Best possible solution:

Land the narrow test-only speedup after required CI finishes green, while keeping the production 10s scheduler shutdown grace and the existing 27-case coverage intact.

Do we have a high-confidence way to reproduce the issue?

Not applicable as a test-performance cleanup rather than a product bug. Current source shows the parent-signal proof exercises the real 10s shutdown grace, and the PR body provides before/after timing evidence.

Is this the best way to solve the issue?

Yes. The patch accelerates only the disposable spawned proof process before importing the real scheduler module, which is narrower than changing production grace constants or dropping coverage.

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against 11eeba972f46.

Label changes:

• add P3: This is a low-risk test-performance cleanup with no runtime behavior change.
• add proof: sufficient: Contributor real behavior proof is sufficient. The PR body includes after-change focused local/Linux timing results, pnpm test:changed, format, diff-check, and real-behavior-proof status evidence for this test-only performance change.
• add rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🐚 platinum hermit and patch quality is 🐚 platinum hermit.

Label justifications:

• P3: This is a low-risk test-performance cleanup with no runtime behavior change.
• rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🐚 platinum hermit and patch quality is 🐚 platinum hermit.
• proof: sufficient: Contributor real behavior proof is sufficient. The PR body includes after-change focused local/Linux timing results, pnpm test:changed, format, diff-check, and real-behavior-proof status evidence for this test-only performance change.

PR surface:

Tests +5. Total +5 across 1 file.

What I checked:

• PR diff: The patch changes only test/scripts/docker-all-scheduler.test.ts, adding a spawned-runner Date.now scale before dynamic import and leaving production files untouched. (test/scripts/docker-all-scheduler.test.ts:730, eddd8b076779)
• Current parent-signal test: Current main has a POSIX parent-signal proof that starts a long-lived child, sends SIGTERM to the runner, expects exit 143, verifies the first grandchild is cleaned, and verifies the second command never starts. (test/scripts/docker-all-scheduler.test.ts:699, 11eeba972f46)
• Scheduler grace contract: runShellCommand tracks active children, uses a 10s default shutdown grace, waits for process-group exit with Date.now-based deadlines, then force-kills survivors; the PR accelerates only this test's spawned process clock. (scripts/test-docker-all.mjs:571, 11eeba972f46)
• Scoped policy: The scoped test guide warns against shared Vitest fake timers in unit-fast; this patch does not use Vitest fake timers and confines the clock override to a disposable spawned .mjs process. (test/AGENTS.md:3, 11eeba972f46)
• Coverage shape: The current scheduler test file still has 27 it/posixIt cases, matching the PR body's 27 -> 27 coverage claim. (test/scripts/docker-all-scheduler.test.ts:86, 11eeba972f46)
• Live PR state: Live GitHub data shows head eddd8b0, mergeable state MERGEABLE/UNSTABLE, no reviews or human comments, a protected maintainer label, a successful real-behavior-proof check, and some CI still in progress during review. (eddd8b076779)

Likely related people:

• steipete: Authored the current PR and recently landed adjacent test-performance work on test/scripts/crabbox-wrapper.test.ts, including the same clock-scaling test helper pattern. (role: recent adjacent contributor; confidence: high; commits: eddd8b076779, 11eeba972f46; files: test/scripts/docker-all-scheduler.test.ts, test/scripts/crabbox-wrapper.test.ts)
• Vincent Koc: The shipped scheduler helper and test file appear in release-tagged commit e085fa1, authored and committed by Vincent Koc. (role: released area introducer; confidence: medium; commits: e085fa1a3ffd; files: scripts/test-docker-all.mjs, test/scripts/docker-all-scheduler.test.ts)

• 🦀 challenger crab: rare, exceptional readiness with strong proof, clean implementation, and convincing validation.
• 🦞 diamond lobster: very strong readiness with only minor maintainer review expected.
• 🐚 platinum hermit: good normal PR, likely mergeable with ordinary maintainer review.
• 🦐 gold shrimp: useful signal, but proof or patch confidence is still limited.
• 🦪 silver shellfish: thin signal; proof, validation, or implementation needs work.
• 🧂 unranked krab: not merge-ready because proof is missing/unusable or there are serious correctness or safety concerns.
• 🌊 off-meta tidepool: rating does not apply to this item.

Shiny media proof means a screenshot, video, or linked artifact directly shows the changed behavior. Runtime, network, CSP, and security claims still need visible diagnostics.

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