diff --git a/src/chongming/app/__init__.py b/src/chongming/app/__init__.py
index 21a877e..f7201a4 100644
--- a/src/chongming/app/__init__.py
+++ b/src/chongming/app/__init__.py
@@ -19,6 +19,7 @@ from fastapi.middleware.gzip import GZipMiddleware
 from fastapi.middleware.cors import CORSMiddleware
 
 from chongming_config import get_config
+from starlette.types import ASGIApp, Message, Receive, Scope, Send
 from .core.logger import get_logger
 from sqlite_vfs.contrib.fastapi_static import SVFSStaticFiles
 from .core import lifespan_setup, call_stats
@@ -198,41 +199,67 @@ def _should_log_access(status_code: int, sample_rate: float = ACCESS_SAMPLE_RATE
     return next(_access_log_counter) % denom == 0
 
 
-@app.middleware("http")
-async def access_log_middleware(request: Request, call_next):
+def _log_access(scope: Scope, status_code: int, start: float) -> None:
+    """按采样规则写一条访问日志（成功按 access_sample_rate，错误 >=400 全量）"""
+    if not _should_log_access(status_code):
+        return
+    client = scope.get("client")
+    logger.info(
+        "%s %s status=%s duration=%.2fms client=%s",
+        scope.get("method", "-"), scope.get("path", "-"), status_code,
+        (time.perf_counter() - start) * 1000, client[0] if client else "-",
+        extra={"status_code": status_code},
+    )
+
+
+class AccessLogMiddleware:
     """
-    HTTP访问日志中间件，记录每个请求的详细信息。
+    HTTP访问日志中间件（纯 ASGI 实现），记录每个请求的详细信息。
 
     记录的信息包括：
     - 请求方法和路径
     - 响应状态码
-    - 请求处理时长（毫秒）
+    - 请求处理时长（毫秒，按慢路径：从进入中间件到响应头产出）
     - 客户端IP地址
 
     高吞吐优化：
     - 采样：成功请求按 access_sample_rate 记录，错误（>=400）全量
     - 异步：% 参数化消息 + 队列日志（QueueHandler），格式化与文件 I/O
       在后台监听线程执行，主线程仅入队
-
-    参数:
-        request: FastAPI请求对象
-        call_next: 下一个中间件或路由处理函数
-
-    返回:
-        Response: 处理后的响应对象
+    - 不用 BaseHTTPMiddleware（@app.middleware("http")）：它会为每请求建 anyio
+      task group 并把响应体经内存流过一手，压测实测高并发下吃掉 30~50% 吞吐；
+      这里只包一层 send 截获 response.start，无缓冲、无额外任务
     """
-    start = time.perf_counter()
-    response = await call_next(request)
-    duration = (time.perf_counter() - start) * 1000
-    client = request.client.host if request.client else "-"
 
-    if _should_log_access(response.status_code):
-        logger.info(
-            "%s %s status=%s duration=%.2fms client=%s",
-            request.method, request.url.path, response.status_code, duration, client,
-            extra={"status_code": response.status_code},
-        )
-    return response
+    def __init__(self, app: ASGIApp) -> None:
+        self.app = app
+
+    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
+        if scope["type"] != "http":
+            await self.app(scope, receive, send)
+            return
+
+        start = time.perf_counter()
+        logged = False
+
+        async def send_wrapper(message: Message) -> None:
+            nonlocal logged
+            # 响应头产出即记录（流式响应因此只计到首字节，不计整段流）
+            if message["type"] == "http.response.start" and not logged:
+                logged = True
+                _log_access(scope, message["status"], start)
+            await send(message)
+
+        try:
+            await self.app(scope, receive, send_wrapper)
+        except Exception:
+            # 未产出响应就异常（外层 500）：补一条全量错误日志后原样抛出
+            if not logged:
+                _log_access(scope, 500, start)
+            raise
+
+
+app.add_middleware(AccessLogMiddleware)
 
 
 @app.get("/", summary="根路径")