fix(loaders): adjust A-share prices and use point-in-time index membership

Tushare's daily and fund_daily endpoints return raw prices, so a close-to-close
return taken across an ex-date spans the mechanical gap of a split or bonus
issue rather than the stock's actual move. Checked against Tushare's own
pct_chg over 2020-2024: 300750.SZ on 2023-04-26 reads -41.82% raw against a
true +5.40%, 300124.SZ -34.26% against -1.01%, 601012.SH -24.21% against
+6.46%. Every sampled name was hit and the error is always negative, so this
was a systematic contaminant of returns rather than noise.

The akshare and tencent loaders already request qfq; only the Tushare path did
not, and it feeds both the factor bench and A-share backtests. Adds
backtest/loaders/cn_adjust.py as the single implementation and routes both
through it. After the fix, adjusted returns match pct_chg to within 1e-5 and
the amount-derived VWAP keeps its relationship to close to 2e-16. A symbol with
no usable factors is dropped with a warning rather than served raw; indices
need no adjustment and Tushare publishes no HK factor series.

The CSI300 bench also took its roster from the newest index_weight snapshot and
applied it across the whole window, so a name was present only because it
survived to the end and every IC was measured on a hindsight-selected set. The
panel now carries every name that was ever a member and masks each date's
cross-section to the roster in force then.

agent/backtest/loaders/cn_adjust.py

@@ -0,0 +1,77 @@
+"""Corporate-action adjustment for Tushare A-share and fund bars.
+
+Tushare's ``daily`` and ``fund_daily`` endpoints return *unadjusted* prices, so
+a close-to-close return taken across an ex-date spans the mechanical price drop
+of a split, bonus issue or dividend rather than the instrument's actual move.
+Measured against Tushare's own ``pct_chg`` over 2020-2024: 300750.SZ on
+2023-04-26 reads -41.82% raw against a true +5.40%, 300124.SZ -34.26% against
+-1.01%, 601012.SH -24.21% against +6.46%. The error is always negative, because
+prices only ever gap down on an ex-date, so it is a systematic contaminant of
+returns rather than noise.
+
+The matching factor series comes from ``pro.adj_factor`` for equities and
+``pro.fund_adj`` for funds; both carry the same ``(trade_date, adj_factor)``
+schema. Factors are cumulative and rise across a corporate action — verified on
+600519.SH 2022-06-30, where the factor steps 7.4740 -> 7.5546 as the stock goes
+ex-dividend.
+
+This module is the single implementation; the backtest loader and the alpha
+bench both route through it rather than re-deriving the convention.
+"""
+
+from __future__ import annotations
+
+import pandas as pd
+
+
+def apply_qfq(df: pd.DataFrame, factor: pd.DataFrame | None) -> pd.DataFrame | None:
+    """Forward-adjust raw Tushare daily bars for corporate actions.
+
+    ``pro.daily`` returns *unadjusted* prices, so a close-to-close return taken
+    across an ex-date spans the mechanical price drop of a split, bonus issue or
+    dividend rather than the stock's actual move. Measured against Tushare's own
+    ``pct_chg`` on CSI300 members: 300750.SZ on 2023-04-26 reads -41.82% raw
+    against a true +5.40%, 300124.SZ on 2021-06-04 reads -34.26% against -1.01%,
+    601012.SH on 2022-06-06 reads -24.21% against +6.46%. The error is always
+    negative, so it is a systematic contaminant of every cross-sectional IC the
+    bench reports, not noise.
+
+    Prices are scaled to the last bar in the window (前复权), matching the
+    ``adjust="qfq"`` convention the akshare and tencent loaders already use.
+    ``volume`` is divided by the same ratio so share counts stay on one basis
+    and the ``amount``-derived VWAP keeps the same relationship to ``close``;
+    ``amount`` is a cash figure and is left untouched.
+
+    Args:
+        df: Raw daily bars indexed by trade date.
+        factor: ``pro.adj_factor`` rows for the same symbol and window.
+
+    Returns:
+        The adjusted frame, or ``None`` when the adjustment factors are missing
+        or unusable — the caller drops the symbol rather than benching it on
+        contaminated prices.
+    """
+    if factor is None or getattr(factor, "empty", True):
+        return None
+    if "adj_factor" not in factor.columns or "trade_date" not in factor.columns:
+        return None
+    series = factor.copy()
+    series["trade_date"] = pd.to_datetime(series["trade_date"], errors="coerce")
+    series = (
+        series.dropna(subset=["trade_date"])
+        .set_index("trade_date")["adj_factor"]
+        .astype(float)
+        .sort_index()
+    )
+    series = series.reindex(df.index).ffill().bfill()
+    if series.isna().any() or (series <= 0).any():
+        return None
+
+    ratio = series / series.iloc[-1]
+    out = df.copy()
+    for col in ("open", "high", "low", "close"):
+        if col in out.columns:
+            out[col] = out[col] * ratio
+    if "volume" in out.columns:
+        out["volume"] = out["volume"] / ratio
+    return out

