diff --git a/backend/app/services/task_service.py b/backend/app/services/task_service.py
index 962cdcb..34947da 100644
--- a/backend/app/services/task_service.py
+++ b/backend/app/services/task_service.py
@@ -872,12 +872,6 @@ async def complete_task(
     """
     task = await _get_task_or_404(db, task_id)
 
-    # 注入子任务数据到当前对象以便后续检查
-    children_result = await db.execute(
-        select(Task).where(Task.parent_task_id == task_id)
-    )
-    task.child_tasks = children_result.scalars().all()
-
     # --- 1. 幂等检查 ---
     if task.status == TASK_STATUS_COMPLETED:
         raise HTTPException(
@@ -914,6 +908,7 @@ async def complete_task(
             task_name=request.next_task_name,
             assignee_id=request.next_assignee_id,
             status=TASK_STATUS_PENDING,
+            task_type=task.task_type,  # 🚀 继承父任务基因：主线→主线，协助→协助
             notify_parent_on_complete=False,
         )
         db.add(next_task)