ci: run Vitest in parallel and stop PRs saving Windows caches

.claude/skills/merge-upstream-vscode/SKILL.md

@@ -199,7 +199,7 @@ further by hand, then confirm with `npm ci --dry-run`.
 
 #### Check for new postinstall artifacts
 
-The `test / unit` CI job fails with `npm install created N files outside
+The `test / vscode` CI job fails with `npm install created N files outside
 node_modules/` if postinstall writes a file that isn't in
 `.github/cache-scripts/cache-paths.sh`. On a cache hit postinstall is skipped, so
 an uncached artifact would be missing. Upstream changes to the install scripts

.github/cache-scripts/log-cache-status.sh

@@ -161,7 +161,7 @@ fi
 
 # Only emit a summary for restore operations, and only when the caller opts in
 # via EMIT_CACHE_SUMMARY=true. Cache state is identical across jobs in a
-# workflow, so we opt in from one job (test/unit) to avoid duplication.
+# workflow, so we opt in from one job (test/vscode) to avoid duplication.
 # Save events are redundant with restore misses (a save only happens because
 # the matching restore missed), so we never emit a save summary.
 if [[ -z "${GITHUB_STEP_SUMMARY:-}" \

.github/workflows/test-e2e-windows-run.yml

@@ -3,10 +3,13 @@ name: "Test: E2E (Windows) — Sharded"
 # Cache Save Strategy:
 # This workflow has a save_cache parameter to prevent race conditions when multiple jobs
 # try to save the same cache key simultaneously. Only ONE job per calling workflow should
-# set save_cache: true, and only shard 1 actually saves. Examples:
-# - test-pull-request.yml: windows e2e saves (save_cache: true, shard 1 only)
+# set save_cache: true, and only shard 1 actually saves. The uv, R, and Graphviz caches
+# save from shard 1 on any non-PR run instead. PRs never save: a cache saved on a PR
+# ref is readable only by that PR, so it just evicts main's caches from the 10 GB repo
+# limit. Examples:
+# - test-pull-request.yml: only restores (save_cache: false)
 # - test-merge.yml: windows e2e saves (save_cache: true, shard 1 only)
-# - test-full-suite.yml: only restores (save_cache: false or omitted)
+# - test-full-suite.yml: saves uv/R/Graphviz only (save_cache omitted)
 
 on:
   workflow_call:
@@ -341,7 +344,7 @@ jobs:
           uv pip install --system trcli
 
       - name: Save Python packages cache
-        if: ${{ matrix.shard == 1 && steps.cache-python.outputs.cache-hit != 'true' }}
+        if: ${{ github.event_name != 'pull_request' && matrix.shard == 1 && steps.cache-python.outputs.cache-hit != 'true' }}
         continue-on-error: true
         uses: actions/cache/save@v6
         with:
@@ -427,7 +430,7 @@ jobs:
           Rscript -e "options(repos = c(CRAN = Sys.getenv('PPM_REPO'))); pak::local_install_dev_deps(ask = FALSE, upgrade = FALSE)"
 
       - name: Save R packages cache
-        if: ${{ matrix.shard == 1 && steps.cache-r.outputs.cache-hit != 'true' }}
+        if: ${{ github.event_name != 'pull_request' && matrix.shard == 1 && steps.cache-r.outputs.cache-hit != 'true' }}
         continue-on-error: true
         uses: actions/cache/save@v6
         with:
@@ -445,8 +448,10 @@ jobs:
           rig add ${{ steps.r-versions.outputs.r_alt_version }}
           rig ls
 
-      - name: Cache Graphviz
-        uses: actions/cache@v6
+      - name: Restore Graphviz cache
+        id: cache-graphviz
+        continue-on-error: true
+        uses: actions/cache/restore@v6
         with:
           path: ${{ runner.temp }}\graphviz
           key: graphviz-win64-${{ env.GRAPHVIZ_VERSION }}
@@ -518,6 +523,15 @@ jobs:
               throw "dot -V failed with exit code $LASTEXITCODE"
             }
 
