -68,7 +68,7 @@ struct CmdAddFile : CmdAddToStore
 {
     CmdAddFile()
     {
-        caMethod = FileIngestionMethod::Flat;
+        caMethod = ContentAddressMethod::Raw::Flat;
     }
 
     std::string description() override
diff --git a/src/nix/build-remote b/src/nix/build-remote
new file mode 120000
index 00000000000..2cea44d46c2
--- /dev/null
+++ b/src/nix/build-remote
@@ -0,0 +1 @@
+../build-remote
\ No newline at end of file
diff --git a/src/nix/build-utils-meson b/src/nix/build-utils-meson
new file mode 120000
index 00000000000..91937f18372
--- /dev/null
+++ b/src/nix/build-utils-meson
@@ -0,0 +1 @@
+../../build-utils-meson/
\ No newline at end of file
diff --git a/src/nix/bundle.cc b/src/nix/bundle.cc
index 2e50392f7aa..554c3654022 100644
--- a/src/nix/bundle.cc
+++ b/src/nix/bundle.cc
@@ -100,6 +100,8 @@ struct CmdBundle : InstallableValueCommand
         NixStringContext context2;
         auto drvPath = evalState->coerceToStorePath(attr1->pos, *attr1->value, context2, "");
 
+        drvPath.requireDerivation();
+
         auto attr2 = vRes->attrs()->get(evalState->sOutPath);
         if (!attr2)
             throw Error("the bundler '%s' does not produce a derivation", bundler.what());
diff --git a/src/nix/config-check.cc b/src/nix/config-check.cc
index f7c4cebecc0..9575bf33887 100644
--- a/src/nix/config-check.cc
+++ b/src/nix/config-check.cc
@@ -101,13 +101,14 @@ struct CmdConfigCheck : StoreCommand
                 Path userEnv = canonPath(profileDir, true);
 
                 if (store->isStorePath(userEnv) && hasSuffix(userEnv, "user-environment")) {
-                    while (profileDir.find("/profiles/") == std::string::npos && isLink(profileDir))
+                    while (profileDir.find("/profiles/") == std::string::npos && std::filesystem::is_symlink(profileDir))
                         profileDir = absPath(readLink(profileDir), dirOf(profileDir));
 
                     if (profileDir.find("/profiles/") == std::string::npos)
                         dirs.insert(dir);
                 }
-            } catch (SystemError &) {}
+            } catch (SystemError &) {
+            } catch (std::filesystem::filesystem_error &) {}
         }
 
         if (!dirs.empty()) {
diff --git a/src/nix/config.cc b/src/nix/config.cc
index 52706afcf37..07f975a006a 100644
--- a/src/nix/config.cc
+++ b/src/nix/config.cc
@@ -2,6 +2,7 @@
 #include "common-args.hh"
 #include "shared.hh"
 #include "store-api.hh"
+#include "config-global.hh"
 
 #include <nlohmann/json.hpp>
 
diff --git a/src/nix/derivation-show.md b/src/nix/derivation-show.md
index 2437ea08f41..9fff58ef97a 100644
--- a/src/nix/derivation-show.md
+++ b/src/nix/derivation-show.md
@@ -50,7 +50,7 @@ By default, this command only shows top-level derivations, but with
 
 `nix derivation show` outputs a JSON map of [store path]s to derivations in the following format:
 
-[store path]: @docroot@/glossary.md#gloss-store-path
+[store path]: @docroot@/store/store-path.md
 
 {{#include ../../protocols/json/derivation.md}}
 
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 35d3da9120c..6bd3dc9efc6 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -1,3 +1,4 @@
+#include "config-global.hh"
 #include "eval.hh"
 #include "installable-flake.hh"
 #include "command-installable-value.hh"
@@ -14,6 +15,7 @@
 
 #include <iterator>
 #include <memory>
+#include <sstream>
 #include <nlohmann/json.hpp>
 #include <algorithm>
 
@@ -237,7 +239,7 @@ static StorePath getDerivationEnvironment(ref<Store> store, ref<Store> evalStore
     auto getEnvShPath = ({
         StringSource source { getEnvSh };
         evalStore->addToStoreFromDump(
-            source, "get-env.sh", FileSerialisationMethod::Flat, TextIngestionMethod {}, HashAlgorithm::SHA256, {});
+            source, "get-env.sh", FileSerialisationMethod::Flat, ContentAddressMethod::Raw::Text, HashAlgorithm::SHA256, {});
     });
 
     drv.args = {store->printStorePath(getEnvShPath)};
@@ -336,8 +338,8 @@ struct Common : InstallableCommand, MixProfile
     std::string makeRcScript(
         ref<Store> store,
         const BuildEnvironment & buildEnvironment,
-        const Path & tmpDir,
-        const Path & outputsDir = absPath(".") + "/outputs")
+        const std::filesystem::path & tmpDir,
+        const std::filesystem::path & outputsDir = std::filesystem::path { absPath(".") } / "outputs")
     {
         // A list of colon-separated environment variables that should be
         // prepended to, rather than overwritten, in order to keep the shell usable.
@@ -376,13 +378,19 @@ struct Common : InstallableCommand, MixProfile
         StringMap rewrites;
         if (buildEnvironment.providesStructuredAttrs()) {
             for (auto & [outputName, from] : BuildEnvironment::getAssociative(outputs->second)) {
-                rewrites.insert({from, outputsDir + "/" + outputName});
+                rewrites.insert({
+                    from,
+                    (outputsDir / outputName).string()
+                });
             }
         } else {
             for (auto & outputName : BuildEnvironment::getStrings(outputs->second)) {
                 auto from = buildEnvironment.vars.find(outputName);
                 assert(from != buildEnvironment.vars.end());
-                rewrites.insert({BuildEnvironment::getString(from->second), outputsDir + "/" + outputName});
+                rewrites.insert({
+                    BuildEnvironment::getString(from->second),
+                    (outputsDir / outputName).string(),
+                });
             }
         }
 
@@ -405,7 +413,7 @@ struct Common : InstallableCommand, MixProfile
 
         if (buildEnvironment.providesStructuredAttrs()) {
             fixupStructuredAttrs(
-                "sh",
+                PATHNG_LITERAL("sh"),
                 "NIX_ATTRS_SH_FILE",
                 buildEnvironment.getAttrsSH(),
                 rewrites,
@@ -413,7 +421,7 @@ struct Common : InstallableCommand, MixProfile
                 tmpDir
             );
             fixupStructuredAttrs(
-                "json",
+                PATHNG_LITERAL("json"),
                 "NIX_ATTRS_JSON_FILE",
                 buildEnvironment.getAttrsJSON(),
                 rewrites,
@@ -430,19 +438,21 @@ struct Common : InstallableCommand, MixProfile
      * that's accessible from the interactive shell session.
      */
     void fixupStructuredAttrs(
-        const std::string & ext,
+        PathViewNG::string_view ext,
         const std::string & envVar,
         const std::string & content,
         StringMap & rewrites,
         const BuildEnvironment & buildEnvironment,
-        const Path & tmpDir)
+        const std::filesystem::path & tmpDir)
     {
-        auto targetFilePath = tmpDir + "/.attrs." + ext;
-        writeFile(targetFilePath, content);
+        auto targetFilePath = tmpDir / PATHNG_LITERAL(".attrs.");
+        targetFilePath += ext;
+
+        writeFile(targetFilePath.string(), content);
 
         auto fileInBuilderEnv = buildEnvironment.vars.find(envVar);
         assert(fileInBuilderEnv != buildEnvironment.vars.end());
-        rewrites.insert({BuildEnvironment::getString(fileInBuilderEnv->second), targetFilePath});
+        rewrites.insert({BuildEnvironment::getString(fileInBuilderEnv->second), targetFilePath.string()});
     }
 
     Strings getDefaultFlakeAttrPaths() override
@@ -578,7 +588,7 @@ struct CmdDevelop : Common, MixEnvironment
 
         AutoDelete tmpDir(createTempDir("", "nix-develop"), true);
 
-        auto script = makeRcScript(store, buildEnvironment, (Path) tmpDir);
+        auto script = makeRcScript(store, buildEnvironment, tmpDir);
 
         if (verbosity >= lvlDebug)
             script += "set -x\n";
@@ -602,7 +612,7 @@ struct CmdDevelop : Common, MixEnvironment
         }
 
         else {
-            script = "[ -n \"$PS1\" ] && [ -e ~/.bashrc ] && source ~/.bashrc;\n" + script;
+            script = "[ -n \"$PS1\" ] && [ -e ~/.bashrc ] && source ~/.bashrc;\nshopt -u expand_aliases\n" + script + "\nshopt -s expand_aliases\n";
             if (developSettings.bashPrompt != "")
                 script += fmt("[ -n \"$PS1\" ] && PS1=%s;\n",
                     shellEscape(developSettings.bashPrompt.get()));
@@ -687,7 +697,7 @@ struct CmdDevelop : Common, MixEnvironment
             }
         }
 
-        runProgramInStore(store, UseSearchPath::Use, shell, args, buildEnvironment.getSystem());
+        runProgramInStore(store, UseLookupPath::Use, shell, args, buildEnvironment.getSystem());
 #endif
     }
 };
diff --git a/src/nix/doc b/src/nix/doc
new file mode 120000
index 00000000000..7e57b0f5825
--- /dev/null
+++ b/src/nix/doc
@@ -0,0 +1 @@
+../../doc
\ No newline at end of file
diff --git a/src/nix/env.cc b/src/nix/env.cc
new file mode 100644
index 00000000000..021c47cbbd0
--- /dev/null
+++ b/src/nix/env.cc
@@ -0,0 +1,106 @@
+#include "command.hh"
+#include "run.hh"
+#include <queue>
+
+using namespace nix;
+
+struct CmdEnv : NixMultiCommand
+{
+    CmdEnv()
+        : NixMultiCommand("env", RegisterCommand::getCommandsFor({"env"}))
+    {
+    }
+
+    std::string description() override
+    {
+        return "manipulate the process environment";
+    }
+
+    Category category() override
+    {
+        return catUtility;
+    }
+};
+
+static auto rCmdEnv = registerCommand<CmdEnv>("env");
+
+struct CmdShell : InstallablesCommand, MixEnvironment
+{
+
+    using InstallablesCommand::run;
+
+    std::vector<std::string> command = {getEnv("SHELL").value_or("bash")};
+
+    CmdShell()
+    {
+        addFlag(
+            {.longName = "command",
+             .shortName = 'c',
+             .description = "Command and arguments to be executed, defaulting to `$SHELL`",
+             .labels = {"command", "args"},
+             .handler = {[&](std::vector<std::string> ss) {
+                 if (ss.empty())
+                     throw UsageError("--command requires at least one argument");
+                 command = ss;
+             }}});
+    }
+
+    std::string description() override
+    {
+        return "run a shell in which the specified packages are available";
+    }
+
+    std::string doc() override
+    {
+        return
+#include "shell.md"
+            ;
+    }
+
+    void run(ref<Store> store, Installables && installables) override
+    {
+        auto outPaths =
+            Installable::toStorePaths(getEvalStore(), store, Realise::Outputs, OperateOn::Output, installables);
+
+        auto accessor = store->getFSAccessor();
+
+        std::unordered_set<StorePath> done;
+        std::queue<StorePath> todo;
+        for (auto & path : outPaths)
+            todo.push(path);
+
+        setEnviron();
+
+        std::vector<std::string> pathAdditions;
+
+        while (!todo.empty()) {
+            auto path = todo.front();
+            todo.pop();
+            if (!done.insert(path).second)
+                continue;
+
+            if (true)
+                pathAdditions.push_back(store->printStorePath(path) + "/bin");
+
+            auto propPath = accessor->resolveSymlinks(
+                CanonPath(store->printStorePath(path)) / "nix-support" / "propagated-user-env-packages");
+            if (auto st = accessor->maybeLstat(propPath); st && st->type == SourceAccessor::tRegular) {
+                for (auto & p : tokenizeString<Paths>(accessor->readFile(propPath)))
+                    todo.push(store->parseStorePath(p));
+            }
+        }
+
+        auto unixPath = tokenizeString<Strings>(getEnv("PATH").value_or(""), ":");
+        unixPath.insert(unixPath.begin(), pathAdditions.begin(), pathAdditions.end());
+        auto unixPathString = concatStringsSep(":", unixPath);
+        setEnv("PATH", unixPathString.c_str());
+
+        Strings args;
+        for (auto & arg : command)
+            args.push_back(arg);
+
+        runProgramInStore(store, UseLookupPath::Use, *command.begin(), args);
+    }
+};
+
+static auto rCmdShell = registerCommand2<CmdShell>({"env", "shell"});
diff --git a/src/nix/flake-metadata.md b/src/nix/flake-metadata.md
index 5a009409b5c..adfd3dc96bb 100644
--- a/src/nix/flake-metadata.md
+++ b/src/nix/flake-metadata.md
@@ -2,10 +2,10 @@ R""(
 
 # Examples
 
-* Show what `nixpkgs` resolves to:
+* Show what `dwarffs` resolves to:
 
   ```console
-  # nix flake metadata nixpkgs
+  # nix flake metadata dwarffs
   Resolved URL:  github:edolstra/dwarffs
   Locked URL:    github:edolstra/dwarffs/f691e2c991e75edb22836f1dbe632c40324215c5
   Description:   A filesystem that fetches DWARF debug info from the Internet on demand
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 4825ab0e132..84c659023a5 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -7,6 +7,7 @@
 #include "eval-settings.hh"
 #include "flake/flake.hh"
 #include "get-drvs.hh"
+#include "signals.hh"
 #include "store-api.hh"
 #include "derivations.hh"
 #include "outputs-spec.hh"
@@ -232,6 +233,8 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
                 j["lastModified"] = *lastModified;
             j["path"] = storePath;
             j["locks"] = lockedFlake.lockFile.toJSON().first;
+            if (auto fingerprint = lockedFlake.getFingerprint(store))
+                j["fingerprint"] = fingerprint->to_string(HashFormat::Base16, false);
             logger->cout("%s", j.dump());
         } else {
             logger->cout(
@@ -264,6 +267,10 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
                 logger->cout(
                     ANSI_BOLD "Last modified:" ANSI_NORMAL " %s",
                     std::put_time(std::localtime(&*lastModified), "%F %T"));
+            if (auto fingerprint = lockedFlake.getFingerprint(store))
+                logger->cout(
+                    ANSI_BOLD "Fingerprint:" ANSI_NORMAL "   %s",
+                    fingerprint->to_string(HashFormat::Base16, false));
 
             if (!lockedFlake.lockFile.root->inputs.empty())
                 logger->cout(ANSI_BOLD "Inputs:" ANSI_NORMAL);
@@ -454,11 +461,6 @@ struct CmdFlakeCheck : FlakeCommand
                 if (v.payload.lambda.fun->hasFormals()
                     || !argHasName(v.payload.lambda.fun->arg, "final"))
                     throw Error("overlay does not take an argument named 'final'");
-                auto body = dynamic_cast<ExprLambda *>(v.payload.lambda.fun->body);
-                if (!body
-                    || body->hasFormals()
-                    || !argHasName(body->arg, "prev"))
-                    throw Error("overlay does not take an argument named 'prev'");
                 // FIXME: if we have a 'nixpkgs' input, use it to
                 // evaluate the overlay.
             } catch (Error & e) {
@@ -775,6 +777,8 @@ struct CmdFlakeCheck : FlakeCommand
                             || name == "flakeModules"
                             || name == "herculesCI"
                             || name == "homeConfigurations"
+                            || name == "homeModule"
+                            || name == "homeModules"
                             || name == "nixopsConfigurations"
                             )
                             // Known but unchecked community attribute
@@ -871,9 +875,10 @@ struct CmdFlakeInitCommon : virtual Args, EvalCommand
         {
             createDirs(to);
 
-            for (auto & entry : readDirectory(from)) {
-                auto from2 = from + "/" + entry.name;
-                auto to2 = to + "/" + entry.name;
+            for (auto & entry : std::filesystem::directory_iterator{from}) {
+                checkInterrupt();
+                auto from2 = entry.path().string();
+                auto to2 = to + "/" + entry.path().filename().string();
                 auto st = lstat(from2);
                 if (S_ISDIR(st.st_mode))
                     copyDir(from2, to2);
@@ -1181,7 +1186,7 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                 // If we don't recognize it, it's probably content
                 return true;
             } catch (EvalError & e) {
-                // Some attrs may contain errors, eg. legacyPackages of
+                // Some attrs may contain errors, e.g. legacyPackages of
                 // nixpkgs. We still want to recurse into it, instead of
                 // skipping it at all.
                 return true;
diff --git a/src/nix/flake.md b/src/nix/flake.md
index d8b5bf435f1..2f43d02640d 100644
--- a/src/nix/flake.md
+++ b/src/nix/flake.md
@@ -134,7 +134,9 @@ The following generic flake reference attributes are supported:
   repository or tarball. The default is the root directory of the
   flake.
 
-* `narHash`: The hash of the NAR serialisation (in SRI format) of the
+* `narHash`: The hash of the
+  [Nix Archive (NAR) serialisation][Nix Archive]
+  (in SRI format) of the
   contents of the flake. This is useful for flake types such as
   tarballs that lack a unique content identifier such as a Git commit
   hash.
@@ -423,8 +425,9 @@ The following attributes are supported in `flake.nix`:
   * `lastModified`: The commit time of the revision `rev` as an integer
     denoting the number of seconds since 1970.
 
-  * `narHash`: The SHA-256 (in SRI format) of the NAR serialization of
-    the flake's source tree.
+  * `narHash`: The SHA-256 (in SRI format) of the
+    [Nix Archive (NAR) serialisation][Nix Archive]
+    NAR serialization of the flake's source tree.
 
   The value returned by the `outputs` function must be an attribute
   set. The attributes can have arbitrary values; however, various
@@ -439,7 +442,7 @@ The following attributes are supported in `flake.nix`:
    - [`bash-prompt-prefix`](@docroot@/command-ref/conf-file.md#conf-bash-prompt-prefix)
    - [`bash-prompt-suffix`](@docroot@/command-ref/conf-file.md#conf-bash-prompt-suffix)
    - [`flake-registry`](@docroot@/command-ref/conf-file.md#conf-flake-registry)
-   - [`commit-lockfile-summary`](@docroot@/command-ref/conf-file.md#conf-commit-lockfile-summary)
+   - [`commit-lock-file-summary`](@docroot@/command-ref/conf-file.md#conf-commit-lock-file-summary)
 
 ## Flake inputs
 
@@ -703,4 +706,5 @@ will not look at the lock files of dependencies. However, lock file
 generation itself *does* use the lock files of dependencies by
 default.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 )""
diff --git a/src/nix/unix/fmt.cc b/src/nix/fmt.cc
similarity index 95%
rename from src/nix/unix/fmt.cc
rename to src/nix/fmt.cc
index 059904150f3..4b0fbb89dfb 100644
--- a/src/nix/unix/fmt.cc
+++ b/src/nix/fmt.cc
@@ -49,7 +49,7 @@ struct CmdFmt : SourceExprCommand {
             }
         }
 
-        runProgramInStore(store, UseSearchPath::DontUse, app.program, programArgs);
+        runProgramInStore(store, UseLookupPath::DontUse, app.program, programArgs);
     };
 };
 
diff --git a/src/nix/unix/fmt.md b/src/nix/fmt.md
similarity index 100%
rename from src/nix/unix/fmt.md
rename to src/nix/fmt.md
diff --git a/src/nix/hash.cc b/src/nix/hash.cc
index f849bf0cfae..62266fda15a 100644
--- a/src/nix/hash.cc
+++ b/src/nix/hash.cc
@@ -68,7 +68,7 @@ struct CmdHashBase : Command
         switch (mode) {
         case FileIngestionMethod::Flat:
             return "print cryptographic hash of a regular file";
-        case FileIngestionMethod::Recursive:
+        case FileIngestionMethod::NixArchive:
             return "print cryptographic hash of the NAR serialisation of a path";
         case FileIngestionMethod::Git:
             return "print cryptographic hash of the Git serialisation of a path";
@@ -87,30 +87,29 @@ struct CmdHashBase : Command
                     return std::make_unique<HashSink>(hashAlgo);
             };
 
-            auto [accessor_, canonPath] = PosixSourceAccessor::createAtRoot(path);
-            auto & accessor = accessor_;
+            auto path2 = PosixSourceAccessor::createAtRoot(path);
             Hash h { HashAlgorithm::SHA256 }; // throwaway def to appease C++
             switch (mode) {
             case FileIngestionMethod::Flat:
-            case FileIngestionMethod::Recursive:
+            case FileIngestionMethod::NixArchive:
             {
                 auto hashSink = makeSink();
-                dumpPath(accessor, canonPath, *hashSink, (FileSerialisationMethod) mode);
+                dumpPath(path2, *hashSink, (FileSerialisationMethod) mode);
                 h = hashSink->finish().first;
                 break;
             }
             case FileIngestionMethod::Git: {
                 std::function<git::DumpHook> hook;
-                hook = [&](const CanonPath & path) -> git::TreeEntry {
+                hook = [&](const SourcePath & path) -> git::TreeEntry {
                     auto hashSink = makeSink();
-                    auto mode = dump(accessor, path, *hashSink, hook);
+                    auto mode = dump(path, *hashSink, hook);
                     auto hash = hashSink->finish().first;
                     return {
                         .mode = mode,
                         .hash = hash,
                     };
                 };
-                h = hook(canonPath).hash;
+                h = hook(path2).hash;
                 break;
             }
             }
@@ -127,7 +126,7 @@ struct CmdHashBase : Command
 struct CmdHashPath : CmdHashBase
 {
     CmdHashPath()
-        : CmdHashBase(FileIngestionMethod::Recursive)
+        : CmdHashBase(FileIngestionMethod::NixArchive)
     {
         addFlag(flag::hashAlgo("algo", &hashAlgo));
         addFlag(flag::fileIngestionMethod(&mode));
@@ -182,7 +181,7 @@ struct CmdToBase : Command
 
     void run() override
     {
-        warn("The old format conversion sub commands of `nix hash` where deprecated in favor of `nix hash convert`.");
+        warn("The old format conversion sub commands of `nix hash` were deprecated in favor of `nix hash convert`.");
         for (auto s : args)
             logger->cout(Hash::parseAny(s, hashAlgo).to_string(hashFormat, hashFormat == HashFormat::SRI));
     }
@@ -312,7 +311,7 @@ static int compatNixHash(int argc, char * * argv)
     });
 
     if (op == opHash) {
-        CmdHashBase cmd(flat ? FileIngestionMethod::Flat : FileIngestionMethod::Recursive);
+        CmdHashBase cmd(flat ? FileIngestionMethod::Flat : FileIngestionMethod::NixArchive);
         if (!hashAlgo.has_value()) hashAlgo = HashAlgorithm::MD5;
         cmd.hashAlgo = hashAlgo.value();
         cmd.hashFormat = hashFormat;
diff --git a/src/nix/help-stores.md b/src/nix/help-stores.md
new file mode 120000
index 00000000000..5c5624f5ecf
--- /dev/null
+++ b/src/nix/help-stores.md
@@ -0,0 +1 @@
+../../doc/manual/src/store/types/index.md.in
\ No newline at end of file
diff --git a/src/nix/local.mk b/src/nix/local.mk
index 305b0e9dfff..28b30b58619 100644
--- a/src/nix/local.mk
+++ b/src/nix/local.mk
@@ -24,12 +24,17 @@ ifdef HOST_UNIX
   INCLUDE_nix += -I $(d)/unix
 endif
 
-nix_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) $(INCLUDE_libmain) -I src/libcmd -I doc/manual $(INCLUDE_nix)
+nix_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) $(INCLUDE_libflake) $(INCLUDE_libmain) -I src/libcmd -I doc/manual $(INCLUDE_nix)
 
-nix_LIBS = libexpr libmain libfetchers libstore libutil libcmd
+nix_LIBS = libexpr libmain libfetchers libflake libstore libutil libcmd
 
 nix_LDFLAGS = $(THREAD_LDFLAGS) $(SODIUM_LIBS) $(EDITLINE_LIBS) $(BOOST_LDFLAGS) $(LOWDOWN_LIBS)
 
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  nix_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif
+
 $(foreach name, \
   nix-build nix-channel nix-collect-garbage nix-copy-closure nix-daemon nix-env nix-hash nix-instantiate nix-prefetch-url nix-shell nix-store, \
   $(eval $(call install-symlink, nix, $(bindir)/$(name))))
@@ -37,27 +42,16 @@ $(eval $(call install-symlink, $(bindir)/nix, $(libexecdir)/nix/build-remote))
 
 src/nix-env/user-env.cc: src/nix-env/buildenv.nix.gen.hh
 
-src/nix/develop.cc: src/nix/get-env.sh.gen.hh
+$(d)/develop.cc: $(d)/get-env.sh.gen.hh
 
 src/nix-channel/nix-channel.cc: src/nix-channel/unpack-channel.nix.gen.hh
 
-src/nix/main.cc: \
+$(d)/main.cc: \
   doc/manual/generate-manpage.nix.gen.hh \
   doc/manual/utils.nix.gen.hh doc/manual/generate-settings.nix.gen.hh \
   doc/manual/generate-store-info.nix.gen.hh \
-  src/nix/generated-doc/help-stores.md
-
-src/nix/generated-doc/files/%.md: doc/manual/src/command-ref/files/%.md
-	@mkdir -p $$(dirname $@)
-	@cp $< $@
-
-src/nix/profile.cc: src/nix/profile.md src/nix/generated-doc/files/profiles.md.gen.hh
-
-src/nix/generated-doc/help-stores.md: doc/manual/src/store/types/index.md.in
-	@mkdir -p $$(dirname $@)
-	@echo 'R"(' >> $@.tmp
-	@echo >> $@.tmp
-	@cat $^ >> $@.tmp
-	@echo >> $@.tmp
-	@echo ')"' >> $@.tmp
-	@mv $@.tmp $@
+  $(d)/help-stores.md.gen.hh
+
+$(d)/profile.cc: $(d)/profile.md
+
+$(d)/profile.md: $(d)/profiles.md.gen.hh
diff --git a/src/nix/main.cc b/src/nix/main.cc
index c3915af50f5..d6a8e4e31c5 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -14,9 +14,11 @@
 #include "finally.hh"
 #include "loggers.hh"
 #include "markdown.hh"
-#include "memory-input-accessor.hh"
+#include "memory-source-accessor.hh"
 #include "terminal.hh"
 #include "users.hh"
+#include "network-proxy.hh"
+#include "eval-cache.hh"
 #include "auth.hh"
 
 #include <sys/types.h>
@@ -42,26 +44,18 @@ void chrootHelper(int argc, char * * argv);
 
 namespace nix {
 
-#ifdef _WIN32
-[[maybe_unused]]
-#endif
-static bool haveProxyEnvironmentVariables()
-{
-    static const std::vector<std::string> proxyVariables = {
-        "http_proxy",
-        "https_proxy",
-        "ftp_proxy",
-        "HTTP_PROXY",
-        "HTTPS_PROXY",
-        "FTP_PROXY"
-    };
-    for (auto & proxyVariable: proxyVariables) {
-        if (getEnv(proxyVariable).has_value()) {
-            return true;
-        }
-    }
-    return false;
-}
+enum struct AliasStatus {
+    /** Aliases that don't go away */
+    AcceptedShorthand,
+    /** Aliases that will go away */
+    Deprecated,
+};
+
+/** An alias, except for the original syntax, which is in the map key. */
+struct AliasInfo {
+    AliasStatus status;
+    std::vector<std::string> replacement;
+};
 
 /* Check if we have a non-loopback/link-local network interface. */
 static bool haveInternet()
@@ -87,7 +81,7 @@ static bool haveInternet()
         }
     }
 
-    if (haveProxyEnvironmentVariables()) return true;
+    if (haveNetworkProxyConnection()) return true;
 
     return false;
 #else
@@ -155,29 +149,30 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
         });
     }
 
-    std::map<std::string, std::vector<std::string>> aliases = {
-        {"add-to-store", {"store", "add-path"}},
-        {"cat-nar", {"nar", "cat"}},
-        {"cat-store", {"store", "cat"}},
-        {"copy-sigs", {"store", "copy-sigs"}},
-        {"dev-shell", {"develop"}},
-        {"diff-closures", {"store", "diff-closures"}},
-        {"dump-path", {"store", "dump-path"}},
-        {"hash-file", {"hash", "file"}},
-        {"hash-path", {"hash", "path"}},
-        {"ls-nar", {"nar", "ls"}},
-        {"ls-store", {"store", "ls"}},
-        {"make-content-addressable", {"store", "make-content-addressed"}},
-        {"optimise-store", {"store", "optimise"}},
-        {"ping-store", {"store", "ping"}},
-        {"sign-paths", {"store", "sign"}},
-        {"show-derivation", {"derivation", "show"}},
-        {"show-config", {"config", "show"}},
-        {"to-base16", {"hash", "to-base16"}},
-        {"to-base32", {"hash", "to-base32"}},
-        {"to-base64", {"hash", "to-base64"}},
-        {"verify", {"store", "verify"}},
-        {"doctor", {"config", "check"}},
+    std::map<std::string, AliasInfo> aliases = {
+        {"add-to-store", { AliasStatus::Deprecated, {"store", "add-path"}}},
+        {"cat-nar", { AliasStatus::Deprecated, {"nar", "cat"}}},
+        {"cat-store", { AliasStatus::Deprecated, {"store", "cat"}}},
+        {"copy-sigs", { AliasStatus::Deprecated, {"store", "copy-sigs"}}},
+        {"dev-shell", { AliasStatus::Deprecated, {"develop"}}},
+        {"diff-closures", { AliasStatus::Deprecated, {"store", "diff-closures"}}},
+        {"dump-path", { AliasStatus::Deprecated, {"store", "dump-path"}}},
+        {"hash-file", { AliasStatus::Deprecated, {"hash", "file"}}},
+        {"hash-path", { AliasStatus::Deprecated, {"hash", "path"}}},
+        {"ls-nar", { AliasStatus::Deprecated, {"nar", "ls"}}},
+        {"ls-store", { AliasStatus::Deprecated, {"store", "ls"}}},
+        {"make-content-addressable", { AliasStatus::Deprecated, {"store", "make-content-addressed"}}},
+        {"optimise-store", { AliasStatus::Deprecated, {"store", "optimise"}}},
+        {"ping-store", { AliasStatus::Deprecated, {"store", "ping"}}},
+        {"sign-paths", { AliasStatus::Deprecated, {"store", "sign"}}},
+        {"shell", { AliasStatus::AcceptedShorthand, {"env", "shell"}}},
+        {"show-derivation", { AliasStatus::Deprecated, {"derivation", "show"}}},
+        {"show-config", { AliasStatus::Deprecated, {"config", "show"}}},
+        {"to-base16", { AliasStatus::Deprecated, {"hash", "to-base16"}}},
+        {"to-base32", { AliasStatus::Deprecated, {"hash", "to-base32"}}},
+        {"to-base64", { AliasStatus::Deprecated, {"hash", "to-base64"}}},
+        {"verify", { AliasStatus::Deprecated, {"store", "verify"}}},
+        {"doctor", { AliasStatus::Deprecated, {"config", "check"}}},
     };
 
     bool aliasUsed = false;
@@ -188,10 +183,13 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
         auto arg = *pos;
         auto i = aliases.find(arg);
         if (i == aliases.end()) return pos;
-        warn("'%s' is a deprecated alias for '%s'",
-            arg, concatStringsSep(" ", i->second));
+        auto & info = i->second;
+        if (info.status == AliasStatus::Deprecated) {
+            warn("'%s' is a deprecated alias for '%s'",
+                arg, concatStringsSep(" ", info.replacement));
+        }
         pos = args.erase(pos);
-        for (auto j = i->second.rbegin(); j != i->second.rend(); ++j)
+        for (auto j = info.replacement.rbegin(); j != info.replacement.rend(); ++j)
             pos = args.insert(pos, *j);
         aliasUsed = true;
         return pos;
@@ -245,7 +243,7 @@ static void showHelp(std::vector<std::string> subcommand, NixArgs & toplevel)
 
     evalSettings.restrictEval = false;
     evalSettings.pureEval = false;
-    EvalState state({}, openStore("dummy://"));
+    EvalState state({}, openStore("dummy://"), evalSettings);
 
     auto vGenerateManpage = state.allocValue();
     state.eval(state.parseExprFromString(
@@ -336,7 +334,7 @@ struct CmdHelpStores : Command
     std::string doc() override
     {
         return
-          #include "generated-doc/help-stores.md"
+          #include "help-stores.md.gen.hh"
           ;
     }
 
@@ -425,36 +423,29 @@ void mainWrapped(int argc, char * * argv)
             Xp::FetchTree,
         };
         evalSettings.pureEval = false;
-        EvalState state({}, openStore("dummy://"));
-        auto res = nlohmann::json::object();
-        res["builtins"] = ({
-            auto builtinsJson = nlohmann::json::object();
-            for (auto & builtin : *state.baseEnv.values[0]->attrs()) {
-                auto b = nlohmann::json::object();
-                if (!builtin.value->isPrimOp()) continue;
-                auto primOp = builtin.value->primOp();
-                if (!primOp->doc) continue;
-                b["arity"] = primOp->arity;
-                b["args"] = primOp->args;
-                b["doc"] = trim(stripIndentation(primOp->doc));
+        EvalState state({}, openStore("dummy://"), evalSettings);
+        auto builtinsJson = nlohmann::json::object();
+        for (auto & builtin : *state.baseEnv.values[0]->attrs()) {
+            auto b = nlohmann::json::object();
+            if (!builtin.value->isPrimOp()) continue;
+            auto primOp = builtin.value->primOp();
+            if (!primOp->doc) continue;
+            b["args"] = primOp->args;
+            b["doc"] = trim(stripIndentation(primOp->doc));
+            if (primOp->experimentalFeature)
                 b["experimental-feature"] = primOp->experimentalFeature;
-                builtinsJson[state.symbols[builtin.name]] = std::move(b);
-            }
-            std::move(builtinsJson);
-        });
-        res["constants"] = ({
-            auto constantsJson = nlohmann::json::object();
-            for (auto & [name, info] : state.constantInfos) {
-                auto c = nlohmann::json::object();
-                if (!info.doc) continue;
-                c["doc"] = trim(stripIndentation(info.doc));
-                c["type"] = showType(info.type, false);
-                c["impure-only"] = info.impureOnly;
-                constantsJson[name] = std::move(c);
-            }
-            std::move(constantsJson);
-        });
-        logger->cout("%s", res);
+            builtinsJson[state.symbols[builtin.name]] = std::move(b);
+        }
+        for (auto & [name, info] : state.constantInfos) {
+            auto b = nlohmann::json::object();
+            if (!info.doc) continue;
+            b["doc"] = trim(stripIndentation(info.doc));
+            b["type"] = showType(info.type, false);
+            if (info.impureOnly)
+                b["impure-only"] = true;
+            builtinsJson[name] = std::move(b);
+        }
+        logger->cout("%s", builtinsJson);
         return;
     }
 
@@ -540,18 +531,24 @@ void mainWrapped(int argc, char * * argv)
     if (args.command->second->forceImpureByDefault() && !evalSettings.pureEval.overridden) {
         evalSettings.pureEval = false;
     }
-    args.command->second->run();
+
+    try {
+        args.command->second->run();
+    } catch (eval_cache::CachedEvalError & e) {
+        /* Evaluate the original attribute that resulted in this
+           cached error so that we can show the original error to the
+           user. */
+        e.force();
+    }
 }
 
 }
 
 int main(int argc, char * * argv)
 {
-#ifndef _WIN32 // TODO implement on Windows
     // Increase the default stack size for the evaluator and for
     // libstdc++'s std::regex.
     nix::setStackSize(64 * 1024 * 1024);
-#endif
 
     return nix::handleExceptions(argv[0], [&]() {
         nix::mainWrapped(argc, argv);
diff --git a/src/nix/meson.build b/src/nix/meson.build
new file mode 100644
index 00000000000..dd21c4b1bca
--- /dev/null
+++ b/src/nix/meson.build
@@ -0,0 +1,170 @@
+project('nix', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+  dependency('nix-expr'),
+  dependency('nix-fetchers'),
+  dependency('nix-main'),
+  dependency('nix-cmd'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/export-all-symbols')
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-expr.hh',
+  #'-include', 'config-fetchers.hh',
+  '-include', 'config-main.hh',
+  '-include', 'config-cmd.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+subdir('build-utils-meson/generate-header')
+
+nix_sources = files(
+  'add-to-store.cc',
+  'app.cc',
+  'build.cc',
+  'bundle.cc',
+  'cat.cc',
+  'config-check.cc',
+  'config.cc',
+  'copy.cc',
+  'derivation-add.cc',
+  'derivation-show.cc',
+  'derivation.cc',
+  'develop.cc',
+  'diff-closures.cc',
+  'dump-path.cc',
+  'edit.cc',
+  'env.cc',
+  'eval.cc',
+  'flake.cc',
+  'fmt.cc',
+  'hash.cc',
+  'log.cc',
+  'ls.cc',
+  'main.cc',
+  'make-content-addressed.cc',
+  'nar.cc',
+  'optimise-store.cc',
+  'path-from-hash-part.cc',
+  'path-info.cc',
+  'prefetch.cc',
+  'profile.cc',
+  'realisation.cc',
+  'registry.cc',
+  'repl.cc',
+  'run.cc',
+  'search.cc',
+  'sigs.cc',
+  'store-copy-log.cc',
+  'store-delete.cc',
+  'store-gc.cc',
+  'store-info.cc',
+  'store-repair.cc',
+  'store.cc',
+  'unix/daemon.cc',
+  'upgrade-nix.cc',
+  'verify.cc',
+  'why-depends.cc',
+)
+
+nix_sources += [
+  gen_header.process('doc/manual/generate-manpage.nix'),
+  gen_header.process('doc/manual/generate-settings.nix'),
+  gen_header.process('doc/manual/generate-store-info.nix'),
+  gen_header.process('doc/manual/utils.nix'),
+  gen_header.process('get-env.sh'),
+  gen_header.process('profiles.md'),
+  gen_header.process('help-stores.md'),
+]
+
+if host_machine.system() != 'windows'
+  nix_sources += files(
+    'unix/daemon.cc',
+  )
+endif
+
+# The rest of the subdirectories aren't separate components,
+# just source files in another directory, so we process them here.
+
+build_remote_sources = files(
+  'build-remote/build-remote.cc',
+)
+nix_build_sources = files(
+  'nix-build/nix-build.cc',
+)
+nix_channel_sources = files(
+  'nix-channel/nix-channel.cc',
+)
+unpack_channel_gen = gen_header.process('nix-channel/unpack-channel.nix')
+nix_collect_garbage_sources = files(
+  'nix-collect-garbage/nix-collect-garbage.cc',
+)
+nix_copy_closure_sources = files(
+  'nix-copy-closure/nix-copy-closure.cc',
+)
+nix_env_buildenv_gen = gen_header.process('nix-env/buildenv.nix')
+nix_env_sources = files(
+  'nix-env/nix-env.cc',
+  'nix-env/user-env.cc',
+)
+nix_instantiate_sources = files(
+  'nix-instantiate/nix-instantiate.cc',
+)
+nix_store_sources = files(
+  'nix-store/dotgraph.cc',
+  'nix-store/graphml.cc',
+  'nix-store/nix-store.cc',
+)
+
+# Hurray for Meson list flattening!
+sources = [
+  nix_sources,
+  build_remote_sources,
+  nix_build_sources,
+  nix_channel_sources,
+  unpack_channel_gen,
+  nix_collect_garbage_sources,
+  nix_copy_closure_sources,
+  nix_env_buildenv_gen,
+  nix_env_sources,
+  nix_instantiate_sources,
+  nix_store_sources,
+]
+
+include_dirs = [include_directories('.')]
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  install : true,
+)
diff --git a/src/nix/nar-cat.md b/src/nix/nar-cat.md
index 55c481a28c5..1131eb2bf13 100644
--- a/src/nix/nar-cat.md
+++ b/src/nix/nar-cat.md
@@ -2,7 +2,7 @@ R""(
 
 # Examples
 
-* List a file in a NAR and pipe it through `gunzip`:
+* List a file in a [Nix Archive (NAR)][Nix Archive] and pipe it through `gunzip`:
 
   ```console
   # nix nar cat ./hello.nar /share/man/man1/hello.1.gz | gunzip
@@ -16,4 +16,5 @@ R""(
 This command prints on standard output the contents of the regular
 file *path* inside the NAR file *nar*.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 )""
diff --git a/src/nix/nar-dump-path.md b/src/nix/nar-dump-path.md
index de82202decd..4676e4fef9d 100644
--- a/src/nix/nar-dump-path.md
+++ b/src/nix/nar-dump-path.md
@@ -2,7 +2,7 @@ R""(
 
 # Examples
 
-* To serialise directory `foo` as a NAR:
+* To serialise directory `foo` as a [Nix Archive (NAR)][Nix Archive]:
 
   ```console
   # nix nar pack ./foo > foo.nar
@@ -10,8 +10,10 @@ R""(
 
 # Description
 
-This command generates a NAR file containing the serialisation of
+This command generates a [Nix Archive (NAR)][Nix Archive] file containing the serialisation of
 *path*, which must contain only regular files, directories and
 symbolic links. The NAR is written to standard output.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+
 )""
diff --git a/src/nix/nar-ls.md b/src/nix/nar-ls.md
index 5a03c5d828e..27c4b97e62a 100644
--- a/src/nix/nar-ls.md
+++ b/src/nix/nar-ls.md
@@ -2,7 +2,7 @@ R""(
 
 # Examples
 
-* To list a specific file in a NAR:
+* To list a specific file in a [NAR][Nix Archive]:
 
   ```console
   # nix nar ls --long ./hello.nar /bin/hello
@@ -19,6 +19,8 @@ R""(
 
 # Description
 
-This command shows information about a *path* inside NAR file *nar*.
+This command shows information about a *path* inside [Nix Archive (NAR)][Nix Archive] file *nar*.
+
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 
 )""
diff --git a/src/nix/nar.md b/src/nix/nar.md
index a83b5c7647d..b0f70ce93a3 100644
--- a/src/nix/nar.md
+++ b/src/nix/nar.md
@@ -3,11 +3,14 @@ R""(
 # Description
 
 `nix nar` provides several subcommands for creating and inspecting
-*Nix Archives* (NARs).
+[*Nix Archives* (NARs)][Nix Archive].
 
 # File format
 
-For the definition of the NAR file format, see Figure 5.2 in
-https://edolstra.github.io/pubs/phd-thesis.pdf.
+For the definition of the Nix Archive file format, see
+[within the protocols chapter](@docroot@/protocols/nix-archive.md)
+of the manual.
+
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
 
 )""
diff --git a/src/nix/nix-build b/src/nix/nix-build
new file mode 120000
index 00000000000..2954d8ac7a9
--- /dev/null
+++ b/src/nix/nix-build
@@ -0,0 +1 @@
+../nix-build
\ No newline at end of file
diff --git a/src/nix/nix-channel b/src/nix/nix-channel
new file mode 120000
index 00000000000..29b75947369
--- /dev/null
+++ b/src/nix/nix-channel
@@ -0,0 +1 @@
+../nix-channel
\ No newline at end of file
diff --git a/src/nix/nix-collect-garbage b/src/nix/nix-collect-garbage
new file mode 120000
index 00000000000..b037fc1b03f
--- /dev/null
+++ b/src/nix/nix-collect-garbage
@@ -0,0 +1 @@
+../nix-collect-garbage
\ No newline at end of file
diff --git a/src/nix/nix-copy-closure b/src/nix/nix-copy-closure
new file mode 120000
index 00000000000..9063c583ad6
--- /dev/null
+++ b/src/nix/nix-copy-closure
@@ -0,0 +1 @@
+../nix-copy-closure
\ No newline at end of file
diff --git a/src/nix/nix-env b/src/nix/nix-env
new file mode 120000
index 00000000000..f2f19f58091
--- /dev/null
+++ b/src/nix/nix-env
@@ -0,0 +1 @@
+../nix-env
\ No newline at end of file
diff --git a/src/nix/nix-instantiate b/src/nix/nix-instantiate
new file mode 120000
index 00000000000..2d7502ffa2e
--- /dev/null
+++ b/src/nix/nix-instantiate
@@ -0,0 +1 @@
+../nix-instantiate
\ No newline at end of file
diff --git a/src/nix/nix-store b/src/nix/nix-store
new file mode 120000
index 00000000000..e6efcac42c3
--- /dev/null
+++ b/src/nix/nix-store
@@ -0,0 +1 @@
+../nix-store/
\ No newline at end of file
diff --git a/src/nix/package.nix b/src/nix/package.nix
new file mode 100644
index 00000000000..fe83c6969d3
--- /dev/null
+++ b/src/nix/package.nix
@@ -0,0 +1,129 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-store
+, nix-expr
+, nix-main
+, nix-cmd
+
+, rapidcheck
+, gtest
+, runCommand
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions ([
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+
+    # Symbolic links to other dirs
+    ./build-remote
+    ./doc
+    ./nix-build
+    ./nix-channel
+    ./nix-collect-garbage
+    ./nix-copy-closure
+    ./nix-env
+    ./nix-instantiate
+    ./nix-store
+
+    # Doc nix files for --help
+    ../../doc/manual/generate-manpage.nix
+    ../../doc/manual/utils.nix
+    ../../doc/manual/generate-settings.nix
+    ../../doc/manual/generate-store-info.nix
+
+    # Other files to be included as string literals
+    ../nix-channel/unpack-channel.nix
+    ../nix-env/buildenv.nix
+    ./get-env.sh
+    ./help-stores.md
+    ../../doc/manual/src/store/types/index.md.in
+    ./profiles.md
+    ../../doc/manual/src/command-ref/files/profiles.md
+
+    # Files
+  ] ++ lib.concatMap
+    (dir: [
+      (fileset.fileFilter (file: file.hasExt "cc") dir)
+      (fileset.fileFilter (file: file.hasExt "hh") dir)
+      (fileset.fileFilter (file: file.hasExt "md") dir)
+    ])
+    [
+      ./.
+      ../build-remote
+      ../nix-build
+      ../nix-channel
+      ../nix-collect-garbage
+      ../nix-copy-closure
+      ../nix-env
+      ../nix-instantiate
+      ../nix-store
+    ]
+  );
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    nix-store
+    nix-expr
+    nix-main
+    nix-cmd
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/src/nix/path-info.cc b/src/nix/path-info.cc
index 921b25d7fd2..47f9baee505 100644
--- a/src/nix/path-info.cc
+++ b/src/nix/path-info.cc
@@ -139,21 +139,10 @@ struct CmdPathInfo : StorePathsCommand, MixJSON
 
     void printSize(uint64_t value)
     {
-        if (!humanReadable) {
+        if (humanReadable)
+            std::cout << fmt("\t%s", renderSize(value, true));
+        else
             std::cout << fmt("\t%11d", value);
-            return;
-        }
-
-        static const std::array<char, 9> idents{{
-            ' ', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'
-        }};
-        size_t power = 0;
-        double res = value;
-        while (res > 1024 && power < idents.size()) {
-            ++power;
-            res /= 1024;
-        }
-        std::cout << fmt("\t%6.1f%c", res, idents.at(power));
     }
 
     void run(ref<Store> store, StorePaths && storePaths) override
diff --git a/src/nix/path-info.md b/src/nix/path-info.md
index 789984559d5..2e39225b865 100644
--- a/src/nix/path-info.md
+++ b/src/nix/path-info.md
@@ -26,8 +26,8 @@ R""(
 
   ```console
   # nix path-info --recursive --size --closure-size --human-readable nixpkgs#rustc
-  /nix/store/01rrgsg5zk3cds0xgdsq40zpk6g51dz9-ncurses-6.2-dev      386.7K   69.1M
-  /nix/store/0q783wnvixpqz6dxjp16nw296avgczam-libpfm-4.11.0          5.9M   37.4M
+  /nix/store/01rrgsg5zk3cds0xgdsq40zpk6g51dz9-ncurses-6.2-dev      386.7 KiB   69.1 MiB
+  /nix/store/0q783wnvixpqz6dxjp16nw296avgczam-libpfm-4.11.0          5.9 MiB   37.4 MiB
   …
   ```
 
diff --git a/src/nix/prefetch.cc b/src/nix/prefetch.cc
index 8e6a2e805cd..c6e60a53be6 100644
--- a/src/nix/prefetch.cc
+++ b/src/nix/prefetch.cc
@@ -57,7 +57,9 @@ std::tuple<StorePath, Hash> prefetchFile(
         bool unpack,
         bool executable)
 {
-    auto ingestionMethod = unpack || executable ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
+    ContentAddressMethod method = unpack || executable
+        ? ContentAddressMethod::Raw::NixArchive
+        : ContentAddressMethod::Raw::Flat;
 
     /* Figure out a name in the Nix store. */
     if (!name) {
@@ -73,11 +75,10 @@ std::tuple<StorePath, Hash> prefetchFile(
        the store. */
     if (expectedHash) {
         hashAlgo = expectedHash->algo;
-        storePath = store->makeFixedOutputPath(*name, FixedOutputInfo {
-            .method = ingestionMethod,
-            .hash = *expectedHash,
-            .references = {},
-        });
+        storePath = store->makeFixedOutputPathFromCA(*name, ContentAddressWithReferences::fromParts(
+            method,
+            *expectedHash,
+            {}));
         if (store->isValidPath(*storePath))
             hash = expectedHash;
         else
@@ -87,7 +88,7 @@ std::tuple<StorePath, Hash> prefetchFile(
     if (!storePath) {
 
         AutoDelete tmpDir(createTempDir(), true);
-        Path tmpFile = (Path) tmpDir + "/tmp";
+        std::filesystem::path tmpFile = tmpDir.path() / "tmp";
 
         /* Download the file. */
         {
@@ -95,7 +96,7 @@ std::tuple<StorePath, Hash> prefetchFile(
             if (executable)
                 mode = 0700;
 
-            AutoCloseFD fd = toDescriptor(open(tmpFile.c_str(), O_WRONLY | O_CREAT | O_EXCL, mode));
+            AutoCloseFD fd = toDescriptor(open(tmpFile.string().c_str(), O_WRONLY | O_CREAT | O_EXCL, mode));
             if (!fd) throw SysError("creating temporary file '%s'", tmpFile);
 
             FdSink sink(fd.get());
@@ -109,26 +110,27 @@ std::tuple<StorePath, Hash> prefetchFile(
         if (unpack) {
             Activity act(*logger, lvlChatty, actUnknown,
                 fmt("unpacking '%s'", url));
-            Path unpacked = (Path) tmpDir + "/unpacked";
+            auto unpacked = (tmpDir.path() / "unpacked").string();
             createDirs(unpacked);
-            unpackTarfile(tmpFile, unpacked);
+            unpackTarfile(tmpFile.string(), unpacked);
 
+            auto entries = std::filesystem::directory_iterator{unpacked};
             /* If the archive unpacks to a single file/directory, then use
                that as the top-level. */
-            auto entries = readDirectory(unpacked);
-            if (entries.size() == 1)
-                tmpFile = unpacked + "/" + entries[0].name;
-            else
+            tmpFile = entries->path();
+            auto fileCount = std::distance(entries, std::filesystem::directory_iterator{});
+            if (fileCount != 1) {
+                /* otherwise, use the directory itself */
                 tmpFile = unpacked;
+            }
         }
 
         Activity act(*logger, lvlChatty, actUnknown,
             fmt("adding '%s' to the store", url));
 
-        auto [accessor, canonPath] = PosixSourceAccessor::createAtRoot(tmpFile);
         auto info = store->addToStoreSlow(
-            *name, accessor, canonPath,
-            ingestionMethod, hashAlgo, {}, expectedHash);
+            *name, PosixSourceAccessor::createAtRoot(tmpFile),
+            method, hashAlgo, {}, expectedHash);
         storePath = info.path;
         assert(info.ca);
         hash = info.ca->hash;
@@ -193,7 +195,7 @@ static int main_nix_prefetch_url(int argc, char * * argv)
           startProgressBar();
 
         auto store = openStore();
-        auto state = std::make_unique<EvalState>(myArgs.searchPath, store);
+        auto state = std::make_unique<EvalState>(myArgs.lookupPath, store, evalSettings);
 
         Bindings & autoArgs = *myArgs.getAutoArgs(*state);
 
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index a5a40e4f66c..c89b8c9bde6 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -258,7 +258,7 @@ struct ProfileManifest
             *store,
             "profile",
             FixedOutputInfo {
-                .method = FileIngestionMethod::Recursive,
+                .method = FileIngestionMethod::NixArchive,
                 .hash = narHash,
                 .references = {
                     .others = std::move(references),
diff --git a/src/nix/profile.md b/src/nix/profile.md
index 9b2f86f4ac6..83a0b5f2991 100644
--- a/src/nix/profile.md
+++ b/src/nix/profile.md
@@ -11,7 +11,7 @@ them to be rolled back easily.
 
 )""
 
-#include "generated-doc/files/profiles.md.gen.hh"
+#include "profiles.md.gen.hh"
 
 R""(
 
diff --git a/src/nix/profiles.md b/src/nix/profiles.md
new file mode 120000
index 00000000000..c67a86194c0
--- /dev/null
+++ b/src/nix/profiles.md
@@ -0,0 +1 @@
+../../doc/manual/src/command-ref/files/profiles.md
\ No newline at end of file
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index 8bbfe0f0765..a2f3e033e72 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -78,7 +78,7 @@ struct CmdRepl : RawInstallablesCommand
             return values;
         };
         auto repl = AbstractNixRepl::create(
-            searchPath,
+            lookupPath,
             openStore(),
             state,
             getValues
diff --git a/src/nix/unix/run.cc b/src/nix/run.cc
similarity index 67%
rename from src/nix/unix/run.cc
rename to src/nix/run.cc
index dfd8b643ce9..c1aae168577 100644
--- a/src/nix/unix/run.cc
+++ b/src/nix/run.cc
@@ -3,17 +3,18 @@
 #include "command-installable-value.hh"
 #include "common-args.hh"
 #include "shared.hh"
+#include "signals.hh"
 #include "store-api.hh"
 #include "derivations.hh"
-#include "local-store.hh"
+#include "local-fs-store.hh"
 #include "finally.hh"
 #include "source-accessor.hh"
 #include "progress-bar.hh"
 #include "eval.hh"
-#include "build/personality.hh"
 
 #if __linux__
-#include <sys/mount.h>
+# include <sys/mount.h>
+# include "personality.hh"
 #endif
 
 #include <queue>
@@ -25,7 +26,7 @@ std::string chrootHelperName = "__run_in_chroot";
 namespace nix {
 
 void runProgramInStore(ref<Store> store,
-    UseSearchPath useSearchPath,
+    UseLookupPath useLookupPath,
     const std::string & program,
     const Strings & args,
     std::optional<std::string_view> system)
@@ -56,10 +57,12 @@ void runProgramInStore(ref<Store> store,
         throw SysError("could not execute chroot helper");
     }
 
+#if __linux__
     if (system)
-        setPersonality(*system);
+        linux::setPersonality(*system);
+#endif
 
-    if (useSearchPath == UseSearchPath::Use)
+    if (useLookupPath == UseLookupPath::Use)
         execvp(program.c_str(), stringsToCharPtrs(args).data());
     else
         execv(program.c_str(), stringsToCharPtrs(args).data());
@@ -69,83 +72,6 @@ void runProgramInStore(ref<Store> store,
 
 }
 
-struct CmdShell : InstallablesCommand, MixEnvironment
-{
-
-    using InstallablesCommand::run;
-
-    std::vector<std::string> command = { getEnv("SHELL").value_or("bash") };
-
-    CmdShell()
-    {
-        addFlag({
-            .longName = "command",
-            .shortName = 'c',
-            .description = "Command and arguments to be executed, defaulting to `$SHELL`",
-            .labels = {"command", "args"},
-            .handler = {[&](std::vector<std::string> ss) {
-                if (ss.empty()) throw UsageError("--command requires at least one argument");
-                command = ss;
-            }}
-        });
-    }
-
-    std::string description() override
-    {
-        return "run a shell in which the specified packages are available";
-    }
-
-    std::string doc() override
-    {
-        return
-          #include "shell.md"
-          ;
-    }
-
-    void run(ref<Store> store, Installables && installables) override
-    {
-        auto outPaths = Installable::toStorePaths(getEvalStore(), store, Realise::Outputs, OperateOn::Output, installables);
-
-        auto accessor = store->getFSAccessor();
-
-        std::unordered_set<StorePath> done;
-        std::queue<StorePath> todo;
-        for (auto & path : outPaths) todo.push(path);
-
-        setEnviron();
-
-        std::vector<std::string> pathAdditions;
-
-        while (!todo.empty()) {
-            auto path = todo.front();
-            todo.pop();
-            if (!done.insert(path).second) continue;
-
-            if (true)
-                pathAdditions.push_back(store->printStorePath(path) + "/bin");
-
-            auto propPath = accessor->resolveSymlinks(
-                CanonPath(store->printStorePath(path)) / "nix-support" / "propagated-user-env-packages");
-            if (auto st = accessor->maybeLstat(propPath); st && st->type == SourceAccessor::tRegular) {
-                for (auto & p : tokenizeString<Paths>(accessor->readFile(propPath)))
-                    todo.push(store->parseStorePath(p));
-            }
-        }
-
-        auto unixPath = tokenizeString<Strings>(getEnv("PATH").value_or(""), ":");
-        unixPath.insert(unixPath.begin(), pathAdditions.begin(), pathAdditions.end());
-        auto unixPathString = concatStringsSep(":", unixPath);
-        setEnv("PATH", unixPathString.c_str());
-
-        Strings args;
-        for (auto & arg : command) args.push_back(arg);
-
-        runProgramInStore(store, UseSearchPath::Use, *command.begin(), args);
-    }
-};
-
-static auto rCmdShell = registerCommand<CmdShell>("shell");
-
 struct CmdRun : InstallableValueCommand
 {
     using InstallableCommand::run;
@@ -202,7 +128,7 @@ struct CmdRun : InstallableValueCommand
         Strings allArgs{app.program};
         for (auto & i : args) allArgs.push_back(i);
 
-        runProgramInStore(store, UseSearchPath::DontUse, app.program, allArgs);
+        runProgramInStore(store, UseLookupPath::DontUse, app.program, allArgs);
     }
 };
 
@@ -246,9 +172,10 @@ void chrootHelper(int argc, char * * argv)
         if (mount(realStoreDir.c_str(), (tmpDir + storeDir).c_str(), "", MS_BIND, 0) == -1)
             throw SysError("mounting '%s' on '%s'", realStoreDir, storeDir);
 
-        for (auto entry : readDirectory("/")) {
-            auto src = "/" + entry.name;
-            Path dst = tmpDir + "/" + entry.name;
+        for (auto entry : std::filesystem::directory_iterator{"/"}) {
+            checkInterrupt();
+            auto src = entry.path().string();
+            Path dst = tmpDir + "/" + entry.path().filename().string();
             if (pathExists(dst)) continue;
             auto st = lstat(src);
             if (S_ISDIR(st.st_mode)) {
@@ -277,8 +204,10 @@ void chrootHelper(int argc, char * * argv)
     writeFile("/proc/self/uid_map", fmt("%d %d %d", uid, uid, 1));
     writeFile("/proc/self/gid_map", fmt("%d %d %d", gid, gid, 1));
 
+#if __linux__
     if (system != "")
-        setPersonality(system);
+        linux::setPersonality(system);
+#endif
 
     execvp(cmd.c_str(), stringsToCharPtrs(args).data());
 
diff --git a/src/nix/unix/run.hh b/src/nix/run.hh
similarity index 80%
rename from src/nix/unix/run.hh
rename to src/nix/run.hh
index a55917b06d7..2fe6ed86ae6 100644
--- a/src/nix/unix/run.hh
+++ b/src/nix/run.hh
@@ -5,13 +5,13 @@
 
 namespace nix {
 
-enum struct UseSearchPath {
+enum struct UseLookupPath {
     Use,
     DontUse
 };
 
 void runProgramInStore(ref<Store> store,
-    UseSearchPath useSearchPath,
+    UseLookupPath useLookupPath,
     const std::string & program,
     const Strings & args,
     std::optional<std::string_view> system = std::nullopt);
diff --git a/src/nix/unix/run.md b/src/nix/run.md
similarity index 100%
rename from src/nix/unix/run.md
rename to src/nix/run.md
diff --git a/src/nix/store-dump-path.md b/src/nix/store-dump-path.md
index 56e2174b6a8..21467ff329e 100644
--- a/src/nix/store-dump-path.md
+++ b/src/nix/store-dump-path.md
@@ -17,7 +17,9 @@ R""(
 
 # Description
 
-This command generates a NAR file containing the serialisation of the
+This command generates a [Nix Archive (NAR)][Nix Archive] file containing the serialisation of the
 store path [*installable*](./nix.md#installables). The NAR is written to standard output.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+
 )""
diff --git a/src/nix/unix/daemon.cc b/src/nix/unix/daemon.cc
index f9899fa9ece..5d088e3d076 100644
--- a/src/nix/unix/daemon.cc
+++ b/src/nix/unix/daemon.cc
@@ -10,6 +10,7 @@
 #include "serialise.hh"
 #include "archive.hh"
 #include "globals.hh"
+#include "config-global.hh"
 #include "derivations.hh"
 #include "finally.hh"
 #include "legacy.hh"
@@ -58,7 +59,7 @@ struct AuthorizationSettings : Config {
         this, {"root"}, "trusted-users",
         R"(
           A list of user names, separated by whitespace.
-          These users will have additional rights when connecting to the Nix daemon, such as the ability to specify additional [substituters](#conf-substituters), or to import unsigned [NARs](@docroot@/glossary.md#gloss-nar).
+          These users will have additional rights when connecting to the Nix daemon, such as the ability to specify additional [substituters](#conf-substituters), or to import unsigned realisations or unsigned input-addressed store objects.
 
           You can also specify groups by prefixing names with `@`.
           For instance, `@wheel` means all users in the `wheel` group.
@@ -202,7 +203,11 @@ static PeerInfo getPeerInfo(int remote)
 
 #if defined(SO_PEERCRED)
 
-    ucred cred;
+# if defined(__OpenBSD__)
+   struct sockpeercred cred;
+# else
+   ucred cred;
+# endif
     socklen_t credLen = sizeof(cred);
     if (getsockopt(remote, SOL_SOCKET, SO_PEERCRED, &cred, &credLen) == -1)
         throw SysError("getting peer credentials");
@@ -210,9 +215,9 @@ static PeerInfo getPeerInfo(int remote)
 
 #elif defined(LOCAL_PEERCRED)
 
-#if !defined(SOL_LOCAL)
-#define SOL_LOCAL 0
-#endif
+# if !defined(SOL_LOCAL)
+# define SOL_LOCAL 0
+# endif
 
     xucred cred;
     socklen_t credLen = sizeof(cred);
@@ -295,7 +300,7 @@ static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
         if (getEnv("LISTEN_PID") != std::to_string(getpid()) || listenFds != "1")
             throw Error("unexpected systemd environment variables");
         fdSocket = SD_LISTEN_FDS_START;
-        closeOnExec(fdSocket.get());
+        unix::closeOnExec(fdSocket.get());
     }
 
     //  Otherwise, create and bind to a Unix domain socket.
@@ -323,7 +328,7 @@ static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
                 throw SysError("accepting connection");
             }
 
-            closeOnExec(remote.get());
+            unix::closeOnExec(remote.get());
 
             PeerInfo peer { .pidKnown = false };
             TrustedFlag trusted;
diff --git a/src/nix/unix/upgrade-nix.cc b/src/nix/upgrade-nix.cc
similarity index 97%
rename from src/nix/unix/upgrade-nix.cc
rename to src/nix/upgrade-nix.cc
index 4c7a74e16f1..29297253bda 100644
--- a/src/nix/unix/upgrade-nix.cc
+++ b/src/nix/upgrade-nix.cc
@@ -121,7 +121,7 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
         Path profileDir = dirOf(where);
 
         // Resolve profile to /nix/var/nix/profiles/<name> link.
-        while (canonPath(profileDir).find("/profiles/") == std::string::npos && isLink(profileDir))
+        while (canonPath(profileDir).find("/profiles/") == std::string::npos && std::filesystem::is_symlink(profileDir))
             profileDir = readLink(profileDir);
 
         printInfo("found profile '%s'", profileDir);
@@ -147,7 +147,7 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
         auto req = FileTransferRequest((std::string&) settings.upgradeNixStorePathUrl);
         auto res = getFileTransfer()->download(req);
 
-        auto state = std::make_unique<EvalState>(SearchPath{}, store);
+        auto state = std::make_unique<EvalState>(LookupPath{}, store, evalSettings);
         auto v = state->allocValue();
         state->eval(state->parseExprFromString(res.data, state->rootPath(CanonPath("/no-such-path"))), *v);
         Bindings & bindings(*state->allocBindings(0));
diff --git a/src/nix/unix/upgrade-nix.md b/src/nix/upgrade-nix.md
similarity index 100%
rename from src/nix/unix/upgrade-nix.md
rename to src/nix/upgrade-nix.md
diff --git a/src/nix/verify.md b/src/nix/verify.md
index e1d55eab457..ae0b0acd68a 100644
--- a/src/nix/verify.md
+++ b/src/nix/verify.md
@@ -46,4 +46,6 @@ The exit status of this command is the sum of the following values:
 * **4** if any path couldn't be verified for any other reason (such as
   an I/O error).
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+
 )""
diff --git a/src/perl/.version b/src/perl/.version
new file mode 120000
index 00000000000..b7badcd0cc8
--- /dev/null
+++ b/src/perl/.version
@@ -0,0 +1 @@
+../../.version
\ No newline at end of file
diff --git a/src/perl/.yath.rc.in b/src/perl/.yath.rc.in
new file mode 100644
index 00000000000..e6f5f93ecdd
--- /dev/null
+++ b/src/perl/.yath.rc.in
@@ -0,0 +1,2 @@
+[test]
+-I=rel(@lib_dir@)
diff --git a/perl/MANIFEST b/src/perl/MANIFEST
similarity index 100%
rename from perl/MANIFEST
rename to src/perl/MANIFEST
diff --git a/perl/lib/Nix/Config.pm.in b/src/perl/lib/Nix/Config.pm.in
similarity index 100%
rename from perl/lib/Nix/Config.pm.in
rename to src/perl/lib/Nix/Config.pm.in
diff --git a/perl/lib/Nix/CopyClosure.pm b/src/perl/lib/Nix/CopyClosure.pm
similarity index 100%
rename from perl/lib/Nix/CopyClosure.pm
rename to src/perl/lib/Nix/CopyClosure.pm
diff --git a/perl/lib/Nix/Manifest.pm b/src/perl/lib/Nix/Manifest.pm
similarity index 100%
rename from perl/lib/Nix/Manifest.pm
rename to src/perl/lib/Nix/Manifest.pm
diff --git a/perl/lib/Nix/SSH.pm b/src/perl/lib/Nix/SSH.pm
similarity index 100%
rename from perl/lib/Nix/SSH.pm
rename to src/perl/lib/Nix/SSH.pm
diff --git a/perl/lib/Nix/Store.pm b/src/perl/lib/Nix/Store.pm
similarity index 100%
rename from perl/lib/Nix/Store.pm
rename to src/perl/lib/Nix/Store.pm
diff --git a/perl/lib/Nix/Store.xs b/src/perl/lib/Nix/Store.xs
similarity index 96%
rename from perl/lib/Nix/Store.xs
rename to src/perl/lib/Nix/Store.xs
index 1c64cc66b14..f951437c899 100644
--- a/perl/lib/Nix/Store.xs
+++ b/src/perl/lib/Nix/Store.xs
@@ -1,4 +1,5 @@
-#include "config.h"
+#include "config-util.hh"
+#include "config-store.hh"
 
