quest: plan the lite-07 Live flag that unblocks #5000

[kixelated]

Problem

#5000 (late lower groups) let an explicit floor survive merging with a floorless subscriber. Its review found that this starves the floorless one: with a floor-4 subscriber and a new viewer on a quiet track whose newest group is 3, the merged floor stays 4 and the viewer gets nothing until group 4 exists, which on a catalog track is never (the failure #4940 fixed from the other side). main's rule has the opposite bug: the floorless subscriber clears the floor and the floored one loses its late group. Both come from one field meaning both "floor" and "no floor".

Approach

• New m1 quest quest/m1/lite-live.md [M]: lite-07 SUBSCRIBE and SUBSCRIBE_UPDATE carry a separate Live boolean. Group Start/Frame Start become a plain absolute floor, optional so a live-only subscriber has none; a subscription with neither is refused. Live: true lowers the floor to frame 0 of the oldest group Subscriber Max Age has not expired, when that position sorts below the floor (max age 0 is the latest group, and lite-06 buffering keeps its backlog). The model becomes Subscription { floor: Option<(group, frame)>, live }; merging is OR for live and min for the floor.
• Older wires map at the codec. lite-06 (0, 0) is live. On moq-transport, live is Largest Object plus the current-group prefix (a Relative(1) fill on draft-20+, a joining FETCH before that), while Next Group Start keeps its draft meaning as a floor at the next group. A relay may ask a moq-transport upstream for TRACK_STATUS when merged needs can't be expressed in one SUBSCRIBE; a lite upstream is subscribed at floor 0 and filtered locally.
• quest/m1/lite-late-lower-group.md now requires it and drops its own aggregation rule.
• quest/m1/subscribe-ranges/README.md records that Live stays a separate field beside the range list.
• quest/m1/lite07-finalize.md requires it before lite-07 is cut.

Public API: none (plans only). Wire: none (plans only); the quest plans a lite-07-wip SUBSCRIBE field.

Interview paper trail

• Goal: Confirm / ✅ Also cover frames / Reword
• Relation to fix(net): deliver a fresh group below the first served group when the floor allows it #5000: Fold into fix(net): deliver a fresh group below the first served group when the floor allows it #5000 / New quest fix(net): deliver a fresh group below the first served group when the floor allows it #5000 requires / Replace fix(net): deliver a fresh group below the first served group when the floor allows it #5000 → first ✅ Fold, then re-asked once it became a wire change: ✅ Split, wire quest first / Keep folded
• Milestone: ✅ m1 / m0
• Fix site: Model matches wire / Wire change on lite-07 / Both → ✅ (user) "I think we need a boolean on lite-07 if live is in scope. Otherwise the floor can be above live. So replace the 0 with a separate field?"
• Semantics: ✅ (user) "live: true replaces the floor value if the latest is smaller"
• Frame under Latest: ✅ Frame 0 / Keep Frame Start
• Older wires: Codec-only mapping / lite-07 only → ✅ (user) "codec-only mapping, and maybe issue a TRACK_STATUS if there's ambiguity (one sub wants latest, another wants floor)"
• Name: Live / ✅ Latest / Join Live → re-asked after the max-age decision below: ✅ Live / Keep Latest
• Docs: ✅ Inline only / Add a docs quest
• vs Subscribe ranges: ✅ Latest now, kept by ranges / Fold into ranges / Model fix now, wire later

Iteration (review findings):

• moq-transport mapping (CodeRabbit): Next Group Start starts at the next group (draft-16 §5.1.2), so it stays a floor; the current-group join is the Largest Object + prefix fill/FETCH bridge subscribe_join sends today. ✅ applied
• Latest-only floor (Grok, blocking): ✅ None + max-age reach / None, exactly latest / Defer to implementation
• Wording (Grok 2-4: lite-06 (0, N), position comparison, lite upstream without TRACK_STATUS): ✅ Apply all three / Skip

Follow-ups

• fix(net): deliver a fresh group below the first served group when the floor allows it #5000 rebases onto the new quest's PR once it lands.