+      # Fails (and is ignored) when the Chocolatey fallback left nothing to cache.
+      - name: Save Graphviz cache
+        if: ${{ github.event_name != 'pull_request' && matrix.shard == 1 && steps.cache-graphviz.outputs.cache-hit != 'true' }}
+        continue-on-error: true
+        uses: actions/cache/save@v6
+        with:
+          path: ${{ runner.temp }}\graphviz
+          key: graphviz-win64-${{ env.GRAPHVIZ_VERSION }}
+
       - name: Set up Quarto
         uses: quarto-dev/quarto-actions/setup@v2
         env:

.github/workflows/test-full-suite.yml

@@ -556,5 +556,5 @@ jobs:
           tailscale_oauth_secret: ${{ secrets.POSITRON_TAILSCALE_OAUTH_SECRET }}
           repo_id: "positron"
           title: "E2E Full Suite Tests"
-          filter_jobs: "(e2e / ([^0-9]*)|unit|ext-host(-win)?)$"
+          filter_jobs: "(e2e / ([^0-9]*)|vscode|vitest|ext-host(-win)?)$"
           notify_on: ${{ inputs.notify_on }}

.github/workflows/test-merge.yml

@@ -150,7 +150,7 @@ jobs:
           repo_id: "positron"
           # A docs-only push runs only unit-tests; leave out the skipped jobs.
           hide_skipped: ${{ needs.docs-only.outputs.docs_only == 'true' }}
-          filter_jobs: "(e2e / ([^0-9]*)|unit|ext-host(-win)?)$"
+          filter_jobs: "(e2e / ([^0-9]*)|vscode|vitest|ext-host(-win)?)$"
 
   analyze-e2e-failures:
     if: ${{ always() && contains(needs.*.result, 'failure') }}

.github/workflows/test-pull-request.yml

@@ -130,7 +130,7 @@ jobs:
     name: e2e
     uses: ./.github/workflows/test-e2e-windows-run.yml
     with:
-      save_cache: true
+      save_cache: false  # PRs restore from main only; test-merge.yml saves
       grep: ${{ needs.pr-tags.outputs.tags }}
       display_name: "electron-win"
       upload_logs: false
@@ -421,7 +421,7 @@ jobs:
       pull_request: true
 
   # Single always-reported check for every test job in this workflow, meant to
-  # be the one required check in the branch ruleset (in place of test / unit,
+  # be the one required check in the branch ruleset (in place of test / vscode,
   # test / ext-host and e2e / electron).
   #
   # The tag-driven lanes can't be required directly: when a lane's tag is

