diff --git a/pyproject.toml b/pyproject.toml
index 3efed4e..dbaaafd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -21,6 +21,9 @@ science = ["scipy>=1.10,<1.16"]
 web = ["fastapi>=0.110,<1", "uvicorn[standard]>=0.29"]
 # 本地 K 线数据仓库（easy-tdx warehouse ...）：DuckDB 单文件列存
 warehouse = ["duckdb>=1.0"]
+# baostock 自动兜底数据源（TDX 全部路径失败时的最后一级回退，仅日线及以上）。
+# 可选安装：不装则该回退环自动关闭，核心功能不受影响。
+baostock = ["baostock>=0.9"]
 # 打包成桌面 EXE 用：系统托盘（pystray）+ 图标生成（Pillow）。
 # 仅 PyInstaller 打包态需要，开发态 ``pip install -e .[web]`` 不强制装。
 packaging = ["pystray>=0.19", "Pillow>=10.0"]
diff --git a/src/easy_tdx/sources/__init__.py b/src/easy_tdx/sources/__init__.py
new file mode 100644
index 0000000..a3c959c
--- /dev/null
+++ b/src/easy_tdx/sources/__init__.py
@@ -0,0 +1 @@
+"""备选数据源（自动兜底）。"""
diff --git a/src/easy_tdx/sources/baostock.py b/src/easy_tdx/sources/baostock.py
new file mode 100644
index 0000000..ba93cce
--- /dev/null
+++ b/src/easy_tdx/sources/baostock.py
@@ -0,0 +1,171 @@
+"""baostock 自动兜底数据源（仅日线及以上，TDX 全部路径失败时的最后一级回退）。
+
+定位与边界：
+- baostock 是 EOD 数据源，当日数据约 17:30 后才可查，**盘中实时能力为零**；
+  因此本模块只承接 DAY/WEEK/MONTH 的历史 K 线，分钟线/分时/逐笔/板块/实时
+  报价一律返回不可用（None），由上层维持原错误。
+- 启用条件自动判断：已安装 baostock 且未设置环境变量 ``EASY_TDX_BAOSTOCK=0``
+  即启用；未安装时本模块整体静默关闭，核心功能零影响。
+- baostock 客户端是单条全局连接且非线程安全，本模块内部全程持锁串行，
+  供 async 调用方经 ``asyncio.to_thread`` 使用。
+- 数据口径：volume 为股（与 /bars 输出契约一致，无需换算）；停牌日
+  （tradestatus=0 或 volume=0）剔除，与通达信 K 线不含停牌日的口径对齐；
+  复权经 adjustflag 原生支持（QFQ/HFQ/NONE），North Exchange（BJ）不覆盖。
+"""
+
+from __future__ import annotations
+
+import importlib
+import os
+import threading
+from datetime import datetime, timedelta
+
+import pandas as pd
+
+BAOSTOCK_DISABLE_ENV = "EASY_TDX_BAOSTOCK"
+
+# baostock 的全局连接锁（该库单连接、非线程安全）
+_bs_lock = threading.Lock()
+_logged_in = False
+# 兜底路径的锁等待上限：拿不到锁说明另一个兜底请求正在进行，
+# 与其排队不如放弃本次兜底（回退路径宁快勿堵）。
+_LOCK_TIMEOUT_SECONDS = 30.0
+
+# 支持兜底的周期（baostock frequency）：日线及以上；分钟线/季年线不兜
+_FREQ_BY_CATEGORY: dict[str, str] = {"DAY": "d", "WEEK": "w", "MONTH": "m"}
+# 复权映射：baostock adjustflag — 1=后复权 2=前复权 3=不复权
+_ADJUST_FLAG = {"NONE": "3", "QFQ": "2", "HFQ": "1"}
+_MARKET_PREFIX = {"SZ": "sz", "SH": "sh"}  # BJ baostock 不覆盖
+
+# 拉取窗口的日历天数系数（start+count 根 × 周期占的日历天 + 节假日缓冲）
+_WINDOW_DAYS = {"d": (1.6, 30), "w": (7.2, 40), "m": (32.0, 100)}
+# 偏移窗口规模上限（/bars 的 start 无上界，防极端参数把兜底源拖死）
+_MAX_TOTAL_BARS = 10_000
+
+
+def is_enabled() -> bool:
+    """自动判断兜底是否可用：未禁用（环境变量）且 baostock 已安装。"""
+    disabled = os.environ.get(BAOSTOCK_DISABLE_ENV, "").strip().lower() in {"0", "false", "off"}
+    if disabled:
+        return False
+    try:
+        importlib.import_module("baostock")
+    except ImportError:
+        return False
+    return True
+
+
+def _login_if_needed(bs: object) -> None:
+    """确保 baostock 已登录（匿名账户；调用方需已持有 _bs_lock）。"""
+    global _logged_in
+    if _logged_in:
+        return
+    lg = bs.login()  # type: ignore[attr-defined]
+    error_code = str(getattr(lg, "error_code", ""))
+    if error_code != "0":
+        raise RuntimeError(f"baostock 登录失败: {getattr(lg, 'error_msg', error_code)}")
+    _logged_in = True
+
+
+def _query_rows(bs: object, **kwargs: str) -> list[list[str]]:
+    """执行 query_history_k_data_plus 并取回全部行（调用方需已持锁）。"""