 #include "EXTERN.h"
 #include "perl.h"
@@ -256,10 +257,9 @@ SV *
 hashPath(char * algo, int base32, char * path)
     PPCODE:
         try {
-            auto [accessor, canonPath] = PosixSourceAccessor::createAtRoot(path);
             Hash h = hashPath(
-                accessor, canonPath,
-                FileIngestionMethod::Recursive, parseHashAlgo(algo));
+                PosixSourceAccessor::createAtRoot(path),
+                FileIngestionMethod::NixArchive, parseHashAlgo(algo)).first;
             auto s = h.to_string(base32 ? HashFormat::Nix32 : HashFormat::Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
@@ -335,11 +335,10 @@ SV *
 StoreWrapper::addToStore(char * srcPath, int recursive, char * algo)
     PPCODE:
         try {
-            auto method = recursive ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
-            auto [accessor, canonPath] = PosixSourceAccessor::createAtRoot(srcPath);
+            auto method = recursive ? ContentAddressMethod::Raw::NixArchive : ContentAddressMethod::Raw::Flat;
             auto path = THIS->store->addToStore(
                 std::string(baseNameOf(srcPath)),
-                accessor, canonPath,
+                PosixSourceAccessor::createAtRoot(srcPath),
                 method, parseHashAlgo(algo));
             XPUSHs(sv_2mortal(newSVpv(THIS->store->printStorePath(path).c_str(), 0)));
         } catch (Error & e) {
@@ -352,7 +351,7 @@ StoreWrapper::makeFixedOutputPath(int recursive, char * algo, char * hash, char
     PPCODE:
         try {
             auto h = Hash::parseAny(hash, parseHashAlgo(algo));
-            auto method = recursive ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
+            auto method = recursive ? FileIngestionMethod::NixArchive : FileIngestionMethod::Flat;
             auto path = THIS->store->makeFixedOutputPath(name, FixedOutputInfo {
                 .method = method,
                 .hash = h,
diff --git a/perl/lib/Nix/Utils.pm b/src/perl/lib/Nix/Utils.pm
similarity index 100%
rename from perl/lib/Nix/Utils.pm
rename to src/perl/lib/Nix/Utils.pm
diff --git a/src/perl/lib/Nix/meson.build b/src/perl/lib/Nix/meson.build
new file mode 100644
index 00000000000..256e6609652
--- /dev/null
+++ b/src/perl/lib/Nix/meson.build
@@ -0,0 +1,60 @@
+# Nix-Perl Scripts
+#============================================================================
+
+
+
+# Sources
+#-------------------------------------------------
+
+nix_perl_store_xs = files('Store.xs')
+
+nix_perl_scripts = files(
+  'CopyClosure.pm',
+  'Manifest.pm',
+  'SSH.pm',
+  'Store.pm',
+  'Utils.pm',
+)
+
+foreach f : nix_perl_scripts
+  fs.copyfile(f)
+endforeach
+
+
+# Targets
+#---------------------------------------------------
+
+nix_perl_scripts += configure_file(
+  output : 'Config.pm',
+  input : 'Config.pm.in',
+  configuration : nix_perl_conf,
+)
+
+nix_perl_store_cc = custom_target(
+  'Store.cc',
+  output : 'Store.cc',
+  input : nix_perl_store_xs,
+  command : [xsubpp, '@INPUT@', '-output', '@OUTPUT@'],
+)
+
+# Build Nix::Store Library
+#-------------------------------------------------
+nix_perl_store_lib = library(
+  'Store',
+  sources : nix_perl_store_cc,
+  name_prefix  : '',
+  prelink : true, # For C++ static initializers
+  install : true,
+  install_mode : 'rwxr-xr-x',
+  install_dir : join_paths(nix_perl_install_dir, 'auto', 'Nix', 'Store'),
+  dependencies : nix_perl_store_dep_list,
+)
+
+
+# Install Scripts
+#---------------------------------------------------
+install_data(
+  nix_perl_scripts,
+  install_mode : 'rw-r--r--',
+  install_dir : join_paths(nix_perl_install_dir,'Nix'),
+)
diff --git a/src/perl/meson.build b/src/perl/meson.build
new file mode 100644
index 00000000000..5fe7e1e28fa
--- /dev/null
+++ b/src/perl/meson.build
@@ -0,0 +1,163 @@
+# Nix-Perl Meson build
+#============================================================================
+
+
+# init project
+#============================================================================
+project (
+  'nix-perl',
+  'cpp',
+  version : files('.version'),
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+# setup env
+#-------------------------------------------------
+fs = import('fs')
+cpp = meson.get_compiler('cpp')
+nix_perl_conf = configuration_data()
+nix_perl_conf.set('PACKAGE_VERSION', meson.project_version())
+
+
+# set error arguments
+#-------------------------------------------------
+error_args = [
+  '-Werror=unused-result',
+  '-Wdeprecated-copy',
+  '-Wdeprecated-declarations',
+  '-Wignored-qualifiers',
+  '-Wno-pedantic',
+  '-Wno-non-virtual-dtor',
+  '-Wno-unused-parameter',
+  '-Wno-variadic-macros',
+  '-Wno-missing-field-initializers',
+  '-Wno-unknown-warning-option',
+  '-Wno-unused-variable',
+  '-Wno-literal-suffix',
+  '-Wno-reserved-user-defined-literal',
+  '-Wno-duplicate-decl-specifier',
+  '-Wno-pointer-bool-conversion',
+]
+
+add_project_arguments(
+  cpp.get_supported_arguments(error_args),
+  language : 'cpp',
+)
+
+
+# set install directories
+#-------------------------------------------------
+prefix = get_option('prefix')
+libdir = join_paths(prefix, get_option('libdir'))
+
+# Dependencies
+#============================================================================
+
+# Required Programs
+#-------------------------------------------------
+xz = find_program('xz')
+xsubpp = find_program('xsubpp')
+perl = find_program('perl')
+curl = find_program('curl')
+yath = find_program('yath', required : false)
+
+# Required Libraries
+#-------------------------------------------------
+bzip2_dep = dependency('bzip2')
+curl_dep = dependency('libcurl')
+libsodium_dep = dependency('libsodium')
+
+nix_store_dep = dependency('nix-store')
+
+
+# Finding Perl Headers is a pain. as they do not have
+# pkgconfig available, are not in a standard location,
+# and are installed into a version folder. Use the
+# Perl binary to give hints about perl include dir.
+#-------------------------------------------------
+perl_archname = run_command(
+  perl, '-e', 'use Config; print $Config{archname};', check: true).stdout()
+perl_version = run_command(
+  perl, '-e', 'use Config; print $Config{version};', check: true).stdout()
+perl_archlibexp = run_command(
+  perl, '-e', 'use Config; print $Config{archlibexp};', check: true).stdout()
+perl_site_libdir = run_command(
+  perl, '-e', 'use Config; print $Config{installsitearch};', check: true).stdout()
+nix_perl_install_dir = join_paths(
+  libdir, 'perl5', 'site_perl', perl_version, perl_archname)
+
+
+# print perl hints for logs
+#-------------------------------------------------
+message('Perl archname: @0@'.format(perl_archname))
+message('Perl version: @0@'.format(perl_version))
+message('Perl archlibexp: @0@'.format(perl_archlibexp))
+message('Perl install site: @0@'.format(perl_site_libdir))
+message('Assumed Nix-Perl install dir: @0@'.format(nix_perl_install_dir))
+
+# Now find perl modules
+#-------------------------------------------------
+perl_check_dbi = run_command(
+  perl,
+  '-e', 'use DBI; use DBD::SQLite;',
+  '-I@0@'.format(get_option('dbi_path')),
+  '-I@0@'.format(get_option('dbd_sqlite_path')),
+  check: true
+)
+
+if perl_check_dbi.returncode() == 2
+  error('The Perl modules DBI and/or DBD::SQLite are missing.')
+else
+  message('Found Perl Modules: DBI, DBD::SQLite.')
+endif
+
+
+
+# declare perl dependency
+#-------------------------------------------------
+perl_dep = declare_dependency(
+  dependencies : cpp.find_library(
+  'perl',
+  has_headers : [
+    join_paths(perl_archlibexp, 'CORE', 'perl.h'),
+    join_paths(perl_archlibexp, 'CORE', 'EXTERN.h')],
+    dirs : [
+      join_paths(perl_archlibexp, 'CORE'),
+    ],
+  ),
+  include_directories : join_paths(perl_archlibexp, 'CORE'),
+)
+
+# declare dependencies
+#-------------------------------------------------
+nix_perl_store_dep_list = [
+  perl_dep,
+  bzip2_dep,
+  curl_dep,
+  libsodium_dep,
+  nix_store_dep,
+]
+
+# # build
+# #-------------------------------------------------
+lib_dir = join_paths('lib', 'Nix')
+subdir(lib_dir)
+
+if get_option('tests').enabled()
+  yath_rc_conf = configuration_data()
+  yath_rc_conf.set('lib_dir', lib_dir)
+  yath_rc = configure_file(
+    output : '.yath.rc',
+    input : '.yath.rc.in',
+    configuration : yath_rc_conf,
+  )
+  subdir('t')
+  test(
+    'nix-perl-test',
+    yath,
+    args : ['test'],
+    workdir : meson.current_build_dir(),
+    depends : [nix_perl_store_lib],
+  )
+endif
diff --git a/src/perl/meson.options b/src/perl/meson.options
new file mode 100644
index 00000000000..9b5b6b1d9b8
--- /dev/null
+++ b/src/perl/meson.options
@@ -0,0 +1,27 @@
+# Nix-Perl build options
+#============================================================================
+
+
+# compiler args
+#============================================================================
+
+option(
+  'tests',
+  type : 'feature',
+  value : 'disabled',
+  description : 'run nix-perl tests')
+
+
+# Location of Perl Modules
+#============================================================================
+option(
+  'dbi_path',
+  type : 'string',
+  value : '/usr',
+  description : 'path to perl::dbi')
+
+option(
+  'dbd_sqlite_path',
+  type : 'string',
+  value : '/usr',
+  description : 'path to perl::dbd-SQLite')
diff --git a/src/perl/package.nix b/src/perl/package.nix
new file mode 100644
index 00000000000..26856e631a1
--- /dev/null
+++ b/src/perl/package.nix
@@ -0,0 +1,77 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, perl
+, perlPackages
+, meson
+, ninja
+, pkg-config
+, nix-store
+, darwin
+, version
+, curl
+, bzip2
+, libsodium
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+perl.pkgs.toPerlModule (mkMesonDerivation (finalAttrs: {
+  pname = "nix-perl";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions ([
+    ./.version
+    ../../.version
+    ./MANIFEST
+    ./lib
+    ./meson.build
+    ./meson.options
+  ] ++ lib.optionals finalAttrs.doCheck [
+    ./.yath.rc.in
+    ./t
+  ]);
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+    perl
+    curl
+  ];
+
+  buildInputs = [
+    nix-store
+    bzip2
+    libsodium
+  ];
+
+  # `perlPackages.Test2Harness` is marked broken for Darwin
+  doCheck = !stdenv.isDarwin;
+
+  nativeCheckInputs = [
+    perlPackages.Test2Harness
+  ];
+
+  preConfigure =
+    # "Inline" .version so its not a symlink, and includes the suffix
+    ''
+      chmod u+w .version
+      echo ${finalAttrs.version} > .version
+    '';
+
+  mesonFlags = [
+    (lib.mesonOption "dbi_path" "${perlPackages.DBI}/${perl.libPrefix}")
+    (lib.mesonOption "dbd_sqlite_path" "${perlPackages.DBDSQLite}/${perl.libPrefix}")
+    (lib.mesonEnable "tests" finalAttrs.doCheck)
+  ];
+
+  mesonCheckFlags = [
+    "--print-errorlogs"
+  ];
+
+  enableParallelBuilding = true;
+}))
diff --git a/perl/t/init.t b/src/perl/t/init.t
similarity index 100%
rename from perl/t/init.t
rename to src/perl/t/init.t
diff --git a/src/perl/t/meson.build b/src/perl/t/meson.build
new file mode 100644
index 00000000000..dbd1139f327
--- /dev/null
+++ b/src/perl/t/meson.build
@@ -0,0 +1,15 @@
+# Nix-Perl Tests
+#============================================================================
+
+
+# src
+#---------------------------------------------------
+
+nix_perl_tests = files(
+  'init.t',
+)
+
+
+foreach f : nix_perl_tests
+  fs.copyfile(f)
+endforeach
diff --git a/src/toml11/LICENSE b/src/toml11/LICENSE
deleted file mode 100644
index f55c511d6f0..00000000000
--- a/src/toml11/LICENSE
+++ /dev/null
@@ -1,21 +0,0 @@
-The MIT License (MIT)
-
-Copyright (c) 2017 Toru Niina
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in
-all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-THE SOFTWARE.
diff --git a/src/toml11/README.md b/src/toml11/README.md
deleted file mode 100644
index 62b58630579..00000000000
--- a/src/toml11/README.md
+++ /dev/null
@@ -1,1966 +0,0 @@
-toml11
-======
-
-[![Build Status on GitHub Actions](https://github.com/ToruNiina/toml11/workflows/build/badge.svg)](https://github.com/ToruNiina/toml11/actions)
-[![Build Status on TravisCI](https://travis-ci.org/ToruNiina/toml11.svg?branch=master)](https://travis-ci.org/ToruNiina/toml11)
-[![Build status on Appveyor](https://ci.appveyor.com/api/projects/status/m2n08a926asvg5mg/branch/master?svg=true)](https://ci.appveyor.com/project/ToruNiina/toml11/branch/master)
-[![Build status on CircleCI](https://circleci.com/gh/ToruNiina/toml11/tree/master.svg?style=svg)](https://circleci.com/gh/ToruNiina/toml11/tree/master)
-[![Version](https://img.shields.io/github/release/ToruNiina/toml11.svg?style=flat)](https://github.com/ToruNiina/toml11/releases)
-[![License](https://img.shields.io/github/license/ToruNiina/toml11.svg?style=flat)](LICENSE)
-[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.1209136.svg)](https://doi.org/10.5281/zenodo.1209136)
-
-toml11 is a C++11 (or later) header-only toml parser/encoder depending only on C++ standard library.
-
-- It is compatible to the latest version of [TOML v1.0.0](https://toml.io/en/v1.0.0).
-- It is one of the most TOML standard compliant libraries, tested with [the language agnostic test suite for TOML parsers by BurntSushi](https://github.com/BurntSushi/toml-test).
-- It shows highly informative error messages. You can see the error messages about invalid files at [CircleCI](https://circleci.com/gh/ToruNiina/toml11).
-- It has configurable container. You can use any random-access containers and key-value maps as backend containers.
-- It optionally preserves comments without any overhead.
-- It has configurable serializer that supports comments, inline tables, literal strings and multiline strings.
-- It supports user-defined type conversion from/into toml values.
-- It correctly handles UTF-8 sequences, with or without BOM, both on posix and Windows.
-
-## Example
-
-```cpp
-#include <toml.hpp>
-#include <iostream>
-
-int main()
-{
-    // ```toml
-    // title = "an example toml file"
-    // nums  = [3, 1, 4, 1, 5]
-    // ```
-    auto data = toml::parse("example.toml");
-
-    // find a value with the specified type from a table
-    std::string title = toml::find<std::string>(data, "title");
-
-    // convert the whole array into any container automatically
-    std::vector<int> nums = toml::find<std::vector<int>>(data, "nums");
-
-    // access with STL-like manner
-    if(!data.contains("foo"))
-    {
-        data["foo"] = "bar";
-    }
-
-    // pass a fallback
-    std::string name = toml::find_or<std::string>(data, "name", "not found");
-
-    // width-dependent formatting
-    std::cout << std::setw(80) << data << std::endl;
-
-    return 0;
-}
-```
-
-## Table of Contents
-
-- [Integration](#integration)
-- [Decoding a toml file](#decoding-a-toml-file)
-  - [In the case of syntax error](#in-the-case-of-syntax-error)
-  - [Invalid UTF-8 Codepoints](#invalid-utf-8-codepoints)
-- [Finding a toml value](#finding-a-toml-value)
-  - [Finding a value in a table](#finding-a-value-in-a-table)
-  - [In case of error](#in-case-of-error)
-  - [Dotted keys](#dotted-keys)
-- [Casting a toml value](#casting-a-toml-value)
-- [Checking value type](#checking-value-type)
-- [More about conversion](#more-about-conversion)
-  - [Converting an array](#converting-an-array)
-  - [Converting a table](#converting-a-table)
-  - [Getting an array of tables](#getting-an-array-of-tables)
-  - [Cost of conversion](#cost-of-conversion)
-  - [Converting datetime and its variants](#converting-datetime-and-its-variants)
-- [Getting with a fallback](#getting-with-a-fallback)
-- [Expecting conversion](#expecting-conversion)
-- [Visiting a toml::value](#visiting-a-tomlvalue)
-- [Constructing a toml::value](#constructing-a-tomlvalue)
-- [Preserving Comments](#preserving-comments)
-- [Customizing containers](#customizing-containers)
-- [TOML literal](#toml-literal)
-- [Conversion between toml value and arbitrary types](#conversion-between-toml-value-and-arbitrary-types)
-- [Formatting user-defined error messages](#formatting-user-defined-error-messages)
-- [Obtaining location information](#obtaining-location-information)
-- [Exceptions](#exceptions)
-- [Colorize Error Messages](#colorize-error-messages)
-- [Serializing TOML data](#serializing-toml-data)
-- [Underlying types](#underlying-types)
-- [Unreleased TOML features](#unreleased-toml-features)
-- [Breaking Changes from v2](#breaking-changes-from-v2)
-- [Running Tests](#running-tests)
-- [Contributors](#contributors)
-- [Licensing Terms](#licensing-terms)
-
-## Integration
-
-Just include the file after adding it to the include path.
-
-```cpp
-#include <toml.hpp> // that's all! now you can use it.
-#include <iostream>
-
-int main()
-{
-    const auto data  = toml::parse("example.toml");
-    const auto title = toml::find<std::string>(data, "title");
-    std::cout << "the title is " << title << std::endl;
-    return 0;
-}
-```
-
-The convenient way is to add this repository as a git-submodule or to install
-it in your system by CMake.
-
-Note for MSVC: We recommend to set `/Zc:__cplusplus` to detect C++ version correctly.
-
-## Decoding a toml file
-
-To parse a toml file, the only thing you have to do is
-to pass a filename to the `toml::parse` function.
-
-```cpp
-const std::string fname("sample.toml");
-const toml::value data = toml::parse(fname);
-```
-
-As required by the TOML specification, the top-level value is always a table.
-You can find a value inside it, cast it into a table explicitly, and insert it as a value into other `toml::value`.
-
-If it encounters an error while opening a file, it will throw `std::runtime_error`.
-
-You can also pass a `std::istream` to the  `toml::parse` function.
-To show a filename in an error message, however, it is recommended to pass the
-filename with the stream.
-
-```cpp
-std::ifstream ifs("sample.toml", std::ios_base::binary);
-assert(ifs.good());
-const auto data = toml::parse(ifs, /*optional -> */ "sample.toml");
-```
-
-**Note**: When you are **on Windows, open a file in binary mode**.
-If a file is opened in text-mode, CRLF ("\r\n") will automatically be
-converted to LF ("\n") and this causes inconsistency between file size
-and the contents that would be read. This causes weird error.
-
-### In the case of syntax error
-
-If there is a syntax error in a toml file, `toml::parse` will throw
-`toml::syntax_error` that inherits `std::exception`.
-
-toml11 has clean and informative error messages inspired by Rust and
-it looks like the following.
-
-```console
-terminate called after throwing an instance of 'toml::syntax_error'
-  what():  [error] toml::parse_table: invalid line format # error description
- --> example.toml                                         # file name
- 3 | a = 42 = true                                        # line num and content
-   |        ^------ expected newline, but got '='.        # error reason
-```
-
-If you (mistakenly) duplicate tables and got an error, it is helpful to see
-where they are. toml11 shows both at the same time like the following.
-
-```console
-terminate called after throwing an instance of 'toml::syntax_error'
-  what():  [error] toml::insert_value: table ("table") already exists.
- --> duplicate-table.toml
- 1 | [table]
-   | ~~~~~~~ table already exists here
- ...
- 3 | [table]
-   | ~~~~~~~ table defined twice
-```
-
-When toml11 encounters a malformed value, it tries to detect what type it is.
-Then it shows hints to fix the format. An error message while reading one of
-the malformed files in [the language agnostic test suite](https://github.com/BurntSushi/toml-test).
-is shown below.
-
-```console
-what(): [error] bad time: should be HH:MM:SS.subsec
- --> ./datetime-malformed-no-secs.toml
- 1 | no-secs = 1987-07-05T17:45Z
-   |                     ^------- HH:MM:SS.subsec
-   |
-Hint: pass: 1979-05-27T07:32:00, 1979-05-27 07:32:00.999999
-Hint: fail: 1979-05-27T7:32:00, 1979-05-27 17:32
-```
-
-You can find other examples in a job named `output_result` on
-[CircleCI](https://circleci.com/gh/ToruNiina/toml11).
-
-Since the error message generation is generally a difficult task, the current
-status is not ideal. If you encounter a weird error message, please let us know
-and contribute to improve the quality!
-
-### Invalid UTF-8 codepoints
-
-It throws `syntax_error` if a value of an escape sequence
-representing unicode character is not a valid UTF-8 codepoint.
-
-```console
-  what():  [error] toml::read_utf8_codepoint: input codepoint is too large.
- --> utf8.toml
- 1 | exceeds_unicode = "\U0011FFFF example"
-   |                              ^--------- should be in [0x00..0x10FFFF]
-```
-
-## Finding a toml value
-
-After parsing successfully, you can obtain the values from the result of
-`toml::parse` using `toml::find` function.
-
-```toml
-# sample.toml
-answer  = 42
-pi      = 3.14
-numbers = [1,2,3]
-time    = 1979-05-27T07:32:00Z
-```
-
-``` cpp
-const auto data      = toml::parse("sample.toml");
-const auto answer    = toml::find<std::int64_t    >(data, "answer");
-const auto pi        = toml::find<double          >(data, "pi");
-const auto numbers   = toml::find<std::vector<int>>(data, "numbers");
-const auto timepoint = toml::find<std::chrono::system_clock::time_point>(data, "time");
-```
-
-By default, `toml::find` returns a `toml::value`.
-
-```cpp
-const toml::value& answer = toml::find(data, "answer");
-```
-
-When you pass an exact TOML type that does not require type conversion,
-`toml::find` returns a reference without copying the value.
-
-```cpp
-const auto  data   = toml::parse("sample.toml");
-const auto& answer = toml::find<toml::integer>(data, "answer");
-```
-
-If the specified type requires conversion, you can't take a reference to the value.
-See also [underlying types](#underlying-types).
-
-**NOTE**: For some technical reason, automatic conversion between `integer` and
-`floating` is not supported. If you want to get a floating value even if a value
-has integer value, you need to convert it manually after obtaining a value,
-like the following.
-
-```cpp
-const auto vx = toml::find(data, "x");
-double x = vx.is_floating() ? vx.as_floating(std::nothrow) :
-           static_cast<double>(vx.as_integer()); // it throws if vx is neither
-                                                 // floating nor integer.
-```
-
-### Finding a value in a table
-
-There are several way to get a value defined in a table.
-First, you can get a table as a normal value and find a value from the table.
-
-```toml
-[fruit]
-name = "apple"
-[fruit.physical]
-color = "red"
-shape = "round"
-```
-
-``` cpp
-const auto  data  = toml::parse("fruit.toml");
-const auto& fruit = toml::find(data, "fruit");
-const auto  name  = toml::find<std::string>(fruit, "name");
-
-const auto& physical = toml::find(fruit, "physical");
-const auto  color    = toml::find<std::string>(physical, "color");
-const auto  shape    = toml::find<std::string>(physical, "shape");
-```
-
-Here, variable `fruit` is a `toml::value` and can be used as the first argument
-of `toml::find`.
-
-Second, you can pass as many arguments as the number of subtables to `toml::find`.
-
-```cpp
-const auto data  = toml::parse("fruit.toml");
-const auto color = toml::find<std::string>(data, "fruit", "physical", "color");
-const auto shape = toml::find<std::string>(data, "fruit", "physical", "shape");
-```
-
-### Finding a value in an array
-
-You can find n-th value in an array by `toml::find`.
-
-```toml
-values = ["foo", "bar", "baz"]
-```
-
-``` cpp
-const auto data   = toml::parse("sample.toml");
-const auto values = toml::find(data, "values");
-const auto bar    = toml::find<std::string>(values, 1);
-```
-
-`toml::find` can also search array recursively.
-
-```cpp
-const auto data = toml::parse("fruit.toml");
-const auto bar  = toml::find<std::string>(data, "values", 1);
-```
-
-Before calling `toml::find`, you can check if a value corresponding to a key
-exists. You can use both `bool toml::value::contains(const key&) const` and
-`std::size_t toml::value::count(const key&) const`. Those behaves like the
-`std::map::contains` and `std::map::count`.
-
-```cpp
-const auto data = toml::parse("fruit.toml");
-if(data.contains("fruit") && data.at("fruit").count("physical") != 0)
-{
-    // ...
-}
-```
-
-### In case of error
-
-If the value does not exist, `toml::find` throws `std::out_of_range` with the
-location of the table.
-
-```console
-terminate called after throwing an instance of 'std::out_of_range'
-  what():  [error] key "answer" not found
- --> example.toml
- 6 | [tab]
-   | ~~~~~ in this table
-```
-
-----
-
-If the specified type differs from the actual value contained, it throws
-`toml::type_error` that inherits `std::exception`.
-
-Similar to the case of syntax error, toml11 also displays clean error messages.
-The error message when you choose `int` to get `string` value would be like this.
-
-```console
-terminate called after throwing an instance of 'toml::type_error'
-  what():  [error] toml::value bad_cast to integer
- --> example.toml
- 3 | title = "TOML Example"
-   |         ~~~~~~~~~~~~~~ the actual type is string
-```
-
-**NOTE**: In order to show this kind of error message, all the toml values have
-a pointer to represent its range in a file. The entire contents of a file is
-shared by `toml::value`s and remains on the heap memory. It is recommended to
-destruct all the `toml::value` classes after configuring your application
-if you have a large TOML file compared to the memory resource.
-
-### Dotted keys
-
-TOML v0.5.0 has a new feature named "dotted keys".
-You can chain keys to represent the structure of the data.
-
-```toml
-physical.color = "orange"
-physical.shape = "round"
-```
-
-This is equivalent to the following.
-
-```toml
-[physical]
-color = "orange"
-shape = "round"
-```
-
-You can get both of the above tables with the same c++ code.
-
-```cpp
-const auto physical = toml::find(data, "physical");
-const auto color    = toml::find<std::string>(physical, "color");
-```
-
-The following code does not work for the above toml file.
-
-```cpp
-// XXX this does not work!
-const auto color = toml::find<std::string>(data, "physical.color");
-```
-
-The above code works with the following toml file.
-
-```toml
-"physical.color" = "orange"
-# equivalent to {"physical.color": "orange"},
-# NOT {"physical": {"color": "orange"}}.
-```
-
-
-## Casting a toml value
-
-### `toml::get`
-
-`toml::parse` returns `toml::value`. `toml::value` is a union type that can
-contain one of the following types.
-
-- `toml::boolean` (`bool`)
-- `toml::integer` (`std::int64_t`)
-- `toml::floating` (`double`)
-- `toml::string` (a type convertible to std::string)
-- `toml::local_date`
-- `toml::local_time`
-- `toml::local_datetime`
-- `toml::offset_datetime`
-- `toml::array` (by default, `std::vector<toml::value>`)
-  - It depends. See [customizing containers](#customizing-containers) for detail.
-- `toml::table` (by default, `std::unordered_map<toml::key, toml::value>`)
-  - It depends. See [customizing containers](#customizing-containers) for detail.
-
-To get a value inside, you can use `toml::get<T>()`. The usage is the same as
-`toml::find<T>` (actually, `toml::find` internally uses `toml::get` after casting
-a value to `toml::table`).
-
-``` cpp
-const toml::value  data    = toml::parse("sample.toml");
-const toml::value  answer_ = toml::get<toml::table >(data).at("answer");
-const std::int64_t answer  = toml::get<std::int64_t>(answer_);
-```
-
-When you pass an exact TOML type that does not require type conversion,
-`toml::get` returns a reference through which you can modify the content
-(if the `toml::value` is `const`, it returns `const` reference).
-
-```cpp
-toml::value   data    = toml::parse("sample.toml");
-toml::value   answer_ = toml::get<toml::table >(data).at("answer");
-toml::integer& answer = toml::get<toml::integer>(answer_);
-answer = 6 * 9; // write to data.answer. now `answer_` contains 54.
-```
-
-If the specified type requires conversion, you can't take a reference to the value.
-See also [underlying types](#underlying-types).
-
-It also throws a `toml::type_error` if the type differs.
-
-### `as_xxx`
-
-You can also use a member function to cast a value.
-
-```cpp
-const std::int64_t answer = data.as_table().at("answer").as_integer();
-```
-
-It also throws a `toml::type_error` if the type differs. If you are sure that
-the value `v` contains a value of the specified type, you can suppress checking
-by passing `std::nothrow`.
-
-```cpp
-const auto& answer = data.as_table().at("answer");
-if(answer.is_integer() && answer.as_integer(std::nothrow) == 42)
-{
-    std::cout << "value is 42" << std::endl;
-}
-```
-
-If `std::nothrow` is passed, the functions are marked as noexcept.
-
-By casting a `toml::value` into an array or a table, you can iterate over the
-elements.
-
-```cpp
-const auto data = toml::parse("example.toml");
-std::cout << "keys in the top-level table are the following: \n";
-for(const auto& [k, v] : data.as_table())
-{
-    std::cout << k << '\n';
-}
-
-const auto& fruits = toml::find(data, "fruits");
-for(const auto& v : fruits.as_array())
-{
-    std::cout << toml::find<std::string>(v, "name") << '\n';
-}
-```
-
-The full list of the functions is below.
-
-```cpp
-namespace toml {
-class value {
-    // ...
-    const boolean&         as_boolean()         const&;
-    const integer&         as_integer()         const&;
-    const floating&        as_floating()        const&;
-    const string&          as_string()          const&;
-    const offset_datetime& as_offset_datetime() const&;
-    const local_datetime&  as_local_datetime()  const&;
-    const local_date&      as_local_date()      const&;
-    const local_time&      as_local_time()      const&;
-    const array&           as_array()           const&;
-    const table&           as_table()           const&;
-    // --------------------------------------------------------
-    // non-const version
-    boolean&               as_boolean()         &;
-    // ditto...
-    // --------------------------------------------------------
-    // rvalue version
-    boolean&&              as_boolean()         &&;
-    // ditto...
-
-    // --------------------------------------------------------
-    // noexcept versions ...
-    const boolean&         as_boolean(const std::nothrow_t&) const& noexcept;
-    boolean&               as_boolean(const std::nothrow_t&) &      noexcept;
-    boolean&&              as_boolean(const std::nothrow_t&) &&     noexcept;
-    // ditto...
-};
-} // toml
-```
-
-### `at()`
-
-You can access to the element of a table and an array by `toml::basic_value::at`.
-
-```cpp
-const toml::value v{1,2,3,4,5};
-std::cout << v.at(2).as_integer() << std::endl; // 3
-
-const toml::value v{{"foo", 42}, {"bar", 3.14}};
-std::cout << v.at("foo").as_integer() << std::endl; // 42
-```
-
-If an invalid key (integer for a table, string for an array), it throws
-`toml::type_error` for the conversion. If the provided key is out-of-range,
-it throws `std::out_of_range`.
-
-Note that, although `std::string` has `at()` member function, `toml::value::at`
-throws if the contained type is a string. Because `std::string` does not
-contain `toml::value`.
-
-### `operator[]`
-
-You can also access to the element of a table and an array by
-`toml::basic_value::operator[]`.
-
-```cpp
-const toml::value v{1,2,3,4,5};
-std::cout << v[2].as_integer() << std::endl; // 3
-
-const toml::value v{{"foo", 42}, {"bar", 3.14}};
-std::cout << v["foo"].as_integer() << std::endl; // 42
-```
-
-When you access to a `toml::value` that is not initialized yet via
-`operator[](const std::string&)`, the `toml::value` will be a table,
-just like the `std::map`.
-
-```cpp
-toml::value v; // not initialized as a table.
-v["foo"] = 42; // OK. `v` will be a table.
-```
-
-Contrary, if you access to a `toml::value` that contains an array via `operator[]`,
-it does not check anything. It converts `toml::value` without type check and then
-access to the n-th element without boundary check, just like the `std::vector::operator[]`.
-
-```cpp
-toml::value v; // not initialized as an array
-v[2] = 42;     // error! UB
-```
-
-Please make sure that the `toml::value` has an array inside when you access to
-its element via `operator[]`.
-
-## Checking value type
-
-You can check the type of a value by `is_xxx` function.
-
-```cpp
-const toml::value v = /* ... */;
-if(v.is_integer())
-{
-    std::cout << "value is an integer" << std::endl;
-}
-```
-
-The complete list of the functions is below.
-
-```cpp
-namespace toml {
-class value {
-    // ...
-    bool is_boolean()         const noexcept;
-    bool is_integer()         const noexcept;
-    bool is_floating()        const noexcept;
-    bool is_string()          const noexcept;
-    bool is_offset_datetime() const noexcept;
-    bool is_local_datetime()  const noexcept;
-    bool is_local_date()      const noexcept;
-    bool is_local_time()      const noexcept;
-    bool is_array()           const noexcept;
-    bool is_table()           const noexcept;
-    bool is_uninitialized()   const noexcept;
-    // ...
-};
-} // toml
-```
-
-Also, you can get `enum class value_t` from `toml::value::type()`.
-
-```cpp
-switch(data.at("something").type())
-{
-    case toml::value_t::integer:  /*do some stuff*/ ; break;
-    case toml::value_t::floating: /*do some stuff*/ ; break;
-    case toml::value_t::string :  /*do some stuff*/ ; break;
-    default : throw std::runtime_error(
-        "unexpected type : " + toml::stringize(data.at("something").type()));
-}
-```
-
-The complete list of the `enum`s can be found in the section
-[underlying types](#underlying-types).
-
-The `enum`s can be used as a parameter of `toml::value::is` function like the following.
-
-```cpp
-toml::value v = /* ... */;
-if(v.is(toml::value_t::boolean)) // ...
-```
-
-## More about conversion
-
-Since `toml::find` internally uses `toml::get`, all the following examples work
-with both `toml::get` and `toml::find`.
-
-### Converting an array
-
-You can get any kind of `container` class from a `toml::array`
-except for `map`-like classes.
-
-``` cpp
-// # sample.toml
-// numbers = [1,2,3]
-
-const auto numbers = toml::find(data, "numbers");
-
-const auto vc  = toml::get<std::vector<int>  >(numbers);
-const auto ls  = toml::get<std::list<int>    >(numbers);
-const auto dq  = toml::get<std::deque<int>   >(numbers);
-const auto ar  = toml::get<std::array<int, 3>>(numbers);
-// if the size of data.at("numbers") is larger than that of std::array,
-// it will throw toml::type_error because std::array is not resizable.
-```
-
-Surprisingly, you can convert `toml::array` into `std::pair` and `std::tuple`.
-
-```cpp
-// numbers = [1,2,3]
-const auto tp = toml::get<std::tuple<short, int, unsigned int>>(numbers);
-```
-
-This functionality is helpful when you have a toml file like the following.
-
-```toml
-array_of_arrays = [[1, 2, 3], ["foo", "bar", "baz"]] # toml allows this
-```
-
-What is the corresponding C++ type?
-Obviously, it is a `std::pair` of `std::vector`s.
-
-```cpp
-const auto array_of_arrays = toml::find(data, "array_of_arrays");
-const auto aofa = toml::get<
-    std::pair<std::vector<int>, std::vector<std::string>>
-    >(array_of_arrays);
-```
-
-If you don't know the type of the elements, you can use `toml::array`,
-which is a `std::vector` of `toml::value`, instead.
-
-```cpp
-const auto a_of_a = toml::get<toml::array>(array_of_arrays);
-const auto first  = toml::get<std::vector<int>>(a_of_a.at(0));
-```
-
-You can change the implementation of `toml::array` with `std::deque` or some
-other array-like container. See [Customizing containers](#customizing-containers)
-for detail.
-
-### Converting a table
-
-When all the values of the table have the same type, toml11 allows you to
-convert a `toml::table` to a `map` that contains the convertible type.
-
-```toml
-[tab]
-key1 = "foo" # all the values are
-key2 = "bar" # toml String
-```
-
-```cpp
-const auto data = toml::parse("sample.toml");
-const auto tab = toml::find<std::map<std::string, std::string>>(data, "tab");
-std::cout << tab["key1"] << std::endl; // foo
-std::cout << tab["key2"] << std::endl; // bar
-```
-
-But since `toml::table` is just an alias of `std::unordered_map<toml::key, toml::value>`,
-normally you don't need to convert it because it has all the functionalities that
-`std::unordered_map` has (e.g. `operator[]`, `count`, and `find`). In most cases
-`toml::table` is sufficient.
-
-```cpp
-toml::table tab = toml::get<toml::table>(data);
-if(data.count("title") != 0)
-{
-    data["title"] = std::string("TOML example");
-}
-```
-
-You can change the implementation of `toml::table` with `std::map` or some
-other map-like container. See [Customizing containers](#customizing-containers)
-for detail.
-
-### Getting an array of tables
-
-An array of tables is just an array of tables.
-You can get it in completely the same way as the other arrays and tables.
-
-```toml
-# sample.toml
-array_of_inline_tables = [{key = "value1"}, {key = "value2"}, {key = "value3"}]
-
-[[array_of_tables]]
-key = "value4"
-[[array_of_tables]]
-key = "value5"
-[[array_of_tables]]
-key = "value6"
-```
-
-```cpp
-const auto data = toml::parse("sample.toml");
-const auto aot1 = toml::find<std::vector<toml::table>>(data, "array_of_inline_tables");
-const auto aot2 = toml::find<std::vector<toml::table>>(data, "array_of_tables");
-```
-
-### Cost of conversion
-
-Although conversion through `toml::(get|find)` is convenient, it has additional
-copy-cost because it copies data contained in `toml::value` to the
-user-specified type. Of course in some cases this overhead is not ignorable.
-
-```cpp
-// the following code constructs a std::vector.
-// it requires heap allocation for vector and element conversion.
-const auto array = toml::find<std::vector<int>>(data, "foo");
-```
-
-By passing the exact types, `toml::get` returns reference that has no overhead.
-
-``` cpp
-const auto& tab     = toml::find<toml::table>(data, "tab");
-const auto& numbers = toml::find<toml::array>(data, "numbers");
-```
-
-Also, `as_xxx` are zero-overhead because they always return a reference.
-
-``` cpp
-const auto& tab     = toml::find(data, "tab"    ).as_table();
-const auto& numbers = toml::find(data, "numbers").as_array();
-```
-
-In this case you need to call `toml::get` each time you access to
-the element of `toml::array` because `toml::array` is an array of `toml::value`.
-
-```cpp
-const auto& num0 = toml::get<toml::integer>(numbers.at(0));
-const auto& num1 = toml::get<toml::integer>(numbers.at(1));
-const auto& num2 = toml::get<toml::integer>(numbers.at(2));
-```
-
-### Converting datetime and its variants
-
-TOML v0.5.0 has 4 different datetime objects, `local_date`, `local_time`,
-`local_datetime`, and `offset_datetime`.
-
-Since `local_date`, `local_datetime`, and `offset_datetime` represent a time
-point, you can convert them to `std::chrono::system_clock::time_point`.
-
-Contrary, `local_time` does not represents a time point because they lack a
-date information, but it can be converted to `std::chrono::duration` that
-represents a duration from the beginning of the day, `00:00:00.000`.
-
-```toml
-# sample.toml
-date = 2018-12-23
-time = 12:30:00
-l_dt = 2018-12-23T12:30:00
-o_dt = 2018-12-23T12:30:00+09:30
-```
-
-```cpp
-const auto data = toml::parse("sample.toml");
-
-const auto date = toml::get<std::chrono::system_clock::time_point>(data.at("date"));
-const auto l_dt = toml::get<std::chrono::system_clock::time_point>(data.at("l_dt"));
-const auto o_dt = toml::get<std::chrono::system_clock::time_point>(data.at("o_dt"));
-
-const auto time = toml::get<std::chrono::minutes>(data.at("time")); // 12 * 60 + 30 min
-```
-
-`local_date` and `local_datetime` are assumed to be in the local timezone when
-they are converted into `time_point`. On the other hand, `offset_datetime` only
-uses the offset part of the data and it does not take local timezone into account.
-
-To contain datetime data, toml11 defines its own datetime types.
-For more detail, you can see the definitions in [toml/datetime.hpp](toml/datetime.hpp).
-
-## Getting with a fallback
-
-`toml::find_or` returns a default value if the value is not found or has a
-different type.
-
-```cpp
-const auto data = toml::parse("example.toml");
-const auto num  = toml::find_or(data, "num", 42);
-```
-
-It works recursively if you pass several keys for subtables.
-In that case, the last argument is considered to be the optional value.
-All other arguments between `toml::value` and the optinoal value are considered as keys.
-
-```cpp
-// [fruit.physical]
-// color = "red"
-auto data  = toml::parse("fruit.toml");
-auto color = toml::find_or(data, "fruit", "physical", "color", "red");
-//                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^  ^^^^^
-//                               arguments                     optional value
-```
-
-Also, `toml::get_or` returns a default value if `toml::get<T>` failed.
-
-```cpp
-toml::value v("foo"); // v contains String
-const int value = toml::get_or(v, 42); // conversion fails. it returns 42.
-```
-
-These functions automatically deduce what type you want to get
-from the default value you passed.
-
-To get a reference through this function, take care about the default value.
-
-```cpp
-toml::value v("foo"); // v contains String
-toml::integer& i = toml::get_or(v, 42); // does not work because binding `42`
-                                        // to `integer&` is invalid
-toml::integer opt = 42;
-toml::integer& i = toml::get_or(v, opt); // this works.
-```
-
-## Expecting conversion
-
-By using `toml::expect`, you will get your expected value or an error message
-without throwing `toml::type_error`.
-
-```cpp
-const auto value = toml::expect<std::string>(data.at("title"));
-if(value.is_ok()) {
-    std::cout << value.unwrap() << std::endl;
-} else {
-    std::cout << value.unwrap_err() << std::endl;
-}
-```
-
-Also, you can pass a function object to modify the expected value.
-
-```cpp
-const auto value = toml::expect<int>(data.at("number"))
-    .map(// function that receives expected type (here, int)
-    [](const int number) -> double {
-        return number * 1.5 + 1.0;
-    }).unwrap_or(/*default value =*/ 3.14);
-```
-
-## Visiting a toml::value
-
-toml11 provides `toml::visit` to apply a function to `toml::value` in the
-same way as `std::variant`.
-
-```cpp
-const toml::value v(3.14);
-toml::visit([](const auto& val) -> void {
-        std::cout << val << std::endl;
-    }, v);
-```
-
-The function object that would be passed to `toml::visit` must be able to
-receive all the possible TOML types. Also, the result types should be the same
-each other.
-
-## Constructing a toml::value
-
-`toml::value` can be constructed in various ways.
-
-```cpp
-toml::value v(true);     // boolean
-toml::value v(42);       // integer
-toml::value v(3.14);     // floating
-toml::value v("foobar"); // string
-toml::value v(toml::local_date(2019, toml::month_t::Apr, 1)); // date
-toml::value v{1, 2, 3, 4, 5};                                 // array
-toml::value v{{"foo", 42}, {"bar", 3.14}, {"baz", "qux"}};    // table
-```
-
-When constructing a string, you can choose to use either literal or basic string.
-By default, it will be a basic string.
-
-```cpp
-toml::value v("foobar", toml::string_t::basic  );
-toml::value v("foobar", toml::string_t::literal);
-```
-
-Datetime objects can be constructed from `std::tm` and
-`std::chrono::system_clock::time_point`. But you need to specify what type
-you use to avoid ambiguity.
-
-```cpp
-const auto now = std::chrono::system_clock::now();
-toml::value v(toml::local_date(now));
-toml::value v(toml::local_datetime(now));
-toml::value v(toml::offset_datetime(now));
-```
-
-Since local time is not equivalent to a time point, because it lacks date
-information, it will be constructed from `std::chrono::duration`.
-
-```cpp
-toml::value v(toml::local_time(std::chrono::hours(10)));
-```
-
-You can construct an array object not only from `initializer_list`, but also
-from STL containers. In that case, the element type must be convertible to
-`toml::value`.
-
-```cpp
-std::vector<int> vec{1,2,3,4,5};
-toml::value v(vec);
-```
-
-When you construct an array value, all the elements of `initializer_list`
-must be convertible into `toml::value`.
-
-If a `toml::value` has an array, you can `push_back` an element in it.
-
-```cpp
-toml::value v{1,2,3,4,5};
-v.push_back(6);
-```
-
-`emplace_back` also works.
-
-## Preserving comments
-
-toml11 v3 or later allows you yo choose whether comments are preserved or not via template parameter
-
-```cpp
-const auto data1 = toml::parse<toml::discard_comments >("example.toml");
-const auto data2 = toml::parse<toml::preserve_comments>("example.toml");
-```
-
-or macro definition.
-
-```cpp
-#define TOML11_PRESERVE_COMMENTS_BY_DEFAULT
-#include <toml11/toml.hpp>
-```
-
-This feature is controlled by template parameter in `toml::basic_value<...>`.
-`toml::value` is an alias of `toml::basic_value<...>`.
-
-If template parameter is explicitly specified, the return value of `toml::parse`
-will be `toml::basic_value<toml::preserve_comments>`.
-If the macro is defined, the alias `toml::value` will be
-`toml::basic_value<toml::preserve_comments>`.
-
-Comments related to a value can be obtained by `toml::value::comments()`.
-The return value has the same interface as `std::vector<std::string>`.
-
-```cpp
-const auto& com = v.comments();
-for(const auto& c : com)
-{
-    std::cout << c << std::endl;
-}
-```
-
-Comments just before and just after (within the same line) a value are kept in a value.
-
-```toml
-# this is a comment for v1.
-v1 = "foo"
-
-v2 = "bar" # this is a comment for v2.
-# Note that this comment is NOT a comment for v2.
-
-# this comment is not related to any value
-# because there are empty lines between v3.
-# this comment will be ignored even if you set `preserve_comments`.
-
-# this is a comment for v3
-# this is also a comment for v3.
-v3 = "baz" # ditto.
-```
-
-Each comment line becomes one element of a `std::vector`.
-
-Hash signs will be removed, but spaces after hash sign will not be removed.
-
-```cpp
-v1.comments().at(0) == " this is a comment for v1."s;
-
-v2.comments().at(1) == " this is a comment for v1."s;
-
-v3.comments().at(0) == " this is a comment for v3."s;
-v3.comments().at(1) == " this is also a comment for v3."s;
-v3.comments().at(2) == " ditto."s;
-```
-
-Note that a comment just after an opening brace of an array will not be a
-comment for the array.
-
-```toml
-# this is a comment for a.
-a = [ # this is not a comment for a. this will be ignored.
-  1, 2, 3,
-  # this is a comment for `42`.
-  42, # this is also a comment for `42`.
-  5
-] # this is a comment for a.
-```
-
-You can also append and modify comments.
-The interfaces are the same as `std::vector<std::string>`.
-
-```cpp
-toml::basic_value<toml::preserve_comments> v(42);
-v.comments().push_back(" add this comment.");
-// # add this comment.
-// i = 42
-```
-
-Also, you can pass a `std::vector<std::string>` when constructing a
-`toml::basic_value<toml::preserve_comments>`.
-
-```cpp
-std::vector<std::string> comments{"comment 1", "comment 2"};
-const toml::basic_value<toml::preserve_comments> v1(42, std::move(comments));
-const toml::basic_value<toml::preserve_comments> v2(42, {"comment 1", "comment 2"});
-```
-
-When `toml::discard_comments` is chosen, comments will not be contained in a value.
-`value::comments()` will always be kept empty.
-All the modification on comments would be ignored.
-All the element access in a `discard_comments` causes the same error as accessing
-an element of an empty `std::vector`.
-
-The comments will also be serialized. If comments exist, those comments will be
-added just before the values.
-
-__NOTE__: Result types from `toml::parse(...)` and
-`toml::parse<toml::preserve_comments>(...)` are different.
-
-## Customizing containers
-
-Actually, `toml::basic_value` has 3 template arguments.
-
-```cpp
-template<typename Comment, // discard/preserve_comment
-         template<typename ...> class Table = std::unordered_map,
-         template<typename ...> class Array = std::vector>
-class basic_value;
-```
-
-This enables you to change the containers used inside. E.g. you can use
-`std::map` to contain a table object instead of `std::unordered_map`.
-And also can use `std::deque` as a array object instead of `std::vector`.
-
-You can set these parameters while calling `toml::parse` function.
-
-```cpp
-const auto data = toml::parse<
-    toml::preserve_comments, std::map, std::deque
-    >("example.toml");
-```
-
-Needless to say, the result types from `toml::parse(...)` and
-`toml::parse<Com, Map, Cont>(...)` are different (unless you specify the same
-types as default).
-
-Note that, since `toml::table` and `toml::array` is an alias for a table and an
-array of a default `toml::value`, so it is different from the types actually
-contained in a `toml::basic_value` when you customize containers.
-To get the actual type in a generic way, use
-`typename toml::basic_type<C, T, A>::table_type` and
-`typename toml::basic_type<C, T, A>::array_type`.
-
-## TOML literal
-
-toml11 supports `"..."_toml` literal.
-It accept both a bare value and a file content.
-
-```cpp
-using namespace toml::literals::toml_literals;
-
-// `_toml` can convert a bare value without key
-const toml::value v = u8"0xDEADBEEF"_toml;
-// v is an Integer value containing 0xDEADBEEF.
-
-// raw string literal (`R"(...)"` is useful for this purpose)
-const toml::value t = u8R"(
-    title = "this is TOML literal"
-    [table]
-    key = "value"
-)"_toml;
-// the literal will be parsed and the result will be contained in t
-```
-
-The literal function is defined in the same way as the standard library literals
-such as `std::literals::string_literals::operator""s`.
-
-```cpp
-namespace toml
-{
-inline namespace literals
-{
-inline namespace toml_literals
-{
-toml::value operator"" _toml(const char* str, std::size_t len);
-} // toml_literals
-} // literals
-} // toml
-```
-
-Access to the operator can be gained with `using namespace toml::literals;`,
-`using namespace toml::toml_literals`, and `using namespace toml::literals::toml_literals`.
-
-Note that a key that is composed only of digits is allowed in TOML.
-And, unlike the file parser, toml-literal allows a bare value without a key.
-Thus it is difficult to distinguish arrays having integers and definitions of
-tables that are named as digits.
-Currently, literal `[1]` becomes a table named "1".
-To ensure a literal to be considered as an array with one element, you need to
-add a comma after the first element (like `[1,]`).
-
-```cpp
-"[1,2,3]"_toml;   // This is an array
-"[table]"_toml;   // This is a table that has an empty table named "table" inside.
-"[[1,2,3]]"_toml; // This is an array of arrays
-"[[table]]"_toml; // This is a table that has an array of tables inside.
-
-"[[1]]"_toml;     // This literal is ambiguous.
-                  // Currently, it becomes a table that has array of table "1".
-"1 = [{}]"_toml;  // This is a table that has an array of table named 1.
-"[[1,]]"_toml;    // This is an array of arrays.
-"[[1],]"_toml;    // ditto.
-```
-
-NOTE: `_toml` literal returns a `toml::value`  that does not have comments.
-
-## Conversion between toml value and arbitrary types
-
-You can also use `toml::get` and other related functions with the types
-you defined after you implement a way to convert it.
-
-```cpp
-namespace ext
-{
-struct foo
-{
-    int         a;
-    double      b;
-    std::string c;
-};
-} // ext
-
-const auto data = toml::parse("example.toml");
-
-// to do this
-const foo f = toml::find<ext::foo>(data, "foo");
-```
-
-There are 3 ways to use `toml::get` with the types that you defined.
-
-The first one is to implement `from_toml(const toml::value&)` member function.
-
-```cpp
-namespace ext
-{
-struct foo
-{
-    int         a;
-    double      b;
-    std::string c;
-
-    void from_toml(const toml::value& v)
-    {
-        this->a = toml::find<int        >(v, "a");
-        this->b = toml::find<double     >(v, "b");
-        this->c = toml::find<std::string>(v, "c");
-        return;
-    }
-};
-} // ext
-```
-
-In this way, because `toml::get` first constructs `foo` without arguments,
-the type should be default-constructible.
-
-The second is to implement `constructor(const toml::value&)`.
-
-```cpp
-namespace ext
-{
-struct foo
-{
-    explicit foo(const toml::value& v)
-        : a(toml::find<int>(v, "a")), b(toml::find<double>(v, "b")),
-          c(toml::find<std::string>(v, "c"))
-    {}
-
-    int         a;
-    double      b;
-    std::string c;
-};
-} // ext
-```
-
-Note that implicit default constructor declaration will be suppressed
-when a constructor is defined. If you want to use the struct (here, `foo`)
-in a container (e.g. `std::vector<foo>`), you may need to define default
-constructor explicitly.
-
-The third is to implement specialization of `toml::from` for your type.
-
-```cpp
-namespace ext
-{
-struct foo
-{
-    int         a;
-    double      b;
-    std::string c;
-};
-} // ext
-
-namespace toml
-{
-template<>
-struct from<ext::foo>
-{
-    static ext::foo from_toml(const value& v)
-    {
-        ext::foo f;
-        f.a = find<int        >(v, "a");
-        f.b = find<double     >(v, "b");
-        f.c = find<std::string>(v, "c");
-        return f;
-    }
-};
-} // toml
-```
-
-In this way, since the conversion function is defined outside of the class,
-you can add conversion between `toml::value` and classes defined in another library.
-
-In some cases, a class has a templatized constructor that takes a template, `T`.
-It confuses `toml::get/find<T>` because it makes the class "constructible" from
-`toml::value`. To avoid this problem, `toml::from` and `from_toml` always
-precede constructor. It makes easier to implement conversion between
-`toml::value` and types defined in other libraries because it skips constructor.
-
-But, importantly, you cannot define `toml::from<T>` and `T.from_toml` at the same
-time because it causes ambiguity in the overload resolution of `toml::get<T>` and `toml::find<T>`.
-
-So the precedence is `toml::from<T>` == `T.from_toml()` > `T(toml::value)`.
-
-If you want to convert any versions of `toml::basic_value`,
-you need to templatize the conversion function as follows.
-
-```cpp
-struct foo
-{
-    template<typename C, template<typename ...> class M, template<typename ...> class A>
-    void from_toml(const toml::basic_value<C, M, A>& v)
-    {
-        this->a = toml::find<int        >(v, "a");
-        this->b = toml::find<double     >(v, "b");
-        this->c = toml::find<std::string>(v, "c");
-        return;
-    }
-};
-// or
-namespace toml
-{
-template<>
-struct from<ext::foo>
-{
-    template<typename C, template<typename ...> class M, template<typename ...> class A>
-    static ext::foo from_toml(const basic_value<C, M, A>& v)
-    {
-        ext::foo f;
-        f.a = find<int        >(v, "a");
-        f.b = find<double     >(v, "b");
-        f.c = find<std::string>(v, "c");
-        return f;
-    }
-};
-} // toml
-```
-
-----
-
-The opposite direction is also supported in a similar way. You can directly
-pass your type to `toml::value`'s constructor by introducing `into_toml` or
-`toml::into<T>`.
-
-```cpp
-namespace ext
-{
-struct foo
-{
-    int         a;
-    double      b;
-    std::string c;
-
-    toml::value into_toml() const // you need to mark it const.
-    {
-        return toml::value{{"a", this->a}, {"b", this->b}, {"c", this->c}};
-    }
-};
-} // ext
-
-ext::foo    f{42, 3.14, "foobar"};
-toml::value v(f);
-```
-
-The definition of `toml::into<T>` is similar to `toml::from<T>`.
-
-```cpp
-namespace ext
-{
-struct foo
-{
-    int         a;
-    double      b;
-    std::string c;
-};
-} // ext
-
-namespace toml
-{
-template<>
-struct into<ext::foo>
-{
-    static toml::value into_toml(const ext::foo& f)
-    {
-        return toml::value{{"a", f.a}, {"b", f.b}, {"c", f.c}};
-    }
-};
-} // toml
-
-ext::foo    f{42, 3.14, "foobar"};
-toml::value v(f);
-```
-
-Any type that can be converted to `toml::value`, e.g. `int`, `toml::table` and
-`toml::array` are okay to return from `into_toml`.
-
-You can also return a custom `toml::basic_value` from `toml::into`.
-
-```cpp
-namespace toml
-{
-template<>
-struct into<ext::foo>
-{
-    static toml::basic_value<toml::preserve_comments> into_toml(const ext::foo& f)
-    {
-        toml::basic_value<toml::preserve_comments> v{{"a", f.a}, {"b", f.b}, {"c", f.c}};
-        v.comments().push_back(" comment");
-        return v;
-    }
-};
-} // toml
-```
-
-But note that, if this `basic_value` would be assigned into other `toml::value`
-that discards `comments`, the comments would be dropped.
-
-### Macro to automatically define conversion functions
-
-There is a helper macro that automatically generates conversion functions `from` and `into` for a simple struct.
-
-```cpp
-namespace foo
-{
-struct Foo
-{
-    std::string s;
-    double      d;
-    int         i;
-};
-} // foo
-
-TOML11_DEFINE_CONVERSION_NON_INTRUSIVE(foo::Foo, s, d, i)
-
-int main()
-{
-    const auto file = toml::parse("example.toml");
-    auto f = toml::find<foo::Foo>(file, "foo");
-}
-```
-
-And then you can use `toml::find<foo::Foo>(file, "foo");`
-
-**Note** that, because of a slight difference in implementation of preprocessor between gcc/clang and MSVC, [you need to define `/Zc:preprocessor`](https://github.com/ToruNiina/toml11/issues/139#issuecomment-803683682) to use it in MSVC (Thank you @glebm !).
-
-## Formatting user-defined error messages
-
-When you encounter an error after you read the toml value, you may want to
-show the error with the value.
-
-toml11 provides you a function that formats user-defined error message with
-related values. With a code like the following,
-
-```cpp
-const auto value = toml::find<int>(data, "num");
-if(value < 0)
-{
-    std::cerr << toml::format_error("[error] value should be positive",
-                                    data.at("num"), "positive number required")
-              << std::endl;
-}
-```
-
-you will get an error message like this.
-
-```console
-[error] value should be positive
- --> example.toml
- 3 | num = -42
-   |       ~~~ positive number required
-```
-
-When you pass two values to `toml::format_error`,
-
-```cpp
-const auto min = toml::find<int>(range, "min");
-const auto max = toml::find<int>(range, "max");
-if(max < min)
-{
-    std::cerr << toml::format_error("[error] max should be larger than min",
-                                    data.at("min"), "minimum number here",
-                                    data.at("max"), "maximum number here");
-              << std::endl;
-}
-```
-
-you will get an error message like this.
-
-```console
-[error] max should be larger than min
- --> example.toml
- 3 | min = 54
-   |       ~~ minimum number here
- ...
- 4 | max = 42
-   |       ~~ maximum number here
-```
-
-You can print hints at the end of the message.
-
-```cpp
-std::vector<std::string> hints;
-hints.push_back("positive number means n >= 0.");
-hints.push_back("negative number is not positive.");
-std::cerr << toml::format_error("[error] value should be positive",
-                                data.at("num"), "positive number required", hints)
-          << std::endl;
-```
-
-```console
-[error] value should be positive
- --> example.toml
- 2 | num = 42
-   |       ~~ positive number required
-   |
-Hint: positive number means n >= 0.
-Hint: negative number is not positive.
-```
-
-## Obtaining location information
-
-You can also format error messages in your own way by using `source_location`.
-
-```cpp
-struct source_location
-{
-    std::uint_least32_t line()      const noexcept;
-    std::uint_least32_t column()    const noexcept;
-    std::uint_least32_t region()    const noexcept;
-    std::string const&  file_name() const noexcept;
-    std::string const&  line_str()  const noexcept;
-};
-// +-- line()       +--- length of the region (here, region() == 9)
-// v            .---+---.
-// 12 | value = "foo bar" <- line_str() returns the line itself.
-//              ^-------- column() points here
-```
-
-You can get this by
-```cpp
-const toml::value           v   = /*...*/;
-const toml::source_location loc = v.location();
-```
-
-## Exceptions
-
-The following `exception` classes inherits `toml::exception` that inherits
-`std::exception`.
-
-```cpp
-namespace toml {
-struct exception      : public std::exception  {/**/};
-struct syntax_error   : public toml::exception {/**/};
-struct type_error     : public toml::exception {/**/};
-struct internal_error : public toml::exception {/**/};
-} // toml
-```
-
-`toml::exception` has `toml::exception::location()` member function that returns
-`toml::source_location`, in addition to `what()`.
-
-```cpp
-namespace toml {
-struct exception : public std::exception
-{
-    // ...
-    source_location const& location() const noexcept;
-};
-} // toml
-```
-
-It represents where the error occurs.
-
-`syntax_error` will be thrown from `toml::parse` and `_toml` literal.
-`type_error` will be thrown from `toml::get/find`, `toml::value::as_xxx()`, and
-other functions that takes a content inside of `toml::value`.
-
-Note that, currently, from `toml::value::at()` and `toml::find(value, key)`
-may throw an `std::out_of_range` that does not inherits `toml::exception`.
-
-Also, in some cases, most likely in the file open error, it will throw an
-`std::runtime_error`.
-
-## Colorize Error Messages
-
-By defining `TOML11_COLORIZE_ERROR_MESSAGE`, the error messages from
-`toml::parse` and `toml::find|get` will be colorized. By default, this feature
-is turned off.
-
-With the following toml file taken from `toml-lang/toml/tests/hard_example.toml`,
-
-```toml
-[error]
-array = [
-         "This might most likely happen in multiline arrays",
-         Like here,
-         "or here,
-         and here"
-        ]     End of array comment, forgot the #
-```
-
-the error message would be like this.
-
-![error-message-1](https://github.com/ToruNiina/toml11/blob/misc/misc/toml11-err-msg-1.png)
-
-With the following,
-
-```toml
-[error]
-# array = [
-#          "This might most likely happen in multiline arrays",
-#          Like here,
-#          "or here,
-#          and here"
-#         ]     End of array comment, forgot the #
-number = 3.14  pi <--again forgot the #
-```
-
-the error message would be like this.
-
-![error-message-2](https://github.com/ToruNiina/toml11/blob/misc/misc/toml11-err-msg-2.png)
-
-The message would be messy when it is written to a file, not a terminal because
-it uses [ANSI escape code](https://en.wikipedia.org/wiki/ANSI_escape_code).
-
-Without `TOML11_COLORIZE_ERROR_MESSAGE`, you can still colorize user-defined
-error message by passing `true` to the `toml::format_error` function.
-If you define `TOML11_COLORIZE_ERROR_MESSAGE`, the value is `true` by default.
-If not, the default value would be `false`.
-
-```cpp
-std::cerr << toml::format_error("[error] value should be positive",
-                                data.at("num"), "positive number required",
-                                hints, /*colorize = */ true) << std::endl;
-```
-
-Note: It colorize `[error]` in red. That means that it detects `[error]` prefix
-at the front of the error message. If there is no `[error]` prefix,
-`format_error` adds it to the error message.
-
-## Serializing TOML data
-
-toml11 enables you to serialize data into toml format.
-
-```cpp
-const toml::value data{{"foo", 42}, {"bar", "baz"}};
-std::cout << data << std::endl;
-// bar = "baz"
-// foo = 42
-```
-
-toml11 automatically makes a small table and small array inline.
-You can specify the width to make them inline by `std::setw` for streams.
-
-```cpp
-const toml::value data{
-    {"qux",    {{"foo", 42}, {"bar", "baz"}}},
-    {"quux",   {"small", "array", "of", "strings"}},
-    {"foobar", {"this", "array", "of", "strings", "is", "too", "long",
-                "to", "print", "into", "single", "line", "isn't", "it?"}},
-};
-
-// the threshold becomes 80.
-std::cout << std::setw(80) << data << std::endl;
-// foobar = [
-// "this","array","of","strings","is","too","long","to","print","into",
-// "single","line","isn't","it?",
-// ]
-// quux = ["small","array","of","strings"]
-// qux = {bar="baz",foo=42}
-
-
-// the width is 0. nothing become inline.
-std::cout << std::setw(0) << data << std::endl;
-// foobar = [
-// "this",
-// ... (snip)
-// "it?",
-// ]
-// quux = [
-// "small",
-// "array",
-// "of",
-// "strings",
-// ]
-// [qux]
-// bar = "baz"
-// foo = 42
-```
-
-It is recommended to set width before printing data. Some I/O functions changes
-width to 0, and it makes all the stuff (including `toml::array`) multiline.
-The resulting files becomes too long.
-
-To control the precision of floating point numbers, you need to pass
-`std::setprecision` to stream.
-
-```cpp
-const toml::value data{
-    {"pi", 3.141592653589793},
-    {"e",  2.718281828459045}
-};
-std::cout << std::setprecision(17) << data << std::endl;
-// e = 2.7182818284590451
-// pi = 3.1415926535897931
-std::cout << std::setprecision( 7) << data << std::endl;
-// e = 2.718282
-// pi = 3.141593
-```
-
-There is another way to format toml values, `toml::format()`.
-It returns `std::string` that represents a value.
-
-```cpp
-const toml::value v{{"a", 42}};
-const std::string fmt = toml::format(v);
-// a = 42
-```
-
-Note that since `toml::format` formats a value, the resulting string may lack
-the key value.
-
-```cpp
-const toml::value v{3.14};
-const std::string fmt = toml::format(v);
-// 3.14
-```
-
-To control the width and precision, `toml::format` receives optional second and
-third arguments to set them. By default, the width is 80 and the precision is
-`std::numeric_limits<double>::max_digit10`.
-
-```cpp
-const auto serial = toml::format(data, /*width = */ 0, /*prec = */ 17);
-```
-
-When you pass a comment-preserving-value, the comment will also be serialized.
-An array or a table containing a value that has a comment would not be inlined.
-
-## Underlying types
-
-The toml types (can be used as `toml::*` in this library) and corresponding `enum` names are listed in the table below.
-
-| TOML type      | underlying c++ type                | enum class                       |
-| -------------- | ---------------------------------- | -------------------------------- |
-| Boolean        | `bool`                             | `toml::value_t::boolean`         |
-| Integer        | `std::int64_t`                     | `toml::value_t::integer`         |
-| Float          | `double`                           | `toml::value_t::floating`        |
-| String         | `toml::string`                     | `toml::value_t::string`          |
-| LocalDate      | `toml::local_date`                 | `toml::value_t::local_date`      |
-| LocalTime      | `toml::local_time`                 | `toml::value_t::local_time`      |
-| LocalDatetime  | `toml::local_datetime`             | `toml::value_t::local_datetime`  |
-| OffsetDatetime | `toml::offset_datetime`            | `toml::value_t::offset_datetime` |
-| Array          | `array-like<toml::value>`          | `toml::value_t::array`           |
-| Table          | `map-like<toml::key, toml::value>` | `toml::value_t::table`           |
-
-`array-like` and `map-like` are the STL containers that works like a `std::vector` and
-`std::unordered_map`, respectively. By default, `std::vector` and `std::unordered_map`
-are used. See [Customizing containers](#customizing-containers) for detail.
-
-`toml::string` is effectively the same as `std::string` but has an additional
-flag that represents a kind of a string, `string_t::basic` and `string_t::literal`.
-Although `std::string` is not an exact toml type, still you can get a reference
-that points to internal `std::string` by using `toml::get<std::string>()` for convenience.
-The most important difference between `std::string` and `toml::string` is that
-`toml::string` will be formatted as a TOML string when outputted with `ostream`.
-This feature is introduced to make it easy to write a custom serializer.
-
-`Datetime` variants are `struct` that are defined in this library.
-Because `std::chrono::system_clock::time_point` is a __time point__,
-not capable of representing a Local Time independent from a specific day.
-
-## Unreleased TOML features
-
-Since TOML v1.0.0-rc.1 has been released, those features are now activated by
-default. We no longer need to define `TOML11_USE_UNRELEASED_FEATURES`.
-
-- Leading zeroes in exponent parts of floats are permitted.
-  - e.g. `1.0e+01`, `5e+05`
-  - [toml-lang/toml/PR/656](https://github.com/toml-lang/toml/pull/656)
-- Allow raw tab characters in basic strings and multi-line basic strings.
-  - [toml-lang/toml/PR/627](https://github.com/toml-lang/toml/pull/627)
-- Allow heterogeneous arrays
-  - [toml-lang/toml/PR/676](https://github.com/toml-lang/toml/pull/676)
-
-## Note about heterogeneous arrays
-
-Although `toml::parse` allows heterogeneous arrays, constructor of `toml::value`
-does not. Here the reason is explained.
-
-```cpp
-// this won't be compiled
-toml::value v{
-    "foo", 3.14, 42, {1,2,3,4,5}, {{"key", "value"}}
-}
-```
-
-There is a workaround for this. By explicitly converting values into
-`toml::value`, you can initialize `toml::value` with a heterogeneous array.
-Also, you can first initialize a `toml::value` with an array and then
-`push_back` into it.
-
-```cpp
-// OK!
-toml::value v{
-    toml::value("foo"), toml::value(3.14), toml::value(42),
-    toml::value{1,2,3,4,5}, toml::value{{"key", "value"}}
-}
-
-// OK!
-toml::value v(toml::array{});
-v.push_back("foo");
-v.push_back(3.14);
-
-// OK!
-toml::array a;
-a.push_back("foo");
-a.push_back(3.14);
-toml::value v(std::move(a));
-```
-
-The reason why the first example is not allowed is the following.
-Let's assume that you are initializing a `toml::value` with a table.
-
-```cpp
-                    // # expecting TOML table.
-toml::value v{      // [v]
-    {"answer", 42}, // answer = 42
-    {"pi",   3.14}, // pi = 3.14
-    {"foo", "bar"}  // foo = "bar"
-};
-```
-
-This is indistinguishable from a (heterogeneous) TOML array definition.
-
-```toml
-v = [
-    ["answer", 42],
-    ["pi",   3.14],
-    ["foo", "bar"],
-]
-```
-
-This means that the above C++ code makes constructor's overload resolution
-ambiguous. So a constructor that allows both "table as an initializer-list" and
-"heterogeneous array as an initializer-list" cannot be implemented.
-
-Thus, although it is painful, we need to explicitly cast values into
-`toml::value` when you initialize heterogeneous array in a C++ code.
-
-```cpp
-toml::value v{
-    toml::value("foo"), toml::value(3.14), toml::value(42),
-    toml::value{1,2,3,4,5}, toml::value{{"key", "value"}}
-};
-```
-
-## Breaking Changes from v2
-
-Although toml11 is relatively new library (it's three years old now), it had
-some confusing and inconvenient user-interfaces because of historical reasons.
-
-Between v2 and v3, those interfaces are rearranged.
-
-- `toml::parse` now returns a `toml::value`, not `toml::table`.
-- `toml::value` is now an alias of `toml::basic_value<discard_comment, std::vector, std::unordered_map>`.
-  - See [Customizing containers](#customizing-containers) for detail.
-- The elements of `toml::value_t` are renamed as `snake_case`.
-  - See [Underlying types](#underlying-types) for detail.
-- Supports for the CamelCaseNames are dropped.
-  - See [Underlying types](#underlying-types) for detail.
-- `(is|as)_float` has been removed to make the function names consistent with others.
-  - Since `float` is a keyword, toml11 named a float type as `toml::floating`.
-  - Also a `value_t` corresponds to `toml::floating` is named `value_t::floating`.
-  - So `(is|as)_floating` is introduced and `is_float` has been removed.
-  - See [Casting a toml::value](#casting-a-tomlvalue) and [Checking value type](#checking-value-type) for detail.
-- An overload of `toml::find` for `toml::table` has been dropped. Use `toml::value` version instead.
-  - Because type conversion between a table and a value causes ambiguity while overload resolution
-  - Since `toml::parse` now returns a `toml::value`, this feature becomes less important.
-  - Also because `toml::table` is a normal STL container, implementing utility function is easy.
-  - See [Finding a toml::value](#finding-a-toml-value) for detail.
-- An overload of `operator<<` and `toml::format` for `toml::table`s are dropped.
-  - Use `toml::value` instead.
-  - See [Serializing TOML data](#serializing-toml-data) for detail.
-- Interface around comments.
-  - See [Preserving Comments](#preserving-comments) for detail.
-- An ancient `from_toml/into_toml` has been removed. Use arbitrary type conversion support.
-  - See [Conversion between toml value and arbitrary types](#conversion-between-toml-value-and-arbitrary-types) for detail.
-
-Such a big change will not happen in the coming years.
-
-## Running Tests
-
-After cloning this repository, run the following command (thank you @jwillikers
-for automating test set fetching!).
-
-```sh
-$ mkdir build
-$ cd build
-$ cmake .. -Dtoml11_BUILD_TEST=ON
-$ make
-$ make test
-```
-
-To run the language agnostic test suite, you need to compile
-`tests/check_toml_test.cpp` and pass it to the tester.
-
-## Contributors
-
-I appreciate the help of the contributors who introduced the great feature to this library.
-
-- Guillaume Fraux (@Luthaf)
-  - Windows support and CI on Appvayor
-  - Intel Compiler support
-- Quentin Khan (@xaxousis)
-  - Found & Fixed a bug around ODR
-  - Improved error messages for invalid keys to show the location where the parser fails
-- Petr Beneš (@wbenny)
-  - Fixed warnings on MSVC
-- Ivan Shynkarenka (@chronoxor)
-  - Fixed Visual Studio 2019 warnings
-- @khoitd1997
-  - Fixed warnings while type conversion
-- @KerstinKeller
-  - Added installation script to CMake
-- J.C. Moyer (@jcmoyer)
-  - Fixed an example code in the documentation
-- Jt Freeman (@blockparty-sh)
-  - Fixed feature test macro around `localtime_s`
-  - Suppress warnings in Debug mode
-- OGAWA Kenichi (@kenichiice)
-  - Suppress warnings on intel compiler
-- Jordan Williams (@jwillikers)
-  - Fixed clang range-loop-analysis warnings
-  - Fixed feature test macro to suppress -Wundef
-  - Use cache variables in CMakeLists.txt
-  - Automate test set fetching, update and refactor CMakeLists.txt
-- Scott McCaskill
-  - Parse 9 digits (nanoseconds) of fractional seconds in a `local_time`
-- Shu Wang (@halfelf)
-  - fix "Finding a value in an array" example in README
-- @maass-tv and @SeverinLeonhardt
-  - Fix MSVC warning C4866
-- OGAWA KenIchi (@kenichiice)
-  - Fix include path in README
-- Mohammed Alyousef (@MoAlyousef)
-  - Made testing optional in CMake
-- Ivan Shynkarenka (@chronoxor)
-  - Fix compilation error in `<filesystem>` with MinGW
-- Alex Merry (@amerry)
-  - Add missing include files
-- sneakypete81 (@sneakypete81)
-  - Fix typo in error message
-- Oliver Kahrmann (@founderio)
-  - Fix missing filename in error message if parsed file is empty
-- Karl Nilsson (@karl-nilsson)
-  - Fix many spelling errors
-- ohdarling88 (@ohdarling)
-  - Fix a bug in a constructor of serializer
-- estshorter (@estshorter)
-  - Fix MSVC warning C26478
-- Philip Top (@phlptp)
-  - Improve checking standard library feature availability check
-- Louis Marascio (@marascio)
-  - Fix free-nonheap-object warning
-
-
-## Licensing terms
-
-This product is licensed under the terms of the [MIT License](LICENSE).
-
-- Copyright (c) 2017-2021 Toru Niina
-
-All rights reserved.
diff --git a/src/toml11/toml.hpp b/src/toml11/toml.hpp
deleted file mode 100644
index f34cfcccaf3..00000000000
--- a/src/toml11/toml.hpp
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
- * The MIT License (MIT)
- *
- * Copyright (c) 2017 Toru Niina
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#ifndef TOML_FOR_MODERN_CPP
-#define TOML_FOR_MODERN_CPP
-
-#ifndef __cplusplus
-#    error "__cplusplus is not defined"
-#endif
-
-#if __cplusplus < 201103L && _MSC_VER < 1900
-#    error "toml11 requires C++11 or later."
-#endif
-
-#define TOML11_VERSION_MAJOR 3
-#define TOML11_VERSION_MINOR 7
-#define TOML11_VERSION_PATCH 0
-
-#include "toml/parser.hpp"
-#include "toml/literal.hpp"
-#include "toml/serializer.hpp"
-#include "toml/get.hpp"
-#include "toml/macros.hpp"
-
-#endif// TOML_FOR_MODERN_CPP
diff --git a/src/toml11/toml/color.hpp b/src/toml11/toml/color.hpp
deleted file mode 100644
index 4cb572cb089..00000000000
--- a/src/toml11/toml/color.hpp
+++ /dev/null
@@ -1,64 +0,0 @@
-#ifndef TOML11_COLOR_HPP
-#define TOML11_COLOR_HPP
-#include <cstdint>
-#include <ostream>
-
-#ifdef TOML11_COLORIZE_ERROR_MESSAGE
-#define TOML11_ERROR_MESSAGE_COLORIZED true
-#else
-#define TOML11_ERROR_MESSAGE_COLORIZED false
-#endif
-
-namespace toml
-{
-
-// put ANSI escape sequence to ostream
-namespace color_ansi
-{
-namespace detail
-{
-inline int colorize_index()
-{
-    static const int index = std::ios_base::xalloc();
-    return index;
-}
-} // detail
-
-inline std::ostream& colorize(std::ostream& os)
-{
-    // by default, it is zero.
-    os.iword(detail::colorize_index()) = 1;
-    return os;
-}
-inline std::ostream& nocolorize(std::ostream& os)
-{
-    os.iword(detail::colorize_index()) = 0;
-    return os;
-}
-inline std::ostream& reset  (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[00m";} return os;}
-inline std::ostream& bold   (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[01m";} return os;}
-inline std::ostream& grey   (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[30m";} return os;}
-inline std::ostream& red    (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[31m";} return os;}
-inline std::ostream& green  (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[32m";} return os;}
-inline std::ostream& yellow (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[33m";} return os;}
-inline std::ostream& blue   (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[34m";} return os;}
-inline std::ostream& magenta(std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[35m";} return os;}
-inline std::ostream& cyan   (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[36m";} return os;}
-inline std::ostream& white  (std::ostream& os)
-{if(os.iword(detail::colorize_index()) == 1) {os << "\033[37m";} return os;}
-} // color_ansi
-
-// ANSI escape sequence is the only and default colorization method currently
-namespace color = color_ansi;
-
-} // toml
-#endif// TOML11_COLOR_HPP
diff --git a/src/toml11/toml/combinator.hpp b/src/toml11/toml/combinator.hpp
deleted file mode 100644
index 33ecca1eb55..00000000000
--- a/src/toml11/toml/combinator.hpp
+++ /dev/null
@@ -1,306 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_COMBINATOR_HPP
-#define TOML11_COMBINATOR_HPP
-#include <cassert>
-#include <cctype>
-#include <cstdio>
-
-#include <array>
-#include <iomanip>
-#include <iterator>
-#include <limits>
-#include <type_traits>
-
-#include "region.hpp"
-#include "result.hpp"
-#include "traits.hpp"
-#include "utility.hpp"
-
-// they scans characters and returns region if it matches to the condition.
-// when they fail, it does not change the location.
-// in lexer.hpp, these are used.
-
-namespace toml
-{
-namespace detail
-{
-
-// to output character as an error message.
-inline std::string show_char(const char c)
-{
-    // It suppresses an error that occurs only in Debug mode of MSVC++ on Windows.
-    // I'm not completely sure but they check the value of char to be in the
-    // range [0, 256) and some of the COMPLETELY VALID utf-8 character sometimes
-    // has negative value (if char has sign). So here it re-interprets c as
-    // unsigned char through pointer. In general, converting pointer to a
-    // pointer that has different type cause UB, but `(signed|unsigned)?char`
-    // are one of the exceptions. Converting pointer only to char and std::byte
-    // (c++17) are valid.
-    if(std::isgraph(*reinterpret_cast<unsigned char const*>(std::addressof(c))))
-    {
-        return std::string(1, c);
-    }
-    else
-    {
-        std::array<char, 5> buf;
-        buf.fill('\0');
-        const auto r = std::snprintf(
-                buf.data(), buf.size(), "0x%02x", static_cast<int>(c) & 0xFF);
-        (void) r; // Unused variable warning
-        assert(r == static_cast<int>(buf.size()) - 1);
-        return std::string(buf.data());
-    }
-}
-
-template<char C>
-struct character
-{
-    static constexpr char target = C;
-
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        if(loc.iter() == loc.end()) {return none();}
-        const auto first = loc.iter();
-
-        const char c = *(loc.iter());
-        if(c != target)
-        {
-            return none();
-        }
-        loc.advance(); // update location
-
-        return ok(region(loc, first, loc.iter()));
-    }
-};
-template<char C>
-constexpr char character<C>::target;
-
-// closed interval [Low, Up]. both Low and Up are included.
-template<char Low, char Up>
-struct in_range
-{
-    // assuming ascii part of UTF-8...
-    static_assert(Low <= Up, "lower bound should be less than upper bound.");
-
-    static constexpr char upper = Up;
-    static constexpr char lower = Low;
-
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        if(loc.iter() == loc.end()) {return none();}
-        const auto first = loc.iter();
-
-        const char c = *(loc.iter());
-        if(c < lower || upper < c)
-        {
-            return none();
-        }
-
-        loc.advance();
-        return ok(region(loc, first, loc.iter()));
-    }
-};
-template<char L, char U> constexpr char in_range<L, U>::upper;
-template<char L, char U> constexpr char in_range<L, U>::lower;
-
-// keep iterator if `Combinator` matches. otherwise, increment `iter` by 1 char.
-// for detecting invalid characters, like control sequences in toml string.
-template<typename Combinator>
-struct exclude
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        if(loc.iter() == loc.end()) {return none();}
-        auto first = loc.iter();
-
-        auto rslt = Combinator::invoke(loc);
-        if(rslt.is_ok())
-        {
-            loc.reset(first);
-            return none();
-        }
-        loc.reset(std::next(first)); // XXX maybe loc.advance() is okay but...
-        return ok(region(loc, first, loc.iter()));
-    }
-};
-
-// increment `iter`, if matches. otherwise, just return empty string.
-template<typename Combinator>
-struct maybe
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        const auto rslt = Combinator::invoke(loc);
-        if(rslt.is_ok())
-        {
-            return rslt;
-        }
-        return ok(region(loc));
-    }
-};
-
-template<typename ... Ts>
-struct sequence;
-
-template<typename Head, typename ... Tail>
-struct sequence<Head, Tail...>
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        const auto first = loc.iter();
-        auto rslt = Head::invoke(loc);
-        if(rslt.is_err())
-        {
-            loc.reset(first);
-            return none();
-        }
-        return sequence<Tail...>::invoke(loc, std::move(rslt.unwrap()), first);
-    }
-
-    // called from the above function only, recursively.
-    template<typename Iterator>
-    static result<region, none_t>
-    invoke(location& loc, region reg, Iterator first)
-    {
-        const auto rslt = Head::invoke(loc);
-        if(rslt.is_err())
-        {
-            loc.reset(first);
-            return none();
-        }
-        reg += rslt.unwrap(); // concat regions
-        return sequence<Tail...>::invoke(loc, std::move(reg), first);
-    }
-};
-
-template<typename Head>
-struct sequence<Head>
-{
-    // would be called from sequence<T ...>::invoke only.
-    template<typename Iterator>
-    static result<region, none_t>
-    invoke(location& loc, region reg, Iterator first)
-    {
-        const auto rslt = Head::invoke(loc);
-        if(rslt.is_err())
-        {
-            loc.reset(first);
-            return none();
-        }
-        reg += rslt.unwrap(); // concat regions
-        return ok(reg);
-    }
-};
-
-template<typename ... Ts>
-struct either;
-
-template<typename Head, typename ... Tail>
-struct either<Head, Tail...>
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        const auto rslt = Head::invoke(loc);
-        if(rslt.is_ok()) {return rslt;}
-        return either<Tail...>::invoke(loc);
-    }
-};
-template<typename Head>
-struct either<Head>
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        return Head::invoke(loc);
-    }
-};
-
-template<typename T, typename N>
-struct repeat;
-
-template<std::size_t N> struct exactly{};
-template<std::size_t N> struct at_least{};
-struct unlimited{};
-
-template<typename T, std::size_t N>
-struct repeat<T, exactly<N>>
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        region retval(loc);
-        const auto first = loc.iter();
-        for(std::size_t i=0; i<N; ++i)
-        {
-            auto rslt = T::invoke(loc);
-            if(rslt.is_err())
-            {
-                loc.reset(first);
-                return none();
-            }
-            retval += rslt.unwrap();
-        }
-        return ok(std::move(retval));
-    }
-};
-
-template<typename T, std::size_t N>
-struct repeat<T, at_least<N>>
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        region retval(loc);
-
-        const auto first = loc.iter();
-        for(std::size_t i=0; i<N; ++i)
-        {
-            auto rslt = T::invoke(loc);
-            if(rslt.is_err())
-            {
-                loc.reset(first);
-                return none();
-            }
-            retval += rslt.unwrap();
-        }
-        while(true)
-        {
-            auto rslt = T::invoke(loc);
-            if(rslt.is_err())
-            {
-                return ok(std::move(retval));
-            }
-            retval += rslt.unwrap();
-        }
-    }
-};
-
-template<typename T>
-struct repeat<T, unlimited>
-{
-    static result<region, none_t>
-    invoke(location& loc)
-    {
-        region retval(loc);
-        while(true)
-        {
-            auto rslt = T::invoke(loc);
-            if(rslt.is_err())
-            {
-                return ok(std::move(retval));
-            }
-            retval += rslt.unwrap();
-        }
-    }
-};
-
-} // detail
-} // toml
-#endif// TOML11_COMBINATOR_HPP
diff --git a/src/toml11/toml/comments.hpp b/src/toml11/toml/comments.hpp
deleted file mode 100644
index ec250411755..00000000000
--- a/src/toml11/toml/comments.hpp
+++ /dev/null
@@ -1,472 +0,0 @@
-//     Copyright Toru Niina 2019.
-// Distributed under the MIT License.
-#ifndef TOML11_COMMENTS_HPP
-#define TOML11_COMMENTS_HPP
-#include <initializer_list>
-#include <iterator>
-#include <stdexcept>
-#include <string>
-#include <type_traits>
-#include <utility>
-#include <vector>
-
-#ifdef TOML11_PRESERVE_COMMENTS_BY_DEFAULT
-#  define TOML11_DEFAULT_COMMENT_STRATEGY ::toml::preserve_comments
-#else
-#  define TOML11_DEFAULT_COMMENT_STRATEGY ::toml::discard_comments
-#endif
-
-// This file provides mainly two classes, `preserve_comments` and `discard_comments`.
-// Those two are a container that have the same interface as `std::vector<std::string>`
-// but bahaves in the opposite way. `preserve_comments` is just the same as
-// `std::vector<std::string>` and each `std::string` corresponds to a comment line.
-// Conversely, `discard_comments` discards all the strings and ignores everything
-// assigned in it. `discard_comments` is always empty and you will encounter an
-// error whenever you access to the element.
-namespace toml
-{
-struct discard_comments; // forward decl
-
-// use it in the following way
-//
-// const toml::basic_value<toml::preserve_comments> data =
-//     toml::parse<toml::preserve_comments>("example.toml");
-//
-// the interface is almost the same as std::vector<std::string>.
-struct preserve_comments
-{
-    // `container_type` is not provided in discard_comments.
-    // do not use this inner-type in a generic code.
-    using container_type         = std::vector<std::string>;
-
-    using size_type              = container_type::size_type;
-    using difference_type        = container_type::difference_type;
-    using value_type             = container_type::value_type;
-    using reference              = container_type::reference;
-    using const_reference        = container_type::const_reference;
-    using pointer                = container_type::pointer;
-    using const_pointer          = container_type::const_pointer;
-    using iterator               = container_type::iterator;
-    using const_iterator         = container_type::const_iterator;
-    using reverse_iterator       = container_type::reverse_iterator;
-    using const_reverse_iterator = container_type::const_reverse_iterator;
-
-    preserve_comments()  = default;
-    ~preserve_comments() = default;
-    preserve_comments(preserve_comments const&) = default;
-    preserve_comments(preserve_comments &&)     = default;
-    preserve_comments& operator=(preserve_comments const&) = default;
-    preserve_comments& operator=(preserve_comments &&)     = default;
-
-    explicit preserve_comments(const std::vector<std::string>& c): comments(c){}
-    explicit preserve_comments(std::vector<std::string>&& c)
-        : comments(std::move(c))
-    {}
-    preserve_comments& operator=(const std::vector<std::string>& c)
-    {
-        comments = c;
-        return *this;
-    }
-    preserve_comments& operator=(std::vector<std::string>&& c)
-    {
-        comments = std::move(c);
-        return *this;
-    }
-
-    explicit preserve_comments(const discard_comments&) {}
-
-    explicit preserve_comments(size_type n): comments(n) {}
-    preserve_comments(size_type n, const std::string& x): comments(n, x) {}
-    preserve_comments(std::initializer_list<std::string> x): comments(x) {}
-    template<typename InputIterator>
-    preserve_comments(InputIterator first, InputIterator last)
-        : comments(first, last)
-    {}
-
-    template<typename InputIterator>
-    void assign(InputIterator first, InputIterator last) {comments.assign(first, last);}
-    void assign(std::initializer_list<std::string> ini)  {comments.assign(ini);}
-    void assign(size_type n, const std::string& val)     {comments.assign(n, val);}
-
-    // Related to the issue #97.
-    //
-    // It is known that `std::vector::insert` and `std::vector::erase` in
-    // the standard library implementation included in GCC 4.8.5 takes
-    // `std::vector::iterator` instead of `std::vector::const_iterator`.
-    // Because of the const-correctness, we cannot convert a `const_iterator` to
-    // an `iterator`. It causes compilation error in GCC 4.8.5.
-#if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__) && !defined(__clang__)
-#  if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) <= 40805
-#    define TOML11_WORKAROUND_GCC_4_8_X_STANDARD_LIBRARY_IMPLEMENTATION
-#  endif
-#endif
-
-#ifdef TOML11_WORKAROUND_GCC_4_8_X_STANDARD_LIBRARY_IMPLEMENTATION
-    iterator insert(iterator p, const std::string& x)
-    {
-        return comments.insert(p, x);
-    }
-    iterator insert(iterator p, std::string&&      x)
-    {
-        return comments.insert(p, std::move(x));
-    }
-    void insert(iterator p, size_type n, const std::string& x)
-    {
-        return comments.insert(p, n, x);
-    }
-    template<typename InputIterator>
-    void insert(iterator p, InputIterator first, InputIterator last)
-    {
-        return comments.insert(p, first, last);
-    }
-    void insert(iterator p, std::initializer_list<std::string> ini)
-    {
-        return comments.insert(p, ini);
-    }
-
-    template<typename ... Ts>
-    iterator emplace(iterator p, Ts&& ... args)
-    {
-        return comments.emplace(p, std::forward<Ts>(args)...);
-    }
-
-    iterator erase(iterator pos) {return comments.erase(pos);}
-    iterator erase(iterator first, iterator last)
-    {
-        return comments.erase(first, last);
-    }
-#else
-    iterator insert(const_iterator p, const std::string& x)
-    {
-        return comments.insert(p, x);
-    }
-    iterator insert(const_iterator p, std::string&&      x)
-    {
-        return comments.insert(p, std::move(x));
-    }
-    iterator insert(const_iterator p, size_type n, const std::string& x)
-    {
-        return comments.insert(p, n, x);
-    }
-    template<typename InputIterator>
-    iterator insert(const_iterator p, InputIterator first, InputIterator last)
-    {
-        return comments.insert(p, first, last);
-    }
-    iterator insert(const_iterator p, std::initializer_list<std::string> ini)
-    {
-        return comments.insert(p, ini);
-    }
-
-    template<typename ... Ts>
-    iterator emplace(const_iterator p, Ts&& ... args)
-    {
-        return comments.emplace(p, std::forward<Ts>(args)...);
-    }
-
-    iterator erase(const_iterator pos) {return comments.erase(pos);}
-    iterator erase(const_iterator first, const_iterator last)
-    {
-        return comments.erase(first, last);
-    }
-#endif
-
-    void swap(preserve_comments& other) {comments.swap(other.comments);}
-
-    void push_back(const std::string& v) {comments.push_back(v);}
-    void push_back(std::string&&      v) {comments.push_back(std::move(v));}
-    void pop_back()                      {comments.pop_back();}
-
-    template<typename ... Ts>
-    void emplace_back(Ts&& ... args) {comments.emplace_back(std::forward<Ts>(args)...);}
-
-    void clear() {comments.clear();}
-
-    size_type size()     const noexcept {return comments.size();}
-    size_type max_size() const noexcept {return comments.max_size();}
-    size_type capacity() const noexcept {return comments.capacity();}
-    bool      empty()    const noexcept {return comments.empty();}
-
-    void reserve(size_type n)                      {comments.reserve(n);}
-    void resize(size_type n)                       {comments.resize(n);}
-    void resize(size_type n, const std::string& c) {comments.resize(n, c);}
-    void shrink_to_fit()                           {comments.shrink_to_fit();}
-
-    reference       operator[](const size_type n)       noexcept {return comments[n];}
-    const_reference operator[](const size_type n) const noexcept {return comments[n];}
-    reference       at(const size_type n)       {return comments.at(n);}
-    const_reference at(const size_type n) const {return comments.at(n);}
-    reference       front()       noexcept {return comments.front();}
-    const_reference front() const noexcept {return comments.front();}
-    reference       back()        noexcept {return comments.back();}
-    const_reference back()  const noexcept {return comments.back();}
-
-    pointer         data()        noexcept {return comments.data();}
-    const_pointer   data()  const noexcept {return comments.data();}
-
-    iterator       begin()        noexcept {return comments.begin();}
-    iterator       end()          noexcept {return comments.end();}
-    const_iterator begin()  const noexcept {return comments.begin();}
-    const_iterator end()    const noexcept {return comments.end();}
-    const_iterator cbegin() const noexcept {return comments.cbegin();}
-    const_iterator cend()   const noexcept {return comments.cend();}
-
-    reverse_iterator       rbegin()        noexcept {return comments.rbegin();}
-    reverse_iterator       rend()          noexcept {return comments.rend();}
-    const_reverse_iterator rbegin()  const noexcept {return comments.rbegin();}
-    const_reverse_iterator rend()    const noexcept {return comments.rend();}
-    const_reverse_iterator crbegin() const noexcept {return comments.crbegin();}
-    const_reverse_iterator crend()   const noexcept {return comments.crend();}
-
-    friend bool operator==(const preserve_comments&, const preserve_comments&);
-    friend bool operator!=(const preserve_comments&, const preserve_comments&);
-    friend bool operator< (const preserve_comments&, const preserve_comments&);
-    friend bool operator<=(const preserve_comments&, const preserve_comments&);
-    friend bool operator> (const preserve_comments&, const preserve_comments&);
-    friend bool operator>=(const preserve_comments&, const preserve_comments&);
-
-    friend void swap(preserve_comments&, std::vector<std::string>&);
-    friend void swap(std::vector<std::string>&, preserve_comments&);
-
-  private:
-
-    container_type comments;
-};
-
-inline bool operator==(const preserve_comments& lhs, const preserve_comments& rhs) {return lhs.comments == rhs.comments;}
-inline bool operator!=(const preserve_comments& lhs, const preserve_comments& rhs) {return lhs.comments != rhs.comments;}
-inline bool operator< (const preserve_comments& lhs, const preserve_comments& rhs) {return lhs.comments <  rhs.comments;}
-inline bool operator<=(const preserve_comments& lhs, const preserve_comments& rhs) {return lhs.comments <= rhs.comments;}
-inline bool operator> (const preserve_comments& lhs, const preserve_comments& rhs) {return lhs.comments >  rhs.comments;}
-inline bool operator>=(const preserve_comments& lhs, const preserve_comments& rhs) {return lhs.comments >= rhs.comments;}
-
-inline void swap(preserve_comments& lhs, preserve_comments& rhs)
-{
-    lhs.swap(rhs);
-    return;
-}
-inline void swap(preserve_comments& lhs, std::vector<std::string>& rhs)
-{
-    lhs.comments.swap(rhs);
-    return;
-}
-inline void swap(std::vector<std::string>& lhs, preserve_comments& rhs)
-{
-    lhs.swap(rhs.comments);
-    return;
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const preserve_comments& com)
-{
-    for(const auto& c : com)
-    {
-        os << '#' << c << '\n';
-    }
-    return os;
-}
-
-namespace detail
-{
-
-// To provide the same interface with `preserve_comments`, `discard_comments`
-// should have an iterator. But it does not contain anything, so we need to
-// add an iterator that points nothing.
-//
-// It always points null, so DO NOT unwrap this iterator. It always crashes
-// your program.
-template<typename T, bool is_const>
-struct empty_iterator
-{
-    using value_type        = T;
-    using reference_type    = typename std::conditional<is_const, T const&, T&>::type;
-    using pointer_type      = typename std::conditional<is_const, T const*, T*>::type;
-    using difference_type   = std::ptrdiff_t;
-    using iterator_category = std::random_access_iterator_tag;
-
-    empty_iterator()  = default;
-    ~empty_iterator() = default;
-    empty_iterator(empty_iterator const&) = default;
-    empty_iterator(empty_iterator &&)     = default;
-    empty_iterator& operator=(empty_iterator const&) = default;
-    empty_iterator& operator=(empty_iterator &&)     = default;
-
-    // DO NOT call these operators.
-    reference_type operator*()  const noexcept {std::terminate();}
-    pointer_type   operator->() const noexcept {return nullptr;}
-    reference_type operator[](difference_type) const noexcept {return this->operator*();}
-
-    // These operators do nothing.
-    empty_iterator& operator++()    noexcept {return *this;}
-    empty_iterator  operator++(int) noexcept {return *this;}
-    empty_iterator& operator--()    noexcept {return *this;}
-    empty_iterator  operator--(int) noexcept {return *this;}
-
-    empty_iterator& operator+=(difference_type) noexcept {return *this;}
-    empty_iterator& operator-=(difference_type) noexcept {return *this;}
-
-    empty_iterator  operator+(difference_type) const noexcept {return *this;}
-    empty_iterator  operator-(difference_type) const noexcept {return *this;}
-};
-
-template<typename T, bool C>
-bool operator==(const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return true;}
-template<typename T, bool C>
-bool operator!=(const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return false;}
-template<typename T, bool C>
-bool operator< (const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return false;}
-template<typename T, bool C>
-bool operator<=(const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return true;}
-template<typename T, bool C>
-bool operator> (const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return false;}
-template<typename T, bool C>
-bool operator>=(const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return true;}
-
-template<typename T, bool C>
-typename empty_iterator<T, C>::difference_type
-operator-(const empty_iterator<T, C>&, const empty_iterator<T, C>&) noexcept {return 0;}
-
-template<typename T, bool C>
-empty_iterator<T, C>
-operator+(typename empty_iterator<T, C>::difference_type, const empty_iterator<T, C>& rhs) noexcept {return rhs;}
-template<typename T, bool C>
-empty_iterator<T, C>
-operator+(const empty_iterator<T, C>& lhs, typename empty_iterator<T, C>::difference_type) noexcept {return lhs;}
-
-} // detail
-
-// The default comment type. It discards all the comments. It requires only one
-// byte to contain, so the memory footprint is smaller than preserve_comments.
-//
-// It just ignores `push_back`, `insert`, `erase`, and any other modifications.
-// IT always returns size() == 0, the iterator taken by `begin()` is always the
-// same as that of `end()`, and accessing through `operator[]` or iterators
-// always causes a segmentation fault. DO NOT access to the element of this.
-//
-// Why this is chose as the default type is because the last version (2.x.y)
-// does not contain any comments in a value. To minimize the impact on the
-// efficiency, this is chosen as a default.
-//
-// To reduce the memory footprint, later we can try empty base optimization (EBO).
-struct discard_comments
-{
-    using size_type              = std::size_t;
-    using difference_type        = std::ptrdiff_t;
-    using value_type             = std::string;
-    using reference              = std::string&;
-    using const_reference        = std::string const&;
-    using pointer                = std::string*;
-    using const_pointer          = std::string const*;
-    using iterator               = detail::empty_iterator<std::string, false>;
-    using const_iterator         = detail::empty_iterator<std::string, true>;
-    using reverse_iterator       = detail::empty_iterator<std::string, false>;
-    using const_reverse_iterator = detail::empty_iterator<std::string, true>;
-
-    discard_comments() = default;
-    ~discard_comments() = default;
-    discard_comments(discard_comments const&) = default;
-    discard_comments(discard_comments &&)     = default;
-    discard_comments& operator=(discard_comments const&) = default;
-    discard_comments& operator=(discard_comments &&)     = default;
-
-    explicit discard_comments(const std::vector<std::string>&) noexcept {}
-    explicit discard_comments(std::vector<std::string>&&)      noexcept {}
-    discard_comments& operator=(const std::vector<std::string>&) noexcept {return *this;}
-    discard_comments& operator=(std::vector<std::string>&&)      noexcept {return *this;}
-
-    explicit discard_comments(const preserve_comments&)        noexcept {}
-
-    explicit discard_comments(size_type) noexcept {}
-    discard_comments(size_type, const std::string&) noexcept {}
-    discard_comments(std::initializer_list<std::string>) noexcept {}
-    template<typename InputIterator>
-    discard_comments(InputIterator, InputIterator) noexcept {}
-
-    template<typename InputIterator>
-    void assign(InputIterator, InputIterator)       noexcept {}
-    void assign(std::initializer_list<std::string>) noexcept {}
-    void assign(size_type, const std::string&)      noexcept {}
-
-    iterator insert(const_iterator, const std::string&)                 {return iterator{};}
-    iterator insert(const_iterator, std::string&&)                      {return iterator{};}
-    iterator insert(const_iterator, size_type, const std::string&)      {return iterator{};}
-    template<typename InputIterator>
-    iterator insert(const_iterator, InputIterator, InputIterator)       {return iterator{};}
-    iterator insert(const_iterator, std::initializer_list<std::string>) {return iterator{};}
-
-    template<typename ... Ts>
-    iterator emplace(const_iterator, Ts&& ...)     {return iterator{};}
-    iterator erase(const_iterator)                 {return iterator{};}
-    iterator erase(const_iterator, const_iterator) {return iterator{};}
-
-    void swap(discard_comments&) {return;}
-
-    void push_back(const std::string&) {return;}
-    void push_back(std::string&&     ) {return;}
-    void pop_back()                    {return;}
-
-    template<typename ... Ts>
-    void emplace_back(Ts&& ...) {return;}
-
-    void clear() {return;}
-
-    size_type size()     const noexcept {return 0;}
-    size_type max_size() const noexcept {return 0;}
-    size_type capacity() const noexcept {return 0;}
-    bool      empty()    const noexcept {return true;}
-
-    void reserve(size_type)                    {return;}
-    void resize(size_type)                     {return;}
-    void resize(size_type, const std::string&) {return;}
-    void shrink_to_fit()                       {return;}
-
-    // DO NOT access to the element of this container. This container is always
-    // empty, so accessing through operator[], front/back, data causes address
-    // error.
-
-    reference       operator[](const size_type)       noexcept {return *data();}
-    const_reference operator[](const size_type) const noexcept {return *data();}
-    reference       at(const size_type)       {throw std::out_of_range("toml::discard_comment is always empty.");}
-    const_reference at(const size_type) const {throw std::out_of_range("toml::discard_comment is always empty.");}
-    reference       front()       noexcept {return *data();}
-    const_reference front() const noexcept {return *data();}
-    reference       back()        noexcept {return *data();}
-    const_reference back()  const noexcept {return *data();}
-
-    pointer         data()        noexcept {return nullptr;}
-    const_pointer   data()  const noexcept {return nullptr;}
-
-    iterator       begin()        noexcept {return iterator{};}
-    iterator       end()          noexcept {return iterator{};}
-    const_iterator begin()  const noexcept {return const_iterator{};}
-    const_iterator end()    const noexcept {return const_iterator{};}
-    const_iterator cbegin() const noexcept {return const_iterator{};}
-    const_iterator cend()   const noexcept {return const_iterator{};}
-
-    reverse_iterator       rbegin()        noexcept {return iterator{};}
-    reverse_iterator       rend()          noexcept {return iterator{};}
-    const_reverse_iterator rbegin()  const noexcept {return const_iterator{};}
-    const_reverse_iterator rend()    const noexcept {return const_iterator{};}
-    const_reverse_iterator crbegin() const noexcept {return const_iterator{};}
-    const_reverse_iterator crend()   const noexcept {return const_iterator{};}
-};
-
-inline bool operator==(const discard_comments&, const discard_comments&) noexcept {return true;}
-inline bool operator!=(const discard_comments&, const discard_comments&) noexcept {return false;}
-inline bool operator< (const discard_comments&, const discard_comments&) noexcept {return false;}
-inline bool operator<=(const discard_comments&, const discard_comments&) noexcept {return true;}
-inline bool operator> (const discard_comments&, const discard_comments&) noexcept {return false;}
-inline bool operator>=(const discard_comments&, const discard_comments&) noexcept {return true;}
-
-inline void swap(const discard_comments&, const discard_comments&) noexcept {return;}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const discard_comments&)
-{
-    return os;
-}
-
-} // toml11
-#endif// TOML11_COMMENTS_HPP
diff --git a/src/toml11/toml/datetime.hpp b/src/toml11/toml/datetime.hpp
deleted file mode 100644
index d8127c150a9..00000000000
--- a/src/toml11/toml/datetime.hpp
+++ /dev/null
@@ -1,631 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_DATETIME_HPP
-#define TOML11_DATETIME_HPP
-#include <cstdint>
-#include <cstdlib>
-#include <ctime>
-
-#include <array>
-#include <chrono>
-#include <iomanip>
-#include <ostream>
-#include <tuple>
-
-namespace toml
-{
-
-// To avoid non-threadsafe std::localtime. In C11 (not C++11!), localtime_s is
-// provided in the absolutely same purpose, but C++11 is actually not compatible
-// with C11. We need to dispatch the function depending on the OS.
-namespace detail
-{
-// TODO: find more sophisticated way to handle this
-#if (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 1) || defined(_XOPEN_SOURCE) || defined(_BSD_SOURCE) || defined(_SVID_SOURCE) || defined(_POSIX_SOURCE)
-inline std::tm localtime_s(const std::time_t* src)
-{
-    std::tm dst;
-    const auto result = ::localtime_r(src, &dst);
-    if (!result) { throw std::runtime_error("localtime_r failed."); }
-    return dst;
-}
-inline std::tm gmtime_s(const std::time_t* src)
-{
-    std::tm dst;
-    const auto result = ::gmtime_r(src, &dst);
-    if (!result) { throw std::runtime_error("gmtime_r failed."); }
-    return dst;
-}
-#elif defined(_MSC_VER)
-inline std::tm localtime_s(const std::time_t* src)
-{
-    std::tm dst;
-    const auto result = ::localtime_s(&dst, src);
-    if (result) { throw std::runtime_error("localtime_s failed."); }
-    return dst;
-}
-inline std::tm gmtime_s(const std::time_t* src)
-{
-    std::tm dst;
-    const auto result = ::gmtime_s(&dst, src);
-    if (result) { throw std::runtime_error("gmtime_s failed."); }
-    return dst;
-}
-#else // fallback. not threadsafe
-inline std::tm localtime_s(const std::time_t* src)
-{
-    const auto result = std::localtime(src);
-    if (!result) { throw std::runtime_error("localtime failed."); }
-    return *result;
-}
-inline std::tm gmtime_s(const std::time_t* src)
-{
-    const auto result = std::gmtime(src);
-    if (!result) { throw std::runtime_error("gmtime failed."); }
-    return *result;
-}
-#endif
-} // detail
-
-enum class month_t : std::uint8_t
-{
-    Jan =  0,
-    Feb =  1,
-    Mar =  2,
-    Apr =  3,
-    May =  4,
-    Jun =  5,
-    Jul =  6,
-    Aug =  7,
-    Sep =  8,
-    Oct =  9,
-    Nov = 10,
-    Dec = 11
-};
-
-struct local_date
-{
-    std::int16_t year;   // A.D. (like, 2018)
-    std::uint8_t month;  // [0, 11]
-    std::uint8_t day;    // [1, 31]
-
-    local_date(int y, month_t m, int d)
-        : year (static_cast<std::int16_t>(y)),
-          month(static_cast<std::uint8_t>(m)),
-          day  (static_cast<std::uint8_t>(d))
-    {}
-
-    explicit local_date(const std::tm& t)
-        : year (static_cast<std::int16_t>(t.tm_year + 1900)),
-          month(static_cast<std::uint8_t>(t.tm_mon)),
-          day  (static_cast<std::uint8_t>(t.tm_mday))
-    {}
-
-    explicit local_date(const std::chrono::system_clock::time_point& tp)
-    {
-        const auto t    = std::chrono::system_clock::to_time_t(tp);
-        const auto time = detail::localtime_s(&t);
-        *this = local_date(time);
-    }
-
-    explicit local_date(const std::time_t t)
-        : local_date(std::chrono::system_clock::from_time_t(t))
-    {}
-
-    operator std::chrono::system_clock::time_point() const
-    {
-        // std::mktime returns date as local time zone. no conversion needed
-        std::tm t;
-        t.tm_sec   = 0;
-        t.tm_min   = 0;
-        t.tm_hour  = 0;
-        t.tm_mday  = static_cast<int>(this->day);
-        t.tm_mon   = static_cast<int>(this->month);
-        t.tm_year  = static_cast<int>(this->year) - 1900;
-        t.tm_wday  = 0; // the value will be ignored
-        t.tm_yday  = 0; // the value will be ignored
-        t.tm_isdst = -1;
-        return std::chrono::system_clock::from_time_t(std::mktime(&t));
-    }
-
-    operator std::time_t() const
-    {
-        return std::chrono::system_clock::to_time_t(
-                std::chrono::system_clock::time_point(*this));
-    }
-
-    local_date() = default;
-    ~local_date() = default;
-    local_date(local_date const&) = default;
-    local_date(local_date&&)      = default;
-    local_date& operator=(local_date const&) = default;
-    local_date& operator=(local_date&&)      = default;
-};
-
-inline bool operator==(const local_date& lhs, const local_date& rhs)
-{
-    return std::make_tuple(lhs.year, lhs.month, lhs.day) ==
-           std::make_tuple(rhs.year, rhs.month, rhs.day);
-}
-inline bool operator!=(const local_date& lhs, const local_date& rhs)
-{
-    return !(lhs == rhs);
-}
-inline bool operator< (const local_date& lhs, const local_date& rhs)
-{
-    return std::make_tuple(lhs.year, lhs.month, lhs.day) <
-           std::make_tuple(rhs.year, rhs.month, rhs.day);
-}
-inline bool operator<=(const local_date& lhs, const local_date& rhs)
-{
-    return (lhs < rhs) || (lhs == rhs);
-}
-inline bool operator> (const local_date& lhs, const local_date& rhs)
-{
-    return !(lhs <= rhs);
-}
-inline bool operator>=(const local_date& lhs, const local_date& rhs)
-{
-    return !(lhs < rhs);
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const local_date& date)
-{
-    os << std::setfill('0') << std::setw(4) << static_cast<int>(date.year )     << '-';
-    os << std::setfill('0') << std::setw(2) << static_cast<int>(date.month) + 1 << '-';
-    os << std::setfill('0') << std::setw(2) << static_cast<int>(date.day  )    ;
-    return os;
-}
-
-struct local_time
-{
-    std::uint8_t  hour;        // [0, 23]
-    std::uint8_t  minute;      // [0, 59]
-    std::uint8_t  second;      // [0, 60]
-    std::uint16_t millisecond; // [0, 999]
-    std::uint16_t microsecond; // [0, 999]
-    std::uint16_t nanosecond;  // [0, 999]
-
-    local_time(int h, int m, int s,
-               int ms = 0, int us = 0, int ns = 0)
-        : hour  (static_cast<std::uint8_t>(h)),
-          minute(static_cast<std::uint8_t>(m)),
-          second(static_cast<std::uint8_t>(s)),
-          millisecond(static_cast<std::uint16_t>(ms)),
-          microsecond(static_cast<std::uint16_t>(us)),
-          nanosecond (static_cast<std::uint16_t>(ns))
-    {}
-
-    explicit local_time(const std::tm& t)
-        : hour  (static_cast<std::uint8_t>(t.tm_hour)),
-          minute(static_cast<std::uint8_t>(t.tm_min)),
-          second(static_cast<std::uint8_t>(t.tm_sec)),
-          millisecond(0), microsecond(0), nanosecond(0)
-    {}
-
-    template<typename Rep, typename Period>
-    explicit local_time(const std::chrono::duration<Rep, Period>& t)
-    {
-        const auto h = std::chrono::duration_cast<std::chrono::hours>(t);
-        this->hour = static_cast<std::uint8_t>(h.count());
-        const auto t2 = t - h;
-        const auto m = std::chrono::duration_cast<std::chrono::minutes>(t2);
-        this->minute = static_cast<std::uint8_t>(m.count());
-        const auto t3 = t2 - m;
-        const auto s = std::chrono::duration_cast<std::chrono::seconds>(t3);
-        this->second = static_cast<std::uint8_t>(s.count());
-        const auto t4 = t3 - s;
-        const auto ms = std::chrono::duration_cast<std::chrono::milliseconds>(t4);
-        this->millisecond = static_cast<std::uint16_t>(ms.count());
-        const auto t5 = t4 - ms;
-        const auto us = std::chrono::duration_cast<std::chrono::microseconds>(t5);
-        this->microsecond = static_cast<std::uint16_t>(us.count());
-        const auto t6 = t5 - us;
-        const auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(t6);
-        this->nanosecond = static_cast<std::uint16_t>(ns.count());
-    }
-
-    operator std::chrono::nanoseconds() const
-    {
-        return std::chrono::nanoseconds (this->nanosecond)  +
-               std::chrono::microseconds(this->microsecond) +
-               std::chrono::milliseconds(this->millisecond) +
-               std::chrono::seconds(this->second) +
-               std::chrono::minutes(this->minute) +
-               std::chrono::hours(this->hour);
-    }
-
-    local_time() = default;
-    ~local_time() = default;
-    local_time(local_time const&) = default;
-    local_time(local_time&&)      = default;
-    local_time& operator=(local_time const&) = default;
-    local_time& operator=(local_time&&)      = default;
-};
-
-inline bool operator==(const local_time& lhs, const local_time& rhs)
-{
-    return std::make_tuple(lhs.hour, lhs.minute, lhs.second, lhs.millisecond, lhs.microsecond, lhs.nanosecond) ==
-           std::make_tuple(rhs.hour, rhs.minute, rhs.second, rhs.millisecond, rhs.microsecond, rhs.nanosecond);
-}
-inline bool operator!=(const local_time& lhs, const local_time& rhs)
-{
-    return !(lhs == rhs);
-}
-inline bool operator< (const local_time& lhs, const local_time& rhs)
-{
-    return std::make_tuple(lhs.hour, lhs.minute, lhs.second, lhs.millisecond, lhs.microsecond, lhs.nanosecond) <
-           std::make_tuple(rhs.hour, rhs.minute, rhs.second, rhs.millisecond, rhs.microsecond, rhs.nanosecond);
-}
-inline bool operator<=(const local_time& lhs, const local_time& rhs)
-{
-    return (lhs < rhs) || (lhs == rhs);
-}
-inline bool operator> (const local_time& lhs, const local_time& rhs)
-{
-    return !(lhs <= rhs);
-}
-inline bool operator>=(const local_time& lhs, const local_time& rhs)
-{
-    return !(lhs < rhs);
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const local_time& time)
-{
-    os << std::setfill('0') << std::setw(2) << static_cast<int>(time.hour  ) << ':';
-    os << std::setfill('0') << std::setw(2) << static_cast<int>(time.minute) << ':';
-    os << std::setfill('0') << std::setw(2) << static_cast<int>(time.second);
-    if(time.millisecond != 0 || time.microsecond != 0 || time.nanosecond != 0)
-    {
-        os << '.';
-        os << std::setfill('0') << std::setw(3) << static_cast<int>(time.millisecond);
-        if(time.microsecond != 0 || time.nanosecond != 0)
-        {
-            os << std::setfill('0') << std::setw(3) << static_cast<int>(time.microsecond);
-            if(time.nanosecond != 0)
-            {
-                os << std::setfill('0') << std::setw(3) << static_cast<int>(time.nanosecond);
-            }
-        }
-    }
-    return os;
-}
-
-struct time_offset
-{
-    std::int8_t hour;   // [-12, 12]
-    std::int8_t minute; // [-59, 59]
-
-    time_offset(int h, int m)
-        : hour  (static_cast<std::int8_t>(h)),
-          minute(static_cast<std::int8_t>(m))
-    {}
-
-    operator std::chrono::minutes() const
-    {
-        return std::chrono::minutes(this->minute) +
-               std::chrono::hours(this->hour);
-    }
-
-    time_offset() = default;
-    ~time_offset() = default;
-    time_offset(time_offset const&) = default;
-    time_offset(time_offset&&)      = default;
-    time_offset& operator=(time_offset const&) = default;
-    time_offset& operator=(time_offset&&)      = default;
-};
-
-inline bool operator==(const time_offset& lhs, const time_offset& rhs)
-{
-    return std::make_tuple(lhs.hour, lhs.minute) ==
-           std::make_tuple(rhs.hour, rhs.minute);
-}
-inline bool operator!=(const time_offset& lhs, const time_offset& rhs)
-{
-    return !(lhs == rhs);
-}
-inline bool operator< (const time_offset& lhs, const time_offset& rhs)
-{
-    return std::make_tuple(lhs.hour, lhs.minute) <
-           std::make_tuple(rhs.hour, rhs.minute);
-}
-inline bool operator<=(const time_offset& lhs, const time_offset& rhs)
-{
-    return (lhs < rhs) || (lhs == rhs);
-}
-inline bool operator> (const time_offset& lhs, const time_offset& rhs)
-{
-    return !(lhs <= rhs);
-}
-inline bool operator>=(const time_offset& lhs, const time_offset& rhs)
-{
-    return !(lhs < rhs);
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const time_offset& offset)
-{
-    if(offset.hour == 0 && offset.minute == 0)
-    {
-        os << 'Z';
-        return os;
-    }
-    int minute = static_cast<int>(offset.hour) * 60 + offset.minute;
-    if(minute < 0){os << '-'; minute = std::abs(minute);} else {os << '+';}
-    os << std::setfill('0') << std::setw(2) << minute / 60 << ':';
-    os << std::setfill('0') << std::setw(2) << minute % 60;
-    return os;
-}
-
-struct local_datetime
-{
-    local_date date;
-    local_time time;
-
-    local_datetime(local_date d, local_time t): date(d), time(t) {}
-
-    explicit local_datetime(const std::tm& t): date(t), time(t){}
-
-    explicit local_datetime(const std::chrono::system_clock::time_point& tp)
-    {
-        const auto t = std::chrono::system_clock::to_time_t(tp);
-        std::tm ltime = detail::localtime_s(&t);
-
-        this->date = local_date(ltime);
-        this->time = local_time(ltime);
-
-        // std::tm lacks subsecond information, so diff between tp and tm
-        // can be used to get millisecond & microsecond information.
-        const auto t_diff = tp -
-            std::chrono::system_clock::from_time_t(std::mktime(&ltime));
-        this->time.millisecond = static_cast<std::uint16_t>(
-          std::chrono::duration_cast<std::chrono::milliseconds>(t_diff).count());
-        this->time.microsecond = static_cast<std::uint16_t>(
-          std::chrono::duration_cast<std::chrono::microseconds>(t_diff).count());
-        this->time.nanosecond = static_cast<std::uint16_t>(
-          std::chrono::duration_cast<std::chrono::nanoseconds >(t_diff).count());
-    }
-
-    explicit local_datetime(const std::time_t t)
-        : local_datetime(std::chrono::system_clock::from_time_t(t))
-    {}
-
-    operator std::chrono::system_clock::time_point() const
-    {
-        using internal_duration =
-            typename std::chrono::system_clock::time_point::duration;
-
-        // Normally DST begins at A.M. 3 or 4. If we re-use conversion operator
-        // of local_date and local_time independently, the conversion fails if
-        // it is the day when DST begins or ends. Since local_date considers the
-        // time is 00:00 A.M. and local_time does not consider DST because it
-        // does not have any date information. We need to consider both date and
-        // time information at the same time to convert it correctly.
-
-        std::tm t;
-        t.tm_sec   = static_cast<int>(this->time.second);
-        t.tm_min   = static_cast<int>(this->time.minute);
-        t.tm_hour  = static_cast<int>(this->time.hour);
-        t.tm_mday  = static_cast<int>(this->date.day);
-        t.tm_mon   = static_cast<int>(this->date.month);
-        t.tm_year  = static_cast<int>(this->date.year) - 1900;
-        t.tm_wday  = 0; // the value will be ignored
-        t.tm_yday  = 0; // the value will be ignored
-        t.tm_isdst = -1;
-
-        // std::mktime returns date as local time zone. no conversion needed
-        auto dt = std::chrono::system_clock::from_time_t(std::mktime(&t));
-        dt += std::chrono::duration_cast<internal_duration>(
-                std::chrono::milliseconds(this->time.millisecond) +
-                std::chrono::microseconds(this->time.microsecond) +
-                std::chrono::nanoseconds (this->time.nanosecond));
-        return dt;
-    }
-
-    operator std::time_t() const
-    {
-        return std::chrono::system_clock::to_time_t(
-                std::chrono::system_clock::time_point(*this));
-    }
-
-    local_datetime() = default;
-    ~local_datetime() = default;
-    local_datetime(local_datetime const&) = default;
-    local_datetime(local_datetime&&)      = default;
-    local_datetime& operator=(local_datetime const&) = default;
-    local_datetime& operator=(local_datetime&&)      = default;
-};
-
-inline bool operator==(const local_datetime& lhs, const local_datetime& rhs)
-{
-    return std::make_tuple(lhs.date, lhs.time) ==
-           std::make_tuple(rhs.date, rhs.time);
-}
-inline bool operator!=(const local_datetime& lhs, const local_datetime& rhs)
-{
-    return !(lhs == rhs);
-}
-inline bool operator< (const local_datetime& lhs, const local_datetime& rhs)
-{
-    return std::make_tuple(lhs.date, lhs.time) <
-           std::make_tuple(rhs.date, rhs.time);
-}
-inline bool operator<=(const local_datetime& lhs, const local_datetime& rhs)
-{
-    return (lhs < rhs) || (lhs == rhs);
-}
-inline bool operator> (const local_datetime& lhs, const local_datetime& rhs)
-{
-    return !(lhs <= rhs);
-}
-inline bool operator>=(const local_datetime& lhs, const local_datetime& rhs)
-{
-    return !(lhs < rhs);
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const local_datetime& dt)
-{
-    os << dt.date << 'T' << dt.time;
-    return os;
-}
-
-struct offset_datetime
-{
-    local_date  date;
-    local_time  time;
-    time_offset offset;
-
-    offset_datetime(local_date d, local_time t, time_offset o)
-        : date(d), time(t), offset(o)
-    {}
-    offset_datetime(const local_datetime& dt, time_offset o)
-        : date(dt.date), time(dt.time), offset(o)
-    {}
-    explicit offset_datetime(const local_datetime& ld)
-        : date(ld.date), time(ld.time), offset(get_local_offset(nullptr))
-          // use the current local timezone offset
-    {}
-    explicit offset_datetime(const std::chrono::system_clock::time_point& tp)
-        : offset(0, 0) // use gmtime
-    {
-        const auto timet = std::chrono::system_clock::to_time_t(tp);
-        const auto tm    = detail::gmtime_s(&timet);
-        this->date = local_date(tm);
-        this->time = local_time(tm);
-    }
-    explicit offset_datetime(const std::time_t& t)
-        : offset(0, 0) // use gmtime
-    {
-        const auto tm    = detail::gmtime_s(&t);
-        this->date = local_date(tm);
-        this->time = local_time(tm);
-    }
-    explicit offset_datetime(const std::tm& t)
-        : offset(0, 0) // assume gmtime
-    {
-        this->date = local_date(t);
-        this->time = local_time(t);
-    }
-
-    operator std::chrono::system_clock::time_point() const
-    {
-        // get date-time
-        using internal_duration =
-            typename std::chrono::system_clock::time_point::duration;
-
-        // first, convert it to local date-time information in the same way as
-        // local_datetime does. later we will use time_t to adjust time offset.
-        std::tm t;
-        t.tm_sec   = static_cast<int>(this->time.second);
-        t.tm_min   = static_cast<int>(this->time.minute);
-        t.tm_hour  = static_cast<int>(this->time.hour);
-        t.tm_mday  = static_cast<int>(this->date.day);
-        t.tm_mon   = static_cast<int>(this->date.month);
-        t.tm_year  = static_cast<int>(this->date.year) - 1900;
-        t.tm_wday  = 0; // the value will be ignored
-        t.tm_yday  = 0; // the value will be ignored
-        t.tm_isdst = -1;
-        const std::time_t tp_loc = std::mktime(std::addressof(t));
-
-        auto tp = std::chrono::system_clock::from_time_t(tp_loc);
-        tp += std::chrono::duration_cast<internal_duration>(
-                std::chrono::milliseconds(this->time.millisecond) +
-                std::chrono::microseconds(this->time.microsecond) +
-                std::chrono::nanoseconds (this->time.nanosecond));
-
-        // Since mktime uses local time zone, it should be corrected.
-        // `12:00:00+09:00` means `03:00:00Z`. So mktime returns `03:00:00Z` if
-        // we are in `+09:00` timezone. To represent `12:00:00Z` there, we need
-        // to add `+09:00` to `03:00:00Z`.
-        //    Here, it uses the time_t converted from date-time info to handle
-        // daylight saving time.
-        const auto ofs = get_local_offset(std::addressof(tp_loc));
-        tp += std::chrono::hours  (ofs.hour);
-        tp += std::chrono::minutes(ofs.minute);
-
-        // We got `12:00:00Z` by correcting local timezone applied by mktime.
-        // Then we will apply the offset. Let's say `12:00:00-08:00` is given.
-        // And now, we have `12:00:00Z`. `12:00:00-08:00` means `20:00:00Z`.
-        // So we need to subtract the offset.
-        tp -= std::chrono::minutes(this->offset);
-        return tp;
-    }
-
-    operator std::time_t() const
-    {
-        return std::chrono::system_clock::to_time_t(
-                std::chrono::system_clock::time_point(*this));
-    }
-
-    offset_datetime() = default;
-    ~offset_datetime() = default;
-    offset_datetime(offset_datetime const&) = default;
-    offset_datetime(offset_datetime&&)      = default;
-    offset_datetime& operator=(offset_datetime const&) = default;
-    offset_datetime& operator=(offset_datetime&&)      = default;
-
-  private:
-
-    static time_offset get_local_offset(const std::time_t* tp)
-    {
-        // get local timezone with the same date-time information as mktime
-        const auto t = detail::localtime_s(tp);
-
-        std::array<char, 6> buf;
-        const auto result = std::strftime(buf.data(), 6, "%z", &t); // +hhmm\0
-        if(result != 5)
-        {
-            throw std::runtime_error("toml::offset_datetime: cannot obtain "
-                                     "timezone information of current env");
-        }
-        const int ofs = std::atoi(buf.data());
-        const int ofs_h = ofs / 100;
-        const int ofs_m = ofs - (ofs_h * 100);
-        return time_offset(ofs_h, ofs_m);
-    }
-};
-
-inline bool operator==(const offset_datetime& lhs, const offset_datetime& rhs)
-{
-    return std::make_tuple(lhs.date, lhs.time, lhs.offset) ==
-           std::make_tuple(rhs.date, rhs.time, rhs.offset);
-}
-inline bool operator!=(const offset_datetime& lhs, const offset_datetime& rhs)
-{
-    return !(lhs == rhs);
-}
-inline bool operator< (const offset_datetime& lhs, const offset_datetime& rhs)
-{
-    return std::make_tuple(lhs.date, lhs.time, lhs.offset) <
-           std::make_tuple(rhs.date, rhs.time, rhs.offset);
-}
-inline bool operator<=(const offset_datetime& lhs, const offset_datetime& rhs)
-{
-    return (lhs < rhs) || (lhs == rhs);
-}
-inline bool operator> (const offset_datetime& lhs, const offset_datetime& rhs)
-{
-    return !(lhs <= rhs);
-}
-inline bool operator>=(const offset_datetime& lhs, const offset_datetime& rhs)
-{
-    return !(lhs < rhs);
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const offset_datetime& dt)
-{
-    os << dt.date << 'T' << dt.time << dt.offset;
-    return os;
-}
-
-}//toml
-#endif// TOML11_DATETIME
diff --git a/src/toml11/toml/exception.hpp b/src/toml11/toml/exception.hpp
deleted file mode 100644
index c64651d0ada..00000000000
--- a/src/toml11/toml/exception.hpp
+++ /dev/null
@@ -1,65 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_EXCEPTION_HPP
-#define TOML11_EXCEPTION_HPP
-#include <stdexcept>
-#include <string>
-
-#include "source_location.hpp"
-
-namespace toml
-{
-
-struct exception : public std::exception
-{
-  public:
-    explicit exception(const source_location& loc): loc_(loc) {}
-    virtual ~exception() noexcept override = default;
-    virtual const char* what() const noexcept override {return "";}
-    virtual source_location const& location() const noexcept {return loc_;}
-
-  protected:
-    source_location loc_;
-};
-
-struct syntax_error : public toml::exception
-{
-  public:
-    explicit syntax_error(const std::string& what_arg, const source_location& loc)
-        : exception(loc), what_(what_arg)
-    {}
-    virtual ~syntax_error() noexcept override = default;
-    virtual const char* what() const noexcept override {return what_.c_str();}
-
-  protected:
-    std::string what_;
-};
-
-struct type_error : public toml::exception
-{
-  public:
-    explicit type_error(const std::string& what_arg, const source_location& loc)
-        : exception(loc), what_(what_arg)
-    {}
-    virtual ~type_error() noexcept override = default;
-    virtual const char* what() const noexcept override {return what_.c_str();}
-
-  protected:
-    std::string what_;
-};
-
-struct internal_error : public toml::exception
-{
-  public:
-    explicit internal_error(const std::string& what_arg, const source_location& loc)
-        : exception(loc), what_(what_arg)
-    {}
-    virtual ~internal_error() noexcept override = default;
-    virtual const char* what() const noexcept override {return what_.c_str();}
-
-  protected:
-    std::string what_;
-};
-
-} // toml
-#endif // TOML_EXCEPTION
diff --git a/src/toml11/toml/from.hpp b/src/toml11/toml/from.hpp
deleted file mode 100644
index 10815caf56f..00000000000
--- a/src/toml11/toml/from.hpp
+++ /dev/null
@@ -1,19 +0,0 @@
-//     Copyright Toru Niina 2019.
-// Distributed under the MIT License.
-#ifndef TOML11_FROM_HPP
-#define TOML11_FROM_HPP
-
-namespace toml
-{
-
-template<typename T>
-struct from;
-// {
-//     static T from_toml(const toml::value& v)
-//     {
-//         // User-defined conversions ...
-//     }
-// };
-
-} // toml
-#endif // TOML11_FROM_HPP
diff --git a/src/toml11/toml/get.hpp b/src/toml11/toml/get.hpp
deleted file mode 100644
index d7fdf553b22..00000000000
--- a/src/toml11/toml/get.hpp
+++ /dev/null
@@ -1,1117 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_GET_HPP
-#define TOML11_GET_HPP
-#include <algorithm>
-
-#include "from.hpp"
-#include "result.hpp"
-#include "value.hpp"
-
-namespace toml
-{
-
-// ============================================================================
-// exact toml::* type
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T> &
-get(basic_value<C, M, V>& v)
-{
-    return v.template cast<detail::type_to_enum<T, basic_value<C, M, V>>::value>();
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T> const&
-get(const basic_value<C, M, V>& v)
-{
-    return v.template cast<detail::type_to_enum<T, basic_value<C, M, V>>::value>();
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>
-get(basic_value<C, M, V>&& v)
-{
-    return T(std::move(v).template cast<detail::type_to_enum<T, basic_value<C, M, V>>::value>());
-}
-
-// ============================================================================
-// T == toml::value; identity transformation.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, basic_value<C, M, V>>::value, T>&
-get(basic_value<C, M, V>& v)
-{
-    return v;
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, basic_value<C, M, V>>::value, T> const&
-get(const basic_value<C, M, V>& v)
-{
-    return v;
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, basic_value<C, M, V>>::value, T>
-get(basic_value<C, M, V>&& v)
-{
-    return basic_value<C, M, V>(std::move(v));
-}
-
-// ============================================================================
-// T == toml::basic_value<C2, M2, V2>; basic_value -> basic_value
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<detail::conjunction<detail::is_basic_value<T>,
-    detail::negation<std::is_same<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    return T(v);
-}
-
-// ============================================================================
-// integer convertible from toml::Integer
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<detail::conjunction<
-    std::is_integral<T>,                            // T is integral
-    detail::negation<std::is_same<T, bool>>,        // but not bool
-    detail::negation<                               // but not toml::integer
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    return static_cast<T>(v.as_integer());
-}
-
-// ============================================================================
-// floating point convertible from toml::Float
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<detail::conjunction<
-    std::is_floating_point<T>,                      // T is floating_point
-    detail::negation<                               // but not toml::floating
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    return static_cast<T>(v.as_floating());
-}
-
-// ============================================================================
-// std::string; toml uses its own toml::string, but it should be convertible to
-// std::string seamlessly
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, std::string>::value, std::string>&
-get(basic_value<C, M, V>& v)
-{
-    return v.as_string().str;
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, std::string>::value, std::string> const&
-get(const basic_value<C, M, V>& v)
-{
-    return v.as_string().str;
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, std::string>::value, std::string>
-get(basic_value<C, M, V>&& v)
-{
-    return std::string(std::move(v.as_string().str));
-}
-
-// ============================================================================
-// std::string_view
-
-#if defined(TOML11_USING_STRING_VIEW) && TOML11_USING_STRING_VIEW>0
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<std::is_same<T, std::string_view>::value, std::string_view>
-get(const basic_value<C, M, V>& v)
-{
-    return std::string_view(v.as_string().str);
-}
-#endif
-
-// ============================================================================
-// std::chrono::duration from toml::local_time.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<detail::is_chrono_duration<T>::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    return std::chrono::duration_cast<T>(
-            std::chrono::nanoseconds(v.as_local_time()));
-}
-
-// ============================================================================
-// std::chrono::system_clock::time_point from toml::datetime variants
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-inline detail::enable_if_t<
-    std::is_same<std::chrono::system_clock::time_point, T>::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    switch(v.type())
-    {
-        case value_t::local_date:
-        {
-            return std::chrono::system_clock::time_point(v.as_local_date());
-        }
-        case value_t::local_datetime:
-        {
-            return std::chrono::system_clock::time_point(v.as_local_datetime());
-        }
-        case value_t::offset_datetime:
-        {
-            return std::chrono::system_clock::time_point(v.as_offset_datetime());
-        }
-        default:
-        {
-            throw type_error(detail::format_underline("toml::value: "
-                "bad_cast to std::chrono::system_clock::time_point", {
-                    {v.location(), concat_to_string("the actual type is ", v.type())}
-                }), v.location());
-        }
-    }
-}
-
-// ============================================================================
-// forward declaration to use this recursively. ignore this and go ahead.
-
-// array-like type with push_back(value) method
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::is_container<T>,         // T is a container
-    detail::has_push_back_method<T>, // T::push_back(value) works
-    detail::negation<                // but not toml::array
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>&);
-
-// array-like type without push_back(value) method
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::is_container<T>,                           // T is a container
-    detail::negation<detail::has_push_back_method<T>>, // w/o push_back(...)
-    detail::negation<                                  // not toml::array
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>&);
-
-// std::pair<T1, T2>
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_std_pair<T>::value, T>
-get(const basic_value<C, M, V>&);
-
-// std::tuple<T1, T2, ...>
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_std_tuple<T>::value, T>
-get(const basic_value<C, M, V>&);
-
-// map-like classes
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::is_map<T>, // T is map
-    detail::negation<  // but not toml::table
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>&);
-
-// T.from_toml(v)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::negation<                         // not a toml::* type
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>,
-    detail::has_from_toml_method<T, C, M, V>, // but has from_toml(toml::value)
-    std::is_default_constructible<T>          // and default constructible
-    >::value, T>
-get(const basic_value<C, M, V>&);
-
-// toml::from<T>::from_toml(v)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::has_specialized_from<T>::value, T>
-get(const basic_value<C, M, V>&);
-
-// T(const toml::value&) and T is not toml::basic_value,
-// and it does not have `from<T>` nor `from_toml`.
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::negation<detail::is_basic_value<T>>,
-    std::is_constructible<T, const basic_value<C, M, V>&>,
-    detail::negation<detail::has_from_toml_method<T, C, M, V>>,
-    detail::negation<detail::has_specialized_from<T>>
-    >::value, T>
-get(const basic_value<C, M, V>&);
-
-// ============================================================================
-// array-like types; most likely STL container, like std::vector, etc.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::is_container<T>,         // T is a container
-    detail::has_push_back_method<T>, // container.push_back(elem) works
-    detail::negation<                // but not toml::array
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    using value_type = typename T::value_type;
-    const auto& ary = v.as_array();
-
-    T container;
-    try_reserve(container, ary.size());
-
-    for(const auto& elem : ary)
-    {
-        container.push_back(get<value_type>(elem));
-    }
-    return container;
-}
-
-// ============================================================================
-// std::forward_list does not have push_back, insert, or emplace.
-// It has insert_after, emplace_after, push_front.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_std_forward_list<T>::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    using value_type = typename T::value_type;
-    T container;
-    for(const auto& elem : v.as_array())
-    {
-        container.push_front(get<value_type>(elem));
-    }
-    container.reverse();
-    return container;
-}
-
-// ============================================================================
-// array-like types, without push_back(). most likely [std|boost]::array.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::is_container<T>,                           // T is a container
-    detail::negation<detail::has_push_back_method<T>>, // w/o push_back
-    detail::negation<                                  // T is not toml::array
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    using value_type = typename T::value_type;
-    const auto& ar = v.as_array();
-
-    T container;
-    if(ar.size() != container.size())
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "toml::get: specified container size is ", container.size(),
-            " but there are ", ar.size(), " elements in toml array."), {
-                {v.location(), "here"}
-            }));
-    }
-    for(std::size_t i=0; i<ar.size(); ++i)
-    {
-        container[i] = ::toml::get<value_type>(ar[i]);
-    }
-    return container;
-}
-
-// ============================================================================
-// std::pair.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_std_pair<T>::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    using first_type  = typename T::first_type;
-    using second_type = typename T::second_type;
-
-    const auto& ar = v.as_array();
-    if(ar.size() != 2)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "toml::get: specified std::pair but there are ", ar.size(),
-            " elements in toml array."), {{v.location(), "here"}}));
-    }
-    return std::make_pair(::toml::get<first_type >(ar.at(0)),
-                          ::toml::get<second_type>(ar.at(1)));
-}
-
-// ============================================================================
-// std::tuple.
-
-namespace detail
-{
-template<typename T, typename Array, std::size_t ... I>
-T get_tuple_impl(const Array& a, index_sequence<I...>)
-{
-    return std::make_tuple(
-        ::toml::get<typename std::tuple_element<I, T>::type>(a.at(I))...);
-}
-} // detail
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_std_tuple<T>::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    const auto& ar = v.as_array();
-    if(ar.size() != std::tuple_size<T>::value)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "toml::get: specified std::tuple with ",
-            std::tuple_size<T>::value, " elements, but there are ", ar.size(),
-            " elements in toml array."), {{v.location(), "here"}}));
-    }
-    return detail::get_tuple_impl<T>(ar,
-            detail::make_index_sequence<std::tuple_size<T>::value>{});
-}
-
-// ============================================================================
-// map-like types; most likely STL map, like std::map or std::unordered_map.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::is_map<T>, // T is map
-    detail::negation<  // but not toml::array
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    using key_type    = typename T::key_type;
-    using mapped_type = typename T::mapped_type;
-    static_assert(std::is_convertible<std::string, key_type>::value,
-                  "toml::get only supports map type of which key_type is "
-                  "convertible from std::string.");
-    T map;
-    for(const auto& kv : v.as_table())
-    {
-        map.emplace(key_type(kv.first), get<mapped_type>(kv.second));
-    }
-    return map;
-}
-
-// ============================================================================
-// user-defined, but compatible types.
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::negation<                         // not a toml::* type
-        detail::is_exact_toml_type<T, basic_value<C, M, V>>>,
-    detail::has_from_toml_method<T, C, M, V>, // but has from_toml(toml::value) memfn
-    std::is_default_constructible<T>          // and default constructible
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    T ud;
-    ud.from_toml(v);
-    return ud;
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::has_specialized_from<T>::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    return ::toml::from<T>::from_toml(v);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::negation<detail::is_basic_value<T>>,                // T is not a toml::value
-    std::is_constructible<T, const basic_value<C, M, V>&>,      // T is constructible from toml::value
-    detail::negation<detail::has_from_toml_method<T, C, M, V>>, // and T does not have T.from_toml(v);
-    detail::negation<detail::has_specialized_from<T>>           // and T does not have toml::from<T>{};
-    >::value, T>
-get(const basic_value<C, M, V>& v)
-{
-    return T(v);
-}
-
-// ============================================================================
-// find
-
-// ----------------------------------------------------------------------------
-// these overloads do not require to set T. and returns value itself.
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> const& find(const basic_value<C, M, V>& v, const key& ky)
-{
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0)
-    {
-        detail::throw_key_not_found_error(v, ky);
-    }
-    return tab.at(ky);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>& find(basic_value<C, M, V>& v, const key& ky)
-{
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0)
-    {
-        detail::throw_key_not_found_error(v, ky);
-    }
-    return tab.at(ky);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> find(basic_value<C, M, V>&& v, const key& ky)
-{
-    typename basic_value<C, M, V>::table_type tab = std::move(v).as_table();
-    if(tab.count(ky) == 0)
-    {
-        detail::throw_key_not_found_error(v, ky);
-    }
-    return basic_value<C, M, V>(std::move(tab.at(ky)));
-}
-
-// ----------------------------------------------------------------------------
-// find(value, idx)
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> const&
-find(const basic_value<C, M, V>& v, const std::size_t idx)
-{
-    const auto& ary = v.as_array();
-    if(ary.size() <= idx)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "index ", idx, " is out of range"), {{v.location(), "in this array"}}));
-    }
-    return ary.at(idx);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>& find(basic_value<C, M, V>& v, const std::size_t idx)
-{
-    auto& ary = v.as_array();
-    if(ary.size() <= idx)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "index ", idx, " is out of range"), {{v.location(), "in this array"}}));
-    }
-    return ary.at(idx);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> find(basic_value<C, M, V>&& v, const std::size_t idx)
-{
-    auto& ary = v.as_array();
-    if(ary.size() <= idx)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "index ", idx, " is out of range"), {{v.location(), "in this array"}}));
-    }
-    return basic_value<C, M, V>(std::move(ary.at(idx)));
-}
-
-// ----------------------------------------------------------------------------
-// find<T>(value, key);
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V> const&>()))
-find(const basic_value<C, M, V>& v, const key& ky)
-{
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0)
-    {
-        detail::throw_key_not_found_error(v, ky);
-    }
-    return ::toml::get<T>(tab.at(ky));
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))
-find(basic_value<C, M, V>& v, const key& ky)
-{
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0)
-    {
-        detail::throw_key_not_found_error(v, ky);
-    }
-    return ::toml::get<T>(tab.at(ky));
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))
-find(basic_value<C, M, V>&& v, const key& ky)
-{
-    typename basic_value<C, M, V>::table_type tab = std::move(v).as_table();
-    if(tab.count(ky) == 0)
-    {
-        detail::throw_key_not_found_error(v, ky);
-    }
-    return ::toml::get<T>(std::move(tab.at(ky)));
-}
-
-// ----------------------------------------------------------------------------
-// find<T>(value, idx)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V> const&>()))
-find(const basic_value<C, M, V>& v, const std::size_t idx)
-{
-    const auto& ary = v.as_array();
-    if(ary.size() <= idx)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "index ", idx, " is out of range"), {{v.location(), "in this array"}}));
-    }
-    return ::toml::get<T>(ary.at(idx));
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))
-find(basic_value<C, M, V>& v, const std::size_t idx)
-{
-    auto& ary = v.as_array();
-    if(ary.size() <= idx)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "index ", idx, " is out of range"), {{v.location(), "in this array"}}));
-    }
-    return ::toml::get<T>(ary.at(idx));
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))
-find(basic_value<C, M, V>&& v, const std::size_t idx)
-{
-    typename basic_value<C, M, V>::array_type ary = std::move(v).as_array();
-    if(ary.size() <= idx)
-    {
-        throw std::out_of_range(detail::format_underline(concat_to_string(
-            "index ", idx, " is out of range"), {{v.location(), "in this array"}}));
-    }
-    return ::toml::get<T>(std::move(ary.at(idx)));
-}
-
-// --------------------------------------------------------------------------
-// toml::find(toml::value, toml::key, Ts&& ... keys)
-
-namespace detail
-{
-// It suppresses warnings by -Wsign-conversion. Let's say we have the following
-// code.
-// ```cpp
-// const auto x = toml::find<std::string>(data, "array", 0);
-// ```
-// Here, the type of literal number `0` is `int`. `int` is a signed integer.
-// `toml::find` takes `std::size_t` as an index. So it causes implicit sign
-// conversion and `-Wsign-conversion` warns about it. Using `0u` instead of `0`
-// suppresses the warning, but it makes user code messy.
-//     To suppress this warning, we need to be aware of type conversion caused
-// by `toml::find(v, key1, key2, ... keys)`. But the thing is that the types of
-// keys can be any combination of {string-like, size_t-like}. Of course we can't
-// write down all the combinations. Thus we need to use some function that
-// recognize the type of argument and cast it into `std::string` or
-// `std::size_t` depending on the context.
-//     `key_cast` does the job. It has 2 overloads. One is invoked when the
-// argument type is an integer and cast the argument into `std::size_t`. The
-// other is invoked when the argument type is not an integer, possibly one of
-// std::string, const char[N] or const char*, and construct std::string from
-// the argument.
-//     `toml::find(v, k1, k2, ... ks)` uses `key_cast` before passing `ks` to
-// `toml::find(v, k)` to suppress -Wsign-conversion.
-
-template<typename T>
-enable_if_t<conjunction<std::is_integral<remove_cvref_t<T>>,
-            negation<std::is_same<remove_cvref_t<T>, bool>>>::value, std::size_t>
-key_cast(T&& v) noexcept
-{
-    return std::size_t(v);
-}
-template<typename T>
-enable_if_t<negation<conjunction<std::is_integral<remove_cvref_t<T>>,
-            negation<std::is_same<remove_cvref_t<T>, bool>>>>::value, std::string>
-key_cast(T&& v) noexcept
-{
-    return std::string(std::forward<T>(v));
-}
-} // detail
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename Key1, typename Key2, typename ... Keys>
-const basic_value<C, M, V>&
-find(const basic_value<C, M, V>& v, Key1&& k1, Key2&& k2, Keys&& ... keys)
-{
-    return ::toml::find(::toml::find(v, detail::key_cast(k1)),
-            detail::key_cast(k2), std::forward<Keys>(keys)...);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename Key1, typename Key2, typename ... Keys>
-basic_value<C, M, V>&
-find(basic_value<C, M, V>& v, Key1&& k1, Key2&& k2, Keys&& ... keys)
-{
-    return ::toml::find(::toml::find(v, detail::key_cast(k1)),
-            detail::key_cast(k2), std::forward<Keys>(keys)...);
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename Key1, typename Key2, typename ... Keys>
-basic_value<C, M, V>
-find(basic_value<C, M, V>&& v, Key1&& k1, Key2&& k2, Keys&& ... keys)
-{
-    return ::toml::find(::toml::find(std::move(v), std::forward<Key1>(k1)),
-            detail::key_cast(k2), std::forward<Keys>(keys)...);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename Key1, typename Key2, typename ... Keys>
-decltype(::toml::get<T>(std::declval<const basic_value<C, M, V>&>()))
-find(const basic_value<C, M, V>& v, Key1&& k1, Key2&& k2, Keys&& ... keys)
-{
-    return ::toml::find<T>(::toml::find(v, detail::key_cast(k1)),
-            detail::key_cast(k2), std::forward<Keys>(keys)...);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename Key1, typename Key2, typename ... Keys>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&>()))
-find(basic_value<C, M, V>& v, Key1&& k1, Key2&& k2, Keys&& ... keys)
-{
-    return ::toml::find<T>(::toml::find(v, detail::key_cast(k1)),
-            detail::key_cast(k2), std::forward<Keys>(keys)...);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V,
-         typename Key1, typename Key2, typename ... Keys>
-decltype(::toml::get<T>(std::declval<basic_value<C, M, V>&&>()))
-find(basic_value<C, M, V>&& v, Key1&& k1, Key2&& k2, Keys&& ... keys)
-{
-    return ::toml::find<T>(::toml::find(std::move(v), detail::key_cast(k1)),
-            detail::key_cast(k2), std::forward<Keys>(keys)...);
-}
-
-// ============================================================================
-// get_or(value, fallback)
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> const&
-get_or(const basic_value<C, M, V>& v, const basic_value<C, M, V>&)
-{
-    return v;
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>&
-get_or(basic_value<C, M, V>& v, basic_value<C, M, V>&)
-{
-    return v;
-}
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>
-get_or(basic_value<C, M, V>&& v, basic_value<C, M, V>&&)
-{
-    return v;
-}
-
-// ----------------------------------------------------------------------------
-// specialization for the exact toml types (return type becomes lvalue ref)
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T> const&
-get_or(const basic_value<C, M, V>& v, const T& opt)
-{
-    try
-    {
-        return get<detail::remove_cvref_t<T>>(v);
-    }
-    catch(...)
-    {
-        return opt;
-    }
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>&
-get_or(basic_value<C, M, V>& v, T& opt)
-{
-    try
-    {
-        return get<detail::remove_cvref_t<T>>(v);
-    }
-    catch(...)
-    {
-        return opt;
-    }
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_exact_toml_type<detail::remove_cvref_t<T>,
-    basic_value<C, M, V>>::value, detail::remove_cvref_t<T>>
-get_or(basic_value<C, M, V>&& v, T&& opt)
-{
-    try
-    {
-        return get<detail::remove_cvref_t<T>>(std::move(v));
-    }
-    catch(...)
-    {
-        return detail::remove_cvref_t<T>(std::forward<T>(opt));
-    }
-}
-
-// ----------------------------------------------------------------------------
-// specialization for std::string (return type becomes lvalue ref)
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<detail::remove_cvref_t<T>, std::string>::value,
-    std::string> const&
-get_or(const basic_value<C, M, V>& v, const T& opt)
-{
-    try
-    {
-        return v.as_string().str;
-    }
-    catch(...)
-    {
-        return opt;
-    }
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string>&
-get_or(basic_value<C, M, V>& v, T& opt)
-{
-    try
-    {
-        return v.as_string().str;
-    }
-    catch(...)
-    {
-        return opt;
-    }
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    std::is_same<detail::remove_cvref_t<T>, std::string>::value, std::string>
-get_or(basic_value<C, M, V>&& v, T&& opt)
-{
-    try
-    {
-        return std::move(v.as_string().str);
-    }
-    catch(...)
-    {
-        return std::string(std::forward<T>(opt));
-    }
-}
-
-// ----------------------------------------------------------------------------
