diff --git a/app/models/alerts.py b/app/models/alerts.py
index 18152b1..c749a56 100644
--- a/app/models/alerts.py
+++ b/app/models/alerts.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import math
 from dataclasses import asdict, dataclass
 from pathlib import Path
 from typing import Any
@@ -25,6 +26,22 @@ class AlertEvent:
     updated_at: str
     email_alerts_enabled: bool
 
+    def __post_init__(self) -> None:
+        for field_name in ("severity", "message", "updated_at"):
+            value = getattr(self, field_name)
+            if not isinstance(value, str):
+                raise TypeError(f"{field_name} must be a string")
+        for field_name in ("ltv_ratio", "warning_threshold", "critical_threshold", "spot_price"):
+            value = getattr(self, field_name)
+            if isinstance(value, bool) or not isinstance(value, (int, float)):
+                raise TypeError(f"{field_name} must be numeric")
+            numeric_value = float(value)
+            if not math.isfinite(numeric_value):
+                raise ValueError(f"{field_name} must be finite")
+            setattr(self, field_name, numeric_value)
+        if not isinstance(self.email_alerts_enabled, bool):
+            raise TypeError("email_alerts_enabled must be a bool")
+
     def to_dict(self) -> dict[str, Any]:
         return asdict(self)
 
diff --git a/tests/test_alerts.py b/tests/test_alerts.py
index 84e0a6d..ef64653 100644
--- a/tests/test_alerts.py
+++ b/tests/test_alerts.py
@@ -188,6 +188,15 @@ def test_alert_history_repository_raises_on_non_list_payload(tmp_path: Path) ->
         repository.load()
 
 
+def test_alert_history_repository_raises_on_non_object_entry(tmp_path: Path) -> None:
+    history_path = tmp_path / "alert_history.json"
+    history_path.write_text('["bad entry"]', encoding="utf-8")
+    repository = AlertHistoryRepository(history_path=history_path)
+
+    with pytest.raises(AlertHistoryLoadError, match="Alert history entry 0 must be an object"):
+        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")
@@ -197,6 +206,20 @@ def test_alert_history_repository_raises_on_invalid_list_entry(tmp_path: Path) -
         repository.load()
 
 
+def test_alert_history_repository_raises_on_wrong_typed_fields(tmp_path: Path) -> None:
+    history_path = tmp_path / "alert_history.json"
+    history_path.write_text(
+        '[{"severity": "warning", "message": "bad", "ltv_ratio": "oops", "warning_threshold": 0.7, '
+        '"critical_threshold": 0.75, "spot_price": 215.0, "updated_at": "2026-03-24T12:00:00Z", '
+        '"email_alerts_enabled": false}]',
+        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(