[kixelated]

Finishes quest/m1/stats-group-tracks.md.

Problem

At depth 1 or more, a stats producer announced one <prefix>/<group>/node/<node> broadcast per group per node. Group churn cost announce traffic across the whole cluster, a reader had to follow N announcements to see one node, and one oversize group took a whole broadcast down with it.

Approach

Every node publishes one <prefix>/node/<node> broadcast for its life, and that is now the only layout.

• Tracks. The broadcast carries totals.json (node-wide), one <group>/group.json track per depth group, and the on-demand presence and prefix tracks for any label or prefix. At depth 0 the one group is group.json. The per-tier publisher.json / subscriber.json / sessions.json tracks are gone, along with their request quota and parking.
• Group track. One name with the moq-net compress flag and no .z sibling: moq-json snapshots with merge-patch deltas and refresh(8). Each frame is a GroupFrame, { "epoch", "tiers": { <tier>: { publisher, subscriber, sessions, paths, labels } } }. A tier's top-level fields are the group's totals, so a Totals reader parses them unchanged. A path's side that never moved is left out and reads as zero, which keeps the depth-0 snapshot the size of the old publisher.json.
• Lifetime. At depth 0 the group's track lives for the producer's life. At depth 1 or more, a track is listed from the group's first entry until it has lingered empty (linger), then finished and unlisted. A group that comes back later is a new instance: a new epoch, counted from zero. Its group numbers count publish intervals, so they continue past the old instance's.
• Discovery. Only through the track listing (TRACKS on lite-07, SUBSCRIBE_TRACKS on draft 18+). Over a hop that cannot list, the listing is empty or refused, and the docs say so.
• Aggregation. aggregate::Consumer::group(group) folds one group's track across every node. It resolves each node's broadcast and waits for the listing to offer the track. It re-subscribes when the listing offers the next instance, and resets that node's group fold on a new epoch. Totals keep their old readout as a baseline. Paths start over. Labels are a gauge that leaves with the node. The fold is generic over a Shape, so totals, presence, and prefix keep their existing semantics.
• Readers. Consumer::group / consume::GroupConsumer read one node's group. The demo dashboard reads group.json. moq inspect docs fetch totals.json.
• moq-net forgets gone names. A broadcast no longer keeps a per-name sequence namespace (BroadcastState::sequences, JS TrackSequences) for tracks that ended. A node broadcast that never ends stays bounded by its live tracks, however many group names it retires. A replacement track starts at 0, and the publisher that recreates a name continues past its predecessor's groups itself. This reverts the library-side checks from fix(net): one dynamic track per name, sequences continue across replacements #4929, fix(net)!: the application owns a replacement track's start sequence #5068, and fix(net): an empty replacement track ends past its predecessor's groups #6376.
• Group numbers count publish intervals. Each drain numbers its groups by its scheduled tick divided by stats.interval, counted at full resolution, and a track opens at most one group per interval. A recreated track's groups land past its predecessor's with nothing kept per name.
• moq-transcode finishes only with its source. A rung track finishes only when its source track finished. Retiring, closing, losing the source without a finish, or an error abort it instead.

Bench (producer_tick, 1 tier, 10% of paths moving). The host ran at load 60 on 24 cores, so the bytes and allocations are the trustworthy columns:

row	layout	heldB	allocs/tick	ms/tick
stats/tick/1000p	old broadcast, publisher.json	415001	7673	1.7
stats/tick/1000p	one track, both sides per path	843663	16221	3.0
stats/tick/1000p	now	430663	8721	1.6
stats/tick/10000p	old broadcast	4150001	75182	29
stats/tick/10000p	now	4291666	85600	37

stats/groups now sweeps a depth-1 producer: 1000 paths cost 2.5 / 1.9 / 8.9 ms over 1 / 100 / 1000 groups. decode reads one group frame per tick, and aggregate folds group tracks.

