diff --git a/viewer/image_viewer/JFJochImage.cpp b/viewer/image_viewer/JFJochImage.cpp
index c266660b..46711144 100644
--- a/viewer/image_viewer/JFJochImage.cpp
+++ b/viewer/image_viewer/JFJochImage.cpp
@@ -43,6 +43,15 @@ JFJochImage::JFJochImage(QWidget *parent) : QGraphicsView(parent) {
 }
 
 void JFJochImage::onScroll(int value) {
+    // While the user drags a pan, the scene scrolls natively and overlay items
+    // (which live in scene coordinates) move with it - no rebuild is needed. A
+    // single pan step emits up to two scrollbar valueChanged signals; rebuilding
+    // the overlay on each would tear down and recreate every item for no visual
+    // change - the dominant lag over remote X. The overlay is refreshed once
+    // when the pan ends (mouseReleaseEvent -> updateROI -> updateOverlay), which
+    // re-runs spot/prediction culling for the newly revealed viewport.
+    if (mouse_event_type == MouseEventType::Panning)
+        return;
     scheduleOverlayUpdate();
 }
 
@@ -221,7 +230,9 @@ void JFJochImage::mouseMoveEvent(QMouseEvent *event) {
             horizontalScrollBar()->setValue(horizontalScrollBar()->value() - viewDelta.x());
             verticalScrollBar()->setValue(verticalScrollBar()->value() - viewDelta.y());
 
-            scheduleOverlayUpdate();
+            // No overlay rebuild while dragging: the scene scrolls natively and
+            // items move with it. onScroll() skips rebuilds during a pan and the
+            // overlay is refreshed once on mouse release.
             emitViewportChanged();
             break;
         }