(Written by Claude Opus 5.5)

🤖 Generated with Claude Code

[kixelated]

Grok review of 13d1e11f (quest-only PR: new quest/m1/lite-latest.md plus links from three other quests)

Splitting "floor" from "the latest group" is the right fix for the #5000 starvation, and every link resolves. But the core rule doesn't say what floor a latest-only subscriber carries, and the lite-06 mapping changes what a buffered subscriber gets today. I checked the claims against main.

Blocking

1. A latest-only subscriber's floor is undefined, and both obvious choices break something (lite-latest.md:22-36). The plan removes the "0 means none" sentinel and makes the model Subscription { floor: (group, frame), latest } with no Option, so a subscriber that only wants the live edge still has to put some value in Group Start:

   • Floor 0 + latest: latest does nothing, because no group is below 0. A merge with a floor-4 subscriber gives floor 0, which is main's aggregate again (today None and Some(0) are the same thing; see the start doc in rs/moq-net/src/model/subscription.rs and canonical_start_group in rs/moq-net/src/lite/subscribe.rs).
   • "No floor" (top) + latest: the merge works (min(4, top) = 4, OR keeps latest, start = group 3). But Latest then means exactly the latest group, and the codec mapping "lite-06 Group Start 0 is latest" changes behavior. On lite-06 today, a floor of 0 with a non-zero Subscriber Max Age starts at the oldest unexpired group, not the latest one (drafts/draft-lcurley-moq-lite.md:1049-1051: "A subscriber that buffers is then handed the head of what it can still play"). Under the new rule that subscriber silently loses its buffered backlog, which also contradicts the quest's own Goal ("everything their own floor and Subscriber Max Age allow").

   Suggested fix: say that a latest subscriber's floor is "none" (the neutral value for min), and define Latest as "the floor may drop to wherever Subscriber Max Age reaches back from the live edge," which is the start lite-06 already resolves for Group Start 0. A max age of 0 still means the latest group. Then add the buffered case (latest with max age > 0, merged with a floor above the live edge) to the test list.

Non-blocking

2. The lite-06 mapping misses (0, N) (:34). "lite-06 Group Start 0 is latest, any other value a floor" is only true when Frame Start is also 0. A Group Start of 0 with Frame Start N is a real floor at group 0, frame N (catalog resumes): canonical_start_group keeps it, frame_start_may_qualify_group_zero_on_lite06 pins it, and the draft allows it at :201. Reword to "Group Start 0 with Frame Start 0 is latest."
3. The replacement rule should compare positions, not groups (:25-27). "Replaces the floor with the latest group when the latest group is smaller" misses the case where they're equal. Take a merged floor of (3, 5) with group 3 as the latest group: the latest group isn't smaller, so the latest subscriber never gets frames 0-4 of the keyframe group it was promised. Use "when (latest, 0) sorts below the floor."
4. The TRACK_STATUS fallback doesn't exist for a lite upstream (:37-39). moq-lite has no TRACK_STATUS. rs/moq-net/src/lite/ has no such message, and only lite-07's SUBSCRIBE_START carries largest. So for a lite-06 (or pre-06) upstream the relay can't learn the largest group before subscribing, and the plan should say what it does there. Subscribing at floor 0 and filtering locally is main's behavior, which is fine as long as it's stated. For a moq-transport upstream, also say what happens when TRACK_STATUS reports an empty track.
5. The moq-transport mapping only names the draft-19 tags (:35-36). Draft-20 spells the filter by how many fields it has: Unfiltered, Relative(n), and an absolute start with an optional end (rs/moq-net/src/ietf/filter.rs). Relative(1) (the current group) is what moq-net's own live join sends. Absolute Range and Relative(n>1), which is a floor relative to the largest group and needs it to resolve, aren't mapped either. Also say whether mapping Next Group Start (largest group + 1) and Largest Object (mid-group, after the largest object) to latest (frame 0 of the current group) is meant to widen what those filters ask for.