+    rs = bs.query_history_k_data_plus(**kwargs)  # type: ignore[attr-defined]
+    if str(getattr(rs, "error_code", "")) != "0":
+        raise RuntimeError(f"baostock 查询失败: {getattr(rs, 'error_msg', '')}")
+    rows: list[list[str]] = []
+    while rs.next() or False:
+        rows.append(rs.get_row_data())
+    return rows
+
+
+def fetch_bars(
+    market: str,
+    code: str,
+    category: str,
+    start: int,
+    count: int,
+    adjust: str,
+) -> pd.DataFrame | None:
+    """拉取日线及以上 K 线，输出对齐 /bars 契约的 DataFrame。
+
+    Args:
+        market: "SZ" / "SH"（BJ 不支持，返回 None）。
+        code: 6 位代码。
+        category: 周期名（DAY/WEEK/MONTH 之外返回 None）。
+        start: 跳过最新 start 根（与 TDX offset 语义一致）。
+        count: 最多返回 count 根。
+        adjust: "NONE" / "QFQ" / "HFQ"。
+
+    Returns:
+        按 [date, open, close, high, low, vol, amount] 列序、时间升序的
+        DataFrame；兜底不可用 / 不适用 / 无数据时返回 None（调用方继续
+        维持原错误，不吞异常）。
+    """
+    global _logged_in
+    if not is_enabled():
+        return None
+    prefix = _MARKET_PREFIX.get(market.upper())
+    frequency = _FREQ_BY_CATEGORY.get(category.upper())
+    adjustflag = _ADJUST_FLAG.get(adjust.upper())
+    if prefix is None or frequency is None or adjustflag is None:
+        return None
+
+    total = start + count
+    if total <= 0 or total > _MAX_TOTAL_BARS:
+        return None
+    coef, buffer_days = _WINDOW_DAYS[frequency]
+    end_date = datetime.now()
+    start_date = end_date - timedelta(days=total * coef + buffer_days)
+
+    # baostock 全局单连接：持锁串行；等待超时则放弃本次兜底
+    if not _bs_lock.acquire(timeout=_LOCK_TIMEOUT_SECONDS):
+        return None
+    try:
+        bs = importlib.import_module("baostock")
+        try:
+            _login_if_needed(bs)
+            rows = _query_rows(
+                bs,
+                code=f"{prefix}.{code}",
+                fields="date,open,high,low,close,volume,amount,tradestatus",
+                start_date=start_date.strftime("%Y-%m-%d"),
+                end_date=end_date.strftime("%Y-%m-%d"),
+                frequency=frequency,
+                adjustflag=adjustflag,
+            )
+        except Exception:
+            # 连接可能中途断开：重置登录态，下次兜底重新登录
+            _logged_in = False
+            raise
+    except Exception:
+        # 兜底源自身的任何失败都不向上抛：调用方按"无兜底数据"处理
+        return None
+    finally:
+        _bs_lock.release()
+
+    if not rows:
+        return None
+    df = pd.DataFrame(
+        rows, columns=["date", "open", "high", "low", "close", "vol", "amount", "tradestatus"]
+    )
+    for col in ("open", "high", "low", "close", "vol", "amount"):
+        df[col] = pd.to_numeric(df[col], errors="coerce")
+    # 停牌日剔除（tradestatus=0 或无成交），对齐通达信 K 线不含停牌日的口径
+    if "tradestatus" in df.columns:
+        df = df[df["tradestatus"] != "0"]
+    df = df.dropna(subset=["close"])
+    df = df[df["close"] > 0]
+    df = df[df["vol"] > 0]
+    if df.empty:
+        return None
+    df["date"] = pd.to_datetime(df["date"]).dt.normalize()
+
+    # TDX offset 语义：跳过最新 start 根，再取至多 count 根（时间升序）
+    end_pos = len(df) - start
+    if end_pos <= 0:
+        return None
+    df = df.iloc[max(0, end_pos - count) : end_pos]
+    if df.empty:
+        return None
+