-// specialization for string literal
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::is_string_literal<
-    typename std::remove_reference<T>::type>::value, std::string>
-get_or(const basic_value<C, M, V>& v, T&& opt)
-{
-    try
-    {
-        return std::move(v.as_string().str);
-    }
-    catch(...)
-    {
-        return std::string(std::forward<T>(opt));
-    }
-}
-
-// ----------------------------------------------------------------------------
-// others (require type conversion and return type cannot be lvalue reference)
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    detail::negation<detail::is_exact_toml_type<detail::remove_cvref_t<T>,
-        basic_value<C, M, V>>>,
-    detail::negation<std::is_same<std::string, detail::remove_cvref_t<T>>>,
-    detail::negation<detail::is_string_literal<
-        typename std::remove_reference<T>::type>>
-    >::value, detail::remove_cvref_t<T>>
-get_or(const basic_value<C, M, V>& v, T&& opt)
-{
-    try
-    {
-        return get<detail::remove_cvref_t<T>>(v);
-    }
-    catch(...)
-    {
-        return detail::remove_cvref_t<T>(std::forward<T>(opt));
-    }
-}
-
-// ===========================================================================
-// find_or(value, key, fallback)
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V> const&
-find_or(const basic_value<C, M, V>& v, const key& ky,
-        const basic_value<C, M, V>& opt)
-{
-    if(!v.is_table()) {return opt;}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return tab.at(ky);
-}
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>&
-find_or(basic_value<C, M, V>& v, const toml::key& ky, basic_value<C, M, V>& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return tab.at(ky);
-}
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-basic_value<C, M, V>
-find_or(basic_value<C, M, V>&& v, const toml::key& ky, basic_value<C, M, V>&& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto tab = std::move(v).as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return basic_value<C, M, V>(std::move(tab.at(ky)));
-}
-
-// ---------------------------------------------------------------------------
-// exact types (return type can be a reference)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T> const&
-find_or(const basic_value<C, M, V>& v, const key& ky, const T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value, T>&
-find_or(basic_value<C, M, V>& v, const toml::key& ky, T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_exact_toml_type<T, basic_value<C, M, V>>::value,
-    detail::remove_cvref_t<T>>
-find_or(basic_value<C, M, V>&& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::forward<T>(opt);}
-    auto tab = std::move(v).as_table();
-    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
-    return get_or(std::move(tab.at(ky)), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// std::string (return type can be a reference)
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string> const&
-find_or(const basic_value<C, M, V>& v, const key& ky, const T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string>&
-find_or(basic_value<C, M, V>& v, const toml::key& ky, T& opt)
-{
-    if(!v.is_table()) {return opt;}
-    auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return opt;}
-    return get_or(tab.at(ky), opt);
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<std::is_same<T, std::string>::value, std::string>
-find_or(basic_value<C, M, V>&& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::forward<T>(opt);}
-    auto tab = std::move(v).as_table();
-    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
-    return get_or(std::move(tab.at(ky)), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// string literal (deduced as std::string)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<
-    detail::is_string_literal<typename std::remove_reference<T>::type>::value,
-    std::string>
-find_or(const basic_value<C, M, V>& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::string(opt);}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return std::string(opt);}
-    return get_or(tab.at(ky), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// others (require type conversion and return type cannot be lvalue reference)
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-detail::enable_if_t<detail::conjunction<
-    // T is not an exact toml type
-    detail::negation<detail::is_exact_toml_type<
-        detail::remove_cvref_t<T>, basic_value<C, M, V>>>,
-    // T is not std::string
-    detail::negation<std::is_same<std::string, detail::remove_cvref_t<T>>>,
-    // T is not a string literal
-    detail::negation<detail::is_string_literal<
-        typename std::remove_reference<T>::type>>
-    >::value, detail::remove_cvref_t<T>>
-find_or(const basic_value<C, M, V>& v, const toml::key& ky, T&& opt)
-{
-    if(!v.is_table()) {return std::forward<T>(opt);}
-    const auto& tab = v.as_table();
-    if(tab.count(ky) == 0) {return std::forward<T>(opt);}
-    return get_or(tab.at(ky), std::forward<T>(opt));
-}
-
-// ---------------------------------------------------------------------------
-// recursive find-or with type deduction (find_or(value, keys, opt))
-
-template<typename Value, typename ... Ks,
-         typename detail::enable_if_t<(sizeof...(Ks) > 1), std::nullptr_t> = nullptr>
-         // here we need to add SFINAE in the template parameter to avoid
-         // infinite recursion in type deduction on gcc
-auto find_or(Value&& v, const toml::key& ky, Ks&& ... keys)
-    -> decltype(find_or(std::forward<Value>(v), ky, detail::last_one(std::forward<Ks>(keys)...)))
-{
-    if(!v.is_table())
-    {
-        return detail::last_one(std::forward<Ks>(keys)...);
-    }
-    auto&& tab = std::forward<Value>(v).as_table();
-    if(tab.count(ky) == 0)
-    {
-        return detail::last_one(std::forward<Ks>(keys)...);
-    }
-    return find_or(std::forward<decltype(tab)>(tab).at(ky), std::forward<Ks>(keys)...);
-}
-
-// ---------------------------------------------------------------------------
-// recursive find_or with explicit type specialization, find_or<int>(value, keys...)
-
-template<typename T, typename Value, typename ... Ks,
-         typename detail::enable_if_t<(sizeof...(Ks) > 1), std::nullptr_t> = nullptr>
-         // here we need to add SFINAE in the template parameter to avoid
-         // infinite recursion in type deduction on gcc
-auto find_or(Value&& v, const toml::key& ky, Ks&& ... keys)
-    -> decltype(find_or<T>(std::forward<Value>(v), ky, detail::last_one(std::forward<Ks>(keys)...)))
-{
-    if(!v.is_table())
-    {
-        return detail::last_one(std::forward<Ks>(keys)...);
-    }
-    auto&& tab = std::forward<Value>(v).as_table();
-    if(tab.count(ky) == 0)
-    {
-        return detail::last_one(std::forward<Ks>(keys)...);
-    }
-    return find_or(std::forward<decltype(tab)>(tab).at(ky), std::forward<Ks>(keys)...);
-}
-
-// ============================================================================
-// expect
-
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-result<T, std::string> expect(const basic_value<C, M, V>& v) noexcept
-{
-    try
-    {
-        return ok(get<T>(v));
-    }
-    catch(const std::exception& e)
-    {
-        return err(e.what());
-    }
-}
-template<typename T, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-result<T, std::string>
-expect(const basic_value<C, M, V>& v, const toml::key& k) noexcept
-{
-    try
-    {
-        return ok(find<T>(v, k));
-    }
-    catch(const std::exception& e)
-    {
-        return err(e.what());
-    }
-}
-
-} // toml
-#endif// TOML11_GET
diff --git a/src/toml11/toml/into.hpp b/src/toml11/toml/into.hpp
deleted file mode 100644
index 74495560e75..00000000000
--- a/src/toml11/toml/into.hpp
+++ /dev/null
@@ -1,19 +0,0 @@
-//     Copyright Toru Niina 2019.
-// Distributed under the MIT License.
-#ifndef TOML11_INTO_HPP
-#define TOML11_INTO_HPP
-
-namespace toml
-{
-
-template<typename T>
-struct into;
-// {
-//     static toml::value into_toml(const T& user_defined_type)
-//     {
-//         // User-defined conversions ...
-//     }
-// };
-
-} // toml
-#endif // TOML11_INTO_HPP
diff --git a/src/toml11/toml/lexer.hpp b/src/toml11/toml/lexer.hpp
deleted file mode 100644
index ea5050b8dd1..00000000000
--- a/src/toml11/toml/lexer.hpp
+++ /dev/null
@@ -1,293 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_LEXER_HPP
-#define TOML11_LEXER_HPP
-#include <istream>
-#include <sstream>
-#include <stdexcept>
-#include <fstream>
-
-#include "combinator.hpp"
-
-namespace toml
-{
-namespace detail
-{
-
-// these scans contents from current location in a container of char
-// and extract a region that matches their own pattern.
-// to see the implementation of each component, see combinator.hpp.
-
-using lex_wschar  = either<character<' '>, character<'\t'>>;
-using lex_ws      = repeat<lex_wschar, at_least<1>>;
-using lex_newline = either<character<'\n'>,
-                           sequence<character<'\r'>, character<'\n'>>>;
-using lex_lower   = in_range<'a', 'z'>;
-using lex_upper   = in_range<'A', 'Z'>;
-using lex_alpha   = either<lex_lower, lex_upper>;
-using lex_digit   = in_range<'0', '9'>;
-using lex_nonzero = in_range<'1', '9'>;
-using lex_oct_dig = in_range<'0', '7'>;
-using lex_bin_dig = in_range<'0', '1'>;
-using lex_hex_dig = either<lex_digit, in_range<'A', 'F'>, in_range<'a', 'f'>>;
-
-using lex_hex_prefix = sequence<character<'0'>, character<'x'>>;
-using lex_oct_prefix = sequence<character<'0'>, character<'o'>>;
-using lex_bin_prefix = sequence<character<'0'>, character<'b'>>;
-using lex_underscore = character<'_'>;
-using lex_plus       = character<'+'>;
-using lex_minus      = character<'-'>;
-using lex_sign       = either<lex_plus, lex_minus>;
-
-// digit | nonzero 1*(digit | _ digit)
-using lex_unsigned_dec_int = either<sequence<lex_nonzero, repeat<
-    either<lex_digit, sequence<lex_underscore, lex_digit>>, at_least<1>>>,
-    lex_digit>;
-// (+|-)? unsigned_dec_int
-using lex_dec_int = sequence<maybe<lex_sign>, lex_unsigned_dec_int>;
-
-// hex_prefix hex_dig *(hex_dig | _ hex_dig)
-using lex_hex_int = sequence<lex_hex_prefix, sequence<lex_hex_dig, repeat<
-    either<lex_hex_dig, sequence<lex_underscore, lex_hex_dig>>, unlimited>>>;
-// oct_prefix oct_dig *(oct_dig | _ oct_dig)
-using lex_oct_int = sequence<lex_oct_prefix, sequence<lex_oct_dig, repeat<
-    either<lex_oct_dig, sequence<lex_underscore, lex_oct_dig>>, unlimited>>>;
-// bin_prefix bin_dig *(bin_dig | _ bin_dig)
-using lex_bin_int = sequence<lex_bin_prefix, sequence<lex_bin_dig, repeat<
-    either<lex_bin_dig, sequence<lex_underscore, lex_bin_dig>>, unlimited>>>;
-
-// (dec_int | hex_int | oct_int | bin_int)
-using lex_integer = either<lex_bin_int, lex_oct_int, lex_hex_int, lex_dec_int>;
-
-// ===========================================================================
-
-using lex_inf = sequence<character<'i'>, character<'n'>, character<'f'>>;
-using lex_nan = sequence<character<'n'>, character<'a'>, character<'n'>>;
-using lex_special_float = sequence<maybe<lex_sign>, either<lex_inf, lex_nan>>;
-
-using lex_zero_prefixable_int = sequence<lex_digit, repeat<either<lex_digit,
-    sequence<lex_underscore, lex_digit>>, unlimited>>;
-
-using lex_fractional_part = sequence<character<'.'>, lex_zero_prefixable_int>;
-
-using lex_exponent_part   = sequence<either<character<'e'>, character<'E'>>,
-        maybe<lex_sign>, lex_zero_prefixable_int>;
-
-using lex_float = either<lex_special_float,
-      sequence<lex_dec_int, either<lex_exponent_part,
-      sequence<lex_fractional_part, maybe<lex_exponent_part>>>>>;
-
-// ===========================================================================
-
-using lex_true = sequence<character<'t'>, character<'r'>,
-                          character<'u'>, character<'e'>>;
-using lex_false = sequence<character<'f'>, character<'a'>, character<'l'>,
-                           character<'s'>, character<'e'>>;
-using lex_boolean = either<lex_true, lex_false>;
-
-// ===========================================================================
-
-using lex_date_fullyear = repeat<lex_digit, exactly<4>>;
-using lex_date_month    = repeat<lex_digit, exactly<2>>;
-using lex_date_mday     = repeat<lex_digit, exactly<2>>;
-using lex_time_delim    = either<character<'T'>, character<'t'>, character<' '>>;
-using lex_time_hour     = repeat<lex_digit, exactly<2>>;
-using lex_time_minute   = repeat<lex_digit, exactly<2>>;
-using lex_time_second   = repeat<lex_digit, exactly<2>>;
-using lex_time_secfrac  = sequence<character<'.'>,
-                                   repeat<lex_digit, at_least<1>>>;
-
-using lex_time_numoffset = sequence<either<character<'+'>, character<'-'>>,
-                                    sequence<lex_time_hour, character<':'>,
-                                             lex_time_minute>>;
-using lex_time_offset = either<character<'Z'>, character<'z'>,
-                               lex_time_numoffset>;
-
-using lex_partial_time = sequence<lex_time_hour,   character<':'>,
-                                  lex_time_minute, character<':'>,
-                                  lex_time_second, maybe<lex_time_secfrac>>;
-using lex_full_date    = sequence<lex_date_fullyear, character<'-'>,
-                                  lex_date_month,    character<'-'>,
-                                  lex_date_mday>;
-using lex_full_time    = sequence<lex_partial_time, lex_time_offset>;
-
-using lex_offset_date_time = sequence<lex_full_date, lex_time_delim, lex_full_time>;
-using lex_local_date_time  = sequence<lex_full_date, lex_time_delim, lex_partial_time>;
-using lex_local_date       = lex_full_date;
-using lex_local_time       = lex_partial_time;
-
-// ===========================================================================
-
-using lex_quotation_mark  = character<'"'>;
-using lex_basic_unescaped = exclude<either<in_range<0x00, 0x08>, // 0x09 (tab) is allowed
-                                           in_range<0x0A, 0x1F>,
-                                           character<0x22>, character<0x5C>,
-                                           character<0x7F>>>;
-
-using lex_escape          = character<'\\'>;
-using lex_escape_unicode_short = sequence<character<'u'>,
-                                          repeat<lex_hex_dig, exactly<4>>>;
-using lex_escape_unicode_long  = sequence<character<'U'>,
-                                          repeat<lex_hex_dig, exactly<8>>>;
-using lex_escape_seq_char = either<character<'"'>, character<'\\'>,
-                                   character<'b'>, character<'f'>,
-                                   character<'n'>, character<'r'>,
-                                   character<'t'>,
-                                   lex_escape_unicode_short,
-                                   lex_escape_unicode_long
-                                   >;
-using lex_escaped      = sequence<lex_escape, lex_escape_seq_char>;
-using lex_basic_char   = either<lex_basic_unescaped, lex_escaped>;
-using lex_basic_string = sequence<lex_quotation_mark,
-                                  repeat<lex_basic_char, unlimited>,
-                                  lex_quotation_mark>;
-
-// After toml post-v0.5.0, it is explicitly clarified how quotes in ml-strings
-// are allowed to be used.
-// After this, the following strings are *explicitly* allowed.
-// - One or two `"`s in a multi-line basic string is allowed wherever it is.
-// - Three consecutive `"`s in a multi-line basic string is considered as a delimiter.
-// - One or two `"`s can appear just before or after the delimiter.
-// ```toml
-// str4 = """Here are two quotation marks: "". Simple enough."""
-// str5 = """Here are three quotation marks: ""\"."""
-// str6 = """Here are fifteen quotation marks: ""\"""\"""\"""\"""\"."""
-// str7 = """"This," she said, "is just a pointless statement.""""
-// ```
-// In the current implementation (v3.3.0), it is difficult to parse `str7` in
-// the above example. It is difficult to recognize `"` at the end of string body
-// collectly. It will be misunderstood as a `"""` delimiter and an additional,
-// invalid `"`. Like this:
-// ```console
-//   what():  [error] toml::parse_table: invalid line format
-//  --> hoge.toml
-//     |
-//  13 | str7 = """"This," she said, "is just a pointless statement.""""
-//     |                                                               ^- expected newline, but got '"'.
-// ```
-// As a quick workaround for this problem, `lex_ml_basic_string_delim` was
-// split into two, `lex_ml_basic_string_open` and `lex_ml_basic_string_close`.
-// `lex_ml_basic_string_open` allows only `"""`. `_close` allows 3-5 `"`s.
-// In parse_ml_basic_string() function, the trailing `"`s will be attached to
-// the string body.
-//
-using lex_ml_basic_string_delim = repeat<lex_quotation_mark, exactly<3>>;
-using lex_ml_basic_string_open  = lex_ml_basic_string_delim;
-using lex_ml_basic_string_close = sequence<
-        repeat<lex_quotation_mark, exactly<3>>,
-        maybe<lex_quotation_mark>, maybe<lex_quotation_mark>
-    >;
-
-using lex_ml_basic_unescaped    = exclude<either<in_range<0x00, 0x08>, // 0x09 is tab
-                                                 in_range<0x0A, 0x1F>,
-                                                 character<0x5C>, // backslash
-                                                 character<0x7F>, // DEL
-                                                 lex_ml_basic_string_delim>>;
-
-using lex_ml_basic_escaped_newline = sequence<
-        lex_escape, maybe<lex_ws>, lex_newline,
-        repeat<either<lex_ws, lex_newline>, unlimited>>;
-
-using lex_ml_basic_char = either<lex_ml_basic_unescaped, lex_escaped>;
-using lex_ml_basic_body = repeat<either<lex_ml_basic_char, lex_newline,
-                                        lex_ml_basic_escaped_newline>,
-                                 unlimited>;
-using lex_ml_basic_string = sequence<lex_ml_basic_string_open,
-                                     lex_ml_basic_body,
-                                     lex_ml_basic_string_close>;
-
-using lex_literal_char = exclude<either<in_range<0x00, 0x08>, in_range<0x0A, 0x1F>,
-                                        character<0x7F>, character<0x27>>>;
-using lex_apostrophe = character<'\''>;
-using lex_literal_string = sequence<lex_apostrophe,
-                                    repeat<lex_literal_char, unlimited>,
-                                    lex_apostrophe>;
-
-// the same reason as above.
-using lex_ml_literal_string_delim = repeat<lex_apostrophe, exactly<3>>;
-using lex_ml_literal_string_open  = lex_ml_literal_string_delim;
-using lex_ml_literal_string_close = sequence<
-        repeat<lex_apostrophe, exactly<3>>,
-        maybe<lex_apostrophe>, maybe<lex_apostrophe>
-    >;
-
-using lex_ml_literal_char = exclude<either<in_range<0x00, 0x08>,
-                                           in_range<0x0A, 0x1F>,
-                                           character<0x7F>,
-                                           lex_ml_literal_string_delim>>;
-using lex_ml_literal_body = repeat<either<lex_ml_literal_char, lex_newline>,
-                                   unlimited>;
-using lex_ml_literal_string = sequence<lex_ml_literal_string_open,
-                                       lex_ml_literal_body,
-                                       lex_ml_literal_string_close>;
-
-using lex_string = either<lex_ml_basic_string,   lex_basic_string,
-                          lex_ml_literal_string, lex_literal_string>;
-
-// ===========================================================================
-using lex_dot_sep = sequence<maybe<lex_ws>, character<'.'>, maybe<lex_ws>>;
-
-using lex_unquoted_key = repeat<either<lex_alpha, lex_digit,
-                                       character<'-'>, character<'_'>>,
-                                at_least<1>>;
-using lex_quoted_key = either<lex_basic_string, lex_literal_string>;
-using lex_simple_key = either<lex_unquoted_key, lex_quoted_key>;
-using lex_dotted_key = sequence<lex_simple_key,
-                                repeat<sequence<lex_dot_sep, lex_simple_key>,
-                                       at_least<1>
-                                       >
-                                >;
-using lex_key = either<lex_dotted_key, lex_simple_key>;
-
-using lex_keyval_sep = sequence<maybe<lex_ws>,
-                                character<'='>,
-                                maybe<lex_ws>>;
-
-using lex_std_table_open  = character<'['>;
-using lex_std_table_close = character<']'>;
-using lex_std_table       = sequence<lex_std_table_open,
-                                     maybe<lex_ws>,
-                                     lex_key,
-                                     maybe<lex_ws>,
-                                     lex_std_table_close>;
-
-using lex_array_table_open  = sequence<lex_std_table_open,  lex_std_table_open>;
-using lex_array_table_close = sequence<lex_std_table_close, lex_std_table_close>;
-using lex_array_table       = sequence<lex_array_table_open,
-                                       maybe<lex_ws>,
-                                       lex_key,
-                                       maybe<lex_ws>,
-                                       lex_array_table_close>;
-
-using lex_utf8_1byte = in_range<0x00, 0x7F>;
-using lex_utf8_2byte = sequence<
-        in_range<static_cast<char>(0xC2), static_cast<char>(0xDF)>,
-        in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>
-    >;
-using lex_utf8_3byte = sequence<either<
-        sequence<character<static_cast<char>(0xE0)>,                          in_range<static_cast<char>(0xA0), static_cast<char>(0xBF)>>,
-        sequence<in_range <static_cast<char>(0xE1), static_cast<char>(0xEC)>, in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>>,
-        sequence<character<static_cast<char>(0xED)>,                          in_range<static_cast<char>(0x80), static_cast<char>(0x9F)>>,
-        sequence<in_range <static_cast<char>(0xEE), static_cast<char>(0xEF)>, in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>>
-    >, in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>>;
-using lex_utf8_4byte = sequence<either<
-        sequence<character<static_cast<char>(0xF0)>,                          in_range<static_cast<char>(0x90), static_cast<char>(0xBF)>>,
-        sequence<in_range <static_cast<char>(0xF1), static_cast<char>(0xF3)>, in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>>,
-        sequence<character<static_cast<char>(0xF4)>,                          in_range<static_cast<char>(0x80), static_cast<char>(0x8F)>>
-    >, in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>,
-       in_range<static_cast<char>(0x80), static_cast<char>(0xBF)>>;
-using lex_utf8_code = either<
-        lex_utf8_1byte,
-        lex_utf8_2byte,
-        lex_utf8_3byte,
-        lex_utf8_4byte
-    >;
-
-using lex_comment_start_symbol = character<'#'>;
-using lex_non_eol_ascii = either<character<0x09>, in_range<0x20, 0x7E>>;
-using lex_comment = sequence<lex_comment_start_symbol, repeat<either<
-    lex_non_eol_ascii, lex_utf8_2byte, lex_utf8_3byte, lex_utf8_4byte>, unlimited>>;
-
-} // detail
-} // toml
-#endif // TOML_LEXER_HPP
diff --git a/src/toml11/toml/literal.hpp b/src/toml11/toml/literal.hpp
deleted file mode 100644
index 04fbbc13e18..00000000000
--- a/src/toml11/toml/literal.hpp
+++ /dev/null
@@ -1,113 +0,0 @@
-//     Copyright Toru Niina 2019.
-// Distributed under the MIT License.
-#ifndef TOML11_LITERAL_HPP
-#define TOML11_LITERAL_HPP
-#include "parser.hpp"
-
-namespace toml
-{
-inline namespace literals
-{
-inline namespace toml_literals
-{
-
-// implementation
-inline ::toml::basic_value<TOML11_DEFAULT_COMMENT_STRATEGY, std::unordered_map, std::vector>
-literal_internal_impl(::toml::detail::location loc)
-{
-    using value_type = ::toml::basic_value<
-        TOML11_DEFAULT_COMMENT_STRATEGY, std::unordered_map, std::vector>;
-    // if there are some comments or empty lines, skip them.
-    using skip_line = ::toml::detail::repeat<toml::detail::sequence<
-            ::toml::detail::maybe<::toml::detail::lex_ws>,
-            ::toml::detail::maybe<::toml::detail::lex_comment>,
-            ::toml::detail::lex_newline
-        >, ::toml::detail::at_least<1>>;
-    skip_line::invoke(loc);
-
-    // if there are some whitespaces before a value, skip them.
-    using skip_ws = ::toml::detail::repeat<
-        ::toml::detail::lex_ws, ::toml::detail::at_least<1>>;
-    skip_ws::invoke(loc);
-
-    // to distinguish arrays and tables, first check it is a table or not.
-    //
-    // "[1,2,3]"_toml;   // this is an array
-    // "[table]"_toml;   // a table that has an empty table named "table" inside.
-    // "[[1,2,3]]"_toml; // this is an array of arrays
-    // "[[table]]"_toml; // this is a table that has an array of tables inside.
-    //
-    // "[[1]]"_toml;     // this can be both... (currently it becomes a table)
-    // "1 = [{}]"_toml;  // this is a table that has an array of table named 1.
-    // "[[1,]]"_toml;    // this is an array of arrays.
-    // "[[1],]"_toml;    // this also.
-
-    const auto the_front = loc.iter();
-
-    const bool is_table_key = ::toml::detail::lex_std_table::invoke(loc);
-    loc.reset(the_front);
-
-    const bool is_aots_key  = ::toml::detail::lex_array_table::invoke(loc);
-    loc.reset(the_front);
-
-    // If it is neither a table-key or a array-of-table-key, it may be a value.
-    if(!is_table_key && !is_aots_key)
-    {
-        if(auto data = ::toml::detail::parse_value<value_type>(loc))
-        {
-            return data.unwrap();
-        }
-    }
-
-    // Note that still it can be a table, because the literal might be something
-    // like the following.
-    // ```cpp
-    // R"( // c++11 raw string literals
-    //   key = "value"
-    //   int = 42
-    // )"_toml;
-    // ```
-    // It is a valid toml file.
-    // It should be parsed as if we parse a file with this content.
-
-    if(auto data = ::toml::detail::parse_toml_file<value_type>(loc))
-    {
-        return data.unwrap();
-    }
-    else // none of them.
-    {
-        throw ::toml::syntax_error(data.unwrap_err(), source_location(loc));
-    }
-
-}
-
-inline ::toml::basic_value<TOML11_DEFAULT_COMMENT_STRATEGY, std::unordered_map, std::vector>
-operator"" _toml(const char* str, std::size_t len)
-{
-    ::toml::detail::location loc(
-            std::string("TOML literal encoded in a C++ code"),
-            std::vector<char>(str, str + len));
-    // literal length does not include the null character at the end.
-    return literal_internal_impl(std::move(loc));
-}
-
-// value of __cplusplus in C++2a/20 mode is not fixed yet along compilers.
-// So here we use the feature test macro for `char8_t` itself.
-#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
-// value of u8"" literal has been changed from char to char8_t and char8_t is
-// NOT compatible to char
-inline ::toml::basic_value<TOML11_DEFAULT_COMMENT_STRATEGY, std::unordered_map, std::vector>
-operator"" _toml(const char8_t* str, std::size_t len)
-{
-    ::toml::detail::location loc(
-            std::string("TOML literal encoded in a C++ code"),
-            std::vector<char>(reinterpret_cast<const char*>(str),
-                              reinterpret_cast<const char*>(str) + len));
-    return literal_internal_impl(std::move(loc));
-}
-#endif
-
-} // toml_literals
-} // literals
-} // toml
-#endif//TOML11_LITERAL_HPP
diff --git a/src/toml11/toml/macros.hpp b/src/toml11/toml/macros.hpp
deleted file mode 100644
index e8f91aecd44..00000000000
--- a/src/toml11/toml/macros.hpp
+++ /dev/null
@@ -1,121 +0,0 @@
-#ifndef TOML11_MACROS_HPP
-#define TOML11_MACROS_HPP
-
-#define TOML11_STRINGIZE_AUX(x) #x
-#define TOML11_STRINGIZE(x)     TOML11_STRINGIZE_AUX(x)
-
-#define TOML11_CONCATENATE_AUX(x, y) x##y
-#define TOML11_CONCATENATE(x, y)     TOML11_CONCATENATE_AUX(x, y)
-
-// ============================================================================
-// TOML11_DEFINE_CONVERSION_NON_INTRUSIVE
-
-#ifndef TOML11_WITHOUT_DEFINE_NON_INTRUSIVE
-
-// ----------------------------------------------------------------------------
-// TOML11_ARGS_SIZE
-
-#define TOML11_INDEX_RSEQ() \
-    32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, \
-    16, 15, 14, 13, 12, 11, 10,  9,  8,  7,  6,  5,  4,  3,  2,  1, 0
-#define TOML11_ARGS_SIZE_IMPL(\
-    ARG1,  ARG2,  ARG3,  ARG4,  ARG5,  ARG6,  ARG7,  ARG8,  ARG9,  ARG10, \
-    ARG11, ARG12, ARG13, ARG14, ARG15, ARG16, ARG17, ARG18, ARG19, ARG20, \
-    ARG21, ARG22, ARG23, ARG24, ARG25, ARG26, ARG27, ARG28, ARG29, ARG30, \
-    ARG31, ARG32, N, ...) N
-#define TOML11_ARGS_SIZE_AUX(...) TOML11_ARGS_SIZE_IMPL(__VA_ARGS__)
-#define TOML11_ARGS_SIZE(...) TOML11_ARGS_SIZE_AUX(__VA_ARGS__, TOML11_INDEX_RSEQ())
-
-// ----------------------------------------------------------------------------
-// TOML11_FOR_EACH_VA_ARGS
-
-#define TOML11_FOR_EACH_VA_ARGS_AUX_1( FUNCTOR, ARG1     ) FUNCTOR(ARG1)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_2( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_1( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_3( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_2( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_4( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_3( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_5( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_4( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_6( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_5( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_7( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_6( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_8( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_7( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_9( FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_8( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_10(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_9( FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_11(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_10(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_12(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_11(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_13(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_12(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_14(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_13(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_15(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_14(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_16(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_15(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_17(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_16(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_18(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_17(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_19(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_18(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_20(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_19(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_21(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_20(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_22(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_21(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_23(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_22(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_24(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_23(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_25(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_24(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_26(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_25(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_27(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_26(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_28(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_27(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_29(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_28(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_30(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_29(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_31(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_30(FUNCTOR, __VA_ARGS__)
-#define TOML11_FOR_EACH_VA_ARGS_AUX_32(FUNCTOR, ARG1, ...) FUNCTOR(ARG1) TOML11_FOR_EACH_VA_ARGS_AUX_31(FUNCTOR, __VA_ARGS__)
-
-#define TOML11_FOR_EACH_VA_ARGS(FUNCTOR, ...)\
-    TOML11_CONCATENATE(TOML11_FOR_EACH_VA_ARGS_AUX_, TOML11_ARGS_SIZE(__VA_ARGS__))(FUNCTOR, __VA_ARGS__)
-
-// ----------------------------------------------------------------------------
-// TOML11_DEFINE_CONVERSION_NON_INTRUSIVE
-
-// use it in the following way.
-// ```cpp
-// namespace foo
-// {
-// struct Foo
-// {
-//     std::string s;
-//     double      d;
-//     int         i;
-// };
-// } // foo
-//
-// TOML11_DEFINE_CONVERSION_NON_INTRUSIVE(foo::Foo, s, d, i)
-// ```
-// And then you can use `toml::find<foo::Foo>(file, "foo");`
-//
-#define TOML11_FIND_MEMBER_VARIABLE_FROM_VALUE(VAR_NAME)\
-    obj.VAR_NAME = toml::find<decltype(obj.VAR_NAME)>(v, TOML11_STRINGIZE(VAR_NAME));
-
-#define TOML11_ASSIGN_MEMBER_VARIABLE_TO_VALUE(VAR_NAME)\
-    v[TOML11_STRINGIZE(VAR_NAME)] = obj.VAR_NAME;
-
-#define TOML11_DEFINE_CONVERSION_NON_INTRUSIVE(NAME, ...)\
-    namespace toml {                                                                     \
-    template<>                                                                           \
-    struct from<NAME>                                                                    \
-    {                                                                                    \
-        template<typename C, template<typename ...> class T,                             \
-                 template<typename ...> class A>                                         \
-        static NAME from_toml(const basic_value<C, T, A>& v)                             \
-        {                                                                                \
-            NAME obj;                                                                    \
-            TOML11_FOR_EACH_VA_ARGS(TOML11_FIND_MEMBER_VARIABLE_FROM_VALUE, __VA_ARGS__) \
-            return obj;                                                                  \
-        }                                                                                \
-    };                                                                                   \
-    template<>                                                                           \
-    struct into<NAME>                                                                    \
-    {                                                                                    \
-        static value into_toml(const NAME& obj)                                          \
-        {                                                                                \
-            ::toml::value v = ::toml::table{};                                           \
-            TOML11_FOR_EACH_VA_ARGS(TOML11_ASSIGN_MEMBER_VARIABLE_TO_VALUE, __VA_ARGS__) \
-            return v;                                                                    \
-        }                                                                                \
-    };                                                                                   \
-    } /* toml */
-
-#endif// TOML11_WITHOUT_DEFINE_NON_INTRUSIVE
-
-#endif// TOML11_MACROS_HPP
diff --git a/src/toml11/toml/parser.hpp b/src/toml11/toml/parser.hpp
deleted file mode 100644
index e3117991811..00000000000
--- a/src/toml11/toml/parser.hpp
+++ /dev/null
@@ -1,2364 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_PARSER_HPP
-#define TOML11_PARSER_HPP
-#include <cstring>
-#include <fstream>
-#include <sstream>
-
-#include "combinator.hpp"
-#include "lexer.hpp"
-#include "region.hpp"
-#include "result.hpp"
-#include "types.hpp"
-#include "value.hpp"
-
-#ifndef TOML11_DISABLE_STD_FILESYSTEM
-#ifdef __cpp_lib_filesystem
-#if __has_include(<filesystem>)
-#define TOML11_HAS_STD_FILESYSTEM
-#include <filesystem>
-#endif // has_include(<string_view>)
-#endif // __cpp_lib_filesystem
-#endif // TOML11_DISABLE_STD_FILESYSTEM
-
-namespace toml
-{
-namespace detail
-{
-
-inline result<std::pair<boolean, region>, std::string>
-parse_boolean(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_boolean::invoke(loc))
-    {
-        const auto reg = token.unwrap();
-        if     (reg.str() == "true")  {return ok(std::make_pair(true,  reg));}
-        else if(reg.str() == "false") {return ok(std::make_pair(false, reg));}
-        else // internal error.
-        {
-            throw internal_error(format_underline(
-                "toml::parse_boolean: internal error",
-                {{source_location(reg), "invalid token"}}),
-                source_location(reg));
-        }
-    }
-    loc.reset(first); //rollback
-    return err(format_underline("toml::parse_boolean: ",
-               {{source_location(loc), "the next token is not a boolean"}}));
-}
-
-inline result<std::pair<integer, region>, std::string>
-parse_binary_integer(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_bin_int::invoke(loc))
-    {
-        auto str = token.unwrap().str();
-        assert(str.size() > 2); // minimum -> 0b1
-        integer retval(0), base(1);
-        for(auto i(str.rbegin()), e(str.rend() - 2); i!=e; ++i)
-        {
-            if     (*i == '1'){retval += base; base *= 2;}
-            else if(*i == '0'){base *= 2;}
-            else if(*i == '_'){/* do nothing. */}
-            else // internal error.
-            {
-                throw internal_error(format_underline(
-                    "toml::parse_integer: internal error",
-                    {{source_location(token.unwrap()), "invalid token"}}),
-                    source_location(loc));
-            }
-        }
-        return ok(std::make_pair(retval, token.unwrap()));
-    }
-    loc.reset(first);
-    return err(format_underline("toml::parse_binary_integer:",
-               {{source_location(loc), "the next token is not an integer"}}));
-}
-
-inline result<std::pair<integer, region>, std::string>
-parse_octal_integer(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_oct_int::invoke(loc))
-    {
-        auto str = token.unwrap().str();
-        str.erase(std::remove(str.begin(), str.end(), '_'), str.end());
-        str.erase(str.begin()); str.erase(str.begin()); // remove `0o` prefix
-
-        std::istringstream iss(str);
-        integer retval(0);
-        iss >> std::oct >> retval;
-        return ok(std::make_pair(retval, token.unwrap()));
-    }
-    loc.reset(first);
-    return err(format_underline("toml::parse_octal_integer:",
-               {{source_location(loc), "the next token is not an integer"}}));
-}
-
-inline result<std::pair<integer, region>, std::string>
-parse_hexadecimal_integer(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_hex_int::invoke(loc))
-    {
-        auto str = token.unwrap().str();
-        str.erase(std::remove(str.begin(), str.end(), '_'), str.end());
-        str.erase(str.begin()); str.erase(str.begin()); // remove `0x` prefix
-
-        std::istringstream iss(str);
-        integer retval(0);
-        iss >> std::hex >> retval;
-        return ok(std::make_pair(retval, token.unwrap()));
-    }
-    loc.reset(first);
-    return err(format_underline("toml::parse_hexadecimal_integer",
-               {{source_location(loc), "the next token is not an integer"}}));
-}
-
-inline result<std::pair<integer, region>, std::string>
-parse_integer(location& loc)
-{
-    const auto first = loc.iter();
-    if(first != loc.end() && *first == '0')
-    {
-        const auto second = std::next(first);
-        if(second == loc.end()) // the token is just zero.
-        {
-            loc.advance();
-            return ok(std::make_pair(0, region(loc, first, second)));
-        }
-
-        if(*second == 'b') {return parse_binary_integer     (loc);} // 0b1100
-        if(*second == 'o') {return parse_octal_integer      (loc);} // 0o775
-        if(*second == 'x') {return parse_hexadecimal_integer(loc);} // 0xC0FFEE
-
-        if(std::isdigit(*second))
-        {
-            return err(format_underline("toml::parse_integer: "
-                "leading zero in an Integer is not allowed.",
-                {{source_location(loc), "leading zero"}}));
-        }
-        else if(std::isalpha(*second))
-        {
-             return err(format_underline("toml::parse_integer: "
-                "unknown integer prefix appeared.",
-                {{source_location(loc), "none of 0x, 0o, 0b"}}));
-        }
-    }
-
-    if(const auto token = lex_dec_int::invoke(loc))
-    {
-        auto str = token.unwrap().str();
-        str.erase(std::remove(str.begin(), str.end(), '_'), str.end());
-
-        std::istringstream iss(str);
-        integer retval(0);
-        iss >> retval;
-        return ok(std::make_pair(retval, token.unwrap()));
-    }
-    loc.reset(first);
-    return err(format_underline("toml::parse_integer: ",
-               {{source_location(loc), "the next token is not an integer"}}));
-}
-
-inline result<std::pair<floating, region>, std::string>
-parse_floating(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_float::invoke(loc))
-    {
-        auto str = token.unwrap().str();
-        if(str == "inf" || str == "+inf")
-        {
-            if(std::numeric_limits<floating>::has_infinity)
-            {
-                return ok(std::make_pair(
-                    std::numeric_limits<floating>::infinity(), token.unwrap()));
-            }
-            else
-            {
-                throw std::domain_error("toml::parse_floating: inf value found"
-                    " but the current environment does not support inf. Please"
-                    " make sure that the floating-point implementation conforms"
-                    " IEEE 754/ISO 60559 international standard.");
-            }
-        }
-        else if(str == "-inf")
-        {
-            if(std::numeric_limits<floating>::has_infinity)
-            {
-                return ok(std::make_pair(
-                    -std::numeric_limits<floating>::infinity(), token.unwrap()));
-            }
-            else
-            {
-                throw std::domain_error("toml::parse_floating: inf value found"
-                    " but the current environment does not support inf. Please"
-                    " make sure that the floating-point implementation conforms"
-                    " IEEE 754/ISO 60559 international standard.");
-            }
-        }
-        else if(str == "nan" || str == "+nan")
-        {
-            if(std::numeric_limits<floating>::has_quiet_NaN)
-            {
-                return ok(std::make_pair(
-                    std::numeric_limits<floating>::quiet_NaN(), token.unwrap()));
-            }
-            else if(std::numeric_limits<floating>::has_signaling_NaN)
-            {
-                return ok(std::make_pair(
-                    std::numeric_limits<floating>::signaling_NaN(), token.unwrap()));
-            }
-            else
-            {
-                throw std::domain_error("toml::parse_floating: NaN value found"
-                    " but the current environment does not support NaN. Please"
-                    " make sure that the floating-point implementation conforms"
-                    " IEEE 754/ISO 60559 international standard.");
-            }
-        }
-        else if(str == "-nan")
-        {
-            if(std::numeric_limits<floating>::has_quiet_NaN)
-            {
-                return ok(std::make_pair(
-                    -std::numeric_limits<floating>::quiet_NaN(), token.unwrap()));
-            }
-            else if(std::numeric_limits<floating>::has_signaling_NaN)
-            {
-                return ok(std::make_pair(
-                    -std::numeric_limits<floating>::signaling_NaN(), token.unwrap()));
-            }
-            else
-            {
-                throw std::domain_error("toml::parse_floating: NaN value found"
-                    " but the current environment does not support NaN. Please"
-                    " make sure that the floating-point implementation conforms"
-                    " IEEE 754/ISO 60559 international standard.");
-            }
-        }
-        str.erase(std::remove(str.begin(), str.end(), '_'), str.end());
-        std::istringstream iss(str);
-        floating v(0.0);
-        iss >> v;
-        return ok(std::make_pair(v, token.unwrap()));
-    }
-    loc.reset(first);
-    return err(format_underline("toml::parse_floating: ",
-               {{source_location(loc), "the next token is not a float"}}));
-}
-
-inline std::string read_utf8_codepoint(const region& reg, const location& loc)
-{
-    const auto str = reg.str().substr(1);
-    std::uint_least32_t codepoint;
-    std::istringstream iss(str);
-    iss >> std::hex >> codepoint;
-
-    const auto to_char = [](const std::uint_least32_t i) noexcept -> char {
-        const auto uc = static_cast<unsigned char>(i);
-        return *reinterpret_cast<const char*>(std::addressof(uc));
-    };
-
-    std::string character;
-    if(codepoint < 0x80) // U+0000 ... U+0079 ; just an ASCII.
-    {
-        character += static_cast<char>(codepoint);
-    }
-    else if(codepoint < 0x800) //U+0080 ... U+07FF
-    {
-        // 110yyyyx 10xxxxxx; 0x3f == 0b0011'1111
-        character += to_char(0xC0| codepoint >> 6);
-        character += to_char(0x80|(codepoint & 0x3F));
-    }
-    else if(codepoint < 0x10000) // U+0800...U+FFFF
-    {
-        if(0xD800 <= codepoint && codepoint <= 0xDFFF)
-        {
-            throw syntax_error(format_underline(
-                "toml::read_utf8_codepoint: codepoints in the range "
-                "[0xD800, 0xDFFF] are not valid UTF-8.", {{
-                    source_location(loc), "not a valid UTF-8 codepoint"
-                }}), source_location(loc));
-        }
-        assert(codepoint < 0xD800 || 0xDFFF < codepoint);
-        // 1110yyyy 10yxxxxx 10xxxxxx
-        character += to_char(0xE0| codepoint >> 12);
-        character += to_char(0x80|(codepoint >> 6 & 0x3F));
-        character += to_char(0x80|(codepoint      & 0x3F));
-    }
-    else if(codepoint < 0x110000) // U+010000 ... U+10FFFF
-    {
-        // 11110yyy 10yyxxxx 10xxxxxx 10xxxxxx
-        character += to_char(0xF0| codepoint >> 18);
-        character += to_char(0x80|(codepoint >> 12 & 0x3F));
-        character += to_char(0x80|(codepoint >> 6  & 0x3F));
-        character += to_char(0x80|(codepoint       & 0x3F));
-    }
-    else // out of UTF-8 region
-    {
-        throw syntax_error(format_underline("toml::read_utf8_codepoint:"
-            " input codepoint is too large.",
-            {{source_location(loc), "should be in [0x00..0x10FFFF]"}}),
-            source_location(loc));
-    }
-    return character;
-}
-
-inline result<std::string, std::string> parse_escape_sequence(location& loc)
-{
-    const auto first = loc.iter();
-    if(first == loc.end() || *first != '\\')
-    {
-        return err(format_underline("toml::parse_escape_sequence: ", {{
-            source_location(loc), "the next token is not a backslash \"\\\""}}));
-    }
-    loc.advance();
-    switch(*loc.iter())
-    {
-        case '\\':{loc.advance(); return ok(std::string("\\"));}
-        case '"' :{loc.advance(); return ok(std::string("\""));}
-        case 'b' :{loc.advance(); return ok(std::string("\b"));}
-        case 't' :{loc.advance(); return ok(std::string("\t"));}
-        case 'n' :{loc.advance(); return ok(std::string("\n"));}
-        case 'f' :{loc.advance(); return ok(std::string("\f"));}
-        case 'r' :{loc.advance(); return ok(std::string("\r"));}
-        case 'u' :
-        {
-            if(const auto token = lex_escape_unicode_short::invoke(loc))
-            {
-                return ok(read_utf8_codepoint(token.unwrap(), loc));
-            }
-            else
-            {
-                return err(format_underline("parse_escape_sequence: "
-                           "invalid token found in UTF-8 codepoint uXXXX.",
-                           {{source_location(loc), "here"}}));
-            }
-        }
-        case 'U':
-        {
-            if(const auto token = lex_escape_unicode_long::invoke(loc))
-            {
-                return ok(read_utf8_codepoint(token.unwrap(), loc));
-            }
-            else
-            {
-                return err(format_underline("parse_escape_sequence: "
-                           "invalid token found in UTF-8 codepoint Uxxxxxxxx",
-                           {{source_location(loc), "here"}}));
-            }
-        }
-    }
-
-    const auto msg = format_underline("parse_escape_sequence: "
-           "unknown escape sequence appeared.", {{source_location(loc),
-           "escape sequence is one of \\, \", b, t, n, f, r, uxxxx, Uxxxxxxxx"}},
-           /* Hints = */{"if you want to write backslash as just one backslash, "
-           "use literal string like: regex    = '<\\i\\c*\\s*>'"});
-    loc.reset(first);
-    return err(msg);
-}
-
-inline std::ptrdiff_t check_utf8_validity(const std::string& reg)
-{
-    location loc("tmp", reg);
-    const auto u8 = repeat<lex_utf8_code, unlimited>::invoke(loc);
-    if(!u8 || loc.iter() != loc.end())
-    {
-        const auto error_location = std::distance(loc.begin(), loc.iter());
-        assert(0 <= error_location);
-        return error_location;
-    }
-    return -1;
-}
-
-inline result<std::pair<toml::string, region>, std::string>
-parse_ml_basic_string(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_ml_basic_string::invoke(loc))
-    {
-        auto inner_loc = loc;
-        inner_loc.reset(first);
-
-        std::string retval;
-        retval.reserve(token.unwrap().size());
-
-        auto delim = lex_ml_basic_string_open::invoke(inner_loc);
-        if(!delim)
-        {
-            throw internal_error(format_underline(
-                "parse_ml_basic_string: invalid token",
-                {{source_location(inner_loc), "should be \"\"\""}}),
-                source_location(inner_loc));
-        }
-        // immediate newline is ignored (if exists)
-        /* discard return value */ lex_newline::invoke(inner_loc);
-
-        delim = none();
-        while(!delim)
-        {
-            using lex_unescaped_seq = repeat<
-                either<lex_ml_basic_unescaped, lex_newline>, unlimited>;
-            if(auto unescaped = lex_unescaped_seq::invoke(inner_loc))
-            {
-                retval += unescaped.unwrap().str();
-            }
-            if(auto escaped = parse_escape_sequence(inner_loc))
-            {
-                retval += escaped.unwrap();
-            }
-            if(auto esc_nl = lex_ml_basic_escaped_newline::invoke(inner_loc))
-            {
-                // ignore newline after escape until next non-ws char
-            }
-            if(inner_loc.iter() == inner_loc.end())
-            {
-                throw internal_error(format_underline(
-                    "parse_ml_basic_string: unexpected end of region",
-                    {{source_location(inner_loc), "not sufficient token"}}),
-                    source_location(inner_loc));
-            }
-            delim = lex_ml_basic_string_close::invoke(inner_loc);
-        }
-        // `lex_ml_basic_string_close` allows 3 to 5 `"`s to allow 1 or 2 `"`s
-        // at just before the delimiter. Here, we need to attach `"`s at the
-        // end of the string body, if it exists.
-        // For detail, see the definition of `lex_ml_basic_string_close`.
-        assert(std::all_of(delim.unwrap().first(), delim.unwrap().last(),
-                           [](const char c) noexcept {return c == '\"';}));
-        switch(delim.unwrap().size())
-        {
-            case 3: {break;}
-            case 4: {retval += "\"";  break;}
-            case 5: {retval += "\"\""; break;}
-            default:
-            {
-                throw internal_error(format_underline(
-                    "parse_ml_basic_string: closing delimiter has invalid length",
-                    {{source_location(inner_loc), "end of this"}}),
-                    source_location(inner_loc));
-            }
-        }
-
-        const auto err_loc = check_utf8_validity(token.unwrap().str());
-        if(err_loc == -1)
-        {
-            return ok(std::make_pair(toml::string(retval), token.unwrap()));
-        }
-        else
-        {
-            inner_loc.reset(first);
-            inner_loc.advance(err_loc);
-            throw syntax_error(format_underline(
-                "parse_ml_basic_string: invalid utf8 sequence found",
-                {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-        }
-    }
-    else
-    {
-        loc.reset(first);
-        return err(format_underline("toml::parse_ml_basic_string: "
-                   "the next token is not a valid multiline string",
-                   {{source_location(loc), "here"}}));
-    }
-}
-
-inline result<std::pair<toml::string, region>, std::string>
-parse_basic_string(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_basic_string::invoke(loc))
-    {
-        auto inner_loc = loc;
-        inner_loc.reset(first);
-
-        auto quot = lex_quotation_mark::invoke(inner_loc);
-        if(!quot)
-        {
-            throw internal_error(format_underline("parse_basic_string: "
-                "invalid token", {{source_location(inner_loc), "should be \""}}),
-                source_location(inner_loc));
-        }
-
-        std::string retval;
-        retval.reserve(token.unwrap().size());
-
-        quot = none();
-        while(!quot)
-        {
-            using lex_unescaped_seq = repeat<lex_basic_unescaped, unlimited>;
-            if(auto unescaped = lex_unescaped_seq::invoke(inner_loc))
-            {
-                retval += unescaped.unwrap().str();
-            }
-            if(auto escaped = parse_escape_sequence(inner_loc))
-            {
-                retval += escaped.unwrap();
-            }
-            if(inner_loc.iter() == inner_loc.end())
-            {
-                throw internal_error(format_underline(
-                    "parse_basic_string: unexpected end of region",
-                    {{source_location(inner_loc), "not sufficient token"}}),
-                    source_location(inner_loc));
-            }
-            quot = lex_quotation_mark::invoke(inner_loc);
-        }
-
-        const auto err_loc = check_utf8_validity(token.unwrap().str());
-        if(err_loc == -1)
-        {
-            return ok(std::make_pair(toml::string(retval), token.unwrap()));
-        }
-        else
-        {
-            inner_loc.reset(first);
-            inner_loc.advance(err_loc);
-            throw syntax_error(format_underline(
-                "parse_ml_basic_string: invalid utf8 sequence found",
-                {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-        }
-    }
-    else
-    {
-        loc.reset(first); // rollback
-        return err(format_underline("toml::parse_basic_string: "
-                   "the next token is not a valid string",
-                   {{source_location(loc), "here"}}));
-    }
-}
-
-inline result<std::pair<toml::string, region>, std::string>
-parse_ml_literal_string(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_ml_literal_string::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-
-        const auto open = lex_ml_literal_string_open::invoke(inner_loc);
-        if(!open)
-        {
-            throw internal_error(format_underline(
-                "parse_ml_literal_string: invalid token",
-                {{source_location(inner_loc), "should be '''"}}),
-                source_location(inner_loc));
-        }
-        // immediate newline is ignored (if exists)
-        /* discard return value */ lex_newline::invoke(inner_loc);
-
-        const auto body = lex_ml_literal_body::invoke(inner_loc);
-
-        const auto close = lex_ml_literal_string_close::invoke(inner_loc);
-        if(!close)
-        {
-            throw internal_error(format_underline(
-                "parse_ml_literal_string: invalid token",
-                {{source_location(inner_loc), "should be '''"}}),
-                source_location(inner_loc));
-        }
-        // `lex_ml_literal_string_close` allows 3 to 5 `'`s to allow 1 or 2 `'`s
-        // at just before the delimiter. Here, we need to attach `'`s at the
-        // end of the string body, if it exists.
-        // For detail, see the definition of `lex_ml_basic_string_close`.
-
-        std::string retval = body.unwrap().str();
-        assert(std::all_of(close.unwrap().first(), close.unwrap().last(),
-                           [](const char c) noexcept {return c == '\'';}));
-        switch(close.unwrap().size())
-        {
-            case 3: {break;}
-            case 4: {retval += "'";  break;}
-            case 5: {retval += "''"; break;}
-            default:
-            {
-                throw internal_error(format_underline(
-                    "parse_ml_literal_string: closing delimiter has invalid length",
-                    {{source_location(inner_loc), "end of this"}}),
-                    source_location(inner_loc));
-            }
-        }
-
-        const auto err_loc = check_utf8_validity(token.unwrap().str());
-        if(err_loc == -1)
-        {
-            return ok(std::make_pair(toml::string(retval, toml::string_t::literal),
-                                     token.unwrap()));
-        }
-        else
-        {
-            inner_loc.reset(first);
-            inner_loc.advance(err_loc);
-            throw syntax_error(format_underline(
-                "parse_ml_basic_string: invalid utf8 sequence found",
-                {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-        }
-    }
-    else
-    {
-        loc.reset(first); // rollback
-        return err(format_underline("toml::parse_ml_literal_string: "
-                   "the next token is not a valid multiline literal string",
-                   {{source_location(loc), "here"}}));
-    }
-}
-
-inline result<std::pair<toml::string, region>, std::string>
-parse_literal_string(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_literal_string::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-
-        const auto open = lex_apostrophe::invoke(inner_loc);
-        if(!open)
-        {
-            throw internal_error(format_underline(
-                "parse_literal_string: invalid token",
-                {{source_location(inner_loc), "should be '"}}),
-                source_location(inner_loc));
-        }
-
-        const auto body = repeat<lex_literal_char, unlimited>::invoke(inner_loc);
-
-        const auto close = lex_apostrophe::invoke(inner_loc);
-        if(!close)
-        {
-            throw internal_error(format_underline(
-                "parse_literal_string: invalid token",
-                {{source_location(inner_loc), "should be '"}}),
-                source_location(inner_loc));
-        }
-
-        const auto err_loc = check_utf8_validity(token.unwrap().str());
-        if(err_loc == -1)
-        {
-            return ok(std::make_pair(
-                      toml::string(body.unwrap().str(), toml::string_t::literal),
-                      token.unwrap()));
-        }
-        else
-        {
-            inner_loc.reset(first);
-            inner_loc.advance(err_loc);
-            throw syntax_error(format_underline(
-                "parse_ml_basic_string: invalid utf8 sequence found",
-                {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-        }
-    }
-    else
-    {
-        loc.reset(first); // rollback
-        return err(format_underline("toml::parse_literal_string: "
-                   "the next token is not a valid literal string",
-                   {{source_location(loc), "here"}}));
-    }
-}
-
-inline result<std::pair<toml::string, region>, std::string>
-parse_string(location& loc)
-{
-    if(loc.iter() != loc.end() && *(loc.iter()) == '"')
-    {
-        if(loc.iter() + 1 != loc.end() && *(loc.iter() + 1) == '"' &&
-           loc.iter() + 2 != loc.end() && *(loc.iter() + 2) == '"')
-        {
-            return parse_ml_basic_string(loc);
-        }
-        else
-        {
-            return parse_basic_string(loc);
-        }
-    }
-    else if(loc.iter() != loc.end() && *(loc.iter()) == '\'')
-    {
-        if(loc.iter() + 1 != loc.end() && *(loc.iter() + 1) == '\'' &&
-           loc.iter() + 2 != loc.end() && *(loc.iter() + 2) == '\'')
-        {
-            return parse_ml_literal_string(loc);
-        }
-        else
-        {
-            return parse_literal_string(loc);
-        }
-    }
-    return err(format_underline("toml::parse_string: ",
-                {{source_location(loc), "the next token is not a string"}}));
-}
-
-inline result<std::pair<local_date, region>, std::string>
-parse_local_date(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_local_date::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-
-        const auto y = lex_date_fullyear::invoke(inner_loc);
-        if(!y || inner_loc.iter() == inner_loc.end() || *inner_loc.iter() != '-')
-        {
-            throw internal_error(format_underline(
-                "toml::parse_inner_local_date: invalid year format",
-                {{source_location(inner_loc), "should be `-`"}}),
-                source_location(inner_loc));
-        }
-        inner_loc.advance();
-        const auto m = lex_date_month::invoke(inner_loc);
-        if(!m || inner_loc.iter() == inner_loc.end() || *inner_loc.iter() != '-')
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_date: invalid month format",
-                {{source_location(inner_loc), "should be `-`"}}),
-                source_location(inner_loc));
-        }
-        inner_loc.advance();
-        const auto d = lex_date_mday::invoke(inner_loc);
-        if(!d)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_date: invalid day format",
-                {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-        }
-
-        const auto year  = static_cast<std::int16_t>(from_string<int>(y.unwrap().str(), 0));
-        const auto month = static_cast<std::int8_t >(from_string<int>(m.unwrap().str(), 0));
-        const auto day   = static_cast<std::int8_t >(from_string<int>(d.unwrap().str(), 0));
-
-        // We briefly check whether the input date is valid or not. But here, we
-        // only check if the RFC3339 compliance.
-        //     Actually there are several special date that does not exist,
-        // because of historical reasons, such as 1582/10/5-1582/10/14 (only in
-        // several countries). But here, we do not care about such a complicated
-        // rule. It makes the code complicated and there is only low probability
-        // that such a specific date is needed in practice. If someone need to
-        // validate date accurately, that means that the one need a specialized
-        // library for their purpose in a different layer.
-        {
-            const bool is_leap = (year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0));
-            const auto max_day = (month == 2) ? (is_leap ? 29 : 28) :
-                ((month == 4 || month == 6 || month == 9 || month == 11) ? 30 : 31);
-
-            if((month < 1 || 12 < month) || (day < 1 || max_day < day))
-            {
-                throw syntax_error(format_underline("toml::parse_date: "
-                    "invalid date: it does not conform RFC3339.", {{
-                    source_location(loc), "month should be 01-12, day should be"
-                    " 01-28,29,30,31, depending on month/year."
-                    }}), source_location(inner_loc));
-            }
-        }
-        return ok(std::make_pair(local_date(year, static_cast<month_t>(month - 1), day),
-                                 token.unwrap()));
-    }
-    else
-    {
-        loc.reset(first);
-        return err(format_underline("toml::parse_local_date: ",
-            {{source_location(loc), "the next token is not a local_date"}}));
-    }
-}
-
-inline result<std::pair<local_time, region>, std::string>
-parse_local_time(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_local_time::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-
-        const auto h = lex_time_hour::invoke(inner_loc);
-        if(!h || inner_loc.iter() == inner_loc.end() || *inner_loc.iter() != ':')
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_time: invalid year format",
-                {{source_location(inner_loc), "should be `:`"}}),
-                source_location(inner_loc));
-        }
-        inner_loc.advance();
-        const auto m = lex_time_minute::invoke(inner_loc);
-        if(!m || inner_loc.iter() == inner_loc.end() || *inner_loc.iter() != ':')
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_time: invalid month format",
-                {{source_location(inner_loc), "should be `:`"}}),
-                source_location(inner_loc));
-        }
-        inner_loc.advance();
-        const auto s = lex_time_second::invoke(inner_loc);
-        if(!s)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_time: invalid second format",
-                {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-        }
-
-        const int hour   = from_string<int>(h.unwrap().str(), 0);
-        const int minute = from_string<int>(m.unwrap().str(), 0);
-        const int second = from_string<int>(s.unwrap().str(), 0);
-
-        if((hour   < 0 || 23 < hour) || (minute < 0 || 59 < minute) ||
-           (second < 0 || 60 < second)) // it may be leap second
-        {
-            throw syntax_error(format_underline("toml::parse_time: "
-                "invalid time: it does not conform RFC3339.", {{
-                source_location(loc), "hour should be 00-23, minute should be"
-                " 00-59, second should be 00-60 (depending on the leap"
-                " second rules.)"}}), source_location(inner_loc));
-        }
-
-        local_time time(hour, minute, second, 0, 0);
-
-        const auto before_secfrac = inner_loc.iter();
-        if(const auto secfrac = lex_time_secfrac::invoke(inner_loc))
-        {
-            auto sf = secfrac.unwrap().str();
-            sf.erase(sf.begin()); // sf.front() == '.'
-            switch(sf.size() % 3)
-            {
-                case 2:  sf += '0';  break;
-                case 1:  sf += "00"; break;
-                case 0:  break;
-                default: break;
-            }
-            if(sf.size() >= 9)
-            {
-                time.millisecond = from_string<std::uint16_t>(sf.substr(0, 3), 0u);
-                time.microsecond = from_string<std::uint16_t>(sf.substr(3, 3), 0u);
-                time.nanosecond  = from_string<std::uint16_t>(sf.substr(6, 3), 0u);
-            }
-            else if(sf.size() >= 6)
-            {
-                time.millisecond = from_string<std::uint16_t>(sf.substr(0, 3), 0u);
-                time.microsecond = from_string<std::uint16_t>(sf.substr(3, 3), 0u);
-            }
-            else if(sf.size() >= 3)
-            {
-                time.millisecond = from_string<std::uint16_t>(sf, 0u);
-                time.microsecond = 0u;
-            }
-        }
-        else
-        {
-            if(before_secfrac != inner_loc.iter())
-            {
-                throw internal_error(format_underline(
-                    "toml::parse_local_time: invalid subsecond format",
-                    {{source_location(inner_loc), "here"}}),
-                source_location(inner_loc));
-            }
-        }
-        return ok(std::make_pair(time, token.unwrap()));
-    }
-    else
-    {
-        loc.reset(first);
-        return err(format_underline("toml::parse_local_time: ",
-            {{source_location(loc), "the next token is not a local_time"}}));
-    }
-}
-
-inline result<std::pair<local_datetime, region>, std::string>
-parse_local_datetime(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_local_date_time::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-        const auto date = parse_local_date(inner_loc);
-        if(!date || inner_loc.iter() == inner_loc.end())
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_datetime: invalid datetime format",
-                {{source_location(inner_loc), "date, not datetime"}}),
-                source_location(inner_loc));
-        }
-        const char delim = *(inner_loc.iter());
-        if(delim != 'T' && delim != 't' && delim != ' ')
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_datetime: invalid datetime format",
-                {{source_location(inner_loc), "should be `T` or ` ` (space)"}}),
-                source_location(inner_loc));
-        }
-        inner_loc.advance();
-        const auto time = parse_local_time(inner_loc);
-        if(!time)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_local_datetime: invalid datetime format",
-                {{source_location(inner_loc), "invalid time format"}}),
-                source_location(inner_loc));
-        }
-        return ok(std::make_pair(
-            local_datetime(date.unwrap().first, time.unwrap().first),
-            token.unwrap()));
-    }
-    else
-    {
-        loc.reset(first);
-        return err(format_underline("toml::parse_local_datetime: ",
-            {{source_location(loc), "the next token is not a local_datetime"}}));
-    }
-}
-
-inline result<std::pair<offset_datetime, region>, std::string>
-parse_offset_datetime(location& loc)
-{
-    const auto first = loc.iter();
-    if(const auto token = lex_offset_date_time::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-        const auto datetime = parse_local_datetime(inner_loc);
-        if(!datetime || inner_loc.iter() == inner_loc.end())
-        {
-            throw internal_error(format_underline(
-                "toml::parse_offset_datetime: invalid datetime format",
-                {{source_location(inner_loc), "date, not datetime"}}),
-                source_location(inner_loc));
-        }
-        time_offset offset(0, 0);
-        if(const auto ofs = lex_time_numoffset::invoke(inner_loc))
-        {
-            const auto str = ofs.unwrap().str();
-
-            const auto hour   = from_string<int>(str.substr(1,2), 0);
-            const auto minute = from_string<int>(str.substr(4,2), 0);
-
-            if((hour < 0 || 23 < hour) || (minute < 0 || 59 < minute))
-            {
-                throw syntax_error(format_underline("toml::parse_offset_datetime: "
-                    "invalid offset: it does not conform RFC3339.", {{
-                    source_location(loc), "month should be 01-12, day should be"
-                    " 01-28,29,30,31, depending on month/year."
-                    }}), source_location(inner_loc));
-            }
-
-            if(str.front() == '+')
-            {
-                offset = time_offset(hour, minute);
-            }
-            else
-            {
-                offset = time_offset(-hour, -minute);
-            }
-        }
-        else if(*inner_loc.iter() != 'Z' && *inner_loc.iter() != 'z')
-        {
-            throw internal_error(format_underline(
-                "toml::parse_offset_datetime: invalid datetime format",
-                {{source_location(inner_loc), "should be `Z` or `+HH:MM`"}}),
-                source_location(inner_loc));
-        }
-        return ok(std::make_pair(offset_datetime(datetime.unwrap().first, offset),
-                                 token.unwrap()));
-    }
-    else
-    {
-        loc.reset(first);
-        return err(format_underline("toml::parse_offset_datetime: ",
-            {{source_location(loc), "the next token is not a offset_datetime"}}));
-    }
-}
-
-inline result<std::pair<key, region>, std::string>
-parse_simple_key(location& loc)
-{
-    if(const auto bstr = parse_basic_string(loc))
-    {
-        return ok(std::make_pair(bstr.unwrap().first.str, bstr.unwrap().second));
-    }
-    if(const auto lstr = parse_literal_string(loc))
-    {
-        return ok(std::make_pair(lstr.unwrap().first.str, lstr.unwrap().second));
-    }
-    if(const auto bare = lex_unquoted_key::invoke(loc))
-    {
-        const auto reg = bare.unwrap();
-        return ok(std::make_pair(reg.str(), reg));
-    }
-    return err(format_underline("toml::parse_simple_key: ",
-            {{source_location(loc), "the next token is not a simple key"}}));
-}
-
-// dotted key become vector of keys
-inline result<std::pair<std::vector<key>, region>, std::string>
-parse_key(location& loc)
-{
-    const auto first = loc.iter();
-    // dotted key -> `foo.bar.baz` where several single keys are chained by
-    // dots. Whitespaces between keys and dots are allowed.
-    if(const auto token = lex_dotted_key::invoke(loc))
-    {
-        const auto reg = token.unwrap();
-        location inner_loc(loc.name(), reg.str());
-        std::vector<key> keys;
-
-        while(inner_loc.iter() != inner_loc.end())
-        {
-            lex_ws::invoke(inner_loc);
-            if(const auto k = parse_simple_key(inner_loc))
-            {
-                keys.push_back(k.unwrap().first);
-            }
-            else
-            {
-                throw internal_error(format_underline(
-                    "toml::detail::parse_key: dotted key contains invalid key",
-                    {{source_location(inner_loc), k.unwrap_err()}}),
-                    source_location(inner_loc));
-            }
-
-            lex_ws::invoke(inner_loc);
-            if(inner_loc.iter() == inner_loc.end())
-            {
-                break;
-            }
-            else if(*inner_loc.iter() == '.')
-            {
-                inner_loc.advance(); // to skip `.`
-            }
-            else
-            {
-                throw internal_error(format_underline("toml::parse_key: "
-                    "dotted key contains invalid key ",
-                    {{source_location(inner_loc), "should be `.`"}}),
-                    source_location(inner_loc));
-            }
-        }
-        return ok(std::make_pair(keys, reg));
-    }
-    loc.reset(first);
-
-    // simple_key: a single (basic_string|literal_string|bare key)
-    if(const auto smpl = parse_simple_key(loc))
-    {
-        return ok(std::make_pair(std::vector<key>(1, smpl.unwrap().first),
-                                 smpl.unwrap().second));
-    }
-    return err(format_underline("toml::parse_key: an invalid key appeared.",
-                {{source_location(loc), "is not a valid key"}}, {
-                "bare keys  : non-empty strings composed only of [A-Za-z0-9_-].",
-                "quoted keys: same as \"basic strings\" or 'literal strings'.",
-                "dotted keys: sequence of bare or quoted keys joined with a dot."
-                }));
-}
-
-// forward-decl to implement parse_array and parse_table
-template<typename Value>
-result<Value, std::string> parse_value(location&);
-
-template<typename Value>
-result<std::pair<typename Value::array_type, region>, std::string>
-parse_array(location& loc)
-{
-    using value_type = Value;
-    using array_type = typename value_type::array_type;
-
-    const auto first = loc.iter();
-    if(loc.iter() == loc.end())
-    {
-        return err("toml::parse_array: input is empty");
-    }
-    if(*loc.iter() != '[')
-    {
-        return err("toml::parse_array: token is not an array");
-    }
-    loc.advance();
-
-    using lex_ws_comment_newline = repeat<
-        either<lex_wschar, lex_newline, lex_comment>, unlimited>;
-
-    array_type retval;
-    while(loc.iter() != loc.end())
-    {
-        lex_ws_comment_newline::invoke(loc); // skip
-
-        if(loc.iter() != loc.end() && *loc.iter() == ']')
-        {
-            loc.advance(); // skip ']'
-            return ok(std::make_pair(retval,
-                      region(loc, first, loc.iter())));
-        }
-
-        if(auto val = parse_value<value_type>(loc))
-        {
-            // After TOML v1.0.0-rc.1, array becomes to be able to have values
-            // with different types. So here we will omit this by default.
-            //
-            // But some of the test-suite checks if the parser accepts a hetero-
-            // geneous arrays, so we keep this for a while.
-#ifdef TOML11_DISALLOW_HETEROGENEOUS_ARRAYS
-            if(!retval.empty() && retval.front().type() != val.as_ok().type())
-            {
-                auto array_start_loc = loc;
-                array_start_loc.reset(first);
-
-                throw syntax_error(format_underline("toml::parse_array: "
-                    "type of elements should be the same each other.", {
-                        {source_location(array_start_loc), "array starts here"},
-                        {
-                            retval.front().location(),
-                            "value has type " + stringize(retval.front().type())
-                        },
-                        {
-                            val.unwrap().location(),
-                            "value has different type, " + stringize(val.unwrap().type())
-                        }
-                    }), source_location(loc));
-            }
-#endif
-            retval.push_back(std::move(val.unwrap()));
-        }
-        else
-        {
-            auto array_start_loc = loc;
-            array_start_loc.reset(first);
-
-            throw syntax_error(format_underline("toml::parse_array: "
-                "value having invalid format appeared in an array", {
-                    {source_location(array_start_loc), "array starts here"},
-                    {source_location(loc), "it is not a valid value."}
-                }), source_location(loc));
-        }
-
-        using lex_array_separator = sequence<maybe<lex_ws_comment_newline>, character<','>>;
-        const auto sp = lex_array_separator::invoke(loc);
-        if(!sp)
-        {
-            lex_ws_comment_newline::invoke(loc);
-            if(loc.iter() != loc.end() && *loc.iter() == ']')
-            {
-                loc.advance(); // skip ']'
-                return ok(std::make_pair(retval,
-                          region(loc, first, loc.iter())));
-            }
-            else
-            {
-                auto array_start_loc = loc;
-                array_start_loc.reset(first);
-
-                throw syntax_error(format_underline("toml::parse_array:"
-                    " missing array separator `,` after a value", {
-                        {source_location(array_start_loc), "array starts here"},
-                        {source_location(loc),             "should be `,`"}
-                    }), source_location(loc));
-            }
-        }
-    }
-    loc.reset(first);
-    throw syntax_error(format_underline("toml::parse_array: "
-            "array did not closed by `]`",
-            {{source_location(loc), "should be closed"}}),
-            source_location(loc));
-}
-
-template<typename Value>
-result<std::pair<std::pair<std::vector<key>, region>, Value>, std::string>
-parse_key_value_pair(location& loc)
-{
-    using value_type = Value;
-
-    const auto first = loc.iter();
-    auto key_reg = parse_key(loc);
-    if(!key_reg)
-    {
-        std::string msg = std::move(key_reg.unwrap_err());
-        // if the next token is keyvalue-separator, it means that there are no
-        // key. then we need to show error as "empty key is not allowed".
-        if(const auto keyval_sep = lex_keyval_sep::invoke(loc))
-        {
-            loc.reset(first);
-            msg = format_underline("toml::parse_key_value_pair: "
-                "empty key is not allowed.",
-                {{source_location(loc), "key expected before '='"}});
-        }
-        return err(std::move(msg));
-    }
-
-    const auto kvsp = lex_keyval_sep::invoke(loc);
-    if(!kvsp)
-    {
-        std::string msg;
-        // if the line contains '=' after the invalid sequence, possibly the
-        // error is in the key (like, invalid character in bare key).
-        const auto line_end = std::find(loc.iter(), loc.end(), '\n');
-        if(std::find(loc.iter(), line_end, '=') != line_end)
-        {
-            msg = format_underline("toml::parse_key_value_pair: "
-                "invalid format for key",
-                {{source_location(loc), "invalid character in key"}},
-                {"Did you forget '.' to separate dotted-key?",
-                "Allowed characters for bare key are [0-9a-zA-Z_-]."});
-        }
-        else // if not, the error is lack of key-value separator.
-        {
-            msg = format_underline("toml::parse_key_value_pair: "
-                "missing key-value separator `=`",
-                {{source_location(loc), "should be `=`"}});
-        }
-        loc.reset(first);
-        return err(std::move(msg));
-    }
-
-    const auto after_kvsp = loc.iter(); // err msg
-    auto val = parse_value<value_type>(loc);
-    if(!val)
-    {
-        std::string msg;
-        loc.reset(after_kvsp);
-        // check there is something not a comment/whitespace after `=`
-        if(sequence<maybe<lex_ws>, maybe<lex_comment>, lex_newline>::invoke(loc))
-        {
-            loc.reset(after_kvsp);
-            msg = format_underline("toml::parse_key_value_pair: "
-                    "missing value after key-value separator '='",
-                    {{source_location(loc), "expected value, but got nothing"}});
-        }
-        else // there is something not a comment/whitespace, so invalid format.
-        {
-            msg = std::move(val.unwrap_err());
-        }
-        loc.reset(first);
-        return err(msg);
-    }
-    return ok(std::make_pair(std::move(key_reg.unwrap()),
-                             std::move(val.unwrap())));
-}
-
-// for error messages.
-template<typename InputIterator>
-std::string format_dotted_keys(InputIterator first, const InputIterator last)
-{
-    static_assert(std::is_same<key,
-        typename std::iterator_traits<InputIterator>::value_type>::value,"");
-
-    std::string retval(*first++);
-    for(; first != last; ++first)
-    {
-        retval += '.';
-        retval += *first;
-    }
-    return retval;
-}
-
-// forward decl for is_valid_forward_table_definition
-result<std::pair<std::vector<key>, region>, std::string>
-parse_table_key(location& loc);
-template<typename Value>
-result<std::pair<typename Value::table_type, region>, std::string>
-parse_inline_table(location& loc);
-
-// The following toml file is allowed.
-// ```toml
-// [a.b.c]     # here, table `a` has element `b`.
-// foo = "bar"
-// [a]         # merge a = {baz = "qux"} to a = {b = {...}}
-// baz = "qux"
-// ```
-// But the following is not allowed.
-// ```toml
-// [a]
-// b.c.foo = "bar"
-// [a]             # error! the same table [a] defined!
-// baz = "qux"
-// ```
-// The following is neither allowed.
-// ```toml
-// a = { b.c.foo = "bar"}
-// [a]             # error! the same table [a] defined!
-// baz = "qux"
-// ```
-// Here, it parses region of `tab->at(k)` as a table key and check the depth
-// of the key. If the key region points deeper node, it would be allowed.
-// Otherwise, the key points the same node. It would be rejected.
-template<typename Value, typename Iterator>
-bool is_valid_forward_table_definition(const Value& fwd, const Value& inserting,
-        Iterator key_first, Iterator key_curr, Iterator key_last)
-{
-    // ------------------------------------------------------------------------
-    // check type of the value to be inserted/merged
-
-    std::string inserting_reg = "";
-    if(const auto ptr = detail::get_region(inserting))
-    {
-        inserting_reg = ptr->str();
-    }
-    location inserting_def("internal", std::move(inserting_reg));
-    if(const auto inlinetable = parse_inline_table<Value>(inserting_def))
-    {
-        // check if we are overwriting existing table.
-        // ```toml
-        // # NG
-        // a.b = 42
-        // a = {d = 3.14}
-        // ```
-        // Inserting an inline table to a existing super-table is not allowed in
-        // any case. If we found it, we can reject it without further checking.
-        return false;
-    }
-
-    // ------------------------------------------------------------------------
-    // check table defined before
-
-    std::string internal = "";
-    if(const auto ptr = detail::get_region(fwd))
-    {
-        internal = ptr->str();
-    }
-    location def("internal", std::move(internal));
-    if(const auto tabkeys = parse_table_key(def)) // [table.key]
-    {
-        // table keys always contains all the nodes from the root.
-        const auto& tks = tabkeys.unwrap().first;
-        if(std::size_t(std::distance(key_first, key_last)) == tks.size() &&
-           std::equal(tks.begin(), tks.end(), key_first))
-        {
-            // the keys are equivalent. it is not allowed.
-            return false;
-        }
-        // the keys are not equivalent. it is allowed.
-        return true;
-    }
-    if(const auto dotkeys = parse_key(def))
-    {
-        // consider the following case.
-        // [a]
-        // b.c = {d = 42}
-        // [a.b.c]
-        // e = 2.71
-        // this defines the table [a.b.c] twice. no?
-
-        // a dotted key starts from the node representing a table in which the
-        // dotted key belongs to.
-        const auto& dks = dotkeys.unwrap().first;
-        if(std::size_t(std::distance(key_curr, key_last)) == dks.size() &&
-           std::equal(dks.begin(), dks.end(), key_curr))
-        {
-            // the keys are equivalent. it is not allowed.
-            return false;
-        }
-        // the keys are not equivalent. it is allowed.
-        return true;
-    }
-    return false;
-}
-
-template<typename Value, typename InputIterator>
-result<bool, std::string>
-insert_nested_key(typename Value::table_type& root, const Value& v,
-                  InputIterator iter, const InputIterator last,
-                  region key_reg,
-                  const bool is_array_of_table = false)
-{
-    static_assert(std::is_same<key,
-        typename std::iterator_traits<InputIterator>::value_type>::value,"");
-
-    using value_type = Value;
-    using table_type = typename value_type::table_type;
-    using array_type = typename value_type::array_type;
-
-    const auto first = iter;
-    assert(iter != last);
-
-    table_type* tab = std::addressof(root);
-    for(; iter != last; ++iter) // search recursively
-    {
-        const key& k = *iter;
-        if(std::next(iter) == last) // k is the last key
-        {
-            // XXX if the value is array-of-tables, there can be several
-            //     tables that are in the same array. in that case, we need to
-            //     find the last element and insert it to there.
-            if(is_array_of_table)
-            {
-                if(tab->count(k) == 1) // there is already an array of table
-                {
-                    if(tab->at(k).is_table())
-                    {
-                        // show special err msg for conflicting table
-                        throw syntax_error(format_underline(concat_to_string(
-                            "toml::insert_value: array of table (\"",
-                            format_dotted_keys(first, last),
-                            "\") cannot be defined"), {
-                                {tab->at(k).location(), "table already defined"},
-                                {v.location(), "this conflicts with the previous table"}
-                            }), v.location());
-                    }
-                    else if(!(tab->at(k).is_array()))
-                    {
-                        throw syntax_error(format_underline(concat_to_string(
-                            "toml::insert_value: array of table (\"",
-                            format_dotted_keys(first, last), "\") collides with"
-                            " existing value"), {
-                                {tab->at(k).location(),
-                                 concat_to_string("this ", tab->at(k).type(),
-                                                  " value already exists")},
-                                {v.location(),
-                                 "while inserting this array-of-tables"}
-                            }), v.location());
-                    }
-                    // the above if-else-if checks tab->at(k) is an array
-                    auto& a = tab->at(k).as_array();
-                    // If table element is defined as [[array_of_tables]], it
-                    // cannot be an empty array. If an array of tables is
-                    // defined as `aot = []`, it cannot be appended.
-                    if(a.empty() || !(a.front().is_table()))
-                    {
-                        throw syntax_error(format_underline(concat_to_string(
-                            "toml::insert_value: array of table (\"",
-                            format_dotted_keys(first, last), "\") collides with"
-                            " existing value"), {
-                                {tab->at(k).location(),
-                                 concat_to_string("this ", tab->at(k).type(),
-                                                  " value already exists")},
-                                {v.location(),
-                                 "while inserting this array-of-tables"}
-                            }), v.location());
-                    }
-                    // avoid conflicting array of table like the following.
-                    // ```toml
-                    // a = [{b = 42}] # define a as an array of *inline* tables
-                    // [[a]]          # a is an array of *multi-line* tables
-                    // b = 54
-                    // ```
-                    // Here, from the type information, these cannot be detected
-                    // because inline table is also a table.
-                    // But toml v0.5.0 explicitly says it is invalid. The above
-                    // array-of-tables has a static size and appending to the
-                    // array is invalid.
-                    // In this library, multi-line table value has a region
-                    // that points to the key of the table (e.g. [[a]]). By
-                    // comparing the first two letters in key, we can detect
-                    // the array-of-table is inline or multiline.
-                    if(const auto ptr = detail::get_region(a.front()))
-                    {
-                        if(ptr->str().substr(0,2) != "[[")
-                        {
-                            throw syntax_error(format_underline(concat_to_string(
-                                "toml::insert_value: array of table (\"",
-                                format_dotted_keys(first, last), "\") collides "
-                                "with existing array-of-tables"), {
-                                    {tab->at(k).location(),
-                                     concat_to_string("this ", tab->at(k).type(),
-                                                      " value has static size")},
-                                    {v.location(),
-                                     "appending it to the statically sized array"}
-                                }), v.location());
-                        }
-                    }
-                    a.push_back(v);
-                    return ok(true);
-                }
-                else // if not, we need to create the array of table
-                {
-                    // XXX: Consider the following array of tables.
-                    // ```toml
-                    // # This is a comment.
-                    // [[aot]]
-                    // foo = "bar"
-                    // ```
-                    // Here, the comment is for `aot`. But here, actually two
-                    // values are defined. An array that contains tables, named
-                    // `aot`, and the 0th element of the `aot`, `{foo = "bar"}`.
-                    // Those two are different from each other. But both of them
-                    // points to the same portion of the TOML file, `[[aot]]`,
-                    // so `key_reg.comments()` returns `# This is a comment`.
-                    // If it is assigned as a comment of `aot` defined here, the
-                    // comment will be duplicated. Both the `aot` itself and
-                    // the 0-th element will have the same comment. This causes
-                    // "duplication of the same comments" bug when the data is
-                    // serialized.
-                    //     Next, consider the following.
-                    // ```toml
-                    // # comment 1
-                    // aot = [
-                    //     # comment 2
-                    //     {foo = "bar"},
-                    // ]
-                    // ```
-                    // In this case, we can distinguish those two comments. So
-                    // here we need to add "comment 1" to the `aot` and
-                    // "comment 2" to the 0th element of that.
-                    //     To distinguish those two, we check the key region.
-                    std::vector<std::string> comments{/* empty by default */};
-                    if(key_reg.str().substr(0, 2) != "[[")
-                    {
-                        comments = key_reg.comments();
-                    }
-                    value_type aot(array_type(1, v), key_reg, std::move(comments));
-                    tab->insert(std::make_pair(k, aot));
-                    return ok(true);
-                }
-            } // end if(array of table)
-
-            if(tab->count(k) == 1)
-            {
-                if(tab->at(k).is_table() && v.is_table())
-                {
-                    if(!is_valid_forward_table_definition(
-                                tab->at(k), v, first, iter, last))
-                    {
-                        throw syntax_error(format_underline(concat_to_string(
-                            "toml::insert_value: table (\"",
-                            format_dotted_keys(first, last),
-                            "\") already exists."), {
-                                {tab->at(k).location(), "table already exists here"},
-                                {v.location(), "table defined twice"}
-                            }), v.location());
-                    }
-                    // to allow the following toml file.
-                    // [a.b.c]
-                    // d = 42
-                    // [a]
-                    // e = 2.71
-                    auto& t = tab->at(k).as_table();
-                    for(const auto& kv : v.as_table())
-                    {
-                        if(tab->at(k).contains(kv.first))
-                        {
-                            throw syntax_error(format_underline(concat_to_string(
-                                "toml::insert_value: value (\"",
-                                format_dotted_keys(first, last),
-                                "\") already exists."), {
-                                    {t.at(kv.first).location(), "already exists here"},
-                                    {v.location(), "this defined twice"}
-                                }), v.location());
-                        }
-                        t[kv.first] = kv.second;
-                    }
-                    detail::change_region(tab->at(k), key_reg);
-                    return ok(true);
-                }
-                else if(v.is_table()                     &&
-                        tab->at(k).is_array()            &&
-                        tab->at(k).as_array().size() > 0 &&
-                        tab->at(k).as_array().front().is_table())
-                {
-                    throw syntax_error(format_underline(concat_to_string(
-                        "toml::insert_value: array of tables (\"",
-                        format_dotted_keys(first, last), "\") already exists."), {
-                            {tab->at(k).location(), "array of tables defined here"},
-                            {v.location(), "table conflicts with the previous array of table"}
-                        }), v.location());
-                }
-                else
-                {
-                    throw syntax_error(format_underline(concat_to_string(
-                        "toml::insert_value: value (\"",
-                        format_dotted_keys(first, last), "\") already exists."), {
-                            {tab->at(k).location(), "value already exists here"},
-                            {v.location(), "value defined twice"}
-                        }), v.location());
-                }
-            }
-            tab->insert(std::make_pair(k, v));
-            return ok(true);
-        }
-        else // k is not the last one, we should insert recursively
-        {
-            // if there is no corresponding value, insert it first.
-            // related: you don't need to write
-            // # [x]
-            // # [x.y]
-            // to write
-            // [x.y.z]
-            if(tab->count(k) == 0)
-            {
-                // a table that is defined implicitly doesn't have any comments.
-                (*tab)[k] = value_type(table_type{}, key_reg, {/*no comment*/});
-            }
-
-            // type checking...
-            if(tab->at(k).is_table())
-            {
-                // According to toml-lang/toml:36d3091b3 "Clarify that inline
-                // tables are immutable", check if it adds key-value pair to an
-                // inline table.
-                if(const auto* ptr = get_region(tab->at(k)))
-                {
-                    // here, if the value is a (multi-line) table, the region
-                    // should be something like `[table-name]`.
-                    if(ptr->front() == '{')
-                    {
-                        throw syntax_error(format_underline(concat_to_string(
-                            "toml::insert_value: inserting to an inline table (",
-                            format_dotted_keys(first, std::next(iter)),
-                            ") but inline tables are immutable"), {
-                                {tab->at(k).location(), "inline tables are immutable"},
-                                {v.location(), "inserting this"}
-                            }), v.location());
-                    }
-                }
-                tab = std::addressof((*tab)[k].as_table());
-            }
-            else if(tab->at(k).is_array()) // inserting to array-of-tables?
-            {
-                auto& a = (*tab)[k].as_array();
-                if(!a.back().is_table())
-                {
-                    throw syntax_error(format_underline(concat_to_string(
-                        "toml::insert_value: target (",
-                        format_dotted_keys(first, std::next(iter)),
-                        ") is neither table nor an array of tables"), {
-                            {a.back().location(), concat_to_string(
-                                    "actual type is ", a.back().type())},
-                            {v.location(), "inserting this"}
-                        }), v.location());
-                }
-                tab = std::addressof(a.back().as_table());
-            }
-            else
-            {
-                throw syntax_error(format_underline(concat_to_string(
-                    "toml::insert_value: target (",
-                    format_dotted_keys(first, std::next(iter)),
-                    ") is neither table nor an array of tables"), {
-                        {tab->at(k).location(), concat_to_string(
-                                "actual type is ", tab->at(k).type())},
-                        {v.location(), "inserting this"}
-                    }), v.location());
-            }
-        }
-    }
-    return err(std::string("toml::detail::insert_nested_key: never reach here"));
-}
-
-template<typename Value>
-result<std::pair<typename Value::table_type, region>, std::string>
-parse_inline_table(location& loc)
-{
-    using value_type = Value;
-    using table_type = typename value_type::table_type;
-
-    const auto first = loc.iter();
-    table_type retval;
-    if(!(loc.iter() != loc.end() && *loc.iter() == '{'))
-    {
-        return err(format_underline("toml::parse_inline_table: ",
-            {{source_location(loc), "the next token is not an inline table"}}));
-    }
-    loc.advance();
-
-    // check if the inline table is an empty table = { }
-    maybe<lex_ws>::invoke(loc);
-    if(loc.iter() != loc.end() && *loc.iter() == '}')
-    {
-        loc.advance(); // skip `}`
-        return ok(std::make_pair(retval, region(loc, first, loc.iter())));
-    }
-
-    // it starts from "{". it should be formatted as inline-table
-    while(loc.iter() != loc.end())
-    {
-        const auto kv_r = parse_key_value_pair<value_type>(loc);
-        if(!kv_r)
-        {
-            return err(kv_r.unwrap_err());
-        }
-
-        const auto&              kvpair  = kv_r.unwrap();
-        const std::vector<key>&  keys    = kvpair.first.first;
-        const auto&              key_reg = kvpair.first.second;
-        const value_type&        val     = kvpair.second;
-
-        const auto inserted =
-            insert_nested_key(retval, val, keys.begin(), keys.end(), key_reg);
-        if(!inserted)
-        {
-            throw internal_error("toml::parse_inline_table: "
-                "failed to insert value into table: " + inserted.unwrap_err(),
-                source_location(loc));
-        }
-
-        using lex_table_separator = sequence<maybe<lex_ws>, character<','>>;
-        const auto sp = lex_table_separator::invoke(loc);
-
-        if(!sp)
-        {
-            maybe<lex_ws>::invoke(loc);
-
-            if(loc.iter() == loc.end())
-            {
-                throw syntax_error(format_underline(
-                    "toml::parse_inline_table: missing table separator `}` ",
-                    {{source_location(loc), "should be `}`"}}),
-                    source_location(loc));
-            }
-            else if(*loc.iter() == '}')
-            {
-                loc.advance(); // skip `}`
-                return ok(std::make_pair(
-                            retval, region(loc, first, loc.iter())));
-            }
-            else if(*loc.iter() == '#' || *loc.iter() == '\r' || *loc.iter() == '\n')
-            {
-                throw syntax_error(format_underline(
-                    "toml::parse_inline_table: missing curly brace `}`",
-                    {{source_location(loc), "should be `}`"}}),
-                    source_location(loc));
-            }
-            else
-            {
-                throw syntax_error(format_underline(
-                    "toml::parse_inline_table: missing table separator `,` ",
-                    {{source_location(loc), "should be `,`"}}),
-                    source_location(loc));
-            }
-        }
-        else // `,` is found
-        {
-            maybe<lex_ws>::invoke(loc);
-            if(loc.iter() != loc.end() && *loc.iter() == '}')
-            {
-                throw syntax_error(format_underline(
-                    "toml::parse_inline_table: trailing comma is not allowed in"
-                    " an inline table",
-                    {{source_location(loc), "should be `}`"}}),
-                    source_location(loc));
-            }
-        }
-    }
-    loc.reset(first);
-    throw syntax_error(format_underline("toml::parse_inline_table: "
-            "inline table did not closed by `}`",
-            {{source_location(loc), "should be closed"}}),
-            source_location(loc));
-}
-
-inline result<value_t, std::string> guess_number_type(const location& l)
-{
-    // This function tries to find some (common) mistakes by checking characters
-    // that follows the last character of a value. But it is often difficult
-    // because some non-newline characters can appear after a value. E.g.
-    // spaces, tabs, commas (in an array or inline table), closing brackets
-    // (of an array or inline table), comment-sign (#). Since this function
-    // does not parse further, those characters are always allowed to be there.
-    location loc = l;
-
-    if(lex_offset_date_time::invoke(loc)) {return ok(value_t::offset_datetime);}
-    loc.reset(l.iter());
-
-    if(lex_local_date_time::invoke(loc))
-    {
-        // bad offset may appear after this.
-        if(loc.iter() != loc.end() && (*loc.iter() == '+' || *loc.iter() == '-'
-                    || *loc.iter() == 'Z' || *loc.iter() == 'z'))
-        {
-            return err(format_underline("bad offset: should be [+-]HH:MM or Z",
-                        {{source_location(loc), "[+-]HH:MM or Z"}},
-                        {"pass: +09:00, -05:30", "fail: +9:00, -5:30"}));
-        }
-        return ok(value_t::local_datetime);
-    }
-    loc.reset(l.iter());
-
-    if(lex_local_date::invoke(loc))
-    {
-        // bad time may appear after this.
-        // A space is allowed as a delimiter between local time. But there are
-        // both cases in which a space becomes valid or invalid.
-        // - invalid: 2019-06-16 7:00:00
-        // - valid  : 2019-06-16 07:00:00
-        if(loc.iter() != loc.end())
-        {
-            const auto c = *loc.iter();
-            if(c == 'T' || c == 't')
-            {
-                return err(format_underline("bad time: should be HH:MM:SS.subsec",
-                        {{source_location(loc), "HH:MM:SS.subsec"}},
-                        {"pass: 1979-05-27T07:32:00, 1979-05-27 07:32:00.999999",
-                         "fail: 1979-05-27T7:32:00, 1979-05-27 17:32"}));
-            }
-            if('0' <= c && c <= '9')
-            {
-                return err(format_underline("bad time: missing T",
-                        {{source_location(loc), "T or space required here"}},
-                        {"pass: 1979-05-27T07:32:00, 1979-05-27 07:32:00.999999",
-                         "fail: 1979-05-27T7:32:00, 1979-05-27 7:32"}));
-            }
-            if(c == ' ' && std::next(loc.iter()) != loc.end() &&
-                ('0' <= *std::next(loc.iter()) && *std::next(loc.iter())<= '9'))
-            {
-                loc.advance();
-                return err(format_underline("bad time: should be HH:MM:SS.subsec",
-                        {{source_location(loc), "HH:MM:SS.subsec"}},
-                        {"pass: 1979-05-27T07:32:00, 1979-05-27 07:32:00.999999",
-                         "fail: 1979-05-27T7:32:00, 1979-05-27 7:32"}));
-            }
-        }
-        return ok(value_t::local_date);
-    }
-    loc.reset(l.iter());
-
-    if(lex_local_time::invoke(loc)) {return ok(value_t::local_time);}
-    loc.reset(l.iter());
-
-    if(lex_float::invoke(loc))
-    {
-        if(loc.iter() != loc.end() && *loc.iter() == '_')
-        {
-            return err(format_underline("bad float: `_` should be surrounded by digits",
-                        {{source_location(loc), "here"}},
-                        {"pass: +1.0, -2e-2, 3.141_592_653_589, inf, nan",
-                         "fail: .0, 1., _1.0, 1.0_, 1_.0, 1.0__0"}));
-        }
-        return ok(value_t::floating);
-    }
-    loc.reset(l.iter());
-
-    if(lex_integer::invoke(loc))
-    {
-        if(loc.iter() != loc.end())
-        {
-            const auto c = *loc.iter();
-            if(c == '_')
-            {
-                return err(format_underline("bad integer: `_` should be surrounded by digits",
-                            {{source_location(loc), "here"}},
-                            {"pass: -42, 1_000, 1_2_3_4_5, 0xC0FFEE, 0b0010, 0o755",
-                             "fail: 1__000, 0123"}));
-            }
-            if('0' <= c && c <= '9')
-            {
-                // leading zero. point '0'
-                loc.retrace();
-                return err(format_underline("bad integer: leading zero",
-                            {{source_location(loc), "here"}},
-                            {"pass: -42, 1_000, 1_2_3_4_5, 0xC0FFEE, 0b0010, 0o755",
-                             "fail: 1__000, 0123"}));
-            }
-            if(c == ':' || c == '-')
-            {
-                return err(format_underline("bad datetime: invalid format",
-                            {{source_location(loc), "here"}},
-                            {"pass: 1979-05-27T07:32:00-07:00, 1979-05-27 07:32:00.999999Z",
-                             "fail: 1979-05-27T7:32:00-7:00, 1979-05-27 7:32-00:30"}));
-            }
-            if(c == '.' || c == 'e' || c == 'E')
-            {
-                return err(format_underline("bad float: invalid format",
-                            {{source_location(loc), "here"}},
-                            {"pass: +1.0, -2e-2, 3.141_592_653_589, inf, nan",
-                             "fail: .0, 1., _1.0, 1.0_, 1_.0, 1.0__0"}));
-            }
-        }
-        return ok(value_t::integer);
-    }
-    if(loc.iter() != loc.end() && *loc.iter() == '.')
-    {
-        return err(format_underline("bad float: invalid format",
-                {{source_location(loc), "integer part required before this"}},
-                {"pass: +1.0, -2e-2, 3.141_592_653_589, inf, nan",
-                 "fail: .0, 1., _1.0, 1.0_, 1_.0, 1.0__0"}));
-    }
-    if(loc.iter() != loc.end() && *loc.iter() == '_')
-    {
-        return err(format_underline("bad number: `_` should be surrounded by digits",
-                {{source_location(loc), "`_` is not surrounded by digits"}},
-                {"pass: -42, 1_000, 1_2_3_4_5, 0xC0FFEE, 0b0010, 0o755",
-                 "fail: 1__000, 0123"}));
-    }
-    return err(format_underline("bad format: unknown value appeared",
-                {{source_location(loc), "here"}}));
-}
-
-inline result<value_t, std::string> guess_value_type(const location& loc)
-{
-    switch(*loc.iter())
-    {
-        case '"' : {return ok(value_t::string);  }
-        case '\'': {return ok(value_t::string);  }
-        case 't' : {return ok(value_t::boolean); }
-        case 'f' : {return ok(value_t::boolean); }
-        case '[' : {return ok(value_t::array);   }
-        case '{' : {return ok(value_t::table);   }
-        case 'i' : {return ok(value_t::floating);} // inf.
-        case 'n' : {return ok(value_t::floating);} // nan.
-        default  : {return guess_number_type(loc);}
-    }
-}
-
-template<typename Value, typename T>
-result<Value, std::string>
-parse_value_helper(result<std::pair<T, region>, std::string> rslt)
-{
-    if(rslt.is_ok())
-    {
-        auto comments = rslt.as_ok().second.comments();
-        return ok(Value(std::move(rslt.as_ok()), std::move(comments)));
-    }
-    else
-    {
-        return err(std::move(rslt.as_err()));
-    }
-}
-
-template<typename Value>
-result<Value, std::string> parse_value(location& loc)
-{
-    const auto first = loc.iter();
-    if(first == loc.end())
-    {
-        return err(format_underline("toml::parse_value: input is empty",
-                   {{source_location(loc), ""}}));
-    }
-
-    const auto type = guess_value_type(loc);
-    if(!type)
-    {
-        return err(type.unwrap_err());
-    }
-
-    switch(type.unwrap())
-    {
-        case value_t::boolean        : {return parse_value_helper<Value>(parse_boolean(loc)            );}
-        case value_t::integer        : {return parse_value_helper<Value>(parse_integer(loc)            );}
-        case value_t::floating       : {return parse_value_helper<Value>(parse_floating(loc)           );}
-        case value_t::string         : {return parse_value_helper<Value>(parse_string(loc)             );}
-        case value_t::offset_datetime: {return parse_value_helper<Value>(parse_offset_datetime(loc)    );}
-        case value_t::local_datetime : {return parse_value_helper<Value>(parse_local_datetime(loc)     );}
-        case value_t::local_date     : {return parse_value_helper<Value>(parse_local_date(loc)         );}
-        case value_t::local_time     : {return parse_value_helper<Value>(parse_local_time(loc)         );}
-        case value_t::array          : {return parse_value_helper<Value>(parse_array<Value>(loc)       );}
-        case value_t::table          : {return parse_value_helper<Value>(parse_inline_table<Value>(loc));}
-        default:
-        {
-            const auto msg = format_underline("toml::parse_value: "
-                    "unknown token appeared", {{source_location(loc), "unknown"}});
-            loc.reset(first);
-            return err(msg);
-        }
-    }
-}
-
-inline result<std::pair<std::vector<key>, region>, std::string>
-parse_table_key(location& loc)
-{
-    if(auto token = lex_std_table::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-
-        const auto open = lex_std_table_open::invoke(inner_loc);
-        if(!open || inner_loc.iter() == inner_loc.end())
-        {
-            throw internal_error(format_underline(
-                "toml::parse_table_key: no `[`",
-                {{source_location(inner_loc), "should be `[`"}}),
-                source_location(inner_loc));
-        }
-        // to skip [ a . b . c ]
-        //          ^----------- this whitespace
-        lex_ws::invoke(inner_loc);
-        const auto keys = parse_key(inner_loc);
-        if(!keys)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_table_key: invalid key",
-                {{source_location(inner_loc), "not key"}}),
-                source_location(inner_loc));
-        }
-        // to skip [ a . b . c ]
-        //                    ^-- this whitespace
-        lex_ws::invoke(inner_loc);
-        const auto close = lex_std_table_close::invoke(inner_loc);
-        if(!close)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_table_key: no `]`",
-                {{source_location(inner_loc), "should be `]`"}}),
-                source_location(inner_loc));
-        }
-
-        // after [table.key], newline or EOF(empty table) required.
-        if(loc.iter() != loc.end())
-        {
-            using lex_newline_after_table_key =
-                sequence<maybe<lex_ws>, maybe<lex_comment>, lex_newline>;
-            const auto nl = lex_newline_after_table_key::invoke(loc);
-            if(!nl)
-            {
-                throw syntax_error(format_underline(
-                    "toml::parse_table_key: newline required after [table.key]",
-                    {{source_location(loc), "expected newline"}}),
-                    source_location(loc));
-            }
-        }
-        return ok(std::make_pair(keys.unwrap().first, token.unwrap()));
-    }
-    else
-    {
-        return err(format_underline("toml::parse_table_key: "
-            "not a valid table key", {{source_location(loc), "here"}}));
-    }
-}
-
-inline result<std::pair<std::vector<key>, region>, std::string>
-parse_array_table_key(location& loc)
-{
-    if(auto token = lex_array_table::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-
-        const auto open = lex_array_table_open::invoke(inner_loc);
-        if(!open || inner_loc.iter() == inner_loc.end())
-        {
-            throw internal_error(format_underline(
-                "toml::parse_array_table_key: no `[[`",
-                {{source_location(inner_loc), "should be `[[`"}}),
-                source_location(inner_loc));
-        }
-        lex_ws::invoke(inner_loc);
-        const auto keys = parse_key(inner_loc);
-        if(!keys)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_array_table_key: invalid key",
-                {{source_location(inner_loc), "not a key"}}),
-                source_location(inner_loc));
-        }
-        lex_ws::invoke(inner_loc);
-        const auto close = lex_array_table_close::invoke(inner_loc);
-        if(!close)
-        {
-            throw internal_error(format_underline(
-                "toml::parse_table_key: no `]]`",
-                {{source_location(inner_loc), "should be `]]`"}}),
-                source_location(inner_loc));
-        }
-
-        // after [[table.key]], newline or EOF(empty table) required.
-        if(loc.iter() != loc.end())
-        {
-            using lex_newline_after_table_key =
-                sequence<maybe<lex_ws>, maybe<lex_comment>, lex_newline>;
-            const auto nl = lex_newline_after_table_key::invoke(loc);
-            if(!nl)
-            {
-                throw syntax_error(format_underline("toml::"
-                    "parse_array_table_key: newline required after [[table.key]]",
-                    {{source_location(loc), "expected newline"}}),
-                    source_location(loc));
-            }
-        }
-        return ok(std::make_pair(keys.unwrap().first, token.unwrap()));
-    }
-    else
-    {
-        return err(format_underline("toml::parse_array_table_key: "
-            "not a valid table key", {{source_location(loc), "here"}}));
-    }
-}
-
-// parse table body (key-value pairs until the iter hits the next [tablekey])
-template<typename Value>
-result<typename Value::table_type, std::string>
-parse_ml_table(location& loc)
-{
-    using value_type = Value;
-    using table_type = typename value_type::table_type;
-
-    const auto first = loc.iter();
-    if(first == loc.end())
-    {
-        return ok(table_type{});
-    }
-
-    // XXX at lest one newline is needed.
-    using skip_line = repeat<
-        sequence<maybe<lex_ws>, maybe<lex_comment>, lex_newline>, at_least<1>>;
-    skip_line::invoke(loc);
-    lex_ws::invoke(loc);
-
-    table_type tab;
-    while(loc.iter() != loc.end())
-    {
-        lex_ws::invoke(loc);
-        const auto before = loc.iter();
-        if(const auto tmp = parse_array_table_key(loc)) // next table found
-        {
-            loc.reset(before);
-            return ok(tab);
-        }
-        if(const auto tmp = parse_table_key(loc)) // next table found
-        {
-            loc.reset(before);
-            return ok(tab);
-        }
-
-        if(const auto kv = parse_key_value_pair<value_type>(loc))
-        {
-            const auto&              kvpair  = kv.unwrap();
-            const std::vector<key>&  keys    = kvpair.first.first;
-            const auto&              key_reg = kvpair.first.second;
-            const value_type&        val     = kvpair.second;
-            const auto inserted =
-                insert_nested_key(tab, val, keys.begin(), keys.end(), key_reg);
-            if(!inserted)
-            {
-                return err(inserted.unwrap_err());
-            }
-        }
-        else
-        {
-            return err(kv.unwrap_err());
-        }
-
-        // comment lines are skipped by the above function call.
-        // However, since the `skip_line` requires at least 1 newline, it fails
-        // if the file ends with ws and/or comment without newline.
-        // `skip_line` matches `ws? + comment? + newline`, not `ws` or `comment`
-        // itself. To skip the last ws and/or comment, call lexers.
-        // It does not matter if these fails, so the return value is discarded.
-        lex_ws::invoke(loc);
-        lex_comment::invoke(loc);
-
-        // skip_line is (whitespace? comment? newline)_{1,}. multiple empty lines
-        // and comments after the last key-value pairs are allowed.
-        const auto newline = skip_line::invoke(loc);
-        if(!newline && loc.iter() != loc.end())
-        {
-            const auto before2 = loc.iter();
-            lex_ws::invoke(loc); // skip whitespace
-            const auto msg = format_underline("toml::parse_table: "
-                "invalid line format", {{source_location(loc), concat_to_string(
-                "expected newline, but got '", show_char(*loc.iter()), "'.")}});
-            loc.reset(before2);
-            return err(msg);
-        }
-
-        // the skip_lines only matches with lines that includes newline.
-        // to skip the last line that includes comment and/or whitespace
-        // but no newline, call them one more time.
-        lex_ws::invoke(loc);
-        lex_comment::invoke(loc);
-    }
-    return ok(tab);
-}
-
-template<typename Value>
-result<Value, std::string> parse_toml_file(location& loc)
-{
-    using value_type = Value;
-    using table_type = typename value_type::table_type;
-
-    const auto first = loc.iter();
-    if(first == loc.end())
-    {
-        // For empty files, return an empty table with an empty region (zero-length).
-        // Without the region, error messages would miss the filename.
-        return ok(value_type(table_type{}, region(loc, first, first), {}));
-    }
-
-    // put the first line as a region of a file
-    // Here first != loc.end(), so taking std::next is okay
-    const region file(loc, first, std::next(loc.iter()));
-
-    // The first successive comments that are separated from the first value
-    // by an empty line are for a file itself.
-    // ```toml
-    // # this is a comment for a file.
-    //
-    // key = "the first value"
-    // ```
-    // ```toml
-    // # this is a comment for "the first value".
-    // key = "the first value"
-    // ```
-    std::vector<std::string> comments;
-    using lex_first_comments = sequence<
-        repeat<sequence<maybe<lex_ws>, lex_comment, lex_newline>, at_least<1>>,
-        sequence<maybe<lex_ws>, lex_newline>
-        >;
-    if(const auto token = lex_first_comments::invoke(loc))
-    {
-        location inner_loc(loc.name(), token.unwrap().str());
-        while(inner_loc.iter() != inner_loc.end())
-        {
-            maybe<lex_ws>::invoke(inner_loc); // remove ws if exists
-            if(lex_newline::invoke(inner_loc))
-            {
-                assert(inner_loc.iter() == inner_loc.end());
-                break; // empty line found.
-            }
-            auto com = lex_comment::invoke(inner_loc).unwrap().str();
-            com.erase(com.begin()); // remove # sign
-            comments.push_back(std::move(com));
-            lex_newline::invoke(inner_loc);
-        }
-    }
-
-    table_type data;
-    // root object is also a table, but without [tablename]
-    if(const auto tab = parse_ml_table<value_type>(loc))
-    {
-        data = std::move(tab.unwrap());
-    }
-    else // failed (empty table is regarded as success in parse_ml_table)
-    {
-        return err(tab.unwrap_err());
-    }
-    while(loc.iter() != loc.end())
-    {
-        // here, the region of [table] is regarded as the table-key because
-        // the table body is normally too big and it is not so informative
-        // if the first key-value pair of the table is shown in the error
-        // message.
-        if(const auto tabkey = parse_array_table_key(loc))
-        {
-            const auto tab = parse_ml_table<value_type>(loc);
-            if(!tab){return err(tab.unwrap_err());}
-
-            const auto& tk   = tabkey.unwrap();
-            const auto& keys = tk.first;
-            const auto& reg  = tk.second;
-
-            const auto inserted = insert_nested_key(data,
-                    value_type(tab.unwrap(), reg, reg.comments()),
-                    keys.begin(), keys.end(), reg,
-                    /*is_array_of_table=*/ true);
-            if(!inserted) {return err(inserted.unwrap_err());}
-
-            continue;
-        }
-        if(const auto tabkey = parse_table_key(loc))
-        {
-            const auto tab = parse_ml_table<value_type>(loc);
-            if(!tab){return err(tab.unwrap_err());}
-
-            const auto& tk   = tabkey.unwrap();
-            const auto& keys = tk.first;
-            const auto& reg  = tk.second;
-
-            const auto inserted = insert_nested_key(data,
-                value_type(tab.unwrap(), reg, reg.comments()),
-                keys.begin(), keys.end(), reg);
-            if(!inserted) {return err(inserted.unwrap_err());}
-
-            continue;
-        }
-        return err(format_underline("toml::parse_toml_file: "
-            "unknown line appeared", {{source_location(loc), "unknown format"}}));
-    }
-
-    return ok(Value(std::move(data), file, comments));
-}
-
-} // detail
-
-template<typename                     Comment = TOML11_DEFAULT_COMMENT_STRATEGY,
-         template<typename ...> class Table   = std::unordered_map,
-         template<typename ...> class Array   = std::vector>
-basic_value<Comment, Table, Array>
-parse(std::istream& is, const std::string& fname = "unknown file")
-{
-    using value_type = basic_value<Comment, Table, Array>;
-
-    const auto beg = is.tellg();
-    is.seekg(0, std::ios::end);
-    const auto end = is.tellg();
-    const auto fsize = end - beg;
-    is.seekg(beg);
-
-    // read whole file as a sequence of char
-    assert(fsize >= 0);
-    std::vector<char> letters(static_cast<std::size_t>(fsize));
-    is.read(letters.data(), fsize);
-
-    // append LF.
-    // Although TOML does not require LF at the EOF, to make parsing logic
-    // simpler, we "normalize" the content by adding LF if it does not exist.
-    // It also checks if the last char is CR, to avoid changing the meaning.
-    // This is not the *best* way to deal with the last character, but is a
-    // simple and quick fix.
-    if(!letters.empty() && letters.back() != '\n' && letters.back() != '\r')
-    {
-        letters.push_back('\n');
-    }
-
-    detail::location loc(std::move(fname), std::move(letters));
-
-    // skip BOM if exists.
-    // XXX component of BOM (like 0xEF) exceeds the representable range of
-    // signed char, so on some (actually, most) of the environment, these cannot
-    // be compared to char. However, since we are always out of luck, we need to
-    // check our chars are equivalent to BOM. To do this, first we need to
-    // convert char to unsigned char to guarantee the comparability.
-    if(loc.source()->size() >= 3)
-    {
-        std::array<unsigned char, 3> BOM;
-        std::memcpy(BOM.data(), loc.source()->data(), 3);
-        if(BOM[0] == 0xEF && BOM[1] == 0xBB && BOM[2] == 0xBF)
-        {
-            loc.advance(3); // BOM found. skip.
-        }
-    }
-
-    const auto data = detail::parse_toml_file<value_type>(loc);
-    if(!data)
-    {
-        throw syntax_error(data.unwrap_err(), source_location(loc));
-    }
-    return data.unwrap();
-}
-
-template<typename                     Comment = TOML11_DEFAULT_COMMENT_STRATEGY,
-         template<typename ...> class Table   = std::unordered_map,
-         template<typename ...> class Array   = std::vector>
-basic_value<Comment, Table, Array> parse(const std::string& fname)
-{
-    std::ifstream ifs(fname.c_str(), std::ios_base::binary);
-    if(!ifs.good())
-    {
-        throw std::runtime_error("toml::parse: file open error -> " + fname);
-    }
-    return parse<Comment, Table, Array>(ifs, fname);
-}
-
-#ifdef TOML11_HAS_STD_FILESYSTEM
-// This function just forwards `parse("filename.toml")` to std::string version
-// to avoid the ambiguity in overload resolution.
-//
-// Both std::string and std::filesystem::path are convertible from const char*.
-// Without this, both parse(std::string) and parse(std::filesystem::path)
-// matches to parse("filename.toml"). This breaks the existing code.
-//
-// This function exactly matches to the invocation with c-string.
-// So this function is preferred than others and the ambiguity disappears.
-template<typename                     Comment = TOML11_DEFAULT_COMMENT_STRATEGY,
-         template<typename ...> class Table   = std::unordered_map,
-         template<typename ...> class Array   = std::vector>
-basic_value<Comment, Table, Array> parse(const char* fname)
-{
-    return parse<Comment, Table, Array>(std::string(fname));
-}
-
-template<typename                     Comment = TOML11_DEFAULT_COMMENT_STRATEGY,
-         template<typename ...> class Table   = std::unordered_map,
-         template<typename ...> class Array   = std::vector>
-basic_value<Comment, Table, Array> parse(const std::filesystem::path& fpath)
-{
-    std::ifstream ifs(fpath, std::ios_base::binary);
-    if(!ifs.good())
-    {
-        throw std::runtime_error("toml::parse: file open error -> " +
-                                 fpath.string());
-    }
-    return parse<Comment, Table, Array>(ifs, fpath.string());
-}
-#endif // TOML11_HAS_STD_FILESYSTEM
-
-} // toml
-#endif// TOML11_PARSER_HPP
diff --git a/src/toml11/toml/region.hpp b/src/toml11/toml/region.hpp
deleted file mode 100644
index 2e01e51d086..00000000000
--- a/src/toml11/toml/region.hpp
+++ /dev/null
@@ -1,417 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_REGION_HPP
-#define TOML11_REGION_HPP
-#include <memory>
-#include <vector>
-#include <algorithm>
-#include <initializer_list>
-#include <iterator>
-#include <iomanip>
-#include <cassert>
-#include "color.hpp"
-
-namespace toml
-{
-namespace detail
-{
-
-// helper function to avoid std::string(0, 'c') or std::string(iter, iter)
-template<typename Iterator>
-std::string make_string(Iterator first, Iterator last)
-{
-    if(first == last) {return "";}
-    return std::string(first, last);
-}
-inline std::string make_string(std::size_t len, char c)
-{
-    if(len == 0) {return "";}
-    return std::string(len, c);
-}
-
-// region_base is a base class of location and region that are defined below.
-// it will be used to generate better error messages.
-struct region_base
-{
-    region_base() = default;
-    virtual ~region_base() = default;
-    region_base(const region_base&) = default;
-    region_base(region_base&&     ) = default;
-    region_base& operator=(const region_base&) = default;
-    region_base& operator=(region_base&&     ) = default;
-
-    virtual bool is_ok()           const noexcept {return false;}
-    virtual char front()           const noexcept {return '\0';}
-
-    virtual std::string str()      const {return std::string("unknown region");}
-    virtual std::string name()     const {return std::string("unknown file");}
-    virtual std::string line()     const {return std::string("unknown line");}
-    virtual std::string line_num() const {return std::string("?");}
-
-    // length of the region
-    virtual std::size_t size()     const noexcept {return 0;}
-    // number of characters in the line before the region
-    virtual std::size_t before()   const noexcept {return 0;}
-    // number of characters in the line after the region
-    virtual std::size_t after()    const noexcept {return 0;}
-
-    virtual std::vector<std::string> comments() const {return {};}
-    // ```toml
-    // # comment_before
-    // key = "value" # comment_inline
-    // ```
-};
-
-// location represents a position in a container, which contains a file content.
-// it can be considered as a region that contains only one character.
-//
-// it contains pointer to the file content and iterator that points the current
-// location.
-struct location final : public region_base
-{
-    using const_iterator  = typename std::vector<char>::const_iterator;
-    using difference_type = typename const_iterator::difference_type;
-    using source_ptr      = std::shared_ptr<const std::vector<char>>;
-
-    location(std::string source_name, std::vector<char> cont)
-      : source_(std::make_shared<std::vector<char>>(std::move(cont))),
-        line_number_(1), source_name_(std::move(source_name)), iter_(source_->cbegin())
-    {}
-    location(std::string source_name, const std::string& cont)
-      : source_(std::make_shared<std::vector<char>>(cont.begin(), cont.end())),
-        line_number_(1), source_name_(std::move(source_name)), iter_(source_->cbegin())
-    {}
-
-    location(const location&) = default;
-    location(location&&)      = default;
-    location& operator=(const location&) = default;
-    location& operator=(location&&)      = default;
-    ~location() = default;
-
-    bool is_ok() const noexcept override {return static_cast<bool>(source_);}
-    char front() const noexcept override {return *iter_;}
-
-    // this const prohibits codes like `++(loc.iter())`.
-    const const_iterator iter()  const noexcept {return iter_;}
-
-    const_iterator begin() const noexcept {return source_->cbegin();}
-    const_iterator end()   const noexcept {return source_->cend();}
-
-    // XXX `location::line_num()` used to be implemented using `std::count` to
-    // count a number of '\n'. But with a long toml file (typically, 10k lines),
-    // it becomes intolerably slow because each time it generates error messages,
-    // it counts '\n' from thousands of characters. To workaround it, I decided
-    // to introduce `location::line_number_` member variable and synchronize it
-    // to the location changes the point to look. So an overload of `iter()`
-    // which returns mutable reference is removed and `advance()`, `retrace()`
-    // and `reset()` is added.
-    void advance(difference_type n = 1) noexcept
-    {
-        this->line_number_ += static_cast<std::size_t>(
-                std::count(this->iter_, std::next(this->iter_, n), '\n'));
-        this->iter_ += n;
-        return;
-    }
-    void retrace(difference_type n = 1) noexcept
-    {
-        this->line_number_ -= static_cast<std::size_t>(
-                std::count(std::prev(this->iter_, n), this->iter_, '\n'));
-        this->iter_ -= n;
-        return;
-    }
-    void reset(const_iterator rollback) noexcept
-    {
-        // since c++11, std::distance works in both ways for random-access
-        // iterators and returns a negative value if `first > last`.
-        if(0 <= std::distance(rollback, this->iter_)) // rollback < iter
-        {
-            this->line_number_ -= static_cast<std::size_t>(
-                    std::count(rollback, this->iter_, '\n'));
-        }
-        else // iter < rollback [[unlikely]]
-        {
-            this->line_number_ += static_cast<std::size_t>(
-                    std::count(this->iter_, rollback, '\n'));
-        }
-        this->iter_ = rollback;
-        return;
-    }
-
-    std::string str()  const override {return make_string(1, *this->iter());}
-    std::string name() const override {return source_name_;}
-
-    std::string line_num() const override
-    {
-        return std::to_string(this->line_number_);
-    }
-
-    std::string line() const override
-    {
-        return make_string(this->line_begin(), this->line_end());
-    }
-
-    const_iterator line_begin() const noexcept
-    {
-        using reverse_iterator = std::reverse_iterator<const_iterator>;
-        return std::find(reverse_iterator(this->iter()),
-                         reverse_iterator(this->begin()), '\n').base();
-    }
-    const_iterator line_end() const noexcept
-    {
-        return std::find(this->iter(), this->end(), '\n');
-    }
-
-    // location is always points a character. so the size is 1.
-    std::size_t size() const noexcept override
-    {
-        return 1u;
-    }
-    std::size_t before() const noexcept override
-    {
-        const auto sz = std::distance(this->line_begin(), this->iter());
-        assert(sz >= 0);
-        return static_cast<std::size_t>(sz);
-    }
-    std::size_t after() const noexcept override
-    {
-        const auto sz = std::distance(this->iter(), this->line_end());
-        assert(sz >= 0);
-        return static_cast<std::size_t>(sz);
-    }
-
-    source_ptr const& source() const& noexcept {return source_;}
-    source_ptr&&      source() &&     noexcept {return std::move(source_);}
-
-  private:
-
-    source_ptr     source_;
-    std::size_t    line_number_;
-    std::string    source_name_;
-    const_iterator iter_;
-};
-
-// region represents a range in a container, which contains a file content.
-//
-// it contains pointer to the file content and iterator that points the first
-// and last location.
-struct region final : public region_base
-{
-    using const_iterator = typename std::vector<char>::const_iterator;
-    using source_ptr     = std::shared_ptr<const std::vector<char>>;
-
-    // delete default constructor. source_ never be null.
-    region() = delete;
-
-    explicit region(const location& loc)
-      : source_(loc.source()), source_name_(loc.name()),
-        first_(loc.iter()), last_(loc.iter())
-    {}
-    explicit region(location&& loc)
-      : source_(loc.source()), source_name_(loc.name()),
-        first_(loc.iter()), last_(loc.iter())
-    {}
-
-    region(const location& loc, const_iterator f, const_iterator l)
-      : source_(loc.source()), source_name_(loc.name()), first_(f), last_(l)
-    {}
-    region(location&& loc, const_iterator f, const_iterator l)
-      : source_(loc.source()), source_name_(loc.name()), first_(f), last_(l)
-    {}
-
-    region(const region&) = default;
-    region(region&&)      = default;
-    region& operator=(const region&) = default;
-    region& operator=(region&&)      = default;
-    ~region() = default;
-
-    region& operator+=(const region& other)
-    {
-        // different regions cannot be concatenated
-        assert(this->begin() == other.begin() && this->end() == other.end() &&
-               this->last_   == other.first_);
-
-        this->last_ = other.last_;
-        return *this;
-    }
-
-    bool is_ok() const noexcept override {return static_cast<bool>(source_);}
-    char front() const noexcept override {return *first_;}
-
-    std::string str()  const override {return make_string(first_, last_);}
-    std::string line() const override
-    {
-        if(this->contain_newline())
-        {
-            return make_string(this->line_begin(),
-                    std::find(this->line_begin(), this->last(), '\n'));
-        }
-        return make_string(this->line_begin(), this->line_end());
-    }
-    std::string line_num() const override
-    {
-        return std::to_string(1 + std::count(this->begin(), this->first(), '\n'));
-    }
-
-    std::size_t size() const noexcept override
-    {
-        const auto sz = std::distance(first_, last_);
-        assert(sz >= 0);
-        return static_cast<std::size_t>(sz);
-    }
-    std::size_t before() const noexcept override
-    {
-        const auto sz = std::distance(this->line_begin(), this->first());
-        assert(sz >= 0);
-        return static_cast<std::size_t>(sz);
-    }
-    std::size_t after() const noexcept override
-    {
-        const auto sz = std::distance(this->last(), this->line_end());
-        assert(sz >= 0);
-        return static_cast<std::size_t>(sz);
-    }
-
-    bool contain_newline() const noexcept
-    {
-        return std::find(this->first(), this->last(), '\n') != this->last();
-    }
-
-    const_iterator line_begin() const noexcept
-    {
-        using reverse_iterator = std::reverse_iterator<const_iterator>;
-        return std::find(reverse_iterator(this->first()),
-                         reverse_iterator(this->begin()), '\n').base();
-    }
-    const_iterator line_end() const noexcept
-    {
-        return std::find(this->last(), this->end(), '\n');
-    }
-
-    const_iterator begin() const noexcept {return source_->cbegin();}
-    const_iterator end()   const noexcept {return source_->cend();}
-    const_iterator first() const noexcept {return first_;}
-    const_iterator last()  const noexcept {return last_;}
-
-    source_ptr const& source() const& noexcept {return source_;}
-    source_ptr&&      source() &&     noexcept {return std::move(source_);}
-
-    std::string name() const override {return source_name_;}
-
-    std::vector<std::string> comments() const override
-    {
-        // assuming the current region (`*this`) points a value.
-        // ```toml
-        // a = "value"
-        //     ^^^^^^^- this region
-        // ```
-        using rev_iter = std::reverse_iterator<const_iterator>;
-
-        std::vector<std::string> com{};
-        {
-            // find comments just before the current region.
-            // ```toml
-            // # this should be collected.
-            // # this also.
-            // a = value # not this.
-            // ```
-
-            // # this is a comment for `a`, not array elements.
-            // a = [1, 2, 3, 4, 5]
-            if(this->first() == std::find_if(this->line_begin(), this->first(),
-                [](const char c) noexcept -> bool {return c == '[' || c == '{';}))
-            {
-                auto iter = this->line_begin(); // points the first character
-                while(iter != this->begin())
-                {
-                    iter = std::prev(iter);
-
-                    // range [line_start, iter) represents the previous line
-                    const auto line_start   = std::find(
-                            rev_iter(iter), rev_iter(this->begin()), '\n').base();
-                    const auto comment_found = std::find(line_start, iter, '#');
-                    if(comment_found == iter)
-                    {
-                        break; // comment not found.
-                    }
-
-                    // exclude the following case.
-                    // > a = "foo" # comment // <-- this is not a comment for b but a.
-                    // > b = "current value"
-                    if(std::all_of(line_start, comment_found,
-                            [](const char c) noexcept -> bool {
-                                return c == ' ' || c == '\t';
-                            }))
-                    {
-                        // unwrap the first '#' by std::next.
-                        auto s = make_string(std::next(comment_found), iter);
-                        if(!s.empty() && s.back() == '\r') {s.pop_back();}
-                        com.push_back(std::move(s));
-                    }
-                    else
-                    {
-                        break;
-                    }
-                    iter = line_start;
-                }
-            }
-        }
-
-        if(com.size() > 1)
-        {
-            std::reverse(com.begin(), com.end());
-        }
-
-        {
-            // find comments just after the current region.
-            // ```toml
-            // # not this.
-            // a = value # this one.
-            // a = [ # not this (technically difficult)
-            //
-            // ] # and this.
-            // ```
-            // The reason why it's difficult is that it requires parsing in the
-            // following case.
-            // ```toml
-            // a = [ 10 # this comment is for `10`. not for `a` but `a[0]`.
-            // # ...
-            // ] # this is apparently a comment for a.
-            //
-            // b = [
-            // 3.14 ] # there is no way to add a comment to `3.14` currently.
-            //
-            // c = [
-            //   3.14 # do this if you need a comment here.
-            // ]
-            // ```
-            const auto comment_found =
-                std::find(this->last(), this->line_end(), '#');
-            if(comment_found != this->line_end()) // '#' found
-            {
-                // table = {key = "value"} # what is this for?
-                // the above comment is not for "value", but {key="value"}.
-                if(comment_found == std::find_if(this->last(), comment_found,
-                    [](const char c) noexcept -> bool {
-                        return !(c == ' ' || c == '\t' || c == ',');
-                    }))
-                {
-                    // unwrap the first '#' by std::next.
-                    auto s = make_string(std::next(comment_found), this->line_end());
-                    if(!s.empty() && s.back() == '\r') {s.pop_back();}
-                    com.push_back(std::move(s));
-                }
-            }
-        }
-        return com;
-    }
-
-  private:
-
-    source_ptr     source_;
-    std::string    source_name_;
-    const_iterator first_, last_;
-};
-
-} // detail
-} // toml
-#endif// TOML11_REGION_H
diff --git a/src/toml11/toml/result.hpp b/src/toml11/toml/result.hpp
deleted file mode 100644
index 77cd46c6486..00000000000
--- a/src/toml11/toml/result.hpp
+++ /dev/null
@@ -1,717 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_RESULT_HPP
-#define TOML11_RESULT_HPP
-#include "traits.hpp"
-#include <type_traits>
-#include <stdexcept>
-#include <utility>
-#include <new>
-#include <string>
-#include <sstream>
-#include <cassert>
-
-namespace toml
-{
-
-template<typename T>
-struct success
-{
-    using value_type = T;
-    value_type value;
-
-    explicit success(const value_type& v)
-        noexcept(std::is_nothrow_copy_constructible<value_type>::value)
-        : value(v)
-    {}
-    explicit success(value_type&& v)
-        noexcept(std::is_nothrow_move_constructible<value_type>::value)
-        : value(std::move(v))
-    {}
-
-    template<typename U>
-    explicit success(U&& v): value(std::forward<U>(v)) {}
-
-    template<typename U>
-    explicit success(const success<U>& v): value(v.value) {}
-    template<typename U>
-    explicit success(success<U>&& v): value(std::move(v.value)) {}
-
-    ~success() = default;
-    success(const success&) = default;
-    success(success&&)      = default;
-    success& operator=(const success&) = default;
-    success& operator=(success&&)      = default;
-};
-
-template<typename T>
-struct failure
-{
-    using value_type = T;
-    value_type value;
-
-    explicit failure(const value_type& v)
-        noexcept(std::is_nothrow_copy_constructible<value_type>::value)
-        : value(v)
-    {}
-    explicit failure(value_type&& v)
-        noexcept(std::is_nothrow_move_constructible<value_type>::value)
-        : value(std::move(v))
-    {}
-
-    template<typename U>
-    explicit failure(U&& v): value(std::forward<U>(v)) {}
-
-    template<typename U>
-    explicit failure(const failure<U>& v): value(v.value) {}
-    template<typename U>
-    explicit failure(failure<U>&& v): value(std::move(v.value)) {}
-
-    ~failure() = default;
-    failure(const failure&) = default;
-    failure(failure&&)      = default;
-    failure& operator=(const failure&) = default;
-    failure& operator=(failure&&)      = default;
-};
-
-template<typename T>
-success<typename std::remove_cv<typename std::remove_reference<T>::type>::type>
-ok(T&& v)
-{
-    return success<
-        typename std::remove_cv<typename std::remove_reference<T>::type>::type
-        >(std::forward<T>(v));
-}
-template<typename T>
-failure<typename std::remove_cv<typename std::remove_reference<T>::type>::type>
-err(T&& v)
-{
-    return failure<
-        typename std::remove_cv<typename std::remove_reference<T>::type>::type
-        >(std::forward<T>(v));
-}
-
-inline success<std::string> ok(const char* literal)
-{
-    return success<std::string>(std::string(literal));
-}
-inline failure<std::string> err(const char* literal)
-{
-    return failure<std::string>(std::string(literal));
-}
-
-
-template<typename T, typename E>
-struct result
-{
-    using value_type = T;
-    using error_type = E;
-    using success_type = success<value_type>;
-    using failure_type = failure<error_type>;
-
-    result(const success_type& s): is_ok_(true)
-    {
-        auto tmp = ::new(std::addressof(this->succ)) success_type(s);
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-    }
-    result(const failure_type& f): is_ok_(false)
-    {
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(f);
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-    }
-    result(success_type&& s): is_ok_(true)
-    {
-        auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(s));
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-    }
-    result(failure_type&& f): is_ok_(false)
-    {
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(f));
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-    }
-
-    template<typename U>
-    result(const success<U>& s): is_ok_(true)
-    {
-        auto tmp = ::new(std::addressof(this->succ)) success_type(s.value);
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-    }
-    template<typename U>
-    result(const failure<U>& f): is_ok_(false)
-    {
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(f.value);
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-    }
-    template<typename U>
-    result(success<U>&& s): is_ok_(true)
-    {
-        auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(s.value));
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-    }
-    template<typename U>
-    result(failure<U>&& f): is_ok_(false)
-    {
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(f.value));
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-    }
-
-    result& operator=(const success_type& s)
-    {
-        this->cleanup();
-        this->is_ok_ = true;
-        auto tmp = ::new(std::addressof(this->succ)) success_type(s);
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-        return *this;
-    }
-    result& operator=(const failure_type& f)
-    {
-        this->cleanup();
-        this->is_ok_ = false;
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(f);
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-        return *this;
-    }
-    result& operator=(success_type&& s)
-    {
-        this->cleanup();
-        this->is_ok_ = true;
-        auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(s));
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-        return *this;
-    }
-    result& operator=(failure_type&& f)
-    {
-        this->cleanup();
-        this->is_ok_ = false;
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(f));
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-        return *this;
-    }
-
-    template<typename U>
-    result& operator=(const success<U>& s)
-    {
-        this->cleanup();
-        this->is_ok_ = true;
-        auto tmp = ::new(std::addressof(this->succ)) success_type(s.value);
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-        return *this;
-    }
-    template<typename U>
-    result& operator=(const failure<U>& f)
-    {
-        this->cleanup();
-        this->is_ok_ = false;
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(f.value);
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-        return *this;
-    }
-    template<typename U>
-    result& operator=(success<U>&& s)
-    {
-        this->cleanup();
-        this->is_ok_ = true;
-        auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(s.value));
-        assert(tmp == std::addressof(this->succ));
-        (void)tmp;
-        return *this;
-    }
-    template<typename U>
-    result& operator=(failure<U>&& f)
-    {
-        this->cleanup();
-        this->is_ok_ = false;
-        auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(f.value));
-        assert(tmp == std::addressof(this->fail));
-        (void)tmp;
-        return *this;
-    }
-
-    ~result() noexcept {this->cleanup();}
-
-    result(const result& other): is_ok_(other.is_ok())
-    {
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(other.as_ok());
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(other.as_err());
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-    }
-    result(result&& other): is_ok_(other.is_ok())
-    {
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(other.as_ok()));
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(other.as_err()));
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-    }
-
-    template<typename U, typename F>
-    result(const result<U, F>& other): is_ok_(other.is_ok())
-    {
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(other.as_ok());
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(other.as_err());
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-    }
-    template<typename U, typename F>
-    result(result<U, F>&& other): is_ok_(other.is_ok())
-    {
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(other.as_ok()));
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(other.as_err()));
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-    }
-
-    result& operator=(const result& other)
-    {
-        this->cleanup();
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(other.as_ok());
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(other.as_err());
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-        is_ok_ = other.is_ok();
-        return *this;
-    }
-    result& operator=(result&& other)
-    {
-        this->cleanup();
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(other.as_ok()));
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(other.as_err()));
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-        is_ok_ = other.is_ok();
-        return *this;
-    }
-
-    template<typename U, typename F>
-    result& operator=(const result<U, F>& other)
-    {
-        this->cleanup();
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(other.as_ok());
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(other.as_err());
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-        is_ok_ = other.is_ok();
-        return *this;
-    }
-    template<typename U, typename F>
-    result& operator=(result<U, F>&& other)
-    {
-        this->cleanup();
-        if(other.is_ok())
-        {
-            auto tmp = ::new(std::addressof(this->succ)) success_type(std::move(other.as_ok()));
-            assert(tmp == std::addressof(this->succ));
-            (void)tmp;
-        }
-        else
-        {
-            auto tmp = ::new(std::addressof(this->fail)) failure_type(std::move(other.as_err()));
-            assert(tmp == std::addressof(this->fail));
-            (void)tmp;
-        }
-        is_ok_ = other.is_ok();
-        return *this;
-    }
-
-    bool is_ok()  const noexcept {return is_ok_;}
-    bool is_err() const noexcept {return !is_ok_;}
-
-    operator bool() const noexcept {return is_ok_;}
-
-    value_type&       unwrap() &
-    {
-        if(is_err())
-        {
-            throw std::runtime_error("toml::result: bad unwrap: " +
-                                     format_error(this->as_err()));
-        }
-        return this->succ.value;
-    }
-    value_type const& unwrap() const&
-    {
-        if(is_err())
-        {
-            throw std::runtime_error("toml::result: bad unwrap: " +
-                                     format_error(this->as_err()));
-        }
-        return this->succ.value;
-    }
-    value_type&&      unwrap() &&
-    {
-        if(is_err())
-        {
-            throw std::runtime_error("toml::result: bad unwrap: " +
-                                     format_error(this->as_err()));
-        }
-        return std::move(this->succ.value);
-    }
-
-    value_type&       unwrap_or(value_type& opt) &
-    {
-        if(is_err()) {return opt;}
-        return this->succ.value;
-    }
-    value_type const& unwrap_or(value_type const& opt) const&
-    {
-        if(is_err()) {return opt;}
-        return this->succ.value;
-    }
-    value_type        unwrap_or(value_type opt) &&
-    {
-        if(is_err()) {return opt;}
-        return this->succ.value;
-    }
-
-    error_type&       unwrap_err() &
-    {
-        if(is_ok()) {throw std::runtime_error("toml::result: bad unwrap_err");}
-        return this->fail.value;
-    }
-    error_type const& unwrap_err() const&
-    {
-        if(is_ok()) {throw std::runtime_error("toml::result: bad unwrap_err");}
-        return this->fail.value;
-    }
-    error_type&&      unwrap_err() &&
-    {
-        if(is_ok()) {throw std::runtime_error("toml::result: bad unwrap_err");}
-        return std::move(this->fail.value);
-    }
-
-    value_type&       as_ok() &      noexcept {return this->succ.value;}
-    value_type const& as_ok() const& noexcept {return this->succ.value;}
-    value_type&&      as_ok() &&     noexcept {return std::move(this->succ.value);}
-
-    error_type&       as_err() &      noexcept {return this->fail.value;}
-    error_type const& as_err() const& noexcept {return this->fail.value;}
-    error_type&&      as_err() &&     noexcept {return std::move(this->fail.value);}
-
-
-    // prerequisities
-    // F: T -> U
-    // retval: result<U, E>
-    template<typename F>
-    result<detail::return_type_of_t<F, value_type&>, error_type>
-    map(F&& f) &
-    {
-        if(this->is_ok()){return ok(f(this->as_ok()));}
-        return err(this->as_err());
-    }
-    template<typename F>
-    result<detail::return_type_of_t<F, value_type const&>, error_type>
-    map(F&& f) const&
-    {
-        if(this->is_ok()){return ok(f(this->as_ok()));}
-        return err(this->as_err());
-    }
-    template<typename F>
-    result<detail::return_type_of_t<F, value_type &&>, error_type>
-    map(F&& f) &&
-    {
-        if(this->is_ok()){return ok(f(std::move(this->as_ok())));}
-        return err(std::move(this->as_err()));
-    }
-
-    // prerequisities
-    // F: E -> F
-    // retval: result<T, F>
-    template<typename F>
-    result<value_type, detail::return_type_of_t<F, error_type&>>
-    map_err(F&& f) &
-    {
-        if(this->is_err()){return err(f(this->as_err()));}
-        return ok(this->as_ok());
-    }
-    template<typename F>
-    result<value_type, detail::return_type_of_t<F, error_type const&>>
