diff --git a/backend/app/main.py b/backend/app/main.py
index 902022f..09ea0f2 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import logging
+import sys
 import threading
 from contextlib import asynccontextmanager
 from pathlib import Path
@@ -32,6 +33,28 @@ logging.basicConfig(
 )
 logger = logging.getLogger(__name__)
 
+# 追加文件日志: uvicorn (含 --reload 开发模式) 默认只有 StreamHandler, 同步/管道等
+# 运行时日志仅出现在 dev 终端, 关掉或滚屏后即丢失, 排查「同步后日志没落」时无处可查。
+# 落盘到 data/backend.log 与桌面版 (desktop.py:_setup_logging → desktop.log) 行为对齐,
+# 事后可查。桌面版 (frozen) 已由 desktop.py 写 desktop.log, 此处跳过避免重复落盘。
+# RotatingFileHandler 防止长期运行/频繁 reload 导致文件无限增长。
+if not getattr(sys, "frozen", False):
+    try:
+        from logging.handlers import RotatingFileHandler
+
+        _log_path = settings.data_dir / "backend.log"
+        _log_path.parent.mkdir(parents=True, exist_ok=True)
+        _file_handler = RotatingFileHandler(
+            _log_path, maxBytes=10 * 1024 * 1024, backupCount=3,
+            mode="a", encoding="utf-8", errors="replace",
+        )
+        _file_handler.setFormatter(
+            logging.Formatter("%(asctime)s [%(levelname)s] %(name)s: %(message)s")
+        )
+        logging.getLogger().addHandler(_file_handler)
+    except Exception as _e:  # noqa: BLE001
+        logger.warning("文件日志初始化失败, 仅输出到终端: %s", _e)
+
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):