diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0b72c61ac2f..9e5445eb6ad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -205,7 +205,9 @@ jobs:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@main
       - uses: DeterminateSystems/magic-nix-cache-action@main
-      - run: nix build -L .#hydraJobs.build.{nix-fetchers,nix-store,nix-util}.$(nix-instantiate --eval --expr builtins.currentSystem | sed -e 's/"//g')
+      # Only meson packages that don't have a tests.run derivation.
+      # Those that have it are already built and tested as part of nix flake check.
+      - run: nix build -L .#hydraJobs.build.{nix-cmd,nix-main}.$(nix-instantiate --eval --expr builtins.currentSystem | sed -e 's/"//g')
 
   flake_regressions:
     needs: vm_tests
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/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/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/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/src/SUMMARY.md.in b/doc/manual/src/SUMMARY.md.in
index 6e5c1aee17a..a6a2101e9af 100644
--- a/doc/manual/src/SUMMARY.md.in
+++ b/doc/manual/src/SUMMARY.md.in
@@ -32,11 +32,10 @@
     - [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)
diff --git a/doc/manual/src/_redirects b/doc/manual/src/_redirects
index c52ca0dddfa..578c48f06f1 100644
--- a/doc/manual/src/_redirects
+++ b/doc/manual/src/_redirects
@@ -29,6 +29,7 @@
 /expressions/* /language/:splat 301!
 /language/values /language/types 301!
 /language/constructs /language/syntax 301!
+/language/builtin-constants /language/builtins 301!
 
 /installation/installation /installation 301!
 
diff --git a/doc/manual/src/contributing/hacking.md b/doc/manual/src/contributing/hacking.md
index 08ba84faa53..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.
 
diff --git a/doc/manual/src/contributing/testing.md b/doc/manual/src/contributing/testing.md
index 717deabd71d..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/${library_name_without-nix}`.
-Given an interface (header) and implementation pair in the original library, say, `src/libexpr/value/context.{hh,cc}`, we write tests for it in `tests/unit/libexpr/tests/value/context.cc`, and (possibly) declare/define additional interfaces for testing purposes in `tests/unit/libexpr-support/tests/value/context.{hh,cc}`.
+The tests for each Nix library (`libnixexpr`, `libnixstore`, etc..) live inside a directory `src/${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
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/lookup-path.md b/doc/manual/src/language/constructs/lookup-path.md
index 11278f3a81c..11b9fe88c2a 100644
--- a/doc/manual/src/language/constructs/lookup-path.md
+++ b/doc/manual/src/language/constructs/lookup-path.md
@@ -6,7 +6,7 @@
 
 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 8879fe7069d..8e3f0f79174 100644
--- a/doc/manual/src/language/derivations.md
+++ b/doc/manual/src/language/derivations.md
@@ -64,7 +64,7 @@ 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/types.md#type-path) | [String](@docroot@/language/types.md#type-string))
 
diff --git a/doc/manual/src/language/types.md b/doc/manual/src/language/types.md
index 1b3e6b24793..c6cfb3c6909 100644
--- a/doc/manual/src/language/types.md
+++ b/doc/manual/src/language/types.md
@@ -37,7 +37,7 @@ 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`](builtin-constants.md#builtins-builtins) as [`builtins.true`](builtin-constants.md#builtins-true) and [`builtins.false`](builtin-constants.md#builtins-false).
+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}
@@ -60,7 +60,7 @@ 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`](builtin-constants.md#builtins-builtins) attribute set as [`builtins.null`](builtin-constants.md#builtins-null).
+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
 
diff --git a/flake.nix b/flake.nix
index 582a946c42e..d83c2ecad36 100644
--- a/flake.nix
+++ b/flake.nix
@@ -25,7 +25,6 @@
 
     let
       inherit (nixpkgs) lib;
-      inherit (lib) fileset;
 
       officialRelease = false;
 
@@ -145,9 +144,7 @@
           nix = final.nixComponents.nix;
 
           nix_noTests = final.nix.override {
-            doCheck = false;
             doInstallCheck = false;
-            installUnitTests = false;
           };
 
           # See https://github.com/NixOS/nixpkgs/pull/214409
@@ -207,7 +204,7 @@
           #       https://github.com/NixOS/nixpkgs/issues/320448
           "static-" = nixpkgsFor.${system}.static;
         })
-        (nixpkgsPrefix: nixpkgs: 
+        (nixpkgsPrefix: nixpkgs:
           flatMapAttrs nixpkgs.nixComponents
             (pkgName: pkg:
               flatMapAttrs pkg.tests or {}
@@ -304,8 +301,8 @@
           env = {
             # Needed for Meson to find Boost.
             # https://github.com/NixOS/nixpkgs/issues/86131.
-            BOOST_INCLUDEDIR = "${lib.getDev pkgs.boost}/include";
-            BOOST_LIBRARYDIR = "${lib.getLib pkgs.boost}/lib";
+            BOOST_INCLUDEDIR = "${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}";
@@ -326,6 +323,7 @@
             ++ 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)
@@ -336,6 +334,10 @@
             ++ 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
             ;
         });
diff --git a/meson.build b/meson.build
index 085ac086500..356d978dc8e 100644
--- a/meson.build
+++ b/meson.build
@@ -9,13 +9,29 @@ project('nix-dev-shell', 'cpp',
 subproject('libutil')
 subproject('libstore')
 subproject('libfetchers')
-subproject('perl')
+subproject('libexpr')
+subproject('libflake')
+subproject('libmain')
+subproject('libcmd')
+
+# Docs
 subproject('internal-api-docs')
 subproject('external-api-docs')
 
 # C wrappers
 subproject('libutil-c')
+subproject('libstore-c')
+subproject('libexpr-c')
+
+# Language Bindings
+subproject('perl')
 
 # Testing
-subproject('libutil-test-support')
-subproject('libutil-test')
+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/mk/common-test.sh b/mk/common-test.sh
index c80abd3813a..817422c402d 100644
--- a/mk/common-test.sh
+++ b/mk/common-test.sh
@@ -4,7 +4,7 @@
 # remove file extension.
 
 test_name=$(echo -n "${test?must be defined by caller (test runner)}" | sed \
-    -e "s|^tests/unit/[^/]*/data/||" \
+    -e "s|^src/[^/]*-test/data/||" \
     -e "s|^tests/functional/||" \
     -e "s|\.sh$||" \
     )
diff --git a/package.nix b/package.nix
index 158696f304b..c3e565399e8 100644
--- a/package.nix
+++ b/package.nix
@@ -33,7 +33,7 @@
 , rapidcheck
 , sqlite
 , toml11
-, util-linux
+, unixtools
 , xz
 
 , busybox-sandbox-shell ? null
@@ -175,7 +175,7 @@ in {
           (fileset.difference ./src ./src/perl)
           ./COPYING
           ./scripts/local.mk
-        ] ++ lib.optionals buildUnitTests [
+        ] ++ lib.optionals enableManual [
           ./doc/manual
         ] ++ lib.optionals buildUnitTests [
           ./tests/unit
@@ -213,11 +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 stdenv.hostPlatform.isStatic unixtools.hexdump
   ;
 
   buildInputs = lib.optionals doBuild [
-    boost
     brotli
     bzip2
     curl
@@ -226,10 +225,7 @@ in {
     libsodium
     openssl
     sqlite
-    (toml11.overrideAttrs (old: {
-      # TODO change in Nixpkgs, Windows works fine.
-      meta.platforms = lib.platforms.all;
-    }))
+    toml11
     xz
     ({ inherit readline editline; }.${readlineFlavor})
   ] ++ lib.optionals enableMarkdown [
@@ -248,34 +244,13 @@ 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")
@@ -322,11 +297,6 @@ 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
diff --git a/packaging/components.nix b/packaging/components.nix
index b5e47969e05..f1cd3b9c6d3 100644
--- a/packaging/components.nix
+++ b/packaging/components.nix
@@ -8,21 +8,32 @@ in
   nix = callPackage ../package.nix { };
 
   nix-util = callPackage ../src/libutil/package.nix { };
-
-  nix-util-test-support = callPackage ../tests/unit/libutil-support/package.nix { };
-
-  nix-util-test = callPackage ../tests/unit/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-perl-bindings = callPackage ../src/perl/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-internal-api-docs = callPackage ../src/internal-api-docs/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 { };
 
