fix(alerts): treat naive detected_at datetimes as UTC before timezone conversion

elementary/monitor/alerts/alert.py

@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime, timezone as dt_timezone
 from typing import Dict, List, Optional
 
 from dateutil import tz
@@ -58,8 +58,16 @@ def __init__(
         self.detected_at = None
         if detected_at is not None:
             try:
-                self.detected_at_utc = detected_at
-                self.detected_at = detected_at.astimezone(
+                # Timestamps from the DB are stored as UTC but arrive as naive
+                # datetimes.  Python's astimezone() interprets a naive datetime
+                # as *local* time, so we must attach UTC tzinfo first.
+                detected_at_utc_aware = (
+                    detected_at.replace(tzinfo=dt_timezone.utc)
+                    if detected_at.tzinfo is None
+                    else detected_at
+                )
+                self.detected_at_utc = detected_at_utc_aware
+                self.detected_at = detected_at_utc_aware.astimezone(
                     tz.gettz(timezone) if timezone else tz.tzlocal()
                 )
             except Exception:

elementary/monitor/data_monitoring/schema.py

@@ -22,6 +22,7 @@ class Status(str, Enum):
     ERROR = "error"
     RUNTIME_ERROR = "runtime error"
     PARTIAL_SUCCESS = "partial success"
+    REUSED = "reused"
 
 
 class ResourceType(str, Enum):

tests/unit/alerts/test_alert_detected_at_timezone.py

@@ -0,0 +1,58 @@
+"""
+Regression tests for issue #2304:
+AlertModel must treat naive detected_at values as UTC, not local time.
+"""
+from datetime import datetime, timezone as dt_timezone
+
+import pytest
+
+from elementary.monitor.alerts.alert import AlertModel
+
+
+def _make_alert(detected_at, timezone=None):
+    return AlertModel(
+        id="test",
+        alert_class_id="cls",
+        detected_at=detected_at,
+        timezone=timezone,
+    )
+
+
+def test_naive_detected_at_treated_as_utc_not_local():
+    """A naive datetime must be interpreted as UTC, not as local wall-clock time.
+
+    Regression: alert.detected_at_utc must equal the naive input with UTC tzinfo
+    attached, regardless of the process timezone.
+    """
+    naive_utc = datetime(2026, 7, 22, 9, 8, 22)
+    alert = _make_alert(naive_utc, timezone="Asia/Tokyo")
+
+    expected_utc = naive_utc.replace(tzinfo=dt_timezone.utc)
+    assert alert.detected_at_utc == expected_utc, (
+        "detected_at_utc must be the naive input with UTC tzinfo, "
+        f"got {alert.detected_at_utc!r}"
+    )
+
+    # After conversion to JST (+09:00) the hour must be 18 (9 + 9)
+    assert alert.detected_at is not None
+    assert alert.detected_at.hour == 18, (
+        "09:08:22 UTC converted to JST (+09:00) must be 18:08:22, "
+        f"got {alert.detected_at}"
+    )
+
+
+def test_aware_detected_at_is_not_re_interpreted():
+    """An already-aware datetime must be used as-is (no double-conversion)."""
+    aware_utc = datetime(2026, 7, 22, 9, 8, 22, tzinfo=dt_timezone.utc)
+    alert = _make_alert(aware_utc, timezone="Asia/Tokyo")
+
+    assert alert.detected_at_utc == aware_utc
+    assert alert.detected_at is not None
+    assert alert.detected_at.hour == 18
+
+
+def test_none_detected_at_leaves_fields_none():
+    alert = _make_alert(None)
+    assert alert.detected_at is None
+    assert alert.detected_at_utc is None
+    assert alert.detected_at_str == "N/A"

tests/unit/monitor/api/alerts/test_alert_filters.py

@@ -1004,3 +1004,49 @@ def test_multi_filters():
         "test_alert_1",
         "test_alert_2",
     ]
+
+
+def test_reused_status_does_not_crash_filter_alerts():
+    """Regression test for dbt State 'reused' status crashing filter_alerts.
+
+    dbt State (v1.11+) introduces a 'reused' run status for models skipped
+    because their state hasn't changed. When such an alert reached
+    filter_alerts the call to Status('reused') raised ValueError because
+    'reused' was not a member of the Status enum.
+    """
+    reused_alert = PendingAlertSchema(
+        id="reused_model_alert",
+        alert_class_id="elementary.model_id_reused",
+        type=AlertTypes.MODEL,
+        detected_at=datetime(2022, 10, 10, 10, 0, 0),
+        created_at=datetime(2022, 10, 10, 10, 0, 0),
+        updated_at=datetime(2022, 10, 10, 10, 0, 0),
+        status=AlertStatus.PENDING,
+        data=ModelAlertDataSchema(
+            id="reused_1",
+            alert_class_id="elementary.model_id_reused",
+            model_unique_id="elementary.model_id_reused",
+            alias="reused_model",
+            path="my/path",
+            original_path="",
+            materialization="table",
+            message="",
+            full_refresh=False,
+            detected_at=datetime(2022, 10, 10, 10, 0, 0),
+            tags=[],
+            model_meta={},
+            status="reused",
+            database_name="test_db",
+            schema_name="test_schema",
+            resource_type=ResourceType.MODEL,
+        ),
+    )
+
+    # Must not raise ValueError("'reused' is not a valid Status").
+    # The alert is correctly filtered out by the default status filter (which
+    # only surfaces FAIL / ERROR / RUNTIME_ERROR / WARN).
+    result = filter_alerts([reused_alert], FiltersSchema())
+    assert len(result) == 0
+
+    # Status enum must include REUSED
+    assert Status("reused") is Status.REUSED