+    return df[["date", "open", "close", "high", "low", "vol", "amount"]].reset_index(drop=True)
diff --git a/src/easy_tdx/web/routers/bars.py b/src/easy_tdx/web/routers/bars.py
index 4fe9c94..0e03b7c 100644
--- a/src/easy_tdx/web/routers/bars.py
+++ b/src/easy_tdx/web/routers/bars.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import asyncio
 import logging
 from typing import Any
 
@@ -18,7 +19,7 @@ from easy_tdx.web.convert import (
     period_times_from_category,
 )
 from easy_tdx.web.deps import get_client, get_mac_client_optional
-from easy_tdx.web.schemas import DataFrameResponse
+from easy_tdx.web.schemas import BarsResponse, DataFrameResponse
 
 _logger = logging.getLogger(__name__)
 
@@ -216,7 +217,40 @@ async def _fetch_120m(
     return _resample_pairs(df, count)
 
 
-@router.get("/bars", response_model=DataFrameResponse)
+async def _baostock_last_resort(
+    market: str, code: str, category: str, start: int, count: int, adjust: str
+) -> tuple[pd.DataFrame | None, str | None]:
+    """TDX 全部路径失败/为空后的最后一级兜底：baostock（仅日线及以上）。
+
+    未安装 baostock / 设置了 EASY_TDX_BAOSTOCK=0 / 周期不适用 / 查询失败
+    一律返回 ``(None, None)``——兜底源自身的任何失败都不影响原错误语义。
+    baostock 客户端阻塞且非线程安全：丢线程池执行，模块内部持锁串行。
+    """
+    from easy_tdx.sources import baostock as baostock_source
+
+    if not baostock_source.is_enabled():
+        return None, None
+    try:
+        df = await asyncio.to_thread(
+            baostock_source.fetch_bars, market, code, category, start, count, adjust
+        )
+    except Exception as exc:  # noqa: BLE001 — 兜底失败不改变原错误路径
+        _logger.warning("/bars baostock 兜底异常 (%s%s): %s", market, code, exc)
+        return None, None
+    if df is None or df.empty:
+        return None, None
+    _logger.info("/bars 已启用 baostock 兜底 (%s%s %s，%d 根)", market, code, category, len(df))
+    return df, "baostock"
+
+
+def _bars_resp(df: pd.DataFrame | None, source: str | None) -> BarsResponse:
+    """构建带来源标注的 K 线响应（source 非 None = 命中兜底源）。"""
+    resp = BarsResponse.from_dataframe(df)
+    resp.source = source
+    return resp
+
+
+@router.get("/bars", response_model=BarsResponse)
 async def security_bars(
     market: str = Query(..., description="市场: SZ, SH, BJ"),
     code: str = Query(..., min_length=6, max_length=6),
@@ -237,11 +271,14 @@ async def security_bars(
     ),
     mac_client: Any = Depends(get_mac_client_optional),
     client: Any = Depends(get_client),
-) -> DataFrameResponse:
+) -> BarsResponse:
     """获取股票K线数据（MAC 协议，支持复权）。
 
-    优先走 AsyncMacClient.get_stock_kline（支持 NONE/QFQ/HFQ 复权 + QFQ 负价兜底）；
-    MAC 主机未连接时自动回退 AsyncTdxClient.get_security_bars（无复权，adjust 参数忽略）。
+    多级自动回退：MAC 优先（支持 NONE/QFQ/HFQ 复权 + QFQ 负价兜底）→
+    失败/为空转标准 TdxClient（无复权，adjust 参数忽略）→ 仍失败/为空且
+    周期为日线及以上时，最后一级自动兜底 baostock（需 ``pip install
+    easy-tdx[baostock]``，可用 ``EASY_TDX_BAOSTOCK=0`` 关闭）。兜底命中时
+    响应带 ``source: "baostock"``，否则该字段为 null。
     输出契约与旧版一致：日线返回 ``date`` 列，分钟线返回 ``datetime`` 列。
 
     ``category=MIN_120`` 为 120 分钟线：MAC 原生 ``Period.MINS × times=120``
@@ -256,37 +293,65 @@ async def security_bars(
     成交量/100，回退路径（标准 TdxClient）已 ×100 还原为股。
     """
     if category.upper() in _MIN_120_ALIASES:
-        df = await _fetch_120m(market, code, start, count, adjust, bar_time, mac_client, client)
