Vapi WebSocket Tester

A webapp for testing WebSocket transport calls with Vapi. Includes bidirectional audio streaming, a realtime event viewer, and call control messages.

Copy the .env example file:

cp .env.example .env

Edit .env and fill in your values:

Install dependencies:

npm install

Build and run:

npm run build
npm start

Run in dev mode (automatically reloads when the code changes):

npm run dev

Open http://localhost:8000 in your browser to access.

1. Pick Assistant or Squad in the header and enter its ID (or leave the ID blank if VAPI_DEFAULT_TARGET is set in .env)
2. Click Start Call - the server creates a vapi.websocket call and proxies the WebSocket connection
3. Click the microphone button to start sending audio from your mic
4. Incoming audio from the assistant plays automatically
5. All events from Vapi appear in the Event Log - click any entry to expand the full JSON
6. Use the Controls panel to send messages:
   • Say - make the assistant speak a specific string
   • Add Message - inject a message into the conversation history
   • Control - mute/unmute the assistant or customer, trigger the first message
   • Raw JSON - send any arbitrary JSON message
   • Manual Audio - advanced audio control
7. Click End Call or send {"type": "end-call"} via Raw JSON to terminate

The Node server acts as a WebSocket proxy so the Vapi API key never reaches the browser.

Browser <-> ws://localhost:8000/ws <-> Node server <-> wss://... <-> Vapi
        <- assistant audio (binary PCM)
        <- server events (JSON)
        -> customer audio (binary PCM)
        -> call control messages (JSON)

Audio format: PCM signed 16-bit little-endian, mono, configurable sample rate.