qwen-code Hosted event streams lack heartbeats, leaving readers parked on half-open connections
wenshao · ghdev · 2026-10-14
A qwen-code follow-up issue details a reliability flaw in the Hosted Harness event stream:
- No heartbeats from the Harness: GET /session/:id/events pumps the journal every 250ms but writes only when there are events, so legitimately quiet turns (long thinking, slow tools) can send nothing for a long time — while other SSE routes in the same server already emit comment heartbeats.
- No idle bound in the Java client: HarnessEventStream builds its SseReader with a no-op activity callback, unlike the non-hosted DaemonSessionClient which has an idle watchdog.
- Result: on a half-open connection (network partition, pod replaced on another node), the reader blocks forever in stream.next(), parking the Turn's coordinator wait. #13877 only made close() able to end such a read.
Real-stack evidence from H4f acceptance: thread dumps after SIGKILLing the Harness showed Turn readers still parked in HarnessEventStream.next.
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