diff --git a/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/UnifiedAutomationReadCustomDataTypeExample1.java b/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/UnifiedAutomationReadCustomDataTypeExample1.java
index 3e81a4994..e9501d179 100644
--- a/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/UnifiedAutomationReadCustomDataTypeExample1.java
+++ b/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/UnifiedAutomationReadCustomDataTypeExample1.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 the Eclipse Milo Authors
+ * Copyright (c) 2025 the Eclipse Milo Authors
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -18,9 +18,10 @@
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import org.eclipse.milo.opcua.sdk.client.OpcUaClient;
-import org.eclipse.milo.opcua.sdk.core.types.DynamicEnum;
-import org.eclipse.milo.opcua.sdk.core.types.DynamicOptionSet;
-import org.eclipse.milo.opcua.sdk.core.types.DynamicStruct;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicEnumType;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicOptionSetType;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicStructType;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicType;
 import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
 import org.eclipse.milo.opcua.stack.core.security.SecurityPolicy;
 import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
@@ -64,25 +65,25 @@ public void run(OpcUaClient client, CompletableFuture<OpcUaClient> future) throw
   private void readWriteReadPerson(OpcUaClient client) throws Exception {
     NodeId nodeId = NodeId.parse("ns=3;s=Person1");
 
-    DynamicStruct value = readScalarValue(client, nodeId);
+    DynamicStructType value = (DynamicStructType) readScalarValue(client, nodeId);
     logger.info("Person1: {}", value);
 
     Random r = new Random();
-    DynamicEnum gender = (DynamicEnum) value.getMembers().get("Gender");
+    DynamicEnumType gender = (DynamicEnumType) value.getMembers().get("Gender");
     value.getMembers().put("Name", "Fat Boy" + r.nextInt(100));
-    value.getMembers().put("Gender", new DynamicEnum(gender.getDataType(), r.nextInt(2)));
+    value.getMembers().put("Gender", new DynamicEnumType(gender.getDataType(), r.nextInt(2)));
 
     StatusCode status = writeValue(client, nodeId, value);
     System.out.println("write status: " + status);
 
-    value = readScalarValue(client, nodeId);
+    value = (DynamicStructType) readScalarValue(client, nodeId);
     logger.info("Person1': {}", value);
   }
 
   private void readWriteReadWorkOrder(OpcUaClient client) throws Exception {
     NodeId nodeId = NodeId.parse("ns=3;s=Demo.Static.Scalar.WorkOrder");
 
-    DynamicStruct value = readScalarValue(client, nodeId);
+    DynamicStructType value = (DynamicStructType) readScalarValue(client, nodeId);
     logger.info("WorkOrder: {}", value);
 
     value.getMembers().put("ID", UUID.randomUUID());
@@ -90,14 +91,14 @@ private void readWriteReadWorkOrder(OpcUaClient client) throws Exception {
     StatusCode status = writeValue(client, nodeId, value);
     System.out.println("write status: " + status);
 
-    value = readScalarValue(client, nodeId);
+    value = (DynamicStructType) readScalarValue(client, nodeId);
     logger.info("WorkOrder': {}", value);
   }
 
   private void readWriteCarExtras(OpcUaClient client) throws Exception {
     NodeId nodeId = NodeId.parse("ns=3;s=Demo.Static.Scalar.CarExtras");
 
-    DynamicOptionSet value = (DynamicOptionSet) readScalarValue(client, nodeId);
+    DynamicOptionSetType value = (DynamicOptionSetType) readScalarValue(client, nodeId);
     logger.info("CarExtras: {}", value);
 
     byte b = requireNonNull(value.getValue().bytes())[0];
@@ -106,14 +107,14 @@ private void readWriteCarExtras(OpcUaClient client) throws Exception {
     StatusCode status = writeValue(client, nodeId, value);
     System.out.println("write status: " + status);
 
-    value = (DynamicOptionSet) readScalarValue(client, nodeId);
+    value = (DynamicOptionSetType) readScalarValue(client, nodeId);
     logger.info("CarExtras': {}", value);
   }
 
   private void readWorkOrderArray(OpcUaClient client) throws Exception {
     NodeId nodeId = NodeId.parse("ns=3;s=Demo.Static.Arrays.WorkOrder");
 
-    DynamicStruct[] value = readArrayValue(client, nodeId);
+    DynamicType[] value = readArrayValue(client, nodeId);
 
     logger.info("WorkOrderArray:");
     for (int i = 0; i < value.length; i++) {
@@ -121,18 +122,17 @@ private void readWorkOrderArray(OpcUaClient client) throws Exception {
     }
   }
 
-  private static DynamicStruct readScalarValue(OpcUaClient client, NodeId nodeId) throws Exception {
+  private static DynamicType readScalarValue(OpcUaClient client, NodeId nodeId) throws Exception {
     DataValue dataValue =
         client.readValues(0.0, TimestampsToReturn.Neither, List.of(nodeId)).get(0);
 
     ExtensionObject xo = (ExtensionObject) dataValue.getValue().getValue();
     assert xo != null;
 
-    return (DynamicStruct) xo.decode(client.getDynamicEncodingContext());
+    return (DynamicType) xo.decode(client.getDynamicEncodingContext());
   }
 
-  private static DynamicStruct[] readArrayValue(OpcUaClient client, NodeId nodeId)
-      throws Exception {
+  private static DynamicType[] readArrayValue(OpcUaClient client, NodeId nodeId) throws Exception {
     DataValue dataValue =
         client.readValues(0.0, TimestampsToReturn.Neither, List.of(nodeId)).get(0);
 
@@ -141,13 +141,12 @@ private static DynamicStruct[] readArrayValue(OpcUaClient client, NodeId nodeId)
 
     EncodingContext ctx = client.getDynamicEncodingContext();
 
-    return Arrays.stream(xos)
-        .map(xo -> (DynamicStruct) xo.decode(ctx))
-        .toArray(DynamicStruct[]::new);
+    return Arrays.stream(xos).map(xo -> (DynamicType) xo.decode(ctx)).toArray(DynamicType[]::new);
   }
 
-  private static StatusCode writeValue(OpcUaClient client, NodeId nodeId, DynamicStruct value)
+  private static StatusCode writeValue(OpcUaClient client, NodeId nodeId, DynamicType value)
       throws Exception {
+
     ExtensionObject xo =
         ExtensionObject.encodeDefaultBinary(
             client.getDynamicEncodingContext(), value, value.getDataType().getBinaryEncodingId());
diff --git a/opc-ua-sdk/integration-tests/src/test/java/org/eclipse/milo/opcua/sdk/client/DynamicMatrixTestTypeTest.java b/opc-ua-sdk/integration-tests/src/test/java/org/eclipse/milo/opcua/sdk/client/DynamicMatrixTestTypeTest.java
index 93b72d185..7aa6fd233 100644
--- a/opc-ua-sdk/integration-tests/src/test/java/org/eclipse/milo/opcua/sdk/client/DynamicMatrixTestTypeTest.java
+++ b/opc-ua-sdk/integration-tests/src/test/java/org/eclipse/milo/opcua/sdk/client/DynamicMatrixTestTypeTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 the Eclipse Milo Authors
+ * Copyright (c) 2025 the Eclipse Milo Authors
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -14,7 +14,7 @@
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
 import org.eclipse.milo.opcua.sdk.client.nodes.UaVariableNode;
-import org.eclipse.milo.opcua.sdk.core.types.DynamicStruct;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicStructType;
 import org.eclipse.milo.opcua.sdk.test.AbstractClientServerTest;
 import org.eclipse.milo.opcua.sdk.test.MatrixTestType;
 import org.eclipse.milo.opcua.stack.core.UaException;
@@ -38,7 +38,7 @@ public void read() throws UaException {
     ExtensionObject xo = (ExtensionObject) value.getValue().getValue();
     assert xo != null;
 