+  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
index 484385128bb..34b3449718d 100644
--- a/packaging/dependencies.nix
+++ b/packaging/dependencies.nix
@@ -10,12 +10,20 @@
   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
-      root = ../.;
       workDirPath =
         # Ideally we'd pick finalAttrs.workDir, but for now `mkDerivation` has
         # the requirement that everything except passthru and meta must be
@@ -39,6 +47,7 @@ let
 in
 scope: {
   inherit stdenv versionSuffix;
+  version = lib.fileContents ../.version + versionSuffix;
 
   libseccomp = pkgs.libseccomp.overrideAttrs (_: rec {
     version = "2.5.5";
@@ -52,6 +61,19 @@ scope: {
     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;
@@ -83,5 +105,13 @@ scope: {
     '';
   });
 
+  # 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
index a1691ed3898..0bbbc31f77b 100644
--- a/packaging/hydra.nix
+++ b/packaging/hydra.nix
@@ -38,9 +38,21 @@ let
     "nix-util"
     "nix-util-c"
     "nix-util-test-support"
-    "nix-util-test"
+    "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"
   ];
 in
 {
diff --git a/src/external-api-docs/package.nix b/src/external-api-docs/package.nix
index 352698360c5..da136bbe1fc 100644
--- a/src/external-api-docs/package.nix
+++ b/src/external-api-docs/package.nix
@@ -1,5 +1,5 @@
 { lib
-, stdenv
+, mkMesonDerivation
 
 , meson
 , ninja
@@ -7,34 +7,34 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
+, version
 }:
 
 let
   inherit (lib) fileset;
 in
 
-stdenv.mkDerivation (finalAttrs: {
+mkMesonDerivation (finalAttrs: {
   pname = "nix-external-api-docs";
-  version = lib.fileContents ./.version + versionSuffix;
-
-  src = fileset.toSource {
-    root = ../..;
-    fileset =
-      let
-        cpp = fileset.fileFilter (file: file.hasExt "cc" || file.hasExt "h");
-      in
-      fileset.unions [
-        ./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)
-      ];
-  };
+  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
@@ -42,14 +42,10 @@ stdenv.mkDerivation (finalAttrs: {
     doxygen
   ];
 
-  postUnpack = ''
-    sourceRoot=$sourceRoot/src/external-api-docs
-  '';
-
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix
     ''
-      echo ${finalAttrs.version} > .version
+      chmod u+w ./.version
+      echo ${finalAttrs.version} > ./.version
     '';
 
   postInstall = ''
diff --git a/src/internal-api-docs/doxygen.cfg.in b/src/internal-api-docs/doxygen.cfg.in
index 9e74255813c..f1ef75b380d 100644
--- a/src/internal-api-docs/doxygen.cfg.in
+++ b/src/internal-api-docs/doxygen.cfg.in
@@ -38,27 +38,27 @@ GENERATE_LATEX         = NO
 # so they can expand variables despite configure variables.
 
 INPUT                  = \
-  @src@/src/libcmd \
-  @src@/src/libexpr \
-  @src@/src/libexpr/flake \
-  @src@/tests/unit/libexpr \
-  @src@/tests/unit/libexpr/value \
-  @src@/tests/unit/libexpr/test \
-  @src@/tests/unit/libexpr/test/value \
-  @src@/src/libexpr/value \
-  @src@/src/libfetchers \
-  @src@/src/libmain \
-  @src@/src/libstore \
-  @src@/src/libstore/build \
-  @src@/src/libstore/builtins \
-  @src@/tests/unit/libstore \
-  @src@/tests/unit/libstore/test \
-  @src@/src/libutil \
-  @src@/tests/unit/libutil \
-  @src@/tests/unit/libutil/test \
-  @src@/src/nix \
-  @src@/src/nix-env \
-  @src@/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
index 2568c56cf4c..54eb7e5dd47 100644
--- a/src/internal-api-docs/meson.build
+++ b/src/internal-api-docs/meson.build
@@ -12,7 +12,7 @@ doxygen_cfg = configure_file(
   configuration : {
     'PROJECT_NUMBER': meson.project_version(),
     'OUTPUT_DIRECTORY' : meson.current_build_dir(),
-    'src' : fs.parent(fs.parent(meson.project_source_root())),
+    'src' : fs.parent(fs.parent(meson.project_source_root())) / 'src',
   },
 )
 
diff --git a/src/internal-api-docs/package.nix b/src/internal-api-docs/package.nix
index fa54d55f3a7..f2077dcafa4 100644
--- a/src/internal-api-docs/package.nix
+++ b/src/internal-api-docs/package.nix
@@ -1,5 +1,5 @@
 { lib
-, stdenv
+, mkMesonDerivation
 
 , meson
 , ninja
@@ -7,30 +7,29 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
+, version
 }:
 
 let
   inherit (lib) fileset;
 in
 
-stdenv.mkDerivation (finalAttrs: {
+mkMesonDerivation (finalAttrs: {
   pname = "nix-internal-api-docs";
-  version = lib.fileContents ./.version + versionSuffix;
-
-  src = fileset.toSource {
-    root = ../..;
-    fileset = let
-      cpp = fileset.fileFilter (file: file.hasExt "cc" || file.hasExt "hh");
-    in fileset.unions [
-      ./meson.build
-      ./doxygen.cfg.in
-      # Source is not compiled, but still must be available for Doxygen
-      # to gather comments.
-      (cpp ../.)
-      (cpp ../../tests/unit)
-    ];
-  };
+  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
@@ -38,14 +37,10 @@ stdenv.mkDerivation (finalAttrs: {
     doxygen
   ];
 
-  postUnpack = ''
-    sourceRoot=$sourceRoot/src/internal-api-docs
-  '';
-
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix
     ''
-      echo ${finalAttrs.version} > .version
+      chmod u+w ./.version
+      echo ${finalAttrs.version} > ./.version
     '';
 
   postInstall = ''
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/common-eval-args.cc b/src/libcmd/common-eval-args.cc
index 5dced249ad3..37b3905a861 100644
--- a/src/libcmd/common-eval-args.cc
+++ b/src/libcmd/common-eval-args.cc
@@ -11,6 +11,8 @@
 #include "command.hh"
 #include "tarball.hh"
 #include "fetch-to-store.hh"
+#include "compatibility-settings.hh"
+#include "eval-settings.hh"
 
 namespace nix {
 
@@ -33,6 +35,11 @@ EvalSettings evalSettings {
 
 static GlobalConfig::Register rEvalSettings(&evalSettings);
 
+CompatibilitySettings compatibilitySettings {};
+
+static GlobalConfig::Register rCompatibilitySettings(&compatibilitySettings);
+
+
 MixEvalArgs::MixEvalArgs()
 {
     addFlag({
diff --git a/src/libcmd/common-eval-args.hh b/src/libcmd/common-eval-args.hh
index 189abf0ed52..8d303ee7c13 100644
--- a/src/libcmd/common-eval-args.hh
+++ b/src/libcmd/common-eval-args.hh
@@ -13,6 +13,7 @@ namespace nix {
 class Store;
 class EvalState;
 struct EvalSettings;
+struct CompatibilitySettings;
 class Bindings;
 struct SourcePath;
 
@@ -21,6 +22,11 @@ struct SourcePath;
  */
 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";
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/meson.build b/src/libcmd/meson.build
new file mode 100644
index 00000000000..2c8a9fa3374
--- /dev/null
+++ b/src/libcmd/meson.build
@@ -0,0 +1,127 @@
+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-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/network-proxy.cc b/src/libcmd/network-proxy.cc
index 4b7d2441f3f..738bf614729 100644
--- a/src/libcmd/network-proxy.cc
+++ b/src/libcmd/network-proxy.cc
@@ -1,7 +1,6 @@
 #include "network-proxy.hh"
 
 #include <algorithm>
-#include <boost/algorithm/string.hpp>
 
 #include "environment-variables.hh"
 
@@ -13,7 +12,10 @@ static StringSet getAllVariables()
 {
     StringSet variables = lowercaseVariables;
     for (const auto & variable : lowercaseVariables) {
-        variables.insert(boost::to_upper_copy(variable));
+        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;
 }
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 53dd94c7a1d..ce1c5af6997 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -3,7 +3,7 @@
 #include <cstring>
 #include <climits>
 
-#include "libcmd/repl-interacter.hh"
+#include "repl-interacter.hh"
 #include "repl.hh"
 
 #include "ansicolor.hh"
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/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 100%
rename from src/libexpr/flake/call-flake.nix
rename to src/libexpr/call-flake.nix
diff --git a/src/libexpr/eval-settings.hh b/src/libexpr/eval-settings.hh
index 55d83108572..af9725d96c0 100644
--- a/src/libexpr/eval-settings.hh
+++ b/src/libexpr/eval-settings.hh
@@ -72,7 +72,7 @@ struct EvalSettings : Config
         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
 
