WebSocket API

Kurier provides a WebSocket endpoint for real-time job status updates. Instead of polling the REST API, you can open a persistent connection and receive instant notifications as your proofs move through the verification pipeline.

Connecting

Open a WebSocket connection to the testnet endpoint with your API key as a query parameter:

wss://api-testnet.kurier.xyz/api/v1/ws?apiKey=YOUR_API_KEY

On success, the server sends a confirmation message:

{
  "type": "connected",
  "connectionId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "message": "Connected successfully"
}

info

Your API key is authenticated on connect. Invalid or missing keys will result in the connection being closed with code 1008 (Unauthorized).

Message Protocol

All messages are JSON. The client sends commands and the server sends responses and events.

Client Commands

Message	Description
{ "type": "ping" }	Keep-alive ping
{ "type": "subscribe", "jobId": "<uuid>" }	Subscribe to a specific job's status updates
{ "type": "unsubscribe", "jobId": "<uuid>" }	Unsubscribe from a specific job
{ "type": "subscribe-all" }	Subscribe to updates for all your jobs
{ "type": "unsubscribe-all" }	Unsubscribe from all jobs

Server Responses

Message Type	Description
connected	Initial connection confirmation with connectionId
pong	Response to ping, includes timestamp
subscribed	Confirms subscription to a specific jobId
unsubscribed	Confirms unsubscription from a specific jobId
subscribed-all	Confirms subscribe-all
unsubscribed-all	Confirms unsubscribe-all
job-status-update	Job status change event with full job details
error	Error with message, optional code and retryAfterSeconds

Job Status Updates

When a job you are subscribed to changes status, you receive a job-status-update message:

{
  "type": "job-status-update",
  "data": {
    "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "status": "Finalized",
    "statusId": 6,
    "event": "finalized",
    "proofType": "groth16",
    "chainId": 1,
    "txHash": "0x...",
    "blockHash": "0x...",
    "createdAt": "2026-03-27T12:00:00.000Z",
    "updatedAt": "2026-03-27T12:01:30.000Z"
  }
}

The data object includes all fields from the REST job status endpoint. See Job Statuses for the full list of status values.

note

When a job reaches a final state (Finalized, Aggregated, or Failed), you are automatically unsubscribed from that job. There is no need to send an explicit unsubscribe.

Example: JavaScript Client

const ws = new WebSocket(
  'wss://api-testnet.kurier.xyz/api/v1/ws?apiKey=YOUR_API_KEY'
);

ws.onopen = () => {
  console.log('Connected');
};

ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);

  switch (msg.type) {
    case 'connected':
      console.log('Connection ID:', msg.connectionId);
      // Subscribe to a specific job after submitting a proof
      ws.send(JSON.stringify({ type: 'subscribe', jobId: 'YOUR_JOB_ID' }));
      break;

    case 'job-status-update':
      console.log(`Job ${msg.data.jobId}: ${msg.data.status}`);
      if (['Finalized', 'Aggregated', 'Failed'].includes(msg.data.status)) {
        console.log('Job complete, auto-unsubscribed');
      }
      break;

    case 'pong':
      console.log('Server alive at', msg.timestamp);
      break;

    case 'error':
      console.error('Error:', msg.message);
      if (msg.retryAfterSeconds) {
        console.log(`Retry after ${msg.retryAfterSeconds}s`);
      }
      break;
  }
};

// Keep-alive ping every 30 seconds
setInterval(() => {
  if (ws.readyState === WebSocket.OPEN) {
    ws.send(JSON.stringify({ type: 'ping' }));
  }
}, 30_000);

Example: Subscribe to All Jobs

If you want to receive updates for every job submitted under your API key, use subscribe-all instead of subscribing to individual job IDs:

ws.onopen = () => {
  ws.send(JSON.stringify({ type: 'subscribe-all' }));
};

ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);
  if (msg.type === 'job-status-update') {
    console.log(`Job ${msg.data.jobId} is now ${msg.data.status}`);
  }
};

Connection Limits

Limit	Default
Max connections per API key	10
Max connection duration	24 hours

Connections that exceed the maximum duration are closed automatically. Reconnect and re-subscribe as needed.

Error Handling

Error messages include a code field to help with programmatic handling:

Code	Meaning
CONNECTION_LIMIT_EXCEEDED	Too many open connections for this API key
RATE_LIMIT_EXCEEDED	Too many subscribe/unsubscribe operations (includes retryAfterSeconds)
UNKNOWN_MESSAGE_TYPE	Unrecognized message type
INVALID_MESSAGE	Malformed JSON or missing required fields

WebSocket vs. Polling

	WebSocket	REST Polling
Latency	Instant on status change	Depends on poll interval
Efficiency	Single persistent connection	Repeated HTTP requests
Best for	Real-time UIs, automated pipelines	Simple scripts, one-off checks
Endpoint	wss://api-testnet.kurier.xyz/api/v1/ws	GET /api/v1/job-status/<apiKey>/<jobId>

Both approaches return the same job status data. Use whichever fits your use case.