diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/OpcUa/OpcUaPublishActor.cs b/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/OpcUa/OpcUaPublishActor.cs
index f069a77f..c317a8aa 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/OpcUa/OpcUaPublishActor.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/OpcUa/OpcUaPublishActor.cs
@@ -58,6 +58,9 @@ public sealed class OpcUaPublishActor : ReceiveActor, IWithTimers
     public sealed record RebuildAddressSpace(CorrelationId Correlation, DeploymentId? DeploymentId = null);
 
     /// <summary>Inject driver-discovered nodes (FixedTree) under an equipment at runtime (post-connect).</summary>
+    /// <param name="EquipmentRootNodeId">The OPC UA NodeId of the equipment root folder to inject the
+    /// discovered nodes under (e.g. "EQ-3686c0272279"); also the node the NodeAdded model-change is
+    /// announced under.</param>
     public sealed record MaterialiseDiscoveredNodes(
         string EquipmentRootNodeId,
         IReadOnlyList<DiscoveredFolder> Folders,
@@ -399,10 +402,17 @@ public sealed class OpcUaPublishActor : ReceiveActor, IWithTimers
     }
 
     /// <summary>Forwards driver-discovered (FixedTree) nodes to the applier so they are injected under
-    /// the equipment at runtime. No-op when no applier is wired (dev/Mac/legacy seam), matching the
+    /// the equipment at runtime. No-op (logged) when no applier is wired (dev/Mac/legacy seam), matching the
     /// optional-applier tolerance of <see cref="HandleRebuild"/>.</summary>
     private void HandleMaterialiseDiscovered(MaterialiseDiscoveredNodes msg)
-        => _applier?.MaterialiseDiscoveredNodes(msg.EquipmentRootNodeId, msg.Folders, msg.Variables);
+    {
+        if (_applier is null)
+        {
+            _log.Debug("OpcUaPublish: no applier wired — discarding MaterialiseDiscoveredNodes for {Equipment}", msg.EquipmentRootNodeId);
+            return;
+        }
+        _applier.MaterialiseDiscoveredNodes(msg.EquipmentRootNodeId, msg.Folders, msg.Variables);
+    }
 
     private void HandleServiceLevelChanged(ServiceLevelChanged msg)
     {