Reconnect a Live Session

Network disconnect, retry, and resume design.

Recommended design for handling WebSocket disconnects in realtime sessions.

Reconnect decision matrix

Close code	Meaning	Action
1000	Normal close	Do not reconnect
4408	Idle timeout	Reconnect immediately
1008	Session duration limit	Reconnect immediately (new session)
1009	Frame too large	Fix frame size, then reconnect
1011	Client socket error	Reconnect with backoff
1013	Upstream unavailable	Exponential backoff

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}`
  );
}

Connection Lifecycle — close codes and timeouts
Reconnection & Retries — production retry strategies
Authentication — session token refresh

Save a Transcript

Persist the complete transcript after a session ends.

API Reference Overview

Base URL, REST/WebSocket endpoints, versioning.