diff --git a/api/services/billing_service.py b/api/services/billing_service.py
index 5ab47c799a..70d4ce1ee6 100644
--- a/api/services/billing_service.py
+++ b/api/services/billing_service.py
@@ -335,7 +335,11 @@ class BillingService:
                         # Redis returns bytes, decode to string and parse JSON
                         json_str = cached_value.decode("utf-8") if isinstance(cached_value, bytes) else cached_value
                         plan_dict = json.loads(json_str)
+                        # NOTE (hj24): New billing versions may return timestamp as str, and validate_python
+                        # in non-strict mode will coerce it to the expected int type.
+                        # To preserve compatibility, always keep non-strict mode here and avoid strict mode.
                         subscription_plan = subscription_adapter.validate_python(plan_dict)
+                        # NOTE END
                         tenant_plans[tenant_id] = subscription_plan
                     except Exception:
                         logger.exception(
diff --git a/api/tests/unit_tests/services/test_billing_service.py b/api/tests/unit_tests/services/test_billing_service.py
index eecb3c7672..316381f0ca 100644
--- a/api/tests/unit_tests/services/test_billing_service.py
+++ b/api/tests/unit_tests/services/test_billing_service.py
@@ -1303,6 +1303,24 @@ class TestBillingServiceSubscriptionOperations:
         # Assert
         assert result == {}
 
+    def test_get_plan_bulk_converts_string_expiration_date_to_int(self, mock_send_request):
+        """Test bulk plan retrieval converts string expiration_date to int."""
+        # Arrange
+        tenant_ids = ["tenant-1"]
+        mock_send_request.return_value = {
+            "data": {
+                "tenant-1": {"plan": "sandbox", "expiration_date": "1735689600"},
+            }
+        }
+
+        # Act
+        result = BillingService.get_plan_bulk(tenant_ids)
+
+        # Assert
+        assert "tenant-1" in result
+        assert isinstance(result["tenant-1"]["expiration_date"], int)
+        assert result["tenant-1"]["expiration_date"] == 1735689600
+
     def test_get_plan_bulk_with_invalid_tenant_plan_skipped(self, mock_send_request):
         """Test bulk plan retrieval when one tenant has invalid plan data (should skip that tenant)."""
         # Arrange