-    map_err(F&& f) const&
-    {
-        if(this->is_err()){return err(f(this->as_err()));}
-        return ok(this->as_ok());
-    }
-    template<typename F>
-    result<value_type, detail::return_type_of_t<F, error_type&&>>
-    map_err(F&& f) &&
-    {
-        if(this->is_err()){return err(f(std::move(this->as_err())));}
-        return ok(std::move(this->as_ok()));
-    }
-
-    // prerequisities
-    // F: T -> U
-    // retval: U
-    template<typename F, typename U>
-    detail::return_type_of_t<F, value_type&>
-    map_or_else(F&& f, U&& opt) &
-    {
-        if(this->is_err()){return std::forward<U>(opt);}
-        return f(this->as_ok());
-    }
-    template<typename F, typename U>
-    detail::return_type_of_t<F, value_type const&>
-    map_or_else(F&& f, U&& opt) const&
-    {
-        if(this->is_err()){return std::forward<U>(opt);}
-        return f(this->as_ok());
-    }
-    template<typename F, typename U>
-    detail::return_type_of_t<F, value_type&&>
-    map_or_else(F&& f, U&& opt) &&
-    {
-        if(this->is_err()){return std::forward<U>(opt);}
-        return f(std::move(this->as_ok()));
-    }
-
-    // prerequisities
-    // F: E -> U
-    // retval: U
-    template<typename F, typename U>
-    detail::return_type_of_t<F, error_type&>
-    map_err_or_else(F&& f, U&& opt) &
-    {
-        if(this->is_ok()){return std::forward<U>(opt);}
-        return f(this->as_err());
-    }
-    template<typename F, typename U>
-    detail::return_type_of_t<F, error_type const&>
-    map_err_or_else(F&& f, U&& opt) const&
-    {
-        if(this->is_ok()){return std::forward<U>(opt);}
-        return f(this->as_err());
-    }
-    template<typename F, typename U>
-    detail::return_type_of_t<F, error_type&&>
-    map_err_or_else(F&& f, U&& opt) &&
-    {
-        if(this->is_ok()){return std::forward<U>(opt);}
-        return f(std::move(this->as_err()));
-    }
-
-    // prerequisities:
-    // F: func T -> U
-    // toml::err(error_type) should be convertible to U.
-    // normally, type U is another result<S, F> and E is convertible to F
-    template<typename F>
-    detail::return_type_of_t<F, value_type&>
-    and_then(F&& f) &
-    {
-        if(this->is_ok()){return f(this->as_ok());}
-        return err(this->as_err());
-    }
-    template<typename F>
-    detail::return_type_of_t<F, value_type const&>
-    and_then(F&& f) const&
-    {
-        if(this->is_ok()){return f(this->as_ok());}
-        return err(this->as_err());
-    }
-    template<typename F>
-    detail::return_type_of_t<F, value_type&&>
-    and_then(F&& f) &&
-    {
-        if(this->is_ok()){return f(std::move(this->as_ok()));}
-        return err(std::move(this->as_err()));
-    }
-
-    // prerequisities:
-    // F: func E -> U
-    // toml::ok(value_type) should be convertible to U.
-    // normally, type U is another result<S, F> and T is convertible to S
-    template<typename F>
-    detail::return_type_of_t<F, error_type&>
-    or_else(F&& f) &
-    {
-        if(this->is_err()){return f(this->as_err());}
-        return ok(this->as_ok());
-    }
-    template<typename F>
-    detail::return_type_of_t<F, error_type const&>
-    or_else(F&& f) const&
-    {
-        if(this->is_err()){return f(this->as_err());}
-        return ok(this->as_ok());
-    }
-    template<typename F>
-    detail::return_type_of_t<F, error_type&&>
-    or_else(F&& f) &&
-    {
-        if(this->is_err()){return f(std::move(this->as_err()));}
-        return ok(std::move(this->as_ok()));
-    }
-
-    // if *this is error, returns *this. otherwise, returns other.
-    result and_other(const result& other) const&
-    {
-        return this->is_err() ? *this : other;
-    }
-    result and_other(result&& other) &&
-    {
-        return this->is_err() ? std::move(*this) : std::move(other);
-    }
-
-    // if *this is okay, returns *this. otherwise, returns other.
-    result or_other(const result& other) const&
-    {
-        return this->is_ok() ? *this : other;
-    }
-    result or_other(result&& other) &&
-    {
-        return this->is_ok() ? std::move(*this) : std::move(other);
-    }
-
-    void swap(result<T, E>& other)
-    {
-        result<T, E> tmp(std::move(*this));
-        *this = std::move(other);
-        other = std::move(tmp);
-        return ;
-    }
-
-  private:
-
-    static std::string format_error(std::exception const& excpt)
-    {
-        return std::string(excpt.what());
-    }
-    template<typename U, typename std::enable_if<!std::is_base_of<
-        std::exception, U>::value, std::nullptr_t>::type = nullptr>
-    static std::string format_error(U const& others)
-    {
-        std::ostringstream oss; oss << others;
-        return oss.str();
-    }
-
-    void cleanup() noexcept
-    {
-        if(this->is_ok_) {this->succ.~success_type();}
-        else             {this->fail.~failure_type();}
-        return;
-    }
-
-  private:
-
-    bool      is_ok_;
-    union
-    {
-        success_type succ;
-        failure_type fail;
-    };
-};
-
-template<typename T, typename E>
-void swap(result<T, E>& lhs, result<T, E>& rhs)
-{
-    lhs.swap(rhs);
-    return;
-}
-
-// this might be confusing because it eagerly evaluated, while in the other
-// cases operator && and || are short-circuited.
-//
-// template<typename T, typename E>
-// inline result<T, E>
-// operator&&(const result<T, E>& lhs, const result<T, E>& rhs) noexcept
-// {
-//     return lhs.is_ok() ? rhs : lhs;
-// }
-//
-// template<typename T, typename E>
-// inline result<T, E>
-// operator||(const result<T, E>& lhs, const result<T, E>& rhs) noexcept
-// {
-//     return lhs.is_ok() ? lhs : rhs;
-// }
-
-// ----------------------------------------------------------------------------
-// re-use result<T, E> as a optional<T> with none_t
-
-namespace detail
-{
-struct none_t {};
-inline bool operator==(const none_t&, const none_t&) noexcept {return true;}
-inline bool operator!=(const none_t&, const none_t&) noexcept {return false;}
-inline bool operator< (const none_t&, const none_t&) noexcept {return false;}
-inline bool operator<=(const none_t&, const none_t&) noexcept {return true;}
-inline bool operator> (const none_t&, const none_t&) noexcept {return false;}
-inline bool operator>=(const none_t&, const none_t&) noexcept {return true;}
-template<typename charT, typename traitsT>
-std::basic_ostream<charT, traitsT>&
-operator<<(std::basic_ostream<charT, traitsT>& os, const none_t&)
-{
-    os << "none";
-    return os;
-}
-inline failure<none_t> none() noexcept {return failure<none_t>{none_t{}};}
-} // detail
-} // toml11
-#endif// TOML11_RESULT_H
diff --git a/src/toml11/toml/serializer.hpp b/src/toml11/toml/serializer.hpp
deleted file mode 100644
index 88ae775a83d..00000000000
--- a/src/toml11/toml/serializer.hpp
+++ /dev/null
@@ -1,922 +0,0 @@
-//     Copyright Toru Niina 2019.
-// Distributed under the MIT License.
-#ifndef TOML11_SERIALIZER_HPP
-#define TOML11_SERIALIZER_HPP
-#include <cmath>
-#include <cstdio>
-
-#include <limits>
-
-#include "lexer.hpp"
-#include "value.hpp"
-
-namespace toml
-{
-
-// This function serialize a key. It checks a string is a bare key and
-// escapes special characters if the string is not compatible to a bare key.
-// ```cpp
-// std::string k("non.bare.key"); // the key itself includes `.`s.
-// std::string formatted = toml::format_key(k);
-// assert(formatted == "\"non.bare.key\"");
-// ```
-//
-// This function is exposed to make it easy to write a user-defined serializer.
-// Since toml restricts characters available in a bare key, generally a string
-// should be escaped. But checking whether a string needs to be surrounded by
-// a `"` and escaping some special character is boring.
-template<typename charT, typename traits, typename Alloc>
-std::basic_string<charT, traits, Alloc>
-format_key(const std::basic_string<charT, traits, Alloc>& k)
-{
-    if(k.empty())
-    {
-        return std::string("\"\"");
-    }
-
-    // check the key can be a bare (unquoted) key
-    detail::location loc(k, std::vector<char>(k.begin(), k.end()));
-    detail::lex_unquoted_key::invoke(loc);
-    if(loc.iter() == loc.end())
-    {
-        return k; // all the tokens are consumed. the key is unquoted-key.
-    }
-
-    //if it includes special characters, then format it in a "quoted" key.
-    std::basic_string<charT, traits, Alloc> serialized("\"");
-    for(const char c : k)
-    {
-        switch(c)
-        {
-            case '\\': {serialized += "\\\\"; break;}
-            case '\"': {serialized += "\\\""; break;}
-            case '\b': {serialized += "\\b";  break;}
-            case '\t': {serialized += "\\t";  break;}
-            case '\f': {serialized += "\\f";  break;}
-            case '\n': {serialized += "\\n";  break;}
-            case '\r': {serialized += "\\r";  break;}
-            default  : {serialized += c;      break;}
-        }
-    }
-    serialized += "\"";
-    return serialized;
-}
-
-template<typename charT, typename traits, typename Alloc>
-std::basic_string<charT, traits, Alloc>
-format_keys(const std::vector<std::basic_string<charT, traits, Alloc>>& keys)
-{
-    if(keys.empty())
-    {
-        return std::string("\"\"");
-    }
-
-    std::basic_string<charT, traits, Alloc> serialized;
-    for(const auto& ky : keys)
-    {
-        serialized += format_key(ky);
-        serialized += charT('.');
-    }
-    serialized.pop_back(); // remove the last dot '.'
-    return serialized;
-}
-
-template<typename Value>
-struct serializer
-{
-    static_assert(detail::is_basic_value<Value>::value,
-                  "toml::serializer is for toml::value and its variants, "
-                  "toml::basic_value<...>.");
-
-    using value_type           = Value;
-    using key_type             = typename value_type::key_type            ;
-    using comment_type         = typename value_type::comment_type        ;
-    using boolean_type         = typename value_type::boolean_type        ;
-    using integer_type         = typename value_type::integer_type        ;
-    using floating_type        = typename value_type::floating_type       ;
-    using string_type          = typename value_type::string_type         ;
-    using local_time_type      = typename value_type::local_time_type     ;
-    using local_date_type      = typename value_type::local_date_type     ;
-    using local_datetime_type  = typename value_type::local_datetime_type ;
-    using offset_datetime_type = typename value_type::offset_datetime_type;
-    using array_type           = typename value_type::array_type          ;
-    using table_type           = typename value_type::table_type          ;
-
-    serializer(const std::size_t w              = 80u,
-               const int         float_prec     = std::numeric_limits<toml::floating>::max_digits10,
-               const bool        can_be_inlined = false,
-               const bool        no_comment     = false,
-               std::vector<toml::key> ks        = {},
-               const bool     value_has_comment = false)
-        : can_be_inlined_(can_be_inlined), no_comment_(no_comment),
-          value_has_comment_(value_has_comment && !no_comment),
-          float_prec_(float_prec), width_(w), keys_(std::move(ks))
-    {}
-    ~serializer() = default;
-
-    std::string operator()(const boolean_type& b) const
-    {
-        return b ? "true" : "false";
-    }
-    std::string operator()(const integer_type i) const
-    {
-        return std::to_string(i);
-    }
-    std::string operator()(const floating_type f) const
-    {
-        if(std::isnan(f))
-        {
-            if(std::signbit(f))
-            {
-                return std::string("-nan");
-            }
-            else
-            {
-                return std::string("nan");
-            }
-        }
-        else if(!std::isfinite(f))
-        {
-            if(std::signbit(f))
-            {
-                return std::string("-inf");
-            }
-            else
-            {
-                return std::string("inf");
-            }
-        }
-
-        const auto fmt = "%.*g";
-        const auto bsz = std::snprintf(nullptr, 0, fmt, this->float_prec_, f);
-        // +1 for null character(\0)
-        std::vector<char> buf(static_cast<std::size_t>(bsz + 1), '\0');
-        std::snprintf(buf.data(), buf.size(), fmt, this->float_prec_, f);
-
-        std::string token(buf.begin(), std::prev(buf.end()));
-        if(!token.empty() && token.back() == '.') // 1. => 1.0
-        {
-            token += '0';
-        }
-
-        const auto e = std::find_if(
-            token.cbegin(), token.cend(), [](const char c) noexcept -> bool {
-                return c == 'e' || c == 'E';
-            });
-        const auto has_exponent = (token.cend() != e);
-        const auto has_fraction = (token.cend() != std::find(
-            token.cbegin(), token.cend(), '.'));
-
-        if(!has_exponent && !has_fraction)
-        {
-            // the resulting value does not have any float specific part!
-            token += ".0";
-        }
-        return token;
-    }
-    std::string operator()(const string_type& s) const
-    {
-        if(s.kind == string_t::basic)
-        {
-            if((std::find(s.str.cbegin(), s.str.cend(), '\n') != s.str.cend() ||
-                std::find(s.str.cbegin(), s.str.cend(), '\"') != s.str.cend()) &&
-               this->width_ != (std::numeric_limits<std::size_t>::max)())
-            {
-                // if linefeed or double-quote is contained,
-                // make it multiline basic string.
-                const auto escaped = this->escape_ml_basic_string(s.str);
-                std::string open("\"\"\"");
-                std::string close("\"\"\"");
-                if(escaped.find('\n') != std::string::npos ||
-                   this->width_ < escaped.size() + 6)
-                {
-                    // if the string body contains newline or is enough long,
-                    // add newlines after and before delimiters.
-                    open += "\n";
-                    close = std::string("\\\n") + close;
-                }
-                return open + escaped + close;
-            }
-
-            // no linefeed. try to make it oneline-string.
-            std::string oneline = this->escape_basic_string(s.str);
-            if(oneline.size() + 2 < width_ || width_ < 2)
-            {
-                const std::string quote("\"");
-                return quote + oneline + quote;
-            }
-
-            // the line is too long compared to the specified width.
-            // split it into multiple lines.
-            std::string token("\"\"\"\n");
-            while(!oneline.empty())
-            {
-                if(oneline.size() < width_)
-                {
-                    token += oneline;
-                    oneline.clear();
-                }
-                else if(oneline.at(width_-2) == '\\')
-                {
-                    token += oneline.substr(0, width_-2);
-                    token += "\\\n";
-                    oneline.erase(0, width_-2);
-                }
-                else
-                {
-                    token += oneline.substr(0, width_-1);
-                    token += "\\\n";
-                    oneline.erase(0, width_-1);
-                }
-            }
-            return token + std::string("\\\n\"\"\"");
-        }
-        else // the string `s` is literal-string.
-        {
-            if(std::find(s.str.cbegin(), s.str.cend(), '\n') != s.str.cend() ||
-               std::find(s.str.cbegin(), s.str.cend(), '\'') != s.str.cend() )
-            {
-                std::string open("'''");
-                if(this->width_ + 6 < s.str.size())
-                {
-                    open += '\n'; // the first newline is ignored by TOML spec
-                }
-                const std::string close("'''");
-                return open + s.str + close;
-            }
-            else
-            {
-                const std::string quote("'");
-                return quote + s.str + quote;
-            }
-        }
-    }
-
-    std::string operator()(const local_date_type& d) const
-    {
-        std::ostringstream oss;
-        oss << d;
-        return oss.str();
-    }
-    std::string operator()(const local_time_type& t) const
-    {
-        std::ostringstream oss;
-        oss << t;
-        return oss.str();
-    }
-    std::string operator()(const local_datetime_type& dt) const
-    {
-        std::ostringstream oss;
-        oss << dt;
-        return oss.str();
-    }
-    std::string operator()(const offset_datetime_type& odt) const
-    {
-        std::ostringstream oss;
-        oss << odt;
-        return oss.str();
-    }
-
-    std::string operator()(const array_type& v) const
-    {
-        if(v.empty())
-        {
-            return std::string("[]");
-        }
-        if(this->is_array_of_tables(v))
-        {
-            return make_array_of_tables(v);
-        }
-
-        // not an array of tables. normal array.
-        // first, try to make it inline if none of the elements have a comment.
-        if( ! this->has_comment_inside(v))
-        {
-            const auto inl = this->make_inline_array(v);
-            if(inl.size() < this->width_ &&
-               std::find(inl.cbegin(), inl.cend(), '\n') == inl.cend())
-            {
-                return inl;
-            }
-        }
-
-        // if the length exceeds this->width_, print multiline array.
-        // key = [
-        //   # ...
-        //   42,
-        //   ...
-        // ]
-        std::string token;
-        std::string current_line;
-        token += "[\n";
-        for(const auto& item : v)
-        {
-            if( ! item.comments().empty() && !no_comment_)
-            {
-                // if comment exists, the element must be the only element in the line.
-                // e.g. the following is not allowed.
-                // ```toml
-                // array = [
-                // # comment for what?
-                // 1, 2, 3, 4, 5
-                // ]
-                // ```
-                if(!current_line.empty())
-                {
-                    if(current_line.back() != '\n')
-                    {
-                        current_line += '\n';
-                    }
-                    token += current_line;
-                    current_line.clear();
-                }
-                for(const auto& c : item.comments())
-                {
-                    token += '#';
-                    token += c;
-                    token += '\n';
-                }
-                token += toml::visit(*this, item);
-                if(!token.empty() && token.back() == '\n') {token.pop_back();}
-                token += ",\n";
-                continue;
-            }
-            std::string next_elem;
-            if(item.is_table())
-            {
-                serializer ser(*this);
-                ser.can_be_inlined_ = true;
-                ser.width_ = (std::numeric_limits<std::size_t>::max)();
-                next_elem += toml::visit(ser, item);
-            }
-            else
-            {
-                next_elem += toml::visit(*this, item);
-            }
-
-            // comma before newline.
-            if(!next_elem.empty() && next_elem.back() == '\n') {next_elem.pop_back();}
-
-            // if current line does not exceeds the width limit, continue.
-            if(current_line.size() + next_elem.size() + 1 < this->width_)
-            {
-                current_line += next_elem;
-                current_line += ',';
-            }
-            else if(current_line.empty())
-            {
-                // if current line was empty, force put the next_elem because
-                // next_elem is not splittable
-                token += next_elem;
-                token += ",\n";
-                // current_line is kept empty
-            }
-            else // reset current_line
-            {
-                assert(current_line.back() == ',');
-                token += current_line;
-                token += '\n';
-                current_line = next_elem;
-                current_line += ',';
-            }
-        }
-        if(!current_line.empty())
-        {
-            if(!current_line.empty() && current_line.back() != '\n')
-            {
-                current_line += '\n';
-            }
-            token += current_line;
-        }
-        token += "]\n";
-        return token;
-    }
-
-    // templatize for any table-like container
-    std::string operator()(const table_type& v) const
-    {
-        // if an element has a comment, then it can't be inlined.
-        // table = {# how can we write a comment for this? key = "value"}
-        if(this->can_be_inlined_ && !(this->has_comment_inside(v)))
-        {
-            std::string token;
-            if(!this->keys_.empty())
-            {
-                token += format_key(this->keys_.back());
-                token += " = ";
-            }
-            token += this->make_inline_table(v);
-            if(token.size() < this->width_ &&
-               token.end() == std::find(token.begin(), token.end(), '\n'))
-            {
-                return token;
-            }
-        }
-
-        std::string token;
-        if(!keys_.empty())
-        {
-            token += '[';
-            token += format_keys(keys_);
-            token += "]\n";
-        }
-        token += this->make_multiline_table(v);
-        return token;
-    }
-
-  private:
-
-    std::string escape_basic_string(const std::string& s) const
-    {
-        //XXX assuming `s` is a valid utf-8 sequence.
-        std::string retval;
-        for(const char c : s)
-        {
-            switch(c)
-            {
-                case '\\': {retval += "\\\\"; break;}
-                case '\"': {retval += "\\\""; break;}
-                case '\b': {retval += "\\b";  break;}
-                case '\t': {retval += "\\t";  break;}
-                case '\f': {retval += "\\f";  break;}
-                case '\n': {retval += "\\n";  break;}
-                case '\r': {retval += "\\r";  break;}
-                default  :
-                {
-                    if((0x00 <= c && c <= 0x08) || (0x0A <= c && c <= 0x1F) || c == 0x7F)
-                    {
-                        retval += "\\u00";
-                        retval += char(48 + (c / 16));
-                        retval += char((c % 16 < 10 ? 48 : 55) + (c % 16));
-                    }
-                    else
-                    {
-                        retval += c;
-                    }
-                }
-            }
-        }
-        return retval;
-    }
-
-    std::string escape_ml_basic_string(const std::string& s) const
-    {
-        std::string retval;
-        for(auto i=s.cbegin(), e=s.cend(); i!=e; ++i)
-        {
-            switch(*i)
-            {
-                case '\\': {retval += "\\\\"; break;}
-                // One or two consecutive "s are allowed.
-                // Later we will check there are no three consecutive "s.
-                //   case '\"': {retval += "\\\""; break;}
-                case '\b': {retval += "\\b";  break;}
-                case '\t': {retval += "\\t";  break;}
-                case '\f': {retval += "\\f";  break;}
-                case '\n': {retval += "\n";   break;}
-                case '\r':
-                {
-                    if(std::next(i) != e && *std::next(i) == '\n')
-                    {
-                        retval += "\r\n";
-                        ++i;
-                    }
-                    else
-                    {
-                        retval += "\\r";
-                    }
-                    break;
-                }
-                default  :
-                {
-                    const auto c = *i;
-                    if((0x00 <= c && c <= 0x08) || (0x0A <= c && c <= 0x1F) || c == 0x7F)
-                    {
-                        retval += "\\u00";
-                        retval += char(48 + (c / 16));
-                        retval += char((c % 16 < 10 ? 48 : 55) + (c % 16));
-                    }
-                    else
-                    {
-                        retval += c;
-                    }
-                }
-
-            }
-        }
-        // Only 1 or 2 consecutive `"`s are allowed in multiline basic string.
-        // 3 consecutive `"`s are considered as a closing delimiter.
-        // We need to check if there are 3 or more consecutive `"`s and insert
-        // backslash to break them down into several short `"`s like the `str6`
-        // in the following example.
-        // ```toml
-        // str4 = """Here are two quotation marks: "". Simple enough."""
-        // # str5 = """Here are three quotation marks: """."""  # INVALID
-        // str5 = """Here are three quotation marks: ""\"."""
-        // str6 = """Here are fifteen quotation marks: ""\"""\"""\"""\"""\"."""
-        // ```
-        auto found_3_quotes = retval.find("\"\"\"");
-        while(found_3_quotes != std::string::npos)
-        {
-            retval.replace(found_3_quotes, 3, "\"\"\\\"");
-            found_3_quotes = retval.find("\"\"\"");
-        }
-        return retval;
-    }
-
-    // if an element of a table or an array has a comment, it cannot be inlined.
-    bool has_comment_inside(const array_type& a) const noexcept
-    {
-        // if no_comment is set, comments would not be written.
-        if(this->no_comment_) {return false;}
-
-        for(const auto& v : a)
-        {
-            if(!v.comments().empty()) {return true;}
-        }
-        return false;
-    }
-    bool has_comment_inside(const table_type& t) const noexcept
-    {
-        // if no_comment is set, comments would not be written.
-        if(this->no_comment_) {return false;}
-
-        for(const auto& kv : t)
-        {
-            if(!kv.second.comments().empty()) {return true;}
-        }
-        return false;
-    }
-
-    std::string make_inline_array(const array_type& v) const
-    {
-        assert(!has_comment_inside(v));
-        std::string token;
-        token += '[';
-        bool is_first = true;
-        for(const auto& item : v)
-        {
-            if(is_first) {is_first = false;} else {token += ',';}
-            token += visit(serializer(
-                (std::numeric_limits<std::size_t>::max)(), this->float_prec_,
-                /* inlined */ true, /*no comment*/ false, /*keys*/ {},
-                /*has_comment*/ !item.comments().empty()), item);
-        }
-        token += ']';
-        return token;
-    }
-
-    std::string make_inline_table(const table_type& v) const
-    {
-        assert(!has_comment_inside(v));
-        assert(this->can_be_inlined_);
-        std::string token;
-        token += '{';
-        bool is_first = true;
-        for(const auto& kv : v)
-        {
-            // in inline tables, trailing comma is not allowed (toml-lang #569).
-            if(is_first) {is_first = false;} else {token += ',';}
-            token += format_key(kv.first);
-            token += '=';
-            token += visit(serializer(
-                (std::numeric_limits<std::size_t>::max)(), this->float_prec_,
-                /* inlined */ true, /*no comment*/ false, /*keys*/ {},
-                /*has_comment*/ !kv.second.comments().empty()), kv.second);
-        }
-        token += '}';
-        return token;
-    }
-
-    std::string make_multiline_table(const table_type& v) const
-    {
-        std::string token;
-
-        // print non-table elements first.
-        // ```toml
-        // [foo]         # a table we're writing now here
-        // key = "value" # <- non-table element, "key"
-        // # ...
-        // [foo.bar] # <- table element, "bar"
-        // ```
-        // because after printing [foo.bar], the remaining non-table values will
-        // be assigned into [foo.bar], not [foo]. Those values should be printed
-        // earlier.
-        for(const auto& kv : v)
-        {
-            if(kv.second.is_table() || is_array_of_tables(kv.second))
-            {
-                continue;
-            }
-
-            token += write_comments(kv.second);
-
-            const auto key_and_sep    = format_key(kv.first) + " = ";
-            const auto residual_width = (this->width_ > key_and_sep.size()) ?
-                                        this->width_ - key_and_sep.size() : 0;
-            token += key_and_sep;
-            token += visit(serializer(residual_width, this->float_prec_,
-                /*can be inlined*/ true, /*no comment*/ false, /*keys*/ {},
-                /*has_comment*/ !kv.second.comments().empty()), kv.second);
-
-            if(token.back() != '\n')
-            {
-                token += '\n';
-            }
-        }
-
-        // normal tables / array of tables
-
-        // after multiline table appeared, the other tables cannot be inline
-        // because the table would be assigned into the table.
-        // [foo]
-        // ...
-        // bar = {...} # <- bar will be a member of [foo].
-        bool multiline_table_printed = false;
-        for(const auto& kv : v)
-        {
-            if(!kv.second.is_table() && !is_array_of_tables(kv.second))
-            {
-                continue; // other stuff are already serialized. skip them.
-            }
-
-            std::vector<toml::key> ks(this->keys_);
-            ks.push_back(kv.first);
-
-            auto tmp = visit(serializer(this->width_, this->float_prec_,
-                !multiline_table_printed, this->no_comment_, ks,
-                /*has_comment*/ !kv.second.comments().empty()), kv.second);
-
-            // If it is the first time to print a multi-line table, it would be
-            // helpful to separate normal key-value pair and subtables by a
-            // newline.
-            // (this checks if the current key-value pair contains newlines.
-            //  but it is not perfect because multi-line string can also contain
-            //  a newline. in such a case, an empty line will be written) TODO
-            if((!multiline_table_printed) &&
-               std::find(tmp.cbegin(), tmp.cend(), '\n') != tmp.cend())
-            {
-                multiline_table_printed = true;
-                token += '\n'; // separate key-value pairs and subtables
-
-                token += write_comments(kv.second);
-                token += tmp;
-
-                // care about recursive tables (all tables in each level prints
-                // newline and there will be a full of newlines)
-                if(tmp.substr(tmp.size() - 2, 2) != "\n\n" &&
-                   tmp.substr(tmp.size() - 4, 4) != "\r\n\r\n" )
-                {
-                    token += '\n';
-                }
-            }
-            else
-            {
-                token += write_comments(kv.second);
-                token += tmp;
-                token += '\n';
-            }
-        }
-        return token;
-    }
-
-    std::string make_array_of_tables(const array_type& v) const
-    {
-        // if it's not inlined, we need to add `[[table.key]]`.
-        // but if it can be inlined, we can format it as the following.
-        // ```
-        // table.key = [
-        //   {...},
-        //   # comment
-        //   {...},
-        // ]
-        // ```
-        // This function checks if inlinization is possible or not, and then
-        // format the array-of-tables in a proper way.
-        //
-        // Note about comments:
-        //
-        // If the array itself has a comment (value_has_comment_ == true), we
-        // should try to make it inline.
-        // ```toml
-        // # comment about array
-        // array = [
-        //   # comment about table element
-        //   {of = "table"}
-        // ]
-        // ```
-        // If it is formatted as a multiline table, the two comments becomes
-        // indistinguishable.
-        // ```toml
-        // # comment about array
-        // # comment about table element
-        // [[array]]
-        // of = "table"
-        // ```
-        // So we need to try to make it inline, and it force-inlines regardless
-        // of the line width limit.
-        //     It may fail if the element of a table has comment. In that case,
-        // the array-of-tables will be formatted as a multiline table.
-        if(this->can_be_inlined_ || this->value_has_comment_)
-        {
-            std::string token;
-            if(!keys_.empty())
-            {
-                token += format_key(keys_.back());
-                token += " = ";
-            }
-
-            bool failed = false;
-            token += "[\n";
-            for(const auto& item : v)
-            {
-                // if an element of the table has a comment, the table
-                // cannot be inlined.
-                if(this->has_comment_inside(item.as_table()))
-                {
-                    failed = true;
-                    break;
-                }
-                // write comments for the table itself
-                token += write_comments(item);
-
-                const auto t = this->make_inline_table(item.as_table());
-
-                if(t.size() + 1 > width_ || // +1 for the last comma {...},
-                   std::find(t.cbegin(), t.cend(), '\n') != t.cend())
-                {
-                    // if the value itself has a comment, ignore the line width limit
-                    if( ! this->value_has_comment_)
-                    {
-                        failed = true;
-                        break;
-                    }
-                }
-                token += t;
-                token += ",\n";
-            }
-
-            if( ! failed)
-            {
-                token += "]\n";
-                return token;
-            }
-            // if failed, serialize them as [[array.of.tables]].
-        }
-
-        std::string token;
-        for(const auto& item : v)
-        {
-            token += write_comments(item);
-            token += "[[";
-            token += format_keys(keys_);
-            token += "]]\n";
-            token += this->make_multiline_table(item.as_table());
-        }
-        return token;
-    }
-
-    std::string write_comments(const value_type& v) const
-    {
-        std::string retval;
-        if(this->no_comment_) {return retval;}
-
-        for(const auto& c : v.comments())
-        {
-            retval += '#';
-            retval += c;
-            retval += '\n';
-        }
-        return retval;
-    }
-
-    bool is_array_of_tables(const value_type& v) const
-    {
-        if(!v.is_array() || v.as_array().empty()) {return false;}
-        return is_array_of_tables(v.as_array());
-    }
-    bool is_array_of_tables(const array_type& v) const
-    {
-        // Since TOML v0.5.0, heterogeneous arrays are allowed. So we need to
-        // check all the element in an array to check if the array is an array
-        // of tables.
-        return std::all_of(v.begin(), v.end(), [](const value_type& elem) {
-                return elem.is_table();
-            });
-    }
-
-  private:
-
-    bool        can_be_inlined_;
-    bool        no_comment_;
-    bool        value_has_comment_;
-    int         float_prec_;
-    std::size_t width_;
-    std::vector<toml::key> keys_;
-};
-
-template<typename C,
-         template<typename ...> class M, template<typename ...> class V>
-std::string
-format(const basic_value<C, M, V>& v, std::size_t w = 80u,
-       int fprec = std::numeric_limits<toml::floating>::max_digits10,
-       bool no_comment = false, bool force_inline = false)
-{
-    using value_type = basic_value<C, M, V>;
-    // if value is a table, it is considered to be a root object.
-    // the root object can't be an inline table.
-    if(v.is_table())
-    {
-        std::ostringstream oss;
-        if(!v.comments().empty())
-        {
-            oss << v.comments();
-            oss << '\n'; // to split the file comment from the first element
-        }
-        const auto serialized = visit(serializer<value_type>(w, fprec, false, no_comment), v);
-        oss << serialized;
-        return oss.str();
-    }
-    return visit(serializer<value_type>(w, fprec, force_inline), v);
-}
-
-namespace detail
-{
-template<typename charT, typename traits>
-int comment_index(std::basic_ostream<charT, traits>&)
-{
-    static const int index = std::ios_base::xalloc();
-    return index;
-}
-} // detail
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-nocomment(std::basic_ostream<charT, traits>& os)
-{
-    // by default, it is zero. and by default, it shows comments.
-    os.iword(detail::comment_index(os)) = 1;
-    return os;
-}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-showcomment(std::basic_ostream<charT, traits>& os)
-{
-    // by default, it is zero. and by default, it shows comments.
-    os.iword(detail::comment_index(os)) = 0;
-    return os;
-}
-
-template<typename charT, typename traits, typename C,
-         template<typename ...> class M, template<typename ...> class V>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const basic_value<C, M, V>& v)
-{
-    using value_type = basic_value<C, M, V>;
-
-    // get status of std::setw().
-    const auto w     = static_cast<std::size_t>(os.width());
-    const int  fprec = static_cast<int>(os.precision());
-    os.width(0);
-
-    // by default, iword is initialized by 0. And by default, toml11 outputs
-    // comments. So `0` means showcomment. 1 means nocommnet.
-    const bool no_comment = (1 == os.iword(detail::comment_index(os)));
-
-    if(!no_comment && v.is_table() && !v.comments().empty())
-    {
-        os << v.comments();
-        os << '\n'; // to split the file comment from the first element
-    }
-    // the root object can't be an inline table. so pass `false`.
-    const auto serialized = visit(serializer<value_type>(w, fprec, no_comment, false), v);
-    os << serialized;
-
-    // if v is a non-table value, and has only one comment, then
-    // put a comment just after a value. in the following way.
-    //
-    // ```toml
-    // key = "value" # comment.
-    // ```
-    //
-    // Since the top-level toml object is a table, one who want to put a
-    // non-table toml value must use this in a following way.
-    //
-    // ```cpp
-    // toml::value v;
-    // std::cout << "user-defined-key = " << v << std::endl;
-    // ```
-    //
-    // In this case, it is impossible to put comments before key-value pair.
-    // The only way to preserve comments is to put all of them after a value.
-    if(!no_comment && !v.is_table() && !v.comments().empty())
-    {
-        os << " #";
-        for(const auto& c : v.comments()) {os << c;}
-    }
-    return os;
-}
-
-} // toml
-#endif// TOML11_SERIALIZER_HPP
diff --git a/src/toml11/toml/source_location.hpp b/src/toml11/toml/source_location.hpp
deleted file mode 100644
index fa175b5b48d..00000000000
--- a/src/toml11/toml/source_location.hpp
+++ /dev/null
@@ -1,233 +0,0 @@
-//     Copyright Toru Niina 2019.
-// Distributed under the MIT License.
-#ifndef TOML11_SOURCE_LOCATION_HPP
-#define TOML11_SOURCE_LOCATION_HPP
-#include <cstdint>
-#include <sstream>
-
-#include "region.hpp"
-
-namespace toml
-{
-
-// A struct to contain location in a toml file.
-// The interface imitates std::experimental::source_location,
-// but not completely the same.
-//
-// It would be constructed by toml::value. It can be used to generate
-// user-defined error messages.
-//
-// - std::uint_least32_t line() const noexcept
-//   - returns the line number where the region is on.
-// - std::uint_least32_t column() const noexcept
-//   - returns the column number where the region starts.
-// - std::uint_least32_t region() const noexcept
-//   - returns the size of the region.
-//
-// +-- line()       +-- region of interest (region() == 9)
-// v            .---+---.
-// 12 | value = "foo bar"
-//              ^
-//              +-- column()
-//
-// - std::string const& file_name() const noexcept;
-//   - name of the file.
-// - std::string const& line_str() const noexcept;
-//   - the whole line that contains the region of interest.
-//
-struct source_location
-{
-  public:
-
-    source_location()
-        : line_num_(1), column_num_(1), region_size_(1),
-          file_name_("unknown file"), line_str_("")
-    {}
-
-    explicit source_location(const detail::region_base* reg)
-        : line_num_(1), column_num_(1), region_size_(1),
-          file_name_("unknown file"), line_str_("")
-    {
-        if(reg)
-        {
-            if(reg->line_num() != detail::region_base().line_num())
-            {
-                line_num_ = static_cast<std::uint_least32_t>(
-                        std::stoul(reg->line_num()));
-            }
-            column_num_  = static_cast<std::uint_least32_t>(reg->before() + 1);
-            region_size_ = static_cast<std::uint_least32_t>(reg->size());
-            file_name_   = reg->name();
-            line_str_    = reg->line();
-        }
-    }
-
-    explicit source_location(const detail::region& reg)
-        : line_num_(static_cast<std::uint_least32_t>(std::stoul(reg.line_num()))),
-          column_num_(static_cast<std::uint_least32_t>(reg.before() + 1)),
-          region_size_(static_cast<std::uint_least32_t>(reg.size())),
-          file_name_(reg.name()),
-          line_str_ (reg.line())
-    {}
-    explicit source_location(const detail::location& loc)
-        : line_num_(static_cast<std::uint_least32_t>(std::stoul(loc.line_num()))),
-          column_num_(static_cast<std::uint_least32_t>(loc.before() + 1)),
-          region_size_(static_cast<std::uint_least32_t>(loc.size())),
-          file_name_(loc.name()),
-          line_str_ (loc.line())
-    {}
-
-    ~source_location() = default;
-    source_location(source_location const&) = default;
-    source_location(source_location &&)     = default;
-    source_location& operator=(source_location const&) = default;
-    source_location& operator=(source_location &&)     = default;
-
-    std::uint_least32_t line()      const noexcept {return line_num_;}
-    std::uint_least32_t column()    const noexcept {return column_num_;}
-    std::uint_least32_t region()    const noexcept {return region_size_;}
-
-    std::string const&  file_name() const noexcept {return file_name_;}
-    std::string const&  line_str()  const noexcept {return line_str_;}
-
-  private:
-
-    std::uint_least32_t line_num_;
-    std::uint_least32_t column_num_;
-    std::uint_least32_t region_size_;
-    std::string         file_name_;
-    std::string         line_str_;
-};
-
-namespace detail
-{
-
-// internal error message generation.
-inline std::string format_underline(const std::string& message,
-        const std::vector<std::pair<source_location, std::string>>& loc_com,
-        const std::vector<std::string>& helps = {},
-        const bool colorize = TOML11_ERROR_MESSAGE_COLORIZED)
-{
-    std::size_t line_num_width = 0;
-    for(const auto& lc : loc_com)
-    {
-        std::uint_least32_t line = lc.first.line();
-        std::size_t        digit = 0;
-        while(line != 0)
-        {
-            line  /= 10;
-            digit +=  1;
-        }
-        line_num_width = (std::max)(line_num_width, digit);
-    }
-    // 1 is the minimum width
-    line_num_width = std::max<std::size_t>(line_num_width, 1);
-
-    std::ostringstream retval;
-
-    if(colorize)
-    {
-        retval << color::colorize; // turn on ANSI color
-    }
-
-    // XXX
-    // Here, before `colorize` support, it does not output `[error]` prefix
-    // automatically. So some user may output it manually and this change may
-    // duplicate the prefix. To avoid it, check the first 7 characters and
-    // if it is "[error]", it removes that part from the message shown.
-    if(message.size() > 7 && message.substr(0, 7) == "[error]")
-    {
-        retval << color::bold << color::red << "[error]" << color::reset
-               << color::bold << message.substr(7) << color::reset << '\n';
-    }
-    else
-    {
-        retval << color::bold << color::red << "[error] " << color::reset
-               << color::bold << message << color::reset << '\n';
-    }
-
-    const auto format_one_location = [line_num_width]
-        (std::ostringstream& oss,
-         const source_location& loc, const std::string& comment) -> void
-        {
-            oss << ' ' << color::bold << color::blue
-                << std::setw(static_cast<int>(line_num_width))
-                << std::right << loc.line() << " | "  << color::reset
-                << loc.line_str() << '\n';
-
-            oss << make_string(line_num_width + 1, ' ')
-                << color::bold << color::blue << " | " << color::reset
-                << make_string(loc.column()-1 /*1-origin*/, ' ');
-
-            if(loc.region() == 1)
-            {
-                // invalid
-                // ^------
-                oss << color::bold << color::red << "^---" << color::reset;
-            }
-            else
-            {
-                // invalid
-                // ~~~~~~~
-                const auto underline_len = (std::min)(
-                    static_cast<std::size_t>(loc.region()), loc.line_str().size());
-                oss << color::bold << color::red
-                    << make_string(underline_len, '~') << color::reset;
-            }
-            oss << ' ';
-            oss << comment;
-            return;
-        };
-
-    assert(!loc_com.empty());
-
-    // --> example.toml
-    //   |
-    retval << color::bold << color::blue << " --> " << color::reset
-           << loc_com.front().first.file_name() << '\n';
-    retval << make_string(line_num_width + 1, ' ')
-           << color::bold << color::blue << " |\n"  << color::reset;
-    // 1 | key value
-    //   |    ^--- missing =
-    format_one_location(retval, loc_com.front().first, loc_com.front().second);
-
-    // process the rest of the locations
-    for(std::size_t i=1; i<loc_com.size(); ++i)
-    {
-        const auto& prev = loc_com.at(i-1);
-        const auto& curr = loc_com.at(i);
-
-        retval << '\n';
-        // if the filenames are the same, print "..."
-        if(prev.first.file_name() == curr.first.file_name())
-        {
-            retval << color::bold << color::blue << " ...\n" << color::reset;
-        }
-        else // if filename differs, print " --> filename.toml" again
-        {
-            retval << color::bold << color::blue << " --> " << color::reset
-                   << curr.first.file_name() << '\n';
-            retval << make_string(line_num_width + 1, ' ')
-                   << color::bold << color::blue << " |\n"  << color::reset;
-        }
-
-        format_one_location(retval, curr.first, curr.second);
-    }
-
-    if(!helps.empty())
-    {
-        retval << '\n';
-        retval << make_string(line_num_width + 1, ' ');
-        retval << color::bold << color::blue << " |" << color::reset;
-        for(const auto& help : helps)
-        {
-            retval << color::bold << "\nHint: " << color::reset;
-            retval << help;
-        }
-    }
-    return retval.str();
-}
-
-} // detail
-} // toml
-#endif// TOML11_SOURCE_LOCATION_HPP
diff --git a/src/toml11/toml/storage.hpp b/src/toml11/toml/storage.hpp
deleted file mode 100644
index 202f9035fd3..00000000000
--- a/src/toml11/toml/storage.hpp
+++ /dev/null
@@ -1,43 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_STORAGE_HPP
-#define TOML11_STORAGE_HPP
-#include "utility.hpp"
-
-namespace toml
-{
-namespace detail
-{
-
-// this contains pointer and deep-copy the content if copied.
-// to avoid recursive pointer.
-template<typename T>
-struct storage
-{
-    using value_type = T;
-
-    explicit storage(value_type const& v): ptr(toml::make_unique<T>(v)) {}
-    explicit storage(value_type&&      v): ptr(toml::make_unique<T>(std::move(v))) {}
-    ~storage() = default;
-    storage(const storage& rhs): ptr(toml::make_unique<T>(*rhs.ptr)) {}
-    storage& operator=(const storage& rhs)
-    {
-        this->ptr = toml::make_unique<T>(*rhs.ptr);
-        return *this;
-    }
-    storage(storage&&) = default;
-    storage& operator=(storage&&) = default;
-
-    bool is_ok() const noexcept {return static_cast<bool>(ptr);}
-
-    value_type&       value() &      noexcept {return *ptr;}
-    value_type const& value() const& noexcept {return *ptr;}
-    value_type&&      value() &&     noexcept {return std::move(*ptr);}
-
-  private:
-    std::unique_ptr<value_type> ptr;
-};
-
-} // detail
-} // toml
-#endif// TOML11_STORAGE_HPP
diff --git a/src/toml11/toml/string.hpp b/src/toml11/toml/string.hpp
deleted file mode 100644
index 5136d8c568c..00000000000
--- a/src/toml11/toml/string.hpp
+++ /dev/null
@@ -1,225 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_STRING_HPP
-#define TOML11_STRING_HPP
-#include <cstdint>
-
-#include <algorithm>
-#include <string>
-
-#if __cplusplus >= 201703L
-#if __has_include(<string_view>)
-#define TOML11_USING_STRING_VIEW 1
-#include <string_view>
-#endif
-#endif
-
-namespace toml
-{
-
-enum class string_t : std::uint8_t
-{
-    basic   = 0,
-    literal = 1,
-};
-
-struct string
-{
-    string()  = default;
-    ~string() = default;
-    string(const string& s) = default;
-    string(string&& s)      = default;
-    string& operator=(const string& s) = default;
-    string& operator=(string&& s)      = default;
-
-    string(const std::string& s): kind(string_t::basic), str(s){}
-    string(const std::string& s, string_t k):   kind(k), str(s){}
-    string(const char* s):        kind(string_t::basic), str(s){}
-    string(const char* s,        string_t k):   kind(k), str(s){}
-
-    string(std::string&& s): kind(string_t::basic), str(std::move(s)){}
-    string(std::string&& s, string_t k):   kind(k), str(std::move(s)){}
-
-    string& operator=(const std::string& s)
-    {kind = string_t::basic; str = s; return *this;}
-    string& operator=(std::string&& s)
-    {kind = string_t::basic; str = std::move(s); return *this;}
-
-    operator std::string&       () &      noexcept {return str;}
-    operator std::string const& () const& noexcept {return str;}
-    operator std::string&&      () &&     noexcept {return std::move(str);}
-
-    string& operator+=(const char*        rhs) {str += rhs; return *this;}
-    string& operator+=(const char         rhs) {str += rhs; return *this;}
-    string& operator+=(const std::string& rhs) {str += rhs; return *this;}
-    string& operator+=(const string&      rhs) {str += rhs.str; return *this;}
-
-#if defined(TOML11_USING_STRING_VIEW) && TOML11_USING_STRING_VIEW>0
-    explicit string(std::string_view s): kind(string_t::basic), str(s){}
-    string(std::string_view s, string_t k): kind(k), str(s){}
-
-    string& operator=(std::string_view s)
-    {kind = string_t::basic; str = s; return *this;}
-
-    explicit operator std::string_view() const noexcept
-    {return std::string_view(str);}
-
-    string& operator+=(const std::string_view& rhs) {str += rhs; return *this;}
-#endif
-
-    string_t    kind;
-    std::string str;
-};
-
-inline bool operator==(const string& lhs, const string& rhs)
-{
-    return lhs.kind == rhs.kind && lhs.str == rhs.str;
-}
-inline bool operator!=(const string& lhs, const string& rhs)
-{
-    return !(lhs == rhs);
-}
-inline bool operator<(const string& lhs, const string& rhs)
-{
-    return (lhs.kind == rhs.kind) ? (lhs.str < rhs.str) : (lhs.kind < rhs.kind);
-}
-inline bool operator>(const string& lhs, const string& rhs)
-{
-    return rhs < lhs;
-}
-inline bool operator<=(const string& lhs, const string& rhs)
-{
-    return !(rhs < lhs);
-}
-inline bool operator>=(const string& lhs, const string& rhs)
-{
-    return !(lhs < rhs);
-}
-
-inline bool
-operator==(const string& lhs, const std::string& rhs) {return lhs.str == rhs;}
-inline bool
-operator!=(const string& lhs, const std::string& rhs) {return lhs.str != rhs;}
-inline bool
-operator< (const string& lhs, const std::string& rhs) {return lhs.str <  rhs;}
-inline bool
-operator> (const string& lhs, const std::string& rhs) {return lhs.str >  rhs;}
-inline bool
-operator<=(const string& lhs, const std::string& rhs) {return lhs.str <= rhs;}
-inline bool
-operator>=(const string& lhs, const std::string& rhs) {return lhs.str >= rhs;}
-
-inline bool
-operator==(const std::string& lhs, const string& rhs) {return lhs == rhs.str;}
-inline bool
-operator!=(const std::string& lhs, const string& rhs) {return lhs != rhs.str;}
-inline bool
-operator< (const std::string& lhs, const string& rhs) {return lhs <  rhs.str;}
-inline bool
-operator> (const std::string& lhs, const string& rhs) {return lhs >  rhs.str;}
-inline bool
-operator<=(const std::string& lhs, const string& rhs) {return lhs <= rhs.str;}
-inline bool
-operator>=(const std::string& lhs, const string& rhs) {return lhs >= rhs.str;}
-
-inline bool
-operator==(const string& lhs, const char* rhs) {return lhs.str == std::string(rhs);}
-inline bool
-operator!=(const string& lhs, const char* rhs) {return lhs.str != std::string(rhs);}
-inline bool
-operator< (const string& lhs, const char* rhs) {return lhs.str <  std::string(rhs);}
-inline bool
-operator> (const string& lhs, const char* rhs) {return lhs.str >  std::string(rhs);}
-inline bool
-operator<=(const string& lhs, const char* rhs) {return lhs.str <= std::string(rhs);}
-inline bool
-operator>=(const string& lhs, const char* rhs) {return lhs.str >= std::string(rhs);}
-
-inline bool
-operator==(const char* lhs, const string& rhs) {return std::string(lhs) == rhs.str;}
-inline bool
-operator!=(const char* lhs, const string& rhs) {return std::string(lhs) != rhs.str;}
-inline bool
-operator< (const char* lhs, const string& rhs) {return std::string(lhs) <  rhs.str;}
-inline bool
-operator> (const char* lhs, const string& rhs) {return std::string(lhs) >  rhs.str;}
-inline bool
-operator<=(const char* lhs, const string& rhs) {return std::string(lhs) <= rhs.str;}
-inline bool
-operator>=(const char* lhs, const string& rhs) {return std::string(lhs) >= rhs.str;}
-
-template<typename charT, typename traits>
-std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, const string& s)
-{
-    if(s.kind == string_t::basic)
-    {
-        if(std::find(s.str.cbegin(), s.str.cend(), '\n') != s.str.cend())
-        {
-            // it contains newline. make it multiline string.
-            os << "\"\"\"\n";
-            for(auto i=s.str.cbegin(), e=s.str.cend(); i!=e; ++i)
-            {
-                switch(*i)
-                {
-                    case '\\': {os << "\\\\"; break;}
-                    case '\"': {os << "\\\""; break;}
-                    case '\b': {os << "\\b";  break;}
-                    case '\t': {os << "\\t";  break;}
-                    case '\f': {os << "\\f";  break;}
-                    case '\n': {os << '\n';   break;}
-                    case '\r':
-                    {
-                        // since it is a multiline string,
-                        // CRLF is not needed to be escaped.
-                        if(std::next(i) != e && *std::next(i) == '\n')
-                        {
-                            os << "\r\n";
-                            ++i;
-                        }
-                        else
-                        {
-                            os << "\\r";
-                        }
-                        break;
-                    }
-                    default: {os << *i; break;}
-                }
-            }
-            os << "\\\n\"\"\"";
-            return os;
-        }
-        // no newline. make it inline.
-        os << "\"";
-        for(const auto c : s.str)
-        {
-            switch(c)
-            {
-                case '\\': {os << "\\\\"; break;}
-                case '\"': {os << "\\\""; break;}
-                case '\b': {os << "\\b";  break;}
-                case '\t': {os << "\\t";  break;}
-                case '\f': {os << "\\f";  break;}
-                case '\n': {os << "\\n";  break;}
-                case '\r': {os << "\\r";  break;}
-                default  : {os << c;      break;}
-            }
-        }
-        os << "\"";
-        return os;
-    }
-    // the string `s` is literal-string.
-    if(std::find(s.str.cbegin(), s.str.cend(), '\n') != s.str.cend() ||
-       std::find(s.str.cbegin(), s.str.cend(), '\'') != s.str.cend() )
-    {
-        // contains newline or single quote. make it multiline.
-        os << "'''\n" << s.str << "'''";
-        return os;
-    }
-    // normal literal string
-    os << '\'' << s.str << '\'';
-    return os;
-}
-
-} // toml
-#endif// TOML11_STRING_H
diff --git a/src/toml11/toml/traits.hpp b/src/toml11/toml/traits.hpp
deleted file mode 100644
index 5495c93b244..00000000000
--- a/src/toml11/toml/traits.hpp
+++ /dev/null
@@ -1,327 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_TRAITS_HPP
-#define TOML11_TRAITS_HPP
-
-#include "from.hpp"
-#include "into.hpp"
-
-#include <chrono>
-#include <forward_list>
-#include <string>
-#include <tuple>
-#include <type_traits>
-#include <utility>
-
-#if __cplusplus >= 201703L
-#if __has_include(<string_view>)
-#include <string_view>
-#endif // has_include(<string_view>)
-#endif // cplusplus   >= C++17
-
-namespace toml
-{
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-class basic_value;
-
-namespace detail
-{
-// ---------------------------------------------------------------------------
-// check whether type T is a kind of container/map class
-
-struct has_iterator_impl
-{
-    template<typename T> static std::true_type  check(typename T::iterator*);
-    template<typename T> static std::false_type check(...);
-};
-struct has_value_type_impl
-{
-    template<typename T> static std::true_type  check(typename T::value_type*);
-    template<typename T> static std::false_type check(...);
-};
-struct has_key_type_impl
-{
-    template<typename T> static std::true_type  check(typename T::key_type*);
-    template<typename T> static std::false_type check(...);
-};
-struct has_mapped_type_impl
-{
-    template<typename T> static std::true_type  check(typename T::mapped_type*);
-    template<typename T> static std::false_type check(...);
-};
-struct has_reserve_method_impl
-{
-    template<typename T> static std::false_type check(...);
-    template<typename T> static std::true_type  check(
-        decltype(std::declval<T>().reserve(std::declval<std::size_t>()))*);
-};
-struct has_push_back_method_impl
-{
-    template<typename T> static std::false_type check(...);
-    template<typename T> static std::true_type  check(
-        decltype(std::declval<T>().push_back(std::declval<typename T::value_type>()))*);
-};
-struct is_comparable_impl
-{
-    template<typename T> static std::false_type check(...);
-    template<typename T> static std::true_type  check(
-        decltype(std::declval<T>() < std::declval<T>())*);
-};
-
-struct has_from_toml_method_impl
-{
-    template<typename T, typename C,
-             template<typename ...> class Tb, template<typename ...> class A>
-    static std::true_type  check(
-        decltype(std::declval<T>().from_toml(
-                std::declval<::toml::basic_value<C, Tb, A>>()))*);
-
-    template<typename T, typename C,
-             template<typename ...> class Tb, template<typename ...> class A>
-    static std::false_type check(...);
-};
-struct has_into_toml_method_impl
-{
-    template<typename T>
-    static std::true_type  check(decltype(std::declval<T>().into_toml())*);
-    template<typename T>
-    static std::false_type check(...);
-};
-
-struct has_specialized_from_impl
-{
-    template<typename T>
-    static std::false_type check(...);
-    template<typename T, std::size_t S = sizeof(::toml::from<T>)>
-    static std::true_type check(::toml::from<T>*);
-};
-struct has_specialized_into_impl
-{
-    template<typename T>
-    static std::false_type check(...);
-    template<typename T, std::size_t S = sizeof(::toml::into<T>)>
-    static std::true_type check(::toml::from<T>*);
-};
-
-
-/// Intel C++ compiler can not use decltype in parent class declaration, here
-/// is a hack to work around it. https://stackoverflow.com/a/23953090/4692076
-#ifdef __INTEL_COMPILER
-#define decltype(...) std::enable_if<true, decltype(__VA_ARGS__)>::type
-#endif
-
-template<typename T>
-struct has_iterator    : decltype(has_iterator_impl::check<T>(nullptr)){};
-template<typename T>
-struct has_value_type  : decltype(has_value_type_impl::check<T>(nullptr)){};
-template<typename T>
-struct has_key_type    : decltype(has_key_type_impl::check<T>(nullptr)){};
-template<typename T>
-struct has_mapped_type : decltype(has_mapped_type_impl::check<T>(nullptr)){};
-template<typename T>
-struct has_reserve_method : decltype(has_reserve_method_impl::check<T>(nullptr)){};
-template<typename T>
-struct has_push_back_method : decltype(has_push_back_method_impl::check<T>(nullptr)){};
-template<typename T>
-struct is_comparable : decltype(is_comparable_impl::check<T>(nullptr)){};
-
-template<typename T, typename C,
-         template<typename ...> class Tb, template<typename ...> class A>
-struct has_from_toml_method
-: decltype(has_from_toml_method_impl::check<T, C, Tb, A>(nullptr)){};
-
-template<typename T>
-struct has_into_toml_method
-: decltype(has_into_toml_method_impl::check<T>(nullptr)){};
-
-template<typename T>
-struct has_specialized_from : decltype(has_specialized_from_impl::check<T>(nullptr)){};
-template<typename T>
-struct has_specialized_into : decltype(has_specialized_into_impl::check<T>(nullptr)){};
-
-#ifdef __INTEL_COMPILER
-#undef decltype
-#endif
-
-// ---------------------------------------------------------------------------
-// C++17 and/or/not
-
-#if __cplusplus >= 201703L
-
-using std::conjunction;
-using std::disjunction;
-using std::negation;
-
-#else
-
-template<typename ...> struct conjunction : std::true_type{};
-template<typename T>   struct conjunction<T> : T{};
-template<typename T, typename ... Ts>
-struct conjunction<T, Ts...> :
-    std::conditional<static_cast<bool>(T::value), conjunction<Ts...>, T>::type
-{};
-
-template<typename ...> struct disjunction : std::false_type{};
-template<typename T>   struct disjunction<T> : T {};
-template<typename T, typename ... Ts>
-struct disjunction<T, Ts...> :
-    std::conditional<static_cast<bool>(T::value), T, disjunction<Ts...>>::type
-{};
-
-template<typename T>
-struct negation : std::integral_constant<bool, !static_cast<bool>(T::value)>{};
-
-#endif
-
-// ---------------------------------------------------------------------------
-// type checkers
-
-template<typename T> struct is_std_pair : std::false_type{};
-template<typename T1, typename T2>
-struct is_std_pair<std::pair<T1, T2>> : std::true_type{};
-
-template<typename T> struct is_std_tuple : std::false_type{};
-template<typename ... Ts>
-struct is_std_tuple<std::tuple<Ts...>> : std::true_type{};
-
-template<typename T> struct is_std_forward_list : std::false_type{};
-template<typename T>
-struct is_std_forward_list<std::forward_list<T>> : std::true_type{};
-
-template<typename T> struct is_chrono_duration: std::false_type{};
-template<typename Rep, typename Period>
-struct is_chrono_duration<std::chrono::duration<Rep, Period>>: std::true_type{};
-
-template<typename T>
-struct is_map : conjunction< // map satisfies all the following conditions
-    has_iterator<T>,         // has T::iterator
-    has_value_type<T>,       // has T::value_type
-    has_key_type<T>,         // has T::key_type
-    has_mapped_type<T>       // has T::mapped_type
-    >{};
-template<typename T> struct is_map<T&>                : is_map<T>{};
-template<typename T> struct is_map<T const&>          : is_map<T>{};
-template<typename T> struct is_map<T volatile&>       : is_map<T>{};
-template<typename T> struct is_map<T const volatile&> : is_map<T>{};
-
-template<typename T>
-struct is_container : conjunction<
-    negation<is_map<T>>,                         // not a map
-    negation<std::is_same<T, std::string>>,      // not a std::string
-#if __cplusplus >= 201703L
-#if __has_include(<string_view>)
-    negation<std::is_same<T, std::string_view>>, // not a std::string_view
-#endif // has_include(<string_view>)
-#endif
-    has_iterator<T>,                             // has T::iterator
-    has_value_type<T>                            // has T::value_type
-    >{};
-template<typename T> struct is_container<T&>                : is_container<T>{};
-template<typename T> struct is_container<T const&>          : is_container<T>{};
-template<typename T> struct is_container<T volatile&>       : is_container<T>{};
-template<typename T> struct is_container<T const volatile&> : is_container<T>{};
-
-template<typename T>
-struct is_basic_value: std::false_type{};
-template<typename T> struct is_basic_value<T&>                : is_basic_value<T>{};
-template<typename T> struct is_basic_value<T const&>          : is_basic_value<T>{};
-template<typename T> struct is_basic_value<T volatile&>       : is_basic_value<T>{};
-template<typename T> struct is_basic_value<T const volatile&> : is_basic_value<T>{};
-template<typename C, template<typename ...> class M, template<typename ...> class V>
-struct is_basic_value<::toml::basic_value<C, M, V>>: std::true_type{};
-
-// ---------------------------------------------------------------------------
-// C++14 index_sequence
-
-#if __cplusplus >= 201402L
-
-using std::index_sequence;
-using std::make_index_sequence;
-
-#else
-
-template<std::size_t ... Ns> struct index_sequence{};
-
-template<typename IS, std::size_t N> struct push_back_index_sequence{};
-template<std::size_t N, std::size_t ... Ns>
-struct push_back_index_sequence<index_sequence<Ns...>, N>
-{
-    typedef index_sequence<Ns..., N> type;
-};
-
-template<std::size_t N>
-struct index_sequence_maker
-{
-    typedef typename push_back_index_sequence<
-        typename index_sequence_maker<N-1>::type, N>::type type;
-};
-template<>
-struct index_sequence_maker<0>
-{
-    typedef index_sequence<0> type;
-};
-template<std::size_t N>
-using make_index_sequence = typename index_sequence_maker<N-1>::type;
-
-#endif // __cplusplus >= 2014
-
-// ---------------------------------------------------------------------------
-// C++14 enable_if_t
-
-#if __cplusplus >= 201402L
-
-using std::enable_if_t;
-
-#else
-
-template<bool B, typename T>
-using enable_if_t = typename std::enable_if<B, T>::type;
-
-#endif // __cplusplus >= 2014
-
-// ---------------------------------------------------------------------------
-// return_type_of_t
-
-#if __cplusplus >= 201703L && defined(__cpp_lib_is_invocable) && __cpp_lib_is_invocable>=201703
-
-template<typename F, typename ... Args>
-using return_type_of_t = std::invoke_result_t<F, Args...>;
-
-#else
-// result_of is deprecated after C++17
-template<typename F, typename ... Args>
-using return_type_of_t = typename std::result_of<F(Args...)>::type;
-
-#endif
-
-// ---------------------------------------------------------------------------
-// is_string_literal
-//
-// to use this, pass `typename remove_reference<T>::type` to T.
-
-template<typename T>
-struct is_string_literal:
-disjunction<
-    std::is_same<const char*, T>,
-    conjunction<
-        std::is_array<T>,
-        std::is_same<const char, typename std::remove_extent<T>::type>
-        >
-    >{};
-
-// ---------------------------------------------------------------------------
-// C++20 remove_cvref_t
-
-template<typename T>
-struct remove_cvref
-{
-    using type = typename std::remove_cv<
-        typename std::remove_reference<T>::type>::type;
-};
-
-template<typename T>
-using remove_cvref_t = typename remove_cvref<T>::type;
-
-}// detail
-}//toml
-#endif // TOML_TRAITS
diff --git a/src/toml11/toml/types.hpp b/src/toml11/toml/types.hpp
deleted file mode 100644
index 1e420e7fd37..00000000000
--- a/src/toml11/toml/types.hpp
+++ /dev/null
@@ -1,173 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_TYPES_HPP
-#define TOML11_TYPES_HPP
-#include <unordered_map>
-#include <vector>
-
-#include "comments.hpp"
-#include "datetime.hpp"
-#include "string.hpp"
-#include "traits.hpp"
-
-namespace toml
-{
-
-template<typename Comment, // discard/preserve_comment
-         template<typename ...> class Table, // map-like class
-         template<typename ...> class Array> // vector-like class
-class basic_value;
-
-using character = char;
-using key = std::string;
-
-#if !defined(__clang__) && defined(__GNUC__) && __GNUC__ <= 4
-#  pragma GCC diagnostic push
-#  pragma GCC diagnostic ignored "-Wshadow"
-#endif
-
-using boolean        = bool;
-using integer        = std::int64_t;
-using floating       = double; // "float" is a keyword, cannot use it here.
-// the following stuffs are structs defined here, so aliases are not needed.
-// - string
-// - offset_datetime
-// - offset_datetime
-// - local_datetime
-// - local_date
-// - local_time
-
-#if defined(__GNUC__) && !defined(__clang__)
-#  pragma GCC diagnostic pop
-#endif
-
-// default toml::value and default array/table. these are defined after defining
-// basic_value itself.
-// using value = basic_value<discard_comments, std::unordered_map, std::vector>;
-// using array = typename value::array_type;
-// using table = typename value::table_type;
-
-// to avoid warnings about `value_t::integer` is "shadowing" toml::integer in
-// GCC -Wshadow=global.
-#if defined(__GNUC__) && !defined(__clang__)
-#  pragma GCC diagnostic push
-#  if 7 <= __GNUC__
-#    pragma GCC diagnostic ignored "-Wshadow=global"
-#  else // gcc-6 or older
-#    pragma GCC diagnostic ignored "-Wshadow"
-#  endif
-#endif
-enum class value_t : std::uint8_t
-{
-    empty           =  0,
-    boolean         =  1,
-    integer         =  2,
-    floating        =  3,
-    string          =  4,
-    offset_datetime =  5,
-    local_datetime  =  6,
-    local_date      =  7,
-    local_time      =  8,
-    array           =  9,
-    table           = 10,
-};
-#if defined(__GNUC__) && !defined(__clang__)
-#  pragma GCC diagnostic pop
-#endif
-
-template<typename charT, typename traits>
-inline std::basic_ostream<charT, traits>&
-operator<<(std::basic_ostream<charT, traits>& os, value_t t)
-{
-    switch(t)
-    {
-        case value_t::boolean         : os << "boolean";         return os;
-        case value_t::integer         : os << "integer";         return os;
-        case value_t::floating        : os << "floating";        return os;
-        case value_t::string          : os << "string";          return os;
-        case value_t::offset_datetime : os << "offset_datetime"; return os;
-        case value_t::local_datetime  : os << "local_datetime";  return os;
-        case value_t::local_date      : os << "local_date";      return os;
-        case value_t::local_time      : os << "local_time";      return os;
-        case value_t::array           : os << "array";           return os;
-        case value_t::table           : os << "table";           return os;
-        case value_t::empty           : os << "empty";           return os;
-        default                       : os << "unknown";         return os;
-    }
-}
-
-template<typename charT = char,
-         typename traits = std::char_traits<charT>,
-         typename alloc = std::allocator<charT>>
-inline std::basic_string<charT, traits, alloc> stringize(value_t t)
-{
-    std::basic_ostringstream<charT, traits, alloc> oss;
-    oss << t;
-    return oss.str();
-}
-
-namespace detail
-{
-
-// helper to define a type that represents a value_t value.
-template<value_t V>
-using value_t_constant = std::integral_constant<value_t, V>;
-
-// meta-function that convertes from value_t to the exact toml type that corresponds to.
-// It takes toml::basic_value type because array and table types depend on it.
-template<value_t t, typename Value> struct enum_to_type                      {using type = void                      ;};
-template<typename Value> struct enum_to_type<value_t::empty          , Value>{using type = void                      ;};
-template<typename Value> struct enum_to_type<value_t::boolean        , Value>{using type = boolean                   ;};
-template<typename Value> struct enum_to_type<value_t::integer        , Value>{using type = integer                   ;};
-template<typename Value> struct enum_to_type<value_t::floating       , Value>{using type = floating                  ;};
-template<typename Value> struct enum_to_type<value_t::string         , Value>{using type = string                    ;};
-template<typename Value> struct enum_to_type<value_t::offset_datetime, Value>{using type = offset_datetime           ;};
-template<typename Value> struct enum_to_type<value_t::local_datetime , Value>{using type = local_datetime            ;};
-template<typename Value> struct enum_to_type<value_t::local_date     , Value>{using type = local_date                ;};
-template<typename Value> struct enum_to_type<value_t::local_time     , Value>{using type = local_time                ;};
-template<typename Value> struct enum_to_type<value_t::array          , Value>{using type = typename Value::array_type;};
-template<typename Value> struct enum_to_type<value_t::table          , Value>{using type = typename Value::table_type;};
-
-// meta-function that converts from an exact toml type to the enum that corresponds to.
-template<typename T, typename Value>
-struct type_to_enum : std::conditional<
-    std::is_same<T, typename Value::array_type>::value, // if T == array_type,
-    value_t_constant<value_t::array>,                   // then value_t::array
-    typename std::conditional<                          // else...
-        std::is_same<T, typename Value::table_type>::value, // if T == table_type
-        value_t_constant<value_t::table>,               // then value_t::table
-        value_t_constant<value_t::empty>                // else value_t::empty
-        >::type
-    >::type {};
-template<typename Value> struct type_to_enum<boolean        , Value>: value_t_constant<value_t::boolean        > {};
-template<typename Value> struct type_to_enum<integer        , Value>: value_t_constant<value_t::integer        > {};
-template<typename Value> struct type_to_enum<floating       , Value>: value_t_constant<value_t::floating       > {};
-template<typename Value> struct type_to_enum<string         , Value>: value_t_constant<value_t::string         > {};
-template<typename Value> struct type_to_enum<offset_datetime, Value>: value_t_constant<value_t::offset_datetime> {};
-template<typename Value> struct type_to_enum<local_datetime , Value>: value_t_constant<value_t::local_datetime > {};
-template<typename Value> struct type_to_enum<local_date     , Value>: value_t_constant<value_t::local_date     > {};
-template<typename Value> struct type_to_enum<local_time     , Value>: value_t_constant<value_t::local_time     > {};
-
-// meta-function that checks the type T is the same as one of the toml::* types.
-template<typename T, typename Value>
-struct is_exact_toml_type : disjunction<
-    std::is_same<T, boolean        >,
-    std::is_same<T, integer        >,
-    std::is_same<T, floating       >,
-    std::is_same<T, string         >,
-    std::is_same<T, offset_datetime>,
-    std::is_same<T, local_datetime >,
-    std::is_same<T, local_date     >,
-    std::is_same<T, local_time     >,
-    std::is_same<T, typename Value::array_type>,
-    std::is_same<T, typename Value::table_type>
-    >{};
-template<typename T, typename V> struct is_exact_toml_type<T&, V>               : is_exact_toml_type<T, V>{};
-template<typename T, typename V> struct is_exact_toml_type<T const&, V>         : is_exact_toml_type<T, V>{};
-template<typename T, typename V> struct is_exact_toml_type<T volatile&, V>      : is_exact_toml_type<T, V>{};
-template<typename T, typename V> struct is_exact_toml_type<T const volatile&, V>: is_exact_toml_type<T, V>{};
-
-} // detail
-} // toml
-
-#endif// TOML11_TYPES_H
diff --git a/src/toml11/toml/utility.hpp b/src/toml11/toml/utility.hpp
deleted file mode 100644
index 4a6b4309d7f..00000000000
--- a/src/toml11/toml/utility.hpp
+++ /dev/null
@@ -1,149 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_UTILITY_HPP
-#define TOML11_UTILITY_HPP
-#include <memory>
-#include <sstream>
-#include <utility>
-
-#include "traits.hpp"
-
-#if __cplusplus >= 201402L
-#  define TOML11_MARK_AS_DEPRECATED(msg) [[deprecated(msg)]]
-#elif defined(__GNUC__)
-#  define TOML11_MARK_AS_DEPRECATED(msg) __attribute__((deprecated(msg)))
-#elif defined(_MSC_VER)
-#  define TOML11_MARK_AS_DEPRECATED(msg) __declspec(deprecated(msg))
-#else
-#  define TOML11_MARK_AS_DEPRECATED
-#endif
-
-namespace toml
-{
-
-#if __cplusplus >= 201402L
-
-using std::make_unique;
-
-#else
-
-template<typename T, typename ... Ts>
-inline std::unique_ptr<T> make_unique(Ts&& ... args)
-{
-    return std::unique_ptr<T>(new T(std::forward<Ts>(args)...));
-}
-
-#endif // __cplusplus >= 2014
-
-namespace detail
-{
-template<typename Container>
-void try_reserve_impl(Container& container, std::size_t N, std::true_type)
-{
-    container.reserve(N);
-    return;
-}
-template<typename Container>
-void try_reserve_impl(Container&, std::size_t, std::false_type) noexcept
-{
-    return;
-}
-} // detail
-
-template<typename Container>
-void try_reserve(Container& container, std::size_t N)
-{
-    if(N <= container.size()) {return;}
-    detail::try_reserve_impl(container, N, detail::has_reserve_method<Container>{});
-    return;
-}
-
-namespace detail
-{
-inline std::string concat_to_string_impl(std::ostringstream& oss)
-{
-    return oss.str();
-}
-template<typename T, typename ... Ts>
-std::string concat_to_string_impl(std::ostringstream& oss, T&& head, Ts&& ... tail)
-{
-    oss << std::forward<T>(head);
-    return concat_to_string_impl(oss, std::forward<Ts>(tail) ... );
-}
-} // detail
-
-template<typename ... Ts>
-std::string concat_to_string(Ts&& ... args)
-{
-    std::ostringstream oss;
-    oss << std::boolalpha << std::fixed;
-    return detail::concat_to_string_impl(oss, std::forward<Ts>(args) ...);
-}
-
-template<typename T>
-T from_string(const std::string& str, T opt)
-{
-    T v(opt);
-    std::istringstream iss(str);
-    iss >> v;
-    return v;
-}
-
-namespace detail
-{
-#if __cplusplus >= 201402L
-template<typename T>
-decltype(auto) last_one(T&& tail) noexcept
-{
-    return std::forward<T>(tail);
-}
-
-template<typename T, typename ... Ts>
-decltype(auto) last_one(T&& /*head*/, Ts&& ... tail) noexcept
-{
-    return last_one(std::forward<Ts>(tail)...);
-}
-#else // C++11
-// The following code
-// ```cpp
-//  1 | template<typename T, typename ... Ts>
-//  2 | auto last_one(T&& /*head*/, Ts&& ... tail)
-//  3 |  -> decltype(last_one(std::forward<Ts>(tail)...))
-//  4 | {
-//  5 |     return last_one(std::forward<Ts>(tail)...);
-//  6 | }
-// ```
-// does not work because the function `last_one(...)` is not yet defined at
-// line #3, so `decltype()` cannot deduce the type returned from `last_one`.
-// So we need to determine return type in a different way, like a meta func.
-
-template<typename T, typename ... Ts>
-struct last_one_in_pack
-{
-    using type = typename last_one_in_pack<Ts...>::type;
-};
-template<typename T>
-struct last_one_in_pack<T>
-{
-    using type = T;
-};
-template<typename ... Ts>
-using last_one_in_pack_t = typename last_one_in_pack<Ts...>::type;
-
-template<typename T>
-T&& last_one(T&& tail) noexcept
-{
-    return std::forward<T>(tail);
-}
-template<typename T, typename ... Ts>
-enable_if_t<(sizeof...(Ts) > 0), last_one_in_pack_t<Ts&& ...>>
-last_one(T&& /*head*/, Ts&& ... tail)
-{
-    return last_one(std::forward<Ts>(tail)...);
-}
-
-#endif
-} // detail
-
-}// toml
-#endif // TOML11_UTILITY
diff --git a/src/toml11/toml/value.hpp b/src/toml11/toml/value.hpp
deleted file mode 100644
index 1b43db8d4c7..00000000000
--- a/src/toml11/toml/value.hpp
+++ /dev/null
@@ -1,2035 +0,0 @@
-//     Copyright Toru Niina 2017.
-// Distributed under the MIT License.
-#ifndef TOML11_VALUE_HPP
-#define TOML11_VALUE_HPP
-#include <cassert>
-
-#include "comments.hpp"
-#include "exception.hpp"
-#include "into.hpp"
-#include "region.hpp"
-#include "source_location.hpp"
-#include "storage.hpp"
-#include "traits.hpp"
-#include "types.hpp"
-#include "utility.hpp"
-
-namespace toml
-{
-
-namespace detail
-{
-
-// to show error messages. not recommended for users.
-template<typename Value>
-inline region_base const* get_region(const Value& v)
-{
-    return v.region_info_.get();
-}
-
-template<typename Value>
-void change_region(Value& v, region reg)
-{
-    v.region_info_ = std::make_shared<region>(std::move(reg));
-    return;
-}
-
-template<value_t Expected, typename Value>
-[[noreturn]] inline void
-throw_bad_cast(const std::string& funcname, value_t actual, const Value& v)
-{
-    throw type_error(detail::format_underline(
-        concat_to_string(funcname, "bad_cast to ", Expected), {
-            {v.location(), concat_to_string("the actual type is ", actual)}
-        }), v.location());
-}
-
-// Throw `out_of_range` from `toml::value::at()` and `toml::find()`
-// after generating an error message.
-//
-// The implementation is a bit complicated and there are many edge-cases.
-// If you are not interested in the error message generation, just skip this.
-template<typename Value>
-[[noreturn]] void
-throw_key_not_found_error(const Value& v, const key& ky)
-{
-    // The top-level table has its region at the first character of the file.
-    // That means that, in the case when a key is not found in the top-level
-    // table, the error message points to the first character. If the file has
-    // its first table at the first line, the error message would be like this.
-    // ```console
-    // [error] key "a" not found
-    //  --> example.toml
-    //    |
-    //  1 | [table]
-    //    | ^------ in this table
-    // ```
-    // It actually points to the top-level table at the first character,
-    // not `[table]`. But it is too confusing. To avoid the confusion, the error
-    // message should explicitly say "key not found in the top-level table",
-    // or "the parsed file is empty" if there is no content at all (0 bytes in file).
-    const auto loc = v.location();
-    if(loc.line() == 1 && loc.region() == 0)
-    {
-        // First line with a zero-length region means "empty file".
-        // The region will be generated at `parse_toml_file` function
-        // if the file contains no bytes.
-        throw std::out_of_range(format_underline(concat_to_string(
-            "key \"", ky, "\" not found in the top-level table"), {
-                {loc, "the parsed file is empty"}
-            }));
-    }
-    else if(loc.line() == 1 && loc.region() == 1)
-    {
-        // Here it assumes that top-level table starts at the first character.
-        // The region corresponds to the top-level table will be generated at
-        // `parse_toml_file` function.
-        //     It also assumes that the top-level table size is just one and
-        // the line number is `1`. It is always satisfied. And those conditions
-        // are satisfied only if the table is the top-level table.
-        //
-        // 1. one-character dot-key at the first line
-        // ```toml
-        // a.b = "c"
-        // ```
-        // toml11 counts whole key as the table key. Here, `a.b` is the region
-        // of the table "a". It could be counter intuitive, but it works.
-        // The size of the region is 3, not 1. The above example is the shortest
-        // dot-key example. The size cannot be 1.
-        //
-        // 2. one-character inline-table at the first line
-        // ```toml
-        // a = {b = "c"}
-        // ```
-        // toml11 considers the inline table body as the table region. Here,
-        // `{b = "c"}` is the region of the table "a". The size of the region
-        // is 9, not 1. The shotest inline table still has two characters, `{`
-        // and `}`. The size cannot be 1.
-        //
-        // 3. one-character table declaration at the first line
-        // ```toml
-        // [a]
-        // ```
-        // toml11 considers the whole table key as the table region. Here,
-        // `[a]` is the table region. The size is 3, not 1.
-        //
-        throw std::out_of_range(format_underline(concat_to_string(
-            "key \"", ky, "\" not found in the top-level table"), {
-                {loc, "the top-level table starts here"}
-            }));
-    }
-    else
-    {
-        // normal table.
-        throw std::out_of_range(format_underline(concat_to_string(
-            "key \"", ky, "\" not found"), { {loc, "in this table"} }));
-    }
-}
-
-// switch by `value_t` at the compile time.
-template<value_t T>
-struct switch_cast {};
-#define TOML11_GENERATE_SWITCH_CASTER(TYPE) \
-    template<>                                                           \
-    struct switch_cast<value_t::TYPE>                                    \
-    {                                                                    \
-        template<typename Value>                                         \
-        static typename Value::TYPE##_type& invoke(Value& v)             \
-        {                                                                \
-            return v.as_##TYPE();                                        \
-        }                                                                \
-        template<typename Value>                                         \
-        static typename Value::TYPE##_type const& invoke(const Value& v) \
-        {                                                                \
-            return v.as_##TYPE();                                        \
-        }                                                                \
-        template<typename Value>                                         \
-        static typename Value::TYPE##_type&& invoke(Value&& v)           \
-        {                                                                \
-            return std::move(v).as_##TYPE();                             \
-        }                                                                \
-    };                                                                   \
-    /**/
-TOML11_GENERATE_SWITCH_CASTER(boolean)
-TOML11_GENERATE_SWITCH_CASTER(integer)
-TOML11_GENERATE_SWITCH_CASTER(floating)
-TOML11_GENERATE_SWITCH_CASTER(string)
-TOML11_GENERATE_SWITCH_CASTER(offset_datetime)
-TOML11_GENERATE_SWITCH_CASTER(local_datetime)
-TOML11_GENERATE_SWITCH_CASTER(local_date)
-TOML11_GENERATE_SWITCH_CASTER(local_time)
-TOML11_GENERATE_SWITCH_CASTER(array)
-TOML11_GENERATE_SWITCH_CASTER(table)
-
-#undef TOML11_GENERATE_SWITCH_CASTER
-
-}// detail
-
-template<typename Comment, // discard/preserve_comment
-         template<typename ...> class Table = std::unordered_map,
-         template<typename ...> class Array = std::vector>
-class basic_value
-{
-    template<typename T, typename U>
-    static void assigner(T& dst, U&& v)
-    {
-        const auto tmp = ::new(std::addressof(dst)) T(std::forward<U>(v));
-        assert(tmp == std::addressof(dst));
-        (void)tmp;
-    }
-
-    using region_base = detail::region_base;
-
-    template<typename C, template<typename ...> class T,
-             template<typename ...> class A>
-    friend class basic_value;
-
-  public:
-
-    using comment_type         = Comment;
-    using key_type             = ::toml::key;
-    using value_type           = basic_value<comment_type, Table, Array>;
-    using boolean_type         = ::toml::boolean;
-    using integer_type         = ::toml::integer;
-    using floating_type        = ::toml::floating;
-    using string_type          = ::toml::string;
-    using local_time_type      = ::toml::local_time;
-    using local_date_type      = ::toml::local_date;
-    using local_datetime_type  = ::toml::local_datetime;
-    using offset_datetime_type = ::toml::offset_datetime;
-    using array_type           = Array<value_type>;
-    using table_type           = Table<key_type, value_type>;
-
-  public:
-
-    basic_value() noexcept
-        : type_(value_t::empty),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {}
-    ~basic_value() noexcept {this->cleanup();}
-
-    basic_value(const basic_value& v)
-        : type_(v.type()), region_info_(v.region_info_), comments_(v.comments_)
-    {
-        switch(v.type())
-        {
-            case value_t::boolean        : assigner(boolean_        , v.boolean_        ); break;
-            case value_t::integer        : assigner(integer_        , v.integer_        ); break;
-            case value_t::floating       : assigner(floating_       , v.floating_       ); break;
-            case value_t::string         : assigner(string_         , v.string_         ); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, v.offset_datetime_); break;
-            case value_t::local_datetime : assigner(local_datetime_ , v.local_datetime_ ); break;
-            case value_t::local_date     : assigner(local_date_     , v.local_date_     ); break;
-            case value_t::local_time     : assigner(local_time_     , v.local_time_     ); break;
-            case value_t::array          : assigner(array_          , v.array_          ); break;
-            case value_t::table          : assigner(table_          , v.table_          ); break;
-            default: break;
-        }
-    }
-    basic_value(basic_value&& v)
-        : type_(v.type()), region_info_(std::move(v.region_info_)),
-          comments_(std::move(v.comments_))
-    {
-        switch(this->type_) // here this->type_ is already initialized
-        {
-            case value_t::boolean        : assigner(boolean_        , std::move(v.boolean_        )); break;
-            case value_t::integer        : assigner(integer_        , std::move(v.integer_        )); break;
-            case value_t::floating       : assigner(floating_       , std::move(v.floating_       )); break;
-            case value_t::string         : assigner(string_         , std::move(v.string_         )); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, std::move(v.offset_datetime_)); break;
-            case value_t::local_datetime : assigner(local_datetime_ , std::move(v.local_datetime_ )); break;
-            case value_t::local_date     : assigner(local_date_     , std::move(v.local_date_     )); break;
-            case value_t::local_time     : assigner(local_time_     , std::move(v.local_time_     )); break;
-            case value_t::array          : assigner(array_          , std::move(v.array_          )); break;
-            case value_t::table          : assigner(table_          , std::move(v.table_          )); break;
-            default: break;
-        }
-    }
-    basic_value& operator=(const basic_value& v)
-    {
-        this->cleanup();
-        this->region_info_ = v.region_info_;
-        this->comments_ = v.comments_;
-        this->type_ = v.type();
-        switch(this->type_)
-        {
-            case value_t::boolean        : assigner(boolean_        , v.boolean_        ); break;
-            case value_t::integer        : assigner(integer_        , v.integer_        ); break;
-            case value_t::floating       : assigner(floating_       , v.floating_       ); break;
-            case value_t::string         : assigner(string_         , v.string_         ); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, v.offset_datetime_); break;
-            case value_t::local_datetime : assigner(local_datetime_ , v.local_datetime_ ); break;
-            case value_t::local_date     : assigner(local_date_     , v.local_date_     ); break;
-            case value_t::local_time     : assigner(local_time_     , v.local_time_     ); break;
-            case value_t::array          : assigner(array_          , v.array_          ); break;
-            case value_t::table          : assigner(table_          , v.table_          ); break;
-            default: break;
-        }
-        return *this;
-    }
-    basic_value& operator=(basic_value&& v)
-    {
-        this->cleanup();
-        this->region_info_ = std::move(v.region_info_);
-        this->comments_ = std::move(v.comments_);
-        this->type_ = v.type();
-        switch(this->type_)
-        {
-            case value_t::boolean        : assigner(boolean_        , std::move(v.boolean_        )); break;
-            case value_t::integer        : assigner(integer_        , std::move(v.integer_        )); break;
-            case value_t::floating       : assigner(floating_       , std::move(v.floating_       )); break;
-            case value_t::string         : assigner(string_         , std::move(v.string_         )); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, std::move(v.offset_datetime_)); break;
-            case value_t::local_datetime : assigner(local_datetime_ , std::move(v.local_datetime_ )); break;
-            case value_t::local_date     : assigner(local_date_     , std::move(v.local_date_     )); break;
-            case value_t::local_time     : assigner(local_time_     , std::move(v.local_time_     )); break;
-            case value_t::array          : assigner(array_          , std::move(v.array_          )); break;
-            case value_t::table          : assigner(table_          , std::move(v.table_          )); break;
-            default: break;
-        }
-        return *this;
-    }
-
-    // overwrite comments ----------------------------------------------------
-
-    basic_value(const basic_value& v, std::vector<std::string> com)
-        : type_(v.type()), region_info_(v.region_info_),
-          comments_(std::move(com))
-    {
-        switch(v.type())
-        {
-            case value_t::boolean        : assigner(boolean_        , v.boolean_        ); break;
-            case value_t::integer        : assigner(integer_        , v.integer_        ); break;
-            case value_t::floating       : assigner(floating_       , v.floating_       ); break;
-            case value_t::string         : assigner(string_         , v.string_         ); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, v.offset_datetime_); break;
-            case value_t::local_datetime : assigner(local_datetime_ , v.local_datetime_ ); break;
-            case value_t::local_date     : assigner(local_date_     , v.local_date_     ); break;
-            case value_t::local_time     : assigner(local_time_     , v.local_time_     ); break;
-            case value_t::array          : assigner(array_          , v.array_          ); break;
-            case value_t::table          : assigner(table_          , v.table_          ); break;
-            default: break;
-        }
-    }
-
-    basic_value(basic_value&& v, std::vector<std::string> com)
-        : type_(v.type()), region_info_(std::move(v.region_info_)),
-          comments_(std::move(com))
-    {
-        switch(this->type_) // here this->type_ is already initialized
-        {
-            case value_t::boolean        : assigner(boolean_        , std::move(v.boolean_        )); break;
-            case value_t::integer        : assigner(integer_        , std::move(v.integer_        )); break;
-            case value_t::floating       : assigner(floating_       , std::move(v.floating_       )); break;
-            case value_t::string         : assigner(string_         , std::move(v.string_         )); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, std::move(v.offset_datetime_)); break;
-            case value_t::local_datetime : assigner(local_datetime_ , std::move(v.local_datetime_ )); break;
-            case value_t::local_date     : assigner(local_date_     , std::move(v.local_date_     )); break;
-            case value_t::local_time     : assigner(local_time_     , std::move(v.local_time_     )); break;
-            case value_t::array          : assigner(array_          , std::move(v.array_          )); break;
-            case value_t::table          : assigner(table_          , std::move(v.table_          )); break;
-            default: break;
-        }
-    }
-
-    // -----------------------------------------------------------------------
-    // conversion between different basic_values.
-    template<typename C,
-             template<typename ...> class T,
-             template<typename ...> class A>
-    basic_value(const basic_value<C, T, A>& v)
-        : type_(v.type()), region_info_(v.region_info_), comments_(v.comments())
-    {
-        switch(v.type())
-        {
-            case value_t::boolean        : assigner(boolean_        , v.boolean_        ); break;
-            case value_t::integer        : assigner(integer_        , v.integer_        ); break;
-            case value_t::floating       : assigner(floating_       , v.floating_       ); break;
-            case value_t::string         : assigner(string_         , v.string_         ); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, v.offset_datetime_); break;
-            case value_t::local_datetime : assigner(local_datetime_ , v.local_datetime_ ); break;
-            case value_t::local_date     : assigner(local_date_     , v.local_date_     ); break;
-            case value_t::local_time     : assigner(local_time_     , v.local_time_     ); break;
-            case value_t::array          :
-            {
-                array_type tmp(v.as_array(std::nothrow).begin(),
-                               v.as_array(std::nothrow).end());
-                assigner(array_, std::move(tmp));
-                break;
-            }
-            case value_t::table          :
-            {
-                table_type tmp(v.as_table(std::nothrow).begin(),
-                               v.as_table(std::nothrow).end());
-                assigner(table_, std::move(tmp));
-                break;
-            }
-            default: break;
-        }
-    }
-    template<typename C,
-             template<typename ...> class T,
-             template<typename ...> class A>
-    basic_value(const basic_value<C, T, A>& v, std::vector<std::string> com)
-        : type_(v.type()), region_info_(v.region_info_),
-          comments_(std::move(com))
-    {
-        switch(v.type())
-        {
-            case value_t::boolean        : assigner(boolean_        , v.boolean_        ); break;
-            case value_t::integer        : assigner(integer_        , v.integer_        ); break;
-            case value_t::floating       : assigner(floating_       , v.floating_       ); break;
-            case value_t::string         : assigner(string_         , v.string_         ); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, v.offset_datetime_); break;
-            case value_t::local_datetime : assigner(local_datetime_ , v.local_datetime_ ); break;
-            case value_t::local_date     : assigner(local_date_     , v.local_date_     ); break;
-            case value_t::local_time     : assigner(local_time_     , v.local_time_     ); break;
-            case value_t::array          :
-            {
-                array_type tmp(v.as_array(std::nothrow).begin(),
-                               v.as_array(std::nothrow).end());
-                assigner(array_, std::move(tmp));
-                break;
-            }
-            case value_t::table          :
-            {
-                table_type tmp(v.as_table(std::nothrow).begin(),
-                               v.as_table(std::nothrow).end());
-                assigner(table_, std::move(tmp));
-                break;
-            }
-            default: break;
-        }
-    }
-    template<typename C,
-             template<typename ...> class T,
-             template<typename ...> class A>
-    basic_value& operator=(const basic_value<C, T, A>& v)
-    {
-        this->region_info_ = v.region_info_;
-        this->comments_    = comment_type(v.comments());
-        this->type_        = v.type();
-        switch(v.type())
-        {
-            case value_t::boolean        : assigner(boolean_        , v.boolean_        ); break;
-            case value_t::integer        : assigner(integer_        , v.integer_        ); break;
-            case value_t::floating       : assigner(floating_       , v.floating_       ); break;
-            case value_t::string         : assigner(string_         , v.string_         ); break;
-            case value_t::offset_datetime: assigner(offset_datetime_, v.offset_datetime_); break;
-            case value_t::local_datetime : assigner(local_datetime_ , v.local_datetime_ ); break;
-            case value_t::local_date     : assigner(local_date_     , v.local_date_     ); break;
-            case value_t::local_time     : assigner(local_time_     , v.local_time_     ); break;
-            case value_t::array          :
-            {
-                array_type tmp(v.as_array(std::nothrow).begin(),
-                               v.as_array(std::nothrow).end());
-                assigner(array_, std::move(tmp));
-                break;
-            }
-            case value_t::table          :
-            {
-                table_type tmp(v.as_table(std::nothrow).begin(),
-                               v.as_table(std::nothrow).end());
-                assigner(table_, std::move(tmp));
-                break;
-            }
-            default: break;
-        }
-        return *this;
-    }
-
-    // boolean ==============================================================
-
-    basic_value(boolean b)
-        : type_(value_t::boolean),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->boolean_, b);
-    }
-    basic_value& operator=(boolean b)
-    {
-        this->cleanup();
-        this->type_ = value_t::boolean;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->boolean_, b);
-        return *this;
-    }
-    basic_value(boolean b, std::vector<std::string> com)
-        : type_(value_t::boolean),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->boolean_, b);
-    }
-
-    // integer ==============================================================
-
-    template<typename T, typename std::enable_if<detail::conjunction<
-        std::is_integral<T>, detail::negation<std::is_same<T, boolean>>>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value(T i)
-        : type_(value_t::integer),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->integer_, static_cast<integer>(i));
-    }
-
-    template<typename T, typename std::enable_if<detail::conjunction<
-        std::is_integral<T>, detail::negation<std::is_same<T, boolean>>>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value& operator=(T i)
-    {
-        this->cleanup();
-        this->type_ = value_t::integer;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->integer_, static_cast<integer>(i));
-        return *this;
-    }
-
-    template<typename T, typename std::enable_if<detail::conjunction<
-        std::is_integral<T>, detail::negation<std::is_same<T, boolean>>>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value(T i, std::vector<std::string> com)
-        : type_(value_t::integer),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->integer_, static_cast<integer>(i));
-    }
-
-    // floating =============================================================
-
-    template<typename T, typename std::enable_if<
-        std::is_floating_point<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value(T f)
-        : type_(value_t::floating),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->floating_, static_cast<floating>(f));
-    }
-
-
-    template<typename T, typename std::enable_if<
-        std::is_floating_point<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value& operator=(T f)
-    {
-        this->cleanup();
-        this->type_ = value_t::floating;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->floating_, static_cast<floating>(f));
-        return *this;
-    }
-
-    template<typename T, typename std::enable_if<
-        std::is_floating_point<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value(T f, std::vector<std::string> com)
-        : type_(value_t::floating),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->floating_, f);
-    }
-
-    // string ===============================================================
-
-    basic_value(toml::string s)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, std::move(s));
-    }
-    basic_value& operator=(toml::string s)
-    {
-        this->cleanup();
-        this->type_ = value_t::string ;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->string_, s);
-        return *this;
-    }
-    basic_value(toml::string s, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, std::move(s));
-    }
-
-    basic_value(std::string s)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, toml::string(std::move(s)));
-    }
-    basic_value& operator=(std::string s)
-    {
-        this->cleanup();
-        this->type_ = value_t::string ;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->string_, toml::string(std::move(s)));
-        return *this;
-    }
-    basic_value(std::string s, string_t kind)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, toml::string(std::move(s), kind));
-    }
-    basic_value(std::string s, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, toml::string(std::move(s)));
-    }
-    basic_value(std::string s, string_t kind, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, toml::string(std::move(s), kind));
-    }
-
-    basic_value(const char* s)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, toml::string(std::string(s)));
-    }
-    basic_value& operator=(const char* s)
-    {
-        this->cleanup();
-        this->type_ = value_t::string ;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->string_, toml::string(std::string(s)));
-        return *this;
-    }
-    basic_value(const char* s, string_t kind)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, toml::string(std::string(s), kind));
-    }
-    basic_value(const char* s, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, toml::string(std::string(s)));
-    }
-    basic_value(const char* s, string_t kind, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, toml::string(std::string(s), kind));
-    }
-
-#if defined(TOML11_USING_STRING_VIEW) && TOML11_USING_STRING_VIEW>0
-    basic_value(std::string_view s)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, toml::string(s));
-    }
-    basic_value& operator=(std::string_view s)
-    {
-        this->cleanup();
-        this->type_ = value_t::string ;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->string_, toml::string(s));
-        return *this;
-    }
-    basic_value(std::string_view s, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, toml::string(s));
-    }
-    basic_value(std::string_view s, string_t kind)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->string_, toml::string(s, kind));
-    }
-    basic_value(std::string_view s, string_t kind, std::vector<std::string> com)
-        : type_(value_t::string),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->string_, toml::string(s, kind));
-    }
-#endif
-
-    // local date ===========================================================
-
-    basic_value(const local_date& ld)
-        : type_(value_t::local_date),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->local_date_, ld);
-    }
-    basic_value& operator=(const local_date& ld)
-    {
-        this->cleanup();
-        this->type_ = value_t::local_date;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->local_date_, ld);
-        return *this;
-    }
-    basic_value(const local_date& ld, std::vector<std::string> com)
-        : type_(value_t::local_date),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->local_date_, ld);
-    }
-
-    // local time ===========================================================
-
-    basic_value(const local_time& lt)
-        : type_(value_t::local_time),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->local_time_, lt);
-    }
-    basic_value(const local_time& lt, std::vector<std::string> com)
-        : type_(value_t::local_time),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->local_time_, lt);
-    }
-    basic_value& operator=(const local_time& lt)
-    {
-        this->cleanup();
-        this->type_ = value_t::local_time;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->local_time_, lt);
-        return *this;
-    }
-
-    template<typename Rep, typename Period>
-    basic_value(const std::chrono::duration<Rep, Period>& dur)
-        : type_(value_t::local_time),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->local_time_, local_time(dur));
-    }
-    template<typename Rep, typename Period>
-    basic_value(const std::chrono::duration<Rep, Period>& dur,
-                std::vector<std::string> com)
-        : type_(value_t::local_time),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->local_time_, local_time(dur));
-    }
-    template<typename Rep, typename Period>
-    basic_value& operator=(const std::chrono::duration<Rep, Period>& dur)
-    {
-        this->cleanup();
-        this->type_ = value_t::local_time;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->local_time_, local_time(dur));
-        return *this;
-    }
-
-    // local datetime =======================================================
-
-    basic_value(const local_datetime& ldt)
-        : type_(value_t::local_datetime),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->local_datetime_, ldt);
-    }
-    basic_value(const local_datetime& ldt, std::vector<std::string> com)
-        : type_(value_t::local_datetime),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->local_datetime_, ldt);
-    }
-    basic_value& operator=(const local_datetime& ldt)
-    {
-        this->cleanup();
-        this->type_ = value_t::local_datetime;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->local_datetime_, ldt);
-        return *this;
-    }
-
-    // offset datetime ======================================================
-
-    basic_value(const offset_datetime& odt)
-        : type_(value_t::offset_datetime),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->offset_datetime_, odt);
-    }
-    basic_value(const offset_datetime& odt, std::vector<std::string> com)
-        : type_(value_t::offset_datetime),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->offset_datetime_, odt);
-    }
-    basic_value& operator=(const offset_datetime& odt)
-    {
-        this->cleanup();
-        this->type_ = value_t::offset_datetime;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->offset_datetime_, odt);
-        return *this;
-    }
-    basic_value(const std::chrono::system_clock::time_point& tp)
-        : type_(value_t::offset_datetime),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->offset_datetime_, offset_datetime(tp));
-    }
-    basic_value(const std::chrono::system_clock::time_point& tp,
-                std::vector<std::string> com)
-        : type_(value_t::offset_datetime),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->offset_datetime_, offset_datetime(tp));
-    }
-    basic_value& operator=(const std::chrono::system_clock::time_point& tp)
-    {
-        this->cleanup();
-        this->type_ = value_t::offset_datetime;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->offset_datetime_, offset_datetime(tp));
-        return *this;
-    }
-
-    // array ================================================================
-
-    basic_value(const array_type& ary)
-        : type_(value_t::array),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->array_, ary);
-    }
-    basic_value(const array_type& ary, std::vector<std::string> com)
-        : type_(value_t::array),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->array_, ary);
-    }
-    basic_value& operator=(const array_type& ary)
-    {
-        this->cleanup();
-        this->type_ = value_t::array ;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->array_, ary);
-        return *this;
-    }
-
-    // array (initializer_list) ----------------------------------------------
-
-    template<typename T, typename std::enable_if<
-            std::is_convertible<T, value_type>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value(std::initializer_list<T> list)
-        : type_(value_t::array),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        array_type ary(list.begin(), list.end());
-        assigner(this->array_, std::move(ary));
-    }
-    template<typename T, typename std::enable_if<
-            std::is_convertible<T, value_type>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value(std::initializer_list<T> list, std::vector<std::string> com)
-        : type_(value_t::array),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        array_type ary(list.begin(), list.end());
-        assigner(this->array_, std::move(ary));
-    }
-    template<typename T, typename std::enable_if<
-            std::is_convertible<T, value_type>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value& operator=(std::initializer_list<T> list)
-    {
-        this->cleanup();
-        this->type_ = value_t::array;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-
-        array_type ary(list.begin(), list.end());
-        assigner(this->array_, std::move(ary));
-        return *this;
-    }
-
-    // array (STL Containers) ------------------------------------------------
-
-    template<typename T, typename std::enable_if<detail::conjunction<
-            detail::negation<std::is_same<T, array_type>>,
-            detail::is_container<T>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value(const T& list)
-        : type_(value_t::array),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        static_assert(std::is_convertible<typename T::value_type, value_type>::value,
-            "elements of a container should be convertible to toml::value");
-
-        array_type ary(list.size());
-        std::copy(list.begin(), list.end(), ary.begin());
-        assigner(this->array_, std::move(ary));
-    }
-    template<typename T, typename std::enable_if<detail::conjunction<
-            detail::negation<std::is_same<T, array_type>>,
-            detail::is_container<T>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value(const T& list, std::vector<std::string> com)
-        : type_(value_t::array),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        static_assert(std::is_convertible<typename T::value_type, value_type>::value,
-            "elements of a container should be convertible to toml::value");
-
-        array_type ary(list.size());
-        std::copy(list.begin(), list.end(), ary.begin());
-        assigner(this->array_, std::move(ary));
-    }
-    template<typename T, typename std::enable_if<detail::conjunction<
-            detail::negation<std::is_same<T, array_type>>,
-            detail::is_container<T>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value& operator=(const T& list)
-    {
-        static_assert(std::is_convertible<typename T::value_type, value_type>::value,
-            "elements of a container should be convertible to toml::value");
-
-        this->cleanup();
-        this->type_ = value_t::array;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-
-        array_type ary(list.size());
-        std::copy(list.begin(), list.end(), ary.begin());
-        assigner(this->array_, std::move(ary));
-        return *this;
-    }
-
-    // table ================================================================
-
-    basic_value(const table_type& tab)
-        : type_(value_t::table),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        assigner(this->table_, tab);
-    }
-    basic_value(const table_type& tab, std::vector<std::string> com)
-        : type_(value_t::table),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        assigner(this->table_, tab);
-    }
-    basic_value& operator=(const table_type& tab)
-    {
-        this->cleanup();
-        this->type_ = value_t::table;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-        assigner(this->table_, tab);
-        return *this;
-    }
-
-    // initializer-list ------------------------------------------------------
-
-    basic_value(std::initializer_list<std::pair<key, basic_value>> list)
-        : type_(value_t::table),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        table_type tab;
-        for(const auto& elem : list) {tab[elem.first] = elem.second;}
-        assigner(this->table_, std::move(tab));
-    }
-
-    basic_value(std::initializer_list<std::pair<key, basic_value>> list,
-                std::vector<std::string> com)
-        : type_(value_t::table),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        table_type tab;
-        for(const auto& elem : list) {tab[elem.first] = elem.second;}
-        assigner(this->table_, std::move(tab));
-    }
-    basic_value& operator=(std::initializer_list<std::pair<key, basic_value>> list)
-    {
-        this->cleanup();
-        this->type_ = value_t::table;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-
-        table_type tab;
-        for(const auto& elem : list) {tab[elem.first] = elem.second;}
-        assigner(this->table_, std::move(tab));
-        return *this;
-    }
-
-    // other table-like -----------------------------------------------------
-
-    template<typename Map, typename std::enable_if<detail::conjunction<
-            detail::negation<std::is_same<Map, table_type>>,
-            detail::is_map<Map>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value(const Map& mp)
-        : type_(value_t::table),
-          region_info_(std::make_shared<region_base>(region_base{}))
-    {
-        table_type tab;
-        for(const auto& elem : mp) {tab[elem.first] = elem.second;}
-        assigner(this->table_, std::move(tab));
-    }
-    template<typename Map, typename std::enable_if<detail::conjunction<
-            detail::negation<std::is_same<Map, table_type>>,
-            detail::is_map<Map>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value(const Map& mp, std::vector<std::string> com)
-        : type_(value_t::table),
-          region_info_(std::make_shared<region_base>(region_base{})),
-          comments_(std::move(com))
-    {
-        table_type tab;
-        for(const auto& elem : mp) {tab[elem.first] = elem.second;}
-        assigner(this->table_, std::move(tab));
-    }
-    template<typename Map, typename std::enable_if<detail::conjunction<
-            detail::negation<std::is_same<Map, table_type>>,
-            detail::is_map<Map>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value& operator=(const Map& mp)
-    {
-        this->cleanup();
-        this->type_ = value_t::table;
-        this->region_info_ = std::make_shared<region_base>(region_base{});
-
-        table_type tab;
-        for(const auto& elem : mp) {tab[elem.first] = elem.second;}
-        assigner(this->table_, std::move(tab));
-        return *this;
-    }
-
-    // user-defined =========================================================
-
-    // convert using into_toml() method -------------------------------------
-
-    template<typename T, typename std::enable_if<
-        detail::has_into_toml_method<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value(const T& ud): basic_value(ud.into_toml()) {}
-
-    template<typename T, typename std::enable_if<
-        detail::has_into_toml_method<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value(const T& ud, std::vector<std::string> com)
-        : basic_value(ud.into_toml(), std::move(com))
-    {}
-    template<typename T, typename std::enable_if<
-        detail::has_into_toml_method<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value& operator=(const T& ud)
-    {
-        *this = ud.into_toml();
-        return *this;
-    }
-
-    // convert using into<T> struct -----------------------------------------
-
-    template<typename T, std::size_t S = sizeof(::toml::into<T>)>
-    basic_value(const T& ud): basic_value(::toml::into<T>::into_toml(ud)) {}
-    template<typename T, std::size_t S = sizeof(::toml::into<T>)>
-    basic_value(const T& ud, std::vector<std::string> com)
-        : basic_value(::toml::into<T>::into_toml(ud), std::move(com))
-    {}
-    template<typename T, std::size_t S = sizeof(::toml::into<T>)>
-    basic_value& operator=(const T& ud)
-    {
-        *this = ::toml::into<T>::into_toml(ud);
-        return *this;
-    }
-
-    // for internal use ------------------------------------------------------
-    //
-    // Those constructors take detail::region that contains parse result.
-
-    basic_value(boolean b, detail::region reg, std::vector<std::string> cm)
-        : type_(value_t::boolean),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->boolean_, b);
-    }
-    template<typename T, typename std::enable_if<
-        detail::conjunction<
-            std::is_integral<T>, detail::negation<std::is_same<T, boolean>>
-        >::value, std::nullptr_t>::type = nullptr>
-    basic_value(T i, detail::region reg, std::vector<std::string> cm)
-        : type_(value_t::integer),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->integer_, static_cast<integer>(i));
-    }
-    template<typename T, typename std::enable_if<
-        std::is_floating_point<T>::value, std::nullptr_t>::type = nullptr>
-    basic_value(T f, detail::region reg, std::vector<std::string> cm)
-        : type_(value_t::floating),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->floating_, static_cast<floating>(f));
-    }
-    basic_value(toml::string s, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::string),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->string_, std::move(s));
-    }
-    basic_value(const local_date& ld, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::local_date),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->local_date_, ld);
-    }
-    basic_value(const local_time& lt, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::local_time),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->local_time_, lt);
-    }
-    basic_value(const local_datetime& ldt, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::local_datetime),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->local_datetime_, ldt);
-    }
-    basic_value(const offset_datetime& odt, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::offset_datetime),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->offset_datetime_, odt);
-    }
-    basic_value(const array_type& ary, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::array),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->array_, ary);
-    }
-    basic_value(const table_type& tab, detail::region reg,
-                std::vector<std::string> cm)
-        : type_(value_t::table),
-          region_info_(std::make_shared<detail::region>(std::move(reg))),
-          comments_(std::move(cm))
-    {
-        assigner(this->table_, tab);
-    }
-
-    template<typename T, typename std::enable_if<
-        detail::is_exact_toml_type<T, value_type>::value,
-        std::nullptr_t>::type = nullptr>
-    basic_value(std::pair<T, detail::region> parse_result, std::vector<std::string> com)
-        : basic_value(std::move(parse_result.first),
-                      std::move(parse_result.second),
-                      std::move(com))
-    {}
-
-    // type checking and casting ============================================
-
-    template<typename T, typename std::enable_if<
-        detail::is_exact_toml_type<T, value_type>::value,
-        std::nullptr_t>::type = nullptr>
-    bool is() const noexcept
-    {
-        return detail::type_to_enum<T, value_type>::value == this->type_;
-    }
-    bool is(value_t t) const noexcept {return t == this->type_;}
-
-    bool is_uninitialized()   const noexcept {return this->is(value_t::empty          );}
-    bool is_boolean()         const noexcept {return this->is(value_t::boolean        );}
-    bool is_integer()         const noexcept {return this->is(value_t::integer        );}
-    bool is_floating()        const noexcept {return this->is(value_t::floating       );}
-    bool is_string()          const noexcept {return this->is(value_t::string         );}
-    bool is_offset_datetime() const noexcept {return this->is(value_t::offset_datetime);}
-    bool is_local_datetime()  const noexcept {return this->is(value_t::local_datetime );}
-    bool is_local_date()      const noexcept {return this->is(value_t::local_date     );}
-    bool is_local_time()      const noexcept {return this->is(value_t::local_time     );}
-    bool is_array()           const noexcept {return this->is(value_t::array          );}
-    bool is_table()           const noexcept {return this->is(value_t::table          );}
-
-    value_t type() const noexcept {return type_;}
-
-    template<value_t T>
-    typename detail::enum_to_type<T, value_type>::type&       cast() &
-    {
-        if(this->type_ != T)
-        {
-            detail::throw_bad_cast<T>("toml::value::cast: ", this->type_, *this);
-        }
-        return detail::switch_cast<T>::invoke(*this);
-    }
-    template<value_t T>
-    typename detail::enum_to_type<T, value_type>::type const& cast() const&
-    {
-        if(this->type_ != T)
-        {
-            detail::throw_bad_cast<T>("toml::value::cast: ", this->type_, *this);
-        }
-        return detail::switch_cast<T>::invoke(*this);
-    }
-    template<value_t T>
-    typename detail::enum_to_type<T, value_type>::type&&      cast() &&
-    {
-        if(this->type_ != T)
-        {
-            detail::throw_bad_cast<T>("toml::value::cast: ", this->type_, *this);
-        }
-        return detail::switch_cast<T>::invoke(std::move(*this));
-    }
-
-    // ------------------------------------------------------------------------
-    // nothrow version
-
-    boolean         const& as_boolean        (const std::nothrow_t&) const& noexcept {return this->boolean_;}
-    integer         const& as_integer        (const std::nothrow_t&) const& noexcept {return this->integer_;}
-    floating        const& as_floating       (const std::nothrow_t&) const& noexcept {return this->floating_;}
-    string          const& as_string         (const std::nothrow_t&) const& noexcept {return this->string_;}
-    offset_datetime const& as_offset_datetime(const std::nothrow_t&) const& noexcept {return this->offset_datetime_;}
-    local_datetime  const& as_local_datetime (const std::nothrow_t&) const& noexcept {return this->local_datetime_;}
-    local_date      const& as_local_date     (const std::nothrow_t&) const& noexcept {return this->local_date_;}
-    local_time      const& as_local_time     (const std::nothrow_t&) const& noexcept {return this->local_time_;}
-    array_type      const& as_array          (const std::nothrow_t&) const& noexcept {return this->array_.value();}
-    table_type      const& as_table          (const std::nothrow_t&) const& noexcept {return this->table_.value();}
-
-    boolean        & as_boolean        (const std::nothrow_t&) & noexcept {return this->boolean_;}
-    integer        & as_integer        (const std::nothrow_t&) & noexcept {return this->integer_;}
-    floating       & as_floating       (const std::nothrow_t&) & noexcept {return this->floating_;}
-    string         & as_string         (const std::nothrow_t&) & noexcept {return this->string_;}
-    offset_datetime& as_offset_datetime(const std::nothrow_t&) & noexcept {return this->offset_datetime_;}
-    local_datetime & as_local_datetime (const std::nothrow_t&) & noexcept {return this->local_datetime_;}
-    local_date     & as_local_date     (const std::nothrow_t&) & noexcept {return this->local_date_;}
-    local_time     & as_local_time     (const std::nothrow_t&) & noexcept {return this->local_time_;}
-    array_type     & as_array          (const std::nothrow_t&) & noexcept {return this->array_.value();}
-    table_type     & as_table          (const std::nothrow_t&) & noexcept {return this->table_.value();}
-
-    boolean        && as_boolean        (const std::nothrow_t&) && noexcept {return std::move(this->boolean_);}
-    integer        && as_integer        (const std::nothrow_t&) && noexcept {return std::move(this->integer_);}
-    floating       && as_floating       (const std::nothrow_t&) && noexcept {return std::move(this->floating_);}
-    string         && as_string         (const std::nothrow_t&) && noexcept {return std::move(this->string_);}
-    offset_datetime&& as_offset_datetime(const std::nothrow_t&) && noexcept {return std::move(this->offset_datetime_);}
-    local_datetime && as_local_datetime (const std::nothrow_t&) && noexcept {return std::move(this->local_datetime_);}
-    local_date     && as_local_date     (const std::nothrow_t&) && noexcept {return std::move(this->local_date_);}
-    local_time     && as_local_time     (const std::nothrow_t&) && noexcept {return std::move(this->local_time_);}
-    array_type     && as_array          (const std::nothrow_t&) && noexcept {return std::move(this->array_.value());}
-    table_type     && as_table          (const std::nothrow_t&) && noexcept {return std::move(this->table_.value());}
-
-    // ========================================================================
-    // throw version
-    // ------------------------------------------------------------------------
-    // const reference {{{
-
-    boolean const& as_boolean() const&
-    {
-        if(this->type_ != value_t::boolean)
-        {
-            detail::throw_bad_cast<value_t::boolean>(
-                    "toml::value::as_boolean(): ", this->type_, *this);
-        }
-        return this->boolean_;
-    }
-    integer const& as_integer() const&
-    {
-        if(this->type_ != value_t::integer)
-        {
-            detail::throw_bad_cast<value_t::integer>(
-                    "toml::value::as_integer(): ", this->type_, *this);
-        }
-        return this->integer_;
-    }
-    floating const& as_floating() const&
-    {
-        if(this->type_ != value_t::floating)
-        {
-            detail::throw_bad_cast<value_t::floating>(
-                    "toml::value::as_floating(): ", this->type_, *this);
-        }
-        return this->floating_;
-    }
-    string const& as_string() const&
-    {
-        if(this->type_ != value_t::string)
-        {
-            detail::throw_bad_cast<value_t::string>(
-                    "toml::value::as_string(): ", this->type_, *this);
-        }
-        return this->string_;
-    }
-    offset_datetime const& as_offset_datetime() const&
-    {
-        if(this->type_ != value_t::offset_datetime)
-        {
-            detail::throw_bad_cast<value_t::offset_datetime>(
-                    "toml::value::as_offset_datetime(): ", this->type_, *this);
-        }
-        return this->offset_datetime_;
-    }
-    local_datetime const& as_local_datetime() const&
-    {
-        if(this->type_ != value_t::local_datetime)
-        {
-            detail::throw_bad_cast<value_t::local_datetime>(
-                    "toml::value::as_local_datetime(): ", this->type_, *this);
-        }
-        return this->local_datetime_;
-    }
-    local_date const& as_local_date() const&
-    {
-        if(this->type_ != value_t::local_date)
-        {
-            detail::throw_bad_cast<value_t::local_date>(
-                    "toml::value::as_local_date(): ", this->type_, *this);
-        }
-        return this->local_date_;
-    }
-    local_time const& as_local_time() const&
-    {
-        if(this->type_ != value_t::local_time)
-        {
-            detail::throw_bad_cast<value_t::local_time>(
-                    "toml::value::as_local_time(): ", this->type_, *this);
-        }
-        return this->local_time_;
-    }
-    array_type const& as_array() const&
-    {
-        if(this->type_ != value_t::array)
-        {
-            detail::throw_bad_cast<value_t::array>(
-                    "toml::value::as_array(): ", this->type_, *this);
-        }
-        return this->array_.value();
-    }
-    table_type const& as_table() const&
-    {
-        if(this->type_ != value_t::table)
-        {
-            detail::throw_bad_cast<value_t::table>(
-                    "toml::value::as_table(): ", this->type_, *this);
-        }
-        return this->table_.value();
-    }
-    // }}}
-    // ------------------------------------------------------------------------
-    // nonconst reference {{{
-
-    boolean & as_boolean() &
-    {
-        if(this->type_ != value_t::boolean)
-        {
-            detail::throw_bad_cast<value_t::boolean>(
-                    "toml::value::as_boolean(): ", this->type_, *this);
-        }
-        return this->boolean_;
-    }
-    integer & as_integer() &
-    {
-        if(this->type_ != value_t::integer)
-        {
-            detail::throw_bad_cast<value_t::integer>(
-                    "toml::value::as_integer(): ", this->type_, *this);
-        }
-        return this->integer_;
-    }
-    floating & as_floating() &
-    {
-        if(this->type_ != value_t::floating)
-        {
-            detail::throw_bad_cast<value_t::floating>(
-                    "toml::value::as_floating(): ", this->type_, *this);
-        }
-        return this->floating_;
-    }
-    string & as_string() &
-    {
-        if(this->type_ != value_t::string)
-        {
-            detail::throw_bad_cast<value_t::string>(
-                    "toml::value::as_string(): ", this->type_, *this);
-        }
-        return this->string_;
-    }
-    offset_datetime & as_offset_datetime() &
-    {
-        if(this->type_ != value_t::offset_datetime)
-        {
-            detail::throw_bad_cast<value_t::offset_datetime>(
-                    "toml::value::as_offset_datetime(): ", this->type_, *this);
-        }
-        return this->offset_datetime_;
-    }
-    local_datetime & as_local_datetime() &
-    {
-        if(this->type_ != value_t::local_datetime)
-        {
-            detail::throw_bad_cast<value_t::local_datetime>(
-                    "toml::value::as_local_datetime(): ", this->type_, *this);
-        }
-        return this->local_datetime_;
-    }
-    local_date & as_local_date() &
-    {
-        if(this->type_ != value_t::local_date)
-        {
-            detail::throw_bad_cast<value_t::local_date>(
-                    "toml::value::as_local_date(): ", this->type_, *this);
-        }
-        return this->local_date_;
-    }
-    local_time & as_local_time() &
-    {
-        if(this->type_ != value_t::local_time)
-        {
-            detail::throw_bad_cast<value_t::local_time>(
-                    "toml::value::as_local_time(): ", this->type_, *this);
-        }
-        return this->local_time_;
-    }
-    array_type & as_array() &
-    {
-        if(this->type_ != value_t::array)
-        {
-            detail::throw_bad_cast<value_t::array>(
-                    "toml::value::as_array(): ", this->type_, *this);
-        }
-        return this->array_.value();
-    }
-    table_type & as_table() &
-    {
-        if(this->type_ != value_t::table)
-        {
-            detail::throw_bad_cast<value_t::table>(
-                    "toml::value::as_table(): ", this->type_, *this);
-        }
-        return this->table_.value();
-    }
-
-    // }}}
-    // ------------------------------------------------------------------------
-    // rvalue reference {{{
-
-    boolean && as_boolean() &&
-    {
-        if(this->type_ != value_t::boolean)
-        {
-            detail::throw_bad_cast<value_t::boolean>(
-                    "toml::value::as_boolean(): ", this->type_, *this);
-        }
-        return std::move(this->boolean_);
-    }
-    integer && as_integer() &&
-    {
-        if(this->type_ != value_t::integer)
-        {
-            detail::throw_bad_cast<value_t::integer>(
-                    "toml::value::as_integer(): ", this->type_, *this);
-        }
-        return std::move(this->integer_);
-    }
-    floating && as_floating() &&
-    {
-        if(this->type_ != value_t::floating)
-        {
-            detail::throw_bad_cast<value_t::floating>(
-                    "toml::value::as_floating(): ", this->type_, *this);
-        }
-        return std::move(this->floating_);
-    }
-    string && as_string() &&
-    {
-        if(this->type_ != value_t::string)
-        {
-            detail::throw_bad_cast<value_t::string>(
-                    "toml::value::as_string(): ", this->type_, *this);
-        }
-        return std::move(this->string_);
-    }
-    offset_datetime && as_offset_datetime() &&
-    {
-        if(this->type_ != value_t::offset_datetime)
-        {
-            detail::throw_bad_cast<value_t::offset_datetime>(
-                    "toml::value::as_offset_datetime(): ", this->type_, *this);
-        }
-        return std::move(this->offset_datetime_);
-    }
-    local_datetime && as_local_datetime() &&
-    {
-        if(this->type_ != value_t::local_datetime)
-        {
-            detail::throw_bad_cast<value_t::local_datetime>(
-                    "toml::value::as_local_datetime(): ", this->type_, *this);
-        }
-        return std::move(this->local_datetime_);
-    }
-    local_date && as_local_date() &&
-    {
-        if(this->type_ != value_t::local_date)
-        {
-            detail::throw_bad_cast<value_t::local_date>(
-                    "toml::value::as_local_date(): ", this->type_, *this);
-        }
-        return std::move(this->local_date_);
-    }
-    local_time && as_local_time() &&
-    {
-        if(this->type_ != value_t::local_time)
-        {
-            detail::throw_bad_cast<value_t::local_time>(
-                    "toml::value::as_local_time(): ", this->type_, *this);
-        }
-        return std::move(this->local_time_);
-    }
-    array_type && as_array() &&
-    {
-        if(this->type_ != value_t::array)
-        {
-            detail::throw_bad_cast<value_t::array>(
-                    "toml::value::as_array(): ", this->type_, *this);
-        }
-        return std::move(this->array_.value());
-    }
-    table_type && as_table() &&
-    {
-        if(this->type_ != value_t::table)
-        {
-            detail::throw_bad_cast<value_t::table>(
-                    "toml::value::as_table(): ", this->type_, *this);
-        }
-        return std::move(this->table_.value());
-    }
-    // }}}
-
-    // accessors =============================================================
-    //
-    // may throw type_error or out_of_range
-    //
-    value_type&       at(const key& k)
-    {
-        if(!this->is_table())
-        {
-            detail::throw_bad_cast<value_t::table>(
-                "toml::value::at(key): ", this->type_, *this);
-        }
-        if(this->as_table(std::nothrow).count(k) == 0)
-        {
-            detail::throw_key_not_found_error(*this, k);
-        }
-        return this->as_table(std::nothrow).at(k);
-    }
-    value_type const& at(const key& k) const
-    {
-        if(!this->is_table())
-        {
-            detail::throw_bad_cast<value_t::table>(
-                "toml::value::at(key): ", this->type_, *this);
-        }
-        if(this->as_table(std::nothrow).count(k) == 0)
-        {
-            detail::throw_key_not_found_error(*this, k);
-        }
-        return this->as_table(std::nothrow).at(k);
-    }
-    value_type&       operator[](const key& k)
-    {
-        if(this->is_uninitialized())
-        {
-            *this = table_type{};
-        }
-        else if(!this->is_table()) // initialized, but not a table
-        {
-            detail::throw_bad_cast<value_t::table>(
-                "toml::value::operator[](key): ", this->type_, *this);
-        }
-        return this->as_table(std::nothrow)[k];
-    }
-
-    value_type&       at(const std::size_t idx)
-    {
-        if(!this->is_array())
-        {
-            detail::throw_bad_cast<value_t::array>(
-                "toml::value::at(idx): ", this->type_, *this);
-        }
-        if(this->as_array(std::nothrow).size() <= idx)
-        {
-            throw std::out_of_range(detail::format_underline(
-                "toml::value::at(idx): no element corresponding to the index", {
-                    {this->location(), concat_to_string("the length is ",
-                        this->as_array(std::nothrow).size(),
-                        ", and the specified index is ", idx)}
-                }));
-        }
-        return this->as_array().at(idx);
-    }
-    value_type const& at(const std::size_t idx) const
-    {
-        if(!this->is_array())
-        {
-            detail::throw_bad_cast<value_t::array>(
-                "toml::value::at(idx): ", this->type_, *this);
-        }
-        if(this->as_array(std::nothrow).size() <= idx)
-        {
-            throw std::out_of_range(detail::format_underline(
-                "toml::value::at(idx): no element corresponding to the index", {
-                    {this->location(), concat_to_string("the length is ",
-                        this->as_array(std::nothrow).size(),
-                        ", and the specified index is ", idx)}
-                }));
-        }
-        return this->as_array(std::nothrow).at(idx);
-    }
-
-    value_type&       operator[](const std::size_t idx) noexcept
-    {
-        // no check...
-        return this->as_array(std::nothrow)[idx];
-    }
-    value_type const& operator[](const std::size_t idx) const noexcept
-    {
-        // no check...
-        return this->as_array(std::nothrow)[idx];
-    }
-
-    void push_back(const value_type& x)
-    {
-        if(!this->is_array())
-        {
-            detail::throw_bad_cast<value_t::array>(
-                "toml::value::push_back(value): ", this->type_, *this);
-        }
-        this->as_array(std::nothrow).push_back(x);
-        return;
-    }
-    void push_back(value_type&& x)
-    {
-        if(!this->is_array())
-        {
-            detail::throw_bad_cast<value_t::array>(
-                "toml::value::push_back(value): ", this->type_, *this);
-        }
-        this->as_array(std::nothrow).push_back(std::move(x));
-        return;
-    }
-
-    template<typename ... Ts>
-    value_type& emplace_back(Ts&& ... args)
-    {
-        if(!this->is_array())
-        {
-            detail::throw_bad_cast<value_t::array>(
-                "toml::value::emplace_back(...): ", this->type_, *this);
-        }
-        this->as_array(std::nothrow).emplace_back(std::forward<Ts>(args) ...);
-        return this->as_array(std::nothrow).back();
-    }
-
-    std::size_t size() const
-    {
-        switch(this->type_)
-        {
-            case value_t::array:
-            {
-                return this->as_array(std::nothrow).size();
-            }
-            case value_t::table:
-            {
-                return this->as_table(std::nothrow).size();
-            }
-            case value_t::string:
-            {
-                return this->as_string(std::nothrow).str.size();
-            }
-            default:
-            {
-                throw type_error(detail::format_underline(
-                    "toml::value::size(): bad_cast to container types", {
-                        {this->location(),
-                         concat_to_string("the actual type is ", this->type_)}
-                    }), this->location());
-            }
-        }
-    }
-
-    std::size_t count(const key_type& k) const
-    {
-        if(!this->is_table())
-        {
-            detail::throw_bad_cast<value_t::table>(
-                "toml::value::count(key): ", this->type_, *this);
-        }
-        return this->as_table(std::nothrow).count(k);
-    }
-
-    bool contains(const key_type& k) const
-    {
-        if(!this->is_table())
-        {
-            detail::throw_bad_cast<value_t::table>(
-                "toml::value::contains(key): ", this->type_, *this);
-        }
-        return (this->as_table(std::nothrow).count(k) != 0);
-    }
-
-    source_location location() const
-    {
-        return source_location(this->region_info_.get());
-    }
-
-    comment_type const& comments() const noexcept {return this->comments_;}
-    comment_type&       comments()       noexcept {return this->comments_;}
-
-  private:
-
-    void cleanup() noexcept
-    {
-        switch(this->type_)
-        {
-            case value_t::string  : {string_.~string();       return;}
-            case value_t::array   : {array_.~array_storage(); return;}
-            case value_t::table   : {table_.~table_storage(); return;}
-            default              : return;
-        }
-    }
-
-    // for error messages
-    template<typename Value>
-    friend region_base const* detail::get_region(const Value& v);
-
-    template<typename Value>
-    friend void detail::change_region(Value& v, detail::region reg);
-
-  private:
-
-    using array_storage = detail::storage<array_type>;
-    using table_storage = detail::storage<table_type>;
-
-    value_t type_;
-    union
-    {
-        boolean         boolean_;
-        integer         integer_;
-        floating        floating_;
-        string          string_;
-        offset_datetime offset_datetime_;
-        local_datetime  local_datetime_;
-        local_date      local_date_;
-        local_time      local_time_;
-        array_storage   array_;
-        table_storage   table_;
-    };
-    std::shared_ptr<region_base> region_info_;
-    comment_type                 comments_;
-};
-
-// default toml::value and default array/table.
-// TOML11_DEFAULT_COMMENT_STRATEGY is defined in comments.hpp
-using value = basic_value<TOML11_DEFAULT_COMMENT_STRATEGY, std::unordered_map, std::vector>;
-using array = typename value::array_type;
-using table = typename value::table_type;
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-inline bool
-operator==(const basic_value<C, T, A>& lhs, const basic_value<C, T, A>& rhs)
-{
-    if(lhs.type()     != rhs.type())     {return false;}
-    if(lhs.comments() != rhs.comments()) {return false;}
-
-    switch(lhs.type())
-    {
-        case value_t::boolean  :
-        {
-            return lhs.as_boolean() == rhs.as_boolean();
-        }
-        case value_t::integer  :
-        {
-            return lhs.as_integer() == rhs.as_integer();
-        }
-        case value_t::floating :
-        {
-            return lhs.as_floating() == rhs.as_floating();
-        }
-        case value_t::string   :
-        {
-            return lhs.as_string() == rhs.as_string();
-        }
-        case value_t::offset_datetime:
-        {
-            return lhs.as_offset_datetime() == rhs.as_offset_datetime();
-        }
-        case value_t::local_datetime:
-        {
-            return lhs.as_local_datetime() == rhs.as_local_datetime();
-        }
-        case value_t::local_date:
-        {
-            return lhs.as_local_date() == rhs.as_local_date();
-        }
-        case value_t::local_time:
-        {
-            return lhs.as_local_time() == rhs.as_local_time();
-        }
-        case value_t::array    :
-        {
-            return lhs.as_array() == rhs.as_array();
-        }
-        case value_t::table    :
-        {
-            return lhs.as_table() == rhs.as_table();
-        }
-        case value_t::empty    : {return true; }
-        default:                 {return false;}
-    }
-}
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-inline bool operator!=(const basic_value<C, T, A>& lhs, const basic_value<C, T, A>& rhs)
-{
-    return !(lhs == rhs);
-}
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-typename std::enable_if<detail::conjunction<
-    detail::is_comparable<typename basic_value<C, T, A>::array_type>,
-    detail::is_comparable<typename basic_value<C, T, A>::table_type>
-    >::value, bool>::type
-operator<(const basic_value<C, T, A>& lhs, const basic_value<C, T, A>& rhs)
-{
-    if(lhs.type() != rhs.type()){return (lhs.type() < rhs.type());}
-    switch(lhs.type())
-    {
-        case value_t::boolean  :
-        {
-            return lhs.as_boolean() <  rhs.as_boolean() ||
-                  (lhs.as_boolean() == rhs.as_boolean() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::integer  :
-        {
-            return lhs.as_integer() <  rhs.as_integer() ||
-                  (lhs.as_integer() == rhs.as_integer() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::floating :
-        {
-            return lhs.as_floating() <  rhs.as_floating() ||
-                  (lhs.as_floating() == rhs.as_floating() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::string   :
-        {
-            return lhs.as_string() <  rhs.as_string() ||
-                  (lhs.as_string() == rhs.as_string() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::offset_datetime:
-        {
-            return lhs.as_offset_datetime() <  rhs.as_offset_datetime() ||
-                  (lhs.as_offset_datetime() == rhs.as_offset_datetime() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::local_datetime:
-        {
-            return lhs.as_local_datetime() <  rhs.as_local_datetime() ||
-                  (lhs.as_local_datetime() == rhs.as_local_datetime() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::local_date:
-        {
-            return lhs.as_local_date() <  rhs.as_local_date() ||
-                  (lhs.as_local_date() == rhs.as_local_date() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::local_time:
-        {
-            return lhs.as_local_time() <  rhs.as_local_time() ||
-                  (lhs.as_local_time() == rhs.as_local_time() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::array    :
-        {
-            return lhs.as_array() <  rhs.as_array() ||
-                  (lhs.as_array() == rhs.as_array() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::table    :
-        {
-            return lhs.as_table() <  rhs.as_table() ||
-                  (lhs.as_table() == rhs.as_table() &&
-                   lhs.comments() < rhs.comments());
-        }
-        case value_t::empty    :
-        {
-            return lhs.comments() < rhs.comments();
-        }
-        default:
-        {
-            return lhs.comments() < rhs.comments();
-        }
-    }
-}
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-typename std::enable_if<detail::conjunction<
-    detail::is_comparable<typename basic_value<C, T, A>::array_type>,
-    detail::is_comparable<typename basic_value<C, T, A>::table_type>
-    >::value, bool>::type
-operator<=(const basic_value<C, T, A>& lhs, const basic_value<C, T, A>& rhs)
-{
-    return (lhs < rhs) || (lhs == rhs);
-}
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-typename std::enable_if<detail::conjunction<
-    detail::is_comparable<typename basic_value<C, T, A>::array_type>,
-    detail::is_comparable<typename basic_value<C, T, A>::table_type>
-    >::value, bool>::type
-operator>(const basic_value<C, T, A>& lhs, const basic_value<C, T, A>& rhs)
-{
-    return !(lhs <= rhs);
-}
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-typename std::enable_if<detail::conjunction<
-    detail::is_comparable<typename basic_value<C, T, A>::array_type>,
-    detail::is_comparable<typename basic_value<C, T, A>::table_type>
-    >::value, bool>::type
-operator>=(const basic_value<C, T, A>& lhs, const basic_value<C, T, A>& rhs)
-{
-    return !(lhs < rhs);
-}
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-inline std::string format_error(const std::string& err_msg,
-        const basic_value<C, T, A>& v, const std::string& comment,
-        std::vector<std::string> hints = {},
-        const bool colorize = TOML11_ERROR_MESSAGE_COLORIZED)
-{
-    return detail::format_underline(err_msg, {{v.location(), comment}},
-                                    std::move(hints), colorize);
-}
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-inline std::string format_error(const std::string& err_msg,
-        const toml::basic_value<C, T, A>& v1, const std::string& comment1,
-        const toml::basic_value<C, T, A>& v2, const std::string& comment2,
-        std::vector<std::string> hints = {},
-        const bool colorize = TOML11_ERROR_MESSAGE_COLORIZED)
-{
-    return detail::format_underline(err_msg, {
-            {v1.location(), comment1}, {v2.location(), comment2}
-        }, std::move(hints), colorize);
-}
-
-template<typename C, template<typename ...> class T, template<typename ...> class A>
-inline std::string format_error(const std::string& err_msg,
-        const toml::basic_value<C, T, A>& v1, const std::string& comment1,
-        const toml::basic_value<C, T, A>& v2, const std::string& comment2,
-        const toml::basic_value<C, T, A>& v3, const std::string& comment3,
-        std::vector<std::string> hints = {},
-        const bool colorize = TOML11_ERROR_MESSAGE_COLORIZED)
-{
-    return detail::format_underline(err_msg, {{v1.location(), comment1},
-            {v2.location(), comment2}, {v3.location(), comment3}
-        }, std::move(hints), colorize);
-}
-
-template<typename Visitor, typename C,
-         template<typename ...> class T, template<typename ...> class A>
-detail::return_type_of_t<Visitor, const toml::boolean&>
-visit(Visitor&& visitor, const toml::basic_value<C, T, A>& v)
-{
-    switch(v.type())
-    {
-        case value_t::boolean        : {return visitor(v.as_boolean        ());}
-        case value_t::integer        : {return visitor(v.as_integer        ());}
-        case value_t::floating       : {return visitor(v.as_floating       ());}
-        case value_t::string         : {return visitor(v.as_string         ());}
-        case value_t::offset_datetime: {return visitor(v.as_offset_datetime());}
-        case value_t::local_datetime : {return visitor(v.as_local_datetime ());}
-        case value_t::local_date     : {return visitor(v.as_local_date     ());}
-        case value_t::local_time     : {return visitor(v.as_local_time     ());}
-        case value_t::array          : {return visitor(v.as_array          ());}
-        case value_t::table          : {return visitor(v.as_table          ());}
-        case value_t::empty          : break;
-        default: break;
-    }
-    throw std::runtime_error(format_error("[error] toml::visit: toml::basic_value "
-            "does not have any valid basic_value.", v, "here"));
-}
-
-template<typename Visitor, typename C,
-         template<typename ...> class T, template<typename ...> class A>
-detail::return_type_of_t<Visitor, toml::boolean&>
-visit(Visitor&& visitor, toml::basic_value<C, T, A>& v)
-{
-    switch(v.type())
-    {
-        case value_t::boolean        : {return visitor(v.as_boolean        ());}
-        case value_t::integer        : {return visitor(v.as_integer        ());}
-        case value_t::floating       : {return visitor(v.as_floating       ());}
-        case value_t::string         : {return visitor(v.as_string         ());}
-        case value_t::offset_datetime: {return visitor(v.as_offset_datetime());}
-        case value_t::local_datetime : {return visitor(v.as_local_datetime ());}
-        case value_t::local_date     : {return visitor(v.as_local_date     ());}
-        case value_t::local_time     : {return visitor(v.as_local_time     ());}
-        case value_t::array          : {return visitor(v.as_array          ());}
-        case value_t::table          : {return visitor(v.as_table          ());}
-        case value_t::empty          : break;
-        default: break;
-    }
-    throw std::runtime_error(format_error("[error] toml::visit: toml::basic_value "
-            "does not have any valid basic_value.", v, "here"));
-}
-
-template<typename Visitor, typename C,
-         template<typename ...> class T, template<typename ...> class A>
-detail::return_type_of_t<Visitor, toml::boolean&&>
-visit(Visitor&& visitor, toml::basic_value<C, T, A>&& v)
-{
-    switch(v.type())
-    {
-        case value_t::boolean        : {return visitor(std::move(v.as_boolean        ()));}
-        case value_t::integer        : {return visitor(std::move(v.as_integer        ()));}
-        case value_t::floating       : {return visitor(std::move(v.as_floating       ()));}
-        case value_t::string         : {return visitor(std::move(v.as_string         ()));}
-        case value_t::offset_datetime: {return visitor(std::move(v.as_offset_datetime()));}
-        case value_t::local_datetime : {return visitor(std::move(v.as_local_datetime ()));}
-        case value_t::local_date     : {return visitor(std::move(v.as_local_date     ()));}
-        case value_t::local_time     : {return visitor(std::move(v.as_local_time     ()));}
-        case value_t::array          : {return visitor(std::move(v.as_array          ()));}
-        case value_t::table          : {return visitor(std::move(v.as_table          ()));}
-        case value_t::empty          : break;
-        default: break;
-    }
-    throw std::runtime_error(format_error("[error] toml::visit: toml::basic_value "
-            "does not have any valid basic_value.", v, "here"));
-}
-
-}// toml
-#endif// TOML11_VALUE
diff --git a/tests/functional/add.sh b/tests/functional/add.sh
old mode 100644
new mode 100755
index a4bb0e225ab..3b37ee7d47f
--- a/tests/functional/add.sh
+++ b/tests/functional/add.sh
@@ -1,10 +1,12 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 path1=$(nix-store --add ./dummy)
-echo $path1
+echo "$path1"
 
