diff --git a/backend/app/agent/agent_service.py b/backend/app/agent/agent_service.py
index 4e15210..e5127b9 100644
--- a/backend/app/agent/agent_service.py
+++ b/backend/app/agent/agent_service.py
@@ -37,6 +37,9 @@ class AIAgentService:
         if rag_tool:
             self.tools.append(rag_tool)
             self.tools_by_name[rag_tool.name] = rag_tool
+            # 关键：设置全局 RAG 工具，供 rag_nodes.py 使用
+            from app.main_graph.nodes.rag_nodes import set_global_rag_tool
+            set_global_rag_tool(rag_tool)
 
         # 2. 构建各模型的 Graph（使用新版 React 模式）
         chat_services = get_all_chat_services()