Record node toggles in undo history

src/store/modelerStore.test.ts

@@ -130,6 +130,29 @@ describe('Modeler editing scenarios', () => {
       expect(getState().tree!.params.radius).toBe(20); // default
     });
 
+    it('clears a selection that the undone tree no longer contains', () => {
+      getState().addPrimitive('box');
+      const boxId = getState().tree!.id;
+      getState().selectNode(boxId);
+      expect(getState().selectedNodeId).toBe(boxId);
+
+      // Undo back past the box's creation — the selected node is gone.
+      getState().undo();
+      expect(getState().tree).toBeNull();
+      expect(getState().selectedNodeId).toBeNull();
+    });
+
+    it('keeps a selection that survives the undo', () => {
+      getState().addPrimitive('box');
+      const boxId = getState().tree!.id;
+      getState().updateNodeParams(boxId, { radius: 3 });
+      getState().selectNode(boxId);
+
+      getState().undo();
+      expect(getState().tree!.id).toBe(boxId);
+      expect(getState().selectedNodeId).toBe(boxId);
+    });
+
     it('undoes wrap operation', () => {
       getState().addPrimitive('box');
       const boxId = getState().tree!.id;
@@ -236,6 +259,40 @@ describe('Modeler editing scenarios', () => {
       expect(getState().tree!.enabled).toBe(true);
     });
 
+    it('records the toggle in history so undo reverts only the toggle', () => {
+      getState().addPrimitive('box');
+      const id = getState().tree!.id;
+      getState().updateNodeParams(id, { radius: 7 });
+
+      getState().toggleNode(id);
+      expect(getState().tree!.enabled).toBe(false);
+
+      // Undo should restore the enabled box with radius 7 — not discard the
+      // parameter edit along with the toggle.
+      getState().undo();
+      expect(getState().tree!.enabled).toBe(true);
+      expect(getState().tree!.params.radius).toBe(7);
+    });
+
+    it('keeps tree in sync with history[historyIndex] after a toggle', () => {
+      getState().addPrimitive('box');
+      getState().toggleNode(getState().tree!.id);
+
+      const { tree, history, historyIndex } = getState();
+      expect(history[historyIndex]).toEqual(tree);
+    });
+
+    it('redoes a toggle', () => {
+      getState().addPrimitive('box');
+      const id = getState().tree!.id;
+      getState().toggleNode(id);
+      getState().undo();
+      expect(getState().tree!.enabled).toBe(true);
+
+      getState().redo();
+      expect(getState().tree!.enabled).toBe(false);
+    });
+
     it('disabled nodes pass tree validation', () => {
       getState().addPrimitive('box');
       const boxId = getState().tree!.id;

src/store/modelerStore.ts

@@ -76,6 +76,16 @@ function cloneTree(node: SDFNodeUI): SDFNodeUI {
   return JSON.parse(JSON.stringify(node));
 }
 
+/**
+ * The selection to keep after the tree is replaced wholesale. Undo/redo can
+ * restore a tree in which the selected node no longer exists; leaving the id
+ * dangling makes every `findNode` consumer silently no-op.
+ */
+function surviving(tree: SDFNodeUI | null, selectedNodeId: string | null): string | null {
+  if (!tree || !selectedNodeId) return null;
+  return findNode(tree, selectedNodeId) ? selectedNodeId : null;
+}
+
 function findNode(tree: SDFNodeUI, id: string): SDFNodeUI | null {
   if (tree.id === id) return tree;
   for (const child of tree.children) {
@@ -258,10 +268,17 @@ export const useModelerStore = create<ModelerState>()((set, get) => ({
   },
 
   toggleNode: (id) => {
-    const { tree } = get();
+    const state = get();
+    const { tree } = state;
     if (!tree) return;
     const newTree = updateInTree(tree, id, (node) => ({ ...node, enabled: !node.enabled }));
-    set({ tree: newTree });
+    // Disabling a node changes the rendered geometry and the exported mesh, so
+    // this is a document mutation and belongs in history like any other.
+    // Without the push, `tree` and `history[historyIndex]` diverge and a
+    // subsequent undo discards one more edit than the user asked for.
+    const newHistory = state.history.slice(0, state.historyIndex + 1);
+    newHistory.push(cloneTree(newTree));
+    set({ tree: newTree, history: newHistory, historyIndex: newHistory.length - 1 });
   },
 
   toggleExpanded: (id) => {
@@ -683,15 +700,17 @@ export const useModelerStore = create<ModelerState>()((set, get) => ({
     const { historyIndex, history } = get();
     if (historyIndex > 0) {
       const newIndex = historyIndex - 1;
-      set({ tree: history[newIndex] ? cloneTree(history[newIndex]!) : null, historyIndex: newIndex });
+      const restored = history[newIndex] ? cloneTree(history[newIndex]!) : null;
+      set({ tree: restored, historyIndex: newIndex, selectedNodeId: surviving(restored, get().selectedNodeId) });
     }
   },
 
   redo: () => {
     const { historyIndex, history } = get();
     if (historyIndex < history.length - 1) {
       const newIndex = historyIndex + 1;
-      set({ tree: history[newIndex] ? cloneTree(history[newIndex]!) : null, historyIndex: newIndex });
+      const restored = history[newIndex] ? cloneTree(history[newIndex]!) : null;
+      set({ tree: restored, historyIndex: newIndex, selectedNodeId: surviving(restored, get().selectedNodeId) });
     }
   },