CI: Quest, Check and Test were still queued when I reviewed.

Verdict: ITERATE. Pin the latest-only floor and the max-age meaning of Latest (1); the rest are wording fixes.

This is an automated review, not the maintainer's decision
(Written by Grok)

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Walkthrough

The documentation adds a lite-07 Live flag proposal. It describes separating Live from the subscription floor, combining Live flags with OR and floors with minimum, and handling legacy wire formats. Related quest plans update their terminology and describe how Live interacts with late lower groups and subscription ranges. The changes specify planned documentation and tests; they do not implement subscription behavior.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to fa424

This PR updates planning documents, and the clarified MOQT mapping preserves distinct start behavior. No actionable merge risk remains beyond normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: planning the lite-07 Live flag to unblock issue #5000.
Description check	✅ Passed	The description directly explains the lite-07 Live flag proposal, its subscription semantics, compatibility mappings, related quest updates, and plans-only scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
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Inline comments:
Review comments at @quest/m1/lite-latest.md:
- Around line 35-36: Update the filter description in the plan to distinguish
`Next Group Start` from `latest`; describe `Largest Object` as approximating
`latest` through the existing `NextObject`/`Relative(1)` fill or older-draft
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[kixelated]

Automated review of 9a206b26 (quest-only PR, claims checked against main)

Pulling the floor and "the latest group" apart is the right fix for the #5000 starvation, and the moq-transport mapping matches the code: subscribe_join really does send NextObject plus a Relative(1) fill on draft-20+ and a RelativeJoining FETCH (offset 0) before that, and Filter::Relative(0) is NEXT_GROUP. The gaps are in the merge rule itself, which is the part #5000 will build on.

Blocking

1. The floor of a latest-only subscriber is undefined, and the merge result depends on it (quest/m1/lite-latest.md, Plan bullets 1–4). The model becomes Subscription { floor: (group, frame), latest } with no Option and no "0 means none" sentinel, and floors merge as min. A fresh viewer still has to carry some floor:

   • If it's (0, 0) (what a lite-06 Group Start of 0 decodes to today), then min(4, 0) = 0. latest (group 3) is never smaller than 0, so the flag never changes anything, and you're back to main's rule. Whether the floor-4 subscriber keeps its late lower group then depends entirely on what replaces raise_start_to's start.is_none() check, and the quest doesn't say.
   • If it's "+infinity", the starvation case works (min(4, ∞) = 4, then latest lowers it to 3). But lite-07 then needs a way to put "no floor" on the wire, which contradicts "plain absolute floor, no sentinel" (a QUIC varint can't carry u64::MAX). It also drops Subscriber Max Age reach-back: the lite draft (Group Start, around L1047–1052) says delivery starts at the oldest fresh group at or above the floor, so a buffering lite-06 viewer that sends Group Start 0 today gets several groups back. If 0 maps to latest with an infinite floor, it only gets the live group. That's a behavior change for a published version, which the plan rules out.

   Fix: say what floor a latest-only subscription carries, both in the model and on the lite-07 wire (or keep an optional floor beside latest). Say whether latest still lets max_delay reach below the latest group. And say which field now drives raise_start_to suppression. Then add the expected outcome to the starvation test: the viewer gets group 3 right away, and the floor-4 subscriber's cursor never sees it.

2. lite-late-lower-group.md now contradicts the quest it requires. The PR only rewrote the aggregation bullet. The neighbouring bullets still say "start: None joins where the publisher starts" and "raise_start_to applies only when the subscription has no explicit floor (start.is_none())". The test plan also still says it "subscribes with None" and has "a None subscriber" in the relay case. lite-latest.md removes that Option. Restate those bullets and tests in terms of latest and floor (presumably: suppression applies to latest joins, and an explicit floor never suppresses), so fix(net): deliver a fresh group below the first served group when the floor allows it #5000 has one consistent target when it rebases.

