export interface ChunkFrame {
    id: string;
    index: number;
    total: number;
    data: string;
}
/**
 * Accumulates chunk frames and returns the reassembled serialised string once
 * all chunks have arrived. Returns null if more chunks are still expected, or
 * if the frame is rejected due to validation failure.
 */
export declare function reassemble(frame: ChunkFrame): string | null;
