Reconnect a Live Session

Recommended design for handling WebSocket disconnects in realtime sessions.

Reconnect decision matrix

Exponential backoff

function reconnectWithBackoff(url, maxRetries = 5) {
  let attempt = 0;
  let lastLanguage = 'zh';

  function connect() {
    const ws = new WebSocket(url);

    ws.onopen = () => {
      console.log('Connected');
      attempt = 0; // reset backoff on success
      // Re-send session configuration
      ws.send(JSON.stringify({ type: 'session.update', language: lastLanguage }));
    };

    ws.onclose = (event) => {
      if (event.code === 1000) return; // normal close

      if (attempt < maxRetries) {
        const delay = Math.min(1000 * Math.pow(2, attempt), 30000);
        attempt++;
        console.log(`Reconnecting in ${delay}ms (attempt ${attempt})`);
        setTimeout(connect, delay);
      }
    };

    ws.onmessage = (event) => {
      // Handle events as normal
    };
  }

  connect();
}

Session continuation

After reconnecting:

You get a new session_id — sessions do not resume

Re-send session.update to restore language, VAD, and other settings

Previous utterances are not re-delivered

If you need the complete transcript, accumulate segments client-side

Keep-alive strategies

To avoid idle timeout (4408):

// Send silent frames to keep connection alive
function keepAlive(ws) {
  setInterval(() => {
    if (ws.readyState === WebSocket.OPEN) {
      const silence = new ArrayBuffer(3200); // 100ms of silence
      ws.send(silence);
    }
  }, 5000); // every 5 seconds
}

Session token refresh

Browser connections: session tokens expire in 60 seconds. If reconnection happens after token expiry:

async function connectWithFreshToken() {
  const { token } = await fetch('/session-token', { method: 'POST' }).then(r => r.json());
  return new WebSocket(
    `wss://audio.lansonai.com/v1/audio/transcriptions/stream?access_token=${token}`
  );
}

Related

Connection Lifecycle — close codes and timeouts

Reconnection & Retries — production retry strategies

Authentication — session token refresh