diff --git a/backend/app/services/product_service.py b/backend/app/services/product_service.py
index 2098823..6407d2e 100644
--- a/backend/app/services/product_service.py
+++ b/backend/app/services/product_service.py
@@ -15,11 +15,19 @@ from app.schemas.task import TaskSummaryResponse, TaskResponse, TaskRecordRespon
 
 def _task_to_response(task: Task) -> TaskResponse:
     """将 Task ORM 对象递归转为 TaskResponse（含子任务树）"""
+    product_sn = ""
+    product_material = ""
+    try:
+        if task.product:
+            product_sn = task.product.serial_number or ""
+            product_material = (task.product.material_name or task.product.material_id or "")
+    except Exception:
+        pass
     return TaskResponse(
         id=task.id,
         product_id=task.product_id,
-        product_sn=task.product.serial_number if task.product else "",
-        product_material=task.product.material_name or task.product.material_id or "" if task.product else "",
+        product_sn=product_sn,
+        product_material=product_material,
         parent_task_id=task.parent_task_id,
         task_name=task.task_name,
         assignee_id=task.assignee_id,
diff --git a/backend/app/services/task_service.py b/backend/app/services/task_service.py
index d237529..dbf5f13 100644
--- a/backend/app/services/task_service.py
+++ b/backend/app/services/task_service.py
@@ -93,11 +93,19 @@ async def _get_task_with_children_recursive(db: AsyncSession, task_id: uuid.UUID
 
 def _to_response(task: Task) -> TaskResponse:
     """将 Task ORM 对象转为递归 TaskResponse"""
+    product_sn = ""
+    product_material = ""
+    try:
+        if task.product:
+            product_sn = task.product.serial_number or ""
+            product_material = (task.product.material_name or task.product.material_id or "")
+    except Exception:
+        pass
     return TaskResponse(
         id=task.id,
         product_id=task.product_id,
-        product_sn=task.product.serial_number if task.product else "",
-        product_material=task.product.material_name or task.product.material_id or "" if task.product else "",
+        product_sn=product_sn,
+        product_material=product_material,
         parent_task_id=task.parent_task_id,
         task_name=task.task_name,
         assignee_id=task.assignee_id,
@@ -295,11 +303,7 @@ async def spawn_subtask(
     db.add(child)
     await db.flush()
 
-    # 同步产品宏观状态
-    product_result = await db.execute(select(Product).where(Product.id == task.product_id))
-    product = product_result.scalar_one_or_none()
-    if product and data.task_name:
-        product.overall_status = "在库" if "virtual_warehouse" in data.task_name else data.task_name
+    # 协助分支不改变产品宏观状态（只有主分支影响 overall_status）
 
     await _create_task_log(db, child.id, action_type="create", operator_id=operator_id,
         remark=f"协助分支（由「{task.task_name}」派发，分配给 {data.assignee_id}）")