-        return _df_resp(_attach_derived(df))
+        df120 = await _fetch_120m(market, code, start, count, adjust, bar_time, mac_client, client)
+        return _bars_resp(_attach_derived(df120), None)
 
     cat = category_from_str(category)
+    df: pd.DataFrame | None = None
+    source: str | None = None
+    last_exc: Exception | None = None
+
     if mac_client is not None:
-        period, times = period_times_from_category(cat)
-        df = await mac_client.get_stock_kline(
-            market_value_from_str(market),
-            code,
-            period,
-            start,
-            count,
-            times,
-            adjust=adjust_from_str(adjust),
-            bar_time=bar_time,
-        )
-        # daily_plus：日线及以上周期 datetime→date（枚举值无序，显式查表判定）
-        df = _normalize_mac_df(df, daily_plus=_is_daily_plus(cat))
-    else:
-        # MAC 不可用：回退标准 TdxClient（无复权），adjust 参数忽略
-        _logger.warning(
-            "/bars MAC 客户端未连接，回退标准 TdxClient（不支持复权，adjust=%s 被忽略）",
-            adjust,
-        )
-        df = await client.get_security_bars(
-            market_from_str(market), code, cat, start, count, bar_time=bar_time
-        )
-    return _df_resp(_attach_derived(df))
+        try:
+            period, times = period_times_from_category(cat)
+            df = await mac_client.get_stock_kline(
+                market_value_from_str(market),
+                code,
+                period,
+                start,
+                count,
+                times,
+                adjust=adjust_from_str(adjust),
+                bar_time=bar_time,
+            )
+            # daily_plus：日线及以上周期 datetime→date（枚举值无序，显式查表判定）
+            df = _normalize_mac_df(df, daily_plus=_is_daily_plus(cat))
+        except Exception as exc:  # noqa: BLE001 — 降级到标准客户端，不中断
+            last_exc = exc
+            df = None
+            _logger.warning("/bars MAC 获取失败，转标准 TdxClient (%s%s): %s", market, code, exc)
+    if df is None or df.empty:
+        if mac_client is None:
+            _logger.warning(
+                "/bars MAC 客户端未连接，回退标准 TdxClient（不支持复权，adjust=%s 被忽略）",
+                adjust,
+            )
+        elif df is not None and df.empty:
+            # MAC 抛异常的情况已在 except 分支记录
+            _logger.info("/bars MAC 返回空，转标准 TdxClient (%s%s)", market, code)
+        try:
+            df = await client.get_security_bars(
+                market_from_str(market), code, cat, start, count, bar_time=bar_time
+            )
+        except Exception as exc:  # noqa: BLE001 — 降级到 baostock，不中断
+            last_exc = exc
+            df = None
+            _logger.warning("/bars 标准 TdxClient 获取失败 (%s%s): %s", market, code, exc)
+
+    if df is None or df.empty:
+        bdf, bsource = await _baostock_last_resort(market, code, category, start, count, adjust)
+        if bdf is not None:
+            df, source = bdf, bsource
+
+    if df is None:
+        # TDX 两级都抛了异常且兜底不可用：维持原错误语义（503/500）
+        if last_exc is not None:
+            raise last_exc
+        df = pd.DataFrame()
+    return _bars_resp(_attach_derived(df), source)
 
 
-@router.get("/bars/index", response_model=DataFrameResponse)