-    DynamicStruct decoded = (DynamicStruct) xo.decode(client.getDynamicEncodingContext());
+    DynamicStructType decoded = (DynamicStructType) xo.decode(client.getDynamicEncodingContext());
     assertEquals(
         MatrixTestType.TYPE_ID,
         decoded.getTypeId().absolute(client.getNamespaceTable()).orElseThrow());
diff --git a/opc-ua-sdk/sdk-client/src/main/java/org/eclipse/milo/opcua/sdk/client/OpcUaClient.java b/opc-ua-sdk/sdk-client/src/main/java/org/eclipse/milo/opcua/sdk/client/OpcUaClient.java
index 7bde03e22..a7e8fec50 100644
--- a/opc-ua-sdk/sdk-client/src/main/java/org/eclipse/milo/opcua/sdk/client/OpcUaClient.java
+++ b/opc-ua-sdk/sdk-client/src/main/java/org/eclipse/milo/opcua/sdk/client/OpcUaClient.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 the Eclipse Milo Authors
+ * Copyright (c) 2025 the Eclipse Milo Authors
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -39,7 +39,7 @@
 import org.eclipse.milo.opcua.sdk.client.subscriptions.OpcUaSubscription;
 import org.eclipse.milo.opcua.sdk.client.subscriptions.PublishingManager;
 import org.eclipse.milo.opcua.sdk.client.typetree.DataTypeTreeBuilder;
-import org.eclipse.milo.opcua.sdk.core.types.DynamicCodecFactory;
+import org.eclipse.milo.opcua.sdk.core.types.codec.DynamicCodecFactory;
 import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
 import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
 import org.eclipse.milo.opcua.stack.core.AttributeId;
diff --git a/opc-ua-sdk/sdk-core/pom.xml b/opc-ua-sdk/sdk-core/pom.xml
index 146a589ed..ac3eece4a 100644
--- a/opc-ua-sdk/sdk-core/pom.xml
+++ b/opc-ua-sdk/sdk-core/pom.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
-  ~ Copyright (c) 2024 the Eclipse Milo Authors
+  ~ Copyright (c) 2025 the Eclipse Milo Authors
   ~
   ~ This program and the accompanying materials are made
   ~ available under the terms of the Eclipse Public License 2.0
@@ -51,6 +51,18 @@
       <version>${junit.version}</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-params</artifactId>
+      <version>${junit.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <version>5.11.0</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicEnum.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicEnum.java
deleted file mode 100644
index 03d4e9fe1..000000000
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicEnum.java
+++ /dev/null
@@ -1,105 +0,0 @@
-/*
- * Copyright (c) 2024 the Eclipse Milo Authors
- *
- * This program and the accompanying materials are made
- * available under the terms of the Eclipse Public License 2.0
- * which is available at https://www.eclipse.org/legal/epl-2.0/
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-
-package org.eclipse.milo.opcua.sdk.core.types;
-
-import static java.util.Objects.requireNonNullElse;
-
-import java.util.function.Function;
-import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
-import org.eclipse.milo.opcua.stack.core.types.UaEnumeratedType;
-import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
-import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
-import org.eclipse.milo.opcua.stack.core.types.structured.EnumDefinition;
-import org.eclipse.milo.opcua.stack.core.types.structured.EnumField;
-import org.jspecify.annotations.Nullable;
-
-public class DynamicEnum implements UaEnumeratedType {
-
-  private final DataType dataType;
-  private final String name;
-  private final int value;
-  private final LocalizedText displayName;
-  private final LocalizedText description;
-
-  public DynamicEnum(DataType dataType, int value) {
-    this.dataType = dataType;
-
-    EnumDefinition definition = (EnumDefinition) dataType.getDataTypeDefinition();
-    assert definition != null;
-
-    EnumField[] fields = requireNonNullElse(definition.getFields(), new EnumField[0]);
-
-    for (EnumField field : fields) {
-      if (field.getValue() == value) {
-        this.name = field.getName();
-        this.value = field.getValue().intValue();
-        this.displayName = field.getDisplayName();
-        this.description = field.getDescription();
-        return;
-      }
-    }
-
-    // if we reach this point the value doesn't match any of the fields
-    throw new IllegalArgumentException("value: " + value);
-  }
-
-  public DynamicEnum(
-      DataType dataType,
-      String name,
-      int value,
-      LocalizedText displayName,
-      LocalizedText description) {
-    this.dataType = dataType;
-    this.name = name;
-    this.value = value;
-    this.displayName = displayName;
-    this.description = description;
-  }
-
-  @Override
-  public ExpandedNodeId getTypeId() {
-    return dataType.getNodeId().expanded();
-  }
-
-  @Override
-  public int getValue() {
-    return value;
-  }
-
-  public DataType getDataType() {
-    return dataType;
-  }
-
-  public @Nullable String getName() {
-    return name;
-  }
-
-  public LocalizedText getDisplayName() {
-    return displayName;
-  }
-
-  public LocalizedText getDescription() {
-    return description;
-  }
-
-  @Override
-  public String toString() {
-    return "DynamicEnum{" + "name='" + name + '\'' + ", value=" + value + '}';
-  }
-
-  public static DynamicEnum newInstance(DataType dataType, int value) {
-    return new DynamicEnum(dataType, value);
-  }
-
-  public static Function<Integer, DynamicEnum> newInstanceFactory(DataType dataType) {
-    return value -> new DynamicEnum(dataType, value);
-  }
-}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicEnumType.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicEnumType.java
new file mode 100644
index 000000000..02a4a280c
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicEnumType.java
@@ -0,0 +1,150 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import static java.util.Objects.requireNonNull;
+import static java.util.Objects.requireNonNullElse;
+
+import java.util.Objects;
+import java.util.StringJoiner;
+import java.util.function.Function;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.stack.core.types.UaEnumeratedType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.structured.EnumDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.EnumField;
+
+public final class DynamicEnumType extends DynamicType implements UaEnumeratedType {
+
+  private final String name;
+  private final LocalizedText displayName;
+  private final LocalizedText description;
+
+  private final DataType dataType;
+  private final int value;
+
+  public DynamicEnumType(DataType dataType, int value) {
+    this.dataType = dataType;
+    this.value = value;
+
+    EnumDefinition definition = (EnumDefinition) dataType.getDataTypeDefinition();
+    assert definition != null;
+
+    EnumField[] fields = requireNonNullElse(definition.getFields(), new EnumField[0]);
+
+    for (EnumField field : fields) {
+      if (field.getValue() == value) {
+        this.name = field.getName() != null ? field.getName() : "";
+        this.displayName =
+            field.getDisplayName() != null ? field.getDisplayName() : LocalizedText.NULL_VALUE;
+        this.description =
+            field.getDescription() != null ? field.getDescription() : LocalizedText.NULL_VALUE;
+        return;
+      }
+    }
+
+    // if we reach this point the value doesn't match any of the fields
+    throw new IllegalArgumentException("value: " + value);
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return dataType.getNodeId().expanded();
+  }
+
+  @Override
+  public int getValue() {
+    return value;
+  }
+
+  @Override
+  public DataType getDataType() {
+    return dataType;
+  }
+
+  @Override
+  public EnumDefinition getDataTypeDefinition() {
+    return (EnumDefinition) requireNonNull(dataType.getDataTypeDefinition());
+  }
+
+  /**
+   * Get the name associated with this enum value.
+   *
+   * @return the name associated with this enum value.
+   */
+  public String getName() {
+    return name;
+  }
+
+  /**
+   * Get the display name associated with this enum value.
+   *
+   * @return the display name associated with this enum value.
+   */
+  public LocalizedText getDisplayName() {
+    return displayName;
+  }
+
+  /**
+   * Get the description associated with this enum value.
+   *
+   * @return the description associated with this enum value.
+   */
+  public LocalizedText getDescription() {
+    return description;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == null || getClass() != o.getClass()) return false;
+    DynamicEnumType that = (DynamicEnumType) o;
+    return value == that.value
+        && Objects.equals(dataType.getNodeId(), that.dataType.getNodeId())
+        && Objects.equals(name, that.name);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(dataType.getNodeId(), name, value);
+  }
+
+  @Override
+  public String toString() {
+    return new StringJoiner(", ", DynamicEnumType.class.getSimpleName() + "[", "]")
+        .add("dataType=" + dataType.getNodeId().toParseableString())
+        .add("name=" + name)
+        .add("value=" + value)
+        .toString();
+  }
+
+  /**
+   * Create a new DynamicEnumType using the given DataType and value.
+   *
+   * @param dataType the {@link DataType} of the enum.
+   * @param value the value of the enum.
+   * @return a new DynamicEnumType with the given DataType and value.
+   */
+  public static DynamicEnumType newInstance(DataType dataType, int value) {
+    return new DynamicEnumType(dataType, value);
+  }
+
+  /**
+   * Create a new instance "factory" that produces new DynamicEnumType instances of the given
+   * DataType.
+   *
+   * @param dataType the {@link DataType} of the enum.
+   * @return a new instance "factory".
+   */
+  public static Function<Integer, DynamicEnumType> newInstanceFactory(DataType dataType) {
+    return value -> new DynamicEnumType(dataType, value);
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSet.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSet.java
deleted file mode 100644
index 092c23a9d..000000000
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSet.java
+++ /dev/null
@@ -1,97 +0,0 @@
-/*
- * Copyright (c) 2024 the Eclipse Milo Authors
- *
- * This program and the accompanying materials are made
- * available under the terms of the Eclipse Public License 2.0
- * which is available at https://www.eclipse.org/legal/epl-2.0/
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-
-package org.eclipse.milo.opcua.sdk.core.types;
-
-import static java.util.Objects.requireNonNullElse;
-
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.LinkedHashMap;
-import java.util.Map;
-import java.util.StringJoiner;
-import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
-import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
-import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
-import org.eclipse.milo.opcua.stack.core.types.structured.EnumDefinition;
-import org.eclipse.milo.opcua.stack.core.types.structured.EnumField;
-import org.eclipse.milo.opcua.stack.core.util.Lazy;
-import org.jspecify.annotations.Nullable;
-
-public class DynamicOptionSet extends DynamicStruct {
-
-  private final Lazy<Map<Integer, EnumField>> lazyFieldMap = new Lazy<>();
-
-  public DynamicOptionSet(DataType dataType) {
-    this(dataType, new LinkedHashMap<>());
-  }
-
-  public DynamicOptionSet(DataType dataType, LinkedHashMap<String, Object> members) {
-    super(dataType, members);
-  }
-
-  public ByteString getValue() {
-    return (ByteString) getMembers().get("Value");
-  }
-
-  public ByteString getValidBits() {
-    return (ByteString) getMembers().get("ValidBits");
-  }
-
-  public void setValue(ByteString value) {
-    getMembers().put("Value", value);
-  }
-
-  public void setValidBits(ByteString validBits) {
-    getMembers().put("ValidBits", validBits);
-  }
-
-  public @Nullable LocalizedText getDisplayName(int bitIndex) {
-    EnumField enumField = getFieldMap().get(bitIndex);
-
-    return enumField != null ? enumField.getDisplayName() : null;
-  }
-
-  private Map<Integer, EnumField> getFieldMap() {
-    return lazyFieldMap.get(
-        () -> {
-          Map<Integer, EnumField> fieldMap = Collections.synchronizedMap(new HashMap<>());
-
-          EnumDefinition definition = (EnumDefinition) getDataType().getDataTypeDefinition();
-          assert definition != null;
-
-          EnumField[] fields = requireNonNullElse(definition.getFields(), new EnumField[0]);
-
-          for (EnumField field : fields) {
-            fieldMap.put(field.getValue().intValue(), field);
-          }
-
-          return fieldMap;
-        });
-  }
-
-  @Override
-  public String toString() {
-    return new StringJoiner(", ", DynamicOptionSet.class.getSimpleName() + "{", "}")
-        .add("value=" + toBitString(getValue()))
-        .add("validBits=" + toBitString(getValidBits()))
-        .toString();
-  }
-
-  private static String toBitString(ByteString bs) {
-    var sb = new StringBuilder();
-    for (byte b : bs.bytesOrEmpty()) {
-      for (int i = 0; i < 8; i++) {
-        sb.append((b >> i & 1) == 1 ? "1" : "0");
-      }
-    }
-    return sb.toString();
-  }
-}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSetType.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSetType.java
new file mode 100644
index 000000000..19ee28f7d
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSetType.java
@@ -0,0 +1,215 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import static java.util.Objects.requireNonNull;
+import static java.util.Objects.requireNonNullElse;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.StringJoiner;
+import java.util.function.BiFunction;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.structured.EnumDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.EnumField;
+import org.eclipse.milo.opcua.stack.core.util.Lazy;
+
+public final class DynamicOptionSetType extends DynamicType implements UaStructuredType {
+
+  private final Lazy<Map<Integer, EnumField>> lazyFieldMap = new Lazy<>();
+
+  private volatile ByteString value;
+  private volatile ByteString validBits;
+
+  private final DataType dataType;
+
+  public DynamicOptionSetType(DataType dataType, ByteString value, ByteString validBits) {
+    this.dataType = dataType;
+
+    this.value = value;
+    this.validBits = validBits;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return dataType.getNodeId().expanded();
+  }
+
+  @Override
+  public DataType getDataType() {
+    return dataType;
+  }
+
+  @Override
+  public EnumDefinition getDataTypeDefinition() {
+    return (EnumDefinition) requireNonNull(dataType.getDataTypeDefinition());
+  }
+
+  /**
+   * Get the value of the option set.
+   *
+   * <p>The value is an array of bytes representing the bits in the option set. The length depends
+   * on the number of bits, and the number of bytes may be larger than needed for the valid bits.
+   *
+   * @return the value of the option set.
+   */
+  public ByteString getValue() {
+    return value;
+  }
+
+  /**
+   * Get the valid bits of the option set.
+   *
+   * <p>The value is an array of bytes the same length as the value, where each bit represents
+   * whether the corresponding bit in the value is valid.
+   *
+   * @return the valid bits of the option set.
+   */
+  public ByteString getValidBits() {
+    return validBits;
+  }
+
+  /**
+   * Set the value of the option set.
+   *
+   * @param value the value of the option set.
+   */
+  public void setValue(ByteString value) {
+    requireNonNull(value);
+
+    this.value = value;
+  }
+
+  /**
+   * Set the valid bits of the option set.
+   *
+   * @param validBits the valid bits of the option set.
+   */
+  public void setValidBits(ByteString validBits) {
+    requireNonNull(validBits);
+
+    this.validBits = validBits;
+  }
+
+  /**
+   * Get the name of the field at the given bit index.
+   *
+   * @param bitIndex the bit index.
+   * @return the name of the field at the given bit index, or {@link Optional#empty()} if no field
+   *     exists at the given bit index.
+   */
+  public Optional<String> getName(int bitIndex) {
+    EnumField enumField = getFieldMap().get(bitIndex);
+
+    return Optional.ofNullable(enumField).map(EnumField::getName);
+  }
+
+  /**
+   * Get the display name of the field at the given bit index.
+   *
+   * @param bitIndex the bit index.
+   * @return the display name of the field at the given bit index, or {@link Optional#empty()} if no
+   *     field exists at the given bit index.
+   */
+  public Optional<LocalizedText> getDisplayName(int bitIndex) {
+    EnumField enumField = getFieldMap().get(bitIndex);
+
+    return Optional.ofNullable(enumField).map(EnumField::getDisplayName);
+  }
+
+  /**
+   * Get the description of the field at the given bit index.
+   *
+   * @param bitIndex the bit index.
+   * @return the description of the field at the given bit index, or {@link Optional#empty()} if no
+   *     field exists at the given bit index.
+   */
+  public Optional<LocalizedText> getDescription(int bitIndex) {
+    EnumField enumField = getFieldMap().get(bitIndex);
+
+    return Optional.ofNullable(enumField).map(EnumField::getDescription);
+  }
+
+  private Map<Integer, EnumField> getFieldMap() {
+    return lazyFieldMap.get(
+        () -> {
+          Map<Integer, EnumField> fieldMap = Collections.synchronizedMap(new HashMap<>());
+
+          EnumDefinition definition = (EnumDefinition) dataType.getDataTypeDefinition();
+          assert definition != null;
+
+          EnumField[] fields = requireNonNullElse(definition.getFields(), new EnumField[0]);
+
+          for (EnumField field : fields) {
+            fieldMap.put(field.getValue().intValue(), field);
+          }
+
+          return fieldMap;
+        });
+  }
+
+  /**
+   * The value and validBit bit strings are displayed left to right, bit 0 to N.
+   *
+   * @return a string representation of this {@link DynamicOptionSetType}.
+   */
+  @Override
+  public String toString() {
+    return new StringJoiner(", ", DynamicOptionSetType.class.getSimpleName() + "[", "]")
+        .add("dataType=" + dataType.getNodeId().toParseableString())
+        .add("value=" + toBitString(getValue()))
+        .add("validBits=" + toBitString(getValidBits()))
+        .toString();
+  }
+
+  private static String toBitString(ByteString bs) {
+    var sb = new StringBuilder();
+    for (byte b : bs.bytesOrEmpty()) {
+      for (int i = 0; i < 8; i++) {
+        sb.append((b >> i & 1) == 1 ? "1" : "0");
+      }
+    }
+    return sb.toString();
+  }
+
+  /**
+   * Create a new instance of {@link DynamicOptionSetType} using the given DataType.
+   *
+   * @param dataType the {@link DataType} of the OptionSet.
+   * @param value the value of the OptionSet.
+   * @param validBits the valid bits of the OptionSet.
+   * @return a new {@link DynamicOptionSetType} with the given DataType.
+   */
+  public static DynamicOptionSetType newInstance(
+      DataType dataType, ByteString value, ByteString validBits) {
+
+    return new DynamicOptionSetType(dataType, value, validBits);
+  }
+
+  /**
+   * Create a new instance "factory" that produces new {@link DynamicOptionSetType} instances of the
+   * given DataType.
+   *
+   * @param dataType the {@link DataType} of the OptionSet.
+   * @return a new instance "factory".
+   */
+  public static BiFunction<ByteString, ByteString, DynamicOptionSetType> newInstanceFactory(
+      DataType dataType) {
+
+    return (value, validBits) -> newInstance(dataType, value, validBits);
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStruct.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStruct.java
deleted file mode 100644
index 14f86050e..000000000
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStruct.java
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * Copyright (c) 2024 the Eclipse Milo Authors
- *
- * This program and the accompanying materials are made
- * available under the terms of the Eclipse Public License 2.0
- * which is available at https://www.eclipse.org/legal/epl-2.0/
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-
-package org.eclipse.milo.opcua.sdk.core.types;
-
-import java.util.Arrays;
-import java.util.LinkedHashMap;
-import java.util.function.Supplier;
-import java.util.stream.Collectors;
-import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
-import org.eclipse.milo.opcua.stack.core.types.UaDataType;
-import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
-
-public class DynamicStruct implements UaDataType {
-
-  private final DataType dataType;
-  private final LinkedHashMap<String, Object> members;
-
-  public DynamicStruct(DataType dataType, LinkedHashMap<String, Object> members) {
-    this.dataType = dataType;
-    this.members = members;
-  }
-
-  public DataType getDataType() {
-    return dataType;
-  }
-
-  public LinkedHashMap<String, Object> getMembers() {
-    return members;
-  }
-
-  @Override
-  public ExpandedNodeId getTypeId() {
-    return dataType.getNodeId().expanded();
-  }
-
-  @Override
-  public String toString() {
-    return "DynamicStruct{" + "members={" + joinMembers(members) + "}}";
-  }
-
-  private static String joinMembers(LinkedHashMap<String, Object> members) {
-    return members.entrySet().stream()
-        .map(
-            e -> {
-              String k = e.getKey();
-              Object v = e.getValue();
-              if (v instanceof Object[]) {
-                return String.format("%s=%s", k, Arrays.toString((Object[]) v));
-              } else {
-                return String.format("%s=%s", k, v);
-              }
-            })
-        .collect(Collectors.joining(", "));
-  }
-
-  public static DynamicStruct newInstance(DataType dataType) {
-    return new DynamicStruct(dataType, new LinkedHashMap<>());
-  }
-
-  public static Supplier<DynamicStruct> newInstanceFactory(DataType dataType) {
-    return () -> new DynamicStruct(dataType, new LinkedHashMap<>());
-  }
-}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStructCodec.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStructCodec.java
deleted file mode 100644
index 5ac5c56cf..000000000
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStructCodec.java
+++ /dev/null
@@ -1,692 +0,0 @@
-/*
- * Copyright (c) 2024 the Eclipse Milo Authors
- *
- * This program and the accompanying materials are made
- * available under the terms of the Eclipse Public License 2.0
- * which is available at https://www.eclipse.org/legal/epl-2.0/
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-
-package org.eclipse.milo.opcua.sdk.core.types;
-
-import static java.util.Objects.requireNonNullElse;
-
-import java.util.Arrays;
-import java.util.LinkedHashMap;
-import java.util.Map;
-import java.util.UUID;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.function.Function;
-import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
-import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
-import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
-import org.eclipse.milo.opcua.stack.core.StatusCodes;
-import org.eclipse.milo.opcua.stack.core.UaSerializationException;
-import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
-import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
-import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
-import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
-import org.eclipse.milo.opcua.stack.core.types.UaEnumeratedType;
-import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
-import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
-import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
-import org.eclipse.milo.opcua.stack.core.types.builtin.DiagnosticInfo;
-import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
-import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
-import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
-import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
-import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
-import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
-import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
-import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
-import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
-import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
-import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
-import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
-import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
-import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
-import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
-import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
-import org.jspecify.annotations.NonNull;
-
-public class DynamicStructCodec extends GenericDataTypeCodec<DynamicStruct> {
-
-  private final Map<StructureField, Object> fieldHints = new ConcurrentHashMap<>();
-
-  private final Map<NodeId, Function<Integer, DynamicEnum>> enumFactories =
-      new ConcurrentHashMap<>();
-
-  private final DataType dataType;
-  private final StructureDefinition definition;
-
-  public DynamicStructCodec(DataType dataType, DataTypeTree dataTypeTree) {
-    this.dataType = dataType;
-    this.definition = (StructureDefinition) dataType.getDataTypeDefinition();
-
-    assert definition != null;
-
-    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
-
-    for (StructureField field : fields) {
-      NodeId dataTypeId = field.getDataType();
-
-      Object hint;
-      if (BuiltinDataType.isBuiltin(dataTypeId)) {
-        hint = BuiltinDataType.fromNodeId(dataTypeId);
-      } else if (dataTypeTree.isEnumType(dataTypeId)) {
-        hint = TypeHint.ENUM;
-
-        DataType enumDataType = dataTypeTree.getDataType(dataTypeId);
-        enumFactories.put(dataTypeId, DynamicEnum.newInstanceFactory(enumDataType));
-      } else if (dataTypeTree.isStructType(dataTypeId)) {
-        hint = TypeHint.STRUCT;
-      } else {
-        hint = dataTypeTree.getBuiltinType(dataTypeId);
-      }
-      fieldHints.put(field, hint);
-    }
-  }
-
-  @Override
-  public Class<DynamicStruct> getType() {
-    return DynamicStruct.class;
-  }
-
-  @Override
-  public DynamicStruct decodeType(EncodingContext context, UaDecoder decoder)
-      throws UaSerializationException {
-    switch (definition.getStructureType()) {
-      case Structure:
-      case StructureWithOptionalFields:
-      case StructureWithSubtypedValues:
-        return decodeStruct(decoder);
-      case Union:
-      case UnionWithSubtypedValues:
-        return decodeUnion(decoder);
-      default:
-        throw new IllegalArgumentException(
-            "unhandled StructureType: " + definition.getStructureType());
-    }
-  }
-
-  @Override
-  public void encodeType(EncodingContext context, UaEncoder encoder, DynamicStruct value)
-      throws UaSerializationException {
-
-    switch (definition.getStructureType()) {
-      case Structure:
-      case StructureWithOptionalFields:
-      case StructureWithSubtypedValues:
-        encodeStruct(encoder, value);
-        break;
-      case Union:
-      case UnionWithSubtypedValues:
-        encodeUnion(encoder, value);
-        break;
-      default:
-        throw new IllegalArgumentException(
-            "unhandled StructureType: " + definition.getStructureType());
-    }
-  }
-
-  private @NonNull DynamicStruct decodeStruct(UaDecoder decoder) {
-    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
-
-    LinkedHashMap<String, Object> members = new LinkedHashMap<>();
-
-    long switchField = 0xFFFFFFFFL;
-    if (definition.getStructureType() == StructureType.StructureWithOptionalFields) {
-      switchField = decoder.decodeUInt32("SwitchField").longValue();
-    }
-
-    for (int i = 0; i < fields.length; i++) {
-      StructureField field = fields[i];
-
-      if (!field.getIsOptional() || ((switchField >>> i) & 1) == 1) {
-        Object value = decodeFieldValue(decoder, field);
-
-        members.put(field.getName(), value);
-      }
-    }
-
-    return new DynamicStruct(dataType, members);
-  }
-
-  private @NonNull DynamicUnion decodeUnion(UaDecoder decoder) {
-    int switchField = decoder.decodeUInt32("SwitchField").intValue();
-
-    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
-
-    if (switchField == 0) {
-      return DynamicUnion.ofNull(dataType);
-    } else if (switchField <= fields.length) {
-      StructureField field = fields[switchField - 1];
-
-      Object value = decodeFieldValue(decoder, field);
-
-      return DynamicUnion.of(dataType, field.getName(), value);
-    } else {
-      throw new UaSerializationException(
-          StatusCodes.Bad_DecodingError, "invalid Union SwitchField value: " + switchField);
-    }
-  }
-
-  private void encodeStruct(UaEncoder encoder, DynamicStruct struct) {
-    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
-
-    long switchField = 0xFFFFFFFFL;
-    if (definition.getStructureType() == StructureType.StructureWithOptionalFields) {
-      switchField = 0L;
-      for (int i = 0; i < fields.length; i++) {
-        StructureField field = fields[i];
-        if (!field.getIsOptional()
-            || (field.getIsOptional() && struct.getMembers().containsKey(field.getName()))) {
-
-          switchField |= (1L << i);
-        }
-      }
-      encoder.encodeUInt32("SwitchField", UInteger.valueOf(switchField));
-    }
-
-    for (int i = 0; i < fields.length; i++) {
-      StructureField field = fields[i];
-
-      if (!field.getIsOptional() || ((switchField >>> i) & 1) == 1) {
-        Object value = struct.getMembers().get(field.getName());
-
-        encodeFieldValue(encoder, field, value);
-      }
-    }
-  }
-
-  private void encodeUnion(UaEncoder encoder, DynamicStruct struct) {
-    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
-
-    if (struct.getMembers().isEmpty()) {
-      encoder.encodeUInt32("SwitchValue", UInteger.valueOf(0));
-    } else {
-      for (int i = 0; i < fields.length; i++) {
-        StructureField field = fields[i];
-        String fieldName = field.getName();
-
-        if (struct.getMembers().containsKey(fieldName)) {
-          encoder.encodeUInt32("SwitchValue", UInteger.valueOf(i + 1));
-
-          Object value = struct.getMembers().get(fieldName);
-
-          encodeFieldValue(encoder, field, value);
-
-          // Return as soon as a field has been encoded.
-          // Unions are only one field, indicated by SwitchValue.
-          return;
-        }
-      }
-
-      // struct contained no members or the name didn't match a field name... encoding failure.
-      throw new UaSerializationException(StatusCodes.Bad_EncodingError, "no Union value found");
-    }
-  }
-
-  private Object decodeFieldValue(UaDecoder decoder, StructureField field) {
-    String fieldName = field.getName();
-    NodeId dataTypeId = field.getDataType();
-
-    // Note: shall be scalar or fixed dimension
-    Integer valueRank = field.getValueRank();
-    if (valueRank == -1) {
-      Object value;
-
-      Object hint = fieldHints.get(field);
-      if (hint instanceof BuiltinDataType) {
-        value = decodeBuiltinDataType(decoder, fieldName, (BuiltinDataType) hint);
-      } else {
-        TypeHint typeHint = (TypeHint) hint;
-
-        switch (typeHint) {
-          case ENUM:
-            {
-              Function<Integer, DynamicEnum> factory = enumFactories.get(dataTypeId);
-              Integer enumValue = decoder.decodeEnum(fieldName);
-              value = factory.apply(enumValue);
-              break;
-            }
-          case STRUCT:
-            value = decoder.decodeStruct(fieldName, dataTypeId);
-            break;
-          default:
-            throw new RuntimeException("codecType: " + typeHint);
-        }
-      }
-
-      return value;
-    } else if (valueRank == 1) {
-      Object value;
-
-      Object hint = fieldHints.get(field);
-      if (hint instanceof BuiltinDataType) {
-        value = decodeBuiltinDataTypeArray(decoder, fieldName, (BuiltinDataType) hint);
-      } else {
-        TypeHint typeHint = (TypeHint) hint;
-
-        switch (typeHint) {
-          case ENUM:
-            {
-              Function<Integer, DynamicEnum> factory = enumFactories.get(dataTypeId);
-              Integer[] enumValues = decoder.decodeEnumArray(fieldName);
-              value = Arrays.stream(enumValues).map(factory).toArray(DynamicEnum[]::new);
-              break;
-            }
-          case STRUCT:
-            value = decoder.decodeStructArray(fieldName, dataTypeId);
-            break;
-          default:
-            throw new RuntimeException("codecType: " + typeHint);
-        }
-      }
-
-      return value;
-    } else if (valueRank > 1) {
-      Object value;
-
-      Object hint = fieldHints.get(field);
-      if (hint instanceof BuiltinDataType) {
-        BuiltinDataType builtinDataType = (BuiltinDataType) hint;
-
-        value = decoder.decodeMatrix(fieldName, builtinDataType);
-      } else {
-        TypeHint typeHint = (TypeHint) hint;
-
-        switch (typeHint) {
-          case ENUM:
-            {
-              Matrix matrix = decoder.decodeEnumMatrix(fieldName);
-
-              if (matrix.isNotNull()) {
-                Function<Integer, DynamicEnum> factory = enumFactories.get(dataTypeId);
-                assert factory != null;
-
-                value = matrix.transform(o -> factory.apply((Integer) o));
-              } else {
-                value = matrix;
-              }
-              break;
-            }
-          case STRUCT:
-            value = decoder.decodeStructMatrix(fieldName, dataTypeId);
-            break;
-          default:
-            throw new RuntimeException("codecType: " + typeHint);
-        }
-      }
-
-      return value;
-    } else {
-      throw new UaSerializationException(
-          StatusCodes.Bad_DecodingError, "illegal ValueRank: " + valueRank);
-    }
-  }
-
-  private void encodeFieldValue(UaEncoder encoder, StructureField field, Object value) {
-    String fieldName = field.getName();
-    NodeId dataTypeId = field.getDataType();
-
-    // Note: shall be scalar or fixed dimension
-    Integer valueRank = field.getValueRank();
-    if (valueRank == -1) {
-      Object hint = fieldHints.get(field);
-      if (hint instanceof BuiltinDataType) {
-        encodeBuiltinDataType(encoder, fieldName, (BuiltinDataType) hint, value);
-      } else {
-        TypeHint typeHint = (TypeHint) hint;
-
-        switch (typeHint) {
-          case ENUM:
-            encoder.encodeEnum(fieldName, (UaEnumeratedType) value);
-            break;
-          case STRUCT:
-            encoder.encodeStruct(fieldName, value, dataTypeId);
-            break;
-          default:
-            throw new RuntimeException("codecType: " + typeHint);
-        }
-      }
-    } else if (valueRank == 1) {
-      Object hint = fieldHints.get(field);
-      if (hint instanceof BuiltinDataType) {
-        encodeBuiltinDataTypeArray(encoder, fieldName, (BuiltinDataType) hint, value);
-      } else {
-        TypeHint typeHint = (TypeHint) hint;
-
-        switch (typeHint) {
-          case ENUM:
-            encoder.encodeEnumArray(fieldName, (UaEnumeratedType[]) value);
-            break;
-          case STRUCT:
-            encoder.encodeStructArray(fieldName, (Object[]) value, dataTypeId);
-            break;
-          default:
-            throw new RuntimeException("codecType: " + typeHint);
-        }
-      }
-    } else if (valueRank > 1) {
-      Matrix matrix = (Matrix) value;
-
-      Object hint = fieldHints.get(field);
-      if (hint instanceof BuiltinDataType) {
-        encoder.encodeMatrix(fieldName, matrix);
-      } else {
-        TypeHint typeHint = (TypeHint) hint;
-
-        switch (typeHint) {
-          case ENUM:
-            encoder.encodeEnumMatrix(fieldName, matrix);
-            break;
-          case STRUCT:
-            encoder.encodeStructMatrix(fieldName, matrix, dataTypeId);
-            break;
-          default:
-            throw new RuntimeException("codecType: " + typeHint);
-        }
-      }
-    } else {
-      throw new UaSerializationException(
-          StatusCodes.Bad_EncodingError, "illegal ValueRank: " + valueRank);
-    }
-  }
-
-  private static Object decodeBuiltinDataType(
-      UaDecoder decoder, String fieldName, BuiltinDataType builtinDataType) {
-
-    switch (builtinDataType) {
-      case Boolean:
-        return decoder.decodeBoolean(fieldName);
-      case SByte:
-        return decoder.decodeSByte(fieldName);
-      case Byte:
-        return decoder.decodeByte(fieldName);
-      case Int16:
-        return decoder.decodeInt16(fieldName);
-      case UInt16:
-        return decoder.decodeUInt16(fieldName);
-      case Int32:
-        return decoder.decodeInt32(fieldName);
-      case UInt32:
-        return decoder.decodeUInt32(fieldName);
-      case Int64:
-        return decoder.decodeInt64(fieldName);
-      case UInt64:
-        return decoder.decodeUInt64(fieldName);
-      case Float:
-        return decoder.decodeFloat(fieldName);
-      case Double:
-        return decoder.decodeDouble(fieldName);
-      case String:
-        return decoder.decodeString(fieldName);
-      case DateTime:
-        return decoder.decodeDateTime(fieldName);
-      case Guid:
-        return decoder.decodeGuid(fieldName);
-      case ByteString:
-        return decoder.decodeByteString(fieldName);
-      case XmlElement:
-        return decoder.decodeXmlElement(fieldName);
-      case NodeId:
-        return decoder.decodeNodeId(fieldName);
-      case ExpandedNodeId:
-        return decoder.decodeExpandedNodeId(fieldName);
-      case StatusCode:
-        return decoder.decodeStatusCode(fieldName);
-      case QualifiedName:
-        return decoder.decodeQualifiedName(fieldName);
-      case LocalizedText:
-        return decoder.decodeLocalizedText(fieldName);
-      case ExtensionObject:
-        return decoder.decodeExtensionObject(fieldName);
-      case DataValue:
-        return decoder.decodeDataValue(fieldName);
-      case Variant:
-        return decoder.decodeVariant(fieldName);
-      case DiagnosticInfo:
-        return decoder.decodeDiagnosticInfo(fieldName);
-      default:
-        // Shouldn't happen
-        throw new RuntimeException("unhandled BuiltinDataType: " + builtinDataType);
-    }
-  }
-
-  private static Object decodeBuiltinDataTypeArray(
-      UaDecoder decoder, String fieldName, BuiltinDataType builtinDataType) {
-
-    switch (builtinDataType) {
-      case Boolean:
-        return decoder.decodeBooleanArray(fieldName);
-      case SByte:
-        return decoder.decodeSByteArray(fieldName);
-      case Byte:
-        return decoder.decodeByteArray(fieldName);
-      case Int16:
-        return decoder.decodeInt16Array(fieldName);
-      case UInt16:
-        return decoder.decodeUInt16Array(fieldName);
-      case Int32:
-        return decoder.decodeInt32Array(fieldName);
-      case UInt32:
-        return decoder.decodeUInt32Array(fieldName);
-      case Int64:
-        return decoder.decodeInt64Array(fieldName);
-      case UInt64:
-        return decoder.decodeUInt64Array(fieldName);
-      case Float:
-        return decoder.decodeFloatArray(fieldName);
-      case Double:
-        return decoder.decodeDoubleArray(fieldName);
-      case String:
-        return decoder.decodeStringArray(fieldName);
-      case DateTime:
-        return decoder.decodeDateTimeArray(fieldName);
-      case Guid:
-        return decoder.decodeGuidArray(fieldName);
-      case ByteString:
-        return decoder.decodeByteStringArray(fieldName);
-      case XmlElement:
-        return decoder.decodeXmlElementArray(fieldName);
-      case NodeId:
-        return decoder.decodeNodeIdArray(fieldName);
-      case ExpandedNodeId:
-        return decoder.decodeExpandedNodeIdArray(fieldName);
-      case StatusCode:
-        return decoder.decodeStatusCodeArray(fieldName);
-      case QualifiedName:
-        return decoder.decodeQualifiedNameArray(fieldName);
-      case LocalizedText:
-        return decoder.decodeLocalizedTextArray(fieldName);
-      case ExtensionObject:
-        return decoder.decodeExtensionObjectArray(fieldName);
-      case DataValue:
-        return decoder.decodeDataValueArray(fieldName);
-      case Variant:
-        return decoder.decodeVariantArray(fieldName);
-      case DiagnosticInfo:
-        return decoder.decodeDiagnosticInfoArray(fieldName);
-      default:
-        // Shouldn't happen
-        throw new RuntimeException("unhandled BuiltinDataType: " + builtinDataType);
-    }
-  }
-
-  private static void encodeBuiltinDataType(
-      UaEncoder encoder, String fieldName, BuiltinDataType builtinDataType, Object value) {
-
-    switch (builtinDataType) {
-      case Boolean:
-        encoder.encodeBoolean(fieldName, (Boolean) value);
-        break;
-      case SByte:
-        encoder.encodeSByte(fieldName, (Byte) value);
-        break;
-      case Byte:
-        encoder.encodeByte(fieldName, (UByte) value);
-        break;
-      case Int16:
-        encoder.encodeInt16(fieldName, (Short) value);
-        break;
-      case UInt16:
-        encoder.encodeUInt16(fieldName, (UShort) value);
-        break;
-      case Int32:
-        encoder.encodeInt32(fieldName, (Integer) value);
-        break;
-      case UInt32:
-        encoder.encodeUInt32(fieldName, (UInteger) value);
-        break;
-      case Int64:
-        encoder.encodeInt64(fieldName, (Long) value);
-        break;
-      case UInt64:
-        encoder.encodeUInt64(fieldName, (ULong) value);
-        break;
-      case Float:
-        encoder.encodeFloat(fieldName, (Float) value);
-        break;
-      case Double:
-        encoder.encodeDouble(fieldName, (Double) value);
-        break;
-      case String:
-        encoder.encodeString(fieldName, (String) value);
-        break;
-      case DateTime:
-        encoder.encodeDateTime(fieldName, (DateTime) value);
-        break;
-      case Guid:
-        encoder.encodeGuid(fieldName, (UUID) value);
-        break;
-      case ByteString:
-        encoder.encodeByteString(fieldName, (ByteString) value);
-        break;
-      case XmlElement:
-        encoder.encodeXmlElement(fieldName, (XmlElement) value);
-        break;
-      case NodeId:
-        encoder.encodeNodeId(fieldName, (NodeId) value);
-        break;
-      case ExpandedNodeId:
-        encoder.encodeExpandedNodeId(fieldName, (ExpandedNodeId) value);
-        break;
-      case StatusCode:
-        encoder.encodeStatusCode(fieldName, (StatusCode) value);
-        break;
-      case QualifiedName:
-        encoder.encodeQualifiedName(fieldName, (QualifiedName) value);
-        break;
-      case LocalizedText:
-        encoder.encodeLocalizedText(fieldName, (LocalizedText) value);
-        break;
-      case ExtensionObject:
-        encoder.encodeExtensionObject(fieldName, (ExtensionObject) value);
-        break;
-      case DataValue:
-        encoder.encodeDataValue(fieldName, (DataValue) value);
-        break;
-      case Variant:
-        encoder.encodeVariant(fieldName, (Variant) value);
-        break;
-      case DiagnosticInfo:
-        encoder.encodeDiagnosticInfo(fieldName, (DiagnosticInfo) value);
-        break;
-      default:
-        // Shouldn't happen
-        throw new RuntimeException("unhandled BuiltinDataType: " + builtinDataType);
-    }
-  }
-
-  private static void encodeBuiltinDataTypeArray(
-      UaEncoder encoder, String fieldName, BuiltinDataType builtinDataType, Object value) {
-
-    switch (builtinDataType) {
-      case Boolean:
-        encoder.encodeBooleanArray(fieldName, (Boolean[]) value);
-        break;
-      case SByte:
-        encoder.encodeSByteArray(fieldName, (Byte[]) value);
-        break;
-      case Byte:
-        encoder.encodeByteArray(fieldName, (UByte[]) value);
-        break;
-      case Int16:
-        encoder.encodeInt16Array(fieldName, (Short[]) value);
-        break;
-      case UInt16:
-        encoder.encodeUInt16Array(fieldName, (UShort[]) value);
-        break;
-      case Int32:
-        encoder.encodeInt32Array(fieldName, (Integer[]) value);
-        break;
-      case UInt32:
-        encoder.encodeUInt32Array(fieldName, (UInteger[]) value);
-        break;
-      case Int64:
-        encoder.encodeInt64Array(fieldName, (Long[]) value);
-        break;
-      case UInt64:
-        encoder.encodeUInt64Array(fieldName, (ULong[]) value);
-        break;
-      case Float:
-        encoder.encodeFloatArray(fieldName, (Float[]) value);
-        break;
-      case Double:
-        encoder.encodeDoubleArray(fieldName, (Double[]) value);
-        break;
-      case String:
-        encoder.encodeStringArray(fieldName, (String[]) value);
-        break;
-      case DateTime:
-        encoder.encodeDateTimeArray(fieldName, (DateTime[]) value);
-        break;
-      case Guid:
-        encoder.encodeGuidArray(fieldName, (UUID[]) value);
-        break;
-      case ByteString:
-        encoder.encodeByteStringArray(fieldName, (ByteString[]) value);
-        break;
-      case XmlElement:
-        encoder.encodeXmlElementArray(fieldName, (XmlElement[]) value);
-        break;
-      case NodeId:
-        encoder.encodeNodeIdArray(fieldName, (NodeId[]) value);
-        break;
-      case ExpandedNodeId:
-        encoder.encodeExpandedNodeIdArray(fieldName, (ExpandedNodeId[]) value);
-        break;
-      case StatusCode:
-        encoder.encodeStatusCodeArray(fieldName, (StatusCode[]) value);
-        break;
-      case QualifiedName:
-        encoder.encodeQualifiedNameArray(fieldName, (QualifiedName[]) value);
-        break;
-      case LocalizedText:
-        encoder.encodeLocalizedTextArray(fieldName, (LocalizedText[]) value);
-        break;
-      case ExtensionObject:
-        encoder.encodeExtensionObjectArray(fieldName, (ExtensionObject[]) value);
-        break;
-      case DataValue:
-        encoder.encodeDataValueArray(fieldName, (DataValue[]) value);
-        break;
-      case Variant:
-        encoder.encodeVariantArray(fieldName, (Variant[]) value);
-        break;
-      case DiagnosticInfo:
-        encoder.encodeDiagnosticInfoArray(fieldName, (DiagnosticInfo[]) value);
-        break;
-      default:
-        // Shouldn't happen
-        throw new RuntimeException("unhandled BuiltinDataType: " + builtinDataType);
-    }
-  }
-
-  private enum TypeHint {
-    ENUM,
-    STRUCT
-  }
-}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStructType.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStructType.java
new file mode 100644
index 000000000..ee3595dba
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicStructType.java
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import static java.util.Objects.requireNonNull;
+
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.Objects;
+import java.util.StringJoiner;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+
+public final class DynamicStructType extends DynamicType implements UaStructuredType {
+
+  private final DataType dataType;
+  private final LinkedHashMap<String, Object> members;
+
+  public DynamicStructType(DataType dataType, LinkedHashMap<String, Object> members) {
+    this.dataType = dataType;
+    this.members = members;
+  }
+
+  @Override
+  public DataType getDataType() {
+    return dataType;
+  }
+
+  @Override
+  public StructureDefinition getDataTypeDefinition() {
+    return (StructureDefinition) requireNonNull(dataType.getDataTypeDefinition());
+  }
+
+  /**
+   * Get the members of this struct.
+   *
+   * <p>The members are a map of member names to their values.
+   *
+   * @return the members of this struct.
+   */
+  public LinkedHashMap<String, Object> getMembers() {
+    return members;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return dataType.getNodeId().expanded();
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    NodeId binaryEncodingId = dataType.getBinaryEncodingId();
+    return binaryEncodingId != null ? binaryEncodingId.expanded() : ExpandedNodeId.NULL_VALUE;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    NodeId xmlEncodingId = dataType.getXmlEncodingId();
+    return xmlEncodingId != null ? xmlEncodingId.expanded() : ExpandedNodeId.NULL_VALUE;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    NodeId jsonEncodingId = dataType.getJsonEncodingId();
+    return jsonEncodingId != null ? jsonEncodingId.expanded() : ExpandedNodeId.NULL_VALUE;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == null || getClass() != o.getClass()) return false;
+    DynamicStructType that = (DynamicStructType) o;
+    return Objects.equals(dataType.getNodeId(), that.dataType.getNodeId())
+        && Objects.equals(members, that.members);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(dataType.getNodeId(), members);
+  }
+
+  @Override
+  public String toString() {
+    var joiner = new StringJoiner(", ", DynamicStructType.class.getSimpleName() + "[", "]");
+    joiner.add("dataType=" + dataType.getNodeId().toParseableString());
+    joiner.add("members=" + joinMembers(members));
+    return joiner.toString();
+  }
+
+  private static String joinMembers(LinkedHashMap<String, Object> members) {
+    return members.entrySet().stream()
+        .map(
+            e -> {
+              String k = e.getKey();
+              Object v = e.getValue();
+              if (v instanceof Object[]) {
+                return String.format("%s=%s", k, Arrays.toString((Object[]) v));
+              } else {
+                return String.format("%s=%s", k, v);
+              }
+            })
+        .collect(Collectors.joining(", "));
+  }
+
+  /**
+   * Create a new DynamicStructType using the given DataType.
+   *
+   * <p>The members of the struct are empty.
+   *
+   * @param dataType the {@link DataType} of the struct.
+   * @return a new DynamicStructType with the given DataType.
+   */
+  public static DynamicStructType newInstance(DataType dataType) {
+    return new DynamicStructType(dataType, new LinkedHashMap<>());
+  }
+
+  /**
+   * Create a new instance "factory" that produces new DynamicStructType instances of the given
+   * DataType.
+   *
+   * @param dataType the {@link DataType} of the struct.
+   * @return a new instance "factory".
+   */
+  public static Supplier<DynamicStructType> newInstanceFactory(DataType dataType) {
+    return () -> newInstance(dataType);
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicType.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicType.java
new file mode 100644
index 000000000..3d9b7763b
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicType.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.stack.core.types.UaDataType;
+import org.eclipse.milo.opcua.stack.core.types.structured.DataTypeDefinition;
+
+/**
+ * Base class for an instance of a "dynamic" type, i.e. one that is defined dynamically at runtime
+ * as opposed to statically at compile time.
+ */
+public abstract sealed class DynamicType implements UaDataType
+    permits DynamicEnumType, DynamicOptionSetType, DynamicStructType, DynamicUnionType {
+
+  /**
+   * Get the {@link DataType} that defines this type.
+   *
+   * @return the {@link DataType} that defines this type.
+   */
+  public abstract DataType getDataType();
+
+  /**
+   * Get the {@link DataTypeDefinition} that defines this type.
+   *
+   * <p>Subclasses may refine the return type to either {@link
+   * org.eclipse.milo.opcua.stack.core.types.structured.EnumDefinition} or {@link
+   * org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition}.
+   *
+   * @return the {@link DataTypeDefinition} that defines this type.
+   */
+  public abstract DataTypeDefinition getDataTypeDefinition();
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicUnion.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicUnion.java
deleted file mode 100644
index 15f05f6bb..000000000
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicUnion.java
+++ /dev/null
@@ -1,70 +0,0 @@
-/*
- * Copyright (c) 2024 the Eclipse Milo Authors
- *
- * This program and the accompanying materials are made
- * available under the terms of the Eclipse Public License 2.0
- * which is available at https://www.eclipse.org/legal/epl-2.0/
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-
-package org.eclipse.milo.opcua.sdk.core.types;
-
-import java.util.Arrays;
-import java.util.LinkedHashMap;
-import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
-import org.jspecify.annotations.Nullable;
-
-public class DynamicUnion extends DynamicStruct {
-
-  public DynamicUnion(DataType dataType) {
-    this(dataType, new LinkedHashMap<>());
-  }
-
-  public DynamicUnion(DataType dataType, LinkedHashMap<String, Object> members) {
-    super(dataType, members);
-  }
-
-  public @Nullable String getFieldName() {
-    return getMembers().keySet().stream().findFirst().orElse(null);
-  }
-
-  public @Nullable Object getFieldValue() {
-    return getMembers().values().stream().findFirst().orElse(null);
-  }
-
-  public boolean isNull() {
-    return getMembers().isEmpty();
-  }
-
-  @Override
-  public String toString() {
-    return "DynamicUnion{" + joinMembers(getMembers()) + "}";
-  }
-
-  private static String joinMembers(LinkedHashMap<String, Object> members) {
-    return members.entrySet().stream()
-        .findFirst()
-        .map(
-            e -> {
-              String k = e.getKey();
-              Object v = e.getValue();
-              if (v instanceof Object[]) {
-                return String.format("%s=%s", k, Arrays.toString((Object[]) v));
-              } else {
-                return String.format("%s=%s", k, v);
-              }
-            })
-        .orElse("null");
-  }
-
-  static DynamicUnion ofNull(DataType dataType) {
-    return new DynamicUnion(dataType);
-  }
-
-  static DynamicUnion of(DataType dataType, String fieldName, Object fieldValue) {
-    LinkedHashMap<String, Object> members = new LinkedHashMap<>();
-    members.put(fieldName, fieldValue);
-    return new DynamicUnion(dataType, members);
-  }
-}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicUnionType.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicUnionType.java
new file mode 100644
index 000000000..55d22004e
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicUnionType.java
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import static java.util.Objects.requireNonNull;
+
+import java.util.Objects;
+import java.util.Optional;
+import java.util.StringJoiner;
+import java.util.function.Function;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.jspecify.annotations.Nullable;
+
+public final class DynamicUnionType extends DynamicType implements UaStructuredType {
+
+  private final DataType dataType;
+  private final @Nullable UnionValue value;
+
+  public DynamicUnionType(DataType dataType) {
+    this(dataType, null);
+  }
+
+  public DynamicUnionType(DataType dataType, @Nullable UnionValue value) {
+    this.dataType = dataType;
+    this.value = value;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return dataType.getNodeId().expanded();
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    NodeId binaryEncodingId = dataType.getBinaryEncodingId();
+    return binaryEncodingId != null ? binaryEncodingId.expanded() : ExpandedNodeId.NULL_VALUE;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    NodeId xmlEncodingId = dataType.getXmlEncodingId();
+    return xmlEncodingId != null ? xmlEncodingId.expanded() : ExpandedNodeId.NULL_VALUE;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    NodeId jsonEncodingId = dataType.getJsonEncodingId();
+    return jsonEncodingId != null ? jsonEncodingId.expanded() : ExpandedNodeId.NULL_VALUE;
+  }
+
+  @Override
+  public DataType getDataType() {
+    return dataType;
+  }
+
+  @Override
+  public StructureDefinition getDataTypeDefinition() {
+    return (StructureDefinition) requireNonNull(dataType.getDataTypeDefinition());
+  }
+
+  /**
+   * Get the value of this union.
+   *
+   * @return the value of this union, or {@link Optional#empty()} if the value is {@code null}.
+   */
+  public Optional<UnionValue> getValue() {
+    return Optional.ofNullable(value);
+  }
+
+  /**
+   * Check if this union contains a value for the given field name.
+   *
+   * @param fieldName the field name to check.
+   * @return {@code true} if the value is not {@code null} and its field name matches the given
+   *     field name, {@code false} otherwise.
+   */
+  public boolean is(String fieldName) {
+    return value != null && value.fieldName().equals(fieldName);
+  }
+
+  /**
+   * @return {@code true} if the value is {@code null}, {@code false} otherwise.
+   */
+  public boolean isNull() {
+    return value == null;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == null || getClass() != o.getClass()) return false;
+    DynamicUnionType that = (DynamicUnionType) o;
+    return Objects.equals(dataType.getNodeId(), that.dataType.getNodeId())
+        && Objects.equals(value, that.value);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(dataType, value);
+  }
+
+  @Override
+  public String toString() {
+    var joiner = new StringJoiner(", ", DynamicUnionType.class.getSimpleName() + "[", "]");
+    joiner.add("dataType=" + dataType.getNodeId().toParseableString());
+    if (value != null) {
+      joiner.add("%s=%s".formatted(value.fieldName(), value.fieldValue()));
+    } else {
+      joiner.add("null");
+    }
+    return joiner.toString();
+  }
+
+  /**
+   * Pair of a union's field name and its value.
+   *
+   * @param fieldName the field name.
+   * @param fieldValue the field's value.
+   */
+  public record UnionValue(String fieldName, Object fieldValue) {
+    public UnionValue {
+      requireNonNull(fieldName);
+      requireNonNull(fieldValue);
+    }
+  }
+
+  /**
+   * Create a new DynamicUnionType using the given DataType and value.
+   *
+   * @param dataType the {@link DataType} of the union.
+   * @param value the {@link UnionValue} of the union.
+   * @return a new DynamicUnionType with the given DataType and value.
+   */
+  public static DynamicUnionType newInstance(DataType dataType, @Nullable UnionValue value) {
+    return new DynamicUnionType(dataType, value);
+  }
+
+  /**
+   * Create a new instance "factory" that produces new DynamicUnionType instances of the given
+   * DataType.
+   *
+   * @param dataType the {@link DataType} of the union.
+   * @return a new instance "factory".
+   */
+  public static Function<UnionValue, DynamicUnionType> newInstanceFactory(DataType dataType) {
+    return value -> new DynamicUnionType(dataType, value);
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicCodecFactory.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicCodecFactory.java
similarity index 70%
rename from opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicCodecFactory.java
rename to opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicCodecFactory.java
index d92ee20f5..e5e3197ec 100644
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicCodecFactory.java
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicCodecFactory.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 the Eclipse Milo Authors
+ * Copyright (c) 2025 the Eclipse Milo Authors
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -8,8 +8,9 @@
  * SPDX-License-Identifier: EPL-2.0
  */
 
-package org.eclipse.milo.opcua.sdk.core.types;
+package org.eclipse.milo.opcua.sdk.core.types.codec;
 
+import org.eclipse.milo.opcua.sdk.core.types.DynamicStructType;
 import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
 import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
 import org.eclipse.milo.opcua.stack.core.encoding.DataTypeCodec;
@@ -19,7 +20,7 @@
 
 /**
  * A {@link DataTypeCodec} factory that creates codecs that decodes and encodes types based on
- * {@link DynamicStruct}.
+ * {@link DynamicStructType}.
  */
 public class DynamicCodecFactory {
 
@@ -31,8 +32,12 @@ public static DataTypeCodec create(DataType dataType, DataTypeTree dataTypeTree)
       // that means it's an OptionSet subclass. True enumerations are encoded/decoded as
       // integers, so they don't have a corresponding codec.
       return new DynamicOptionSetCodec(dataType);
-    } else if (definition instanceof StructureDefinition) {
-      return new DynamicStructCodec(dataType, dataTypeTree);
+    } else if (definition instanceof StructureDefinition structureDefinition) {
+      return switch (structureDefinition.getStructureType()) {
+        case Structure, StructureWithOptionalFields, StructureWithSubtypedValues ->
+            new DynamicStructCodec(dataType, dataTypeTree);
+        case Union, UnionWithSubtypedValues -> new DynamicUnionCodec(dataType, dataTypeTree);
+      };
     } else {
       throw new RuntimeException("unknown DataTypeDefinition: " + definition);
     }
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSetCodec.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicOptionSetCodec.java
similarity index 74%
rename from opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSetCodec.java
rename to opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicOptionSetCodec.java
index 851a1e5e7..edc7949cf 100644
--- a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/DynamicOptionSetCodec.java
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicOptionSetCodec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 the Eclipse Milo Authors
+ * Copyright (c) 2025 the Eclipse Milo Authors
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -8,8 +8,9 @@
  * SPDX-License-Identifier: EPL-2.0
  */
 
-package org.eclipse.milo.opcua.sdk.core.types;
+package org.eclipse.milo.opcua.sdk.core.types.codec;
 
+import org.eclipse.milo.opcua.sdk.core.types.DynamicOptionSetType;
 import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
 import org.eclipse.milo.opcua.stack.core.UaSerializationException;
 import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
@@ -18,7 +19,7 @@
 import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
 import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
 
-class DynamicOptionSetCodec extends GenericDataTypeCodec<DynamicOptionSet> {
+class DynamicOptionSetCodec extends GenericDataTypeCodec<DynamicOptionSetType> {
 
   private final DataType dataType;
 
@@ -27,25 +28,21 @@ class DynamicOptionSetCodec extends GenericDataTypeCodec<DynamicOptionSet> {
   }
 
   @Override
-  public Class<DynamicOptionSet> getType() {
-    return DynamicOptionSet.class;
+  public Class<DynamicOptionSetType> getType() {
+    return DynamicOptionSetType.class;
   }
 
   @Override
-  public DynamicOptionSet decodeType(EncodingContext context, UaDecoder decoder)
+  public DynamicOptionSetType decodeType(EncodingContext context, UaDecoder decoder)
       throws UaSerializationException {
     ByteString value = decoder.decodeByteString("Value");
     ByteString validBits = decoder.decodeByteString("ValidBits");
 
-    var optionSet = new DynamicOptionSet(dataType);
-    optionSet.setValue(value);
-    optionSet.setValidBits(validBits);
-
-    return optionSet;
+    return new DynamicOptionSetType(dataType, value, validBits);
   }
 
