Rate Limits

Connection limits, timeouts, and reconnection guidance.

Function Timeout

The SSE endpoint runs as a Vercel Serverless Function with maxDuration set to 300 seconds (5 minutes). After 5 minutes, the function terminates and the stream closes.

Your client must reconnect to continue receiving events.

Reconnection Strategy

Custom clients

Implement exponential backoff with jitter:

EventSource handles reconnection automatically with its built-in backoff. For custom fetch-based clients:

let retries = 0;
 
function connect() {
  const response = await fetch(URL, { headers: { Authorization: `Bearer ${TOKEN}` } });
  retries = 0; // reset on successful connection
 
  // ... read stream ...
 
  // On stream end or error:
  retries++;
  const delay = Math.min(1000 * 2 ** retries, 30000) + Math.random() * 1000;
  setTimeout(connect, delay);
}

Retry	Delay range
1	2 -- 3 s
2	4 -- 5 s
3	8 -- 9 s
4	16 -- 17 s
5+	30 -- 31 s (capped)

Tip

For production automations, reconnect immediately on the expected 5-minute timeout (no backoff needed) and only apply exponential backoff for unexpected disconnections.

Concurrent Connections

There is no enforced limit on concurrent SSE connections per token. However, each connection consumes a Vercel Serverless Function invocation. For most use cases, a single connection is sufficient.

Warning

Opening many concurrent connections from the same token wastes resources. Each connection receives identical events. Use one connection and fan out in your application.

Token Expiry Mid-Stream

Tokens are validated only at connection time. If a token expires while a stream is active, the stream continues until it closes naturally (function timeout or client disconnect). The next reconnection attempt will fail with .

Keep-Alive

The SSE endpoint does not send periodic keep-alive pings. The stream is silent between tip events. EventSource clients handle idle connections correctly — no heartbeat is needed on the client side.

If your custom client has an idle timeout, set it above 300 seconds or disable it for this connection.