> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> multilingual STT) — or Pulse 2.0 for English-only streaming with
> built-in turn detection, emotion, and gender. 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.

# Pulse 2.0 launch: built-in end-of-turn detection, emotion, and gender

**New model: Pulse 2.0.** English-only, streaming-only speech to text on the unified live endpoint. Select it with `?model=pulse-2` on `wss://api.smallest.ai/waves/v1/stt/live` - the same endpoint Pulse streams on.

**Built-in end-of-turn (EOT) detection.** Finals close on turn boundaries instead of a fixed silence timeout or word count, so finals are fewer and longer. There are no tuning knobs. `eou_timeout_ms`, `finalize_on_words`, and `max_words` are ignored by default on `model=pulse-2` - don't send them. If you do, they still take effect and compete with end-of-turn detection. Finals closed by EOT carry `eot_finalized: true`.

**Per-utterance emotion and gender, on by default.** `emotion_detection` adds a six-class `emotion` object (`neutral`, `happy`, `angry`, `sad`, `fear`, `disgust`) with confidence and the full score distribution to every final. `gender_detection` adds a `gender` object (`male`, `female`) with confidence and scores. Both default to `true`; set either to `false` to opt out.

**English only, streaming only.** Any `language` other than `en` returns `LANGUAGE_NOT_SUPPORTED_BY_MODEL` and closes the socket. There is no pre-recorded/batch mode - for multilingual or batch transcription, use standard [Pulse](/model-cards/speech-to-text/pulse) or [Pulse Pro](/model-cards/speech-to-text/pulse-pro).

Pricing: **\$0.005 per minute** of audio (Standard plan). Standard plan rate limits default to 100 concurrent WebSocket sessions, same as Pulse streaming.

→ [Pulse 2.0 model card](/model-cards/speech-to-text/pulse-2-0)