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dfdf07269d41007071a19ce97dc862be3f5288b7
amethyst/nestsClient/plans/2026-05-09-moq-lite-rfc-compliance.md
T
Claude dfdf07269d docs(nestsclient): record L1/L2/L3 closures in moq-lite Lite-03/04 audit 
Adds Fix #6 (L2 — SubscribeOk narrowing), Fix #7 (L3 —
subscriber-driven Probe API), and Fix #8 (L1 — version-aware
Lite-03/04 codec + ALPN negotiation) to the compliance audit
document. Updates the gap matrix (L1/L2/L3 → ✅) and the TL;DR
(now reads "nine shipped fixes + M6 closed; every gap is now
resolved, no items remain deferred").

The "what's deliberately deferred" section now lists only the
external follow-up — a `kixelated/moq` feature request
suggesting per-deployment tuning of moq-rs's per-subscriber
forward-queue starvation behavior. That's an upstream-relay
concern, not a moq-lite gap.

Updates the audio-rooms completion-plan pointer to reflect the
shipped count and the absence of remaining deferrals. Audit doc
title acknowledges Lite-04 alongside Lite-03 since the codec
now speaks both.

https://claude.ai/code/session_012TGfo99Ugz7fcCPv85a8Tq
2026-05-09 15:08:12 +00:00

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# moq-lite Lite-03 compliance audit
**Date:** 2026-05-09
**Branch:** `claude/audit-moq-lite-compliance-NSuPk`
**Scope:** `nestsClient/src/commonMain/kotlin/com/vitorpamplona/nestsclient/moq/lite/` plus
the audio glue under `…/audio/` that drives moq-lite. The IETF
`draft-ietf-moq-transport-17` reference impl in `…/moq/` (no `lite/`)
is OUT of scope — it stays as a unit-test target only. The QUIC layer
(`:quic`) is OUT of scope; recently audited and locked.
## TL;DR
The moq-lite Lite-03 implementation is **wire-compatible** with
kixelated's reference relay (moq-rs / moq-lite-03). All on-the-wire
codec primitives — control type discriminators, AnnouncePlease,
Announce, Subscribe (incl. the `Option<u64>` off-by-one and `Duration`
millis-as-varint conventions), SubscribeOk/Drop (with the
type-outside-size-prefix framing peculiar to Lite-03), GroupHeader,
Probe — match the reference Rust impl byte-for-byte. The known gaps
are all spec-loose / future-fragile (🟡 / 🟦), not wire-incompatible
(🔴).
**This audit shipped nine fixes** (M1, M2, M3, M4, M5, L1, L2, L3,
L5) and **closed M6** (verified via WebFetch that Goaway has no
body in the spec, so our existing handler is canonical). **L4**
is subsumed by the M1 fix. M2/M3 originally deferred under the
"`:quic` is locked" constraint; after a merge from `main` brought
in the full RFC-compliant `:quic` layer, the user lifted the
constraint and M2/M3 landed end-to-end. L1/L2/L3 originally
parked as 🟦 non-fixes; the user re-prioritised them and all
three landed with regression tests. **Every gap from the matrix
is now resolved (✅) or explicitly closed.** No 🔴, 🟡, or 🟦
items remain open.
## Methodology
1. Walked every Kotlin file under `moq/lite/` and traced data flow
speaker → relay → listener.
2. Cross-referenced each on-wire message + control byte against
kixelated's reference Rust impl at
`https://github.com/kixelated/moq/tree/main/rs/moq-lite/src/`,
reading specifically:
- `coding/decode.rs`, `coding/encode.rs`, `coding/varint.rs`
(primitive codings — confirmed `Option<u64>` is `0=None /
n=Some(n-1)`, `Duration` is `millis-as-varint`, `bool` is 1
byte 0/1).
- `lite/stream.rs` (ControlType + DataType discriminator codes).
- `lite/announce.rs` (AnnouncePlease + Announce body shape).
- `lite/subscribe.rs` (Subscribe + SubscribeResponse Lite-03
framing).
- `lite/publisher.rs` (`Publisher::serve_group` priority handle,
uni-stream open + group header).
- `lite/subscriber.rs` (Probe direction, group decode loop,
unsubscribe = FIN).
- `lite/probe.rs` (Probe body: `bitrate u62` only on Lite-03).
3. Verified the team's prior `2026-04-26-moq-lite-gap.md` against
live source — every claimed item still holds (see "Verified
working" below).
4. Built the gap matrix (see "Gap matrix" below).
5. Shipped fixes for the two 🟡 items closest to being 🔴 — see
"Fixes shipped" at bottom.
