chore: attempt to speed up tests

Author: parthea

.github/workflows/unittest.yml

@@ -48,16 +48,18 @@ jobs:
         TARGET_BRANCH: ${{ github.base_ref || github.event.merge_group.base_ref }}
         TEST_TYPE: unit
         PY_VERSION: ${{ matrix.python }}
-        # Use UV to speed up testing
-        # Force standard venv backend for 3.15, leave empty to let nox-uv handle others
-        NOX_FORCE_VENV_BACKEND: ${{ matrix.python == '3.15' && 'venv' || '' }}
-        # Unset the global uv seeder for 3.15 so the standard venv backend doesn't try to use virtualenv internals
         VIRTUALENV_SEEDER: ${{ matrix.python == '3.15' && '' || 'uv' }}
         # Workaround: Allows libcst to compile on Python 3.15+ while PyO3 catches up
         # Can be removed once libcst releases a version with native Python 3.15 wheels
         # Follow https://github.com/Instagram/LibCST/issues/1445 for updates.
         PYO3_USE_ABI3_FORWARD_COMPATIBILITY: "1"
       run: |
+        # Only inject overrides if we are strictly on the 3.15 pre-release
+        # This is needed to speed up builds
+        if [ "${{ matrix.python }}" = "3.15" ]; then
+          export NOX_FORCE_VENV_BACKEND="venv"
+          export VIRTUALENV_SEEDER=""
+        fi
         ci/run_conditional_tests.sh
     - name: Upload coverage results
       uses: actions/upload-artifact@v5