[kixelated]

Completes and deletes quest/m1/quic/peer-limits.md.

What

A session admitted with a peer grant now widens its QUIC connection before the SETUP reply: MAX_STREAMS (both directions), the connection receive window (MAX_DATA), and the send window. Viewers keep the [quic] limits. This works on the tokio listener and the io_uring workers. Links the cluster dials are all peers, so Cluster owns its dials: every static, API and LAN dial is built by one path from the Cluster::with_connect template plus the [peer.quic] limits. Static and API peers share one client on the template's bind address, as before, so a fixed [connect] bind port stays the cluster's egress port; each LAN dial takes an ephemeral port. No embedder can hand it a client with viewer limits. Since the cluster owns those clients, it also closes them: Cluster::close stops every dial task and sends each dialed peer its close before the runtime stops, on any transport, so the peer drops the link and its routes at once instead of at its idle timeout. Relay::run and moq-cli call it on exit.

A new [peer.quic] table takes [quic]'s key names: max_streams, receive_window, and send_window (--peer-quic-max-streams, --peer-quic-receive-window, --peer-quic-send-window, MOQ_PEER_QUIC_*). Defaults are 10x the [quic] defaults: 100,000 streams and 640 MiB for each window. No value is validated against [quic]. All three are NonZeroU64, so zero streams or a zero window, which would wedge SETUP, fails to parse. A stream count past 2^60 (which a peer refuses with FRAME_ENCODING_ERROR) or a receive window past a QUIC varint is refused when the relay loads, in [peer.quic] and [quic] alike. Both bounds live in moq_tokio::quic: Config::validate checks [quic] and Limits::validate checks [peer.quic] and every runtime setter.

[peer.quic]
max_streams = 100000
receive_window = 671088640
send_window = 671088640

Settled decisions

1. Where the setter lives
   • ✅ Backend-specific setters: moq_tokio::server::Request::set_quic_limits and moq_uring::quic::web::Session::set_limits.
   • A set_limits method on moq-net's transport trait (the original quest plan). moq_net::server::Handshake and Session do not expose the transport, so this would add a Handshake method plus unsupported defaults in the ffi, wasm, memory, ietf and mock adapters. This matches the 2026-10-08 decision in quest/m2/transport-adapter-dedup.md, and quest/m2/rate-quic.md is updated to extend this seam.
2. Defaults
   • ✅ 640 MiB for both windows and 100,000 streams (10x the [quic] defaults).
   • Send window at about 10x the backend send defaults (around 160 MiB).
3. Config shape
   • Flat [peer] max_streams / receive_window / send_window (--peer-max-streams, MOQ_PEER_*).
   • ✅ Nested [peer.quic] mirroring [quic]'s key names, with --peer-quic-* flags and MOQ_PEER_QUIC_* env vars.
   • Reusing moq_tokio::quic::Config (or another shared settings type) for [peer.quic]. Not taken: usage-rs flags are literal per field, so a shared struct cannot carry both --quic-* and --peer-quic-*, and quic::Config holds knobs (GSO, idle timeout, congestion control, qlog) a peer cannot change after the handshake. limits::Quic is a 3-field relay struct that resolves to moq_tokio::quic::Limits.
4. Peer values below [quic]
   • A startup check refusing them, guessing 64 MiB for unset [quic] windows.
   • ✅ No validation. A shrink is a debt the peer pays down, so it is not a misconfiguration: the stream limit drops as peer streams close, receive_window_shrink_debt absorbs returned credit before new MAX_DATA, and the send window is local. Reconfirmed after a Codex finding.
5. How cluster dials get the peer limits
   • Client::with_quic_limits widening a handed-in Cluster::with_client client, sharing its socket. Rejected as an awkward extra client knob.
   • ✅ Cluster owns dials: it builds each peer client from the with_connect template and the [quic] settings with the three limits replaced, through one path shared with LAN. Static and API peers share one client bound at the template's address; LAN dials, which each pin their own TLS, take an ephemeral port.
6. moq-cli and a fixed --connect-bind
   • ✅ moq-cli builds its own client only for --connect <url>, so a fixed bind with a WAN cluster peer is the cluster's alone. In a QUIC build, a fixed bind with both --connect and a WAN peer is refused at validation, naming the fix (port 0, or drop --connect or unset MOQ_CONNECT).
   • Hand the cluster an ephemeral-port template in moq-cli, or add a Cluster accessor for its shared client.