 path2=$(nix-store --add-fixed sha256 --recursive ./dummy)
-echo $path2
+echo "$path2"
 
 if test "$path1" != "$path2"; then
     echo "nix-store --add and --add-fixed mismatch"
@@ -12,24 +14,24 @@ if test "$path1" != "$path2"; then
 fi
 
 path3=$(nix-store --add-fixed sha256 ./dummy)
-echo $path3
+echo "$path3"
 test "$path1" != "$path3" || exit 1
 
 path4=$(nix-store --add-fixed sha1 --recursive ./dummy)
-echo $path4
+echo "$path4"
 test "$path1" != "$path4" || exit 1
 
-hash1=$(nix-store -q --hash $path1)
-echo $hash1
+hash1=$(nix-store -q --hash "$path1")
+echo "$hash1"
 
 hash2=$(nix-hash --type sha256 --base32 ./dummy)
-echo $hash2
+echo "$hash2"
 
 test "$hash1" = "sha256:$hash2"
 
 #### New style commands
 
-clearStore
+clearStoreIfPossible
 
 (
     path1=$(nix store add ./dummy)
diff --git a/tests/functional/bash-profile.sh b/tests/functional/bash-profile.sh
old mode 100644
new mode 100755
index 3faeaaba1dc..4228d4a20e5
--- a/tests/functional/bash-profile.sh
+++ b/tests/functional/bash-profile.sh
@@ -1,9 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-sed -e "s|@localstatedir@|$TEST_ROOT/profile-var|g" -e "s|@coreutils@|$coreutils|g" < ../../scripts/nix-profile.sh.in > $TEST_ROOT/nix-profile.sh
+sed -e "s|@localstatedir@|$TEST_ROOT/profile-var|g" -e "s|@coreutils@|$coreutils|g" < ../../scripts/nix-profile.sh.in > "$TEST_ROOT"/nix-profile.sh
 
 user=$(whoami)
-rm -rf $TEST_HOME $TEST_ROOT/profile-var
-mkdir -p $TEST_HOME
+rm -rf "$TEST_HOME" "$TEST_ROOT/profile-var"
+mkdir -p "$TEST_HOME"
 USER=$user $SHELL -e -c ". $TEST_ROOT/nix-profile.sh; set"
 USER=$user $SHELL -e -c ". $TEST_ROOT/nix-profile.sh" # test idempotency
diff --git a/tests/functional/binary-cache-build-remote.sh b/tests/functional/binary-cache-build-remote.sh
old mode 100644
new mode 100755
index 81cd21a4aa8..5046d0064de
--- a/tests/functional/binary-cache-build-remote.sh
+++ b/tests/functional/binary-cache-build-remote.sh
@@ -1,6 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+TODO_NixOS
+
+clearStoreIfPossible
 clearCacheCache
 
 # Fails without remote builders
@@ -10,7 +14,7 @@ clearCacheCache
 outPath=$(nix-build --store "file://$cacheDir" --builders 'auto - - 1 1' -j0 dependencies.nix)
 
 # Test that the path exactly exists in the destination store.
-nix path-info --store "file://$cacheDir" $outPath
+nix path-info --store "file://$cacheDir" "$outPath"
 
 # Succeeds without any build capability because no-op
 nix-build --store "file://$cacheDir" -j0 dependencies.nix
diff --git a/tests/functional/binary-cache.sh b/tests/functional/binary-cache.sh
old mode 100644
new mode 100755
index 2a8d5ccdb18..6a177b65775
--- a/tests/functional/binary-cache.sh
+++ b/tests/functional/binary-cache.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 needLocalStore "'--no-require-sigs' can’t be used with the daemon"
 
 # We can produce drvs directly into the binary cache
@@ -12,9 +16,9 @@ clearStore
 clearCache
 outPath=$(nix-build dependencies.nix --no-out-link)
 
-nix copy --to file://$cacheDir $outPath
+nix copy --to "file://$cacheDir" "$outPath"
 
-readarray -t paths < <(nix path-info --all --json --store file://$cacheDir | jq 'keys|sort|.[]' -r)
+readarray -t paths < <(nix path-info --all --json --store "file://$cacheDir" | jq 'keys|sort|.[]' -r)
 [[ "${#paths[@]}" -eq 3 ]]
 for path in "${paths[@]}"; do
     [[ "$path" =~ -dependencies-input-0$ ]] \
@@ -23,16 +27,16 @@ for path in "${paths[@]}"; do
 done
 
 # Test copying build logs to the binary cache.
-expect 1 nix log --store file://$cacheDir $outPath 2>&1 | grep 'is not available'
-nix store copy-log --to file://$cacheDir $outPath
-nix log --store file://$cacheDir $outPath | grep FOO
-rm -rf $TEST_ROOT/var/log/nix
-expect 1 nix log $outPath 2>&1 | grep 'is not available'
-nix log --substituters file://$cacheDir $outPath | grep FOO
+expect 1 nix log --store "file://$cacheDir" "$outPath" 2>&1 | grep 'is not available'
+nix store copy-log --to "file://$cacheDir" "$outPath"
+nix log --store "file://$cacheDir" "$outPath" | grep FOO
+rm -rf "$TEST_ROOT/var/log/nix"
+expect 1 nix log "$outPath" 2>&1 | grep 'is not available'
+nix log --substituters "file://$cacheDir" "$outPath" | grep FOO
 
 # Test copying build logs from the binary cache.
-nix store copy-log --from file://$cacheDir $(nix-store -qd $outPath)^'*'
-nix log $outPath | grep FOO
+nix store copy-log --from "file://$cacheDir" "$(nix-store -qd "$outPath")"^'*'
+nix log "$outPath" | grep FOO
 
 basicDownloadTests() {
     # No uploading tests bcause upload with force HTTP doesn't work.
@@ -44,15 +48,15 @@ basicDownloadTests() {
 
     nix-env --substituters "file://$cacheDir" -f dependencies.nix -qas \* | grep -- "---"
 
-    nix-store --substituters "file://$cacheDir" --no-require-sigs -r $outPath
+    nix-store --substituters "file://$cacheDir" --no-require-sigs -r "$outPath"
 
-    [ -x $outPath/program ]
+    [ -x "$outPath/program" ]
 
 
     # But with the right configuration, "nix-env -qas" should also work.
     clearStore
     clearCacheCache
-    echo "WantMassQuery: 1" >> $cacheDir/nix-cache-info
+    echo "WantMassQuery: 1" >> "$cacheDir/nix-cache-info"
 
     nix-env --substituters "file://$cacheDir" -f dependencies.nix -qas \* | grep -- "--S"
     nix-env --substituters "file://$cacheDir" -f dependencies.nix -qas \* | grep -- "--S"
@@ -60,12 +64,12 @@ basicDownloadTests() {
     x=$(nix-env -f dependencies.nix -qas \* --prebuilt-only)
     [ -z "$x" ]
 
-    nix-store --substituters "file://$cacheDir" --no-require-sigs -r $outPath
+    nix-store --substituters "file://$cacheDir" --no-require-sigs -r "$outPath"
 
-    nix-store --check-validity $outPath
-    nix-store -qR $outPath | grep input-2
+    nix-store --check-validity "$outPath"
+    nix-store -qR "$outPath" | grep input-2
 
-    echo "WantMassQuery: 0" >> $cacheDir/nix-cache-info
+    echo "WantMassQuery: 0" >> "$cacheDir/nix-cache-info"
 }
 
 
@@ -81,22 +85,22 @@ basicDownloadTests
 # Test whether Nix notices if the NAR doesn't match the hash in the NAR info.
 clearStore
 
-nar=$(ls $cacheDir/nar/*.nar.xz | head -n1)
-mv $nar $nar.good
-mkdir -p $TEST_ROOT/empty
-nix-store --dump $TEST_ROOT/empty | xz > $nar
+nar=$(find "$cacheDir/nar/" -type f -name "*.nar.xz" | head -n1)
+mv "$nar" "$nar".good
+mkdir -p "$TEST_ROOT/empty"
+nix-store --dump "$TEST_ROOT/empty" | xz > "$nar"
 
-expect 1 nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o $TEST_ROOT/result 2>&1 | tee $TEST_ROOT/log
-grepQuiet "hash mismatch" $TEST_ROOT/log
+expect 1 nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o "$TEST_ROOT/result" 2>&1 | tee "$TEST_ROOT/log"
+grepQuiet "hash mismatch" "$TEST_ROOT/log"
 
-mv $nar.good $nar
+mv "$nar".good "$nar"
 
 
 # Test whether this unsigned cache is rejected if the user requires signed caches.
 clearStore
 clearCacheCache
 
-if nix-store --substituters "file://$cacheDir" -r $outPath; then
+if nix-store --substituters "file://$cacheDir" -r "$outPath"; then
     echo "unsigned binary cache incorrectly accepted"
     exit 1
 fi
@@ -105,131 +109,134 @@ fi
 # Test whether fallback works if a NAR has disappeared. This does not require --fallback.
 clearStore
 
-mv $cacheDir/nar $cacheDir/nar2
+mv "$cacheDir/nar" "$cacheDir/nar2"
 
-nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o $TEST_ROOT/result
+nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o "$TEST_ROOT/result"
 
-mv $cacheDir/nar2 $cacheDir/nar
+mv "$cacheDir/nar2" "$cacheDir/nar"
 
 
 # Test whether fallback works if a NAR is corrupted. This does require --fallback.
 clearStore
 
-mv $cacheDir/nar $cacheDir/nar2
-mkdir $cacheDir/nar
-for i in $(cd $cacheDir/nar2 && echo *); do touch $cacheDir/nar/$i; done
+mv "$cacheDir/nar" "$cacheDir/nar2"
+mkdir "$cacheDir/nar"
+for i in $(cd "$cacheDir/nar2" && echo *); do touch "$cacheDir"/nar/"$i"; done
 
-(! nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o $TEST_ROOT/result)
+(! nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o "$TEST_ROOT/result")
 
-nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o $TEST_ROOT/result --fallback
+nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o "$TEST_ROOT/result" --fallback
 
-rm -rf $cacheDir/nar
-mv $cacheDir/nar2 $cacheDir/nar
+rm -rf "$cacheDir/nar"
+mv "$cacheDir/nar2" "$cacheDir/nar"
 
 
 # Test whether building works if the binary cache contains an
 # incomplete closure.
 clearStore
 
-rm -v $(grep -l "StorePath:.*dependencies-input-2" $cacheDir/*.narinfo)
+rm -v "$(grep -l "StorePath:.*dependencies-input-2" "$cacheDir"/*.narinfo)"
 
-nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o $TEST_ROOT/result 2>&1 | tee $TEST_ROOT/log
-grepQuiet "copying path.*input-0" $TEST_ROOT/log
-grepQuiet "copying path.*input-2" $TEST_ROOT/log
-grepQuiet "copying path.*top" $TEST_ROOT/log
+nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o "$TEST_ROOT/result" 2>&1 | tee "$TEST_ROOT/log"
+grepQuiet "copying path.*input-0" "$TEST_ROOT/log"
+grepQuiet "copying path.*input-2" "$TEST_ROOT/log"
+grepQuiet "copying path.*top" "$TEST_ROOT/log"
 
 
 # Idem, but without cached .narinfo.
 clearStore
 clearCacheCache
 
-nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o $TEST_ROOT/result 2>&1 | tee $TEST_ROOT/log
-grepQuiet "don't know how to build" $TEST_ROOT/log
-grepQuiet "building.*input-1" $TEST_ROOT/log
-grepQuiet "building.*input-2" $TEST_ROOT/log
-grepQuiet "copying path.*input-0" $TEST_ROOT/log
-grepQuiet "copying path.*top" $TEST_ROOT/log
+nix-build --substituters "file://$cacheDir" --no-require-sigs dependencies.nix -o "$TEST_ROOT/result" 2>&1 | tee "$TEST_ROOT/log"
+grepQuiet "don't know how to build" "$TEST_ROOT/log"
+grepQuiet "building.*input-1" "$TEST_ROOT/log"
+grepQuiet "building.*input-2" "$TEST_ROOT/log"
+grepQuiet "copying path.*input-0" "$TEST_ROOT/log"
+grepQuiet "copying path.*top" "$TEST_ROOT/log"
 
 
 # Create a signed binary cache.
 clearCache
 clearCacheCache
 
-nix key generate-secret --key-name test.nixos.org-1 > $TEST_ROOT/sk1
-publicKey=$(nix key convert-secret-to-public < $TEST_ROOT/sk1)
+nix key generate-secret --key-name test.nixos.org-1 > "$TEST_ROOT/sk1"
+publicKey=$(nix key convert-secret-to-public < "$TEST_ROOT/sk1")
 
-nix key generate-secret --key-name test.nixos.org-1 > $TEST_ROOT/sk2
-badKey=$(nix key convert-secret-to-public < $TEST_ROOT/sk2)
+nix key generate-secret --key-name test.nixos.org-1 > "$TEST_ROOT/sk2"
+badKey=$(nix key convert-secret-to-public < "$TEST_ROOT/sk2")
 
-nix key generate-secret --key-name foo.nixos.org-1 > $TEST_ROOT/sk3
-otherKey=$(nix key convert-secret-to-public < $TEST_ROOT/sk3)
+nix key generate-secret --key-name foo.nixos.org-1 > "$TEST_ROOT/sk3"
+otherKey=$(nix key convert-secret-to-public < "$TEST_ROOT/sk3")
 
-_NIX_FORCE_HTTP= nix copy --to file://$cacheDir?secret-key=$TEST_ROOT/sk1 $outPath
+_NIX_FORCE_HTTP='' nix copy --to "file://$cacheDir"?secret-key="$TEST_ROOT"/sk1 "$outPath"
 
 
 # Downloading should fail if we don't provide a key.
 clearStore
 clearCacheCache
 
-(! nix-store -r $outPath --substituters "file://$cacheDir")
+(! nix-store -r "$outPath" --substituters "file://$cacheDir")
 
 
 # And it should fail if we provide an incorrect key.
 clearStore
 clearCacheCache
 
-(! nix-store -r $outPath --substituters "file://$cacheDir" --trusted-public-keys "$badKey")
+(! nix-store -r "$outPath" --substituters "file://$cacheDir" --trusted-public-keys "$badKey")
 
 
 # It should succeed if we provide the correct key.
-nix-store -r $outPath --substituters "file://$cacheDir" --trusted-public-keys "$otherKey $publicKey"
+nix-store -r "$outPath" --substituters "file://$cacheDir" --trusted-public-keys "$otherKey $publicKey"
 
 
 # It should fail if we corrupt the .narinfo.
 clearStore
 
 cacheDir2=$TEST_ROOT/binary-cache-2
-rm -rf $cacheDir2
-cp -r $cacheDir $cacheDir2
+rm -rf "$cacheDir2"
+cp -r "$cacheDir" "$cacheDir2"
 
-for i in $cacheDir2/*.narinfo; do
-    grep -v References $i > $i.tmp
-    mv $i.tmp $i
+for i in "$cacheDir2"/*.narinfo; do
+    grep -v References "$i" > "$i".tmp
+    mv "$i".tmp "$i"
 done
 
 clearCacheCache
 
-(! nix-store -r $outPath --substituters "file://$cacheDir2" --trusted-public-keys "$publicKey")
+(! nix-store -r "$outPath" --substituters "file://$cacheDir2" --trusted-public-keys "$publicKey")
 
 # If we provide a bad and a good binary cache, it should succeed.
 
-nix-store -r $outPath --substituters "file://$cacheDir2 file://$cacheDir" --trusted-public-keys "$publicKey"
+nix-store -r "$outPath" --substituters "file://$cacheDir2 file://$cacheDir" --trusted-public-keys "$publicKey"
 
 
 unset _NIX_FORCE_HTTP
 
 
 # Test 'nix verify --all' on a binary cache.
-nix store verify -vvvvv --all --store file://$cacheDir --no-trust
+nix store verify -vvvvv --all --store "file://$cacheDir" --no-trust
 
 
 # Test local NAR caching.
 narCache=$TEST_ROOT/nar-cache
-rm -rf $narCache
-mkdir $narCache
+rm -rf "$narCache"
+mkdir "$narCache"
 
-[[ $(nix store cat --store "file://$cacheDir?local-nar-cache=$narCache" $outPath/foobar) = FOOBAR ]]
+[[ $(nix store cat --store "file://$cacheDir?local-nar-cache=$narCache" "$outPath/foobar") = FOOBAR ]]
 
 rm -rfv "$cacheDir/nar"
 
-[[ $(nix store cat --store "file://$cacheDir?local-nar-cache=$narCache" $outPath/foobar) = FOOBAR ]]
+[[ $(nix store cat --store "file://$cacheDir?local-nar-cache=$narCache" "$outPath/foobar") = FOOBAR ]]
 
-(! nix store cat --store file://$cacheDir $outPath/foobar)
+(! nix store cat --store "file://$cacheDir" "$outPath/foobar")
 
 
 # Test NAR listing generation.
 clearCache
 
+
+# preserve quotes variables in the single-quoted string
+# shellcheck disable=SC2016
 outPath=$(nix-build --no-out-link -E '
   with import ./config.nix;
   mkDerivation {
@@ -238,16 +245,18 @@ outPath=$(nix-build --no-out-link -E '
   }
 ')
 
-nix copy --to file://$cacheDir?write-nar-listing=1 $outPath
+nix copy --to "file://$cacheDir"?write-nar-listing=1 "$outPath"
 
 diff -u \
-    <(jq -S < $cacheDir/$(basename $outPath | cut -c1-32).ls) \
+    <(jq -S < "$cacheDir/$(basename "$outPath" | cut -c1-32).ls") \
     <(echo '{"version":1,"root":{"type":"directory","entries":{"bar":{"type":"regular","size":4,"narOffset":232},"link":{"type":"symlink","target":"xyzzy"}}}}' | jq -S)
 
 
 # Test debug info index generation.
 clearCache
 
+# preserve quotes variables in the single-quoted string
+# shellcheck disable=SC2016
 outPath=$(nix-build --no-out-link -E '
   with import ./config.nix;
   mkDerivation {
@@ -256,14 +265,16 @@ outPath=$(nix-build --no-out-link -E '
   }
 ')
 
-nix copy --to "file://$cacheDir?index-debug-info=1&compression=none" $outPath
+nix copy --to "file://$cacheDir?index-debug-info=1&compression=none" "$outPath"
 
 diff -u \
-    <(cat $cacheDir/debuginfo/02623eda209c26a59b1a8638ff7752f6b945c26b.debug | jq -S) \
+    <(jq -S < "$cacheDir"/debuginfo/02623eda209c26a59b1a8638ff7752f6b945c26b.debug) \
     <(echo '{"archive":"../nar/100vxs724qr46phz8m24iswmg9p3785hsyagz0kchf6q6gf06sw6.nar","member":"lib/debug/.build-id/02/623eda209c26a59b1a8638ff7752f6b945c26b.debug"}' | jq -S)
 
 # Test against issue https://github.com/NixOS/nix/issues/3964
-#
+
+# preserve quotes variables in the single-quoted string
+# shellcheck disable=SC2016
 expr='
   with import ./config.nix;
   mkDerivation {
@@ -273,22 +284,22 @@ expr='
   }
 '
 outPath=$(nix-build --no-out-link -E "$expr")
-docPath=$(nix-store -q --references $outPath)
+docPath=$(nix-store -q --references "$outPath")
 
 # $ nix-store -q --tree $outPath
 # ...-multi-output
 # +---...-multi-output-doc
 
-nix copy --to "file://$cacheDir" $outPath
+nix copy --to "file://$cacheDir" "$outPath"
 
 hashpart() {
   basename "$1" | cut -c1-32
 }
 
 # break the closure of out by removing doc
-rm $cacheDir/$(hashpart $docPath).narinfo
+rm "$cacheDir/$(hashpart "$docPath")".narinfo
 
-nix-store --delete $outPath $docPath
+nix-store --delete "$outPath" "$docPath"
 # -vvv is the level that logs during the loop
 timeout 60 nix-build --no-out-link -E "$expr" --option substituters "file://$cacheDir" \
   --option trusted-binary-caches "file://$cacheDir"  --no-require-sigs
diff --git a/tests/functional/brotli.sh b/tests/functional/brotli.sh
old mode 100644
new mode 100755
index dc9bbdb66cb..327eab4a554
--- a/tests/functional/brotli.sh
+++ b/tests/functional/brotli.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 clearCache
 
@@ -7,15 +11,15 @@ cacheURI="file://$cacheDir?compression=br"
 
 outPath=$(nix-build dependencies.nix --no-out-link)
 
-nix copy --to $cacheURI $outPath
+nix copy --to "$cacheURI" "$outPath"
 
-HASH=$(nix hash path $outPath)
+HASH=$(nix hash path "$outPath")
 
 clearStore
 clearCacheCache
 
-nix copy --from $cacheURI $outPath --no-check-sigs
+nix copy --from "$cacheURI" "$outPath" --no-check-sigs
 
-HASH2=$(nix hash path $outPath)
+HASH2=$(nix hash path "$outPath")
 
-[[ $HASH = $HASH2 ]]
+[[ $HASH == "$HASH2" ]]
diff --git a/tests/functional/build-delete.sh b/tests/functional/build-delete.sh
old mode 100644
new mode 100755
index 9c56b00e8de..18841509d50
--- a/tests/functional/build-delete.sh
+++ b/tests/functional/build-delete.sh
@@ -1,28 +1,30 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 # https://github.com/NixOS/nix/issues/6572
 issue_6572_independent_outputs() {
-    nix build -f multiple-outputs.nix --json independent --no-link > $TEST_ROOT/independent.json
+    nix build -f multiple-outputs.nix --json independent --no-link > "$TEST_ROOT"/independent.json
 
     # Make sure that 'nix build' can build a derivation that depends on both outputs of another derivation.
     p=$(nix build -f multiple-outputs.nix use-independent --no-link --print-out-paths)
     nix-store --delete "$p" # Clean up for next test
 
     # Make sure that 'nix build' tracks input-outputs correctly when a single output is already present.
-    nix-store --delete "$(jq -r <$TEST_ROOT/independent.json .[0].outputs.first)"
+    nix-store --delete "$(jq -r <"$TEST_ROOT"/independent.json .[0].outputs.first)"
     p=$(nix build -f multiple-outputs.nix use-independent --no-link --print-out-paths)
-    cmp $p <<EOF
+    cmp "$p" <<EOF
 first
 second
 EOF
     nix-store --delete "$p" # Clean up for next test
 
     # Make sure that 'nix build' tracks input-outputs correctly when a single output is already present.
-    nix-store --delete "$(jq -r <$TEST_ROOT/independent.json .[0].outputs.second)"
+    nix-store --delete "$(jq -r <"$TEST_ROOT"/independent.json .[0].outputs.second)"
     p=$(nix build -f multiple-outputs.nix use-independent --no-link --print-out-paths)
-    cmp $p <<EOF
+    cmp "$p" <<EOF
 first
 second
 EOF
@@ -34,16 +36,16 @@ issue_6572_independent_outputs
 # https://github.com/NixOS/nix/issues/6572
 issue_6572_dependent_outputs() {
 
-    nix build -f multiple-outputs.nix --json a --no-link > $TEST_ROOT/a.json
+    nix build -f multiple-outputs.nix --json a --no-link > "$TEST_ROOT"/a.json
 
     # # Make sure that 'nix build' can build a derivation that depends on both outputs of another derivation.
     p=$(nix build -f multiple-outputs.nix use-a --no-link --print-out-paths)
     nix-store --delete "$p" # Clean up for next test
 
     # Make sure that 'nix build' tracks input-outputs correctly when a single output is already present.
-    nix-store --delete "$(jq -r <$TEST_ROOT/a.json .[0].outputs.second)"
+    nix-store --delete "$(jq -r <"$TEST_ROOT"/a.json .[0].outputs.second)"
     p=$(nix build -f multiple-outputs.nix use-a --no-link --print-out-paths)
-    cmp $p <<EOF
+    cmp "$p" <<EOF
 first
 second
 EOF
diff --git a/tests/functional/build-dry.sh b/tests/functional/build-dry.sh
old mode 100644
new mode 100755
index 6d1754af5c2..cff0f9a49fe
--- a/tests/functional/build-dry.sh
+++ b/tests/functional/build-dry.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 ###################################################
 # Check that --dry-run isn't confused with read-only mode
 # https://github.com/NixOS/nix/issues/1795
@@ -33,17 +37,17 @@ clearStore
 clearCache
 
 RESULT=$TEST_ROOT/result-link
-rm -f $RESULT
+rm -f "$RESULT"
 
-nix-build dependencies.nix -o $RESULT --dry-run
+nix-build dependencies.nix -o "$RESULT" --dry-run
 
 [[ ! -h $RESULT ]] || fail "nix-build --dry-run created output link"
 
-nix build -f dependencies.nix -o $RESULT --dry-run
+nix build -f dependencies.nix -o "$RESULT" --dry-run
 
 [[ ! -h $RESULT ]] || fail "nix build --dry-run created output link"
 
-nix build -f dependencies.nix -o $RESULT
+nix build -f dependencies.nix -o "$RESULT"
 
 [[ -h $RESULT ]]
 
@@ -56,12 +60,12 @@ RES=$(nix build -f dependencies.nix --dry-run --json)
 
 if [[ -z "${NIX_TESTS_CA_BY_DEFAULT-}" ]]; then
     echo "$RES" | jq '.[0] | [
-        (.drvPath | test("'$NIX_STORE_DIR'.*\\.drv")),
-        (.outputs.out | test("'$NIX_STORE_DIR'"))
+        (.drvPath | test("'"$NIX_STORE_DIR"'.*\\.drv")),
+        (.outputs.out | test("'"$NIX_STORE_DIR"'"))
     ] | all'
 else
     echo "$RES" | jq '.[0] | [
-        (.drvPath | test("'$NIX_STORE_DIR'.*\\.drv")),
+        (.drvPath | test("'"$NIX_STORE_DIR"'.*\\.drv")),
         .outputs.out == null
     ] | all'
 fi
diff --git a/tests/functional/build-remote-content-addressed-fixed.sh b/tests/functional/build-remote-content-addressed-fixed.sh
old mode 100644
new mode 100755
index ae744159113..61a1f4a464b
--- a/tests/functional/build-remote-content-addressed-fixed.sh
+++ b/tests/functional/build-remote-content-addressed-fixed.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 file=build-hook-ca-fixed.nix
diff --git a/tests/functional/build-remote-content-addressed-floating.sh b/tests/functional/build-remote-content-addressed-floating.sh
old mode 100644
new mode 100755
index e83b42b4150..33d667f9211
--- a/tests/functional/build-remote-content-addressed-floating.sh
+++ b/tests/functional/build-remote-content-addressed-floating.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 file=build-hook-ca-floating.nix
diff --git a/tests/functional/build-remote-input-addressed.sh b/tests/functional/build-remote-input-addressed.sh
old mode 100644
new mode 100755
index 49d15c38963..11199a4088d
--- a/tests/functional/build-remote-input-addressed.sh
+++ b/tests/functional/build-remote-input-addressed.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 file=build-hook.nix
@@ -11,17 +13,17 @@ registerBuildHook () {
     # Dummy post-build-hook just to ensure that it's executed correctly.
     # (we can't reuse the one from `$PWD/push-to-store.sh` because of
     # https://github.com/NixOS/nix/issues/4341)
-    cat <<EOF > $TEST_ROOT/post-build-hook.sh
+    cat <<EOF > "$TEST_ROOT/post-build-hook.sh"
 #!/bin/sh
 
 echo "Post hook ran successfully"
 # Add an empty line to a counter file, just to check that this hook ran properly
 echo "" >> $TEST_ROOT/post-hook-counter
 EOF
-    chmod +x $TEST_ROOT/post-build-hook.sh
-    rm -f $TEST_ROOT/post-hook-counter
+    chmod +x "$TEST_ROOT/post-build-hook.sh"
+    rm -f "$TEST_ROOT/post-hook-counter"
 
-    echo "post-build-hook = $TEST_ROOT/post-build-hook.sh" >> $NIX_CONF_DIR/nix.conf
+    echo "post-build-hook = $TEST_ROOT/post-build-hook.sh" >> "$test_nix_conf"
 }
 
 registerBuildHook
@@ -30,4 +32,4 @@ source build-remote.sh
 # `build-hook.nix` has four derivations to build, and the hook runs twice for
 # each derivation (once on the builder and once on the host), so the counter
 # should contain eight lines now
-[[ $(cat $TEST_ROOT/post-hook-counter | wc -l) -eq 8 ]]
+[[ $(wc -l < "$TEST_ROOT/post-hook-counter") -eq 8 ]]
diff --git a/tests/functional/build-remote-trustless-after.sh b/tests/functional/build-remote-trustless-after.sh
index 19f59e6aea8..2fcdbf10a01 100644
--- a/tests/functional/build-remote-trustless-after.sh
+++ b/tests/functional/build-remote-trustless-after.sh
@@ -1,2 +1,7 @@
-outPath=$(readlink -f $TEST_ROOT/result)
-grep 'FOO BAR BAZ' ${remoteDir}/${outPath}
+# shellcheck shell=bash
+
+# Variables must be defined by caller, so
+# shellcheck disable=SC2154
+
+outPath=$(readlink -f "$TEST_ROOT/result")
+grep 'FOO BAR BAZ' "${remoteDir}/${outPath}"
diff --git a/tests/functional/build-remote-trustless-should-fail-0.sh b/tests/functional/build-remote-trustless-should-fail-0.sh
old mode 100644
new mode 100755
index 3d4a4b0979e..4eccb73e0ee
--- a/tests/functional/build-remote-trustless-should-fail-0.sh
+++ b/tests/functional/build-remote-trustless-should-fail-0.sh
@@ -1,7 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "daemon-trust-override"
 
+TODO_NixOS
 restartDaemon
 
 requireSandboxSupport
@@ -22,8 +25,12 @@ nix-build build-hook.nix -A passthru.input2 \
 # copy our already-build `input2` to the remote store. That store object
 # is input-addressed, so this will fail.
 
+# For script below
+# shellcheck disable=SC2034
 file=build-hook.nix
+# shellcheck disable=SC2034
 prog=$(readlink -e ./nix-daemon-untrusting.sh)
+# shellcheck disable=SC2034
 proto=ssh-ng
 
 expectStderr 1 source build-remote-trustless.sh \
diff --git a/tests/functional/build-remote-trustless-should-pass-0.sh b/tests/functional/build-remote-trustless-should-pass-0.sh
old mode 100644
new mode 100755
index 2a7ebd8c69c..b810609074d
--- a/tests/functional/build-remote-trustless-should-pass-0.sh
+++ b/tests/functional/build-remote-trustless-should-pass-0.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Remote trusts us
diff --git a/tests/functional/build-remote-trustless-should-pass-1.sh b/tests/functional/build-remote-trustless-should-pass-1.sh
old mode 100644
new mode 100755
index 516bdf092df..b8dc038bf36
--- a/tests/functional/build-remote-trustless-should-pass-1.sh
+++ b/tests/functional/build-remote-trustless-should-pass-1.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Remote trusts us
diff --git a/tests/functional/build-remote-trustless-should-pass-2.sh b/tests/functional/build-remote-trustless-should-pass-2.sh
old mode 100644
new mode 100755
index b769a88f0cf..34ce7fbe48f
--- a/tests/functional/build-remote-trustless-should-pass-2.sh
+++ b/tests/functional/build-remote-trustless-should-pass-2.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "daemon-trust-override"
 
+TODO_NixOS
+
 restartDaemon
 
 # Remote doesn't trust us
diff --git a/tests/functional/build-remote-trustless-should-pass-3.sh b/tests/functional/build-remote-trustless-should-pass-3.sh
old mode 100644
new mode 100755
index 40f81da5a5e..d01d7919190
--- a/tests/functional/build-remote-trustless-should-pass-3.sh
+++ b/tests/functional/build-remote-trustless-should-pass-3.sh
@@ -1,7 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "daemon-trust-override"
 
+TODO_NixOS
 restartDaemon
 
 # Remote doesn't trusts us, but this is fine because we are only
diff --git a/tests/functional/build-remote-trustless.sh b/tests/functional/build-remote-trustless.sh
index 81e5253bf29..c498d46c301 100644
--- a/tests/functional/build-remote-trustless.sh
+++ b/tests/functional/build-remote-trustless.sh
@@ -1,5 +1,11 @@
+# shellcheck shell=bash
+
+# All variables should be defined externally by the scripts that source
+# this, `set -u` will catch any that are forgotten.
+# shellcheck disable=SC2154
+
 requireSandboxSupport
-[[ $busybox =~ busybox ]] || skipTest "no busybox"
+[[ "$busybox" =~ busybox ]] || skipTest "no busybox"
 
 unset NIX_STORE_DIR
 unset NIX_STATE_DIR
@@ -8,7 +14,7 @@ remoteDir=$TEST_ROOT/remote
 
 # Note: ssh{-ng}://localhost bypasses ssh. See tests/functional/build-remote.sh for
 # more details.
-nix-build $file -o $TEST_ROOT/result --max-jobs 0 \
-  --arg busybox $busybox \
-  --store $TEST_ROOT/local \
+nix-build "$file" -o "$TEST_ROOT/result" --max-jobs 0 \
+  --arg busybox "$busybox" \
+  --store "$TEST_ROOT/local" \
   --builders "$proto://localhost?remote-program=$prog&remote-store=${remoteDir}%3Fsystem-features=foo%20bar%20baz - - 1 1 foo,bar,baz"
diff --git a/tests/functional/build-remote-with-mounted-ssh-ng.sh b/tests/functional/build-remote-with-mounted-ssh-ng.sh
old mode 100644
new mode 100755
index 443acb6ca78..e2627af394c
--- a/tests/functional/build-remote-with-mounted-ssh-ng.sh
+++ b/tests/functional/build-remote-with-mounted-ssh-ng.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireSandboxSupport
@@ -6,17 +8,17 @@ requireSandboxSupport
 enableFeatures mounted-ssh-store
 
 nix build -Lvf simple.nix \
-  --arg busybox $busybox \
-  --out-link $TEST_ROOT/result-from-remote \
+  --arg busybox "$busybox" \
+  --out-link "$TEST_ROOT/result-from-remote" \
   --store mounted-ssh-ng://localhost
 
 nix build -Lvf simple.nix \
-  --arg busybox $busybox \
-  --out-link $TEST_ROOT/result-from-remote-new-cli \
+  --arg busybox "$busybox" \
+  --out-link "$TEST_ROOT/result-from-remote-new-cli" \
   --store 'mounted-ssh-ng://localhost?remote-program=nix daemon'
 
 # This verifies that the out link was actually created and valid. The ability
 # to create out links (permanent gc roots) is the distinguishing feature of
 # the mounted-ssh-ng store.
-cat $TEST_ROOT/result-from-remote/hello | grepQuiet 'Hello World!'
-cat $TEST_ROOT/result-from-remote-new-cli/hello | grepQuiet 'Hello World!'
+grepQuiet 'Hello World!' < "$TEST_ROOT/result-from-remote/hello"
+grepQuiet 'Hello World!' < "$TEST_ROOT/result-from-remote-new-cli/hello"
diff --git a/tests/functional/build-remote.sh b/tests/functional/build-remote.sh
index d2a2132c1a4..1a53345778d 100644
--- a/tests/functional/build-remote.sh
+++ b/tests/functional/build-remote.sh
@@ -1,5 +1,9 @@
+# shellcheck shell=bash
+
+: "${file?must be defined by caller (remote building test case using this)}"
+
 requireSandboxSupport
-[[ $busybox =~ busybox ]] || skipTest "no busybox"
+[[ "${busybox-}" =~ busybox ]] || skipTest "no busybox"
 
 # Avoid store dir being inside sandbox build-dir
 unset NIX_STORE_DIR
@@ -15,50 +19,50 @@ fi
 builders=(
   # system-features will automatically be added to the outer URL, but not inner
   # remote-store URL.
-  "ssh://localhost?remote-store=$TEST_ROOT/machine1?system-features=$(join_by "%20" foo ${EXTRA_SYSTEM_FEATURES[@]}) - - 1 1 $(join_by "," foo ${EXTRA_SYSTEM_FEATURES[@]})"
-  "$TEST_ROOT/machine2 - - 1 1 $(join_by "," bar ${EXTRA_SYSTEM_FEATURES[@]})"
-  "ssh-ng://localhost?remote-store=$TEST_ROOT/machine3?system-features=$(join_by "%20" baz ${EXTRA_SYSTEM_FEATURES[@]}) - - 1 1 $(join_by "," baz ${EXTRA_SYSTEM_FEATURES[@]})"
+  "ssh://localhost?remote-store=$TEST_ROOT/machine1?system-features=$(join_by "%20" foo "${EXTRA_SYSTEM_FEATURES[@]}") - - 1 1 $(join_by "," foo "${EXTRA_SYSTEM_FEATURES[@]}")"
+  "$TEST_ROOT/machine2 - - 1 1 $(join_by "," bar "${EXTRA_SYSTEM_FEATURES[@]}")"
+  "ssh-ng://localhost?remote-store=$TEST_ROOT/machine3?system-features=$(join_by "%20" baz "${EXTRA_SYSTEM_FEATURES[@]}") - - 1 1 $(join_by "," baz "${EXTRA_SYSTEM_FEATURES[@]}")"
 )
 
-chmod -R +w $TEST_ROOT/machine* || true
-rm -rf $TEST_ROOT/machine* || true
+chmod -R +w "$TEST_ROOT/machine"* || true
+rm -rf "$TEST_ROOT/machine"* || true
 
 # Note: ssh://localhost bypasses ssh, directly invoking nix-store as a
 # child process. This allows us to test LegacySSHStore::buildDerivation().
 # ssh-ng://... likewise allows us to test RemoteStore::buildDerivation().
-nix build -L -v -f $file -o $TEST_ROOT/result --max-jobs 0 \
-  --arg busybox $busybox \
-  --store $TEST_ROOT/machine0 \
+nix build -L -v -f "$file" -o "$TEST_ROOT/result" --max-jobs 0 \
+  --arg busybox "$busybox" \
+  --store "$TEST_ROOT/machine0" \
   --builders "$(join_by '; ' "${builders[@]}")"
 
-outPath=$(readlink -f $TEST_ROOT/result)
+outPath=$(readlink -f "$TEST_ROOT/result")
 
-grep 'FOO BAR BAZ' $TEST_ROOT/machine0/$outPath
+grep 'FOO BAR BAZ' "$TEST_ROOT/machine0/$outPath"
 
-testPrintOutPath=$(nix build -L -v -f $file --no-link --print-out-paths --max-jobs 0 \
-  --arg busybox $busybox \
-  --store $TEST_ROOT/machine0 \
+testPrintOutPath=$(nix build -L -v -f "$file" --no-link --print-out-paths --max-jobs 0 \
+  --arg busybox "$busybox" \
+  --store "$TEST_ROOT/machine0" \
   --builders "$(join_by '; ' "${builders[@]}")"
 )
 
 [[ $testPrintOutPath =~ store.*build-remote ]]
 
 # Ensure that input1 was built on store1 due to the required feature.
-output=$(nix path-info --store $TEST_ROOT/machine1 --all)
+output=$(nix path-info --store "$TEST_ROOT/machine1" --all)
 echo "$output" | grepQuiet builder-build-remote-input-1.sh
 echo "$output" | grepQuietInverse builder-build-remote-input-2.sh
 echo "$output" | grepQuietInverse builder-build-remote-input-3.sh
 unset output
 
 # Ensure that input2 was built on store2 due to the required feature.
-output=$(nix path-info --store $TEST_ROOT/machine2 --all)
+output=$(nix path-info --store "$TEST_ROOT/machine2" --all)
 echo "$output" | grepQuietInverse builder-build-remote-input-1.sh
 echo "$output" | grepQuiet builder-build-remote-input-2.sh
 echo "$output" | grepQuietInverse builder-build-remote-input-3.sh
 unset output
 
 # Ensure that input3 was built on store3 due to the required feature.
-output=$(nix path-info --store $TEST_ROOT/machine3 --all)
+output=$(nix path-info --store "$TEST_ROOT/machine3" --all)
 echo "$output" | grepQuietInverse builder-build-remote-input-1.sh
 echo "$output" | grepQuietInverse builder-build-remote-input-2.sh
 echo "$output" | grepQuiet builder-build-remote-input-3.sh
@@ -66,7 +70,7 @@ unset output
 
 
 for i in input1 input3; do
-nix log --store $TEST_ROOT/machine0 --file "$file" --arg busybox $busybox passthru."$i" | grep hi-$i
+nix log --store "$TEST_ROOT/machine0" --file "$file" --arg busybox "$busybox" "passthru.$i" | grep hi-$i
 done
 
 # Behavior of keep-failed
@@ -74,9 +78,9 @@ out="$(nix-build 2>&1 failing.nix \
   --no-out-link \
   --builders "$(join_by '; ' "${builders[@]}")"  \
   --keep-failed \
-  --store $TEST_ROOT/machine0 \
+  --store "$TEST_ROOT/machine0" \
   -j0 \
-  --arg busybox $busybox)" || true
+  --arg busybox "$busybox")" || true
 
 [[ "$out" =~ .*"note: keeping build directory".* ]]
 
diff --git a/tests/functional/build.sh b/tests/functional/build.sh
old mode 100644
new mode 100755
index 7fbdb0f0749..9de953d8cbf
--- a/tests/functional/build.sh
+++ b/tests/functional/build.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 # Make sure that 'nix build' returns all outputs by default.
 nix build -f multiple-outputs.nix --json a b --no-link | jq --exit-status '
@@ -43,6 +45,14 @@ nix build -f multiple-outputs.nix --json e --no-link | jq --exit-status '
     (.outputs | keys == ["a_a", "b"]))
 '
 
+# Tests that we can handle empty 'outputsToInstall' (assuming that default
+# output "out" exists).
+nix build -f multiple-outputs.nix --json nothing-to-install --no-link | jq --exit-status '
+  (.[0] |
+    (.drvPath | match(".*nothing-to-install.drv")) and
+    (.outputs | keys == ["out"]))
+'
+
 # But not when it's overriden.
 nix build -f multiple-outputs.nix --json e^a_a --no-link
 nix build -f multiple-outputs.nix --json e^a_a --no-link | jq --exit-status '
@@ -133,3 +143,35 @@ nix build --impure -f multiple-outputs.nix --json e --no-link | jq --exit-status
 # Make sure that `--stdin` works and does not apply any defaults
 printf "" | nix build --no-link --stdin --json | jq --exit-status '. == []'
 printf "%s\n" "$drv^*" | nix build --no-link --stdin --json | jq --exit-status '.[0]|has("drvPath")'
+
+# --keep-going and FOD
+out="$(nix build -f fod-failing.nix -L 2>&1)" && status=0 || status=$?
+test "$status" = 1
+# one "hash mismatch" error, one "build of ... failed"
+test "$(<<<"$out" grep -E '^error:' | wc -l)" = 2
+<<<"$out" grepQuiet -E "hash mismatch in fixed-output derivation '.*-x1\\.drv'"
+<<<"$out" grepQuiet -vE "hash mismatch in fixed-output derivation '.*-x3\\.drv'"
+<<<"$out" grepQuiet -vE "hash mismatch in fixed-output derivation '.*-x2\\.drv'"
+<<<"$out" grepQuiet -E "error: build of '.*-x[1-4]\\.drv\\^out', '.*-x[1-4]\\.drv\\^out', '.*-x[1-4]\\.drv\\^out', '.*-x[1-4]\\.drv\\^out' failed"
+
+out="$(nix build -f fod-failing.nix -L x1 x2 x3 --keep-going 2>&1)" && status=0 || status=$?
+test "$status" = 1
+# three "hash mismatch" errors - for each failing fod, one "build of ... failed"
+test "$(<<<"$out" grep -E '^error:' | wc -l)" = 4
+<<<"$out" grepQuiet -E "hash mismatch in fixed-output derivation '.*-x1\\.drv'"
+<<<"$out" grepQuiet -E "hash mismatch in fixed-output derivation '.*-x3\\.drv'"
+<<<"$out" grepQuiet -E "hash mismatch in fixed-output derivation '.*-x2\\.drv'"
+<<<"$out" grepQuiet -E "error: build of '.*-x[1-3]\\.drv\\^out', '.*-x[1-3]\\.drv\\^out', '.*-x[1-3]\\.drv\\^out' failed"
+
+out="$(nix build -f fod-failing.nix -L x4 2>&1)" && status=0 || status=$?
+test "$status" = 1
+test "$(<<<"$out" grep -E '^error:' | wc -l)" = 2
+<<<"$out" grepQuiet -E "error: 1 dependencies of derivation '.*-x4\\.drv' failed to build"
+<<<"$out" grepQuiet -E "hash mismatch in fixed-output derivation '.*-x2\\.drv'"
+
+out="$(nix build -f fod-failing.nix -L x4 --keep-going 2>&1)" && status=0 || status=$?
+test "$status" = 1
+test "$(<<<"$out" grep -E '^error:' | wc -l)" = 3
+<<<"$out" grepQuiet -E "error: 2 dependencies of derivation '.*-x4\\.drv' failed to build"
+<<<"$out" grepQuiet -vE "hash mismatch in fixed-output derivation '.*-x3\\.drv'"
+<<<"$out" grepQuiet -vE "hash mismatch in fixed-output derivation '.*-x2\\.drv'"
diff --git a/tests/functional/ca/build-cache.sh b/tests/functional/ca/build-cache.sh
index 6a4080fecf5..5cc71823ee6 100644
--- a/tests/functional/ca/build-cache.sh
+++ b/tests/functional/ca/build-cache.sh
@@ -26,7 +26,8 @@ copyAttr () {
     # Note: to copy CA derivations, we need to copy the realisations, which
     # currently requires naming the installables, not just the derivation output
     # path.
-    nix copy --to file://$cacheDir "${args[@]}"
+
+    nix copy --to "file://$cacheDir" "${args[@]}"
 }
 
 testRemoteCacheFor () {
@@ -35,7 +36,7 @@ testRemoteCacheFor () {
     copyAttr "$derivationPath" 1
     clearStore
     # Check nothing gets built.
-    buildAttr "$derivationPath" 1 --option substituters file://$cacheDir --no-require-sigs |& grepQuietInverse " will be built:"
+    buildAttr "$derivationPath" 1 --option substituters "file://$cacheDir" --no-require-sigs |& grepQuietInverse " will be built:"
 }
 
 testRemoteCache () {
@@ -48,4 +49,4 @@ testRemoteCache () {
 }
 
 clearStore
-testRemoteCache
\ No newline at end of file
+testRemoteCache
diff --git a/tests/functional/ca/build.sh b/tests/functional/ca/build.sh
index e1a8a76252b..e5ad9d2a0f5 100644
--- a/tests/functional/ca/build.sh
+++ b/tests/functional/ca/build.sh
@@ -20,11 +20,11 @@ testDeterministicCA () {
 
 testCutoffFor () {
     local out1 out2
-    out1=$(buildAttr $1 1)
+    out1=$(buildAttr "$1" 1)
     # The seed only changes the root derivation, and not it's output, so the
     # dependent derivations should only need to be built once.
     buildAttr rootCA 2
-    out2=$(buildAttr $1 2 -j0)
+    out2=$(buildAttr "$1" 2 -j0)
     test "$out1" == "$out2"
 }
 
@@ -41,7 +41,7 @@ testGC () {
     nix-instantiate ./content-addressed.nix -A rootCA --arg seed 5
     nix-collect-garbage --option keep-derivations true
     clearStore
-    buildAttr rootCA 1 --out-link $TEST_ROOT/rootCA
+    buildAttr rootCA 1 --out-link "$TEST_ROOT"/rootCA
     nix-collect-garbage
     buildAttr rootCA 1 -j0
 }
@@ -55,7 +55,7 @@ testNixCommand () {
 testNormalization () {
     clearStore
     outPath=$(buildAttr rootCA 1)
-    test "$(stat -c %Y $outPath)" -eq 1
+    test "$(stat -c %Y "$outPath")" -eq 1
 }
 
 clearStore
diff --git a/tests/functional/ca/common.sh b/tests/functional/ca/common.sh
index b104b5a7846..48f1ac46bc6 100644
--- a/tests/functional/ca/common.sh
+++ b/tests/functional/ca/common.sh
@@ -2,4 +2,6 @@ source ../common.sh
 
 enableFeatures "ca-derivations"
 
+TODO_NixOS
+
 restartDaemon
diff --git a/tests/functional/ca/derivation-json.sh b/tests/functional/ca/derivation-json.sh
index c1480fd17cd..1e2a8fe35f6 100644
--- a/tests/functional/ca/derivation-json.sh
+++ b/tests/functional/ca/derivation-json.sh
@@ -1,29 +1,31 @@
+#!/usr/bin/env bash
+#
 source common.sh
 
 export NIX_TESTS_CA_BY_DEFAULT=1
 
 drvPath=$(nix-instantiate ../simple.nix)
 
-nix derivation show $drvPath | jq .[] > $TEST_HOME/simple.json
+nix derivation show "$drvPath" | jq .[] > "$TEST_HOME"/simple.json
 
-drvPath2=$(nix derivation add < $TEST_HOME/simple.json)
+drvPath2=$(nix derivation add < "$TEST_HOME"/simple.json)
 
 [[ "$drvPath" = "$drvPath2" ]]
 
 # Content-addressed derivations can be renamed.
-jq '.name = "foo"' < $TEST_HOME/simple.json > $TEST_HOME/foo.json
-drvPath3=$(nix derivation add --dry-run < $TEST_HOME/foo.json)
+jq '.name = "foo"' < "$TEST_HOME"/simple.json > "$TEST_HOME"/foo.json
+drvPath3=$(nix derivation add --dry-run < "$TEST_HOME"/foo.json)
 # With --dry-run nothing is actually written
 [[ ! -e "$drvPath3" ]]
 
 # But the JSON is rejected without the experimental feature
-expectStderr 1 nix derivation add < $TEST_HOME/foo.json --experimental-features nix-command | grepQuiet "experimental Nix feature 'ca-derivations' is disabled"
+expectStderr 1 nix derivation add < "$TEST_HOME"/foo.json --experimental-features nix-command | grepQuiet "experimental Nix feature 'ca-derivations' is disabled"
 
 # Without --dry-run it is actually written
-drvPath4=$(nix derivation add < $TEST_HOME/foo.json)
+drvPath4=$(nix derivation add < "$TEST_HOME"/foo.json)
 [[ "$drvPath4" = "$drvPath3" ]]
 [[ -e "$drvPath3" ]]
 
 # The modified derivation read back as JSON matches
-nix derivation show $drvPath3 | jq .[] > $TEST_HOME/foo-read.json
-diff $TEST_HOME/foo.json $TEST_HOME/foo-read.json
+nix derivation show "$drvPath3" | jq .[] > "$TEST_HOME"/foo-read.json
+diff "$TEST_HOME"/foo.json "$TEST_HOME"/foo-read.json
diff --git a/tests/functional/ca/duplicate-realisation-in-closure.sh b/tests/functional/ca/duplicate-realisation-in-closure.sh
index da9cd8fb499..0baf15cc202 100644
--- a/tests/functional/ca/duplicate-realisation-in-closure.sh
+++ b/tests/functional/ca/duplicate-realisation-in-closure.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireDaemonNewerThan "2.4pre20210625"
@@ -5,7 +7,7 @@ requireDaemonNewerThan "2.4pre20210625"
 export REMOTE_STORE_DIR="$TEST_ROOT/remote_store"
 export REMOTE_STORE="file://$REMOTE_STORE_DIR"
 
-rm -rf $REMOTE_STORE_DIR
+rm -rf "$REMOTE_STORE_DIR"
 clearStore
 
 # Build dep1 and push that to the binary cache.
diff --git a/tests/functional/ca/nix-copy.sh b/tests/functional/ca/nix-copy.sh
index 7a8307a4e9a..f77b0003034 100755
--- a/tests/functional/ca/nix-copy.sh
+++ b/tests/functional/ca/nix-copy.sh
@@ -15,13 +15,13 @@ testOneCopy () {
     rm -rf "$REMOTE_STORE_DIR"
 
     attrPath="$1"
-    nix copy --to $REMOTE_STORE "$attrPath" --file ./content-addressed.nix
+    nix copy --to "$REMOTE_STORE" "$attrPath" --file ./content-addressed.nix
 
     ensureCorrectlyCopied "$attrPath"
 
     # Ensure that we can copy back what we put in the store
     clearStore
-    nix copy --from $REMOTE_STORE \
+    nix copy --from "$REMOTE_STORE" \
         --file ./content-addressed.nix "$attrPath" \
         --no-check-sigs
 }
diff --git a/tests/functional/ca/nix-run.sh b/tests/functional/ca/nix-run.sh
index 5f46518e877..920950c110a 100755
--- a/tests/functional/ca/nix-run.sh
+++ b/tests/functional/ca/nix-run.sh
@@ -4,4 +4,4 @@ source common.sh
 
 FLAKE_PATH=path:$PWD
 
-nix run --no-write-lock-file $FLAKE_PATH#runnable
+nix run --no-write-lock-file "$FLAKE_PATH#runnable"
diff --git a/tests/functional/ca/signatures.sh b/tests/functional/ca/signatures.sh
index eb18a41302b..f69a205d203 100644
--- a/tests/functional/ca/signatures.sh
+++ b/tests/functional/ca/signatures.sh
@@ -1,10 +1,12 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
 clearCache
 
-nix-store --generate-binary-cache-key cache1.example.org $TEST_ROOT/sk1 $TEST_ROOT/pk1
-pk1=$(cat $TEST_ROOT/pk1)
+nix-store --generate-binary-cache-key cache1.example.org "$TEST_ROOT/sk1" "$TEST_ROOT/pk1"
+pk1=$(cat "$TEST_ROOT/pk1")
 
 export REMOTE_STORE_DIR="$TEST_ROOT/remote_store"
 export REMOTE_STORE="file://$REMOTE_STORE_DIR"
@@ -19,16 +21,16 @@ testOneCopy () {
     rm -rf "$REMOTE_STORE_DIR"
 
     attrPath="$1"
-    nix copy -vvvv --to $REMOTE_STORE "$attrPath" --file ./content-addressed.nix \
+    nix copy -vvvv --to "$REMOTE_STORE" "$attrPath" --file ./content-addressed.nix \
         --secret-key-files "$TEST_ROOT/sk1" --show-trace
 
     ensureCorrectlyCopied "$attrPath"
 
     # Ensure that we can copy back what we put in the store
     clearStore
-    nix copy --from $REMOTE_STORE \
+    nix copy --from "$REMOTE_STORE" \
         --file ./content-addressed.nix "$attrPath" \
-        --trusted-public-keys $pk1
+        --trusted-public-keys "$pk1"
 }
 
 for attrPath in rootCA dependentCA transitivelyDependentCA dependentNonCA dependentFixedOutput; do
diff --git a/tests/functional/ca/substitute.sh b/tests/functional/ca/substitute.sh
index ea981adc4b0..9728470f0b8 100644
--- a/tests/functional/ca/substitute.sh
+++ b/tests/functional/ca/substitute.sh
@@ -4,9 +4,10 @@
 
 source common.sh
 
+# shellcheck disable=SC1111
 needLocalStore "“--no-require-sigs” can’t be used with the daemon"
 
-rm -rf $TEST_ROOT/binary_cache
+rm -rf "$TEST_ROOT/binary_cache"
 
 export REMOTE_STORE_DIR=$TEST_ROOT/binary_cache
 export REMOTE_STORE=file://$REMOTE_STORE_DIR
@@ -17,11 +18,11 @@ buildDrvs () {
 
 # Populate the remote cache
 clearStore
-nix copy --to $REMOTE_STORE --file ./content-addressed.nix
+nix copy --to "$REMOTE_STORE" --file ./content-addressed.nix
 
 # Restart the build on an empty store, ensuring that we don't build
 clearStore
-buildDrvs --substitute --substituters $REMOTE_STORE --no-require-sigs -j0 transitivelyDependentCA
+buildDrvs --substitute --substituters "$REMOTE_STORE" --no-require-sigs -j0 transitivelyDependentCA
 # Check that the thing we’ve just substituted has its realisation stored
 nix realisation info --file ./content-addressed.nix transitivelyDependentCA
 # Check that its dependencies have it too
@@ -63,9 +64,9 @@ clearStore
 # Add the realisations of rootCA to the cachecache
 clearCacheCache
 export _NIX_FORCE_HTTP=1
-buildDrvs --substitute --substituters $REMOTE_STORE --no-require-sigs -j0
+buildDrvs --substitute --substituters "$REMOTE_STORE" --no-require-sigs -j0
 # Try rebuilding, but remove the realisations from the remote cache to force
 # using the cachecache
 clearStore
-rm $REMOTE_STORE_DIR/realisations/*
-buildDrvs --substitute --substituters $REMOTE_STORE --no-require-sigs -j0
+rm "$REMOTE_STORE_DIR"/realisations/*
+buildDrvs --substitute --substituters "$REMOTE_STORE" --no-require-sigs -j0
diff --git a/tests/functional/case-hack.sh b/tests/functional/case-hack.sh
old mode 100644
new mode 100755
index 61bf9b94bf5..feddc65831e
--- a/tests/functional/case-hack.sh
+++ b/tests/functional/case-hack.sh
@@ -1,19 +1,24 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
-rm -rf $TEST_ROOT/case
+rm -rf "$TEST_ROOT/case"
 
-opts="--option use-case-hack true"
+opts=("--option" "use-case-hack" "true")
 
 # Check whether restoring and dumping a NAR that contains case
 # collisions is round-tripping, even on a case-insensitive system.
-nix-store $opts  --restore $TEST_ROOT/case < case.nar
-nix-store $opts --dump $TEST_ROOT/case > $TEST_ROOT/case.nar
-cmp case.nar $TEST_ROOT/case.nar
-[ "$(nix-hash $opts --type sha256 $TEST_ROOT/case)" = "$(nix-hash --flat --type sha256 case.nar)" ]
+
+nix-store "${opts[@]}" --restore "$TEST_ROOT/case" < case.nar
+nix-store "${opts[@]}" --dump "$TEST_ROOT/case" > "$TEST_ROOT/case.nar"
+cmp case.nar "$TEST_ROOT/case.nar"
+[ "$(nix-hash "${opts[@]}" --type sha256 "$TEST_ROOT/case")" = "$(nix-hash --flat --type sha256 case.nar)" ]
 
 # Check whether we detect true collisions (e.g. those remaining after
 # removal of the suffix).
 touch "$TEST_ROOT/case/xt_CONNMARK.h~nix~case~hack~3"
-(! nix-store $opts --dump $TEST_ROOT/case > /dev/null)
+(! nix-store "${opts[@]}" --dump "$TEST_ROOT/case" > /dev/null)
diff --git a/tests/functional/lang-test-infra.sh b/tests/functional/characterisation-test-infra.sh
old mode 100644
new mode 100755
similarity index 97%
rename from tests/functional/lang-test-infra.sh
rename to tests/functional/characterisation-test-infra.sh
index 30da8977b6a..27945455061
--- a/tests/functional/lang-test-infra.sh
+++ b/tests/functional/characterisation-test-infra.sh
@@ -1,7 +1,9 @@
+#!/usr/bin/env bash
+
 # Test the function for lang.sh
 source common.sh
 
-source lang/framework.sh
+source characterisation/framework.sh
 
 # We are testing this, so don't want outside world to affect us.
 unset _NIX_TEST_ACCEPT
diff --git a/tests/functional/lang/empty.exp b/tests/functional/characterisation/empty
similarity index 100%
rename from tests/functional/lang/empty.exp
rename to tests/functional/characterisation/empty
diff --git a/tests/functional/characterisation/framework.sh b/tests/functional/characterisation/framework.sh
new file mode 100644
index 00000000000..913fdd9673d
--- /dev/null
+++ b/tests/functional/characterisation/framework.sh
@@ -0,0 +1,77 @@
+# shellcheck shell=bash
+
+# Golden test support
+#
+# Test that the output of the given test matches what is expected. If
+# `_NIX_TEST_ACCEPT` is non-empty also update the expected output so
+# that next time the test succeeds.
+function diffAndAcceptInner() {
+    local -r testName=$1
+    local -r got="$2"
+    local -r expected="$3"
+
+    # Absence of expected file indicates empty output expected.
+    if test -e "$expected"; then
+        local -r expectedOrEmpty="$expected"
+    else
+        local -r expectedOrEmpty=characterisation/empty
+    fi
+
+    # Diff so we get a nice message
+    if ! diff --color=always --unified "$expectedOrEmpty" "$got"; then
+        echo "FAIL: evaluation result of $testName not as expected"
+        # shellcheck disable=SC2034
+        badDiff=1
+    fi
+
+    # Update expected if `_NIX_TEST_ACCEPT` is non-empty.
+    if test -n "${_NIX_TEST_ACCEPT-}"; then
+        cp "$got" "$expected"
+        # Delete empty expected files to avoid bloating the repo with
+        # empty files.
+        if ! test -s "$expected"; then
+            rm "$expected"
+        fi
+    fi
+}
+
+function characterisationTestExit() {
+    # Make sure shellcheck knows all these will be defined by the caller
+    : "${badDiff?} ${badExitCode?}"
+
+    if test -n "${_NIX_TEST_ACCEPT-}"; then
+        if (( "$badDiff" )); then
+            set +x
+            echo 'Output did mot match, but accepted output as the persisted expected output.'
+            echo 'That means the next time the tests are run, they should pass.'
+            set -x
+        else
+            set +x
+            echo 'NOTE: Environment variable _NIX_TEST_ACCEPT is defined,'
+            echo 'indicating the unexpected output should be accepted as the expected output going forward,'
+            echo 'but no tests had unexpected output so there was no expected output to update.'
+            set -x
+        fi
+        if (( "$badExitCode" )); then
+            exit "$badExitCode"
+        else
+            skipTest "regenerating golden masters"
+        fi
+    else
+        if (( "$badDiff" )); then
+            set +x
+            echo ''
+            echo 'You can rerun this test with:'
+            echo ''
+            echo "    _NIX_TEST_ACCEPT=1 make tests/functional/${TEST_NAME}.test"
+            echo ''
+            echo 'to regenerate the files containing the expected output,'
+            echo 'and then view the git diff to decide whether a change is'
+            echo 'good/intentional or bad/unintentional.'
+            echo 'If the diff contains arbitrary or impure information,'
+            echo 'please improve the normalization that the test applies to the output.'
+            set -x
+        fi
+        exit $(( "$badExitCode" + "$badDiff" ))
+    fi
+}
diff --git a/tests/functional/check-refs.sh b/tests/functional/check-refs.sh
old mode 100644
new mode 100755
index 3b587d1e56f..5c3ac915ecf
--- a/tests/functional/check-refs.sh
+++ b/tests/functional/check-refs.sh
@@ -1,53 +1,62 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 RESULT=$TEST_ROOT/result
 
-dep=$(nix-build -o $RESULT check-refs.nix -A dep)
+dep=$(nix-build -o "$RESULT" check-refs.nix -A dep)
 
 # test1 references dep, not itself.
-test1=$(nix-build -o $RESULT check-refs.nix -A test1)
-nix-store -q --references $test1 | grepQuietInverse $test1
-nix-store -q --references $test1 | grepQuiet $dep
+test1=$(nix-build -o "$RESULT" check-refs.nix -A test1)
+nix-store -q --references "$test1" | grepQuietInverse "$test1"
+nix-store -q --references "$test1" | grepQuiet "$dep"
 
 # test2 references src, not itself nor dep.
-test2=$(nix-build -o $RESULT check-refs.nix -A test2)
-nix-store -q --references $test2 | grepQuietInverse $test2
-nix-store -q --references $test2 | grepQuietInverse $dep
-nix-store -q --references $test2 | grepQuiet aux-ref
+test2=$(nix-build -o "$RESULT" check-refs.nix -A test2)
+nix-store -q --references "$test2" | grepQuietInverse "$test2"
+nix-store -q --references "$test2" | grepQuietInverse "$dep"
+nix-store -q --references "$test2" | grepQuiet aux-ref
 
 # test3 should fail (unallowed ref).
-(! nix-build -o $RESULT check-refs.nix -A test3)
+(! nix-build -o "$RESULT" check-refs.nix -A test3)
 
 # test4 should succeed.
-nix-build -o $RESULT check-refs.nix -A test4
+nix-build -o "$RESULT" check-refs.nix -A test4
 
 # test5 should succeed.
-nix-build -o $RESULT check-refs.nix -A test5
+nix-build -o "$RESULT" check-refs.nix -A test5
 
 # test6 should fail (unallowed self-ref).
-(! nix-build -o $RESULT check-refs.nix -A test6)
+(! nix-build -o "$RESULT" check-refs.nix -A test6)
 
 # test7 should succeed (allowed self-ref).
-nix-build -o $RESULT check-refs.nix -A test7
+nix-build -o "$RESULT" check-refs.nix -A test7
 
 # test8 should fail (toFile depending on derivation output).
-(! nix-build -o $RESULT check-refs.nix -A test8)
+(! nix-build -o "$RESULT" check-refs.nix -A test8)
 
 # test9 should fail (disallowed reference).
-(! nix-build -o $RESULT check-refs.nix -A test9)
+(! nix-build -o "$RESULT" check-refs.nix -A test9)
 
 # test10 should succeed (no disallowed references).
-nix-build -o $RESULT check-refs.nix -A test10
+nix-build -o "$RESULT" check-refs.nix -A test10
+
+if ! isTestOnNixOS; then
+    # If we have full control over our store, we can test some more things.
+
+    if isDaemonNewer 2.12pre20230103; then
+        if ! isDaemonNewer 2.16.0; then
+            enableFeatures discard-references
+            restartDaemon
+        fi
 
-if isDaemonNewer 2.12pre20230103; then
-    if ! isDaemonNewer 2.16.0; then
-        enableFeatures discard-references
-        restartDaemon
+        # test11 should succeed.
+        test11=$(nix-build -o "$RESULT" check-refs.nix -A test11)
+        [[ -z $(nix-store -q --references "$test11") ]]
     fi
 
-    # test11 should succeed.
-    test11=$(nix-build -o $RESULT check-refs.nix -A test11)
-    [[ -z $(nix-store -q --references "$test11") ]]
 fi
diff --git a/tests/functional/check-reqs.sh b/tests/functional/check-reqs.sh
old mode 100644
new mode 100755
index 856c94cec37..34eb133db22
--- a/tests/functional/check-reqs.sh
+++ b/tests/functional/check-reqs.sh
@@ -1,16 +1,18 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 RESULT=$TEST_ROOT/result
 
-nix-build -o $RESULT check-reqs.nix -A test1
+nix-build -o "$RESULT" check-reqs.nix -A test1
 
-(! nix-build -o $RESULT check-reqs.nix -A test2)
-(! nix-build -o $RESULT check-reqs.nix -A test3)
-(! nix-build -o $RESULT check-reqs.nix -A test4) 2>&1 | grepQuiet 'check-reqs-dep1'
-(! nix-build -o $RESULT check-reqs.nix -A test4) 2>&1 | grepQuiet 'check-reqs-dep2'
-(! nix-build -o $RESULT check-reqs.nix -A test5)
-(! nix-build -o $RESULT check-reqs.nix -A test6)
+(! nix-build -o "$RESULT" check-reqs.nix -A test2)
+(! nix-build -o "$RESULT" check-reqs.nix -A test3)
+(! nix-build -o "$RESULT" check-reqs.nix -A test4) 2>&1 | grepQuiet 'check-reqs-dep1'
+(! nix-build -o "$RESULT" check-reqs.nix -A test4) 2>&1 | grepQuiet 'check-reqs-dep2'
+(! nix-build -o "$RESULT" check-reqs.nix -A test5)
+(! nix-build -o "$RESULT" check-reqs.nix -A test6)
 
-nix-build -o $RESULT check-reqs.nix -A test7
+nix-build -o "$RESULT" check-reqs.nix -A test7
diff --git a/tests/functional/check.sh b/tests/functional/check.sh
old mode 100644
new mode 100755
index 38883c5d71e..9b15dccb626
--- a/tests/functional/check.sh
+++ b/tests/functional/check.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # XXX: This shouldn’t be, but #4813 cause this test to fail
@@ -13,6 +15,8 @@ checkBuildTempDirRemoved ()
 # written to build temp directories to verify created by this instance
 checkBuildId=$(date +%s%N)
 
+TODO_NixOS
+
 clearStore
 
 nix-build dependencies.nix --no-out-link
@@ -44,7 +48,10 @@ test_custom_build_dir() {
       --no-out-link --keep-failed --option build-dir "$TEST_ROOT/custom-build-dir" 2> $TEST_ROOT/log || status=$?
   [ "$status" = "100" ]
   [[ 1 == "$(count "$customBuildDir/nix-build-"*)" ]]
-  local buildDir="$customBuildDir/nix-build-"*
+  local buildDir="$customBuildDir/nix-build-"*""
+  if [[ -e $buildDir/build ]]; then
+      buildDir=$buildDir/build
+  fi
   grep $checkBuildId $buildDir/checkBuildId
 }
 test_custom_build_dir
@@ -74,6 +81,8 @@ grep 'may not be deterministic' $TEST_ROOT/log
 [ "$status" = "104" ]
 if checkBuildTempDirRemoved $TEST_ROOT/log; then false; fi
 
+TODO_NixOS
+
 clearStore
 
 path=$(nix-build check.nix -A fetchurl --no-out-link)
diff --git a/tests/functional/chroot-store.sh b/tests/functional/chroot-store.sh
old mode 100644
new mode 100755
index 9e589d04b66..03803a2b9fa
--- a/tests/functional/chroot-store.sh
+++ b/tests/functional/chroot-store.sh
@@ -1,33 +1,35 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-echo example > $TEST_ROOT/example.txt
-mkdir -p $TEST_ROOT/x
+echo example > "$TEST_ROOT"/example.txt
+mkdir -p "$TEST_ROOT/x"
 
 export NIX_STORE_DIR=/nix2/store
 
-CORRECT_PATH=$(cd $TEST_ROOT && nix-store --store ./x --add example.txt)
+CORRECT_PATH=$(cd "$TEST_ROOT" && nix-store --store ./x --add example.txt)
 
 [[ $CORRECT_PATH =~ ^/nix2/store/.*-example.txt$ ]]
 
-PATH1=$(cd $TEST_ROOT && nix path-info --store ./x $CORRECT_PATH)
-[ $CORRECT_PATH == $PATH1 ]
+PATH1=$(cd "$TEST_ROOT" && nix path-info --store ./x "$CORRECT_PATH")
+[ "$CORRECT_PATH" == "$PATH1" ]
 
-PATH2=$(nix path-info --store "$TEST_ROOT/x" $CORRECT_PATH)
-[ $CORRECT_PATH == $PATH2 ]
+PATH2=$(nix path-info --store "$TEST_ROOT/x" "$CORRECT_PATH")
+[ "$CORRECT_PATH" == "$PATH2" ]
 
-PATH3=$(nix path-info --store "local?root=$TEST_ROOT/x" $CORRECT_PATH)
-[ $CORRECT_PATH == $PATH3 ]
+PATH3=$(nix path-info --store "local?root=$TEST_ROOT/x" "$CORRECT_PATH")
+[ "$CORRECT_PATH" == "$PATH3" ]
 
 # Ensure store info trusted works with local store
-nix --store $TEST_ROOT/x store info --json | jq -e '.trusted'
+nix --store "$TEST_ROOT/x" store info --json | jq -e '.trusted'
 
 # Test building in a chroot store.
 if canUseSandbox; then
 
     flakeDir=$TEST_ROOT/flake
-    mkdir -p $flakeDir
+    mkdir -p "$flakeDir"
 
-    cat > $flakeDir/flake.nix <<EOF
+    cat > "$flakeDir"/flake.nix <<EOF
 {
   outputs = inputs: rec {
     packages.$system.default = import ./simple.nix;
@@ -35,11 +37,14 @@ if canUseSandbox; then
 }
 EOF
 
-    cp simple.nix shell.nix simple.builder.sh config.nix $flakeDir/
+    cp simple.nix shell.nix simple.builder.sh config.nix "$flakeDir/"
+
+    TODO_NixOS
 
-    outPath=$(nix build --print-out-paths --no-link --sandbox-paths '/nix? /bin? /lib? /lib64? /usr?' --store $TEST_ROOT/x path:$flakeDir)
+    outPath=$(nix build --print-out-paths --no-link --sandbox-paths '/nix? /bin? /lib? /lib64? /usr?' --store "$TEST_ROOT/x" path:"$flakeDir")
 
     [[ $outPath =~ ^/nix2/store/.*-simple$ ]]
 
-    [[ $(cat $TEST_ROOT/x/nix/store/$(basename $outPath)/hello) = 'Hello World!' ]]
+    base=$(basename "$outPath")
+    [[ $(cat "$TEST_ROOT"/x/nix/store/"$base"/hello) = 'Hello World!' ]]
 fi
diff --git a/tests/functional/common.sh b/tests/functional/common.sh
index 7b0922c9f32..d038aaf59dd 100644
--- a/tests/functional/common.sh
+++ b/tests/functional/common.sh
@@ -1,10 +1,16 @@
+# shellcheck shell=bash
+
 set -eu -o pipefail
 
 if [[ -z "${COMMON_SH_SOURCED-}" ]]; then
 
 COMMON_SH_SOURCED=1
 
-source "$(readlink -f "$(dirname "${BASH_SOURCE[0]-$0}")")/common/vars-and-functions.sh"
+functionalTestsDir="$(readlink -f "$(dirname "${BASH_SOURCE[0]-$0}")")"
+
+source "$functionalTestsDir/common/vars-and-functions.sh"
+source "$functionalTestsDir/common/init.sh"
+
 if [[ -n "${NIX_DAEMON_PACKAGE:-}" ]]; then
     startDaemon
 fi
diff --git a/tests/functional/common/init.sh b/tests/functional/common/init.sh
new file mode 100755
index 00000000000..d33ad5d5744
--- /dev/null
+++ b/tests/functional/common/init.sh
@@ -0,0 +1,71 @@
+# shellcheck shell=bash
+
+# for shellcheck
+: "${test_nix_conf_dir?}" "${test_nix_conf?}"
+
+if isTestOnNixOS; then
+
+  mkdir -p "$test_nix_conf_dir" "$TEST_HOME"
+
+  export NIX_USER_CONF_FILES="$test_nix_conf_dir/nix.conf"
+  mkdir -p "$test_nix_conf_dir" "$TEST_HOME"
+  ! test -e "$test_nix_conf"
+  cat > "$test_nix_conf_dir/nix.conf" <<EOF
+# TODO: this is not needed for all tests and prevents stable commands from be tested in isolation
+experimental-features = nix-command flakes
+flake-registry = $TEST_ROOT/registry.json
+show-trace = true
+EOF
+
+  # When we're doing everything in the same store, we need to bring
+  # dependencies into context.
+  sed -i "$(dirname "${BASH_SOURCE[0]}")"/../config.nix \
+    -e 's^\(shell\) = "/nix/store/\([^/]*\)/\(.*\)";^\1 = builtins.appendContext "/nix/store/\2" { "/nix/store/\2".path = true; } + "/\3";^' \
+    -e 's^\(path\) = "/nix/store/\([^/]*\)/\(.*\)";^\1 = builtins.appendContext "/nix/store/\2" { "/nix/store/\2".path = true; } + "/\3";^' \
+    ;
+
+else
+
+test -n "$TEST_ROOT"
+# We would delete any daemon socket, so let's stop the daemon first.
+killDaemon
+# Destroy the test directory that may have persisted from previous runs
+if [[ -e "$TEST_ROOT" ]]; then
+    chmod -R u+w "$TEST_ROOT"
+    rm -rf "$TEST_ROOT"
+fi
+mkdir -p "$TEST_ROOT"
+mkdir "$TEST_HOME"
+
+mkdir "$NIX_STORE_DIR"
+mkdir "$NIX_LOCALSTATE_DIR"
+mkdir -p "$NIX_LOG_DIR/drvs"
+mkdir "$NIX_STATE_DIR"
+mkdir "$NIX_CONF_DIR"
+
+cat > "$NIX_CONF_DIR"/nix.conf <<EOF
+build-users-group =
+keep-derivations = false
+sandbox = false
+experimental-features = nix-command
+gc-reserved-space = 0
+substituters =
+flake-registry = $TEST_ROOT/registry.json
+show-trace = true
+include nix.conf.extra
+trusted-users = $(whoami)
+EOF
+
+cat > "$NIX_CONF_DIR"/nix.conf.extra <<EOF
+fsync-metadata = false
+extra-experimental-features = flakes
+!include nix.conf.extra.not-there
+EOF
+
+# Initialise the database.
+# The flag itself does nothing, but running the command touches the store
+nix-store --init
+# Sanity check
+test -e "$NIX_STATE_DIR"/db/db.sqlite
+
+fi # !isTestOnNixOS
diff --git a/tests/functional/common/paths.sh b/tests/functional/common/paths.sh
new file mode 100644
index 00000000000..938b9089989
--- /dev/null
+++ b/tests/functional/common/paths.sh
@@ -0,0 +1,20 @@
+# shellcheck shell=bash
+
+commonDir="$(readlink -f "$(dirname "${BASH_SOURCE[0]-$0}")")"
+
+# Since this is a generated file
+# shellcheck disable=SC1091
+source "$commonDir/subst-vars.sh"
+# Make sure shellcheck knows this will be defined by the above generated snippet
+: "${bindir?}"
+
+export PATH="$bindir:$PATH"
+
+if [[ -n "${NIX_CLIENT_PACKAGE:-}" ]]; then
+  export PATH="$NIX_CLIENT_PACKAGE/bin":$PATH
+fi
+
+DAEMON_PATH="$PATH"
+if [[ -n "${NIX_DAEMON_PACKAGE:-}" ]]; then
+  DAEMON_PATH="${NIX_DAEMON_PACKAGE}/bin:$DAEMON_PATH"
+fi
diff --git a/tests/functional/common/subst-vars.sh.in b/tests/functional/common/subst-vars.sh.in
new file mode 100644
index 00000000000..90f8923928a
--- /dev/null
+++ b/tests/functional/common/subst-vars.sh.in
@@ -0,0 +1,25 @@
+# NOTE: instances of @variable@ are substituted as defined in /mk/templates.mk
+
+if [[ -z "${COMMON_SUBST_VARS_SH_SOURCED-}" ]]; then
+
+COMMON_SUBST_VARS_SH_SOURCED=1
+
+bindir=@bindir@
+export coreutils=@coreutils@
+#lsof=@lsof@
+
+export dot=@dot@
+export PAGER=cat
+export busybox="@sandbox_shell@"
+
+export version=@PACKAGE_VERSION@
+export system=@system@
+
+export BUILD_SHARED_LIBS=@BUILD_SHARED_LIBS@
+
+if ! isTestOnNixOS; then
+  export SHELL="@bash@"
+  export PATH=@bindir@:$PATH
+fi
+
+fi
diff --git a/tests/functional/common/test-root.sh b/tests/functional/common/test-root.sh
new file mode 100644
index 00000000000..b50a062672a
--- /dev/null
+++ b/tests/functional/common/test-root.sh
@@ -0,0 +1,4 @@
+# shellcheck shell=bash
+
+TEST_ROOT=$(realpath "${TMPDIR:-/tmp}/nix-test")/${TEST_NAME:-default/tests\/functional//}
+export TEST_ROOT
diff --git a/tests/functional/common/vars-and-functions.sh.in b/tests/functional/common/vars-and-functions.sh
similarity index 68%
rename from tests/functional/common/vars-and-functions.sh.in
rename to tests/functional/common/vars-and-functions.sh
index e7e2fc77002..4316a30d5ce 100644
--- a/tests/functional/common/vars-and-functions.sh.in
+++ b/tests/functional/common/vars-and-functions.sh
@@ -1,61 +1,66 @@
+# NOTE: instances of @variable@ are substituted as defined in /mk/templates.mk
+
 set -eu -o pipefail
 
 if [[ -z "${COMMON_VARS_AND_FUNCTIONS_SH_SOURCED-}" ]]; then
 
 COMMON_VARS_AND_FUNCTIONS_SH_SOURCED=1
 
+isTestOnNixOS() {
+  [[ "${isTestOnNixOS:-}" == 1 ]]
+}
+
+die() {
+  echo "unexpected fatal error: $*" >&2
+  exit 1
+}
+
 set +x
 
-export TEST_ROOT=$(realpath ${TMPDIR:-/tmp}/nix-test)/${TEST_NAME:-default/tests\/functional//}
-export NIX_STORE_DIR
-if ! NIX_STORE_DIR=$(readlink -f $TEST_ROOT/store 2> /dev/null); then
-    # Maybe the build directory is symlinked.
-    export NIX_IGNORE_SYMLINK_STORE=1
-    NIX_STORE_DIR=$TEST_ROOT/store
-fi
-export NIX_LOCALSTATE_DIR=$TEST_ROOT/var
-export NIX_LOG_DIR=$TEST_ROOT/var/log/nix
-export NIX_STATE_DIR=$TEST_ROOT/var/nix
-export NIX_CONF_DIR=$TEST_ROOT/etc
-export NIX_DAEMON_SOCKET_PATH=$TEST_ROOT/dSocket
-unset NIX_USER_CONF_FILES
-export _NIX_TEST_SHARED=$TEST_ROOT/shared
-if [[ -n $NIX_STORE ]]; then
-    export _NIX_TEST_NO_SANDBOX=1
-fi
-export _NIX_IN_TEST=$TEST_ROOT/shared
-export _NIX_TEST_NO_LSOF=1
-export NIX_REMOTE=${NIX_REMOTE_-}
-unset NIX_PATH
+commonDir="$(readlink -f "$(dirname "${BASH_SOURCE[0]-$0}")")"
+
+source "$commonDir/subst-vars.sh"
+# Make sure shellcheck knows all these will be defined by the above generated snippet
+: "${bindir?} ${coreutils?} ${dot?} ${SHELL?} ${PAGER?} ${busybox?} ${version?} ${system?} ${BUILD_SHARED_LIBS?}"
+
+source "$commonDir/paths.sh"
+source "$commonDir/test-root.sh"
+
+test_nix_conf_dir=$TEST_ROOT/etc
+test_nix_conf=$test_nix_conf_dir/nix.conf
+
 export TEST_HOME=$TEST_ROOT/test-home
+
+if ! isTestOnNixOS; then
+  export NIX_STORE_DIR
+  if ! NIX_STORE_DIR=$(readlink -f $TEST_ROOT/store 2> /dev/null); then
+      # Maybe the build directory is symlinked.
+      export NIX_IGNORE_SYMLINK_STORE=1
+      NIX_STORE_DIR=$TEST_ROOT/store
+  fi
+  export NIX_LOCALSTATE_DIR=$TEST_ROOT/var
+  export NIX_LOG_DIR=$TEST_ROOT/var/log/nix
+  export NIX_STATE_DIR=$TEST_ROOT/var/nix
+  export NIX_CONF_DIR=$test_nix_conf_dir
+  export NIX_DAEMON_SOCKET_PATH=$TEST_ROOT/dSocket
+  unset NIX_USER_CONF_FILES
+  export _NIX_TEST_SHARED=$TEST_ROOT/shared
+  if [[ -n $NIX_STORE ]]; then
+      export _NIX_TEST_NO_SANDBOX=1
+  fi
+  export _NIX_IN_TEST=$TEST_ROOT/shared
+  export _NIX_TEST_NO_LSOF=1
+  export NIX_REMOTE=${NIX_REMOTE_-}
+
+fi # ! isTestOnNixOS
+
+unset NIX_PATH
 export HOME=$TEST_HOME
 unset XDG_STATE_HOME
 unset XDG_DATA_HOME
 unset XDG_CONFIG_HOME
 unset XDG_CONFIG_DIRS
 unset XDG_CACHE_HOME
-mkdir -p $TEST_HOME
-
-export PATH=@bindir@:$PATH
-if [[ -n "${NIX_CLIENT_PACKAGE:-}" ]]; then
-  export PATH="$NIX_CLIENT_PACKAGE/bin":$PATH
-fi
-DAEMON_PATH="$PATH"
-if [[ -n "${NIX_DAEMON_PACKAGE:-}" ]]; then
-  DAEMON_PATH="${NIX_DAEMON_PACKAGE}/bin:$DAEMON_PATH"
-fi
-coreutils=@coreutils@
-lsof=@lsof@
-
-export dot=@dot@
-export SHELL="@bash@"
-export PAGER=cat
-export busybox="@sandbox_shell@"
-
-export version=@PACKAGE_VERSION@
-export system=@system@
-
-export BUILD_SHARED_LIBS=@BUILD_SHARED_LIBS@
 
 export IMPURE_VAR1=foo
 export IMPURE_VAR2=bar
@@ -71,7 +76,25 @@ clearProfiles() {
     rm -rf "$profiles"
 }
 
+# Clear the store, but do not fail if we're in an environment where we can't.
+# This allows the test to run in a NixOS test environment, where we use the system store.
+# See doc/manual/src/contributing/testing.md / Running functional tests on NixOS.
+clearStoreIfPossible() {
+    if isTestOnNixOS; then
+        echo "clearStoreIfPossible: Not clearing store, because we're on NixOS. Moving on."
+    else
+        doClearStore
+    fi
+}
+
 clearStore() {
+    if isTestOnNixOS; then
+      die "clearStore: not supported when testing on NixOS. If not essential, call clearStoreIfPossible. If really needed, add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+    doClearStore
+}
+
+doClearStore() {
     echo "clearing store..."
     chmod -R +w "$NIX_STORE_DIR"
     rm -rf "$NIX_STORE_DIR"
@@ -90,6 +113,10 @@ clearCacheCache() {
 }
 
 startDaemon() {
+    if isTestOnNixOS; then
+      die "startDaemon: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     # Don’t start the daemon twice, as this would just make it loop indefinitely
     if [[ "${_NIX_TEST_DAEMON_PID-}" != '' ]]; then
         return
@@ -116,6 +143,10 @@ startDaemon() {
 }
 
 killDaemon() {
+    if isTestOnNixOS; then
+      die "killDaemon: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     # Don’t fail trying to stop a non-existant daemon twice
     if [[ "${_NIX_TEST_DAEMON_PID-}" == '' ]]; then
         return
@@ -136,6 +167,10 @@ killDaemon() {
 }
 
 restartDaemon() {
+    if isTestOnNixOS; then
+      die "restartDaemon: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     [[ -z "${_NIX_TEST_DAEMON_PID:-}" ]] && return 0
 
     killDaemon
@@ -158,6 +193,12 @@ skipTest () {
     exit 99
 }
 
+TODO_NixOS() {
+    if isTestOnNixOS; then
+        skipTest "This test has not been adapted for NixOS yet"
+    fi
+}
+
 requireDaemonNewerThan () {
     isDaemonNewer "$1" || skipTest "Daemon is too old"
 }
@@ -175,7 +216,7 @@ requireGit() {
 }
 
 fail() {
-    echo "$1" >&2
+    echo "test failed: $*" >&2
     exit 1
 }
 
@@ -240,7 +281,7 @@ buggyNeedLocalStore() {
 
 enableFeatures() {
     local features="$1"
-    sed -i 's/experimental-features .*/& '"$features"'/' "$NIX_CONF_DIR"/nix.conf
+    sed -i 's/experimental-features .*/& '"$features"'/' "$test_nix_conf_dir"/nix.conf
 }
 
 set -x
diff --git a/tests/functional/completions.sh b/tests/functional/completions.sh
old mode 100644
new mode 100755
index d3d5bbd48b1..9164c5013c5
--- a/tests/functional/completions.sh
+++ b/tests/functional/completions.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 cd "$TEST_ROOT"
diff --git a/tests/functional/compression-levels.sh b/tests/functional/compression-levels.sh
old mode 100644
new mode 100755
index 85f12974ac7..399265f9c91
--- a/tests/functional/compression-levels.sh
+++ b/tests/functional/compression-levels.sh
@@ -1,22 +1,24 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 clearCache
 
 outPath=$(nix-build dependencies.nix --no-out-link)
 
 cacheURI="file://$cacheDir?compression=xz&compression-level=0"
 
