import { AssistantMode } from './types';
/**
 * Keeps the sandbox alive while the panel is open and a session is live.
 *
 * The sandbox is reaped on TTL expiry, so without this a user reading a long
 * answer loses the environment mid-conversation and the next turn pays a full
 * cold provision. Fires immediately on mount as well as on the interval, because
 * the panel may be reopened onto a session whose TTL is already nearly spent.
 *
 * Best-effort by contract: a failed ping is logged, never surfaced. The user has
 * their answer; the worst case is the reprovision this was avoiding.
 */
export declare function useAssistantHeartbeat(sessionId: string | null, mode: AssistantMode | null, isOpen: boolean): void;
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