Impact

• moq-stats (breaking). Removed: produce::Layout, produce::Config::{layout, with_layout}, TrafficFrame, SessionsFrame, traffic_track, sessions_track, NodePath, Consumer::{traffic, sessions}, consume::{TrafficConsumer, SessionsConsumer}, aggregate::Config::{depth, with_depth}, aggregate::Consumer::{traffic, sessions}, aggregate::{TrafficConsumer, SessionsConsumer}. parse_node_path(prefix, path) drops its depth argument and returns the node path. Added: GroupFrame, Group, group_track, parse_group_track, Consumer::group, consume::GroupConsumer, aggregate::Consumer::group, aggregate::GroupConsumer. Migrate: read a tier's per-path traffic from group(group)'s tiers[tier].paths[path].publisher / .subscriber, and its sessions from .labels. A missing side is zero. Drop depth from aggregate::Config, since every group shares the node broadcast. New dependency: serde_with (workspace), for the epoch field.
• moq-net (breaking). stats::Tier::track_name is removed; build names with moq_stats::group_track. A track that replaces an ended one of the same name appends from 0 instead of returning Error::Duplicate, and its finish() / close() / finish_at() are no longer checked against the predecessor. Migrate: a publisher that recreates a name numbers its groups past the old instance's itself.
• @moq/net (breaking). The same replacement behavior: no duplicate sequence throw, and a producer removed with removeTrack stays writable after a replacement claims the name.
• moq-relay (behavior). [stats] depth now publishes one group track per bucket on .stats/node/<node> instead of one broadcast per bucket. linger keeps an empty group's track listed. No option was added or removed. A token can no longer scope stats reads to one group, because every group shares the node broadcast path.
• moq-transcode (behavior). A retired rung's subscriber sees Cancel instead of a clean end.
• Wire. Stats tracks change as above: <group>/group.json replaces the per-tier tracks, and depth groups no longer announce. The protocol is unchanged.

MIGRATE entries are not added here: since #6610 they are written at the breaking cut from each ! PR's Impact section.

Alternatives

1. Layout option (superseded): keep both layouts behind layout = "broadcast" | "track". The maintainer chose the track layout as the only one, so the enum, --stats-layout, and every broadcast-layout reader are gone.
2. Continuation instead of an explicit reset: rejected. Each track instance carries a minted epoch, and a group returning after its linger counts from zero. Continuation keeps totals for every group ever seen, and a subscriber can mint groups at depth 2+ by fetching arbitrary paths, so it grows without bound under a hostile peer.
3. Keeping retired names in moq-net's sequence map: rejected, as were rotating the node broadcast's epoch and reclaiming only finished names (Codex finding). Each keeps the library guessing at continuity the publisher owns.
4. Flooring same-interval snapshots at last + 1: rejected. It lets a track run ahead of the clock and collide with its own replacement.
5. Finishing a rung on retire: rejected (Codex P1). A finish only follows the source's.
6. Serializing both sides of every path: rejected after measuring. It doubled the depth-0 snapshot (843663 B vs 415001 B at 1000 paths) and its allocations.

Follow-ups

• moq-net: an aborted track read through an origin on an epoch route ends with NotFound, not its cause. The subscriber's resume re-requests the ended name, and the handler's refusal replaces FrameTooLarge. Reproduced in this branch, and the oversize test reads the broadcast directly for that reason.
• Compress migrate (/quest/m1/compress/migrate.md) moves the remaining .z siblings (totals, presence, prefix) onto the flag.
• Finish-only-on-source-finish elsewhere. moq-gst's sink finishes on caps renegotiation and release_pad, then reserves the same name. That is the hazard moq-transcode had. Lower risk: moq-mux timeline publish error, moq-cli echo retire, moq-rtsp jump/cancel, moq-rtmp disconnect, cpp/obs restart, js/publish teardown, moq-net IETF SUBSCRIPTION_ENDED.

