diff --git a/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs b/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs
index 342756c..19346a4 100644
--- a/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs
@@ -380,10 +380,19 @@ public sealed class AlarmSubtagLiveSmokeTests
 
         // Advise the alarm subtags (InAlarm/Acked/Priority/AckMsg).
         consumer.Subscribe(string.Format(@"\\{0}\Galaxy!{1}", Environment.MachineName, Group));
-        // Also advise the source attribute so it is an active, writable item
-        // (MXAccess rejects writes to added-but-not-advised items).
-        source.Advise(new List<string> { AlarmSourceTag });
-        Log("Subscribed + advised source. Pumping to activate items ...");
+        // Also advise the source attribute + AlarmExtension diagnostic fields so
+        // we can discover which attribute actually drives the alarm
+        // (AlarmSourceAttr names it) before attempting to write.
+        source.Advise(new List<string>
+        {
+            AlarmSourceTag,
+            AlarmSourceTag + ".AlarmSourceAttr",
+            AlarmSourceTag + ".Condition",
+            AlarmSourceTag + ".AlarmMode",
+            AlarmSourceTag + ".ActiveAlarmState",
+            AlarmSourceTag + ".DescAttrName",
+        });
+        Log("Subscribed + advised source + diagnostics. Pumping to activate items ...");
         PumpFor(TimeSpan.FromSeconds(7));
 
         // Baseline OFF: drive the source false and drain whatever transitions