diff --git a/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs b/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs
index d33b3ebd..ea3d6950 100644
--- a/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs
@@ -296,8 +296,12 @@ public class RealOpcUaClient : IOpcUaClient
     /// optional server-side WhereClause (M2.4 / #8). Only standard types appear
     /// here; vendor/custom type names cannot be mapped without browsing the server
     /// type tree, so they are handled by the client-side gate alone.
+    /// <para>
+    /// Single source of truth for both directions: <see cref="ConditionTypeNamesById"/>
+    /// is derived from this map, so the friendly-name and NodeId sides cannot drift.
+    /// </para>
     /// </summary>
-    private static readonly IReadOnlyDictionary<string, NodeId> KnownConditionTypeIds =
+    internal static readonly IReadOnlyDictionary<string, NodeId> KnownConditionTypeIds =
         new Dictionary<string, NodeId>(StringComparer.OrdinalIgnoreCase)
         {
             ["ConditionType"] = ObjectTypeIds.ConditionType,
@@ -322,6 +326,40 @@ public class RealOpcUaClient : IOpcUaClient
             ["CertificateExpirationAlarmType"] = ObjectTypeIds.CertificateExpirationAlarmType,
         };
 
+    /// <summary>
+    /// Inverse of <see cref="KnownConditionTypeIds"/> (NodeId → friendly name), derived
+    /// from it so the two cannot drift (M2.4 / #8). Used by <see cref="ResolveAlarmTypeName"/>
+    /// to translate the event-type NodeId an OPC UA server sends back into the friendly
+    /// type name the conditionFilter gate and server-side WhereClause both key off.
+    /// </summary>
+    private static readonly IReadOnlyDictionary<NodeId, string> ConditionTypeNamesById =
+        KnownConditionTypeIds.ToDictionary(kv => kv.Value, kv => kv.Key);
+
+    /// <summary>
+    /// Resolves an event-type <see cref="NodeId"/> to the friendly condition-type name the
+    /// <c>conditionFilter</c> gate (and the server-side WhereClause) use (M2.4 / #8).
+    ///
+    /// <para>
+    /// Standard A&amp;C types are returned as their friendly name (e.g. <c>i=9341</c> →
+    /// <c>"ExclusiveLevelAlarmType"</c>) so the client-side gate — which compares against
+    /// the friendly names in <see cref="KnownConditionTypeIds"/> — actually matches the
+    /// events the server delivers. Vendor/custom subtypes that are not in the map fall back
+    /// to the NodeId string; that is consistent because the WhereClause is likewise omitted
+    /// for unmapped names, so such a filter can only be expressed (and matched) as the NodeId
+    /// string. A <c>null</c> event type yields the empty string.
+    /// </para>
+    /// </summary>
+    /// <param name="eventType">The event-type NodeId from the A&amp;C notification, or <c>null</c>.</param>
+    /// <returns>The friendly type name when known; otherwise the NodeId string (or "" when null).</returns>
+    internal static string ResolveAlarmTypeName(NodeId? eventType)
+    {
+        if (eventType is null)
+            return "";
+        return ConditionTypeNamesById.TryGetValue(eventType, out var friendly)
+            ? friendly
+            : eventType.ToString();
+    }
+
     /// <summary>
     /// Builds the event filter selecting the base event fields plus the
     /// AlarmConditionType / AcknowledgeableConditionType state sub-variables we mirror,
@@ -446,7 +484,12 @@ public class RealOpcUaClient : IOpcUaClient
             return;
         }
 
-        var sourceName = fields[1].Value is NodeId ? (fields[2].Value as string ?? "") : (fields[2].Value as string ?? "");
+        // Field layout (AlarmStateFields): [1]=SourceNode (NodeId), [2]=SourceName (string).
+        // Prefer the human-readable SourceName; fall back to the SourceNode NodeId string
+        // only when SourceName is absent/empty, so the condition still has a stable key.
+        var sourceName = fields[2].Value as string;
+        if (string.IsNullOrEmpty(sourceName))
+            sourceName = (fields[1].Value as NodeId)?.ToString() ?? "";
         var conditionName = fields.Count > 11 ? fields[11].Value as string : null;
         var sourceObjectRef = sourceName;
         var sourceRef = string.IsNullOrEmpty(conditionName) ? sourceName : $"{sourceName}.{conditionName}";
@@ -476,7 +519,9 @@ public class RealOpcUaClient : IOpcUaClient
         onTransition(new NativeAlarmTransition(
             SourceReference: sourceRef,
             SourceObjectReference: sourceObjectRef,
-            AlarmTypeName: eventType?.ToString() ?? "",
+            // Resolve the event-type NodeId (e.g. "i=9341") to the friendly type name
+            // the conditionFilter gate keys off (M2.4 / #8); NodeId-string for custom types.
