export interface TurnHeartbeat {
    /** Throttled beat driven by the engine stream. Safe to call per delta. */
    beat(): void;
    stop(): void;
}
/**
 * Keep `lastActivity` fresh while a turn is in flight, so the status reconciler
 * can tell a live turn from a gateway that died mid-turn. Self-disarms when the
 * session is deleted: `engine.run` may not resolve for minutes, and we must not
 * keep writing `running` rows for a session the user already removed.
 *
 * The same beat renews the lease on the Todo this session is working, so the
 * claim an agent holds stays alive on the evidence that it is still working
 * rather than on the agent remembering to say so.
 */
export declare function armTurnHeartbeat(sessionId: string, attemptToken: string): TurnHeartbeat;
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