/**
 * Generic on-disk TTL cache helpers shared by model-limits, model-catalog-cache,
 * and model-benchmarks.
 *
 * Each cache file has the same envelope shape:
 *   { version: 1, fetchedAt: number, ttlMs: number, <payload> }
 *
 * Only the envelope fields and the single payload key/kind differ between caches;
 * those differences are captured by the arguments to validateTtlCacheEnvelope.
 */
/** 24-hour TTL in milliseconds. */
export declare const TTL_24H_MS = 86400000;
/** Base envelope fields shared by all on-disk TTL caches. */
export interface TtlCacheEnvelope {
    version: number;
    fetchedAt: number;
    ttlMs: number;
}
/**
 * Returns true when the cache has exceeded its declared TTL.
 */
export declare function isTtlCacheStale(cache: Pick<TtlCacheEnvelope, 'fetchedAt' | 'ttlMs'>): boolean;
/**
 * Validate the shared TTL cache envelope and one payload field.
 *
 * @param value       Raw parsed JSON value.
 * @param payloadKey  Name of the payload field (e.g. `'models'`, `'entries'`).
 * @param payloadKind Whether the payload should be an `'object'` or `'array'`.
 * @returns `{ cache: T }` on success, or `{ cache: null, reason }` on failure.
 */
export declare function validateTtlCacheEnvelope<T>(value: unknown, payloadKey: string, payloadKind: 'object' | 'array', expectedVersion?: number): {
    cache: T | null;
    reason?: string;
};
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