This is the “real app” version of the 5-minute quickstart: a polished UI, AudioWorklet mic capture, temporary-token auth, and full barge-in handling. The AssemblyAI Voice Agent API does the speech recognition, the LLM, and the TTS server-side — you’re just shuttling audio bytes.

Why One WebSocket Beats a Multi-Service Pipeline

A traditional browser voice agent needs you to wire up streaming STT, an LLM, and a TTS provider, then orchestrate audio routing between them in the browser. Every hop adds latency, every provider needs a key, and every glue layer adds a failure mode.

Multi-service browser pipeline Voice Agent API

Services to wire up STT + LLM + TTS (3+ vendors)

API keys to manage 3+

Round trips per turn 3 (mic→STT→LLM→TTS→speaker)

Browser key exposure Hard to avoid

Turn detection Configure separately

Barge-in / interruption Implement yourself

Tool calling Wire LLM tools manually

The endpoint is one URL: wss://agents.assemblyai.com/v1/ws. Send 24 kHz PCM, get 24 kHz PCM back.…