Public API

• moq_tokio::quic::Limits { max_streams, receive_window, send_window }, each NonZeroU64 (new), with Limits::validate(&self) -> Result<()> (new).
• moq_tokio::quic::Config::validate is now pub (was pub(crate)) and also refuses max_streams above 2^60, with the new moq_tokio::Error::StreamsRange. The relay calls it at load, since Relay::client() no longer builds a client that checked it.
• moq_tokio::server::Request::set_quic_limits(&self, Limits) -> Result<()> (new). It errors with the new moq_tokio::Error::QuicLimits(Transport) on qmux and iroh, and with Limits::validate's error on an unadvertisable limit, changing nothing.
• moq_tokio::quic::DEFAULT_RECEIVE_WINDOW is now pub. It was pub(crate).
• moq_uring::quic::Limits (new, the same NonZeroU64 fields), moq_uring::quic::Connection::set_limits and moq_uring::quic::web::Session::set_limits (new), returning Result<(), moq_uring::Error>, with the new moq_uring::Error::WindowRange and Error::StreamsRange for a receive window past a QUIC varint or a stream count past 2^60.
• moq_relay::cluster::Cluster::with_client is removed (breaking). Cluster::with_connect(connect::Config, quic::Config) is now required whenever peers are configured, and start() fails without it. start() binds the shared static client as its last fallible step, so a taken [connect] bind port fails there, and a start that fails earlier binds nothing. The client joins the registry Cluster::close drains only when Started::run begins.
• moq_relay::cluster::Cluster::close(&self) (new, async): stops every dial task (ending its link on any transport), closes every dial QUIC client, waits until each peer has been sent its close, and refuses further dials on every clone. Concurrent calls on any clones all await one shared shutdown. Relay::run calls it on exit, and Started::run passes every return through it. A cancelled run aborts every dial task, peer-list and LAN dials included, which starts each link's close but cannot wait for it.
• moq_relay::cluster::Cluster::with_iroh(iroh::Endpoint) (new, iroh feature): cluster dials to iroh:// peers use this endpoint.
• moq_relay::Relay::client() is removed (breaking). Nothing in the repo used it; an embedder that needs an outbound client builds one with config.connect.clone().init(config.quic.clone()).
• moq_relay::limits::Peer gains quic: moq_relay::limits::Quic (new type, #[non_exhaustive], fields NonZeroU64).
• Relay config: [peer.quic] max_streams / receive_window / send_window, plus --peer-quic-* and MOQ_PEER_QUIC_*.

Wire

No MoQ wire change. QUIC sends the standard MAX_STREAMS and MAX_DATA frames earlier and with larger values. Interop was not run because no MoQ framing, ffi, or gateway code changed.

Tests

• rs/moq-relay/tests/integration/peer_limits.rs uses a raw QUIC client against a relay whose quic.max_streams is 4. After SETUP, a peer session gets credit for 16 uni streams (the probe awaits each one, since MAX_STREAMS and SETUP can travel in separate packets) and receives MAX_DATA. A viewer, checked with the credit it holds when SETUP arrives, is held to the limit and gets no MAX_DATA. It covers the tokio and io_uring paths (MOQ_STRICT=1, both pass), and both fail when the widening is removed.

• cluster_dials_widen_a_plain_client in the same file hands Cluster::with_connect a [quic] config whose max_streams is 4 and checks, from a bare QUIC server, that the cluster dial still lets the server open 16 streams. It fails without the fix (4 opened).

• unadvertisable_quic_limits_are_refused_at_load in the same file checks that Relay::load refuses a peer.quic.receive_window of 2^62, a peer.quic.max_streams of 2^60 + 1 and a quic.max_streams of 2^60 + 1. quic::tests::stream_limits_must_fit_a_stream_id covers both validators at the boundary.

• args::tests::a_fixed_connect_bind_serves_one_dialer checks that moq-cli refuses a fixed --connect-bind port with both --connect and a WAN cluster peer, before anything binds, and accepts port 0 or either side alone. In a build without quic, nothing binds the port, so it accepts the fixed port too.

• tokio_worker_peer_session_widens_quic_limits in peer_limits.rs covers the tokio worker shards (runtime.workers, from feat(quic)!: shard the relay's QUIC endpoint per core by default #5688).

• tests::a_fixed_connect_bind_with_a_cluster_peer_starts in moq-cli checks that a fixed --connect-bind with a --cluster-connect peer and no --connect starts. It fails if moq-cli builds its client unconditionally.

• cluster::tests::a_critical_failure_closes_the_dials checks that Started::run returning on a critical failure sends a dialed peer the shutdown close, since a caller that consumed the cluster has no handle left to close it.

• cluster::tests::cancelling_run_stops_its_dynamic_dials checks that aborting Started::run ends a --cluster-connect-api dial's task, which tokio::spawn puts outside run's own tasks. It times out without the abort-on-drop guard.

• cluster::tests::a_failed_start_leaves_the_dial_bind_free checks that a start failing on a missing token file leaves a fixed [connect] port free for a corrected start, and that an unrun start registers nothing.

• tests::a_stream_bind_failure_starts_no_dial in moq-cli checks that --connect dials only after the listener starts, so a bind failure leaves no live dial dropped without its close.

• static_peer_dials_from_the_configured_bind in the same file checks that a static peer dial comes from the [connect] bind port. Both new relay tests fail without their fixes.