6. Ran `:nestsClient:jvmTest` after each fix — green throughout.
## What's verified working
The shipped Lite-03 surface holds up against the reference Rust impl
at the byte / control-flow level:
| Surface | Verdict | Evidence (file:line) |
| ------------------------------------------------------------------------------------------------------------------------------------ | ------- | -------------------- |
| ALPN `"moq-lite-03"` advertised as the only sub-protocol | ✅ | `MoqLiteAlpn.kt:47`, `QuicWebTransportFactory.kt:88-113` |
| No SETUP / no in-band session message (Lite-03 = WT handshake IS the handshake) | ✅ | `MoqLiteSession.kt:1374-1378` (`client(...)` returns immediately, no SETUP coroutine) |
| `ControlType` codes — `Session=0, Announce=1, Subscribe=2, Fetch=3, Probe=4, Goaway=5` | ✅ | `MoqLiteControlCodes.kt:39-65` (all five recognised + dispatched in `handleInboundBidi`) |
| `DataType::Group=0` on uni-stream open | ✅ | `MoqLiteControlCodes.kt:74-85`, `MoqLiteSession.kt:1047` |
| Path normalisation (strip leading/trailing `/`, collapse runs) | ✅ | `MoqLitePath.kt:44-99` (matches `rs/moq-lite/src/path.rs::Path::new`) |
| Path normalisation applied at every wire boundary | ✅ | `MoqLiteCodec.kt:54, 70, 92` (encode side); `:60, 81, 105` (decode side) |
| AnnouncePlease body shape — `prefix: string` | ✅ | `MoqLiteCodec.kt:52-63` |
| Announce body shape — `status u8, suffix string, hops u62 varint` | ✅ | `MoqLiteCodec.kt:67-85`; status enum `Ended=0, Active=1` matches `rs/moq-lite/src/lite/announce.rs:84-90` |
| Subscribe body — 8 fields: `id u62, broadcast string, track string, priority u8, ordered u8, maxLatency varint, startGroup, endGroup` | ✅ | `MoqLiteCodec.kt:89-100` |
| `Option<u64>` off-by-one collapse: `0=None, n=Some(n-1)` | ✅ | `MoqLiteCodec.kt:286-288` matches `rs/moq-lite/src/coding/decode.rs::impl Decode for Option<u64>` |
| `Duration` encoded as millis-as-varint | ✅ | `MoqLiteCodec.kt:96` matches `rs/moq-lite/src/coding/encode.rs::impl Encode for std::time::Duration` |
| SubscribeResponse framing: type discriminator OUTSIDE size prefix (Lite-03+) | ✅ | `MoqLiteCodec.kt:152-167` matches `rs/moq-lite/src/lite/subscribe.rs::SubscribeResponse::encode` Lite-03 arm |
| SubscribeOk body — 5 fields (priority, ordered, maxLatency, startGroup, endGroup) without id/broadcast/track | ✅ | `MoqLiteCodec.kt:127-135` |
| SubscribeDrop body — `errorCode varint + reasonPhrase string` | ✅ | `MoqLiteCodec.kt:137-142` |
| Group uni-stream layout: `DataType=0` + size-prefixed `(subscribeId, sequence)` + size-prefixed frame loop until FIN | ✅ | `MoqLiteSession.kt:1021-1050` (publisher), `:594-668` (listener `drainOneGroup`) |
| Probe body — `bitrate u62 varint` only (rtt is Lite-04+) | ✅ | `MoqLiteCodec.kt:262-266` (encode), `:247-251` (decode) |
| Probe direction — subscriber opens bidi, publisher writes Probe messages | ✅ | `MoqLiteSession.kt:925-944` (publisher arm of `handleInboundBidi`) |
| Subscribe id allocation — per-session, monotonic, varint | ✅ | `MoqLiteSession.kt:83, 246-251` (incremented under `state` mutex) |
| Group sequence allocation — per-publisher, monotonic, varint, hot-swap-aware (`startSequence` parameter) | ✅ | `MoqLiteSession.kt:716-746, 1129-1132, 1306-1329` |
| Per-group end = QUIC FIN | ✅ | `MoqLiteSession.kt:1264-1271` (`endGroup`) |
| Broadcast ended = `Announce(Ended)` BEFORE FIN (correct ordering) | ✅ | `MoqLiteSession.kt:1273-1304` (`PublisherStateImpl.close`) |
| Unsubscribe = FIN subscribe bidi's send side (no UNSUBSCRIBE message) | ✅ | `MoqLiteSession.kt:670-675` |
| Reliable QUIC streams for groups (NOT bestEffort; matches kixelated) | ✅ | `MoqLiteSession.kt:1024-1039` + comment block explaining the prior bestEffort regression |
| Stream priority hint — newer groups (higher sequence) drain first under congestion | ✅ | `MoqLiteSession.kt:1040-1046`; sequence-as-priority is monotonically increasing, same direction as kixelated's `PriorityHandle.insert(track.priority, sequence)` |
| Auth — purely WebTransport-CONNECT-time (JWT in `?jwt=` query); moq-lite layer touches no claims | ✅ | `MoqLiteSession.kt` has zero references to JWT / claims / auth |
| Reconnect — no moq-lite-layer message; transport drop ⇒ open new WT session and resubscribe | ✅ | Reconnect lives in `connectReconnectingNestsListener` / `…NestsSpeaker` (transport-layer concern) |
| Goaway recognised + FIN'd cleanly (no body decode today; relay migration not implemented) | ✅ | `MoqLiteControlCodes.kt:50-58`, `MoqLiteSession.kt:973-990` |
| Catalog publisher emits one frame per inbound subscriber via `setOnNewSubscriber` hook (matches hang.live consumer expectations) | ✅ | `MoqLitePublisherHandle.kt:91-114`, `MoqLiteNestsSpeaker.kt:160-181` |
| `hang` "legacy" container: each frame is `varint(timestamp_us) + raw_opus_packet` | ✅ | `NestMoqLiteBroadcaster.kt:212-345` (encode), `MoqLiteNestsListener.kt:279-285` (decode strip) |
The team's `2026-04-26-moq-lite-gap.md` (✅ DONE banner) holds — every
phase claim is still accurate against the live source.
