import type { ServerResponse } from 'node:http';
export type ChangeKind = 'nodes' | 'inbox';
export interface EventHub {
    /** Register an SSE client: writes the event-stream headers, streams events
     *  until the connection closes, and self-removes on close. */
    addClient: (res: ServerResponse) => void;
    /** Internal, in-process subscription to the same invalidations SSE clients
     *  receive — for a server-side consumer (the push diff engine) that needs
     *  the trigger without opening an HTTP/SSE connection to itself. Returns an
     *  unsubscribe function. */
    subscribe: (listener: (kind: ChangeKind) => void) => () => void;
    /** Tear down watchers + heartbeat and end all open streams. */
    close: () => void;
}
/** Start the change-event hub: open the two fs watchers once, fan their
 *  debounced invalidations out to every connected SSE client. Watchers run for
 *  the server's lifetime (cheap — two inotify/FSEvents registrations), not
 *  per-client, so N browsers share one watch. */
export declare function startEventHub(): EventHub;