Checks

On 30c4192e9f, after merging main, then cargo nextest run -p moq-relay -p moq-stats (494 passed) on ba9036ac7b after merging #6705, whose public stats::Config::linger() stays:

• just rs lint-changed and just rs test-changed: the workspace passed (10317 tests).
• just js check-changed and just js test-changed: passed.
• sh/markdown.sh check, just gh check / test, and quest check: passed.
• nix flake check: fails building the runner image (unshare: write failed /proc/self/uid_map), a host-only limit.
• Benches producer_tick, decode, and aggregate ran to completion.

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[kixelated]

The quest is implemented and pushed. just check passed, and so did quest check. The PR stays a draft because two decisions in the body are the maintainer's call: the option's name and shape (my recommendation: the layout enum), and explicit reset vs continuation (my recommendation: an explicit reset with a per-instance epoch). Suggested follow-ups are listed in the body.

(written by Claude Opus 5.5)

[coderabbitai]

Walkthrough

The stats producer adds a track layout alongside the existing broadcast layout. Track layout publishes group data on group tracks within one node broadcast, with interval-based group numbering and linger-based track removal. The JavaScript and Rust networking implementations remove shared sequence history across same-name track replacements. A replacement now uses its own sequence state and can continue an earlier sequence through an explicit starting sequence.

Priority: Normal

Merge Risk: Moderate · up to 637ce

After a track is replaced, the old producer can still write to it while the new one starts at sequence 0, so subscribers could receive conflicting content under one track name. Close the predecessor when it is removed for replacement, and add a test for it, before merging. The earlier documentation and comment issues are already fixed.

Pre-merge checks: 5

Check name	Status	Explanation
Docstring Coverage		Docstring coverage is 84.26% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 108 functions across 14 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title is concise and accurately identifies the primary change: publishing stats groups as tracks within one node broadcast.
Description check		The PR description is specific and closely tied to the changeset. It explains the single track layout for stats (one node broadcast with per-group group.json tracks, lifetime and discovery rules), the…

Full details: Description check

Explanation

The PR description is specific and closely tied to the changeset. It explains the single track layout for stats (one node broadcast with per-group group.json tracks, lifetime and discovery rules), the moq-net and @moq/net replacement-track sequence changes, the moq-transcode finish behavior, and the removed public APIs in moq-stats. It also lists the benchmark and test results. The description matches the raw summary, which covers the stats docs, moq-stats, moq-relay, moq-net, @moq/net, and the removed quest file.

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⚠️ Outside diff range comments (2)

🟡 Minor · Update the stale comment: group numbers no longer start over. · produce.rs:2883-2884

rs/moq-stats/src/produce.rs:2883-2884
📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win

Update the stale comment: group numbers no longer start over.

This PR changes Snapshot::update (Line 578) to number groups by publish interval. A returning group's broadcast now continues group numbers past the old instance. It does not start them over. The PR also removed the assertion that checked a lower sequence after the linger. The comment at Line 2883-2884 still says "with group numbers starting over". The new docs in doc/concept/stats.md (Line 143-145) say the opposite.

Proposed fix

-		// A return after the linger is a new epoch counted from zero, with group
-		// numbers starting over.
+		// A return after the linger is a new epoch counted from zero; group
+		// numbers count publish intervals, so they continue past the old epoch's.

As per coding guidelines: "Fix any outdated docs and comments inline; don't add a separate PR for it."

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Review comment at @rs/moq-stats/src/produce.rs around lines 2883 - 2884:
Update the stale comment near Snapshot::update to state that a returning group's
group numbers continue past the old epoch, reflecting that numbering follows
publish intervals rather than restarting. Keep the comment’s scope limited to
this correction.

Source: Coding guidelines

🟡 Minor · Remove the stale "earlier producer" throw from the append docs. · track.ts:1372-1381

js/net/src/track.ts:1372-1381
📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win

Remove the stale "earlier producer" throw from the append docs.

The appendGroup doc still says "Throws if an earlier producer of the name in this broadcast already wrote that sequence". The appendDatagram doc still says "Like appendGroup, throws if an earlier producer of the name already wrote that sequence".

This change removed the broadcast-wide sequence namespace. #nextSequence now returns this.#received and runs only the #writable closure and end checks, so neither method throws for a predecessor's sequence. A replacement appends from 0, as js/net/MIGRATE.md now states. The Rust counterparts were updated in this PR.