## Gap matrix
Severity legend (matches the prior QUIC audit):
- 🔴 **High** — wire-incompatible with the reference relay; audio
doesn't work.
- 🟡 **Medium** — works against the reference relay today but
violates spec; future relay versions may break.
- 🟦 **Low** — diagnostic / observability gap; no functional impact.
| # | Spec § / Behavior | Severity | Gap | Evidence (file:line) | Status |
| -- | --------------------------------------------------------------------------------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------- | ------ |
| H0 | (none — no wire-incompatible items found) | 🔴 | — | — | n/a |
| M1 | `Publisher::serve_group` priority parity | 🟡 → ✅ | We assigned each new group `priority = sequence (i32 cast)`, ignoring `track.priority` and never re-prioritising in flight. kixelated computes `let priority = priority.insert(track.priority, sequence); stream.set_priority(priority.current())` (per `rs/moq-lite/src/lite/publisher.rs::serve_group`). For our single Opus track at 1 group/sec the difference was unobservable (newer-first ordering still held). | `MoqLiteSession.kt:openGroupStream` (pre-fix) | **fixed in this audit** — see `Fix #3` |
| M2 | `STOP_SENDING` for single-group cancel | 🟡 → ✅ | The Lite-03 spec lets a receiver cancel a specific group via `STOP_SENDING` on its uni stream. Pre-fix we closed the consumer-facing frames channel only — the publisher's uni stream stayed open until natural FIN, wasting bandwidth on frames the listener would discard plus relay queue pressure on the per-subscriber forward pipeline. The `:quic` `QuicStream.stopSending(errorCode)` API existed but wasn't exposed through `WebTransportReadStream`. Now plumbed end-to-end: extended `WebTransportReadStream` with `stopSending(code)`, plumbed through `:quic`'s `StrippedWtStream`, and `MoqLiteSession.drainOneGroup` fires `stopSending(SUBSCRIPTION_GONE)` once on the first frame that observes `sub == null`. | `MoqLiteSession.kt:drainOneGroup` (pre-fix), `WebTransportSession.kt` (read interface) | **fixed in this audit** — see `Fix #5` |
| M3 | `RESET_STREAM` with `Error::to_code()` | 🟡 → ✅ | Pre-fix all error / cancel paths FIN'd gracefully via `runCatching { bidi.finish() }`. Lite-03 spec says errors on any stream are conveyed by `RESET_STREAM(application_error_code u32)`. The `SubscribeDrop` reply paths now write the body and then `RESET_STREAM(errorCode)` instead of `finish()`, so a peer watching only the QUIC layer (no body decode) can distinguish typed rejection from graceful "publisher gone" FIN. Plumbing extended `WebTransportWriteStream` with `reset(code)` and routed through both QUIC-backed adapters + `:quic`'s `StrippedWtStream`. | `MoqLiteSession.kt:handleInboundBidi` Drop replies (pre-fix) | **fixed in this audit** — see `Fix #5` |
| M4 | AnnouncePlease prefix-mismatch falls back to full suffix | 🟡 → ✅ | When the relay opened an Announce bidi with `prefix="X"`, our publisher emitted `Active(suffix=ourFullSuffix)` even when our suffix didn't start with `X`. The relay would observe an Active update for a broadcast it didn't ask about. In production the relay always asks for `prefix=""`, so this never bit empirically — but it's a spec violation. | `MoqLiteSession.kt:841-852` (pre-fix) | **fixed in this audit** — see `Fix #1` |
| M5 | Inbound Subscribe doesn't validate broadcast field | 🟡 → ✅ | When the relay opened a Subscribe bidi, we matched on `track` only, never checking `sub.broadcast == publisher.suffix`. A relay (or peer) could subscribe to broadcast `"otherPubkey"` on our connection and we'd happily route OUR audio to them. The production relay routes correctly, so this never bit empirically — but it's a spec violation. | `MoqLiteSession.kt:861-898` (pre-fix) | **fixed in this audit** — see `Fix #2` |
| M6 | Goaway body decoding + migration handler | 🟡 → ✅ | We recognise `ControlType::Goaway = 5` and FIN cleanly. WebFetched the kixelated reference (`rs/moq-lite/src/lite/{stream,client}.rs`): **Goaway has no body schema in moq-lite Lite-03** — it's a single ControlType byte with no payload, not even a migration URL. Our existing handler (recognise, log, FIN) is the canonical implementation; "no body decode" was never a gap. | `MoqLiteSession.kt:973-990`, `MoqLiteControlCodes.kt:50-58` | **closed in this audit** — see `M6 closure` |
