diff --git a/Editor/ClusterViewer.cs b/Editor/ClusterViewer.cs
index 46e303c..41dee0c 100644
--- a/Editor/ClusterViewer.cs
+++ b/Editor/ClusterViewer.cs
@@ -327,7 +327,7 @@ namespace NanoBrain {
                 if (nucleus is Neuron neuron)
                     receivers = neuron.receivers;
                 else if (nucleus is Cluster cluster)
-                    receivers = cluster.CollectReceivers();
+                    receivers = cluster.CollectReceivers(true);
                 else
                     return;
 
@@ -357,7 +357,6 @@ namespace NanoBrain {
                 float margin = 10 + spacing / 2;
 
                 int row = 0;
-                List<Nucleus[]> drawnArrays = new();
                 foreach (Nucleus receiver in receivers) {
                     Nucleus receiverNucleus = receiver;
                     if (receiverNucleus == null)
@@ -733,7 +732,7 @@ namespace NanoBrain {
                 if (nucleus == this.currentNucleus) {
                     if (Application.isPlaying) {
                         if (nucleus is Cluster)
-                            expandArray = !expandArray;                        
+                            expandArray = !expandArray;
                         else
                             expandArray = false;
                     }
diff --git a/Runtime/Scripts/Core/Cluster.cs b/Runtime/Scripts/Core/Cluster.cs
index 2f061ab..c358f14 100644
--- a/Runtime/Scripts/Core/Cluster.cs
+++ b/Runtime/Scripts/Core/Cluster.cs
@@ -716,7 +716,7 @@ namespace NanoBrain {
 
         #region Receivers
 
-        public virtual List<Nucleus> CollectReceivers() {
+        public virtual List<Nucleus> CollectReceivers(bool removeDuplicates = false) {
             List<Nucleus> receivers = new();
             foreach (Nucleus outputNucleus in this.clusterNuclei) {
                 if (outputNucleus is not Neuron output)
@@ -725,10 +725,11 @@ namespace NanoBrain {
                 // Debug.Log($"output {this.name} {outputNucleus.name}");
                 foreach (Nucleus receiver in output.receivers) {
                     // Debug.Log($"output    {receiver.name}");
-                    // Only add receivers outside this cluster
+                    // Only add receivers outside this cluster                    
                     if (receiver.clusterPrefab != this.prefab) {
-                        // Debug.Log($"   YES");
-                        receivers.Add(receiver);
+                        if (removeDuplicates && receivers.Contains(receiver) == false)
+                            // Debug.Log($"   YES");
+                            receivers.Add(receiver);
                     }
                 }
             }