diff --git a/sanguo_portfolio/providers/local_unified_provider.py b/sanguo_portfolio/providers/local_unified_provider.py
index caf22dd..eb0a9e2 100644
--- a/sanguo_portfolio/providers/local_unified_provider.py
+++ b/sanguo_portfolio/providers/local_unified_provider.py
@@ -15,6 +15,7 @@ import logging
 import os
 import re
 import sqlite3
+import threading
 from concurrent.futures import ThreadPoolExecutor
 from datetime import datetime
 from typing import Any, Dict, List, Optional, Union
@@ -161,16 +162,20 @@ class LocalUnifiedProvider(DataProvider):  # type: ignore[misc]
         cfg = config or {}
         self.db_path: str = cfg.get("db_path", _DEFAULT_DB)
         self.data_dir: str = cfg.get("data_dir", _DEFAULT_DATA_DIR)
-        self._conn: Optional[sqlite3.Connection] = None
+        # thread-local:引擎跨日存活后回调线程会变(2026-09-01 live_19 事故),
+        # 单例连接跨线程复用直接 ProgrammingError;每线程各持一条连接
+        self._tls = threading.local()
         self._val_bs_cache: Dict[int, pd.DataFrame] = {}  # year -> valuation_baostock
         self._lpp_helper: Any = None
 
     def _connect(self) -> sqlite3.Connection:
-        """惰性连接 dbbardata sqlite(单连接复用)。"""
-        if self._conn is None:
-            self._conn = sqlite3.connect(self.db_path, timeout=30)
-            self._conn.execute("PRAGMA busy_timeout = 30000")
-        return self._conn
+        """惰性连接 dbbardata sqlite(thread-local 连接复用)。"""
+        conn = getattr(self._tls, "conn", None)
+        if conn is None:
+            conn = sqlite3.connect(self.db_path, timeout=30)
+            conn.execute("PRAGMA busy_timeout = 30000")
+            self._tls.conn = conn
+        return conn
 
     @staticmethod
     def _to_date_str(value: Optional[Union[str, datetime]]) -> Optional[str]:
diff --git a/tests/portfolio/test_local_unified_provider.py b/tests/portfolio/test_local_unified_provider.py
index 25edbab..70f5d91 100644
--- a/tests/portfolio/test_local_unified_provider.py
+++ b/tests/portfolio/test_local_unified_provider.py
@@ -12,6 +12,7 @@ Mac 本地 TDD: sqlite tmp_path + tmp parquet fixture,零 VPS 依赖,零网络
 from __future__ import annotations
 
 import sqlite3
+import threading
 from typing import Any, Dict, List
 
 import pandas as pd
@@ -863,3 +864,45 @@ class TestMixedDatetimeFormat:
         p = LocalUnifiedProvider({"db_path": str(db), "data_dir": str(tmp_path)})
         df = p.get_price("600519.XSHG", start_date="2024-09-25", end_date="2024-09-27", fq="raw")
         assert len(df) == 3  # 不崩 + 返 3 行(混合格式解析 OK)
+
+
+# ======================== Task N: _connect thread-local ========================
+class TestConnectThreadLocal:
+    """2026-09-01 live_19 事故:引擎首次跨日存活后回调线程变化(连接建于线程A、
+    用在线程B),单例 sqlite 连接跨线程复用直接 ProgrammingError → 牛熊分界
+    不可用跳过调仓。_connect 改 thread-local 后每线程自建连接,互不共享。"""
+
+    def test_connect_cross_thread_usable(self, tmp_path):
+        db = _make_security_info_fixture(tmp_path)
+        p = LocalUnifiedProvider({"db_path": str(db), "data_dir": str(tmp_path)})
+        conn_main = p._connect()  # 主线程先建连(旧实现会缓存单例)
+
+        errs: List[Any] = []
+
+        def worker():
+            try:
+                c = p._connect()
+                c.execute("SELECT 1").fetchall()  # 子线程直接用,不得抛错
+            except Exception as exc:  # noqa: BLE001 - 收集给断言看
+                errs.append(exc)
+
+        t = threading.Thread(target=worker)
+        t.start()
+        t.join()
+        assert not errs, f"跨线程取连接报错: {errs}"
+        # 主线程连接仍是原对象(thread-local 各持各的)
+        assert p._connect() is conn_main
+
+    def test_two_threads_get_distinct_connections(self, tmp_path):
+        db = _make_security_info_fixture(tmp_path)
+        p = LocalUnifiedProvider({"db_path": str(db), "data_dir": str(tmp_path)})
+        got: Dict[str, Any] = {}
+
+        def worker():
+            got["conn"] = p._connect()
+
+        t = threading.Thread(target=worker)
+        t.start()
+        t.join()
+        assert got["conn"] is not None
+        assert got["conn"] is not p._connect()  # 不是同一个连接对象