+            AlarmTypeName: ResolveAlarmTypeName(eventType),
             Kind: kind,
             Condition: OpcUaAlarmMapper.BuildCondition(active, acked, confirmed, shelve, suppressed, severity),
             Category: "",
diff --git a/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/AlarmConditionFilterTests.cs b/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/AlarmConditionFilterTests.cs
index b7589e35..4cd9122f 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/AlarmConditionFilterTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/AlarmConditionFilterTests.cs
@@ -96,4 +96,18 @@ public class AlarmConditionFilterTests
         Assert.Equal(new[] { "AnalogLimit.Hi", "DiscreteAlarm" }, f.Names.OrderBy(n => n).ToArray());
         Assert.Empty(AlarmConditionFilter.Parse(null).Names);
     }
+
+    [Fact]
+    public void IsAllowed_OpcUaResolvedFriendlyName_MatchesFriendlyNameFilter()
+    {
+        // M2.4 (#8) regression: OPC UA delivers events whose AlarmTypeName, after
+        // RealOpcUaClient.ResolveAlarmTypeName, is a standard friendly type name
+        // (e.g. "ExclusiveLevelAlarmType"). A friendly-name filter on that source
+        // built a correct server WhereClause; the client gate must agree and deliver,
+        // not drop every event (which the prior NodeId-string AlarmTypeName caused).
+        var f = AlarmConditionFilter.Parse("ExclusiveLevelAlarmType,DiscreteAlarmType");
+        Assert.True(f.IsAllowed(Tx("ExclusiveLevelAlarmType")));
+        Assert.True(f.IsAllowed(Tx("DiscreteAlarmType")));
+        Assert.False(f.IsAllowed(Tx("OffNormalAlarmType")));
+    }
 }
diff --git a/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/RealOpcUaClientAlarmFilterTests.cs b/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/RealOpcUaClientAlarmFilterTests.cs
new file mode 100644
index 00000000..852a5608
--- /dev/null
+++ b/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/RealOpcUaClientAlarmFilterTests.cs
@@ -0,0 +1,63 @@
+using Opc.Ua;
+using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;
+
+namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests;
+
+/// <summary>
+/// M2.4 (#8) regression: standard OPC UA A&amp;C events carry an event-type
+/// <see cref="NodeId"/> (e.g. <c>i=9341</c> for ExclusiveLevelAlarmType), but the
+/// client-side conditionFilter gate — and the server-side WhereClause — both key off
+/// the friendly type names in <see cref="RealOpcUaClient.KnownConditionTypeIds"/>.
+/// <see cref="RealOpcUaClient.ResolveAlarmTypeName"/> bridges the two by resolving the
+/// event-type NodeId back to its friendly name (NodeId-string fallback for custom
+/// types), so a friendly-name filter actually matches the events the server delivers.
+/// </summary>
+public class RealOpcUaClientAlarmFilterTests
+{
+    [Fact]
+    public void ResolveAlarmTypeName_KnownStandardNodeId_ReturnsFriendlyName()
+    {
+        // The well-known NodeId for ExclusiveLevelAlarmType (i=9341) must resolve to
+        // the friendly name the conditionFilter/WhereClause use.
+        var resolved = RealOpcUaClient.ResolveAlarmTypeName(ObjectTypeIds.ExclusiveLevelAlarmType);
+        Assert.Equal("ExclusiveLevelAlarmType", resolved);
+    }
+
+    [Fact]
+    public void ResolveAlarmTypeName_DiscreteAlarmNodeId_ReturnsFriendlyName()
+    {
+        var resolved = RealOpcUaClient.ResolveAlarmTypeName(ObjectTypeIds.DiscreteAlarmType);
+        Assert.Equal("DiscreteAlarmType", resolved);
+    }
+
+    [Fact]
+    public void ResolveAlarmTypeName_UnknownCustomNodeId_ReturnsNodeIdString()
+    {
+        // A vendor/custom subtype not in KnownConditionTypeIds: we cannot map it to a
+        // friendly name, so we fall back to its NodeId string. This is consistent —
+        // the WhereClause is also omitted for unknown names, so the client gate matches
+        // the NodeId string, which is the only thing such a filter could carry.
+        var custom = new NodeId(987654u, 7);
+        var resolved = RealOpcUaClient.ResolveAlarmTypeName(custom);
+        Assert.Equal(custom.ToString(), resolved);
+    }
+
+    [Fact]
+    public void ResolveAlarmTypeName_Null_ReturnsEmptyString()
+    {
+        Assert.Equal("", RealOpcUaClient.ResolveAlarmTypeName(null));
+    }
+
+    [Fact]
+    public void InverseMap_RoundTrips_EveryKnownConditionType()
+    {
+        // The friendly→NodeId map (KnownConditionTypeIds) and the NodeId→friendly map
+        // are derived from a single source of truth, so they must round-trip for every
+        // entry — guards against the two maps drifting apart.
+        foreach (var (friendlyName, nodeId) in RealOpcUaClient.KnownConditionTypeIds)
+        {
+            var resolved = RealOpcUaClient.ResolveAlarmTypeName(nodeId);
+            Assert.Equal(friendlyName, resolved);
+        }
+    }
+}