diff --git a/scripts/data_platform/corpus_download.py b/scripts/data_platform/corpus_download.py
index 1c80488..6c3375b 100644
--- a/scripts/data_platform/corpus_download.py
+++ b/scripts/data_platform/corpus_download.py
@@ -536,6 +536,17 @@ def _filter_new(domain, norm_rows, ledger, recent):
             if not kl and not kr]
 
 
+def _absorb_new(domain, norm_rows, ledgers, recents):
+    """过滤已知 id → 追加分区+账本+近窗(daily/backfill 共用)。返回新行。"""
+    new = _filter_new(domain, norm_rows, ledgers[domain], recents[domain])
+    if new:
+        append_parquet(domain, new, ID_KEYS[domain])
+        keys = [_row_key(domain, r) for r in new]
+        ledgers[domain].add(keys)
+        recents[domain].add(keys)
+    return new
+
+
 def _record_depth(ctx, source, code, date_str):
     if not date_str:
         return
@@ -598,12 +609,8 @@ def _run_ann_increment(ctx, pool, cl_cn, ledgers, recents):
             continue
         candidates.extend(collect_pdf_candidates(rows))
         norm = [norm_ann_row(r, first_seen) for r in rows]
-        new = _filter_new("ann_meta", norm, ledgers["ann_meta"], recents["ann_meta"])
+        new = _absorb_new("ann_meta", norm, ledgers, recents)
         if new:
-            append_parquet("ann_meta", new, "announcement_id")
-            keys = [_row_key("ann_meta", r) for r in new]
-            ledgers["ann_meta"].add(keys)
-            recents["ann_meta"].add(keys)
             for r in new:
                 _record_depth(ctx, "ann", r["sec_code"] or code,
                               (r["ann_time"] or "")[:10])
@@ -635,12 +642,8 @@ def _run_news_increment(ctx, pool, cl_em, ledgers, recents, new_articles):
             log.warning("news unit %s 失败(不标done): %s", code, e)
             continue
         norm = [norm_news_search_row(r, code) for r in rows]
-        new = _filter_new("news_meta", norm, ledgers["news_meta"], recents["news_meta"])
+        new = _absorb_new("news_meta", norm, ledgers, recents)
         if new:
-            append_parquet("news_meta", new, ["art_code", "stock_code"])
-            keys = [_row_key("news_meta", r) for r in new]
-            ledgers["news_meta"].add(keys)
-            recents["news_meta"].add(keys)
             for r in new:
                 _record_depth(ctx, "news", code, (r["show_time"] or "")[:10])
                 new_articles.append((r["art_code"], r["url"], r["show_time"]))
@@ -778,11 +781,101 @@ def run_daily(ctx, pool):
         led.flush()
 
 
-# ---------- backfill lane(T2 占位, ①②=T4 ③④=T5) ----------
+# ---------- backfill lane(①ann_meta ②news_meta;③④=T5) ----------
+
+def _run_ann_backfill(ctx, pool, cl_cn, ledgers, recents):
+    """①公告元数据回补 2000→今, unit=(stock,year), 逐年按池序(探测优先:空年=合法)。"""
+    today = dt.date.today()
+    first_seen = today.isoformat()
+    since_flush = 0
+    for year in range(BACKFILL_FROM_YEAR, today.year + 1):
+        year_end = today.isoformat() if year == today.year else f"{year}-12-31"
+        for code, org in pool:
+            unit = f"{code}_{year}"
+            if ctx.limit is not None and ctx.units >= ctx.limit:
+                return
+            if is_done(ctx.lane, "ann", unit):
+                continue
+            try:
+                rows = fetch_cninfo_announcements(cl_cn, code, org,
+                                                  f"{year}-01-01", year_end)
+            except DomainCooldown as e:
+                log.warning("backfill ann 域冷却 @%s: %s", unit, e)
