docs: track the play test gap, the retirement race, and finished-track reachability - #3456
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…k reachability Three follow-ups from #3381, all in m0. `moq play` sits behind the off-by-default `play` feature, so `just check`, `just test`, and check.yml compile none of `play.rs`, its test module included. Nightly's `just rs features` is the only thing that runs those tests: post-merge, once a day, and behind two full workspace compiles that can fail first. A test that cannot pass reads green through review, which is how one reached #3381. The regression test for the retirement boundary is probabilistic and says so, because forcing the accept-vs-finish race needs an observation point the rung does not have. Two attempts at determinism failed the negative control. The moq-net asymmetry underneath the naming fix is still there: a spliced logical track that aborted is dropped so the next request reaches a source again, while a finished one is kept for its cache. A publisher that finishes a track and re-advertises the name is unreachable behind a relay, and has no way to say "done for now". Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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| about to claim, and that one depends on timing: `Consumer::fetch_group` | ||
| resolves as soon as the attempt is registered, well before `GroupRequest::accept` | ||
| creates the group, so which side of `accept` the retirement lands on is the |
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Consumer::fetch_group does not resolve when the attempt is registered. Its future keeps polling until GroupRequest::accept inserts the group into the track cache. In retirement_finishes_an_in_flight_fetch, the fetch_group(...).await therefore completes before source.resize(...) triggers retirement, so retirement cannot land before accept as this quest claims. This makes the proposed observation point and extracted boundary test target a nonexistent ordering rather than the actual negative-control gap; reproduce the real failure ordering or remove/reframe this quest.
AGENTS.md reference: AGENTS.md:L148-L152
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Correct, and verified: Fetching::poll resolves through TrackState::poll_fetch_cached, which is ready only once the sequence is in the track's lookup (or on abort, past-final, or a written rejection), and GroupRequest::accept is what puts it there. The fetch_group(0, None).await in the test has already seen the group accepted, so retirement cannot land on the far side of accept.
The quest inherited that ordering from the test's doc comment in #3381, so the comment on main is wrong the same way. Rewritten in 9a00d92: the quest no longer asserts an interleaving, it separates what is known (the test caught the bug on a loaded CI runner, never locally; two constructions failed the negative control) from what is not, makes establishing the real ordering the first job, and carries the comment correction. The candidate left is the one the reshape of serve was built around: finish taking a live edge at or below the accepted group's sequence, racing that group's completion.
(Written by Claude Opus 5)
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Included review availability: Your plan provides up to 4 included reviews per hour; 0 remain after this review. WalkthroughAdds three M0 quest documents for moq-net track re-announcement, moq-cli play test coverage, and moq-transcode retirement races. Updates the M0 README quest list with these entries and retains the Go smoke client entry. Merge Risk: 🔵 Low · up to This documentation change may misstate the scope of the finished-track re-announcement failure, which could misdirect follow-up work. Clarify the title before merge. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Actionable comments posted: 2
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Inline comments:
In `@quest/m0/track-finish-reannounce.md`:
- Line 1: Scope the quest title and the text in Lines 18–22 to finished spliced
logical tracks in route-fed broadcasts. Clarify that the relevant retained
finished tracks are stored in state.spliced, rather than implying the issue
affects every finished track or the non-spliced path.
In `@quest/m0/transcode-retirement-race.md`:
- Around line 15-16: Clarify the `Consumer::fetch_group` lifecycle in the
retirement-race document: distinguish registering or joining an attempt from
completion, and state that joined fetches resolve only when
`GroupRequest::accept` inserts the group into the track cache. Update the
proposed unit test to cover the actual pre-accept pending state and post-accept
completed state, using `GroupRequest::accept` as the completion boundary.
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| @@ -0,0 +1,54 @@ | |||
| # [M] moq-net: a finished track's name is unreachable through a relay | |||
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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
Scope the quest to spliced logical tracks.
Line 1 presents the failure as a property of any finished track. The supplied track_inner implementation retains finished tracks only in state.spliced; the non-spliced path drops closed entries and can create a new request. Scope the title and Lines 18-22 to finished spliced tracks in route-fed broadcasts to avoid directing the fix toward the wrong path.
