[kixelated]

Problem

relay_upstream_close checks that a relay ends a finished track cleanly downstream after the publisher's session closes. The mock transport acknowledged a FIN only once the relay read it, so the publisher's close could not drain until the relay already had every SUBSCRIBE FIN. QUIC acknowledges a FIN when it arrives, before the application reads it. So a draining close can finish, and the session can close, while the relay still has the FIN unread.

That is the race #6741 fixed, but the test only caught it on Lite03 and Lite04, through their tail grace. With #6741's poll_drain change reverted, Lite05 and Lite06 still passed. A real relay in that window ends a downstream subscription Unroutable after every frame arrived, instead of finishing it.

Approach

The publisher's transport acknowledges FINs on arrival (ack_fins), as QUIC does. With #6741's subscriber change reverted, the test now fails on every Lite version through 06:

assertion `left == right` failed: moq-lite-05 Close track0: result=Err(Stream(Unroutable))
assertion `left == right` failed: moq-lite-06 Close track0: result=Err(Stream(Unroutable))

It passes on main for every listed version, for both close and abort. The doc comments now say why the close drains before the relay reads.

Impact

• None. Test only; no API or wire change.

Alternatives

• A separate test for the Lite05/06 case. Rejected: it would repeat this test's setup, and the gap was only the mock's acknowledgement timing.

Follow-ups

• None.

🤖 Generated with Claude Code

(Written by Claude Opus 5.5)

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Reviewing files that changed from the base of the PR and between cdd0196 and 00d376a.

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• rs/moq-net/tests/integration/relay_upstream_close.rs

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

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[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 2026-10-28T09:03:49.663963Z	00d376a	PR opened

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[kixelated]

Automated review by review (OpenAI)

Reviewed commit: 00d376a

No actionable bugs found. The direction is sound: enabling ack_fins() on the publishing upstream transport before finishing the tracks removes the mock's read-before-ack dependency, exercising the unread-FIN/session-close race while preserving the existing frame-completeness and clean-end assertions. Reusing this test and the existing transport knob is simpler than adding a duplicate scenario; no production API or wire behavior changes.

Verification: inspected the changed test, connection harness, and mock FIN acknowledgment implementation on GitHub. Tests and the reported regression-revert experiment were not run independently.

[kixelated]

Merge summary: no changes were needed. CI passed on 00d376ac9a158abf02718a2c8720e276ce071de8, the Codex review (thumbs up) and the automated review had no findings, the PR merges cleanly into main, and quest check passed. Landing this head with a squash.

(Written by Claude Opus 5.5)