+                ctx.rate_limited |= e.rate_limited
+                ctx.hard_cool |= not e.rate_limited
+                return
+            except (TransportError, HttpDeterministicError) as e:
+                ctx.failed += 1
+                log.warning("backfill ann %s 失败(不标done): %s", unit, e)
+                continue
+            norm = [norm_ann_row(r, first_seen) for r in rows]
+            new = _absorb_new("ann_meta", norm, ledgers, recents)
+            for r in new:
+                _record_depth(ctx, "ann", r["sec_code"] or code,
+                              (r["ann_time"] or "")[:10])
+            if new:
+                log.info("backfill ann %s: +%d/%d", unit, len(new), len(rows))
+            if ctx.limit is None:
+                mark_done(ctx.lane, "ann", unit)
+            ctx.units += 1
+            since_flush = _maybe_flush(ledgers, since_flush + 1)
+            ctx.stop_now()
+
+
+def _run_news_backfill(ctx, pool, cl_em, ledgers, recents):
+    """②新闻标题级回补(np-listapi), unit=(stock,page), 翻到空页或 page≥200 止。"""
+    for code, _org in pool:
+        if is_done(ctx.lane, "news_end", code):
+            continue
+        mkt = "1" if code.startswith("6") else "0"
+        capped = False
+        for page in range(1, NEWS_BACKFILL_MAX_PAGE + 1):
+            unit = f"{code}_p{page}"
+            if ctx.limit is not None and ctx.units >= ctx.limit:
+                return
+            if is_done(ctx.lane, "news", unit):
+                continue
+            try:
+                rows = fetch_news_backfill_page(cl_em, code, mkt, page)
+            except DomainCooldown as e:
+                log.warning("backfill news 域冷却 @%s: %s", unit, e)
+                ctx.rate_limited |= e.rate_limited
+                ctx.hard_cool |= not e.rate_limited
+                return
+            except (TransportError, HttpDeterministicError) as e:
+                ctx.failed += 1
+                log.warning("backfill news %s 失败(断点留此页): %s", unit, e)
+                break
+            if not rows:
+                if ctx.limit is None:
+                    mark_done(ctx.lane, "news", unit)
+                    mark_done(ctx.lane, "news_end", code)
+                log.info("backfill news %s: 到头(空页@%d)", code, page)
+                break
+            norm = [norm_news_np_row(r, code) for r in rows]
+            new = _absorb_new("news_meta", norm, ledgers, recents)
+            for r in new:
+                _record_depth(ctx, "news", code, (r["show_time"] or "")[:10])
+            if ctx.limit is None:
+                mark_done(ctx.lane, "news", unit)
+            ctx.units += 1
+            if page == NEWS_BACKFILL_MAX_PAGE:
+                capped = True
+            ctx.stop_now()
+        if capped and ctx.limit is None:
+            mark_done(ctx.lane, "news_end", code)
+            log.info("backfill news %s: page=%d 硬顶止", code, NEWS_BACKFILL_MAX_PAGE)
+
 
 def run_backfill(ctx, pool):
-    log.warning("backfill lane 未实施(T4/T5): 让路退出, daily 数据不受影响")
-    return
+    ledgers = {d: IdLedger(d) for d in ID_KEYS}
+    recents = {d: RecentIndex(d) for d in ID_KEYS}
+    cl_cn = DomainClient("cninfo")
+    cl_em = DomainClient("eastmoney")
+    _run_ann_backfill(ctx, pool, cl_cn, ledgers, recents)
+    _run_news_backfill(ctx, pool, cl_em, ledgers, recents)
+    for led in ledgers.values():
+        led.flush()
 
 
