import type { Heartbeat } from "./types.js";
export interface HeartbeatSchedulerDeps {
    intervalMs?: number;
    /** Test override. */
    now?: () => number;
    /** Test override; defaults to the durable session outbox. */
    deliver?: (heartbeat: Heartbeat, fireCount: number) => void;
    /** Test override; defaults to the session registry. */
    ownerExists?: (sessionId: string) => boolean;
}
/**
 * One sweep: deliver every heartbeat whose deadline has passed, then reschedule
 * or disarm it. Returns the number delivered. Exported for tests.
 */
export declare function sweepOnce(deps?: HeartbeatSchedulerDeps): number;
/** Start the periodic sweep. Returns a stop function. */
export declare function startHeartbeatScheduler(deps?: HeartbeatSchedulerDeps): () => void;
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