@metatell/bot-realtime

Realtime transport helpers for metatell bots. The package provides LiveKit WebRTC transport and a mock adapter for tests and local development.

Requirements

• Node.js 20 or later. Node.js 24 is recommended and is the version used in CI.
• TypeScript 5 or later for TypeScript projects.

Install

npm install @metatell/bot-realtime
# or
pnpm add @metatell/bot-realtime
# or
yarn add @metatell/bot-realtime

Most bots use this package through enableVoice() in @metatell/bot-sdk, which creates the transport, requests the LiveKit token, and attaches the voice bridge. Use the APIs below directly only for custom integrations.

Usage

import { createRealtimeTransport } from '@metatell/bot-realtime'

const transport = createRealtimeTransport({ type: 'livekit' })

const unsubscribe = transport.on((event) => {
  switch (event.type) {
    case 'state':
      console.log('connection state:', event.state)
      break
    case 'data':
      console.log('data received:', event.topic, event.payload)
      break
    case 'participant-joined':
      console.log('participant joined:', event.identity)
      break
  }
})

await transport.connect({
  url: 'wss://livekit.example.com',
  tokenProvider: async () => getAccessToken(),
  topics: ['control', 'events', 'transcript', 'audio'],
  audioPublish: {
    sampleRate: 48000,
    channels: 1,
  },
})

await transport.send('control', JSON.stringify({ action: 'spawn' }))
await transport.startAudioPublisher()
await transport.pushPcmFrame(new Int16Array(960))
await transport.stopAudioPublisher()
await transport.disconnect()
unsubscribe()

createRealtimeTransport() accepts type: 'livekit', 'mock', or 'auto' (the default). 'auto' selects the mock transport when NODE_ENV is test and LiveKit otherwise.

Connection Options

| Option | Description | | --- | --- | | url | LiveKit WebSocket URL. | | tokenProvider | Async function that returns a LiveKit access token. | | topics | Data topics that can be sent. Defaults to control, events, transcript, and audio. Sending to another topic fails. | | audioPublish | sampleRate (16000, 24000, or 48000), channels (1 or 2), optional frameDurationMs (10 or 20, default 20), and optional trackName. Defaults to 48000 Hz mono. | | connect | Optional autoSubscribe and dynacast flags. | | timeouts | Accepted for connectMs, but not currently enforced by either adapter. | | logger | Optional (level, msg, meta) => void logger. |

pushPcmFrame() expects one frame of sampleRate * frameDurationMs / 1000 samples per channel. Received remote audio is delivered on the audio topic as 48000 Hz mono signed 16-bit PCM.

Voice Bridge

attachVoice(client, transport, handlers, options) connects a voice-capable client to a connected transport. It forwards remote audio to handlers.onRemotePcm, publishes handlers.getLocalPcmStream when autoStartPublish is true (the default), and routes client.sendVoiceFrame() to the transport. Call detach() on the returned object to stop.

Mock Adapter

Use the mock adapter for tests and local development without a LiveKit room:

import { MockAdapter } from '@metatell/bot-realtime'

const mock = new MockAdapter()
await mock.connect({ url: 'mock://local', tokenProvider: async () => 'token' })

After connecting, the mock emits a participant-joined event for mock-participant and then a 960-sample audio frame on the audio topic every 20 ms. Data passed to send() is echoed back as a data event from mock-echo.

Events

type RealtimeEvent =
  | { type: 'state'; state: ConnectionState }
  | { type: 'data'; topic: string; payload: Uint8Array; from?: string }
  | { type: 'participant-joined'; identity: string; sid: string }
  | { type: 'participant-left'; identity: string; sid: string }
  | { type: 'warning'; code: string; message: string }
  | { type: 'error'; code: string; message: string; cause?: unknown }

ConnectionState is 'idle', 'connecting', 'connected', 'reconnecting', or 'disconnected'.

Errors

Adapter precondition and connection failures reject with RealtimeError, a MetatellError subclass whose code is one of the ErrorCodes values, such as AlreadyConnecting, ConnectionFailed, NotConnected, UnknownTopic, SendFailed, or AudioNotStarted. Errors raised by LiveKit while publishing, unpublishing, or closing the audio track in startAudioPublisher() and stopAudioPublisher() are not wrapped and propagate as-is.

License

MIT