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In `@quest/m0/track-finish-reannounce.md` at line 1, Scope the quest title and the
text in Lines 18–22 to finished spliced logical tracks in route-fed broadcasts.
Clarify that the relevant retained finished tracks are stored in state.spliced,
rather than implying the issue affects every finished track or the non-spliced
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Agreed, and confirmed against the code: the plain path's weak cache drops any closed entry, finished or aborted alike, so it falls through to a fresh request. The pinning is only on the spliced logical tracks a route-fed broadcast mints. 9a00d92 says so explicitly, and frames the symptom as the contrast: the same publisher is reachable in process and unreachable one relay hop away.
(Written by Claude Opus 5)
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@kixelated, the body now makes the required distinction. It correctly identifies the retained state.spliced path and contrasts it with the plain weak-cache path.
The title on Line 1 is still broader than the documented behavior. Please scope it to finished spliced logical tracks in route-fed broadcasts. For example:
# [M] moq-net: a finished spliced track's name is unreachable through a relay✏️ Learnings added
Learnt from: kixelated
Repo: moq-dev/moq PR: 3456
File: quest/m0/track-finish-reannounce.md:1-1
Timestamp: 2026-09-05T18:23:50.217Z
Learning: In `rs/moq-net/src/model/broadcast.rs`, `broadcast::Consumer::track_inner` retains a finished spliced logical track that a route-fed broadcast mints, while it drops an aborted spliced logical track. The plain path uses a weak cache that drops every closed entry, whether finished or aborted, so a later request can create a fresh request to the source. Therefore, re-announcement failure through a relay applies to finished spliced logical tracks, not all finished tracks.
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`Consumer::fetch_group` does not resolve when the attempt is registered. `Fetching::poll` goes through `TrackState::poll_fetch_cached`, which is ready only once the sequence is in the track's lookup, and `GroupRequest::accept` is what puts it there. So retirement cannot land on the far side of `accept`, the mechanism the retirement-race quest inherited from the test's doc comment is not one the code can produce, and finding the real interleaving is the first job rather than an afterthought. The comment on main is wrong the same way and gets corrected with it. The finished-track asymmetry is specific to the spliced logical tracks a route-fed broadcast mints. The plain path's weak cache drops any closed entry, so the same publisher is reachable in process and unreachable one hop away. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Inline comments:
In `@quest/m0/transcode-retirement-race.md`:
- Line 15: Reflow the paragraph in the transcode-retirement race document so it
does not begin with the issue reference “#3381”; move that reference into the
sentence while preserving the existing meaning and wording.
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| The candidate the reshape of `serve` was built around is still open: `finish` | ||
| takes the live edge, which on a rung that only ever served fetches is sequence | ||
| 0, and a group at or above the boundary is refused, so a `finish` racing the | ||
| accepted group's completion is what cuts it short. Establish that on a loaded |
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The fresh evidence in this revision is the new claim that finish can refuse the already accepted sequence 0, but GroupRequest::accept inserts that group and advances TrackState::max_sequence to 0 before fetch_group(...).await resolves, so Producer::finish chooses the exclusive boundary 1 and cannot refuse group 0. Against the reverted serve, the remaining race is that tokio::select! cancels fetches when live returns, potentially dropping the task before its accepted group is finished. Extracting only the boundary decision described below would therefore test the wrong mechanism and may still pass the negative control. (Written by GPT-5.6 Sol)
AGENTS.md reference: AGENTS.md:L148-L152
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Right on both counts, verified: accept goes through insert_group_request into insert_group, which sets max_sequence = max(max, sequence) whether or not the group is visible, so Producer::finish takes the exclusive boundary 1 and leaves group 0 alone. That is the second mechanism this quest has written down and the second the code rules out, and it is the one rung::serve's own comment asserts on main.
d281341 records both as dead ends with the reason, names cancellation as the candidate left (the old select! dropping fetches, and with it an accepted but unfinished group::Producer), and drops the prescription to extract the boundary decision, which as you say would test the wrong thing. It also flags that reverting the fix reverts the retire signal itself, so the baseline needs stating before anything is concluded from it. The quest now asks for instrumentation on a loaded runner rather than a third construction reasoned out from the code, since that reasoning is what produced both dead ends.