| L1 | Lite-04 ALPN constant defined but codec is Lite-03 only | 🟦 → ✅ | Pre-fix `MoqLiteAlpn.LITE_04` was a documented constant but the codec was hard-wired to Lite-03 — advertising Lite-04 would have caused the very first Announce to desync. Now full Lite-04 support: codec is version-aware via a new `MoqLiteVersion` enum, all three differing fields (Announce.hops as `OriginList`, AnnouncePlease.excludeHop, Probe.rtt) are encoded / decoded correctly, ALPN negotiation surfaces the server's pick via `WebTransportSession.negotiatedSubProtocol`, and `connectNestsListener` / `connectNestsSpeaker` advertise both versions and use whichever the relay echoes. | `MoqLiteCodec.kt`, `MoqLiteSession.kt`, `MoqLiteAlpn.kt`, `QuicWebTransportFactory.kt`, `WebTransportSession.kt`, `NestsConnect.kt` | **fixed in this audit** — see `Fix #8` |
| L2 | SubscribeOk always echoes `null/null` for startGroup/endGroup | 🟦 → ✅ | Per spec the publisher MAY narrow the subscriber's requested group bounds. Pre-fix we echoed `null/null` and lost the diagnostic "which group am I about to start sending?" signal. Now the publisher narrows `startGroup` to its `nextSequence` — useful for hot-swap continuations where the seeded `startSequence` is non-zero. `endGroup` stays null (live broadcast, no end). | `MoqLiteSession.kt` Subscribe accept arm | **fixed in this audit** — see `Fix #6` |
| L3 | No subscriber-driven Probe API | 🟦 → ✅ | Pre-fix the publisher-side Probe handler existed but no subscriber-side counterpart did, leaving the protocol surface incomplete. New `MoqLiteSession.probe()` opens a Probe bidi (writes `ControlType=4`) and returns a `MoqLiteProbeHandle` whose `updates` flow yields each `MoqLiteProbe` the publisher pushes. Mirrors kixelated's `Subscriber::run_probe_stream`. No production consumer (audio rooms are fixed-rate Opus, no ABR), but the API completes the surface for diagnostic tools. | `MoqLiteSession.kt` `probe()` (new), `MoqLiteHandles.kt` `MoqLiteProbeHandle` (new) | **fixed in this audit** — see `Fix #7` |
| L4 | Stream-priority overflow guard is a saturating cast | 🟦 | Pre-fix, `setPriority(sequence.coerceAtMost(Int.MAX_VALUE).toInt())` saturated at `Int.MAX_VALUE` (≈ 71 yrs at 1 grp/sec). After the M1 fix, sequence saturates at the 24-bit boundary (≈ 6 days within a single track) but the per-track high byte keeps cross-track ordering intact. Defensive only; production sessions cycle on JWT refresh every 9 min. | `MoqLiteSession.kt:openGroupStream` (post-M1) | closed (subsumed by M1 fix) |
| L5 | Inbound bidi pump captures `publishersSnapshot` at bidi-arrival time | 🟦 → ✅ | If a new publisher was added to the session (`session.publish(track="…")`) AFTER an inbound bidi opened, the dispatcher couldn't see it. In practice both nests publishers (`audio/data` and `catalog.json`) register before any subscriber arrives, so this never bit. Tightened anyway: snapshot is now read at first-byte dispatch time. | `MoqLiteSession.kt:781-790` (pre-fix) | **fixed in this audit** — see `Fix #4` |
## Specifically checked items (per audit-prompt request)
- **Stream priorities + the "stream cliff":** the priority assignment
drains newer groups first (sequence is monotonically increasing,
higher value = higher priority per `:quic`'s `QuicStream.priority`
contract). The stream cliff investigation (`2026-05-01-quic-stream-
cliff-investigation.md`) traced the production cliff to TWO
separate root causes, neither of which was a moq-lite priority
violation: (a) `:quic` not emitting `MAX_STREAMS_UNI` (real bug,
fixed in `:quic`); (b) the production relay's per-subscriber
forward-stream-rate ceiling (≈40 streams/sec) being lower than our
`framesPerGroup=1` push rate of 50 streams/sec. The mitigation
(`framesPerGroup=50` in production / `=5` in interop tests) is a
cadence tuning, not a spec violation. Verified: under the current
default the listener and speaker both stream cleanly for
multi-minute sessions in production logs.