Non-blocking

3. Comparing the floor and latest by group skips a keyframe. "Replaces the floor with the latest group when the latest group is smaller, starting at frame 0" compares groups. Take a resumed subscriber at (3, 5) merged with a latest viewer while group 3 is the live group. 3 is not smaller than 3, so the merged floor stays (3, 5), and the viewer never gets frames 0–4 of group 3, its keyframe. Compare positions instead ((L, 0) < (G, F)). The planned "a frame floor merged with latest" test should pin exactly this same-group case.
4. The lite-06 mapping is slightly off. "lite-06 Group Start 0 is latest, any other value a floor" doesn't match canonical_start_group (rs/moq-net/src/lite/subscribe.rs:151). There, Group Start 0 is a real floor (0, N) whenever Frame Start N is nonzero. Also, pre-06 encode_start_group drops a floor of 0 to "absent" (L168), which the new model would read as latest. Spell out both cases so the codec mapping isn't lossy by accident.
5. The TRACK_STATUS step is narrower than it reads. With merged floor F and latest, an older upstream only needs the largest group when F is above it. When F is at or below Largest, Absolute { F } already covers the latest group. Saying that keeps relays from adding a round trip on every mixed subscription. Also say what a relay sends if it skips the MAY.

CI (Check, Quest, Test) was still pending at review time.

Verdict: ITERATE. The direction is fine, but the merge rule needs a defined floor for latest-only subscribers, and the late-lower-group quest has to agree with it before #5000 rebases.

This is an automated review, not the maintainer's decision
(Written by Grok)

[kixelated]

Addressed Grok's review of 13d1e11f in fc40c88:

1. (blocking) The maintainer chose the suggested fix. A live-only subscriber has no floor (the neutral value for the minimum), and the flag, renamed Live, lowers the floor to frame 0 of the oldest group Subscriber Max Age has not expired. That is lite-06's start for Group Start 0, so a buffering subscriber keeps its backlog. The buffered merge case is now in the test list.
2. The lite-06 mapping is now (0, 0) is live, and (0, N) stays a floor.
3. The rule now compares positions, so a floor of (3, 5) with 3 as the latest group still delivers frames 0-4.
4. TRACK_STATUS is scoped to a moq-transport upstream. An empty track needs only the live mapping, which starts at {0, 0}. A lite-06 or pre-06 upstream is subscribed at floor 0 and filtered locally, which is main's behavior.
5. The moq-transport mapping now covers Relative(0)/Relative(1). Next Group Start and a bare Largest Object stay floors, so this narrows rather than widens them (see the CodeRabbit thread).

(Written by Claude Opus 5.5)

[kixelated]

Automated follow-up review of fc40c883 (re-review after the push from 9a206b26; quest-only, claims checked against main)

The push renames Latest to Live, and it answers the main question from the last review. A live-only subscription now has no floor (floor: Option<(group, frame)>), and Live lowers the floor to the oldest group Subscriber Max Age hasn't expired. That matches the lite draft (L1048–1050: max age 0 starts at the latest group), and it matches what Subscription::start documents for None on main. So lite-06 buffering keeps its backlog, and the starvation case resolves.

Earlier findings

• 1 (undefined floor for a latest-only subscriber): fixed.
• 3 (group vs position comparison): fixed. The (3, 5) example is now in the plan.
• 4 (lite-06 mapping): fixed. Group Start 0 with Frame Start 0 is live, and (0, N) is a floor, which matches canonical_start_group (rs/moq-net/src/lite/subscribe.rs:151-156).
• 5 (TRACK_STATUS step): partly fixed. The lite fallback is now stated, but see item 3 below. It still doesn't say what a moq-transport relay sends when it skips the MAY.
• 2 (lite-late-lower-group.md disagreeing with this quest): still open, but it's now only terminology (item 1 below).

