diff --git a/weed/s3api/s3api_object_handlers.go b/weed/s3api/s3api_object_handlers.go
index 581bf761b..b0f2bfff8 100644
--- a/weed/s3api/s3api_object_handlers.go
+++ b/weed/s3api/s3api_object_handlers.go
@@ -1000,10 +1000,15 @@ func (s3a *S3ApiServer) streamFromVolumeServers(w http.ResponseWriter, r *http.R
 				entry = cachedEntry
 				glog.V(1).Infof("streamFromVolumeServers: successfully cached remote object, got %d chunks", len(chunks))
 			} else {
-				// Caching failed - return error to client
-				glog.Errorf("streamFromVolumeServers: failed to cache remote object for streaming")
-				s3err.WriteErrorResponse(w, r, s3err.ErrInternalError)
-				return newStreamErrorWithResponse(fmt.Errorf("failed to cache remote object for streaming"))
+				// Client disconnected: report cancellation, not 503.
+				if ctxErr := r.Context().Err(); ctxErr != nil {
+					return ctxErr
+				}
+				// Cache still filling: 503 + Retry-After so SDKs back off and retry.
+				glog.V(1).Infof("streamFromVolumeServers: remote object %s/%s not cached yet, returning 503 for retry", bucket, object)
+				w.Header().Set("Retry-After", "5")
+				s3err.WriteErrorResponse(w, r, s3err.ErrServiceUnavailable)
+				return newStreamErrorWithResponse(fmt.Errorf("remote object not cached yet"))
 			}
 		} else if totalSize > 0 && len(entry.Content) == 0 {
 			// Not a remote entry but has size without content - this is a data integrity issue