diff --git a/crates/oa-desktop/src/app.rs b/crates/oa-desktop/src/app.rs
index a228b69a..e12ccd37 100644
--- a/crates/oa-desktop/src/app.rs
+++ b/crates/oa-desktop/src/app.rs
@@ -1278,6 +1278,11 @@ impl App {
         {
             return Task::none();
         }
+        // A validated preview measurement only retains display state. Do not
+        // turn each wheel report into source interaction or scan shared boundaries.
+        if let Message::SourceRename(event @ source_rename::Event::PreviewScrolled(..)) = message {
+            return self.source_rename_event(event);
+        }
         let usage_viewport = self.diagram_reveal_viewport(&message);
         let window_resized = matches!(&message, Message::WindowResized(_));
         // Reject stale measurements before legacy viewport handlers can change
diff --git a/crates/oa-desktop/src/app/source_rename/preview_scroll_tests.rs b/crates/oa-desktop/src/app/source_rename/preview_scroll_tests.rs
index 0d03c317..98387022 100644
--- a/crates/oa-desktop/src/app/source_rename/preview_scroll_tests.rs
+++ b/crates/oa-desktop/src/app/source_rename/preview_scroll_tests.rs
@@ -444,10 +444,17 @@ async fn details_remount_restores_wheel_offset_before_any_rescroll() {
             offset > 10.,
             "real wheel input must move the overflowing fixture"
         );
+        let interaction = app.source_symbols.interaction;
+        let camera = app.camera_boundary();
+        let allocation = app.allocation_boundary();
         for message in reports.iter().cloned() {
             let task = app.update(message);
             assert_eq!(mounted.execute(&app, task).await, 0);
         }
+        assert_eq!(app.source_symbols.interaction, interaction);
+        assert!(app.camera_boundary() == camera);
+        assert!(app.allocation_boundary() == allocation);
+        assert_eq!(evidence(&app), before);
         assert_eq!(
             app.source_rename.form.as_ref().unwrap().preview_offset,
             offset