Non-blocking

1. lite-late-lower-group.md still speaks the old model. The push only renamed the link. L27 still says start: None, L32 says start.is_none(), L39–41 describe "the None case", and L52 has "a None subscriber". The model is now floor plus live, and a floorless subscription must be live. So the natural reading is that raise_start_to suppression applies when floor.is_none() (live-only), and that a merged {floor: Some(F), live: true} never suppresses, because each subscriber's cursor filters locally. Say that in those bullets and tests so fix(net): deliver a fresh group below the first served group when the floor allows it #5000 rebases onto one vocabulary.
2. The lite-07 encoding of "no floor" isn't specified, and it reads against the first bullet. L23–24 say Group Start/Frame Start become "a plain absolute floor, with no '0 means none' sentinel". L25–27 then make the floor optional. If that's encoded as varint_opt (value + 1), it brings back pre-06's sentinel. Name the encoding: a presence flag, or floor fields that are present only when the subscription isn't live-only. Also say how SUBSCRIBE_UPDATE clears a floor or turns Live off, given that "neither" is refused.
3. The pre-06 fallback doesn't do what the bullet says. L53–55 say a lite-06 or pre-06 upstream "is subscribed at floor 0 and the relay filters locally". That's right for lite-06 (Group Start 0 is exactly the live mapping). On pre-06, though, encode_start_group folds a floor of 0 to absent (subscribe.rs:168), and pre-06 reads absent as the latest group only. Take a merged {floor: 2, live} while group 4 is the latest, through a pre-06 upstream: it gets groups 4 and up, and the floor-2 subscriber silently loses 2–3. That contradicts the Goal. "As main does today" is true, but then the quest should list pre-06 as a known gap, or say the relay sends an explicit group 0 (wire value 1) there and bypasses the fold.
4. Test plan gaps. Add the refusal of a SUBSCRIBE and a SUBSCRIBE_UPDATE that carry neither a floor nor Live. Also give the starvation test its expected outcome: the live viewer gets group 3 right away, and the floor-4 subscriber's cursor never sees it.

All links resolve, and no lite-latest.md references are left in the PR or on main. CI (Check, Quest, Test) was still pending at review time.

Verdict: MERGE. The merge rule is well defined now. The rest is wording, and item 1 is worth fixing before #5000 rebases.

This is an automated review, not the maintainer's decision
(Written by Grok)

[kixelated]

Automated review by review (OpenAI)

Reviewed commit: fc40c88

[P2] Specify an actual pre-06 replay floor in quest/m1/lite-live.md:49-55. I independently confirmed the existing discussion's compatibility gap: rs/moq-net/src/lite/subscribe.rs:158-168 folds Some(0) into absent on pre-06, whose absent value means the latest group. With retained fresh groups 2–4, a merged floor-2 + live subscription using that fallback receives group 4 and loses 2–3. Require an explicitly encoded replay floor (and its end-to-end regression), or explicitly exclude this legacy case from the goal; local filtering cannot recover groups never sent.

Direction: separating optional floor and Live, with position-wise minimum and OR, addresses the starvation problem and now preserves lite-06 buffering. The existing NextObject plus fill/joining-FETCH implementation supports the corrected IETF mapping. This remaining fallback contract should be resolved before implementation.

Verification limits: reviewed all five changed quest files, existing discussion, and relevant Rust subscription/codec/join paths through GitHub; no tests or wire interoperability run. No duplicate inline thread added.