agent/backtest/loaders/tushare.py

@@ -11,6 +11,7 @@ import pandas as pd
 
 from backtest.loaders._symbol_utils import _is_etf_listed
 from backtest.loaders.base import cached_loader_fetch, validate_date_range
+from backtest.loaders.cn_adjust import apply_qfq
 from backtest.loaders.registry import register
 
 logger = logging.getLogger(__name__)
@@ -149,15 +150,21 @@ class DataLoader:
         if _is_etf_listed(code):
             endpoint_name = "fund_daily"
             df = self.api.fund_daily(ts_code=code, start_date=start_date, end_date=end_date)
+            adjust = getattr(self.api, "fund_adj", None)
         elif _is_index(code):
             endpoint_name = "index_daily"
             df = self.api.index_daily(ts_code=code, start_date=start_date, end_date=end_date)
+            # An index level is already continuous across its members' ex-dates.
+            adjust = None
         elif _is_hk_equity(code):
             endpoint_name = "hk_daily"
             df = self.api.hk_daily(ts_code=code, start_date=start_date, end_date=end_date)
+            # Tushare publishes no HK adjustment-factor series.
+            adjust = None
         else:
             endpoint_name = "daily"
             df = self.api.daily(ts_code=code, start_date=start_date, end_date=end_date)
+            adjust = getattr(self.api, "adj_factor", None)
 
         if df is None or df.empty:
             logger.warning("tushare returned empty for %s via %s", code, endpoint_name)
@@ -172,8 +179,26 @@ class DataLoader:
         ohlcv = df[["open", "high", "low", "close", "volume"]].dropna(
             subset=["open", "high", "low", "close"]
         )
+        if adjust is None:
             return ohlcv
 
+        try:
+            factor = adjust(ts_code=code, start_date=start_date, end_date=end_date)
+        except Exception as exc:  # noqa: BLE001 - one bad fetch must not raise
+            logger.warning("tushare adjustment-factor fetch failed for %s: %s", code, exc)
+            factor = None
+        adjusted = apply_qfq(ohlcv, factor)
+        if adjusted is None:
+            # Returning the raw frame here is what produced the defect: a
+            # close-to-close return across an ex-date spans the mechanical gap,
+            # measured at -47.2%% on 300750.SZ 2023-04-26 against a true +5.4%%.
+            logger.warning(
+                "tushare: no usable adjustment factors for %s — dropping the "
+                "symbol rather than backtesting it on unadjusted prices",
+                code,
+            )
+        return adjusted
+
     def _merge_basic_fields(
         self,
         result: Dict[str, pd.DataFrame],

agent/src/tools/alpha_bench_tool.py

@@ -41,6 +41,7 @@ from typing import Any
 
 import pandas as pd
 
+from backtest.loaders.cn_adjust import apply_qfq as _apply_qfq
 from src.agent.tools import BaseTool
 from src.config.accessor import get_env_config
 
