diff --git a/tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/AlarmsViewModelTests.cs b/tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/AlarmsViewModelTests.cs
index 503ab5b3..73ac6e10 100644
--- a/tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/AlarmsViewModelTests.cs
+++ b/tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/AlarmsViewModelTests.cs
@@ -342,6 +342,47 @@ public class AlarmsViewModelTests
         message.ShouldContain("Confirm failed");
     }
 
+    /// <summary>Verifies that confirming an alarm without a ConditionNodeId is rejected without a service call.</summary>
+    [Fact]
+    public async Task ConfirmAlarm_MissingConditionNodeId_Fails_NoServiceCall()
+    {
+        _vm.IsConnected = true;
+        var alarm = BuildAlarm(conditionNodeId: null);
+
+        var (ok, _) = await _vm.ConfirmAlarmAsync(alarm, "note");
+
+        ok.ShouldBeFalse();
+        _service.ConfirmCallCount.ShouldBe(0);
+    }
+
+    /// <summary>Verifies that a transport exception from ShelveAlarmAsync is caught and surfaced as an error message.</summary>
+    [Fact]
+    public async Task ShelveAlarm_ServiceThrows_ReturnsError()
+    {
+        _vm.IsConnected = true;
+        _service.ShelveException = new InvalidOperationException("transport error");
+        var alarm = BuildAlarm();
+
+        var (ok, message) = await _vm.ShelveAlarmAsync(alarm, ShelveKind.OneShot, 0);
+
+        ok.ShouldBeFalse();
+        message.ShouldContain("Error");
+    }
+
+    /// <summary>Verifies that a transport exception from ConfirmAlarmAsync is caught and surfaced as an error message.</summary>
+    [Fact]
+    public async Task ConfirmAlarm_ServiceThrows_ReturnsError()
+    {
+        _vm.IsConnected = true;
+        _service.ConfirmException = new InvalidOperationException("transport error");
+        var alarm = BuildAlarm();
+
+        var (ok, message) = await _vm.ConfirmAlarmAsync(alarm, "note");
+
+        ok.ShouldBeFalse();
+        message.ShouldContain("Error");
+    }
+
     // --- CanShelve / CanConfirm predicates ---
 
     /// <summary>Verifies CanShelve is true when a ConditionNodeId is present.</summary>