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.

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

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.