> ## Documentation Index
> Fetch the complete documentation index at: https://docs.boson.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Turn detection and interruptions

> Configure automatic or manual turns and keep the conversation aligned during barge-in.

## Turn detection

Set `audio.input.turn_detection` to `{"type": "server_vad"}` for automatic turn taking, `{"type": "semantic_vad"}` for smarter end-of-turn judgment, or `null` for manual `input_audio_buffer.commit` control.

With server VAD active, the model automatically responds when you stop speaking, and user speech during playback interrupts the assistant (barge-in).

`server_vad` parameters:

| Parameter             | Default | Description                                 |
| --------------------- | ------- | ------------------------------------------- |
| `threshold`           | `0.55`  | VAD detection threshold (0.0–1.0)           |
| `prefix_padding_ms`   | `300`   | Audio included before detected speech       |
| `silence_duration_ms` | `500`   | Silence needed to end a turn                |
| `min_speech_duration` | `0.125` | Minimum speech (seconds) to start a segment |

`semantic_vad` extends `server_vad` with a semantic judgment of whether the user has truly finished speaking, reducing premature cut-offs during natural pauses.

## Interruptions (barge-in)

User speech during assistant playback cancels the in-flight response: audio output stops, the assistant's conversation item is truncated at the interruption point, and a new user turn begins immediately. Clients can also truncate played-back items explicitly with [`conversation.item.truncate`](/api-reference/realtime/client-events#conversation-item-truncate) (by `audio_end_ms`) so the stored transcript matches what the user actually heard.

<Card title="Barge-in signal reference" icon="waveform" href="/api-reference/realtime/server-events#input_audio_buffer-speech_started">
  `input_audio_buffer.speech_started` is the event to listen for — stop local playback when it arrives.
</Card>