fix(agents): keep downstream-cancelled stream channels from leaking unhandled rejections

[anzemur]

What

Since 1.7.0, forwardAudio cancels its reader on abort (reader.cancel() with no reason). Cancelling the readable side of a stream channel errors the writable side with undefined, so every later fire-and-forget write() / close() from a realtime producer rejects with undefined and surfaces as an unhandled promise rejection (Error: undefined, no application frames).

In production (google realtime plugin, livekit-agents worker on node 22) this fires on every barge-in: the plugin keeps writing the frames that arrive after the interrupt into the cancelled audio channel (realtime_api.ts gen.audioChannel.write(audioFrame) / markCurrentGenerationDone → audioChannel.close()). We saw ~640 events across 54 users in 24h after upgrading.

Fix

At the createStreamChannel seam, so every producer is covered:

• Watch writer.closed so the channel learns about downstream cancellation / errors, flips isClosed, and debug-logs the transition (also fixes the stale closed getter).
• write() attaches a handler to each write promise (no more unhandled rejections from fire-and-forget producers) while returning the original promise, so awaiting callers keep exact backpressure and rejection semantics.
• close() swallows "already closed or errored" failures instead of only TypeError instances — an undefined cancel reason slipped past the e instanceof Error check.
• Logging is best-effort via a new tryLog() export next to log() - it returns the logger or undefined before initializeLogger() has run (log() throws there, and a throw inside these handlers would recreate the unhandled rejection).

Complementary one-liner: forwardAudio now cancels with new Error('audio forwarding aborted') so anything that still observes the reason sees a real error instead of undefined. Note this line alone does NOT fix the bug - it only relabels the rejections; the createStreamChannel hardening is what removes them (verified below).

Tests

• New: a cancelled-mid-stream consumer no longer produces unhandled rejections and flips closed; an awaited write() after cancel still rejects with the cancel reason.
• Full agents suite passes (2283 tests).

Live verification

Ran our production voice agent (google realtime plugin, real LiveKit + Gemini session) with this fix applied to the installed 1.7.0 dist:

• Full smoke suite passes patched (opening, barge-in, text filter, seeded history, typed text, tool injection, closing TTS) with warning sets identical to the unpatched control - no functional regression.
• The live race is hard to script: interrupt() closes the audio channel via markCurrentGenerationDone() whenever the generation already has output, so a scripted interrupt lands after that window. A deterministic replay of the plugin's exact post-cancel calls (gen.audioChannel.write(audioFrame) and audioChannel.close() after forwardAudio's reader.cancel()) shows 8 unhandled rejections unpatched (including the undefined-reason ones we see in Sentry) vs 0 patched, on both the ESM and CJS builds.
• The new debug line (stream channel writable errored or was cancelled downstream) doubles as a detector for the bug condition in the wild.

[changeset-bot]

🦋 Changeset detected

Latest commit: 32f2784

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 39 packages

Name	Type
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-anthropic	Patch
@livekit/agents-plugin-assemblyai	Patch
@livekit/agents-plugin-azure	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cartesia	Patch
@livekit/agents-plugin-cerebras	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-did	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-fishaudio	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-hedra	Patch
@livekit/agents-plugin-hume	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-krisp	Patch
@livekit/agents-plugin-lemonslice	Patch
@livekit/agents-plugin-liveavatar	Patch
@livekit/agents-plugin-livekit	Patch
@livekit/agents-plugin-minimax	Patch
@livekit/agents-plugin-mistral	Patch
@livekit/agents-plugin-mistralai	Patch
@livekit/agents-plugin-neuphonic	Patch
@livekit/agents-plugin-openai	Patch
@livekit/agents-plugin-perplexity	Patch
@livekit/agents-plugin-phonic	Patch
@livekit/agents-plugin-protoface	Patch
@livekit/agents-plugin-resemble	Patch
@livekit/agents-plugin-rime	Patch
@livekit/agents-plugin-runway	Patch
@livekit/agents-plugin-sarvam	Patch
@livekit/agents-plugin-silero	Patch
@livekit/agents-plugin-soniox	Patch
@livekit/agents-plugin-tavus	Patch
@livekit/agents-plugins-test	Patch
@livekit/agents-plugin-trugen	Patch
@livekit/agents-plugin-xai	Patch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.