fix(data): reject stale yfinance OHLCV instead of reporting wrong prices

yfinance intermittently returns a year-old partial frame (e.g. June 2025 rows
for a June 2026 request) that still has rows and a Close, so it passed the
empty-check and silently fed a wrong close price and indicators into the report
(#1021). Add a freshness guard that rejects a frame whose latest row is far
older than the requested date, on both the raw OHLCV path and the indicator
path. It raises the existing NoMarketDataError with a stale-specific detail, so
the vendor router's try-next-vendor and single unavailable-signal handling apply
unchanged; the sentinel now surfaces that detail so the agent reports the
specific reason rather than fabricating a value.

tests/test_yfinance_stale_ohlcv_guard.py

@@ -0,0 +1,113 @@
+"""Stale OHLCV guard (#1021): a vendor returning a year-old partial frame must
+be rejected, not fed into the report as if it were current.
+
+The guard raises NoMarketDataError with a stale-specific detail, so the router's
+existing try-next-vendor + single-sentinel handling applies and the sentinel
+surfaces the reason.
+"""
+import copy
+import unittest
+from unittest import mock
+
+import pandas as pd
+import pytest
+
+import tradingagents.dataflows.config as config_module
+import tradingagents.dataflows.y_finance as y_finance
+import tradingagents.default_config as default_config
+from tradingagents.dataflows import interface
+from tradingagents.dataflows.config import set_config
+from tradingagents.dataflows.stockstats_utils import _assert_ohlcv_not_stale
+from tradingagents.dataflows.symbol_utils import NoMarketDataError
+
+
+def _frame(date):
+    return pd.DataFrame(
+        {
+            "Date": [pd.Timestamp(date)],
+            "Open": [330.0],
+            "High": [332.0],
+            "Low": [328.0],
+            "Close": [330.58],
+            "Volume": [1_000_000],
+        }
+    )
+
+
+@pytest.mark.unit
+class StaleGuardUnitTests(unittest.TestCase):
+    def test_recent_prior_trading_day_is_accepted(self):
+        # 1 day before curr_date — well within the freshness window.
+        _assert_ohlcv_not_stale(_frame("2026-06-10"), "2026-06-11", "CB")
+
+    def test_year_old_row_is_rejected_with_detail(self):
+        with self.assertRaises(NoMarketDataError) as ctx:
+            _assert_ohlcv_not_stale(_frame("2025-06-11"), "2026-06-11", "CB", "CB")
+        msg = str(ctx.exception)
+        self.assertIn("2025-06-11", msg)
+        self.assertIn("2026-06-11", msg)
+        self.assertIn("stale", msg)
+
+    def test_empty_frame_is_left_to_caller(self):
+        # Empty is a no-data condition handled elsewhere, not a staleness one.
+        _assert_ohlcv_not_stale(
+            pd.DataFrame(columns=["Date", "Close"]), "2026-06-11", "X"
+        )
+
+    def test_long_holiday_gap_within_threshold_is_accepted(self):
+        _assert_ohlcv_not_stale(_frame("2026-06-02"), "2026-06-11", "X")  # 9 days
+
+
+@pytest.mark.unit
+class StaleGuardPropagationTests(unittest.TestCase):
+    def test_get_yfin_data_online_raises_on_stale_frame(self):
+        stale = pd.DataFrame(
+            {
+                "Open": [280.0], "High": [286.0], "Low": [278.0],
+                "Close": [284.45], "Volume": [1_000_000],
+            },
+            index=pd.DatetimeIndex([pd.Timestamp("2025-06-11")], name="Date"),
+        )
+
+        class DummyTicker:
+            def __init__(self, symbol):
+                pass
+
+            def history(self, start, end):
+                return stale
+
+        with mock.patch.object(y_finance.yf, "Ticker", DummyTicker), \
+                self.assertRaises(NoMarketDataError):
+            y_finance.get_YFin_data_online("CB", "2026-06-01", "2026-06-11")
+
+
+@pytest.mark.unit
+class StaleGuardRoutingTests(unittest.TestCase):
+    def setUp(self):
+        config_module._config = copy.deepcopy(default_config.DEFAULT_CONFIG)
+
+    def tearDown(self):
+        config_module._config = copy.deepcopy(default_config.DEFAULT_CONFIG)
+
+    def test_router_sentinel_surfaces_stale_reason(self):
+        set_config({"data_vendors": {"core_stock_apis": "yfinance"}})
+
+        def _stale(symbol, *a, **k):
+            raise NoMarketDataError(
+                symbol, symbol, "latest row is 2025-06-11, 365 days before ... (stale)"
+            )
+
+        with mock.patch.dict(
+            interface.VENDOR_METHODS,
+            {"get_stock_data": {"yfinance": _stale}},
+            clear=False,
+        ):
+            out = interface.route_to_vendor(
+                "get_stock_data", "CB", "2026-06-01", "2026-06-11"
+            )
+        self.assertIn("NO_DATA_AVAILABLE", out)
+        self.assertIn("stale", out)  # the typed detail is surfaced to the agent
+
+
+if __name__ == "__main__":
+    unittest.main()