@@ -93,7 +93,7 @@ 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)
@@ -114,7 +114,7 @@ struct EvalSettings : Config
         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).
         )"};
@@ -125,10 +125,10 @@ 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)
         )"
         };
 
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index a732811d11d..6cbc2e32d1a 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -298,7 +298,7 @@ EvalState::EvalState(
     )}
     , 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)
@@ -2728,7 +2728,7 @@ void EvalState::printStatistics()
 }
 
 
-SourcePath resolveExprPath(SourcePath path)
+SourcePath resolveExprPath(SourcePath path, bool addDefaultNix)
 {
     unsigned int followCount = 0, maxFollow = 1024;
 
@@ -2744,7 +2744,7 @@ SourcePath resolveExprPath(SourcePath path)
     }
 
     /* If `path' refers to a directory, append `/default.nix'. */
-    if (path.resolveSymlinks().lstat().type == SourceAccessor::tDirectory)
+    if (addDefaultNix && path.resolveSymlinks().lstat().type == SourceAccessor::tDirectory)
         return path / "default.nix";
 
     return path;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 31c129be7df..55879aa867d 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -900,8 +900,10 @@ 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/get-drvs.cc b/src/libexpr/get-drvs.cc
index 0d2aecc58f2..8967334237a 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -374,21 +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/local.mk b/src/libexpr/local.mk
index 26958bf2cd6..68518e184b5 100644
--- a/src/libexpr/local.mk
+++ b/src/libexpr/local.mk
@@ -47,4 +47,4 @@ $(foreach i, $(wildcard src/libexpr/value/*.hh), \
 
 $(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 $(d)/flake/call-flake.nix.gen.hh
+$(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..9fe7c17c4e5
--- /dev/null
+++ b/src/libexpr/meson.build
@@ -0,0 +1,204 @@
+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',
+  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',
+)
+
+generated_headers = []
+foreach header : [
+  'imported-drv-to-derivation.nix',
+  'fetchurl.nix',
+  'call-flake.nix',
+]
+  generated_headers += custom_target(
+    command : [ 'bash', '-c', '{ echo \'R"__NIX_STR(\' && cat @INPUT@ && echo \')__NIX_STR"\'; } > "$1"', '_ignored_argv0', '@OUTPUT@' ],
+    input : header,
+    output : '@PLAINNAME@.gen.hh',
+  )
+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/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/primops.cc b/src/libexpr/primops.cc
index 8231d8942be..bd79d08acc8 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1920,7 +1920,7 @@ static RegisterPrimOp primop_findFile(PrimOp {
       - 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>
@@ -4590,7 +4590,7 @@ 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:
 
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 1968df51bc0..e86b934d13d 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"
diff --git a/src/libexpr/primops/meson.build b/src/libexpr/primops/meson.build
new file mode 100644
index 00000000000..96a1dd07ecf
--- /dev/null
+++ b/src/libexpr/primops/meson.build
@@ -0,0 +1,17 @@
+foreach header : [
+  'derivation.nix',
+]
+  generated_headers += custom_target(
+    command : [ 'bash', '-c', '{ echo \'R"__NIX_STR(\' && cat @INPUT@ && echo \')__NIX_STR"\'; } > "$1"', '_ignored_argv0', '@OUTPUT@' ],
+    input : header,
+    output : '@PLAINNAME@.gen.hh',
+  )
+endforeach
+
+sources += files(
+  'context.cc',
+  'fetchClosure.cc',
+  'fetchMercurial.cc',
+  'fetchTree.cc',
+  'fromTOML.cc',
+)
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/fetchers.cc b/src/libfetchers/fetchers.cc
index ae9885c1d96..2b93c5fca37 100644
--- a/src/libfetchers/fetchers.cc
+++ b/src/libfetchers/fetchers.cc
@@ -247,9 +247,8 @@ std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(ref<Store> sto
 
     auto [accessor, final] = scheme->getAccessor(store, *this);
 
-    if (!accessor->fingerprint)
-        // FIXME: remove getFingerprint()?
-        accessor->fingerprint = scheme->getFingerprint(store, final);
+    assert(!accessor->fingerprint);
+    accessor->fingerprint = scheme->getFingerprint(store, final);
 
     return {accessor, std::move(final)};
 }
@@ -384,7 +383,7 @@ namespace nlohmann {
 using namespace nix;
 
 fetchers::PublicKey adl_serializer<fetchers::PublicKey>::from_json(const json & json) {
-    fetchers::PublicKey res = {  };
+    fetchers::PublicKey res = { };
     if (auto type = optionalValueAt(json, "type"))
         res.type = getString(*type);
 
diff --git a/src/libfetchers/meson.build b/src/libfetchers/meson.build
index d7975ac65f7..c39fe99f316 100644
--- a/src/libfetchers/meson.build
+++ b/src/libfetchers/meson.build
@@ -14,62 +14,35 @@ project('nix-fetchers', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-# See note in ../nix-util/meson.build
-deps_private = [ ]
-
-# See note in ../nix-util/meson.build
-deps_public = [ ]
-
-# See note in ../nix-util/meson.build
-deps_other = [ ]
+subdir('build-utils-meson/deps-lists')
 
 configdata = configuration_data()
 
-nix_util = dependency('nix-util')
-if nix_util.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util
-else
-  deps_public += nix_util
-endif
-
-nix_store = dependency('nix-store')
-if nix_store.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_store
-else
-  deps_public += nix_store
-endif
-
+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_public += 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.h',
-  '-include', 'config-store.h',
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
   # '-include', 'config-fetchers.h',
-  '-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`.
-  #
-  # FIXME: remove when we get meson 1.4.0 which will default this to on for us:
-  # https://mesonbuild.com/Release-notes-for-1-4-0.html#ndebug-setting-now-controls-c-stdlib-assertions
-  '-D_GLIBCXX_ASSERTIONS=1',
   language : 'cpp',
 )
 
+subdir('build-utils-meson/diagnostics')
+
 sources = files(
   'attrs.cc',
   'cache.cc',
@@ -89,6 +62,8 @@ sources = files(
   'tarball.cc',
 )
 
+include_dirs = [include_directories('.')]
+
 headers = files(
   'attrs.hh',
   'cache.hh',
@@ -107,36 +82,12 @@ 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)
 
-requires = []
-if nix_util.type_name() == 'internal'
-  # `requires` cannot contain declared dependencies (from the
-  # subproject), so we need to do this manually
-  requires += 'nix-util'
-endif
-if nix_store.type_name() == 'internal'
-  requires += 'nix-store'
-endif
-requires += 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,
-  requires_private : deps_private,
-)
+libraries_private = []
 
-meson.override_dependency(meson.project_name(), declare_dependency(
-  include_directories : include_directories('.'),
-  link_with : this_library,
-  compile_args : ['-std=c++2a'],
-  dependencies : [nix_util, nix_store],
-))
+subdir('build-utils-meson/export')
diff --git a/src/libfetchers/package.nix b/src/libfetchers/package.nix
index a5583d14cd2..b4abb144b50 100644
--- a/src/libfetchers/package.nix
+++ b/src/libfetchers/package.nix
@@ -1,5 +1,6 @@
 { lib
 , stdenv
+, mkMesonDerivation
 , releaseTools
 
 , meson
@@ -14,41 +15,27 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
-
-# Check test coverage of Nix. Probably want to use with with at least
-# one of `doCheck` or `doInstallCheck` enabled.
-, withCoverageChecks ? false
-
+, version
 }:
 
 let
   inherit (lib) fileset;
-
-  version = lib.fileContents ./.version + versionSuffix;
-
-  mkDerivation =
-    if withCoverageChecks
-    then
-      # TODO support `finalAttrs` args function in
-      # `releaseTools.coverageAnalysis`.
-      argsFun:
-         releaseTools.coverageAnalysis (let args = argsFun args; in args)
-    else stdenv.mkDerivation;
 in
 
-mkDerivation (finalAttrs: {
+mkMesonDerivation (finalAttrs: {
   pname = "nix-fetchers";
   inherit version;
 
-  src = fileset.toSource {
-    root = ./.;
-    fileset = fileset.unions [
-      ./meson.build
-      (fileset.fileFilter (file: file.hasExt "cc") ./.)
-      (fileset.fileFilter (file: file.hasExt "hh") ./.)
-    ];
-  };
+  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" ];
 