• rs/moq-relay/tests/integration/cluster_close.rs runs the dialer on its own runtime and shuts it down right after, as a process exit would, against a peer whose idle timeout is 300s. closing_a_cluster_closes_its_static_dials and a_relay_shutdown_closes_its_cluster_dials check that the peer gets the client shutdown close within 10s, and cluster::tests::closing_a_cluster_closes_its_lan_dials checks that a LAN peer drops the dialer's route. closing_a_cluster_ends_its_websocket_dials checks that a WebSocket peer's socket is closed by the time close returns, on a runtime that keeps running. cluster::tests::concurrent_closes_share_one_shutdown checks that a second close stays pending until the shutdown the first started finishes, even after the first caller is cancelled. All five fail without their fix (the concurrent one returns at once): the static, LAN and WebSocket ones time out, and the relay one gets only a racy dropped close.

• config::tests::zero_peer_quic_limits_are_refused checks that a zero stream limit or window is refused from TOML and from the flags.

• config::tests::peer_quic_table_merges_with_flags checks that [peer.quic] merges with --peer-quic-* flags without touching [quic], and that the flat [peer] max_streams key is refused.

• The settings registry drift test covers the new peer.quic.* keys.

• The existing cluster tests (goaway_cluster, hidden_cluster, cluster_idle, upstream_links, lan_mesh with --ignored) pass on the new dial path.

• just check against main passes (4418 workspace Rust tests plus the io_uring, feature-matrix, JS and doc runs, lint and format), and quest check passes.

drills bursts_cross_a_transport_peer::impaired

CI's io_uring job failed this drill once ("the route was withdrawn while the peer link was up"). Its static peer link does go through the new peer_client path with the [peer.quic] limits, so I compared locally with io_uring at load below 24:

• 100 random-seed iterations: 2 failures on this branch, 0 on main (977223d). That gap is not significant (p ≈ 0.25), so I replayed the two failing shaper seeds.
• Seed 13777473187891923846: 11 of 20 failed on this branch, 10 of 20 on main.
• Seed 7291640207369166737: 10 of 20 failed on this branch, 12 of 20 on main.

The failure follows the shaper seed and occurs at the same rate on main, so it is the drill's existing flake, not this change.

TS validation video-content failures

CI's TS compliance and TS fragmented PES headers steps failed video-content ("decoded pictures are not an intact suffix of the source") on three of five heads here (the latest head passes). This was the flake tracked as #5565, which #5713 (now merged into this branch) fixed at its root (an export that starts on a group cut short by the zero-budget live-edge subscription), not this change:

• Locally, just test ts --fragment-pes failed 1 of 4 runs on this branch (the failing run had load 52 on 24 cores) and passed 4 of 4 on the base branch (feat(quic)!: run moq-tokio and moq-uring on moq-quic #5664 head c1f4cfd) at load 18 to 27. The failing run has the quest's exact signature: 0.avc3 subscribed with max_delay: 0ns, then 8 ms later the exporter logged current group evicted; skipping to next buffered group track="0.avc3" group=1 error=Hang(Moq(Stream(Old))), and the capture lost 10 pictures early in its first group.
• The same failure hit perf(net): count track demand incrementally #5670 (based on main, no QUIC changes) and, since 2026-10-15 12:00 UTC, the announce-live, ietf-extension/dynamic-groups, open-gop-leading-pictures and play-resume branches.
• That relay serves anonymous sessions with no cluster. This PR changes nothing on that path: Cluster::quic_limits returns None without a peer grant, and the widened dial config only reaches cluster dials.

Open decisions

• On non-QUIC transports (WebSocket, TCP, iroh), a peer keeps its transport limits and the relay logs it at debug. iroh could implement the same setters on noq; that would be a follow-up.

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(Written by Claude Opus 5.5)

[kixelated]

Quest outcome: done and left as a draft, stacked on #5664.

Peer sessions now widen MAX_STREAMS and MAX_DATA plus the send window before SETUP OK, on both tokio and io_uring. Links the cluster dials get the same limits from the handshake on. A [peer] value below [quic] is refused at startup.

This diverges from the plan: the setters are backend methods rather than a moq-net trait method. The PR body has the reasoning. Two decisions are still open: the 640 MiB send-window default, and whether iroh peers should get the same setters.

(Written by Claude Opus 5.5)

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Walkthrough

The relay adds configurable stream and receive/send window limits for peer QUIC connections. It applies limits to admitted peer sessions and outbound peer links. Cluster setup now uses connection settings instead of a prebuilt client, and cluster shutdown closes tracked dials. CLI validation rejects a fixed bind port when an explicit connection and WAN cluster dial share it. Integration tests cover peer and viewer limits, worker paths, and cluster shutdown.

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to e09b4

No actionable merge-blocking issue remains after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 79.53% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 127 functions across 28 files. (1 skipped…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
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.
Description check		The description directly explains the QUIC limit changes, cluster dial ownership, shutdown behavior, configuration, public API changes, tests, and reported CI failures.
Title check		The title clearly and concisely identifies the primary change: widening QUIC limits for cluster peers.

Full details: Docstring Coverage

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Docstring coverage is 79.53% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 127 functions across 28 files. (1 skipped: 1 unsupported.)

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Inline comments:
Review comments at @doc/bin/cli.md:
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