📝 Proposed doc fix

 	/**
 	 * Append a new group with the next sequence number: one past this producer's own writes.
 	 *
-	 * Throws if an earlier producer of the name in this broadcast already wrote that sequence.
-	 * A replacement picks where it starts by writing its first group with {@link writeGroup}.
+	 * A replacement starts at 0; to continue past its predecessor's groups, write its first
+	 * group with {@link writeGroup} at an explicit sequence.

-	 * relay preserving upstream numbering uses {@link insertDatagram}. Like {@link appendGroup},
-	 * throws if an earlier producer of the name already wrote that sequence.
+	 * relay preserving upstream numbering uses {@link insertDatagram}.

As per coding guidelines: "Fix any outdated docs and comments inline; don't add a separate PR for it."

Also applies to: 1443-1458

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Review comment at @js/net/src/track.ts around lines 1372 - 1381:
Update the appendGroup and appendDatagram documentation to remove the obsolete
claim that appending throws when a predecessor wrote the same sequence. Clarify
that a replacement starts at sequence 0 and can continue at an explicit sequence
by writing its first group with writeGroup; remove the corresponding stale claim
from appendDatagram’s docs.

Source: Coding guidelines

---

• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @rs/moq-net/src/model/track.rs:
- Around line 2650-2652: Update the replacement-producer sequence handling
around Self::create_group to reject any sequence already assigned to the
broadcast, rather than allowing resume filtering to hide reused groups. Require
replacements to continue after their predecessor using create_group or the
equivalent explicit-sequence API.

---

Outside diff comments:
Review comments at @js/net/src/track.ts:
- Around line 1372-1381: Update the appendGroup and appendDatagram documentation
to remove the obsolete claim that appending throws when a predecessor wrote the
same sequence. Clarify that a replacement starts at sequence 0 and can continue
at an explicit sequence by writing its first group with writeGroup; remove the
corresponding stale claim from appendDatagram’s docs.

Review comments at @rs/moq-stats/src/produce.rs:
- Around line 2883-2884: Update the stale comment near Snapshot::update to state
that a returning group's group numbers continue past the old epoch, reflecting
that numbering follows publish intervals rather than restarting. Keep the
comment’s scope limited to this correction.

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⛔ Files ignored due to path filters: 1

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📒 Files selected for processing: 28

• doc/bin/relay/config.md
• doc/concept/stats.md
• doc/lib/js/net.md
• doc/lib/rs/moq-net.md
• js/net/MIGRATE.md
• js/net/src/broadcast.test.ts
• js/net/src/broadcast.ts
• js/net/src/internal.ts
• js/net/src/track.test.ts
• js/net/src/track.ts
• quest/m1/README.md
• quest/m1/stats-group-tracks.md
• rs/moq-net/MIGRATE.md
• rs/moq-net/src/model/broadcast.rs
• rs/moq-net/src/model/track.rs
• rs/moq-net/src/model/track/demand.rs
• rs/moq-net/tests/integration/empty_replacement.rs
• rs/moq-net/tests/integration/main.rs
• rs/moq-net/tests/integration/route_change.rs
• rs/moq-relay/src/config.rs
• rs/moq-relay/src/settings.rs
• rs/moq-relay/src/stats.rs
• rs/moq-stats/Cargo.toml
• rs/moq-stats/benches/producer_tick.rs
• rs/moq-stats/src/consume.rs
• rs/moq-stats/src/lib.rs
• rs/moq-stats/src/produce.rs
• rs/moq-stats/src/produce_bench.rs

💤 Files with no reviewable changes: 6

• quest/m1/README.md
• js/net/src/track.test.ts
• js/net/src/internal.ts
• rs/moq-net/tests/integration/main.rs
• rs/moq-net/tests/integration/empty_replacement.rs
• quest/m1/stats-group-tracks.md

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⚠️ Outside diff range comments (1)

🟠 Major · Invalidate the predecessor during replacement. · track.ts:1359

js/net/src/track.ts:1359
🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win

Invalidate the predecessor during replacement.