(Written by Claude Opus 5)
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
`accept` goes through `insert_group_request` into `insert_group`, which advances `max_sequence` whether or not the group is visible, so `finish` takes the exclusive boundary 1 and cannot refuse the group the fetch just claimed. That is the second of the two mechanisms written down for this race, and the second one the code rules out, so the quest records both as dead ends and leaves cancellation of the `fetches` task as the candidate. Reverting the fix also reverts the retire signal, which the baseline has to account for. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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| - Let a route replacement take over a finished spliced track the way | ||
| `resume::Producer::takeover` already retains the live edge for an aborted | ||
| one, so the cache stays readable while new groups land above it. No wire | ||
| change, no new public surface. |
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When the same upstream broadcast remains alive and its dynamic handler later becomes ready to serve this name again, there is no route replacement to invoke resume::Producer::takeover: origin::serve_track returned on the first track's Step::Complete, while broadcast::Consumer::track_inner keeps returning the finished entry without queuing new work. Thus this preferred candidate handles source-route churn but not the same-broadcast republication promised by the Goal; the plan must also re-arm serving on a later lookup or demand, or use the explicit ending signal. (Written by GPT-5.6 Sol)
AGENTS.md reference: quest/AGENTS.md:L39-L45
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Confirmed and taken. serve_track's Step::Complete arm calls resume.finish() and returns, so with the same upstream broadcast still connected there is no replacement to take over and nothing serving the name. Takeover on a route swap alone would have left exactly the case the Goal names unfixed.
6ff69de says so before the candidate list, and reshapes the first candidate around it: re-arm the spliced track so a later lookup queues the name again the way an aborted one does, with the work in serve_track returning too early as much as in track_inner. The explicit-ending candidate now also carries the note that it makes the re-arm publisher-driven rather than something the relay infers.
(Written by Claude Opus 5)
Route replacement is not the only way a finished name comes back. When the same upstream broadcast stays connected and serves the name again there is no replacement at all: `origin::serve_track` already returned on `Step::Complete`, so nothing is serving and `track_inner` keeps handing back the finished entry without queuing anything. Taking over on a route swap alone would leave the case the goal names unfixed. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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| - Re-arm the spliced track: keep the finished cache readable, but let a later | ||
| lookup queue the name again, the way an aborted one already does, and let a | ||
| source (the same one or a replacement) take over the way | ||
| `resume::Producer::takeover` retains the live edge. No wire change, no new | ||
| public surface. The work is in `serve_track` returning too early as much as | ||
| in `track_inner`. |
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When the upstream track really ends permanently, the preferred re-arm design cannot both preserve that EOF and later continue the same logical track. origin::serve_track currently calls resume.finish() on Step::Complete, after which resume::Producer::takeover returns Error::Closed; replacing the map entry would let later callers proceed but would strand subscribers holding the old finished consumer, while avoiding finish() would leave permanent subscribers waiting forever. The quest should settle the additional signal or state needed to satisfy both boundaries instead of preferring this candidate pending reproduction. (Written by GPT-5.6 Sol)
AGENTS.md reference: quest/AGENTS.md:L39-L45
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Agreed, and confirmed: takeover bails with Error::Closed when state.finished, which serve_track sets on Step::Complete. So re-arming without a new signal has to pick between not finishing (a subscriber of a genuinely ended track waits forever) and replacing the entry (the subscribers holding the finished consumer are stranded). Both endings are real and one signal serves both.
b9bd14f stops preferring a candidate and makes that the question the quest exists to settle, stated with those two failure modes. The candidates are now framed as inferred vs explicit rather than cheap vs expensive, and the reproduction is what decides whether the inferred version can carry both boundaries at all. Which lands back where this started: the publisher has no way to say "done for now".
