Listener cliffs at uni stream #61 even though MAX_STREAMS_UNI(150)
was emitted at count=50 — and the cliff number is variable across
runs (124 in one trace, 61 in another), which strongly suggests the
limiter isn't the stream-id cap any more. Need visibility into what
QUIC flow-control state looks like at the moment streams stop.
QuicWebTransportSession now optionally takes a parentScope and, when
provided, launches a daemon coroutine that calls
QuicConnection.flowControlSnapshot() every 5 s. The snapshot dumps
the fields the cliff-investigation plan
(nestsClient/plans/2026-05-01-quic-stream-cliff-investigation.md)
identified as smoking-gun candidates:
- peerInitiatedUniCount + advertisedMaxStreamsUni (stream-id cap)
- peerInitMaxStreamsUni (peer's view of our cap, from handshake)
- sendCredit + consumed (connection-level data flow control)
- pendingBytes / pendingStreams (anything stuck in send buffers)
- udpRecvDatagrams + udpRecvBytes (raw socket-level reception)
The factory passes its parentScope into the session so the snapshot
job dies cleanly with the same supervisor that owns the driver.
QuicWebTransportFactory tests and SendTraceScenario don't pass a
scope and won't see the periodic logger.
Filter `adb logcat -s NestQuic:D` and look for "snapshot peerInitiatedUni=…".
At cliff time the snapshot will print whichever counter is wedged.
https://claude.ai/code/session_01PYYez8a6sjiakyjAxsfCEQ
Claude
36c707f98a