diff --git a/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractCompositeField.java b/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractCompositeField.java
index 88299585040..becdaa6be4e 100644
--- a/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractCompositeField.java
+++ b/org.eclipse.scout.rt.client/src/main/java/org/eclipse/scout/rt/client/ui/form/fields/AbstractCompositeField.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2023 BSI Business Systems Integration AG
+ * Copyright (c) 2010, 2026 BSI Business Systems Integration AG
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -15,6 +15,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 
@@ -144,14 +145,18 @@ protected void initConfig() {
 
   @Override
   public void addField(IFormField f) {
-    CompositeFieldUtility.addField(f, this, getFieldsInternal());
+    List<IFormField> writableFields = new LinkedList<>(getFieldsInternal());
+    CompositeFieldUtility.addField(f, this, writableFields);
+    propertySupport.setPropertyNoFire(PROP_FIELDS, writableFields);
     addChildFieldPropertyChangeListener(f);
     handleFieldsChanged();
   }
 
   @Override
   public void removeField(IFormField f) {
-    CompositeFieldUtility.removeField(f, this, getFieldsInternal());
+    List<IFormField> writableFields = new LinkedList<>(getFieldsInternal());
+    CompositeFieldUtility.removeField(f, this, writableFields);
+    propertySupport.setPropertyNoFire(PROP_FIELDS, writableFields);
     removeChildFieldPropertyChangeListener(f);
     handleFieldsChanged();
   }
diff --git a/org.eclipse.scout.rt.platform/src/main/java/org/eclipse/scout/rt/platform/reflect/BasicPropertySupport.java b/org.eclipse.scout.rt.platform/src/main/java/org/eclipse/scout/rt/platform/reflect/BasicPropertySupport.java
index 24441395115..5b4574dab6d 100644
--- a/org.eclipse.scout.rt.platform/src/main/java/org/eclipse/scout/rt/platform/reflect/BasicPropertySupport.java
+++ b/org.eclipse.scout.rt.platform/src/main/java/org/eclipse/scout/rt/platform/reflect/BasicPropertySupport.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2023 BSI Business Systems Integration AG
+ * Copyright (c) 2010, 2026 BSI Business Systems Integration AG
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -16,9 +16,11 @@
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.ConcurrentModificationException;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -238,16 +240,17 @@ public <T> boolean setPropertyListAlwaysFire(String name, List<T> newValue) {
 
   private <T> boolean setPropertyList(String name, List<T> newValue, boolean alwaysFire) {
     Object oldValue = m_props.get(name);
+    newValue = optimizeList(newValue);
     boolean propChanged = setPropertyNoFire(name, newValue);
     if (propChanged || alwaysFire) {
       Object eventOldValue = null;
       if (oldValue instanceof List) {
-        eventOldValue = CollectionUtility.arrayList((Collection<?>) oldValue);
+        eventOldValue = List.copyOf((Collection<?>) oldValue);
       }
       // fire a copy
       List<T> eventNewValue = null;
       if (newValue != null) {
-        eventNewValue = CollectionUtility.arrayList(newValue);
+        eventNewValue = List.copyOf(newValue);
       }
       firePropertyChangeImpl(name, eventOldValue, eventNewValue);
       return propChanged;
@@ -255,6 +258,22 @@ private <T> boolean setPropertyList(String name, List<T> newValue, boolean alway
     return false;
   }
 
+  public <T> List<T> optimizeList(List<T> newValue) {
+    if (newValue == null) {
+      return null;
+    }
+    if (newValue.isEmpty()) {
+      return Collections.emptyList();
+    }
+    if (newValue.size() == 1) {
+      return Collections.singletonList(newValue.getFirst());
+    }
+    if (newValue.size() == 2) {
+      return List.of(newValue.get(0), newValue.get(1));
+    }
+    return List.copyOf(newValue);
+  }
+
   @SuppressWarnings("unchecked")
   public <T> List<T> getPropertyList(String name) {
     return (List<T>) m_props.get(name);
@@ -270,6 +289,7 @@ public <T> boolean setPropertySetAlwaysFire(String name, Set<T> newValue) {
 
   private <T> boolean setPropertySet(String name, Set<T> newValue, boolean alwaysFire) {
     Object oldValue = m_props.get(name);
+    newValue = optimizeSet(newValue);
     boolean propChanged = setPropertyNoFire(name, newValue);
     if (propChanged || alwaysFire) {
       Object eventOldValue = null;
@@ -287,6 +307,23 @@ private <T> boolean setPropertySet(String name, Set<T> newValue, boolean alwaysF
     return false;
   }
 
+  public <T> Set<T> optimizeSet(Set<T> newValue) {
+    if (newValue == null) {
+      return null;
+    }
+    if (newValue.isEmpty()) {
+      return Collections.emptySet();
+    }
+    if (newValue.size() == 1) {
+      return Collections.singleton(newValue.iterator().next());
+    }
+    if (newValue.size() == 2) {
+      Iterator<T> it = newValue.iterator();
+      return Set.of(it.next(), it.next());
+    }
+    return Set.copyOf(newValue);
+  }
+
   @SuppressWarnings("unchecked")
   public <T> Set<T> getPropertySet(String name) {
     return (Set<T>) m_props.get(name);