优化查询代码，优化工具代码

backend/app/agent/stream_handler.py

@@ -0,0 +1,78 @@
+"""
+流式处理模块 - 处理 Agent 执行的流式输出
+"""
+
+import asyncio
+from typing import AsyncGenerator, Dict, Any
+
+from backend.app.logger import info, error
+from .stream_context import set_stream_queue
+
+
+async def run_graph_stream(
+    graph,
+    input_state: Dict[str, Any],
+    config: Dict[str, Any],
+) -> AsyncGenerator[Dict[str, Any], None]:
+    """
+    运行图并通过队列流式输出事件
+
+    Args:
+        graph: 编译后的 LangGraph
+        input_state: 输入状态
+        config: 配置
+
+    Yields:
+        流式事件
+    """
+    queue: asyncio.Queue = asyncio.Queue()
+    set_stream_queue(queue)
+
+    async def run_graph():
+        """后台任务：运行 graph"""
+        try:
+            info(f"📡 开始调用 graph.astream()...")
+            async for _ in graph.astream(
+                input_state,
+                config=config,
+                stream_mode=["updates"],
+                version="v2",
+                subgraphs=True
+            ):
+                # 流式事件都从 agent.py 节点内部通过队列发送了
+                pass
+        except Exception as e:
+            error(f"❌ 执行图时出错: {e}")
+            import traceback
+            error(f"📋 堆栈: {traceback.format_exc()}")
+            await queue.put({"type": "error", "message": str(e)})
+        finally:
+            await queue.put(None)  # 结束哨兵
+
+    # 启动后台任务
+    bg_task = asyncio.create_task(run_graph())
+
+    try:
+        while True:
+            event = await queue.get()
+            if event is None:
+                break
+            yield event
+
+    except GeneratorExit:
+        info("⚠️ GeneratorExit，取消后台任务")
+        bg_task.cancel()
+        raise
+    finally:
+        await _cleanup_task(bg_task)
+
+
+async def _cleanup_task(bg_task: asyncio.Task) -> None:
+    """清理后台任务"""
+    if not bg_task.done():
+        info("⏹️ 清理后台任务")
+        bg_task.cancel()
+        try:
+            await bg_task
+        except asyncio.CancelledError:
+            info("✅ 后台任务已取消")