import { EventSourceMessage } from "./eventSourceParse.js";
export type BuildEventSourceHeaders = (lastEventId: string | undefined) => Record<string, string>;
export interface FetchEventSourceInit extends RequestInit {
    onMessage: (ev: EventSourceMessage) => void;
    buildHeaders?: BuildEventSourceHeaders;
    openWhenHidden?: boolean;
}
export declare function fetchEventSource(eventSourceFetch: typeof fetch, input: RequestInfo, options: FetchEventSourceInit): Promise<void>;