PR #75257: fix(voice-call): await STT readiness before initial greeting (#75197)

• Repository: openclaw/openclaw
• Author: PfanP
• State: open | merged: False
• Link: https://github.com/openclaw/openclaw/pull/75257

Description (problem / solution / changelog)

The Twilio media-stream startup raced TTS playback against the OpenAI realtime transcription WebSocket handshake: handleStart called onConnect (which fires manager.speakInitialMessage immediately) and then started sttSession.connect() fire-and-forget. Under event-loop contention from TTS startup the STT WS handshake timed out at 10s, leaving the call half-functional - greeting played, caller speech never reached the agent - while a direct OpenAI realtime WebSocket probe from the same host succeeded in ~1.1s.

Establish STT readiness before firing onConnect so TTS startup cannot starve the STT handshake. When the STT connect rejects, close the STT session, end the Twilio media stream with a 1011 close code, and fire onDisconnect so the voice-call manager hangs up the call on the existing grace path instead of silently leaving the caller on a deaf stream.

Fixes #75197.

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Changed files

• CHANGELOG.md (modified, +1/-0)
• extensions/voice-call/src/media-stream.test.ts (modified, +110/-0)
• extensions/voice-call/src/media-stream.ts (modified, +29/-7)