- **Group lifetime / stream retirement:** out of scope per audit
prompt (`:quic` is locked). At the moq-lite layer we're confident
groups are short-lived (one per `framesPerGroup * 20ms` =
`framesPerGroup * 0.02s`); each ends in QUIC FIN, and the
per-publisher `currentGroup` reference is dropped on every
`endGroup` so the GC root chain doesn't pin retired streams.
- **Subscribe / Announce flow:** verified end-to-end — see
`MoqLiteSessionTest.subscribe_writes_request_and_returns_handle_on_ok`
+ `…publisher_acks_subscribe_and_pushes_group_data_on_uni_stream` +
`…publisher_replies_to_announcePlease_with_active_announce`.
Wire-shape matches the byte-level reference in
`2026-04-26-moq-lite-gap.md`.
- **Authentication:** moq-lite Lite-03 has no auth message inside the
WT session — auth is purely the WT-CONNECT JWT in `?jwt=` query.
Verified: `MoqLiteSession.kt` has zero auth references; all auth
lives in `OkHttpNestsClient.mintToken` and the WT factory's URL
construction.
- **Reconnect:** moq-lite has no reconnect message; on transport
drop the `connectReconnectingNests*` wrapper opens a new WT
session, mints a new moq-lite session, and re-issues subscribes
(`ReconnectingNestsListener.kt:317-465`). Speaker side hot-swaps
the publisher reference inside a long-running broadcaster
(`NestMoqLiteBroadcaster.swapPublisher`), continuing the group
sequence across the swap so kixelated/hang's `Container.Consumer.#run`
doesn't drop our post-swap groups.
- **Best-effort vs reliable:** verified reliable. The previous
`bestEffort=true` shape was reverted (see comment block at
`MoqLiteSession.kt:1024-1039`); kixelated's reference uses
reliable QUIC streams in `Publisher::serve_group`. Match.
## What's deliberately deferred
Nothing. Every gap surfaced by the audit is now resolved. The
remaining open items are external follow-ups (not moq-lite gaps):
- **`kixelated/moq` feature request** — file an issue
describing the production stream-cliff symptom (relay's
per-subscriber forward queue starvation under sustained
push) and propose: (a) per-deployment tuning of the
unbounded `FuturesUnordered` task pool, and (b) a deadline
on `serve_group()`'s `open_uni().await` derived from the
active subscriber's smallest `max_latency`. This is a
feature request against the upstream relay, not a defect in
our code.
## Closed in this audit (no fix needed)
### M6 closure — Goaway has no body in moq-lite Lite-03
A second WebFetch pass against
`https://raw.githubusercontent.com/kixelated/moq/main/rs/moq-lite/src/lite/stream.rs`
and `…/client.rs` confirmed: **`ControlType::Goaway = 5` is a bare
discriminator with no payload schema in moq-lite Lite-03.** No URL,
no preferred-relay address, no error code — it's just the byte. The
"no body decode" comment in our existing handler
(`MoqLiteSession.kt:973-990`) was never a gap; there was nothing to
decode. The wrapper-layer `connectReconnectingNests*` already absorbs
the eventual hard disconnect, and a Goaway with no body has nothing
more to say than "I'm shutting down, expect FIN." Our recognise + log
+ FIN behavior is the canonical implementation.
If a future Lite-04+ revision adds a Goaway body (URL, etc.) we'd
need to decode it — that becomes part of the L1 Lite-04 codec work.
## Fixes shipped in this audit
### Fix #1 — Don't emit Active for non-matching AnnouncePlease prefix (M4)
When the relay opened an Announce bidi with a `prefix` that didn't
match our broadcast suffix, we'd fall through `MoqLitePath.stripPrefix`'s
null result and emit `Active(suffix=ourFullSuffix, hops=0)` anyway,
falsely advertising our broadcast under a prefix the subscriber didn't
ask for. The reference Rust implementation
(`rs/moq-lite/src/lite/announce.rs::Producer`) only emits Active
updates for broadcasts whose path starts with the requested prefix.
Production never hit this because the relay's announce bidi to us
always asks for `prefix=""` — but a future relay version (or a
direct peer-to-peer subscriber asking about a specific room) would
see ghost broadcasts under their requested prefix.
The fix: when `MoqLitePath.stripPrefix(please.prefix, ourSuffix)`
returns null, FIN the announce bidi without writing any Announce.
Subscriber sees a clean end-of-flow.
Regression test:
`MoqLiteSessionTest.publisher_skips_announce_when_announce_please_prefix_does_not_match`.
