/**
 * Snapshot of a task's execution state, enabling mid-execution resume.
 * Saved at structured pause points during the task lifecycle.
 */
export interface CheckpointData {
    /** Task ID this checkpoint belongs to */
    task_id: string;
    /** Unique identifier for this checkpoint instance */
    checkpoint_id: string;
    /** Current phase label (e.g., "research", "implementation", "verification") */
    phase: string;
    /** Items that have been successfully completed so far */
    completed_items: string[];
    /** Items remaining to be processed */
    remaining_items: string[];
    /** Optional arbitrary metadata for extensibility */
    metadata?: Record<string, unknown>;
    /** ISO 8601 timestamp when this checkpoint was created */
    created_at: string;
    /** Time-to-live in milliseconds — the checkpoint may be garbage-collected after this duration */
    ttl_ms: number;
}
/**
 * Persistence contract for checkpoint operations.
 * Implementations may use an in-memory Map, SQLite, or any other backend.
 * All methods are async to support persistent backends without API changes.
 */
export interface CheckpointStore {
    /** Persist a checkpoint snapshot for the given task */
    saveCheckpoint(taskId: string, data: CheckpointData): Promise<void>;
    /** Retrieve the most recent checkpoint for a task, or null if none exist */
    getLatestCheckpoint(taskId: string): Promise<CheckpointData | null>;
    /** List all checkpoints for a task, newest first */
    listCheckpoints(taskId: string): Promise<CheckpointData[]>;
    /** Delete all checkpoints for a given task */
    deleteCheckpoint(taskId: string): Promise<void>;
    /** Remove expired checkpoints whose (created_at + ttl_ms) is in the past */
    cleanupExpired(ttlMs: number): Promise<void>;
    /** Build a human-readable retry context string from the latest checkpoint.
     *  Returns null when no checkpoint exists or the task is fully complete. */
    /** Check if at least one checkpoint exists for the given task.
     *  Cheaper than calling getLatestCheckpoint when only existence matters. */
    hasCheckpoint(taskId: string): Promise<boolean>;
}
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