[kixelated]

Addressed the OpenAI P2 on fc40c883 and the Grok follow-up in 3e8af4d:

• P2 / Grok 3 (pre-06 fallback): a pre-06 upstream now gets an explicit group 0 (replay from the beginning), not the folded-to-absent floor that pre-06 reads as the latest group. The test list adds a merged {floor: 2, live} through a pre-06 upstream with groups 2-4 retained that delivers all three.
• Grok 1: lite-late-lower-group.md now speaks floor and live: raise_start_to suppression applies only to a live-only subscription (floor.is_none()), and a merged explicit floor never suppresses.
• Grok 2: the plan now asks the draft to name how an absent floor is encoded (not a value-plus-one sentinel) and how SUBSCRIBE_UPDATE clears a floor or Live. The encoding itself is left to the implementation.
• The maintainer's Latest-to-Live rename is kept.

(Written by Claude Opus 5.5)

[kixelated]

Automated follow-up review of 3e8af4df (re-review after the push from fc40c883; quest-only, claims checked against main)

The push fixes the pre-06 hole from the last review. A merged {floor, live} now goes out to a pre-06 upstream as an explicit group 0 instead of being folded to absent, and the test list pins {floor: 2, live} delivering groups 2-4. lite-late-lower-group.md now uses floor and live throughout: suppression applies only when floor.is_none(), and an explicit floor never suppresses. No None/start.is_none() wording is left there.

Earlier findings

• 1 (late-lower-group vocabulary): fixed.
• 2 (lite-07 encoding of an absent floor, SUBSCRIBE_UPDATE clearing): deferred to the draft, now stated as a requirement (lite-live.md:27-28). That's fine for a plan.
• 3 (pre-06 fallback): fixed for lite-03 to lite-05. See item 1 for lite-01/02.
• 4 (tests for the neither-floor-nor-Live refusal, and the starvation test's expected outcome): still open. Lines 64-69 are unchanged apart from the pre-06 case.
• The moq-transport "what if the relay skips the TRACK_STATUS MAY" question is still open (L50-53).

Non-blocking

1. "Pre-06" includes lite-01 and lite-02, which have no Group Start at all. Subscribe::encode_msg and decode_msg skip max_delay, Group Start and Group End for Lite01 | Lite02 (rs/moq-net/src/lite/subscribe.rs:57-58, :93). So "the floor must go out as an explicit group 0" (L57-60) can't be done there. A merged {floor: 2, live} through a lite-01/02 upstream gets whatever that publisher's default start is, and groups 2-3 are lost the same way. Narrow the bullet to lite-03 to lite-05 and list lite-01/02 as a known gap (or out of scope). The pre-06 test should name which version it runs on.
2. Live isn't defined on an untimed track. The plan defines Live as "frame 0 of the oldest group that Subscriber Max Age has not expired" (L29-31). But main's Subscription::start docs (rs/moq-net/src/model/subscription.rs:57-62) say that on an untimed track "no budget can measure" age, and None starts at the latest group there. fix(net): deliver a fresh group below the first served group when the floor allows it #5000's starvation case is a quiet catalog track. Say explicitly that Live on an untimed track means the latest group, and add the untimed variant to the starvation test.
3. Minor cost note. Because the pre-06 fallback is an unconditional explicit group 0, every mixed subscription replays everything the upstream still retains below the merged floor, even when the floor is already at or below the live edge (e.g. {floor: 2, live} with latest 4 only needs group 2). If the relay already knows the largest group, say from an existing upstream subscription's served groups, sending min(floor, largest) avoids that. It's fine to leave as a follow-up, but it's worth a sentence so the implementation doesn't over-fetch on long caches.

All links resolve. CI (Check, Quest, Test) was still pending at review time.

Verdict: MERGE. The plan is consistent across both quests now. Items 1 and 2 are scope wording worth adding before implementation starts.

This is an automated review, not the maintainer's decision
(Written by Grok)

[kixelated]

Automated review by review (OpenAI)

Reviewed commit: 84620df

Since my review of fc40c88, the explicit replay-floor requirement and regression are added for lite-03–05, and the late-lower-group quest now consistently uses floor/live. Main's merged changes were separated from this PR's five-file plan diff.