@@ -69,9 +56,11 @@ mkDerivation (finalAttrs: {
   ];
 
   preConfigure =
-    # "Inline" .version so its not a symlink, and includes the suffix
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
     ''
-      echo ${version} > .version
+      chmod u+w ./.version
+      echo ${version} > ../../.version
     '';
 
   env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
@@ -80,16 +69,11 @@ mkDerivation (finalAttrs: {
 
   enableParallelBuilding = true;
 
-  postInstall =
-    # Remove absolute path to boost libs
-    ''
-    '';
-
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
   # TODO `releaseTools.coverageAnalysis` in Nixpkgs needs to be updated
   # to work with `strictDeps`.
-  strictDeps = !withCoverageChecks;
+  strictDeps = true;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
@@ -97,8 +81,4 @@ mkDerivation (finalAttrs: {
     platforms = lib.platforms.unix ++ lib.platforms.windows;
   };
 
-} // lib.optionalAttrs withCoverageChecks {
-  lcovFilter = [ "*-tab.*" ];
-
-  hardeningDisable = ["fortify"];
 })
diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index 50b9674427c..aa8ff652f07 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -360,14 +360,21 @@ struct TarballInputScheme : CurlInputScheme
         if (result.lastModified && !input.attrs.contains("lastModified"))
             input.attrs.insert_or_assign("lastModified", uint64_t(result.lastModified));
 
-        auto narHash = getTarballCache()->treeHashToNarHash(result.treeHash).to_string(HashFormat::SRI, true);
-
-        input.attrs.insert_or_assign("narHash", narHash);
-
-        result.accessor->fingerprint = narHash;
+        input.attrs.insert_or_assign("narHash",
+            getTarballCache()->treeHashToNarHash(result.treeHash).to_string(HashFormat::SRI, true));
 
         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/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/flake.cc b/src/libflake/flake/flake.cc
index 58d153cb221..4136e6f406b 100644
--- a/src/libflake/flake/flake.cc
+++ b/src/libflake/flake/flake.cc
@@ -972,10 +972,20 @@ 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/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/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/shared.cc b/src/libmain/shared.cc
index c1c9362489b..fc55fe3f1b2 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -320,6 +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/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/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/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/globals.hh b/src/libstore/globals.hh
index 439e9f4fc10..dfe25f31726 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.
diff --git a/src/libstore/meson.build b/src/libstore/meson.build
index d9237c55a5c..7444cba20b5 100644
--- a/src/libstore/meson.build
+++ b/src/libstore/meson.build
@@ -14,14 +14,7 @@ project('nix-store', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-# See note in ../nix-util/meson.build
-deps_private = [ ]
-
-# See note in ../nix-util/meson.build
-deps_public = [ ]
-
-# See note in ../nix-util/meson.build
-deps_other = [ ]
+subdir('build-utils-meson/deps-lists')
 
 configdata = configuration_data()
 
@@ -30,13 +23,12 @@ configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
 
 configdata.set_quoted('SYSTEM', host_machine.system())
 
-nix_util = dependency('nix-util')
-if nix_util.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util
-else
-  deps_public += nix_util
-endif
+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',
@@ -75,12 +67,7 @@ has_acl_support = cxx.has_header('sys/xattr.h') \
   and cxx.has_function('lremovexattr')
 configdata.set('HAVE_ACL_SUPPORT', has_acl_support.to_int())
 
-# 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
+subdir('build-utils-meson/threads')
 
 boost = dependency(
   'boost',
@@ -112,27 +99,28 @@ deps_public += nlohmann_json
 sqlite = dependency('sqlite3', 'sqlite', version : '>=3.6.19')
 deps_private += sqlite
 
-
-enable_embedded_sandbox_shell = get_option('embedded-sandbox-shell')
-if enable_embedded_sandbox_shell
-  # This one goes in config.h
-  # The path to busybox is passed as a -D flag when compiling this_library.
-  # Idk why, ask the old buildsystem.
-  configdata.set('HAVE_EMBEDDED_SANDBOX_SHELL', 1)
-endif
-
 generated_headers = []
-foreach header : [ 'schema.sql', 'ca-specific-schema.sql' ]
+foreach header : [
+  'schema.sql',
+  'ca-specific-schema.sql',
+]
   generated_headers += custom_target(
     command : [ 'bash', '-c', '{ echo \'R"__NIX_STR(\' && cat @INPUT@ && echo \')__NIX_STR"\'; } > "$1"', '_ignored_argv0', '@OUTPUT@' ],
     input : header,
     output : '@PLAINNAME@.gen.hh',
     install : true,
-    install_dir : get_option('includedir') / 'nix'
+    install_dir : get_option('includedir') / 'nix',
   )
 endforeach
 
-if enable_embedded_sandbox_shell
+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',
@@ -152,30 +140,19 @@ endif
 
 config_h = configure_file(
   configuration : configdata,
-  output : 'config-store.h',
+  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.h',
-  '-include', 'config-store.h',
-  '-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`.
-  #
-  # FIXME: remove when we get meson 1.4.0 which will default this to on for us:
-  # https://mesonbuild.com/Release-notes-for-1-4-0.html#ndebug-setting-now-controls-c-stdlib-assertions
-  '-D_GLIBCXX_ASSERTIONS=1',
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
   language : 'cpp',
 )
 
+subdir('build-utils-meson/diagnostics')
+
 sources = files(
   'binary-cache-store.cc',
   'build-result.cc',
@@ -248,7 +225,7 @@ include_dirs = [
   include_directories('build'),
 ]
 
-headers = [config_h] +files(
+headers = [config_h] + files(
   'binary-cache-store.hh',
   'build-result.hh',
   'build/derivation-goal.hh',
@@ -392,11 +369,15 @@ cpp_str_defines += {
   'LSOF': lsof_path
 }
 
-#if busybox.found()
+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()
+    'SANDBOX_SHELL': busybox.full_path()
   }
-#endif
+endif
 
 cpp_args = []
 
@@ -406,12 +387,7 @@ foreach name, value : cpp_str_defines
   ]
 endforeach
 
-if host_machine.system() == 'cygwin' or host_machine.system() == 'windows'
-  # See note in `../nix-util/meson.build`
-  linker_export_flags = ['-Wl,--export-all-symbols']
-else
-  linker_export_flags = []
-endif
+subdir('build-utils-meson/export-all-symbols')
 
 this_library = library(
   'nixstore',
@@ -421,34 +397,12 @@ this_library = library(
   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)
 
-requires = []
-if nix_util.type_name() == 'internal'
-  # `requires` cannot contain declared dependencies (from the
-  # subproject), so we need to do this manually
-  requires += 'nix-util'
-endif
-requires += 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,
-  requires_private : deps_private,
-  libraries_private : ['-lboost_container'],
-)
+libraries_private = []
 
-meson.override_dependency(meson.project_name(), declare_dependency(
-  include_directories : include_dirs,
-  link_with : this_library,
-  compile_args : ['-std=c++2a'],
-  dependencies : [nix_util],
-))
+subdir('build-utils-meson/export')
diff --git a/src/libstore/package.nix b/src/libstore/package.nix
index e118f3cd21f..0a2ace91e40 100644
--- a/src/libstore/package.nix
+++ b/src/libstore/package.nix
@@ -1,10 +1,12 @@
 { lib
 , stdenv
+, mkMesonDerivation
 , releaseTools
 
 , meson
 , ninja
 , pkg-config
+, unixtools
 
 , nix-util
 , boost
@@ -18,50 +20,36 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
+, version
 
-# Check test coverage of Nix. Probably want to use with at least
-# one of `doCheck` or `doInstallCheck` enabled.
-, withCoverageChecks ? false
-
-# Avoid setting things that would interfere with a functioning devShell
-, forDevShell ? false
+, embeddedSandboxShell ? stdenv.hostPlatform.isStatic
 }:
 
 let
   inherit (lib) fileset;
-
-  version = lib.fileContents ./.version + versionSuffix;
-
-  mkDerivation =
-    if withCoverageChecks
-    then
-      # TODO support `finalAttrs` args function in
-      # `releaseTools.coverageAnalysis`.
-      argsFun:
-         releaseTools.coverageAnalysis (let args = argsFun args; in args)
-    else stdenv.mkDerivation;
 in
 
-mkDerivation (finalAttrs: {
+mkMesonDerivation (finalAttrs: {
   pname = "nix-store";
   inherit version;
 
-  src = fileset.toSource {
-    root = ./.;
-    fileset = fileset.unions [
-      ./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") ./.)
-    ];
-  };
+  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" ];
 
@@ -69,7 +57,7 @@ mkDerivation (finalAttrs: {
     meson
     ninja
     pkg-config
-  ];
+  ] ++ lib.optional embeddedSandboxShell unixtools.hexdump;
 
   buildInputs = [
     boost
@@ -89,17 +77,17 @@ mkDerivation (finalAttrs: {
     nlohmann_json
   ];
 
