CI: default macOS-15 jobs to WarpBuild instead of dead Blacksmith pool

[lawrencecchen]

Problem

The Blacksmith macOS pool is retired. Any CI run already queued against blacksmith-6vcpu-macos-15 sits queued forever (GitHub never re-evaluates runs-on after a job is queued), which is what stuck the last push run on main for ~7.5h with every Linux job green and only the macOS jobs (swift-package-tests, app-host unit tests, release-ghostty-cli-helper, ui-regressions) hung.

The runner labels are driven by repo variables (MACOS_RUNNER_15, MACOS_RUNNER_DISPLAY), which already point at warp-macos-15-arm64-6x. But the in-workflow || '...' fallbacks still named the dead Blacksmith pool, so clearing/unsetting a var would silently route these jobs back into the permanently-queued state.

Change

Point every macOS-15 fallback in ci.yml at warp-macos-15-arm64-6x to match the live repo vars. release-build keeps its Blacksmith macOS-26 fallback (disk-heavy universal build; that fallback is explicitly enforced by tests/test_ci_self_hosted_guard.sh). Updated the stale app-host comment.

No behavior change while the vars are set; this only fixes the failure mode when a var is cleared.

Verification

• ./tests/test_ci_self_hosted_guard.sh passes locally (exit 0).
• The live main CI (post var-flip) already ran fully green on WarpBuild: https://github.com/manaflow-ai/cmux/actions/runs/28735661079

Meta/CI-only change; no tagged app build.

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Note

Low Risk
Workflow-only runner label fallbacks; no app code or release-build macOS-26 lane changes.

Overview
Updates .github/workflows/ci.yml so macOS-15 jobs no longer fall back to the retired blacksmith-6vcpu-macos-15 pool when MACOS_RUNNER_15 / MACOS_RUNNER_DISPLAY are unset. Every affected runs-on and display-runner validation step now uses warp-macos-15-arm64-6x, aligned with the live repo variables.

Touched jobs: app-host unit tests, swift-package-tests, tests-build-and-lag, release-ghostty-cli-helper, and ui-regressions. The app-host job comment is refreshed to reference Warp instead of Blacksmith. release-build is unchanged and still defaults to blacksmith-6vcpu-macos-26.

No change while vars are set; this only fixes jobs that would otherwise queue forever on a dead label.

^{Reviewed by Cursor Bugbot for commit 6338d15. Bugbot is set up for automated code reviews on this repo. Configure here.}

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Summary by cubic

Default macOS-15 CI jobs to WarpBuild to prevent hangs on the retired Blacksmith pool. Aligns ci.yml fallbacks with MACOS_RUNNER_15 and MACOS_RUNNER_DISPLAY so clearing a var won’t stall runs.

• Bug Fixes
  • Switch macOS-15 runs-on fallbacks to warp-macos-15-arm64-6x in ci.yml (app-host tests, Swift package tests, UI regressions, release-ghostty-cli-helper); refreshed the app-host comment.
  • Keep release-build fallback to Blacksmith macOS-26 (guarded by tests/test_ci_self_hosted_guard.sh); update tests/test_ci_release_sdk_lane.sh to expect Warp for release-ghostty-cli-helper.

^{Written for commit bab26e9. Summary will update on new commits.}

Summary by CodeRabbit

• Chores
  • Updated multiple macOS CI jobs to run on the new warp-macos-15-arm64-6x runner.
  • Adjusted CI runner identity validation for the release SDK lane to match the updated macOS runner default.
  • Updated inline workflow notes to reflect the new macOS build environment.

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Project	Deployment	Actions	Updated (UTC)
cmux	Ready	Preview, Comment	Jul 5, 2026 11:27am
cmux-staging	Building	Preview, Comment	Jul 5, 2026 11:27am

[coderabbitai]

📝 Walkthrough

Walkthrough

Updates macOS CI jobs to default to warp-macos-15-arm64-6x, adjusts two display-runner guard defaults, and updates a release lane test expectation to match the new runner value.

Changes

CI Runner Migration

Layer / File(s)	Summary
Update macOS job runner defaults .github/workflows/ci.yml	Changes runs-on defaults for app-host-unit-tests, swift-package-tests, tests-build-and-lag, release-ghostty-cli-helper, and ui-regressions to warp-macos-15-arm64-6x, and updates the REQUESTED_RUNNER default in the tests-build-and-lag and ui-regressions display-runner guards.
Adjust release lane expectation tests/test_ci_release_sdk_lane.sh	Updates the build-ghostty-cli-helper runner assertion in release.yml to expect warp-macos-15-arm64-6x.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 25