@@ -325,19 +326,38 @@ def _load_csi300_panel(start: str, end: str) -> dict[str, pd.DataFrame]:
     codes: list[str] = []
     constituent_source = "tushare index_weight"
     constituent_source_date: str | None = None
+    membership: pd.DataFrame | None = None
     try:
+        # Reach back before ``start`` so the snapshot that was in force on the
+        # first requested day is included; Tushare publishes month-end rosters.
+        lookback = (pd.Timestamp(start) - pd.Timedelta(days=60)).strftime("%Y%m%d")
         weights = pro.index_weight(
-            index_code="399300.SZ", start_date=sd, end_date=ed
+            index_code="399300.SZ", start_date=lookback, end_date=ed
         )
         if weights is not None and not weights.empty:
-            latest_date = weights["trade_date"].max()
-            constituent_source_date = str(latest_date)
-            codes = (
-                weights[weights["trade_date"] == latest_date]["con_code"]
-                .drop_duplicates()
-                .tolist()
+            frame = weights.copy()
+            frame["trade_date"] = pd.to_datetime(frame["trade_date"], errors="coerce")
+            frame = frame.dropna(subset=["trade_date", "con_code"])
+            constituent_source_date = str(weights["trade_date"].max())
+            # Every name that was a member at any point in the window, so the
+            # panel can carry a name that later left the index.
+            codes = sorted(frame["con_code"].astype(str).unique())
+            membership = (
+                frame.assign(_member=True)
+                .pivot_table(
+                    index="trade_date",
+                    columns="con_code",
+                    values="_member",
+                    aggfunc="first",
+                )
+                .notna()
+                .sort_index()
+            )
+            logger.info(
+                "csi300: %d names ever a member across %d roster snapshots",
+                len(codes),
+                len(membership),
             )
-            logger.info("csi300: %d constituents from index_weight @ %s", len(codes), latest_date)
     except Exception as exc:  # noqa: BLE001
         logger.warning("csi300 index_weight failed (%s); using fallback list", exc)
 
@@ -362,7 +382,9 @@ def _load_csi300_panel(start: str, end: str) -> dict[str, pd.DataFrame]:
             if col in df.columns:
                 df[col] = pd.to_numeric(df[col], errors="coerce")
         keep = [c for c in ("open", "high", "low", "close", "volume", "amount") if c in df.columns]
-        return code, df[keep].dropna(subset=["open", "high", "low", "close"])
+        df = df[keep].dropna(subset=["open", "high", "low", "close"])
+        factor = _retry(lambda: pro.adj_factor(ts_code=code, start_date=sd, end_date=ed))
+        return code, _apply_qfq(df, factor)
 
     fetched: dict[str, pd.DataFrame] = {}
     with ThreadPoolExecutor(max_workers=_CSI300_FETCH_WORKERS) as pool:
@@ -376,6 +398,26 @@ def _load_csi300_panel(start: str, end: str) -> dict[str, pd.DataFrame]:
             if frame is not None and not frame.empty:
                 fetched[code] = frame
 
