voice-agent-ai-sdk

Streaming voice/text agent SDK built on AI SDK with optional WebSocket transport.

Current status

• Streaming text generation is implemented via streamText.
• Tool calling is supported in-stream.
• Speech synthesis is implemented with chunked streaming TTS.
• Audio transcription is supported (when transcriptionModel is configured).
• WebSocket protocol events are emitted for stream, tool, and speech lifecycle.

Prerequisites

• Node.js 20+
• pnpm
• OpenAI API key

Setup

1. Install dependencies:

   pnpm install

2. Configure environment variables in .env:

   OPENAI_API_KEY=your_openai_api_key VOICE_WS_ENDPOINT=ws://localhost:8080

VOICE_WS_ENDPOINT is optional for text-only usage.

VoiceAgent configuration

The agent accepts:

• model (required): chat model
• transcriptionModel (optional): STT model
• speechModel (optional): TTS model
• instructions (optional): system prompt
• stopWhen (optional): stopping condition
• tools (optional): AI SDK tools map
• endpoint (optional): WebSocket endpoint
• voice (optional): TTS voice, default alloy
• speechInstructions (optional): style instructions for TTS
• outputFormat (optional): audio format, default mp3
• streamingSpeech (optional):
  • minChunkSize
  • maxChunkSize
  • parallelGeneration
  • maxParallelRequests

Run (text-only check)

This validates LLM + tool + streaming speech without requiring WebSocket:

pnpm demo

Expected logs include text, chunk:text_delta, tool events, and speech chunk events.

Run (WebSocket check)

1. Start local WS server:

   pnpm ws:server

2. In another terminal, run demo:

   pnpm demo

The demo will:

• run sendText() first (text-only sanity check), then
• connect to VOICE_WS_ENDPOINT if provided,
• emit streaming protocol messages (text_delta, tool_call, audio_chunk, response_complete, etc.).

Browser voice client (HTML)

A simple browser client is available at example/voice-client.html.

What it does:

• captures microphone speech using Web Speech API (speech-to-text)
• sends transcript to the agent via WebSocket (type: "transcript")
• receives streaming audio_chunk messages and plays them in order

How to use:

1. Start your agent server/WebSocket endpoint.
2. Open example/voice-client.html in a browser (Chrome/Edge recommended).
3. Connect to ws://localhost:8080 (or your endpoint), then click Start Mic.

Scripts

• pnpm build – build TypeScript
• pnpm dev – watch TypeScript
• pnpm demo – run demo client
• pnpm ws:server – run local test WebSocket server

Notes

• If VOICE_WS_ENDPOINT is empty, WebSocket connect is skipped.
• The sample WS server sends a mock transcript message for end-to-end testing.
• Streaming TTS uses chunk queueing and supports interruption (interrupt).