diff --git a/weed/s3api/filer_multipart.go b/weed/s3api/filer_multipart.go
index 22a061852..dc71a6371 100644
--- a/weed/s3api/filer_multipart.go
+++ b/weed/s3api/filer_multipart.go
@@ -325,6 +325,8 @@ func (s3a *S3ApiServer) completeMultipartUpload(r *http.Request, input *s3.Compl
 			}
 			versionEntry.Extended[s3_constants.ExtVersionIdKey] = []byte(versionId)
 			versionEntry.Extended[s3_constants.SeaweedFSUploadId] = []byte(*input.UploadId)
+			// Store parts count for x-amz-mp-parts-count header
+			versionEntry.Extended[s3_constants.SeaweedFSMultipartPartsCount] = []byte(fmt.Sprintf("%d", len(completedPartNumbers)))
 
 			// Set object owner for versioned multipart objects
 			amzAccountId := r.Header.Get(s3_constants.AmzAccountId)
@@ -387,6 +389,8 @@ func (s3a *S3ApiServer) completeMultipartUpload(r *http.Request, input *s3.Compl
 				entry.Extended = make(map[string][]byte)
 			}
 			entry.Extended[s3_constants.ExtVersionIdKey] = []byte("null")
+			// Store parts count for x-amz-mp-parts-count header
+			entry.Extended[s3_constants.SeaweedFSMultipartPartsCount] = []byte(fmt.Sprintf("%d", len(completedPartNumbers)))
 
 			// Set object owner for suspended versioning multipart objects
 			amzAccountId := r.Header.Get(s3_constants.AmzAccountId)
@@ -440,6 +444,8 @@ func (s3a *S3ApiServer) completeMultipartUpload(r *http.Request, input *s3.Compl
 				entry.Extended = make(map[string][]byte)
 			}
 			entry.Extended[s3_constants.SeaweedFSUploadId] = []byte(*input.UploadId)
+			// Store parts count for x-amz-mp-parts-count header
+			entry.Extended[s3_constants.SeaweedFSMultipartPartsCount] = []byte(fmt.Sprintf("%d", len(completedPartNumbers)))
 
 			// Set object owner for non-versioned multipart objects
 			amzAccountId := r.Header.Get(s3_constants.AmzAccountId)
diff --git a/weed/s3api/s3_constants/header.go b/weed/s3api/s3_constants/header.go
index 77ed310d9..019ac63ed 100644
--- a/weed/s3api/s3_constants/header.go
+++ b/weed/s3api/s3_constants/header.go
@@ -39,10 +39,12 @@ const (
 	AmzObjectTaggingDirective = "X-Amz-Tagging-Directive"
 	AmzTagCount               = "x-amz-tagging-count"
 
-	SeaweedFSIsDirectoryKey = "X-Seaweedfs-Is-Directory-Key"
-	SeaweedFSPartNumber     = "X-Seaweedfs-Part-Number"
-	SeaweedFSUploadId       = "X-Seaweedfs-Upload-Id"
-	SeaweedFSExpiresS3      = "X-Seaweedfs-Expires-S3"
+	SeaweedFSIsDirectoryKey         = "X-Seaweedfs-Is-Directory-Key"
+	SeaweedFSPartNumber             = "X-Seaweedfs-Part-Number"
+	SeaweedFSUploadId               = "X-Seaweedfs-Upload-Id"
+	SeaweedFSMultipartPartsCount    = "X-Seaweedfs-Multipart-Parts-Count"
+	SeaweedFSExpiresS3              = "X-Seaweedfs-Expires-S3"
+	AmzMpPartsCount                 = "x-amz-mp-parts-count"
 
 	// S3 ACL headers
 	AmzCannedAcl      = "X-Amz-Acl"
@@ -70,8 +72,6 @@ const (
 	AmzCopySourceIfModifiedSince   = "X-Amz-Copy-Source-If-Modified-Since"
 	AmzCopySourceIfUnmodifiedSince = "X-Amz-Copy-Source-If-Unmodified-Since"
 
