diff --git a/backend/app/data/catalog_jobs.py b/backend/app/data/catalog_jobs.py
index 48c37056..d63c0313 100644
--- a/backend/app/data/catalog_jobs.py
+++ b/backend/app/data/catalog_jobs.py
@@ -474,7 +474,6 @@ class _JobRun:
         self._started: set[str] = set()
         self.source: Any = None
         self.actor: str | None = None
-        self.at = ""
 
     # ---------------------------------------------------------------- 库写入
 
@@ -553,7 +552,7 @@ class _JobRun:
                 except catalog.CatalogModelUnavailable as e:
                     raise _JobFailed(str(e)) from e
                 existing = {t: e.notes for t, e in (await catalog.read_catalog(session, source.id)).items()}
-        self.source, self.at = source, catalog.now_iso()
+        self.source = source
         all_tables = (getattr(source, "schema_cache", None) or {}).get("tables") or {}
         names = [n for n in pending if isinstance(all_tables.get(n), dict)]
         gone = [n for n in pending if n not in names]
@@ -653,9 +652,12 @@ class _JobRun:
 
     async def _write_part(self, session: AsyncSession, table: str, written: catalog_draft.PartWrite) -> None:
         """宽表写出了一段：马上并入目录（这一次不删任何东西），记下写进去的段数、累加计数。写不进去只记日志：整张表结束
-        时收尾那次还会把它带上。"""
+        时收尾那次还会把它带上。
+
+        新增、更新的项的修改时间是这一次写入的时间（每次写入各取一次）：以前整个任务只在开始时取一次，起草了几十分钟的宽表，
+        每一段写进去的项都记成任务开始那一刻，比任务的开始时间还早。"""
         try:
-            found = await write_part(session, self.source, table, written.notes, at=self.at, actor=self.actor)
+            found = await write_part(session, self.source, table, written.notes, at=catalog.now_iso(), actor=self.actor)
         except Exception:  # noqa: BLE001 - 这一段写不进去不影响起草
             logger.exception("起草任务 %s 把表 %s 写出来的一段并入数据目录时出错", self.job_id, table)
             await session.rollback()
@@ -674,9 +676,10 @@ class _JobRun:
     async def _write_table(self, session: AsyncSession, table: str,
                            outcome: catalog_draft.ModelOutcome | None) -> None:
         """一张表结束：并入目录、写入（宽表写过的段已经并入过，这里是整张表的收尾），记下这张表的结果。计数加在逐段写入
-        的计数上。"""
+        的计数上。修改时间取这一次写入的时间（同 _write_part）：逐段写进去、内容没变的项留着那一段的时间。"""
         try:
-            result = await catalog.write_draft(session, self.source, table, outcome, at=self.at, actor=self.actor)
+            result = await catalog.write_draft(session, self.source, table, outcome, at=catalog.now_iso(),
+                                               actor=self.actor)
         except Exception as e:  # noqa: BLE001 - 这一张写不进去不影响别的表
             from app.core.errors import describe_exception, first_line
 
diff --git a/backend/tests/test_catalog_draft_jobs.py b/backend/tests/test_catalog_draft_jobs.py
index 81840b34..2ce4aef9 100644
--- a/backend/tests/test_catalog_draft_jobs.py
+++ b/backend/tests/test_catalog_draft_jobs.py
@@ -17,7 +17,9 @@
 from __future__ import annotations
 
 import asyncio
+import itertools
 import uuid
+from datetime import datetime, timedelta, timezone
 from types import SimpleNamespace
 from urllib.parse import quote
 
@@ -1052,3 +1054,27 @@ async def test_a_dropped_filter_is_logged_on_the_task_not_failed(client, monkeyp
     assert by["channels"]["log"] == []
     notes = (await client.get(f"{_base(sid)}/gates")).json()["notes"]
     assert "valid_filter" not in notes and notes["label"]["value"] == "闸口"
+
+
+async def test_each_write_of_a_job_stamps_its_own_time(client, monkeypatch):
+    """起草任务写进目录的项，修改时间是那一次写入的时间：宽表逐段落盘的每一段、整张表收尾各取一次当时的时间。以前只在任务
+    开始时取一次（截到秒），整个任务写进去的项都是开始那一刻，比任务的开始时间还早，也看不出哪一段是什么时候写的。
+
+    时钟换成每取一次走一分钟的假时钟；同时只起草一段，各段的先后是定的：表级那段、第 2、3 段逐段落盘，第 4 段由收尾写进去。"""
+    ticks = itertools.count()
+    start = datetime(2026, 10, 14, 3, tzinfo=timezone.utc)
+    monkeypatch.setattr(catalog, "now_iso",
+                        lambda: (start + timedelta(minutes=next(ticks))).isoformat(timespec="seconds"))
+    monkeypatch.setattr(catalog, "MODEL_CONCURRENCY", 1)
+    sid = await _source(_wide())
+    job = await _draft(client, sid, monkeypatch, FakeModel(_wide_reply()), ["wide"])
+    task = job["tasks"][0]
+    assert task["status"] == "ok" and task["parts_written"] == 4
+    notes = (await client.get(f"{_base(sid)}/wide")).json()["notes"]
+    cols = notes["columns"]
+    parts = [{cols[f"c{i:03d}"]["label"]["updated_at"] for i in range(lo, hi + 1)}
+             for lo, hi in ((1, 32), (33, 64), (65, 95))]
+    assert all(len(p) == 1 for p in parts), "同一段的项是同一次写进去的"
+    assert notes["kind"]["updated_at"] == notes["label"]["updated_at"], "表级那段的两项是同一次写进去的"
+    stamps = [notes["label"]["updated_at"], *(p.pop() for p in parts)]
+    assert len(set(stamps)) == 4 and stamps == sorted(stamps), stamps