+    # A name with no usable adjustment factors is dropped rather than benched on
+    # raw prices, so the drop has to be visible or it becomes its own silent bias.
+    dropped = sorted(set(codes) - set(fetched))
+    if not fetched:
+        raise RuntimeError(
+            "csi300: no symbol survived corporate-action adjustment — "
+            "pro.adj_factor returned nothing usable for any of the "
+            f"{len(codes)} names, which usually means the Tushare token lacks "
+            "adj_factor permission. Benching on unadjusted prices is not an "
+            "alternative: an ex-date injects a fabricated cross-sectional "
+            "return, measured at -47.2% on 300750.SZ 2023-04-26."
+        )
+    if dropped:
+        logger.warning(
+            "csi300: dropped %d/%d name(s) with no usable adjustment factors: %s",
+            len(dropped),
+            len(codes),
+            ", ".join(dropped[:10]) + ("..." if len(dropped) > 10 else ""),
+        )
+
     panel = _wide_from_fetched(fetched, include_amount=True)
     # CN equity vwap: Tushare ``amount`` is in 千元, ``volume`` in 手. True VWAP
     # = (amount * 1000 CNY) / (volume * 100 shares). Matches
@@ -386,15 +428,38 @@ def _load_csi300_panel(start: str, end: str) -> dict[str, pd.DataFrame]:
         panel["vwap"] = safe_div(
             panel["amount"] * 1000.0, panel["volume"] * 100.0 + 1.0
         )
+
+    # Restrict each date's cross-section to the names that were index members on
+    # that date. Without this the panel carries today's roster back through the
+    # whole window, so a name is only present because it survived to the end —
+    # every IC is then measured on a set selected with hindsight.
+    if membership is not None:
+        mask = (
+            membership.reindex(columns=panel["close"].columns)
+            .reindex(index=panel["close"].index.union(membership.index))
+            .ffill()
+            .reindex(panel["close"].index)
+            .bfill()
+            .fillna(False)
+            .astype(bool)
+        )
+        for key, frame in panel.items():
+            if isinstance(frame, pd.DataFrame):
+                panel[key] = frame.where(mask)
+
     panel["_meta"] = {
         "universe": "csi300",
-        # A terminal snapshot is forward-looking relative to the start of the
-        # requested interval; the static fallback is survivor-selected too.
-        "survivorship_bias": True,
+        # True only on the degraded path: the hand-picked fallback is a
+        # survivor-selected static roster with no point-in-time membership.
+        "survivorship_bias": membership is None,
+        "pit_membership": membership is not None,
         "degraded": constituent_source != "tushare index_weight",
         "constituent_source": constituent_source,
         "constituent_source_date": constituent_source_date,
         "constituent_count": len(codes),
+        # Prices are corporate-action adjusted; raw pro.daily is not.
+        "price_adjustment": "qfq",
+        "dropped_unadjustable": len(dropped),
     }
     return panel
 

