diff --git a/backend/app/services/task_service.py b/backend/app/services/task_service.py
index 8da022c..c47c3a6 100644
--- a/backend/app/services/task_service.py
+++ b/backend/app/services/task_service.py
@@ -792,12 +792,16 @@ async def transfer_task(
     created_tasks: list[Task] = []
 
     for task_name, assignee_id in real_branches:
+        # 🔧 动态推导 task_type：禁止分支任务转交被硬编码为 TRANSFER（否则 is_main 判定误升为主线）
         if is_fission:
             new_parent_task_id = task.id
+            new_task_type = "SPAWN"          # 裂变产生新分支
         elif is_child_task:
             new_parent_task_id = task.parent_task_id
+            new_task_type = task.task_type or "SPAWN"   # 继承父任务的分支血统
         else:
             new_parent_task_id = task.id
+            new_task_type = "TRANSFER"       # 主干常规流转
 
         new_task = Task(
             product_id=task.product_id,
@@ -805,7 +809,7 @@ async def transfer_task(
             task_name=task_name,
             assignee_id=assignee_id,
             status=TASK_STATUS_PENDING,
-            task_type="TRANSFER",
+            task_type=new_task_type,         # ← 使用动态推导的类型
             notify_parent_on_complete=False,
             is_rework=False,
             remark=request.note or None,