ci: classify mux/ as macOS-neutral so mux-only PRs pass the routing guard

[lawrencecchen]

Problem

Every mux-only PR fails the tests and ci-status routing checks (e.g. #7609), while the mux workflow itself passes. The guard reports app-host unit tests were required but did not pass: skipped.

Root cause: scripts/ci/detect_ci_change_areas.py's is_macos_change is a catch-all — any path not explicitly in is_macos_neutral counts as a macOS change. mux/ isn't listed, so mux-only PRs resolve macos=true. After #7583 staged the macOS app-host shards behind the linux preflight, those shards report skipped while changes.macos=true, and the aggregator guard (if macos == "true" and tests["result"] != "success") fails.

Fix

cmux-mux is a standalone Rust project gated by its own mux workflow; it never affects the macOS app build or app-host tests. Add mux/ to is_macos_neutral so mux-only PRs resolve macos=false, the app-host job skips legitimately, and the guard's macos != "true" branch accepts the skip.

Verified: Resolved areas: macos=false for a mux-only file set; all 36 detector tests pass including the new test_mux_only_skips_macos.

🤖 Generated with Claude Code

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Note

Low Risk
CI routing-only change with a focused unit test; no runtime app or mux build behavior changes.

Overview
Fixes mux-only PRs failing tests / ci-status when macOS app-host shards are legitimately skipped. Paths under mux/ were treated as macOS changes because they were not in the neutral prefix list, so changes.macos=true conflicted with skipped app-host jobs after the linux preflight gate.

is_macos_neutral in detect_ci_change_areas.py now includes mux/, matching the standalone cmux-mux Rust tree covered by the separate mux workflow. Mux-only diffs resolve macos=false (and not web/go) so guards accept skipped macOS jobs.

Adds test_mux_only_skips_macos to lock in classification for typical mux paths.

^{Reviewed by Cursor Bugbot for commit ce33f77. Bugbot is set up for automated code reviews on this repo. Configure here.}

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Summary by cubic

Classify mux/ as macOS-neutral in the CI change detector so mux-only PRs correctly skip macOS app-host tests and pass the routing guard.

• Bug Fixes
  • Include mux/ in is_macos_neutral() to avoid false macos=true.
  • Add test_mux_only_skips_macos to lock the behavior.
  • Result: mux-only changes run only the mux workflow; tests/ci-status no longer fail due to skipped app-host shards.

^{Written for commit ce33f77. Summary will update on new commits.}

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Project	Deployment	Actions	Updated (UTC)
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Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between b51ee74 and ce33f77.

📒 Files selected for processing (2)

• scripts/ci/detect_ci_change_areas.py
• tests/test_ci_change_areas.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-ci-mux-macos-neutral

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[greptile-apps]

Greptile Summary

This PR updates CI routing for mux-only changes. The main changes are:

• mux/ is now treated as macOS-neutral in the CI area detector.
• The detector comment documents mux/ as a standalone Rust project.
• A regression test covers mux-only source, README, and docs paths.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
scripts/ci/detect_ci_change_areas.py	Adds mux/ to the macOS-neutral path list so mux-only changes do not require macOS app-host jobs.
tests/test_ci_change_areas.py	Adds coverage for mux-only changes resolving without macOS, web, or Go areas.

_{Reviews (1): Last reviewed commit: "ci: classify mux/ as macOS-neutral so mu..." | Re-trigger Greptile}