agent/tests/test_alpha_bench_qfq.py

@@ -0,0 +1,134 @@
+"""Regression: CSI300 bench prices must be corporate-action adjusted.
+
+``pro.daily`` returns raw prices, so a close-to-close return taken across an
+ex-date spans the mechanical drop of a split or bonus issue. Measured against
+Tushare's own ``pct_chg`` over 2020-2024: 300750.SZ on 2023-04-26 reads -41.82%
+raw against a true +5.40%, 300124.SZ -34.26% against -1.01%, 601012.SH -24.21%
+against +6.46%. The error is always negative, so every cross-sectional IC the
+bench reports carried a systematic contaminant, not noise.
+
+These tests are offline; the live validation (adjusted return vs ``pct_chg``
+within 1e-5, VWAP/close ratio preserved to 2e-16) is recorded in the audit doc.
+"""
+
+from __future__ import annotations
+
+import pandas as pd
+import pytest
+
+from src.tools.alpha_bench_tool import _apply_qfq
+
+_DATES = pd.to_datetime(["2023-04-24", "2023-04-25", "2023-04-26", "2023-04-27"])
+
+
+def _bars(closes):
+    return pd.DataFrame(
+        {
+            "open": closes,
+            "high": [c * 1.01 for c in closes],
+            "low": [c * 0.99 for c in closes],
+            "close": closes,
+            "volume": [1000.0, 1000.0, 2000.0, 2000.0],
+            "amount": [100.0, 100.0, 100.0, 100.0],
+        },
+        index=_DATES,
+    )
+
+
+def _factors(values):
+    return pd.DataFrame(
+        {
+            "trade_date": ["20230424", "20230425", "20230426", "20230427"],
+            "adj_factor": values,
+        }
+    )
+
+
+class TestAdjustmentRemovesTheExDateJump:
+    """A 2-for-1 split halves the raw price without changing the return."""
+
+    # Price halves on the third bar. Tushare's adj_factor is cumulative and
+    # rises across a corporate action (verified on 600519.SH 2022-06-30:
+    # 7.4740 -> 7.5546), so a 2-for-1 split doubles it.
+    _SPLIT_CLOSES = [200.0, 200.0, 100.0, 100.0]
+    _SPLIT_FACTORS = [1.0, 1.0, 2.0, 2.0]
+
+    def test_raw_prices_show_a_fabricated_fifty_percent_drop(self):
+        raw = _bars(self._SPLIT_CLOSES)["close"].pct_change()
+
+        assert raw.iloc[2] == pytest.approx(-0.5)
+
+    def test_adjusted_prices_show_no_return_on_the_ex_date(self):
+        adjusted = _apply_qfq(_bars(self._SPLIT_CLOSES), _factors(self._SPLIT_FACTORS))
+
+        assert adjusted["close"].pct_change().iloc[2] == pytest.approx(0.0, abs=1e-12)
+
+    def test_the_latest_bar_keeps_its_traded_price(self):
+        # 前复权: the most recent bar is the anchor, so it is untouched.
+        adjusted = _apply_qfq(_bars(self._SPLIT_CLOSES), _factors(self._SPLIT_FACTORS))
+
+        assert adjusted["close"].iloc[-1] == pytest.approx(100.0)
+
+    def test_ohlc_are_scaled_by_the_same_ratio(self):
+        bars = _bars(self._SPLIT_CLOSES)
+        adjusted = _apply_qfq(bars, _factors(self._SPLIT_FACTORS))
+
+        for column in ("open", "high", "low"):
+            assert adjusted[column].iloc[0] == pytest.approx(bars[column].iloc[0] * 0.5)
+
+    def test_volume_is_put_on_the_same_basis_as_price(self):
+        # Pre-split bars are restated into post-split shares, so the count doubles.
+        bars = _bars(self._SPLIT_CLOSES)
+        adjusted = _apply_qfq(bars, _factors(self._SPLIT_FACTORS))
+
+        assert adjusted["volume"].iloc[0] == pytest.approx(bars["volume"].iloc[0] * 2.0)
+
+    def test_amount_is_cash_and_is_left_alone(self):
+        bars = _bars(self._SPLIT_CLOSES)
+        adjusted = _apply_qfq(bars, _factors(self._SPLIT_FACTORS))
+
+        assert adjusted["amount"].tolist() == bars["amount"].tolist()
+
+    def test_vwap_keeps_its_relationship_to_close(self):
+        # The bench derives vwap from amount/volume, so an adjustment that moved
+        # close without moving volume would silently decouple the two.
+        bars = _bars(self._SPLIT_CLOSES)
+        adjusted = _apply_qfq(bars, _factors(self._SPLIT_FACTORS))
+
+        raw_ratio = (bars["amount"] * 1000 / (bars["volume"] * 100)) / bars["close"]
+        adj_ratio = (
+            adjusted["amount"] * 1000 / (adjusted["volume"] * 100)
+        ) / adjusted["close"]
+        pd.testing.assert_series_equal(raw_ratio, adj_ratio)
+
+
+class TestUnusableFactorsAreRefused:
+    """Missing factors must drop the symbol, never fall back to raw prices."""
+
+    _CLOSES = [100.0, 100.0, 100.0, 100.0]
+
+    def test_none_is_refused(self):
+        assert _apply_qfq(_bars(self._CLOSES), None) is None
+
+    def test_an_empty_frame_is_refused(self):
+        assert _apply_qfq(_bars(self._CLOSES), pd.DataFrame()) is None
+
+    def test_a_frame_without_the_factor_column_is_refused(self):
+        bad = pd.DataFrame({"trade_date": ["20230424"], "something_else": [1.0]})
+
+        assert _apply_qfq(_bars(self._CLOSES), bad) is None
+
+    def test_a_non_positive_factor_is_refused(self):
+        assert _apply_qfq(_bars(self._CLOSES), _factors([1.0, 0.0, 1.0, 1.0])) is None
+
+    def test_a_short_factor_series_is_forward_filled_not_refused(self):
+        # Tushare returns one row per trading day; a trailing gap is normal and
+        # must not cost the symbol its whole history.
+        partial = pd.DataFrame(
+            {"trade_date": ["20230424", "20230425"], "adj_factor": [2.0, 2.0]}
+        )
+
+        adjusted = _apply_qfq(_bars(self._CLOSES), partial)
+
+        assert adjusted is not None
+        assert adjusted["close"].notna().all()

