quest: plan the TS export's remaining MP2 join hole by kixelated · Pull Request #5874 · moq-dev/moq

kixelated · 2026-10-17T16:20:31Z

Problem

TS validation's "TS full multiplex at its own rate" step still loses MP2 media after #5854. Run 39042472016 (#5857, on main with #5854) shows one 120 ms hole that the exporter reported itself, about 60 ms after subscribing, despite max_delay: 450ms on the SUBSCRIBE. The maintainer asked for a quest, not a fix now.

Approach

Adds quest/m1/test-flakes-2/ts-mp2-join-hole.md [M], recording:

the evidence from that run, and what fix(mux): put a live export's budget on its first SUBSCRIBE #5854 already rules out
the unverified suspicion about fix(mux): put a live export's budget on its first SUBSCRIBE #5854's live latch, which starts at the newest announced group
the first step: trace the consumer's skip and latch decisions against the run's artifact (retained until about 2026-10-24), then reproduce deterministically before fixing

It also cross-links quest/m2/audio-join-budget.md, which may share the race.

Decisions (made by the planning agent, which could not prompt; the maintainer fixed the content and should confirm these in review):

Where does it live?
- ✅ Child of m1/test-flakes-2, ranked first (recommended): a CI flake, and the round ranks children by how likely each hides a product bug. This one is confirmed media loss.
- Child of m1/ts-reliability: about the TS contract, but that epic is planning and contracts, not flakes.
- Standalone in m2: too low for a flake on a PR-gating workflow.
Merge with audio-join-budget?
- ✅ Keep separate and cross-link (recommended): each is independently completable, and only a suspicion links them.
- One epic for both: premature until a shared cause is shown.
How prescriptive is the plan?
- ✅ Goal plus evidence plus first step, with the fix left open (recommended, as asked).

Impact

No public API or wire change. Quest files only.

Alternatives

A GitHub issue instead: a quest is preferred for work needing durable scope.

Follow-ups

None beyond the quest.

(written by Claude Opus 5.5)

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

chatgpt-codex-connector · 2026-10-17T16:20:43Z

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📝 Code Review	✅ Completed 2026-10-17T16:22:44.302467Z	`ddc68c6`	PR opened

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chatgpt-codex-connector · 2026-10-17T16:22:41Z

+First step: trace the consumer's skip and latch decisions against that run's artifact
+(the `ts-failure` upload, retained until about 2026-10-24) to find which rule declared
+the gap. Then reproduce it deterministically over `moq_net::transport::memory`, the way


Preserve the diagnostic evidence before it expires

This quest may be picked up after 2026-10-24, at which point its required first step cannot inspect the only artifact that contains the consumer decisions behind the failure. Preserve the relevant trace and media evidence in a durable location, or extract enough diagnostic detail into the repository now, so the quest remains executable after the Actions artifact expires.

AGENTS.md reference: AGENTS.md:L48-L48

Useful? React with 👍 / 👎.

Fixed in the latest push. The artifact only ever held INFO logs and captures, not the consumer's decisions, so the first step no longer depends on it. The quest now records the run's key facts (subscribe and skip times, budget, start points, MP2 grouping), and the first step is a deterministic reproduction instead.

(written by Claude Opus 5.5)

chatgpt-codex-connector · 2026-10-17T16:22:42Z

+reproduces) is not this. The skip was declared about 60 ms after `subscribe started`,
+far inside the budget, so a budget expiry can't explain it either. The subscriber


Do not rule out media-age skipping by wall time

The 60 ms elapsed since subscribe started does not show that the 450 ms budget could not have fired: Consumer::poll_event applies max_delay to the media-timestamp distance max_timestamp.saturating_sub(next_start), not to wall time since subscription. A burst or timestamp lead can therefore cross that threshold immediately, so excluding this path here can send the root-cause investigation away from the predicate that actually declares skips.

Useful? React with 👍 / 👎.

Agreed, fixed in the latest push. The quest now says the budget is measured in media time (max_timestamp - next_start), so 60 ms after subscribing is no bound. It also notes the publisher had run about 2 s before the join, so its cache could supply a backlog spanning that much media time, and the reproduction should include that backlog.

(written by Claude Opus 5.5)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

coderabbitai · 2026-10-17T16:27:37Z

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quest/m1/test-flakes-2/README.md
quest/m1/test-flakes-2/ts-mp2-join-hole.md
quest/m2/audio-join-budget.md

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kixelated · 2026-10-17T17:28:38Z

Merging. This adds quest quest/m1/test-flakes-2/ts-mp2-join-hole.md [M], ranked first in the second flakes round, cross-linked with quest/m2/audio-join-budget.md.

Codex's two findings are fixed in 1c70e2b, with replies. The quest now keeps the expiring artifact's facts and no longer rules out a media-time budget skip.
Codex left no new review on that push.
The placement decisions in the description were made without the maintainer and remain open to revision.

(written by Claude Opus 5.5)

quest: plan the TS export's remaining MP2 join hole

ddc68c6

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

chatgpt-codex-connector Bot reviewed Oct 17, 2026

View reviewed changes

quest: keep the run's evidence and don't rule out a media-time skip

1c70e2b

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated added this pull request to the merge queue Oct 17, 2026

Merged via the queue into main with commit c92830e Oct 17, 2026
6 checks passed

kixelated deleted the plan/ts-mp2-join-hole branch October 17, 2026 17:36

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quest: plan the TS export's remaining MP2 join hole - #5874

quest: plan the TS export's remaining MP2 join hole#5874
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		reproduces) is not this. The skip was declared about 60 ms after `subscribe started`,
		far inside the budget, so a budget expiry can't explain it either. The subscriber

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