   @Override
-  public void encodeType(EncodingContext context, UaEncoder encoder, DynamicOptionSet value)
+  public void encodeType(EncodingContext context, UaEncoder encoder, DynamicOptionSetType value)
       throws UaSerializationException {
     encoder.encodeByteString("Valid", value.getValue());
     encoder.encodeByteString("ValidBits", value.getValidBits());
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicStructCodec.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicStructCodec.java
new file mode 100644
index 000000000..bbb876442
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicStructCodec.java
@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.codec;
+
+import static java.util.Objects.requireNonNull;
+import static java.util.Objects.requireNonNullElse;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicStructType;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
+import org.eclipse.milo.opcua.stack.core.UaSerializationException;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.Lazy;
+import org.jspecify.annotations.NonNull;
+
+public class DynamicStructCodec extends GenericDataTypeCodec<DynamicStructType> {
+
+  private final Lazy<Map<StructureField, FieldUtil.FieldHint>> fieldHints = new Lazy<>();
+
+  private final StructureDefinition definition;
+
+  private final DataType dataType;
+  private final DataTypeTree dataTypeTree;
+
+  public DynamicStructCodec(DataType dataType, DataTypeTree dataTypeTree) {
+    this.dataType = dataType;
+    this.dataTypeTree = dataTypeTree;
+
+    this.definition = (StructureDefinition) requireNonNull(dataType.getDataTypeDefinition());
+  }
+
+  @Override
+  public Class<DynamicStructType> getType() {
+    return DynamicStructType.class;
+  }
+
+  @Override
+  public DynamicStructType decodeType(EncodingContext context, UaDecoder decoder)
+      throws UaSerializationException {
+
+    return switch (definition.getStructureType()) {
+      case Structure, StructureWithOptionalFields, StructureWithSubtypedValues ->
+          decodeStruct(decoder);
+      default ->
+          throw new IllegalArgumentException("StructureType: " + definition.getStructureType());
+    };
+  }
+
+  @Override
+  public void encodeType(EncodingContext context, UaEncoder encoder, DynamicStructType value)
+      throws UaSerializationException {
+
+    switch (definition.getStructureType()) {
+      case Structure, StructureWithOptionalFields, StructureWithSubtypedValues ->
+          encodeStruct(encoder, value);
+      default ->
+          throw new IllegalArgumentException("StructureType: " + definition.getStructureType());
+    }
+  }
+
+  private @NonNull DynamicStructType decodeStruct(UaDecoder decoder) {
+    LinkedHashMap<String, Object> members = new LinkedHashMap<>();
+
+    long switchField = 0xFFFFFFFFL;
+    if (definition.getStructureType() == StructureType.StructureWithOptionalFields) {
+      switchField = decoder.decodeUInt32("SwitchField").longValue();
+    }
+
+    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
+
+    if (definition.getStructureType() == StructureType.StructureWithOptionalFields) {
+      int optionalFieldIndex = 0;
+      for (StructureField field : fields) {
+        if (!field.getIsOptional() || (switchField >>> optionalFieldIndex++ & 1L) == 1L) {
+          Object value = FieldUtil.decodeFieldValue(decoder, definition, field, getFieldHints());
+
+          members.put(requireNonNull(field.getName()), value);
+        }
+      }
+    } else {
+      for (StructureField field : fields) {
+        Object value = FieldUtil.decodeFieldValue(decoder, definition, field, getFieldHints());
+
+        members.put(requireNonNull(field.getName()), value);
+      }
+    }
+
+    return new DynamicStructType(dataType, members);
+  }
+
+  private void encodeStruct(UaEncoder encoder, DynamicStructType struct) {
+    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
+
+    var switchField = 0L;
+    if (definition.getStructureType() == StructureType.StructureWithOptionalFields) {
+      int optionalFieldIndex = 0;
+      for (StructureField field : fields) {
+        if (field.getIsOptional()
+            && struct.getMembers().containsKey(requireNonNull(field.getName()))) {
+          switchField = switchField | (1L << optionalFieldIndex++);
+        }
+      }
+      encoder.encodeUInt32("SwitchField", UInteger.valueOf(switchField));
+    }
+
+    if (definition.getStructureType() == StructureType.StructureWithOptionalFields) {
+      int optionalFieldIndex = 0;
+      for (StructureField field : fields) {
+        if (!field.getIsOptional() || ((switchField >>> optionalFieldIndex++) & 1L) == 1L) {
+          Object value = struct.getMembers().get(field.getName());
+          FieldUtil.encodeFieldValue(encoder, definition, field, getFieldHints(), value);
+        }
+      }
+    } else {
+      for (StructureField field : fields) {
+        Object value = struct.getMembers().get(field.getName());
+        FieldUtil.encodeFieldValue(encoder, definition, field, getFieldHints(), value);
+      }
+    }
+  }
+
+  private Map<StructureField, FieldUtil.FieldHint> getFieldHints() {
+    return fieldHints.get(() -> FieldUtil.createFieldHints(definition, dataTypeTree));
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicUnionCodec.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicUnionCodec.java
new file mode 100644
index 000000000..bd221c7f2
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/DynamicUnionCodec.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.codec;
+
+import static java.util.Objects.requireNonNull;
+import static java.util.Objects.requireNonNullElse;
+
+import java.util.Map;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicUnionType;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicUnionType.UnionValue;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
+import org.eclipse.milo.opcua.stack.core.StatusCodes;
+import org.eclipse.milo.opcua.stack.core.UaSerializationException;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.Lazy;
+
+public class DynamicUnionCodec extends GenericDataTypeCodec<DynamicUnionType> {
+
+  private final Lazy<Map<StructureField, FieldUtil.FieldHint>> fieldHints = new Lazy<>();
+
+  private final StructureDefinition definition;
+
+  private final DataType dataType;
+  private final DataTypeTree dataTypeTree;
+
+  public DynamicUnionCodec(DataType dataType, DataTypeTree dataTypeTree) {
+    this.dataType = dataType;
+    this.dataTypeTree = dataTypeTree;
+
+    definition = (StructureDefinition) requireNonNull(dataType.getDataTypeDefinition());
+  }
+
+  @Override
+  public Class<DynamicUnionType> getType() {
+    return DynamicUnionType.class;
+  }
+
+  @Override
+  public DynamicUnionType decodeType(EncodingContext context, UaDecoder decoder)
+      throws UaSerializationException {
+
+    return switch (definition.getStructureType()) {
+      case Union, UnionWithSubtypedValues -> decodeUnion(decoder);
+      default ->
+          throw new IllegalArgumentException("StructureType: " + definition.getStructureType());
+    };
+  }
+
+  @Override
+  public void encodeType(EncodingContext context, UaEncoder encoder, DynamicUnionType value)
+      throws UaSerializationException {
+
+    switch (definition.getStructureType()) {
+      case Union, UnionWithSubtypedValues -> encodeUnion(encoder, value);
+      default ->
+          throw new IllegalArgumentException("StructureType: " + definition.getStructureType());
+    }
+  }
+
+  private DynamicUnionType decodeUnion(UaDecoder decoder) {
+    int switchField = decoder.decodeUInt32("SwitchField").intValue();
+
+    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
+
+    if (switchField == 0) {
+      return DynamicUnionType.newInstance(dataType, null);
+    } else if (switchField <= fields.length) {
+      StructureField field = fields[switchField - 1];
+
+      Object value = FieldUtil.decodeFieldValue(decoder, definition, field, getFieldHints());
+
+      return DynamicUnionType.newInstance(
+          dataType, new UnionValue(requireNonNull(field.getName()), value));
+    } else {
+      throw new UaSerializationException(
+          StatusCodes.Bad_DecodingError, "invalid Union SwitchField value: " + switchField);
+    }
+  }
+
+  private void encodeUnion(UaEncoder encoder, DynamicUnionType union) {
+    StructureField[] fields = requireNonNullElse(definition.getFields(), new StructureField[0]);
+
+    if (union.isNull()) {
+      encoder.encodeUInt32("SwitchValue", UInteger.valueOf(0));
+    } else {
+      UnionValue value = union.getValue().orElseThrow();
+
+      for (int i = 0; i < fields.length; i++) {
+        StructureField field = fields[i];
+        String fieldName = field.getName();
+
+        if (value.fieldName().equals(fieldName)) {
+          encoder.encodeUInt32("SwitchValue", UInteger.valueOf(i + 1));
+
+          FieldUtil.encodeFieldValue(
+              encoder, definition, field, getFieldHints(), value.fieldValue());
+
+          // Return as soon as a field has been encoded.
+          // Unions are only one field, indicated by SwitchValue.
+          return;
+        }
+      }
+
+      // struct contained no members or the name didn't match a field name... encoding failure.
+      throw new UaSerializationException(StatusCodes.Bad_EncodingError, "no Union value found");
+    }
+  }
+
+  private Map<StructureField, FieldUtil.FieldHint> getFieldHints() {
+    return fieldHints.get(() -> FieldUtil.createFieldHints(definition, dataTypeTree));
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/FieldUtil.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/FieldUtil.java
new file mode 100644
index 000000000..ef03a6ae0
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/FieldUtil.java
@@ -0,0 +1,505 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.codec;
+
+import static java.util.Objects.requireNonNull;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.UUID;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicEnumType;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicStructType;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NodeIds;
+import org.eclipse.milo.opcua.stack.core.StatusCodes;
+import org.eclipse.milo.opcua.stack.core.UaSerializationException;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaEnumeratedType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DiagnosticInfo;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+
+/** Field serialization logic shared by {@link DynamicStructCodec} and {@link DynamicUnionCodec}. */
+class FieldUtil {
+
+  private FieldUtil() {}
+
+  static Object decodeFieldValue(
+      UaDecoder decoder,
+      StructureDefinition definition,
+      StructureField field,
+      Map<StructureField, FieldHint> fieldHints) {
+
+    String fieldName = requireNonNull(field.getName());
+    NodeId dataTypeId = field.getDataType();
+
+    FieldHint fieldHint = fieldHints.get(field);
+
+    // Note: shall be scalar or fixed dimension
+    Integer valueRank = field.getValueRank();
+
+    if (valueRank == -1) {
+      if (fieldHint instanceof FieldHint.Builtin hint) {
+        return decodeBuiltinDataType(decoder, fieldName, hint.dataType);
+      } else if (fieldHint instanceof FieldHint.Enum hint) {
+        Integer enumValue = decoder.decodeEnum(fieldName);
+
+        return new DynamicEnumType(hint.dataType, enumValue);
+      } else if (fieldHint instanceof FieldHint.Struct) {
+        if (dataTypeId.equals(NodeIds.Structure) || fieldAllowsSubtyping(definition, field)) {
+          ExtensionObject xo = decoder.decodeExtensionObject(fieldName);
+
+          return xo.decode(decoder.getEncodingContext());
+        } else {
+          return decoder.decodeStruct(fieldName, dataTypeId);
+        }
+      } else {
+        throw new IllegalArgumentException("hint: " + fieldHint);
+      }
+    } else if (valueRank == 1) {
+      if (fieldHint instanceof FieldHint.Builtin hint) {
+        return decodeBuiltinDataTypeArray(decoder, fieldName, hint.dataType);
+      } else if (fieldHint instanceof FieldHint.Enum hint) {
+        Integer[] enumValues = decoder.decodeEnumArray(fieldName);
+
+        return Arrays.stream(enumValues)
+            .map(value -> new DynamicEnumType(hint.dataType, value))
+            .toArray(DynamicEnumType[]::new);
+      } else if (fieldHint instanceof FieldHint.Struct) {
+        if (dataTypeId.equals(NodeIds.Structure) || fieldAllowsSubtyping(definition, field)) {
+          ExtensionObject[] xos = decoder.decodeExtensionObjectArray(fieldName);
+
+          return Arrays.stream(xos)
+              .map(xo -> (DynamicStructType) xo.decode(decoder.getEncodingContext()))
+              .toArray(DynamicStructType[]::new);
+        } else {
+          return decoder.decodeStructArray(fieldName, dataTypeId);
+        }
+      } else {
+        throw new IllegalArgumentException("hint: " + fieldHint);
+      }
+    } else if (valueRank > 1) {
+      if (fieldHint instanceof FieldHint.Builtin hint) {
+        return decoder.decodeMatrix(fieldName, hint.dataType);
+      } else if (fieldHint instanceof FieldHint.Enum hint) {
+        Matrix matrix = decoder.decodeEnumMatrix(fieldName);
+
+        return matrix.transform(v -> new DynamicEnumType(hint.dataType, (Integer) v));
+      } else if (fieldHint instanceof FieldHint.Struct) {
+        if (dataTypeId.equals(NodeIds.Structure) || fieldAllowsSubtyping(definition, field)) {
+          Matrix matrix = decoder.decodeMatrix(fieldName, BuiltinDataType.ExtensionObject);
+
+          return matrix.transform(
+              o -> {
+                ExtensionObject xo = (ExtensionObject) o;
+                return xo.decode(decoder.getEncodingContext());
+              });
+        } else {
+          return decoder.decodeStructMatrix(fieldName, dataTypeId);
+        }
+      } else {
+        throw new IllegalArgumentException("hint: " + fieldHint);
+      }
+    } else {
+      throw new UaSerializationException(
+          StatusCodes.Bad_DecodingError, "illegal ValueRank: " + valueRank);
+    }
+  }
+
+  static void encodeFieldValue(
+      UaEncoder encoder,
+      StructureDefinition definition,
+      StructureField field,
+      Map<StructureField, FieldHint> fieldHints,
+      Object value) {
+
+    String fieldName = requireNonNull(field.getName());
+    NodeId dataTypeId = field.getDataType();
+
+    FieldHint fieldHint = fieldHints.get(field);
+
+    // Note: shall be scalar or fixed dimension
+    Integer valueRank = field.getValueRank();
+
+    if (valueRank == -1) {
+      if (fieldHint instanceof FieldHint.Builtin hint) {
+        encodeBuiltinDataType(encoder, fieldName, hint.dataType, value);
+      } else if (fieldHint instanceof FieldHint.Enum) {
+        encoder.encodeEnum(fieldName, (UaEnumeratedType) value);
+      } else if (fieldHint instanceof FieldHint.Struct) {
+        if (dataTypeId.equals(NodeIds.Structure) || fieldAllowsSubtyping(definition, field)) {
+          DynamicStructType structValue = (DynamicStructType) value;
+          ExtensionObject xo = ExtensionObject.encode(encoder.getEncodingContext(), structValue);
+          encoder.encodeExtensionObject(fieldName, xo);
+        } else {
+          encoder.encodeStruct(fieldName, value, dataTypeId);
+        }
+      } else {
+        throw new IllegalArgumentException("hint: " + fieldHint);
+      }
+    } else if (valueRank == 1) {
+      if (fieldHint instanceof FieldHint.Builtin hint) {
+        encodeBuiltinDataTypeArray(encoder, fieldName, hint.dataType, value);
+      } else if (fieldHint instanceof FieldHint.Enum) {
+        encoder.encodeEnumArray(fieldName, (UaEnumeratedType[]) value);
+      } else if (fieldHint instanceof FieldHint.Struct) {
+        if (dataTypeId.equals(NodeIds.Structure) || fieldAllowsSubtyping(definition, field)) {
+          DynamicStructType[] structArray = (DynamicStructType[]) value;
+
+          ExtensionObject[] xoArray =
+              Arrays.stream(structArray)
+                  .map(s -> ExtensionObject.encode(encoder.getEncodingContext(), s))
+                  .toArray(ExtensionObject[]::new);
+
+          encoder.encodeExtensionObjectArray(fieldName, xoArray);
+        } else {
+          encoder.encodeStructArray(fieldName, (Object[]) value, dataTypeId);
+        }
+      } else {
+        throw new IllegalArgumentException("hint: " + fieldHint);
+      }
+    } else if (valueRank > 1) {
+      if (fieldHint instanceof FieldHint.Builtin) {
+        encoder.encodeMatrix(fieldName, (Matrix) value);
+      } else if (fieldHint instanceof FieldHint.Enum) {
+        encoder.encodeEnumMatrix(fieldName, (Matrix) value);
+      } else if (fieldHint instanceof FieldHint.Struct) {
+        if (dataTypeId.equals(NodeIds.Structure) || fieldAllowsSubtyping(definition, field)) {
+          Matrix matrix = (Matrix) value;
+          Matrix xoMatrix =
+              matrix.transform(
+                  o -> {
+                    DynamicStructType structValue = (DynamicStructType) o;
+                    return ExtensionObject.encode(encoder.getEncodingContext(), structValue);
+                  });
+
+          encoder.encodeMatrix(fieldName, xoMatrix);
+        } else {
+          encoder.encodeStructMatrix(fieldName, (Matrix) value, dataTypeId);
+        }
+      } else {
+        throw new IllegalArgumentException("hint: " + fieldHint);
+      }
+    } else {
+      throw new UaSerializationException(
+          StatusCodes.Bad_EncodingError, "illegal ValueRank: " + valueRank);
+    }
+  }
+
+  /**
+   * Check if a field allows subtyping.
+   *
+   * <p>In Structures and Unions this means the field is encoded as an ExtensionObject.
+   *
+   * @param field the {@link StructureField} to check.
+   * @return {@code true} if the field allows subtyping.
+   */
+  static boolean fieldAllowsSubtyping(StructureDefinition definition, StructureField field) {
+    return field.getIsOptional()
+        && (definition.getStructureType() == StructureType.StructureWithSubtypedValues
+            || definition.getStructureType() == StructureType.UnionWithSubtypedValues);
+  }
+
+  static Map<StructureField, FieldHint> createFieldHints(
+      StructureDefinition definition, DataTypeTree dataTypeTree) {
+
+    StructureField[] fields =
+        Objects.requireNonNullElse(definition.getFields(), new StructureField[0]);
+
+    Map<StructureField, FieldHint> fieldHints = new HashMap<>();
+
+    for (StructureField field : fields) {
+      NodeId dataTypeId = field.getDataType();
+
+      FieldHint hint;
+      if (BuiltinDataType.isBuiltin(dataTypeId)) {
+        BuiltinDataType dataType = requireNonNull(BuiltinDataType.fromNodeId(dataTypeId));
+        hint = new FieldHint.Builtin(dataType);
+      } else if (dataTypeTree.isEnumType(dataTypeId)) {
+        DataType dataType = requireNonNull(dataTypeTree.getDataType(dataTypeId));
+        hint = new FieldHint.Enum(dataType);
+      } else if (dataTypeTree.isStructType(dataTypeId)) {
+        hint = new FieldHint.Struct();
+      } else {
+        // simple/alias type resolved to its builtin type
+        hint = new FieldHint.Builtin(dataTypeTree.getBuiltinType(dataTypeId));
+      }
+      fieldHints.put(field, hint);
+    }
+
+    return fieldHints;
+  }
+
+  private static Object decodeBuiltinDataType(
+      UaDecoder decoder, String fieldName, BuiltinDataType builtinDataType) {
+
+    return switch (builtinDataType) {
+      case Boolean -> decoder.decodeBoolean(fieldName);
+      case SByte -> decoder.decodeSByte(fieldName);
+      case Byte -> decoder.decodeByte(fieldName);
+      case Int16 -> decoder.decodeInt16(fieldName);
+      case UInt16 -> decoder.decodeUInt16(fieldName);
+      case Int32 -> decoder.decodeInt32(fieldName);
+      case UInt32 -> decoder.decodeUInt32(fieldName);
+      case Int64 -> decoder.decodeInt64(fieldName);
+      case UInt64 -> decoder.decodeUInt64(fieldName);
+      case Float -> decoder.decodeFloat(fieldName);
+      case Double -> decoder.decodeDouble(fieldName);
+      case String -> decoder.decodeString(fieldName);
+      case DateTime -> decoder.decodeDateTime(fieldName);
+      case Guid -> decoder.decodeGuid(fieldName);
+      case ByteString -> decoder.decodeByteString(fieldName);
+      case XmlElement -> decoder.decodeXmlElement(fieldName);
+      case NodeId -> decoder.decodeNodeId(fieldName);
+      case ExpandedNodeId -> decoder.decodeExpandedNodeId(fieldName);
+      case StatusCode -> decoder.decodeStatusCode(fieldName);
+      case QualifiedName -> decoder.decodeQualifiedName(fieldName);
+      case LocalizedText -> decoder.decodeLocalizedText(fieldName);
+      case ExtensionObject -> decoder.decodeExtensionObject(fieldName);
+      case DataValue -> decoder.decodeDataValue(fieldName);
+      case Variant -> decoder.decodeVariant(fieldName);
+      case DiagnosticInfo -> decoder.decodeDiagnosticInfo(fieldName);
+    };
+  }
+
+  private static Object decodeBuiltinDataTypeArray(
+      UaDecoder decoder, String fieldName, BuiltinDataType builtinDataType) {
+
+    return switch (builtinDataType) {
+      case Boolean -> decoder.decodeBooleanArray(fieldName);
+      case SByte -> decoder.decodeSByteArray(fieldName);
+      case Byte -> decoder.decodeByteArray(fieldName);
+      case Int16 -> decoder.decodeInt16Array(fieldName);
+      case UInt16 -> decoder.decodeUInt16Array(fieldName);
+      case Int32 -> decoder.decodeInt32Array(fieldName);
+      case UInt32 -> decoder.decodeUInt32Array(fieldName);
+      case Int64 -> decoder.decodeInt64Array(fieldName);
+      case UInt64 -> decoder.decodeUInt64Array(fieldName);
+      case Float -> decoder.decodeFloatArray(fieldName);
+      case Double -> decoder.decodeDoubleArray(fieldName);
+      case String -> decoder.decodeStringArray(fieldName);
+      case DateTime -> decoder.decodeDateTimeArray(fieldName);
+      case Guid -> decoder.decodeGuidArray(fieldName);
+      case ByteString -> decoder.decodeByteStringArray(fieldName);
+      case XmlElement -> decoder.decodeXmlElementArray(fieldName);
+      case NodeId -> decoder.decodeNodeIdArray(fieldName);
+      case ExpandedNodeId -> decoder.decodeExpandedNodeIdArray(fieldName);
+      case StatusCode -> decoder.decodeStatusCodeArray(fieldName);
+      case QualifiedName -> decoder.decodeQualifiedNameArray(fieldName);
+      case LocalizedText -> decoder.decodeLocalizedTextArray(fieldName);
+      case ExtensionObject -> decoder.decodeExtensionObjectArray(fieldName);
+      case DataValue -> decoder.decodeDataValueArray(fieldName);
+      case Variant -> decoder.decodeVariantArray(fieldName);
+      case DiagnosticInfo -> decoder.decodeDiagnosticInfoArray(fieldName);
+    };
+  }
+
+  private static void encodeBuiltinDataType(
+      UaEncoder encoder, String fieldName, BuiltinDataType builtinDataType, Object value) {
+
+    switch (builtinDataType) {
+      case Boolean:
+        encoder.encodeBoolean(fieldName, (Boolean) value);
+        break;
+      case SByte:
+        encoder.encodeSByte(fieldName, (Byte) value);
+        break;
+      case Byte:
+        encoder.encodeByte(fieldName, (UByte) value);
+        break;
+      case Int16:
+        encoder.encodeInt16(fieldName, (Short) value);
+        break;
+      case UInt16:
+        encoder.encodeUInt16(fieldName, (UShort) value);
+        break;
+      case Int32:
+        encoder.encodeInt32(fieldName, (Integer) value);
+        break;
+      case UInt32:
+        encoder.encodeUInt32(fieldName, (UInteger) value);
+        break;
+      case Int64:
+        encoder.encodeInt64(fieldName, (Long) value);
+        break;
+      case UInt64:
+        encoder.encodeUInt64(fieldName, (ULong) value);
+        break;
+      case Float:
+        encoder.encodeFloat(fieldName, (Float) value);
+        break;
+      case Double:
+        encoder.encodeDouble(fieldName, (Double) value);
+        break;
+      case String:
+        encoder.encodeString(fieldName, (String) value);
+        break;
+      case DateTime:
+        encoder.encodeDateTime(fieldName, (DateTime) value);
+        break;
+      case Guid:
+        encoder.encodeGuid(fieldName, (UUID) value);
+        break;
+      case ByteString:
+        encoder.encodeByteString(fieldName, (ByteString) value);
+        break;
+      case XmlElement:
+        encoder.encodeXmlElement(fieldName, (XmlElement) value);
+        break;
+      case NodeId:
+        encoder.encodeNodeId(fieldName, (NodeId) value);
+        break;
+      case ExpandedNodeId:
+        encoder.encodeExpandedNodeId(fieldName, (ExpandedNodeId) value);
+        break;
+      case StatusCode:
+        encoder.encodeStatusCode(fieldName, (StatusCode) value);
+        break;
+      case QualifiedName:
+        encoder.encodeQualifiedName(fieldName, (QualifiedName) value);
+        break;
+      case LocalizedText:
+        encoder.encodeLocalizedText(fieldName, (LocalizedText) value);
+        break;
+      case ExtensionObject:
+        encoder.encodeExtensionObject(fieldName, (ExtensionObject) value);
+        break;
+      case DataValue:
+        encoder.encodeDataValue(fieldName, (DataValue) value);
+        break;
+      case Variant:
+        encoder.encodeVariant(fieldName, (Variant) value);
+        break;
+      case DiagnosticInfo:
+        encoder.encodeDiagnosticInfo(fieldName, (DiagnosticInfo) value);
+        break;
+      default:
+        // Shouldn't happen
+        throw new RuntimeException("unhandled BuiltinDataType: " + builtinDataType);
+    }
+  }
+
+  private static void encodeBuiltinDataTypeArray(
+      UaEncoder encoder, String fieldName, BuiltinDataType builtinDataType, Object value) {
+
+    switch (builtinDataType) {
+      case Boolean:
+        encoder.encodeBooleanArray(fieldName, (Boolean[]) value);
+        break;
+      case SByte:
+        encoder.encodeSByteArray(fieldName, (Byte[]) value);
+        break;
+      case Byte:
+        encoder.encodeByteArray(fieldName, (UByte[]) value);
+        break;
+      case Int16:
+        encoder.encodeInt16Array(fieldName, (Short[]) value);
+        break;
+      case UInt16:
+        encoder.encodeUInt16Array(fieldName, (UShort[]) value);
+        break;
+      case Int32:
+        encoder.encodeInt32Array(fieldName, (Integer[]) value);
+        break;
+      case UInt32:
+        encoder.encodeUInt32Array(fieldName, (UInteger[]) value);
+        break;
+      case Int64:
+        encoder.encodeInt64Array(fieldName, (Long[]) value);
+        break;
+      case UInt64:
+        encoder.encodeUInt64Array(fieldName, (ULong[]) value);
+        break;
+      case Float:
+        encoder.encodeFloatArray(fieldName, (Float[]) value);
+        break;
+      case Double:
+        encoder.encodeDoubleArray(fieldName, (Double[]) value);
+        break;
+      case String:
+        encoder.encodeStringArray(fieldName, (String[]) value);
+        break;
+      case DateTime:
+        encoder.encodeDateTimeArray(fieldName, (DateTime[]) value);
+        break;
+      case Guid:
+        encoder.encodeGuidArray(fieldName, (UUID[]) value);
+        break;
+      case ByteString:
+        encoder.encodeByteStringArray(fieldName, (ByteString[]) value);
+        break;
+      case XmlElement:
+        encoder.encodeXmlElementArray(fieldName, (XmlElement[]) value);
+        break;
+      case NodeId:
+        encoder.encodeNodeIdArray(fieldName, (NodeId[]) value);
+        break;
+      case ExpandedNodeId:
+        encoder.encodeExpandedNodeIdArray(fieldName, (ExpandedNodeId[]) value);
+        break;
+      case StatusCode:
+        encoder.encodeStatusCodeArray(fieldName, (StatusCode[]) value);
+        break;
+      case QualifiedName:
+        encoder.encodeQualifiedNameArray(fieldName, (QualifiedName[]) value);
+        break;
+      case LocalizedText:
+        encoder.encodeLocalizedTextArray(fieldName, (LocalizedText[]) value);
+        break;
+      case ExtensionObject:
+        encoder.encodeExtensionObjectArray(fieldName, (ExtensionObject[]) value);
+        break;
+      case DataValue:
+        encoder.encodeDataValueArray(fieldName, (DataValue[]) value);
+        break;
+      case Variant:
+        encoder.encodeVariantArray(fieldName, (Variant[]) value);
+        break;
+      case DiagnosticInfo:
+        encoder.encodeDiagnosticInfoArray(fieldName, (DiagnosticInfo[]) value);
+        break;
+      default:
+        // Shouldn't happen
+        throw new RuntimeException("unhandled BuiltinDataType: " + builtinDataType);
+    }
+  }
+
+  sealed interface FieldHint permits FieldHint.Builtin, FieldHint.Enum, FieldHint.Struct {
+
+    record Builtin(BuiltinDataType dataType) implements FieldHint {}
+
+    record Enum(DataType dataType) implements FieldHint {}
+
+    record Struct() implements FieldHint {}
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/package-info.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/package-info.java
new file mode 100644
index 000000000..d20b3bd41
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/codec/package-info.java
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+@NullMarked
+package org.eclipse.milo.opcua.sdk.core.types.codec;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/package-info.java b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/package-info.java
new file mode 100644
index 000000000..5b565cc92
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/main/java/org/eclipse/milo/opcua/sdk/core/types/package-info.java
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+@NullMarked
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/DynamicTypeSerializationTest.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/DynamicTypeSerializationTest.java
new file mode 100644
index 000000000..7cb746556
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/DynamicTypeSerializationTest.java
@@ -0,0 +1,842 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types;
+
+import static org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned.ubyte;
+import static org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned.uint;
+import static org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned.ulong;
+import static org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned.ushort;
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.LinkedHashMap;
+import java.util.UUID;
+import java.util.stream.Stream;
+import org.eclipse.milo.opcua.sdk.core.types.DynamicUnionType.UnionValue;
+import org.eclipse.milo.opcua.sdk.core.types.util.DynamicEncodingContext;
+import org.eclipse.milo.opcua.sdk.core.types.util.StaticEncodingContext;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.ApplicationType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelExType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessRestrictionType;
+import org.eclipse.milo.opcua.stack.core.types.structured.XVType;
+import org.eclipse.milo.opcua.test.types.ConcreteTestType;
+import org.eclipse.milo.opcua.test.types.ConcreteTestTypeEx;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinArrayFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinMatrixFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinScalarFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureScalarFields;
+import org.eclipse.milo.opcua.test.types.TestEnumType;
+import org.eclipse.milo.opcua.test.types.UnionOfArray;
+import org.eclipse.milo.opcua.test.types.UnionOfMatrix;
+import org.eclipse.milo.opcua.test.types.UnionOfScalar;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class DynamicTypeSerializationTest {
+
+  private final DynamicEncodingContext dynamicEncodingContext = new DynamicEncodingContext();
+  private final StaticEncodingContext staticEncodingContext = new StaticEncodingContext();
+
+  @Test
+  void structWithScalarFields() {
+    var struct =
+        new StructWithBuiltinScalarFields(
+            false,
+            (byte) 0,
+            ubyte(0),
+            (short) 0,
+            ushort(0),
+            0,
+            uint(0),
+            0L,
+            ulong(0L),
+            0.0f,
+            0.0d,
+            "",
+            DateTime.MIN_DATE_TIME,
+            UUID.fromString("00000000-0000-0000-0000-000000000000"),
+            ByteString.of(new byte[] {0}),
+            XmlElement.of(""),
+            new NodeId(0, 0),
+            new ExpandedNodeId(ushort(0), null, uint(0)),
+            StatusCode.GOOD,
+            new QualifiedName(0, ""),
+            LocalizedText.NULL_VALUE,
+            new DataValue(new Variant(0)),
+            Variant.ofInt32(0));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+
+    var members = new LinkedHashMap<String, Object>();
+    members.put("Boolean", struct.getBoolean());
+    members.put("SByte", struct.getSByte());
+    members.put("Byte", struct.getByte());
+    members.put("Int16", struct.getInt16());
+    members.put("UInt16", struct.getUInt16());
+    members.put("Int32", struct.getInt32());
+    members.put("UInt32", struct.getUInt32());
+    members.put("Int64", struct.getInt64());
+    members.put("UInt64", struct.getUInt64());
+    members.put("Float", struct.getFloat());
+    members.put("Double", struct.getDouble());
+    members.put("String", struct.getString());
+    members.put("DateTime", struct.getDateTime());
+    members.put("Guid", struct.getGuid());
+    members.put("ByteString", struct.getByteString());
+    members.put("XmlElement", struct.getXmlElement());
+    members.put("NodeId", struct.getNodeId());
+    members.put("ExpandedNodeId", struct.getExpandedNodeId());
+    members.put("StatusCode", struct.getStatusCode());
+    members.put("QualifiedName", struct.getQualifiedName());
+    members.put("LocalizedText", struct.getLocalizedText());
+    members.put("DataValue", struct.getDataValue());
+    members.put("Variant", struct.getVariant());
+    DynamicStructType expected = new DynamicStructType(decoded.getDataType(), members);
+
+    assertEquals(expected, decoded);
+  }
+
+  @Test
+  void structWithScalarFieldsEx() {
+    var struct =
+        new StructWithBuiltinScalarFieldsEx(
+            false,
+            (byte) 0,
+            ubyte(0),
+            (short) 0,
+            ushort(0),
+            0,
+            uint(0),
+            0L,
+            ulong(0L),
+            0.0f,
+            0.0d,
+            "",
+            DateTime.MIN_DATE_TIME,
+            UUID.fromString("00000000-0000-0000-0000-000000000000"),
+            ByteString.of(new byte[] {0}),
+            XmlElement.of(""),
+            new NodeId(0, 0),
+            new ExpandedNodeId(ushort(0), null, uint(0)),
+            StatusCode.GOOD,
+            new QualifiedName(0, ""),
+            LocalizedText.NULL_VALUE,
+            new DataValue(new Variant(0)),
+            Variant.ofInt32(0),
+            0.0,
+            ApplicationType.Server,
+            TestEnumType.A,
+            new XVType(0.0d, 0.0f),
+            new ConcreteTestType((short) 0, 0.0, "", false),
+            UnionOfScalar.ofBoolean(false),
+            UnionOfArray.ofBoolean(new Boolean[] {false, false}),
+            AccessLevelType.of(),
+            AccessRestrictionType.of(),
+            AccessLevelExType.of(),
+            ulong(0));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+
+    var members = new LinkedHashMap<String, Object>();
+    members.put("Boolean", struct.getBoolean());
+    members.put("SByte", struct.getSByte());
+    members.put("Byte", struct.getByte());
+    members.put("Int16", struct.getInt16());
+    members.put("UInt16", struct.getUInt16());
+    members.put("Int32", struct.getInt32());
+    members.put("UInt32", struct.getUInt32());
+    members.put("Int64", struct.getInt64());
+    members.put("UInt64", struct.getUInt64());
+    members.put("Float", struct.getFloat());
+    members.put("Double", struct.getDouble());
+    members.put("String", struct.getString());
+    members.put("DateTime", struct.getDateTime());
+    members.put("Guid", struct.getGuid());
+    members.put("ByteString", struct.getByteString());
+    members.put("XmlElement", struct.getXmlElement());
+    members.put("NodeId", struct.getNodeId());
+    members.put("ExpandedNodeId", struct.getExpandedNodeId());
+    members.put("StatusCode", struct.getStatusCode());
+    members.put("QualifiedName", struct.getQualifiedName());
+    members.put("LocalizedText", struct.getLocalizedText());
+    members.put("DataValue", struct.getDataValue());
+    members.put("Variant", struct.getVariant());
+    members.put("Duration", struct.getDuration());
+
+    // Ideally we wouldn't just grab the same value decoded since it's the object we're testing but
+    // these are difficult to construct right now without easy access to a corresponding DataType
