> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. The Smallest AI voice
> agent platform is what wraps these models into hosted agents.

# Speech to Text: VAD events on the live WebSocket API reference

> The Pulse STT live WebSocket now models the acoustic voice-activity events in the API reference: speech_started and speech_ended, emitted alongside.

The Pulse STT live WebSocket now models the acoustic voice-activity events in the API reference: `speech_started` and `speech_ended`, emitted alongside `transcription` messages when the connection sets `vad_events=true`. See [VAD events](/models/speech-to-text/features/vad-events) for the payloads and usage.

The events have been in production; this documents them on the WebSocket reference.

> The Pulse STT live WebSocket now models the acoustic voice-activity events in the API reference: speech_started and speech_ended, emitted alongside.