-nix copy --to $cacheURI $outPath
+nix copy --to "$cacheURI" "$outPath"
 
-FILESIZES=$(cat ${cacheDir}/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
+FILESIZES=$(cat "${cacheDir}"/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
 
 clearCache
 
 cacheURI="file://$cacheDir?compression=xz&compression-level=5"
 
-nix copy --to $cacheURI $outPath
+nix copy --to "$cacheURI" "$outPath"
 
-FILESIZES2=$(cat ${cacheDir}/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
+FILESIZES2=$(cat "${cacheDir}"/*.narinfo | awk '/FileSize: /{sum+=$2}END{print sum}')
 
 [[ $FILESIZES -gt $FILESIZES2 ]]
diff --git a/tests/functional/compute-levels.sh b/tests/functional/compute-levels.sh
old mode 100644
new mode 100755
index de3da2ebddf..a8bd27610c3
--- a/tests/functional/compute-levels.sh
+++ b/tests/functional/compute-levels.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 if [[ $(uname -ms) = "Linux x86_64" ]]; then
diff --git a/tests/functional/config.sh b/tests/functional/config.sh
old mode 100644
new mode 100755
index efdf2a95850..50858eaa48a
--- a/tests/functional/config.sh
+++ b/tests/functional/config.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Isolate the home for this test.
@@ -26,6 +28,8 @@ nix registry remove userhome-with-xdg
 # Assert the .config folder hasn't been created.
 [ ! -e "$HOME/.config" ]
 
+TODO_NixOS # Very specific test setup not compatible with the NixOS test environment?
+
 # Test that files are loaded from XDG by default
 export XDG_CONFIG_HOME=$TEST_ROOT/confighome
 export XDG_CONFIG_DIRS=$TEST_ROOT/dir1:$TEST_ROOT/dir2
@@ -66,4 +70,9 @@ exp_features=$(nix config show | grep '^experimental-features' | cut -d '=' -f 2
 # Test that it's possible to retrieve a single setting's value
 val=$(nix config show | grep '^warn-dirty' | cut -d '=' -f  2 | xargs)
 val2=$(nix config show warn-dirty)
-[[ $val == $val2 ]]
\ No newline at end of file
+[[ $val == $val2 ]]
+
+# Test unit prefixes.
+[[ $(nix config show --min-free 64K min-free) = 65536 ]]
+[[ $(nix config show --min-free 1M min-free) = 1048576 ]]
+[[ $(nix config show --min-free 2G min-free) = 2147483648 ]]
diff --git a/tests/functional/db-migration.sh b/tests/functional/db-migration.sh
old mode 100644
new mode 100755
index 44cd16bc09b..6feabb90dd2
--- a/tests/functional/db-migration.sh
+++ b/tests/functional/db-migration.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test that we can successfully migrate from an older db schema
 
 source common.sh
@@ -8,6 +10,8 @@ if [[ -z "${NIX_DAEMON_PACKAGE-}" ]]; then
     skipTest "not using the Nix daemon"
 fi
 
+TODO_NixOS
+
 killDaemon
 
 # Fill the db using the older Nix
diff --git a/tests/functional/debugger.sh b/tests/functional/debugger.sh
old mode 100644
new mode 100755
index 63d88cbf35b..b96b7e5d3f7
--- a/tests/functional/debugger.sh
+++ b/tests/functional/debugger.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 # regression #9932
 echo ":env" | expect 1 nix eval --debugger --expr '(_: throw "oh snap") 42'
diff --git a/tests/functional/dependencies.sh b/tests/functional/dependencies.sh
old mode 100644
new mode 100755
index b93dacac0b9..972bc5a9bd6
--- a/tests/functional/dependencies.sh
+++ b/tests/functional/dependencies.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 drvPath=$(nix-instantiate dependencies.nix)
 
@@ -31,7 +33,7 @@ nix-store -q --tree "$outPath" | grep '───.*dependencies-input-2'
 
 echo "output path is $outPath"
 
-text=$(cat "$outPath"/foobar)
+text=$(cat "$outPath/foobar")
 if test "$text" != "FOOBAR"; then exit 1; fi
 
 deps=$(nix-store -quR "$drvPath")
@@ -63,6 +65,8 @@ drvPath2=$(nix-instantiate dependencies.nix --argstr hashInvalidator yay)
 # now --valid-derivers returns both
 test "$(nix-store -q --valid-derivers "$outPath" | sort)" = "$(sort <<< "$drvPath"$'\n'"$drvPath2")"
 
+TODO_NixOS # The following --delete fails, because it seems to be still alive. This might be caused by a different test using the same path. We should try make the derivations unique, e.g. naming after tests, and adding a timestamp that's constant for that test script run.
+
 # check that nix-store --valid-derivers only returns existing drv
 nix-store --delete "$drvPath"
 test "$(nix-store -q --valid-derivers "$outPath")" = "$drvPath2"
diff --git a/tests/functional/derivation-advanced-attributes.sh b/tests/functional/derivation-advanced-attributes.sh
new file mode 100755
index 00000000000..6c0c76b4cee
--- /dev/null
+++ b/tests/functional/derivation-advanced-attributes.sh
@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+source common/test-root.sh
+source common/paths.sh
+
+set -o pipefail
+
+source characterisation/framework.sh
+
+badDiff=0
+badExitCode=0
+
+store="$TEST_ROOT/store"
+
+for nixFile in derivation/*.nix; do
+    drvPath=$(nix-instantiate --store "$store" --pure-eval --expr "$(< "$nixFile")")
+    testName=$(basename "$nixFile" .nix)
+    got="${store}${drvPath}"
+    expected="derivation/$testName.drv"
+    diffAndAcceptInner "$testName" "$got" "$expected"
+done
+
+characterisationTestExit
diff --git a/tests/functional/derivation-json.sh b/tests/functional/derivation-json.sh
old mode 100644
new mode 100755
index b6be5d977da..06f934cfe0a
--- a/tests/functional/derivation-json.sh
+++ b/tests/functional/derivation-json.sh
@@ -1,12 +1,14 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 drvPath=$(nix-instantiate simple.nix)
 
-nix derivation show $drvPath | jq .[] > $TEST_HOME/simple.json
+nix derivation show "$drvPath" | jq .[] > "$TEST_HOME"/simple.json
 
-drvPath2=$(nix derivation add < $TEST_HOME/simple.json)
+drvPath2=$(nix derivation add < "$TEST_HOME"/simple.json)
 
 [[ "$drvPath" = "$drvPath2" ]]
 
 # Input addressed derivations cannot be renamed.
-jq '.name = "foo"' < $TEST_HOME/simple.json | expectStderr 1 nix derivation add | grepQuiet "has incorrect output"
+jq '.name = "foo"' < "$TEST_HOME"/simple.json | expectStderr 1 nix derivation add | grepQuiet "has incorrect output"
diff --git a/tests/functional/derivation/advanced-attributes-defaults.drv b/tests/functional/derivation/advanced-attributes-defaults.drv
new file mode 100644
index 00000000000..391c6ab807c
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes-defaults.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/1qsc7svv43m4dw2prh6mvyf7cai5czji-advanced-attributes-defaults","","")],[],[],"my-system","/bin/bash",["-c","echo hello > $out"],[("builder","/bin/bash"),("name","advanced-attributes-defaults"),("out","/nix/store/1qsc7svv43m4dw2prh6mvyf7cai5czji-advanced-attributes-defaults"),("system","my-system")])
\ No newline at end of file
diff --git a/tests/functional/derivation/advanced-attributes-defaults.nix b/tests/functional/derivation/advanced-attributes-defaults.nix
new file mode 100644
index 00000000000..51a8d0e7e1a
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes-defaults.nix
@@ -0,0 +1,6 @@
+derivation {
+  name = "advanced-attributes-defaults";
+  system = "my-system";
+  builder = "/bin/bash";
+  args = [ "-c" "echo hello > $out" ];
+}
diff --git a/tests/functional/derivation/advanced-attributes-structured-attrs-defaults.drv b/tests/functional/derivation/advanced-attributes-structured-attrs-defaults.drv
new file mode 100644
index 00000000000..9dd4020571c
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes-structured-attrs-defaults.drv
@@ -0,0 +1 @@
+Derive([("dev","/nix/store/8bazivnbipbyi569623skw5zm91z6kc2-advanced-attributes-structured-attrs-defaults-dev","",""),("out","/nix/store/f8f8nvnx32bxvyxyx2ff7akbvwhwd9dw-advanced-attributes-structured-attrs-defaults","","")],[],[],"my-system","/bin/bash",["-c","echo hello > $out"],[("__json","{\"builder\":\"/bin/bash\",\"name\":\"advanced-attributes-structured-attrs-defaults\",\"outputs\":[\"out\",\"dev\"],\"system\":\"my-system\"}"),("dev","/nix/store/8bazivnbipbyi569623skw5zm91z6kc2-advanced-attributes-structured-attrs-defaults-dev"),("out","/nix/store/f8f8nvnx32bxvyxyx2ff7akbvwhwd9dw-advanced-attributes-structured-attrs-defaults")])
\ No newline at end of file
diff --git a/tests/functional/derivation/advanced-attributes-structured-attrs-defaults.nix b/tests/functional/derivation/advanced-attributes-structured-attrs-defaults.nix
new file mode 100644
index 00000000000..0c13a76911f
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes-structured-attrs-defaults.nix
@@ -0,0 +1,8 @@
+derivation {
+  name = "advanced-attributes-structured-attrs-defaults";
+  system = "my-system";
+  builder = "/bin/bash";
+  args = [ "-c" "echo hello > $out" ];
+  outputs = [ "out" "dev" ];
+  __structuredAttrs = true;
+}
diff --git a/tests/functional/derivation/advanced-attributes-structured-attrs.drv b/tests/functional/derivation/advanced-attributes-structured-attrs.drv
new file mode 100644
index 00000000000..e47a41ad525
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes-structured-attrs.drv
@@ -0,0 +1 @@
+Derive([("bin","/nix/store/pbzb48v0ycf80jgligcp4n8z0rblna4n-advanced-attributes-structured-attrs-bin","",""),("dev","/nix/store/7xapi8jv7flcz1qq8jhw55ar8ag8hldh-advanced-attributes-structured-attrs-dev","",""),("out","/nix/store/mpq3l1l1qc2yr50q520g08kprprwv79f-advanced-attributes-structured-attrs","","")],[("/nix/store/4xm4wccqsvagz9gjksn24s7rip2fdy7v-foo.drv",["out"]),("/nix/store/plsq5jbr5nhgqwcgb2qxw7jchc09dnl8-bar.drv",["out"])],[],"my-system","/bin/bash",["-c","echo hello > $out"],[("__json","{\"__darwinAllowLocalNetworking\":true,\"__impureHostDeps\":[\"/usr/bin/ditto\"],\"__noChroot\":true,\"__sandboxProfile\":\"sandcastle\",\"allowSubstitutes\":false,\"builder\":\"/bin/bash\",\"impureEnvVars\":[\"UNICORN\"],\"name\":\"advanced-attributes-structured-attrs\",\"outputChecks\":{\"bin\":{\"disallowedReferences\":[\"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar\"],\"disallowedRequisites\":[\"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar\"]},\"dev\":{\"maxClosureSize\":5909,\"maxSize\":789},\"out\":{\"allowedReferences\":[\"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo\"],\"allowedRequisites\":[\"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo\"]}},\"outputs\":[\"out\",\"bin\",\"dev\"],\"preferLocalBuild\":true,\"requiredSystemFeatures\":[\"rainbow\",\"uid-range\"],\"system\":\"my-system\"}"),("bin","/nix/store/pbzb48v0ycf80jgligcp4n8z0rblna4n-advanced-attributes-structured-attrs-bin"),("dev","/nix/store/7xapi8jv7flcz1qq8jhw55ar8ag8hldh-advanced-attributes-structured-attrs-dev"),("out","/nix/store/mpq3l1l1qc2yr50q520g08kprprwv79f-advanced-attributes-structured-attrs")])
\ No newline at end of file
diff --git a/tests/functional/derivation/advanced-attributes-structured-attrs.nix b/tests/functional/derivation/advanced-attributes-structured-attrs.nix
new file mode 100644
index 00000000000..0044b65fd41
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes-structured-attrs.nix
@@ -0,0 +1,45 @@
+let
+  system = "my-system";
+  foo = derivation {
+    inherit system;
+    name = "foo";
+    builder = "/bin/bash";
+    args = ["-c" "echo foo > $out"];
+  };
+  bar = derivation {
+    inherit system;
+    name = "bar";
+    builder = "/bin/bash";
+    args = ["-c" "echo bar > $out"];
+  };
+in
+derivation {
+  inherit system;
+  name = "advanced-attributes-structured-attrs";
+  builder = "/bin/bash";
+  args = [ "-c" "echo hello > $out" ];
+  __sandboxProfile = "sandcastle";
+  __noChroot = true;
+  __impureHostDeps = ["/usr/bin/ditto"];
+  impureEnvVars = ["UNICORN"];
+  __darwinAllowLocalNetworking = true;
+  outputs = [ "out" "bin" "dev" ];
+  __structuredAttrs = true;
+  outputChecks = {
+    out = {
+      allowedReferences = [foo];
+      allowedRequisites = [foo];
+    };
+    bin = {
+      disallowedReferences = [bar];
+      disallowedRequisites = [bar];
+    };
+    dev = {
+      maxSize = 789;
+      maxClosureSize = 5909;
+    };
+  };
+  requiredSystemFeatures = ["rainbow" "uid-range"];
+  preferLocalBuild = true;
+  allowSubstitutes = false;
+}
diff --git a/tests/functional/derivation/advanced-attributes.drv b/tests/functional/derivation/advanced-attributes.drv
new file mode 100644
index 00000000000..ec3112ab2b1
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes.drv
@@ -0,0 +1 @@
+Derive([("out","/nix/store/33a6fdmn8q9ih9d7npbnrxn2q56a4l8q-advanced-attributes","","")],[("/nix/store/4xm4wccqsvagz9gjksn24s7rip2fdy7v-foo.drv",["out"]),("/nix/store/plsq5jbr5nhgqwcgb2qxw7jchc09dnl8-bar.drv",["out"])],[],"my-system","/bin/bash",["-c","echo hello > $out"],[("__darwinAllowLocalNetworking","1"),("__impureHostDeps","/usr/bin/ditto"),("__noChroot","1"),("__sandboxProfile","sandcastle"),("allowSubstitutes",""),("allowedReferences","/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo"),("allowedRequisites","/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo"),("builder","/bin/bash"),("disallowedReferences","/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar"),("disallowedRequisites","/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar"),("impureEnvVars","UNICORN"),("name","advanced-attributes"),("out","/nix/store/33a6fdmn8q9ih9d7npbnrxn2q56a4l8q-advanced-attributes"),("preferLocalBuild","1"),("requiredSystemFeatures","rainbow uid-range"),("system","my-system")])
\ No newline at end of file
diff --git a/tests/functional/derivation/advanced-attributes.nix b/tests/functional/derivation/advanced-attributes.nix
new file mode 100644
index 00000000000..ff680c5677f
--- /dev/null
+++ b/tests/functional/derivation/advanced-attributes.nix
@@ -0,0 +1,33 @@
+let
+  system = "my-system";
+  foo = derivation {
+    inherit system;
+    name = "foo";
+    builder = "/bin/bash";
+    args = ["-c" "echo foo > $out"];
+  };
+  bar = derivation {
+    inherit system;
+    name = "bar";
+    builder = "/bin/bash";
+    args = ["-c" "echo bar > $out"];
+  };
+in
+derivation {
+  inherit system;
+  name = "advanced-attributes";
+  builder = "/bin/bash";
+  args = [ "-c" "echo hello > $out" ];
+  __sandboxProfile = "sandcastle";
+  __noChroot = true;
+  __impureHostDeps = ["/usr/bin/ditto"];
+  impureEnvVars = ["UNICORN"];
+  __darwinAllowLocalNetworking = true;
+  allowedReferences = [foo];
+  allowedRequisites = [foo];
+  disallowedReferences = [bar];
+  disallowedRequisites = [bar];
+  requiredSystemFeatures = ["rainbow" "uid-range"];
+  preferLocalBuild = true;
+  allowSubstitutes = false;
+}
diff --git a/tests/functional/dump-db.sh b/tests/functional/dump-db.sh
old mode 100644
new mode 100755
index 48647f40382..14181b4b63d
--- a/tests/functional/dump-db.sh
+++ b/tests/functional/dump-db.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 needLocalStore "--dump-db requires a local store"
 
 clearStore
diff --git a/tests/functional/dyn-drv/common.sh b/tests/functional/dyn-drv/common.sh
index c786f6925fb..0d95881b6ab 100644
--- a/tests/functional/dyn-drv/common.sh
+++ b/tests/functional/dyn-drv/common.sh
@@ -5,4 +5,6 @@ requireDaemonNewerThan "2.16.0pre20230419"
 
 enableFeatures "ca-derivations dynamic-derivations"
 
+TODO_NixOS
+
 restartDaemon
diff --git a/tests/functional/dyn-drv/text-hashed-output.sh b/tests/functional/dyn-drv/text-hashed-output.sh
index f3e5aa93bb7..2cc877219ac 100644
--- a/tests/functional/dyn-drv/text-hashed-output.sh
+++ b/tests/functional/dyn-drv/text-hashed-output.sh
@@ -20,7 +20,7 @@ nix show-derivation "$drvProducingDrv"
 
 out1=$(nix-build ./text-hashed-output.nix -A producingDrv --no-out-link)
 
-nix path-info $drv --derivation --json | jq
-nix path-info $out1 --derivation --json | jq
+nix path-info "$drv" --derivation --json | jq
+nix path-info "$out1" --derivation --json | jq
 
-test $out1 == $drv
+test "$out1" == "$drv"
diff --git a/tests/functional/eval-store.sh b/tests/functional/eval-store.sh
old mode 100644
new mode 100755
index 9937ecbce65..202e7b00413
--- a/tests/functional/eval-store.sh
+++ b/tests/functional/eval-store.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 # Using `--eval-store` with the daemon will eventually copy everything
 # to the build store, invalidating most of the tests here
 needLocalStore "“--eval-store” doesn't achieve much with the daemon"
diff --git a/tests/functional/eval.sh b/tests/functional/eval.sh
old mode 100644
new mode 100755
index c6a475cd090..27cdce478e3
--- a/tests/functional/eval.sh
+++ b/tests/functional/eval.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 testStdinHeredoc=$(nix eval -f - <<EOF
 {
@@ -52,3 +54,7 @@ fi
 
 # Test --arg-from-stdin.
 [[ "$(echo bla | nix eval --raw --arg-from-stdin foo --expr '{ foo }: { inherit foo; }' foo)" = bla ]]
+
+# Test that unknown settings are warned about
+out="$(expectStderr 0 nix eval --option foobar baz --expr '""' --raw)"
+[[ "$(echo "$out" | grep foobar | wc -l)" = 1 ]]
diff --git a/tests/functional/experimental-features.sh b/tests/functional/experimental-features.sh
old mode 100644
new mode 100755
index 12112b2931d..d7216992d4e
--- a/tests/functional/experimental-features.sh
+++ b/tests/functional/experimental-features.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Skipping these two for now, because we actually *do* want flags and
@@ -31,35 +33,35 @@ source common.sh
 NIX_CONFIG='
   experimental-features = nix-command
   accept-flake-config = true
-' expect 1 nix config show accept-flake-config 1>$TEST_ROOT/stdout 2>$TEST_ROOT/stderr
-[[ $(cat $TEST_ROOT/stdout) = '' ]]
-grepQuiet "Ignoring setting 'accept-flake-config' because experimental feature 'flakes' is not enabled" $TEST_ROOT/stderr
-grepQuiet "error: could not find setting 'accept-flake-config'" $TEST_ROOT/stderr
+' expect 1 nix config show accept-flake-config 1>"$TEST_ROOT"/stdout 2>"$TEST_ROOT"/stderr
+[[ $(cat "$TEST_ROOT/stdout") = '' ]]
+grepQuiet "Ignoring setting 'accept-flake-config' because experimental feature 'flakes' is not enabled" "$TEST_ROOT/stderr"
+grepQuiet "error: could not find setting 'accept-flake-config'" "$TEST_ROOT/stderr"
 
 # 'flakes' experimental-feature is disabled after, ignore and warn
 NIX_CONFIG='
   accept-flake-config = true
   experimental-features = nix-command
-' expect 1 nix config show accept-flake-config 1>$TEST_ROOT/stdout 2>$TEST_ROOT/stderr
-[[ $(cat $TEST_ROOT/stdout) = '' ]]
-grepQuiet "Ignoring setting 'accept-flake-config' because experimental feature 'flakes' is not enabled" $TEST_ROOT/stderr
-grepQuiet "error: could not find setting 'accept-flake-config'" $TEST_ROOT/stderr
+' expect 1 nix config show accept-flake-config 1>"$TEST_ROOT"/stdout 2>"$TEST_ROOT"/stderr
+[[ $(cat "$TEST_ROOT/stdout") = '' ]]
+grepQuiet "Ignoring setting 'accept-flake-config' because experimental feature 'flakes' is not enabled" "$TEST_ROOT/stderr"
+grepQuiet "error: could not find setting 'accept-flake-config'" "$TEST_ROOT/stderr"
 
 # 'flakes' experimental-feature is enabled before, process
 NIX_CONFIG='
   experimental-features = nix-command flakes
   accept-flake-config = true
-' nix config show accept-flake-config 1>$TEST_ROOT/stdout 2>$TEST_ROOT/stderr
-grepQuiet "true" $TEST_ROOT/stdout
-grepQuietInverse "Ignoring setting 'accept-flake-config'" $TEST_ROOT/stderr
+' nix config show accept-flake-config 1>"$TEST_ROOT"/stdout 2>"$TEST_ROOT"/stderr
+grepQuiet "true" "$TEST_ROOT/stdout"
+grepQuietInverse "Ignoring setting 'accept-flake-config'" "$TEST_ROOT/stderr"
 
 # 'flakes' experimental-feature is enabled after, process
 NIX_CONFIG='
   accept-flake-config = true
   experimental-features = nix-command flakes
-' nix config show accept-flake-config 1>$TEST_ROOT/stdout 2>$TEST_ROOT/stderr
-grepQuiet "true" $TEST_ROOT/stdout
-grepQuietInverse "Ignoring setting 'accept-flake-config'" $TEST_ROOT/stderr
+' nix config show accept-flake-config 1>"$TEST_ROOT"/stdout 2>"$TEST_ROOT"/stderr
+grepQuiet "true" "$TEST_ROOT/stdout"
+grepQuietInverse "Ignoring setting 'accept-flake-config'" "$TEST_ROOT/stderr"
 
 function exit_code_both_ways {
     expect 1 nix --experimental-features 'nix-command' "$@" 1>/dev/null
diff --git a/tests/functional/export-graph.sh b/tests/functional/export-graph.sh
old mode 100644
new mode 100755
index 1f6232a406e..b507b6d3a12
--- a/tests/functional/export-graph.sh
+++ b/tests/functional/export-graph.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 clearProfiles
 
diff --git a/tests/functional/export.sh b/tests/functional/export.sh
old mode 100644
new mode 100755
index 2238539bcca..3e895a5402d
--- a/tests/functional/export.sh
+++ b/tests/functional/export.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 outPath=$(nix-build dependencies.nix --no-out-link)
diff --git a/tests/functional/extra-sandbox-profile.nix b/tests/functional/extra-sandbox-profile.nix
new file mode 100644
index 00000000000..aa680b918a6
--- /dev/null
+++ b/tests/functional/extra-sandbox-profile.nix
@@ -0,0 +1,19 @@
+{ destFile, seed }:
+
+with import ./config.nix;
+
+mkDerivation {
+  name = "simple";
+  __sandboxProfile = ''
+    # Allow writing any file in the filesystem
+    (allow file*)
+  '';
+  inherit seed;
+  buildCommand = ''
+    (
+      set -x
+      touch ${destFile}
+      touch $out
+    )
+  '';
+}
diff --git a/tests/functional/extra-sandbox-profile.sh b/tests/functional/extra-sandbox-profile.sh
new file mode 100755
index 00000000000..672e5779d21
--- /dev/null
+++ b/tests/functional/extra-sandbox-profile.sh
@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+source common.sh
+
+if [[ $(uname) != Darwin ]]; then skipTest "Need Darwin"; fi
+
+DEST_FILE="${TEST_ROOT}/foo"
+
+testSandboxProfile () (
+    set -e
+
+    sandboxMode="$1"
+
+    rm -f "${DEST_FILE}"
+    nix-build --no-out-link ./extra-sandbox-profile.nix \
+        --option sandbox "$sandboxMode" \
+        --argstr seed "$RANDOM" \
+        --argstr destFile "${DEST_FILE}"
+
+    ls -l "${DEST_FILE}"
+)
+
+testSandboxProfile "false"
+expectStderr 2 testSandboxProfile "true"
+testSandboxProfile "relaxed"
diff --git a/tests/functional/fetchClosure.sh b/tests/functional/fetchClosure.sh
old mode 100644
new mode 100755
index a02d1ce7a28..7ef635d3677
--- a/tests/functional/fetchClosure.sh
+++ b/tests/functional/fetchClosure.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "fetch-closure"
 
+TODO_NixOS
+
 clearStore
 clearCacheCache
 
diff --git a/tests/functional/fetchGit.sh b/tests/functional/fetchGit.sh
old mode 100644
new mode 100755
index 74d6de4e39f..78925b5cdd6
--- a/tests/functional/fetchGit.sh
+++ b/tests/functional/fetchGit.sh
@@ -1,8 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireGit
 
-clearStore
+clearStoreIfPossible
 
 # Intentionally not in a canonical form
 # See https://github.com/NixOS/nix/issues/6195
diff --git a/tests/functional/fetchGitRefs.sh b/tests/functional/fetchGitRefs.sh
old mode 100644
new mode 100755
index d643fea04dd..ee054fabc5b
--- a/tests/functional/fetchGitRefs.sh
+++ b/tests/functional/fetchGitRefs.sh
@@ -1,8 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireGit
 
-clearStore
+clearStoreIfPossible
 
 repo="$TEST_ROOT/git"
 
@@ -12,7 +14,7 @@ git init "$repo"
 git -C "$repo" config user.email "foobar@example.com"
 git -C "$repo" config user.name "Foobar"
 
-echo utrecht > "$repo"/hello
+echo utrecht > "$repo/hello"
 git -C "$repo" add hello
 git -C "$repo" commit -m 'Bla1'
 
diff --git a/tests/functional/fetchGitSubmodules.sh b/tests/functional/fetchGitSubmodules.sh
old mode 100644
new mode 100755
index cd180815d69..4a3e4c347ec
--- a/tests/functional/fetchGitSubmodules.sh
+++ b/tests/functional/fetchGitSubmodules.sh
@@ -1,10 +1,12 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 set -u
 
 requireGit
 
-clearStore
+clearStoreIfPossible
 
 rootRepo=$TEST_ROOT/gitSubmodulesRoot
 subRepo=$TEST_ROOT/gitSubmodulesSub
@@ -170,3 +172,45 @@ pathWithSubmodules=$(nix eval --impure --raw --expr "(builtins.fetchGit { url =
 
 [[ -e $pathWithoutExportIgnore/exclude-from-root ]]
 [[ -e $pathWithoutExportIgnore/sub/exclude-from-sub ]]
+
+test_submodule_nested() {
+  local repoA=$TEST_ROOT/submodule_nested/a
+  local repoB=$TEST_ROOT/submodule_nested/b
+  local repoC=$TEST_ROOT/submodule_nested/c
+
+  rm -rf $repoA $repoB $repoC $TEST_HOME/.cache/nix
+
+  initGitRepo $repoC
+  touch $repoC/inside-c
+  git -C $repoC add inside-c
+  addGitContent $repoC
+
+  initGitRepo $repoB
+  git -C $repoB submodule add $repoC c
+  git -C $repoB add c
+  addGitContent $repoB
+
+  initGitRepo $repoA
+  git -C $repoA submodule add $repoB b
+  git -C $repoA add b
+  addGitContent $repoA
+
+
+  # Check non-worktree fetch
+  local rev=$(git -C $repoA rev-parse HEAD)
+  out=$(nix eval --impure --raw --expr "(builtins.fetchGit { url = \"file://$repoA\"; rev = \"$rev\"; submodules = true; }).outPath")
+  test -e $out/b/c/inside-c
+  test -e $out/content
+  test -e $out/b/content
+  test -e $out/b/c/content
+  local nonWorktree=$out
+
+  # Check worktree based fetch
+  # TODO: make it work without git submodule update
+  git -C $repoA submodule update --init --recursive
+  out=$(nix eval --impure --raw --expr "(builtins.fetchGit { url = \"file://$repoA\"; submodules = true; }).outPath")
+  find $out
+  [[ $out == $nonWorktree ]] || { find $out; false; }
+
+}
+test_submodule_nested
diff --git a/tests/functional/fetchGitVerification.sh b/tests/functional/fetchGitVerification.sh
old mode 100644
new mode 100755
index b80e061b5f5..4012d82290e
--- a/tests/functional/fetchGitVerification.sh
+++ b/tests/functional/fetchGitVerification.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireGit
@@ -5,7 +7,7 @@ requireGit
 
 enableFeatures "verified-fetches"
 
-clearStore
+clearStoreIfPossible
 
 repo="$TEST_ROOT/git"
 
diff --git a/tests/functional/fetchMercurial.sh b/tests/functional/fetchMercurial.sh
old mode 100644
new mode 100755
index e133df1f8a0..6de19286587
--- a/tests/functional/fetchMercurial.sh
+++ b/tests/functional/fetchMercurial.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 [[ $(type -p hg) ]] || skipTest "Mercurial not installed"
 
+TODO_NixOS
+
 clearStore
 
 # Intentionally not in a canonical form
@@ -101,6 +105,7 @@ path4=$(nix eval --impure --refresh --raw --expr "(builtins.fetchMercurial file:
 [[ $path2 = $path4 ]]
 
 echo paris > $repo/hello
+
 # Passing a `name` argument should be reflected in the output path
 path5=$(nix eval -vvvvv --impure --refresh --raw --expr "(builtins.fetchMercurial { url = \"file://$repo\"; name = \"foo\"; } ).outPath")
 [[ $path5 =~ -foo$ ]]
diff --git a/tests/functional/fetchPath.sh b/tests/functional/fetchPath.sh
old mode 100644
new mode 100755
index 29be38ce2f5..560a270c1a9
--- a/tests/functional/fetchPath.sh
+++ b/tests/functional/fetchPath.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-touch $TEST_ROOT/foo -t 202211111111
+touch "$TEST_ROOT/foo" -t 202211111111
 # We only check whether 2022-11-1* **:**:** is the last modified date since
 # `lastModified` is transformed into UTC in `builtins.fetchTarball`.
 [[ "$(nix eval --impure --raw --expr "(builtins.fetchTree \"path://$TEST_ROOT/foo\").lastModifiedDate")" =~ 2022111.* ]]
diff --git a/tests/functional/fetchTree-file.sh b/tests/functional/fetchTree-file.sh
old mode 100644
new mode 100755
index be698ea35d4..66be928c7b6
--- a/tests/functional/fetchTree-file.sh
+++ b/tests/functional/fetchTree-file.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 cd "$TEST_ROOT"
@@ -88,7 +92,7 @@ EOF
 EOF
 
     # Test tarball URLs on the command line.
-    [[ $(nix flake metadata --json file://$PWD/test_input_no_ext | jq -r .resolved.type) = tarball ]]
+    [[ $(nix flake metadata --json "file://$PWD/test_input_no_ext" | jq -r .resolved.type) = tarball ]]
 
     popd
 
diff --git a/tests/functional/fetchurl.sh b/tests/functional/fetchurl.sh
old mode 100644
new mode 100755
index a3620f52b6f..5af44fcf277
--- a/tests/functional/fetchurl.sh
+++ b/tests/functional/fetchurl.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 # Test fetching a flat file.
diff --git a/tests/functional/filter-source.sh b/tests/functional/filter-source.sh
old mode 100644
new mode 100755
index ba34d2eac86..b32f5b59d52
--- a/tests/functional/filter-source.sh
+++ b/tests/functional/filter-source.sh
@@ -1,25 +1,27 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-rm -rf $TEST_ROOT/filterin
-mkdir $TEST_ROOT/filterin
-mkdir $TEST_ROOT/filterin/foo
-touch $TEST_ROOT/filterin/foo/bar
-touch $TEST_ROOT/filterin/xyzzy
-touch $TEST_ROOT/filterin/b
-touch $TEST_ROOT/filterin/bak
-touch $TEST_ROOT/filterin/bla.c.bak
-ln -s xyzzy $TEST_ROOT/filterin/link
+rm -rf "$TEST_ROOT/filterin"
+mkdir "$TEST_ROOT/filterin"
+mkdir "$TEST_ROOT/filterin/foo"
+touch "$TEST_ROOT/filterin/foo/bar"
+touch "$TEST_ROOT/filterin/xyzzy"
+touch "$TEST_ROOT/filterin/b"
+touch "$TEST_ROOT/filterin/bak"
+touch "$TEST_ROOT"/filterin/bla.c.bak
+ln -s xyzzy "$TEST_ROOT/filterin/link"
 
 checkFilter() {
-    test ! -e $1/foo/bar
-    test -e $1/xyzzy
-    test -e $1/bak
-    test ! -e $1/bla.c.bak
-    test ! -L $1/link
+    test ! -e "$1/foo/bar"
+    test -e "$1/xyzzy"
+    test -e "$1/bak"
+    test ! -e "$1"/bla.c.bak
+    test ! -L "$1/link"
 }
 
-nix-build ./filter-source.nix -o $TEST_ROOT/filterout1
-checkFilter $TEST_ROOT/filterout1
+nix-build ./filter-source.nix -o "$TEST_ROOT/filterout1"
+checkFilter "$TEST_ROOT/filterout1"
 
-nix-build ./path.nix -o $TEST_ROOT/filterout2
-checkFilter $TEST_ROOT/filterout2
+nix-build ./path.nix -o "$TEST_ROOT/filterout2"
+checkFilter "$TEST_ROOT/filterout2"
diff --git a/tests/functional/fixed.sh b/tests/functional/fixed.sh
old mode 100644
new mode 100755
index 7bbecda9163..d98769e6435
--- a/tests/functional/fixed.sh
+++ b/tests/functional/fixed.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 path=$(nix-store -q $(nix-instantiate fixed.nix -A good.0))
diff --git a/tests/functional/flakes/absolute-attr-paths.sh b/tests/functional/flakes/absolute-attr-paths.sh
old mode 100644
new mode 100755
index 491adceb72e..b0e6225d87d
--- a/tests/functional/flakes/absolute-attr-paths.sh
+++ b/tests/functional/flakes/absolute-attr-paths.sh
@@ -1,9 +1,11 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 flake1Dir=$TEST_ROOT/flake1
 
-mkdir -p $flake1Dir
-cat > $flake1Dir/flake.nix <<EOF
+mkdir -p "$flake1Dir"
+cat > "$flake1Dir"/flake.nix <<EOF
 {
     outputs = { self }: {
         x = 1;
@@ -12,6 +14,6 @@ cat > $flake1Dir/flake.nix <<EOF
 }
 EOF
 
-[ "$(nix eval --impure --json $flake1Dir#.x)" -eq 1 ]
-[ "$(nix eval --impure --json $flake1Dir#x)" -eq 2 ]
-[ "$(nix eval --impure --json $flake1Dir#.packages.$system.x)" -eq 2 ]
+[ "$(nix eval --impure --json "$flake1Dir"#.x)" -eq 1 ]
+[ "$(nix eval --impure --json "$flake1Dir#x")" -eq 2 ]
+[ "$(nix eval --impure --json "$flake1Dir"#.packages."$system".x)" -eq 2 ]
diff --git a/tests/functional/flakes/absolute-paths.sh b/tests/functional/flakes/absolute-paths.sh
old mode 100644
new mode 100755
index e7bfba12d17..a355a7a1c07
--- a/tests/functional/flakes/absolute-paths.sh
+++ b/tests/functional/flakes/absolute-paths.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/build-paths.sh b/tests/functional/flakes/build-paths.sh
old mode 100644
new mode 100755
index 4e5c6809567..f8486528bb6
--- a/tests/functional/flakes/build-paths.sh
+++ b/tests/functional/flakes/build-paths.sh
@@ -1,17 +1,19 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 flake1Dir=$TEST_ROOT/flake1
 flake2Dir=$TEST_ROOT/flake2
 
-mkdir -p $flake1Dir $flake2Dir
+mkdir -p "$flake1Dir" "$flake2Dir"
 
-writeSimpleFlake $flake2Dir
-tar cfz $TEST_ROOT/flake.tar.gz -C $TEST_ROOT flake2
-hash=$(nix hash path $flake2Dir)
+writeSimpleFlake "$flake2Dir"
+tar cfz "$TEST_ROOT"/flake.tar.gz -C "$TEST_ROOT" flake2
+hash=$(nix hash path "$flake2Dir")
 
 dep=$(nix store add-path ./common.sh)
 
-cat > $flake1Dir/flake.nix <<EOF
+cat > "$flake1Dir"/flake.nix <<EOF
 {
   inputs.flake2.url = "file://$TEST_ROOT/flake.tar.gz";
 
@@ -77,43 +79,43 @@ cat > $flake1Dir/flake.nix <<EOF
 }
 EOF
 
-cp ../simple.nix ../simple.builder.sh ../config.nix $flake1Dir/
+cp ../simple.nix ../simple.builder.sh ../config.nix "$flake1Dir/"
 
-echo bar > $flake1Dir/foo
+echo bar > "$flake1Dir/foo"
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a1
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a1"
 [[ -e $TEST_ROOT/result/simple.nix ]]
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a2
-[[ $(cat $TEST_ROOT/result) = bar ]]
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a2"
+[[ $(cat "$TEST_ROOT/result") = bar ]]
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a3
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a3"
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a4
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a4"
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a6
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a6"
 [[ -e $TEST_ROOT/result/simple.nix ]]
 
-nix build --impure --json --out-link $TEST_ROOT/result $flake1Dir#a8
-diff common.sh $TEST_ROOT/result
+nix build --impure --json --out-link "$TEST_ROOT/result" "$flake1Dir#a8"
+diff common.sh "$TEST_ROOT/result"
 
-expectStderr 1 nix build --impure --json --out-link $TEST_ROOT/result $flake1Dir#a9 \
+expectStderr 1 nix build --impure --json --out-link "$TEST_ROOT/result" "$flake1Dir#a9" \
   | grepQuiet "has 0 entries in its context. It should only have exactly one entry"
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a10
-[[ $(readlink -e $TEST_ROOT/result) = *simple.drv ]]
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir"#a10
+[[ $(readlink -e "$TEST_ROOT/result") = *simple.drv ]]
 
-expectStderr 1 nix build --json --out-link $TEST_ROOT/result $flake1Dir#a11 \
+expectStderr 1 nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a11" \
   | grepQuiet "has a context which refers to a complete source and binary closure"
 
-nix build --json --out-link $TEST_ROOT/result $flake1Dir#a12
+nix build --json --out-link "$TEST_ROOT/result" "$flake1Dir#a12"
 [[ -e $TEST_ROOT/result/hello ]]
 
-expectStderr 1 nix build --impure --json --out-link $TEST_ROOT/result $flake1Dir#a13 \
+expectStderr 1 nix build --impure --json --out-link "$TEST_ROOT/result" "$flake1Dir#a13" \
   | grepQuiet "has 2 entries in its context. It should only have exactly one entry"
 
 # Test accessing output in installables with `.` (foobarbaz.<output>)
-nix build --json --no-link $flake1Dir#a14.foo | jq --exit-status '
+nix build --json --no-link "$flake1Dir"#a14.foo | jq --exit-status '
   (.[0] |
     (.drvPath | match(".*dot-installable.drv")) and
     (.outputs | keys == ["foo"]))
diff --git a/tests/functional/flakes/bundle.sh b/tests/functional/flakes/bundle.sh
old mode 100644
new mode 100755
index 67bbb05ac5b..5e185cbf62d
--- a/tests/functional/flakes/bundle.sh
+++ b/tests/functional/flakes/bundle.sh
@@ -1,8 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-cp ../simple.nix ../simple.builder.sh ../config.nix $TEST_HOME
+cp ../simple.nix ../simple.builder.sh ../config.nix "$TEST_HOME"
 
-cd $TEST_HOME
+cd "$TEST_HOME"
 
 cat <<EOF > flake.nix
 {
@@ -25,8 +27,8 @@ EOF
 
 nix build .#
 nix bundle --bundler .# .#
-nix bundle --bundler .#bundlers.$system.default .#packages.$system.default
-nix bundle --bundler .#bundlers.$system.simple  .#packages.$system.default
+nix bundle --bundler .#bundlers."$system".default .#packages."$system".default
+nix bundle --bundler .#bundlers."$system".simple  .#packages."$system".default
 
-nix bundle --bundler .#bundlers.$system.default .#apps.$system.default
-nix bundle --bundler .#bundlers.$system.simple  .#apps.$system.default
+nix bundle --bundler .#bundlers."$system".default .#apps."$system".default
+nix bundle --bundler .#bundlers."$system".simple  .#apps."$system".default
diff --git a/tests/functional/flakes/check.sh b/tests/functional/flakes/check.sh
old mode 100644
new mode 100755
index 0433e5335de..3b83dcafe4b
--- a/tests/functional/flakes/check.sh
+++ b/tests/functional/flakes/check.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 flakeDir=$TEST_ROOT/flake3
diff --git a/tests/functional/flakes/circular.sh b/tests/functional/flakes/circular.sh
old mode 100644
new mode 100755
index d3bb8e8a36b..5304496ba57
--- a/tests/functional/flakes/circular.sh
+++ b/tests/functional/flakes/circular.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test circular flake dependencies.
 source ./common.sh
 
@@ -6,10 +8,10 @@ requireGit
 flakeA=$TEST_ROOT/flakeA
 flakeB=$TEST_ROOT/flakeB
 
-createGitRepo $flakeA
-createGitRepo $flakeB
+createGitRepo "$flakeA"
+createGitRepo "$flakeB"
 
-cat > $flakeA/flake.nix <<EOF
+cat > "$flakeA"/flake.nix <<EOF
 {
   inputs.b.url = git+file://$flakeB;
   inputs.b.inputs.a.follows = "/";
@@ -21,9 +23,9 @@ cat > $flakeA/flake.nix <<EOF
 }
 EOF
 
-git -C $flakeA add flake.nix
+git -C "$flakeA" add flake.nix
 
-cat > $flakeB/flake.nix <<EOF
+cat > "$flakeB"/flake.nix <<EOF
 {
   inputs.a.url = git+file://$flakeA;
 
@@ -33,18 +35,18 @@ cat > $flakeB/flake.nix <<EOF
 }
 EOF
 
-git -C $flakeB add flake.nix
-git -C $flakeB commit -a -m 'Foo'
+git -C "$flakeB" add flake.nix
+git -C "$flakeB" commit -a -m 'Foo'
 
-[[ $(nix eval $flakeA#foo) = 1579 ]]
-[[ $(nix eval $flakeA#foo) = 1579 ]]
+[[ $(nix eval "$flakeA#foo") = 1579 ]]
+[[ $(nix eval "$flakeA#foo") = 1579 ]]
 
-sed -i $flakeB/flake.nix -e 's/456/789/'
-git -C $flakeB commit -a -m 'Foo'
+sed -i "$flakeB"/flake.nix -e 's/456/789/'
+git -C "$flakeB" commit -a -m 'Foo'
 
-nix flake update b --flake $flakeA
-[[ $(nix eval $flakeA#foo) = 1912 ]]
+nix flake update b --flake "$flakeA"
+[[ $(nix eval "$flakeA#foo") = 1912 ]]
 
 # Test list-inputs with circular dependencies
-nix flake metadata $flakeA
+nix flake metadata "$flakeA"
 
diff --git a/tests/functional/flakes/common.sh b/tests/functional/flakes/common.sh
index fc45cf7bfa3..f83a02aba73 100644
--- a/tests/functional/flakes/common.sh
+++ b/tests/functional/flakes/common.sh
@@ -21,6 +21,12 @@ writeSimpleFlake() {
 
     # To test "nix flake init".
     legacyPackages.$system.hello = import ./simple.nix;
+
+    parent = builtins.dirOf ./.;
+
+    baseName = builtins.baseNameOf ./.;
+
+    root = ./.;
   };
 }
 EOF
diff --git a/tests/functional/flakes/config.sh b/tests/functional/flakes/config.sh
old mode 100644
new mode 100755
index d1941a6bea3..4f390611835
--- a/tests/functional/flakes/config.sh
+++ b/tests/functional/flakes/config.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 cp ../simple.nix ../simple.builder.sh ../config.nix $TEST_HOME
@@ -26,6 +28,7 @@ EOF
 # Without --accept-flake-config, the post hook should not run.
 nix build < /dev/null
 (! [[ -f post-hook-ran ]])
+TODO_NixOS
 clearStore
 
 nix build --accept-flake-config
diff --git a/tests/functional/flakes/develop.sh b/tests/functional/flakes/develop.sh
old mode 100644
new mode 100755
index e1e53d36428..60abf3ef226
--- a/tests/functional/flakes/develop.sh
+++ b/tests/functional/flakes/develop.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source ../common.sh
 
+TODO_NixOS
+
 clearStore
 rm -rf $TEST_HOME/.cache $TEST_HOME/.config $TEST_HOME/.local
 
diff --git a/tests/functional/flakes/edit.sh b/tests/functional/flakes/edit.sh
new file mode 100755
index 00000000000..0fdf8b95a0b
--- /dev/null
+++ b/tests/functional/flakes/edit.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+source ./common.sh
+
+requireGit
+
+flake1Dir=$TEST_ROOT/flake1
+
+createGitRepo "$flake1Dir"
+createSimpleGitFlake "$flake1Dir"
+
+export EDITOR=cat
+nix edit "$flake1Dir#" | grepQuiet simple.builder.sh
diff --git a/tests/functional/flakes/eval-cache.sh b/tests/functional/flakes/eval-cache.sh
new file mode 100755
index 00000000000..e3fd0bbfe8c
--- /dev/null
+++ b/tests/functional/flakes/eval-cache.sh
@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+
+source ./common.sh
+
+requireGit
+
+flake1Dir="$TEST_ROOT/eval-cache-flake"
+
+createGitRepo "$flake1Dir" ""
+cp ../simple.nix ../simple.builder.sh ../config.nix "$flake1Dir/"
+git -C "$flake1Dir" add simple.nix simple.builder.sh config.nix
+git -C "$flake1Dir" commit -m "config.nix"
+
+cat >"$flake1Dir/flake.nix" <<EOF
+{
+  description = "Fnord";
+  outputs = { self }: let inherit (import ./config.nix) mkDerivation; in {
+    foo.bar = throw "breaks";
+    drv = mkDerivation {
+      name = "build";
+      buildCommand = ''
+        echo true > \$out
+      '';
+    };
+    ifd = assert (import self.drv); self.drv;
+  };
+}
+EOF
+
+git -C "$flake1Dir" add flake.nix
+git -C "$flake1Dir" commit -m "Init"
+
+expect 1 nix build "$flake1Dir#foo.bar" 2>&1 | grepQuiet 'error: breaks'
+expect 1 nix build "$flake1Dir#foo.bar" 2>&1 | grepQuiet 'error: breaks'
+
+# Conditional error should not be cached
+expect 1 nix build "$flake1Dir#ifd" --option allow-import-from-derivation false 2>&1 \
+  | grepQuiet 'error: cannot build .* during evaluation because the option '\''allow-import-from-derivation'\'' is disabled'
+nix build --no-link "$flake1Dir#ifd"
diff --git a/tests/functional/flakes/flake-in-submodule.sh b/tests/functional/flakes/flake-in-submodule.sh
old mode 100644
new mode 100755
index 85a4d33898f..817f77783c0
--- a/tests/functional/flakes/flake-in-submodule.sh
+++ b/tests/functional/flakes/flake-in-submodule.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Tests that:
@@ -13,6 +15,8 @@ source common.sh
 
 requireGit
 
+TODO_NixOS
+
 clearStore
 
 # Submodules can't be fetched locally by default.
@@ -25,8 +29,8 @@ rootRepo=$TEST_ROOT/rootRepo
 subRepo=$TEST_ROOT/submodule
 
 
-createGitRepo $subRepo
-cat > $subRepo/flake.nix <<EOF
+createGitRepo "$subRepo"
+cat > "$subRepo"/flake.nix <<EOF
 {
     outputs = { self }: {
         sub = import ./sub.nix;
@@ -34,28 +38,28 @@ cat > $subRepo/flake.nix <<EOF
     };
 }
 EOF
-echo '"expression in submodule"' > $subRepo/sub.nix
-git -C $subRepo add flake.nix sub.nix
-git -C $subRepo commit -m Initial
+echo '"expression in submodule"' > "$subRepo"/sub.nix
+git -C "$subRepo" add flake.nix sub.nix
+git -C "$subRepo" commit -m Initial
 
-createGitRepo $rootRepo
+createGitRepo "$rootRepo"
 
-git -C $rootRepo submodule init
-git -C $rootRepo submodule add $subRepo submodule
-echo '"expression in root repo"' > $rootRepo/root.nix
-git -C $rootRepo add root.nix
-git -C $rootRepo commit -m "Add root.nix"
+git -C "$rootRepo" submodule init
+git -C "$rootRepo" submodule add "$subRepo" submodule
+echo '"expression in root repo"' > "$rootRepo"/root.nix
+git -C "$rootRepo" add root.nix
+git -C "$rootRepo" commit -m "Add root.nix"
 
 flakeref=git+file://$rootRepo\?submodules=1\&dir=submodule
 
 # Flake can live inside a submodule and can be accessed via ?dir=submodule
-[[ $(nix eval --json $flakeref#sub ) = '"expression in submodule"' ]]
+[[ $(nix eval --json "$flakeref#sub" ) = '"expression in submodule"' ]]
 
 # The flake can access content outside of the submodule
-[[ $(nix eval --json $flakeref#root ) = '"expression in root repo"' ]]
+[[ $(nix eval --json "$flakeref#root" ) = '"expression in root repo"' ]]
 
 # Check that dirtying a submodule makes the entire thing dirty.
-[[ $(nix flake metadata --json $flakeref | jq -r .locked.rev) != null ]]
-echo '"foo"' > $rootRepo/submodule/sub.nix
-[[ $(nix eval --json $flakeref#sub ) = '"foo"' ]]
-[[ $(nix flake metadata --json $flakeref | jq -r .locked.rev) = null ]]
+[[ $(nix flake metadata --json "$flakeref" | jq -r .locked.rev) != null ]]
+echo '"foo"' > "$rootRepo"/submodule/sub.nix
+[[ $(nix eval --json "$flakeref#sub" ) = '"foo"' ]]
+[[ $(nix flake metadata --json "$flakeref" | jq -r .locked.rev) = null ]]
diff --git a/tests/functional/flakes/flakes.sh b/tests/functional/flakes/flakes.sh
old mode 100644
new mode 100755
index 4f41cae0aef..26b91eda751
--- a/tests/functional/flakes/flakes.sh
+++ b/tests/functional/flakes/flakes.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
+TODO_NixOS
+
 requireGit
 
 clearStore
@@ -15,13 +19,17 @@ flake7Dir=$TEST_ROOT/flake7
 nonFlakeDir=$TEST_ROOT/nonFlake
 badFlakeDir=$TEST_ROOT/badFlake
 flakeGitBare=$TEST_ROOT/flakeGitBare
+lockfileSummaryFlake=$TEST_ROOT/lockfileSummaryFlake
 
-for repo in "$flake1Dir" "$flake2Dir" "$flake3Dir" "$flake7Dir" "$nonFlakeDir"; do
+for repo in "$flake1Dir" "$flake2Dir" "$flake3Dir" "$flake7Dir" "$nonFlakeDir" "$lockfileSummaryFlake"; do
     # Give one repo a non-main initial branch.
     extraArgs=
     if [[ "$repo" == "$flake2Dir" ]]; then
       extraArgs="--initial-branch=main"
     fi
+    if [[ "$repo" == "$lockfileSummaryFlake" ]]; then
+      extraArgs="--initial-branch=main"
+    fi
 
     createGitRepo "$repo" "$extraArgs"
 done
@@ -187,6 +195,7 @@ json=$(nix flake metadata flake1 --json | jq .)
 [[ -d $(echo "$json" | jq -r .path) ]]
 [[ $(echo "$json" | jq -r .lastModified) = $(git -C "$flake1Dir" log -n1 --format=%ct) ]]
 hash1=$(echo "$json" | jq -r .revision)
+[[ -n $(echo "$json" | jq -r .fingerprint) ]]
 
 echo foo > "$flake1Dir/foo"
 git -C "$flake1Dir" add $flake1Dir/foo
@@ -231,6 +240,17 @@ nix build -o "$TEST_ROOT/result" --expr "(builtins.getFlake \"$flake1Dir\").pack
 # 'getFlake' on a locked flakeref should succeed even in pure mode.
 nix build -o "$TEST_ROOT/result" --expr "(builtins.getFlake \"git+file://$flake1Dir?rev=$hash2\").packages.$system.default"
 
+# Regression test for dirOf on the root of the flake.
+[[ $(nix eval --json flake1#parent) = \""$NIX_STORE_DIR"\" ]]
+
+# Regression test for baseNameOf on the root of the flake.
+[[ $(nix eval --raw flake1#baseName) =~ ^[a-z0-9]+-source$ ]]
+
+# Test that the root of a tree returns a path named /nix/store/<hash1>-<hash2>-source.
+# This behavior is *not* desired, but has existed for a while.
+# Issue #10627 what to do about it.
+[[ $(nix eval --raw flake1#root) =~ ^.*/[a-z0-9]+-[a-z0-9]+-source$ ]]
+
 # Building a flake with an unlocked dependency should fail in pure mode.
 (! nix build -o "$TEST_ROOT/result" flake2#bar --no-registries)
 (! nix build -o "$TEST_ROOT/result" flake2#bar --no-use-registries)
@@ -629,3 +649,37 @@ expectStderr 1 nix flake metadata "$flake2Dir" --no-allow-dirty --reference-lock
 [[ $($nonFlakeDir/shebang-inline-expr.sh baz) = "foo"$'\n'"baz" ]]
 [[ $($nonFlakeDir/shebang-file.sh baz) = "foo"$'\n'"baz" ]]
 expect 1 $nonFlakeDir/shebang-reject.sh 2>&1 | grepQuiet -F 'error: unsupported unquoted character in nix shebang: *. Use double backticks to escape?'
+
+# Test that the --commit-lock-file-summary flag and its alias work
+cat > "$lockfileSummaryFlake/flake.nix" <<EOF
+{
+  inputs = {
+    flake1.url = "git+file://$flake1Dir";
+  };
+
+  description = "lockfileSummaryFlake";
+
+  outputs = inputs: rec {
+    packages.$system.default = inputs.flake1.packages.$system.foo;
+  };
+}
+EOF
+
+git -C "$lockfileSummaryFlake" add flake.nix
+git -C "$lockfileSummaryFlake" commit -m 'Add lockfileSummaryFlake'
+
+testSummary="test summary 1"
+nix flake lock "$lockfileSummaryFlake" --commit-lock-file --commit-lock-file-summary "$testSummary"
+[[ -e "$lockfileSummaryFlake/flake.lock" ]]
+[[ -z $(git -C "$lockfileSummaryFlake" diff main || echo failed) ]]
+[[ "$(git -C "$lockfileSummaryFlake" log --format=%s -n 1)" = "$testSummary" ]]
+
+git -C "$lockfileSummaryFlake" rm :/:flake.lock
+git -C "$lockfileSummaryFlake" commit -m "remove flake.lock"
+testSummary="test summary 2"
+# NOTE(cole-h): We use `--option` here because Nix settings do not currently support flag-ifying the
+# alias of a setting: https://github.com/NixOS/nix/issues/10989
+nix flake lock "$lockfileSummaryFlake" --commit-lock-file --option commit-lockfile-summary "$testSummary"
+[[ -e "$lockfileSummaryFlake/flake.lock" ]]
+[[ -z $(git -C "$lockfileSummaryFlake" diff main || echo failed) ]]
+[[ "$(git -C "$lockfileSummaryFlake" log --format=%s -n 1)" = "$testSummary" ]]
diff --git a/tests/functional/flakes/follow-paths.sh b/tests/functional/flakes/follow-paths.sh
old mode 100644
new mode 100755
index 1afd91bd2f8..ea56b950389
--- a/tests/functional/flakes/follow-paths.sh
+++ b/tests/functional/flakes/follow-paths.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/init.sh b/tests/functional/flakes/init.sh
old mode 100644
new mode 100755
index 2d4c77ba166..9e484f71cc0
--- a/tests/functional/flakes/init.sh
+++ b/tests/functional/flakes/init.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
@@ -6,16 +8,16 @@ templatesDir=$TEST_ROOT/templates
 flakeDir=$TEST_ROOT/flake
 nixpkgsDir=$TEST_ROOT/nixpkgs
 
-nix registry add --registry $registry templates git+file://$templatesDir
-nix registry add --registry $registry nixpkgs git+file://$nixpkgsDir
+nix registry add --registry "$registry" templates "git+file://$templatesDir"
+nix registry add --registry "$registry" nixpkgs "git+file://$nixpkgsDir"
 
-createGitRepo $nixpkgsDir
-createSimpleGitFlake $nixpkgsDir
+createGitRepo "$nixpkgsDir"
+createSimpleGitFlake "$nixpkgsDir"
 
 # Test 'nix flake init'.
-createGitRepo $templatesDir
+createGitRepo "$templatesDir"
 
-cat > $templatesDir/flake.nix <<EOF
+cat > "$templatesDir"/flake.nix <<EOF
 {
   description = "Some templates";
 
@@ -34,9 +36,9 @@ cat > $templatesDir/flake.nix <<EOF
 }
 EOF
 
-mkdir $templatesDir/trivial
+mkdir "$templatesDir/trivial"
 
-cat > $templatesDir/trivial/flake.nix <<EOF
+cat > "$templatesDir"/trivial/flake.nix <<EOF
 {
   description = "A flake for building Hello World";
 
@@ -48,40 +50,40 @@ cat > $templatesDir/trivial/flake.nix <<EOF
   };
 }
 EOF
-echo a > $templatesDir/trivial/a
-echo b > $templatesDir/trivial/b
+echo a > "$templatesDir/trivial/a"
+echo b > "$templatesDir/trivial/b"
 
-git -C $templatesDir add flake.nix trivial/
-git -C $templatesDir commit -m 'Initial'
+git -C "$templatesDir" add flake.nix trivial/
+git -C "$templatesDir" commit -m 'Initial'
 
 nix flake check templates
 nix flake show templates
 nix flake show templates --json | jq
 
-createGitRepo $flakeDir
-(cd $flakeDir && nix flake init)
-(cd $flakeDir && nix flake init) # check idempotence
-git -C $flakeDir add flake.nix
-nix flake check $flakeDir
-nix flake show $flakeDir
-nix flake show $flakeDir --json | jq
-git -C $flakeDir commit -a -m 'Initial'
+createGitRepo "$flakeDir"
+(cd "$flakeDir" && nix flake init)
+(cd "$flakeDir" && nix flake init) # check idempotence
+git -C "$flakeDir" add flake.nix
+nix flake check "$flakeDir"
+nix flake show "$flakeDir"
+nix flake show "$flakeDir" --json | jq
+git -C "$flakeDir" commit -a -m 'Initial'
 
 # Test 'nix flake init' with benign conflicts
 createGitRepo "$flakeDir"
-echo a > $flakeDir/a
-(cd $flakeDir && nix flake init) # check idempotence
+echo a > "$flakeDir/a"
+(cd "$flakeDir" && nix flake init) # check idempotence
 
 # Test 'nix flake init' with conflicts
 createGitRepo "$flakeDir"
-echo b > $flakeDir/a
-pushd $flakeDir
+echo b > "$flakeDir/a"
+pushd "$flakeDir"
 (! nix flake init) |& grep "refusing to overwrite existing file '$flakeDir/a'"
 popd
-git -C $flakeDir commit -a -m 'Changed'
+git -C "$flakeDir" commit -a -m 'Changed'
 
 # Test 'nix flake new'.
-rm -rf $flakeDir
-nix flake new -t templates#trivial $flakeDir
-nix flake new -t templates#trivial $flakeDir # check idempotence
-nix flake check $flakeDir
+rm -rf "$flakeDir"
+nix flake new -t templates#trivial "$flakeDir"
+nix flake new -t templates#trivial "$flakeDir" # check idempotence
+nix flake check "$flakeDir"
diff --git a/tests/functional/flakes/inputs.sh b/tests/functional/flakes/inputs.sh
old mode 100644
new mode 100755
index 80620488a56..bc0603f1b1b
--- a/tests/functional/flakes/inputs.sh
+++ b/tests/functional/flakes/inputs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
@@ -6,12 +8,12 @@ requireGit
 test_subdir_self_path() {
     baseDir=$TEST_ROOT/$RANDOM
     flakeDir=$baseDir/b-low
-    mkdir -p $flakeDir
-    writeSimpleFlake $baseDir
-    writeSimpleFlake $flakeDir
+    mkdir -p "$flakeDir"
+    writeSimpleFlake "$baseDir"
+    writeSimpleFlake "$flakeDir"
 
-    echo all good > $flakeDir/message
-    cat > $flakeDir/flake.nix <<EOF
+    echo all good > "$flakeDir/message"
+    cat > "$flakeDir"/flake.nix <<EOF
 {
   outputs = inputs: rec {
     packages.$system = rec {
@@ -24,7 +26,7 @@ test_subdir_self_path() {
 }
 EOF
     (
-        nix build $baseDir?dir=b-low --no-link
+        nix build "$baseDir"?dir=b-low --no-link
     )
 }
 test_subdir_self_path
@@ -32,14 +34,14 @@ test_subdir_self_path
 
 test_git_subdir_self_path() {
     repoDir=$TEST_ROOT/repo-$RANDOM
-    createGitRepo $repoDir
+    createGitRepo "$repoDir"
     flakeDir=$repoDir/b-low
-    mkdir -p $flakeDir
-    writeSimpleFlake $repoDir
-    writeSimpleFlake $flakeDir
+    mkdir -p "$flakeDir"
+    writeSimpleFlake "$repoDir"
+    writeSimpleFlake "$flakeDir"
 
-    echo all good > $flakeDir/message
-    cat > $flakeDir/flake.nix <<EOF
+    echo all good > "$flakeDir/message"
+    cat > "$flakeDir"/flake.nix <<EOF
 {
   outputs = inputs: rec {
     packages.$system = rec {
@@ -53,15 +55,15 @@ test_git_subdir_self_path() {
 }
 EOF
     (
-        cd $flakeDir
+        cd "$flakeDir"
         git add .
         git commit -m init
         # nix build
     )
 
     clientDir=$TEST_ROOT/client-$RANDOM
-    mkdir -p $clientDir
-    cat > $clientDir/flake.nix <<EOF
+    mkdir -p "$clientDir"
+    cat > "$clientDir"/flake.nix <<EOF
 {
   inputs.inp = {
     type = "git";
@@ -74,7 +76,7 @@ EOF
   };
 }
 EOF
-    nix build $clientDir --no-link
+    nix build "$clientDir" --no-link
 
 }
 test_git_subdir_self_path
diff --git a/tests/functional/flakes/mercurial.sh b/tests/functional/flakes/mercurial.sh
old mode 100644
new mode 100755
index 7074af6f7d4..b9045bf6bad
--- a/tests/functional/flakes/mercurial.sh
+++ b/tests/functional/flakes/mercurial.sh
@@ -1,43 +1,45 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 [[ $(type -p hg) ]] || skipTest "Mercurial not installed"
 
 flake1Dir=$TEST_ROOT/flake-hg1
-mkdir -p $flake1Dir
-writeSimpleFlake $flake1Dir
-hg init $flake1Dir
+mkdir -p "$flake1Dir"
+writeSimpleFlake "$flake1Dir"
+hg init "$flake1Dir"
 
-nix registry add --registry $registry flake1 hg+file://$flake1Dir
+nix registry add --registry "$registry" flake1 "hg+file://$flake1Dir"
 
 flake2Dir=$TEST_ROOT/flake-hg2
-mkdir -p $flake2Dir
-writeDependentFlake $flake2Dir
-hg init $flake2Dir
+mkdir -p "$flake2Dir"
+writeDependentFlake "$flake2Dir"
+hg init "$flake2Dir"
 
-hg add $flake1Dir/*
-hg commit --config ui.username=foobar@example.org $flake1Dir -m 'Initial commit'
+hg add "$flake1Dir"/*
+hg commit --config ui.username=foobar@example.org "$flake1Dir" -m 'Initial commit'
 
-hg add $flake2Dir/flake.nix
-hg commit --config ui.username=foobar@example.org $flake2Dir -m 'Initial commit'
+hg add "$flake2Dir"/flake.nix
+hg commit --config ui.username=foobar@example.org "$flake2Dir" -m 'Initial commit'
 
-nix build -o $TEST_ROOT/result hg+file://$flake2Dir
+nix build -o "$TEST_ROOT/result" "hg+file://$flake2Dir"
 [[ -e $TEST_ROOT/result/hello ]]
 
-(! nix flake metadata --json hg+file://$flake2Dir | jq -e -r .revision)
+(! nix flake metadata --json "hg+file://$flake2Dir" | jq -e -r .revision)
 
-nix eval hg+file://$flake2Dir#expr
+nix eval "hg+file://$flake2Dir"#expr
 
-nix eval hg+file://$flake2Dir#expr
+nix eval "hg+file://$flake2Dir"#expr
 
-(! nix eval hg+file://$flake2Dir#expr --no-allow-dirty)
+(! nix eval "hg+file://$flake2Dir"#expr --no-allow-dirty)
 
-(! nix flake metadata --json hg+file://$flake2Dir | jq -e -r .revision)
+(! nix flake metadata --json "hg+file://$flake2Dir" | jq -e -r .revision)
 
-hg commit --config ui.username=foobar@example.org $flake2Dir -m 'Add lock file'
+hg commit --config ui.username=foobar@example.org "$flake2Dir" -m 'Add lock file'
 
-nix flake metadata --json hg+file://$flake2Dir --refresh | jq -e -r .revision
-nix flake metadata --json hg+file://$flake2Dir
-[[ $(nix flake metadata --json hg+file://$flake2Dir | jq -e -r .revCount) = 1 ]]
+nix flake metadata --json "hg+file://$flake2Dir" --refresh | jq -e -r .revision
+nix flake metadata --json "hg+file://$flake2Dir"
+[[ $(nix flake metadata --json "hg+file://$flake2Dir" | jq -e -r .revCount) = 1 ]]
 
-nix build -o $TEST_ROOT/result hg+file://$flake2Dir --no-registries --no-allow-dirty
-nix build -o $TEST_ROOT/result hg+file://$flake2Dir --no-use-registries --no-allow-dirty
+nix build -o "$TEST_ROOT/result" "hg+file://$flake2Dir" --no-registries --no-allow-dirty
+nix build -o "$TEST_ROOT/result" "hg+file://$flake2Dir" --no-use-registries --no-allow-dirty
diff --git a/tests/functional/flakes/prefetch.sh b/tests/functional/flakes/prefetch.sh
new file mode 100755
index 00000000000..a451b712009
--- /dev/null
+++ b/tests/functional/flakes/prefetch.sh
@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+source common.sh
+
+# Test symlinks in zip files (#10649).
+path=$(nix flake prefetch --json file://$(pwd)/tree.zip | jq -r .storePath)
+[[ $(cat $path/foo) = foo ]]
+[[ $(readlink $path/bar) = foo ]]
diff --git a/tests/functional/flakes/run.sh b/tests/functional/flakes/run.sh
old mode 100644
new mode 100755
index 9fa51d1c73a..c2c345ed2cb
--- a/tests/functional/flakes/run.sh
+++ b/tests/functional/flakes/run.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source ../common.sh
 
+TODO_NixOS
+
 clearStore
 rm -rf $TEST_HOME/.cache $TEST_HOME/.config $TEST_HOME/.local
 cp ../shell-hello.nix ../config.nix $TEST_HOME
diff --git a/tests/functional/flakes/search-root.sh b/tests/functional/flakes/search-root.sh
old mode 100644
new mode 100755
index 6b137aa860c..1ee29fac4b5
--- a/tests/functional/flakes/search-root.sh
+++ b/tests/functional/flakes/search-root.sh
@@ -1,9 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
-writeSimpleFlake $TEST_HOME
-cd $TEST_HOME
+writeSimpleFlake "$TEST_HOME"
+cd "$TEST_HOME"
 mkdir -p foo/subdir
 
 echo '{ outputs = _: {}; }' > foo/flake.nix
@@ -25,11 +27,11 @@ success=("" . .# .#test ../subdir ../subdir#test "$PWD")
 failure=("path:$PWD" "../simple.nix")
 
 for i in "${success[@]}"; do
-    nix build $i || fail "flake should be found by searching up directories"
+    nix build "$i" || fail "flake should be found by searching up directories"
 done
 
 for i in "${failure[@]}"; do
-    ! nix build $i || fail "flake should not search up directories when using 'path:'"
+    ! nix build "$i" || fail "flake should not search up directories when using 'path:'"
 done
 
 popd
@@ -43,7 +45,7 @@ if [[ -n $(type -p git) ]]; then
     pushd subdir
     git init
     for i in "${success[@]}" "${failure[@]}"; do
-        ! nix build $i || fail "flake should not search past a git repository"
+        ! nix build "$i" || fail "flake should not search past a git repository"
     done
     rm -rf .git
     popd
diff --git a/tests/functional/flakes/show.sh b/tests/functional/flakes/show.sh
old mode 100644
new mode 100755
index a3d30055233..22e1f419376
--- a/tests/functional/flakes/show.sh
+++ b/tests/functional/flakes/show.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 flakeDir=$TEST_ROOT/flake
diff --git a/tests/functional/flakes/tree.zip b/tests/functional/flakes/tree.zip
new file mode 100644
index 00000000000..f9e4d225fe0
Binary files /dev/null and b/tests/functional/flakes/tree.zip differ
diff --git a/tests/functional/flakes/unlocked-override.sh b/tests/functional/flakes/unlocked-override.sh
old mode 100644
new mode 100755
index 8abc8b7d3e7..a17a0c2afe7
--- a/tests/functional/flakes/unlocked-override.sh
+++ b/tests/functional/flakes/unlocked-override.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
@@ -5,26 +7,26 @@ requireGit
 flake1Dir=$TEST_ROOT/flake1
 flake2Dir=$TEST_ROOT/flake2
 
-createGitRepo $flake1Dir
-cat > $flake1Dir/flake.nix <<EOF
+createGitRepo "$flake1Dir"
+cat > "$flake1Dir"/flake.nix <<EOF
 {
     outputs = { self }: { x = import ./x.nix; };
 }
 EOF
-echo 123 > $flake1Dir/x.nix
-git -C $flake1Dir add flake.nix x.nix
-git -C $flake1Dir commit -m Initial
+echo 123 > "$flake1Dir"/x.nix
+git -C "$flake1Dir" add flake.nix x.nix
+git -C "$flake1Dir" commit -m Initial
 
-createGitRepo $flake2Dir
-cat > $flake2Dir/flake.nix <<EOF
+createGitRepo "$flake2Dir"
+cat > "$flake2Dir"/flake.nix <<EOF
 {
     outputs = { self, flake1 }: { x = flake1.x; };
 }
 EOF
-git -C $flake2Dir add flake.nix
+git -C "$flake2Dir" add flake.nix
 
-[[ $(nix eval --json $flake2Dir#x --override-input flake1 $TEST_ROOT/flake1) = 123 ]]
+[[ $(nix eval --json "$flake2Dir#x" --override-input flake1 "$TEST_ROOT/flake1") = 123 ]]
 
-echo 456 > $flake1Dir/x.nix
+echo 456 > "$flake1Dir"/x.nix
 
-[[ $(nix eval --json $flake2Dir#x --override-input flake1 $TEST_ROOT/flake1) = 456 ]]
+[[ $(nix eval --json "$flake2Dir#x" --override-input flake1 "$TEST_ROOT/flake1") = 456 ]]
diff --git a/tests/functional/fmt.sh b/tests/functional/fmt.sh
old mode 100644
new mode 100755
index 3c1bd998988..b29fe64d6bc
--- a/tests/functional/fmt.sh
+++ b/tests/functional/fmt.sh
@@ -1,6 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+TODO_NixOS # Provide a `shell` variable. Try not to `export` it, perhaps.
+
+clearStoreIfPossible
 rm -rf $TEST_HOME/.cache $TEST_HOME/.config $TEST_HOME/.local
 
 cp ./simple.nix ./simple.builder.sh ./fmt.simple.sh ./config.nix $TEST_HOME
@@ -29,5 +33,3 @@ EOF
 nix fmt ./file ./folder | grep 'Formatting: ./file ./folder'
 nix flake check
 nix flake show | grep -P "package 'formatter'"
-
-clearStore
diff --git a/tests/functional/fod-failing.nix b/tests/functional/fod-failing.nix
new file mode 100644
index 00000000000..37c04fe12f8
--- /dev/null
+++ b/tests/functional/fod-failing.nix
@@ -0,0 +1,39 @@
+with import ./config.nix;
+rec {
+  x1 = mkDerivation {
+    name = "x1";
+    builder = builtins.toFile "builder.sh"
+      ''
+        echo $name > $out
+      '';
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
+  x2 = mkDerivation {
+    name = "x2";
+    builder = builtins.toFile "builder.sh"
+      ''
+        echo $name > $out
+      '';
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
+  x3 = mkDerivation {
+    name = "x3";
+    builder = builtins.toFile "builder.sh"
+      ''
+        echo $name > $out
+      '';
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
+  x4 = mkDerivation {
+    name = "x4";
+    inherit x2 x3;
+    builder = builtins.toFile "builder.sh"
+      ''
+        echo $x2 $x3
+        exit 1
+      '';
+  };
+}
diff --git a/tests/functional/function-trace.sh b/tests/functional/function-trace.sh
index bd804bf18a6..7524afdf219 100755
--- a/tests/functional/function-trace.sh
+++ b/tests/functional/function-trace.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 set +x
@@ -19,12 +21,12 @@ expect_trace() {
                <(echo "$expect") \
                <(echo "$actual")
     ) && result=0 || result=$?
-    if [ $result -eq 0 ]; then
+    if [ "$result" -eq 0 ]; then
         echo " ok."
     else
         echo " failed. difference:"
         echo "$msg"
-        return $result
+        return "$result"
     fi
 }
 
diff --git a/tests/functional/gc-auto.sh b/tests/functional/gc-auto.sh
old mode 100644
new mode 100755
index 521d9e53969..8f25be3e978
--- a/tests/functional/gc-auto.sh
+++ b/tests/functional/gc-auto.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "“min-free” and “max-free” are daemon options"
 
+TODO_NixOS
+
 clearStore
 
 garbage1=$(nix store add-path --name garbage1 ./nar-access.sh)
@@ -62,11 +66,11 @@ EOF
 )
 
 nix build --impure -v -o $TEST_ROOT/result-A -L --expr "$expr" \
-    --min-free 1000 --max-free 2000 --min-free-check-interval 1 &
+    --min-free 1K --max-free 2K --min-free-check-interval 1 &
 pid1=$!
 
 nix build --impure -v -o $TEST_ROOT/result-B -L --expr "$expr2" \
-    --min-free 1000 --max-free 2000 --min-free-check-interval 1 &
+    --min-free 1K --max-free 2K --min-free-check-interval 1 &
 pid2=$!
 
 # Once the first build is done, unblock the second one.
diff --git a/tests/functional/gc-concurrent.sh b/tests/functional/gc-concurrent.sh
old mode 100644
new mode 100755
index 2c6622c626c..df180b14fd7
--- a/tests/functional/gc-concurrent.sh
+++ b/tests/functional/gc-concurrent.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 lockFifo1=$TEST_ROOT/test1.fifo
@@ -18,8 +22,8 @@ outPath3=$(nix-store -r $drvPath3)
 touch $outPath3.lock
 
 rm -f "$NIX_STATE_DIR"/gcroots/foo*
-ln -s $drvPath2 "$NIX_STATE_DIR"/gcroots/foo
-ln -s $outPath3 "$NIX_STATE_DIR"/gcroots/foo2
+ln -s $drvPath2 "$NIX_STATE_DIR/gcroots/foo"
+ln -s $outPath3 "$NIX_STATE_DIR/gcroots/foo2"
 
 # Start build #1 in the background.  It starts immediately.
 nix-store -rvv "$drvPath1" &
diff --git a/tests/functional/gc-non-blocking.sh b/tests/functional/gc-non-blocking.sh
old mode 100644
new mode 100755
index ec280badbc1..de10837eb77
--- a/tests/functional/gc-non-blocking.sh
+++ b/tests/functional/gc-non-blocking.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 # Test whether the collector is non-blocking, i.e. a build can run in
 # parallel with it.
 source common.sh
 
+TODO_NixOS
+
 needLocalStore "the GC test needs a synchronisation point"
 
 clearStore
diff --git a/tests/functional/gc-runtime.sh b/tests/functional/gc-runtime.sh
old mode 100644
new mode 100755
index dc1826a557b..0cccaaf16ab
--- a/tests/functional/gc-runtime.sh
+++ b/tests/functional/gc-runtime.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 case $system in
@@ -9,28 +11,30 @@ esac
 
 set -m # enable job control, needed for kill
 
+TODO_NixOS
+
 profiles="$NIX_STATE_DIR"/profiles
-rm -rf $profiles
+rm -rf "$profiles"
 
-nix-env -p $profiles/test -f ./gc-runtime.nix -i gc-runtime
+nix-env -p "$profiles/test" -f ./gc-runtime.nix -i gc-runtime
 
-outPath=$(nix-env -p $profiles/test -q --no-name --out-path gc-runtime)
-echo $outPath
+outPath=$(nix-env -p "$profiles/test" -q --no-name --out-path gc-runtime)
+echo "$outPath"
 
 echo "backgrounding program..."
-$profiles/test/program &
+"$profiles"/test/program &
 sleep 2 # hack - wait for the program to get started
 child=$!
 echo PID=$child
 
-nix-env -p $profiles/test -e gc-runtime
-nix-env -p $profiles/test --delete-generations old
+nix-env -p "$profiles/test" -e gc-runtime
+nix-env -p "$profiles/test" --delete-generations old
 
 nix-store --gc
 
 kill -- -$child
 
-if ! test -e $outPath; then
+if ! test -e "$outPath"; then
     echo "running program was garbage collected!"
     exit 1
 fi
diff --git a/tests/functional/gc.sh b/tests/functional/gc.sh
old mode 100644
new mode 100755
index ad09a8b3915..7707a7e2722
--- a/tests/functional/gc.sh
+++ b/tests/functional/gc.sh
@@ -1,13 +1,17 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 drvPath=$(nix-instantiate dependencies.nix)
 outPath=$(nix-store -rvv "$drvPath")
 
 # Set a GC root.
-rm -f "$NIX_STATE_DIR"/gcroots/foo
-ln -sf $outPath "$NIX_STATE_DIR"/gcroots/foo
+rm -f "$NIX_STATE_DIR/gcroots/foo"
+ln -sf $outPath "$NIX_STATE_DIR/gcroots/foo"
 
 [ "$(nix-store -q --roots $outPath)" = "$NIX_STATE_DIR/gcroots/foo -> $outPath" ]
 
@@ -40,7 +44,7 @@ cat $outPath/reference-to-input-2/bar
 # Check that the derivation has been GC'd.
 if test -e $drvPath; then false; fi
 
-rm "$NIX_STATE_DIR"/gcroots/foo
+rm "$NIX_STATE_DIR/gcroots/foo"
 
 nix-collect-garbage
 
diff --git a/tests/functional/git-hashing/common.sh b/tests/functional/git-hashing/common.sh
index 572cea43818..29c518fea26 100644
--- a/tests/functional/git-hashing/common.sh
+++ b/tests/functional/git-hashing/common.sh
@@ -1,5 +1,7 @@
 source ../common.sh
 
+TODO_NixOS # Need to enable git hashing feature and make sure test is ok for store we don't clear
+
 clearStore
 clearCache
 
diff --git a/tests/functional/hash-convert.sh b/tests/functional/hash-convert.sh
old mode 100644
new mode 100755
index 9b3afc10b27..3a099950ff9
--- a/tests/functional/hash-convert.sh
+++ b/tests/functional/hash-convert.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Conversion with `nix hash` `nix-hash` and `nix hash convert`
diff --git a/tests/functional/hash-path.sh b/tests/functional/hash-path.sh
old mode 100644
new mode 100755
index 4ad9f8ff2ec..86d782a9589
--- a/tests/functional/hash-path.sh
+++ b/tests/functional/hash-path.sh
@@ -1,7 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 try () {
-    printf "%s" "$2" > $TEST_ROOT/vector
+    printf "%s" "$2" > "$TEST_ROOT/vector"
     hash="$(nix-hash --flat ${FORMAT+--$FORMAT} --type "$1" "$TEST_ROOT/vector")"
     if ! (( "${NO_TEST_CLASSIC-}" )) && test "$hash" != "$3"; then
         echo "try nix-hash: hash $1, expected $3, got $hash"
@@ -59,7 +61,7 @@ NO_TEST_NIX_COMMAND=1 try sha512 "abc" "ddaf35a193617abacc417349ae20413112e6fa4e
 NO_TEST_CLASSIC=1 try sha512 "abc" "sha512-3a81oZNherrMQXNJriBBMRLm+k6JqX6iCp7u5ktV05ohkpkqJ0/BqDa6PCOj/uu9RU1EI2Q86A4qmslPpUyknw=="
 
 try2 () {
-    hash=$(nix-hash --type "$1" $TEST_ROOT/hash-path)
+    hash=$(nix-hash --type "$1" "$TEST_ROOT/hash-path")
     if test "$hash" != "$2"; then
         echo "try nix-hash; hash $1, expected $2, got $hash"
         exit 1
@@ -71,22 +73,22 @@ try2 () {
     fi
 }
 
-rm -rf $TEST_ROOT/hash-path
-mkdir $TEST_ROOT/hash-path
-echo "Hello World" > $TEST_ROOT/hash-path/hello
+rm -rf "$TEST_ROOT/hash-path"
+mkdir "$TEST_ROOT/hash-path"
+echo "Hello World" > "$TEST_ROOT/hash-path/hello"
 
 try2 md5 "ea9b55537dd4c7e104515b2ccfaf4100"
 
 # Execute bit matters.
-chmod +x $TEST_ROOT/hash-path/hello
+chmod +x "$TEST_ROOT/hash-path/hello"
 try2 md5 "20f3ffe011d4cfa7d72bfabef7882836"
 
 # Mtime and other bits don't.
-touch -r . $TEST_ROOT/hash-path/hello
-chmod 744 $TEST_ROOT/hash-path/hello
+touch -r . "$TEST_ROOT/hash-path/hello"
+chmod 744 "$TEST_ROOT/hash-path/hello"
 try2 md5 "20f3ffe011d4cfa7d72bfabef7882836"
 
 # File type (e.g., symlink) does.
-rm $TEST_ROOT/hash-path/hello
-ln -s x $TEST_ROOT/hash-path/hello
+rm "$TEST_ROOT/hash-path/hello"
+ln -s x "$TEST_ROOT/hash-path/hello"
 try2 md5 "f78b733a68f5edbdf9413899339eaa4a"
diff --git a/tests/functional/help.sh b/tests/functional/help.sh
old mode 100644
new mode 100755
index 868f5d2e921..61efc1cb2a7
--- a/tests/functional/help.sh
+++ b/tests/functional/help.sh
@@ -1,6 +1,6 @@
-source common.sh
+#!/usr/bin/env bash
 
-clearStore
+source common.sh
 
 # test help output
 
diff --git a/tests/functional/import-derivation.sh b/tests/functional/import-derivation.sh
old mode 100644
new mode 100755
index 98d61ef49b9..68ddcfa4a9d
--- a/tests/functional/import-derivation.sh
+++ b/tests/functional/import-derivation.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 if nix-instantiate --readonly-mode ./import-derivation.nix; then
     echo "read-only evaluation of an imported derivation unexpectedly failed"
@@ -9,4 +11,4 @@ fi
 
 outPath=$(nix-build ./import-derivation.nix --no-out-link)
 
-[ "$(cat $outPath)" = FOO579 ]
+[ "$(cat "$outPath")" = FOO579 ]
diff --git a/tests/functional/impure-derivations.sh b/tests/functional/impure-derivations.sh
old mode 100644
new mode 100755
index 54ed6f5ddf2..5dea220fec7
--- a/tests/functional/impure-derivations.sh
+++ b/tests/functional/impure-derivations.sh
@@ -1,11 +1,15 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireDaemonNewerThan "2.8pre20220311"
 
+TODO_NixOS
+
 enableFeatures "ca-derivations impure-derivations"
 restartDaemon
 
-clearStore
+clearStoreIfPossible
 
 # Basic test of impure derivations: building one a second time should not use the previous result.
 printf 0 > $TEST_ROOT/counter
diff --git a/tests/functional/impure-env.sh b/tests/functional/impure-env.sh
old mode 100644
new mode 100755
index cfea4cae9bf..ca32c103001
--- a/tests/functional/impure-env.sh
+++ b/tests/functional/impure-env.sh
@@ -1,8 +1,12 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Needs the config option 'impure-env' to work
 requireDaemonNewerThan "2.19.0"
 
+TODO_NixOS
+
 enableFeatures "configurable-impure-env"
 restartDaemon
 
@@ -18,13 +22,13 @@ startDaemon
 
 varTest env_name value --impure-env env_name=value
 
-echo 'impure-env = set_in_config=config_value' >> "$NIX_CONF_DIR/nix.conf"
+echo 'impure-env = set_in_config=config_value' >> "$test_nix_conf"
 set_in_config=daemon_value restartDaemon
 
 varTest set_in_config config_value
 varTest set_in_config client_value --impure-env set_in_config=client_value
 
-sed -i -e '/^trusted-users =/d' "$NIX_CONF_DIR/nix.conf"
+sed -i -e '/^trusted-users =/d' "$test_nix_conf"
 
 env_name=daemon_value restartDaemon
 
diff --git a/tests/functional/impure-eval.sh b/tests/functional/impure-eval.sh
old mode 100644
new mode 100755
index 6c72f01d7af..33a5ea4092a
--- a/tests/functional/impure-eval.sh
+++ b/tests/functional/impure-eval.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 export REMOTE_STORE="dummy://"
diff --git a/tests/functional/init.sh b/tests/functional/init.sh
deleted file mode 100755
index 97b1b058753..00000000000
--- a/tests/functional/init.sh
+++ /dev/null
@@ -1,42 +0,0 @@
-# Don't start the daemon
-source common/vars-and-functions.sh
-
-test -n "$TEST_ROOT"
-if test -d "$TEST_ROOT"; then
-    chmod -R u+rw "$TEST_ROOT"
-    # We would delete any daemon socket, so let's stop the daemon first.
-    killDaemon
-    rm -rf "$TEST_ROOT"
-fi
-mkdir "$TEST_ROOT"
-
-mkdir "$NIX_STORE_DIR"
-mkdir "$NIX_LOCALSTATE_DIR"
-mkdir -p "$NIX_LOG_DIR"/drvs
-mkdir "$NIX_STATE_DIR"
-mkdir "$NIX_CONF_DIR"
-
-cat > "$NIX_CONF_DIR"/nix.conf <<EOF
-build-users-group =
-keep-derivations = false
-sandbox = false
-experimental-features = nix-command
-gc-reserved-space = 0
-substituters =
-flake-registry = $TEST_ROOT/registry.json
-show-trace = true
-include nix.conf.extra
-trusted-users = $(whoami)
-EOF
-
-cat > "$NIX_CONF_DIR"/nix.conf.extra <<EOF
-fsync-metadata = false
-extra-experimental-features = flakes
-!include nix.conf.extra.not-there
-EOF
-
-# Initialise the database.
-nix-store --init
-
-# Did anything happen?
-test -e "$NIX_STATE_DIR"/db/db.sqlite
diff --git a/tests/functional/lang.sh b/tests/functional/lang.sh
index e35795a7af0..8cb8e98fb7e 100755
--- a/tests/functional/lang.sh
+++ b/tests/functional/lang.sh
@@ -1,8 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 set -o pipefail
 
-source lang/framework.sh
+source characterisation/framework.sh
 
 # specialize function a bit
 function diffAndAccept() {
@@ -24,6 +26,9 @@ nix-instantiate --eval -E 'builtins.traceVerbose "Hello" 123' 2>&1 | grepQuietIn
 nix-instantiate --show-trace --eval -E 'builtins.addErrorContext "Hello" 123' 2>&1 | grepQuietInverse Hello
 expectStderr 1 nix-instantiate --show-trace --eval -E 'builtins.addErrorContext "Hello" (throw "Foo")' | grepQuiet Hello
 expectStderr 1 nix-instantiate --show-trace --eval -E 'builtins.addErrorContext "Hello %" (throw "Foo")' | grepQuiet 'Hello %'
+# Relies on parsing the expression derivation as a derivation, can't use --eval
+expectStderr 1 nix-instantiate --show-trace lang/non-eval-fail-bad-drvPath.nix | grepQuiet "store path '8qlfcic10lw5304gqm8q45nr7g7jl62b-cachix-1.7.3-bin' is not a valid derivation path"
+
 
 nix-instantiate --eval -E 'let x = builtins.trace { x = x; } true; in x' \
   2>&1 | grepQuiet -E 'trace: { x = «potential infinite recursion»; }'
@@ -31,6 +36,15 @@ nix-instantiate --eval -E 'let x = builtins.trace { x = x; } true; in x' \
 nix-instantiate --eval -E 'let x = { repeating = x; tracing = builtins.trace x true; }; in x.tracing'\
   2>&1 | grepQuiet -F 'trace: { repeating = «repeated»; tracing = «potential infinite recursion»; }'
 
+nix-instantiate --eval -E 'builtins.warn "Hello" 123' 2>&1 | grepQuiet 'warning: Hello'
+nix-instantiate --eval -E 'builtins.addErrorContext "while doing ${"something"} interesting" (builtins.warn "Hello" 123)' 2>/dev/null | grepQuiet 123
+
+# warn does not accept non-strings for now
+expectStderr 1 nix-instantiate --eval -E 'let x = builtins.warn { x = x; } true; in x' \
+  | grepQuiet "expected a string but found a set"
+expectStderr 1 nix-instantiate --eval --abort-on-warn -E 'builtins.warn "Hello" 123' | grepQuiet Hello
+NIX_ABORT_ON_WARN=1 expectStderr 1 nix-instantiate --eval -E 'builtins.addErrorContext "while doing ${"something"} interesting" (builtins.warn "Hello" 123)' | grepQuiet "while doing something interesting"
+
 set +x
 
 badDiff=0
@@ -72,7 +86,7 @@ for i in lang/eval-fail-*.nix; do
         if [[ -e "lang/$i.flags" ]]; then
             sed -e 's/#.*//' < "lang/$i.flags"
         else
-            # note that show-trace is also set by init.sh
+            # note that show-trace is also set by common/init.sh
             echo "--eval --strict --show-trace"
         fi
     )"
@@ -124,32 +138,4 @@ for i in lang/eval-okay-*.nix; do
     fi
 done
 
-if test -n "${_NIX_TEST_ACCEPT-}"; then
-    if (( "$badDiff" )); then
-        echo 'Output did mot match, but accepted output as the persisted expected output.'
-        echo 'That means the next time the tests are run, they should pass.'
-    else
-        echo 'NOTE: Environment variable _NIX_TEST_ACCEPT is defined,'
-        echo 'indicating the unexpected output should be accepted as the expected output going forward,'
-        echo 'but no tests had unexpected output so there was no expected output to update.'
-    fi
-    if (( "$badExitCode" )); then
-        exit "$badExitCode"
-    else
-        skipTest "regenerating golden masters"
-    fi
-else
-    if (( "$badDiff" )); then
-        echo ''
-        echo 'You can rerun this test with:'
-        echo ''
-        echo '    _NIX_TEST_ACCEPT=1 make tests/functional/lang.sh.test'
-        echo ''
-        echo 'to regenerate the files containing the expected output,'
-        echo 'and then view the git diff to decide whether a change is'
-        echo 'good/intentional or bad/unintentional.'
-        echo 'If the diff contains arbitrary or impure information,'
-        echo 'please improve the normalization that the test applies to the output.'
-    fi
-    exit $(( "$badExitCode" + "$badDiff" ))
-fi
+characterisationTestExit
diff --git a/tests/functional/lang/eval-fail-bad-string-interpolation-4.err.exp b/tests/functional/lang/eval-fail-bad-string-interpolation-4.err.exp
index 6f907106b3f..b262e814dbc 100644
--- a/tests/functional/lang/eval-fail-bad-string-interpolation-4.err.exp
+++ b/tests/functional/lang/eval-fail-bad-string-interpolation-4.err.exp
@@ -6,4 +6,4 @@ error:
              |   ^
            10|
 
-       error: cannot coerce a set to a string: { a = { a = { a = { a = "ha"; b = "ha"; c = "ha"; d = "ha"; e = "ha"; f = "ha"; g = "ha"; h = "ha"; j = "ha"; }; «4294967295 attributes elided» }; «4294967294 attributes elided» }; «4294967293 attributes elided» }
+       error: cannot coerce a set to a string: { a = { a = { a = { a = "ha"; b = "ha"; c = "ha"; d = "ha"; e = "ha"; f = "ha"; g = "ha"; h = "ha"; j = "ha"; }; «8 attributes elided» }; «8 attributes elided» }; «8 attributes elided» }
diff --git a/tests/functional/lang/eval-fail-derivation-name.err.exp b/tests/functional/lang/eval-fail-derivation-name.err.exp
new file mode 100644
index 00000000000..eb2206df16d
--- /dev/null
+++ b/tests/functional/lang/eval-fail-derivation-name.err.exp
@@ -0,0 +1,26 @@
+error:
+       … while evaluating the attribute 'outPath'
+         at <nix/derivation-internal.nix>:19:9:
+           18|       value = commonAttrs // {
+           19|         outPath = builtins.getAttr outputName strict;
+             |         ^
+           20|         drvPath = strict.drvPath;
+
+       … while calling the 'getAttr' builtin
+         at <nix/derivation-internal.nix>:19:19:
+           18|       value = commonAttrs // {
+           19|         outPath = builtins.getAttr outputName strict;
+             |                   ^
+           20|         drvPath = strict.drvPath;
+
+       … while calling the 'derivationStrict' builtin
+         at <nix/derivation-internal.nix>:9:12:
+            8|
+            9|   strict = derivationStrict drvAttrs;
+             |            ^
+           10|
+
+       … while evaluating derivation '~jiggle~'
+         whose name attribute is located at /pwd/lang/eval-fail-derivation-name.nix:2:3
+
+       error: invalid derivation name: name '~jiggle~' contains illegal character '~'. Please pass a different 'name'.
diff --git a/tests/functional/lang/eval-fail-derivation-name.nix b/tests/functional/lang/eval-fail-derivation-name.nix
new file mode 100644
index 00000000000..e779ad6ff5e
--- /dev/null
+++ b/tests/functional/lang/eval-fail-derivation-name.nix
@@ -0,0 +1,5 @@
+derivation {
+  name = "~jiggle~";
+  system = "some-system";
+  builder = "/dontcare";
+}
diff --git a/tests/functional/lang/eval-fail-fetchurl-baseName-attrs-name.err.exp b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs-name.err.exp
new file mode 100644
index 00000000000..30f8b6a3544
--- /dev/null
+++ b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs-name.err.exp
@@ -0,0 +1,8 @@
+error:
+       … while calling the 'fetchurl' builtin
+         at /pwd/lang/eval-fail-fetchurl-baseName-attrs-name.nix:1:1:
+            1| builtins.fetchurl { url = "https://example.com/foo.tar.gz"; name = "~wobble~"; }
+             | ^
+            2|
+
+       error: invalid store path name when fetching URL 'https://example.com/foo.tar.gz': name '~wobble~' contains illegal character '~'. Please change the value for the 'name' attribute passed to 'fetchurl', so that it can create a valid store path.
diff --git a/tests/functional/lang/eval-fail-fetchurl-baseName-attrs-name.nix b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs-name.nix
new file mode 100644
index 00000000000..5838055390d
--- /dev/null
+++ b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs-name.nix
@@ -0,0 +1 @@
+builtins.fetchurl { url = "https://example.com/foo.tar.gz"; name = "~wobble~"; }
diff --git a/tests/functional/lang/eval-fail-fetchurl-baseName-attrs.err.exp b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs.err.exp
new file mode 100644
index 00000000000..cef532e9476
--- /dev/null
+++ b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs.err.exp
@@ -0,0 +1,8 @@
+error:
+       … while calling the 'fetchurl' builtin
+         at /pwd/lang/eval-fail-fetchurl-baseName-attrs.nix:1:1:
+            1| builtins.fetchurl { url = "https://example.com/~wiggle~"; }
+             | ^
+            2|
+
+       error: invalid store path name when fetching URL 'https://example.com/~wiggle~': name '~wiggle~' contains illegal character '~'. Please add a valid 'name' attribute to the argument for 'fetchurl', so that it can create a valid store path.
diff --git a/tests/functional/lang/eval-fail-fetchurl-baseName-attrs.nix b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs.nix
new file mode 100644
index 00000000000..068120edbbe
--- /dev/null
+++ b/tests/functional/lang/eval-fail-fetchurl-baseName-attrs.nix
@@ -0,0 +1 @@
+builtins.fetchurl { url = "https://example.com/~wiggle~"; }
diff --git a/tests/functional/lang/eval-fail-fetchurl-baseName.err.exp b/tests/functional/lang/eval-fail-fetchurl-baseName.err.exp
new file mode 100644
index 00000000000..0950e8e70ab
--- /dev/null
+++ b/tests/functional/lang/eval-fail-fetchurl-baseName.err.exp
@@ -0,0 +1,8 @@
+error:
+       … while calling the 'fetchurl' builtin
+         at /pwd/lang/eval-fail-fetchurl-baseName.nix:1:1:
+            1| builtins.fetchurl "https://example.com/~wiggle~"
+             | ^
+            2|
+
+       error: invalid store path name when fetching URL 'https://example.com/~wiggle~': name '~wiggle~' contains illegal character '~'. Please pass an attribute set with 'url' and 'name' attributes to 'fetchurl',  so that it can create a valid store path.
diff --git a/tests/functional/lang/eval-fail-fetchurl-baseName.nix b/tests/functional/lang/eval-fail-fetchurl-baseName.nix
new file mode 100644
index 00000000000..96509384304
--- /dev/null
+++ b/tests/functional/lang/eval-fail-fetchurl-baseName.nix
@@ -0,0 +1 @@
+builtins.fetchurl "https://example.com/~wiggle~"
diff --git a/tests/functional/lang/eval-fail-infinite-recursion-lambda.err.exp b/tests/functional/lang/eval-fail-infinite-recursion-lambda.err.exp
index 5d843d827c9..712dd75a898 100644
--- a/tests/functional/lang/eval-fail-infinite-recursion-lambda.err.exp
+++ b/tests/functional/lang/eval-fail-infinite-recursion-lambda.err.exp
@@ -29,7 +29,7 @@ error:
              |              ^
             2|
 
-       (19997 duplicate frames omitted)
+       (197 duplicate frames omitted)
 
        error: stack overflow; max-call-depth exceeded
        at /pwd/lang/eval-fail-infinite-recursion-lambda.nix:1:14:
diff --git a/tests/functional/lang/eval-fail-infinite-recursion-lambda.flags b/tests/functional/lang/eval-fail-infinite-recursion-lambda.flags
new file mode 100644
index 00000000000..59e20ec9c6d
--- /dev/null
+++ b/tests/functional/lang/eval-fail-infinite-recursion-lambda.flags
@@ -0,0 +1 @@
+--max-call-depth 100
\ No newline at end of file
diff --git a/tests/functional/lang/eval-fail-nested-list-items.err.exp b/tests/functional/lang/eval-fail-nested-list-items.err.exp
new file mode 100644
index 00000000000..90d43906165
--- /dev/null
+++ b/tests/functional/lang/eval-fail-nested-list-items.err.exp
@@ -0,0 +1,9 @@
+error:
+       … while evaluating a path segment
+         at /pwd/lang/eval-fail-nested-list-items.nix:11:6:
+           10|
+           11| "" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)
+             |      ^
+           12|
+
+       error: cannot coerce a list to a string: [ [ 1 2 3 4 5 6 7 8 ] [ 1 «3 items elided» ] ]
diff --git a/tests/functional/lang/eval-fail-nested-list-items.nix b/tests/functional/lang/eval-fail-nested-list-items.nix
new file mode 100644
index 00000000000..af45b1dd49a
--- /dev/null
+++ b/tests/functional/lang/eval-fail-nested-list-items.nix
@@ -0,0 +1,11 @@
+# This reproduces https://github.com/NixOS/nix/issues/10993, for lists
+# $ nix run nix/2.23.1 -- eval --expr '"" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)'
+# error:
+#        … while evaluating a path segment
+#          at «string»:1:6:
+#             1| "" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)
+#              |      ^
+#
+#        error: cannot coerce a list to a string: [ [ 1 2 3 4 5 6 7 8 ] [ 1 «4294967290 items elided» ] ]
+
+"" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)
diff --git a/tests/functional/lang/eval-okay-derivation-legacy.err.exp b/tests/functional/lang/eval-okay-derivation-legacy.err.exp
new file mode 100644
index 00000000000..94f0854dd2c
--- /dev/null
+++ b/tests/functional/lang/eval-okay-derivation-legacy.err.exp
@@ -0,0 +1,6 @@
+warning: In a derivation named 'eval-okay-derivation-legacy', 'structuredAttrs' disables the effect of the derivation attribute 'allowedReferences'; use 'outputChecks.<output>.allowedReferences' instead
+warning: In a derivation named 'eval-okay-derivation-legacy', 'structuredAttrs' disables the effect of the derivation attribute 'allowedRequisites'; use 'outputChecks.<output>.allowedRequisites' instead
+warning: In a derivation named 'eval-okay-derivation-legacy', 'structuredAttrs' disables the effect of the derivation attribute 'disallowedReferences'; use 'outputChecks.<output>.disallowedReferences' instead
+warning: In a derivation named 'eval-okay-derivation-legacy', 'structuredAttrs' disables the effect of the derivation attribute 'disallowedRequisites'; use 'outputChecks.<output>.disallowedRequisites' instead
+warning: In a derivation named 'eval-okay-derivation-legacy', 'structuredAttrs' disables the effect of the derivation attribute 'maxClosureSize'; use 'outputChecks.<output>.maxClosureSize' instead
+warning: In a derivation named 'eval-okay-derivation-legacy', 'structuredAttrs' disables the effect of the derivation attribute 'maxSize'; use 'outputChecks.<output>.maxSize' instead
diff --git a/tests/functional/lang/eval-okay-derivation-legacy.exp b/tests/functional/lang/eval-okay-derivation-legacy.exp
new file mode 100644
index 00000000000..4f374a1aac8
--- /dev/null
+++ b/tests/functional/lang/eval-okay-derivation-legacy.exp
@@ -0,0 +1 @@
+"/nix/store/mzgwvrjjir216ra58mwwizi8wj6y9ddr-eval-okay-derivation-legacy"
diff --git a/tests/functional/lang/eval-okay-derivation-legacy.nix b/tests/functional/lang/eval-okay-derivation-legacy.nix
new file mode 100644
index 00000000000..b529cdf9029
--- /dev/null
+++ b/tests/functional/lang/eval-okay-derivation-legacy.nix
@@ -0,0 +1,12 @@
+(builtins.derivationStrict {
+  name = "eval-okay-derivation-legacy";
+  system = "x86_64-linux";
+  builder = "/dontcare";
+  __structuredAttrs = true;
+  allowedReferences = [ ];
+  disallowedReferences = [ ];
+  allowedRequisites = [ ];
+  disallowedRequisites = [ ];
+  maxSize = 1234;
+  maxClosureSize = 12345;
+}).out
diff --git a/tests/functional/lang/framework.sh b/tests/functional/lang/framework.sh
deleted file mode 100644
index 9b886e9835a..00000000000
--- a/tests/functional/lang/framework.sh
+++ /dev/null
@@ -1,33 +0,0 @@
-# Golden test support
-#
-# Test that the output of the given test matches what is expected. If
-# `_NIX_TEST_ACCEPT` is non-empty also update the expected output so
-# that next time the test succeeds.
-function diffAndAcceptInner() {
-    local -r testName=$1
-    local -r got="$2"
-    local -r expected="$3"
-
-    # Absence of expected file indicates empty output expected.
-    if test -e "$expected"; then
-        local -r expectedOrEmpty="$expected"
-    else
-        local -r expectedOrEmpty=lang/empty.exp
-    fi
-
-    # Diff so we get a nice message
-    if ! diff --color=always --unified "$expectedOrEmpty" "$got"; then
-        echo "FAIL: evaluation result of $testName not as expected"
-        badDiff=1
-    fi
-
-    # Update expected if `_NIX_TEST_ACCEPT` is non-empty.
-    if test -n "${_NIX_TEST_ACCEPT-}"; then
-        cp "$got" "$expected"
-        # Delete empty expected files to avoid bloating the repo with
-        # empty files.
-        if ! test -s "$expected"; then
-            rm "$expected"
-        fi
-    fi
-}
diff --git a/tests/functional/lang/non-eval-fail-bad-drvPath.nix b/tests/functional/lang/non-eval-fail-bad-drvPath.nix
new file mode 100644
index 00000000000..23639bc5465
--- /dev/null
+++ b/tests/functional/lang/non-eval-fail-bad-drvPath.nix
@@ -0,0 +1,14 @@
+let
+  package = {
+    type = "derivation";
+    name = "cachix-1.7.3";
+    system = builtins.currentSystem;
+    outputs = [ "out" ];
+    # Illegal, because does not end in `.drv`
+    drvPath = "${builtins.storeDir}/8qlfcic10lw5304gqm8q45nr7g7jl62b-cachix-1.7.3-bin";
+    outputName = "out";
+    outPath = "${builtins.storeDir}/8qlfcic10lw5304gqm8q45nr7g7jl62b-cachix-1.7.3-bin";
+    out = package;
+  };
+in
+package
diff --git a/tests/functional/legacy-ssh-store.sh b/tests/functional/legacy-ssh-store.sh
old mode 100644
new mode 100755
index 56b4c2d204c..3a1a7b02264
--- a/tests/functional/legacy-ssh-store.sh
+++ b/tests/functional/legacy-ssh-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 store_uri="ssh://localhost?remote-store=$TEST_ROOT/other-store"
diff --git a/tests/functional/linux-sandbox.sh b/tests/functional/linux-sandbox.sh
old mode 100644
new mode 100755
index e553791d90e..653a3873ffa
--- a/tests/functional/linux-sandbox.sh
+++ b/tests/functional/linux-sandbox.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "the sandbox only runs on the builder side, so it makes no sense to test it with the daemon"
 
+TODO_NixOS
+
 clearStore
 
 requireSandboxSupport
diff --git a/tests/functional/local-overlay-store/add-lower.sh b/tests/functional/local-overlay-store/add-lower.sh
index f0ac46a91b5..33bf20ebdd3 100755
--- a/tests/functional/local-overlay-store/add-lower.sh
+++ b/tests/functional/local-overlay-store/add-lower.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/bad-uris.sh b/tests/functional/local-overlay-store/bad-uris.sh
index 2517681dd84..b7930e32e24 100644
--- a/tests/functional/local-overlay-store/bad-uris.sh
+++ b/tests/functional/local-overlay-store/bad-uris.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
@@ -14,6 +15,8 @@ declare -a storesBad=(
     "$storeBadRoot" "$storeBadLower" "$storeBadUpper"
 )
 
+TODO_NixOS
+
 for i in "${storesBad[@]}"; do
     echo $i
     unshare --mount --map-root-user bash <<EOF
diff --git a/tests/functional/local-overlay-store/build.sh b/tests/functional/local-overlay-store/build.sh
index 758585400d8..2251be7e788 100755
--- a/tests/functional/local-overlay-store/build.sh
+++ b/tests/functional/local-overlay-store/build.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/check-post-init.sh b/tests/functional/local-overlay-store/check-post-init.sh
index 985bf978e5d..e0c2602762d 100755
--- a/tests/functional/local-overlay-store/check-post-init.sh
+++ b/tests/functional/local-overlay-store/check-post-init.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/common.sh b/tests/functional/local-overlay-store/common.sh
index 2634f8c8f84..b171f91f499 100644
--- a/tests/functional/local-overlay-store/common.sh
+++ b/tests/functional/local-overlay-store/common.sh
@@ -1,4 +1,6 @@
-source ../common.sh
+source ../common/vars-and-functions.sh
+
+TODO_NixOS
 
 # The new Linux mount interface does not seem to support remounting
 # OverlayFS mount points.
@@ -31,16 +33,15 @@ requireEnvironment () {
 }
 
 addConfig () {
-    echo "$1" >> "$NIX_CONF_DIR/nix.conf"
+    echo "$1" >> "$test_nix_conf"
 }
 
 setupConfig () {
   addConfig "require-drop-supplementary-groups = false"
   addConfig "build-users-group = "
+  enableFeatures "local-overlay-store"
 }
 
-enableFeatures "local-overlay-store"
-
 setupStoreDirs () {
   # Attempt to create store dirs on tmpfs volume.
   # This ensures lowerdir, upperdir and workdir will be on
diff --git a/tests/functional/local-overlay-store/delete-duplicate.sh b/tests/functional/local-overlay-store/delete-duplicate.sh
index 0c0b1a3b202..e3b94e1cb74 100644
--- a/tests/functional/local-overlay-store/delete-duplicate.sh
+++ b/tests/functional/local-overlay-store/delete-duplicate.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/delete-refs.sh b/tests/functional/local-overlay-store/delete-refs.sh
index 942d7fbdc1c..62295aaa19a 100755
--- a/tests/functional/local-overlay-store/delete-refs.sh
+++ b/tests/functional/local-overlay-store/delete-refs.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/gc-inner.sh b/tests/functional/local-overlay-store/gc-inner.sh
index ea92154d209..687fed89745 100644
--- a/tests/functional/local-overlay-store/gc-inner.sh
+++ b/tests/functional/local-overlay-store/gc-inner.sh
@@ -20,8 +20,8 @@ outPath=$(nix-build ../hermetic.nix --no-out-link --arg busybox "$busybox" --arg
 
 # Set a GC root.
 mkdir -p "$stateB"
-rm -f "$stateB"/gcroots/foo
-ln -sf $outPath "$stateB"/gcroots/foo
+rm -f "$stateB/gcroots/foo"
+ln -sf $outPath "$stateB/gcroots/foo"
 
 [ "$(nix-store -q --roots $outPath)" = "$stateB/gcroots/foo -> $outPath" ]
 
@@ -46,7 +46,7 @@ nix-collect-garbage
 # Check that the root and its dependencies haven't been deleted.
 cat "$storeBRoot/$outPath"
 
-rm "$stateB"/gcroots/foo
+rm "$stateB/gcroots/foo"
 
 nix-collect-garbage
 
diff --git a/tests/functional/local-overlay-store/gc.sh b/tests/functional/local-overlay-store/gc.sh
index 1e1fb203ea8..f3420d0b813 100755
--- a/tests/functional/local-overlay-store/gc.sh
+++ b/tests/functional/local-overlay-store/gc.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/optimise.sh b/tests/functional/local-overlay-store/optimise.sh
index 569afa248a9..a524a675e1c 100755
--- a/tests/functional/local-overlay-store/optimise.sh
+++ b/tests/functional/local-overlay-store/optimise.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/redundant-add.sh b/tests/functional/local-overlay-store/redundant-add.sh
index fbd4799e74a..b4f04b2e1eb 100755
--- a/tests/functional/local-overlay-store/redundant-add.sh
+++ b/tests/functional/local-overlay-store/redundant-add.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/stale-file-handle.sh b/tests/functional/local-overlay-store/stale-file-handle.sh
index 5e75628ca47..684b8ce23d4 100755
--- a/tests/functional/local-overlay-store/stale-file-handle.sh
+++ b/tests/functional/local-overlay-store/stale-file-handle.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local-overlay-store/verify.sh b/tests/functional/local-overlay-store/verify.sh
index 8b44603ff83..d73d1a57d66 100755
--- a/tests/functional/local-overlay-store/verify.sh
+++ b/tests/functional/local-overlay-store/verify.sh
@@ -1,4 +1,5 @@
 source common.sh
+source ../common/init.sh
 
 requireEnvironment
 setupConfig
diff --git a/tests/functional/local.mk b/tests/functional/local.mk
index 5cc474cdc49..3273ab119c4 100644
--- a/tests/functional/local.mk
+++ b/tests/functional/local.mk
@@ -1,8 +1,8 @@
 nix_tests = \
   test-infra.sh \
-  init.sh \
   flakes/flakes.sh \
   flakes/develop.sh \
+  flakes/edit.sh \
   flakes/run.sh \
   flakes/mercurial.sh \
   flakes/circular.sh \
@@ -16,12 +16,14 @@ nix_tests = \
   flakes/absolute-attr-paths.sh \
   flakes/build-paths.sh \
   flakes/flake-in-submodule.sh \
+  flakes/prefetch.sh \
+  flakes/eval-cache.sh \
   gc.sh \
   nix-collect-garbage-d.sh \
   remote-store.sh \
   legacy-ssh-store.sh \
   lang.sh \
-  lang-test-infra.sh \
+  characterisation-test-infra.sh \
   experimental-features.sh \
   fetchMercurial.sh \
   gc-auto.sh \
@@ -104,6 +106,7 @@ nix_tests = \
   eval-store.sh \
   why-depends.sh \
   derivation-json.sh \
+  derivation-advanced-attributes.sh \
   import-derivation.sh \
   nix_path.sh \
   case-hack.sh \
@@ -130,6 +133,7 @@ nix_tests = \
   nested-sandboxing.sh \
   impure-env.sh \
   debugger.sh \
+  extra-sandbox-profile.sh \
   help.sh \
   auth.sh
 
@@ -153,7 +157,7 @@ $(d)/plugins.sh.test $(d)/plugins.sh.test-debug: \
 install-tests += $(foreach x, $(nix_tests), $(d)/$(x))
 
 test-clean-files := \
-  $(d)/common/vars-and-functions.sh \
+  $(d)/common/subst-vars.sh \
   $(d)/config.nix
 
 clean-files += $(test-clean-files)
diff --git a/tests/functional/logging.sh b/tests/functional/logging.sh
old mode 100644
new mode 100755
index 1ccc21d0bce..bd80a91635f
--- a/tests/functional/logging.sh
+++ b/tests/functional/logging.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 path=$(nix-build dependencies.nix --no-out-link)
diff --git a/tests/functional/misc.sh b/tests/functional/misc.sh
old mode 100644
new mode 100755
index af96d20bd4a..7d63756b7f4
--- a/tests/functional/misc.sh
+++ b/tests/functional/misc.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Tests miscellaneous commands.
@@ -11,6 +13,9 @@ source common.sh
 # Can we ask for the version number?
 nix-env --version | grep "$version"
 
+nix_env=$(type -P nix-env)
+(PATH=""; ! $nix_env --help 2>&1 ) | grepQuiet -F "The 'man' command was not found, but it is needed for 'nix-env' and some other 'nix-*' commands' help text. Perhaps you could install the 'man' command?"
+
 # Usage errors.
 expect 1 nix-env --foo 2>&1 | grep "no operation"
 expect 1 nix-env -q --foo 2>&1 | grep "unknown flag"
@@ -30,3 +35,12 @@ expectStderr 1 nix-instantiate --eval -E '[]' -A 'x' | grepQuiet "should be a se
 expectStderr 1 nix-instantiate --eval -E '{}' -A '1' | grepQuiet "should be a list"
 expectStderr 1 nix-instantiate --eval -E '{}' -A '.' | grepQuiet "empty attribute name"
 expectStderr 1 nix-instantiate --eval -E '[]' -A '1' | grepQuiet "out of range"
+
+# Unknown setting warning
+# NOTE(cole-h): behavior is different depending on the order, which is why we test an unknown option
+# before and after the `'{}'`!
+out="$(expectStderr 0 nix-instantiate --option foobar baz --expr '{}')"
+[[ "$(echo "$out" | grep foobar | wc -l)" = 1 ]]
+
+out="$(expectStderr 0 nix-instantiate '{}' --option foobar baz --expr )"
+[[ "$(echo "$out" | grep foobar | wc -l)" = 1 ]]
diff --git a/tests/functional/multiple-outputs.nix b/tests/functional/multiple-outputs.nix
index 413d392e42b..6ba7c523d8e 100644
--- a/tests/functional/multiple-outputs.nix
+++ b/tests/functional/multiple-outputs.nix
@@ -96,6 +96,12 @@ rec {
     buildCommand = "mkdir $a_a $b $c";
   };
 
+  nothing-to-install = mkDerivation {
+    name = "nothing-to-install";
+    meta.outputsToInstall = [ ];
+    buildCommand = "mkdir $out";
+  };
+
   independent = mkDerivation {
     name = "multiple-outputs-independent";
     outputs = [ "first" "second" ];
diff --git a/tests/functional/multiple-outputs.sh b/tests/functional/multiple-outputs.sh
old mode 100644
new mode 100755
index 330600d08ec..35a78d152c7
--- a/tests/functional/multiple-outputs.sh
+++ b/tests/functional/multiple-outputs.sh
@@ -1,6 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+TODO_NixOS
+
+clearStoreIfPossible
 
 rm -f $TEST_ROOT/result*
 
@@ -33,7 +37,7 @@ outPath=$(nix-store -q $drvPath)
 echo "building b..."
 outPath=$(nix-build multiple-outputs.nix -A b --no-out-link)
 echo "output path is $outPath"
-[ "$(cat "$outPath"/file)" = "success" ]
+[ "$(cat "$outPath/file")" = "success" ]
 
 # Test nix-build on a derivation with multiple outputs.
 outPath1=$(nix-build multiple-outputs.nix -A a -o $TEST_ROOT/result)
diff --git a/tests/functional/nar-access.sh b/tests/functional/nar-access.sh
old mode 100644
new mode 100755
index 87981e7d902..b254081cfc4
--- a/tests/functional/nar-access.sh
+++ b/tests/functional/nar-access.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo "building test path"
@@ -25,6 +27,8 @@ diff -u baz.cat-nar $storePath/foo/baz
 nix store cat $storePath/foo/baz > baz.cat-nar
 diff -u baz.cat-nar $storePath/foo/baz
 
+TODO_NixOS
+
 # Check that 'nix store cat' fails on invalid store paths.
 invalidPath="$(dirname $storePath)/99999999999999999999999999999999-foo"
 cp -r $storePath $invalidPath
diff --git a/tests/functional/nested-sandboxing.sh b/tests/functional/nested-sandboxing.sh
old mode 100644
new mode 100755
index 61fe043c6a8..ae0256de2d6
--- a/tests/functional/nested-sandboxing.sh
+++ b/tests/functional/nested-sandboxing.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 # This test is run by `tests/functional/nested-sandboxing/runner.nix` in an extra layer of sandboxing.
 [[ -d /nix/store ]] || skipTest "running this test without Nix's deps being drawn from /nix/store is not yet supported"
 
+TODO_NixOS
+
 requireSandboxSupport
 
 source ./nested-sandboxing/command.sh
diff --git a/tests/functional/nix-build.sh b/tests/functional/nix-build.sh
old mode 100644
new mode 100755
index 44a5a14cd28..091e429e02d
--- a/tests/functional/nix-build.sh
+++ b/tests/functional/nix-build.sh
@@ -1,6 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+TODO_NixOS
+
+clearStoreIfPossible
 
 outPath=$(nix-build dependencies.nix -o $TEST_ROOT/result)
 test "$(cat $TEST_ROOT/result/foobar)" = FOOBAR
diff --git a/tests/functional/nix-channel.sh b/tests/functional/nix-channel.sh
old mode 100644
new mode 100755
index ca5df3bddcb..a4870e7a806
--- a/tests/functional/nix-channel.sh
+++ b/tests/functional/nix-channel.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearProfiles
diff --git a/tests/functional/nix-collect-garbage-d.sh b/tests/functional/nix-collect-garbage-d.sh
old mode 100644
new mode 100755
index bf30f893860..119efe62925
--- a/tests/functional/nix-collect-garbage-d.sh
+++ b/tests/functional/nix-collect-garbage-d.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 ## Test `nix-collect-garbage -d`
diff --git a/tests/functional/nix-copy-ssh-common.sh b/tests/functional/nix-copy-ssh-common.sh
index cc8314ff7fa..5eea9612d0d 100644
--- a/tests/functional/nix-copy-ssh-common.sh
+++ b/tests/functional/nix-copy-ssh-common.sh
@@ -2,6 +2,8 @@ proto=$1
 shift
 (( $# == 0 ))
 
+TODO_NixOS
+
 clearStore
 clearCache
 
diff --git a/tests/functional/nix-copy-ssh-ng.sh b/tests/functional/nix-copy-ssh-ng.sh
old mode 100644
new mode 100755
index 62e99cd2477..41958c2c3c3
--- a/tests/functional/nix-copy-ssh-ng.sh
+++ b/tests/functional/nix-copy-ssh-ng.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 source nix-copy-ssh-common.sh "ssh-ng"
 
+TODO_NixOS
+
 clearStore
 clearRemoteStore
 
diff --git a/tests/functional/nix-copy-ssh.sh b/tests/functional/nix-copy-ssh.sh
old mode 100644
new mode 100755
index 12e8346bcfd..1dc256e49b3
--- a/tests/functional/nix-copy-ssh.sh
+++ b/tests/functional/nix-copy-ssh.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 source nix-copy-ssh-common.sh "ssh"
diff --git a/tests/functional/nix-profile.sh b/tests/functional/nix-profile.sh
old mode 100644
new mode 100755
index 7c4da628327..e2f19b99e0a
--- a/tests/functional/nix-profile.sh
+++ b/tests/functional/nix-profile.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 clearProfiles
 
diff --git a/tests/functional/nix-shell.sh b/tests/functional/nix-shell.sh
old mode 100644
new mode 100755
index 04c83138e7c..65ff279f868
--- a/tests/functional/nix-shell.sh
+++ b/tests/functional/nix-shell.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 if [[ -n ${CONTENT_ADDRESSED:-} ]]; then
     shellDotNix="$PWD/ca-shell.nix"
@@ -19,6 +21,10 @@ output=$(nix-shell --pure "$shellDotNix" -A shellDrv --run \
 
 [ "$output" = " - foo - bar - true" ]
 
+output=$(nix-shell --pure "$shellDotNix" -A shellDrv --option nix-shell-always-looks-for-shell-nix false --run \
+    'echo "$IMPURE_VAR - $VAR_FROM_STDENV_SETUP - $VAR_FROM_NIX - $TEST_inNixShell"')
+[ "$output" = " - foo - bar - true" ]
+
 # Test --keep
 output=$(nix-shell --pure --keep SELECTED_IMPURE_VAR "$shellDotNix" -A shellDrv --run \
     'echo "$IMPURE_VAR - $VAR_FROM_STDENV_SETUP - $VAR_FROM_NIX - $SELECTED_IMPURE_VAR"')
@@ -89,6 +95,55 @@ sed -e "s|@ENV_PROG@|$(type -P env)|" shell.shebang.nix > $TEST_ROOT/shell.sheba
 chmod a+rx $TEST_ROOT/shell.shebang.nix
 $TEST_ROOT/shell.shebang.nix
 
+mkdir $TEST_ROOT/lookup-test $TEST_ROOT/empty
+
+echo "import $shellDotNix" > $TEST_ROOT/lookup-test/shell.nix
+cp config.nix $TEST_ROOT/lookup-test/
+echo 'abort "do not load default.nix!"' > $TEST_ROOT/lookup-test/default.nix
+
+nix-shell $TEST_ROOT/lookup-test -A shellDrv --run 'echo "it works"' | grepQuiet "it works"
+# https://github.com/NixOS/nix/issues/4529
+nix-shell -I "testRoot=$TEST_ROOT" '<testRoot/lookup-test>' -A shellDrv --run 'echo "it works"' | grepQuiet "it works"
+
+expectStderr 1 nix-shell $TEST_ROOT/lookup-test -A shellDrv --run 'echo "it works"' --option nix-shell-always-looks-for-shell-nix false \
+  | grepQuiet -F "do not load default.nix!" # we did, because we chose to enable legacy behavior
+expectStderr 1 nix-shell $TEST_ROOT/lookup-test -A shellDrv --run 'echo "it works"' --option nix-shell-always-looks-for-shell-nix false \
+  | grepQuiet "Skipping .*lookup-test/shell\.nix.*, because the setting .*nix-shell-always-looks-for-shell-nix.* is disabled. This is a deprecated behavior\. Consider enabling .*nix-shell-always-looks-for-shell-nix.*"
+
+(
+  cd $TEST_ROOT/empty;
+  expectStderr 1 nix-shell | \
+    grepQuiet "error.*no argument specified and no .*shell\.nix.* or .*default\.nix.* file found in the working directory"
+)
+
+expectStderr 1 nix-shell -I "testRoot=$TEST_ROOT" '<testRoot/empty>' |
+  grepQuiet "error.*neither .*shell\.nix.* nor .*default\.nix.* found in .*/empty"
+
+cat >$TEST_ROOT/lookup-test/shebangscript <<EOF
+#!$(type -P env) nix-shell
+#!nix-shell -A shellDrv -i bash
+[[ \$VAR_FROM_NIX == bar ]]
+echo "script works"
+EOF
+chmod +x $TEST_ROOT/lookup-test/shebangscript
+
+$TEST_ROOT/lookup-test/shebangscript | grepQuiet "script works"
+
+# https://github.com/NixOS/nix/issues/5431
+mkdir $TEST_ROOT/marco{,/polo}
+echo 'abort "marco/shell.nix must not be used, but its mere existence used to cause #5431"' > $TEST_ROOT/marco/shell.nix
+cat >$TEST_ROOT/marco/polo/default.nix <<EOF
+#!$(type -P env) nix-shell
+(import $TEST_ROOT/lookup-test/shell.nix {}).polo
+EOF
+chmod a+x $TEST_ROOT/marco/polo/default.nix
+(cd $TEST_ROOT/marco && ./polo/default.nix | grepQuiet "Polo")
+
+
+#####################
+# Flake equivalents #
+#####################
+
 # Test 'nix develop'.
 nix develop -f "$shellDotNix" shellDrv -c bash -c '[[ -n $stdenv ]]'
 
diff --git a/tests/functional/nix_path.sh b/tests/functional/nix_path.sh
old mode 100644
new mode 100755
index 2b222b4a1e4..e6a2193f397
--- a/tests/functional/nix_path.sh
+++ b/tests/functional/nix_path.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Regression for https://github.com/NixOS/nix/issues/5998 and https://github.com/NixOS/nix/issues/5980
 
 source common.sh
diff --git a/tests/functional/optimise-store.sh b/tests/functional/optimise-store.sh
old mode 100644
new mode 100755
index 8c2d05cd542..0bedafc4304
--- a/tests/functional/optimise-store.sh
+++ b/tests/functional/optimise-store.sh
@@ -1,10 +1,15 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 outPath1=$(echo 'with import ./config.nix; mkDerivation { name = "foo1"; builder = builtins.toFile "builder" "mkdir $out; echo hello > $out/foo"; }' | nix-build - --no-out-link --auto-optimise-store)
 outPath2=$(echo 'with import ./config.nix; mkDerivation { name = "foo2"; builder = builtins.toFile "builder" "mkdir $out; echo hello > $out/foo"; }' | nix-build - --no-out-link --auto-optimise-store)
 
+TODO_NixOS # ignoring the client-specified setting 'auto-optimise-store', because it is a restricted setting and you are not a trusted user
+  # TODO: only continue when trusted user or root
+
 inode1="$(stat --format=%i $outPath1/foo)"
 inode2="$(stat --format=%i $outPath2/foo)"
 if [ "$inode1" != "$inode2" ]; then
diff --git a/tests/functional/output-normalization.sh b/tests/functional/output-normalization.sh
old mode 100644
new mode 100755
index 0f6df5e317f..c55f1b1d148
--- a/tests/functional/output-normalization.sh
+++ b/tests/functional/output-normalization.sh
@@ -1,6 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 testNormalization () {
+    TODO_NixOS
     clearStore
     outPath=$(nix-build ./simple.nix --no-out-link)
     test "$(stat -c %Y $outPath)" -eq 1
diff --git a/tests/functional/parallel.sh b/tests/functional/parallel.sh
index 3b7bbe5a225..7e420688d4f 100644
--- a/tests/functional/parallel.sh
+++ b/tests/functional/parallel.sh
@@ -4,6 +4,8 @@ source common.sh
 # First, test that -jN performs builds in parallel.
 echo "testing nix-build -j..."
 
