fix: telemetry single persistent connection + lock (kill concurrent write lock)

tests/unit/test_telemetry.py

@@ -146,3 +146,50 @@ async def test_concurrent_writes_no_lock_error(recorder, db_path):
     count = conn.execute("SELECT COUNT(*) FROM llm_calls").fetchone()[0]
     conn.close()
     assert count == 16
+
+
+def test_high_concurrency_writes_zero_loss(recorder, db_path):
+    """64 路线程并发直压 _write 应零丢失——复现生产 concurrency 下 database is locked 丢失。
+
+    直接压同步 _write（不经 to_thread 排队），最大化并发连接数以逼出锁竞争；
+    单连接 + threading.Lock 串行化模式下应全部落库、零丢失（对齐 HarnessLog）。
+    """
+    import concurrent.futures
+
+    n = 64
+    kwargs_list = [_make_call_kwargs() for _ in range(n)]
+    with concurrent.futures.ThreadPoolExecutor(max_workers=n) as executor:
+        list(executor.map(lambda kw: recorder._write(**kw), kwargs_list))
+
+    conn = sqlite3.connect(str(db_path))
+    count = conn.execute("SELECT COUNT(*) FROM llm_calls").fetchone()[0]
+    conn.close()
+    assert count == n, f"并发写丢失 {n - count} 条（database is locked 降级丢弃）: 落库 {count}/{n}"
+
+
+def test_uses_single_persistent_connection(db_path, monkeypatch):
+    """对齐 HarnessLog：单持久连接（构造时建一次），写入复用而非每次新建。
+
+    每次写新建连接是并发锁竞争根源（多连接争 SQLite 写锁，撑爆 busy_timeout）；
+    单连接 + 进程内 Lock 串行化把并发控制拉到进程内，消除 SQLite 层锁竞争。
+    """
+    connect_calls = {"n": 0}
+    real_connect = sqlite3.connect
+
+    def _counting_connect(*args, **kwargs):
+        connect_calls["n"] += 1
+        return real_connect(*args, **kwargs)
+
+    monkeypatch.setattr(sqlite3, "connect", _counting_connect)
+
+    recorder = SQLiteTelemetryRecorder(db_path=db_path)
+    after_init = connect_calls["n"]
+    for _ in range(10):
+        recorder._write(**_make_call_kwargs())
+    after_writes = connect_calls["n"]
+
+    assert after_init >= 1, "构造时应建立持久连接（对齐 HarnessLog）"
+    assert after_writes == after_init, (
+        f"写入期间新建了 {after_writes - after_init} 个连接（应复用单持久连接，"
+        "每次新连接是并发锁竞争根源）"
+    )