diff --git a/backend/app/desktop.py b/backend/app/desktop.py
index 6e9e00f7..a2a4006e 100644
--- a/backend/app/desktop.py
+++ b/backend/app/desktop.py
@@ -300,6 +300,11 @@ def _run_uvmicorn(port: int, ready_event: threading.Event) -> None:
         log_level="info",
         access_log=False,    # 桌面版不需要访问日志
         loop="auto",
+        # log_config=None: uvicorn 默认给 uvicorn.* 挂独立 console handler 且
+        # propagate=False, windowed 模式下 stderr 已被守护替换, lifespan 启动
+        # 失败的 "Application startup failed" 永远到不了 desktop.log (失败页
+        # 承诺的排查入口)。置 None 让 uvicorn 日志走 root 的 FileHandler 落盘。
+        log_config=None,
     )
     server = uvicorn.Server(config)
 
@@ -416,7 +421,13 @@ def main() -> int:
     conflict = _precheck_mining_lock()
     if conflict is not None:
         logger.error("启动预检: %s", conflict.replace("\n", " "))
-        _open_static_window(_failed_html(conflict))
+        try:
+            _open_static_window(_failed_html(conflict))
+        except Exception:
+            # 失败页自身也打不开 (如缺 webview 依赖) 时不能让异常裸穿 main():
+            # console=False 下进程闪退无反馈, 且本路径在 try/finally 之外,
+            # 单实例锁会跳过释放
+            logger.exception("启动失败页窗口打开失败")
         _release_single_instance()
         return 1
 
diff --git a/backend/app/main.py b/backend/app/main.py
index 3488effe..1ef54036 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -57,7 +57,7 @@ from app.extensions.loader import (
 )
 from app.jobs import daily_pipeline
 from app.services.matrix_prewarm_owner import MatrixCachePrewarmOwner
-from app.services.mining_process_lock import MiningProcessLock
+from app.services.mining_process_lock import MiningProcessLock, MiningProcessLockError
 from app.services.quote_service import QuoteService
 from app.tickflow import client as tf_client
 from app.tickflow.policy import detect_capabilities
@@ -493,7 +493,13 @@ async def _application_lifespan(app: FastAPI):
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     mining_process_lock = MiningProcessLock(settings.data_dir)
-    mining_process_lock.acquire()
+    try:
+        mining_process_lock.acquire()
+    except MiningProcessLockError:
+        # uvicorn 吞掉 lifespan 异常只留一行 startup failed; 桌面版失败页指向
+        # data/desktop.log, 先把真因 (含 traceback) 落盘, 不依赖 uvicorn 的日志行为
+        logger.error("挖掘锁被其他后端实例占用, lifespan 启动失败", exc_info=True)
+        raise
     try:
         async with _application_lifespan(app):
             yield
diff --git a/backend/tests/test_desktop_startup.py b/backend/tests/test_desktop_startup.py
index 8ca901aa..1bcb97da 100644
--- a/backend/tests/test_desktop_startup.py
+++ b/backend/tests/test_desktop_startup.py
@@ -12,6 +12,7 @@ import time
 
 import pytest
 
+import app.desktop as desktop
 from app.config import settings
 from app.desktop import (
     _failed_html,
@@ -94,3 +95,32 @@ def test_precheck_mining_lock_detects_conflict(data_dir):
     assert "结束残留的 python" in reason
     holder.release()
     assert _precheck_mining_lock() is None
+
+
+# ---------- main() 预检冲突路径 ----------
+
+def test_main_releases_lock_when_failure_window_crashes(
+    tmp_path, monkeypatch, caplog
+):
+    """预检冲突 + 失败页窗口自身崩溃 (如缺 webview 依赖): 异常不得裸穿 main()。
+
+    该路径在 main() 的 try/finally 之外, 不兜底会导致 console=False 闪退无反馈、
+    .desktop.lock 跳过释放。断言: 记录异常日志、单实例锁仍释放、退出码 1。
+    """
+    monkeypatch.setattr(settings, "data_dir", tmp_path, raising=False)
+    monkeypatch.setattr(desktop, "_guard_streams", lambda: None)
+    monkeypatch.setattr(desktop, "_setup_logging", lambda: None)
+    monkeypatch.setattr(desktop, "_precheck_mining_lock", lambda: "冲突原因")
+
+    def _boom(_html_text):
+        raise RuntimeError("webview unavailable")
+
+    monkeypatch.setattr(desktop, "_open_static_window", _boom)
+
+    import logging
+
+    with caplog.at_level(logging.ERROR, logger="app.desktop"):
+        assert desktop.main() == 1
+
+    assert "启动失败页窗口打开失败" in caplog.text
+    assert not (tmp_path / ".desktop.lock").exists()
diff --git a/backend/tests/test_main_mining_lifespan.py b/backend/tests/test_main_mining_lifespan.py
index 8b6e9e0b..4181649c 100644
--- a/backend/tests/test_main_mining_lifespan.py
+++ b/backend/tests/test_main_mining_lifespan.py
@@ -81,3 +81,36 @@ def test_lifespan_releases_lock_when_application_shutdown_raises(monkeypatch) ->
         asyncio.run(exercise())
 
     assert events == ["acquired", "released"]
+
+
+def test_lifespan_logs_true_cause_when_lock_held(monkeypatch, caplog) -> None:
+    """抢锁失败: 先落 ERROR 日志 (桌面版失败页指向 desktop.log 的排查依据) 再上抛。
+
+    uvicorn 会吞掉 lifespan 异常只留一行笼统的 startup failed, 真因必须由
+    app 自己先写日志, 否则用户按失败页指引打开 desktop.log 查无对证。
+    """
+    from app.services.mining_process_lock import MiningProcessLockError
+
+    class LockStub:
+        def __init__(self, data_dir) -> None:
+            del data_dir
+
+        def acquire(self) -> None:
+            raise MiningProcessLockError("another process owns mining")
+
+        def release(self) -> None:
+            raise AssertionError("acquire 失败后不应调用 release")
+
+    monkeypatch.setattr(main_module, "MiningProcessLock", LockStub)
+
+    async def exercise() -> None:
+        async with main_module.lifespan(SimpleNamespace()):
+            pass
+
+    with (
+        caplog.at_level("ERROR", logger="app.main"),
+        pytest.raises(MiningProcessLockError),
+    ):
+        asyncio.run(exercise())
+
+    assert "挖掘锁" in caplog.text