fix(harness): change _runs INSERT OR IGNORE to ON CONFLICT DO UPDATE for incremental infer

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/test_harness_log.py

@@ -8,6 +8,7 @@ from __future__ import annotations
 
 import sqlite3
 import threading
+import time
 from typing import TYPE_CHECKING
 
 import pytest
@@ -118,8 +119,8 @@ class TestHarnessLog:
 
         assert row["status"] == "failed"
 
-    def test_insert_or_ignore_idempotent(self, db_path: str, run_id: str) -> None:
-        """同一 run_id 多次创建 HarnessLog 不报错（INSERT OR IGNORE 幂等）。"""
+    def test_upsert_idempotent(self, db_path: str, run_id: str) -> None:
+        """同一 run_id 多次创建 HarnessLog 不报错（ON CONFLICT DO UPDATE 幂等）。"""
         with HarnessLog(db_path, run_id):
             pass
 
@@ -134,7 +135,7 @@ class TestHarnessLog:
         ).fetchone()[0]
         conn.close()
 
-        assert count == 1, "INSERT OR IGNORE 应保证 _runs 只有一行"
+        assert count == 1, "ON CONFLICT DO UPDATE 应保证 _runs 只有一行"
 
     def test_wal_mode(self, db_path: str, run_id: str) -> None:
         """连接初始化后 journal_mode 应为 WAL。"""
@@ -195,6 +196,34 @@ class TestHarnessLog:
         assert rows[0]["val"] == "2"
 
 
+# ===========================================================================
+# HarnessLog upsert 行为测试
+# ===========================================================================
+
+
+class TestHarnessLogUpsert:
+    """_runs 表 upsert 行为。"""
+
+    def test_same_run_id_updates_started_at(self, tmp_path: Path) -> None:
+        """同 run_id 第二次创建 HarnessLog 应更新 started_at。"""
+        db = str(tmp_path / "test.db")
+        with HarnessLog(db, "run_1", git_sha="abc") as log1:
+            rows = log1.query("SELECT started_at FROM _runs WHERE run_id='run_1'")
+            first_time = rows[0]["started_at"]
+
+        time.sleep(0.05)
+
+        with HarnessLog(db, "run_1", git_sha="abc") as log2:
+            rows = log2.query("SELECT started_at FROM _runs WHERE run_id='run_1'")
+            second_time = rows[0]["started_at"]
+
+        assert second_time > first_time
+
+        with HarnessLog(db, "run_1") as log3:
+            rows = log3.query("SELECT COUNT(*) as cnt FROM _runs WHERE run_id='run_1'")
+            assert rows[0]["cnt"] == 1
+
+
 # ===========================================================================
 # RunLogImpl 测试
 # ===========================================================================