+@router.get("/bars/index", response_model=BarsResponse)
 async def index_bars(
     market: str = Query(..., description="市场: SZ, SH"),
     code: str = Query(..., min_length=6, max_length=6),
@@ -297,19 +362,44 @@ async def index_bars(
         "start", description="时间戳: start=bar开始时间(默认) / end=bar结束时间(对齐Tushare)"
     ),
     client: Any = Depends(get_client),
-) -> DataFrameResponse:
+) -> BarsResponse:
     """获取指数K线数据。
 
+    指数K线并非所有 TDX 服务器都提供：失败/为空时自动兜底 baostock
+    （仅日线及以上，见 /bars 说明），命中时响应带 ``source: "baostock"``。
+
     vol 单位：日线/周线/月线/季线/年线 = 成交量(手)（周及以上周期服务端
     原样返回真实成交量/100，已 ×100 还原）；**分钟线协议不提供成交量**
     （报文中该字段实为成交额/100），vol 为 ``null``，请勿当作成交量使用。
 
     每根 bar 同样附带 ``pre_close/change/change_pct/amplitude_pct`` 衍生字段。
     """
-    df = await client.get_index_bars(
-        market_from_str(market), code, category_from_str(category), start, count, bar_time=bar_time
-    )
-    return _df_resp(_attach_derived(df))
+    df: pd.DataFrame | None = None
+    source: str | None = None
+    last_exc: Exception | None = None
+    try:
+        df = await client.get_index_bars(
+            market_from_str(market),
+            code,
+            category_from_str(category),
+            start,
+            count,
+            bar_time=bar_time,
+        )
+    except Exception as exc:  # noqa: BLE001 — 降级到 baostock，不中断
+        last_exc = exc
+        _logger.warning("/bars/index TdxClient 获取失败 (%s%s): %s", market, code, exc)
+
+    if df is None or df.empty:
+        bdf, bsource = await _baostock_last_resort(market, code, category, start, count, "QFQ")
+        if bdf is not None:
+            df, source = bdf, bsource
+
+    if df is None:
+        if last_exc is not None:
+            raise last_exc
+        df = pd.DataFrame()
+    return _bars_resp(_attach_derived(df), source)
 
 
 @router.get("/minute", response_model=DataFrameResponse)
diff --git a/src/easy_tdx/web/schemas.py b/src/easy_tdx/web/schemas.py
index d3d3752..1bd3e89 100644
--- a/src/easy_tdx/web/schemas.py
+++ b/src/easy_tdx/web/schemas.py
@@ -124,6 +124,18 @@ class DataFrameResponse(BaseModel):
         return cls(data=[], count=0)
 
 
+class BarsResponse(DataFrameResponse):
+    """K 线响应。``source`` 非 None 表示数据来自自动兜底源（如 baostock，
+    TDX 全部路径失败时启用）——口径透明：调用方可据此展示数据来源。"""
+
+    source: str | None = None
+
+    @classmethod
+    def from_dataframe(cls, df: Any) -> BarsResponse:
+        resp = DataFrameResponse.from_dataframe(df)
+        return cls(data=resp.data, count=resp.count)
+
+
 class DictResponse(BaseModel):
     """通用 dict 响应（用于非 DataFrame 返回值）。"""
 
diff --git a/tests/unit/test_baostock_source.py b/tests/unit/test_baostock_source.py
new file mode 100644
index 0000000..e24e3c2
--- /dev/null
+++ b/tests/unit/test_baostock_source.py
@@ -0,0 +1,284 @@
+"""baostock 自动兜底数据源单测（离线，注入假 baostock 模块）。
+
+覆盖：参数映射（代码/周期/复权）、offset 切片语义、停牌日剔除、
+可用性门控（环境变量 / 未安装）、/bars 与 /bars/index 的端到端兜底、
+TDX 正常时绝不触发兜底。
+"""
+
+from __future__ import annotations
+
+import sys
+import types
+
+import pandas as pd
+import pytest
+
+# ---------------------------------------------------------------------------
+# 假 baostock 模块
+# ---------------------------------------------------------------------------
+
+
+class _FakeLoginResult:
