import http from 'node:http';
export interface StreamEvent {
    type: string;
    data: unknown;
}
/**
 * ObservationStream — WebSocket server for real-time dashboard push.
 *
 * Attaches to an existing http.Server on path '/ws'.
 * Broadcasts typed events (observation:new, stats:update, etc.) to all
 * connected clients. Heartbeat ping/pong every 30s per RFC 6455.
 */
export declare class ObservationStream {
    private wss;
    private clients;
    private heartbeatInterval;
    private static readonly MAX_CLIENTS;
    constructor(server: http.Server);
    /**
     * Broadcast an event to all connected clients with open sockets.
     */
    broadcast(event: StreamEvent): void;
    /**
     * Gracefully stop the WebSocket server, clear heartbeat, close all clients.
     */
    stop(): void;
    /** Number of connected clients (useful for diagnostics). */
    get clientCount(): number;
    private handleConnection;
    private ping;
}
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