-  disallowedReferences = [ boost ];
-
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
     ''
-      echo ${version} > .version
+      chmod u+w ./.version
+      echo ${version} > ../../.version
     '';
 
   mesonFlags = [
     (lib.mesonEnable "seccomp-sandboxing" stdenv.hostPlatform.isLinux)
-    (lib.mesonBool "embedded-sandbox-shell" stdenv.hostPlatform.isStatic)
+    (lib.mesonBool "embedded-sandbox-shell" embeddedSandboxShell)
   ] ++ lib.optionals stdenv.hostPlatform.isLinux [
     (lib.mesonOption "sandbox-shell" "${busybox-sandbox-shell}/bin/busybox")
   ];
@@ -115,18 +103,9 @@ mkDerivation (finalAttrs: {
 
   enableParallelBuilding = true;
 
-  postInstall =
-    # Remove absolute path to boost libs that ends up in `Libs.private`
-    # by default, and would clash with out `disallowedReferences`. Part
-    # of the https://github.com/NixOS/nixpkgs/issues/45462 workaround.
-    ''
-      sed -i "$out/lib/pkgconfig/nix-store.pc" -e 's, ${lib.getLib boost}[^ ]*,,g'
-    '';
-
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
-  # TODO Always true after https://github.com/NixOS/nixpkgs/issues/318564
-  strictDeps = !withCoverageChecks;
+  strictDeps = true;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
@@ -134,8 +113,4 @@ mkDerivation (finalAttrs: {
     platforms = lib.platforms.unix ++ lib.platforms.windows;
   };
 
-} // lib.optionalAttrs withCoverageChecks {
-  lcovFilter = [ "*/boost/*" "*-tab.*" ];
-
-  hardeningDisable = [ "fortify" ];
 })
diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index e9850dce6dd..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());
diff --git a/src/libstore/unix/build/local-derivation-goal.cc b/src/libstore/unix/build/local-derivation-goal.cc
index a20ed530074..d5a3e0034f9 100644
--- a/src/libstore/unix/build/local-derivation-goal.cc
+++ b/src/libstore/unix/build/local-derivation-goal.cc
@@ -503,13 +503,23 @@ void LocalDerivationGoal::startBuilder()
 
     /* 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. */
-        tmpDir = tmpDir + "/build";
+           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);
 
@@ -2980,7 +2990,7 @@ 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 (like a copy of netrc). */
         if (settings.keepFailed && !force && !drv->isBuiltin()) {
@@ -2988,7 +2998,8 @@ 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 77d07de9899..4bcf5c9d457 100644
--- a/src/libstore/unix/build/local-derivation-goal.hh
+++ b/src/libstore/unix/build/local-derivation-goal.hh
@@ -27,10 +27,16 @@ 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.
      */
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
index 5de288e18ca..3f0d9628201 100644
--- a/src/libutil-c/meson.build
+++ b/src/libutil-c/meson.build
@@ -14,76 +14,53 @@ project('nix-util-c', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-# See note in ../nix-util/meson.build
-deps_private = [ ]
+subdir('build-utils-meson/deps-lists')
 
-# See note in ../nix-util/meson.build
-deps_public = [ ]
+configdata = configuration_data()
 
-# See note in ../nix-util/meson.build
-deps_other = [ ]
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
 
-configdata = configuration_data()
+# 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',
-  # '-include', 'config-store.h',
-  '-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`.
-  #
-  # FIXME: remove when we get meson 1.4.0 which will default this to on for us:
-  # https://mesonbuild.com/Release-notes-for-1-4-0.html#ndebug-setting-now-controls-c-stdlib-assertions
-  '-D_GLIBCXX_ASSERTIONS=1',
   language : 'cpp',
 )
 
+subdir('build-utils-meson/diagnostics')
+
 sources = files(
   'nix_api_util.cc',
 )
 
 include_dirs = [include_directories('.')]
 
-headers = files(
+headers = [config_h] + files(
   'nix_api_util.h',
-  'nix_api_util_internal.h',
 )
 
-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
-
-nix_util = dependency('nix-util')
-if nix_util.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util
-else
-  deps_public += nix_util
-endif
+# TODO don't install this once tests don't use it.
+headers += files('nix_api_util_internal.h')
 
-# 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',
-)
+subdir('build-utils-meson/export-all-symbols')
 
 this_library = library(
   'nixutilc',
@@ -91,6 +68,7 @@ this_library = library(
   dependencies : deps_public + deps_private + deps_other,
   include_directories : include_dirs,
   link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
   install : true,
 )
 
@@ -98,21 +76,4 @@ install_headers(headers, subdir : 'nix', preserve_path : true)
 
 libraries_private = []
 
-import('pkgconfig').generate(
-  this_library,
-  filebase : meson.project_name(),
-  name : 'Nix',
-  description : 'Nix Package Manager',
-  subdirs : ['nix'],
-  extra_cflags : ['-std=c++2a'],
-  requires : deps_public,
-  requires_private : deps_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 : [],
-))
+subdir('build-utils-meson/export')
diff --git a/src/libutil-c/package.nix b/src/libutil-c/package.nix
index 05a26c17e6c..53451998dca 100644
--- a/src/libutil-c/package.nix
+++ b/src/libutil-c/package.nix
@@ -1,5 +1,6 @@
 { lib
 , stdenv
+, mkMesonDerivation
 , releaseTools
 
 , meson
@@ -10,42 +11,29 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
-
-# Check test coverage of Nix. Probably want to use with at least
-# one of `doCheck` or `doInstallCheck` enabled.
-, withCoverageChecks ? false
+, version
 }:
 
 let
   inherit (lib) fileset;
-
-  version = lib.fileContents ./.version + versionSuffix;
-
-  mkDerivation =
-    if withCoverageChecks
-    then
-      # TODO support `finalAttrs` args function in
-      # `releaseTools.coverageAnalysis`.
-      argsFun:
-         releaseTools.coverageAnalysis (let args = argsFun args; in args)
-    else stdenv.mkDerivation;
 in
 
-mkDerivation (finalAttrs: {
+mkMesonDerivation (finalAttrs: {
   pname = "nix-util-c";
   inherit version;
 
-  src = fileset.toSource {
-    root = ./.;
-    fileset = fileset.unions [
-      ./meson.build
-      ./meson.options
-      (fileset.fileFilter (file: file.hasExt "cc") ./.)
-      (fileset.fileFilter (file: file.hasExt "hh") ./.)
-      (fileset.fileFilter (file: file.hasExt "h") ./.)
-    ];
-  };
+  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" ];
 
@@ -55,19 +43,16 @@ mkDerivation (finalAttrs: {
     pkg-config
   ];
 
-  buildInputs = [
-    nix-util
-  ]
-  ;
-
   propagatedBuildInputs = [
     nix-util
   ];
 
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
     ''
-      echo ${version} > .version
+      chmod u+w ./.version
+      echo ${version} > ../../.version
     '';
 
   mesonFlags = [
@@ -81,8 +66,7 @@ mkDerivation (finalAttrs: {
 
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
-  # TODO Always true after https://github.com/NixOS/nixpkgs/issues/318564
-  strictDeps = !withCoverageChecks;
+  strictDeps = true;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
@@ -90,8 +74,4 @@ mkDerivation (finalAttrs: {
     platforms = lib.platforms.unix ++ lib.platforms.windows;
   };
 
-} // lib.optionalAttrs withCoverageChecks {
-  lcovFilter = [ "*/boost/*" "*-tab.*" ];
-
-  hardeningDisable = [ "fortify" ];
 })
diff --git a/src/libutil-test b/src/libutil-test
deleted file mode 120000
index 62c86f54bbb..00000000000
--- a/src/libutil-test
+++ /dev/null
@@ -1 +0,0 @@
-../tests/unit/libutil/
\ No newline at end of file
diff --git a/src/libutil-test-support b/src/libutil-test-support
deleted file mode 120000
index f7da46d4cd6..00000000000
--- a/src/libutil-test-support
+++ /dev/null
@@ -1 +0,0 @@
-../tests/unit/libutil-support/
\ No newline at end of file
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/config.cc b/src/libutil/config.cc
index 192a4ecb951..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)
diff --git a/src/libutil/experimental-features.cc b/src/libutil/experimental-features.cc
index 9b7000f9f3e..1c080e372f6 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",
     },
diff --git a/src/libutil/fs-sink.cc b/src/libutil/fs-sink.cc
index 597272ec98c..194e86fdd6b 100644
--- a/src/libutil/fs-sink.cc
+++ b/src/libutil/fs-sink.cc
@@ -82,13 +82,17 @@ struct RestoreRegularFile : CreateRegularFileSink {
     void preallocateContents(uint64_t size) override;
 };
 
