Cancellation

Cancel a pending or running workflow with engine.cancel(runId):

const run = await engine.enqueue('order-fulfillment', { orderId: 'ORD_1', amount: 100 })

const cancelled = await engine.cancel(run.id)
// true if cancelled, false if the run already completed / failed / cancelled

Cancellation aborts the current step's AbortSignal immediately and prevents later steps from starting. The run's status becomes cancelled.

Cooperate with the signal

If a handler ignores its signal, the underlying work may keep running outside Reflow — the run is still marked cancelled, but the in-flight I/O won't stop on its own. Forward the signal to abortable APIs so cancellation takes effect immediately:

.step('fetch-profile', async ({ input, signal }) => {
  const response = await fetch(`https://api.example.com/users/${input.userId}`, { signal })
  return await response.json()
})

The same signal is aborted on lease loss and step timeout, so cooperative handlers get fast, uniform cancellation across all three cases.

Cancellation is not failure

A cancelled run does not trigger onFailure or the onRunFailed hook — cancellation is an intentional stop, not an error. If you cancel a run that's paused on stream backpressure, the cancellation still releases it cleanly.