fix(yahoo): read Yahoo's answer that a window has no prices as no data

- a chart with no prices, or Yahoo saying the data does not exist, is an empty answer; yfinance's same error for an error status or a service failure, and a missing time zone, stay unavailable

tests/test_yahoo_rate_limit.py

@@ -240,3 +240,45 @@ def test_yahoo_answering_not_found_is_no_data(yahoo, call):
     except NoMarketDataError:
         return
     assert out.startswith("No insider transactions"), out   # an empty filing list is not an error
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize("debug, reason, absent", [
+    pytest.param(" (1d 2026-09-26 -> 2026-09-27)", None, True, id="a_chart_with_no_prices"),
+    pytest.param(" (1d 1970-01-01 -> 1970-02-01)", "Data doesn't exist for startDate = 18000, endDate = 2696400",
+                 True, id="yahoo_says_the_data_does_not_exist"),
+    pytest.param(" (1d 2026-09-21 -> 2026-09-25)(Yahoo status_code = 503)", None, False, id="an_http_error"),
+    pytest.param(" (1d 2026-09-21 -> 2026-09-25)", "Service temporarily unavailable", False,
+                 id="yahoo_reports_a_service_failure"),
+])
+def test_only_yahoo_saying_a_window_has_no_prices_is_no_data(yahoo, debug, reason, absent):
+    """yfinance raises YFPricesMissingError both when Yahoo answered with no prices
+    and when its answer was an error; only the first is a fact about the symbol."""
+    from yfinance.exceptions import YFPricesMissingError
+
+    from tradingagents.dataflows.errors import NoMarketDataError
+    from tradingagents.dataflows.vendors.yahoo import market
+
+    def no_prices(self, **kwargs):
+        raise YFPricesMissingError("AAPL", debug, yahoo_reason=reason)
+
+    yahoo.setattr(yf.Ticker, "history", no_prices)
+
+    with pytest.raises(NoMarketDataError if absent else VendorUnavailableError):
+        market.get_YFin_data_online("AAPL", "2026-09-21", "2026-09-25")
+
+
+@pytest.mark.unit
+def test_a_missing_time_zone_is_not_taken_for_an_answer(yahoo):
+    """yfinance reports a failed time-zone lookup the same way as a symbol without one."""
+    from yfinance.exceptions import YFTzMissingError
+
+    from tradingagents.dataflows.vendors.yahoo import market
+
+    def no_tz(self, **kwargs):
+        raise YFTzMissingError("AAPL")
+
+    yahoo.setattr(yf.Ticker, "history", no_tz)
+
+    with pytest.raises(VendorUnavailableError):
+        market.get_YFin_data_online("AAPL", "2026-09-21", "2026-09-25")

tradingagents/dataflows/vendors/yahoo/common.py

@@ -4,7 +4,7 @@ import logging
 import time
 
 import yfinance as yf
-from yfinance.exceptions import YFRateLimitError
+from yfinance.exceptions import YFPricesMissingError, YFRateLimitError
 
 from tradingagents.dataflows.errors import NoMarketDataError, VendorUnavailableError
 from tradingagents.dataflows.net import vendor_reachable
@@ -30,8 +30,19 @@ def raise_for_empty(symbol: str, canonical: str, what: str) -> None:
 yf.config.debug.hide_exceptions = False
 
 
-def _not_found(exc: Exception) -> bool:
-    """Whether Yahoo answered that it has no such symbol (HTTP 404)."""
+def _answered_empty(exc: Exception) -> bool:
+    """Whether Yahoo answered that it has nothing: no such symbol (HTTP 404), or a
+    price window with no prices in it.
+
+    yfinance raises YFPricesMissingError for that answer and also for an answer
+    that was an error (an error status, or Yahoo describing a failure), so only
+    a chart with no prices, or Yahoo saying the data does not exist, counts.
+    A missing time zone is not an answer: yfinance reports a failed lookup the same way.
+    """
+    if isinstance(exc, YFPricesMissingError):
+        reason = exc.yahoo_reason
+        return "status_code" not in (exc.debug_info or "") and (
+            reason is None or reason.startswith("Data doesn't exist"))
     return getattr(getattr(exc, "response", None), "status_code", None) == 404
 
 
@@ -42,7 +53,7 @@ def yf_retry(func, max_retries=3, base_delay=2.0):
     retry them internally, so this wrapper retries them. A rate limit that
     outlasts the retries, or any other exception, is raised as
     VendorUnavailableError: it failed in transit and says nothing about the
-    symbol. Yahoo answering that it has no such symbol (HTTP 404) returns None,
+    symbol. Yahoo answering that it has nothing for the symbol returns None,
     an empty answer. ``func`` should build its own Ticker and make the request
     itself: a Ticker keeps a failed ``info`` fetch as done, so asking the same
     one again reads an empty profile.
@@ -60,6 +71,6 @@ def yf_retry(func, max_retries=3, base_delay=2.0):
                     f"Yahoo Finance rate limited after {max_retries} retries: {exc}"
                 ) from exc
         except Exception as exc:
-            if _not_found(exc):
+            if _answered_empty(exc):
                 return None
             raise VendorUnavailableError(f"Yahoo Finance request failed: {type(exc).__name__}") from exc