-void RestoreSink::createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func)
+static std::filesystem::path append(const std::filesystem::path & src, const CanonPath & path)
 {
-    auto p = dstPath;
+    auto dst = src;
+    if (!path.rel().empty())
+        dst /= path.rel();
+    return dst;
+}
 
-    if (!path.rel().empty()) {
-        p = p / path.rel();
-    }
+void RestoreSink::createRegularFile(const CanonPath & path, std::function<void(CreateRegularFileSink &)> func)
+{
+    auto p = append(dstPath, path);
 
     RestoreRegularFile crf;
     crf.fd =
@@ -140,9 +144,7 @@ void RestoreRegularFile::operator () (std::string_view data)
 
 void RestoreSink::createSymlink(const CanonPath & path, const std::string & target)
 {
-    auto p = dstPath;
-    if (!path.rel().empty())
-        p = dstPath / path.rel();
+    auto p = append(dstPath, path);
     nix::createSymlink(target, p);
 }
 
diff --git a/src/libutil/meson.build b/src/libutil/meson.build
index 099c0c65fdc..ac2b8353674 100644
--- a/src/libutil/meson.build
+++ b/src/libutil/meson.build
@@ -14,39 +14,16 @@ project('nix-util', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-# 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" stablity and not just
-# "API" stability, the private dependencies also matter as they can
-# potentially affect the public ABI.
-deps_public = [ ]
-
-# These are dependencencies without pkg-config files. Ideally they are
-# just private, but they may also be public (e.g. boost).
-deps_other = [ ]
+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`.
@@ -71,12 +48,7 @@ foreach funcspec : check_funcs
   configdata.set(define_name, define_value)
 endforeach
 
-# 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
+subdir('build-utils-meson/threads')
 
 if host_machine.system() == 'windows'
   socket = cxx.find_library('ws2_32')
@@ -132,29 +104,18 @@ deps_public += nlohmann_json
 
 config_h = configure_file(
   configuration : configdata,
-  output : 'config-util.h',
+  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.h',
-  '-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`.
-  #
-  # FIXME: remove when we get meson 1.4.0 which will default this to on for us:
-  # https://mesonbuild.com/Release-notes-for-1-4-0.html#ndebug-setting-now-controls-c-stdlib-assertions
-  '-D_GLIBCXX_ASSERTIONS=1',
+  '-include', 'config-util.hh',
   language : 'cpp',
 )
 
+subdir('build-utils-meson/diagnostics')
+
 sources = files(
   'archive.cc',
   'args.cc',
@@ -280,17 +241,7 @@ else
   subdir('unix')
 endif
 
-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
+subdir('build-utils-meson/export-all-symbols')
 
 this_library = library(
   'nixutil',
@@ -298,38 +249,17 @@ this_library = library(
   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)
 
-# Part of how we copy boost libraries to a separate installation to
-# reduce closure size. These libraries will be copied to our `$out/bin`,
-# and these `-l` flags will pick them up there.
-#
-# https://github.com/NixOS/nixpkgs/issues/45462
-libraries_private = ['-lboost_context', '-lboost_coroutine']
+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
 
-import('pkgconfig').generate(
-  this_library,
-  filebase : meson.project_name(),
-  name : 'Nix',
-  description : 'Nix Package Manager',
-  subdirs : ['nix'],
-  extra_cflags : ['-std=c++2a'],
-  requires : deps_public,
-  requires_private : deps_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 : [],
-))
+subdir('build-utils-meson/export')
diff --git a/src/libutil/package.nix b/src/libutil/package.nix
index 8ba6daa2a4b..28d7d8f0edb 100644
--- a/src/libutil/package.nix
+++ b/src/libutil/package.nix
@@ -17,26 +17,11 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
-
-# Check test coverage of Nix. Probably want to use with at least
-# one of `doCheck` or `doInstallCheck` enabled.
-, withCoverageChecks ? false
+, version
 }:
 
 let
   inherit (lib) fileset;
-
-  version = lib.fileContents ./.version + versionSuffix;
-
-  mkDerivation =
-    if withCoverageChecks
-    then
-      # TODO support `finalAttrs` args function in
-      # `releaseTools.coverageAnalysis`.
-      argsFun:
-         releaseTools.coverageAnalysis (let args = argsFun args; in args)
-    else stdenv.mkDerivation;
 in
 
 mkMesonDerivation (finalAttrs: {
@@ -45,6 +30,8 @@ mkMesonDerivation (finalAttrs: {
 
   workDir = ./.;
   fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
     ../../.version
     ./.version
     ./meson.build
@@ -65,7 +52,6 @@ mkMesonDerivation (finalAttrs: {
   ];
 
   buildInputs = [
-    boost
     brotli
     libsodium
     openssl
@@ -73,37 +59,21 @@ mkMesonDerivation (finalAttrs: {
   ;
 
   propagatedBuildInputs = [
-    boost.dev
+    boost
     libarchive
     nlohmann_json
   ];
 
-  disallowedReferences = [ boost ];
-
   preConfigure =
-    # TODO: change release process to add `pre` in `.version`, remove it before tagging, and restore after.
+    # "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
-    ''
-    # Copy some boost libraries so we don't get all of Boost in our
-    # closure. https://github.com/NixOS/nixpkgs/issues/45462
-    + lib.optionalString (!stdenv.hostPlatform.isStatic) (''
-      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
-    ''
-  );
+    '';
 
   mesonFlags = [
     (lib.mesonEnable "cpuid" stdenv.hostPlatform.isx86_64)
@@ -120,24 +90,9 @@ mkMesonDerivation (finalAttrs: {
 
   enableParallelBuilding = true;
 
-  postInstall =
-    # Remove absolute path to boost libs that ends up in `Libs.private`
-    # by default, and would clash with out `disallowedReferences`. Part
-    # of the https://github.com/NixOS/nixpkgs/issues/45462 workaround.
-    ''
-      sed -i "$out/lib/pkgconfig/nix-util.pc" -e 's, ${lib.getLib boost}[^ ]*,,g'
-    ''
-    + lib.optionalString stdenv.isDarwin ''
-      install_name_tool \
-      -change ${boost}/lib/libboost_context.dylib \
-      $out/lib/libboost_context.dylib \
-      $out/lib/libnixutil.dylib
-    '';
-
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
-  # TODO Always true after https://github.com/NixOS/nixpkgs/issues/318564
-  strictDeps = !withCoverageChecks;
+  strictDeps = true;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
@@ -145,8 +100,4 @@ mkMesonDerivation (finalAttrs: {
     platforms = lib.platforms.unix ++ lib.platforms.windows;
   };
 
-} // lib.optionalAttrs withCoverageChecks {
-  lcovFilter = [ "*/boost/*" "*-tab.*" ];
-
-  hardeningDisable = [ "fortify" ];
 })
diff --git a/src/libutil/tarfile.cc b/src/libutil/tarfile.cc
index c7faedd1ec0..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}
@@ -78,10 +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_tar(archive);
-        archive_read_support_format_zip(archive);
-    } else {
+    if (!raw)
+        enableSupportedFormats(archive);
+    else {
         archive_read_support_format_raw(archive);
         archive_read_support_format_empty(archive);
     }
@@ -97,8 +107,7 @@ TarArchive::TarArchive(const Path & path)
     , buffer(defaultBufferSize)
 {
     archive_read_support_filter_all(archive);
-    archive_read_support_format_tar(archive);
-    archive_read_support_format_zip(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");
 }
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 57630c8c34b..d37b16bdca0 100644
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -26,6 +26,7 @@
 #include "legacy.hh"
 #include "users.hh"
 #include "network-proxy.hh"
+#include "compatibility-settings.hh"
 
 using namespace nix;
 using namespace std::string_literals;
@@ -90,24 +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;
@@ -132,7 +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");
@@ -186,9 +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";
@@ -206,7 +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") {
@@ -246,7 +273,7 @@ static void main_nix_build(int argc, char * * argv)
             return false;
 
         else
-            left.push_back(*arg);
+            remainingArgs.push_back(*arg);
 
         return true;
     });
@@ -266,7 +293,7 @@ static void main_nix_build(int argc, char * * argv)
     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);
@@ -276,19 +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;
@@ -299,7 +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 {
@@ -310,14 +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));
+                }
             }
         }
 
@@ -330,7 +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;
@@ -381,7 +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");
 