 # ---------- lane 入口 ----------
diff --git a/tests/data_platform/test_corpus_download.py b/tests/data_platform/test_corpus_download.py
index 2896654..4861d56 100644
--- a/tests/data_platform/test_corpus_download.py
+++ b/tests/data_platform/test_corpus_download.py
@@ -532,3 +532,154 @@ def test_main_daily_exit0(root, monkeypatch):
     with pytest.raises(SystemExit) as e:
         cd.main()
     assert e.value.code == 0
+
+
+# ---------- backfill lane ①ann_meta ②news_meta(T4) ----------
+
+def _wire_backfill_ann(monkeypatch, rows_by_unit):
+    """rows_by_unit: {(code, start, end): rows} — 按 unit 窗口回放。
+    必须同时锁死 news 段 fetch(零网络铁律——曾漏锁致真打 np-listapi 40s)。"""
+    monkeypatch.setattr(cd, "load_stock_pool", lambda **kw: POOL)
+    monkeypatch.setattr(cd, "fetch_news_backfill_page", MagicMock(return_value=[]))
+    calls = []
+
+    def fake(client, code, org, start, end, category=""):
+        calls.append((code, start, end))
+        return rows_by_unit.get((code, start, end), [])
+
+    monkeypatch.setattr(cd, "fetch_cninfo_announcements", fake)
+    return calls
+
+
+def test_backfill_ann_units_walk_years_asc_from_2000(root, monkeypatch):
+    """unit=(stock,year), 2000→今年逐年, 每年内按池序; 空年=合法 done。"""
+    import pandas as pd
+    calls = _wire_backfill_ann(monkeypatch, {("000001", "2001-01-01", "2001-12-31"):
+                                             [_ann_raw(aid="b1")]})
+    rc = cd.run_lane("backfill")
+    assert rc == 0
+    t = dt.date.today()
+    n_years = t.year - 2000 + 1
+    assert len(calls) == n_years * 2            # 每股每年 1 req(空窗 1 页即返)
+    assert calls[0] == ("000001", "2000-01-01", "2000-12-31")
+    assert calls[-1][1].startswith(t.isoformat()[:4])   # 今年
+    # 今年窗口右端=今天(相对), 历年=12-31
+    assert calls[-1][2] == t.isoformat()
+    assert cd.is_done("backfill", "ann", "000001_2001")
+    assert cd.is_done("backfill", "ann", "000001_2000")  # 空年也 done
+    today = t.isoformat()
+    ann = pd.read_parquet(root / "ann_meta" / f"dt={today}" / "part-0.parquet")
+    assert len(ann) == 1 and ann.iloc[0]["announcement_id"] == "b1"
+
+
+def test_backfill_ann_marker_skip_on_rerun(root, monkeypatch):
+    """done unit 零重拉(断点续传实证之 mock 版);数据幂等零重复。"""
+    import pandas as pd
+    _wire_backfill_ann(monkeypatch, {("000001", "2001-01-01", "2001-12-31"):
+                                     [_ann_raw(aid="b1")]})
+    cd.run_lane("backfill")
+    calls2 = _wire_backfill_ann(monkeypatch, {("000001", "2001-01-01", "2001-12-31"):
+                                              [_ann_raw(aid="b1")]})
+    cd.run_lane("backfill")
+    assert calls2 == []                          # 全部 done → 零请求
+    today = dt.date.today().isoformat()
+    ann = pd.read_parquet(root / "ann_meta" / f"dt={today}" / "part-0.parquet")
+    assert len(ann) == 1
+
+
+def test_backfill_ann_resume_from_oldest_undone(root, monkeypatch):
+    """手动标 2000/2001 done → 重跑只碰 2002 起。"""
+    cd.mark_done("backfill", "ann", "000001_2000")
+    cd.mark_done("backfill", "ann", "000001_2001")
+    cd.mark_done("backfill", "ann", "600519_2000")
+    cd.mark_done("backfill", "ann", "600519_2001")
+    calls = _wire_backfill_ann(monkeypatch, {})
+    cd.run_lane("backfill")
+    starts = {c[1] for c in calls}
+    assert "2000-01-01" not in starts and "2001-01-01" not in starts
+
+
+def test_backfill_ann_unit_fail_not_marked(root, monkeypatch):
+    calls = _wire_backfill_ann(monkeypatch, {})
