fix(dataflows): make the Yahoo news window UTC and end-exclusive

- the upper bound was inclusive, so an article stamped exactly midnight after
  end_date leaked into a historical run
- flat epoch timestamps were parsed in host-local time and offset-aware stamps had
  tzinfo stripped without converting, making filtering machine-dependent
- normalize every operand to UTC and use a half-open [start, end + 1 day) #1126

tests/test_news_lookahead.py

@@ -2,10 +2,11 @@
 into a historical window.
 
 Regressions for #992 (flat articles bypassed the date filter), #1007 (global
-news injected future articles), #993 (empty-after-filter returned a blank body).
+news injected future articles), #993 (empty-after-filter returned a blank body),
+and #1126 (inclusive upper bound leaked the midnight-after article; host-local
+timestamp parsing made filtering machine-dependent).
 """
-import time
-from datetime import datetime
+from datetime import datetime, timezone
 
 import pytest
 
@@ -13,17 +14,20 @@ import tradingagents.dataflows.yfinance_news as ynews
 
 
 def _epoch(date_str):
-    return int(time.mktime(datetime.strptime(date_str, "%Y-%m-%d").timetuple()))
+    """Epoch seconds for UTC midnight of ``date_str`` (host-timezone independent)."""
+    return int(datetime.strptime(date_str, "%Y-%m-%d").replace(tzinfo=timezone.utc).timestamp())
 
 
 @pytest.mark.unit
 def test_flat_article_publish_time_is_parsed():
     # #992: flat articles now carry a pub_date (was always None -> unfilterable).
+    # #1126: parsed as UTC-aware, so the date can't shift with the host timezone.
     data = ynews._extract_article_data(
         {"title": "X", "publisher": "P", "link": "l", "providerPublishTime": _epoch("2025-05-09")}
     )
     assert data["pub_date"] is not None
-    assert data["pub_date"].strftime("%Y-%m-%d") == "2025-05-09"
+    assert data["pub_date"].tzinfo is not None
+    assert data["pub_date"] == datetime(2025, 5, 9, tzinfo=timezone.utc)
 
 
 @pytest.mark.unit
@@ -40,9 +44,30 @@ def test_window_excludes_future_and_undated_in_backtest():
 @pytest.mark.unit
 def test_window_keeps_undated_in_live_window():
     # Live window (reaches today): undated articles can't be "future", so keep them.
-    start = datetime.now()
-    end = datetime.now()
-    assert ynews._in_news_window(None, start, end) is True
+    now = datetime.now(timezone.utc)
+    assert ynews._in_news_window(None, now, now) is True
+
+
+@pytest.mark.unit
+def test_upper_bound_is_exclusive():
+    # #1126: an article stamped exactly midnight AFTER end_date leaked in under
+    # the old inclusive bound; the whole of end_date itself must still be kept.
+    start = datetime(2025, 5, 1)
+    end = datetime(2025, 5, 9)
+    midnight_after = datetime(2025, 5, 10, 0, 0, 0, tzinfo=timezone.utc)
+    last_moment = datetime(2025, 5, 9, 23, 59, 59, tzinfo=timezone.utc)
+    assert ynews._in_news_window(midnight_after, start, end) is False
+    assert ynews._in_news_window(last_moment, start, end) is True
+
+
+@pytest.mark.unit
+def test_offset_aware_timestamp_is_converted_not_truncated():
+    # #1126: 2025-05-10T01:00+05:00 is really 2025-05-09T20:00Z -> inside the
+    # window. Stripping tzinfo (old behavior) misread it as 05-10 and dropped it.
+    start = datetime(2025, 5, 1)
+    end = datetime(2025, 5, 9)
+    aware = datetime.fromisoformat("2025-05-10T01:00:00+05:00")
+    assert ynews._in_news_window(aware, start, end) is True
 
 
 @pytest.mark.unit