export declare function activeHeartbeatPath(historyDir: string, sessionHash: string): string;
/** Best-effort liveness beat: refreshes the marker's mtime, creating it on
 *  first touch. Failures never block the caller; the remaining sweep guards
 *  (local active set, fail-closed ref deletion) still apply. */
export declare function touchSessionHeartbeat(historyDir: string, sessionHash: string): Promise<void>;
export declare function sessionHeartbeatIsFresh(historyDir: string, sessionHash: string, ttlMs?: number): Promise<boolean>;
/** Removes markers whose owners stopped beating so the history directory
 *  does not accumulate one file per historical session forever. */
export declare function pruneStaleHeartbeats(historyDir: string, ttlMs?: number): Promise<void>;