.github/workflows/test-unit.yml

@@ -32,22 +32,21 @@ permissions:
   packages: read
 
 jobs:
-  unit-tests:
-    name: unit
+  vscode-tests:
+    name: vscode
     runs-on: ubuntu-latest-amd64-4-core
     # The three test steps only account for ~5m; almost all of the wall clock is
     # npm install plus the cache save, and both scale with how many npm caches
-    # missed. A warm-ish run lands at ~35m, but a run that misses all three npm
-    # caches (e.g. run 33655268940) pays ~14m of cold install *and* ~30m of
-    # cache save (npm-core 8m, extensions-volatile 4m, extensions-stable 18m),
-    # reaching the Electron tests at ~57m. 60m cancelled that run 3m into the
-    # first test step. 75m covers the fully-cold ~62m path with headroom while
-    # still capping a genuinely hung run.
-    timeout-minutes: 75
+    # missed. A run that misses all three npm caches (e.g. run 33655268940) pays
+    # ~14m of cold install *and* ~30m of cache save (npm-core 8m,
+    # extensions-volatile 4m, extensions-stable 18m). With Vitest moved to its
+    # own job, that fully-cold path is ~52m; 65m leaves headroom while still
+    # capping a genuinely hung run.
+    timeout-minutes: 65
     # Run inside the shared CI image, which bakes in the system dependencies,
     # Node (matching .nvmrc), and R 4.6.1 + test-files deps that this
     # job used to install at runtime. Built from docker/images/ubuntu24_04.
-    container:
+    container: &container
       image: ghcr.io/posit-dev/positron-ubuntu24:24.22.1-py3.14.7-r4.6.1
       # --shm-size: the Electron unit runner loads each test file's full module
       # graph over file://. A wide graph (>~256 parallel fetches) exhausts the
@@ -58,7 +57,7 @@ jobs:
       credentials:
         username: ${{ secrets.POSITRON_GITHUB_RO_USER }}
         password: ${{ secrets.POSITRON_GITHUB_RO_PAT }}
-    env:
+    env: &env
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       POSITRON_BUILD_NUMBER: 0 # CI skips building releases
       _R_CHECK_FUTURE_FILE_TIMESTAMPS_: false # this check can be flaky in the R pkg tests
@@ -71,11 +70,13 @@ jobs:
       # reticulate 1.47 cannot run on Python 3.14 (rstudio/reticulate#1930); bind the 3.13
       RETICULATE_PYTHON: /root/.pyenv/versions/3.13.0/bin/python
     steps:
-      - uses: actions/checkout@v7
+      - &checkout
+        uses: actions/checkout@v7
         with:
           submodules: recursive
 
-      - name: Checkout specific commit
+      - &checkout-commit
+        name: Checkout specific commit
         if: ${{ inputs.commit != '' }}
         run: |
           git checkout ${{ inputs.commit }}
@@ -87,7 +88,8 @@ jobs:
         with:
           emit-summary: 'true'
 
-      - name: Install node dependencies
+      - &install-node-deps
+        name: Install node dependencies
         if: steps.restore-caches.outputs.cache-npm-core-hit != 'true' ||
             steps.restore-caches.outputs.cache-npm-extensions-volatile-hit != 'true' ||
             steps.restore-caches.outputs.cache-npm-extensions-stable-hit != 'true'
@@ -139,9 +141,6 @@ jobs:
           find . -type f -o -type l | grep -v "node_modules/" | sort > /tmp/files-after-npm-install.txt
           .github/cache-scripts/check-uncached-artifacts.sh /tmp/files-before-npm-install.txt /tmp/files-after-npm-install.txt
 
-      - name: 🧪 Run Vitest Tests
-        run: npm run test:positron
-
       - name: Compile Positron and Download Electron
         run: npm exec -- npm-run-all --max-old-space-size=8192 -p compile "electron x64"
 
@@ -207,3 +206,31 @@ jobs:
         env:
           PLAYWRIGHT_BROWSERS_PATH: .playwright-browsers
         run: DISPLAY=:10 npm run test-browser-no-install -- --browser chromium
+
+  # Vitest needs only node_modules (no compile, Electron, or browsers), so it
+  # runs beside the unit job instead of adding ~10m to its critical path. Same
+  # container as the unit job so the restored npm caches match. Never saves
+  # caches; the unit job owns that.
+  vitest:
+    name: vitest
+    runs-on: ubuntu-latest-amd64-4-core
+    # Container + restore (~6m), a cold install (~15m), and Vitest (~12m), plus
+    # room for one install retry after a hung 30m attempt.
+    timeout-minutes: 70
+    container: *container
+    env: *env
+    steps:
+      - *checkout
+      - *checkout-commit
+
+      - name: 📦 Restore caches
+        id: restore-caches
+        uses: ./.github/actions/restore-build-caches
+        with:
+          restore-builtins: 'false'
+          restore-playwright: 'false'
+
+      - *install-node-deps
+
+      - name: 🧪 Run Vitest Tests
+        run: npm run test:positron