Workers - AbortController and AbortSignal can be created at global scope

new AbortController(), AbortSignal.abort(), new WritableStream(), and request.signal no longer throw when used during module evaluation (that is, at the top level of your Worker module, outside of a request handler). Previously, these APIs required an active request context and would throw if called at the top level.

// This now works — no error during module startup
const controller = new AbortController();

export default {
	async fetch(request) {
		// The signal can be used across requests
		return new Response("OK", { signal: controller.signal });
	},
};

Signals can also be observed and aborted across different requests, making it easier to coordinate cancellation in long-lived Workers such as Durable Objects.

AbortSignal.timeout() still requires an active request context because it needs to schedule a timer.

For more details, refer to the AbortController documentation.