Workflow SDK now supports inflight cancellation

The Workflow SDK 5 beta now supports the standard AbortController and AbortSignal APIs across workflow and step boundaries.

Create a controller inside a workflow, pass its signal into one or more steps, and cancel in-flight operations using the same API fetch already uses.

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import { sleep } from "workflow";
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export async function cancellableWorkflow() {
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  "use workflow";
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  const controller = new AbortController();
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  const result = await Promise.race([
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    fetchReport(controller.signal),
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    sleep("30s").then(() => null),
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  ]);
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  if (result === null) {
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    controller.abort();
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    return { status: "timed-out" };
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  }
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  return result;
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}
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async function fetchReport(signal: AbortSignal) {
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  "use step";
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  const response = await fetch("https://api.example.com/report", {
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    signal,
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  });
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  return response.json();
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}

That signal stays durable across suspensions and deterministic replay. When a step is running, it sees the cancellation, even when it's in a separate function invocation. Cancellation is also cooperative; steps have to inspect the signal or pass it to an API that supports AbortSignal.

Use it to stop a slow step when a durable timeout wins a race, cancel the remaining requests after the first successful response, thread one signal through a multi-step pipeline, or cancel parallel work when an external condition changes.

Try it with workflow@beta and read the cancellation documentation to learn more.