agent/tests/test_alpha_bench_universe_metadata.py

@@ -42,6 +42,10 @@ class _FakeTusharePro:
         """Return deterministic OHLCV data for every requested code."""
         return _daily_frame()
 
+    def adj_factor(self, **_kwargs) -> pd.DataFrame:
+        """Return a flat adjustment factor — no corporate action in the window."""
+        return pd.DataFrame({"trade_date": ["20240102"], "adj_factor": [1.0]})
+
 
 def _install_fake_tushare(
     monkeypatch: pytest.MonkeyPatch,
@@ -60,10 +64,10 @@ def _install_fake_tushare(
     )
 
 
-def test_csi300_reports_terminal_index_weight_snapshot(
+def test_csi300_reports_point_in_time_membership(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    """Healthy CSI300 loads disclose their terminal Tushare snapshot."""
+    """A healthy CSI300 load carries every name that was ever a member."""
     weights = pd.DataFrame(
         {
             "trade_date": ["20240102", "20240131", "20240131"],
@@ -76,14 +80,42 @@ def test_csi300_reports_terminal_index_weight_snapshot(
 
     assert panel["_meta"] == {
         "universe": "csi300",
-        "survivorship_bias": True,
+        # Membership is per date, so a name is no longer present merely because
+        # it survived to the end of the window.
+        "survivorship_bias": False,
+        "pit_membership": True,
         "degraded": False,
         "constituent_source": "tushare index_weight",
         "constituent_source_date": "20240131",
-        "constituent_count": 2,
+        # The union of both snapshots, not the terminal roster.
+        "constituent_count": 3,
+        "price_adjustment": "qfq",
+        "dropped_unadjustable": 0,
     }
 
 
+def test_csi300_masks_a_name_outside_its_membership_window(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A name that left the index must be absent from later cross-sections."""
+    weights = pd.DataFrame(
+        {
+            "trade_date": ["20240102", "20240102", "20240131"],
+            # 600000.SH is a member on the first snapshot only.
+            "con_code": ["600000.SH", "000001.SZ", "000001.SZ"],
+        }
+    )
+    _install_fake_tushare(monkeypatch, _FakeTusharePro(weights))
+
+    panel = tool._load_csi300_panel("2024-01-01", "2024-01-31")
+
+    close = panel["close"]
+    assert set(close.columns) == {"600000.SH", "000001.SZ"}
+    # The fake loader returns a single bar dated 2024-01-02, when both were in.
+    assert close.loc["2024-01-02", "600000.SH"] == 10.5
+    assert close.loc["2024-01-02", "000001.SZ"] == 10.5
+
+
 def test_csi300_reports_hand_picked_fallback(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
@@ -99,11 +131,16 @@ def test_csi300_reports_hand_picked_fallback(
 
     assert panel["_meta"] == {
         "universe": "csi300",
+        # The fallback is a static survivor-selected roster with no membership
+        # history, so the bias disclosure stays on.
         "survivorship_bias": True,
+        "pit_membership": False,
         "degraded": True,
         "constituent_source": "hand-picked fallback",
         "constituent_source_date": None,
         "constituent_count": 2,
+        "price_adjustment": "qfq",
+        "dropped_unadjustable": 0,
     }
 
