优化查询代码，优化工具代码

backend/app/agent/service_config.py

@@ -0,0 +1,46 @@
+"""
+Agent Service 配置模块 - 配置构建和解析
+"""
+
+from typing import Dict, Any, Tuple, Optional
+from langchain_core.messages import HumanMessage
+from backend.app.logger import warning
+
+
+class ServiceConfig:
+    """配置构建器"""
+
+    def __init__(self, chat_services: dict):
+        self.chat_services = chat_services
+
+    def resolve_model(self, model: Optional[str]) -> str:
+        """
+        解析并验证模型名称，不可用时回退到第一个可用模型
+        """
+        if not model or model not in self.chat_services:
+            fallback = next(iter(self.chat_services.keys()))
+            warning(f"模型 '{model}' 不可用，回退到 '{fallback}'")
+            return fallback
+        return model
+
+    def build_invocation(
+        self, message: str, thread_id: str, model: str, user_id: str
+    ) -> Tuple[Dict[str, Any], Dict[str, Any]]:
+        """
+        构建图调用所需的 config 和 input_state
+
+        Returns:
+            (config, input_state) 元组
+        """
+        config = {
+            "configurable": {
+                "thread_id": thread_id,
+            },
+            "metadata": {"user_id": user_id}
+        }
+
+        input_state = {
+            "messages": [HumanMessage(content=message)],
+            "user_id": user_id,
+        }
+        return config, input_state