diff --git a/backend/app/backend.py b/backend/app/backend.py
index 69a48ba..ae63204 100644
--- a/backend/app/backend.py
+++ b/backend/app/backend.py
@@ -20,8 +20,16 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import StreamingResponse
 from pydantic import BaseModel
 from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
-from .agent.agent_service import AIAgentService, create_serde
+from .agent.agent_service import AIAgentService
 from .agent.history import ThreadHistoryService
+
+
+def create_serde():
+    """创建序列化器用于 Postgres Checkpointer"""
+    from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
+    return JsonPlusSerializer()
+
+
 from backend.app.core.human_review import (
     ReviewManager,
     InMemoryReviewStore,
diff --git a/backend/app/main_graph/utils/rag_initializer.py b/backend/app/core/rag_initializer.py
similarity index 100%
rename from backend/app/main_graph/utils/rag_initializer.py
rename to backend/app/core/rag_initializer.py
diff --git a/backend/app/main_graph/utils/retry_utils.py b/backend/app/core/retry_utils.py
similarity index 100%
rename from backend/app/main_graph/utils/retry_utils.py
rename to backend/app/core/retry_utils.py
diff --git a/backend/app/main_graph/nodes/_utils.py b/backend/app/deprecated/_utils.py
similarity index 100%
rename from backend/app/main_graph/nodes/_utils.py
rename to backend/app/deprecated/_utils.py
diff --git a/backend/app/main_graph/nodes/error_handling.py b/backend/app/deprecated/error_handling.py
similarity index 100%
rename from backend/app/main_graph/nodes/error_handling.py
rename to backend/app/deprecated/error_handling.py
diff --git a/backend/app/main_graph/nodes/finalize_new.py b/backend/app/deprecated/finalize_new.py
similarity index 100%
rename from backend/app/main_graph/nodes/finalize_new.py
rename to backend/app/deprecated/finalize_new.py
diff --git a/backend/app/main_graph/nodes/llm_call.py b/backend/app/deprecated/llm_call.py
similarity index 100%
rename from backend/app/main_graph/nodes/llm_call.py
rename to backend/app/deprecated/llm_call.py
diff --git a/backend/app/main_graph/tools/__init__.py b/backend/app/deprecated/main_graph_tools/__init__.py
similarity index 100%
rename from backend/app/main_graph/tools/__init__.py
rename to backend/app/deprecated/main_graph_tools/__init__.py
diff --git a/backend/app/main_graph/tools/common_tools.py b/backend/app/deprecated/main_graph_tools/common_tools.py
similarity index 100%
rename from backend/app/main_graph/tools/common_tools.py
rename to backend/app/deprecated/main_graph_tools/common_tools.py
diff --git a/backend/app/main_graph/tools/graph_tools.py b/backend/app/deprecated/main_graph_tools/graph_tools.py
similarity index 100%
rename from backend/app/main_graph/tools/graph_tools.py
rename to backend/app/deprecated/main_graph_tools/graph_tools.py
diff --git a/backend/app/main_graph/tools/subgraph_tools.py b/backend/app/deprecated/main_graph_tools/subgraph_tools.py
similarity index 100%
rename from backend/app/main_graph/tools/subgraph_tools.py
rename to backend/app/deprecated/main_graph_tools/subgraph_tools.py
diff --git a/backend/app/main_graph/nodes/rag_nodes.py b/backend/app/deprecated/rag_nodes.py
similarity index 100%
rename from backend/app/main_graph/nodes/rag_nodes.py
rename to backend/app/deprecated/rag_nodes.py
diff --git a/backend/app/main_graph/nodes/routing.py b/backend/app/deprecated/routing.py
similarity index 100%
rename from backend/app/main_graph/nodes/routing.py
rename to backend/app/deprecated/routing.py
diff --git a/backend/app/main_graph/nodes/tool_call.py b/backend/app/deprecated/tool_call.py
similarity index 100%
rename from backend/app/main_graph/nodes/tool_call.py
rename to backend/app/deprecated/tool_call.py
diff --git a/backend/app/main_graph/nodes/web_search.py b/backend/app/deprecated/web_search.py
similarity index 100%
rename from backend/app/main_graph/nodes/web_search.py
rename to backend/app/deprecated/web_search.py