diff --git a/apps/ai-game-creator-shell/src/features/ui-editor/stateTransition.ts b/apps/ai-game-creator-shell/src/features/ui-editor/stateTransition.ts
index c4338e0ca..a559e74ed 100644
--- a/apps/ai-game-creator-shell/src/features/ui-editor/stateTransition.ts
+++ b/apps/ai-game-creator-shell/src/features/ui-editor/stateTransition.ts
@@ -93,7 +93,8 @@ export function applyUiEditorCommand(
   if (!tree) return { ok: false, reason: 'missing' };
 
   if (command.type === 'set-tree-offset') {
-    if (!command.min.every(Number.isFinite))
+    // 只校验元素有限不够：`[]` 会让 every 空真通过，缺第二个坐标时 max 会算出 NaN。
+    if (command.min.length !== 2 || !command.min.every(Number.isFinite))
       return { ok: false, reason: 'invalid' };
     const size = imageLogicalSize(next, command.treeId);
     if (!size) return { ok: false, reason: 'invalid' };
diff --git a/apps/ai-game-creator-shell/tests/uiEditorState.test.ts b/apps/ai-game-creator-shell/tests/uiEditorState.test.ts
index 7a117eb69..37c8ba33d 100644
--- a/apps/ai-game-creator-shell/tests/uiEditorState.test.ts
+++ b/apps/ai-game-creator-shell/tests/uiEditorState.test.ts
@@ -138,6 +138,23 @@ describe('useUiEditorState', () => {
     }
   });
 
+  it('rejects a tree offset that is not a two-element tuple', () => {
+    const state: State = {
+      ...structuredClone(EMPTY_UI_EDITOR_STATE),
+      ui_design_images: { page: image('Page') },
+      ui_trees: [{ src_ui_design: 'page', root: pageRoot('root') }],
+    };
+    for (const min of [[12], []] as unknown as [number, number][]) {
+      expect(
+        applyUiEditorCommand(state, {
+          type: 'set-tree-offset',
+          treeId: 'page',
+          min,
+        }),
+      ).toEqual({ ok: false, reason: 'invalid' });
+    }
+  });
+
   it('reports persistable state invariant failures before save', () => {
     const state = structuredClone(EMPTY_UI_EDITOR_STATE);
     state.ui_trees = [{ src_ui_design: 'missing', root: pageRoot('root') }];