/**
 * @module memory/utils
 * @description Utility functions for the memory subsystem.
 */
/**
 * @name truncate
 * @description Truncates a string to the specified byte length, ensuring it
 * doesn't end in the middle of a multi-byte UTF-8 sequence.
 * @param str - The string to truncate.
 * @param maxBytes - Maximum byte length.
 * @returns The truncated string.
 */
export declare function truncate(str: string, maxBytes: number): string;
/**
 * @name decayRelevance
 * @description Computes the decayed relevance score based on days since creation.
 * @param initialScore - Initial relevance score (0-1).
 * @param createdAt - ISO 8601 timestamp of creation.
 * @param decayPerDay - Decay rate per day (e.g. 0.01 = 1% per day).
 * @returns Decayed relevance score, clamped to [0, 1].
 */
export declare function decayRelevance(initialScore: number, createdAt: string, decayPerDay: number): number;
/**
 * @name isExpired
 * @description Checks if a memory record has expired.
 * @param expiresAt - ISO 8601 timestamp or null (null = never expires).
 * @returns True if the memory has expired.
 */
export declare function isExpired(expiresAt: string | null): boolean;
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