Speech-to-Text (STT) converts spoken audio into text. In a custom voice pipeline, STT sits between the call and the LLM: user speaks → STT transcribes → turn signal → LLM → TTS. See Voice Agents for the full wiring guide.
Fast-Whisper runs locally on your machine. Wizper uses Fal.ai cloud — it is not a local model.
STT plugins without built-in turn detection need an external turn detection plugin, or the agent falls back to using the final transcript as the end-of-turn signal.