/**
 * Per-ID ordered message relay queue.
 * Guarantees messages for the same ID are processed sequentially,
 * preventing out-of-order delivery caused by async encryption/compression.
 */
export declare class MessageRelay {
    private queues;
    /**
     * Enqueue a message handler for the given ID.
     * Handlers for the same ID execute in order; different IDs run concurrently.
     */
    enqueue(id: string, handler: () => Promise<void>): void;
    /**
     * Remove the queue for the given ID (call on disconnect).
     */
    cleanup(id: string): void;
}