+    // for each field.
+    members.put(
+        "ApplicationType",
+        new DynamicEnumType(
+            DynamicEncodingContext.APPLICATION_TYPE_DATA_TYPE, ApplicationType.Server.getValue()));
+    members.put("TestEnumType", new DynamicEnumType(dynamicEncodingContext.testEnumType, 0));
+    members.put("XVType", decoded.getMembers().get("XVType"));
+    members.put("ConcreteTestType", decoded.getMembers().get("ConcreteTestType"));
+    members.put(
+        "UnionOfScalar",
+        DynamicUnionType.newInstance(
+            dynamicEncodingContext.unionOfScalar, new UnionValue("Boolean", false)));
+    members.put("UnionOfArray", decoded.getMembers().get("UnionOfArray"));
+    members.put("OptionSetUI8", decoded.getMembers().get("OptionSetUI8"));
+    members.put("OptionSetUI16", decoded.getMembers().get("OptionSetUI16"));
+    members.put("OptionSetUI32", decoded.getMembers().get("OptionSetUI32"));
+    members.put("OptionSetUI64", decoded.getMembers().get("OptionSetUI64"));
+
+    DynamicStructType expected = new DynamicStructType(decoded.getDataType(), members);
+
+    assertEquals(expected, decoded);
+  }
+
+  @Test
+  void structWithArrayFields() {
+    var struct =
+        new StructWithBuiltinArrayFields(
+            new Boolean[] {false, false},
+            new Byte[] {0, 0},
+            new UByte[] {ubyte(0), ubyte(0)},
+            new Short[] {0, 0},
+            new UShort[] {ushort(0), ushort(0)},
+            new Integer[] {0, 0},
+            new UInteger[] {uint(0), uint(0)},
+            new Long[] {0L, 0L},
+            new ULong[] {ulong(0L), ulong(0L)},
+            new Float[] {0.0f, 0.0f},
+            new Double[] {0.0d, 0.0d},
+            new String[] {"", ""},
+            new DateTime[] {DateTime.MIN_DATE_TIME, DateTime.MIN_DATE_TIME},
+            new UUID[] {
+              UUID.fromString("00000000-0000-0000-0000-000000000000"),
+              UUID.fromString("00000000-0000-0000-0000-000000000000")
+            },
+            new ByteString[] {ByteString.of(new byte[] {0}), ByteString.of(new byte[] {0})},
+            new XmlElement[] {XmlElement.of(""), XmlElement.of("")},
+            new NodeId[] {new NodeId(0, 0), new NodeId(0, 0)},
+            new ExpandedNodeId[] {
+              new ExpandedNodeId(ushort(0), null, uint(0)),
+              new ExpandedNodeId(ushort(0), null, uint(0))
+            },
+            new StatusCode[] {StatusCode.GOOD, StatusCode.GOOD},
+            new QualifiedName[] {new QualifiedName(0, ""), new QualifiedName(0, "")},
+            new LocalizedText[] {LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE},
+            new DataValue[] {new DataValue(new Variant(0)), new DataValue(new Variant(0))},
+            new Variant[] {Variant.ofInt32(0), Variant.ofInt32(0)});
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithArrayFieldsEx() {
+    var struct =
+        new StructWithBuiltinArrayFieldsEx(
+            new Boolean[] {false, false},
+            new Byte[] {0, 0},
+            new UByte[] {ubyte(0), ubyte(0)},
+            new Short[] {0, 0},
+            new UShort[] {ushort(0), ushort(0)},
+            new Integer[] {0, 0},
+            new UInteger[] {uint(0), uint(0)},
+            new Long[] {0L, 0L},
+            new ULong[] {ulong(0L), ulong(0L)},
+            new Float[] {0.0f, 0.0f},
+            new Double[] {0.0d, 0.0d},
+            new String[] {"", ""},
+            new DateTime[] {DateTime.MIN_DATE_TIME, DateTime.MIN_DATE_TIME},
+            new UUID[] {
+              UUID.fromString("00000000-0000-0000-0000-000000000000"),
+              UUID.fromString("00000000-0000-0000-0000-000000000000")
+            },
+            new ByteString[] {ByteString.of(new byte[] {0}), ByteString.of(new byte[] {0})},
+            new XmlElement[] {XmlElement.of(""), XmlElement.of("")},
+            new NodeId[] {new NodeId(0, 0), new NodeId(0, 0)},
+            new ExpandedNodeId[] {
+              new ExpandedNodeId(ushort(0), null, uint(0)),
+              new ExpandedNodeId(ushort(0), null, uint(0))
+            },
+            new StatusCode[] {StatusCode.GOOD, StatusCode.GOOD},
+            new QualifiedName[] {new QualifiedName(0, ""), new QualifiedName(0, "")},
+            new LocalizedText[] {LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE},
+            new DataValue[] {new DataValue(new Variant(0)), new DataValue(new Variant(0))},
+            new Variant[] {Variant.ofInt32(0), Variant.ofInt32(0)},
+            new Double[] {0.0, 0.0},
+            new ApplicationType[] {ApplicationType.Server, ApplicationType.Client},
+            new TestEnumType[] {TestEnumType.A, TestEnumType.B},
+            new XVType[] {new XVType(0.0d, 0.0f), new XVType(0.0d, 0.0f)},
+            new ConcreteTestType[] {
+              new ConcreteTestType((short) 0, 0.0, "", false),
+              new ConcreteTestType((short) 0, 0.0, "", false)
+            },
+            new UnionOfScalar[] {UnionOfScalar.ofBoolean(false), UnionOfScalar.ofByte(ubyte(0))},
+            new UnionOfArray[] {
+              UnionOfArray.ofBoolean(new Boolean[] {false, false}),
+              UnionOfArray.ofSByte(new Byte[] {0, 0})
+            },
+            new AccessLevelType[] {AccessLevelType.of(), AccessLevelType.of()},
+            new AccessRestrictionType[] {AccessRestrictionType.of(), AccessRestrictionType.of()},
+            new AccessLevelExType[] {AccessLevelExType.of(), AccessLevelExType.of()},
+            new ULong[] {ulong(0L), ulong(0L)});
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithAbstractScalarFields() {
+    var struct =
+        new StructWithAbstractScalarFields(
+            0,
+            new ConcreteTestType((short) 0, 0.0, "", false),
+            new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0)));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithAbstractArrayFields() {
+    var struct =
+        new StructWithAbstractArrayFields(
+            new Integer[] {0, 0},
+            new ConcreteTestType[] {
+              new ConcreteTestType((short) 0, 0.0, "", false),
+              new ConcreteTestType((short) 0, 0.0, "", false)
+            },
+            new ConcreteTestTypeEx[] {
+              new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0)),
+              new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0))
+            });
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithAbstractMatrixFields() {
+    var struct =
+        new StructWithAbstractMatrixFields(
+            Matrix.ofInt32(new Integer[][] {{0, 0}, {0, 0}}),
+            Matrix.ofStruct(
+                new ConcreteTestType[][] {
+                  {
+                    new ConcreteTestType((short) 0, 0.0, "", false),
+                    new ConcreteTestType((short) 0, 0.0, "", false)
+                  },
+                  {
+                    new ConcreteTestType((short) 0, 0.0, "", false),
+                    new ConcreteTestType((short) 0, 0.0, "", false)
+                  }
+                }),
+            Matrix.ofStruct(
+                new ConcreteTestTypeEx[][] {
+                  {
+                    new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0)),
+                    new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0))
+                  },
+                  {
+                    new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0)),
+                    new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0))
+                  }
+                }));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @ParameterizedTest
+  @MethodSource("structWithOptionalScalarFieldsProvider")
+  void structWithOptionalScalarFields(StructWithOptionalScalarFields struct) {
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @ParameterizedTest
+  @MethodSource("structWithOptionalArrayFieldsProvider")
+  void structWithOptionalArrayFields(StructWithOptionalArrayFields struct) {
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithMatrixFields() {
+    var struct =
+        new StructWithBuiltinMatrixFields(
+            Matrix.ofBoolean(new Boolean[][] {{false, false}, {false, false}}),
+            Matrix.ofSByte(new Byte[][] {{0, 0}, {0, 0}}),
+            Matrix.ofByte(new UByte[][] {{ubyte(0), ubyte(0)}, {ubyte(0), ubyte(0)}}),
+            Matrix.ofInt16(new Short[][] {{0, 0}, {0, 0}}),
+            Matrix.ofUInt16(new UShort[][] {{ushort(0), ushort(0)}, {ushort(0), ushort(0)}}),
+            Matrix.ofInt32(new Integer[][] {{0, 0}, {0, 0}}),
+            Matrix.ofUInt32(new UInteger[][] {{uint(0), uint(0)}, {uint(0), uint(0)}}),
+            Matrix.ofInt64(new Long[][] {{0L, 0L}, {0L, 0L}}),
+            Matrix.ofUInt64(new ULong[][] {{ulong(0L), ulong(0L)}, {ulong(0L), ulong(0L)}}),
+            Matrix.ofFloat(new Float[][] {{0.0f, 0.0f}, {0.0f, 0.0f}}),
+            Matrix.ofDouble(new Double[][] {{0.0d, 0.0d}, {0.0d, 0.0d}}),
+            Matrix.ofString(new String[][] {{"", ""}, {"", ""}}),
+            Matrix.ofDateTime(
+                new DateTime[][] {
+                  {DateTime.MIN_DATE_TIME, DateTime.MIN_DATE_TIME},
+                  {DateTime.MIN_DATE_TIME, DateTime.MIN_DATE_TIME}
+                }),
+            Matrix.ofGuid(
+                new UUID[][] {
+                  {
+                    UUID.fromString("00000000-0000-0000-0000-000000000000"),
+                    UUID.fromString("00000000-0000-0000-0000-000000000000")
+                  },
+                  {
+                    UUID.fromString("00000000-0000-0000-0000-000000000000"),
+                    UUID.fromString("00000000-0000-0000-0000-000000000000")
+                  }
+                }),
+            Matrix.ofByteString(
+                new ByteString[][] {
+                  {ByteString.of(new byte[] {0}), ByteString.of(new byte[] {0})},
+                  {ByteString.of(new byte[] {0}), ByteString.of(new byte[] {0})}
+                }),
+            Matrix.ofXmlElement(
+                new XmlElement[][] {
+                  {XmlElement.of(""), XmlElement.of("")},
+                  {XmlElement.of(""), XmlElement.of("")}
+                }),
+            Matrix.ofNodeId(
+                new NodeId[][] {
+                  {new NodeId(0, 0), new NodeId(0, 0)},
+                  {new NodeId(0, 0), new NodeId(0, 0)}
+                }),
+            Matrix.ofExpandedNodeId(
+                new ExpandedNodeId[][] {
+                  {
+                    new ExpandedNodeId(ushort(0), null, uint(0)),
+                    new ExpandedNodeId(ushort(0), null, uint(0))
+                  },
+                  {
+                    new ExpandedNodeId(ushort(0), null, uint(0)),
+                    new ExpandedNodeId(ushort(0), null, uint(0))
+                  }
+                }),
+            Matrix.ofStatusCode(
+                new StatusCode[][] {
+                  {StatusCode.GOOD, StatusCode.GOOD},
+                  {StatusCode.GOOD, StatusCode.GOOD}
+                }),
+            Matrix.ofQualifiedName(
+                new QualifiedName[][] {
+                  {new QualifiedName(0, ""), new QualifiedName(0, "")},
+                  {new QualifiedName(0, ""), new QualifiedName(0, "")}
+                }),
+            Matrix.ofLocalizedText(
+                new LocalizedText[][] {
+                  {LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE},
+                  {LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE}
+                }),
+            Matrix.ofDataValue(
+                new DataValue[][] {
+                  {new DataValue(new Variant(0)), new DataValue(new Variant(0))},
+                  {new DataValue(new Variant(0)), new DataValue(new Variant(0))}
+                }),
+            Matrix.ofVariant(
+                new Variant[][] {
+                  {Variant.ofInt32(0), Variant.ofInt32(0)},
+                  {Variant.ofInt32(0), Variant.ofInt32(0)}
+                }));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithMatrixFieldsEx() {
+    var struct =
+        new StructWithBuiltinMatrixFieldsEx(
+            Matrix.ofBoolean(new Boolean[][] {{false, false}, {false, false}}),
+            Matrix.ofSByte(new Byte[][] {{0, 0}, {0, 0}}),
+            Matrix.ofByte(new UByte[][] {{ubyte(0), ubyte(0)}, {ubyte(0), ubyte(0)}}),
+            Matrix.ofInt16(new Short[][] {{0, 0}, {0, 0}}),
+            Matrix.ofUInt16(new UShort[][] {{ushort(0), ushort(0)}, {ushort(0), ushort(0)}}),
+            Matrix.ofInt32(new Integer[][] {{0, 0}, {0, 0}}),
+            Matrix.ofUInt32(new UInteger[][] {{uint(0), uint(0)}, {uint(0), uint(0)}}),
+            Matrix.ofInt64(new Long[][] {{0L, 0L}, {0L, 0L}}),
+            Matrix.ofUInt64(new ULong[][] {{ulong(0L), ulong(0L)}, {ulong(0L), ulong(0L)}}),
+            Matrix.ofFloat(new Float[][] {{0.0f, 0.0f}, {0.0f, 0.0f}}),
+            Matrix.ofDouble(new Double[][] {{0.0d, 0.0d}, {0.0d, 0.0d}}),
+            Matrix.ofString(new String[][] {{"", ""}, {"", ""}}),
+            Matrix.ofDateTime(
+                new DateTime[][] {
+                  {DateTime.MIN_DATE_TIME, DateTime.MIN_DATE_TIME},
+                  {DateTime.MIN_DATE_TIME, DateTime.MIN_DATE_TIME}
+                }),
+            Matrix.ofGuid(
+                new UUID[][] {
+                  {
+                    UUID.fromString("00000000-0000-0000-0000-000000000000"),
+                    UUID.fromString("00000000-0000-0000-0000-000000000000")
+                  },
+                  {
+                    UUID.fromString("00000000-0000-0000-0000-000000000000"),
+                    UUID.fromString("00000000-0000-0000-0000-000000000000")
+                  }
+                }),
+            Matrix.ofByteString(
+                new ByteString[][] {
+                  {ByteString.of(new byte[] {0}), ByteString.of(new byte[] {0})},
+                  {ByteString.of(new byte[] {0}), ByteString.of(new byte[] {0})}
+                }),
+            Matrix.ofXmlElement(
+                new XmlElement[][] {
+                  {XmlElement.of(""), XmlElement.of("")},
+                  {XmlElement.of(""), XmlElement.of("")}
+                }),
+            Matrix.ofNodeId(
+                new NodeId[][] {
+                  {new NodeId(0, 0), new NodeId(0, 0)},
+                  {new NodeId(0, 0), new NodeId(0, 0)}
+                }),
+            Matrix.ofExpandedNodeId(
+                new ExpandedNodeId[][] {
+                  {
+                    new ExpandedNodeId(ushort(0), null, uint(0)),
+                    new ExpandedNodeId(ushort(0), null, uint(0))
+                  },
+                  {
+                    new ExpandedNodeId(ushort(0), null, uint(0)),
+                    new ExpandedNodeId(ushort(0), null, uint(0))
+                  }
+                }),
+            Matrix.ofStatusCode(
+                new StatusCode[][] {
+                  {StatusCode.GOOD, StatusCode.GOOD},
+                  {StatusCode.GOOD, StatusCode.GOOD}
+                }),
+            Matrix.ofQualifiedName(
+                new QualifiedName[][] {
+                  {new QualifiedName(0, ""), new QualifiedName(0, "")},
+                  {new QualifiedName(0, ""), new QualifiedName(0, "")}
+                }),
+            Matrix.ofLocalizedText(
+                new LocalizedText[][] {
+                  {LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE},
+                  {LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE}
+                }),
+            Matrix.ofDataValue(
+                new DataValue[][] {
+                  {new DataValue(new Variant(0)), new DataValue(new Variant(0))},
+                  {new DataValue(new Variant(0)), new DataValue(new Variant(0))}
+                }),
+            Matrix.ofVariant(
+                new Variant[][] {
+                  {Variant.ofInt32(0), Variant.ofInt32(0)},
+                  {Variant.ofInt32(0), Variant.ofInt32(0)}
+                }),
+            Matrix.ofDouble(new Double[][] {{0.0, 0.0}, {0.0, 0.0}}),
+            Matrix.ofEnum(
+                new ApplicationType[][] {
+                  {ApplicationType.Server, ApplicationType.Client},
+                  {ApplicationType.Server, ApplicationType.Client}
+                }),
+            Matrix.ofEnum(
+                new TestEnumType[][] {
+                  {TestEnumType.A, TestEnumType.B},
+                  {TestEnumType.A, TestEnumType.B}
+                }),
+            Matrix.ofStruct(
+                new XVType[][] {
+                  {new XVType(0.0d, 0.0f), new XVType(0.0d, 0.0f)},
+                  {new XVType(0.0d, 0.0f), new XVType(0.0d, 0.0f)}
+                }),
+            Matrix.ofStruct(
+                new ConcreteTestType[][] {
+                  {
+                    new ConcreteTestType((short) 0, 0.0, "", false),
+                    new ConcreteTestType((short) 0, 0.0, "", false)
+                  },
+                  {
+                    new ConcreteTestType((short) 0, 0.0, "", false),
+                    new ConcreteTestType((short) 0, 0.0, "", false)
+                  }
+                }),
+            Matrix.ofStruct(
+                new UnionOfScalar[][] {
+                  {UnionOfScalar.ofBoolean(false), UnionOfScalar.ofByte(ubyte(0))},
+                  {UnionOfScalar.ofBoolean(false), UnionOfScalar.ofByte(ubyte(0))}
+                }),
+            Matrix.ofStruct(
+                new UnionOfArray[][] {
+                  {
+                    UnionOfArray.ofBoolean(new Boolean[] {false, false}),
+                    UnionOfArray.ofSByte(new Byte[] {0, 0})
+                  },
+                  {
+                    UnionOfArray.ofBoolean(new Boolean[] {false, false}),
+                    UnionOfArray.ofSByte(new Byte[] {0, 0})
+                  }
+                }),
+            Matrix.ofOptionSetUI(
+                new AccessLevelType[][] {
+                  {AccessLevelType.of(), AccessLevelType.of()},
+                  {AccessLevelType.of(), AccessLevelType.of()}
+                }),
+            Matrix.ofOptionSetUI(
+                new AccessRestrictionType[][] {
+                  {AccessRestrictionType.of(), AccessRestrictionType.of()},
+                  {AccessRestrictionType.of(), AccessRestrictionType.of()}
+                }),
+            Matrix.ofOptionSetUI(
+                new AccessLevelExType[][] {
+                  {AccessLevelExType.of(), AccessLevelExType.of()},
+                  {AccessLevelExType.of(), AccessLevelExType.of()}
+                }),
+            Matrix.ofUInt64(new ULong[][] {{ulong(0), ulong(0)}, {ulong(0), ulong(0)}}));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithStructureScalarFields() {
+    var struct =
+        new StructWithStructureScalarFields(
+            ExtensionObject.encode(staticEncodingContext, new XVType(0.0d, 0.0f)),
+            ExtensionObject.encode(
+                staticEncodingContext, new ConcreteTestType((short) 0, 0.0, "", false)),
+            ExtensionObject.encode(
+                staticEncodingContext, new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0))));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithStructureArrayFields() {
+    var xo1 = ExtensionObject.encode(staticEncodingContext, new XVType(0.0d, 0.0f));
+    var xo2 =
+        ExtensionObject.encode(
+            staticEncodingContext, new ConcreteTestType((short) 0, 0.0, "", false));
+    var xo3 =
+        ExtensionObject.encode(
+            staticEncodingContext, new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0)));
+    var struct =
+        new StructWithStructureArrayFields(
+            new ExtensionObject[] {xo1, xo1},
+            new ExtensionObject[] {xo2, xo2},
+            new ExtensionObject[] {xo3, xo3});
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @Test
+  void structWithStructureMatrixFields() {
+    var xo1 = ExtensionObject.encode(staticEncodingContext, new XVType(0.0d, 0.0f));
+    var xo2 =
+        ExtensionObject.encode(
+            staticEncodingContext, new ConcreteTestType((short) 0, 0.0, "", false));
+    var xo3 =
+        ExtensionObject.encode(
+            staticEncodingContext, new ConcreteTestTypeEx((short) 0, 0.0, "", false, uint(0)));
+    var struct =
+        new StructWithStructureMatrixFields(
+            Matrix.ofExtensionObject(new ExtensionObject[][] {{xo1, xo1}, {xo1, xo1}}),
+            Matrix.ofExtensionObject(new ExtensionObject[][] {{xo2, xo2}, {xo2, xo2}}),
+            Matrix.ofExtensionObject(new ExtensionObject[][] {{xo3, xo3}, {xo3, xo3}}));
+
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, struct);
+    DynamicStructType decoded = (DynamicStructType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @ParameterizedTest
+  @MethodSource("unionOfScalarProvider")
+  void unionOfScalar(UnionOfScalar union) {
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, union);
+    UaStructuredType decoded = (UaStructuredType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @ParameterizedTest
+  @MethodSource("unionOfArrayProvider")
+  void unionOfArray(UnionOfArray union) {
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, union);
+    UaStructuredType decoded = (UaStructuredType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  @ParameterizedTest
+  @MethodSource("unionOfMatrixProvider")
+  void unionOfMatrix(UnionOfMatrix union) {
+    var encoded1 = ExtensionObject.encode(staticEncodingContext, union);
+    UaStructuredType decoded = (UaStructuredType) encoded1.decode(dynamicEncodingContext);
+    var encoded2 = ExtensionObject.encode(dynamicEncodingContext, decoded);
+
+    assertEquals(encoded1, encoded2);
+  }
+
+  private static Stream<Arguments> structWithOptionalScalarFieldsProvider() {
+    return Stream.of(
+        Arguments.of(
+            new StructWithOptionalScalarFields(
+                "",
+                "",
+                0,
+                0,
+                0.0,
+                0.0,
+                new ConcreteTestType((short) 0, 0.0, "", false),
+                new ConcreteTestType((short) 0, 0.0, "", false))),
+        Arguments.of(
+            new StructWithOptionalScalarFields(
+                "",
+                null,
+                0,
+                null,
+                0.0,
+                null,
+                new ConcreteTestType((short) 0, 0.0, "", false),
+                null)));
+  }
+
+  private static Stream<Arguments> structWithOptionalArrayFieldsProvider() {
+    return Stream.of(
+        Arguments.of(
+            new StructWithOptionalArrayFields(
+                new Integer[] {0, 0},
+                new Integer[] {0, 0},
+                new String[] {"", ""},
+                new String[] {"", ""},
+                new Double[] {0.0, 0.0},
+                new Double[] {0.0, 0.0},
+                new ConcreteTestType[] {
+                  new ConcreteTestType((short) 0, 0.0, "", false),
+                  new ConcreteTestType((short) 0, 0.0, "", false)
+                },
+                new ConcreteTestType[] {
+                  new ConcreteTestType((short) 0, 0.0, "", false),
+                  new ConcreteTestType((short) 0, 0.0, "", false)
+                })),
+        Arguments.of(
+            new StructWithOptionalArrayFields(
+                new Integer[] {0, 0},
+                null,
+                new String[] {"", ""},
+                null,
+                new Double[] {0.0, 0.0},
+                null,
+                new ConcreteTestType[] {
+                  new ConcreteTestType((short) 0, 0.0, "", false),
+                  new ConcreteTestType((short) 0, 0.0, "", false)
+                },
+                null)));
+  }
+
+  private static Stream<Arguments> unionOfScalarProvider() {
+    return Stream.of(
+        Arguments.of(UnionOfScalar.ofNull()),
+        Arguments.of(UnionOfScalar.ofBoolean(false)),
+        Arguments.of(UnionOfScalar.ofSByte((byte) 0)),
+        Arguments.of(UnionOfScalar.ofByte(ubyte(0))));
+  }
+
+  private static Stream<Arguments> unionOfArrayProvider() {
+    return Stream.of(
+        Arguments.of(UnionOfArray.ofNull()),
+        Arguments.of(UnionOfArray.ofBoolean(new Boolean[] {false, false})),
+        Arguments.of(UnionOfArray.ofSByte(new Byte[] {0, 0})),
+        Arguments.of(UnionOfArray.ofByte(new UByte[] {ubyte(0), ubyte(0)})));
+  }
+
+  private static Stream<Arguments> unionOfMatrixProvider() {
+    return Stream.of(
+        Arguments.of(UnionOfMatrix.ofNull()),
+        Arguments.of(
+            UnionOfMatrix.ofBoolean(
+                Matrix.ofBoolean(new Boolean[][] {{false, false}, {false, false}}))),
+        Arguments.of(UnionOfMatrix.ofSByte(Matrix.ofSByte(new Byte[][] {{0, 0}, {0, 0}}))),
+        Arguments.of(
+            UnionOfMatrix.ofByte(
+                Matrix.ofByte(new UByte[][] {{ubyte(0), ubyte(0)}, {ubyte(0), ubyte(0)}}))));
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/AbstractDataType.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/AbstractDataType.java
new file mode 100644
index 000000000..a16010dcb
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/AbstractDataType.java
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.util;
+
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.structured.DataTypeDefinition;
+import org.jspecify.annotations.Nullable;
+
+public abstract class AbstractDataType implements DataType {
+
+  public final NodeId nodeId;
+  public final QualifiedName browseName;
+  public final DataTypeDefinition definition;
+  public final boolean isAbstract;
+
+  public AbstractDataType(
+      NodeId nodeId, QualifiedName browseName, DataTypeDefinition definition, boolean isAbstract) {
+    this.nodeId = nodeId;
+    this.browseName = browseName;
+    this.definition = definition;
+    this.isAbstract = isAbstract;
+  }
+
+  @Override
+  public NodeId getNodeId() {
+    return nodeId;
+  }
+
+  @Override
+  public QualifiedName getBrowseName() {
+    return browseName;
+  }
+
+  @Override
+  public @Nullable DataTypeDefinition getDataTypeDefinition() {
+    return definition;
+  }
+
+  @Override
+  public Boolean isAbstract() {
+    return isAbstract;
+  }
+
+  @Override
+  public NodeId getBinaryEncodingId() {
+    return NodeId.NULL_VALUE;
+  }
+
+  @Override
+  public NodeId getXmlEncodingId() {
+    return NodeId.NULL_VALUE;
+  }
+
+  @Override
+  public NodeId getJsonEncodingId() {
+    return NodeId.NULL_VALUE;
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/AbstractEncodingContext.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/AbstractEncodingContext.java
new file mode 100644
index 000000000..426a31115
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/AbstractEncodingContext.java
@@ -0,0 +1,957 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.util;
+
+import org.eclipse.milo.opcua.sdk.core.typetree.DataType;
+import org.eclipse.milo.opcua.sdk.core.typetree.DataTypeTree;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.NodeIds;
+import org.eclipse.milo.opcua.stack.core.ServerTable;
+import org.eclipse.milo.opcua.stack.core.channel.EncodingLimits;
+import org.eclipse.milo.opcua.stack.core.encoding.DefaultEncodingManager;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingManager;
+import org.eclipse.milo.opcua.stack.core.types.DataTypeManager;
+import org.eclipse.milo.opcua.stack.core.types.DefaultDataTypeManager;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.ApplicationType;
+import org.eclipse.milo.opcua.stack.core.types.structured.XVType;
+import org.eclipse.milo.opcua.test.types.AbstractTestType;
+import org.eclipse.milo.opcua.test.types.ConcreteTestType;
+import org.eclipse.milo.opcua.test.types.ConcreteTestTypeEx;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinArrayFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinMatrixFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinScalarFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureScalarFields;
+import org.eclipse.milo.opcua.test.types.TestEnumType;
+import org.eclipse.milo.opcua.test.types.UnionOfArray;
+import org.eclipse.milo.opcua.test.types.UnionOfMatrix;
+import org.eclipse.milo.opcua.test.types.UnionOfScalar;
+import org.mockito.Mockito;
+
+public abstract class AbstractEncodingContext implements EncodingContext {
+
+  public static final DataType XV_DATA_TYPE =
+      new AbstractDataType(
+          NodeIds.XVType,
+          new QualifiedName(0, "XVType"),
+          XVType.definition(new NamespaceTable()),
+          false) {
+
+        @Override
+        public NodeId getBinaryEncodingId() {
+          return NodeIds.XVType_Encoding_DefaultBinary;
+        }
+
+        @Override
+        public NodeId getXmlEncodingId() {
+          return NodeIds.XVType_Encoding_DefaultXml;
+        }
+
+        @Override
+        public NodeId getJsonEncodingId() {
+          return NodeIds.XVType_Encoding_DefaultJson;
+        }
+      };
+
+  public static final DataType APPLICATION_TYPE_DATA_TYPE =
+      new AbstractDataType(
+          NodeIds.ApplicationType,
+          new QualifiedName(0, "ApplicationType"),
+          ApplicationType.definition(),
+          false) {};
+
+  public final DataType abstractTestType;
+  public final DataType concreteTestType;
+  public final DataType concreteTestTypeEx;
+  public final DataType structWithBuiltinScalarFields;
+  public final DataType structWithBuiltinScalarFieldsEx;
+  public final DataType structWithBuiltinArrayFields;
+  public final DataType structWithBuiltinArrayFieldsEx;
+  public final DataType structWithBuiltinMatrixFields;
+  public final DataType structWithBuiltinMatrixFieldsEx;
+  public final DataType structWithAbstractScalarFields;
+  public final DataType structWithAbstractArrayFields;
+  public final DataType structWithAbstractMatrixFields;
+  public final DataType structWithOptionalScalarFields;
+  public final DataType structWithOptionalArrayFields;
+  public final DataType structWithStructureScalarFields;
+  public final DataType structWithStructureArrayFields;
+  public final DataType structWithStructureMatrixFields;
+
+  public final DataType unionOfScalar;
+  public final DataType unionOfArray;
+  public final DataType unionOfMatrix;
+
+  public final DataType testEnumType;
+
+  public DataTypeTree dataTypeTree = Mockito.mock(DataTypeTree.class);
+  public DataTypeManager dataTypeManager = new DefaultDataTypeManager();
+
+  public NamespaceTable namespaceTable = new NamespaceTable();
+
+  public AbstractEncodingContext() {
+    namespaceTable.add("https://github.com/eclipse/milo/DataTypeTest");
+
+    Mockito.when(dataTypeTree.getDataType(XV_DATA_TYPE.getNodeId())).thenReturn(XV_DATA_TYPE);
+
+    Mockito.when(dataTypeTree.getDataType(APPLICATION_TYPE_DATA_TYPE.getNodeId()))
+        .thenReturn(APPLICATION_TYPE_DATA_TYPE);
+
+    dataTypeManager.registerType(
+        XV_DATA_TYPE.getNodeId(),
+        new XVType.Codec(),
+        XV_DATA_TYPE.getBinaryEncodingId(),
+        XV_DATA_TYPE.getXmlEncodingId(),
+        XV_DATA_TYPE.getJsonEncodingId());
+
+    abstractTestType = setupAbstractTestType();
+    concreteTestType = setupConcreteTestType();
+    concreteTestTypeEx = setupConcreteTestTypeEx();
+    structWithBuiltinScalarFields = setupStructWithBuiltinScalarFields();
+    structWithBuiltinScalarFieldsEx = setupStructWithBuiltinScalarFieldsEx();
+    structWithBuiltinArrayFields = setupStructWithBuiltinArrayFields();
+    structWithBuiltinArrayFieldsEx = setupStructWithBuiltinArrayFieldsEx();
+    structWithBuiltinMatrixFields = setupStructWithBuiltinMatrixFields();
+    structWithBuiltinMatrixFieldsEx = setupStructWithBuiltinMatrixFieldsEx();
+    structWithAbstractScalarFields = setupStructWithAbstractScalarFields();
+    structWithAbstractArrayFields = setupStructWithAbstractArrayFields();
+    structWithAbstractMatrixFields = setupStructWithAbstractMatrixFields();
+    structWithOptionalScalarFields = setupStructWithOptionalScalarFields();
+    structWithOptionalArrayFields = setupStructWithOptionalArrayFields();
+    structWithStructureScalarFields = setupStructWithStructureScalarFields();
+    structWithStructureArrayFields = setupStructWithStructureArrayFields();
+    structWithStructureMatrixFields = setupStructWithStructureMatrixFields();
+    unionOfScalar = setupUnionOfScalar();
+    unionOfArray = setupUnionOfArray();
+    unionOfMatrix = setupUnionOfMatrix();
+    testEnumType = setupTestEnumType();
+  }
+
+  @Override
+  public DataTypeManager getDataTypeManager() {
+    return dataTypeManager;
+  }
+
+  @Override
+  public EncodingManager getEncodingManager() {
+    return DefaultEncodingManager.createAndInitialize();
+  }
+
+  @Override
+  public EncodingLimits getEncodingLimits() {
+    return EncodingLimits.DEFAULT;
+  }
+
+  @Override
+  public NamespaceTable getNamespaceTable() {
+    return namespaceTable;
+  }
+
+  @Override
+  public ServerTable getServerTable() {
+    return new ServerTable();
+  }
+
+  protected DataType setupAbstractTestType() {
+    NodeId typeId = AbstractTestType.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "AbstractTestType"),
+            AbstractTestType.definition(getNamespaceTable()),
+            true) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return NodeId.NULL_VALUE;
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return NodeId.NULL_VALUE;
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return NodeId.NULL_VALUE;
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupConcreteTestType() {
+    NodeId typeId = ConcreteTestType.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "ConcreteTestType"),
+            ConcreteTestType.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return ConcreteTestType.BINARY_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return ConcreteTestType.XML_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return ConcreteTestType.JSON_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupConcreteTestTypeEx() {
+    NodeId typeId = ConcreteTestTypeEx.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "ConcreteTestTypeEx"),
+            ConcreteTestTypeEx.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return ConcreteTestTypeEx.BINARY_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return ConcreteTestTypeEx.XML_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return ConcreteTestTypeEx.JSON_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithBuiltinScalarFields() {
+    NodeId typeId =
+        StructWithBuiltinScalarFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithScalarFields"),
+            StructWithBuiltinScalarFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithBuiltinScalarFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithBuiltinScalarFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithBuiltinScalarFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithBuiltinScalarFieldsEx() {
+    NodeId typeId =
+        StructWithBuiltinScalarFieldsEx.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithScalarFieldsEx"),
+            StructWithBuiltinScalarFieldsEx.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithBuiltinScalarFieldsEx.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithBuiltinScalarFieldsEx.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithBuiltinScalarFieldsEx.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.Duration)).thenReturn(BuiltinDataType.Double);
+
+    Mockito.when(dataTypeTree.isEnumType(NodeIds.ApplicationType)).thenReturn(true);
+    Mockito.when(dataTypeTree.getDataType(NodeIds.ApplicationType))
+        .thenReturn(APPLICATION_TYPE_DATA_TYPE);
+
+    Mockito.when(
+            dataTypeTree.isEnumType(
+                TestEnumType.TypeInfo.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow()))
+        .thenReturn(true);
+    Mockito.when(
+            dataTypeTree.getDataType(
+                TestEnumType.TypeInfo.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow()))
+        .thenReturn(testEnumType);
+
+    Mockito.when(dataTypeTree.isStructType(NodeIds.XVType)).thenReturn(true);
+
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.AccessLevelType))
+        .thenReturn(BuiltinDataType.Byte);
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.AccessRestrictionType))
+        .thenReturn(BuiltinDataType.UInt16);
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.AccessLevelExType))
+        .thenReturn(BuiltinDataType.UInt32);
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.BitFieldMaskDataType))
+        .thenReturn(BuiltinDataType.UInt64);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithBuiltinArrayFields() {
+    NodeId typeId =
+        StructWithBuiltinArrayFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithArrayFields"),
+            StructWithBuiltinArrayFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithBuiltinArrayFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithBuiltinArrayFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithBuiltinArrayFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithBuiltinArrayFieldsEx() {
+    NodeId typeId =
+        StructWithBuiltinArrayFieldsEx.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithArrayFieldsEx"),
+            StructWithBuiltinArrayFieldsEx.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithBuiltinArrayFieldsEx.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithBuiltinArrayFieldsEx.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithBuiltinArrayFieldsEx.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithAbstractScalarFields() {
+    NodeId typeId =
+        StructWithAbstractScalarFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithAbstractScalarFields"),
+            StructWithAbstractScalarFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithAbstractScalarFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithAbstractScalarFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithAbstractScalarFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.Number)).thenReturn(BuiltinDataType.Variant);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithAbstractArrayFields() {
+    NodeId typeId =
+        StructWithAbstractArrayFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithAbstractArrayFields"),
+            StructWithAbstractArrayFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithAbstractArrayFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithAbstractArrayFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithAbstractArrayFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.getBuiltinType(NodeIds.Number)).thenReturn(BuiltinDataType.Variant);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithAbstractMatrixFields() {
+    NodeId typeId =
+        StructWithAbstractMatrixFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithAbstractMatrixFields"),
+            StructWithAbstractMatrixFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithAbstractMatrixFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithAbstractMatrixFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithAbstractMatrixFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithOptionalScalarFields() {
+    NodeId typeId =
+        StructWithOptionalScalarFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithOptionalScalarFields"),
+            StructWithOptionalScalarFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithOptionalScalarFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithOptionalScalarFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithOptionalScalarFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithOptionalArrayFields() {
+    NodeId typeId =
+        StructWithOptionalArrayFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithOptionalArrayFields"),
+            StructWithOptionalArrayFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithOptionalArrayFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithOptionalArrayFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithOptionalArrayFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithBuiltinMatrixFields() {
+    NodeId typeId =
+        StructWithBuiltinMatrixFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithMatrixFields"),
+            StructWithBuiltinMatrixFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithBuiltinMatrixFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithBuiltinMatrixFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithBuiltinMatrixFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithBuiltinMatrixFieldsEx() {
+    NodeId typeId =
+        StructWithBuiltinMatrixFieldsEx.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithMatrixFieldsEx"),
+            StructWithBuiltinMatrixFieldsEx.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithBuiltinMatrixFieldsEx.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithBuiltinMatrixFieldsEx.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithBuiltinMatrixFieldsEx.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithStructureScalarFields() {
+    NodeId typeId =
+        StructWithStructureScalarFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithStructureScalarFields"),
+            StructWithStructureScalarFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithStructureScalarFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithStructureScalarFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithStructureScalarFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithStructureArrayFields() {
+    NodeId typeId =
+        StructWithStructureArrayFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithStructureArrayFields"),
+            StructWithStructureArrayFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithStructureArrayFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithStructureArrayFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithStructureArrayFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupStructWithStructureMatrixFields() {
+    NodeId typeId =
+        StructWithStructureMatrixFields.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "StructWithStructureMatrixFields"),
+            StructWithStructureMatrixFields.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return StructWithStructureMatrixFields.BINARY_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return StructWithStructureMatrixFields.XML_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return StructWithStructureMatrixFields.JSON_ENCODING_ID
+                .toNodeId(namespaceTable)
+                .orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+
+    return dataType;
+  }
+
+  protected DataType setupUnionOfScalar() {
+    NodeId typeId = UnionOfScalar.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "UnionOfScalar"),
+            UnionOfScalar.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return UnionOfScalar.BINARY_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return UnionOfScalar.XML_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return UnionOfScalar.JSON_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupUnionOfArray() {
+    NodeId typeId = UnionOfArray.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "UnionOfArray"),
+            UnionOfArray.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return UnionOfArray.BINARY_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return UnionOfArray.XML_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return UnionOfArray.JSON_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupUnionOfMatrix() {
+    NodeId typeId = UnionOfMatrix.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId,
+            new QualifiedName(1, "UnionOfMatrix"),
+            UnionOfMatrix.definition(getNamespaceTable()),
+            false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return UnionOfMatrix.BINARY_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return UnionOfMatrix.XML_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return UnionOfMatrix.JSON_ENCODING_ID.toNodeId(namespaceTable).orElseThrow();
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isStructType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+
+  protected DataType setupTestEnumType() {
+    NodeId typeId = TestEnumType.TypeInfo.TYPE_ID.toNodeId(getNamespaceTable()).orElseThrow();
+
+    var dataType =
+        new AbstractDataType(
+            typeId, new QualifiedName(1, "TestEnumType"), TestEnumType.definition(), false) {
+
+          @Override
+          public NodeId getBinaryEncodingId() {
+            return null;
+          }
+
+          @Override
+          public NodeId getXmlEncodingId() {
+            return null;
+          }
+
+          @Override
+          public NodeId getJsonEncodingId() {
+            return null;
+          }
+        };
+
+    Mockito.when(dataTypeTree.getDataType(typeId)).thenReturn(dataType);
+    Mockito.when(dataTypeTree.isEnumType(typeId)).thenReturn(true);
+
+    return dataType;
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/DynamicEncodingContext.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/DynamicEncodingContext.java
new file mode 100644
index 000000000..05d15d1ca
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/DynamicEncodingContext.java
@@ -0,0 +1,186 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.util;
+
+import org.eclipse.milo.opcua.sdk.core.types.codec.DynamicCodecFactory;
+import org.mockito.Mockito;
+
+public class DynamicEncodingContext extends AbstractEncodingContext {
+
+  public DynamicEncodingContext() {
+    super();
+
+    Mockito.when(dataTypeTree.getDataType(XV_DATA_TYPE.getNodeId())).thenReturn(XV_DATA_TYPE);
+    Mockito.when(dataTypeTree.getDataType(APPLICATION_TYPE_DATA_TYPE.getNodeId()))
+        .thenReturn(APPLICATION_TYPE_DATA_TYPE);
+
+    dataTypeManager.registerType(
+        XV_DATA_TYPE.getNodeId(),
+        DynamicCodecFactory.create(XV_DATA_TYPE, dataTypeTree),
+        XV_DATA_TYPE.getBinaryEncodingId(),
+        XV_DATA_TYPE.getXmlEncodingId(),
+        XV_DATA_TYPE.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        APPLICATION_TYPE_DATA_TYPE.getNodeId(),
+        DynamicCodecFactory.create(APPLICATION_TYPE_DATA_TYPE, dataTypeTree),
+        APPLICATION_TYPE_DATA_TYPE.getBinaryEncodingId(),
+        APPLICATION_TYPE_DATA_TYPE.getXmlEncodingId(),
+        APPLICATION_TYPE_DATA_TYPE.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        abstractTestType.getNodeId(),
+        DynamicCodecFactory.create(abstractTestType, dataTypeTree),
+        abstractTestType.getBinaryEncodingId(),
+        abstractTestType.getXmlEncodingId(),
+        abstractTestType.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        concreteTestType.getNodeId(),
+        DynamicCodecFactory.create(concreteTestType, dataTypeTree),
+        concreteTestType.getBinaryEncodingId(),
+        concreteTestType.getXmlEncodingId(),
+        concreteTestType.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        concreteTestTypeEx.getNodeId(),
+        DynamicCodecFactory.create(concreteTestTypeEx, dataTypeTree),
+        concreteTestTypeEx.getBinaryEncodingId(),
+        concreteTestTypeEx.getXmlEncodingId(),
+        concreteTestTypeEx.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinScalarFields.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinScalarFields, dataTypeTree),
+        structWithBuiltinScalarFields.getBinaryEncodingId(),
+        structWithBuiltinScalarFields.getXmlEncodingId(),
+        structWithBuiltinScalarFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinScalarFields.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinScalarFields, dataTypeTree),
+        structWithBuiltinScalarFields.getBinaryEncodingId(),
+        structWithBuiltinScalarFields.getXmlEncodingId(),
+        structWithBuiltinScalarFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinScalarFieldsEx.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinScalarFieldsEx, dataTypeTree),
+        structWithBuiltinScalarFieldsEx.getBinaryEncodingId(),
+        structWithBuiltinScalarFieldsEx.getXmlEncodingId(),
+        structWithBuiltinScalarFieldsEx.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinArrayFields.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinArrayFields, dataTypeTree),
+        structWithBuiltinArrayFields.getBinaryEncodingId(),
+        structWithBuiltinArrayFields.getXmlEncodingId(),
+        structWithBuiltinArrayFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinArrayFieldsEx.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinArrayFieldsEx, dataTypeTree),
+        structWithBuiltinArrayFieldsEx.getBinaryEncodingId(),
+        structWithBuiltinArrayFieldsEx.getXmlEncodingId(),
+        structWithBuiltinArrayFieldsEx.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithAbstractScalarFields.getNodeId(),
+        DynamicCodecFactory.create(structWithAbstractScalarFields, dataTypeTree),
+        structWithAbstractScalarFields.getBinaryEncodingId(),
+        structWithAbstractScalarFields.getXmlEncodingId(),
+        structWithAbstractScalarFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithAbstractArrayFields.getNodeId(),
+        DynamicCodecFactory.create(structWithAbstractArrayFields, dataTypeTree),
+        structWithAbstractArrayFields.getBinaryEncodingId(),
+        structWithAbstractArrayFields.getXmlEncodingId(),
+        structWithAbstractArrayFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithAbstractMatrixFields.getNodeId(),
+        DynamicCodecFactory.create(structWithAbstractMatrixFields, dataTypeTree),
+        structWithAbstractMatrixFields.getBinaryEncodingId(),
+        structWithAbstractMatrixFields.getXmlEncodingId(),
+        structWithAbstractMatrixFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithOptionalScalarFields.getNodeId(),
+        DynamicCodecFactory.create(structWithOptionalScalarFields, dataTypeTree),
+        structWithOptionalScalarFields.getBinaryEncodingId(),
+        structWithOptionalScalarFields.getXmlEncodingId(),
+        structWithOptionalScalarFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithOptionalArrayFields.getNodeId(),
+        DynamicCodecFactory.create(structWithOptionalArrayFields, dataTypeTree),
+        structWithOptionalArrayFields.getBinaryEncodingId(),
+        structWithOptionalArrayFields.getXmlEncodingId(),
+        structWithOptionalArrayFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinMatrixFields.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinMatrixFields, dataTypeTree),
+        structWithBuiltinMatrixFields.getBinaryEncodingId(),
+        structWithBuiltinMatrixFields.getXmlEncodingId(),
+        structWithBuiltinMatrixFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithBuiltinMatrixFieldsEx.getNodeId(),
+        DynamicCodecFactory.create(structWithBuiltinMatrixFieldsEx, dataTypeTree),
+        structWithBuiltinMatrixFieldsEx.getBinaryEncodingId(),
+        structWithBuiltinMatrixFieldsEx.getXmlEncodingId(),
+        structWithBuiltinMatrixFieldsEx.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithStructureScalarFields.getNodeId(),
+        DynamicCodecFactory.create(structWithStructureScalarFields, dataTypeTree),
+        structWithStructureScalarFields.getBinaryEncodingId(),
+        structWithStructureScalarFields.getXmlEncodingId(),
+        structWithStructureScalarFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithStructureArrayFields.getNodeId(),
+        DynamicCodecFactory.create(structWithStructureArrayFields, dataTypeTree),
+        structWithStructureArrayFields.getBinaryEncodingId(),
+        structWithStructureArrayFields.getXmlEncodingId(),
+        structWithStructureArrayFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        structWithStructureMatrixFields.getNodeId(),
+        DynamicCodecFactory.create(structWithStructureMatrixFields, dataTypeTree),
+        structWithStructureMatrixFields.getBinaryEncodingId(),
+        structWithStructureMatrixFields.getXmlEncodingId(),
+        structWithStructureMatrixFields.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        unionOfScalar.getNodeId(),
+        DynamicCodecFactory.create(unionOfScalar, dataTypeTree),
+        unionOfScalar.getBinaryEncodingId(),
+        unionOfScalar.getXmlEncodingId(),
+        unionOfScalar.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        unionOfArray.getNodeId(),
+        DynamicCodecFactory.create(unionOfArray, dataTypeTree),
+        unionOfArray.getBinaryEncodingId(),
+        unionOfArray.getXmlEncodingId(),
+        unionOfArray.getJsonEncodingId());
+
+    dataTypeManager.registerType(
+        unionOfMatrix.getNodeId(),
+        DynamicCodecFactory.create(unionOfMatrix, dataTypeTree),
+        unionOfMatrix.getBinaryEncodingId(),
+        unionOfMatrix.getXmlEncodingId(),
+        unionOfMatrix.getJsonEncodingId());
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/StaticEncodingContext.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/StaticEncodingContext.java
new file mode 100644
index 000000000..16a691203
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/sdk/core/types/util/StaticEncodingContext.java
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.sdk.core.types.util;
+
+import org.eclipse.milo.opcua.test.DataTypeInitializer;
+
+public class StaticEncodingContext extends AbstractEncodingContext {
+
+  public StaticEncodingContext() {
+    super();
+
+    new DataTypeInitializer().initialize(getNamespaceTable(), getDataTypeManager());
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/DataTypeInitializer.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/DataTypeInitializer.java
new file mode 100644
index 000000000..380d77d18
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/DataTypeInitializer.java
@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test;
+
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.types.DataTypeManager;
+import org.eclipse.milo.opcua.test.types.ConcreteTestType;
+import org.eclipse.milo.opcua.test.types.ConcreteTestTypeEx;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithAbstractScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinArrayFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinMatrixFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithBuiltinScalarFieldsEx;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithOptionalScalarFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureArrayFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureMatrixFields;
+import org.eclipse.milo.opcua.test.types.StructWithStructureScalarFields;
+import org.eclipse.milo.opcua.test.types.UnionOfArray;
+import org.eclipse.milo.opcua.test.types.UnionOfMatrix;
+import org.eclipse.milo.opcua.test.types.UnionOfScalar;
+
+public class DataTypeInitializer {
+  public void initialize(NamespaceTable namespaceTable, DataTypeManager dataTypeManager) {
+    try {
+      registerStructCodecs(namespaceTable, dataTypeManager);
+    } catch (Exception e) {
+      throw new RuntimeException("DataType initialization failed", e);
+    }
+  }
+
+  private void registerStructCodecs(NamespaceTable namespaceTable, DataTypeManager dataTypeManager)
+      throws Exception {
+    dataTypeManager.registerType(
+        UnionOfArray.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new UnionOfArray.Codec(),
+        UnionOfArray.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        UnionOfArray.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        UnionOfArray.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        UnionOfMatrix.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new UnionOfMatrix.Codec(),
+        UnionOfMatrix.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        UnionOfMatrix.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        UnionOfMatrix.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        UnionOfScalar.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new UnionOfScalar.Codec(),
+        UnionOfScalar.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        UnionOfScalar.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        UnionOfScalar.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        ConcreteTestType.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new ConcreteTestType.Codec(),
+        ConcreteTestType.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        ConcreteTestType.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        ConcreteTestType.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        ConcreteTestTypeEx.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new ConcreteTestTypeEx.Codec(),
+        ConcreteTestTypeEx.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        ConcreteTestTypeEx.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        ConcreteTestTypeEx.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithAbstractArrayFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithAbstractArrayFields.Codec(),
+        StructWithAbstractArrayFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithAbstractArrayFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithAbstractArrayFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithAbstractMatrixFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithAbstractMatrixFields.Codec(),
+        StructWithAbstractMatrixFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithAbstractMatrixFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithAbstractMatrixFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithAbstractScalarFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithAbstractScalarFields.Codec(),
+        StructWithAbstractScalarFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithAbstractScalarFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithAbstractScalarFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithBuiltinArrayFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithBuiltinArrayFields.Codec(),
+        StructWithBuiltinArrayFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinArrayFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinArrayFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithBuiltinArrayFieldsEx.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithBuiltinArrayFieldsEx.Codec(),
+        StructWithBuiltinArrayFieldsEx.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinArrayFieldsEx.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinArrayFieldsEx.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithBuiltinMatrixFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithBuiltinMatrixFields.Codec(),
+        StructWithBuiltinMatrixFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinMatrixFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinMatrixFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithBuiltinMatrixFieldsEx.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithBuiltinMatrixFieldsEx.Codec(),
+        StructWithBuiltinMatrixFieldsEx.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinMatrixFieldsEx.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinMatrixFieldsEx.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithOptionalArrayFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithOptionalArrayFields.Codec(),
+        StructWithOptionalArrayFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithOptionalArrayFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithOptionalArrayFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithOptionalMatrixFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithOptionalMatrixFields.Codec(),
+        StructWithOptionalMatrixFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithOptionalMatrixFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithOptionalMatrixFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithOptionalScalarFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithOptionalScalarFields.Codec(),
+        StructWithOptionalScalarFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithOptionalScalarFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithOptionalScalarFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithBuiltinScalarFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithBuiltinScalarFields.Codec(),
+        StructWithBuiltinScalarFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinScalarFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinScalarFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithBuiltinScalarFieldsEx.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithBuiltinScalarFieldsEx.Codec(),
+        StructWithBuiltinScalarFieldsEx.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinScalarFieldsEx.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithBuiltinScalarFieldsEx.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithStructureArrayFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithStructureArrayFields.Codec(),
+        StructWithStructureArrayFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithStructureArrayFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithStructureArrayFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithStructureMatrixFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithStructureMatrixFields.Codec(),
+        StructWithStructureMatrixFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithStructureMatrixFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithStructureMatrixFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+    dataTypeManager.registerType(
+        StructWithStructureScalarFields.TYPE_ID.toNodeIdOrThrow(namespaceTable),
+        new StructWithStructureScalarFields.Codec(),
+        StructWithStructureScalarFields.BINARY_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithStructureScalarFields.XML_ENCODING_ID.toNodeIdOrThrow(namespaceTable),
+        StructWithStructureScalarFields.JSON_ENCODING_ID.toNodeIdOrThrow(namespaceTable));
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/AbstractTestType.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/AbstractTestType.java
new file mode 100644
index 000000000..fb4751cca
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/AbstractTestType.java
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public abstract class AbstractTestType extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3003");
+
+  private final Short int16Field;
+
+  private final Double doubleField;
+
+  private final @Nullable String stringField;
+
+  public AbstractTestType(Short int16Field, Double doubleField, @Nullable String stringField) {
+    this.int16Field = int16Field;
+    this.doubleField = doubleField;
+    this.stringField = stringField;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  public Short getInt16Field() {
+    return int16Field;
+  }
+
+  public Double getDoubleField() {
+    return doubleField;
+  }
+
+  public @Nullable String getStringField() {
+    return stringField;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    AbstractTestType that = (AbstractTestType) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getInt16Field(), that.getInt16Field());
+    eqb.append(getDoubleField(), that.getDoubleField());
+    eqb.append(getStringField(), that.getStringField());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getInt16Field());
+    hcb.append(getDoubleField());
+    hcb.append(getStringField());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner = new StringJoiner(", ", AbstractTestType.class.getSimpleName() + "[", "]");
+    joiner.add("int16Field=" + getInt16Field());
+    joiner.add("doubleField=" + getDoubleField());
+    joiner.add("stringField='" + getStringField() + "'");
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        new NodeId(0, 0),
+        new NodeId(0, 22),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Int16Field",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DoubleField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StringField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/ConcreteTestType.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/ConcreteTestType.java
new file mode 100644
index 000000000..eb7abe62c
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/ConcreteTestType.java
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class ConcreteTestType extends AbstractTestType implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3006");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5001");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5003");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5002");
+
+  private final Boolean booleanField;
+
+  public ConcreteTestType(
+      Short int16Field, Double doubleField, @Nullable String stringField, Boolean booleanField) {
+    super(int16Field, doubleField, stringField);
+    this.booleanField = booleanField;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Boolean getBooleanField() {
+    return booleanField;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    ConcreteTestType that = (ConcreteTestType) object;
+    var eqb = new EqualsBuilder();
+    eqb.appendSuper(super.equals(object));
+    eqb.append(getBooleanField(), that.getBooleanField());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getBooleanField());
+    hcb.appendSuper(super.hashCode());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner = new StringJoiner(", ", ConcreteTestType.class.getSimpleName() + "[", "]");
+    joiner.add("booleanField=" + getBooleanField());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5001")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Int16Field",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DoubleField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StringField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "BooleanField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<ConcreteTestType> {
+    @Override
+    public Class<ConcreteTestType> getType() {
+      return ConcreteTestType.class;
+    }
+
+    @Override
+    public ConcreteTestType decodeType(EncodingContext context, UaDecoder decoder) {
+      final Short int16Field;
+      final Double doubleField;
+      final String stringField;
+      final Boolean booleanField;
+      int16Field = decoder.decodeInt16("Int16Field");
+      doubleField = decoder.decodeDouble("DoubleField");
+      stringField = decoder.decodeString("StringField");
+      booleanField = decoder.decodeBoolean("BooleanField");
+      return new ConcreteTestType(int16Field, doubleField, stringField, booleanField);
+    }
+
+    @Override
+    public void encodeType(EncodingContext context, UaEncoder encoder, ConcreteTestType value) {
+      encoder.encodeInt16("Int16Field", value.getInt16Field());
+      encoder.encodeDouble("DoubleField", value.getDoubleField());
+      encoder.encodeString("StringField", value.getStringField());
+      encoder.encodeBoolean("BooleanField", value.getBooleanField());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/ConcreteTestTypeEx.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/ConcreteTestTypeEx.java
new file mode 100644
index 000000000..623e840bd
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/ConcreteTestTypeEx.java
@@ -0,0 +1,189 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class ConcreteTestTypeEx extends ConcreteTestType implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3009");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5004");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5006");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5005");
+
+  private final UInteger uInt32Field;
+
+  public ConcreteTestTypeEx(
+      Short int16Field,
+      Double doubleField,
+      @Nullable String stringField,
+      Boolean booleanField,
+      UInteger uInt32Field) {
+    super(int16Field, doubleField, stringField, booleanField);
+    this.uInt32Field = uInt32Field;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public UInteger getUInt32Field() {
+    return uInt32Field;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    ConcreteTestTypeEx that = (ConcreteTestTypeEx) object;
+    var eqb = new EqualsBuilder();
+    eqb.appendSuper(super.equals(object));
+    eqb.append(getUInt32Field(), that.getUInt32Field());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getUInt32Field());
+    hcb.appendSuper(super.hashCode());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner = new StringJoiner(", ", ConcreteTestTypeEx.class.getSimpleName() + "[", "]");
+    joiner.add("uInt32Field=" + getUInt32Field());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5004")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Int16Field",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DoubleField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StringField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "BooleanField",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32Field",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<ConcreteTestTypeEx> {
+    @Override
+    public Class<ConcreteTestTypeEx> getType() {
+      return ConcreteTestTypeEx.class;
+    }
+
+    @Override
+    public ConcreteTestTypeEx decodeType(EncodingContext context, UaDecoder decoder) {
+      final Short int16Field;
+      final Double doubleField;
+      final String stringField;
+      final Boolean booleanField;
+      final UInteger uInt32Field;
+      int16Field = decoder.decodeInt16("Int16Field");
+      doubleField = decoder.decodeDouble("DoubleField");
+      stringField = decoder.decodeString("StringField");
+      booleanField = decoder.decodeBoolean("BooleanField");
+      uInt32Field = decoder.decodeUInt32("UInt32Field");
+      return new ConcreteTestTypeEx(
+          int16Field, doubleField, stringField, booleanField, uInt32Field);
+    }
+
+    @Override
+    public void encodeType(EncodingContext context, UaEncoder encoder, ConcreteTestTypeEx value) {
+      encoder.encodeInt16("Int16Field", value.getInt16Field());
+      encoder.encodeDouble("DoubleField", value.getDoubleField());
+      encoder.encodeString("StringField", value.getStringField());
+      encoder.encodeBoolean("BooleanField", value.getBooleanField());
+      encoder.encodeUInt32("UInt32Field", value.getUInt32Field());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractArrayFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractArrayFields.java
new file mode 100644
index 000000000..4c4e240a6
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractArrayFields.java
@@ -0,0 +1,250 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithAbstractArrayFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3005");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5023");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5025");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5024");
+
+  private final Number @Nullable [] number;
+
+  private final AbstractTestType @Nullable [] att1;
+
+  private final AbstractTestType @Nullable [] att2;
+
+  public StructWithAbstractArrayFields(
+      Number @Nullable [] number,
+      AbstractTestType @Nullable [] att1,
+      AbstractTestType @Nullable [] att2) {
+    this.number = number;
+    this.att1 = att1;
+    this.att2 = att2;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Number @Nullable [] getNumber() {
+    return number;
+  }
+
+  public AbstractTestType @Nullable [] getAtt1() {
+    return att1;
+  }
+
+  public AbstractTestType @Nullable [] getAtt2() {
+    return att2;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithAbstractArrayFields that = (StructWithAbstractArrayFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getNumber(), that.getNumber());
+    eqb.append(getAtt1(), that.getAtt1());
+    eqb.append(getAtt2(), that.getAtt2());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getNumber());
+    hcb.append(getAtt1());
+    hcb.append(getAtt2());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithAbstractArrayFields.class.getSimpleName() + "[", "]");
+    joiner.add("number=" + java.util.Arrays.toString(getNumber()));
+    joiner.add("att1=" + java.util.Arrays.toString(getAtt1()));
+    joiner.add("att2=" + java.util.Arrays.toString(getAtt2()));
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5023")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.StructureWithSubtypedValues,
+        new StructureField[] {
+          new StructureField(
+              "Number",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 26),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ATT1",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ATT2",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithAbstractArrayFields> {
+    @Override
+    public Class<StructWithAbstractArrayFields> getType() {
+      return StructWithAbstractArrayFields.class;
+    }
+
+    @Override
+    public StructWithAbstractArrayFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Number[] number;
+      final AbstractTestType[] att1;
+      final AbstractTestType[] att2;
+      {
+        Variant[] variants = decoder.decodeVariantArray("Number");
+        if (variants != null) {
+          number = new Number[variants.length];
+          for (int i = 0; i < number.length; i++) {
+            number[i] = (Number) variants[i].getValue();
+          }
+        } else {
+          number = null;
