/**
 * In-process SSE pub/sub.
 *
 * Each subscribed Express response gets its own write loop with:
 *  - 15s heartbeats so proxies don't kill the connection
 *  - lazy back-pressure: if the client falls behind, drop oldest events
 *  - automatic cleanup on close/error/timeout
 *
 * Zero deps — uses raw res.write with the text/event-stream protocol.
 */
import type { ServerResponse } from 'http';
type Frame = {
    event: string;
    data: any;
    id?: number;
};
export declare class SseHub {
    private clients;
    private nextId;
    private nextEventId;
    private listeners;
    /**
     * Register a server-side listener that fires on every broadcast,
     * regardless of whether any clients are connected. Used to mirror
     * events into in-memory caches (e.g., logStorage) so reloads recover
     * recent state.
     */
    onBroadcast(fn: (event: string, data: any) => void): void;
    subscribe(res: ServerResponse, replay?: Frame[]): number;
    broadcast(event: string, data: any): void;
    size(): number;
    closeAll(): void;
    private send;
    private flush;
    private disconnect;
}
export {};