+    error_code = "0"
+    error_msg = ""
+
+
+class _FakeResultData:
+    def __init__(self, rows: list[list[str]]):
+        self._rows = rows
+        self._i = 0
+        self.error_code = "0"
+        self.error_msg = ""
+
+    def next(self) -> bool:
+        if self._i < len(self._rows):
+            self._i += 1
+            return True
+        return False
+
+    def get_row_data(self) -> list[str]:
+        return self._rows[self._i - 1]
+
+
+def _fake_rows(n: int, end: str = "2026-09-04") -> list[list[str]]:
+    """n 个交易日的日线行：date, open, high, low, close, volume, amount, tradestatus。"""
+    dates = pd.bdate_range(end=end, periods=n).strftime("%Y-%m-%d")
+    return [[d, "10.0", "11.0", "9.5", "10.5", "100000", "1050000.0", "1"] for d in dates]
+
+
+def _install_fake_bs(
+    rows: list[list[str]] | None,
+    captured: dict,
+    *,
+    query_error: bool = False,
+) -> types.ModuleType:
+    mod = types.ModuleType("baostock")
+
+    def _login():  # type: ignore[no-untyped-def]
+        captured["login"] = captured.get("login", 0) + 1
+        return _FakeLoginResult()
+
+    mod.login = _login  # type: ignore[attr-defined]
+    mod.logout = lambda: None  # type: ignore[attr-defined]
+
+    def query_history_k_data_plus(**kwargs):  # type: ignore[no-untyped-def]
+        captured.update(kwargs)
+        captured["calls"] = captured.get("calls", 0) + 1
+        if query_error:
+            result = _FakeResultData([])
+            result.error_code = "10001"
+            result.error_msg = "网络异常"
+            return result
+        return _FakeResultData(rows or [])
+
+    mod.query_history_k_data_plus = query_history_k_data_plus  # type: ignore[attr-defined]
+    sys.modules["baostock"] = mod
+    return mod
+
+
+@pytest.fixture()
+def fake_bs(monkeypatch: pytest.MonkeyPatch):
+    """注入假模块 + 复位模块级登录态；测试结束移除。"""
+    from easy_tdx.sources import baostock as bs_source
+
+    captured: dict = {}
+    monkeypatch.setattr(bs_source, "_logged_in", False)
+    monkeypatch.delenv(bs_source.BAOSTOCK_DISABLE_ENV, raising=False)
+    _install_fake_bs(_fake_rows(10), captured)
+    yield captured
+    sys.modules.pop("baostock", None)
+
+
+# ---------------------------------------------------------------------------
+# 源模块行为
+# ---------------------------------------------------------------------------
+
+
+def test_fetch_maps_args_and_matches_contract(fake_bs):
+    """代码/周期/复权映射正确；输出列序与 vol 单位（股，不换算）符合 /bars 契约。"""
+    from easy_tdx.sources import baostock as bs_source
+
+    df = bs_source.fetch_bars("SH", "600519", "DAY", 0, 5, "QFQ")
+    assert df is not None and len(df) == 5
+    assert list(df.columns) == ["date", "open", "close", "high", "low", "vol", "amount"]
+    assert fake_bs["code"] == "sh.600519"
+    assert fake_bs["frequency"] == "d"
+    assert fake_bs["adjustflag"] == "2"  # QFQ
+    # 时间升序，最后一根是最新交易日
+    assert df["date"].iloc[-1] == pd.Timestamp("2026-09-04")
+    assert (df["vol"] == 100000).all()  # baostock volume=股，与 /bars 契约一致，不换算
+
+
+def test_offset_slice_matches_tdx_semantics(fake_bs):
+    """start=跳过最新 N 根：30 根里 start=5, count=10 → 返回第 16~25 根。"""
+    from easy_tdx.sources import baostock as bs_source
+