When removeTrack is used as the replacement handoff, close the predecessor with an abort before removing it from the broadcast. The current code only removes map and listing ownership, so the old producer remains writable while the new producer starts at sequence 0.

🐛 Suggested fix

 		const track = this.#state.tracks.get(name);
 		if (!track) return;
+		track.close(new Error("track replaced"));
 		this.#state.tracks.delete(name);

Add a test that writes through the old producer after replacement and expects the write to fail.

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Review comment at @js/net/src/track.ts at line 1359:
Update removeTrack to close the predecessor with an abort before removing it
from the broadcast, invalidating the old producer before its replacement starts.
Add a test confirming writes through the old producer fail after replacement.

Source: Coding guidelines

---

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Outside diff comments:
Review comments at @js/net/src/track.ts:
- Line 1359: Update removeTrack to close the predecessor with an abort before
removing it from the broadcast, invalidating the old producer before its
replacement starts. Add a test confirming writes through the old producer fail
after replacement.

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[kixelated]

On CodeRabbit's outside-diff finding on 637cea1 ("Invalidate the predecessor during replacement", removeTrack): declined. removeTrack is unchanged from main and only stops the broadcast from listing and counting the track. A caller who wants the old producer ended closes or aborts it itself. The old producer's writes reach only its own subscribers, never the replacement's, and js/net/MIGRATE.md documents that it stays writable. Closing it inside removeTrack would be a separate behavior change outside this PR's scope.

(Written by Claude Opus 5.5)

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Reviewed commit: a14cdacb76

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Automated review by review (OpenAI)

Reviewed commit: 30c4192

No new actionable bugs found in the group-only layout migration, listing-driven aggregation and benchmark update. Removing the alternate layout simplifies the design; keeping group epochs separate while preserving totals and resetting per-path state is appropriate.

The fractional-interval numbering finding is fixed: #6428 (comment) . The transcode retirement case is addressed: #6428 (comment) . Documented remaining publisher migrations are not newly reported here.

Verification: static changed-code and relevant surrounding-logic review, accounting for merged main changes. No tests or benchmarks run.

[kixelated]

Landing summary for ba9036ac7b:

• The track layout is now the only one. produce::Layout, the per-tier publisher.json / subscriber.json / sessions.json tracks, their request quota, and the per-group broadcasts are gone. Each node publishes totals.json, one <group>/group.json track per depth group, and presence and prefix tracks on request.
• aggregate::Consumer::group folds group tracks across nodes. It follows each node's track listing and resets on a new group epoch: totals keep a baseline, paths start over, and labels act as a gauge. aggregate::Config loses depth.
• The demo dashboard reads group.json. The relay docs, doc/concept/stats.md, and the inspect docs describe the single layout.
• A path's side that never moved is left out of the group frame. This keeps the depth-0 snapshot near the old publisher.json (430663 B vs 415001 B at 1000 paths).
• There are no MIGRATE entries, per docs: write MIGRATE.md at the breaking cut, not per PR #6610. The Impact section carries the migration.
• Reviews on the final head: an OpenAI review found nothing new on 30c4192e9f, and Codex gave 👍 on ba9036ac7b.

(Written by Claude Opus 5.5)

[kixelated]

Re-enqueueing without code changes. The merge-queue run (https://github.com/moq-dev/moq/actions/runs/40169568971) failed only on moq-rtsp client::tests::a_silent_session_stalls and client::tests::rtcp_alone_stalls. This PR does not touch moq-rtsp. It only ran because moq-net changed. Both tests use a 200 ms wall-clock client.timeout that also bounds every RTSP handshake step, so on a loaded runner the client gives up during setup and the fake server panics with "a request before PLAY". That flake is already tracked in quest/m1/test-flakes-2/rtsp-stall-timers.md, with the fix in #6736. quest check passes on head ba9036a.

(Written by Claude Opus 5.5)