+        }
+      }
+      {
+        ExtensionObject[] xos = decoder.decodeExtensionObjectArray("ATT1");
+        if (xos != null) {
+          att1 = new AbstractTestType[xos.length];
+          for (int i = 0; i < xos.length; i++) {
+            att1[i] = (AbstractTestType) xos[i].decode(context);
+          }
+        } else {
+          att1 = null;
+        }
+      }
+      {
+        ExtensionObject[] xos = decoder.decodeExtensionObjectArray("ATT2");
+        if (xos != null) {
+          att2 = new AbstractTestType[xos.length];
+          for (int i = 0; i < xos.length; i++) {
+            att2[i] = (AbstractTestType) xos[i].decode(context);
+          }
+        } else {
+          att2 = null;
+        }
+      }
+      return new StructWithAbstractArrayFields(number, att1, att2);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithAbstractArrayFields value) {
+      {
+        Variant[] variants = null;
+        Number[] number = value.getNumber();
+        if (number != null) {
+          variants = new Variant[number.length];
+          for (int i = 0; i < variants.length; i++) {
+            variants[i] = Variant.of(number[i]);
+          }
+        }
+        encoder.encodeVariantArray("Number", variants);
+      }
+      {
+        ExtensionObject[] xos = null;
+        AbstractTestType[] att1 = value.getAtt1();
+        if (att1 != null) {
+          xos = new ExtensionObject[att1.length];
+          for (int i = 0; i < xos.length; i++) {
+            xos[i] = ExtensionObject.encode(context, att1[i]);
+          }
+        }
+        encoder.encodeExtensionObjectArray("ATT1", xos);
+      }
+      {
+        ExtensionObject[] xos = null;
+        AbstractTestType[] att2 = value.getAtt2();
+        if (att2 != null) {
+          xos = new ExtensionObject[att2.length];
+          for (int i = 0; i < xos.length; i++) {
+            xos[i] = ExtensionObject.encode(context, att2[i]);
+          }
+        }
+        encoder.encodeExtensionObjectArray("ATT2", xos);
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractMatrixFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractMatrixFields.java
new file mode 100644
index 000000000..8263d71be
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractMatrixFields.java
@@ -0,0 +1,225 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithAbstractMatrixFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3022");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5047");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5049");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5048");
+
+  private final @Nullable Matrix number;
+
+  private final @Nullable Matrix att1;
+
+  private final @Nullable Matrix att2;
+
+  public StructWithAbstractMatrixFields(
+      @Nullable Matrix number, @Nullable Matrix att1, @Nullable Matrix att2) {
+    this.number = number;
+    this.att1 = att1;
+    this.att2 = att2;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public @Nullable Matrix getNumber() {
+    return number;
+  }
+
+  public @Nullable Matrix getAtt1() {
+    return att1;
+  }
+
+  public @Nullable Matrix getAtt2() {
+    return att2;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithAbstractMatrixFields that = (StructWithAbstractMatrixFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getNumber(), that.getNumber());
+    eqb.append(getAtt1(), that.getAtt1());
+    eqb.append(getAtt2(), that.getAtt2());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getNumber());
+    hcb.append(getAtt1());
+    hcb.append(getAtt2());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithAbstractMatrixFields.class.getSimpleName() + "[", "]");
+    joiner.add("number=" + getNumber());
+    joiner.add("att1=" + getAtt1());
+    joiner.add("att2=" + getAtt2());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5047")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.StructureWithSubtypedValues,
+        new StructureField[] {
+          new StructureField(
+              "Number",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 26),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ATT1",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ATT2",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithAbstractMatrixFields> {
+    @Override
+    public Class<StructWithAbstractMatrixFields> getType() {
+      return StructWithAbstractMatrixFields.class;
+    }
+
+    @Override
+    public StructWithAbstractMatrixFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Matrix number;
+      final Matrix att1;
+      final Matrix att2;
+      {
+        Matrix matrix = decoder.decodeMatrix("Number", BuiltinDataType.Variant);
+        number = matrix.transform(v -> ((Variant) v).getValue());
+      }
+      {
+        Matrix matrix = decoder.decodeMatrix("ATT1", BuiltinDataType.ExtensionObject);
+        att1 = matrix.transform(v -> ((ExtensionObject) v).decode(context));
+      }
+      {
+        Matrix matrix = decoder.decodeMatrix("ATT2", BuiltinDataType.ExtensionObject);
+        att2 = matrix.transform(v -> ((ExtensionObject) v).decode(context));
+      }
+      return new StructWithAbstractMatrixFields(number, att1, att2);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithAbstractMatrixFields value) {
+      {
+        Matrix matrix;
+        if (value.getNumber() != null) {
+          matrix = value.getNumber().transform(Variant::of);
+        } else {
+          matrix = Matrix.ofNull();
+        }
+        encoder.encodeMatrix("Number", matrix);
+      }
+      {
+        Matrix matrix;
+        if (value.getAtt1() != null) {
+          matrix =
+              value.getAtt1().transform(v -> ExtensionObject.encode(context, (UaStructuredType) v));
+        } else {
+          matrix = Matrix.ofNull();
+        }
+        encoder.encodeMatrix("ATT1", matrix);
+      }
+      {
+        Matrix matrix;
+        if (value.getAtt2() != null) {
+          matrix =
+              value.getAtt2().transform(v -> ExtensionObject.encode(context, (UaStructuredType) v));
+        } else {
+          matrix = Matrix.ofNull();
+        }
+        encoder.encodeMatrix("ATT2", matrix);
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractScalarFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractScalarFields.java
new file mode 100644
index 000000000..096215354
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithAbstractScalarFields.java
@@ -0,0 +1,205 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+
+public class StructWithAbstractScalarFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3012");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5007");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5009");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5008");
+
+  private final Number number;
+
+  private final AbstractTestType att1;
+
+  private final AbstractTestType att2;
+
+  public StructWithAbstractScalarFields(
+      Number number, AbstractTestType att1, AbstractTestType att2) {
+    this.number = number;
+    this.att1 = att1;
+    this.att2 = att2;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Number getNumber() {
+    return number;
+  }
+
+  public AbstractTestType getAtt1() {
+    return att1;
+  }
+
+  public AbstractTestType getAtt2() {
+    return att2;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithAbstractScalarFields that = (StructWithAbstractScalarFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getNumber(), that.getNumber());
+    eqb.append(getAtt1(), that.getAtt1());
+    eqb.append(getAtt2(), that.getAtt2());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getNumber());
+    hcb.append(getAtt1());
+    hcb.append(getAtt2());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithAbstractScalarFields.class.getSimpleName() + "[", "]");
+    joiner.add("number=" + getNumber());
+    joiner.add("att1=" + getAtt1());
+    joiner.add("att2=" + getAtt2());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5007")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.StructureWithSubtypedValues,
+        new StructureField[] {
+          new StructureField(
+              "Number",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 26),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ATT1",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ATT2",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3003")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithAbstractScalarFields> {
+    @Override
+    public Class<StructWithAbstractScalarFields> getType() {
+      return StructWithAbstractScalarFields.class;
+    }
+
+    @Override
+    public StructWithAbstractScalarFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Number number;
+      final AbstractTestType att1;
+      final AbstractTestType att2;
+      {
+        Variant variant = decoder.decodeVariant("Number");
+        number = (Number) variant.getValue();
+      }
+      {
+        ExtensionObject xo = decoder.decodeExtensionObject("ATT1");
+        att1 = (AbstractTestType) xo.decode(context);
+      }
+      {
+        ExtensionObject xo = decoder.decodeExtensionObject("ATT2");
+        att2 = (AbstractTestType) xo.decode(context);
+      }
+      return new StructWithAbstractScalarFields(number, att1, att2);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithAbstractScalarFields value) {
+      {
+        Variant variant = Variant.of(value.getNumber());
+        encoder.encodeVariant("Number", variant);
+      }
+      {
+        ExtensionObject xo = ExtensionObject.encode(context, value.getAtt1());
+        encoder.encodeExtensionObject("ATT1", xo);
+      }
+      {
+        ExtensionObject xo = ExtensionObject.encode(context, value.getAtt2());
+        encoder.encodeExtensionObject("ATT2", xo);
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinArrayFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinArrayFields.java
new file mode 100644
index 000000000..fcf44a6df
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinArrayFields.java
@@ -0,0 +1,658 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import java.util.UUID;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithBuiltinArrayFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3019");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5014");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5016");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5015");
+
+  private final Boolean @Nullable [] _boolean;
+
+  private final Byte @Nullable [] sByte;
+
+  private final UByte @Nullable [] _byte;
+
+  private final Short @Nullable [] int16;
+
+  private final UShort @Nullable [] uInt16;
+
+  private final Integer @Nullable [] int32;
+
+  private final UInteger @Nullable [] uInt32;
+
+  private final Long @Nullable [] int64;
+
+  private final ULong @Nullable [] uInt64;
+
+  private final Float @Nullable [] _float;
+
+  private final Double @Nullable [] _double;
+
+  private final String @Nullable [] string;
+
+  private final DateTime @Nullable [] dateTime;
+
+  private final UUID @Nullable [] guid;
+
+  private final ByteString @Nullable [] byteString;
+
+  private final XmlElement @Nullable [] xmlElement;
+
+  private final NodeId @Nullable [] nodeId;
+
+  private final ExpandedNodeId @Nullable [] expandedNodeId;
+
+  private final StatusCode @Nullable [] statusCode;
+
+  private final QualifiedName @Nullable [] qualifiedName;
+
+  private final LocalizedText @Nullable [] localizedText;
+
+  private final DataValue @Nullable [] dataValue;
+
+  private final Variant @Nullable [] variant;
+
+  public StructWithBuiltinArrayFields(
+      Boolean @Nullable [] _boolean,
+      Byte @Nullable [] sByte,
+      UByte @Nullable [] _byte,
+      Short @Nullable [] int16,
+      UShort @Nullable [] uInt16,
+      Integer @Nullable [] int32,
+      UInteger @Nullable [] uInt32,
+      Long @Nullable [] int64,
+      ULong @Nullable [] uInt64,
+      Float @Nullable [] _float,
+      Double @Nullable [] _double,
+      String @Nullable [] string,
+      DateTime @Nullable [] dateTime,
+      UUID @Nullable [] guid,
+      ByteString @Nullable [] byteString,
+      XmlElement @Nullable [] xmlElement,
+      NodeId @Nullable [] nodeId,
+      ExpandedNodeId @Nullable [] expandedNodeId,
+      StatusCode @Nullable [] statusCode,
+      QualifiedName @Nullable [] qualifiedName,
+      LocalizedText @Nullable [] localizedText,
+      DataValue @Nullable [] dataValue,
+      Variant @Nullable [] variant) {
+    this._boolean = _boolean;
+    this.sByte = sByte;
+    this._byte = _byte;
+    this.int16 = int16;
+    this.uInt16 = uInt16;
+    this.int32 = int32;
+    this.uInt32 = uInt32;
+    this.int64 = int64;
+    this.uInt64 = uInt64;
+    this._float = _float;
+    this._double = _double;
+    this.string = string;
+    this.dateTime = dateTime;
+    this.guid = guid;
+    this.byteString = byteString;
+    this.xmlElement = xmlElement;
+    this.nodeId = nodeId;
+    this.expandedNodeId = expandedNodeId;
+    this.statusCode = statusCode;
+    this.qualifiedName = qualifiedName;
+    this.localizedText = localizedText;
+    this.dataValue = dataValue;
+    this.variant = variant;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Boolean @Nullable [] getBoolean() {
+    return _boolean;
+  }
+
+  public Byte @Nullable [] getSByte() {
+    return sByte;
+  }
+
+  public UByte @Nullable [] getByte() {
+    return _byte;
+  }
+
+  public Short @Nullable [] getInt16() {
+    return int16;
+  }
+
+  public UShort @Nullable [] getUInt16() {
+    return uInt16;
+  }
+
+  public Integer @Nullable [] getInt32() {
+    return int32;
+  }
+
+  public UInteger @Nullable [] getUInt32() {
+    return uInt32;
+  }
+
+  public Long @Nullable [] getInt64() {
+    return int64;
+  }
+
+  public ULong @Nullable [] getUInt64() {
+    return uInt64;
+  }
+
+  public Float @Nullable [] getFloat() {
+    return _float;
+  }
+
+  public Double @Nullable [] getDouble() {
+    return _double;
+  }
+
+  public String @Nullable [] getString() {
+    return string;
+  }
+
+  public DateTime @Nullable [] getDateTime() {
+    return dateTime;
+  }
+
+  public UUID @Nullable [] getGuid() {
+    return guid;
+  }
+
+  public ByteString @Nullable [] getByteString() {
+    return byteString;
+  }
+
+  public XmlElement @Nullable [] getXmlElement() {
+    return xmlElement;
+  }
+
+  public NodeId @Nullable [] getNodeId() {
+    return nodeId;
+  }
+
+  public ExpandedNodeId @Nullable [] getExpandedNodeId() {
+    return expandedNodeId;
+  }
+
+  public StatusCode @Nullable [] getStatusCode() {
+    return statusCode;
+  }
+
+  public QualifiedName @Nullable [] getQualifiedName() {
+    return qualifiedName;
+  }
+
+  public LocalizedText @Nullable [] getLocalizedText() {
+    return localizedText;
+  }
+
+  public DataValue @Nullable [] getDataValue() {
+    return dataValue;
+  }
+
+  public Variant @Nullable [] getVariant() {
+    return variant;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithBuiltinArrayFields that = (StructWithBuiltinArrayFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getBoolean(), that.getBoolean());
+    eqb.append(getSByte(), that.getSByte());
+    eqb.append(getByte(), that.getByte());
+    eqb.append(getInt16(), that.getInt16());
+    eqb.append(getUInt16(), that.getUInt16());
+    eqb.append(getInt32(), that.getInt32());
+    eqb.append(getUInt32(), that.getUInt32());
+    eqb.append(getInt64(), that.getInt64());
+    eqb.append(getUInt64(), that.getUInt64());
+    eqb.append(getFloat(), that.getFloat());
+    eqb.append(getDouble(), that.getDouble());
+    eqb.append(getString(), that.getString());
+    eqb.append(getDateTime(), that.getDateTime());
+    eqb.append(getGuid(), that.getGuid());
+    eqb.append(getByteString(), that.getByteString());
+    eqb.append(getXmlElement(), that.getXmlElement());
+    eqb.append(getNodeId(), that.getNodeId());
+    eqb.append(getExpandedNodeId(), that.getExpandedNodeId());
+    eqb.append(getStatusCode(), that.getStatusCode());
+    eqb.append(getQualifiedName(), that.getQualifiedName());
+    eqb.append(getLocalizedText(), that.getLocalizedText());
+    eqb.append(getDataValue(), that.getDataValue());
+    eqb.append(getVariant(), that.getVariant());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getBoolean());
+    hcb.append(getSByte());
+    hcb.append(getByte());
+    hcb.append(getInt16());
+    hcb.append(getUInt16());
+    hcb.append(getInt32());
+    hcb.append(getUInt32());
+    hcb.append(getInt64());
+    hcb.append(getUInt64());
+    hcb.append(getFloat());
+    hcb.append(getDouble());
+    hcb.append(getString());
+    hcb.append(getDateTime());
+    hcb.append(getGuid());
+    hcb.append(getByteString());
+    hcb.append(getXmlElement());
+    hcb.append(getNodeId());
+    hcb.append(getExpandedNodeId());
+    hcb.append(getStatusCode());
+    hcb.append(getQualifiedName());
+    hcb.append(getLocalizedText());
+    hcb.append(getDataValue());
+    hcb.append(getVariant());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithBuiltinArrayFields.class.getSimpleName() + "[", "]");
+    joiner.add("_boolean=" + java.util.Arrays.toString(getBoolean()));
+    joiner.add("sByte=" + java.util.Arrays.toString(getSByte()));
+    joiner.add("_byte=" + java.util.Arrays.toString(getByte()));
+    joiner.add("int16=" + java.util.Arrays.toString(getInt16()));
+    joiner.add("uInt16=" + java.util.Arrays.toString(getUInt16()));
+    joiner.add("int32=" + java.util.Arrays.toString(getInt32()));
+    joiner.add("uInt32=" + java.util.Arrays.toString(getUInt32()));
+    joiner.add("int64=" + java.util.Arrays.toString(getInt64()));
+    joiner.add("uInt64=" + java.util.Arrays.toString(getUInt64()));
+    joiner.add("_float=" + java.util.Arrays.toString(getFloat()));
+    joiner.add("_double=" + java.util.Arrays.toString(getDouble()));
+    joiner.add("string=" + java.util.Arrays.toString(getString()));
+    joiner.add("dateTime=" + java.util.Arrays.toString(getDateTime()));
+    joiner.add("guid=" + java.util.Arrays.toString(getGuid()));
+    joiner.add("byteString=" + java.util.Arrays.toString(getByteString()));
+    joiner.add("xmlElement=" + java.util.Arrays.toString(getXmlElement()));
+    joiner.add("nodeId=" + java.util.Arrays.toString(getNodeId()));
+    joiner.add("expandedNodeId=" + java.util.Arrays.toString(getExpandedNodeId()));
+    joiner.add("statusCode=" + java.util.Arrays.toString(getStatusCode()));
+    joiner.add("qualifiedName=" + java.util.Arrays.toString(getQualifiedName()));
+    joiner.add("localizedText=" + java.util.Arrays.toString(getLocalizedText()));
+    joiner.add("dataValue=" + java.util.Arrays.toString(getDataValue()));
+    joiner.add("variant=" + java.util.Arrays.toString(getVariant()));
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5014")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 5),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 8),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 9),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Float",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 10),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Double",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DateTime",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 13),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Guid",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 14),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ByteString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XmlElement",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 16),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "NodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 17),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ExpandedNodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 18),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StatusCode",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 19),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "QualifiedName",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 20),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "LocalizedText",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 21),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DataValue",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 23),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Variant",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 24),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithBuiltinArrayFields> {
+    @Override
+    public Class<StructWithBuiltinArrayFields> getType() {
+      return StructWithBuiltinArrayFields.class;
+    }
+
+    @Override
+    public StructWithBuiltinArrayFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Boolean[] _boolean;
+      final Byte[] sByte;
+      final UByte[] _byte;
+      final Short[] int16;
+      final UShort[] uInt16;
+      final Integer[] int32;
+      final UInteger[] uInt32;
+      final Long[] int64;
+      final ULong[] uInt64;
+      final Float[] _float;
+      final Double[] _double;
+      final String[] string;
+      final DateTime[] dateTime;
+      final UUID[] guid;
+      final ByteString[] byteString;
+      final XmlElement[] xmlElement;
+      final NodeId[] nodeId;
+      final ExpandedNodeId[] expandedNodeId;
+      final StatusCode[] statusCode;
+      final QualifiedName[] qualifiedName;
+      final LocalizedText[] localizedText;
+      final DataValue[] dataValue;
+      final Variant[] variant;
+      _boolean = decoder.decodeBooleanArray("Boolean");
+      sByte = decoder.decodeSByteArray("SByte");
+      _byte = decoder.decodeByteArray("Byte");
+      int16 = decoder.decodeInt16Array("Int16");
+      uInt16 = decoder.decodeUInt16Array("UInt16");
+      int32 = decoder.decodeInt32Array("Int32");
+      uInt32 = decoder.decodeUInt32Array("UInt32");
+      int64 = decoder.decodeInt64Array("Int64");
+      uInt64 = decoder.decodeUInt64Array("UInt64");
+      _float = decoder.decodeFloatArray("Float");
+      _double = decoder.decodeDoubleArray("Double");
+      string = decoder.decodeStringArray("String");
+      dateTime = decoder.decodeDateTimeArray("DateTime");
+      guid = decoder.decodeGuidArray("Guid");
+      byteString = decoder.decodeByteStringArray("ByteString");
+      xmlElement = decoder.decodeXmlElementArray("XmlElement");
+      nodeId = decoder.decodeNodeIdArray("NodeId");
+      expandedNodeId = decoder.decodeExpandedNodeIdArray("ExpandedNodeId");
+      statusCode = decoder.decodeStatusCodeArray("StatusCode");
+      qualifiedName = decoder.decodeQualifiedNameArray("QualifiedName");
+      localizedText = decoder.decodeLocalizedTextArray("LocalizedText");
+      dataValue = decoder.decodeDataValueArray("DataValue");
+      variant = decoder.decodeVariantArray("Variant");
+      return new StructWithBuiltinArrayFields(
+          _boolean,
+          sByte,
+          _byte,
+          int16,
+          uInt16,
+          int32,
+          uInt32,
+          int64,
+          uInt64,
+          _float,
+          _double,
+          string,
+          dateTime,
+          guid,
+          byteString,
+          xmlElement,
+          nodeId,
+          expandedNodeId,
+          statusCode,
+          qualifiedName,
+          localizedText,
+          dataValue,
+          variant);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithBuiltinArrayFields value) {
+      encoder.encodeBooleanArray("Boolean", value.getBoolean());
+      encoder.encodeSByteArray("SByte", value.getSByte());
+      encoder.encodeByteArray("Byte", value.getByte());
+      encoder.encodeInt16Array("Int16", value.getInt16());
+      encoder.encodeUInt16Array("UInt16", value.getUInt16());
+      encoder.encodeInt32Array("Int32", value.getInt32());
+      encoder.encodeUInt32Array("UInt32", value.getUInt32());
+      encoder.encodeInt64Array("Int64", value.getInt64());
+      encoder.encodeUInt64Array("UInt64", value.getUInt64());
+      encoder.encodeFloatArray("Float", value.getFloat());
+      encoder.encodeDoubleArray("Double", value.getDouble());
+      encoder.encodeStringArray("String", value.getString());
+      encoder.encodeDateTimeArray("DateTime", value.getDateTime());
+      encoder.encodeGuidArray("Guid", value.getGuid());
+      encoder.encodeByteStringArray("ByteString", value.getByteString());
+      encoder.encodeXmlElementArray("XmlElement", value.getXmlElement());
+      encoder.encodeNodeIdArray("NodeId", value.getNodeId());
+      encoder.encodeExpandedNodeIdArray("ExpandedNodeId", value.getExpandedNodeId());
+      encoder.encodeStatusCodeArray("StatusCode", value.getStatusCode());
+      encoder.encodeQualifiedNameArray("QualifiedName", value.getQualifiedName());
+      encoder.encodeLocalizedTextArray("LocalizedText", value.getLocalizedText());
+      encoder.encodeDataValueArray("DataValue", value.getDataValue());
+      encoder.encodeVariantArray("Variant", value.getVariant());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinArrayFieldsEx.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinArrayFieldsEx.java
new file mode 100644
index 000000000..6c4294c3e
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinArrayFieldsEx.java
@@ -0,0 +1,802 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import java.util.UUID;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.ApplicationType;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelExType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessRestrictionType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.types.structured.XVType;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithBuiltinArrayFieldsEx extends StructWithBuiltinArrayFields
+    implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3008");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5035");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5040");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5036");
+
+  private final Double @Nullable [] duration;
+
+  private final ApplicationType @Nullable [] applicationType;
+
+  private final TestEnumType @Nullable [] testEnumType;
+
+  private final XVType @Nullable [] xvType;
+
+  private final ConcreteTestType @Nullable [] concreteTestType;
+
+  private final UnionOfScalar @Nullable [] unionOfScalar;
+
+  private final UnionOfArray @Nullable [] unionOfArray;
+
+  private final AccessLevelType @Nullable [] optionSetUi8;
+
+  private final AccessRestrictionType @Nullable [] optionSetUi16;
+
+  private final AccessLevelExType @Nullable [] optionSetUi32;
+
+  private final ULong @Nullable [] optionSetUi64;
+
+  public StructWithBuiltinArrayFieldsEx(
+      Boolean @Nullable [] _boolean,
+      Byte @Nullable [] sByte,
+      UByte @Nullable [] _byte,
+      Short @Nullable [] int16,
+      UShort @Nullable [] uInt16,
+      Integer @Nullable [] int32,
+      UInteger @Nullable [] uInt32,
+      Long @Nullable [] int64,
+      ULong @Nullable [] uInt64,
+      Float @Nullable [] _float,
+      Double @Nullable [] _double,
+      String @Nullable [] string,
+      DateTime @Nullable [] dateTime,
+      UUID @Nullable [] guid,
+      ByteString @Nullable [] byteString,
+      XmlElement @Nullable [] xmlElement,
+      NodeId @Nullable [] nodeId,
+      ExpandedNodeId @Nullable [] expandedNodeId,
+      StatusCode @Nullable [] statusCode,
+      QualifiedName @Nullable [] qualifiedName,
+      LocalizedText @Nullable [] localizedText,
+      DataValue @Nullable [] dataValue,
+      Variant @Nullable [] variant,
+      Double @Nullable [] duration,
+      ApplicationType @Nullable [] applicationType,
+      TestEnumType @Nullable [] testEnumType,
+      XVType @Nullable [] xvType,
+      ConcreteTestType @Nullable [] concreteTestType,
+      UnionOfScalar @Nullable [] unionOfScalar,
+      UnionOfArray @Nullable [] unionOfArray,
+      AccessLevelType @Nullable [] optionSetUi8,
+      AccessRestrictionType @Nullable [] optionSetUi16,
+      AccessLevelExType @Nullable [] optionSetUi32,
+      ULong @Nullable [] optionSetUi64) {
+    super(
+        _boolean,
+        sByte,
+        _byte,
+        int16,
+        uInt16,
+        int32,
+        uInt32,
+        int64,
+        uInt64,
+        _float,
+        _double,
+        string,
+        dateTime,
+        guid,
+        byteString,
+        xmlElement,
+        nodeId,
+        expandedNodeId,
+        statusCode,
+        qualifiedName,
+        localizedText,
+        dataValue,
+        variant);
+    this.duration = duration;
+    this.applicationType = applicationType;
+    this.testEnumType = testEnumType;
+    this.xvType = xvType;
+    this.concreteTestType = concreteTestType;
+    this.unionOfScalar = unionOfScalar;
+    this.unionOfArray = unionOfArray;
+    this.optionSetUi8 = optionSetUi8;
+    this.optionSetUi16 = optionSetUi16;
+    this.optionSetUi32 = optionSetUi32;
+    this.optionSetUi64 = optionSetUi64;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Double @Nullable [] getDuration() {
+    return duration;
+  }
+
+  public ApplicationType @Nullable [] getApplicationType() {
+    return applicationType;
+  }
+
+  public TestEnumType @Nullable [] getTestEnumType() {
+    return testEnumType;
+  }
+
+  public XVType @Nullable [] getXvType() {
+    return xvType;
+  }
+
+  public ConcreteTestType @Nullable [] getConcreteTestType() {
+    return concreteTestType;
+  }
+
+  public UnionOfScalar @Nullable [] getUnionOfScalar() {
+    return unionOfScalar;
+  }
+
+  public UnionOfArray @Nullable [] getUnionOfArray() {
+    return unionOfArray;
+  }
+
+  public AccessLevelType @Nullable [] getOptionSetUi8() {
+    return optionSetUi8;
+  }
+
+  public AccessRestrictionType @Nullable [] getOptionSetUi16() {
+    return optionSetUi16;
+  }
+
+  public AccessLevelExType @Nullable [] getOptionSetUi32() {
+    return optionSetUi32;
+  }
+
+  public ULong @Nullable [] getOptionSetUi64() {
+    return optionSetUi64;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithBuiltinArrayFieldsEx that = (StructWithBuiltinArrayFieldsEx) object;
+    var eqb = new EqualsBuilder();
+    eqb.appendSuper(super.equals(object));
+    eqb.append(getDuration(), that.getDuration());
+    eqb.append(getApplicationType(), that.getApplicationType());
+    eqb.append(getTestEnumType(), that.getTestEnumType());
+    eqb.append(getXvType(), that.getXvType());
+    eqb.append(getConcreteTestType(), that.getConcreteTestType());
+    eqb.append(getUnionOfScalar(), that.getUnionOfScalar());
+    eqb.append(getUnionOfArray(), that.getUnionOfArray());
+    eqb.append(getOptionSetUi8(), that.getOptionSetUi8());
+    eqb.append(getOptionSetUi16(), that.getOptionSetUi16());
+    eqb.append(getOptionSetUi32(), that.getOptionSetUi32());
+    eqb.append(getOptionSetUi64(), that.getOptionSetUi64());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getDuration());
+    hcb.append(getApplicationType());
+    hcb.append(getTestEnumType());
+    hcb.append(getXvType());
+    hcb.append(getConcreteTestType());
+    hcb.append(getUnionOfScalar());
+    hcb.append(getUnionOfArray());
+    hcb.append(getOptionSetUi8());
+    hcb.append(getOptionSetUi16());
+    hcb.append(getOptionSetUi32());
+    hcb.append(getOptionSetUi64());
+    hcb.appendSuper(super.hashCode());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithBuiltinArrayFieldsEx.class.getSimpleName() + "[", "]");
+    joiner.add("duration=" + java.util.Arrays.toString(getDuration()));
+    joiner.add("applicationType=" + java.util.Arrays.toString(getApplicationType()));
+    joiner.add("testEnumType=" + java.util.Arrays.toString(getTestEnumType()));
+    joiner.add("xvType=" + java.util.Arrays.toString(getXvType()));
+    joiner.add("concreteTestType=" + java.util.Arrays.toString(getConcreteTestType()));
+    joiner.add("unionOfScalar=" + java.util.Arrays.toString(getUnionOfScalar()));
+    joiner.add("unionOfArray=" + java.util.Arrays.toString(getUnionOfArray()));
+    joiner.add("optionSetUi8=" + java.util.Arrays.toString(getOptionSetUi8()));
+    joiner.add("optionSetUi16=" + java.util.Arrays.toString(getOptionSetUi16()));
+    joiner.add("optionSetUi32=" + java.util.Arrays.toString(getOptionSetUi32()));
+    joiner.add("optionSetUi64=" + java.util.Arrays.toString(getOptionSetUi64()));
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5035")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3019")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 5),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 8),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 9),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Float",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 10),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Double",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DateTime",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 13),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Guid",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 14),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ByteString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XmlElement",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 16),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "NodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 17),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ExpandedNodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 18),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StatusCode",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 19),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "QualifiedName",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 20),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "LocalizedText",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 21),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DataValue",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 23),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Variant",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 24),
+              1,
+              new UInteger[] {UInteger.valueOf(4)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Duration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ApplicationType",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 307),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "TestEnumType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3011")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XVType",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12080),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UnionOfScalar",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3020")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UnionOfArray",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3023")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI8",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15031),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 95),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15406),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11737),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithBuiltinArrayFieldsEx> {
+    @Override
+    public Class<StructWithBuiltinArrayFieldsEx> getType() {
+      return StructWithBuiltinArrayFieldsEx.class;
+    }
+
+    @Override
+    public StructWithBuiltinArrayFieldsEx decodeType(EncodingContext context, UaDecoder decoder) {
+      final Boolean[] _boolean;
+      final Byte[] sByte;
+      final UByte[] _byte;
+      final Short[] int16;
+      final UShort[] uInt16;
+      final Integer[] int32;
+      final UInteger[] uInt32;
+      final Long[] int64;
+      final ULong[] uInt64;
+      final Float[] _float;
+      final Double[] _double;
+      final String[] string;
+      final DateTime[] dateTime;
+      final UUID[] guid;
+      final ByteString[] byteString;
+      final XmlElement[] xmlElement;
+      final NodeId[] nodeId;
+      final ExpandedNodeId[] expandedNodeId;
+      final StatusCode[] statusCode;
+      final QualifiedName[] qualifiedName;
+      final LocalizedText[] localizedText;
+      final DataValue[] dataValue;
+      final Variant[] variant;
+      final Double[] duration;
+      final ApplicationType[] applicationType;
+      final TestEnumType[] testEnumType;
+      final XVType[] xvType;
+      final ConcreteTestType[] concreteTestType;
+      final UnionOfScalar[] unionOfScalar;
+      final UnionOfArray[] unionOfArray;
+      final AccessLevelType[] optionSetUi8;
+      final AccessRestrictionType[] optionSetUi16;
+      final AccessLevelExType[] optionSetUi32;
+      final ULong[] optionSetUi64;
+      _boolean = decoder.decodeBooleanArray("Boolean");
+      sByte = decoder.decodeSByteArray("SByte");
