/**
 * Save MLS group state to a per-group file.
 * State is an opaque serialized string from MLSGroupManager.exportState().
 */
export declare function saveMlsState(dataDir: string, groupId: string, state: string): Promise<void>;
/**
 * Load MLS group state from a per-group file.
 * Returns null if the file doesn't exist (first join or after re-join cleanup).
 */
export declare function loadMlsState(dataDir: string, groupId: string): Promise<string | null>;
/**
 * Delete MLS group state file.
 * Used when re-joining a group (old state is invalid after re-join).
 */
export declare function deleteMlsState(dataDir: string, groupId: string): Promise<void>;
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