✅ Passed checks (25 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Cmux Swift Actor Isolation	✅ Passed	PASS: The PR only changes CI workflow YAML and a shell test; no Swift source, actor, protocol, or UI-store declarations were added or worsened.
Cmux Swift Blocking Runtime	✅ Passed	The diff only updates a shell test expectation; no Swift files or runtime synchronization code are changed.
Cmux Browser Automation Off-Main	✅ Passed	PR only updates a CI lane test expectation for macOS runner labels; no browser automation code, waits, or routing changed.
Cmux Expensive Synchronous Load	✅ Passed	PR changes only CI/test files; HEAD modifies tests/test_ci_release_sdk_lane.sh and no Swift files or agent-history loads are present.
Cmux Cache Substitution Correctness	✅ Passed	PASS: The PR only changes CI YAML and a shell test; no production Swift/TypeScript/JavaScript cache/history/snapshot paths are touched.
Cmux No Hacky Sleeps	✅ Passed	Changed files only retarget CI runner labels and a test assertion; no sleeps, timers, polling, or retry waits were added, and workflow YAML is out of scope.
Cmux Algorithmic Complexity	✅ Passed	PR only changes CI workflow YAML and a test script; no production Swift/TS/JS/runtime code or scalable-collection algorithm changes.
Cmux Swift Concurrency	✅ Passed	PR diff changes only ci.yml and a shell test; no Swift sources or async-pattern changes were introduced.
Cmux Swift @Concurrent	✅ Passed	The PR only changes CI workflow YAML and a shell test; no Swift files or Swift concurrency code paths are modified, so the rule is not applicable.
Cmux Swift File And Package Boundaries	✅ Passed	Only tests/test_ci_release_sdk_lane.sh changed; no Swift files or package-boundary-sensitive production code were touched.
Cmux Swiftpm Lockfiles	✅ Passed	PR only changes ci.yml runner fallbacks and one test; no Package.swift, Package.resolved, .gitignore, or Xcode package-reference changes appear in the diff.
Cmux Swift Logging	✅ Passed	PR diff only changes .github/workflows/ci.yml and a shell test; no Swift source or logging statements were added or modified.
Cmux User-Facing Error Privacy	✅ Passed	Only a test script changed; the rule allows tests, and no user-facing error copy or production text was modified.
Cmux Full Internationalization	✅ Passed	Only a workflow and a test changed; no user-facing Swift/web copy or locale assets were touched, and the policy allows tests/config tokens.
Cmux Swiftui State Layout	✅ Passed	PASS: The PR only changes CI workflow and a shell test; no SwiftUI files or rule-violating state/layout patterns were introduced.
Cmux Architecture Rethink	✅ Passed	Only CI workflow/test runner-label fallbacks changed; no Swift UI/lifecycle code or architectural smell was introduced.
Cmux Swift Auxiliary Window Close Shortcuts	✅ Passed	PR only changes a shell CI test; no Swift windows/controllers or cmux auxiliary-window identifiers were added or modified.
Cmux Source Artifacts	✅ Passed	Diff only touches ci.yml and a test script; no local logs, caches, temp dirs, or other artifact paths are added.
Cmux No Test Or Debug Seam In Production Source	✅ Passed	PR only changes .github/workflows/ci.yml and a test shell script; no production Swift Sources files were modified.
Cmux No Ambient Global State	✅ Passed	The commit only updates tests/test_ci_release_sdk_lane.sh; no Swift sources or ambient-global-state patterns are introduced.
Title check	✅ Passed	The title clearly summarizes the main CI runner fallback change and matches the changeset.
Description check	✅ Passed	The description covers Summary and Testing well; only optional template items like Demo Video, Review Trigger, and Checklist are omitted.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat-ci-warp-macos-defaults

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit 6338d15. Configure here.}

[greptile-apps]

Greptile Summary

This CI-only change fixes the stuck-forever failure mode on main by replacing every blacksmith-6vcpu-macos-15 fallback in ci.yml with warp-macos-15-arm64-6x, matching the live MACOS_RUNNER_15 / MACOS_RUNNER_DISPLAY repo variables. The release-build job's macOS-26 Blacksmith fallback is intentionally kept and guarded by tests/test_ci_self_hosted_guard.sh.

• ci.yml: Six runs-on / REQUESTED_RUNNER substitutions across five jobs (app-host unit tests, swift-package-tests, tests-build-and-lag, release-ghostty-cli-helper, ui-regressions); also refreshes the app-host comment to reference WarpBuild.
• tests/test_ci_release_sdk_lane.sh: Updates the assertion for ci.yml's release-ghostty-cli-helper job to expect the new fallback label; the release.yml assertion (line 35) is correctly left unchanged since release.yml is not part of this PR.

Confidence Score: 5/5

Safe to merge — workflow-only runner label changes with no app code touched and a passing guard test.

All six substitutions in ci.yml are mechanical string replacements of a dead pool label with a live one. The release-build macOS-26 lane is untouched and its guard script still passes. No production Swift, runtime, or build logic is affected.

No files require special attention. The remaining blacksmith-6vcpu-macos-15 references in other workflows are out of scope for this PR but worth a follow-up.

Important Files Changed

Filename	Overview
.github/workflows/ci.yml	Updates six runs-on / REQUESTED_RUNNER fallback values from the retired blacksmith-6vcpu-macos-15 to warp-macos-15-arm64-6x across five jobs; release-build (macOS-26) is intentionally left unchanged.
tests/test_ci_release_sdk_lane.sh	Updates the assertion for ci.yml's release-ghostty-cli-helper job to expect the new warp-macos-15-arm64-6x fallback; the release.yml assertion on line 35 is intentionally left pointing at the Blacksmith fallback since release.yml is not part of this PR.

_{Reviews (2): Last reviewed commit: "test: expect warp-macos-15 fallback for ..." | Re-trigger Greptile}