### Fix #2 — Reject inbound Subscribe whose broadcast doesn't match our suffix (M5)
When the relay opened a Subscribe bidi, we matched the requested
`track` against our publisher set but never checked
`sub.broadcast == ourSuffix`. A relay (or peer) could open a
Subscribe with broadcast `"otherPubkey"` on our connection and we'd
route OUR audio to them.
Production never hit this because moq-rs's relay routes Subscribe
messages to the specific publisher whose broadcast matches the
requested path — but a buggy or malicious peer connecting to us
directly would have been able to siphon our audio under any
broadcast name.
The fix: in the Subscribe arm of `handleInboundBidi`, check
`sub.broadcast == publisher.suffix` (after path normalisation —
both inputs already are, but defensive normalize on the SUBSCRIBE
side too in case a peer skipped it). If mismatch, reply
`SubscribeDrop(errorCode=BROADCAST_DOES_NOT_EXIST,
reason="<requested> not published on this session (we publish
<ours>)")` and FIN.
Regression test:
`MoqLiteSessionTest.publisher_replies_subscribeDrop_when_broadcast_does_not_match`.
### Fix #3 — Pack trackPriority + sequence into stream priority (M1)
`Publisher::serve_group` in kixelated's reference
(`rs/moq-lite/src/lite/publisher.rs`) calls
`priority.insert(track.priority, sequence)` and feeds the resulting
position into `stream.set_priority`. The `PriorityHandle` orders
streams first by `track.priority u8` (higher track = drains ahead
under congestion), then by group `sequence` within a track (newer =
drains ahead).
Pre-fix we passed raw `sequence.toInt()` directly to
`uni.setPriority`, ignoring the per-track byte. For our single-Opus-
track production case this was unobservable — newer-first ordering
held by sequence monotonicity — but a future multi-track broadcast
(audio + companion catalog / status track) would have starved the
lower-rate track the moment audio's outbound queue got congested.
The fix: add `trackPriority: Int = DEFAULT_TRACK_PRIORITY` parameter
to `MoqLiteSession.publish()`; store on `PublisherStateImpl`; bit-pack
in `openGroupStream` as
`((trackPriority and 0xFF) shl 24) or (sequence.toInt() and 0x00FF_FFFF)`.
`DEFAULT_TRACK_PRIORITY = 0x80` matches the existing subscriber-side
`DEFAULT_PRIORITY` midpoint, so all existing call sites keep their
prior behavior. The 24-bit sequence window is ample (≈ 6 days at
1 grp/sec, beyond which all newer groups within a single track tie
— but still beat older groups of any LOWER-priority track via the
top byte).
Test seam: `FakeWebTransport.openUniStream` now records the most-
recent `setPriority` value via a shared `AtomicInteger` cell that the
peer-side `FakeReadStream` exposes as `lastSetPriority`. Lets the
new regression test verify the bit-pack formula on the actual
peer-side read stream rather than peeking into private state.
Regression test:
`MoqLiteSessionTest.publisher_packs_trackPriority_and_sequence_into_setPriority_value`.
### Fix #5 — Plumb RESET_STREAM + STOP_SENDING through WebTransport (M2 + M3)
The two items shipped together because the plumbing is shared. After
the merge from `main` brought in the full RFC-compliant `:quic`
layer (commits `9f7f6a9e..6f32975c`), the user lifted the
"`:quic` is locked" constraint that originally deferred M2/M3.
**Plumbing** (new commit `feat(quic,nestsclient): plumb RESET_STREAM
+ STOP_SENDING through WebTransport`):
- `:quic`'s `StrippedWtStream` gains optional `reset` /
`stopSending` closures, wired in `WtPeerStreamDemux.emitStripped`
through `QuicStream.resetStream(code)` /
`QuicStream.stopSending(code)` + `driver.wakeup()`.
- `WebTransportReadStream.stopSending(code)` and
`WebTransportWriteStream.reset(code)` added to the public
interface — both suspending, both first-call-wins.
- All adapters (`QuicBidiStreamAdapter`,
`QuicUniWriteStreamAdapter`, `StrippedWtBidiStreamAdapter`,
`StrippedWtReadStreamAdapter`) route directly to the underlying
QUIC stream API.
- `FakeWebTransport`'s `FakeBidiStream`, `FakeReadStream`,
`ChannelWriteStream` (now public for test access) record reset
/ stopSending codes in shared `AtomicLong` cells with sentinel
`NO_CODE = Long.MIN_VALUE`. New properties `lastResetCode`,
`lastStopSendingCode`, `lastPeerResetCode`,
`lastPeerStopSendingCode`, `peerStopSendingCode` give tests
typed-error introspection without mock magic.