+TODO_NixOS
+
 clearStore
 
 rm -f $_NIX_TEST_SHARED.cur $_NIX_TEST_SHARED.max
diff --git a/tests/functional/pass-as-file.sh b/tests/functional/pass-as-file.sh
old mode 100644
new mode 100755
index 2c0bc5031ad..6487bfffd2d
--- a/tests/functional/pass-as-file.sh
+++ b/tests/functional/pass-as-file.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 outPath=$(nix-build --no-out-link -E "
 with import ./config.nix;
diff --git a/tests/functional/path-from-hash-part.sh b/tests/functional/path-from-hash-part.sh
old mode 100644
new mode 100755
index bdd10443448..41d1b7410f6
--- a/tests/functional/path-from-hash-part.sh
+++ b/tests/functional/path-from-hash-part.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 path=$(nix build --no-link --print-out-paths -f simple.nix)
diff --git a/tests/functional/path-info.sh b/tests/functional/path-info.sh
old mode 100644
new mode 100755
index 763935eb71e..8597de68341
--- a/tests/functional/path-info.sh
+++ b/tests/functional/path-info.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo foo > $TEST_ROOT/foo
diff --git a/tests/functional/placeholders.sh b/tests/functional/placeholders.sh
old mode 100644
new mode 100755
index cd1bb7bc2aa..33ec0c2b7d7
--- a/tests/functional/placeholders.sh
+++ b/tests/functional/placeholders.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 nix-build --no-out-link -E '
   with import ./config.nix;
diff --git a/tests/functional/plugins.sh b/tests/functional/plugins.sh
old mode 100644
new mode 100755
index baf71a362ce..ab4876df9da
--- a/tests/functional/plugins.sh
+++ b/tests/functional/plugins.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 if [[ $BUILD_SHARED_LIBS != 1 ]]; then
diff --git a/tests/functional/plugins/plugintest.cc b/tests/functional/plugins/plugintest.cc
index e02fd68d5cd..7433ad19008 100644
--- a/tests/functional/plugins/plugintest.cc
+++ b/tests/functional/plugins/plugintest.cc
@@ -1,4 +1,4 @@
-#include "config.hh"
+#include "config-global.hh"
 #include "primops.hh"
 
 using namespace nix;
diff --git a/tests/functional/post-hook.sh b/tests/functional/post-hook.sh
old mode 100644
new mode 100755
index 752f8220cda..94a6d0d6912
--- a/tests/functional/post-hook.sh
+++ b/tests/functional/post-hook.sh
@@ -1,11 +1,15 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 rm -f $TEST_ROOT/result
 
 export REMOTE_STORE=file:$TEST_ROOT/remote_store
-echo 'require-sigs = false' >> $NIX_CONF_DIR/nix.conf
+echo 'require-sigs = false' >> $test_nix_conf
 
 restartDaemon
 
diff --git a/tests/functional/pure-eval.sh b/tests/functional/pure-eval.sh
old mode 100644
new mode 100755
index 5334bf28e9b..25038109982
--- a/tests/functional/pure-eval.sh
+++ b/tests/functional/pure-eval.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 nix eval --expr 'assert 1 + 2 == 3; true'
 
diff --git a/tests/functional/read-only-store.sh b/tests/functional/read-only-store.sh
old mode 100644
new mode 100755
index d63920c1963..f6b6eaf32ff
--- a/tests/functional/read-only-store.sh
+++ b/tests/functional/read-only-store.sh
@@ -1,15 +1,22 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "read-only-local-store"
 
 needLocalStore "cannot open store read-only when daemon has already opened it writeable"
 
+TODO_NixOS
+
 clearStore
 
 happy () {
     # We can do a read-only query just fine with a read-only store
     nix --store local?read-only=true path-info $dummyPath
-    
+
+    # `local://` also works.
+    nix --store local://?read-only=true path-info $dummyPath
+
     # We can "write" an already-present store-path a read-only store, because no IO is actually required
     nix-store --store local?read-only=true --add dummy
 }
diff --git a/tests/functional/readfile-context.sh b/tests/functional/readfile-context.sh
old mode 100644
new mode 100755
index 31e70ddb1fc..cb9ef62347e
--- a/tests/functional/readfile-context.sh
+++ b/tests/functional/readfile-context.sh
@@ -1,11 +1,15 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS # NixOS doesn't provide $NIX_STATE_DIR (and shouldn't)
+
 clearStore
 
 outPath=$(nix-build --no-out-link readfile-context.nix)
 
 # Set a GC root.
-ln -s $outPath "$NIX_STATE_DIR"/gcroots/foo
+ln -s $outPath "$NIX_STATE_DIR/gcroots/foo"
 
 # Check that file exists.
 [ "$(cat $(cat $outPath))" = "Hello World!" ]
diff --git a/tests/functional/recursive.sh b/tests/functional/recursive.sh
old mode 100644
new mode 100755
index 0bf00f8fa75..640fb92d2c5
--- a/tests/functional/recursive.sh
+++ b/tests/functional/recursive.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS # can't enable a sandbox feature easily
+
 enableFeatures 'recursive-nix'
 restartDaemon
 
diff --git a/tests/functional/referrers.sh b/tests/functional/referrers.sh
old mode 100644
new mode 100755
index 81323c280c5..411cdb7c1fb
--- a/tests/functional/referrers.sh
+++ b/tests/functional/referrers.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "uses some low-level store manipulations that aren’t available through the daemon"
 
+TODO_NixOS
+
 clearStore
 
 max=500
@@ -29,7 +33,7 @@ echo "registering..."
 nix-store --register-validity < $TEST_ROOT/reg_info
 
 echo "collecting garbage..."
-ln -sfn $reference "$NIX_STATE_DIR"/gcroots/ref
+ln -sfn $reference "$NIX_STATE_DIR/gcroots/ref"
 nix-store --gc
 
 if [ -n "$(type -p sqlite3)" -a "$(sqlite3 $NIX_STATE_DIR/db/db.sqlite 'select count(*) from Refs')" -ne 0 ]; then
diff --git a/tests/functional/remote-store.sh b/tests/functional/remote-store.sh
old mode 100644
new mode 100755
index cc5dd18338a..841b6b27ae4
--- a/tests/functional/remote-store.sh
+++ b/tests/functional/remote-store.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 # Ensure "fake ssh" remote store works just as legacy fake ssh would.
@@ -23,7 +27,7 @@ fi
 # Test import-from-derivation through the daemon.
 [[ $(nix eval --impure --raw --file ./ifd.nix) = hi ]]
 
-storeCleared=1 NIX_REMOTE_=$NIX_REMOTE $SHELL ./user-envs.sh
+NIX_REMOTE_=$NIX_REMOTE $SHELL ./user-envs-test-case.sh
 
 nix-store --gc --max-freed 1K
 
diff --git a/tests/functional/repair.sh b/tests/functional/repair.sh
old mode 100644
new mode 100755
index c8f07b1c666..1f6004b2c84
--- a/tests/functional/repair.sh
+++ b/tests/functional/repair.sh
@@ -1,7 +1,11 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "--repair needs a local store"
 
+TODO_NixOS
+
 clearStore
 
 path=$(nix-build dependencies.nix -o $TEST_ROOT/result)
diff --git a/tests/functional/repl.sh b/tests/functional/repl.sh
old mode 100644
new mode 100755
index f11fa714053..86cd6f458d0
--- a/tests/functional/repl.sh
+++ b/tests/functional/repl.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 testDir="$PWD"
@@ -20,12 +22,17 @@ replUndefinedVariable="
 import $testDir/undefined-variable.nix
 "
 
+TODO_NixOS
+
 testRepl () {
-    local nixArgs=("$@")
+    local nixArgs
+    nixArgs=("$@")
     rm -rf repl-result-out || true # cleanup from other runs backed by a foreign nix store
-    local replOutput="$(nix repl "${nixArgs[@]}" <<< "$replCmds")"
+    local replOutput
+    replOutput="$(nix repl "${nixArgs[@]}" <<< "$replCmds")"
     echo "$replOutput"
-    local outPath=$(echo "$replOutput" |&
+    local outPath
+    outPath=$(echo "$replOutput" |&
         grep -o -E "$NIX_STORE_DIR/\w*-simple")
     nix path-info "${nixArgs[@]}" "$outPath"
     [ "$(realpath ./repl-result-out)" == "$outPath" ] || fail "nix repl :bl doesn't make a symlink"
@@ -34,11 +41,11 @@ testRepl () {
 
     # simple.nix prints a PATH during build
     echo "$replOutput" | grepQuiet -s 'PATH=' || fail "nix repl :log doesn't output logs"
-    local replOutput="$(nix repl "${nixArgs[@]}" <<< "$replFailingCmds" 2>&1)"
+    replOutput="$(nix repl "${nixArgs[@]}" <<< "$replFailingCmds" 2>&1)"
     echo "$replOutput"
     echo "$replOutput" | grepQuiet -s 'This should fail' \
       || fail "nix repl :log doesn't output logs for a failed derivation"
-    local replOutput="$(nix repl --show-trace "${nixArgs[@]}" <<< "$replUndefinedVariable" 2>&1)"
+    replOutput="$(nix repl --show-trace "${nixArgs[@]}" <<< "$replUndefinedVariable" 2>&1)"
     echo "$replOutput"
     echo "$replOutput" | grepQuiet -s "while evaluating the file" \
       || fail "nix repl --show-trace doesn't show the trace"
@@ -48,7 +55,7 @@ testRepl () {
     nix repl "${nixArgs[@]}" 2>&1 <<< "builtins.currentSystem" \
       | grep "$(nix-instantiate --eval -E 'builtins.currentSystem')"
 
-    expectStderr 1 nix repl ${testDir}/simple.nix \
+    expectStderr 1 nix repl "${testDir}/simple.nix" \
       | grepQuiet -s "error: path '$testDir/simple.nix' is not a flake"
 }
 
@@ -63,10 +70,11 @@ stripColors () {
 }
 
 testReplResponseGeneral () {
-    local grepMode="$1"; shift
-    local commands="$1"; shift
-    local expectedResponse="$1"; shift
-    local response="$(nix repl "$@" <<< "$commands" | stripColors)"
+    local grepMode commands expectedResponse response
+    grepMode="$1"; shift
+    commands="$1"; shift
+    expectedResponse="$1"; shift
+    response="$(nix repl "$@" <<< "$commands" | stripColors)"
     echo "$response" | grepQuiet "$grepMode" -s "$expectedResponse" \
       || fail "repl command set:
 
@@ -91,6 +99,8 @@ testReplResponseNoRegex () {
 }
 
 # :a uses the newest version of a symbol
+#
+# shellcheck disable=SC2016
 testReplResponse '
 :a { a = "1"; }
 :a { a = "2"; }
@@ -101,6 +111,8 @@ testReplResponse '
 # note the escaped \,
 #    \\
 # because the second argument is a regex
+#
+# shellcheck disable=SC2016
 testReplResponseNoRegex '
 "$" + "{hi}"
 ' '"\${hi}"'
@@ -108,12 +120,12 @@ testReplResponseNoRegex '
 testReplResponse '
 drvPath
 ' '".*-simple.drv"' \
---file $testDir/simple.nix
+--file "$testDir/simple.nix"
 
 testReplResponse '
 drvPath
 ' '".*-simple.drv"' \
---file $testDir/simple.nix --experimental-features 'ca-derivations'
+--file "$testDir/simple.nix" --experimental-features 'ca-derivations'
 
 mkdir -p flake && cat <<EOF > flake/flake.nix
 {
diff --git a/tests/functional/restricted.sh b/tests/functional/restricted.sh
old mode 100644
new mode 100755
index 3de26eb36a4..915d973b0dd
--- a/tests/functional/restricted.sh
+++ b/tests/functional/restricted.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 nix-instantiate --restrict-eval --eval -E '1 + 2'
 (! nix-instantiate --eval --restrict-eval ./restricted.nix)
diff --git a/tests/functional/search.sh b/tests/functional/search.sh
old mode 100644
new mode 100755
index d9c7a75da48..3fadecd02dd
--- a/tests/functional/search.sh
+++ b/tests/functional/search.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 clearCache
 
 (( $(nix search -f search.nix '' hello | wc -l) > 0 ))
diff --git a/tests/functional/secure-drv-outputs.sh b/tests/functional/secure-drv-outputs.sh
old mode 100644
new mode 100755
index 50a9c4428d3..5cc4af43521
--- a/tests/functional/secure-drv-outputs.sh
+++ b/tests/functional/secure-drv-outputs.sh
@@ -1,9 +1,13 @@
+#!/usr/bin/env bash
+
 # Test that users cannot register specially-crafted derivations that
 # produce output paths belonging to other derivations.  This could be
 # used to inject malware into the store.
 
 source common.sh
 
+TODO_NixOS
+
 clearStore
 
 startDaemon
diff --git a/tests/functional/selfref-gc.sh b/tests/functional/selfref-gc.sh
old mode 100644
new mode 100755
index 3f1f50eea65..518aea66b14
--- a/tests/functional/selfref-gc.sh
+++ b/tests/functional/selfref-gc.sh
@@ -1,8 +1,10 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireDaemonNewerThan "2.6.0pre20211215"
 
-clearStore
+clearStoreIfPossible
 
 nix-build --no-out-link -E '
   with import ./config.nix;
diff --git a/tests/functional/shell.nix b/tests/functional/shell.nix
index 6a7dd7ad137..750cdf0bcaa 100644
--- a/tests/functional/shell.nix
+++ b/tests/functional/shell.nix
@@ -26,6 +26,9 @@ let pkgs = rec {
     fun() {
       echo blabla
     }
+    runHook() {
+      eval "''${!1}"
+    }
   '';
 
   stdenv = mkDerivation {
@@ -45,6 +48,18 @@ let pkgs = rec {
     TEST_inNixShell = if inNixShell then "true" else "false";
     inherit stdenv;
     outputs = ["dev" "out"];
+  } // {
+    shellHook = abort "Ignore non-drv shellHook attr";
+  };
+
+  # https://github.com/NixOS/nix/issues/5431
+  # See nix-shell.sh
+  polo = mkDerivation {
+    name = "polo";
+    inherit stdenv;
+    shellHook = ''
+      echo Polo
+    '';
   };
 
   # Used by nix-shell -p
diff --git a/tests/functional/shell.sh b/tests/functional/shell.sh
old mode 100644
new mode 100755
index 8a3fef3e7b1..b4c03f5477c
--- a/tests/functional/shell.sh
+++ b/tests/functional/shell.sh
@@ -1,8 +1,15 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 clearCache
 
+# nix shell is an alias for nix env shell. We'll use the shorter form in the rest of the test.
+nix env shell -f shell-hello.nix hello -c hello | grep 'Hello World'
+
 nix shell -f shell-hello.nix hello -c hello | grep 'Hello World'
 nix shell -f shell-hello.nix hello -c hello NixOS | grep 'Hello NixOS'
 
diff --git a/tests/functional/signing.sh b/tests/functional/signing.sh
old mode 100644
new mode 100755
index 942b516306d..890d1446f4f
--- a/tests/functional/signing.sh
+++ b/tests/functional/signing.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 clearCache
 
 nix-store --generate-binary-cache-key cache1.example.org $TEST_ROOT/sk1 $TEST_ROOT/pk1
@@ -13,9 +15,10 @@ outPath=$(nix-build dependencies.nix --no-out-link --secret-key-files "$TEST_ROO
 
 # Verify that the path got signed.
 info=$(nix path-info --json $outPath)
-[[ $info =~ '"ultimate":true' ]]
-[[ $info =~ 'cache1.example.org' ]]
-[[ $info =~ 'cache2.example.org' ]]
+echo $info | jq -e '.[] | .ultimate == true'
+TODO_NixOS # looks like an actual bug? Following line fails on NixOS:
+echo $info | jq -e '.[] | .signatures.[] | select(startswith("cache1.example.org"))'
+echo $info | jq -e '.[] | .signatures.[] | select(startswith("cache2.example.org"))'
 
 # Test "nix store verify".
 nix store verify -r $outPath
@@ -37,8 +40,8 @@ nix store verify -r $outPath
 
 # Verify that the path did not get signed but does have the ultimate bit.
 info=$(nix path-info --json $outPath2)
-[[ $info =~ '"ultimate":true' ]]
-(! [[ $info =~ 'signatures' ]])
+echo $info | jq -e '.[] | .ultimate == true'
+echo $info | jq -e '.[] | .signatures == []'
 
 # Test "nix store verify".
 nix store verify -r $outPath2
@@ -55,7 +58,7 @@ nix store verify -r $outPath2 --sigs-needed 1 --trusted-public-keys $pk1
 # Build something content-addressed.
 outPathCA=$(IMPURE_VAR1=foo IMPURE_VAR2=bar nix-build ./fixed.nix -A good.0 --no-out-link)
 
-[[ $(nix path-info --json $outPathCA) =~ '"ca":"fixed:md5:' ]]
+nix path-info --json $outPathCA | jq -e '.[] | .ca | startswith("fixed:md5:")'
 
 # Content-addressed paths don't need signatures, so they verify
 # regardless of --sigs-needed.
@@ -71,15 +74,15 @@ nix copy --to file://$cacheDir $outPath2
 
 # Verify that signatures got copied.
 info=$(nix path-info --store file://$cacheDir --json $outPath2)
-(! [[ $info =~ '"ultimate":true' ]])
-[[ $info =~ 'cache1.example.org' ]]
-(! [[ $info =~ 'cache2.example.org' ]])
+echo $info | jq -e '.[] | .ultimate == false'
+echo $info | jq -e '.[] | .signatures.[] | select(startswith("cache1.example.org"))'
+echo $info | expect 4 jq -e '.[] | .signatures.[] | select(startswith("cache2.example.org"))'
 
 # Verify that adding a signature to a path in a binary cache works.
 nix store sign --store file://$cacheDir --key-file $TEST_ROOT/sk2 $outPath2
 info=$(nix path-info --store file://$cacheDir --json $outPath2)
-[[ $info =~ 'cache1.example.org' ]]
-[[ $info =~ 'cache2.example.org' ]]
+echo $info | jq -e '.[] | .signatures.[] | select(startswith("cache1.example.org"))'
+echo $info | jq -e '.[] | .signatures.[] | select(startswith("cache2.example.org"))'
 
 # Copying to a diverted store should fail due to a lack of signatures by trusted keys.
 chmod -R u+w $TEST_ROOT/store0 || true
diff --git a/tests/functional/simple.nix b/tests/functional/simple.nix
index 4223c0f23a5..2035ca294cc 100644
--- a/tests/functional/simple.nix
+++ b/tests/functional/simple.nix
@@ -5,4 +5,5 @@ mkDerivation {
   builder = ./simple.builder.sh;
   PATH = "";
   goodPath = path;
+  meta.position = "${__curPos.file}:${toString __curPos.line}";
 }
diff --git a/tests/functional/simple.sh b/tests/functional/simple.sh
old mode 100644
new mode 100755
index 50d44f93f21..86acca0c2d1
--- a/tests/functional/simple.sh
+++ b/tests/functional/simple.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 drvPath=$(nix-instantiate simple.nix)
@@ -12,9 +14,11 @@ echo "output path is $outPath"
 
 (! [ -w $outPath ])
 
-text=$(cat "$outPath"/hello)
+text=$(cat "$outPath/hello")
 if test "$text" != "Hello World!"; then exit 1; fi
 
+TODO_NixOS
+
 # Directed delete: $outPath is not reachable from a root, so it should
 # be deleteable.
 nix-store --delete $outPath
diff --git a/tests/functional/ssh-relay.sh b/tests/functional/ssh-relay.sh
old mode 100644
new mode 100755
index 053b2f00d05..059c664348a
--- a/tests/functional/ssh-relay.sh
+++ b/tests/functional/ssh-relay.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo foo > $TEST_ROOT/hello.sh
diff --git a/tests/functional/store-info.sh b/tests/functional/store-info.sh
old mode 100644
new mode 100755
index 18a8131a92a..f37889fbb1e
--- a/tests/functional/store-info.sh
+++ b/tests/functional/store-info.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 STORE_INFO=$(nix store info 2>&1)
@@ -14,4 +16,6 @@ fi
 expect 127 NIX_REMOTE=unix:$PWD/store nix store info || \
     fail "nix store info on a non-existent store should fail"
 
+TODO_NixOS
+
 [[ "$(echo "$STORE_INFO_JSON" | jq -r ".url")" == "${NIX_REMOTE:-local}" ]]
diff --git a/tests/functional/structured-attrs.sh b/tests/functional/structured-attrs.sh
old mode 100644
new mode 100755
index 6711efbb4f8..ec1282668fd
--- a/tests/functional/structured-attrs.sh
+++ b/tests/functional/structured-attrs.sh
@@ -1,10 +1,12 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # 27ce722638 required some incompatible changes to the nix file, so skip this
 # tests for the older versions
 requireDaemonNewerThan "2.4pre20210712"
 
-clearStore
+clearStoreIfPossible
 
 rm -f $TEST_ROOT/result
 
@@ -19,6 +21,8 @@ env NIX_PATH=nixpkgs=shell.nix nix-shell structured-attrs-shell.nix \
 
 nix develop -f structured-attrs-shell.nix -c bash -c 'test "3" = "$(jq ".my.list|length" < $NIX_ATTRS_JSON_FILE)"'
 
+TODO_NixOS # following line fails.
+
 # `nix develop` is a slightly special way of dealing with environment vars, it parses
 # these from a shell-file exported from a derivation. This is to test especially `outputs`
 # (which is an associative array in thsi case) being fine.
diff --git a/tests/functional/substitute-with-invalid-ca.sh b/tests/functional/substitute-with-invalid-ca.sh
old mode 100644
new mode 100755
index 4d0b01e0f04..d8af67237b8
--- a/tests/functional/substitute-with-invalid-ca.sh
+++ b/tests/functional/substitute-with-invalid-ca.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 BINARY_CACHE=file://$cacheDir
diff --git a/tests/functional/suggestions.sh b/tests/functional/suggestions.sh
old mode 100644
new mode 100755
index f18fefef98f..8db6f7b97f3
--- a/tests/functional/suggestions.sh
+++ b/tests/functional/suggestions.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 cd "$TEST_HOME"
 
diff --git a/tests/functional/supplementary-groups.sh b/tests/functional/supplementary-groups.sh
old mode 100644
new mode 100755
index d18fb24147c..5d329efc9a3
--- a/tests/functional/supplementary-groups.sh
+++ b/tests/functional/supplementary-groups.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireSandboxSupport
@@ -5,6 +7,8 @@ requireSandboxSupport
 if ! command -p -v unshare; then skipTest "Need unshare"; fi
 needLocalStore "The test uses --store always so we would just be bypassing the daemon"
 
+TODO_NixOS
+
 unshare --mount --map-root-user bash <<EOF
   source common.sh
 
diff --git a/tests/functional/tarball.sh b/tests/functional/tarball.sh
old mode 100644
new mode 100755
index 062f27ad61b..f999b7a10cb
--- a/tests/functional/tarball.sh
+++ b/tests/functional/tarball.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 rm -rf $TEST_HOME
 
@@ -52,6 +54,18 @@ test_tarball() {
     # with the content-addressing
     (! nix-instantiate --eval -E "fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"$hash\"; name = \"foo\"; }")
 
+    store_path=$(nix store prefetch-file --json "file://$tarball" | jq -r .storePath)
+    if ! cmp -s "$store_path" "$tarball"; then
+        echo "prefetched tarball differs from original: $store_path vs $tarball" >&2
+        exit 1
+    fi
+    store_path2=$(nix store prefetch-file --json --unpack "file://$tarball" | jq -r .storePath)
+    diff_output=$(diff -r "$store_path2" "$tarroot")
+    if [ -n "$diff_output" ]; then
+        echo "prefetched tarball differs from original: $store_path2 vs $tarroot" >&2
+        echo "$diff_output"
+        exit 1
+    fi
 }
 
 test_tarball '' cat
diff --git a/tests/functional/test-infra.sh b/tests/functional/test-infra.sh
old mode 100644
new mode 100755
index 54ae120e7ee..37322b356d4
--- a/tests/functional/test-infra.sh
+++ b/tests/functional/test-infra.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test the functions for testing themselves!
 # Also test some assumptions on how bash works that they rely on.
 source common.sh
diff --git a/tests/functional/test-libstoreconsumer.sh b/tests/functional/test-libstoreconsumer.sh
old mode 100644
new mode 100755
index 8a77cf5a143..d1a1accb607
--- a/tests/functional/test-libstoreconsumer.sh
+++ b/tests/functional/test-libstoreconsumer.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 drv="$(nix-instantiate simple.nix)"
diff --git a/tests/functional/timeout.sh b/tests/functional/timeout.sh
old mode 100644
new mode 100755
index b179b79a232..f4235453816
--- a/tests/functional/timeout.sh
+++ b/tests/functional/timeout.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test the `--timeout' option.
 
 source common.sh
@@ -9,6 +11,10 @@ messages=$(nix-build -Q timeout.nix -A infiniteLoop --timeout 2 2>&1) && status=
 
 if [ $status -ne 101 ]; then
     echo "error: 'nix-store' exited with '$status'; should have exited 101"
+
+    # FIXME: https://github.com/NixOS/nix/issues/4813
+    skipTest "Do not block CI until fixed"
+
     exit 1
 fi
 
diff --git a/tests/functional/toString-path.sh b/tests/functional/toString-path.sh
old mode 100644
new mode 100755
index 07eb8746588..d790109f41a
--- a/tests/functional/toString-path.sh
+++ b/tests/functional/toString-path.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 mkdir -p $TEST_ROOT/foo
diff --git a/tests/functional/user-envs-migration.sh b/tests/functional/user-envs-migration.sh
old mode 100644
new mode 100755
index 187372b1623..0f33074e156
--- a/tests/functional/user-envs-migration.sh
+++ b/tests/functional/user-envs-migration.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test that the migration of user environments
 # (https://github.com/NixOS/nix/pull/5226) does preserve everything
 
@@ -11,6 +13,8 @@ fi
 killDaemon
 unset NIX_REMOTE
 
+TODO_NixOS
+
 clearStore
 clearProfiles
 rm -rf ~/.nix-profile
diff --git a/tests/functional/user-envs-test-case.sh b/tests/functional/user-envs-test-case.sh
new file mode 100644
index 00000000000..117c6c7a4bc
--- /dev/null
+++ b/tests/functional/user-envs-test-case.sh
@@ -0,0 +1,193 @@
+clearProfiles
+
+# Query installed: should be empty.
+test "$(nix-env -p $profiles/test -q '*' | wc -l)" -eq 0
+
+nix-env --switch-profile $profiles/test
+
+# Query available: should contain several.
+test "$(nix-env -f ./user-envs.nix -qa '*' | wc -l)" -eq 6
+outPath10=$(nix-env -f ./user-envs.nix -qa --out-path --no-name '*' | grep foo-1.0)
+drvPath10=$(nix-env -f ./user-envs.nix -qa --drv-path --no-name '*' | grep foo-1.0)
+[ -n "$outPath10" -a -n "$drvPath10" ]
+
+TODO_NixOS
+
+# Query with json
+nix-env -f ./user-envs.nix -qa --json | jq -e '.[] | select(.name == "bar-0.1") | [
+    .outputName == "out",
+    .outputs.out == null
+] | all'
+nix-env -f ./user-envs.nix -qa --json --out-path | jq -e '.[] | select(.name == "bar-0.1") | [
+    .outputName == "out",
+    (.outputs.out | test("'$NIX_STORE_DIR'.*-0\\.1"))
+] | all'
+nix-env -f ./user-envs.nix -qa --json --drv-path | jq -e '.[] | select(.name == "bar-0.1") | (.drvPath | test("'$NIX_STORE_DIR'.*-0\\.1\\.drv"))'
+
+# Query descriptions.
+nix-env -f ./user-envs.nix -qa '*' --description | grepQuiet silly
+rm -rf $HOME/.nix-defexpr
+ln -s $(pwd)/user-envs.nix $HOME/.nix-defexpr
+nix-env -qa '*' --description | grepQuiet silly
+
+# Query the system.
+nix-env -qa '*' --system | grepQuiet $system
+
+# Install "foo-1.0".
+nix-env -i foo-1.0
+
+# Query installed: should contain foo-1.0 now (which should be
+# executable).
+test "$(nix-env -q '*' | wc -l)" -eq 1
+nix-env -q '*' | grepQuiet foo-1.0
+test "$($profiles/test/bin/foo)" = "foo-1.0"
+
+# Test nix-env -qc to compare installed against available packages, and vice versa.
+nix-env -qc '*' | grepQuiet '< 2.0'
+nix-env -qac '*' | grepQuiet '> 1.0'
+
+# Test the -b flag to filter out source-only packages.
+[ "$(nix-env -qab | wc -l)" -eq 1 ]
+
+# Test the -s flag to get package status.
+nix-env -qas | grepQuiet 'IP-  foo-1.0'
+nix-env -qas | grepQuiet -- '---  bar-0.1'
+
+# Disable foo.
+nix-env --set-flag active false foo
+(! [ -e "$profiles/test/bin/foo" ])
+
+# Enable foo.
+nix-env --set-flag active true foo
+[ -e "$profiles/test/bin/foo" ]
+
+# Store the path of foo-1.0.
+outPath10_=$(nix-env -q --out-path --no-name '*' | grep foo-1.0)
+echo "foo-1.0 = $outPath10"
+[ "$outPath10" = "$outPath10_" ]
+
+# Install "foo-2.0pre1": should remove foo-1.0.
+nix-env -i foo-2.0pre1
+
+# Query installed: should contain foo-2.0pre1 now.
+test "$(nix-env -q '*' | wc -l)" -eq 1
+nix-env -q '*' | grepQuiet foo-2.0pre1
+test "$($profiles/test/bin/foo)" = "foo-2.0pre1"
+
+# Upgrade "foo": should install foo-2.0.
+NIX_PATH=nixpkgs=./user-envs.nix:${NIX_PATH-} nix-env -f '<nixpkgs>' -u foo
+
+# Query installed: should contain foo-2.0 now.
+test "$(nix-env -q '*' | wc -l)" -eq 1
+nix-env -q '*' | grepQuiet foo-2.0
+test "$($profiles/test/bin/foo)" = "foo-2.0"
+
+# Store the path of foo-2.0.
+outPath20=$(nix-env -q --out-path --no-name '*' | grep foo-2.0)
+test -n "$outPath20"
+
+# Install bar-0.1, uninstall foo.
+nix-env -i bar-0.1
+nix-env -e foo
+
+# Query installed: should only contain bar-0.1 now.
+if nix-env -q '*' | grepQuiet foo; then false; fi
+nix-env -q '*' | grepQuiet bar
+
+# Rollback: should bring "foo" back.
+oldGen="$(nix-store -q --resolve $profiles/test)"
+nix-env --rollback
+[ "$(nix-store -q --resolve $profiles/test)" != "$oldGen" ]
+nix-env -q '*' | grepQuiet foo-2.0
+nix-env -q '*' | grepQuiet bar
+
+# Rollback again: should remove "bar".
+nix-env --rollback
+nix-env -q '*' | grepQuiet foo-2.0
+if nix-env -q '*' | grepQuiet bar; then false; fi
+
+# Count generations.
+nix-env --list-generations
+test "$(nix-env --list-generations | wc -l)" -eq 7
+
+# Doing the same operation twice results in the same generation, which triggers
+# "lazy" behaviour and does not create a new symlink.
+
+nix-env -i foo
+nix-env -i foo
+
+# Count generations.
+nix-env --list-generations
+test "$(nix-env --list-generations | wc -l)" -eq 8
+
+# Switch to a specified generation.
+nix-env --switch-generation 7
+[ "$(nix-store -q --resolve $profiles/test)" = "$oldGen" ]
+
+# Install foo-1.0, now using its store path.
+nix-env -i "$outPath10"
+nix-env -q '*' | grepQuiet foo-1.0
+nix-store -qR $profiles/test | grep "$outPath10"
+nix-store -q --referrers-closure $profiles/test | grep "$(nix-store -q --resolve $profiles/test)"
+[ "$(nix-store -q --deriver "$outPath10")" = $drvPath10 ]
+
+# Uninstall foo-1.0, using a symlink to its store path.
+ln -sfn $outPath10/bin/foo $TEST_ROOT/symlink
+nix-env -e $TEST_ROOT/symlink
+if nix-env -q '*' | grepQuiet foo; then false; fi
+nix-store -qR $profiles/test | grepInverse "$outPath10"
+
+# Install foo-1.0, now using a symlink to its store path.
+nix-env -i $TEST_ROOT/symlink
+nix-env -q '*' | grepQuiet foo
+
+# Delete all old generations.
+nix-env --delete-generations old
+
+# Run the garbage collector.  This should get rid of foo-2.0 but not
+# foo-1.0.
+nix-collect-garbage
+test -e "$outPath10"
+(! [ -e "$outPath20" ])
+
+# Uninstall everything
+nix-env -e '*'
+test "$(nix-env -q '*' | wc -l)" -eq 0
+
+# Installing "foo" should only install the newest foo.
+nix-env -i foo
+test "$(nix-env -q '*' | grep foo- | wc -l)" -eq 1
+nix-env -q '*' | grepQuiet foo-2.0
+
+# On the other hand, this should install both (and should fail due to
+# a collision).
+nix-env -e '*'
+(! nix-env -i foo-1.0 foo-2.0)
+
+# Installing "*" should install one foo and one bar.
+nix-env -e '*'
+nix-env -i '*'
+test "$(nix-env -q '*' | wc -l)" -eq 2
+nix-env -q '*' | grepQuiet foo-2.0
+nix-env -q '*' | grepQuiet bar-0.1.1
+
+# Test priorities: foo-0.1 has a lower priority than foo-1.0, so it
+# should be possible to install both without a collision.  Also test
+# ‘--set-flag priority’ to manually override the declared priorities.
+nix-env -e '*'
+nix-env -i foo-0.1 foo-1.0
+[ "$($profiles/test/bin/foo)" = "foo-1.0" ]
+nix-env --set-flag priority 1 foo-0.1
+[ "$($profiles/test/bin/foo)" = "foo-0.1" ]
+
+# Test nix-env --set.
+nix-env --set $outPath10
+[ "$(nix-store -q --resolve $profiles/test)" = $outPath10 ]
+nix-env --set $drvPath10
+[ "$(nix-store -q --resolve $profiles/test)" = $outPath10 ]
+
+# Test the case where $HOME contains a symlink.
+mkdir -p $TEST_ROOT/real-home/alice/.nix-defexpr/channels
+ln -sfn $TEST_ROOT/real-home $TEST_ROOT/home
+ln -sfn $(pwd)/user-envs.nix $TEST_ROOT/home/alice/.nix-defexpr/channels/foo
+HOME=$TEST_ROOT/home/alice nix-env -i foo-0.1
diff --git a/tests/functional/user-envs.sh b/tests/functional/user-envs.sh
old mode 100644
new mode 100755
index 7c643f3553c..ec9d036f8c2
--- a/tests/functional/user-envs.sh
+++ b/tests/functional/user-envs.sh
@@ -1,197 +1,5 @@
-source common.sh
+#!/usr/bin/env bash
 
-if [ -z "${storeCleared-}" ]; then
-    clearStore
-fi
+source ./common.sh
 
-clearProfiles
-
-# Query installed: should be empty.
-test "$(nix-env -p $profiles/test -q '*' | wc -l)" -eq 0
-
-nix-env --switch-profile $profiles/test
-
-# Query available: should contain several.
-test "$(nix-env -f ./user-envs.nix -qa '*' | wc -l)" -eq 6
-outPath10=$(nix-env -f ./user-envs.nix -qa --out-path --no-name '*' | grep foo-1.0)
-drvPath10=$(nix-env -f ./user-envs.nix -qa --drv-path --no-name '*' | grep foo-1.0)
-[ -n "$outPath10" -a -n "$drvPath10" ]
-
-# Query with json
-nix-env -f ./user-envs.nix -qa --json | jq -e '.[] | select(.name == "bar-0.1") | [
-    .outputName == "out",
-    .outputs.out == null
-] | all'
-nix-env -f ./user-envs.nix -qa --json --out-path | jq -e '.[] | select(.name == "bar-0.1") | [
-    .outputName == "out",
-    (.outputs.out | test("'$NIX_STORE_DIR'.*-0\\.1"))
-] | all'
-nix-env -f ./user-envs.nix -qa --json --drv-path | jq -e '.[] | select(.name == "bar-0.1") | (.drvPath | test("'$NIX_STORE_DIR'.*-0\\.1\\.drv"))'
-
-# Query descriptions.
-nix-env -f ./user-envs.nix -qa '*' --description | grepQuiet silly
-rm -rf $HOME/.nix-defexpr
-ln -s $(pwd)/user-envs.nix $HOME/.nix-defexpr
-nix-env -qa '*' --description | grepQuiet silly
-
-# Query the system.
-nix-env -qa '*' --system | grepQuiet $system
-
-# Install "foo-1.0".
-nix-env -i foo-1.0
-
-# Query installed: should contain foo-1.0 now (which should be
-# executable).
-test "$(nix-env -q '*' | wc -l)" -eq 1
-nix-env -q '*' | grepQuiet foo-1.0
-test "$($profiles/test/bin/foo)" = "foo-1.0"
-
-# Test nix-env -qc to compare installed against available packages, and vice versa.
-nix-env -qc '*' | grepQuiet '< 2.0'
-nix-env -qac '*' | grepQuiet '> 1.0'
-
-# Test the -b flag to filter out source-only packages.
-[ "$(nix-env -qab | wc -l)" -eq 1 ]
-
-# Test the -s flag to get package status.
-nix-env -qas | grepQuiet 'IP-  foo-1.0'
-nix-env -qas | grepQuiet -- '---  bar-0.1'
-
-# Disable foo.
-nix-env --set-flag active false foo
-(! [ -e "$profiles/test/bin/foo" ])
-
-# Enable foo.
-nix-env --set-flag active true foo
-[ -e "$profiles/test/bin/foo" ]
-
-# Store the path of foo-1.0.
-outPath10_=$(nix-env -q --out-path --no-name '*' | grep foo-1.0)
-echo "foo-1.0 = $outPath10"
-[ "$outPath10" = "$outPath10_" ]
-
-# Install "foo-2.0pre1": should remove foo-1.0.
-nix-env -i foo-2.0pre1
-
-# Query installed: should contain foo-2.0pre1 now.
-test "$(nix-env -q '*' | wc -l)" -eq 1
-nix-env -q '*' | grepQuiet foo-2.0pre1
-test "$($profiles/test/bin/foo)" = "foo-2.0pre1"
-
-# Upgrade "foo": should install foo-2.0.
-NIX_PATH=nixpkgs=./user-envs.nix:${NIX_PATH-} nix-env -f '<nixpkgs>' -u foo
-
-# Query installed: should contain foo-2.0 now.
-test "$(nix-env -q '*' | wc -l)" -eq 1
-nix-env -q '*' | grepQuiet foo-2.0
-test "$($profiles/test/bin/foo)" = "foo-2.0"
-
-# Store the path of foo-2.0.
-outPath20=$(nix-env -q --out-path --no-name '*' | grep foo-2.0)
-test -n "$outPath20"
-
-# Install bar-0.1, uninstall foo.
-nix-env -i bar-0.1
-nix-env -e foo
-
-# Query installed: should only contain bar-0.1 now.
-if nix-env -q '*' | grepQuiet foo; then false; fi
-nix-env -q '*' | grepQuiet bar
-
-# Rollback: should bring "foo" back.
-oldGen="$(nix-store -q --resolve $profiles/test)"
-nix-env --rollback
-[ "$(nix-store -q --resolve $profiles/test)" != "$oldGen" ]
-nix-env -q '*' | grepQuiet foo-2.0
-nix-env -q '*' | grepQuiet bar
-
-# Rollback again: should remove "bar".
-nix-env --rollback
-nix-env -q '*' | grepQuiet foo-2.0
-if nix-env -q '*' | grepQuiet bar; then false; fi
-
-# Count generations.
-nix-env --list-generations
-test "$(nix-env --list-generations | wc -l)" -eq 7
-
-# Doing the same operation twice results in the same generation, which triggers
-# "lazy" behaviour and does not create a new symlink.
-
-nix-env -i foo
-nix-env -i foo
-
-# Count generations.
-nix-env --list-generations
-test "$(nix-env --list-generations | wc -l)" -eq 8
-
-# Switch to a specified generation.
-nix-env --switch-generation 7
-[ "$(nix-store -q --resolve $profiles/test)" = "$oldGen" ]
-
-# Install foo-1.0, now using its store path.
-nix-env -i "$outPath10"
-nix-env -q '*' | grepQuiet foo-1.0
-nix-store -qR $profiles/test | grep "$outPath10"
-nix-store -q --referrers-closure $profiles/test | grep "$(nix-store -q --resolve $profiles/test)"
-[ "$(nix-store -q --deriver "$outPath10")" = $drvPath10 ]
-
-# Uninstall foo-1.0, using a symlink to its store path.
-ln -sfn $outPath10/bin/foo $TEST_ROOT/symlink
-nix-env -e $TEST_ROOT/symlink
-if nix-env -q '*' | grepQuiet foo; then false; fi
-nix-store -qR $profiles/test | grepInverse "$outPath10"
-
-# Install foo-1.0, now using a symlink to its store path.
-nix-env -i $TEST_ROOT/symlink
-nix-env -q '*' | grepQuiet foo
-
-# Delete all old generations.
-nix-env --delete-generations old
-
-# Run the garbage collector.  This should get rid of foo-2.0 but not
-# foo-1.0.
-nix-collect-garbage
-test -e "$outPath10"
-(! [ -e "$outPath20" ])
-
-# Uninstall everything
-nix-env -e '*'
-test "$(nix-env -q '*' | wc -l)" -eq 0
-
-# Installing "foo" should only install the newest foo.
-nix-env -i foo
-test "$(nix-env -q '*' | grep foo- | wc -l)" -eq 1
-nix-env -q '*' | grepQuiet foo-2.0
-
-# On the other hand, this should install both (and should fail due to
-# a collision).
-nix-env -e '*'
-(! nix-env -i foo-1.0 foo-2.0)
-
-# Installing "*" should install one foo and one bar.
-nix-env -e '*'
-nix-env -i '*'
-test "$(nix-env -q '*' | wc -l)" -eq 2
-nix-env -q '*' | grepQuiet foo-2.0
-nix-env -q '*' | grepQuiet bar-0.1.1
-
-# Test priorities: foo-0.1 has a lower priority than foo-1.0, so it
-# should be possible to install both without a collision.  Also test
-# ‘--set-flag priority’ to manually override the declared priorities.
-nix-env -e '*'
-nix-env -i foo-0.1 foo-1.0
-[ "$($profiles/test/bin/foo)" = "foo-1.0" ]
-nix-env --set-flag priority 1 foo-0.1
-[ "$($profiles/test/bin/foo)" = "foo-0.1" ]
-
-# Test nix-env --set.
-nix-env --set $outPath10
-[ "$(nix-store -q --resolve $profiles/test)" = $outPath10 ]
-nix-env --set $drvPath10
-[ "$(nix-store -q --resolve $profiles/test)" = $outPath10 ]
-
-# Test the case where $HOME contains a symlink.
-mkdir -p $TEST_ROOT/real-home/alice/.nix-defexpr/channels
-ln -sfn $TEST_ROOT/real-home $TEST_ROOT/home
-ln -sfn $(pwd)/user-envs.nix $TEST_ROOT/home/alice/.nix-defexpr/channels/foo
-HOME=$TEST_ROOT/home/alice nix-env -i foo-0.1
+source ./user-envs-test-case.sh
diff --git a/tests/functional/why-depends.sh b/tests/functional/why-depends.sh
old mode 100644
new mode 100755
index 9680bf80ebe..ce53546d8be
--- a/tests/functional/why-depends.sh
+++ b/tests/functional/why-depends.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
+
 source common.sh
 
-clearStore
+clearStoreIfPossible
 
 cp ./dependencies.nix ./dependencies.builder0.sh ./config.nix $TEST_HOME
 
diff --git a/tests/functional/zstd.sh b/tests/functional/zstd.sh
old mode 100644
new mode 100755
index ba7c20501fe..90fe58539b1
--- a/tests/functional/zstd.sh
+++ b/tests/functional/zstd.sh
@@ -1,5 +1,9 @@
+#!/usr/bin/env bash
+
 source common.sh
 
+TODO_NixOS
+
 clearStore
 clearCache
 
diff --git a/tests/installer/default.nix b/tests/installer/default.nix
index 238c6ac8e8d..4aed6eae489 100644
--- a/tests/installer/default.nix
+++ b/tests/installer/default.nix
@@ -13,6 +13,17 @@ let
       '';
     };
 
+    install-both-profile-links = {
+      script = ''
+        tar -xf ./nix.tar.xz
+        mv ./nix-* nix
+        ln -s $HOME/.local/state/nix/profiles/a-profile $HOME/.nix-profile
+        mkdir -p $HOME/.local/state/nix
+        ln -s $HOME/.local/state/nix/profiles/b-profile $HOME/.local/state/nix/profile
+        ./nix/install --no-channel-add
+      '';
+    };
+
     install-force-no-daemon = {
       script = ''
         tar -xf ./nix.tar.xz
diff --git a/tests/nixos/containers/containers.nix b/tests/nixos/containers/containers.nix
index c8ee78a4a58..6773f5628a3 100644
--- a/tests/nixos/containers/containers.nix
+++ b/tests/nixos/containers/containers.nix
@@ -33,30 +33,30 @@
     # Test that 'id' gives the expected result in various configurations.
 
     # Existing UIDs, sandbox.
-    host.succeed("nix build -v --no-auto-allocate-uids --sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-1")
+    host.succeed("nix build --no-auto-allocate-uids --sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-1")
     host.succeed("[[ $(cat ./result) = 'uid=1000(nixbld) gid=100(nixbld) groups=100(nixbld)' ]]")
 
     # Existing UIDs, no sandbox.
-    host.succeed("nix build -v --no-auto-allocate-uids --no-sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-2")
+    host.succeed("nix build --no-auto-allocate-uids --no-sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-2")
     host.succeed("[[ $(cat ./result) = 'uid=30001(nixbld1) gid=30000(nixbld) groups=30000(nixbld)' ]]")
 
     # Auto-allocated UIDs, sandbox.
-    host.succeed("nix build -v --auto-allocate-uids --sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-3")
+    host.succeed("nix build --auto-allocate-uids --sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-3")
     host.succeed("[[ $(cat ./result) = 'uid=1000(nixbld) gid=100(nixbld) groups=100(nixbld)' ]]")
 
     # Auto-allocated UIDs, no sandbox.
-    host.succeed("nix build -v --auto-allocate-uids --no-sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-4")
+    host.succeed("nix build --auto-allocate-uids --no-sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-4")
     host.succeed("[[ $(cat ./result) = 'uid=872415232 gid=30000(nixbld) groups=30000(nixbld)' ]]")
 
     # Auto-allocated UIDs, UID range, sandbox.
-    host.succeed("nix build -v --auto-allocate-uids --sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-5 --arg uidRange true")
+    host.succeed("nix build --auto-allocate-uids --sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-5 --arg uidRange true")
     host.succeed("[[ $(cat ./result) = 'uid=0(root) gid=0(root) groups=0(root)' ]]")
 
     # Auto-allocated UIDs, UID range, no sandbox.
-    host.fail("nix build -v --auto-allocate-uids --no-sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-6 --arg uidRange true")
+    host.fail("nix build --auto-allocate-uids --no-sandbox -L --offline --impure --file ${./id-test.nix} --argstr name id-test-6 --arg uidRange true")
 
     # Run systemd-nspawn in a Nix build.
-    host.succeed("nix build -v --auto-allocate-uids --sandbox -L --offline --impure --file ${./systemd-nspawn.nix} --argstr nixpkgs ${nixpkgs}")
+    host.succeed("nix build --auto-allocate-uids --sandbox -L --offline --impure --file ${./systemd-nspawn.nix} --argstr nixpkgs ${nixpkgs}")
     host.succeed("[[ $(cat ./result/msg) = 'Hello World' ]]")
   '';
 
diff --git a/tests/nixos/default.nix b/tests/nixos/default.nix
index 4edf40c16b8..c0c7b42fd9b 100644
--- a/tests/nixos/default.nix
+++ b/tests/nixos/default.nix
@@ -1,4 +1,4 @@
-{ lib, nixpkgs, nixpkgsFor }:
+{ lib, nixpkgs, nixpkgsFor, self }:
 
 let
 
@@ -7,7 +7,13 @@ let
   # https://nixos.org/manual/nixos/unstable/index.html#sec-calling-nixos-tests
   runNixOSTestFor = system: test:
     (nixos-lib.runTest {
-      imports = [ test ];
+      imports = [
+        test
+
+        # Add the quickBuild attribute to the check packages
+        ./quick-build.nix
+      ];
+
       hostPkgs = nixpkgsFor.${system}.native;
       defaults = {
         nixpkgs.pkgs = nixpkgsFor.${system}.native;
@@ -33,109 +39,79 @@ let
   checkOverrideNixVersion = { pkgs, lib, ... }: {
     # pkgs.nix: The new Nix in this repo
     # We disallow it, to make sure we don't accidentally use it.
-    system.forbiddenDependenciesRegex = lib.strings.escapeRegex "nix-${pkgs.nix.version}";
+    system.forbiddenDependenciesRegexes = [
+      (lib.strings.escapeRegex "nix-${pkgs.nix.version}")
+    ];
   };
-in
-
-{
-  authorization = runNixOSTestFor "x86_64-linux" ./authorization.nix;
-
-  remoteBuilds = runNixOSTestFor "x86_64-linux" ./remote-builds.nix;
-
-  # Test our Nix as a client against remotes that are older
 
-  remoteBuilds_remote_2_3 = runNixOSTestFor "x86_64-linux" {
-    name = "remoteBuilds_remote_2_3";
-    imports = [ ./remote-builds.nix ];
-    builders.config = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_3;
-    };
+  otherNixes.nix_2_3.setNixPackage = { lib, pkgs, ... }: {
+    imports = [ checkOverrideNixVersion ];
+    nix.package = lib.mkForce pkgs.nixVersions.nix_2_3;
   };
 
-  remoteBuilds_remote_2_13 = runNixOSTestFor "x86_64-linux" ({ lib, pkgs, ... }: {
-    name = "remoteBuilds_remote_2_13";
-    imports = [ ./remote-builds.nix ];
-    builders.config = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_3;
-    };
-  });
-
-  # TODO: (nixpkgs update) remoteBuilds_remote_2_18 = ...
+  otherNixes.nix_2_13.setNixPackage = { lib, pkgs, ... }: {
+    imports = [ checkOverrideNixVersion ];
+    nix.package = lib.mkForce (
+      self.inputs.nixpkgs-23-11.legacyPackages.${pkgs.stdenv.hostPlatform.system}.nixVersions.nix_2_13.overrideAttrs (o: {
+        meta = o.meta // { knownVulnerabilities = []; };
+      })
+    );
+  };
 
-  # Test our Nix as a builder for clients that are older
+  otherNixes.nix_2_18.setNixPackage = { lib, pkgs, ... }: {
+    imports = [ checkOverrideNixVersion ];
+    nix.package = lib.mkForce pkgs.nixVersions.nix_2_18;
+  };
 
-  remoteBuilds_local_2_3 = runNixOSTestFor "x86_64-linux" ({ lib, pkgs, ... }: {
-    name = "remoteBuilds_local_2_3";
-    imports = [ ./remote-builds.nix ];
-    nodes.client = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_3;
-    };
-  });
-
-  remoteBuilds_local_2_13 = runNixOSTestFor "x86_64-linux" ({ lib, pkgs, ... }: {
-    name = "remoteBuilds_local_2_13";
-    imports = [ ./remote-builds.nix ];
-    nodes.client = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_13;
-    };
-  });
+in
 
-  # TODO: (nixpkgs update) remoteBuilds_local_2_18 = ...
+{
+  authorization = runNixOSTestFor "x86_64-linux" ./authorization.nix;
 
-  # End remoteBuilds tests
+  remoteBuilds = runNixOSTestFor "x86_64-linux" ./remote-builds.nix;
 
   remoteBuildsSshNg = runNixOSTestFor "x86_64-linux" ./remote-builds-ssh-ng.nix;
 
-  # Test our Nix as a client against remotes that are older
-
-  remoteBuildsSshNg_remote_2_3 = runNixOSTestFor "x86_64-linux" {
-    name = "remoteBuildsSshNg_remote_2_3";
-    imports = [ ./remote-builds-ssh-ng.nix ];
-    builders.config = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_3;
+}
+// lib.concatMapAttrs (
+  nixVersion: { setNixPackage, ... }:
+  {
+    "remoteBuilds_remote_${nixVersion}" = runNixOSTestFor "x86_64-linux" {
+      name = "remoteBuilds_remote_${nixVersion}";
+      imports = [ ./remote-builds.nix ];
+      builders.config = { lib, pkgs, ... }: {
+        imports = [ setNixPackage ];
+      };
     };
-  };
 
-  remoteBuildsSshNg_remote_2_13 = runNixOSTestFor "x86_64-linux" {
-    name = "remoteBuildsSshNg_remote_2_13";
-    imports = [ ./remote-builds-ssh-ng.nix ];
-    builders.config = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_13;
+    "remoteBuilds_local_${nixVersion}" = runNixOSTestFor "x86_64-linux" {
+      name = "remoteBuilds_local_${nixVersion}";
+      imports = [ ./remote-builds.nix ];
+      nodes.client = { lib, pkgs, ... }: {
+        imports = [ setNixPackage ];
+      };
     };
-  };
-
-  # TODO: (nixpkgs update) remoteBuildsSshNg_remote_2_18 = ...
 
-  # Test our Nix as a builder for clients that are older
-
-  # FIXME: these tests don't work yet
-  /*
-  remoteBuildsSshNg_local_2_3 = runNixOSTestFor "x86_64-linux" ({ lib, pkgs, ... }: {
-    name = "remoteBuildsSshNg_local_2_3";
-    imports = [ ./remote-builds-ssh-ng.nix ];
-    nodes.client = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_3;
-    };
-  });
-
-  remoteBuildsSshNg_local_2_13 = runNixOSTestFor "x86_64-linux" ({ lib, pkgs, ... }: {
-    name = "remoteBuildsSshNg_local_2_13";
-    imports = [ ./remote-builds-ssh-ng.nix ];
-    nodes.client = { lib, pkgs, ... }: {
-      imports = [ checkOverrideNixVersion ];
-      nix.package = lib.mkForce pkgs.nixVersions.nix_2_13;
+    "remoteBuildsSshNg_remote_${nixVersion}" = runNixOSTestFor "x86_64-linux" {
+      name = "remoteBuildsSshNg_remote_${nixVersion}";
+      imports = [ ./remote-builds-ssh-ng.nix ];
+      builders.config = { lib, pkgs, ... }: {
+        imports = [ setNixPackage ];
+      };
     };
-  });
 
-  # TODO: (nixpkgs update) remoteBuildsSshNg_local_2_18 = ...
-  */
+    # FIXME: these tests don't work yet
+
+    # "remoteBuildsSshNg_local_${nixVersion}" = runNixOSTestFor "x86_64-linux" {
+    #   name = "remoteBuildsSshNg_local_${nixVersion}";
+    #   imports = [ ./remote-builds-ssh-ng.nix ];
+    #   nodes.client = { lib, pkgs, ... }: {
+    #     imports = [ overridingModule ];
+    #   };
+    # };
+  }
+) otherNixes
+// {
 
   nix-copy-closure = runNixOSTestFor "x86_64-linux" ./nix-copy-closure.nix;
 
@@ -154,7 +130,7 @@ in
   containers = runNixOSTestFor "x86_64-linux" ./containers/containers.nix;
 
   setuid = lib.genAttrs
-    ["i686-linux" "x86_64-linux"]
+    ["x86_64-linux"]
     (system: runNixOSTestFor system ./setuid.nix);
 
   fetch-git = runNixOSTestFor "x86_64-linux" ./fetch-git;
@@ -162,4 +138,12 @@ in
   ca-fd-leak = runNixOSTestFor "x86_64-linux" ./ca-fd-leak;
 
   gzip-content-encoding = runNixOSTestFor "x86_64-linux" ./gzip-content-encoding.nix;
+
+  functional_user = runNixOSTestFor "x86_64-linux" ./functional/as-user.nix;
+
+  functional_trusted = runNixOSTestFor "x86_64-linux" ./functional/as-trusted-user.nix;
+
+  functional_root = runNixOSTestFor "x86_64-linux" ./functional/as-root.nix;
+
+  user-sandboxing = runNixOSTestFor "x86_64-linux" ./user-sandboxing;
 }
diff --git a/tests/nixos/fetch-git/test-cases/fetchTree-shallow/default.nix b/tests/nixos/fetch-git/test-cases/fetchTree-shallow/default.nix
new file mode 100644
index 00000000000..f635df1f879
--- /dev/null
+++ b/tests/nixos/fetch-git/test-cases/fetchTree-shallow/default.nix
@@ -0,0 +1,45 @@
+{
+  description = "fetchTree fetches git repos shallowly by default";
+  script = ''
+    # purge nix git cache to make sure we start with a clean slate
+    client.succeed("rm -rf ~/.cache/nix")
+
+    # add two commits to the repo:
+    #   - one with a large file (2M)
+    #   - another one making the file small again
+    client.succeed(f"""
+      dd if=/dev/urandom of={repo.path}/thailand bs=1M count=2 \
+      && {repo.git} add thailand \
+      && {repo.git} commit -m 'commit1' \
+      && echo 'ThaigerSprint' > {repo.path}/thailand \
+      && {repo.git} add thailand \
+      && {repo.git} commit -m 'commit2' \
+      && {repo.git} push origin main
+    """)
+
+    # memoize the revision
+    commit2_rev = client.succeed(f"""
+      {repo.git} rev-parse HEAD
+    """).strip()
+
+    # construct the fetcher call
+    fetchGit_expr = f"""
+      builtins.fetchTree {{
+        type = "git";
+        url = "{repo.remote}";
+        rev = "{commit2_rev}";
+      }}
+    """
+
+    # fetch the repo via nix
+    fetched1 = client.succeed(f"""
+      nix eval --impure --raw --expr '({fetchGit_expr}).outPath'
+    """)
+
+    # check that the size of ~/.cache/nix is less than 1M
+    cache_size = client.succeed("""
+      du -s ~/.cache/nix
+    """).strip().split()[0]
+    assert int(cache_size) < 1024, f"cache size is {cache_size}K which is larger than 1M"
+  '';
+}
diff --git a/tests/nixos/functional/as-root.nix b/tests/nixos/functional/as-root.nix
new file mode 100644
index 00000000000..96be3d59327
--- /dev/null
+++ b/tests/nixos/functional/as-root.nix
@@ -0,0 +1,12 @@
+{
+  name = "functional-tests-on-nixos_root";
+
+  imports = [ ./common.nix ];
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    machine.succeed("""
+      run-test-suite >&2
+    """)
+  '';
+}
diff --git a/tests/nixos/functional/as-trusted-user.nix b/tests/nixos/functional/as-trusted-user.nix
new file mode 100644
index 00000000000..d6f825697e9
--- /dev/null
+++ b/tests/nixos/functional/as-trusted-user.nix
@@ -0,0 +1,18 @@
+{
+  name = "functional-tests-on-nixos_trusted-user";
+
+  imports = [ ./common.nix ];
+
+  nodes.machine = {
+    users.users.alice = { isNormalUser = true; };
+    nix.settings.trusted-users = [ "alice" ];
+  };
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    machine.succeed("""
+      export TEST_TRUSTED_USER=1
+      su --login --command "run-test-suite" alice >&2
+    """)
+  '';
+}
\ No newline at end of file
diff --git a/tests/nixos/functional/as-user.nix b/tests/nixos/functional/as-user.nix
new file mode 100644
index 00000000000..1443f6e6ccd
--- /dev/null
+++ b/tests/nixos/functional/as-user.nix
@@ -0,0 +1,16 @@
+{
+  name = "functional-tests-on-nixos_user";
+
+  imports = [ ./common.nix ];
+
+  nodes.machine = {
+    users.users.alice = { isNormalUser = true; };
+  };
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    machine.succeed("""
+      su --login --command "run-test-suite" alice >&2
+    """)
+  '';
+}
diff --git a/tests/nixos/functional/common.nix b/tests/nixos/functional/common.nix
new file mode 100644
index 00000000000..51fd768843a
--- /dev/null
+++ b/tests/nixos/functional/common.nix
@@ -0,0 +1,71 @@
+{ lib, ... }:
+
+let
+  # FIXME (roberth) reference issue
+  inputDerivation = pkg: (pkg.overrideAttrs (o: {
+    disallowedReferences = [ ];
+  })).inputDerivation;
+
+in
+{
+  # We rarely change the script in a way that benefits from type checking, so
+  # we skip it to save time.
+  skipTypeCheck = true;
+
+  nodes.machine = { config, pkgs, ... }: {
+
+    virtualisation.writableStore = true;
+    system.extraDependencies = [
+      (inputDerivation config.nix.package)
+    ];
+
+    nix.settings.substituters = lib.mkForce [];
+
+    environment.systemPackages = let
+      run-test-suite = pkgs.writeShellApplication {
+        name = "run-test-suite";
+        runtimeInputs = [ pkgs.gnumake pkgs.jq pkgs.git ];
+        text = ''
+          set -x
+          cat /proc/sys/fs/file-max
+          ulimit -Hn
+          ulimit -Sn
+          cd ~
+          cp -r ${pkgs.nix.overrideAttrs (o: {
+            name = "nix-configured-source";
+            outputs = [ "out" ];
+            separateDebugInfo = false;
+            disallowedReferences = [ ];
+            buildPhase = ":";
+            checkPhase = ":";
+            installPhase = ''
+              cp -r . $out
+            '';
+            installCheckPhase = ":";
+            fixupPhase = ":";
+            doInstallCheck = true;
+          })} nix
+          chmod -R +w nix
+          cd nix
+
+          # Tests we don't need
+          echo >tests/functional/plugins/local.mk
+          sed -i tests/functional/local.mk \
+            -e 's!nix_tests += plugins\.sh!!' \
+            -e 's!nix_tests += test-libstoreconsumer\.sh!!' \
+            ;
+
+          export isTestOnNixOS=1
+          export version=${config.nix.package.version}
+          export NIX_REMOTE_=daemon
+          export NIX_REMOTE=daemon
+          export NIX_STORE=${builtins.storeDir}
+          make -j1 installcheck --keep-going
+        '';
+      };
+    in [
+      run-test-suite
+      pkgs.git
+    ];
+  };
+}
diff --git a/tests/nixos/nss-preload.nix b/tests/nixos/nss-preload.nix
index 00505d11421..610769c8df5 100644
--- a/tests/nixos/nss-preload.nix
+++ b/tests/nixos/nss-preload.nix
@@ -32,6 +32,7 @@ let
 
         impureEnvVars = [
             "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
+            "HTTP_PROXY" "HTTPS_PROXY" "FTP_PROXY" "ALL_PROXY" "NO_PROXY"
         ];
 
         urls = [ "http://example.com" ];
diff --git a/tests/nixos/quick-build.nix b/tests/nixos/quick-build.nix
new file mode 100644
index 00000000000..37169b4e2e0
--- /dev/null
+++ b/tests/nixos/quick-build.nix
@@ -0,0 +1,47 @@
+test@{ lib, extendModules, ... }:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options = {
+    quickBuild = mkOption {
+      description = ''
+        Whether to perform a "quick" build of the Nix package to test.
+
+        When iterating on the functional tests, it's recommended to "set" this
+        to `true`, so that changes to the functional tests don't require any
+        recompilation of the package.
+        You can do so by building the `.quickBuild` attribute on the check package,
+        e.g:
+        ```console
+        nix build .#hydraJobs.functional_user.quickBuild
+        ```
+
+        We don't enable this by default to avoid the mostly unnecessary work of
+        performing an additional build of the package in cases where we build
+        the package normally anyway, such as in our pre-merge CI.
+      '';
+      type = types.bool;
+      default = false;
+    };
+  };
+
+  config = {
+    passthru.quickBuild = 
+      let withQuickBuild = extendModules { modules = [{ quickBuild = true; }]; };
+      in withQuickBuild.config.test;
+
+    defaults = { pkgs, ... }: {
+      config = lib.mkIf test.config.quickBuild {
+        nix.package = pkgs.nix_noTests;
+
+        system.forbiddenDependenciesRegexes = [
+          # This would indicate that the quickBuild feature is broken.
+          # It could happen if NixOS has a dependency on pkgs.nix instead of
+          # config.nix.package somewhere.
+          (builtins.unsafeDiscardStringContext pkgs.nix.outPath)
+        ];
+      };
+    };
+  };
+}
\ No newline at end of file
diff --git a/tests/nixos/tarball-flakes.nix b/tests/nixos/tarball-flakes.nix
index e30d15739e6..84cf377ec5b 100644
--- a/tests/nixos/tarball-flakes.nix
+++ b/tests/nixos/tarball-flakes.nix
@@ -5,7 +5,7 @@ let
 
   root = pkgs.runCommand "nixpkgs-flake" {}
     ''
-      mkdir -p $out/stable
+      mkdir -p $out/{stable,tags}
 
       set -x
       dir=nixpkgs-${nixpkgs.shortRev}
@@ -14,9 +14,13 @@ let
       find $dir -print0 | xargs -0 touch -h -t ${builtins.substring 0 12 nixpkgs.lastModifiedDate}.${builtins.substring 12 2 nixpkgs.lastModifiedDate} --
       tar cfz $out/stable/${nixpkgs.rev}.tar.gz $dir --hard-dereference
 
-      echo 'Redirect "/latest.tar.gz" "/stable/${nixpkgs.rev}.tar.gz"' > $out/.htaccess
-
-      echo 'Header set Link "<http://localhost/stable/${nixpkgs.rev}.tar.gz?rev=${nixpkgs.rev}&revCount=1234>; rel=\"immutable\""' > $out/stable/.htaccess
+      # Set the "Link" header on the redirect but not the final response to
+      # simulate an S3-like serving environment where the final host cannot set
+      # arbitrary headers.
+      cat >$out/tags/.htaccess <<EOF
+      Redirect "/tags/latest.tar.gz" "/stable/${nixpkgs.rev}.tar.gz"
+      Header always set Link "<http://localhost/stable/${nixpkgs.rev}.tar.gz?rev=${nixpkgs.rev}&revCount=1234>; rel=\"immutable\""
+      EOF
     '';
 in
 
@@ -59,26 +63,32 @@ in
 
     machine.wait_for_unit("httpd.service")
 
-    out = machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz")
+    out = machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz")
     print(out)
     info = json.loads(out)
 
     # Check that we got redirected to the immutable URL.
     assert info["locked"]["url"] == "http://localhost/stable/${nixpkgs.rev}.tar.gz"
 
+    # Check that we got a fingerprint for caching.
+    assert info["fingerprint"]
+
     # Check that we got the rev and revCount attributes.
     assert info["revision"] == "${nixpkgs.rev}"
     assert info["revCount"] == 1234
 
+    # Check that a 0-byte HTTP 304 "Not modified" result works.
+    machine.succeed("nix flake metadata --refresh --json http://localhost/tags/latest.tar.gz")
+
     # Check that fetching with rev/revCount/narHash succeeds.
-    machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz?rev=" + info["revision"])
-    machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz?revCount=" + str(info["revCount"]))
-    machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz?narHash=" + info["locked"]["narHash"])
+    machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?rev=" + info["revision"])
+    machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?revCount=" + str(info["revCount"]))
+    machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?narHash=" + info["locked"]["narHash"])
 
     # Check that fetching fails if we provide incorrect attributes.
-    machine.fail("nix flake metadata --json http://localhost/latest.tar.gz?rev=493300eb13ae6fb387fbd47bf54a85915acc31c0")
-    machine.fail("nix flake metadata --json http://localhost/latest.tar.gz?revCount=789")
-    machine.fail("nix flake metadata --json http://localhost/latest.tar.gz?narHash=sha256-tbudgBSg+bHWHiHnlteNzN8TUvI80ygS9IULh4rklEw=")
+    machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?rev=493300eb13ae6fb387fbd47bf54a85915acc31c0")
+    machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?revCount=789")
+    machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?narHash=sha256-tbudgBSg+bHWHiHnlteNzN8TUvI80ygS9IULh4rklEw=")
   '';
 
 }
diff --git a/tests/nixos/user-sandboxing/attacker.c b/tests/nixos/user-sandboxing/attacker.c
new file mode 100644
index 00000000000..3bd729c0444
--- /dev/null
+++ b/tests/nixos/user-sandboxing/attacker.c
@@ -0,0 +1,82 @@
+#define _GNU_SOURCE
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/inotify.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+#define SYS_fchmodat2 452
+
+int fchmodat2(int dirfd, const char *pathname, mode_t mode, int flags) {
+  return syscall(SYS_fchmodat2, dirfd, pathname, mode, flags);
+}
+
+int main(int argc, char **argv) {
+  if (argc <= 1) {
+    // stage 1: place the setuid-builder executable
+
+    // make the build directory world-accessible first
+    chmod(".", 0755);
+
+    if (fchmodat2(AT_FDCWD, "attacker", 06755, AT_SYMLINK_NOFOLLOW) < 0) {
+      perror("Setting the suid bit on attacker");
+      exit(-1);
+    }
+
+  } else {
+    // stage 2: corrupt the victim derivation while it's building
+
+    // prevent the kill
+    if (setresuid(-1, -1, getuid())) {
+      perror("setresuid");
+      exit(-1);
+    }
+
+    if (fork() == 0) {
+
+      // wait for the victim to build
+      int fd = inotify_init();
+      inotify_add_watch(fd, argv[1], IN_CREATE);
+      int dirfd = open(argv[1], O_DIRECTORY);
+      if (dirfd < 0) {
+        perror("opening the global build directory");
+        exit(-1);
+      }
+      char buf[4096];
+      fprintf(stderr, "Entering the inotify loop\n");
+      for (;;) {
+        ssize_t len = read(fd, buf, sizeof(buf));
+        struct inotify_event *ev;
+        for (char *pe = buf; pe < buf + len;
+            pe += sizeof(struct inotify_event) + ev->len) {
+          ev = (struct inotify_event *)pe;
+          fprintf(stderr, "folder %s created\n", ev->name);
+          // wait a bit to prevent racing against the creation
+          sleep(1);
+          int builddir = openat(dirfd, ev->name, O_DIRECTORY);
+          if (builddir < 0) {
+            perror("opening the build directory");
+            continue;
+          }
+          int resultfile = openat(builddir, "build/result", O_WRONLY | O_TRUNC);
+          if (resultfile < 0) {
+            perror("opening the hijacked file");
+            continue;
+          }
+          int writeres = write(resultfile, "bad\n", 4);
+          if (writeres < 0) {
+            perror("writing to the hijacked file");
+            continue;
+          }
+          fprintf(stderr, "Hijacked the build for %s\n", ev->name);
+          return 0;
+        }
+      }
+    }
+
+    exit(0);
+  }
+}
+
diff --git a/tests/nixos/user-sandboxing/default.nix b/tests/nixos/user-sandboxing/default.nix
new file mode 100644
index 00000000000..8a16f44e84d
--- /dev/null
+++ b/tests/nixos/user-sandboxing/default.nix
@@ -0,0 +1,129 @@
+{ config, ... }:
+
+let
+  pkgs = config.nodes.machine.nixpkgs.pkgs;
+
+  attacker = pkgs.runCommandWith {
+    name = "attacker";
+    stdenv = pkgs.pkgsStatic.stdenv;
+  } ''
+    $CC -static -o $out ${./attacker.c}
+  '';
+
+  try-open-build-dir = pkgs.writeScript "try-open-build-dir" ''
+    export PATH=${pkgs.coreutils}/bin:$PATH
+
+    set -x
+
+    chmod 700 .
+    # Shouldn't be able to open the root build directory
+    (! chmod 700 ..)
+
+    touch foo
+
+    # Synchronisation point: create a world-writable fifo and wait for someone
+    # to write into it
+    mkfifo syncPoint
+    chmod 777 syncPoint
+    cat syncPoint
+
+    touch $out
+
+    set +x
+  '';
+
+  create-hello-world = pkgs.writeScript "create-hello-world" ''
+    export PATH=${pkgs.coreutils}/bin:$PATH
+
+    set -x
+
+    echo "hello, world" > result
+
+    # Synchronisation point: create a world-writable fifo and wait for someone
+    # to write into it
+    mkfifo syncPoint
+    chmod 777 syncPoint
+    cat syncPoint
+
+    cp result $out
+
+    set +x
+  '';
+
+in
+{
+  name = "sandbox-setuid-leak";
+
+  nodes.machine =
+    { config, lib, pkgs, ... }:
+    { virtualisation.writableStore = true;
+      nix.settings.substituters = lib.mkForce [ ];
+      nix.nrBuildUsers = 1;
+      virtualisation.additionalPaths = [ pkgs.busybox-sandbox-shell attacker try-open-build-dir create-hello-world pkgs.socat ];
+      boot.kernelPackages = pkgs.linuxPackages_latest;
+      users.users.alice = {
+        isNormalUser = true;
+      };
+    };
+
+  testScript = { nodes }: ''
+    start_all()
+
+    with subtest("A builder can't give access to its build directory"):
+        # Make sure that a builder can't change the permissions on its build
+        # directory to the point of opening it up to external users
+
+        # A derivation whose builder tries to make its build directory as open
+        # as possible and wait for someone to hijack it
+        machine.succeed(r"""
+          nix-build -v -E '
+            builtins.derivation {
+              name = "open-build-dir";
+              system = builtins.currentSystem;
+              builder = "${pkgs.busybox-sandbox-shell}/bin/sh";
+              args = [ (builtins.storePath "${try-open-build-dir}") ];
+          }' >&2 &
+        """.strip())
+
+        # Wait for the build to be ready
+        # This is OK because it runs as root, so we can access everything
+        machine.wait_for_file("/tmp/nix-build-open-build-dir.drv-0/build/syncPoint")
+
+        # But Alice shouldn't be able to access the build directory
+        machine.fail("su alice -c 'ls /tmp/nix-build-open-build-dir.drv-0/build'")
+        machine.fail("su alice -c 'touch /tmp/nix-build-open-build-dir.drv-0/build/bar'")
+        machine.fail("su alice -c 'cat /tmp/nix-build-open-build-dir.drv-0/build/foo'")
+
+        # Tell the user to finish the build
+        machine.succeed("echo foo > /tmp/nix-build-open-build-dir.drv-0/build/syncPoint")
+
+    with subtest("Being able to execute stuff as the build user doesn't give access to the build dir"):
+        machine.succeed(r"""
+          nix-build -E '
+            builtins.derivation {
+              name = "innocent";
+              system = builtins.currentSystem;
+              builder = "${pkgs.busybox-sandbox-shell}/bin/sh";
+              args = [ (builtins.storePath "${create-hello-world}") ];
+          }' >&2 &
+        """.strip())
+        machine.wait_for_file("/tmp/nix-build-innocent.drv-0/build/syncPoint")
+
+        # The build ran as `nixbld1` (which is the only build user on the
+        # machine), but a process running as `nixbld1` outside the sandbox
+        # shouldn't be able to touch the build directory regardless
+        machine.fail("su nixbld1 --shell ${pkgs.busybox-sandbox-shell}/bin/sh -c 'ls /tmp/nix-build-innocent.drv-0/build'")
+        machine.fail("su nixbld1 --shell ${pkgs.busybox-sandbox-shell}/bin/sh -c 'echo pwned > /tmp/nix-build-innocent.drv-0/build/result'")
+
+        # Finish the build
+        machine.succeed("echo foo > /tmp/nix-build-innocent.drv-0/build/syncPoint")
+
+        # Check that the build was not affected
+        machine.succeed(r"""
+          cat ./result
+          test "$(cat ./result)" = "hello, world"
+        """.strip())
+  '';
+
+}
+
diff --git a/tests/repl-completion.nix b/tests/repl-completion.nix
new file mode 100644
index 00000000000..3ba198a9860
--- /dev/null
+++ b/tests/repl-completion.nix
@@ -0,0 +1,40 @@
+{ runCommand, nix, expect }:
+
+# We only use expect when necessary, e.g. for testing tab completion in nix repl.
+# See also tests/functional/repl.sh
+
+runCommand "repl-completion" {
+  nativeBuildInputs = [
+    expect
+    nix
+  ];
+  expectScript = ''
+    # Regression https://github.com/NixOS/nix/pull/10778
+    spawn nix repl --offline --extra-experimental-features nix-command
+    expect "nix-repl>"
+    send "foo = import ./does-not-exist.nix\n"
+    expect "nix-repl>"
+    send "foo.\t"
+    expect {
+      "nix-repl>" {
+        puts "Got another prompt. Good."
+      }
+      eof {
+        puts "Got EOF. Bad."
+        exit 1
+      }
+    }
+    exit 0
+  '';
+  passAsFile = [ "expectScript" ];
+}
+''
+  export NIX_STORE=$TMPDIR/store
+  export NIX_STATE_DIR=$TMPDIR/state
+  export HOME=$TMPDIR/home
+  mkdir $HOME
+
+  nix-store --init
+  expect $expectScriptPath
+  touch $out
+''
\ No newline at end of file
diff --git a/tests/unit/libexpr-support/.version b/tests/unit/libexpr-support/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libexpr-support/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libexpr-support/build-utils-meson b/tests/unit/libexpr-support/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libexpr-support/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libexpr-support/meson.build b/tests/unit/libexpr-support/meson.build
new file mode 100644
index 00000000000..7056722049e
--- /dev/null
+++ b/tests/unit/libexpr-support/meson.build
@@ -0,0 +1,74 @@
+project('nix-expr-test-support', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-util-test-support'),
+  dependency('nix-store'),
+  dependency('nix-store-test-support'),
+  dependency('nix-expr'),
+]
+subdir('build-utils-meson/subprojects')
+
+rapidcheck = dependency('rapidcheck')
+deps_public += rapidcheck
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-expr.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'tests/value/context.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = files(
+  'tests/libexpr.hh',
+  'tests/nix_api_expr.hh',
+  'tests/value/context.hh',
+)
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nix-expr-test-support',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: Remove `-lrapidcheck` when https://github.com/emil-e/rapidcheck/pull/326
+  #       is available. See also ../libutil/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/tests/unit/libexpr-support/package.nix b/tests/unit/libexpr-support/package.nix
new file mode 100644
index 00000000000..0c966c55af1
--- /dev/null
+++ b/tests/unit/libexpr-support/package.nix
@@ -0,0 +1,81 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-store-test-support
+, nix-expr
+
+, rapidcheck
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util-test-support";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-store-test-support
+    nix-expr
+    rapidcheck
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libexpr-support/tests/libexpr.hh b/tests/unit/libexpr-support/tests/libexpr.hh
index 1a431399082..eacbf0d5cac 100644
--- a/tests/unit/libexpr-support/tests/libexpr.hh
+++ b/tests/unit/libexpr-support/tests/libexpr.hh
@@ -19,14 +19,14 @@ namespace nix {
             static void SetUpTestSuite() {
                 LibStoreTest::SetUpTestSuite();
                 initGC();
-                evalSettings.nixPath = {};
             }
 
         protected:
             LibExprTest()
                 : LibStoreTest()
-                , state({}, store)
+                , state({}, store, evalSettings, nullptr)
             {
+                evalSettings.nixPath = {};
             }
             Value eval(std::string input, bool forceValue = true) {
                 Value v;
@@ -42,6 +42,8 @@ namespace nix {
                 return state.symbols.create(value);
             }
 
+            bool readOnlyMode = true;
+            EvalSettings evalSettings{readOnlyMode};
             EvalState state;
     };
 
diff --git a/tests/unit/libexpr-support/tests/nix_api_expr.hh b/tests/unit/libexpr-support/tests/nix_api_expr.hh
index d1840d03432..6ddca0d14d4 100644
--- a/tests/unit/libexpr-support/tests/nix_api_expr.hh
+++ b/tests/unit/libexpr-support/tests/nix_api_expr.hh
@@ -25,7 +25,7 @@ protected:
     }
 
     EvalState * state;
-    Value * value;
+    nix_value * value;
 };
 
 }
diff --git a/tests/unit/libexpr/.version b/tests/unit/libexpr/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libexpr/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libexpr/build-utils-meson b/tests/unit/libexpr/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libexpr/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libexpr/data/.gitkeep b/tests/unit/libexpr/data/.gitkeep
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/unit/libexpr/error_traces.cc b/tests/unit/libexpr/error_traces.cc
index 7b32b320bac..be379a90993 100644
--- a/tests/unit/libexpr/error_traces.cc
+++ b/tests/unit/libexpr/error_traces.cc
@@ -102,6 +102,74 @@ namespace nix {
             , type                                                          \
         )
 
+#define ASSERT_TRACE3(args, type, message, context1, context2)              \
+        ASSERT_THROW(                                                       \
+            std::string expr(args);                                         \
+            std::string name = expr.substr(0, expr.find(" "));              \
+            try {                                                           \
+                Value v = eval("builtins." args);                           \
+                state.forceValueDeep(v);                                    \
+            } catch (BaseError & e) {                                       \
+                ASSERT_EQ(PrintToString(e.info().msg),                      \
+                          PrintToString(message));                          \
+                ASSERT_EQ(e.info().traces.size(), 3) << "while testing " args << std::endl << e.what(); \
+                auto trace = e.info().traces.rbegin();                      \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(context1));                         \
+                ++trace;                                                    \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(context2));                         \
+                ++trace;                                                    \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(HintFmt("while calling the '%s' builtin", name))); \
+                throw;                                                      \
+            }                                                               \
+            , type                                                          \
+        )
+
+#define ASSERT_TRACE4(args, type, message, context1, context2, context3)    \
+        ASSERT_THROW(                                                       \
+            std::string expr(args);                                         \
+            std::string name = expr.substr(0, expr.find(" "));              \
+            try {                                                           \
+                Value v = eval("builtins." args);                           \
+                state.forceValueDeep(v);                                    \
+            } catch (BaseError & e) {                                       \
+                ASSERT_EQ(PrintToString(e.info().msg),                      \
+                          PrintToString(message));                          \
+                ASSERT_EQ(e.info().traces.size(), 4) << "while testing " args << std::endl << e.what(); \
+                auto trace = e.info().traces.rbegin();                      \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(context1));                         \
+                ++trace;                                                    \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(context2));                         \
+                ++trace;                                                    \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(context3));                         \
+                ++trace;                                                    \
+                ASSERT_EQ(PrintToString(trace->hint),                       \
+                          PrintToString(HintFmt("while calling the '%s' builtin", name))); \
+                throw;                                                      \
+            }                                                               \
+            , type                                                          \
+        )
+
+// We assume that expr starts with "builtins.derivationStrict { name =",
+// otherwise the name attribute position (1, 29) would be invalid.
+#define DERIVATION_TRACE_HINTFMT(name)                                      \
+        HintFmt("while evaluating derivation '%s'\n"                        \
+                "  whose name attribute is located at %s",                  \
+                name, Pos(1, 29, Pos::String{.source = make_ref<std::string>(expr)}))
+
+// To keep things simple, we also assume that derivation name is "foo".
+#define ASSERT_DERIVATION_TRACE1(args, type, message)                       \
+        ASSERT_TRACE2(args, type, message, DERIVATION_TRACE_HINTFMT("foo"))
+#define ASSERT_DERIVATION_TRACE2(args, type, message, context)              \
+        ASSERT_TRACE3(args, type, message, context, DERIVATION_TRACE_HINTFMT("foo"))
+#define ASSERT_DERIVATION_TRACE3(args, type, message, context1, context2)   \
+        ASSERT_TRACE4(args, type, message, context1, context2, DERIVATION_TRACE_HINTFMT("foo"))
+
     TEST_F(ErrorTraceTest, genericClosure) {
         ASSERT_TRACE2("genericClosure 1",
                       TypeError,
@@ -1185,7 +1253,6 @@ namespace nix {
     }
 
 
-    /* // Needs different ASSERTs
     TEST_F(ErrorTraceTest, derivationStrict) {
         ASSERT_TRACE2("derivationStrict \"\"",
                       TypeError,
@@ -1197,102 +1264,115 @@ namespace nix {
                       HintFmt("attribute '%s' missing", "name"),
                       HintFmt("in the attrset passed as argument to builtins.derivationStrict"));
 
-        ASSERT_TRACE2("derivationStrict { name = 1; }",
+        ASSERT_TRACE3("derivationStrict { name = 1; }",
                       TypeError,
-                      HintFmt("expected a string but found %s: %s", "an integer", "1"),
-                      HintFmt("while evaluating the `name` attribute passed to builtins.derivationStrict"));
+                      HintFmt("expected a string but found %s: %s", "an integer", Uncolored(ANSI_CYAN "1" ANSI_NORMAL)),
+                      HintFmt("while evaluating the `name` attribute passed to builtins.derivationStrict"),
+                      HintFmt("while evaluating the derivation attribute 'name'"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; }",
-                      TypeError,
-                      HintFmt("required attribute 'builder' missing"),
-                      HintFmt("while evaluating derivation 'foo'"));
+        ASSERT_DERIVATION_TRACE1("derivationStrict { name = \"foo\"; }",
+                      EvalError,
+                      HintFmt("required attribute 'builder' missing"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; __structuredAttrs = 15; }",
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; __structuredAttrs = 15; }",
                       TypeError,
-                      HintFmt("expected a Boolean but found %s: %s", "an integer", "15"),
+                      HintFmt("expected a Boolean but found %s: %s", "an integer", Uncolored(ANSI_CYAN "15" ANSI_NORMAL)),
                       HintFmt("while evaluating the `__structuredAttrs` attribute passed to builtins.derivationStrict"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; __ignoreNulls = 15; }",
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; __ignoreNulls = 15; }",
                       TypeError,
-                      HintFmt("expected a Boolean but found %s: %s", "an integer", "15"),
+                      HintFmt("expected a Boolean but found %s: %s", "an integer", Uncolored(ANSI_CYAN "15" ANSI_NORMAL)),
                       HintFmt("while evaluating the `__ignoreNulls` attribute passed to builtins.derivationStrict"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; outputHashMode = 15; }",
-                      TypeError,
-                      HintFmt("invalid value '15' for 'outputHashMode' attribute"),
-                      HintFmt("while evaluating the attribute 'outputHashMode' of derivation 'foo'"));
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; outputHashMode = 15; }",
+                      EvalError,
+                      HintFmt("invalid value '%s' for 'outputHashMode' attribute", "15"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputHashMode", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; outputHashMode = \"custom\"; }",
-                      TypeError,
-                      HintFmt("invalid value 'custom' for 'outputHashMode' attribute"),
-                      HintFmt("while evaluating the attribute 'outputHashMode' of derivation 'foo'"));
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; outputHashMode = \"custom\"; }",
+                      EvalError,
+                      HintFmt("invalid value '%s' for 'outputHashMode' attribute", "custom"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputHashMode", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = {}; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = {}; }",
                       TypeError,
-                      HintFmt("cannot coerce %s to a string: %s", "a set", "{ }"),
-                      HintFmt("while evaluating the attribute 'system' of derivation 'foo'"));
+                      HintFmt("cannot coerce %s to a string: { }", "a set"),
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "system", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = {}; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = {}; }",
                       TypeError,
-                      HintFmt("cannot coerce %s to a string: %s", "a set", "{ }"),
-                      HintFmt("while evaluating the attribute 'outputs' of derivation 'foo'"));
+                      HintFmt("cannot coerce %s to a string: { }", "a set"),
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputs", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"drv\"; }",
-                      TypeError,
-                      HintFmt("invalid derivation output name 'drv'"),
-                      HintFmt("while evaluating the attribute 'outputs' of derivation 'foo'"));
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"drvPath\"; }",
+                      EvalError,
+                      HintFmt("invalid derivation output name 'drvPath'"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputs", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = []; }",
-                      TypeError,
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; outputs = \"out\"; __structuredAttrs = true; }",
+                      EvalError,
+                      HintFmt("expected a list but found %s: %s", "a string", "\"out\""),
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputs", "foo"));
+
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = []; }",
+                      EvalError,
                       HintFmt("derivation cannot have an empty set of outputs"),
-                      HintFmt("while evaluating the attribute 'outputs' of derivation 'foo'"));
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputs", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = [ \"drv\" ]; }",
-                      TypeError,
-                      HintFmt("invalid derivation output name 'drv'"),
-                      HintFmt("while evaluating the attribute 'outputs' of derivation 'foo'"));
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = [ \"drvPath\" ]; }",
+                      EvalError,
+                      HintFmt("invalid derivation output name 'drvPath'"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputs", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = [ \"out\" \"out\" ]; }",
-                      TypeError,
-                      HintFmt("duplicate derivation output 'out'"),
-                      HintFmt("while evaluating the attribute 'outputs' of derivation 'foo'"));
+        ASSERT_DERIVATION_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = [ \"out\" \"out\" ]; }",
+                      EvalError,
+                      HintFmt("duplicate derivation output '%s'", "out"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "outputs", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; __contentAddressed = \"true\"; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; __contentAddressed = \"true\"; }",
                       TypeError,
                       HintFmt("expected a Boolean but found %s: %s", "a string", "\"true\""),
-                      HintFmt("while evaluating the attribute '__contentAddressed' of derivation 'foo'"));
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "__contentAddressed", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; __impure = \"true\"; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; __impure = \"true\"; }",
                       TypeError,
                       HintFmt("expected a Boolean but found %s: %s", "a string", "\"true\""),
-                      HintFmt("while evaluating the attribute '__impure' of derivation 'foo'"));
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "__impure", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; __impure = \"true\"; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; __impure = \"true\"; }",
                       TypeError,
                       HintFmt("expected a Boolean but found %s: %s", "a string", "\"true\""),
-                      HintFmt("while evaluating the attribute '__impure' of derivation 'foo'"));
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "__impure", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = \"foo\"; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = \"foo\"; }",
                       TypeError,
                       HintFmt("expected a list but found %s: %s", "a string", "\"foo\""),
-                      HintFmt("while evaluating the attribute 'args' of derivation 'foo'"));
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "args", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = [ {} ]; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = [ {} ]; }",
                       TypeError,
-                      HintFmt("cannot coerce %s to a string: %s", "a set", "{ }"),
-                      HintFmt("while evaluating an element of the argument list"));
+                      HintFmt("cannot coerce %s to a string: { }", "a set"),
+                      HintFmt("while evaluating an element of the argument list"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "args", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = [ \"a\" {} ]; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = [ \"a\" {} ]; }",
                       TypeError,
-                      HintFmt("cannot coerce %s to a string: %s", "a set", "{ }"),
-                      HintFmt("while evaluating an element of the argument list"));
+                      HintFmt("cannot coerce %s to a string: { }", "a set"),
+                      HintFmt("while evaluating an element of the argument list"),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "args", "foo"));
 
-        ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; FOO = {}; }",
+        ASSERT_DERIVATION_TRACE3("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; FOO = {}; }",
                       TypeError,
-                      HintFmt("cannot coerce %s to a string: %s", "a set", "{ }"),
-                      HintFmt("while evaluating the attribute 'FOO' of derivation 'foo'"));
-
+                      HintFmt("cannot coerce %s to a string: { }", "a set"),
+                      HintFmt(""),
+                      HintFmt("while evaluating attribute '%s' of derivation '%s'", "FOO", "foo"));
     }
-    */
 
 } /* namespace nix */
diff --git a/tests/unit/libexpr/local.mk b/tests/unit/libexpr/local.mk
index c59191db4d5..1617e282351 100644
--- a/tests/unit/libexpr/local.mk
+++ b/tests/unit/libexpr/local.mk
@@ -4,7 +4,7 @@ programs += libexpr-tests
 
 libexpr-tests_NAME := libnixexpr-tests
 
-libexpr-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+libexpr-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data GTEST_OUTPUT=xml:$$testresults/libexpr-tests.xml
 
 libexpr-tests_DIR := $(d)
 
@@ -38,3 +38,8 @@ libexpr-tests_LIBS = \
     libexpr libexprc libfetchers libstore libstorec libutil libutilc
 
 libexpr-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS) -lgmock
+
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  libexpr-tests_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif
diff --git a/tests/unit/libexpr/meson.build b/tests/unit/libexpr/meson.build
new file mode 100644
index 00000000000..ee35258cf27
--- /dev/null
+++ b/tests/unit/libexpr/meson.build
@@ -0,0 +1,90 @@
+project('nix-expr-tests', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-expr'),
+  dependency('nix-expr-c'),
+  dependency('nix-expr-test-support'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/export-all-symbols')
+
+rapidcheck = dependency('rapidcheck')
+deps_private += rapidcheck
+
+gtest = dependency('gtest')
+deps_private += gtest
+
+gtest = dependency('gmock')
+deps_private += gtest
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-expr.hh',
+  '-include', 'config-util.h',
+  '-include', 'config-store.h',
+  '-include', 'config-expr.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'derived-path.cc',
+  'error_traces.cc',
+  'eval.cc',
+  'json.cc',
+  'main.cc',
+  'nix_api_expr.cc',
+  'nix_api_external.cc',
+  'nix_api_value.cc',
+  'primops.cc',
+  'search-path.cc',
+  'trivial.cc',
+  'value/context.cc',
+  'value/print.cc',
+  'value/value.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: -lrapidcheck, see ../libutil-support/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  install : true,
+)
+
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)
diff --git a/tests/unit/libexpr/nix_api_expr.cc b/tests/unit/libexpr/nix_api_expr.cc
index 0818f1cabac..8b97d692345 100644
--- a/tests/unit/libexpr/nix_api_expr.cc
+++ b/tests/unit/libexpr/nix_api_expr.cc
@@ -39,12 +39,12 @@ TEST_F(nix_api_expr_test, nix_expr_eval_drv)
     ASSERT_EQ(NIX_TYPE_ATTRS, nix_get_type(nullptr, value));
 
     EvalState * stateFn = nix_state_create(nullptr, nullptr, store);
-    Value * valueFn = nix_alloc_value(nullptr, state);
+    nix_value * valueFn = nix_alloc_value(nullptr, state);
     nix_expr_eval_from_string(nullptr, stateFn, "builtins.toString", ".", valueFn);
     ASSERT_EQ(NIX_TYPE_FUNCTION, nix_get_type(nullptr, valueFn));
 
     EvalState * stateResult = nix_state_create(nullptr, nullptr, store);
-    Value * valueResult = nix_alloc_value(nullptr, stateResult);
+    nix_value * valueResult = nix_alloc_value(nullptr, stateResult);
     nix_value_call(ctx, stateResult, valueFn, value, valueResult);
     ASSERT_EQ(NIX_TYPE_STRING, nix_get_type(nullptr, valueResult));
 
@@ -70,7 +70,7 @@ TEST_F(nix_api_expr_test, nix_build_drv)
                               })";
     nix_expr_eval_from_string(nullptr, state, expr, ".", value);
 
-    Value * drvPathValue = nix_get_attr_byname(nullptr, value, state, "drvPath");
+    nix_value * drvPathValue = nix_get_attr_byname(nullptr, value, state, "drvPath");
     std::string drvPath;
     nix_get_string(nullptr, drvPathValue, OBSERVE_STRING(drvPath));
 
@@ -84,7 +84,7 @@ TEST_F(nix_api_expr_test, nix_build_drv)
     StorePath * drvStorePath = nix_store_parse_path(ctx, store, drvPath.c_str());
     ASSERT_EQ(true, nix_store_is_valid_path(ctx, store, drvStorePath));
 
-    Value * outPathValue = nix_get_attr_byname(ctx, value, state, "outPath");
+    nix_value * outPathValue = nix_get_attr_byname(ctx, value, state, "outPath");
     std::string outPath;
     nix_get_string(ctx, outPathValue, OBSERVE_STRING(outPath));
 
@@ -191,4 +191,214 @@ TEST_F(nix_api_expr_test, nix_expr_realise_context)
     nix_realised_string_free(r);
 }
 
+const char * SAMPLE_USER_DATA = "whatever";
+
+static void
+primop_square(void * user_data, nix_c_context * context, EvalState * state, nix_value ** args, nix_value * ret)
+{
+    assert(context);
+    assert(state);
+    assert(user_data == SAMPLE_USER_DATA);
+    auto i = nix_get_int(context, args[0]);
+    nix_init_int(context, ret, i * i);
+}
+
+TEST_F(nix_api_expr_test, nix_expr_primop)
+{
+    PrimOp * primop =
+        nix_alloc_primop(ctx, primop_square, 1, "square", nullptr, "square an integer", (void *) SAMPLE_USER_DATA);
+    assert_ctx_ok();
+    nix_value * primopValue = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_primop(ctx, primopValue, primop);
+    assert_ctx_ok();
+
+    nix_value * three = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_int(ctx, three, 3);
+    assert_ctx_ok();
+
+    nix_value * result = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_value_call(ctx, state, primopValue, three, result);
+    assert_ctx_ok();
+
+    auto r = nix_get_int(ctx, result);
+    ASSERT_EQ(9, r);
+}
+
+static void
+primop_repeat(void * user_data, nix_c_context * context, EvalState * state, nix_value ** args, nix_value * ret)
+{
+    assert(context);
+    assert(state);
+    assert(user_data == SAMPLE_USER_DATA);
+
+    // Get the string to repeat
+    std::string s;
+    if (nix_get_string(context, args[0], OBSERVE_STRING(s)) != NIX_OK)
+        return;
+
+    // Get the number of times to repeat
+    auto n = nix_get_int(context, args[1]);
+    if (nix_err_code(context) != NIX_OK)
+        return;
+
+    // Repeat the string
+    std::string result;
+    for (int i = 0; i < n; ++i)
+        result += s;
+
+    nix_init_string(context, ret, result.c_str());
+}
+
+TEST_F(nix_api_expr_test, nix_expr_primop_arity_2_multiple_calls)
+{
+    PrimOp * primop =
+        nix_alloc_primop(ctx, primop_repeat, 2, "repeat", nullptr, "repeat a string", (void *) SAMPLE_USER_DATA);
+    assert_ctx_ok();
+    nix_value * primopValue = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_primop(ctx, primopValue, primop);
+    assert_ctx_ok();
+
+    nix_value * hello = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_string(ctx, hello, "hello");
+    assert_ctx_ok();
+
+    nix_value * three = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_int(ctx, three, 3);
+    assert_ctx_ok();
+
+    nix_value * partial = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_value_call(ctx, state, primopValue, hello, partial);
+    assert_ctx_ok();
+
+    nix_value * result = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_value_call(ctx, state, partial, three, result);
+    assert_ctx_ok();
+
+    std::string r;
+    nix_get_string(ctx, result, OBSERVE_STRING(r));
+    ASSERT_STREQ("hellohellohello", r.c_str());
+}
+
+TEST_F(nix_api_expr_test, nix_expr_primop_arity_2_single_call)
+{
+    PrimOp * primop =
+        nix_alloc_primop(ctx, primop_repeat, 2, "repeat", nullptr, "repeat a string", (void *) SAMPLE_USER_DATA);
+    assert_ctx_ok();
+    nix_value * primopValue = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_primop(ctx, primopValue, primop);
+    assert_ctx_ok();
+
+    nix_value * hello = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_string(ctx, hello, "hello");
+    assert_ctx_ok();
+
+    nix_value * three = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_int(ctx, three, 3);
+    assert_ctx_ok();
+
+    nix_value * result = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    NIX_VALUE_CALL(ctx, state, result, primopValue, hello, three);
+    assert_ctx_ok();
+
+    std::string r;
+    nix_get_string(ctx, result, OBSERVE_STRING(r));
+    assert_ctx_ok();
+
+    ASSERT_STREQ("hellohellohello", r.c_str());
+}
+
+static void
+primop_bad_no_return(void * user_data, nix_c_context * context, EvalState * state, nix_value ** args, nix_value * ret)
+{
+}
+
+TEST_F(nix_api_expr_test, nix_expr_primop_bad_no_return)
+{
+    PrimOp * primop =
+        nix_alloc_primop(ctx, primop_bad_no_return, 1, "badNoReturn", nullptr, "a broken primop", nullptr);
+    assert_ctx_ok();
+    nix_value * primopValue = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_primop(ctx, primopValue, primop);
+    assert_ctx_ok();
+
+    nix_value * three = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_int(ctx, three, 3);
+    assert_ctx_ok();
+
+    nix_value * result = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_value_call(ctx, state, primopValue, three, result);
+    ASSERT_EQ(ctx->last_err_code, NIX_ERR_NIX_ERROR);
+    ASSERT_THAT(
+        ctx->last_err,
+        testing::Optional(
+            testing::HasSubstr("Implementation error in custom function: return value was not initialized")));
+    ASSERT_THAT(ctx->last_err, testing::Optional(testing::HasSubstr("badNoReturn")));
+}
+
+static void primop_bad_return_thunk(
+    void * user_data, nix_c_context * context, EvalState * state, nix_value ** args, nix_value * ret)
+{
+    nix_init_apply(context, ret, args[0], args[1]);
+}
+TEST_F(nix_api_expr_test, nix_expr_primop_bad_return_thunk)
+{
+    PrimOp * primop =
+        nix_alloc_primop(ctx, primop_bad_return_thunk, 2, "badReturnThunk", nullptr, "a broken primop", nullptr);
+    assert_ctx_ok();
+    nix_value * primopValue = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_primop(ctx, primopValue, primop);
+    assert_ctx_ok();
+
+    nix_value * toString = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_expr_eval_from_string(ctx, state, "builtins.toString", ".", toString);
+    assert_ctx_ok();
+
+    nix_value * four = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    nix_init_int(ctx, four, 4);
+    assert_ctx_ok();
+
+    nix_value * result = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    NIX_VALUE_CALL(ctx, state, result, primopValue, toString, four);
+
+    ASSERT_EQ(ctx->last_err_code, NIX_ERR_NIX_ERROR);
+    ASSERT_THAT(
+        ctx->last_err,
+        testing::Optional(
+            testing::HasSubstr("Implementation error in custom function: return value must not be a thunk")));
+    ASSERT_THAT(ctx->last_err, testing::Optional(testing::HasSubstr("badReturnThunk")));
+}
+
+TEST_F(nix_api_expr_test, nix_value_call_multi_no_args)
+{
+    nix_value * n = nix_alloc_value(ctx, state);
+    nix_init_int(ctx, n, 3);
+    assert_ctx_ok();
+
+    nix_value * r = nix_alloc_value(ctx, state);
+    nix_value_call_multi(ctx, state, n, 0, nullptr, r);
+    assert_ctx_ok();
+
+    auto rInt = nix_get_int(ctx, r);
+    assert_ctx_ok();
+    ASSERT_EQ(3, rInt);
+}
 } // namespace nixC
diff --git a/tests/unit/libexpr/nix_api_external.cc b/tests/unit/libexpr/nix_api_external.cc
index 2391f831766..81ff285a4ab 100644
--- a/tests/unit/libexpr/nix_api_external.cc
+++ b/tests/unit/libexpr/nix_api_external.cc
@@ -49,10 +49,10 @@ TEST_F(nix_api_expr_test, nix_expr_eval_external)
     nix_init_external(ctx, value, val);
 
     EvalState * stateResult = nix_state_create(nullptr, nullptr, store);
-    Value * valueResult = nix_alloc_value(nullptr, stateResult);
+    nix_value * valueResult = nix_alloc_value(nullptr, stateResult);
 
     EvalState * stateFn = nix_state_create(nullptr, nullptr, store);
-    Value * valueFn = nix_alloc_value(nullptr, stateFn);
+    nix_value * valueFn = nix_alloc_value(nullptr, stateFn);
 
     nix_expr_eval_from_string(nullptr, state, "builtins.typeOf", ".", valueFn);
 
diff --git a/tests/unit/libexpr/nix_api_value.cc b/tests/unit/libexpr/nix_api_value.cc
index 7fbb2bbdca0..7fc8b4f641f 100644
--- a/tests/unit/libexpr/nix_api_value.cc
+++ b/tests/unit/libexpr/nix_api_value.cc
@@ -4,20 +4,36 @@
 #include "nix_api_util_internal.h"
 #include "nix_api_expr.h"
 #include "nix_api_value.h"
+#include "nix_api_expr_internal.h"
 
 #include "tests/nix_api_expr.hh"
 #include "tests/string_callback.hh"
 
+#include "gmock/gmock.h"
+#include <cstddef>
 #include <cstdlib>
 #include <gtest/gtest.h>
 
 namespace nixC {
 
-TEST_F(nix_api_expr_test, nix_value_set_get_int)
+TEST_F(nix_api_expr_test, as_nix_value_ptr)
+{
+    // nix_alloc_value casts nix::Value to nix_value
+    // It should be obvious from the decl that that works, but if it doesn't,
+    // the whole implementation would be utterly broken.
+    ASSERT_EQ(sizeof(nix::Value), sizeof(nix_value));
+}
+
+TEST_F(nix_api_expr_test, nix_value_get_int_invalid)
 {
     ASSERT_EQ(0, nix_get_int(ctx, nullptr));
-    ASSERT_DEATH(nix_get_int(ctx, value), "");
+    assert_ctx_err();
+    ASSERT_EQ(0, nix_get_int(ctx, value));
+    assert_ctx_err();
+}
 
+TEST_F(nix_api_expr_test, nix_value_set_get_int)
+{
     int myInt = 1;
     nix_init_int(ctx, value, myInt);
 
