diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index ec7c9f7e7..7d4de3440 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -950,7 +950,13 @@ impl Session {
             return Vec::new();
         }
         let Some(old) = self.develop_of(id) else { return Vec::new() };
-        let Some(mut delta) = json_delta(&old.to_json(), &new.to_json()) else { return Vec::new() };
+        let mut old_json = old.to_json();
+        let mut new_json = new.to_json();
+        // False is omitted from stored profile JSON. Keep it explicit for this comparison so
+        // switching camera local tone mapping off is a change without copying untouched values.
+        old_json["profile"]["camera_local_tone"] = Value::Bool(old.profile.camera_local_tone);
+        new_json["profile"]["camera_local_tone"] = Value::Bool(new.profile.camera_local_tone);
+        let Some(mut delta) = json_delta(&old_json, &new_json) else { return Vec::new() };
         if let Some(o) = delta.as_object_mut() {
             for k in ["spots", "red_eye", "version", "process"] {
                 o.remove(k);
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 400135ce0..8fc80f501 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -917,6 +917,101 @@ fn auto_sync_carries_only_the_changed_settings() {
     assert_eq!(s.develop_of(PhotoId(ids[1])).unwrap().light.exposure, 0.7);
 }
 
+#[test]
+fn auto_sync_camera_local_tone_off_preserves_other_settings() {
+    use lightcraft_catalog::PhotoId;
+    let mut s = demo();
+    let ids: Vec<u64> = s.catalog.photos().take(3).map(|p| p.id.0).collect();
+    for (id, (profile, amount, contrast)) in ids.iter().zip([("lc.color", 100, 0), ("lc.vivid", 37, 25), ("lc.mono", 63, -20)]) {
+        s.execute("library.select", &json!({"ids": [id]})).unwrap();
+        let settings = json!({"profile": {"id": profile, "amount": amount}, "light": {"contrast": contrast}});
+        s.execute("develop.merge", &json!({"settings": settings})).unwrap();
+    }
+    let initial: Vec<_> = ids.iter().map(|id| (*s.develop_of(PhotoId(*id)).unwrap()).clone()).collect();
+    assert!(initial.iter().all(|d| !d.profile.camera_local_tone));
+    s.execute("library.select", &json!({"ids": [ids[0], ids[1]], "active": ids[0]})).unwrap();
+    s.execute("develop.autoSync", &json!({"on": true})).unwrap();
+    let on = json!({"settings": {"profile": {"camera_local_tone": true}}, "label": "Camera Local Tone Mapping"});
+    let off = json!({"settings": {"profile": {"camera_local_tone": false}}, "label": "Camera Local Tone Mapping"});
+
+    // Positive control: On reaches both selected photos, changing only this setting.
+    s.execute("develop.merge", &on).unwrap();
+    let mut synced = initial.clone();
+    for d in synced.iter_mut().take(2) {
+        d.profile.camera_local_tone = true;
+    }
+    for (id, expected) in ids.iter().zip(&synced) {
+        assert_eq!(s.develop_of(PhotoId(*id)).unwrap().as_ref(), expected, "On: photo {id}");
+    }
+
+    let undo_before = s.undo.len();
+    let history_before: Vec<_> = ids.iter().map(|id| s.catalog.photo(PhotoId(*id)).unwrap().history.len()).collect();
+    s.execute("develop.merge", &off).unwrap();
+    assert!(!s.develop_of(PhotoId(ids[0])).unwrap().profile.camera_local_tone);
+    assert!(!s.develop_of(PhotoId(ids[1])).unwrap().profile.camera_local_tone, "Auto Sync must carry camera local tone Off");
+    assert_eq!(s.undo.len(), undo_before + 1, "Off is one undoable edit");
+    for (i, (id, expected)) in ids.iter().zip(&initial).enumerate() {
+        let photo = s.catalog.photo(PhotoId(*id)).unwrap();
+        assert_eq!(photo.develop.as_ref(), expected, "Off: photo {id}");
+        assert_eq!(photo.history.len(), history_before[i] + usize::from(i < 2), "Off history: photo {id}");
+        let stored = photo.develop.to_json();
+        assert!(stored["profile"].get("camera_local_tone").is_none(), "false stays omitted: photo {id}");
+        assert_eq!(&lightcraft_develop::DevelopSettings::from_json(&stored).unwrap(), expected);
+    }
+
+    // One Undo/Redo restores the complete settings of both selected photos, not the third.
