ci(gate): macos-26 back to PR cadence (Aaron 2026-04-28)

.github/workflows/gate.yml

@@ -76,12 +76,22 @@ concurrency:
 
 jobs:
   # Dynamic matrix for build-and-test: pre-merge events (pull_request
-  # and merge_group) get Linux-only (production build path, fast —
-  # keeps PR checks and merge-queue runs short). Push-to-main /
-  # workflow_dispatch get the full set including macos-26
-  # (developer-experience verification) and the Windows experimental
+  # and merge_group) get Linux production legs + macos-26
+  # (developer-experience verification). Push-to-main /
+  # workflow_dispatch additionally include the Windows experimental
   # legs. Standard GitHub-hosted runners are free for public repos so
-  # the post-merge run has no cost downside.
+  # all PR cadence has no cost downside.
+  #
+  # Duration check (maintainer 2026-04-28): the original 25-min
+  # concern that pushed macos-26 to per-merge was an outlier.
+  # Recent build-and-test job durations are typically 1-3 min on
+  # cached runners — comfortably within PR-cadence budget.
+  #
+  # Maintainer 2026-04-28: "mac is less than that too so we might as
+  # wel move that back form per merge to per pr, i think that means
+  # only low memory is per merge now." → macos-26 moves to PR cadence;
+  # only ubuntu-slim (low-memory.yml) + Windows experimental remain
+  # on per-merge.
   matrix-setup:
     name: matrix setup
     runs-on: ubuntu-24.04
@@ -93,20 +103,15 @@ jobs:
         shell: bash
         run: |
           # Pre-merge (pull_request + merge_group): Linux production
-          # legs only (~3 min wall clock).
-          # Push-to-main / workflow_dispatch: full surface incl.
-          # macos-26 (developer-experience) + Windows legs
-          # (peer-harness milestone seeding per maintainer 2026-04-27 —
-          # "start the windows one as a per push to main too/merge to
-          # main, you can start slowly building that out before I get
-          # my windows laptop running the peer-mode agent, windows
-          # will be mostly ready and they can just clean it up").
+          # legs + macos-26 dev-experience leg (~3-4 min total).
+          # Push-to-main / workflow_dispatch: pre-merge legs + Windows
+          # experimental legs (peer-harness milestone seeding).
           # Windows legs are gated by `continue-on-error: true` at the
           # build-and-test job level so initial failures (e.g. missing
           # tools/setup/install.ps1) don't block per-merge runs while
           # the peer-agent polishes the path.
           if [ "${GH_EVENT}" = "pull_request" ] || [ "${GH_EVENT}" = "merge_group" ]; then
-            echo 'os=["ubuntu-24.04","ubuntu-24.04-arm"]' >> "$GITHUB_OUTPUT"
+            echo 'os=["ubuntu-24.04","ubuntu-24.04-arm","macos-26"]' >> "$GITHUB_OUTPUT"
           else
             echo 'os=["ubuntu-24.04","ubuntu-24.04-arm","macos-26","windows-2025","windows-11-arm"]' >> "$GITHUB_OUTPUT"
           fi
@@ -141,30 +146,31 @@ jobs:
     #                       Reference:
     # https://github.blog/changelog/2026-01-22-1-vcpu-linux-runner-now-generally-available-in-github-actions/
     #
-    # Per-merge experimental legs (maintainer 2026-04-27 — replaces
-    # the prior 2026-04-24 deferral so Windows infrastructure is
-    # mostly-ready when the peer-mode agent comes online):
+    # Per-merge experimental legs (maintainer 2026-04-27):
     #   - windows-2025      Windows Server 2025 x64 (4 CPU, 16 GB)
     #   - windows-11-arm    Windows 11 arm64 (4 CPU, 16 GB)
-    # These run only on push-to-main / schedule / workflow_dispatch
-    # (not on PR — same cadence as macos-26). They carry
-    # `continue-on-error: true` because no PowerShell install script
-    # exists yet (`tools/setup/install.ps1` TBD); failures are
-    # visible-but-not-blocking until the peer-agent polishes the
-    # path.
+    # These run only on push-to-main / workflow_dispatch (not on PR).
+    # They carry `continue-on-error: true` because no PowerShell
+    # install script exists yet (`tools/setup/install.ps1` TBD);
+    # failures are visible-but-not-blocking until the peer-agent
+    # polishes the path.
     #
     # fail-fast: false so one leg's failure doesn't cancel the
     # others — we want the full signal across the matrix.
     #
-    # Per-PR / per-merge cadence split (maintainer 2026-04-27):
-    # - macos-26: developer-experience verification, NOT prod build.
-    #   Runs only on push-to-main + schedule + workflow_dispatch.
-    #   Same rationale as the Analyze (csharp) move below.
+    # Per-PR / per-merge cadence split (maintainer 2026-04-28):
+    # - macos-26: developer-experience verification. Runs on every
+    #   PR + merge_group + push-to-main. Originally moved to
+    #   per-merge over a 25-min duration concern; verified 2026-04-28
+    #   that recent gate.yml runs are well under that (typical
+    #   build-and-test job is 1-3 min on cached runners), so back to
+    #   PR cadence per maintainer ask.
     # - ubuntu-24.04 + ubuntu-24.04-arm: production build path; runs
-    #   on every PR + push-to-main.
-    # The matrix is built dynamically by `matrix-setup` so PR runs
-    # only get the Linux legs while push-to-main / schedule /
-    # workflow_dispatch run all three.
+    #   on every PR + merge_group + push-to-main.
+    # The matrix is built dynamically by `matrix-setup` so PR +
+    # merge_group runs include macos-26, while push-to-main /
+    # workflow_dispatch additionally include the Windows experimental
+    # legs.
     name: build-and-test (${{ matrix.os }})
     timeout-minutes: 45
     needs: matrix-setup

tools/hygiene/github-settings.expected.json

@@ -131,6 +131,7 @@
     "required_signatures": false,
     "required_status_checks": {
       "contexts": [
+        "build-and-test (macos-26)",
         "build-and-test (ubuntu-24.04)",
         "build-and-test (ubuntu-24.04-arm)",
         "lint (actionlint)",