[kixelated]

Problem

#5854 fixed the MP2 holes in TS validation, but its tests check the mechanism's inputs: the budget on the first SUBSCRIBE, and the local latch. Nothing reproduces the loss itself deterministically; its repro was 24 staggered joiners under load.

Approach

a_live_start_loses_no_group_the_publisher_bursts (in rs/moq-mux/src/container/source.rs) runs a real lite-07 session over moq_net::transport::memory, with paused time:

1. A live ExportSource subscribes, and the publisher writes group 0.
2. The publisher bursts groups 1..3 in one synchronous pass, one 24 ms frame per group, the way the TS import publishes a PES of MPEG-1 audio. The export reads group 0 in the meantime.
3. Groups 4..7 follow once the session has settled.

Verified on this branch, rebased on main:

• It passes on main, which carries fix(mux): put a live export's budget on its first SUBSCRIBE #5854's fix.
• It fails with fix(mux): put a live export's budget on its first SUBSCRIBE #5854 (7a3890c) reverted. The export reads [0, 72000, 96000, 120000, 144000, 168000]: one 48 ms hole right after the first frame, then nothing lost once the widening lands. That is the CI signature (media skipped upstream ... at=2.917977s skipped=48ms).

While building it I found that a front-resolved track::Subscriber::update reaches the upstream session only on the reader's next poll (resume::Reader mirrors preferences lazily). So the test keeps polling the export the way a real export task does.

This also adds the quest quest/m2/audio-join-budget.md. moq-audio's Start::Latest join with a warmup subscribes with just the warmup and widens after the first frame (joining_latest), the same narrow-then-widen shape, so it should be checked for the same race.

Impact

• No public API or wire change. Test and quest only.

Alternatives

• None worth weighing: this only adds coverage for a fix that already landed.

Follow-ups

• quest/m2/audio-join-budget.md, above.

(written by Claude Opus 5.5)

🤖 Generated with Claude Code

[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 2026-10-17T14:52:43.621230Z	754a5af	Draft marked ready

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[coderabbitai]

Warning

Review limit reached

You've used all free OSS reviews for now. Wait for the free limit to reset to keep reviewing this public repository.

Next included review available in 12 minutes.

Check out review usage here.

View limit details

Limit details: You’ve used all 4 included reviews currently available.

Learn how review limits work.

Review configuration:

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 103bb985-fb57-4994-83bd-85b066d8fa1a

📥 Commits

Reviewing files that changed from the base of the PR and between 2736815 and 754a5af.

📒 Files selected for processing: 3

• quest/m2/README.md
• quest/m2/audio-join-budget.md
• rs/moq-mux/src/container/source.rs

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[kixelated]

Merging. This adds test and quest only, rebased on main after #5854.

• The regression test passes on main, and fails with fix(mux): put a live export's budget on its first SUBSCRIBE #5854 reverted, reproducing the CI signature ([0, 72000, 96000, ...]).
• Required checks (Check, Test) pass. Codex reviewed this head with no findings.
• The optional TS validation check failed on this run: one MP2 hole in "TS full multiplex at its own rate" (skipped=120ms, declared 60 ms after subscribing). This head already carries fix(mux): put a live export's budget on its first SUBSCRIBE #5854, whose 450 ms budget is on the first SUBSCRIBE, so a second cause remains on main. This PR changes no runtime code, so it neither causes nor fixes that. I'm reporting it as a follow-up.

(written by Claude Opus 5.5)