-	AmzMpPartsCount = "X-Amz-Mp-Parts-Count"
-
 	// S3 Server-Side Encryption with Customer-provided Keys (SSE-C)
 	AmzServerSideEncryptionCustomerAlgorithm = "X-Amz-Server-Side-Encryption-Customer-Algorithm"
 	AmzServerSideEncryptionCustomerKey       = "X-Amz-Server-Side-Encryption-Customer-Key"
diff --git a/weed/s3api/s3api_object_handlers.go b/weed/s3api/s3api_object_handlers.go
index 2498f85f2..890e4c088 100644
--- a/weed/s3api/s3api_object_handlers.go
+++ b/weed/s3api/s3api_object_handlers.go
@@ -1091,6 +1091,16 @@ func (s3a *S3ApiServer) HeadObjectHandler(w http.ResponseWriter, r *http.Request
 	totalSize := int64(filer.FileSize(objectEntryForSSE))
 	s3a.setResponseHeaders(w, objectEntryForSSE, totalSize)
 
+	// Check if PartNumber query parameter is present (for multipart objects)
+	partNumberStr := r.URL.Query().Get("partNumber")
+	if partNumberStr != "" && objectEntryForSSE.Extended != nil {
+		// If this is a multipart object, add the parts count header
+		if partsCountStr, exists := objectEntryForSSE.Extended[s3_constants.SeaweedFSMultipartPartsCount]; exists {
+			w.Header().Set(s3_constants.AmzMpPartsCount, string(partsCountStr))
+			glog.V(3).Infof("HeadObject: Set PartsCount=%s for multipart object", string(partsCountStr))
+		}
+	}
+
 	// Detect and handle SSE
 	sseType := s3a.detectPrimarySSEType(objectEntryForSSE)
 	if sseType != "" && sseType != "None" {
diff --git a/weed/s3api/s3api_object_handlers_copy.go b/weed/s3api/s3api_object_handlers_copy.go
index 75165e968..1255571ac 100644
--- a/weed/s3api/s3api_object_handlers_copy.go
+++ b/weed/s3api/s3api_object_handlers_copy.go
@@ -348,9 +348,12 @@ func pathToBucketAndObject(path string) (bucket, object string) {
 		bucket = parts[0]
 		object = "/" + parts[1]
 		return bucket, object
+	} else if len(parts) == 1 && parts[0] != "" {
+		// Only bucket provided, no object
+		return parts[0], ""
 	}
-	// Only bucket provided, no object - this is invalid in copy operations
-	return parts[0], ""
+	// Empty path
+	return "", ""
 }
 
 func pathToBucketObjectAndVersion(path string) (bucket, object, versionId string) {
@@ -393,20 +396,23 @@ func (s3a *S3ApiServer) CopyObjectPartHandler(w http.ResponseWriter, r *http.Req
 	// Copy source path.
 	cpSrcPath := r.Header.Get("X-Amz-Copy-Source")
 	
+	glog.V(2).Infof("CopyObjectPart: Raw copy source header=%q (len=%d)", cpSrcPath, len(cpSrcPath))
+	
 	// Try URL unescaping - AWS SDK sends URL-encoded copy sources
 	unescapedPath, err := url.QueryUnescape(cpSrcPath)
 	if err != nil {
 		// If unescaping fails, log and use original
 		glog.V(2).Infof("CopyObjectPart: Failed to unescape copy source %q: %v, using as-is", cpSrcPath, err)
-	} else {
-		cpSrcPath = unescapedPath
+		unescapedPath = cpSrcPath
 	}
+	cpSrcPath = unescapedPath
 	
-	glog.V(2).Infof("CopyObjectPart: Copy source header=%q, after unescape=%q", r.Header.Get("X-Amz-Copy-Source"), cpSrcPath)
+	glog.V(2).Infof("CopyObjectPart: After unescape=%q (len=%d, bytes=%v)", cpSrcPath, len(cpSrcPath), []byte(cpSrcPath))
 
 	srcBucket, srcObject, srcVersionId := pathToBucketObjectAndVersion(cpSrcPath)
 	
-	glog.V(2).Infof("CopyObjectPart: Parsed srcBucket=%q, srcObject=%q, srcVersionId=%q", srcBucket, srcObject, srcVersionId)
+	glog.V(2).Infof("CopyObjectPart: Parsed srcBucket=%q (len=%d), srcObject=%q (len=%d), srcVersionId=%q", 
+		srcBucket, len(srcBucket), srcObject, len(srcObject), srcVersionId)
 	
 	// If source object is empty or bucket is empty, reply back invalid copy source.
 	// Note: srcObject can be "/" for root-level objects, but empty string means parsing failed