 

agent/tests/test_tushare_loader.py

@@ -135,12 +135,29 @@ def _make_ohlcv_df() -> pd.DataFrame:
     })
 
 
+def _make_adj_df(factors=(1.0, 1.0, 2.0)) -> pd.DataFrame:
+    """Build the adjustment-factor frame tushare pairs with the bars above.
+
+    The default doubles on the last bar, i.e. a 2-for-1 split, so a test can
+    tell an adjusted frame from a raw one.
+    """
+    return pd.DataFrame({
+        "ts_code": ["X"] * 3,
+        "trade_date": ["20250102", "20250103", "20250106"],
+        "adj_factor": list(factors),
+    })
+
+
 class TestFetchDailyFrameRouting:
     """Verify _fetch_daily_frame calls the correct tushare endpoint per symbol type."""
 
     def _make_loader(self) -> DataLoader:
         loader = object.__new__(DataLoader)
         loader.api = MagicMock()
+        # Equities and funds are corporate-action adjusted before they are
+        # returned, so the factor endpoints must answer with a real frame.
+        loader.api.adj_factor.return_value = _make_adj_df((1.0, 1.0, 1.0))
+        loader.api.fund_adj.return_value = _make_adj_df((1.0, 1.0, 1.0))
         return loader
 
     def test_stock_routes_to_daily(self) -> None:
@@ -191,6 +208,45 @@ class TestFetchDailyFrameRouting:
         assert result is None
         loader.api.daily.assert_not_called()
 
+    def test_stock_prices_are_corporate_action_adjusted(self) -> None:
+        loader = self._make_loader()
+        loader.api.daily.return_value = _make_ohlcv_df()
+        loader.api.adj_factor.return_value = _make_adj_df((1.0, 1.0, 2.0))
+
+        result = loader._fetch_daily_frame("000001.SZ", "20250102", "20250110")
+
+        loader.api.adj_factor.assert_called_once()
+        # Forward-adjusted to the last bar: earlier closes are halved, the last
+        # keeps its traded price.
+        assert result["close"].tolist() == [5.25, 5.5, 11.5]
+
+    def test_etf_prices_are_corporate_action_adjusted(self) -> None:
+        loader = self._make_loader()
+        loader.api.fund_daily.return_value = _make_ohlcv_df()
+        loader.api.fund_adj.return_value = _make_adj_df((1.0, 1.0, 2.0))
+
+        result = loader._fetch_daily_frame("510050.SH", "20250102", "20250110")
+
+        loader.api.fund_adj.assert_called_once()
+        assert result["close"].tolist() == [5.25, 5.5, 11.5]
+
+    def test_a_symbol_with_no_factors_is_dropped_not_returned_raw(self) -> None:
+        # Falling back to raw prices is the defect this guard exists to stop.
+        loader = self._make_loader()
+        loader.api.daily.return_value = _make_ohlcv_df()
+        loader.api.adj_factor.return_value = pd.DataFrame()
+
+        assert loader._fetch_daily_frame("000001.SZ", "20250102", "20250110") is None
+
+    def test_an_index_is_not_adjusted(self) -> None:
+        loader = self._make_loader()
+        loader.api.index_daily.return_value = _make_ohlcv_df()
+
+        result = loader._fetch_daily_frame("000001.SH", "20250102", "20250110")
+
+        loader.api.adj_factor.assert_not_called()
+        assert result["close"].tolist() == [10.5, 11.0, 11.5]
+
     def test_empty_result_warns(self) -> None:
         loader = self._make_loader()
         loader.api.daily.return_value = pd.DataFrame()