Speed up Windows x64 Rust tests with archive fanout

Co-authored-by: Codex <noreply@openai.com>

.github/workflows/rust-ci-full.yml

@@ -559,12 +559,6 @@ jobs:
             runs_on:
               group: codex-runners
               labels: codex-linux-arm64
-          - runner: windows-x64
-            target: x86_64-pc-windows-msvc
-            profile: dev
-            runs_on:
-              group: codex-runners
-              labels: codex-windows-x64
           - runner: windows-arm64
             target: aarch64-pc-windows-msvc
             profile: dev
@@ -751,6 +745,153 @@ jobs:
           echo "Tests failed. See logs for details."
           exit 1
 
+  windows_x64_test_archive:
+    name: Build Windows x64 nextest archive
+    runs-on:
+      group: codex-runners
+      labels: codex-windows-x64
+    timeout-minutes: 45
+    defaults:
+      run:
+        working-directory: codex-rs
+    env:
+      CARGO_INCREMENTAL: "0"
+      WINDOWS_X64_ARCHIVE_FILE: windows-x64-nextest-archive.tar.zst
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - uses: dtolnay/rust-toolchain@a0b273b48ed29de4470960879e8381ff45632f26 # 1.93.0
+        with:
+          targets: x86_64-pc-windows-msvc
+      - name: Compute lockfile hash
+        id: lockhash
+        shell: bash
+        run: |
+          set -euo pipefail
+          echo "hash=$(sha256sum Cargo.lock | cut -d' ' -f1)" >> "$GITHUB_OUTPUT"
+          echo "toolchain_hash=$(sha256sum rust-toolchain.toml | cut -d' ' -f1)" >> "$GITHUB_OUTPUT"
+      - name: Restore cargo home cache
+        id: cache_cargo_home_restore
+        uses: actions/cache/restore@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5.0.4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+          key: cargo-home-windows-x64-x86_64-pc-windows-msvc-dev-${{ steps.lockhash.outputs.hash }}-${{ steps.lockhash.outputs.toolchain_hash }}
+          restore-keys: |
+            cargo-home-windows-x64-x86_64-pc-windows-msvc-dev-
+      - uses: taiki-e/install-action@44c6d64aa62cd779e873306675c7a58e86d6d532 # v2.62.49
+        with:
+          tool: nextest
+          version: 0.9.103
+      - name: Build nextest archive
+        shell: bash
+        run: |
+          set -euo pipefail
+          archive_dir="${RUNNER_TEMP}/nextest-archive"
+          mkdir -p "${archive_dir}"
+          cargo nextest archive \
+            --target x86_64-pc-windows-msvc \
+            --cargo-profile ci-test \
+            --timings \
+            --archive-file "${archive_dir}/${WINDOWS_X64_ARCHIVE_FILE}"
+      - name: Upload nextest archive
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        with:
+          name: windows-x64-nextest-archive
+          path: ${{ runner.temp }}/nextest-archive/${{ env.WINDOWS_X64_ARCHIVE_FILE }}
+          if-no-files-found: error
+          retention-days: 1
+      - name: Upload Cargo timings (nextest)
+        if: always()
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        with:
+          name: cargo-timings-rust-ci-nextest-x86_64-pc-windows-msvc-dev
+          path: codex-rs/target/**/cargo-timings/cargo-timing.html
+          if-no-files-found: warn
+      - name: Save cargo home cache
+        if: always() && !cancelled() && steps.cache_cargo_home_restore.outputs.cache-hit != 'true'
+        continue-on-error: true
+        uses: actions/cache/save@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5.0.4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+          key: cargo-home-windows-x64-x86_64-pc-windows-msvc-dev-${{ steps.lockhash.outputs.hash }}-${{ steps.lockhash.outputs.toolchain_hash }}
+
+  windows_x64_archive_tests:
