Workflows, Workers - Stream Workflow instance events in your Worker or via the API with .subscribe()

You can now stream Workflow instance events via WorkflowInstance.subscribe() and the GET /subscribe API endpoint. Workers and HTTP clients can react to workflow and step events, including attempts, sleeps, waits, and rollbacks, without polling for instance status.

A subscription first streams the entire event history of the Workflow instance. After streaming past events, the subscription waits for new events as the instance runs. You can use filter to receive only specific event types or cursor to start a subscription at a specific event.

Use .subscribe() to update Workflow status in user-facing dashboards, send notifications when steps complete, or trigger follow-up work for specific events.

const instance = await env.MY_WORKFLOW.get("report-123");

using subscription = await instance.subscribe();

while (true) {
	const { value, done } = await subscription.next();
	if (done) {
		break;
	}

	console.log(value.type, value);
}

const instance = await env.MY_WORKFLOW.get("report-123");

using subscription = await instance.subscribe();

while (true) {
	const { value, done } = await subscription.next();
	if (done) {
		break;
	}

	console.log(value.type, value);
}

For event types, available fields, and subscription options, refer to Subscribe to events.