**M3 (publisher Drop reply uses RESET_STREAM)** (`fix(nestsclient):
RESET_STREAM with typed code after SubscribeDrop body`):
- In `handleInboundBidi`, both Drop reply paths
(`BROADCAST_DOES_NOT_EXIST`, `TRACK_DOES_NOT_EXIST`) now write
the Drop body and then `bidi.reset(errorCode)` instead of
`bidi.finish()`.
- The errorCode matches the body's `errorCode` field, so a peer
that decodes the Drop sees the same number as one that only
sees the RESET_STREAM frame at the QUIC layer.
- Strengthened the existing M5 + Drop tests to additionally
assert `subBidi.lastPeerResetCode == errorCode` so the
typed-error contract is locked.
**M2 (listener stopSending on dead group)** (`fix(nestsclient):
STOP_SENDING on group uni when subscription already canceled`):
- In `drainOneGroup`, the first frame that observes `sub ==
null` (subscription already canceled) fires
`stream.stopSending(MoqLiteStreamCancelCode.SUBSCRIPTION_GONE)`
once, latched, so the publisher abandons in-flight retransmits
instead of wasting bandwidth.
- New error-code constant
`MoqLiteStreamCancelCode.SUBSCRIPTION_GONE = 0x10L` lives in
`MoqLiteMessages.kt` next to `MoqLiteSubscribeDropCode`.
- Practical impact in production: the relay's per-subscriber
forward pipeline (already documented in the stream-cliff
investigation) keeps queueing groups for slow / canceled
subscribers; an early `stopSending` at the listener side
relieves the relay's queue earlier, complementing the
`framesPerGroup` mitigation.
Regression tests:
- `MoqLiteSessionTest.publisher_replies_subscribeDrop_when_broadcast_does_not_match`
— additional `lastPeerResetCode` assertion (M3).
- `MoqLiteSessionTest.publisher_replies_subscribeDrop_when_track_is_not_published`
— additional `lastPeerResetCode` assertion (M3).
- `MoqLiteSessionTest.listener_stopSending_group_uni_when_subscription_already_canceled`
— new test; verifies `peerStopSendingCode` lands the correct
cancel code (M2).
### Fix #4 — Refresh publisher list per-dispatch on inbound bidi (L5)
`handleInboundBidi` previously snapshotted the publisher list at the
TOP of the function (= bidi-arrival time) and used that snapshot for
the rest of the bidi's lifetime. A publisher registered between
bidi-open and the first inbound chunk would miss the dispatcher's
view, even though the publisher was already live in
`activePublishers` by the time we needed to dispatch.
Practical impact today: zero — both nests publishers register from
`MoqLiteNestsSpeaker.startBroadcasting` before the relay's SUBSCRIBE
bidi for either track lands. The ~few-ms gap is below the network
round-trip floor.
But the contract is narrower if we read the list at first-byte time:
we then see every publisher that was registered up to the moment we
needed to make a routing decision. Move the publishers fetch from
the function-top to inside the `if (!dispatched)` block, after the
control-type byte has been read. On empty publisher list (the case
we previously short-circuited at function-top), we now FIN cleanly so
the peer's wait resolves instead of hanging on an idle bidi.
No new regression test — exercised end-to-end by the existing
publisher tests, which now pass against the freshness-aware
dispatcher.
### Fix #6 — SubscribeOk narrows startGroup to publisher.nextSequence (L2)
When accepting a SUBSCRIBE, the publisher MAY narrow the
subscriber's `startGroup` / `endGroup` request bounds per spec.
Pre-fix we always echoed `null/null`, which lost the diagnostic
"which group am I about to start sending?" information —
particularly useful for hot-swap continuations where
[MoqLitePublisherHandle.nextSequence] is non-zero (the seeded
`startSequence` from the previous moq-lite session).
The fix narrows `startGroup` to `targetPublisher.nextSequence`.
The subscriber decodes this as "the next group on this
subscription will be sequence N" and can log / surface the
join-point. `endGroup` stays null because live audio rooms have
no end in sight; the subscriber's request bound is honoured
implicitly when the publisher closes.
Regression test:
`MoqLiteSessionTest.publisher_subscribeOk_narrows_startGroup_to_next_sequence`.
### Fix #7 — Subscriber-driven Probe API (L3)
`MoqLiteSession.probe()` mirrors kixelated's
`Subscriber::run_probe_stream`
(`rs/moq-lite/src/lite/subscriber.rs`): opens a bidi, writes
`ControlType::Probe` (varint 4), and returns a
`MoqLiteProbeHandle` whose `updates` flow yields each
size-prefixed `MoqLiteProbe` message the publisher pushes. The
handle's `close()` FINs the bidi and cancels the pump.
`updates` is a `MutableSharedFlow(replay=8)` so a collector that
attaches after the publisher's first emit doesn't miss it
(matches the same shape the announce-watch uses).
