Class ElevenLabsVoiceAgent

Live OTel context of the CURRENT voice.turn, published by defaultVoiceCall for background-receive-loop adapters (Pipecat/Twilio) to parent their detached-callback recv spans under the turn (#774 — the reusable pattern Twilio PR5 inherits). undefined between turns, so a callback firing outside a turn skips its span rather than parenting under a closed turn. Internal (underscore) — not a public API.

SET when the AGENT deliberately ended the call (e.g. an ElevenLabs hosted agent invoking the end_call system tool), as opposed to the transport dropping. A scripted turn arriving after this concludes the conversation instead of failing the run — the agent behaved as designed. Assertions and judges can read it to reason about WHO ended the call.

Set when the adapter has emitted its first agent audio chunk for the current turn — gates timing-based barge-in. Concrete adapters expose this so scenario.interrupt can wait for real speech before firing the interruption. Optional: adapters without server-VAD-style interrupt sequencing can leave it undefined.

Declaration of what this adapter can and cannot do. Concrete subclasses MUST publish a non-default value; the base instance defaults to "nothing supported" so capability-gated steps fail safely when an adapter forgets to declare.

Hard cap on a single agent turn's audio. Prevents runaway loops if a transport never signals end-of-stream. 30s = a long sentence.

Tail silence: once the first agent chunk arrives, keep draining receiveAudio until no chunk shows up within this many seconds — that's how we detect the agent finished talking.

Seconds to wait for agent audio after sending user audio: the STT + LLM + TTS budget for one agent turn. Kept identical to Python's VoiceAgentAdapter.response_timeout so the same scenario passes or fails the same way in both SDKs.

Raise it for an agent that runs a tool call or a retrieval step before it speaks:

const agent = elevenLabsAgent({ agentId, apiKey });
agent.responseTimeout = 180; // wait up to 3 minutes
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Incremental transcript text emitted while the agent speaks. Populated by adapters that advertise capabilities.streamingTranscripts. Read by scenario.interrupt when afterWords: N is set.

Bounded grace-wait (seconds) for the agent turn's transcript AFTER audio drains (#734). Audio silence closes the turn (responseTailSilence), but a live voice agent (hosted ElevenLabs) delivers the turn's text on a SEPARATE socket event (agent_response → lastAgentTranscript). When that event lands after the audio-silence boundary, snapshotting lastAgentTranscript at drain-close reads null and the turn reaches the text-only simulator as a bare [audio message] — the simulator then fabricates.

The default call() flow (defaultVoiceCall) polls this field up to this ceiling for a pending transcript before reading it. It short-circuits the INSTANT lastAgentTranscript is already set (zero added latency on the happy path — the common case where the transcript won the race) and only elapses when the transcript genuinely never arrives, so a real ElevenLabs drop still terminates the turn. Set to 0 to disable the wait.