/**
 * AvoStreamId manages an ephemeral stream identifier.
 *
 * The stream ID is generated and stored persistently, but resets after:
 * - 4 hours of total age AND
 * - 2 hours of idle time (no activity)
 *
 * This ensures the ID is truly anonymous by not persisting indefinitely,
 * while still maintaining session continuity during active usage.
 */
export declare class AvoStreamId {
    private static _streamId;
    private static _createdAt;
    private static _lastActivityAt;
    private static readonly MAX_AGE_MS;
    private static readonly IDLE_THRESHOLD_MS;
    private static readonly STREAM_ID_KEY;
    private static readonly CREATED_AT_KEY;
    private static readonly LAST_ACTIVITY_KEY;
    /**
     * Get the stream ID. If it doesn't exist or has expired, generates a new one.
     * Returns "unknown" if storage is not initialized.
     */
    static get streamId(): string;
    /**
     * Check if the stream ID should be reset based on age and idle time.
     */
    private static shouldReset;
    /**
     * Load stream ID and timestamps from storage into cache.
     */
    private static loadFromStorage;
    /**
     * Generate a new stream ID and store it with timestamps.
     */
    private static generateAndStoreNew;
    /**
     * Update the last activity timestamp.
     */
    private static updateLastActivity;
    /**
     * The storage key used to persist the stream ID.
     */
    static get storageKey(): string;
    /**
     * The storage key for created at timestamp.
     */
    static get createdAtKey(): string;
    /**
     * The storage key for last activity timestamp.
     */
    static get lastActivityKey(): string;
    /**
     * Clear the cached stream ID. The next access will reload from storage.
     * This is primarily useful for testing.
     */
    static clearCache(): void;
}