+    _install_fake_bs(_fake_rows(30), fake_bs)
+    df = bs_source.fetch_bars("SZ", "000001", "DAY", 5, 10, "QFQ")
+    assert df is not None and len(df) == 10
+    dates = df["date"].dt.strftime("%Y-%m-%d").tolist()
+    expected = pd.bdate_range(end="2026-09-04", periods=30).strftime("%Y-%m-%d").tolist()
+    assert dates[0] == expected[15]
+    assert dates[-1] == expected[24]
+
+
+def test_suspension_rows_dropped(fake_bs):
+    """停牌日（tradestatus=0 / volume=0）剔除，对齐通达信 K 线口径。"""
+    rows = _fake_rows(6)
+    rows[2] = [rows[2][0], "0", "0", "0", "0", "0", "0", "0"]  # 停牌日
+    _install_fake_bs(rows, fake_bs)
+    from easy_tdx.sources import baostock as bs_source
+
+    df = bs_source.fetch_bars("SZ", "000001", "DAY", 0, 10, "QFQ")
+    assert df is not None and len(df) == 5
+    assert (df["vol"] > 0).all()
+
+
+def test_disabled_via_env(fake_bs, monkeypatch: pytest.MonkeyPatch):
+    """EASY_TDX_BAOSTOCK=0 显式关闭：不安装也不调用。"""
+    from easy_tdx.sources import baostock as bs_source
+
+    monkeypatch.setenv(bs_source.BAOSTOCK_DISABLE_ENV, "0")
+    assert bs_source.is_enabled() is False
+    assert bs_source.fetch_bars("SH", "600519", "DAY", 0, 5, "QFQ") is None
+    assert "login" not in fake_bs
+
+
+def test_missing_module_returns_none(monkeypatch: pytest.MonkeyPatch):
+    """未安装 baostock：静默返回 None（兜底环自动关闭）。"""
+    monkeypatch.delenv("EASY_TDX_BAOSTOCK", raising=False)
+    monkeypatch.setitem(sys.modules, "baostock", None)  # import 时抛 ImportError
+    from easy_tdx.sources import baostock as bs_source
+
+    assert bs_source.is_enabled() is False
+    assert bs_source.fetch_bars("SH", "600519", "DAY", 0, 5, "QFQ") is None
+
+
+def test_unsupported_inputs(fake_bs):
+    """BJ 市场 / 分钟线周期 / 非法复权 / 超大窗口：不适用即 None。"""
+    from easy_tdx.sources import baostock as bs_source
+
+    assert bs_source.fetch_bars("BJ", "430047", "DAY", 0, 5, "QFQ") is None
+    assert bs_source.fetch_bars("SH", "600519", "MIN_5", 0, 5, "QFQ") is None
+    assert bs_source.fetch_bars("SH", "600519", "SEASON", 0, 5, "QFQ") is None
+    assert bs_source.fetch_bars("SH", "600519", "DAY", 0, 5, "FOO") is None
+    assert bs_source.fetch_bars("SH", "600519", "DAY", 99999, 800, "QFQ") is None
+    assert "calls" not in fake_bs
+
+
+def test_query_error_returns_none(fake_bs):
+    """baostock 查询失败：返回 None 且不向上抛（兜底失败不改变原错误路径）。"""
+    _install_fake_bs([], fake_bs, query_error=True)
+    from easy_tdx.sources import baostock as bs_source
+
+    assert bs_source.fetch_bars("SH", "600519", "DAY", 0, 5, "QFQ") is None
+
+
+# ---------------------------------------------------------------------------
+# /bars 与 /bars/index 端到端兜底
+# ---------------------------------------------------------------------------
+
+
+def _bars_app(mac_client, tdx_client):
+    from fastapi import FastAPI
+
+    from easy_tdx.web.errors import register_exception_handlers
+    from easy_tdx.web.routers import bars
+
+    app = FastAPI()
+    register_exception_handlers(app)
+    app.include_router(bars.router, prefix="/api/v1")
+    app.state.tdx_client = tdx_client
+    app.state.mac_client = mac_client
+    return app
+
+
+class _RaisingMac:
+    async def get_stock_kline(self, *args, **kwargs):  # noqa: ANN002, ANN003
