export async function buildGgufHeader(originalFileBlob, updatedMetadata, options) {
  // 1. ✅ Use serializeGgufMetadata for metadata
  const newHeaderBytes = serializeGgufMetadata(updatedMetadata, {
    littleEndian: options.littleEndian,
    alignment,
  });

  // 2. ✅ Preserve original tensor info (missing in serializeGgufMetadata)
  const originalTensorInfoBlob = originalFileBlob.slice(tensorInfoStart, tensorInfoEnd);

  // 3. ✅ Calculate proper alignment (missing in serializeGgufMetadata)  
  const prePadLenNew = kvEndOffset + tensorInfoSize;
  const GGML_PAD = (x, n) => (x + n - 1) & ~(n - 1);
  const targetTensorDataOffset = GGML_PAD(prePadLenNew, alignment);
  const padLen = targetTensorDataOffset - prePadLenNew;

  // 4. ✅ Reconstruct complete, valid header
  return new Blob([
    newHeaderBytes.slice(0, kvEndOffset),  // Metadata from serializeGgufMetadata
    originalTensorInfoBlob,                // Preserved tensor info
    new Uint8Array(padLen)                 // Correct alignment padding
  ]);
}