@@ -26,24 +42,34 @@ TEST_F(nix_api_expr_test, nix_value_set_get_int)
     ASSERT_EQ(NIX_TYPE_INT, nix_get_type(ctx, value));
 }
 
-TEST_F(nix_api_expr_test, nix_value_set_get_float)
+TEST_F(nix_api_expr_test, nix_value_set_get_float_invalid)
 {
-    ASSERT_FLOAT_EQ(0.0, nix_get_float(ctx, nullptr));
-    ASSERT_DEATH(nix_get_float(ctx, value), "");
+    ASSERT_DOUBLE_EQ(0.0, nix_get_float(ctx, nullptr));
+    assert_ctx_err();
+    ASSERT_DOUBLE_EQ(0.0, nix_get_float(ctx, value));
+    assert_ctx_err();
+}
 
-    float myDouble = 1.0;
+TEST_F(nix_api_expr_test, nix_value_set_get_float)
+{
+    double myDouble = 1.0;
     nix_init_float(ctx, value, myDouble);
 
-    ASSERT_FLOAT_EQ(myDouble, nix_get_float(ctx, value));
+    ASSERT_DOUBLE_EQ(myDouble, nix_get_float(ctx, value));
     ASSERT_STREQ("a float", nix_get_typename(ctx, value));
     ASSERT_EQ(NIX_TYPE_FLOAT, nix_get_type(ctx, value));
 }
 
-TEST_F(nix_api_expr_test, nix_value_set_get_bool)
+TEST_F(nix_api_expr_test, nix_value_set_get_bool_invalid)
 {
     ASSERT_EQ(false, nix_get_bool(ctx, nullptr));
-    ASSERT_DEATH(nix_get_bool(ctx, value), "");
+    assert_ctx_err();
+    ASSERT_EQ(false, nix_get_bool(ctx, value));
+    assert_ctx_err();
+}
 
+TEST_F(nix_api_expr_test, nix_value_set_get_bool)
+{
     bool myBool = true;
     nix_init_bool(ctx, value, myBool);
 
@@ -52,12 +78,18 @@ TEST_F(nix_api_expr_test, nix_value_set_get_bool)
     ASSERT_EQ(NIX_TYPE_BOOL, nix_get_type(ctx, value));
 }
 
-TEST_F(nix_api_expr_test, nix_value_set_get_string)
+TEST_F(nix_api_expr_test, nix_value_set_get_string_invalid)
 {
     std::string string_value;
     ASSERT_EQ(NIX_ERR_UNKNOWN, nix_get_string(ctx, nullptr, OBSERVE_STRING(string_value)));
-    ASSERT_DEATH(nix_get_string(ctx, value, OBSERVE_STRING(string_value)), "");
+    assert_ctx_err();
+    ASSERT_EQ(NIX_ERR_UNKNOWN, nix_get_string(ctx, value, OBSERVE_STRING(string_value)));
+    assert_ctx_err();
+}
 
+TEST_F(nix_api_expr_test, nix_value_set_get_string)
+{
+    std::string string_value;
     const char * myString = "some string";
     nix_init_string(ctx, value, myString);
 
@@ -67,21 +99,29 @@ TEST_F(nix_api_expr_test, nix_value_set_get_string)
     ASSERT_EQ(NIX_TYPE_STRING, nix_get_type(ctx, value));
 }
 
-TEST_F(nix_api_expr_test, nix_value_set_get_null)
+TEST_F(nix_api_expr_test, nix_value_set_get_null_invalid)
 {
-    ASSERT_DEATH(nix_get_typename(ctx, value), "");
+    ASSERT_EQ(NULL, nix_get_typename(ctx, value));
+    assert_ctx_err();
+}
 
+TEST_F(nix_api_expr_test, nix_value_set_get_null)
+{
     nix_init_null(ctx, value);
 
     ASSERT_STREQ("null", nix_get_typename(ctx, value));
     ASSERT_EQ(NIX_TYPE_NULL, nix_get_type(ctx, value));
 }
 
-TEST_F(nix_api_expr_test, nix_value_set_get_path)
+TEST_F(nix_api_expr_test, nix_value_set_get_path_invalid)
 {
     ASSERT_EQ(nullptr, nix_get_path_string(ctx, nullptr));
-    ASSERT_DEATH(nix_get_path_string(ctx, value), "");
-
+    assert_ctx_err();
+    ASSERT_EQ(nullptr, nix_get_path_string(ctx, value));
+    assert_ctx_err();
+}
+TEST_F(nix_api_expr_test, nix_value_set_get_path)
+{
     const char * p = "/nix/store/40s0qmrfb45vlh6610rk29ym318dswdr-myname";
     nix_init_path_string(ctx, state, value, p);
 
@@ -90,25 +130,39 @@ TEST_F(nix_api_expr_test, nix_value_set_get_path)
     ASSERT_EQ(NIX_TYPE_PATH, nix_get_type(ctx, value));
 }
 
-TEST_F(nix_api_expr_test, nix_build_and_init_list)
+TEST_F(nix_api_expr_test, nix_build_and_init_list_invalid)
 {
     ASSERT_EQ(nullptr, nix_get_list_byidx(ctx, nullptr, state, 0));
+    assert_ctx_err();
     ASSERT_EQ(0, nix_get_list_size(ctx, nullptr));
+    assert_ctx_err();
 
-    ASSERT_DEATH(nix_get_list_byidx(ctx, value, state, 0), "");
-    ASSERT_DEATH(nix_get_list_size(ctx, value), "");
+    ASSERT_EQ(nullptr, nix_get_list_byidx(ctx, value, state, 0));
+    assert_ctx_err();
+    ASSERT_EQ(0, nix_get_list_size(ctx, value));
+    assert_ctx_err();
+}
 
+TEST_F(nix_api_expr_test, nix_build_and_init_list)
+{
     int size = 10;
     ListBuilder * builder = nix_make_list_builder(ctx, state, size);
 
-    Value * intValue = nix_alloc_value(ctx, state);
+    nix_value * intValue = nix_alloc_value(ctx, state);
+    nix_value * intValue2 = nix_alloc_value(ctx, state);
+
+    // `init` and `insert` can be called in any order
     nix_init_int(ctx, intValue, 42);
     nix_list_builder_insert(ctx, builder, 0, intValue);
+    nix_list_builder_insert(ctx, builder, 1, intValue2);
+    nix_init_int(ctx, intValue2, 43);
+
     nix_make_list(ctx, builder, value);
     nix_list_builder_free(builder);
 
     ASSERT_EQ(42, nix_get_int(ctx, nix_get_list_byidx(ctx, value, state, 0)));
-    ASSERT_EQ(nullptr, nix_get_list_byidx(ctx, value, state, 1));
+    ASSERT_EQ(43, nix_get_int(ctx, nix_get_list_byidx(ctx, value, state, 1)));
+    ASSERT_EQ(nullptr, nix_get_list_byidx(ctx, value, state, 2));
     ASSERT_EQ(10, nix_get_list_size(ctx, value));
 
     ASSERT_STREQ("a list", nix_get_typename(ctx, value));
@@ -118,29 +172,42 @@ TEST_F(nix_api_expr_test, nix_build_and_init_list)
     nix_gc_decref(ctx, intValue);
 }
 
-TEST_F(nix_api_expr_test, nix_build_and_init_attr)
+TEST_F(nix_api_expr_test, nix_build_and_init_attr_invalid)
 {
     ASSERT_EQ(nullptr, nix_get_attr_byname(ctx, nullptr, state, 0));
+    assert_ctx_err();
     ASSERT_EQ(nullptr, nix_get_attr_byidx(ctx, nullptr, state, 0, nullptr));
+    assert_ctx_err();
     ASSERT_EQ(nullptr, nix_get_attr_name_byidx(ctx, nullptr, state, 0));
+    assert_ctx_err();
     ASSERT_EQ(0, nix_get_attrs_size(ctx, nullptr));
+    assert_ctx_err();
     ASSERT_EQ(false, nix_has_attr_byname(ctx, nullptr, state, "no-value"));
+    assert_ctx_err();
+
+    ASSERT_EQ(nullptr, nix_get_attr_byname(ctx, value, state, 0));
+    assert_ctx_err();
+    ASSERT_EQ(nullptr, nix_get_attr_byidx(ctx, value, state, 0, nullptr));
+    assert_ctx_err();
+    ASSERT_EQ(nullptr, nix_get_attr_name_byidx(ctx, value, state, 0));
+    assert_ctx_err();
+    ASSERT_EQ(0, nix_get_attrs_size(ctx, value));
+    assert_ctx_err();
+    ASSERT_EQ(false, nix_has_attr_byname(ctx, value, state, "no-value"));
+    assert_ctx_err();
+}
 
-    ASSERT_DEATH(nix_get_attr_byname(ctx, value, state, 0), "");
-    ASSERT_DEATH(nix_get_attr_byidx(ctx, value, state, 0, nullptr), "");
-    ASSERT_DEATH(nix_get_attr_name_byidx(ctx, value, state, 0), "");
-    ASSERT_DEATH(nix_get_attrs_size(ctx, value), "");
-    ASSERT_DEATH(nix_has_attr_byname(ctx, value, state, "no-value"), "");
-
+TEST_F(nix_api_expr_test, nix_build_and_init_attr)
+{
     int size = 10;
     const char ** out_name = (const char **) malloc(sizeof(char *));
 
     BindingsBuilder * builder = nix_make_bindings_builder(ctx, state, size);
 
-    Value * intValue = nix_alloc_value(ctx, state);
+    nix_value * intValue = nix_alloc_value(ctx, state);
     nix_init_int(ctx, intValue, 42);
 
-    Value * stringValue = nix_alloc_value(ctx, state);
+    nix_value * stringValue = nix_alloc_value(ctx, state);
     nix_init_string(ctx, stringValue, "foo");
 
     nix_bindings_builder_insert(ctx, builder, "a", intValue);
@@ -150,7 +217,7 @@ TEST_F(nix_api_expr_test, nix_build_and_init_attr)
 
     ASSERT_EQ(2, nix_get_attrs_size(ctx, value));
 
-    Value * out_value = nix_get_attr_byname(ctx, value, state, "a");
+    nix_value * out_value = nix_get_attr_byname(ctx, value, state, "a");
     ASSERT_EQ(42, nix_get_int(ctx, out_value));
     nix_gc_decref(ctx, out_value);
 
@@ -187,4 +254,149 @@ TEST_F(nix_api_expr_test, nix_build_and_init_attr)
     free(out_name);
 }
 
+TEST_F(nix_api_expr_test, nix_value_init)
+{
+    // Setup
+
+    // two = 2;
+    // f = a: a * a;
+
+    nix_value * two = nix_alloc_value(ctx, state);
+    nix_init_int(ctx, two, 2);
+
+    nix_value * f = nix_alloc_value(ctx, state);
+    nix_expr_eval_from_string(
+        ctx,
+        state,
+        R"(
+        a: a * a
+    )",
+        "<test>",
+        f);
+
+    // Test
+
+    // r = f two;
+
+    nix_value * r = nix_alloc_value(ctx, state);
+    nix_init_apply(ctx, r, f, two);
+    assert_ctx_ok();
+
+    ValueType t = nix_get_type(ctx, r);
+    assert_ctx_ok();
+
+    ASSERT_EQ(t, NIX_TYPE_THUNK);
+
+    nix_value_force(ctx, state, r);
+
+    t = nix_get_type(ctx, r);
+    assert_ctx_ok();
+
+    ASSERT_EQ(t, NIX_TYPE_INT);
+
+    int n = nix_get_int(ctx, r);
+    assert_ctx_ok();
+
+    ASSERT_EQ(n, 4);
+
+    // Clean up
+    nix_gc_decref(ctx, two);
+    nix_gc_decref(ctx, f);
+    nix_gc_decref(ctx, r);
+}
+
+TEST_F(nix_api_expr_test, nix_value_init_apply_error)
+{
+    nix_value * some_string = nix_alloc_value(ctx, state);
+    nix_init_string(ctx, some_string, "some string");
+    assert_ctx_ok();
+
+    nix_value * v = nix_alloc_value(ctx, state);
+    nix_init_apply(ctx, v, some_string, some_string);
+    assert_ctx_ok();
+
+    // All ok. Call has not been evaluated yet.
+
+    // Evaluate it
+    nix_value_force(ctx, state, v);
+    ASSERT_EQ(ctx->last_err_code, NIX_ERR_NIX_ERROR);
+    ASSERT_THAT(ctx->last_err.value(), testing::HasSubstr("attempt to call something which is not a function but"));
+
+    // Clean up
+    nix_gc_decref(ctx, some_string);
+    nix_gc_decref(ctx, v);
+}
+
+TEST_F(nix_api_expr_test, nix_value_init_apply_lazy_arg)
+{
+    // f is a lazy function: it does not evaluate its argument before returning its return value
+    // g is a helper to produce e
+    // e is a thunk that throws an exception
+    //
+    // r = f e
+    // r should not throw an exception, because e is not evaluated
+
+    nix_value * f = nix_alloc_value(ctx, state);
+    nix_expr_eval_from_string(
+        ctx,
+        state,
+        R"(
+        a: { foo = a; }
+    )",
+        "<test>",
+        f);
+    assert_ctx_ok();
+
+    nix_value * e = nix_alloc_value(ctx, state);
+    {
+        nix_value * g = nix_alloc_value(ctx, state);
+        nix_expr_eval_from_string(
+            ctx,
+            state,
+            R"(
+            _ignore: throw "error message for test case nix_value_init_apply_lazy_arg"
+        )",
+            "<test>",
+            g);
+        assert_ctx_ok();
+
+        nix_init_apply(ctx, e, g, g);
+        assert_ctx_ok();
+        nix_gc_decref(ctx, g);
+    }
+
+    nix_value * r = nix_alloc_value(ctx, state);
+    nix_init_apply(ctx, r, f, e);
+    assert_ctx_ok();
+
+    nix_value_force(ctx, state, r);
+    assert_ctx_ok();
+
+    auto n = nix_get_attrs_size(ctx, r);
+    assert_ctx_ok();
+    ASSERT_EQ(1, n);
+
+    // nix_get_attr_byname isn't lazy (it could have been) so it will throw the exception
+    nix_value * foo = nix_get_attr_byname(ctx, r, state, "foo");
+    ASSERT_EQ(nullptr, foo);
+    ASSERT_THAT(ctx->last_err.value(), testing::HasSubstr("error message for test case nix_value_init_apply_lazy_arg"));
+
+    // Clean up
+    nix_gc_decref(ctx, f);
+    nix_gc_decref(ctx, e);
+}
+
+TEST_F(nix_api_expr_test, nix_copy_value)
+{
+    nix_value * source = nix_alloc_value(ctx, state);
+
+    nix_init_int(ctx, source, 42);
+    nix_copy_value(ctx, value, source);
+
+    ASSERT_EQ(42, nix_get_int(ctx, value));
+
+    // Clean up
+    nix_gc_decref(ctx, source);
+}
+
 }
diff --git a/tests/unit/libexpr/package.nix b/tests/unit/libexpr/package.nix
new file mode 100644
index 00000000000..6b7e12c4a0d
--- /dev/null
+++ b/tests/unit/libexpr/package.nix
@@ -0,0 +1,99 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-expr
+, nix-expr-c
+, nix-expr-test-support
+
+, rapidcheck
+, gtest
+, runCommand
+
+# Configuration Options
+
+, version
+, resolvePath
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-expr-tests";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    nix-expr
+    nix-expr-c
+    nix-expr-test-support
+    rapidcheck
+    gtest
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  passthru = {
+    tests = {
+      run = runCommand "${finalAttrs.pname}-run" {
+      } ''
+        PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
+        export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
+        nix-expr-tests
+        touch $out
+      '';
+    };
+  };
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libexpr/primops.cc b/tests/unit/libexpr/primops.cc
index 5ddc031f73a..5b589823798 100644
--- a/tests/unit/libexpr/primops.cc
+++ b/tests/unit/libexpr/primops.cc
@@ -2,7 +2,7 @@
 #include <gtest/gtest.h>
 
 #include "eval-settings.hh"
-#include "memory-input-accessor.hh"
+#include "memory-source-accessor.hh"
 
 #include "tests/libexpr.hh"
 
diff --git a/tests/unit/libexpr/search-path.cc b/tests/unit/libexpr/search-path.cc
index dbe7ab95fb5..0806793557d 100644
--- a/tests/unit/libexpr/search-path.cc
+++ b/tests/unit/libexpr/search-path.cc
@@ -5,85 +5,85 @@
 
 namespace nix {
 
-TEST(SearchPathElem, parse_justPath) {
+TEST(LookupPathElem, parse_justPath) {
     ASSERT_EQ(
-        SearchPath::Elem::parse("foo"),
-        (SearchPath::Elem {
-            .prefix = SearchPath::Prefix { .s = "" },
-            .path = SearchPath::Path { .s = "foo" },
+        LookupPath::Elem::parse("foo"),
+        (LookupPath::Elem {
+            .prefix = LookupPath::Prefix { .s = "" },
+            .path = LookupPath::Path { .s = "foo" },
         }));
 }
 
-TEST(SearchPathElem, parse_emptyPrefix) {
+TEST(LookupPathElem, parse_emptyPrefix) {
     ASSERT_EQ(
-        SearchPath::Elem::parse("=foo"),
-        (SearchPath::Elem {
-            .prefix = SearchPath::Prefix { .s = "" },
-            .path = SearchPath::Path { .s = "foo" },
+        LookupPath::Elem::parse("=foo"),
+        (LookupPath::Elem {
+            .prefix = LookupPath::Prefix { .s = "" },
+            .path = LookupPath::Path { .s = "foo" },
         }));
 }
 
-TEST(SearchPathElem, parse_oneEq) {
+TEST(LookupPathElem, parse_oneEq) {
     ASSERT_EQ(
-        SearchPath::Elem::parse("foo=bar"),
-        (SearchPath::Elem {
-            .prefix = SearchPath::Prefix { .s = "foo" },
-            .path = SearchPath::Path { .s = "bar" },
+        LookupPath::Elem::parse("foo=bar"),
+        (LookupPath::Elem {
+            .prefix = LookupPath::Prefix { .s = "foo" },
+            .path = LookupPath::Path { .s = "bar" },
         }));
 }
 
-TEST(SearchPathElem, parse_twoEqs) {
+TEST(LookupPathElem, parse_twoEqs) {
     ASSERT_EQ(
-        SearchPath::Elem::parse("foo=bar=baz"),
-        (SearchPath::Elem {
-            .prefix = SearchPath::Prefix { .s = "foo" },
-            .path = SearchPath::Path { .s = "bar=baz" },
+        LookupPath::Elem::parse("foo=bar=baz"),
+        (LookupPath::Elem {
+            .prefix = LookupPath::Prefix { .s = "foo" },
+            .path = LookupPath::Path { .s = "bar=baz" },
         }));
 }
 
 
-TEST(SearchPathElem, suffixIfPotentialMatch_justPath) {
-    SearchPath::Prefix prefix { .s = "" };
+TEST(LookupPathElem, suffixIfPotentialMatch_justPath) {
+    LookupPath::Prefix prefix { .s = "" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("any/thing"), std::optional { "any/thing" });
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_misleadingPrefix1) {
-    SearchPath::Prefix prefix { .s = "foo" };
+TEST(LookupPathElem, suffixIfPotentialMatch_misleadingPrefix1) {
+    LookupPath::Prefix prefix { .s = "foo" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("fooX"), std::nullopt);
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_misleadingPrefix2) {
-    SearchPath::Prefix prefix { .s = "foo" };
+TEST(LookupPathElem, suffixIfPotentialMatch_misleadingPrefix2) {
+    LookupPath::Prefix prefix { .s = "foo" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("fooX/bar"), std::nullopt);
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_partialPrefix) {
-    SearchPath::Prefix prefix { .s = "fooX" };
+TEST(LookupPathElem, suffixIfPotentialMatch_partialPrefix) {
+    LookupPath::Prefix prefix { .s = "fooX" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("foo"), std::nullopt);
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_exactPrefix) {
-    SearchPath::Prefix prefix { .s = "foo" };
+TEST(LookupPathElem, suffixIfPotentialMatch_exactPrefix) {
+    LookupPath::Prefix prefix { .s = "foo" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("foo"), std::optional { "" });
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_multiKey) {
-    SearchPath::Prefix prefix { .s = "foo/bar" };
+TEST(LookupPathElem, suffixIfPotentialMatch_multiKey) {
+    LookupPath::Prefix prefix { .s = "foo/bar" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("foo/bar/baz"), std::optional { "baz" });
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_trailingSlash) {
-    SearchPath::Prefix prefix { .s = "foo" };
+TEST(LookupPathElem, suffixIfPotentialMatch_trailingSlash) {
+    LookupPath::Prefix prefix { .s = "foo" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("foo/"), std::optional { "" });
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_trailingDoubleSlash) {
-    SearchPath::Prefix prefix { .s = "foo" };
+TEST(LookupPathElem, suffixIfPotentialMatch_trailingDoubleSlash) {
+    LookupPath::Prefix prefix { .s = "foo" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("foo//"), std::optional { "/" });
 }
 
-TEST(SearchPathElem, suffixIfPotentialMatch_trailingPath) {
-    SearchPath::Prefix prefix { .s = "foo" };
+TEST(LookupPathElem, suffixIfPotentialMatch_trailingPath) {
+    LookupPath::Prefix prefix { .s = "foo" };
     ASSERT_EQ(prefix.suffixIfPotentialMatch("foo/bar/baz"), std::optional { "bar/baz" });
 }
 
diff --git a/tests/unit/libexpr/value/value.cc b/tests/unit/libexpr/value/value.cc
new file mode 100644
index 00000000000..5762d5891f8
--- /dev/null
+++ b/tests/unit/libexpr/value/value.cc
@@ -0,0 +1,25 @@
+#include "value.hh"
+
+#include "tests/libstore.hh"
+
+namespace nix {
+
+class ValueTest : public LibStoreTest
+{};
+
+TEST_F(ValueTest, unsetValue)
+{
+    Value unsetValue;
+    ASSERT_EQ(false, unsetValue.isValid());
+    ASSERT_EQ(nThunk, unsetValue.type(true));
+    ASSERT_DEATH(unsetValue.type(), "");
+}
+
+TEST_F(ValueTest, vInt)
+{
+    Value vInt;
+    vInt.mkInt(42);
+    ASSERT_EQ(true, vInt.isValid());
+}
+
+} // namespace nix
diff --git a/tests/unit/libfetchers/.version b/tests/unit/libfetchers/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libfetchers/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libfetchers/build-utils-meson b/tests/unit/libfetchers/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libfetchers/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libfetchers/data/public-key/defaultType.json b/tests/unit/libfetchers/data/public-key/defaultType.json
new file mode 100644
index 00000000000..43f02a420d5
--- /dev/null
+++ b/tests/unit/libfetchers/data/public-key/defaultType.json
@@ -0,0 +1,4 @@
+{
+  "key": "ABCDE",
+  "type": "ssh-ed25519"
+}
diff --git a/tests/unit/libfetchers/data/public-key/noRoundTrip.json b/tests/unit/libfetchers/data/public-key/noRoundTrip.json
new file mode 100644
index 00000000000..4dcbf914842
--- /dev/null
+++ b/tests/unit/libfetchers/data/public-key/noRoundTrip.json
@@ -0,0 +1,3 @@
+{
+  "key": "ABCDE"
+}
diff --git a/tests/unit/libfetchers/data/public-key/simple.json b/tests/unit/libfetchers/data/public-key/simple.json
new file mode 100644
index 00000000000..f83b927ac57
--- /dev/null
+++ b/tests/unit/libfetchers/data/public-key/simple.json
@@ -0,0 +1,4 @@
+{
+  "key": "ABCDE",
+  "type": "ssh-rsa"
+}
diff --git a/tests/unit/libfetchers/local.mk b/tests/unit/libfetchers/local.mk
index e9f659fd72e..286a590304a 100644
--- a/tests/unit/libfetchers/local.mk
+++ b/tests/unit/libfetchers/local.mk
@@ -4,7 +4,7 @@ programs += libfetchers-tests
 
 libfetchers-tests_NAME = libnixfetchers-tests
 
-libfetchers-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+libfetchers-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data GTEST_OUTPUT=xml:$$testresults/libfetchers-tests.xml
 
 libfetchers-tests_DIR := $(d)
 
@@ -30,3 +30,8 @@ libfetchers-tests_LIBS = \
     libfetchers libstore libutil
 
 libfetchers-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
+
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  libfetchers-tests_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif
diff --git a/tests/unit/libfetchers/meson.build b/tests/unit/libfetchers/meson.build
new file mode 100644
index 00000000000..d2de9382933
--- /dev/null
+++ b/tests/unit/libfetchers/meson.build
@@ -0,0 +1,71 @@
+project('nix-fetchers-tests', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-store-test-support'),
+  dependency('nix-fetchers'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/export-all-symbols')
+
+rapidcheck = dependency('rapidcheck')
+deps_private += rapidcheck
+
+gtest = dependency('gtest', main : true)
+deps_private += gtest
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  # '-include', 'config-fetchers.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'public-key.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: -lrapidcheck, see ../libutil-support/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  # get main from gtest
+  install : true,
+)
+
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)
diff --git a/tests/unit/libfetchers/package.nix b/tests/unit/libfetchers/package.nix
new file mode 100644
index 00000000000..9522f9639eb
--- /dev/null
+++ b/tests/unit/libfetchers/package.nix
@@ -0,0 +1,97 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-fetchers
+, nix-store-test-support
+
+, rapidcheck
+, gtest
+, runCommand
+
+# Configuration Options
+
+, version
+, resolvePath
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-fetchers-tests";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    nix-fetchers
+    nix-store-test-support
+    rapidcheck
+    gtest
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  passthru = {
+    tests = {
+      run = runCommand "${finalAttrs.pname}-run" {
+      } ''
+        PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
+        export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
+        nix-fetchers-tests
+        touch $out
+      '';
+    };
+  };
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libfetchers/public-key.cc b/tests/unit/libfetchers/public-key.cc
index fcd5c3af0bd..8a639da9f6a 100644
--- a/tests/unit/libfetchers/public-key.cc
+++ b/tests/unit/libfetchers/public-key.cc
@@ -1,18 +1,54 @@
 #include <gtest/gtest.h>
 #include "fetchers.hh"
 #include "json-utils.hh"
+#include <nlohmann/json.hpp>
+#include "tests/characterization.hh"
 
 namespace nix {
-    TEST(PublicKey, jsonSerialization) {
-        auto json = nlohmann::json(fetchers::PublicKey { .key = "ABCDE" });
 
-        ASSERT_EQ(json, R"({ "key": "ABCDE", "type": "ssh-ed25519" })"_json);
+using nlohmann::json;
+
+class PublicKeyTest : public CharacterizationTest
+{
+    Path unitTestData = getUnitTestData() + "/public-key";
+
+public:
+    Path goldenMaster(std::string_view testStem) const override {
+        return unitTestData + "/" + testStem;
     }
-    TEST(PublicKey, jsonDeserialization) {
-        auto pubKeyJson = R"({ "key": "ABCDE", "type": "ssh-ed25519" })"_json;
-        fetchers::PublicKey pubKey = pubKeyJson;
+};
 
-        ASSERT_EQ(pubKey.key, "ABCDE");
-        ASSERT_EQ(pubKey.type, "ssh-ed25519");
+#define TEST_JSON(FIXTURE, NAME, VAL)                                     \
+    TEST_F(FIXTURE, PublicKey_ ## NAME ## _from_json) {                   \
+        readTest(#NAME ".json", [&](const auto & encoded_) {              \
+            fetchers::PublicKey expected { VAL };                         \
+            fetchers::PublicKey got = nlohmann::json::parse(encoded_);    \
+            ASSERT_EQ(got, expected);                                     \
+        });                                                               \
+    }                                                                     \
+                                                                          \
+    TEST_F(FIXTURE, PublicKey_ ## NAME ## _to_json) {                     \
+        writeTest(#NAME ".json", [&]() -> json {                          \
+            return nlohmann::json(fetchers::PublicKey { VAL });           \
+        }, [](const auto & file) {                                        \
+            return json::parse(readFile(file));                           \
+        }, [](const auto & file, const auto & got) {                      \
+            return writeFile(file, got.dump(2) + "\n");                   \
+        });                                                               \
     }
+
+TEST_JSON(PublicKeyTest, simple, (fetchers::PublicKey { .type = "ssh-rsa", .key = "ABCDE" }))
+
+TEST_JSON(PublicKeyTest, defaultType, fetchers::PublicKey { .key = "ABCDE" })
+
+#undef TEST_JSON
+
+TEST_F(PublicKeyTest, PublicKey_noRoundTrip_from_json) {
+    readTest("noRoundTrip.json", [&](const auto & encoded_) {
+        fetchers::PublicKey expected = { .type = "ssh-ed25519", .key = "ABCDE" };
+        fetchers::PublicKey got = nlohmann::json::parse(encoded_);
+        ASSERT_EQ(got, expected);
+    });
+}
+
 }
diff --git a/tests/unit/libflake/.version b/tests/unit/libflake/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libflake/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libflake/build-utils-meson b/tests/unit/libflake/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libflake/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libflake/data/.gitkeep b/tests/unit/libflake/data/.gitkeep
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/unit/libexpr/flake/flakeref.cc b/tests/unit/libflake/flakeref.cc
similarity index 100%
rename from tests/unit/libexpr/flake/flakeref.cc
rename to tests/unit/libflake/flakeref.cc
diff --git a/tests/unit/libflake/local.mk b/tests/unit/libflake/local.mk
new file mode 100644
index 00000000000..590bcf7c031
--- /dev/null
+++ b/tests/unit/libflake/local.mk
@@ -0,0 +1,43 @@
+check: libflake-tests_RUN
+
+programs += libflake-tests
+
+libflake-tests_NAME := libnixflake-tests
+
+libflake-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data GTEST_OUTPUT=xml:$$testresults/libflake-tests.xml
+
+libflake-tests_DIR := $(d)
+
+ifeq ($(INSTALL_UNIT_TESTS), yes)
+  libflake-tests_INSTALL_DIR := $(checkbindir)
+else
+  libflake-tests_INSTALL_DIR :=
+endif
+
+libflake-tests_SOURCES := \
+    $(wildcard $(d)/*.cc) \
+    $(wildcard $(d)/value/*.cc) \
+    $(wildcard $(d)/flake/*.cc)
+
+libflake-tests_EXTRA_INCLUDES = \
+    -I tests/unit/libflake-support \
+    -I tests/unit/libstore-support \
+    -I tests/unit/libutil-support \
+    $(INCLUDE_libflake) \
+    $(INCLUDE_libexpr) \
+    $(INCLUDE_libfetchers) \
+    $(INCLUDE_libstore) \
+    $(INCLUDE_libutil) \
+
+libflake-tests_CXXFLAGS += $(libflake-tests_EXTRA_INCLUDES)
+
+libflake-tests_LIBS = \
+    libexpr-test-support libstore-test-support libutil-test-support \
+    libflake libexpr libfetchers libstore libutil
+
+libflake-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS) -lgmock
+
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  libflake-tests_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif
diff --git a/tests/unit/libflake/meson.build b/tests/unit/libflake/meson.build
new file mode 100644
index 00000000000..2d6bbca0f17
--- /dev/null
+++ b/tests/unit/libflake/meson.build
@@ -0,0 +1,72 @@
+project('nix-flake-tests', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-expr-test-support'),
+  dependency('nix-flake'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/export-all-symbols')
+
+rapidcheck = dependency('rapidcheck')
+deps_private += rapidcheck
+
+gtest = dependency('gtest', main : true)
+deps_private += gtest
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-expr.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'flakeref.cc',
+  'url-name.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: -lrapidcheck, see ../libutil-support/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  # get main from gtest
+  install : true,
+)
+
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)
diff --git a/tests/unit/libflake/package.nix b/tests/unit/libflake/package.nix
new file mode 100644
index 00000000000..859bc49d02e
--- /dev/null
+++ b/tests/unit/libflake/package.nix
@@ -0,0 +1,97 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-flake
+, nix-expr-test-support
+
+, rapidcheck
+, gtest
+, runCommand
+
+# Configuration Options
+
+, version
+, resolvePath
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-flake-tests";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    nix-flake
+    nix-expr-test-support
+    rapidcheck
+    gtest
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  passthru = {
+    tests = {
+      run = runCommand "${finalAttrs.pname}-run" {
+      } ''
+        PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
+        export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
+        nix-flake-tests
+        touch $out
+      '';
+    };
+  };
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libexpr/flake/url-name.cc b/tests/unit/libflake/url-name.cc
similarity index 100%
rename from tests/unit/libexpr/flake/url-name.cc
rename to tests/unit/libflake/url-name.cc
diff --git a/tests/unit/libstore-support/.version b/tests/unit/libstore-support/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libstore-support/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libstore-support/build-utils-meson b/tests/unit/libstore-support/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libstore-support/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libstore-support/meson.build b/tests/unit/libstore-support/meson.build
new file mode 100644
index 00000000000..ddb067c1b52
--- /dev/null
+++ b/tests/unit/libstore-support/meson.build
@@ -0,0 +1,76 @@
+project('nix-store-test-support', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-util-test-support'),
+  dependency('nix-store'),
+]
+subdir('build-utils-meson/subprojects')
+
+rapidcheck = dependency('rapidcheck')
+deps_public += rapidcheck
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'tests/derived-path.cc',
+  'tests/outputs-spec.cc',
+  'tests/path.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = files(
+  'tests/derived-path.hh',
+  'tests/libstore.hh',
+  'tests/nix_api_store.hh',
+  'tests/outputs-spec.hh',
+  'tests/path.hh',
+  'tests/protocol.hh',
+)
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nix-store-test-support',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: Remove `-lrapidcheck` when https://github.com/emil-e/rapidcheck/pull/326
+  #       is available. See also ../libutil/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/tests/unit/libstore-support/package.nix b/tests/unit/libstore-support/package.nix
new file mode 100644
index 00000000000..cb15cdd5f2f
--- /dev/null
+++ b/tests/unit/libstore-support/package.nix
@@ -0,0 +1,81 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util-test-support
+, nix-store
+
+, rapidcheck
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-store-test-support";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-util-test-support
+    nix-store
+    rapidcheck
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libstore-support/tests/libstore.hh b/tests/unit/libstore-support/tests/libstore.hh
index 78b162b9568..84be52c230b 100644
--- a/tests/unit/libstore-support/tests/libstore.hh
+++ b/tests/unit/libstore-support/tests/libstore.hh
@@ -8,19 +8,27 @@
 
 namespace nix {
 
-class LibStoreTest : public virtual ::testing::Test {
-    public:
-        static void SetUpTestSuite() {
-            initLibStore();
-        }
-
-    protected:
-        LibStoreTest()
-            : store(openStore("dummy://"))
-        { }
-
-        ref<Store> store;
+class LibStoreTest : public virtual ::testing::Test
+{
+public:
+    static void SetUpTestSuite()
+    {
+        initLibStore(false);
+    }
+
+protected:
+    LibStoreTest()
+        : store(openStore({
+            .variant =
+                StoreReference::Specified{
+                    .scheme = "dummy",
+                },
+            .params = {},
+        }))
+    {
+    }
+
+    ref<Store> store;
 };
 
-
 } /* namespace nix */
diff --git a/tests/unit/libstore/.version b/tests/unit/libstore/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libstore/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libstore/build-utils-meson b/tests/unit/libstore/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libstore/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libstore/common-protocol.cc b/tests/unit/libstore/common-protocol.cc
index d23805fc368..c8f6dd002d5 100644
--- a/tests/unit/libstore/common-protocol.cc
+++ b/tests/unit/libstore/common-protocol.cc
@@ -83,15 +83,15 @@ CHARACTERIZATION_TEST(
     "content-address",
     (std::tuple<ContentAddress, ContentAddress, ContentAddress> {
         ContentAddress {
-            .method = TextIngestionMethod {},
+            .method = ContentAddressMethod::Raw::Text,
             .hash = hashString(HashAlgorithm::SHA256, "Derive(...)"),
         },
         ContentAddress {
-            .method = FileIngestionMethod::Flat,
+            .method = ContentAddressMethod::Raw::Flat,
             .hash = hashString(HashAlgorithm::SHA1, "blob blob..."),
         },
         ContentAddress {
-            .method = FileIngestionMethod::Recursive,
+            .method = ContentAddressMethod::Raw::NixArchive,
             .hash = hashString(HashAlgorithm::SHA256, "(...)"),
         },
     }))
@@ -178,7 +178,7 @@ CHARACTERIZATION_TEST(
         std::nullopt,
         std::optional {
             ContentAddress {
-                .method = FileIngestionMethod::Flat,
+                .method = ContentAddressMethod::Raw::Flat,
                 .hash = hashString(HashAlgorithm::SHA1, "blob blob..."),
             },
         },
diff --git a/tests/unit/libstore/content-address.cc b/tests/unit/libstore/content-address.cc
index cc1c7fcc69d..72eb84fec11 100644
--- a/tests/unit/libstore/content-address.cc
+++ b/tests/unit/libstore/content-address.cc
@@ -9,11 +9,11 @@ namespace nix {
  * --------------------------------------------------------------------------*/
 
 TEST(ContentAddressMethod, testRoundTripPrintParse_1) {
-    for (const ContentAddressMethod & cam : {
-        ContentAddressMethod { TextIngestionMethod {} },
-        ContentAddressMethod { FileIngestionMethod::Flat },
-        ContentAddressMethod { FileIngestionMethod::Recursive },
-        ContentAddressMethod { FileIngestionMethod::Git },
+    for (ContentAddressMethod cam : {
+        ContentAddressMethod::Raw::Text,
+        ContentAddressMethod::Raw::Flat,
+        ContentAddressMethod::Raw::NixArchive,
+        ContentAddressMethod::Raw::Git,
     }) {
         EXPECT_EQ(ContentAddressMethod::parse(cam.render()), cam);
     }
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes-defaults.drv b/tests/unit/libstore/data/derivation/advanced-attributes-defaults.drv
new file mode 120000
index 00000000000..353090ad84b
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes-defaults.drv
@@ -0,0 +1 @@
+../../../../functional/derivation/advanced-attributes-defaults.drv
\ No newline at end of file
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes-defaults.json b/tests/unit/libstore/data/derivation/advanced-attributes-defaults.json
new file mode 100644
index 00000000000..d58e7d5b586
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes-defaults.json
@@ -0,0 +1,22 @@
+{
+  "args": [
+    "-c",
+    "echo hello > $out"
+  ],
+  "builder": "/bin/bash",
+  "env": {
+    "builder": "/bin/bash",
+    "name": "advanced-attributes-defaults",
+    "out": "/nix/store/1qsc7svv43m4dw2prh6mvyf7cai5czji-advanced-attributes-defaults",
+    "system": "my-system"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "name": "advanced-attributes-defaults",
+  "outputs": {
+    "out": {
+      "path": "/nix/store/1qsc7svv43m4dw2prh6mvyf7cai5czji-advanced-attributes-defaults"
+    }
+  },
+  "system": "my-system"
+}
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs-defaults.drv b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs-defaults.drv
new file mode 120000
index 00000000000..11713da12e3
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs-defaults.drv
@@ -0,0 +1 @@
+../../../../functional/derivation/advanced-attributes-structured-attrs-defaults.drv
\ No newline at end of file
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs-defaults.json b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs-defaults.json
new file mode 100644
index 00000000000..473d006acb5
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs-defaults.json
@@ -0,0 +1,24 @@
+{
+  "args": [
+    "-c",
+    "echo hello > $out"
+  ],
+  "builder": "/bin/bash",
+  "env": {
+    "__json": "{\"builder\":\"/bin/bash\",\"name\":\"advanced-attributes-structured-attrs-defaults\",\"outputs\":[\"out\",\"dev\"],\"system\":\"my-system\"}",
+    "dev": "/nix/store/8bazivnbipbyi569623skw5zm91z6kc2-advanced-attributes-structured-attrs-defaults-dev",
+    "out": "/nix/store/f8f8nvnx32bxvyxyx2ff7akbvwhwd9dw-advanced-attributes-structured-attrs-defaults"
+  },
+  "inputDrvs": {},
+  "inputSrcs": [],
+  "name": "advanced-attributes-structured-attrs-defaults",
+  "outputs": {
+    "dev": {
+      "path": "/nix/store/8bazivnbipbyi569623skw5zm91z6kc2-advanced-attributes-structured-attrs-defaults-dev"
+    },
+    "out": {
+      "path": "/nix/store/f8f8nvnx32bxvyxyx2ff7akbvwhwd9dw-advanced-attributes-structured-attrs-defaults"
+    }
+  },
+  "system": "my-system"
+}
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs.drv b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs.drv
new file mode 120000
index 00000000000..962f8ea3fe1
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs.drv
@@ -0,0 +1 @@
+../../../../functional/derivation/advanced-attributes-structured-attrs.drv
\ No newline at end of file
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs.json b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs.json
new file mode 100644
index 00000000000..32442812467
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes-structured-attrs.json
@@ -0,0 +1,41 @@
+{
+  "args": [
+    "-c",
+    "echo hello > $out"
+  ],
+  "builder": "/bin/bash",
+  "env": {
+    "__json": "{\"__darwinAllowLocalNetworking\":true,\"__impureHostDeps\":[\"/usr/bin/ditto\"],\"__noChroot\":true,\"__sandboxProfile\":\"sandcastle\",\"allowSubstitutes\":false,\"builder\":\"/bin/bash\",\"impureEnvVars\":[\"UNICORN\"],\"name\":\"advanced-attributes-structured-attrs\",\"outputChecks\":{\"bin\":{\"disallowedReferences\":[\"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar\"],\"disallowedRequisites\":[\"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar\"]},\"dev\":{\"maxClosureSize\":5909,\"maxSize\":789},\"out\":{\"allowedReferences\":[\"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo\"],\"allowedRequisites\":[\"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo\"]}},\"outputs\":[\"out\",\"bin\",\"dev\"],\"preferLocalBuild\":true,\"requiredSystemFeatures\":[\"rainbow\",\"uid-range\"],\"system\":\"my-system\"}",
+    "bin": "/nix/store/pbzb48v0ycf80jgligcp4n8z0rblna4n-advanced-attributes-structured-attrs-bin",
+    "dev": "/nix/store/7xapi8jv7flcz1qq8jhw55ar8ag8hldh-advanced-attributes-structured-attrs-dev",
+    "out": "/nix/store/mpq3l1l1qc2yr50q520g08kprprwv79f-advanced-attributes-structured-attrs"
+  },
+  "inputDrvs": {
+    "/nix/store/4xm4wccqsvagz9gjksn24s7rip2fdy7v-foo.drv": {
+      "dynamicOutputs": {},
+      "outputs": [
+        "out"
+      ]
+    },
+    "/nix/store/plsq5jbr5nhgqwcgb2qxw7jchc09dnl8-bar.drv": {
+      "dynamicOutputs": {},
+      "outputs": [
+        "out"
+      ]
+    }
+  },
+  "inputSrcs": [],
+  "name": "advanced-attributes-structured-attrs",
+  "outputs": {
+    "bin": {
+      "path": "/nix/store/pbzb48v0ycf80jgligcp4n8z0rblna4n-advanced-attributes-structured-attrs-bin"
+    },
+    "dev": {
+      "path": "/nix/store/7xapi8jv7flcz1qq8jhw55ar8ag8hldh-advanced-attributes-structured-attrs-dev"
+    },
+    "out": {
+      "path": "/nix/store/mpq3l1l1qc2yr50q520g08kprprwv79f-advanced-attributes-structured-attrs"
+    }
+  },
+  "system": "my-system"
+}
diff --git a/tests/unit/libstore/data/derivation/advanced-attributes.drv b/tests/unit/libstore/data/derivation/advanced-attributes.drv
new file mode 120000
index 00000000000..2a53a05caee
--- /dev/null
+++ b/tests/unit/libstore/data/derivation/advanced-attributes.drv
@@ -0,0 +1 @@
+../../../../functional/derivation/advanced-attributes.drv
\ No newline at end of file
diff --git a/tests/unit/libstore/data/derivation/output-caFixedFlat.json b/tests/unit/libstore/data/derivation/output-caFixedFlat.json
index fe000ea36e3..7001ea0a9fb 100644
--- a/tests/unit/libstore/data/derivation/output-caFixedFlat.json
+++ b/tests/unit/libstore/data/derivation/output-caFixedFlat.json
@@ -1,5 +1,6 @@
 {
   "hash": "894517c9163c896ec31a2adbd33c0681fd5f45b2c0ef08a64c92a03fb97f390f",
   "hashAlgo": "sha256",
+  "method": "flat",
   "path": "/nix/store/rhcg9h16sqvlbpsa6dqm57sbr2al6nzg-drv-name-output-name"
 }
diff --git a/tests/unit/libstore/data/derivation/output-caFixedNAR.json b/tests/unit/libstore/data/derivation/output-caFixedNAR.json
index 1afd602236b..54eb306e672 100644
--- a/tests/unit/libstore/data/derivation/output-caFixedNAR.json
+++ b/tests/unit/libstore/data/derivation/output-caFixedNAR.json
@@ -1,5 +1,6 @@
 {
   "hash": "894517c9163c896ec31a2adbd33c0681fd5f45b2c0ef08a64c92a03fb97f390f",
-  "hashAlgo": "r:sha256",
+  "hashAlgo": "sha256",
+  "method": "nar",
   "path": "/nix/store/c015dhfh5l0lp6wxyvdn7bmwhbbr6hr9-drv-name-output-name"
 }
diff --git a/tests/unit/libstore/data/derivation/output-caFixedText.json b/tests/unit/libstore/data/derivation/output-caFixedText.json
index 0b2cc8bbc42..e8a65186049 100644
--- a/tests/unit/libstore/data/derivation/output-caFixedText.json
+++ b/tests/unit/libstore/data/derivation/output-caFixedText.json
@@ -1,5 +1,6 @@
 {
   "hash": "894517c9163c896ec31a2adbd33c0681fd5f45b2c0ef08a64c92a03fb97f390f",
-  "hashAlgo": "text:sha256",
+  "hashAlgo": "sha256",
+  "method": "text",
   "path": "/nix/store/6s1zwabh956jvhv4w9xcdb5jiyanyxg1-drv-name-output-name"
 }
diff --git a/tests/unit/libstore/data/derivation/output-caFloating.json b/tests/unit/libstore/data/derivation/output-caFloating.json
index 9115de851a1..8b9b5f68196 100644
--- a/tests/unit/libstore/data/derivation/output-caFloating.json
+++ b/tests/unit/libstore/data/derivation/output-caFloating.json
@@ -1,3 +1,4 @@
 {
-  "hashAlgo": "r:sha256"
+  "hashAlgo": "sha256",
+  "method": "nar"
 }
diff --git a/tests/unit/libstore/data/derivation/output-impure.json b/tests/unit/libstore/data/derivation/output-impure.json
index 62b61cdcae7..bec03702b16 100644
--- a/tests/unit/libstore/data/derivation/output-impure.json
+++ b/tests/unit/libstore/data/derivation/output-impure.json
@@ -1,4 +1,5 @@
 {
-  "hashAlgo": "r:sha256",
-  "impure": true
+  "hashAlgo": "sha256",
+  "impure": true,
+  "method": "nar"
 }
diff --git a/tests/unit/libstore/test-data/machines.bad_format b/tests/unit/libstore/data/machines/bad_format
similarity index 100%
rename from tests/unit/libstore/test-data/machines.bad_format
rename to tests/unit/libstore/data/machines/bad_format
diff --git a/tests/unit/libstore/test-data/machines.valid b/tests/unit/libstore/data/machines/valid
similarity index 100%
rename from tests/unit/libstore/test-data/machines.valid
rename to tests/unit/libstore/data/machines/valid
diff --git a/tests/unit/libstore/data/path-info/empty_impure.json b/tests/unit/libstore/data/path-info/empty_impure.json
new file mode 100644
index 00000000000..be982dcef85
--- /dev/null
+++ b/tests/unit/libstore/data/path-info/empty_impure.json
@@ -0,0 +1,10 @@
+{
+  "ca": null,
+  "deriver": null,
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
+  "narSize": 0,
+  "references": [],
+  "registrationTime": null,
+  "signatures": [],
+  "ultimate": false
+}
diff --git a/tests/unit/libstore/data/path-info/empty_pure.json b/tests/unit/libstore/data/path-info/empty_pure.json
new file mode 100644
index 00000000000..10d9f508a36
--- /dev/null
+++ b/tests/unit/libstore/data/path-info/empty_pure.json
@@ -0,0 +1,6 @@
+{
+  "ca": null,
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
+  "narSize": 0,
+  "references": []
+}
diff --git a/tests/unit/libstore/data/store-reference/auto.txt b/tests/unit/libstore/data/store-reference/auto.txt
new file mode 100644
index 00000000000..4d18c3e59ec
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/auto.txt
@@ -0,0 +1 @@
+auto
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/auto_param.txt b/tests/unit/libstore/data/store-reference/auto_param.txt
new file mode 100644
index 00000000000..54adabb25d3
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/auto_param.txt
@@ -0,0 +1 @@
+auto?root=/foo/bar/baz
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/local_1.txt b/tests/unit/libstore/data/store-reference/local_1.txt
new file mode 100644
index 00000000000..74b1b9677f1
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/local_1.txt
@@ -0,0 +1 @@
+local://?root=/foo/bar/baz
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/local_2.txt b/tests/unit/libstore/data/store-reference/local_2.txt
new file mode 100644
index 00000000000..8b5593fb129
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/local_2.txt
@@ -0,0 +1 @@
+local:///foo/bar/baz?trusted=true
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/local_shorthand_1.txt b/tests/unit/libstore/data/store-reference/local_shorthand_1.txt
new file mode 100644
index 00000000000..896189be9dc
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/local_shorthand_1.txt
@@ -0,0 +1 @@
+local?root=/foo/bar/baz
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/local_shorthand_2.txt b/tests/unit/libstore/data/store-reference/local_shorthand_2.txt
new file mode 100644
index 00000000000..7a9dad3b374
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/local_shorthand_2.txt
@@ -0,0 +1 @@
+/foo/bar/baz?trusted=true
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/ssh.txt b/tests/unit/libstore/data/store-reference/ssh.txt
new file mode 100644
index 00000000000..8c61010ec4d
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/ssh.txt
@@ -0,0 +1 @@
+ssh://localhost
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/unix.txt b/tests/unit/libstore/data/store-reference/unix.txt
new file mode 100644
index 00000000000..19548904840
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/unix.txt
@@ -0,0 +1 @@
+unix://?max-connections=7&trusted=true
\ No newline at end of file
diff --git a/tests/unit/libstore/data/store-reference/unix_shorthand.txt b/tests/unit/libstore/data/store-reference/unix_shorthand.txt
new file mode 100644
index 00000000000..0300337e97c
--- /dev/null
+++ b/tests/unit/libstore/data/store-reference/unix_shorthand.txt
@@ -0,0 +1 @@
+daemon?max-connections=7&trusted=true
\ No newline at end of file
diff --git a/tests/unit/libstore/data/worker-protocol/build-mode.bin b/tests/unit/libstore/data/worker-protocol/build-mode.bin
new file mode 100644
index 00000000000..51b239409bc
Binary files /dev/null and b/tests/unit/libstore/data/worker-protocol/build-mode.bin differ
diff --git a/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_30.bin b/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_30.bin
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_33.bin b/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_33.bin
new file mode 100644
index 00000000000..96c6efafc26
Binary files /dev/null and b/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_33.bin differ
diff --git a/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_35.bin b/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_35.bin
new file mode 100644
index 00000000000..e877159aaa2
Binary files /dev/null and b/tests/unit/libstore/data/worker-protocol/client-handshake-info_1_35.bin differ
diff --git a/tests/unit/libstore/data/worker-protocol/handshake-to-client.bin b/tests/unit/libstore/data/worker-protocol/handshake-to-client.bin
new file mode 100644
index 00000000000..bee94fbe53a
Binary files /dev/null and b/tests/unit/libstore/data/worker-protocol/handshake-to-client.bin differ
diff --git a/tests/unit/libstore/derivation-advanced-attrs.cc b/tests/unit/libstore/derivation-advanced-attrs.cc
new file mode 100644
index 00000000000..26cf947a853
--- /dev/null
+++ b/tests/unit/libstore/derivation-advanced-attrs.cc
@@ -0,0 +1,234 @@
+#include <nlohmann/json.hpp>
+#include <gtest/gtest.h>
+#include <optional>
+
+#include "experimental-features.hh"
+#include "derivations.hh"
+
+#include "tests/libstore.hh"
+#include "tests/characterization.hh"
+#include "parsed-derivations.hh"
+#include "types.hh"
+
+namespace nix {
+
+using nlohmann::json;
+
+class DerivationAdvancedAttrsTest : public CharacterizationTest, public LibStoreTest
+{
+    Path unitTestData = getUnitTestData() + "/derivation";
+
+public:
+    Path goldenMaster(std::string_view testStem) const override
+    {
+        return unitTestData + "/" + testStem;
+    }
+};
+
+#define TEST_ATERM_JSON(STEM, NAME)                                                                   \
+    TEST_F(DerivationAdvancedAttrsTest, Derivation_##STEM##_from_json)                                \
+    {                                                                                                 \
+        readTest(NAME ".json", [&](const auto & encoded_) {                                           \
+            auto encoded = json::parse(encoded_);                                                     \
+            /* Use DRV file instead of C++ literal as source of truth. */                             \
+            auto aterm = readFile(goldenMaster(NAME ".drv"));                                         \
+            auto expected = parseDerivation(*store, std::move(aterm), NAME);                          \
+            Derivation got = Derivation::fromJSON(*store, encoded);                                   \
+            EXPECT_EQ(got, expected);                                                                 \
+        });                                                                                           \
+    }                                                                                                 \
+                                                                                                      \
+    TEST_F(DerivationAdvancedAttrsTest, Derivation_##STEM##_to_json)                                  \
+    {                                                                                                 \
+        writeTest(                                                                                    \
+            NAME ".json",                                                                             \
+            [&]() -> json {                                                                           \
+                /* Use DRV file instead of C++ literal as source of truth. */                         \
+                auto aterm = readFile(goldenMaster(NAME ".drv"));                                     \
+                return parseDerivation(*store, std::move(aterm), NAME).toJSON(*store);                \
+            },                                                                                        \
+            [](const auto & file) { return json::parse(readFile(file)); },                            \
+            [](const auto & file, const auto & got) { return writeFile(file, got.dump(2) + "\n"); }); \
+    }                                                                                                 \
+                                                                                                      \
+    TEST_F(DerivationAdvancedAttrsTest, Derivation_##STEM##_from_aterm)                               \
+    {                                                                                                 \
+        readTest(NAME ".drv", [&](auto encoded) {                                                     \
+            /* Use JSON file instead of C++ literal as source of truth. */                            \
+            auto json = json::parse(readFile(goldenMaster(NAME ".json")));                            \
+            auto expected = Derivation::fromJSON(*store, json);                                       \
+            auto got = parseDerivation(*store, std::move(encoded), NAME);                             \
+            EXPECT_EQ(got.toJSON(*store), expected.toJSON(*store));                                   \
+            EXPECT_EQ(got, expected);                                                                 \
+        });                                                                                           \
+    }                                                                                                 \
+                                                                                                      \
+    /* No corresponding write test, because we need to read the drv to write the json file */
+
+TEST_ATERM_JSON(advancedAttributes_defaults, "advanced-attributes-defaults");
+TEST_ATERM_JSON(advancedAttributes, "advanced-attributes-defaults");
+TEST_ATERM_JSON(advancedAttributes_structuredAttrs_defaults, "advanced-attributes-structured-attrs");
+TEST_ATERM_JSON(advancedAttributes_structuredAttrs, "advanced-attributes-structured-attrs-defaults");
+
+#undef TEST_ATERM_JSON
+
+TEST_F(DerivationAdvancedAttrsTest, Derivation_advancedAttributes_defaults)
+{
+    readTest("advanced-attributes-defaults.drv", [&](auto encoded) {
+        auto got = parseDerivation(*store, std::move(encoded), "foo");
+
+        auto drvPath = writeDerivation(*store, got, NoRepair, true);
+
+        ParsedDerivation parsedDrv(drvPath, got);
+
+        EXPECT_EQ(parsedDrv.getStringAttr("__sandboxProfile").value_or(""), "");
+        EXPECT_EQ(parsedDrv.getBoolAttr("__noChroot"), false);
+        EXPECT_EQ(parsedDrv.getStringsAttr("__impureHostDeps").value_or(Strings()), Strings());
+        EXPECT_EQ(parsedDrv.getStringsAttr("impureEnvVars").value_or(Strings()), Strings());
+        EXPECT_EQ(parsedDrv.getBoolAttr("__darwinAllowLocalNetworking"), false);
+        EXPECT_EQ(parsedDrv.getStringsAttr("allowedReferences"), std::nullopt);
+        EXPECT_EQ(parsedDrv.getStringsAttr("allowedRequisites"), std::nullopt);
+        EXPECT_EQ(parsedDrv.getStringsAttr("disallowedReferences"), std::nullopt);
+        EXPECT_EQ(parsedDrv.getStringsAttr("disallowedRequisites"), std::nullopt);
+        EXPECT_EQ(parsedDrv.getRequiredSystemFeatures(), StringSet());
+        EXPECT_EQ(parsedDrv.canBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.willBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.substitutesAllowed(), true);
+        EXPECT_EQ(parsedDrv.useUidRange(), false);
+    });
+};
+
+TEST_F(DerivationAdvancedAttrsTest, Derivation_advancedAttributes)
+{
+    readTest("advanced-attributes.drv", [&](auto encoded) {
+        auto got = parseDerivation(*store, std::move(encoded), "foo");
+
+        auto drvPath = writeDerivation(*store, got, NoRepair, true);
+
+        ParsedDerivation parsedDrv(drvPath, got);
+
+        StringSet systemFeatures{"rainbow", "uid-range"};
+
+        EXPECT_EQ(parsedDrv.getStringAttr("__sandboxProfile").value_or(""), "sandcastle");
+        EXPECT_EQ(parsedDrv.getBoolAttr("__noChroot"), true);
+        EXPECT_EQ(parsedDrv.getStringsAttr("__impureHostDeps").value_or(Strings()), Strings{"/usr/bin/ditto"});
+        EXPECT_EQ(parsedDrv.getStringsAttr("impureEnvVars").value_or(Strings()), Strings{"UNICORN"});
+        EXPECT_EQ(parsedDrv.getBoolAttr("__darwinAllowLocalNetworking"), true);
+        EXPECT_EQ(
+            parsedDrv.getStringsAttr("allowedReferences"), Strings{"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo"});
+        EXPECT_EQ(
+            parsedDrv.getStringsAttr("allowedRequisites"), Strings{"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo"});
+        EXPECT_EQ(
+            parsedDrv.getStringsAttr("disallowedReferences"),
+            Strings{"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar"});
+        EXPECT_EQ(
+            parsedDrv.getStringsAttr("disallowedRequisites"),
+            Strings{"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar"});
+        EXPECT_EQ(parsedDrv.getRequiredSystemFeatures(), systemFeatures);
+        EXPECT_EQ(parsedDrv.canBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.willBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.substitutesAllowed(), false);
+        EXPECT_EQ(parsedDrv.useUidRange(), true);
+    });
+};
+
+TEST_F(DerivationAdvancedAttrsTest, Derivation_advancedAttributes_structuredAttrs_defaults)
+{
+    readTest("advanced-attributes-structured-attrs-defaults.drv", [&](auto encoded) {
+        auto got = parseDerivation(*store, std::move(encoded), "foo");
+
+        auto drvPath = writeDerivation(*store, got, NoRepair, true);
+
+        ParsedDerivation parsedDrv(drvPath, got);
+
+        EXPECT_EQ(parsedDrv.getStringAttr("__sandboxProfile").value_or(""), "");
+        EXPECT_EQ(parsedDrv.getBoolAttr("__noChroot"), false);
+        EXPECT_EQ(parsedDrv.getStringsAttr("__impureHostDeps").value_or(Strings()), Strings());
+        EXPECT_EQ(parsedDrv.getStringsAttr("impureEnvVars").value_or(Strings()), Strings());
+        EXPECT_EQ(parsedDrv.getBoolAttr("__darwinAllowLocalNetworking"), false);
+
+        {
+            auto structuredAttrs_ = parsedDrv.getStructuredAttrs();
+            ASSERT_TRUE(structuredAttrs_);
+            auto & structuredAttrs = *structuredAttrs_;
+
+            auto outputChecks_ = get(structuredAttrs, "outputChecks");
+            ASSERT_FALSE(outputChecks_);
+        }
+
+        EXPECT_EQ(parsedDrv.getRequiredSystemFeatures(), StringSet());
+        EXPECT_EQ(parsedDrv.canBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.willBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.substitutesAllowed(), true);
+        EXPECT_EQ(parsedDrv.useUidRange(), false);
+    });
+};
+
+TEST_F(DerivationAdvancedAttrsTest, Derivation_advancedAttributes_structuredAttrs)
+{
+    readTest("advanced-attributes-structured-attrs.drv", [&](auto encoded) {
+        auto got = parseDerivation(*store, std::move(encoded), "foo");
+
+        auto drvPath = writeDerivation(*store, got, NoRepair, true);
+
+        ParsedDerivation parsedDrv(drvPath, got);
+
+        StringSet systemFeatures{"rainbow", "uid-range"};
+
+        EXPECT_EQ(parsedDrv.getStringAttr("__sandboxProfile").value_or(""), "sandcastle");
+        EXPECT_EQ(parsedDrv.getBoolAttr("__noChroot"), true);
+        EXPECT_EQ(parsedDrv.getStringsAttr("__impureHostDeps").value_or(Strings()), Strings{"/usr/bin/ditto"});
+        EXPECT_EQ(parsedDrv.getStringsAttr("impureEnvVars").value_or(Strings()), Strings{"UNICORN"});
+        EXPECT_EQ(parsedDrv.getBoolAttr("__darwinAllowLocalNetworking"), true);
+
+        {
+            auto structuredAttrs_ = parsedDrv.getStructuredAttrs();
+            ASSERT_TRUE(structuredAttrs_);
+            auto & structuredAttrs = *structuredAttrs_;
+
+            auto outputChecks_ = get(structuredAttrs, "outputChecks");
+            ASSERT_TRUE(outputChecks_);
+            auto & outputChecks = *outputChecks_;
+
+            {
+                auto output_ = get(outputChecks, "out");
+                ASSERT_TRUE(output_);
+                auto & output = *output_;
+                EXPECT_EQ(
+                    get(output, "allowedReferences")->get<Strings>(),
+                    Strings{"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo"});
+                EXPECT_EQ(
+                    get(output, "allowedRequisites")->get<Strings>(),
+                    Strings{"/nix/store/3c08bzb71z4wiag719ipjxr277653ynp-foo"});
+            }
+
+            {
+                auto output_ = get(outputChecks, "bin");
+                ASSERT_TRUE(output_);
+                auto & output = *output_;
+                EXPECT_EQ(
+                    get(output, "disallowedReferences")->get<Strings>(),
+                    Strings{"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar"});
+                EXPECT_EQ(
+                    get(output, "disallowedRequisites")->get<Strings>(),
+                    Strings{"/nix/store/7rhsm8i393hm1wcsmph782awg1hi2f7x-bar"});
+            }
+
+            {
+                auto output_ = get(outputChecks, "dev");
+                ASSERT_TRUE(output_);
+                auto & output = *output_;
+                EXPECT_EQ(get(output, "maxSize")->get<uint64_t>(), 789);
+                EXPECT_EQ(get(output, "maxClosureSize")->get<uint64_t>(), 5909);
+            }
+        }
+
+        EXPECT_EQ(parsedDrv.getRequiredSystemFeatures(), systemFeatures);
+        EXPECT_EQ(parsedDrv.canBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.willBuildLocally(*store), false);
+        EXPECT_EQ(parsedDrv.substitutesAllowed(), false);
+        EXPECT_EQ(parsedDrv.useUidRange(), true);
+    });
+};
+
+}
diff --git a/tests/unit/libstore/derivation.cc b/tests/unit/libstore/derivation.cc
index 7a4b1403aca..71979f88598 100644
--- a/tests/unit/libstore/derivation.cc
+++ b/tests/unit/libstore/derivation.cc
@@ -108,7 +108,7 @@ TEST_JSON(DerivationTest, inputAddressed,
 TEST_JSON(DerivationTest, caFixedFlat,
     (DerivationOutput::CAFixed {
         .ca = {
-            .method = FileIngestionMethod::Flat,
+            .method = ContentAddressMethod::Raw::Flat,
             .hash = Hash::parseAnyPrefixed("sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8="),
         },
     }),
@@ -117,7 +117,7 @@ TEST_JSON(DerivationTest, caFixedFlat,
 TEST_JSON(DerivationTest, caFixedNAR,
     (DerivationOutput::CAFixed {
         .ca = {
-            .method = FileIngestionMethod::Recursive,
+            .method = ContentAddressMethod::Raw::NixArchive,
             .hash = Hash::parseAnyPrefixed("sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8="),
         },
     }),
@@ -126,6 +126,7 @@ TEST_JSON(DerivationTest, caFixedNAR,
 TEST_JSON(DynDerivationTest, caFixedText,
     (DerivationOutput::CAFixed {
         .ca = {
+            .method = ContentAddressMethod::Raw::Text,
             .hash = Hash::parseAnyPrefixed("sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8="),
         },
     }),
@@ -133,7 +134,7 @@ TEST_JSON(DynDerivationTest, caFixedText,
 
 TEST_JSON(CaDerivationTest, caFloating,
     (DerivationOutput::CAFloating {
-        .method = FileIngestionMethod::Recursive,
+        .method = ContentAddressMethod::Raw::NixArchive,
         .hashAlgo = HashAlgorithm::SHA256,
     }),
     "drv-name", "output-name")
@@ -144,7 +145,7 @@ TEST_JSON(DerivationTest, deferred,
 
 TEST_JSON(ImpureDerivationTest, impure,
     (DerivationOutput::Impure {
-        .method = FileIngestionMethod::Recursive,
+        .method = ContentAddressMethod::Raw::NixArchive,
         .hashAlgo = HashAlgorithm::SHA256,
     }),
     "drv-name", "output-name")
diff --git a/tests/unit/libstore/local.mk b/tests/unit/libstore/local.mk
index b8f895fad32..8d3d6b0afe2 100644
--- a/tests/unit/libstore/local.mk
+++ b/tests/unit/libstore/local.mk
@@ -4,7 +4,7 @@ programs += libstore-tests
 
 libstore-tests_NAME = libnixstore-tests
 
-libstore-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+libstore-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data GTEST_OUTPUT=xml:$$testresults/libstore-tests.xml
 
 libstore-tests_DIR := $(d)
 
@@ -31,3 +31,8 @@ libstore-tests_LIBS = \
     libstore libstorec libutil libutilc
 
 libstore-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
+
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  libstore-tests_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif
diff --git a/tests/unit/libstore/machines.cc b/tests/unit/libstore/machines.cc
index 9fd7fda54cc..2307f4d629d 100644
--- a/tests/unit/libstore/machines.cc
+++ b/tests/unit/libstore/machines.cc
@@ -1,46 +1,29 @@
 #include "machines.hh"
-#include "globals.hh"
 #include "file-system.hh"
 #include "util.hh"
 
+#include "tests/characterization.hh"
+
+#include <gtest/gtest.h>
 #include <gmock/gmock-matchers.h>
 
 using testing::Contains;
 using testing::ElementsAre;
-using testing::EndsWith;
 using testing::Eq;
 using testing::Field;
 using testing::SizeIs;
 
-using nix::absPath;
-using nix::FormatError;
-using nix::UsageError;
-using nix::getMachines;
-using nix::Machine;
-using nix::Machines;
-using nix::pathExists;
-using nix::Settings;
-using nix::settings;
-
-class Environment : public ::testing::Environment {
-  public:
-    void SetUp() override { settings.thisSystem = "TEST_ARCH-TEST_OS"; }
-};
-
-testing::Environment* const foo_env =
-    testing::AddGlobalTestEnvironment(new Environment);
+using namespace nix;
 
 TEST(machines, getMachinesWithEmptyBuilders) {
-    settings.builders = "";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({}, "");
     ASSERT_THAT(actual, SizeIs(0));
 }
 
 TEST(machines, getMachinesUriOnly) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({"TEST_ARCH-TEST_OS"}, "nix@scratchy.labs.cs.uu.nl");
     ASSERT_THAT(actual, SizeIs(1));
-    EXPECT_THAT(actual[0], Field(&Machine::storeUri, Eq("ssh://nix@scratchy.labs.cs.uu.nl")));
+    EXPECT_THAT(actual[0], Field(&Machine::storeUri, Eq(StoreReference::parse("ssh://nix@scratchy.labs.cs.uu.nl"))));
     EXPECT_THAT(actual[0], Field(&Machine::systemTypes, ElementsAre("TEST_ARCH-TEST_OS")));
     EXPECT_THAT(actual[0], Field(&Machine::sshKey, SizeIs(0)));
     EXPECT_THAT(actual[0], Field(&Machine::maxJobs, Eq(1)));
@@ -51,10 +34,9 @@ TEST(machines, getMachinesUriOnly) {
 }
 
 TEST(machines, getMachinesDefaults) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl - - - - - - -";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({"TEST_ARCH-TEST_OS"}, "nix@scratchy.labs.cs.uu.nl - - - - - - -");
     ASSERT_THAT(actual, SizeIs(1));
-    EXPECT_THAT(actual[0], Field(&Machine::storeUri, Eq("ssh://nix@scratchy.labs.cs.uu.nl")));
+    EXPECT_THAT(actual[0], Field(&Machine::storeUri, Eq(StoreReference::parse("ssh://nix@scratchy.labs.cs.uu.nl"))));
     EXPECT_THAT(actual[0], Field(&Machine::systemTypes, ElementsAre("TEST_ARCH-TEST_OS")));
     EXPECT_THAT(actual[0], Field(&Machine::sshKey, SizeIs(0)));
     EXPECT_THAT(actual[0], Field(&Machine::maxJobs, Eq(1)));
@@ -64,29 +46,38 @@ TEST(machines, getMachinesDefaults) {
     EXPECT_THAT(actual[0], Field(&Machine::sshPublicHostKey, SizeIs(0)));
 }
 
+MATCHER_P(AuthorityMatches, authority, "") {
+    *result_listener
+        << "where the authority of "
+        << arg.render()
+        << " is "
+        << authority;
+    auto * generic = std::get_if<StoreReference::Specified>(&arg.variant);
+    if (!generic) return false;
+    return generic->authority == authority;
+}
+
 TEST(machines, getMachinesWithNewLineSeparator) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl\nnix@itchy.labs.cs.uu.nl";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl\nnix@itchy.labs.cs.uu.nl");
     ASSERT_THAT(actual, SizeIs(2));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@scratchy.labs.cs.uu.nl"))));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@itchy.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@scratchy.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@itchy.labs.cs.uu.nl"))));
 }
 
 TEST(machines, getMachinesWithSemicolonSeparator) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl ; nix@itchy.labs.cs.uu.nl";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl ; nix@itchy.labs.cs.uu.nl");
     EXPECT_THAT(actual, SizeIs(2));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@scratchy.labs.cs.uu.nl"))));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@itchy.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@scratchy.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@itchy.labs.cs.uu.nl"))));
 }
 
 TEST(machines, getMachinesWithCorrectCompleteSingleBuilder) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl     i686-linux      "
-                        "/home/nix/.ssh/id_scratchy_auto        8 3 kvm "
-                        "benchmark SSH+HOST+PUBLIC+KEY+BASE64+ENCODED==";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({},
+        "nix@scratchy.labs.cs.uu.nl     i686-linux      "
+        "/home/nix/.ssh/id_scratchy_auto        8 3 kvm "
+        "benchmark SSH+HOST+PUBLIC+KEY+BASE64+ENCODED==");
     ASSERT_THAT(actual, SizeIs(1));
-    EXPECT_THAT(actual[0], Field(&Machine::storeUri, EndsWith("nix@scratchy.labs.cs.uu.nl")));
+    EXPECT_THAT(actual[0], Field(&Machine::storeUri, AuthorityMatches("nix@scratchy.labs.cs.uu.nl")));
     EXPECT_THAT(actual[0], Field(&Machine::systemTypes, ElementsAre("i686-linux")));
     EXPECT_THAT(actual[0], Field(&Machine::sshKey, Eq("/home/nix/.ssh/id_scratchy_auto")));
     EXPECT_THAT(actual[0], Field(&Machine::maxJobs, Eq(8)));
@@ -98,13 +89,12 @@ TEST(machines, getMachinesWithCorrectCompleteSingleBuilder) {
 
 TEST(machines,
      getMachinesWithCorrectCompleteSingleBuilderWithTabColumnDelimiter) {
-    settings.builders =
+    auto actual = Machine::parseConfig({},
         "nix@scratchy.labs.cs.uu.nl\ti686-linux\t/home/nix/.ssh/"
         "id_scratchy_auto\t8\t3\tkvm\tbenchmark\tSSH+HOST+PUBLIC+"
-        "KEY+BASE64+ENCODED==";
-    Machines actual = getMachines();
+        "KEY+BASE64+ENCODED==");
     ASSERT_THAT(actual, SizeIs(1));
-    EXPECT_THAT(actual[0], Field(&Machine::storeUri, EndsWith("nix@scratchy.labs.cs.uu.nl")));
+    EXPECT_THAT(actual[0], Field(&Machine::storeUri, AuthorityMatches("nix@scratchy.labs.cs.uu.nl")));
     EXPECT_THAT(actual[0], Field(&Machine::systemTypes, ElementsAre("i686-linux")));
     EXPECT_THAT(actual[0], Field(&Machine::sshKey, Eq("/home/nix/.ssh/id_scratchy_auto")));
     EXPECT_THAT(actual[0], Field(&Machine::maxJobs, Eq(8)));
@@ -115,58 +105,61 @@ TEST(machines,
 }
 
 TEST(machines, getMachinesWithMultiOptions) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl Arch1,Arch2 - - - "
-                        "SupportedFeature1,SupportedFeature2 "
-                        "MandatoryFeature1,MandatoryFeature2";
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({},
+        "nix@scratchy.labs.cs.uu.nl Arch1,Arch2 - - - "
+        "SupportedFeature1,SupportedFeature2 "
+        "MandatoryFeature1,MandatoryFeature2");
     ASSERT_THAT(actual, SizeIs(1));
-    EXPECT_THAT(actual[0], Field(&Machine::storeUri, EndsWith("nix@scratchy.labs.cs.uu.nl")));
+    EXPECT_THAT(actual[0], Field(&Machine::storeUri, AuthorityMatches("nix@scratchy.labs.cs.uu.nl")));
     EXPECT_THAT(actual[0], Field(&Machine::systemTypes, ElementsAre("Arch1", "Arch2")));
     EXPECT_THAT(actual[0], Field(&Machine::supportedFeatures, ElementsAre("SupportedFeature1", "SupportedFeature2")));
     EXPECT_THAT(actual[0], Field(&Machine::mandatoryFeatures, ElementsAre("MandatoryFeature1", "MandatoryFeature2")));
 }
 
 TEST(machines, getMachinesWithIncorrectFormat) {
-    settings.builders = "nix@scratchy.labs.cs.uu.nl - - eight";
-    EXPECT_THROW(getMachines(), FormatError);
-    settings.builders = "nix@scratchy.labs.cs.uu.nl - - -1";
-    EXPECT_THROW(getMachines(), FormatError);
-    settings.builders = "nix@scratchy.labs.cs.uu.nl - - 8 three";
-    EXPECT_THROW(getMachines(), FormatError);
-    settings.builders = "nix@scratchy.labs.cs.uu.nl - - 8 -3";
-    EXPECT_THROW(getMachines(), UsageError);
-    settings.builders = "nix@scratchy.labs.cs.uu.nl - - 8 3 - - BAD_BASE64";
-    EXPECT_THROW(getMachines(), FormatError);
+    EXPECT_THROW(
+        Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl - - eight"),
+        FormatError);
+    EXPECT_THROW(
+        Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl - - -1"),
+        FormatError);
+    EXPECT_THROW(
+        Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl - - 8 three"),
+        FormatError);
+    EXPECT_THROW(
+        Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl - - 8 -3"),
+        UsageError);
+    EXPECT_THROW(
+        Machine::parseConfig({}, "nix@scratchy.labs.cs.uu.nl - - 8 3 - - BAD_BASE64"),
+        FormatError);
 }
 
 TEST(machines, getMachinesWithCorrectFileReference) {
-    auto path = absPath("tests/unit/libstore/test-data/machines.valid");
+    auto path = absPath(getUnitTestData() + "/machines/valid");
     ASSERT_TRUE(pathExists(path));
 
-    settings.builders = std::string("@") + path;
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({}, "@" + path);
     ASSERT_THAT(actual, SizeIs(3));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@scratchy.labs.cs.uu.nl"))));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@itchy.labs.cs.uu.nl"))));
-    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, EndsWith("nix@poochie.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@scratchy.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@itchy.labs.cs.uu.nl"))));
+    EXPECT_THAT(actual, Contains(Field(&Machine::storeUri, AuthorityMatches("nix@poochie.labs.cs.uu.nl"))));
 }
 
 TEST(machines, getMachinesWithCorrectFileReferenceToEmptyFile) {
     auto path = "/dev/null";
     ASSERT_TRUE(pathExists(path));
 
-    settings.builders = std::string("@") + path;
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({}, std::string{"@"} + path);
     ASSERT_THAT(actual, SizeIs(0));
 }
 
 TEST(machines, getMachinesWithIncorrectFileReference) {
-    settings.builders = std::string("@") + absPath("/not/a/file");
-    Machines actual = getMachines();
+    auto actual = Machine::parseConfig({}, "@" + absPath("/not/a/file"));
     ASSERT_THAT(actual, SizeIs(0));
 }
 
 TEST(machines, getMachinesWithCorrectFileReferenceToIncorrectFile) {
-    settings.builders = std::string("@") + absPath("tests/unit/libstore/test-data/machines.bad_format");
-    EXPECT_THROW(getMachines(), FormatError);
+    EXPECT_THROW(
+        Machine::parseConfig({}, "@" + absPath(getUnitTestData() + "/machines/bad_format")),
+        FormatError);
 }
diff --git a/tests/unit/libstore/meson.build b/tests/unit/libstore/meson.build
new file mode 100644
index 00000000000..90e7d3047c7
--- /dev/null
+++ b/tests/unit/libstore/meson.build
@@ -0,0 +1,95 @@
+project('nix-store-tests', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-store'),
+  dependency('nix-store-c'),
+  dependency('nix-store-test-support'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/export-all-symbols')
+
+sqlite = dependency('sqlite3', 'sqlite', version : '>=3.6.19')
+deps_private += sqlite
+
+rapidcheck = dependency('rapidcheck')
+deps_private += rapidcheck
+
+gtest = dependency('gtest', main : true)
+deps_private += gtest
+
+gtest = dependency('gmock')
+deps_private += gtest
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-util.h',
+  '-include', 'config-store.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'common-protocol.cc',
+  'content-address.cc',
+  'derivation-advanced-attrs.cc',
+  'derivation.cc',
+  'derived-path.cc',
+  'downstream-placeholder.cc',
+  'machines.cc',
+  'nar-info-disk-cache.cc',
+  'nar-info.cc',
+  'nix_api_store.cc',
+  'outputs-spec.cc',
+  'path-info.cc',
+  'path.cc',
+  'references.cc',
+  'serve-protocol.cc',
+  'store-reference.cc',
+  'worker-protocol.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: -lrapidcheck, see ../libutil-support/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  # get main from gtest
+  install : true,
+)
+
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)
diff --git a/tests/unit/libstore/nar-info.cc b/tests/unit/libstore/nar-info.cc
index bd10602e73e..a6cb62de4ac 100644
--- a/tests/unit/libstore/nar-info.cc
+++ b/tests/unit/libstore/nar-info.cc
@@ -25,7 +25,7 @@ static NarInfo makeNarInfo(const Store & store, bool includeImpureInfo) {
         store,
         "foo",
         FixedOutputInfo {
-            .method = FileIngestionMethod::Recursive,
+            .method = FileIngestionMethod::NixArchive,
             .hash = hashString(HashAlgorithm::SHA256, "(...)"),
 
             .references = {
diff --git a/tests/unit/libstore/package.nix b/tests/unit/libstore/package.nix
new file mode 100644
index 00000000000..efffd00631b
--- /dev/null
+++ b/tests/unit/libstore/package.nix
@@ -0,0 +1,110 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-store
+, nix-store-c
+, nix-store-test-support
+, sqlite
+
+, rapidcheck
+, gtest
+, runCommand
+
+# Configuration Options
+
+, version
+, filesetToSource
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-store-tests";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    nix-store
+    nix-store-c
+    nix-store-test-support
+    sqlite
+    rapidcheck
+    gtest
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  passthru = {
+    tests = {
+      run = let
+        # Some data is shared with the functional tests: they create it,
+        # we consume it.
+        data = filesetToSource {
+          root = ../..;
+          fileset = lib.fileset.unions [
+            ./data
+            ../../functional/derivation
+          ];
+        };
+      in runCommand "${finalAttrs.pname}-run" {} ''
+        PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
+        export _NIX_TEST_UNIT_DATA=${data + "/unit/libstore/data"}
+        nix-store-tests
+        touch $out
+      '';
+    };
+  };
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libstore/path-info.cc b/tests/unit/libstore/path-info.cc
index 80d6fcfed20..7637cb366aa 100644
--- a/tests/unit/libstore/path-info.cc
+++ b/tests/unit/libstore/path-info.cc
@@ -19,12 +19,20 @@ class PathInfoTest : public CharacterizationTest, public LibStoreTest
     }
 };
 
-static UnkeyedValidPathInfo makePathInfo(const Store & store, bool includeImpureInfo) {
+static UnkeyedValidPathInfo makeEmpty()
+{
+    return {
+        Hash::parseSRI("sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc="),
+    };
+}
+
+static UnkeyedValidPathInfo makeFull(const Store & store, bool includeImpureInfo)
+{
     UnkeyedValidPathInfo info = ValidPathInfo {
         store,
         "foo",
         FixedOutputInfo {
-            .method = FileIngestionMethod::Recursive,
+            .method = FileIngestionMethod::NixArchive,
             .hash = hashString(HashAlgorithm::SHA256, "(...)"),
 
             .references = {
@@ -50,22 +58,21 @@ static UnkeyedValidPathInfo makePathInfo(const Store & store, bool includeImpure
     return info;
 }
 
-#define JSON_TEST(STEM, PURE)                                             \
+#define JSON_TEST(STEM, OBJ, PURE)                                        \
     TEST_F(PathInfoTest, PathInfo_ ## STEM ## _from_json) {               \
         readTest(#STEM, [&](const auto & encoded_) {                      \
             auto encoded = json::parse(encoded_);                         \
             UnkeyedValidPathInfo got = UnkeyedValidPathInfo::fromJSON(    \
                 *store,                                                   \
                 encoded);                                                 \
-            auto expected = makePathInfo(*store, PURE);                   \
+            auto expected = OBJ;                                          \
             ASSERT_EQ(got, expected);                                     \
         });                                                               \
     }                                                                     \
                                                                           \
     TEST_F(PathInfoTest, PathInfo_ ## STEM ## _to_json) {                 \
         writeTest(#STEM, [&]() -> json {                                  \
-            return makePathInfo(*store, PURE)                             \
-                .toJSON(*store, PURE, HashFormat::SRI);                   \
+            return OBJ.toJSON(*store, PURE, HashFormat::SRI);             \
         }, [](const auto & file) {                                        \
             return json::parse(readFile(file));                           \
         }, [](const auto & file, const auto & got) {                      \
@@ -73,7 +80,10 @@ static UnkeyedValidPathInfo makePathInfo(const Store & store, bool includeImpure
         });                                                               \
     }
 
-JSON_TEST(pure, false)
-JSON_TEST(impure, true)
+JSON_TEST(empty_pure, makeEmpty(), false)
+JSON_TEST(empty_impure, makeEmpty(), true)
+
+JSON_TEST(pure, makeFull(*store, false), false)
+JSON_TEST(impure, makeFull(*store, true), true)
 
 }
diff --git a/tests/unit/libstore/path.cc b/tests/unit/libstore/path.cc
index 213b6e95f52..c4c055abf0c 100644
--- a/tests/unit/libstore/path.cc
+++ b/tests/unit/libstore/path.cc
@@ -26,10 +26,19 @@ static std::regex nameRegex { std::string { nameRegexStr } };
     TEST_F(StorePathTest, bad_ ## NAME) {                    \
         std::string_view str =                               \
             STORE_DIR HASH_PART "-" STR;                     \
-        ASSERT_THROW(                                        \
-            store->parseStorePath(str),                      \
-            BadStorePath);                                   \
+        /* ASSERT_THROW generates a duplicate goto label */  \
+        /* A lambda isolates those labels. */                \
+        [&](){                                               \
+            ASSERT_THROW(                                    \
+                store->parseStorePath(str),                  \
+                BadStorePath);                               \
+        }();                                                 \
         std::string name { STR };                            \
+        [&](){                                               \
+            ASSERT_THROW(                                    \
+                nix::checkName(name),                        \
+                BadStorePathName);                           \
+        }();                                                 \
         EXPECT_FALSE(std::regex_match(name, nameRegex));     \
     }
 
@@ -54,6 +63,7 @@ TEST_DONT_PARSE(dot_dash_a, ".-a")
             STORE_DIR HASH_PART "-" STR;                     \
         auto p = store->parseStorePath(str);                 \
         std::string name { p.name() };                       \
+        EXPECT_EQ(p.name(), STR);                            \
         EXPECT_TRUE(std::regex_match(name, nameRegex));      \
     }
 
diff --git a/tests/unit/libstore/serve-protocol.cc b/tests/unit/libstore/serve-protocol.cc
index b2fd0fb8248..2505c5a9a42 100644
--- a/tests/unit/libstore/serve-protocol.cc
+++ b/tests/unit/libstore/serve-protocol.cc
@@ -6,6 +6,7 @@
 
 #include "serve-protocol.hh"
 #include "serve-protocol-impl.hh"
+#include "serve-protocol-connection.hh"
 #include "build-result.hh"
 #include "file-descriptor.hh"
 #include "tests/protocol.hh"
@@ -54,15 +55,15 @@ VERSIONED_CHARACTERIZATION_TEST(
     defaultVersion,
     (std::tuple<ContentAddress, ContentAddress, ContentAddress> {
         ContentAddress {
-            .method = TextIngestionMethod {},
+            .method = ContentAddressMethod::Raw::Text,
             .hash = hashString(HashAlgorithm::SHA256, "Derive(...)"),
         },
         ContentAddress {
-            .method = FileIngestionMethod::Flat,
+            .method = ContentAddressMethod::Raw::Flat,
             .hash = hashString(HashAlgorithm::SHA1, "blob blob..."),
         },
         ContentAddress {
-            .method = FileIngestionMethod::Recursive,
+            .method = ContentAddressMethod::Raw::NixArchive,
             .hash = hashString(HashAlgorithm::SHA256, "(...)"),
         },
     }))
@@ -279,7 +280,7 @@ VERSIONED_CHARACTERIZATION_TEST(
                 *LibStoreTest::store,
                 "foo",
                 FixedOutputInfo {
-                    .method = FileIngestionMethod::Recursive,
+                    .method = FileIngestionMethod::NixArchive,
                     .hash = hashString(HashAlgorithm::SHA256, "(...)"),
                     .references = {
                         .others = {
@@ -397,7 +398,7 @@ VERSIONED_CHARACTERIZATION_TEST(
         std::nullopt,
         std::optional {
             ContentAddress {
-                .method = FileIngestionMethod::Flat,
+                .method = ContentAddressMethod::Raw::Flat,
                 .hash = hashString(HashAlgorithm::SHA1, "blob blob..."),
             },
         },
@@ -505,7 +506,8 @@ TEST_F(ServeProtoTest, handshake_client_corrupted_throws)
             } else {
                 auto ver = ServeProto::BasicClientConnection::handshake(
                     nullSink, in, defaultVersion, "blah");
-                EXPECT_NE(ver, defaultVersion);
+                // `std::min` of this and the other version saves us
+                EXPECT_EQ(ver, defaultVersion);
             }
         }
     });
diff --git a/tests/unit/libstore/store-reference.cc b/tests/unit/libstore/store-reference.cc
new file mode 100644
index 00000000000..052cd7beddd
--- /dev/null
+++ b/tests/unit/libstore/store-reference.cc
@@ -0,0 +1,123 @@
+#include <nlohmann/json.hpp>
+#include <gtest/gtest.h>
+
+#include "file-system.hh"
+#include "store-reference.hh"
+
+#include "tests/characterization.hh"
+#include "tests/libstore.hh"
+
+namespace nix {
+
+using nlohmann::json;
+
+class StoreReferenceTest : public CharacterizationTest, public LibStoreTest
+{
+    Path unitTestData = getUnitTestData() + "/store-reference";
+
+    Path goldenMaster(PathView testStem) const override
+    {
+        return unitTestData + "/" + testStem + ".txt";
+    }
+};
+
+#define URI_TEST_READ(STEM, OBJ)                                \
+    TEST_F(StoreReferenceTest, PathInfo_##STEM##_from_uri)      \
+    {                                                           \
+        readTest(#STEM, ([&](const auto & encoded) {            \
+                     StoreReference expected = OBJ;             \
+                     auto got = StoreReference::parse(encoded); \
+                     ASSERT_EQ(got, expected);                  \
+                 }));                                           \
+    }
+
+#define URI_TEST_WRITE(STEM, OBJ)                                                               \
+    TEST_F(StoreReferenceTest, PathInfo_##STEM##_to_uri)                                        \
+    {                                                                                           \
+        writeTest(                                                                              \
+            #STEM,                                                                              \
+            [&]() -> StoreReference { return OBJ; },                                            \
+            [](const auto & file) { return StoreReference::parse(readFile(file)); },            \
+            [](const auto & file, const auto & got) { return writeFile(file, got.render()); }); \
+    }
+
+#define URI_TEST(STEM, OBJ)  \
+    URI_TEST_READ(STEM, OBJ) \
+    URI_TEST_WRITE(STEM, OBJ)
+
+URI_TEST(
+    auto,
+    (StoreReference{
+        .variant = StoreReference::Auto{},
+        .params = {},
+    }))
+
+URI_TEST(
+    auto_param,
+    (StoreReference{
+        .variant = StoreReference::Auto{},
+        .params =
+            {
+                {"root", "/foo/bar/baz"},
+            },
+    }))
+
+static StoreReference localExample_1{
+    .variant =
+        StoreReference::Specified{
+            .scheme = "local",
+        },
+    .params =
+        {
+            {"root", "/foo/bar/baz"},
+        },
+};
+
+static StoreReference localExample_2{
+    .variant =
+        StoreReference::Specified{
+            .scheme = "local",
+            .authority = "/foo/bar/baz",
+        },
+    .params =
+        {
+            {"trusted", "true"},
+        },
+};
+
+URI_TEST(local_1, localExample_1)
+
+URI_TEST(local_2, localExample_2)
+
+URI_TEST_READ(local_shorthand_1, localExample_1)
+
+URI_TEST_READ(local_shorthand_2, localExample_2)
+
+static StoreReference unixExample{
+    .variant =
+        StoreReference::Specified{
+            .scheme = "unix",
+        },
+    .params =
+        {
+            {"max-connections", "7"},
+            {"trusted", "true"},
+        },
+};
+
+URI_TEST(unix, unixExample)
+
+URI_TEST_READ(unix_shorthand, unixExample)
+
+URI_TEST(
+    ssh,
+    (StoreReference{
+        .variant =
+            StoreReference::Specified{
+                .scheme = "ssh",
+                .authority = "localhost",
+            },
+        .params = {},
+    }))
+
+}
diff --git a/tests/unit/libstore/worker-protocol.cc b/tests/unit/libstore/worker-protocol.cc
index 2b2e559a96a..c1512001093 100644
--- a/tests/unit/libstore/worker-protocol.cc
+++ b/tests/unit/libstore/worker-protocol.cc
@@ -1,9 +1,11 @@
 #include <regex>
+#include <thread>
 
 #include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
 
 #include "worker-protocol.hh"
+#include "worker-protocol-connection.hh"
 #include "worker-protocol-impl.hh"
 #include "derived-path.hh"
 #include "build-result.hh"
@@ -18,9 +20,9 @@ struct WorkerProtoTest : VersionedProtoTest<WorkerProto, workerProtoDir>
 {
     /**
      * For serializers that don't care about the minimum version, we
-     * used the oldest one: 1.0.
+     * used the oldest one: 1.10.
      */
-    WorkerProto::Version defaultVersion = 1 << 8 | 0;
+    WorkerProto::Version defaultVersion = 1 << 8 | 10;
 };
 
 
@@ -54,15 +56,15 @@ VERSIONED_CHARACTERIZATION_TEST(
     defaultVersion,
     (std::tuple<ContentAddress, ContentAddress, ContentAddress> {
         ContentAddress {
-            .method = TextIngestionMethod {},
+            .method = ContentAddressMethod::Raw::Text,
             .hash = hashString(HashAlgorithm::SHA256, "Derive(...)"),
         },
         ContentAddress {
-            .method = FileIngestionMethod::Flat,
+            .method = ContentAddressMethod::Raw::Flat,
             .hash = hashString(HashAlgorithm::SHA1, "blob blob..."),
         },
         ContentAddress {
-            .method = FileIngestionMethod::Recursive,
+            .method = ContentAddressMethod::Raw::NixArchive,
             .hash = hashString(HashAlgorithm::SHA256, "(...)"),
         },
     }))
@@ -510,7 +512,7 @@ VERSIONED_CHARACTERIZATION_TEST(
                 *LibStoreTest::store,
                 "foo",
                 FixedOutputInfo {
-                    .method = FileIngestionMethod::Recursive,
+                    .method = FileIngestionMethod::NixArchive,
                     .hash = hashString(HashAlgorithm::SHA256, "(...)"),
                     .references = {
                         .others = {
@@ -529,6 +531,17 @@ VERSIONED_CHARACTERIZATION_TEST(
         }),
     }))
 
+VERSIONED_CHARACTERIZATION_TEST(
+    WorkerProtoTest,
+    buildMode,
+    "build-mode",
+    defaultVersion,
+    (std::tuple<BuildMode, BuildMode, BuildMode> {
+        bmNormal,
+        bmRepair,
+        bmCheck,
+    }))
+
 VERSIONED_CHARACTERIZATION_TEST(
     WorkerProtoTest,
     optionalTrustedFlag,
@@ -585,10 +598,158 @@ VERSIONED_CHARACTERIZATION_TEST(
         std::nullopt,
         std::optional {
             ContentAddress {
-                .method = FileIngestionMethod::Flat,
+                .method = ContentAddressMethod::Raw::Flat,
                 .hash = hashString(HashAlgorithm::SHA1, "blob blob..."),
             },
         },
     }))
 
+VERSIONED_CHARACTERIZATION_TEST(
+    WorkerProtoTest,
+    clientHandshakeInfo_1_30,
+    "client-handshake-info_1_30",
+    1 << 8 | 30,
+    (std::tuple<WorkerProto::ClientHandshakeInfo> {
+        {},
+    }))
+
+VERSIONED_CHARACTERIZATION_TEST(
+    WorkerProtoTest,
+    clientHandshakeInfo_1_33,
+    "client-handshake-info_1_33",
+    1 << 8 | 33,
+    (std::tuple<WorkerProto::ClientHandshakeInfo, WorkerProto::ClientHandshakeInfo> {
+        {
+            .daemonNixVersion = std::optional { "foo" },
+        },
+        {
+            .daemonNixVersion = std::optional { "bar" },
+        },
+    }))
+
+VERSIONED_CHARACTERIZATION_TEST(
+    WorkerProtoTest,
+    clientHandshakeInfo_1_35,
+    "client-handshake-info_1_35",
+    1 << 8 | 35,
+    (std::tuple<WorkerProto::ClientHandshakeInfo, WorkerProto::ClientHandshakeInfo> {
+        {
+            .daemonNixVersion = std::optional { "foo" },
+            .remoteTrustsUs = std::optional { NotTrusted },
+        },
+        {
+            .daemonNixVersion = std::optional { "bar" },
+            .remoteTrustsUs = std::optional { Trusted },
+        },
+    }))
+
+TEST_F(WorkerProtoTest, handshake_log)
+{
+    CharacterizationTest::writeTest("handshake-to-client", [&]() -> std::string {
+        StringSink toClientLog;
+
+        Pipe toClient, toServer;
+        toClient.create();
+        toServer.create();
+
+        WorkerProto::Version clientResult;
+
+        auto thread = std::thread([&]() {
+            FdSink out { toServer.writeSide.get() };
+            FdSource in0 { toClient.readSide.get() };
+            TeeSource in { in0, toClientLog };
+            clientResult = WorkerProto::BasicClientConnection::handshake(
+                out, in, defaultVersion);
+        });
+
+        {
+            FdSink out { toClient.writeSide.get() };
+            FdSource in { toServer.readSide.get() };
+            WorkerProto::BasicServerConnection::handshake(
+                out, in, defaultVersion);
+        };
+
+        thread.join();
+
+        return std::move(toClientLog.s);
+    });
+}
+
+/// Has to be a `BufferedSink` for handshake.
+struct NullBufferedSink : BufferedSink {
+    void writeUnbuffered(std::string_view data) override { }
+};
+
+TEST_F(WorkerProtoTest, handshake_client_replay)
+{
+    CharacterizationTest::readTest("handshake-to-client", [&](std::string toClientLog) {
+        NullBufferedSink nullSink;
+
+        StringSource in { toClientLog };
+        auto clientResult = WorkerProto::BasicClientConnection::handshake(
+            nullSink, in, defaultVersion);
+
+        EXPECT_EQ(clientResult, defaultVersion);
+    });
+}
+
+TEST_F(WorkerProtoTest, handshake_client_truncated_replay_throws)
+{
+    CharacterizationTest::readTest("handshake-to-client", [&](std::string toClientLog) {
+        for (size_t len = 0; len < toClientLog.size(); ++len) {
+            NullBufferedSink nullSink;
+            StringSource in {
+                // truncate
+                toClientLog.substr(0, len)
+            };
+            if (len < 8) {
+                EXPECT_THROW(
+                    WorkerProto::BasicClientConnection::handshake(
+                        nullSink, in, defaultVersion),
+                    EndOfFile);
+            } else {
+                // Not sure why cannot keep on checking for `EndOfFile`.
+                EXPECT_THROW(
+                    WorkerProto::BasicClientConnection::handshake(
+                        nullSink, in, defaultVersion),
+                    Error);
+            }
+        }
+    });
+}
+
+TEST_F(WorkerProtoTest, handshake_client_corrupted_throws)
+{
+    CharacterizationTest::readTest("handshake-to-client", [&](const std::string toClientLog) {
+        for (size_t idx = 0; idx < toClientLog.size(); ++idx) {
+            // corrupt a copy
+            std::string toClientLogCorrupt = toClientLog;
+            toClientLogCorrupt[idx] *= 4;
+            ++toClientLogCorrupt[idx];
+
+            NullBufferedSink nullSink;
+            StringSource in { toClientLogCorrupt };
+
+            if (idx < 4 || idx == 9) {
+                // magic bytes don't match
+                EXPECT_THROW(
+                    WorkerProto::BasicClientConnection::handshake(
+                        nullSink, in, defaultVersion),
+                    Error);
+            } else if (idx < 8 || idx >= 12) {
+                // Number out of bounds
+                EXPECT_THROW(
+                    WorkerProto::BasicClientConnection::handshake(
+                        nullSink, in, defaultVersion),
+                    SerialisationError);
+            } else {
+                auto ver = WorkerProto::BasicClientConnection::handshake(
+                    nullSink, in, defaultVersion);
+                // `std::min` of this and the other version saves us
+                EXPECT_EQ(ver, defaultVersion);
+            }
+        }
+    });
+}
+
 }
diff --git a/tests/unit/libutil-support/.version b/tests/unit/libutil-support/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libutil-support/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libutil-support/build-utils-meson b/tests/unit/libutil-support/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libutil-support/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libutil-support/meson.build b/tests/unit/libutil-support/meson.build
new file mode 100644
index 00000000000..7d0e9c2fc30
--- /dev/null
+++ b/tests/unit/libutil-support/meson.build
@@ -0,0 +1,70 @@
+project('nix-util-test-support', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+]
+subdir('build-utils-meson/subprojects')
+
+rapidcheck = dependency('rapidcheck')
+deps_public += rapidcheck
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'tests/hash.cc',
+  'tests/string_callback.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = files(
+  'tests/characterization.hh',
+  'tests/hash.hh',
+  'tests/nix_api_util.hh',
+  'tests/string_callback.hh',
+)
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nix-util-test-support',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: Remove `-lrapidcheck` when https://github.com/emil-e/rapidcheck/pull/326
+  #       is available. See also ../libutil/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')
diff --git a/tests/unit/libutil-support/package.nix b/tests/unit/libutil-support/package.nix
new file mode 100644
index 00000000000..fdecdec7226
--- /dev/null
+++ b/tests/unit/libutil-support/package.nix
@@ -0,0 +1,79 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+
+, rapidcheck
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util-test-support";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-util
+    rapidcheck
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libutil-support/tests/characterization.hh b/tests/unit/libutil-support/tests/characterization.hh
index 9d6c850f017..19ba824ac74 100644
--- a/tests/unit/libutil-support/tests/characterization.hh
+++ b/tests/unit/libutil-support/tests/characterization.hh
@@ -5,6 +5,7 @@
 
 #include "types.hh"
 #include "environment-variables.hh"
+#include "file-system.hh"
 
 namespace nix {
 
@@ -12,7 +13,7 @@ namespace nix {
  * The path to the unit test data directory. See the contributing guide
  * in the manual for further details.
  */
-static Path getUnitTestData() {
+static inline Path getUnitTestData() {
     return getEnv("_NIX_TEST_UNIT_DATA").value();
 }
 
@@ -21,7 +22,7 @@ static Path getUnitTestData() {
  * against them. See the contributing guide in the manual for further
  * details.
  */
-static bool testAccept() {
+static inline bool testAccept() {
     return getEnv("_NIX_TEST_ACCEPT") == "1";
 }
 
diff --git a/tests/unit/libutil-support/tests/nix_api_util.hh b/tests/unit/libutil-support/tests/nix_api_util.hh
index 75d302bd6d8..efd2001167d 100644
--- a/tests/unit/libutil-support/tests/nix_api_util.hh
+++ b/tests/unit/libutil-support/tests/nix_api_util.hh
@@ -24,7 +24,9 @@ protected:
 
     nix_c_context * ctx;
 
-    inline void assert_ctx_ok() {
+    inline void assert_ctx_ok()
+    {
+
         if (nix_err_code(ctx) == NIX_OK) {
             return;
         }
@@ -33,5 +35,14 @@ protected:
         std::string msg(p, n);
         FAIL() << "nix_err_code(ctx) != NIX_OK, message: " << msg;
     }
+
+    inline void assert_ctx_err()
+    {
+        if (nix_err_code(ctx) != NIX_OK) {
+            return;
+        }
+        FAIL() << "Got NIX_OK, but expected an error!";
+    }
 };
+
 }
diff --git a/tests/unit/libutil-support/tests/string_callback.hh b/tests/unit/libutil-support/tests/string_callback.hh
index 3a3e545e9d4..a02ea3a1b69 100644
--- a/tests/unit/libutil-support/tests/string_callback.hh
+++ b/tests/unit/libutil-support/tests/string_callback.hh
@@ -11,6 +11,6 @@ inline void * observe_string_cb_data(std::string & out)
 };
 
 #define OBSERVE_STRING(str) \
-  (nix_get_string_callback) nix::testing::observe_string_cb, nix::testing::observe_string_cb_data(str)
+    (nix_get_string_callback) nix::testing::observe_string_cb, nix::testing::observe_string_cb_data(str)
 
 }
diff --git a/tests/unit/libutil/.version b/tests/unit/libutil/.version
new file mode 120000
index 00000000000..0df9915bfaa
--- /dev/null
+++ b/tests/unit/libutil/.version
@@ -0,0 +1 @@
+../../../.version
\ No newline at end of file
diff --git a/tests/unit/libutil/build-utils-meson b/tests/unit/libutil/build-utils-meson
new file mode 120000
index 00000000000..f2d8e8a5093
--- /dev/null
+++ b/tests/unit/libutil/build-utils-meson
@@ -0,0 +1 @@
+../../../build-utils-meson/
\ No newline at end of file
diff --git a/tests/unit/libutil/file-content-address.cc b/tests/unit/libutil/file-content-address.cc
index 294e3980683..27d926a8736 100644
--- a/tests/unit/libutil/file-content-address.cc
+++ b/tests/unit/libutil/file-content-address.cc
@@ -11,7 +11,7 @@ namespace nix {
 TEST(FileSerialisationMethod, testRoundTripPrintParse_1) {
     for (const FileSerialisationMethod fim : {
         FileSerialisationMethod::Flat,
-        FileSerialisationMethod::Recursive,
+        FileSerialisationMethod::NixArchive,
     }) {
         EXPECT_EQ(parseFileSerialisationMethod(renderFileSerialisationMethod(fim)), fim);
     }
@@ -37,7 +37,7 @@ TEST(FileSerialisationMethod, testParseFileSerialisationMethodOptException) {
 TEST(FileIngestionMethod, testRoundTripPrintParse_1) {
     for (const FileIngestionMethod fim : {
         FileIngestionMethod::Flat,
-        FileIngestionMethod::Recursive,
+        FileIngestionMethod::NixArchive,
         FileIngestionMethod::Git,
     }) {
         EXPECT_EQ(parseFileIngestionMethod(renderFileIngestionMethod(fim)), fim);
diff --git a/tests/unit/libutil/git.cc b/tests/unit/libutil/git.cc
index 4f92488d68f..a0125d023ba 100644
--- a/tests/unit/libutil/git.cc
+++ b/tests/unit/libutil/git.cc
@@ -67,7 +67,7 @@ TEST_F(GitTest, blob_read) {
         StringSink out;
         RegularFileSink out2 { out };
         ASSERT_EQ(parseObjectType(in, mockXpSettings), ObjectType::Blob);
-        parseBlob(out2, "", in, BlobMode::Regular, mockXpSettings);
+        parseBlob(out2, CanonPath::root, in, BlobMode::Regular, mockXpSettings);
 
         auto expected = readFile(goldenMaster("hello-world.bin"));
 
@@ -132,8 +132,8 @@ TEST_F(GitTest, tree_read) {
         NullFileSystemObjectSink out;
         Tree got;
         ASSERT_EQ(parseObjectType(in, mockXpSettings), ObjectType::Tree);
-        parseTree(out, "", in, [&](auto & name, auto entry) {
-            auto name2 = name;
+        parseTree(out, CanonPath::root, in, [&](auto & name, auto entry) {
+            auto name2 = std::string{name.rel()};
             if (entry.mode == Mode::Directory)
                 name2 += '/';
             got.insert_or_assign(name2, std::move(entry));
@@ -154,8 +154,8 @@ TEST_F(GitTest, tree_write) {
 TEST_F(GitTest, both_roundrip) {
     using File = MemorySourceAccessor::File;
 
-    MemorySourceAccessor files;
-    files.root = File::Directory {
+    auto files = make_ref<MemorySourceAccessor>();
+    files->root = File::Directory {
         .contents {
             {
                 "foo",
@@ -189,12 +189,12 @@ TEST_F(GitTest, both_roundrip) {
     std::map<Hash, std::string> cas;
 
     std::function<DumpHook> dumpHook;
-    dumpHook = [&](const CanonPath & path) {
+    dumpHook = [&](const SourcePath & path) {
         StringSink s;
         HashSink hashSink { HashAlgorithm::SHA1 };
         TeeSink s2 { s, hashSink };
         auto mode = dump(
-            files, path, s2, dumpHook,
+            path, s2, dumpHook,
             defaultPathFilter, mockXpSettings);
         auto hash = hashSink.finish().first;
         cas.insert_or_assign(hash, std::move(s.s));
@@ -204,20 +204,20 @@ TEST_F(GitTest, both_roundrip) {
         };
     };
 
-    auto root = dumpHook(CanonPath::root);
+    auto root = dumpHook({files});
 
-    MemorySourceAccessor files2;
+    auto files2 = make_ref<MemorySourceAccessor>();
 
-    MemorySink sinkFiles2 { files2 };
+    MemorySink sinkFiles2 { *files2 };
 
-    std::function<void(const Path, const Hash &, BlobMode)> mkSinkHook;
+    std::function<void(const CanonPath, const Hash &, BlobMode)> mkSinkHook;
     mkSinkHook = [&](auto prefix, auto & hash, auto blobMode) {
         StringSource in { cas[hash] };
         parse(
             sinkFiles2, prefix, in, blobMode,
-            [&](const Path & name, const auto & entry) {
+            [&](const CanonPath & name, const auto & entry) {
                 mkSinkHook(
-                    prefix + "/" + name,
+                    prefix / name,
                     entry.hash,
                     // N.B. this cast would not be acceptable in real
                     // code, because it would make an assert reachable,
@@ -227,9 +227,9 @@ TEST_F(GitTest, both_roundrip) {
             mockXpSettings);
     };
 
-    mkSinkHook("", root.hash, BlobMode::Regular);
+    mkSinkHook(CanonPath::root, root.hash, BlobMode::Regular);
 
-    ASSERT_EQ(files, files2);
+    ASSERT_EQ(*files, *files2);
 }
 
 TEST(GitLsRemote, parseSymrefLineWithReference) {
diff --git a/tests/unit/libutil/json-utils.cc b/tests/unit/libutil/json-utils.cc
index ec653fff529..704a4acb05d 100644
--- a/tests/unit/libutil/json-utils.cc
+++ b/tests/unit/libutil/json-utils.cc
@@ -169,7 +169,22 @@ TEST(optionalValueAt, existing) {
 TEST(optionalValueAt, empty) {
     auto json = R"({})"_json;
 
-    ASSERT_EQ(optionalValueAt(json, "string2"), std::nullopt);
+    ASSERT_EQ(optionalValueAt(json, "string"), std::nullopt);
+}
+
+TEST(getNullable, null) {
+    auto json = R"(null)"_json;
+
+    ASSERT_EQ(getNullable(json), nullptr);
+}
+
+TEST(getNullable, empty) {
+    auto json = R"({})"_json;
+
+    auto * p = getNullable(json);
+
+    ASSERT_NE(p, nullptr);
+    ASSERT_EQ(*p, R"({})"_json);
 }
 
 } /* namespace nix */
diff --git a/tests/unit/libutil/local.mk b/tests/unit/libutil/local.mk
index 39b4c0782c4..404f35cf1ac 100644
--- a/tests/unit/libutil/local.mk
+++ b/tests/unit/libutil/local.mk
@@ -4,7 +4,7 @@ programs += libutil-tests
 
 libutil-tests_NAME = libnixutil-tests
 
-libutil-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data
+libutil-tests_ENV := _NIX_TEST_UNIT_DATA=$(d)/data GTEST_OUTPUT=xml:$$testresults/libutil-tests.xml
 
 libutil-tests_DIR := $(d)
 
@@ -27,6 +27,11 @@ libutil-tests_LIBS = libutil-test-support libutil libutilc
 
 libutil-tests_LDFLAGS := -lrapidcheck $(GTEST_LIBS)
 
+ifdef HOST_WINDOWS
+  # Increase the default reserved stack size to 65 MB so Nix doesn't run out of space
+  libutil-tests_LDFLAGS += -Wl,--stack,$(shell echo $$((65 * 1024 * 1024)))
+endif
+
 check: $(d)/data/git/check-data.sh.test
 
 $(eval $(call run-test,$(d)/data/git/check-data.sh))
diff --git a/tests/unit/libutil/meson.build b/tests/unit/libutil/meson.build
new file mode 100644
index 00000000000..4f055cabda0
--- /dev/null
+++ b/tests/unit/libutil/meson.build
@@ -0,0 +1,91 @@
+project('nix-util-tests', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-util-c'),
+  dependency('nix-util-test-support'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/export-all-symbols')
+
+rapidcheck = dependency('rapidcheck')
+deps_private += rapidcheck
+
+gtest = dependency('gtest', main : true)
+deps_private += gtest
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-util.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'args.cc',
+  'canon-path.cc',
+  'chunked-vector.cc',
+  'closure.cc',
+  'compression.cc',
+  'config.cc',
+  'file-content-address.cc',
+  'git.cc',
+  'hash.cc',
+  'hilite.cc',
+  'json-utils.cc',
+  'logging.cc',
+  'lru-cache.cc',
+  'nix_api_util.cc',
+  'pool.cc',
+  'references.cc',
+  'spawn.cc',
+  'suggestions.cc',
+  'tests.cc',
+  'url.cc',
+  'xml-writer.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: -lrapidcheck, see ../libutil-support/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  # get main from gtest
+  install : true,
+)
+
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)
diff --git a/tests/unit/libutil/nix_api_util.cc b/tests/unit/libutil/nix_api_util.cc
index d2999f55b39..2b7e3822525 100644
--- a/tests/unit/libutil/nix_api_util.cc
+++ b/tests/unit/libutil/nix_api_util.cc
@@ -1,4 +1,4 @@
-#include "config.hh"
+#include "config-global.hh"
 #include "args.hh"
 #include "nix_api_util.h"
 #include "nix_api_util_internal.h"
diff --git a/tests/unit/libutil/package.nix b/tests/unit/libutil/package.nix
new file mode 100644
index 00000000000..ad5ff7d1e83
--- /dev/null
+++ b/tests/unit/libutil/package.nix
@@ -0,0 +1,98 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+, nix-util-c
+, nix-util-test-support
+
+, rapidcheck
+, gtest
+, runCommand
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util-tests";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../../build-utils-meson
+    ./build-utils-meson
+    ../../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  buildInputs = [
+    nix-util
+    nix-util-c
+    nix-util-test-support
+    rapidcheck
+    gtest
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  enableParallelBuilding = true;
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  strictDeps = true;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  passthru = {
+    tests = {
+      run = runCommand "${finalAttrs.pname}-run" {
+      } ''
+        PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
+        export _NIX_TEST_UNIT_DATA=${./data}
+        nix-util-tests
+        touch $out
+      '';
+    };
+  };
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})
diff --git a/tests/unit/libutil/spawn.cc b/tests/unit/libutil/spawn.cc
new file mode 100644
index 00000000000..c617acae08e
--- /dev/null
+++ b/tests/unit/libutil/spawn.cc
@@ -0,0 +1,36 @@
+#include <gtest/gtest.h>
+
+#include "processes.hh"
+
+namespace nix {
+
+#ifdef _WIN32
+TEST(SpawnTest, spawnEcho)
+{
+    auto output = runProgram(RunOptions{.program = "cmd.exe", .args = {"/C", "echo", "hello world"}});
+    ASSERT_EQ(output.first, 0);
+    ASSERT_EQ(output.second, "\"hello world\"\r\n");
+}
+
+std::string windowsEscape(const std::string & str, bool cmd);
+
+TEST(SpawnTest, windowsEscape)
+{
+    auto empty = windowsEscape("", false);
+    ASSERT_EQ(empty, R"("")");
+    // There's no quotes in this argument so the input should equal the output
+    auto backslashStr = R"(\\\\)";
+    auto backslashes = windowsEscape(backslashStr, false);
+    ASSERT_EQ(backslashes, backslashStr);
+
+    auto nestedQuotes = windowsEscape(R"(he said: "hello there")", false);
+    ASSERT_EQ(nestedQuotes, R"("he said: \"hello there\"")");
+
+    auto middleQuote = windowsEscape(R"( \\\" )", false);
+    ASSERT_EQ(middleQuote, R"(" \\\\\\\" ")");
+
+    auto space = windowsEscape("hello world", false);
+    ASSERT_EQ(space, R"("hello world")");
+}
+#endif
+}
diff --git a/tests/unit/libutil/tests.cc b/tests/unit/libutil/tests.cc
index b66872a6e3c..9be4a400d02 100644
--- a/tests/unit/libutil/tests.cc
+++ b/tests/unit/libutil/tests.cc
@@ -421,6 +421,23 @@ namespace nix {
         ASSERT_EQ(string2Int<int>("-100"), -100);
     }
 
+    /* ----------------------------------------------------------------------------
+     * renderSize
+     * --------------------------------------------------------------------------*/
+
+    TEST(renderSize, misc) {
+        ASSERT_EQ(renderSize(0, true), "   0.0 KiB");
+        ASSERT_EQ(renderSize(100, true), "   0.1 KiB");
+        ASSERT_EQ(renderSize(100), "0.1 KiB");
+        ASSERT_EQ(renderSize(972, true), "   0.9 KiB");
+        ASSERT_EQ(renderSize(973, true), "   1.0 KiB"); // FIXME: should round down
+        ASSERT_EQ(renderSize(1024, true), "   1.0 KiB");
+        ASSERT_EQ(renderSize(1024 * 1024, true), "1024.0 KiB");
+        ASSERT_EQ(renderSize(1100 * 1024, true), "   1.1 MiB");
+        ASSERT_EQ(renderSize(2ULL * 1024 * 1024 * 1024, true), "   2.0 GiB");
+        ASSERT_EQ(renderSize(2100ULL * 1024 * 1024 * 1024, true), "   2.1 TiB");
+    }
+
 #ifndef _WIN32 // TODO re-enable on Windows, once we can start processes
     /* ----------------------------------------------------------------------------
      * statusOk