+    name: Tests — windows-x64 shard ${{ matrix.shard }}/6
+    needs: windows_x64_test_archive
+    runs-on:
+      group: codex-runners
+      labels: codex-windows-x64
+    timeout-minutes: 45
+    defaults:
+      run:
+        working-directory: codex-rs
+    env:
+      WINDOWS_X64_ARCHIVE_FILE: windows-x64-nextest-archive.tar.zst
+    strategy:
+      fail-fast: false
+      matrix:
+        shard:
+          - 1
+          - 2
+          - 3
+          - 4
+          - 5
+          - 6
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - name: Install DotSlash
+        uses: facebook/install-dotslash@1e4e7b3e07eaca387acb98f1d4720e0bee8dbb6a # v2
+      - uses: dtolnay/rust-toolchain@a0b273b48ed29de4470960879e8381ff45632f26 # 1.93.0
+        with:
+          targets: x86_64-pc-windows-msvc
+      - uses: taiki-e/install-action@44c6d64aa62cd779e873306675c7a58e86d6d532 # v2.62.49
+        with:
+          tool: nextest
+          version: 0.9.103
+      - name: Download nextest archive
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: windows-x64-nextest-archive
+          path: ${{ runner.temp }}/windows-x64-nextest-archive
+      - name: tests
+        id: test
+        shell: bash
+        run: |
+          set -euo pipefail
+          archive_file="${RUNNER_TEMP}/windows-x64-nextest-archive/${WINDOWS_X64_ARCHIVE_FILE}"
+          workspace_root="$(cygpath -w "$(pwd)")"
+          extract_dir_unix="${RUNNER_TEMP}/nextest-extract-shard-${{ matrix.shard }}"
+          mkdir -p "${extract_dir_unix}"
+          extract_dir="$(cygpath -w "${extract_dir_unix}")"
+          archive_file="$(cygpath -w "${archive_file}")"
+          cargo nextest run \
+            --no-fail-fast \
+            --archive-file "${archive_file}" \
+            --workspace-remap "${workspace_root}" \
+            --extract-to "${extract_dir}" \
+            --partition "hash:${{ matrix.shard }}/6" \
+            --test-threads 8
+        env:
+          RUST_BACKTRACE: 1
+          RUST_MIN_STACK: "8388608" # 8 MiB
+          NEXTEST_STATUS_LEVEL: leak
+      - name: verify tests passed
+        if: steps.test.outcome == 'failure'
+        run: |
+          echo "Tests failed. See logs for details."
+          exit 1
+
   # --- Gatherer job for the full post-merge workflow --------------------------
   results:
     name: Full CI results
@@ -762,6 +903,7 @@ jobs:
         argument_comment_lint_prebuilt,
         lint_build,
         tests,
+        windows_x64_archive_tests,
       ]
     if: always()
     runs-on: ubuntu-24.04
@@ -775,12 +917,14 @@ jobs:
           echo "shear  : ${{ needs.cargo_shear.result }}"
           echo "lint   : ${{ needs.lint_build.result }}"
           echo "tests  : ${{ needs.tests.result }}"
+          echo "winx64 : ${{ needs.windows_x64_archive_tests.result }}"
           [[ '${{ needs.argument_comment_lint_package.result }}' == 'success' ]] || { echo 'argument_comment_lint_package failed'; exit 1; }
           [[ '${{ needs.argument_comment_lint_prebuilt.result }}' == 'success' ]] || { echo 'argument_comment_lint_prebuilt failed'; exit 1; }
           [[ '${{ needs.general.result }}' == 'success' ]] || { echo 'general failed'; exit 1; }
           [[ '${{ needs.cargo_shear.result }}' == 'success' ]] || { echo 'cargo_shear failed'; exit 1; }
           [[ '${{ needs.lint_build.result }}' == 'success' ]] || { echo 'lint_build failed'; exit 1; }
           [[ '${{ needs.tests.result }}' == 'success' ]] || { echo 'tests failed'; exit 1; }
+          [[ '${{ needs.windows_x64_archive_tests.result }}' == 'success' ]] || { echo 'windows_x64_archive_tests failed'; exit 1; }
 
       - name: sccache summary note
         if: always()