diff --git a/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.test.ts b/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.test.ts
index 4cdad8ba0..2f551ea9c 100644
--- a/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.test.ts
+++ b/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.test.ts
@@ -577,6 +577,48 @@ describe('3D 生成面板的参数变更', () => {
     ).not.toBe(failedDialog.model3dAttemptNonce);
   });
 
+  it('分件与四边面 / 智能减面互斥：后打开的赢，先打开的自动关掉', () => {
+    const geometryDialog = createDialog({
+      model3dTier: 'geometry-only',
+      model3dGenerateParts: true,
+    });
+
+    const quad = applyModel3dSwitchChange(geometryDialog, {
+      model3dQuad: true,
+    });
+    expect(quad).toMatchObject({
+      model3dQuad: true,
+      model3dGenerateParts: false,
+    });
+
+    const smartLowPoly = applyModel3dSwitchChange(
+      { ...geometryDialog, model3dGenerateParts: false },
+      { model3dSmartLowPoly: true },
+    );
+    expect(smartLowPoly.model3dQuad).toBe(false);
+
+    const parts = applyModel3dSwitchChange(
+      { ...geometryDialog, model3dQuad: true, model3dSmartLowPoly: true },
+      { model3dGenerateParts: true },
+    );
+    expect(parts).toMatchObject({
+      model3dGenerateParts: true,
+      model3dQuad: false,
+      model3dSmartLowPoly: false,
+    });
+  });
+
+  it('只关掉一个开关时不动其它开关', () => {
+    const dialog = createDialog({
+      model3dTier: 'geometry-only',
+      model3dQuad: true,
+    });
+
+    expect(
+      applyModel3dSwitchChange(dialog, { model3dGenerateParts: false }),
+    ).toMatchObject({ model3dQuad: true, model3dGenerateParts: false });
+  });
+
   it('删掉参考图回到空槽位并清掉失败态', () => {
     const dialog = createDialog({
       mode: 'model3d-image-to-model',
diff --git a/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.ts b/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.ts
index df6daaf44..16bd7d847 100644
--- a/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.ts
+++ b/src/components/image-editor/model3d-generation/Model3dGenerationFormModel.ts
@@ -447,6 +447,13 @@ export function applyModel3dModelChange(
   });
 }
 
+/**
+ * 改开关：换代次、清失败态，并把互斥项一起收干净。
+ *
+ * 「生成部件」与「四边面」/「智能减面」不能同时打开（提交前校验会直接拒绝，见
+ * `Model3dGenerationValidation`）。这里让刚刚打开的那个赢、另一个自动关掉：面板上不留
+ * 一个永远提交不了的组合，也不用用户自己去猜该关哪一个（评审 #86）。
+ */
 export function applyModel3dSwitchChange(
   dialog: GenerateDialogState,
   patch: Partial<
@@ -456,7 +463,18 @@ export function applyModel3dSwitchChange(
     >
   >,
 ): GenerateDialogState {
-  return withNewAttemptNonce({ ...resetFailedStatus(dialog), ...patch });
+  const next = { ...resetFailedStatus(dialog), ...patch };
+  if (patch.model3dGenerateParts === true) {
+    return withNewAttemptNonce({
+      ...next,
+      model3dQuad: false,
+      model3dSmartLowPoly: false,
+    });
+  }
+  if (patch.model3dQuad === true || patch.model3dSmartLowPoly === true) {
+    return withNewAttemptNonce({ ...next, model3dGenerateParts: false });
+  }
+  return withNewAttemptNonce(next);
 }
 
 export function applyModel3dPromptChange(