/**
 * Heartbeat loop: ping-pong to detect stale connections.
 * Enabled via createRouter({ heartbeat: { intervalMs, timeoutMs } }).
 *
 * Behavior:
 * - Send ping every intervalMs
 * - Expect pong within timeoutMs
 * - Close connection if timeout
 * - No new API surface (transparent behavior)
 */
import type { ServerWebSocket } from "../ws/platform-adapter.js";
export interface HeartbeatConfig {
    intervalMs?: number;
    timeoutMs?: number;
}
/**
 * Per-connection heartbeat state.
 */
export interface HeartbeatState {
    lastPingAt: number;
    lastPongAt: number;
    isPending: boolean;
}
/**
 * Heartbeat manager (internal).
 */
export declare class HeartbeatManager {
    private config;
    constructor(config: HeartbeatConfig);
    createState(): HeartbeatState;
    tick(clientId: string, ws: ServerWebSocket, state: HeartbeatState): Promise<void>;
    handlePong(state: HeartbeatState): void;
}
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