+        raise RuntimeError("MAC 连接失败")
+
+
+class _RaisingTdx:
+    async def get_security_bars(self, *args, **kwargs):  # noqa: ANN002, ANN003
+        raise RuntimeError("标准协议连接失败")
+
+    async def get_index_bars(self, *args, **kwargs):  # noqa: ANN002, ANN003
+        raise RuntimeError("标准协议连接失败")
+
+
+class _OkMac:
+    async def get_stock_kline(self, *args, **kwargs):  # noqa: ANN002, ANN003
+        return pd.DataFrame(
+            {
+                "datetime": pd.bdate_range(end="2026-09-04", periods=5),
+                "open": [10.0] * 5,
+                "close": [10.5] * 5,
+                "high": [11.0] * 5,
+                "low": [9.5] * 5,
+                "vol": [100000] * 5,
+                "amount": [1050000.0] * 5,
+                "float_shares": [0.0] * 5,
+            }
+        )
+
+
+def test_bars_endpoint_falls_back_to_baostock(fake_bs, monkeypatch: pytest.MonkeyPatch):
+    """MAC 与标准协议都失败 → baostock 兜底命中，响应带 source 字段。"""
+    pytest.importorskip("fastapi")
+    from fastapi.testclient import TestClient
+
+    _install_fake_bs(_fake_rows(10), fake_bs)
+    with TestClient(_bars_app(_RaisingMac(), _RaisingTdx())) as client:
+        resp = client.get("/api/v1/bars", params={"market": "SH", "code": "600519"})
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["source"] == "baostock"
+    assert body["count"] == 10
+    assert "date" in body["data"][0]
+    assert "change_pct" in body["data"][0]
+
+
+def test_bars_endpoint_tdx_ok_never_calls_baostock(fake_bs):
+    """TDX 正常出数时兜底绝不触发：source 为 None，baostock 零调用。"""
+    pytest.importorskip("fastapi")
+    from fastapi.testclient import TestClient
+
+    with TestClient(_bars_app(_OkMac(), _RaisingTdx())) as client:
+        resp = client.get("/api/v1/bars", params={"market": "SH", "code": "600519"})
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["source"] is None
+    assert body["count"] == 5
+    assert "login" not in fake_bs
+
+
+def test_bars_endpoint_no_fallback_available_keeps_error(fake_bs, monkeypatch: pytest.MonkeyPatch):
+    """TDX 全败且兜底不可用：维持原错误语义（500），不返回空数据伪装成功。"""
+    pytest.importorskip("fastapi")
+    from fastapi.testclient import TestClient
+
+    monkeypatch.delenv("EASY_TDX_BAOSTOCK", raising=False)
+    monkeypatch.setitem(sys.modules, "baostock", None)
+    # raise_server_exceptions=False：模拟生产环境由服务端中间件返回 500
+    with TestClient(
+        _bars_app(_RaisingMac(), _RaisingTdx()), raise_server_exceptions=False
+    ) as client:
+        resp = client.get("/api/v1/bars", params={"market": "SH", "code": "600519"})
+    assert resp.status_code == 500
+    assert "连接失败" in resp.json()["detail"]
+
+
+def test_index_endpoint_falls_back_to_baostock(fake_bs):
+    """/bars/index：TDX 失败 → baostock 兜底（指数代码同格式）。"""
+    pytest.importorskip("fastapi")
+    from fastapi.testclient import TestClient
+
+    _install_fake_bs(_fake_rows(10), fake_bs)
+    with TestClient(_bars_app(None, _RaisingTdx())) as client:
+        resp = client.get(
+            "/api/v1/bars/index", params={"market": "SH", "code": "000001", "category": "DAY"}
+        )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["source"] == "baostock"
+    assert fake_bs["code"] == "sh.000001"