+      _byte = decoder.decodeByteArray("Byte");
+      int16 = decoder.decodeInt16Array("Int16");
+      uInt16 = decoder.decodeUInt16Array("UInt16");
+      int32 = decoder.decodeInt32Array("Int32");
+      uInt32 = decoder.decodeUInt32Array("UInt32");
+      int64 = decoder.decodeInt64Array("Int64");
+      uInt64 = decoder.decodeUInt64Array("UInt64");
+      _float = decoder.decodeFloatArray("Float");
+      _double = decoder.decodeDoubleArray("Double");
+      string = decoder.decodeStringArray("String");
+      dateTime = decoder.decodeDateTimeArray("DateTime");
+      guid = decoder.decodeGuidArray("Guid");
+      byteString = decoder.decodeByteStringArray("ByteString");
+      xmlElement = decoder.decodeXmlElementArray("XmlElement");
+      nodeId = decoder.decodeNodeIdArray("NodeId");
+      expandedNodeId = decoder.decodeExpandedNodeIdArray("ExpandedNodeId");
+      statusCode = decoder.decodeStatusCodeArray("StatusCode");
+      qualifiedName = decoder.decodeQualifiedNameArray("QualifiedName");
+      localizedText = decoder.decodeLocalizedTextArray("LocalizedText");
+      dataValue = decoder.decodeDataValueArray("DataValue");
+      variant = decoder.decodeVariantArray("Variant");
+      duration = decoder.decodeDoubleArray("Duration");
+      {
+        Integer[] values = decoder.decodeEnumArray("ApplicationType");
+        if (values != null) {
+          applicationType = new ApplicationType[values.length];
+          for (int i = 0; i < values.length; i++) {
+            applicationType[i] = ApplicationType.from(values[i]);
+          }
+        } else {
+          applicationType = null;
+        }
+      }
+      {
+        Integer[] values = decoder.decodeEnumArray("TestEnumType");
+        if (values != null) {
+          testEnumType = new TestEnumType[values.length];
+          for (int i = 0; i < values.length; i++) {
+            testEnumType[i] = TestEnumType.from(values[i]);
+          }
+        } else {
+          testEnumType = null;
+        }
+      }
+      xvType = (XVType[]) decoder.decodeStructArray("XVType", XVType.TYPE_ID);
+      concreteTestType =
+          (ConcreteTestType[])
+              decoder.decodeStructArray("ConcreteTestType", ConcreteTestType.TYPE_ID);
+      unionOfScalar =
+          (UnionOfScalar[]) decoder.decodeStructArray("UnionOfScalar", UnionOfScalar.TYPE_ID);
+      unionOfArray =
+          (UnionOfArray[]) decoder.decodeStructArray("UnionOfArray", UnionOfArray.TYPE_ID);
+      {
+        UByte[] values = decoder.decodeByteArray("OptionSetUI8");
+        if (values != null) {
+          optionSetUi8 = new AccessLevelType[values.length];
+          for (int i = 0; i < values.length; i++) {
+            optionSetUi8[i] = new AccessLevelType(values[i]);
+          }
+        } else {
+          optionSetUi8 = null;
+        }
+      }
+      {
+        UShort[] values = decoder.decodeUInt16Array("OptionSetUI16");
+        if (values != null) {
+          optionSetUi16 = new AccessRestrictionType[values.length];
+          for (int i = 0; i < values.length; i++) {
+            optionSetUi16[i] = new AccessRestrictionType(values[i]);
+          }
+        } else {
+          optionSetUi16 = null;
+        }
+      }
+      {
+        UInteger[] values = decoder.decodeUInt32Array("OptionSetUI32");
+        if (values != null) {
+          optionSetUi32 = new AccessLevelExType[values.length];
+          for (int i = 0; i < values.length; i++) {
+            optionSetUi32[i] = new AccessLevelExType(values[i]);
+          }
+        } else {
+          optionSetUi32 = null;
+        }
+      }
+      optionSetUi64 = decoder.decodeUInt64Array("OptionSetUI64");
+      return new StructWithBuiltinArrayFieldsEx(
+          _boolean,
+          sByte,
+          _byte,
+          int16,
+          uInt16,
+          int32,
+          uInt32,
+          int64,
+          uInt64,
+          _float,
+          _double,
+          string,
+          dateTime,
+          guid,
+          byteString,
+          xmlElement,
+          nodeId,
+          expandedNodeId,
+          statusCode,
+          qualifiedName,
+          localizedText,
+          dataValue,
+          variant,
+          duration,
+          applicationType,
+          testEnumType,
+          xvType,
+          concreteTestType,
+          unionOfScalar,
+          unionOfArray,
+          optionSetUi8,
+          optionSetUi16,
+          optionSetUi32,
+          optionSetUi64);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithBuiltinArrayFieldsEx value) {
+      encoder.encodeBooleanArray("Boolean", value.getBoolean());
+      encoder.encodeSByteArray("SByte", value.getSByte());
+      encoder.encodeByteArray("Byte", value.getByte());
+      encoder.encodeInt16Array("Int16", value.getInt16());
+      encoder.encodeUInt16Array("UInt16", value.getUInt16());
+      encoder.encodeInt32Array("Int32", value.getInt32());
+      encoder.encodeUInt32Array("UInt32", value.getUInt32());
+      encoder.encodeInt64Array("Int64", value.getInt64());
+      encoder.encodeUInt64Array("UInt64", value.getUInt64());
+      encoder.encodeFloatArray("Float", value.getFloat());
+      encoder.encodeDoubleArray("Double", value.getDouble());
+      encoder.encodeStringArray("String", value.getString());
+      encoder.encodeDateTimeArray("DateTime", value.getDateTime());
+      encoder.encodeGuidArray("Guid", value.getGuid());
+      encoder.encodeByteStringArray("ByteString", value.getByteString());
+      encoder.encodeXmlElementArray("XmlElement", value.getXmlElement());
+      encoder.encodeNodeIdArray("NodeId", value.getNodeId());
+      encoder.encodeExpandedNodeIdArray("ExpandedNodeId", value.getExpandedNodeId());
+      encoder.encodeStatusCodeArray("StatusCode", value.getStatusCode());
+      encoder.encodeQualifiedNameArray("QualifiedName", value.getQualifiedName());
+      encoder.encodeLocalizedTextArray("LocalizedText", value.getLocalizedText());
+      encoder.encodeDataValueArray("DataValue", value.getDataValue());
+      encoder.encodeVariantArray("Variant", value.getVariant());
+      encoder.encodeDoubleArray("Duration", value.getDuration());
+      encoder.encodeEnumArray("ApplicationType", value.getApplicationType());
+      encoder.encodeEnumArray("TestEnumType", value.getTestEnumType());
+      encoder.encodeStructArray("XVType", value.getXvType(), XVType.TYPE_ID);
+      encoder.encodeStructArray(
+          "ConcreteTestType", value.getConcreteTestType(), ConcreteTestType.TYPE_ID);
+      encoder.encodeStructArray("UnionOfScalar", value.getUnionOfScalar(), UnionOfScalar.TYPE_ID);
+      encoder.encodeStructArray("UnionOfArray", value.getUnionOfArray(), UnionOfArray.TYPE_ID);
+      {
+        UByte[] values = null;
+        if (value.getOptionSetUi8() != null) {
+          values = new UByte[value.getOptionSetUi8().length];
+          for (int i = 0; i < values.length; i++) {
+            values[i] = value.getOptionSetUi8()[i].getValue();
+          }
+        }
+        encoder.encodeByteArray("OptionSetUI8", values);
+      }
+      {
+        UShort[] values = null;
+        if (value.getOptionSetUi16() != null) {
+          values = new UShort[value.getOptionSetUi16().length];
+          for (int i = 0; i < values.length; i++) {
+            values[i] = value.getOptionSetUi16()[i].getValue();
+          }
+        }
+        encoder.encodeUInt16Array("OptionSetUI16", values);
+      }
+      {
+        UInteger[] values = null;
+        if (value.getOptionSetUi32() != null) {
+          values = new UInteger[value.getOptionSetUi32().length];
+          for (int i = 0; i < values.length; i++) {
+            values[i] = value.getOptionSetUi32()[i].getValue();
+          }
+        }
+        encoder.encodeUInt32Array("OptionSetUI32", values);
+      }
+      encoder.encodeUInt64Array("OptionSetUI64", value.getOptionSetUi64());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinMatrixFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinMatrixFields.java
new file mode 100644
index 000000000..299e8cda5
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinMatrixFields.java
@@ -0,0 +1,649 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithBuiltinMatrixFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3010");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5041");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5043");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5042");
+
+  private final @Nullable Matrix _boolean;
+
+  private final @Nullable Matrix sByte;
+
+  private final @Nullable Matrix _byte;
+
+  private final @Nullable Matrix int16;
+
+  private final @Nullable Matrix uInt16;
+
+  private final @Nullable Matrix int32;
+
+  private final @Nullable Matrix uInt32;
+
+  private final @Nullable Matrix int64;
+
+  private final @Nullable Matrix uInt64;
+
+  private final @Nullable Matrix _float;
+
+  private final @Nullable Matrix _double;
+
+  private final @Nullable Matrix string;
+
+  private final @Nullable Matrix dateTime;
+
+  private final @Nullable Matrix guid;
+
+  private final @Nullable Matrix byteString;
+
+  private final @Nullable Matrix xmlElement;
+
+  private final @Nullable Matrix nodeId;
+
+  private final @Nullable Matrix expandedNodeId;
+
+  private final @Nullable Matrix statusCode;
+
+  private final @Nullable Matrix qualifiedName;
+
+  private final @Nullable Matrix localizedText;
+
+  private final @Nullable Matrix dataValue;
+
+  private final @Nullable Matrix variant;
+
+  public StructWithBuiltinMatrixFields(
+      @Nullable Matrix _boolean,
+      @Nullable Matrix sByte,
+      @Nullable Matrix _byte,
+      @Nullable Matrix int16,
+      @Nullable Matrix uInt16,
+      @Nullable Matrix int32,
+      @Nullable Matrix uInt32,
+      @Nullable Matrix int64,
+      @Nullable Matrix uInt64,
+      @Nullable Matrix _float,
+      @Nullable Matrix _double,
+      @Nullable Matrix string,
+      @Nullable Matrix dateTime,
+      @Nullable Matrix guid,
+      @Nullable Matrix byteString,
+      @Nullable Matrix xmlElement,
+      @Nullable Matrix nodeId,
+      @Nullable Matrix expandedNodeId,
+      @Nullable Matrix statusCode,
+      @Nullable Matrix qualifiedName,
+      @Nullable Matrix localizedText,
+      @Nullable Matrix dataValue,
+      @Nullable Matrix variant) {
+    this._boolean = _boolean;
+    this.sByte = sByte;
+    this._byte = _byte;
+    this.int16 = int16;
+    this.uInt16 = uInt16;
+    this.int32 = int32;
+    this.uInt32 = uInt32;
+    this.int64 = int64;
+    this.uInt64 = uInt64;
+    this._float = _float;
+    this._double = _double;
+    this.string = string;
+    this.dateTime = dateTime;
+    this.guid = guid;
+    this.byteString = byteString;
+    this.xmlElement = xmlElement;
+    this.nodeId = nodeId;
+    this.expandedNodeId = expandedNodeId;
+    this.statusCode = statusCode;
+    this.qualifiedName = qualifiedName;
+    this.localizedText = localizedText;
+    this.dataValue = dataValue;
+    this.variant = variant;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public @Nullable Matrix getBoolean() {
+    return _boolean;
+  }
+
+  public @Nullable Matrix getSByte() {
+    return sByte;
+  }
+
+  public @Nullable Matrix getByte() {
+    return _byte;
+  }
+
+  public @Nullable Matrix getInt16() {
+    return int16;
+  }
+
+  public @Nullable Matrix getUInt16() {
+    return uInt16;
+  }
+
+  public @Nullable Matrix getInt32() {
+    return int32;
+  }
+
+  public @Nullable Matrix getUInt32() {
+    return uInt32;
+  }
+
+  public @Nullable Matrix getInt64() {
+    return int64;
+  }
+
+  public @Nullable Matrix getUInt64() {
+    return uInt64;
+  }
+
+  public @Nullable Matrix getFloat() {
+    return _float;
+  }
+
+  public @Nullable Matrix getDouble() {
+    return _double;
+  }
+
+  public @Nullable Matrix getString() {
+    return string;
+  }
+
+  public @Nullable Matrix getDateTime() {
+    return dateTime;
+  }
+
+  public @Nullable Matrix getGuid() {
+    return guid;
+  }
+
+  public @Nullable Matrix getByteString() {
+    return byteString;
+  }
+
+  public @Nullable Matrix getXmlElement() {
+    return xmlElement;
+  }
+
+  public @Nullable Matrix getNodeId() {
+    return nodeId;
+  }
+
+  public @Nullable Matrix getExpandedNodeId() {
+    return expandedNodeId;
+  }
+
+  public @Nullable Matrix getStatusCode() {
+    return statusCode;
+  }
+
+  public @Nullable Matrix getQualifiedName() {
+    return qualifiedName;
+  }
+
+  public @Nullable Matrix getLocalizedText() {
+    return localizedText;
+  }
+
+  public @Nullable Matrix getDataValue() {
+    return dataValue;
+  }
+
+  public @Nullable Matrix getVariant() {
+    return variant;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithBuiltinMatrixFields that = (StructWithBuiltinMatrixFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getBoolean(), that.getBoolean());
+    eqb.append(getSByte(), that.getSByte());
+    eqb.append(getByte(), that.getByte());
+    eqb.append(getInt16(), that.getInt16());
+    eqb.append(getUInt16(), that.getUInt16());
+    eqb.append(getInt32(), that.getInt32());
+    eqb.append(getUInt32(), that.getUInt32());
+    eqb.append(getInt64(), that.getInt64());
+    eqb.append(getUInt64(), that.getUInt64());
+    eqb.append(getFloat(), that.getFloat());
+    eqb.append(getDouble(), that.getDouble());
+    eqb.append(getString(), that.getString());
+    eqb.append(getDateTime(), that.getDateTime());
+    eqb.append(getGuid(), that.getGuid());
+    eqb.append(getByteString(), that.getByteString());
+    eqb.append(getXmlElement(), that.getXmlElement());
+    eqb.append(getNodeId(), that.getNodeId());
+    eqb.append(getExpandedNodeId(), that.getExpandedNodeId());
+    eqb.append(getStatusCode(), that.getStatusCode());
+    eqb.append(getQualifiedName(), that.getQualifiedName());
+    eqb.append(getLocalizedText(), that.getLocalizedText());
+    eqb.append(getDataValue(), that.getDataValue());
+    eqb.append(getVariant(), that.getVariant());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getBoolean());
+    hcb.append(getSByte());
+    hcb.append(getByte());
+    hcb.append(getInt16());
+    hcb.append(getUInt16());
+    hcb.append(getInt32());
+    hcb.append(getUInt32());
+    hcb.append(getInt64());
+    hcb.append(getUInt64());
+    hcb.append(getFloat());
+    hcb.append(getDouble());
+    hcb.append(getString());
+    hcb.append(getDateTime());
+    hcb.append(getGuid());
+    hcb.append(getByteString());
+    hcb.append(getXmlElement());
+    hcb.append(getNodeId());
+    hcb.append(getExpandedNodeId());
+    hcb.append(getStatusCode());
+    hcb.append(getQualifiedName());
+    hcb.append(getLocalizedText());
+    hcb.append(getDataValue());
+    hcb.append(getVariant());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithBuiltinMatrixFields.class.getSimpleName() + "[", "]");
+    joiner.add("_boolean=" + getBoolean());
+    joiner.add("sByte=" + getSByte());
+    joiner.add("_byte=" + getByte());
+    joiner.add("int16=" + getInt16());
+    joiner.add("uInt16=" + getUInt16());
+    joiner.add("int32=" + getInt32());
+    joiner.add("uInt32=" + getUInt32());
+    joiner.add("int64=" + getInt64());
+    joiner.add("uInt64=" + getUInt64());
+    joiner.add("_float=" + getFloat());
+    joiner.add("_double=" + getDouble());
+    joiner.add("string=" + getString());
+    joiner.add("dateTime=" + getDateTime());
+    joiner.add("guid=" + getGuid());
+    joiner.add("byteString=" + getByteString());
+    joiner.add("xmlElement=" + getXmlElement());
+    joiner.add("nodeId=" + getNodeId());
+    joiner.add("expandedNodeId=" + getExpandedNodeId());
+    joiner.add("statusCode=" + getStatusCode());
+    joiner.add("qualifiedName=" + getQualifiedName());
+    joiner.add("localizedText=" + getLocalizedText());
+    joiner.add("dataValue=" + getDataValue());
+    joiner.add("variant=" + getVariant());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5041")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 5),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 8),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 9),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Float",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 10),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Double",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DateTime",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 13),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Guid",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 14),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ByteString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XmlElement",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 16),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "NodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 17),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ExpandedNodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 18),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StatusCode",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 19),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "QualifiedName",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 20),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "LocalizedText",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 21),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DataValue",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 23),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Variant",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 24),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithBuiltinMatrixFields> {
+    @Override
+    public Class<StructWithBuiltinMatrixFields> getType() {
+      return StructWithBuiltinMatrixFields.class;
+    }
+
+    @Override
+    public StructWithBuiltinMatrixFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Matrix _boolean;
+      final Matrix sByte;
+      final Matrix _byte;
+      final Matrix int16;
+      final Matrix uInt16;
+      final Matrix int32;
+      final Matrix uInt32;
+      final Matrix int64;
+      final Matrix uInt64;
+      final Matrix _float;
+      final Matrix _double;
+      final Matrix string;
+      final Matrix dateTime;
+      final Matrix guid;
+      final Matrix byteString;
+      final Matrix xmlElement;
+      final Matrix nodeId;
+      final Matrix expandedNodeId;
+      final Matrix statusCode;
+      final Matrix qualifiedName;
+      final Matrix localizedText;
+      final Matrix dataValue;
+      final Matrix variant;
+      _boolean = decoder.decodeMatrix("Boolean", BuiltinDataType.Boolean);
+      sByte = decoder.decodeMatrix("SByte", BuiltinDataType.SByte);
+      _byte = decoder.decodeMatrix("Byte", BuiltinDataType.Byte);
+      int16 = decoder.decodeMatrix("Int16", BuiltinDataType.Int16);
+      uInt16 = decoder.decodeMatrix("UInt16", BuiltinDataType.UInt16);
+      int32 = decoder.decodeMatrix("Int32", BuiltinDataType.Int32);
+      uInt32 = decoder.decodeMatrix("UInt32", BuiltinDataType.UInt32);
+      int64 = decoder.decodeMatrix("Int64", BuiltinDataType.Int64);
+      uInt64 = decoder.decodeMatrix("UInt64", BuiltinDataType.UInt64);
+      _float = decoder.decodeMatrix("Float", BuiltinDataType.Float);
+      _double = decoder.decodeMatrix("Double", BuiltinDataType.Double);
+      string = decoder.decodeMatrix("String", BuiltinDataType.String);
+      dateTime = decoder.decodeMatrix("DateTime", BuiltinDataType.DateTime);
+      guid = decoder.decodeMatrix("Guid", BuiltinDataType.Guid);
+      byteString = decoder.decodeMatrix("ByteString", BuiltinDataType.ByteString);
+      xmlElement = decoder.decodeMatrix("XmlElement", BuiltinDataType.XmlElement);
+      nodeId = decoder.decodeMatrix("NodeId", BuiltinDataType.NodeId);
+      expandedNodeId = decoder.decodeMatrix("ExpandedNodeId", BuiltinDataType.ExpandedNodeId);
+      statusCode = decoder.decodeMatrix("StatusCode", BuiltinDataType.StatusCode);
+      qualifiedName = decoder.decodeMatrix("QualifiedName", BuiltinDataType.QualifiedName);
+      localizedText = decoder.decodeMatrix("LocalizedText", BuiltinDataType.LocalizedText);
+      dataValue = decoder.decodeMatrix("DataValue", BuiltinDataType.DataValue);
+      variant = decoder.decodeMatrix("Variant", BuiltinDataType.Variant);
+      return new StructWithBuiltinMatrixFields(
+          _boolean,
+          sByte,
+          _byte,
+          int16,
+          uInt16,
+          int32,
+          uInt32,
+          int64,
+          uInt64,
+          _float,
+          _double,
+          string,
+          dateTime,
+          guid,
+          byteString,
+          xmlElement,
+          nodeId,
+          expandedNodeId,
+          statusCode,
+          qualifiedName,
+          localizedText,
+          dataValue,
+          variant);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithBuiltinMatrixFields value) {
+      encoder.encodeMatrix("Boolean", value.getBoolean());
+      encoder.encodeMatrix("SByte", value.getSByte());
+      encoder.encodeMatrix("Byte", value.getByte());
+      encoder.encodeMatrix("Int16", value.getInt16());
+      encoder.encodeMatrix("UInt16", value.getUInt16());
+      encoder.encodeMatrix("Int32", value.getInt32());
+      encoder.encodeMatrix("UInt32", value.getUInt32());
+      encoder.encodeMatrix("Int64", value.getInt64());
+      encoder.encodeMatrix("UInt64", value.getUInt64());
+      encoder.encodeMatrix("Float", value.getFloat());
+      encoder.encodeMatrix("Double", value.getDouble());
+      encoder.encodeMatrix("String", value.getString());
+      encoder.encodeMatrix("DateTime", value.getDateTime());
+      encoder.encodeMatrix("Guid", value.getGuid());
+      encoder.encodeMatrix("ByteString", value.getByteString());
+      encoder.encodeMatrix("XmlElement", value.getXmlElement());
+      encoder.encodeMatrix("NodeId", value.getNodeId());
+      encoder.encodeMatrix("ExpandedNodeId", value.getExpandedNodeId());
+      encoder.encodeMatrix("StatusCode", value.getStatusCode());
+      encoder.encodeMatrix("QualifiedName", value.getQualifiedName());
+      encoder.encodeMatrix("LocalizedText", value.getLocalizedText());
+      encoder.encodeMatrix("DataValue", value.getDataValue());
+      encoder.encodeMatrix("Variant", value.getVariant());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinMatrixFieldsEx.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinMatrixFieldsEx.java
new file mode 100644
index 000000000..403811cb4
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinMatrixFieldsEx.java
@@ -0,0 +1,730 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.ApplicationType;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelExType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessRestrictionType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.types.structured.XVType;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithBuiltinMatrixFieldsEx extends StructWithBuiltinMatrixFields
+    implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3017");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5044");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5046");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5045");
+
+  private final @Nullable Matrix duration;
+
+  private final @Nullable Matrix applicationType;
+
+  private final @Nullable Matrix testEnumType;
+
+  private final @Nullable Matrix xvType;
+
+  private final @Nullable Matrix concreteTestType;
+
+  private final @Nullable Matrix unionOfScalar;
+
+  private final @Nullable Matrix unionOfArray;
+
+  private final @Nullable Matrix optionSetUi8;
+
+  private final @Nullable Matrix optionSetUi16;
+
+  private final @Nullable Matrix optionSetUi32;
+
+  private final @Nullable Matrix optionSetUi64;
+
+  public StructWithBuiltinMatrixFieldsEx(
+      @Nullable Matrix _boolean,
+      @Nullable Matrix sByte,
+      @Nullable Matrix _byte,
+      @Nullable Matrix int16,
+      @Nullable Matrix uInt16,
+      @Nullable Matrix int32,
+      @Nullable Matrix uInt32,
+      @Nullable Matrix int64,
+      @Nullable Matrix uInt64,
+      @Nullable Matrix _float,
+      @Nullable Matrix _double,
+      @Nullable Matrix string,
+      @Nullable Matrix dateTime,
+      @Nullable Matrix guid,
+      @Nullable Matrix byteString,
+      @Nullable Matrix xmlElement,
+      @Nullable Matrix nodeId,
+      @Nullable Matrix expandedNodeId,
+      @Nullable Matrix statusCode,
+      @Nullable Matrix qualifiedName,
+      @Nullable Matrix localizedText,
+      @Nullable Matrix dataValue,
+      @Nullable Matrix variant,
+      @Nullable Matrix duration,
+      @Nullable Matrix applicationType,
+      @Nullable Matrix testEnumType,
+      @Nullable Matrix xvType,
+      @Nullable Matrix concreteTestType,
+      @Nullable Matrix unionOfScalar,
+      @Nullable Matrix unionOfArray,
+      @Nullable Matrix optionSetUi8,
+      @Nullable Matrix optionSetUi16,
+      @Nullable Matrix optionSetUi32,
+      @Nullable Matrix optionSetUi64) {
+    super(
+        _boolean,
+        sByte,
+        _byte,
+        int16,
+        uInt16,
+        int32,
+        uInt32,
+        int64,
+        uInt64,
+        _float,
+        _double,
+        string,
+        dateTime,
+        guid,
+        byteString,
+        xmlElement,
+        nodeId,
+        expandedNodeId,
+        statusCode,
+        qualifiedName,
+        localizedText,
+        dataValue,
+        variant);
+    this.duration = duration;
+    this.applicationType = applicationType;
+    this.testEnumType = testEnumType;
+    this.xvType = xvType;
+    this.concreteTestType = concreteTestType;
+    this.unionOfScalar = unionOfScalar;
+    this.unionOfArray = unionOfArray;
+    this.optionSetUi8 = optionSetUi8;
+    this.optionSetUi16 = optionSetUi16;
+    this.optionSetUi32 = optionSetUi32;
+    this.optionSetUi64 = optionSetUi64;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public @Nullable Matrix getDuration() {
+    return duration;
+  }
+
+  public @Nullable Matrix getApplicationType() {
+    return applicationType;
+  }
+
+  public @Nullable Matrix getTestEnumType() {
+    return testEnumType;
+  }
+
+  public @Nullable Matrix getXvType() {
+    return xvType;
+  }
+
+  public @Nullable Matrix getConcreteTestType() {
+    return concreteTestType;
+  }
+
+  public @Nullable Matrix getUnionOfScalar() {
+    return unionOfScalar;
+  }
+
+  public @Nullable Matrix getUnionOfArray() {
+    return unionOfArray;
+  }
+
+  public @Nullable Matrix getOptionSetUi8() {
+    return optionSetUi8;
+  }
+
+  public @Nullable Matrix getOptionSetUi16() {
+    return optionSetUi16;
+  }
+
+  public @Nullable Matrix getOptionSetUi32() {
+    return optionSetUi32;
+  }
+
+  public @Nullable Matrix getOptionSetUi64() {
+    return optionSetUi64;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithBuiltinMatrixFieldsEx that = (StructWithBuiltinMatrixFieldsEx) object;
+    var eqb = new EqualsBuilder();
+    eqb.appendSuper(super.equals(object));
+    eqb.append(getDuration(), that.getDuration());
+    eqb.append(getApplicationType(), that.getApplicationType());
+    eqb.append(getTestEnumType(), that.getTestEnumType());
+    eqb.append(getXvType(), that.getXvType());
+    eqb.append(getConcreteTestType(), that.getConcreteTestType());
+    eqb.append(getUnionOfScalar(), that.getUnionOfScalar());
+    eqb.append(getUnionOfArray(), that.getUnionOfArray());
+    eqb.append(getOptionSetUi8(), that.getOptionSetUi8());
+    eqb.append(getOptionSetUi16(), that.getOptionSetUi16());
+    eqb.append(getOptionSetUi32(), that.getOptionSetUi32());
+    eqb.append(getOptionSetUi64(), that.getOptionSetUi64());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getDuration());
+    hcb.append(getApplicationType());
+    hcb.append(getTestEnumType());
+    hcb.append(getXvType());
+    hcb.append(getConcreteTestType());
+    hcb.append(getUnionOfScalar());
+    hcb.append(getUnionOfArray());
+    hcb.append(getOptionSetUi8());
+    hcb.append(getOptionSetUi16());
+    hcb.append(getOptionSetUi32());
+    hcb.append(getOptionSetUi64());
+    hcb.appendSuper(super.hashCode());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithBuiltinMatrixFieldsEx.class.getSimpleName() + "[", "]");
+    joiner.add("duration=" + getDuration());
+    joiner.add("applicationType=" + getApplicationType());
+    joiner.add("testEnumType=" + getTestEnumType());
+    joiner.add("xvType=" + getXvType());
+    joiner.add("concreteTestType=" + getConcreteTestType());
+    joiner.add("unionOfScalar=" + getUnionOfScalar());
+    joiner.add("unionOfArray=" + getUnionOfArray());
+    joiner.add("optionSetUi8=" + getOptionSetUi8());
+    joiner.add("optionSetUi16=" + getOptionSetUi16());
+    joiner.add("optionSetUi32=" + getOptionSetUi32());
+    joiner.add("optionSetUi64=" + getOptionSetUi64());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5044")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3010")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 5),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 8),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 9),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Float",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 10),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Double",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DateTime",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 13),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Guid",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 14),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ByteString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XmlElement",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 16),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "NodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 17),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ExpandedNodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 18),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StatusCode",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 19),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "QualifiedName",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 20),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "LocalizedText",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 21),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DataValue",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 23),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Variant",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 24),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Duration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ApplicationType",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 307),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "TestEnumType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3011")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XVType",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12080),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UnionOfScalar",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3020")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UnionOfArray",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3023")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI8",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15031),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 95),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15406),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11737),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithBuiltinMatrixFieldsEx> {
+    @Override
+    public Class<StructWithBuiltinMatrixFieldsEx> getType() {
+      return StructWithBuiltinMatrixFieldsEx.class;
+    }
+
+    @Override
+    public StructWithBuiltinMatrixFieldsEx decodeType(EncodingContext context, UaDecoder decoder) {
+      final Matrix _boolean;
+      final Matrix sByte;
+      final Matrix _byte;
+      final Matrix int16;
+      final Matrix uInt16;
+      final Matrix int32;
+      final Matrix uInt32;
+      final Matrix int64;
+      final Matrix uInt64;
+      final Matrix _float;
+      final Matrix _double;
+      final Matrix string;
+      final Matrix dateTime;
+      final Matrix guid;
+      final Matrix byteString;
+      final Matrix xmlElement;
+      final Matrix nodeId;
+      final Matrix expandedNodeId;
+      final Matrix statusCode;
+      final Matrix qualifiedName;
+      final Matrix localizedText;
+      final Matrix dataValue;
+      final Matrix variant;
+      final Matrix duration;
+      final Matrix applicationType;
+      final Matrix testEnumType;
+      final Matrix xvType;
+      final Matrix concreteTestType;
+      final Matrix unionOfScalar;
+      final Matrix unionOfArray;
+      final Matrix optionSetUi8;
+      final Matrix optionSetUi16;
+      final Matrix optionSetUi32;
+      final Matrix optionSetUi64;
+      _boolean = decoder.decodeMatrix("Boolean", BuiltinDataType.Boolean);
+      sByte = decoder.decodeMatrix("SByte", BuiltinDataType.SByte);
+      _byte = decoder.decodeMatrix("Byte", BuiltinDataType.Byte);
+      int16 = decoder.decodeMatrix("Int16", BuiltinDataType.Int16);
+      uInt16 = decoder.decodeMatrix("UInt16", BuiltinDataType.UInt16);
+      int32 = decoder.decodeMatrix("Int32", BuiltinDataType.Int32);
+      uInt32 = decoder.decodeMatrix("UInt32", BuiltinDataType.UInt32);
+      int64 = decoder.decodeMatrix("Int64", BuiltinDataType.Int64);
+      uInt64 = decoder.decodeMatrix("UInt64", BuiltinDataType.UInt64);
+      _float = decoder.decodeMatrix("Float", BuiltinDataType.Float);
+      _double = decoder.decodeMatrix("Double", BuiltinDataType.Double);
+      string = decoder.decodeMatrix("String", BuiltinDataType.String);
+      dateTime = decoder.decodeMatrix("DateTime", BuiltinDataType.DateTime);
+      guid = decoder.decodeMatrix("Guid", BuiltinDataType.Guid);
+      byteString = decoder.decodeMatrix("ByteString", BuiltinDataType.ByteString);
+      xmlElement = decoder.decodeMatrix("XmlElement", BuiltinDataType.XmlElement);
+      nodeId = decoder.decodeMatrix("NodeId", BuiltinDataType.NodeId);
+      expandedNodeId = decoder.decodeMatrix("ExpandedNodeId", BuiltinDataType.ExpandedNodeId);
+      statusCode = decoder.decodeMatrix("StatusCode", BuiltinDataType.StatusCode);
+      qualifiedName = decoder.decodeMatrix("QualifiedName", BuiltinDataType.QualifiedName);
+      localizedText = decoder.decodeMatrix("LocalizedText", BuiltinDataType.LocalizedText);
+      dataValue = decoder.decodeMatrix("DataValue", BuiltinDataType.DataValue);
+      variant = decoder.decodeMatrix("Variant", BuiltinDataType.Variant);
+      duration = decoder.decodeMatrix("Duration", BuiltinDataType.Double);
+      {
+        Matrix matrix = decoder.decodeEnumMatrix("ApplicationType");
+        applicationType = matrix.transform(i -> ApplicationType.from((Integer) i));
+      }
+      {
+        Matrix matrix = decoder.decodeEnumMatrix("TestEnumType");
+        testEnumType = matrix.transform(i -> TestEnumType.from((Integer) i));
+      }
+      xvType = (Matrix) decoder.decodeStructMatrix("XVType", XVType.TYPE_ID);
+      concreteTestType =
+          (Matrix) decoder.decodeStructMatrix("ConcreteTestType", ConcreteTestType.TYPE_ID);
+      unionOfScalar = (Matrix) decoder.decodeStructMatrix("UnionOfScalar", UnionOfScalar.TYPE_ID);
+      unionOfArray = (Matrix) decoder.decodeStructMatrix("UnionOfArray", UnionOfArray.TYPE_ID);
+      {
+        Matrix matrix = decoder.decodeMatrix("OptionSetUI8", BuiltinDataType.Byte);
+        optionSetUi8 = matrix.transform(i -> new AccessLevelType((UByte) i));
+      }
+      {
+        Matrix matrix = decoder.decodeMatrix("OptionSetUI16", BuiltinDataType.UInt16);
+        optionSetUi16 = matrix.transform(i -> new AccessRestrictionType((UShort) i));
+      }
+      {
+        Matrix matrix = decoder.decodeMatrix("OptionSetUI32", BuiltinDataType.UInt32);
+        optionSetUi32 = matrix.transform(i -> new AccessLevelExType((UInteger) i));
+      }
+      optionSetUi64 = decoder.decodeMatrix("OptionSetUI64", BuiltinDataType.UInt64);
+      return new StructWithBuiltinMatrixFieldsEx(
+          _boolean,
+          sByte,
+          _byte,
+          int16,
+          uInt16,
+          int32,
+          uInt32,
+          int64,
+          uInt64,
+          _float,
+          _double,
+          string,
+          dateTime,
+          guid,
+          byteString,
+          xmlElement,
+          nodeId,
+          expandedNodeId,
+          statusCode,
+          qualifiedName,
+          localizedText,
+          dataValue,
+          variant,
+          duration,
+          applicationType,
+          testEnumType,
