/**
 * Run `fn` (and everything it awaits) with `id` bound as the ambient request
 * id. Returns whatever `fn` returns — for the middleware, the `next()` promise.
 */
export declare function runWithRequestId<T>(id: string, fn: () => T): T;
/**
 * Read the ambient request id for the current async context, or `undefined`
 * when called outside a request (or on a runtime without async_hooks). Access
 * is defensive: it never throws, so callers can safely fall back to a context
 * variable or header.
 */
export declare function getRequestId(): string | undefined;