[kixelated]

Problem

ARM near-zero Opus playback on the isolated page develops long arrival gaps, an inflated target, and underruns. The cause remains unresolved, so the quest and existing budgets remain in place.

Approach

Capture native main-thread long tasks alongside arrivals. Opt-in --trace also saves Chromium GC events and a sampled CPU profile. A regression exercises the top-level harness flag, and the quest preserves the controlled evidence.

Untraced ARM controls run both ring orders with identical configuration, including #5569's 80 ms warmup. Isolated-first reaches a 560 ms target and two underrun episodes; the other three rows hold 60 ms with no episodes. Its final profiling command failed because that checkout lacked the wrapper flag; all four untraced captures are valid. The flag omission is now fixed and regression-tested.

Arrival gaps coincide with 227–320 ms main-thread tasks. The GC profile records no GC overlapping the longest tasks. The CPU profile has 100–315 ms sampling gaps across the pauses, with boundary samples in native stream reads. This narrows the browser read/scheduling boundary without establishing its cause. Recorded arrivals produce the same target through either ring in simulated-clock replay.

Impact

• No production public API or wire change.
• The test harness gains --trace and diagnostic capture files.
• The original Nightly workflow is fully restored; its final diff is empty.

Validation

just check and quest check pass, including all 30 audio-quality tests. Real local browser runs exercise untraced capture, GC tracing, sampled CPU profiling, and teardown. Both focused ARM profiles pass. Traced rows are diagnostic evidence and cannot calibrate quality budgets.

Alternatives

A ring or estimator change is not justified by the captured evidence. Budget reductions require clean remeasurement after fixing the cause.

Follow-ups

Lands as diagnostics only. Investigation of native reads and scheduling continues under the existing quest, which stays open with the original product fix and budget goals; no new quest was created.

(Written by GPT-6)

[kixelated]

Outcome: the isolated-first ARM defect is reproduced, and the draft preserves native long-task, GC, and sampled CPU diagnostics plus the top-level trace-flag regression. Required scoped checks and quest validation pass; local real-browser profile capture/teardown and both focused ARM profiles pass. The complete Nightly workflow is restored, and this worktree is clean with no owned validation process left running.

The original product and budget goals remain open. Four untraced controls isolate an order-dependent failure: isolated-first reaches 560 ms and two episodes; the other rows hold 60 ms with no episodes. GC does not overlap the long tasks; sampled CPU captures pause across native stream reads. That evidence is insufficient to choose a product change or attribute the defect to Chromium.

Public API/wire: no production API or wire change; an internal harness diagnostic flag and capture files are added. Recommended follow-up decision: keep this draft and continue native read/scheduling investigation before changing the ring, estimator, or budgets. The quest remains in place for that work.

(Written by GPT-6)

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T00:09:58.800660Z	8be4594	Draft marked ready

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📥 Commits

Reviewing files that changed from the base of the PR and between 810f7cd and 8be4594.

📒 Files selected for processing: 5

• quest/m1/audio-jitter-target/opus-isolated-target.md
• test/audio-quality/README.md
• test/audio-quality/clients/js/cli.test.ts
• test/audio-quality/clients/js/driver.ts
• test/audio-quality/run.sh

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[kixelated]

Automated review by review (OpenAI)

Reviewed commit: 8be4594.

No actionable bugs found. The wrapper forwards trace/capture correctly, long tasks share the arrivals' viewer clock, and capture failures invalidate the row. The linked GitHub artifacts support the reported control/profile observations: one untraced row reaches 560 ms with two underrun episodes versus three 60 ms/no-episode controls, all with 80 ms warmup; the profiles show the described pauses without overlapping recorded GC.

Direction: appropriate diagnostics-only change. Keeping the underlying stall investigation and budgets unchanged is justified; these observations do not establish the cause. The new CLI test proves flag acceptance, not end-to-end trace forwarding or teardown.

Verification: inspected source and the three linked GitHub run artifacts. No fresh tests, browser execution, fault injection or performance reproduction.

[kixelated]

Merge summary:

• Landed as diagnostics only, per the maintainer's choice: --capture now records native long tasks, and opt-in --trace adds a Chromium GC timeline and sampled CPU profile. No estimator, ring, or budget change.
• The audio-jitter-target quest stays open; opus-isolated-target.md keeps the fix and budget goals and gains the captured evidence.
• Updated the Follow-ups section, which still said to keep this a draft, and marked the PR ready.
• No conflicts with main. CI is green, and Codex gave a thumbs up with no findings.

(Written by Opus 5.5)