+    monkeypatch.setattr(cd, "fetch_cninfo_announcements",
+                        MagicMock(side_effect=cd.TransportError("boom")))
+    rc = cd.run_lane("backfill")
+    assert rc == 1
+    assert not cd.is_done("backfill", "ann", "000001_2000")
+
+
+def _wire_news_backfill(monkeypatch, pages):
+    """pages: {page_idx: rows} — 翻页回放。"""
+    monkeypatch.setattr(cd, "load_stock_pool", lambda **kw: [("600519", "o1")])
+    monkeypatch.setattr(cd, "fetch_cninfo_announcements",
+                        MagicMock(return_value=[]))
+    urls = []
+
+    def fake(client, code, mkt, page):
+        urls.append((code, mkt, page))
+        return pages.get(page, [])
+
+    monkeypatch.setattr(cd, "fetch_news_backfill_page", fake)
+    return urls
+
+
+def test_backfill_news_walks_pages_until_empty(root, monkeypatch):
+    import pandas as pd
+    np_rows = [{"Art_Code": f"a{i}", "Art_ShowTime": f"2024-01-0{i} 00:00:00",
+                "Art_Title": f"t{i}", "Art_Url": f"http://x/a{i}.html",
+                "Np_dst": "CMS"} for i in (1, 2, 3)]
+    urls = _wire_news_backfill(monkeypatch, {1: np_rows[:2], 2: np_rows[2:]})
+    rc = cd.run_lane("backfill")
+    assert rc == 0
+    assert urls[:2] == [("600519", "1", 1), ("600519", "1", 2)]
+    assert urls[2] == ("600519", "1", 3)         # 第3页空 → 止
+    assert len(urls) == 3
+    assert cd.is_done("backfill", "news", "600519_p1")
+    assert cd.is_done("backfill", "news_end", "600519")   # 空页=股票到头
+    today = dt.date.today().isoformat()
+    news = pd.read_parquet(root / "news_meta" / f"dt={today}" / "part-0.parquet")
+    assert len(news) == 3
+    assert news.iloc[0]["summary"] is None       # np 段无摘要如实
+
+
+def test_backfill_news_end_sentinel_skips_stock(root, monkeypatch):
+    cd.mark_done("backfill", "news_end", "600519")
+    urls = _wire_news_backfill(monkeypatch, {1: ["x"]})
+    cd.run_lane("backfill")
+    assert urls == []                            # 到头股零请求
+
+
+def test_backfill_news_page_cap_200(root, monkeypatch):
+    """page≥200 止(实测硬顶), 到 200 即算该股完结。"""
+    row = {"Art_Code": "a", "Art_ShowTime": "2020-01-01 00:00:00",
+           "Art_Title": "t", "Art_Url": "http://x/a.html", "Np_dst": "CMS"}
+    urls = _wire_news_backfill(monkeypatch,
+                               {p: [dict(row)] for p in range(1, 201)})
+    cd.run_lane("backfill")
+    assert len(urls) == 200
+    assert cd.is_done("backfill", "news_end", "600519")
+
+
+def test_backfill_news_mkt_prefix_mapping(root, monkeypatch):
+    urls = _wire_news_backfill(monkeypatch, {})
+    cd.run_lane("backfill")
+    assert urls[0][1] == "1"                     # 600519 → SH=1
+    urls2 = _wire_news_backfill(monkeypatch, {})  # 只换 fetch 窗口
+    monkeypatch.setattr(cd, "load_stock_pool", lambda **kw: [("000001", "o")])
+    cd.run_lane("backfill")
+    assert urls2[0][1] == "0"                    # 000001 → SZ=0
+
+
+def test_backfill_limit_smoke_no_markers(root, monkeypatch):
+    _wire_backfill_ann(monkeypatch, {})
+    rc = cd.run_lane("backfill", limit=3)
+    assert rc == 0
+    assert not any((root / "state" / "markers" / "backfill").rglob("*.done"))
+
+
+def test_backfill_wallclock_rc3(root, monkeypatch):
+    _wire_backfill_ann(monkeypatch, {})
+    past = (dt.datetime.now() - dt.timedelta(minutes=1)).strftime("%H:%M")
+    rc = cd.run_lane("backfill", until=past)
+    assert rc == 3
+    assert cd.is_done("backfill", "ann", "000001_2000")  # 首 unit 完成后停