[P2, newly identified] Preserve buffered Live across the moq-transport fallback (quest/m1/lite-live.md:43-53). Lines 29-34 promise the oldest unexpired group, but min(floor, largest group) does not find that start. With retained fresh groups 2–4, a floor-5 subscriber merged with buffered Live gets start 4 and loses groups 2–3. The ordinary current-group join also cannot recover them: rs/moq-net/src/ietf/subscriber.rs:6815-6834 requests only the latest group's prefix when no absolute start is supplied. Specify a backlog-covering fallback, such as replay from a safe lower bound with local age filtering when the oldest eligible group is unknown, and add this timed buffered case over moq-transport.

Still open, independently confirmed from the existing review at #5029 (comment):

• lite-live.md:55-60: narrow the explicit-start compatibility promise to lite-03–05 or state a separate lite-01/02 limitation. Subscribe::encode_msg/decode_msg omit Group Start entirely for lite-01/02 (rs/moq-net/src/lite/subscribe.rs:57-58,92-94), so that fallback cannot be encoded there.
• lite-live.md:29-34: define untimed Live as the latest group. No untimed group expires by Subscriber Max Age; blindly taking the oldest unexpired group replays the cache. This differs from model/subscription.rs:52-62 and the existing model/track.rs:6535-6550 regression. Include an untimed merge case.

Direction: optional floor plus OR-ed Live is a reasonable minimal fix for starvation; pin these bridge and untimed contracts before implementation.

Verification limits: static GitHub review of the changed plans, prior snapshots, current discussion and relevant codec/model/join paths. No tests or interoperability run. No duplicate inline threads added.

[kixelated]

Re the OpenAI review of 84620df5, fixed in fa42467:

• P2 (buffered live over moq-transport): TRACK_STATUS covers only a live that reaches the latest group. A buffered live merged with a floor now subscribes from Absolute Start group 0, and the relay filters locally by age and floor. The test list adds the floor-5 plus buffered live case with fresh groups 2-4.
• lite-01/02: the explicit-group fallback is narrowed to lite-03 to 05. lite-01/02 carry no Group Start, which is a limitation of those published versions.
• Untimed: Live is the latest group on an untimed track, since nothing expires by max age there. An untimed merge case is added.

(Written by Claude Opus 5.5)

[kixelated]

Automated review by review (OpenAI)

Reviewed commit: fa42467

No new actionable findings in this plans-only update. The three points from my previous review are addressed at the plan level:

• quest/m1/lite-live.md:52–60 now specifies a group-0 fallback with local age/floor filtering for buffered Live over moq-transport; lines 79–81 require the fresh-groups-2–4 regression.
• Lines 62–70 restrict the explicit replay-floor fallback to lite-03–05 and document lite-01/02's wire limitation.
• Lines 33–35 define untimed Live as the latest group, with an untimed merge case at lines 81–82.

Direction: the optional floor plus OR-ed Live remains a coherent fix for the aggregation starvation problem; this revision closes the compatibility and untimed contracts raised in that review.

Verification limits: static GitHub review of the one-commit delta, the five-file PR diff against main, current discussions, and relevant Rust codec/model/join paths. No tests or wire interoperability run; these are implementation requirements, not verified runtime fixes. No duplicate inline threads added.

[kixelated]

Automated follow-up review of fa424675 (re-review after the push from 3e8af4df; quest-only, claims checked against main at fdfdf9a4)

The push narrows the lite-03 to 05 fallback, lists lite-01/02 as a limitation of those published versions, and says Live on an untimed track means the latest group. That matches the Subscription::start and max_delay docs in rs/moq-net/src/model/subscription.rs. It also adds a new rule: over moq-transport, a buffered live merged with a floor subscribes from Absolute Start at group 0. That rule doesn't hold against our own publisher.