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-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-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/flake.cc b/src/nix/flake.cc
index 2d0446aee53..e197e65bdcf 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -229,6 +229,8 @@ struct CmdFlakeMetadata : FlakeCommand, MixJSON
             if (auto lastModified = flake.lockedRef.input.getLastModified())
                 j["lastModified"] = *lastModified;
             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(
@@ -258,6 +260,10 @@ 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);
diff --git a/src/nix/main.cc b/src/nix/main.cc
index e95558781f8..de6d89bd371 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -419,35 +419,28 @@ void mainWrapped(int argc, char * * argv)
         };
         evalSettings.pureEval = false;
         EvalState state({}, openStore("dummy://"), evalSettings);
-        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));
+        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;
     }
 
diff --git a/src/nix/prefetch.cc b/src/nix/prefetch.cc
index 5e890f3c8ce..c6e60a53be6 100644
--- a/src/nix/prefetch.cc
+++ b/src/nix/prefetch.cc
@@ -114,14 +114,15 @@ std::tuple<StorePath, Hash> prefetchFile(
             createDirs(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 = std::filesystem::directory_iterator{unpacked};
-            auto file_count = std::distance(entries, std::filesystem::directory_iterator{});
-            if (file_count == 1)
-                tmpFile = entries->path();
-            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,
diff --git a/src/perl/lib/Nix/Store.xs b/src/perl/lib/Nix/Store.xs
index acce25f3a82..f951437c899 100644
--- a/src/perl/lib/Nix/Store.xs
+++ b/src/perl/lib/Nix/Store.xs
@@ -1,5 +1,5 @@
-#include "config-util.h"
-#include "config-store.h"
+#include "config-util.hh"
+#include "config-store.hh"
 
 #include "EXTERN.h"
 #include "perl.h"
diff --git a/src/perl/lib/Nix/meson.build b/src/perl/lib/Nix/meson.build
index 9a79245cd5e..256e6609652 100644
--- a/src/perl/lib/Nix/meson.build
+++ b/src/perl/lib/Nix/meson.build
@@ -43,6 +43,7 @@ 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'),
diff --git a/src/perl/package.nix b/src/perl/package.nix
index 85f1547b7cf..26856e631a1 100644
--- a/src/perl/package.nix
+++ b/src/perl/package.nix
@@ -1,57 +1,53 @@
 { lib
 , stdenv
+, mkMesonDerivation
 , perl
 , perlPackages
 , meson
 , ninja
 , pkg-config
 , nix-store
+, darwin
+, version
 , curl
 , bzip2
-, xz
-, boost
 , libsodium
-, darwin
-, versionSuffix ? ""
 }:
 
 let
   inherit (lib) fileset;
 in
 
-perl.pkgs.toPerlModule (stdenv.mkDerivation (finalAttrs: {
+perl.pkgs.toPerlModule (mkMesonDerivation (finalAttrs: {
   pname = "nix-perl";
-  version = lib.fileContents ./.version + versionSuffix;
+  inherit version;
 
-  src = fileset.toSource {
-    root = ./.;
-    fileset = fileset.unions ([
-      ./MANIFEST
-      ./lib
-      ./meson.build
-      ./meson.options
-    ] ++ lib.optionals finalAttrs.doCheck [
-      ./.yath.rc.in
-      ./t
-    ]);
-  };
+  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
-    curl
     bzip2
-    xz
-    perl
-    boost
-  ]
-  ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
-  ++ lib.optional stdenv.isDarwin darwin.apple_sdk.frameworks.Security;
+    libsodium
+  ];
 
   # `perlPackages.Test2Harness` is marked broken for Darwin
   doCheck = !stdenv.isDarwin;
@@ -63,6 +59,7 @@ perl.pkgs.toPerlModule (stdenv.mkDerivation (finalAttrs: {
   preConfigure =
     # "Inline" .version so its not a symlink, and includes the suffix
     ''
+      chmod u+w .version
       echo ${finalAttrs.version} > .version
     '';
 
diff --git a/tests/functional/flakes/flakes.sh b/tests/functional/flakes/flakes.sh
index 8814704d982..0b859110211 100755
--- a/tests/functional/flakes/flakes.sh
+++ b/tests/functional/flakes/flakes.sh
@@ -196,6 +196,7 @@ json=$(nix flake metadata flake1 --json | jq .)
 [[ $(echo "$json" | jq -r .description) = 'Bla bla' ]]
 [[ $(echo "$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 $flake1Dir/foo
diff --git a/tests/functional/misc.sh b/tests/functional/misc.sh
index a09c3c1de99..d5012d0bfb5 100755
--- a/tests/functional/misc.sh
+++ b/tests/functional/misc.sh
@@ -13,6 +13,9 @@ source common.sh
 # Can we ask for the version number?
 nix-env --version | grep "$version"
 
+nix_env=$(type -P nix-env)
+(PATH=""; ! $nix_env --help 2>&1 ) | grepQuiet -F "The 'man' command was not found, but it is needed for 'nix-env' and some other 'nix-*' commands' help text. Perhaps you could install the 'man' command?"
+
 # Usage errors.
 expect 1 nix-env --foo 2>&1 | grep "no operation"
 expect 1 nix-env -q --foo 2>&1 | grep "unknown flag"
diff --git a/tests/functional/nix-shell.sh b/tests/functional/nix-shell.sh
index 2c94705dec0..65ff279f868 100755
--- a/tests/functional/nix-shell.sh
+++ b/tests/functional/nix-shell.sh
@@ -21,6 +21,10 @@ output=$(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 - $SELECTED_IMPURE_VAR"')
@@ -91,6 +95,55 @@ sed -e "s|@ENV_PROG@|$(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/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/tarball.sh b/tests/functional/tarball.sh
index 514717c9f6a..ceb6b13e8ca 100755
--- a/tests/functional/tarball.sh
+++ b/tests/functional/tarball.sh
@@ -54,6 +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/nixos/tarball-flakes.nix b/tests/nixos/tarball-flakes.nix
index 2e7f98b5e46..84cf377ec5b 100644
--- a/tests/nixos/tarball-flakes.nix
+++ b/tests/nixos/tarball-flakes.nix
@@ -70,12 +70,17 @@ in
     # 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 fetching with rev/revCount/narHash succeeds.
+    # 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/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"])
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/.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/meson.build b/tests/unit/libexpr/meson.build
new file mode 100644
index 00000000000..a7b22f7f1e8
--- /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-store.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/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/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/meson.build b/tests/unit/libfetchers/meson.build
new file mode 100644
index 00000000000..b4bc77a9780
--- /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-store.hh',
+  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/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/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/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/.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/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/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/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
index c0345a6eee4..7d0e9c2fc30 100644
--- a/tests/unit/libutil-support/meson.build
+++ b/tests/unit/libutil-support/meson.build
@@ -14,32 +14,27 @@ project('nix-util-test-support', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-# See note in ../nix-util/meson.build
-deps_private = [ ]
+subdir('build-utils-meson/deps-lists')
 
-# See note in ../nix-util/meson.build
-deps_public = [ ]
+deps_private_maybe_subproject = [
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util'),
+]
+subdir('build-utils-meson/subprojects')
 
-# See note in ../nix-util/meson.build
-deps_other = [ ]
+rapidcheck = dependency('rapidcheck')
+deps_public += rapidcheck
 
 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`.
-  #
-  # FIXME: remove when we get meson 1.4.0 which will default this to on for us:
-  # https://mesonbuild.com/Release-notes-for-1-4-0.html#ndebug-setting-now-controls-c-stdlib-assertions
-  '-D_GLIBCXX_ASSERTIONS=1',
+  # 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',
@@ -54,28 +49,7 @@ headers = files(
   'tests/string_callback.hh',
 )
 
-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
-
-nix_util = dependency('nix-util')
-if nix_util.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util
-else
-  deps_public += nix_util
-endif
-
-rapidcheck = dependency('rapidcheck')
-deps_public += rapidcheck
+subdir('build-utils-meson/export-all-symbols')
 
 this_library = library(
   'nix-util-test-support',
@@ -85,6 +59,7 @@ this_library = library(
   # 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,
 )
 
@@ -92,20 +67,4 @@ install_headers(headers, subdir : 'nix', preserve_path : true)
 
 libraries_private = []
 
