export declare const REALTIME_HEARTBEAT_INTERVAL_MS = 5000;
/**
 * A transport-only event. `intervalMs` is the cadence it is sent at, so a
 * client can size its own dead-stream timeout from the server's real setting
 * instead of hardcoding a constant that drifts from it.
 */
export type RealtimeHeartbeat = {
    type: 'heartbeat';
    intervalMs: number;
};
/**
 * Emits a transport-only event whenever the source has been idle for an
 * interval. Heartbeats are deliberately not published, persisted, or assigned
 * event IDs, so they do not affect replay and resume semantics.
 */
export declare function withRealtimeHeartbeat<T>(source: AsyncIterable<T>, options: {
    intervalMs?: number;
    signal?: AbortSignal;
}): AsyncGenerator<T | RealtimeHeartbeat, void, void>;
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