+    s.execute("edit.undo", &json!({})).unwrap();
+    for (id, expected) in ids.iter().zip(&synced) {
+        assert_eq!(s.develop_of(PhotoId(*id)).unwrap().as_ref(), expected, "Undo: photo {id}");
+    }
+    s.execute("edit.redo", &json!({})).unwrap();
+    for (id, expected) in ids.iter().zip(&initial) {
+        assert_eq!(s.develop_of(PhotoId(*id)).unwrap().as_ref(), expected, "Redo: photo {id}");
+    }
+}
+
+#[test]
+fn auto_sync_camera_local_tone_changes_only_when_edited() {
+    use lightcraft_catalog::PhotoId;
+    let mut s = demo();
+    let ids: Vec<u64> = s.catalog.photos().take(3).map(|p| p.id.0).collect();
+    s.execute("library.select", &json!({"ids": [ids[1]]})).unwrap();
+    let settings = json!({"profile": {"id": "lc.vivid", "amount": 37, "camera_local_tone": true}, "light": {"contrast": 25}});
+    s.execute("develop.merge", &json!({"settings": settings})).unwrap();
+    let mut expected: Vec<_> = ids.iter().map(|id| (*s.develop_of(PhotoId(*id)).unwrap()).clone()).collect();
+    assert!(!expected[0].profile.camera_local_tone);
+    assert!(expected[1].profile.camera_local_tone);
+    s.execute("library.select", &json!({"ids": [ids[0], ids[1]], "active": ids[0]})).unwrap();
+    s.execute("develop.autoSync", &json!({"on": true})).unwrap();
+
+    // An unrelated edit must not copy the active photo's unchanged false over the peer's true.
+    s.execute("develop.set", &json!({"control": "light.exposure", "value": 0.7})).unwrap();
+    for d in expected.iter_mut().take(2) {
+        d.light.exposure = 0.7;
+    }
+    for (id, settings) in ids.iter().zip(&expected) {
+        assert_eq!(s.develop_of(PhotoId(*id)).unwrap().as_ref(), settings, "Unrelated edit: photo {id}");
+    }
+
+    let peer_history = s.catalog.photo(PhotoId(ids[1])).unwrap().history.len();
+    s.execute("develop.merge", &json!({"settings": {"profile": {"camera_local_tone": false}}})).unwrap();
+    assert_eq!(s.catalog.photo(PhotoId(ids[1])).unwrap().history.len(), peer_history, "unchanged toggle adds no peer history");
+    for (id, settings) in ids.iter().zip(&expected) {
+        assert_eq!(s.develop_of(PhotoId(*id)).unwrap().as_ref(), settings, "Unchanged toggle: photo {id}");
+    }
+
+    // Direct unchanged edits may still add an active undo step. With Auto Sync off, real
+    // Boolean changes affect only the active photo; selected and unselected peers stay exact.
+    s.execute("develop.autoSync", &json!({"on": false})).unwrap();
+    for on in [true, false] {
+        s.execute("develop.merge", &json!({"settings": {"profile": {"camera_local_tone": on}}})).unwrap();
+        expected[0].profile.camera_local_tone = on;
+        for (id, settings) in ids.iter().zip(&expected) {
+            assert_eq!(s.develop_of(PhotoId(*id)).unwrap().as_ref(), settings, "Auto Sync disabled: photo {id}");
+        }
+    }
+}
+
 #[test]
 fn json_delta_keeps_only_changes() {
     let a = json!({"light": {"exposure": 0, "contrast": 5}, "masks": [1], "x": 1});