/**
 * A `TaskStore` implementation with post-terminal retention semantics.
 *
 * Unlike the SDK's `InMemoryTaskStore` — which arms a deletion timer at task
 * creation and evicts the record after `ttl` regardless of status — this store
 * treats `ttl` as a *retention window that starts when the task reaches a
 * terminal state*. Consequences:
 *
 * - A non-terminal task (`submitted`/`working`) is immortal: it has no
 *   `expiresAt` and is never evicted, no matter how much time elapses.
 * - Once a task reaches a terminal state (`completed`/`failed`/`cancelled`),
 *   its retention window opens (`expiresAt = now + ttl`). It stays retrievable
 *   until the window elapses, then is evicted lazily on read or by the periodic
 *   `sweepExpired()` sweep.
 *
 * Method contracts and error-message strings mirror `InMemoryTaskStore` so the
 * only behavioral difference is timer semantics.
 *
 * WARNING: builds on the experimental `@modelcontextprotocol/sdk/experimental`
 * Tasks API, which may change without notice.
 */
import type { TaskStore, CreateTaskOptions } from '@modelcontextprotocol/sdk/experimental';
import type { Task, RequestId, Request, Result } from '@modelcontextprotocol/sdk/types.js';
export declare class RetentionTaskStore implements TaskStore {
    private readonly defaultTtl;
    private tasks;
    /**
     * @param defaultTtl Retention window (ms) applied when a task is created
     *   without an explicit `ttl`. `null` means unlimited (no eviction).
     */
    constructor(defaultTtl?: number | null);
    /**
     * Generates a unique task ID (16 random bytes as 32 hex chars), matching
     * `InMemoryTaskStore`.
     */
    private generateTaskId;
    /** True when a stored task's retention window has elapsed. */
    private isExpired;
    /**
     * Evict a task and log a distinct eviction message (never a failure). Logged
     * at `info` so a post-retention `-32602` remains diagnosable under the default
     * `LOG_LEVEL=info` — this is a benign, expected event, not an error.
     */
    private evict;
    /**
     * Look up a live (non-expired) stored task, lazily evicting it if its
     * retention window has elapsed.
     */
    private getLive;
    createTask(taskParams: CreateTaskOptions, requestId: RequestId, request: Request, _sessionId?: string): Promise<Task>;
    getTask(taskId: string, _sessionId?: string): Promise<Task | null>;
    storeTaskResult(taskId: string, status: 'completed' | 'failed', result: Result, _sessionId?: string): Promise<void>;
    getTaskResult(taskId: string, _sessionId?: string): Promise<Result>;
    updateTaskStatus(taskId: string, status: Task['status'], statusMessage?: string, _sessionId?: string): Promise<void>;
    listTasks(cursor?: string, _sessionId?: string): Promise<{
        tasks: Task[];
        nextCursor?: string;
    }>;
    /**
     * Evict every terminal task whose retention window has elapsed. Non-terminal
     * (immortal) tasks are always spared. Returns the number of tasks dropped.
     */
    sweepExpired(): number;
    /** Clear all stored tasks (useful for testing or graceful shutdown). */
    cleanup(): void;
    /** Open a terminal task's retention window from now, if a ttl is configured. */
    private openRetentionWindow;
}
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