Session Configuration

Configure session parameters via session.update messages.

When to configure

After connect: send session.update right after receiving session.created

During session: update parameters at any time

Confirmation: server returns session.updated to confirm

Field	Type	Description
`language`	string	Audio source language (e.g. `zh`, `en`, `auto`)
`prompt`	string	Context hint, max 2000 characters

Field	Snake-case alias	Type	Description
`vad`	—	boolean	Enable VAD
`vadThreshold`	`vad_threshold`	number	Sensitivity threshold
`vadSilenceMs`	`vad_silence_ms`	number	Silence duration to trigger end-of-speech
`vadPrefixMs`	`vad_prefix_ms`	number	Prefix padding
`vadMinSpeechMs`	`vad_min_speech_ms`	number	Minimum speech segment
`vadTargetSpeechMs`	`vad_target_speech_ms`	number	Target speech segment
`vadMaxSpeechMs`	`vad_max_speech_ms`	number	Maximum speech segment
`vadSmartSplitWindowMs`	`vad_smart_split_window_ms`	number	Smart split window

Fixed by the gateway, client cannot change:

{ "format": "pcm_s16le", "sample_rate": 16000, "channels": 1 }

{ "type": "session.update", "language": "zh" }

{ "type": "session.update", "prompt": "Cardiology conference, terms: atrial fibrillation, anticoagulation, warfarin" }

{
  "type": "session.update",
  "vad": true,
  "vadThreshold": 0.5,
  "vadSilenceMs": 800
}

{ "type": "session.update", "language": "en" }

All non-whitelisted fields are stripped before forwarding upstream. These fields are injected by the gateway and cannot be overridden:

request_id

session_id

user_id

Client Messages — message format

Server Events — session.updated event

Live Translation — translation concepts