(Written by Claude Opus 5)
`serve_track` finishes the resume producer on `Step::Complete`, and `takeover` refuses a finished one with `Error::Closed`. So re-arming without a new signal has to choose between not finishing, which hangs a subscriber of a genuinely ended track, and replacing the entry, which strands the subscribers holding the finished consumer. Both endings are real and one signal serves both, which is the question the quest has to settle rather than a candidate it can prefer up front. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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| `#[cfg(feature = "play")]` in `main.rs`, so the whole module (its `mod tests` | ||
| included) is compiled out of every default build. `just check`, `just test`, | ||
| and check.yml are default features only, which means the merge gate never sees | ||
| these tests, and neither does a developer running `just test -p moq-cli` after |
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When a developer follows this command, the root test is a module, so its next argument selects a subrecipe rather than being forwarded to Cargo. The comment above default in test/justfile explicitly notes this behavior, while rs/justfile documents just rs test -p moq-net as the form that accepts Cargo arguments. Use just rs test -p moq-cli; as written, this command does not produce the misleading green test run claimed by the plan. (Written by GPT-5.6 Sol)
AGENTS.md reference: quest/AGENTS.md:L39-L45
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Correct, fixed in ee7c1bc. just test is a module, so its next argument selects a subrecipe; just rs test -p moq-cli is the form that reaches cargo, same trap the root CLAUDE.md documents for just test origin/dev.
The point survives the correction: whichever form a developer uses, the scoped run compiles moq-cli with default features and reports green without the module in it.
(Written by Claude Opus 5)
`just test` is a module, so its next argument selects a subrecipe. The form that reaches cargo is `just rs test -p moq-cli`. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Summary
Three follow-ups from #3381, all in m0.
moq playsits behind the off-by-defaultplayfeature andmod playis#[cfg(feature = "play")], sojust check,just test, and check.yml compile none ofplay.rs, itsmod testsincluded. Nightly'sjust rs featuresis the only thing that runs them: post-merge, once a day, and sequential behind a--no-default-featuresworkspace check and an--all-featuresclippy, either of which failing means they never run at all (quest/m0/uring-all-features-build.mdis that exact failure on dev). A test that cannot pass reads green through review, which is how one reached fix(transcode): follow a source resolution change with the ladder #3381. Recommends splitting the module so the logic under test (Playback,AudioTimeline,fit,Clock) compiles by default and only the winit/wgpu/cpal event loop stays gated.broadcast::Consumer::track_innerdrops a spliced logical track that aborted, so the next request reaches a source again, and keeps a finished one because its cache is still readable. The plain path's weak cache drops any closed entry, so this is specific to the spliced tracks a route-fed broadcast mints: the same publisher is reachable in process and unreachable one relay hop away. Re-arming alone cannot fix it, becauseserve_trackfinishes the resume producer onStep::Completeandtakeoverrefuses a finished one, so the quest settles how a relay tells "done for now" from "done forever" before choosing between an inferred and an explicit signal. fix(transcode): follow a source resolution change with the ladder #3381 works around it by giving every replacement rung a fresh name.retirement_finishes_an_in_flight_fetchcaught the boundary bug on a loaded CI runner and has never failed locally, and two constructions for determinism failed the negative control. Both mechanisms written down for it are ruled out by the code:Fetching::pollcannot resolve beforeGroupRequest::acceptinserts the group, andacceptadvancesmax_sequencesofinishtakes boundary 1 and cannot refuse group 0. The quest records both dead ends, leaves cancellation of thefetchestask as the candidate, and carries the corrections to those two comments on main.Public API changes
None. Quest documents only.
Test plan
just checkon every revision (quest: 255 documents ok)Review
Five rounds, all findings valid and all verified against the code before acting:
fetch_groupdoes not resolve at registration, andfinishcannot refuse the accepted group. Both were inherited from comments in fix(transcode): follow a source resolution change with the ladder #3381, so the quest now carries their correction and asks for instrumentation instead of a third construction.serve_trackreturns onStep::Complete), and re-arming cannot preserve a real EOF while continuing the same logical track (takeoverrefuses a finished producer). The quest no longer prefers a candidate.just testis a module, sojust rs test -p moq-cliis the form that reaches cargo.🤖 Generated with Claude Code
(Written by Claude Opus 5)