-import('pkgconfig').generate(
-  this_library,
-  filebase : meson.project_name(),
-  name : 'Nix',
-  description : 'Nix Package Manager',
-  subdirs : ['nix'],
-  extra_cflags : ['-std=c++2a'],
-  requires : deps_public,
-  requires_private : deps_private,
-)
-
-meson.override_dependency(meson.project_name(), declare_dependency(
-  include_directories : include_dirs,
-  link_with : this_library,
-  compile_args : ['-std=c++2a'],
-  dependencies : [],
-))
+subdir('build-utils-meson/export')
diff --git a/tests/unit/libutil-support/package.nix b/tests/unit/libutil-support/package.nix
index 0be0a9945be..fdecdec7226 100644
--- a/tests/unit/libutil-support/package.nix
+++ b/tests/unit/libutil-support/package.nix
@@ -1,5 +1,6 @@
 { lib
 , stdenv
+, mkMesonDerivation
 , releaseTools
 
 , meson
@@ -12,41 +13,28 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
-
-# Check test coverage of Nix. Probably want to use with at least
-# one of `doCheck` or `doInstallCheck` enabled.
-, withCoverageChecks ? false
+, version
 }:
 
 let
   inherit (lib) fileset;
-
-  version = lib.fileContents ./.version + versionSuffix;
-
-  mkDerivation =
-    if withCoverageChecks
-    then
-      # TODO support `finalAttrs` args function in
-      # `releaseTools.coverageAnalysis`.
-      argsFun:
-         releaseTools.coverageAnalysis (let args = argsFun args; in args)
-    else stdenv.mkDerivation;
 in
 
-mkDerivation (finalAttrs: {
+mkMesonDerivation (finalAttrs: {
   pname = "nix-util-test-support";
   inherit version;
 
-  src = fileset.toSource {
-    root = ./.;
-    fileset = fileset.unions [
-      ./meson.build
-      # ./meson.options
-      (fileset.fileFilter (file: file.hasExt "cc") ./.)
-      (fileset.fileFilter (file: file.hasExt "hh") ./.)
-    ];
-  };
+  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" ];
 
@@ -56,20 +44,17 @@ mkDerivation (finalAttrs: {
     pkg-config
   ];
 
-  buildInputs = [
-    nix-util
-    rapidcheck
-  ]
-  ;
-
   propagatedBuildInputs = [
     nix-util
+    rapidcheck
   ];
 
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
     ''
-      echo ${version} > .version
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
     '';
 
   mesonFlags = [
@@ -83,8 +68,7 @@ mkDerivation (finalAttrs: {
 
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
-  # TODO Always true after https://github.com/NixOS/nixpkgs/issues/318564
-  strictDeps = !withCoverageChecks;
+  strictDeps = true;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
@@ -92,8 +76,4 @@ mkDerivation (finalAttrs: {
     platforms = lib.platforms.unix ++ lib.platforms.windows;
   };
 
-} // lib.optionalAttrs withCoverageChecks {
-  lcovFilter = [ "*/boost/*" "*-tab.*" ];
-
-  hardeningDisable = [ "fortify" ];
 })
diff --git a/tests/unit/libutil/.version b/tests/unit/libutil/.version
deleted file mode 100644
index ad2261920c0..00000000000
--- a/tests/unit/libutil/.version
+++ /dev/null
@@ -1 +0,0 @@
-2.24.0
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/meson.build b/tests/unit/libutil/meson.build
index cc13c436461..4f055cabda0 100644
--- a/tests/unit/libutil/meson.build
+++ b/tests/unit/libutil/meson.build
@@ -1,4 +1,4 @@
-project('nix-util-test', 'cpp',
+project('nix-util-tests', 'cpp',
   version : files('.version'),
   default_options : [
     'cpp_std=c++2a',
@@ -14,45 +14,34 @@ project('nix-util-test', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-# See note in ../nix-util/meson.build
-deps_private = [ ]
+subdir('build-utils-meson/deps-lists')
 
-# See note in ../nix-util/meson.build
-deps_public = [ ]
+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')
 
-# See note in ../nix-util/meson.build
-deps_other = [ ]
+subdir('build-utils-meson/export-all-symbols')
 
-configdata = configuration_data()
+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-test.h',
-  # '-include', 'config-store.h',
-  '-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`.
-  #
-  # FIXME: remove when we get meson 1.4.0 which will default this to on for us:
-  # https://mesonbuild.com/Release-notes-for-1-4-0.html#ndebug-setting-now-controls-c-stdlib-assertions
-  '-D_GLIBCXX_ASSERTIONS=1',
+  '-include', 'config-util.hh',
+  '-include', 'config-util.h',
   language : 'cpp',
 )
 
-# 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-test.h',
-)
+subdir('build-utils-meson/diagnostics')
 
 sources = files(
   'args.cc',
@@ -80,52 +69,11 @@ sources = files(
 
 include_dirs = [include_directories('.')]
 
-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
-
-nix_util = dependency('nix-util')
-if nix_util.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util
-else
-  deps_public += nix_util
-endif
-
-nix_util_c = dependency('nix-util-c')
-if nix_util_c.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util_c
-else
-  deps_public += nix_util_c
-endif
-
-nix_util_test_support = dependency('nix-util-test-support')
-if nix_util_test_support.type_name() == 'internal'
-  # subproject sadly no good for pkg-config module
-  deps_other += nix_util_test_support
-else
-  deps_public += nix_util_test_support
-endif
-
-rapidcheck = dependency('rapidcheck')
-deps_public += rapidcheck
-
-gtest = dependency('gtest', main : true)
-deps_public += gtest
 
 this_exe = executable(
-  'nix-util-test',
+  meson.project_name(),
   sources,
-  dependencies : deps_public + deps_private + deps_other,
+  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'],
@@ -133,11 +81,11 @@ this_exe = executable(
   install : true,
 )
 
-test('nix-util-test', this_exe, env : ['_NIX_TEST_UNIT_DATA=' + meson.current_source_dir() + '/data'])
-
-meson.override_dependency(meson.project_name(), declare_dependency(
-  include_directories : include_dirs,
-  link_with : this_exe,
-  compile_args : ['-std=c++2a'],
-  dependencies : [],
-))
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)
diff --git a/tests/unit/libutil/package.nix b/tests/unit/libutil/package.nix
index 391f8d85326..ad5ff7d1e83 100644
--- a/tests/unit/libutil/package.nix
+++ b/tests/unit/libutil/package.nix
@@ -1,5 +1,6 @@
 { lib
 , stdenv
+, mkMesonDerivation
 , releaseTools
 
 , meson
@@ -16,41 +17,28 @@
 
 # Configuration Options
 
-, versionSuffix ? ""
-
-# Check test coverage of Nix. Probably want to use with at least
-# one of `doCheck` or `doInstallCheck` enabled.
-, withCoverageChecks ? false
+, version
 }:
 
 let
   inherit (lib) fileset;
-
-  version = lib.fileContents ./.version + versionSuffix;
-
-  mkDerivation =
-    if withCoverageChecks
-    then
-      # TODO support `finalAttrs` args function in
-      # `releaseTools.coverageAnalysis`.
-      argsFun:
-         releaseTools.coverageAnalysis (let args = argsFun args; in args)
-    else stdenv.mkDerivation;
 in
 
-mkDerivation (finalAttrs: {
-  pname = "nix-util-test";
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util-tests";
   inherit version;
 
-  src = fileset.toSource {
-    root = ./.;
-    fileset = fileset.unions [
-      ./meson.build
-      # ./meson.options
-      (fileset.fileFilter (file: file.hasExt "cc") ./.)
-      (fileset.fileFilter (file: file.hasExt "hh") ./.)
-    ];
-  };
+  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" ];
 
@@ -69,9 +57,11 @@ mkDerivation (finalAttrs: {
   ];
 
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
     ''
-      echo ${version} > .version
+      chmod u+w ./.version
+      echo ${version} > ../../../.version
     '';
 
   mesonFlags = [
@@ -85,8 +75,7 @@ mkDerivation (finalAttrs: {
 
   separateDebugInfo = !stdenv.hostPlatform.isStatic;
 
-  # TODO Always true after https://github.com/NixOS/nixpkgs/issues/318564
-  strictDeps = !withCoverageChecks;
+  strictDeps = true;
 
   hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
 
@@ -96,7 +85,7 @@ mkDerivation (finalAttrs: {
       } ''
         PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
         export _NIX_TEST_UNIT_DATA=${./data}
-        nix-util-test
+        nix-util-tests
         touch $out
       '';
     };
@@ -106,8 +95,4 @@ mkDerivation (finalAttrs: {
     platforms = lib.platforms.unix ++ lib.platforms.windows;
   };
 
-} // lib.optionalAttrs withCoverageChecks {
-  lcovFilter = [ "*/boost/*" "*-tab.*" ];
-
-  hardeningDisable = [ "fortify" ];
 })