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latestOpenAPI 3.1.0MITraw.githubusercontent.com2026-08-1410673303.5 KB

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Legs

Synthesize speech and hold it for a later commit

Stages a speculative reply. The audio is synthesized and buffered in memory but not played, so that committing it starts playback with no synthesis delay. Intended for the turn-taking loop of a voice agent: start a draft reply on the eager_end_of_turn stt.turn event, then commit it on end_of_turn or discard it on turn_resumed. A tts.staged event reports when the audio is ready; synthesis failures are reported on tts.error. Staged utterances are dropped after TTS_PREFLIGHT_TTL or when the leg ends, and at most TTS_PREFLIGHT_MAX_PER_LEG may be staged on one leg at a time. Preflight is leg-scoped; use POST /rooms/{id}/tts for room announcements.

post/legs/{id}/tts/preflight

Request body

textstring required

Text to synthesize

voicestring required

Provider-specific voice identifier. ElevenLabs: voice name or ID. AWS Polly: voice ID (e.g. Joanna, Matthew). Google Cloud: voice name — either full format (e.g. en-US-Neural2-F) or short name for Gemini models (e.g. Achernar, Kore). Deepgram: model name (e.g. aura-2-asteria-en).

model_idstring required

Provider-specific model/engine. ElevenLabs: model ID. AWS Polly: engine (standard, neural, long-form, generative; default neural). Google Cloud: model name (e.g. gemini-2.5-pro-tts, chirp3-hd).

languagestring

Language code (e.g. "en-US", "pl-pl"). Required for Google Gemini TTS voices that use short names (e.g. Achernar). Auto-extracted from full voice names like en-US-Neural2-F.

promptstring

Style/tone instruction for promptable voice models (Google Gemini TTS only). E.g. "Read aloud in a warm, welcoming tone."

volumeinteger required

Volume adjustment in dB (-8 to 8)

provider'elevenlabs' | 'aws' | 'google' | 'deepgram'

TTS provider: "elevenlabs" (default), "aws", "google", or "deepgram"

api_keystring

ElevenLabs: API key override (falls back to ELEVENLABS_API_KEY env var). AWS: optional ACCESS_KEY:SECRET_KEY override (falls back to default AWS credential chain). Google Cloud: optional API key override (falls back to Application Default Credentials). Deepgram: API key override (falls back to DEEPGRAM_API_KEY env var).

Response

TTS staged

instance_idstring

Instance identifier

statusstring required