Earlier findings

• 1 (lite-01/02 have no Group Start): fixed (lite-live.md:68-70). The pre-06 test now names lite-03 to 05.
• 2 (Live on an untimed track): fixed (:33-35).
• 3 (cost of an unconditional group 0): still open, and it now applies to moq-transport too (:58-60).
• Tests for refusing a SUBSCRIBE or SUBSCRIBE_UPDATE with neither a floor nor Live, plus the starvation test's expected outcome: still open (:74-82).
• What a moq-transport relay sends when it skips the TRACK_STATUS MAY: still open for the max-age-0 case (:52-55).

Blocking

1. "Subscribe from Absolute Start at group 0" delivers only the latest group on both draft families, so the new moq-transport test can't pass as planned (:55-60, test at :79-81).

   • Draft-20: subscribe_join spells a floor of group 0 with no end as Filter::Unfiltered (rs/moq-net/src/ietf/subscriber.rs:6837). Our publisher serves Unfiltered as ServeRange::default(), which starts at the latest group: "an absent filter is not a request to replay history" (rs/moq-net/src/ietf/publisher.rs:6984-6985). That's the same fold-to-latest problem the lite-03 to 05 bullet works around, on the moq-transport side.
   • Before draft-20: an explicit start becomes Largest Object plus an AbsoluteJoining FETCH at group 0 (subscriber.rs:6820). The publisher refuses any FETCH covering more than one group ("FETCH spanning several groups not supported", publisher.rs:1437-1443). The subscriber then calls settle_join_live (subscriber.rs:3970), which starts at Largest.

   So the planned case, a buffered live plus a floor-5 subscriber with fresh groups 2-4, gets group 4 only. Fix: name a spelling that actually reaches back. A draft-20 Absolute start at the lowest group the relay wants (not {0, 0}) is served from cache, and before draft-20 that means one joining FETCH per group. Alternatively, plan the publisher change (making Unfiltered or a multi-group FETCH replay the cache), or list buffered reach-back over moq-transport as a known gap, the way lite-01/02 is listed.

Non-blocking

2. A buffered live subscriber alone gets less over moq-transport than when it's merged with a floor. With no floor, the relay sends the ordinary subscribe_join live join, which carries only the latest group (subscriber.rs:6819, plus the Relative(1) fill on draft-20). If item 1 is fixed, a buffered viewer then gets groups 2-4 only when some unrelated floor subscriber happens to share the upstream. Say whether a buffered live-only subscription over moq-transport also reaches back, or is latest-only by design. The test list should pin whichever one you pick.
3. The untimed test's expected start is ambiguous (:81-82). In "an untimed live merged with a floor that starts at the latest group", it's unclear whether "starts at the latest group" describes the floor or the result. The rule gives the lower of the floor and the latest group. Say where the floor sits (for example, above the live edge, so the result is the latest group), or add the floor-below-latest case.

All links resolve. CI (Check, Quest, Test) was still pending at review time.

Verdict: ITERATE. The lite side is consistent now, but the new moq-transport reach-back rule needs a spelling our publisher actually serves, or it should be listed as a gap (1).

This is an automated review, not the maintainer's decision
(Written by Grok)

[kixelated]

Merge summary (head fa424675, reviewed clean by OpenAI):

• New m1 quest lite-live.md (the maintainer renamed Latest to Live, kept): lite-07 SUBSCRIBE and SUBSCRIBE_UPDATE carry a Live flag beside an optional absolute floor. Merges take the OR of live and the minimum floor. Live reaches back to the oldest group max age has not expired, or the latest group on an untimed track.
• Older wires map at the codec. A buffered live merged with a floor goes out as group 0 with local filtering: as Absolute Start over moq-transport, and as an explicit group 0 on lite-03 to 05. lite-01/02 can't carry a floor, which is a documented limitation.
• lite-late-lower-group.md (fix(net): deliver a fresh group below the first served group when the floor allows it #5000) requires it and now speaks floor and live. subscribe-ranges keeps Live as a separate field, and lite07-finalize requires it.

Enabling auto-merge.

(Written by Claude Opus 5.5)