No production consumer for the API today — Amethyst's nests
listener doesn't run ABR on a fixed-rate Opus encoder. The API
exists to round out the moq-lite Lite-03/04 surface: a
diagnostic tool can now read a publisher's bitrate without
subscribing to its data track.
Regression test:
`MoqLiteSessionTest.subscriber_probe_writes_control_type_and_decodes_publisher_bitrate`.
### Fix #8 — Version-aware Lite-03/04 codec + ALPN negotiation (L1)
Pre-fix the codec was hard-wired to Lite-03; advertising the
documented `MoqLiteAlpn.LITE_04` constant would have caused the
very first Announce to desync because Lite-04 reshapes three
fields. Now full Lite-04 support, gated on a runtime version
discriminator selected by ALPN negotiation.
Wire diff verified via WebFetch against
`kixelated/moq` `main` (2026-05-09) at
`rs/moq-lite/src/lite/{announce,subscribe,probe}.rs` and
`rs/moq-lite/src/model/origin.rs`:
- `Announce.hops`: Lite-03 = single varint count (the spec
fills with `Origin::UNKNOWN` placeholders on decode);
Lite-04 = `varint(count) + count × varint(originId)` (the
`OriginList`). MAX_HOPS = 32.
- `AnnouncePlease.excludeHop`: Lite-03 absent; Lite-04 single
varint after `prefix`. Sentinel `0` = no exclusion.
- `Probe.rtt`: Lite-03 absent; Lite-04 single varint after
`bitrate`. Sentinel `0` = unknown (decoded as null).
Outgoing `Some(0)` clamped to `Some(1)` to avoid colliding
with the sentinel — mirrors kixelated's `encode_msg` clamp.
Surface added:
- `MoqLiteVersion` enum (LITE_03, LITE_04) with `fromAlpn`.
- All affected `MoqLiteCodec` methods take `version:
MoqLiteVersion = LITE_03`.
- `MoqLiteSession.client(transport, scope, version)` carries
the version through every codec invocation.
- Data classes evolved: `MoqLiteAnnouncePlease.excludeHop`
(default 0L), `MoqLiteAnnounce.hops` (`Long` →
`List<Long>`), `MoqLiteProbe.rtt` (`Long?`, default null).
- `WebTransportSession.negotiatedSubProtocol: String?` exposes
the server's `wt-protocol` selection.
`QuicWebTransportFactory` parses the response HEADERS,
extracts the SF-string from `wt-protocol`, and threads it
into `QuicWebTransportSession`.
`FakeWebTransport.pair(negotiatedSubProtocol = …)` lets
tests drive the same path.
- Default advertised list now `[moq-lite-04, moq-lite-03]`.
Lite-04 first to match kixelated's preference; servers that
don't support it fall back to Lite-03 cleanly.
- `connectNestsListener` / `connectNestsSpeaker` resolve the
version via
`resolveMoqLiteVersion(webTransport.negotiatedSubProtocol)`
and pass it to `MoqLiteSession.client(...)`. Falls back to
Lite-03 when the server doesn't echo `wt-protocol` (older
deployments) or echoes an unrecognised value (forward-compat).
Regression tests (all green):
- `MoqLiteCodecTest.announcePlease_lite04_round_trips_excludeHop`
- `MoqLiteCodecTest.announcePlease_lite03_omits_excludeHop_on_wire`
- `MoqLiteCodecTest.announce_lite04_round_trips_full_origin_list`
- `MoqLiteCodecTest.announce_lite03_drops_origin_ids_keeps_count`
- `MoqLiteCodecTest.announce_decoder_rejects_oversize_hop_count`
- `MoqLiteCodecTest.probe_lite04_round_trips_rtt`
- `MoqLiteCodecTest.probe_lite04_clamps_some_zero_to_one_to_avoid_unknown_sentinel`
- `MoqLiteCodecTest.probe_lite04_decodes_zero_rtt_as_null`
- `MoqLiteCodecTest.probe_lite03_wire_omits_rtt`
- `MoqLiteSessionTest.lite04_announce_round_trips_full_origin_list_through_session`
## Build / test verification
Baseline `:nestsClient:jvmTest` was green at audit start
(140 tests). After both fixes + regression tests, still green.
Default-mode tests run in seconds; the `-DnestsInterop=true` Docker
suite is unchanged by these fixes (they only tighten our existing
publisher-side behaviour against malformed input the production
relay never sends).
## Pointers
- Wire spec + IETF gap (DONE banner): `2026-04-26-moq-lite-gap.md`.
- Stream cliff investigation (production-fixed):
`2026-05-01-quic-stream-cliff-investigation.md`.
- Frames-per-group reconciliation (production vs interop):
`2026-05-07-framespergroup-reconciliation.md`.
- Audio-rooms completion plan: `2026-04-26-audio-rooms-completion.md`
(will reference this audit in its compliance section).
- Reference Rust impl: `https://github.com/kixelated/moq/tree/main/rs/moq-lite/src/`.
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