diff --git a/app/models/alerts.py b/app/models/alerts.py
index 16d9b12..18152b1 100644
--- a/app/models/alerts.py
+++ b/app/models/alerts.py
@@ -67,7 +67,18 @@ class AlertHistoryRepository:
             raise AlertHistoryLoadError(self.history_path, f"Alert history could not be read: {exc}") from exc
         if not isinstance(data, list):
             raise AlertHistoryLoadError(self.history_path, "Alert history payload must be a list")
-        return [AlertEvent.from_dict(item) for item in data if isinstance(item, dict)]
+        events: list[AlertEvent] = []
+        for index, item in enumerate(data):
+            if not isinstance(item, dict):
+                raise AlertHistoryLoadError(self.history_path, f"Alert history entry {index} must be an object")
+            try:
+                events.append(AlertEvent.from_dict(item))
+            except (TypeError, ValueError) as exc:
+                raise AlertHistoryLoadError(
+                    self.history_path,
+                    f"Alert history entry {index} is invalid: {exc}",
+                ) from exc
+        return events
 
     def save(self, events: list[AlertEvent]) -> None:
         with self.history_path.open("w") as f:
diff --git a/tests/test_alerts.py b/tests/test_alerts.py
index 7859c55..84e0a6d 100644
--- a/tests/test_alerts.py
+++ b/tests/test_alerts.py
@@ -179,6 +179,24 @@ def test_alert_history_repository_raises_on_corrupt_history_file(tmp_path: Path)
         repository.load()
 
 
+def test_alert_history_repository_raises_on_non_list_payload(tmp_path: Path) -> None:
+    history_path = tmp_path / "alert_history.json"
+    history_path.write_text('{"severity": "warning"}', encoding="utf-8")
+    repository = AlertHistoryRepository(history_path=history_path)
+
+    with pytest.raises(AlertHistoryLoadError, match="Alert history payload must be a list"):
+        repository.load()
+
+
+def test_alert_history_repository_raises_on_invalid_list_entry(tmp_path: Path) -> None:
+    history_path = tmp_path / "alert_history.json"
+    history_path.write_text('[{"severity": "warning"}]', encoding="utf-8")
+    repository = AlertHistoryRepository(history_path=history_path)
+
+    with pytest.raises(AlertHistoryLoadError, match="Alert history entry 0 is invalid"):
+        repository.load()
+
+
 def test_alert_service_marks_history_unavailable_on_corrupt_storage(alert_service: AlertService) -> None:
     alert_service.repository.history_path.write_text("{not valid json", encoding="utf-8")
     config = PortfolioConfig(
@@ -208,7 +226,7 @@ def test_alert_service_marks_history_unavailable_on_corrupt_storage(alert_servic
 
 
 def test_alert_service_preview_marks_history_unavailable_on_corrupt_storage(alert_service: AlertService) -> None:
-    alert_service.repository.history_path.write_text("{not valid json", encoding="utf-8")
+    alert_service.repository.history_path.write_text('[{"severity": "warning"}]', encoding="utf-8")
     config = PortfolioConfig(
         gold_value=215_000.0,
         entry_price=215.0,