export type SyncedStateClient = {
    getState(key: string): Promise<unknown>;
    setState(value: unknown, key: string): Promise<void>;
    subscribe(key: string, handler: (value: unknown) => void): Promise<void>;
    unsubscribe(key: string, handler: (value: unknown) => void): Promise<void>;
};
/**
 * Returns a cached client for the provided endpoint, creating it when necessary.
 * The client is wrapped to track subscriptions for cleanup on page reload.
 * @param endpoint Endpoint to connect to.
 * @returns RPC client instance.
 */
export declare const getSyncedStateClient: (endpoint?: string) => SyncedStateClient;
/**
 * Initializes and caches an RPC client instance for the sync state endpoint.
 * The client is wrapped to track subscriptions for cleanup on page reload.
 * @param options Optional endpoint override.
 * @returns Cached client instance or `null` when running without `window`.
 */
export declare const initSyncedStateClient: (options?: {
    endpoint?: string;
}) => SyncedStateClient | null;
/**
 * Injects a client instance for tests and updates the cached endpoint.
 * Also clears the subscription registry for test isolation.
 * @param client Stub client instance or `null` to clear the cache.
 * @param endpoint Endpoint associated with the injected client.
 */
export declare const setSyncedStateClientForTesting: (client: SyncedStateClient | null, endpoint?: string) => void;