@@ -34,6 +34,16 @@ jobs:
           experimental: true
         - python-version: "3.15t"
           experimental: true
+        - os-type: ubuntu
+          python-version: "3.12"
+          backend: gix
+          build-docs: false
+          experimental: false
+        - os-type: macos
+          python-version: "3.12"
+          backend: gix
+          build-docs: false
+          experimental: false
         - os-type: windows
           python-version: "3.12"
           backend: gix
@@ -65,13 +75,27 @@ jobs:
           test-requirements.txt
           gix-requirements.txt
 
-    - name: Prepare Rust for GixPython's Windows source build
+    - name: Prepare Rust for GixPython source builds
       if: matrix.backend == 'gix'
+      id: rust
       run: |
         # GixPython 0.1.0 publishes macOS wheels only and needs Rust >= 1.89.
         rustup toolchain install stable --profile minimal
         rustup default stable
         rustc --version
+        echo "version=$(rustc --version)" >> "$GITHUB_OUTPUT"
+
+    - name: Cache GixPython Cargo dependencies and build output
+      if: matrix.backend == 'gix'
+      uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: |
+          ~/.cargo/registry
+          ~/.cargo/git
+          ${{ runner.temp }}/gix-target
+        key: gix-${{ runner.os }}-${{ runner.arch }}-py${{ matrix.python-version }}-${{ steps.rust.outputs.version }}-${{ hashFiles('gix-requirements.txt') }}
+        restore-keys: |
+          gix-${{ runner.os }}-${{ runner.arch }}-py${{ matrix.python-version }}-${{ steps.rust.outputs.version }}-
 
     - name: Set up WSL (Windows)
       if: matrix.os-type == 'windows'
@@ -115,6 +139,8 @@ jobs:
       env:
         EXTRAS: ${{ matrix.backend == 'gix' && 'test,gix' || 'test' }}
         EXPECTED_BACKEND: ${{ matrix.backend }}
+        # Keep Cargo output when pip removes its temporary source directory.
+        CARGO_TARGET_DIR: ${{ runner.temp }}/gix-target
 
     - name: Show POSIX file ownership
       # Linux and macOS only. On Windows, Git Bash's `ls -ld` reports a
 
@@ -18,8 +18,9 @@ uv pip install --python .tox/gix/bin/python --editable '.[test,gix]'
 
 GixPython 0.1.0 publishes macOS wheels. On Windows and Linux, installation
 builds the released source distribution and requires Rust 1.89 or newer and
-a platform C/C++ toolchain. Windows CI uses the runner's MSVC tools and a
-stable Rust toolchain, with pip's built-wheel cache enabled.
+a platform C/C++ toolchain. The full-suite Gix CI jobs prepare a stable Rust
+toolchain and cache pip's built wheels, Cargo dependencies and compilation
+output.
 
 Python extras add dependencies; they do not leave a runtime feature bit.
 GitPython selects this backend when `gix` can be imported. Installing GixPython
@@ -848,16 +849,25 @@ Add each conversion with a no-subprocess check and a Git parity check where
 practical, in its own commit. Update this ledger when a limitation changes;
 the runtime report's reason should point to the corresponding entry.
 
-## Windows validation
+## CI coverage
 
-The [Python package workflow](../.github/workflows/pythonpackage.yml) adds a
-Windows/Python 3.12 Gix job while preserving all 28 CLI combinations and their
-existing check names. It installs `.[test,gix]`, verifies the selected backend
-and runs the full suite
-with the same coverage and pytest options. Every job retains JUnit results
+The [Python package workflow](../.github/workflows/pythonpackage.yml) adds one
+Python 3.12 Gix job each on Ubuntu, macOS and Windows, preserving all 28 CLI
+combinations and their existing check names. It installs `.[test,gix]`, verifies
+the selected backend and runs the full suite with the same coverage and pytest
+options. Every job retains JUnit results
 and `--backend-report` operation counts under its `tests-OS-PYTHON-BACKEND`
-artifact, and prints the 30 slowest test durations. The extra Gix job does not
-duplicate the documentation build.
+artifact, and prints the 30 slowest test durations. The extra Gix jobs do not
+duplicate the documentation build. Their check names include `gix`, such as
+`test (ubuntu, 3.12, gix)`.
+
+On platforms without a matching wheel, pip builds the official source release.
+`CARGO_TARGET_DIR` keeps compilation output outside pip's temporary source
+directory. The Cargo cache distinguishes OS, architecture, Python and Rust
+versions and `gix-requirements.txt`; a release change can reuse dependencies
+from the same platform and toolchain.
+
+## Windows validation
 
 Local Windows checks use CPython 3.12.13, Git 2.55.0.windows.3 and GixPython
 0.1.0 built from the released source distribution. The installed extension