Sleep & signals

Real workflows wait — for a delay, or for the outside world. Both kinds of pause are durable: the run is suspended (no compute consumed) and resumes on its own, even across restarts.

Durable sleep

ctx.sleep(duration) suspends the run until the timer is due. Accepts '30s', '2h', '7 days', or milliseconds.

await ctx.step('draft', () => generate(topic));
await ctx.sleep('7 days'); // gather signals for a week — nothing running
await ctx.step('refine', () => refine(topic));

Under the hood the run becomes suspended with a wakeAt; a poller (the TimerPoller, wired by DurableModule) resumes runs whose timer has come due. On resume, the steps before the sleep replay from their checkpoints.

Signals (human-in-the-loop)

ctx.waitForSignal(token) suspends the run — with no timer — until an external engine.signal(token, payload) arrives. Perfect for approvals, webhooks, or any third-party callback.

const decision = await ctx.waitForSignal<{ approved: boolean }>(`approve:${order.id}`);
if (!decision.approved) return { status: 'rejected' };

Deliver the signal from anywhere — typically a controller — via WorkflowService.signal:

@Post('orders/:id/approve')
approve(@Param('id') id: string, @Body() body: { approved: boolean }) {
  return this.workflows.signal(`approve:${id}`, body); // resumes the run with the payload
}

The payload is checkpointed like any step result, so the resumed run sees the same decision even if it replays again later.