+          xvType,
+          concreteTestType,
+          unionOfScalar,
+          unionOfArray,
+          optionSetUi8,
+          optionSetUi16,
+          optionSetUi32,
+          optionSetUi64);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithBuiltinMatrixFieldsEx value) {
+      encoder.encodeMatrix("Boolean", value.getBoolean());
+      encoder.encodeMatrix("SByte", value.getSByte());
+      encoder.encodeMatrix("Byte", value.getByte());
+      encoder.encodeMatrix("Int16", value.getInt16());
+      encoder.encodeMatrix("UInt16", value.getUInt16());
+      encoder.encodeMatrix("Int32", value.getInt32());
+      encoder.encodeMatrix("UInt32", value.getUInt32());
+      encoder.encodeMatrix("Int64", value.getInt64());
+      encoder.encodeMatrix("UInt64", value.getUInt64());
+      encoder.encodeMatrix("Float", value.getFloat());
+      encoder.encodeMatrix("Double", value.getDouble());
+      encoder.encodeMatrix("String", value.getString());
+      encoder.encodeMatrix("DateTime", value.getDateTime());
+      encoder.encodeMatrix("Guid", value.getGuid());
+      encoder.encodeMatrix("ByteString", value.getByteString());
+      encoder.encodeMatrix("XmlElement", value.getXmlElement());
+      encoder.encodeMatrix("NodeId", value.getNodeId());
+      encoder.encodeMatrix("ExpandedNodeId", value.getExpandedNodeId());
+      encoder.encodeMatrix("StatusCode", value.getStatusCode());
+      encoder.encodeMatrix("QualifiedName", value.getQualifiedName());
+      encoder.encodeMatrix("LocalizedText", value.getLocalizedText());
+      encoder.encodeMatrix("DataValue", value.getDataValue());
+      encoder.encodeMatrix("Variant", value.getVariant());
+      encoder.encodeMatrix("Duration", value.getDuration());
+      encoder.encodeEnumMatrix("ApplicationType", value.getApplicationType());
+      encoder.encodeEnumMatrix("TestEnumType", value.getTestEnumType());
+      encoder.encodeStructMatrix("XVType", value.getXvType(), XVType.TYPE_ID);
+      encoder.encodeStructMatrix(
+          "ConcreteTestType", value.getConcreteTestType(), ConcreteTestType.TYPE_ID);
+      encoder.encodeStructMatrix("UnionOfScalar", value.getUnionOfScalar(), UnionOfScalar.TYPE_ID);
+      encoder.encodeStructMatrix("UnionOfArray", value.getUnionOfArray(), UnionOfArray.TYPE_ID);
+      encoder.encodeMatrix("OptionSetUI8", value.getOptionSetUi8());
+      encoder.encodeMatrix("OptionSetUI16", value.getOptionSetUi16());
+      encoder.encodeMatrix("OptionSetUI32", value.getOptionSetUi32());
+      encoder.encodeMatrix("OptionSetUI64", value.getOptionSetUi64());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinScalarFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinScalarFields.java
new file mode 100644
index 000000000..debcc7253
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinScalarFields.java
@@ -0,0 +1,658 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import java.util.UUID;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithBuiltinScalarFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3004");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5020");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5022");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5021");
+
+  private final Boolean _boolean;
+
+  private final Byte sByte;
+
+  private final UByte _byte;
+
+  private final Short int16;
+
+  private final UShort uInt16;
+
+  private final Integer int32;
+
+  private final UInteger uInt32;
+
+  private final Long int64;
+
+  private final ULong uInt64;
+
+  private final Float _float;
+
+  private final Double _double;
+
+  private final @Nullable String string;
+
+  private final DateTime dateTime;
+
+  private final UUID guid;
+
+  private final ByteString byteString;
+
+  private final XmlElement xmlElement;
+
+  private final NodeId nodeId;
+
+  private final ExpandedNodeId expandedNodeId;
+
+  private final StatusCode statusCode;
+
+  private final QualifiedName qualifiedName;
+
+  private final LocalizedText localizedText;
+
+  private final DataValue dataValue;
+
+  private final Variant variant;
+
+  public StructWithBuiltinScalarFields(
+      Boolean _boolean,
+      Byte sByte,
+      UByte _byte,
+      Short int16,
+      UShort uInt16,
+      Integer int32,
+      UInteger uInt32,
+      Long int64,
+      ULong uInt64,
+      Float _float,
+      Double _double,
+      @Nullable String string,
+      DateTime dateTime,
+      UUID guid,
+      ByteString byteString,
+      XmlElement xmlElement,
+      NodeId nodeId,
+      ExpandedNodeId expandedNodeId,
+      StatusCode statusCode,
+      QualifiedName qualifiedName,
+      LocalizedText localizedText,
+      DataValue dataValue,
+      Variant variant) {
+    this._boolean = _boolean;
+    this.sByte = sByte;
+    this._byte = _byte;
+    this.int16 = int16;
+    this.uInt16 = uInt16;
+    this.int32 = int32;
+    this.uInt32 = uInt32;
+    this.int64 = int64;
+    this.uInt64 = uInt64;
+    this._float = _float;
+    this._double = _double;
+    this.string = string;
+    this.dateTime = dateTime;
+    this.guid = guid;
+    this.byteString = byteString;
+    this.xmlElement = xmlElement;
+    this.nodeId = nodeId;
+    this.expandedNodeId = expandedNodeId;
+    this.statusCode = statusCode;
+    this.qualifiedName = qualifiedName;
+    this.localizedText = localizedText;
+    this.dataValue = dataValue;
+    this.variant = variant;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Boolean getBoolean() {
+    return _boolean;
+  }
+
+  public Byte getSByte() {
+    return sByte;
+  }
+
+  public UByte getByte() {
+    return _byte;
+  }
+
+  public Short getInt16() {
+    return int16;
+  }
+
+  public UShort getUInt16() {
+    return uInt16;
+  }
+
+  public Integer getInt32() {
+    return int32;
+  }
+
+  public UInteger getUInt32() {
+    return uInt32;
+  }
+
+  public Long getInt64() {
+    return int64;
+  }
+
+  public ULong getUInt64() {
+    return uInt64;
+  }
+
+  public Float getFloat() {
+    return _float;
+  }
+
+  public Double getDouble() {
+    return _double;
+  }
+
+  public @Nullable String getString() {
+    return string;
+  }
+
+  public DateTime getDateTime() {
+    return dateTime;
+  }
+
+  public UUID getGuid() {
+    return guid;
+  }
+
+  public ByteString getByteString() {
+    return byteString;
+  }
+
+  public XmlElement getXmlElement() {
+    return xmlElement;
+  }
+
+  public NodeId getNodeId() {
+    return nodeId;
+  }
+
+  public ExpandedNodeId getExpandedNodeId() {
+    return expandedNodeId;
+  }
+
+  public StatusCode getStatusCode() {
+    return statusCode;
+  }
+
+  public QualifiedName getQualifiedName() {
+    return qualifiedName;
+  }
+
+  public LocalizedText getLocalizedText() {
+    return localizedText;
+  }
+
+  public DataValue getDataValue() {
+    return dataValue;
+  }
+
+  public Variant getVariant() {
+    return variant;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithBuiltinScalarFields that = (StructWithBuiltinScalarFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getBoolean(), that.getBoolean());
+    eqb.append(getSByte(), that.getSByte());
+    eqb.append(getByte(), that.getByte());
+    eqb.append(getInt16(), that.getInt16());
+    eqb.append(getUInt16(), that.getUInt16());
+    eqb.append(getInt32(), that.getInt32());
+    eqb.append(getUInt32(), that.getUInt32());
+    eqb.append(getInt64(), that.getInt64());
+    eqb.append(getUInt64(), that.getUInt64());
+    eqb.append(getFloat(), that.getFloat());
+    eqb.append(getDouble(), that.getDouble());
+    eqb.append(getString(), that.getString());
+    eqb.append(getDateTime(), that.getDateTime());
+    eqb.append(getGuid(), that.getGuid());
+    eqb.append(getByteString(), that.getByteString());
+    eqb.append(getXmlElement(), that.getXmlElement());
+    eqb.append(getNodeId(), that.getNodeId());
+    eqb.append(getExpandedNodeId(), that.getExpandedNodeId());
+    eqb.append(getStatusCode(), that.getStatusCode());
+    eqb.append(getQualifiedName(), that.getQualifiedName());
+    eqb.append(getLocalizedText(), that.getLocalizedText());
+    eqb.append(getDataValue(), that.getDataValue());
+    eqb.append(getVariant(), that.getVariant());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getBoolean());
+    hcb.append(getSByte());
+    hcb.append(getByte());
+    hcb.append(getInt16());
+    hcb.append(getUInt16());
+    hcb.append(getInt32());
+    hcb.append(getUInt32());
+    hcb.append(getInt64());
+    hcb.append(getUInt64());
+    hcb.append(getFloat());
+    hcb.append(getDouble());
+    hcb.append(getString());
+    hcb.append(getDateTime());
+    hcb.append(getGuid());
+    hcb.append(getByteString());
+    hcb.append(getXmlElement());
+    hcb.append(getNodeId());
+    hcb.append(getExpandedNodeId());
+    hcb.append(getStatusCode());
+    hcb.append(getQualifiedName());
+    hcb.append(getLocalizedText());
+    hcb.append(getDataValue());
+    hcb.append(getVariant());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithBuiltinScalarFields.class.getSimpleName() + "[", "]");
+    joiner.add("_boolean=" + getBoolean());
+    joiner.add("sByte=" + getSByte());
+    joiner.add("_byte=" + getByte());
+    joiner.add("int16=" + getInt16());
+    joiner.add("uInt16=" + getUInt16());
+    joiner.add("int32=" + getInt32());
+    joiner.add("uInt32=" + getUInt32());
+    joiner.add("int64=" + getInt64());
+    joiner.add("uInt64=" + getUInt64());
+    joiner.add("_float=" + getFloat());
+    joiner.add("_double=" + getDouble());
+    joiner.add("string='" + getString() + "'");
+    joiner.add("dateTime=" + getDateTime());
+    joiner.add("guid=" + getGuid());
+    joiner.add("byteString=" + getByteString());
+    joiner.add("xmlElement=" + getXmlElement());
+    joiner.add("nodeId=" + getNodeId());
+    joiner.add("expandedNodeId=" + getExpandedNodeId());
+    joiner.add("statusCode=" + getStatusCode());
+    joiner.add("qualifiedName=" + getQualifiedName());
+    joiner.add("localizedText=" + getLocalizedText());
+    joiner.add("dataValue=" + getDataValue());
+    joiner.add("variant=" + getVariant());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5020")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 5),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 8),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 9),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Float",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 10),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Double",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DateTime",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 13),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Guid",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 14),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ByteString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XmlElement",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 16),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "NodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 17),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ExpandedNodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 18),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StatusCode",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 19),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "QualifiedName",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 20),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "LocalizedText",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 21),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DataValue",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 23),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Variant",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 24),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithBuiltinScalarFields> {
+    @Override
+    public Class<StructWithBuiltinScalarFields> getType() {
+      return StructWithBuiltinScalarFields.class;
+    }
+
+    @Override
+    public StructWithBuiltinScalarFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Boolean _boolean;
+      final Byte sByte;
+      final UByte _byte;
+      final Short int16;
+      final UShort uInt16;
+      final Integer int32;
+      final UInteger uInt32;
+      final Long int64;
+      final ULong uInt64;
+      final Float _float;
+      final Double _double;
+      final String string;
+      final DateTime dateTime;
+      final UUID guid;
+      final ByteString byteString;
+      final XmlElement xmlElement;
+      final NodeId nodeId;
+      final ExpandedNodeId expandedNodeId;
+      final StatusCode statusCode;
+      final QualifiedName qualifiedName;
+      final LocalizedText localizedText;
+      final DataValue dataValue;
+      final Variant variant;
+      _boolean = decoder.decodeBoolean("Boolean");
+      sByte = decoder.decodeSByte("SByte");
+      _byte = decoder.decodeByte("Byte");
+      int16 = decoder.decodeInt16("Int16");
+      uInt16 = decoder.decodeUInt16("UInt16");
+      int32 = decoder.decodeInt32("Int32");
+      uInt32 = decoder.decodeUInt32("UInt32");
+      int64 = decoder.decodeInt64("Int64");
+      uInt64 = decoder.decodeUInt64("UInt64");
+      _float = decoder.decodeFloat("Float");
+      _double = decoder.decodeDouble("Double");
+      string = decoder.decodeString("String");
+      dateTime = decoder.decodeDateTime("DateTime");
+      guid = decoder.decodeGuid("Guid");
+      byteString = decoder.decodeByteString("ByteString");
+      xmlElement = decoder.decodeXmlElement("XmlElement");
+      nodeId = decoder.decodeNodeId("NodeId");
+      expandedNodeId = decoder.decodeExpandedNodeId("ExpandedNodeId");
+      statusCode = decoder.decodeStatusCode("StatusCode");
+      qualifiedName = decoder.decodeQualifiedName("QualifiedName");
+      localizedText = decoder.decodeLocalizedText("LocalizedText");
+      dataValue = decoder.decodeDataValue("DataValue");
+      variant = decoder.decodeVariant("Variant");
+      return new StructWithBuiltinScalarFields(
+          _boolean,
+          sByte,
+          _byte,
+          int16,
+          uInt16,
+          int32,
+          uInt32,
+          int64,
+          uInt64,
+          _float,
+          _double,
+          string,
+          dateTime,
+          guid,
+          byteString,
+          xmlElement,
+          nodeId,
+          expandedNodeId,
+          statusCode,
+          qualifiedName,
+          localizedText,
+          dataValue,
+          variant);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithBuiltinScalarFields value) {
+      encoder.encodeBoolean("Boolean", value.getBoolean());
+      encoder.encodeSByte("SByte", value.getSByte());
+      encoder.encodeByte("Byte", value.getByte());
+      encoder.encodeInt16("Int16", value.getInt16());
+      encoder.encodeUInt16("UInt16", value.getUInt16());
+      encoder.encodeInt32("Int32", value.getInt32());
+      encoder.encodeUInt32("UInt32", value.getUInt32());
+      encoder.encodeInt64("Int64", value.getInt64());
+      encoder.encodeUInt64("UInt64", value.getUInt64());
+      encoder.encodeFloat("Float", value.getFloat());
+      encoder.encodeDouble("Double", value.getDouble());
+      encoder.encodeString("String", value.getString());
+      encoder.encodeDateTime("DateTime", value.getDateTime());
+      encoder.encodeGuid("Guid", value.getGuid());
+      encoder.encodeByteString("ByteString", value.getByteString());
+      encoder.encodeXmlElement("XmlElement", value.getXmlElement());
+      encoder.encodeNodeId("NodeId", value.getNodeId());
+      encoder.encodeExpandedNodeId("ExpandedNodeId", value.getExpandedNodeId());
+      encoder.encodeStatusCode("StatusCode", value.getStatusCode());
+      encoder.encodeQualifiedName("QualifiedName", value.getQualifiedName());
+      encoder.encodeLocalizedText("LocalizedText", value.getLocalizedText());
+      encoder.encodeDataValue("DataValue", value.getDataValue());
+      encoder.encodeVariant("Variant", value.getVariant());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinScalarFieldsEx.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinScalarFieldsEx.java
new file mode 100644
index 000000000..544ecee4d
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithBuiltinScalarFieldsEx.java
@@ -0,0 +1,722 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import java.util.UUID;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
+import org.eclipse.milo.opcua.stack.core.types.builtin.DateTime;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.QualifiedName;
+import org.eclipse.milo.opcua.stack.core.types.builtin.StatusCode;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Variant;
+import org.eclipse.milo.opcua.stack.core.types.builtin.XmlElement;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.ULong;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UShort;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.ApplicationType;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelExType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessLevelType;
+import org.eclipse.milo.opcua.stack.core.types.structured.AccessRestrictionType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.types.structured.XVType;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithBuiltinScalarFieldsEx extends StructWithBuiltinScalarFields
+    implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3015");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5026");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5028");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5027");
+
+  private final Double duration;
+
+  private final ApplicationType applicationType;
+
+  private final TestEnumType testEnumType;
+
+  private final XVType xvType;
+
+  private final ConcreteTestType concreteTestType;
+
+  private final UnionOfScalar unionOfScalar;
+
+  private final UnionOfArray unionOfArray;
+
+  private final AccessLevelType optionSetUi8;
+
+  private final AccessRestrictionType optionSetUi16;
+
+  private final AccessLevelExType optionSetUi32;
+
+  private final ULong optionSetUi64;
+
+  public StructWithBuiltinScalarFieldsEx(
+      Boolean _boolean,
+      Byte sByte,
+      UByte _byte,
+      Short int16,
+      UShort uInt16,
+      Integer int32,
+      UInteger uInt32,
+      Long int64,
+      ULong uInt64,
+      Float _float,
+      Double _double,
+      @Nullable String string,
+      DateTime dateTime,
+      UUID guid,
+      ByteString byteString,
+      XmlElement xmlElement,
+      NodeId nodeId,
+      ExpandedNodeId expandedNodeId,
+      StatusCode statusCode,
+      QualifiedName qualifiedName,
+      LocalizedText localizedText,
+      DataValue dataValue,
+      Variant variant,
+      Double duration,
+      ApplicationType applicationType,
+      TestEnumType testEnumType,
+      XVType xvType,
+      ConcreteTestType concreteTestType,
+      UnionOfScalar unionOfScalar,
+      UnionOfArray unionOfArray,
+      AccessLevelType optionSetUi8,
+      AccessRestrictionType optionSetUi16,
+      AccessLevelExType optionSetUi32,
+      ULong optionSetUi64) {
+    super(
+        _boolean,
+        sByte,
+        _byte,
+        int16,
+        uInt16,
+        int32,
+        uInt32,
+        int64,
+        uInt64,
+        _float,
+        _double,
+        string,
+        dateTime,
+        guid,
+        byteString,
+        xmlElement,
+        nodeId,
+        expandedNodeId,
+        statusCode,
+        qualifiedName,
+        localizedText,
+        dataValue,
+        variant);
+    this.duration = duration;
+    this.applicationType = applicationType;
+    this.testEnumType = testEnumType;
+    this.xvType = xvType;
+    this.concreteTestType = concreteTestType;
+    this.unionOfScalar = unionOfScalar;
+    this.unionOfArray = unionOfArray;
+    this.optionSetUi8 = optionSetUi8;
+    this.optionSetUi16 = optionSetUi16;
+    this.optionSetUi32 = optionSetUi32;
+    this.optionSetUi64 = optionSetUi64;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Double getDuration() {
+    return duration;
+  }
+
+  public ApplicationType getApplicationType() {
+    return applicationType;
+  }
+
+  public TestEnumType getTestEnumType() {
+    return testEnumType;
+  }
+
+  public XVType getXvType() {
+    return xvType;
+  }
+
+  public ConcreteTestType getConcreteTestType() {
+    return concreteTestType;
+  }
+
+  public UnionOfScalar getUnionOfScalar() {
+    return unionOfScalar;
+  }
+
+  public UnionOfArray getUnionOfArray() {
+    return unionOfArray;
+  }
+
+  public AccessLevelType getOptionSetUi8() {
+    return optionSetUi8;
+  }
+
+  public AccessRestrictionType getOptionSetUi16() {
+    return optionSetUi16;
+  }
+
+  public AccessLevelExType getOptionSetUi32() {
+    return optionSetUi32;
+  }
+
+  public ULong getOptionSetUi64() {
+    return optionSetUi64;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithBuiltinScalarFieldsEx that = (StructWithBuiltinScalarFieldsEx) object;
+    var eqb = new EqualsBuilder();
+    eqb.appendSuper(super.equals(object));
+    eqb.append(getDuration(), that.getDuration());
+    eqb.append(getApplicationType(), that.getApplicationType());
+    eqb.append(getTestEnumType(), that.getTestEnumType());
+    eqb.append(getXvType(), that.getXvType());
+    eqb.append(getConcreteTestType(), that.getConcreteTestType());
+    eqb.append(getUnionOfScalar(), that.getUnionOfScalar());
+    eqb.append(getUnionOfArray(), that.getUnionOfArray());
+    eqb.append(getOptionSetUi8(), that.getOptionSetUi8());
+    eqb.append(getOptionSetUi16(), that.getOptionSetUi16());
+    eqb.append(getOptionSetUi32(), that.getOptionSetUi32());
+    eqb.append(getOptionSetUi64(), that.getOptionSetUi64());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getDuration());
+    hcb.append(getApplicationType());
+    hcb.append(getTestEnumType());
+    hcb.append(getXvType());
+    hcb.append(getConcreteTestType());
+    hcb.append(getUnionOfScalar());
+    hcb.append(getUnionOfArray());
+    hcb.append(getOptionSetUi8());
+    hcb.append(getOptionSetUi16());
+    hcb.append(getOptionSetUi32());
+    hcb.append(getOptionSetUi64());
+    hcb.appendSuper(super.hashCode());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithBuiltinScalarFieldsEx.class.getSimpleName() + "[", "]");
+    joiner.add("duration=" + getDuration());
+    joiner.add("applicationType=" + getApplicationType());
+    joiner.add("testEnumType=" + getTestEnumType());
+    joiner.add("xvType=" + getXvType());
+    joiner.add("concreteTestType=" + getConcreteTestType());
+    joiner.add("unionOfScalar=" + getUnionOfScalar());
+    joiner.add("unionOfArray=" + getUnionOfArray());
+    joiner.add("optionSetUi8=" + getOptionSetUi8());
+    joiner.add("optionSetUi16=" + getOptionSetUi16());
+    joiner.add("optionSetUi32=" + getOptionSetUi32());
+    joiner.add("optionSetUi64=" + getOptionSetUi64());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5026")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3004")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 4),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 5),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 7),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Int64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 8),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UInt64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 9),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Float",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 10),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Double",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DateTime",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 13),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Guid",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 14),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ByteString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XmlElement",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 16),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "NodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 17),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ExpandedNodeId",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 18),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "StatusCode",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 19),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "QualifiedName",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 20),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "LocalizedText",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 21),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "DataValue",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 23),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Variant",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 24),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Duration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ApplicationType",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 307),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "TestEnumType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3011")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "XVType",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12080),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "ConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UnionOfScalar",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3020")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "UnionOfArray",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3023")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI8",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15031),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI16",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 95),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 15406),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionSetUI64",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 11737),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithBuiltinScalarFieldsEx> {
+    @Override
+    public Class<StructWithBuiltinScalarFieldsEx> getType() {
+      return StructWithBuiltinScalarFieldsEx.class;
+    }
+
+    @Override
+    public StructWithBuiltinScalarFieldsEx decodeType(EncodingContext context, UaDecoder decoder) {
+      final Boolean _boolean;
+      final Byte sByte;
+      final UByte _byte;
+      final Short int16;
+      final UShort uInt16;
+      final Integer int32;
+      final UInteger uInt32;
+      final Long int64;
+      final ULong uInt64;
+      final Float _float;
+      final Double _double;
+      final String string;
+      final DateTime dateTime;
+      final UUID guid;
+      final ByteString byteString;
+      final XmlElement xmlElement;
+      final NodeId nodeId;
+      final ExpandedNodeId expandedNodeId;
+      final StatusCode statusCode;
+      final QualifiedName qualifiedName;
+      final LocalizedText localizedText;
+      final DataValue dataValue;
+      final Variant variant;
+      final Double duration;
+      final ApplicationType applicationType;
+      final TestEnumType testEnumType;
+      final XVType xvType;
+      final ConcreteTestType concreteTestType;
+      final UnionOfScalar unionOfScalar;
+      final UnionOfArray unionOfArray;
+      final AccessLevelType optionSetUi8;
+      final AccessRestrictionType optionSetUi16;
+      final AccessLevelExType optionSetUi32;
+      final ULong optionSetUi64;
+      _boolean = decoder.decodeBoolean("Boolean");
+      sByte = decoder.decodeSByte("SByte");
+      _byte = decoder.decodeByte("Byte");
+      int16 = decoder.decodeInt16("Int16");
+      uInt16 = decoder.decodeUInt16("UInt16");
+      int32 = decoder.decodeInt32("Int32");
+      uInt32 = decoder.decodeUInt32("UInt32");
+      int64 = decoder.decodeInt64("Int64");
+      uInt64 = decoder.decodeUInt64("UInt64");
+      _float = decoder.decodeFloat("Float");
+      _double = decoder.decodeDouble("Double");
+      string = decoder.decodeString("String");
+      dateTime = decoder.decodeDateTime("DateTime");
+      guid = decoder.decodeGuid("Guid");
+      byteString = decoder.decodeByteString("ByteString");
+      xmlElement = decoder.decodeXmlElement("XmlElement");
+      nodeId = decoder.decodeNodeId("NodeId");
+      expandedNodeId = decoder.decodeExpandedNodeId("ExpandedNodeId");
+      statusCode = decoder.decodeStatusCode("StatusCode");
+      qualifiedName = decoder.decodeQualifiedName("QualifiedName");
+      localizedText = decoder.decodeLocalizedText("LocalizedText");
+      dataValue = decoder.decodeDataValue("DataValue");
+      variant = decoder.decodeVariant("Variant");
+      duration = decoder.decodeDouble("Duration");
+      applicationType = ApplicationType.from(decoder.decodeEnum("ApplicationType"));
+      testEnumType = TestEnumType.from(decoder.decodeEnum("TestEnumType"));
+      xvType = (XVType) decoder.decodeStruct("XVType", XVType.TYPE_ID);
+      concreteTestType =
+          (ConcreteTestType) decoder.decodeStruct("ConcreteTestType", ConcreteTestType.TYPE_ID);
+      unionOfScalar = (UnionOfScalar) decoder.decodeStruct("UnionOfScalar", UnionOfScalar.TYPE_ID);
+      unionOfArray = (UnionOfArray) decoder.decodeStruct("UnionOfArray", UnionOfArray.TYPE_ID);
+      optionSetUi8 = new AccessLevelType(decoder.decodeByte("OptionSetUI8"));
+      optionSetUi16 = new AccessRestrictionType(decoder.decodeUInt16("OptionSetUI16"));
+      optionSetUi32 = new AccessLevelExType(decoder.decodeUInt32("OptionSetUI32"));
+      optionSetUi64 = decoder.decodeUInt64("OptionSetUI64");
+      return new StructWithBuiltinScalarFieldsEx(
+          _boolean,
+          sByte,
+          _byte,
+          int16,
+          uInt16,
+          int32,
+          uInt32,
+          int64,
+          uInt64,
+          _float,
+          _double,
+          string,
+          dateTime,
+          guid,
+          byteString,
+          xmlElement,
+          nodeId,
+          expandedNodeId,
+          statusCode,
+          qualifiedName,
+          localizedText,
+          dataValue,
+          variant,
+          duration,
+          applicationType,
+          testEnumType,
+          xvType,
+          concreteTestType,
+          unionOfScalar,
+          unionOfArray,
+          optionSetUi8,
+          optionSetUi16,
+          optionSetUi32,
+          optionSetUi64);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithBuiltinScalarFieldsEx value) {
+      encoder.encodeBoolean("Boolean", value.getBoolean());
+      encoder.encodeSByte("SByte", value.getSByte());
+      encoder.encodeByte("Byte", value.getByte());
+      encoder.encodeInt16("Int16", value.getInt16());
+      encoder.encodeUInt16("UInt16", value.getUInt16());
+      encoder.encodeInt32("Int32", value.getInt32());
+      encoder.encodeUInt32("UInt32", value.getUInt32());
+      encoder.encodeInt64("Int64", value.getInt64());
+      encoder.encodeUInt64("UInt64", value.getUInt64());
+      encoder.encodeFloat("Float", value.getFloat());
+      encoder.encodeDouble("Double", value.getDouble());
+      encoder.encodeString("String", value.getString());
+      encoder.encodeDateTime("DateTime", value.getDateTime());
+      encoder.encodeGuid("Guid", value.getGuid());
+      encoder.encodeByteString("ByteString", value.getByteString());
+      encoder.encodeXmlElement("XmlElement", value.getXmlElement());
+      encoder.encodeNodeId("NodeId", value.getNodeId());
+      encoder.encodeExpandedNodeId("ExpandedNodeId", value.getExpandedNodeId());
+      encoder.encodeStatusCode("StatusCode", value.getStatusCode());
+      encoder.encodeQualifiedName("QualifiedName", value.getQualifiedName());
+      encoder.encodeLocalizedText("LocalizedText", value.getLocalizedText());
+      encoder.encodeDataValue("DataValue", value.getDataValue());
+      encoder.encodeVariant("Variant", value.getVariant());
+      encoder.encodeDouble("Duration", value.getDuration());
+      encoder.encodeEnum("ApplicationType", value.getApplicationType());
+      encoder.encodeEnum("TestEnumType", value.getTestEnumType());
+      encoder.encodeStruct("XVType", value.getXvType(), XVType.TYPE_ID);
+      encoder.encodeStruct(
+          "ConcreteTestType", value.getConcreteTestType(), ConcreteTestType.TYPE_ID);
+      encoder.encodeStruct("UnionOfScalar", value.getUnionOfScalar(), UnionOfScalar.TYPE_ID);
+      encoder.encodeStruct("UnionOfArray", value.getUnionOfArray(), UnionOfArray.TYPE_ID);
+      encoder.encodeByte("OptionSetUI8", value.getOptionSetUi8().getValue());
+      encoder.encodeUInt16("OptionSetUI16", value.getOptionSetUi16().getValue());
+      encoder.encodeUInt32("OptionSetUI32", value.getOptionSetUi32().getValue());
+      encoder.encodeUInt64("OptionSetUI64", value.getOptionSetUi64());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalArrayFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalArrayFields.java
new file mode 100644
index 000000000..17ed09443
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalArrayFields.java
@@ -0,0 +1,355 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithOptionalArrayFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3007");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5017");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5019");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5018");
+
+  private final Integer @Nullable [] int32;
+
+  private final Integer @Nullable [] optionalInt32;
+
+  private final String @Nullable [] string;
+
+  private final String @Nullable [] optionalString;
+
+  private final Double @Nullable [] duration;
+
+  private final Double @Nullable [] optionalDuration;
+
+  private final ConcreteTestType @Nullable [] concreteTestType;
+
+  private final ConcreteTestType @Nullable [] optionalConcreteTestType;
+
+  public StructWithOptionalArrayFields(
+      Integer @Nullable [] int32,
+      Integer @Nullable [] optionalInt32,
+      String @Nullable [] string,
+      String @Nullable [] optionalString,
+      Double @Nullable [] duration,
+      Double @Nullable [] optionalDuration,
+      ConcreteTestType @Nullable [] concreteTestType,
+      ConcreteTestType @Nullable [] optionalConcreteTestType) {
+    this.int32 = int32;
+    this.optionalInt32 = optionalInt32;
+    this.string = string;
+    this.optionalString = optionalString;
+    this.duration = duration;
+    this.optionalDuration = optionalDuration;
+    this.concreteTestType = concreteTestType;
+    this.optionalConcreteTestType = optionalConcreteTestType;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Integer @Nullable [] getInt32() {
+    return int32;
+  }
+
+  public Integer @Nullable [] getOptionalInt32() {
+    return optionalInt32;
+  }
+
+  public String @Nullable [] getString() {
+    return string;
+  }
+
+  public String @Nullable [] getOptionalString() {
+    return optionalString;
+  }
+
+  public Double @Nullable [] getDuration() {
+    return duration;
+  }
+
+  public Double @Nullable [] getOptionalDuration() {
+    return optionalDuration;
+  }
+
+  public ConcreteTestType @Nullable [] getConcreteTestType() {
+    return concreteTestType;
+  }
+
+  public ConcreteTestType @Nullable [] getOptionalConcreteTestType() {
+    return optionalConcreteTestType;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithOptionalArrayFields that = (StructWithOptionalArrayFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getInt32(), that.getInt32());
+    eqb.append(getOptionalInt32(), that.getOptionalInt32());
+    eqb.append(getString(), that.getString());
+    eqb.append(getOptionalString(), that.getOptionalString());
+    eqb.append(getDuration(), that.getDuration());
+    eqb.append(getOptionalDuration(), that.getOptionalDuration());
+    eqb.append(getConcreteTestType(), that.getConcreteTestType());
+    eqb.append(getOptionalConcreteTestType(), that.getOptionalConcreteTestType());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getInt32());
+    hcb.append(getOptionalInt32());
+    hcb.append(getString());
+    hcb.append(getOptionalString());
+    hcb.append(getDuration());
+    hcb.append(getOptionalDuration());
+    hcb.append(getConcreteTestType());
+    hcb.append(getOptionalConcreteTestType());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithOptionalArrayFields.class.getSimpleName() + "[", "]");
+    joiner.add("int32=" + java.util.Arrays.toString(getInt32()));
+    joiner.add("optionalInt32=" + java.util.Arrays.toString(getOptionalInt32()));
+    joiner.add("string=" + java.util.Arrays.toString(getString()));
+    joiner.add("optionalString=" + java.util.Arrays.toString(getOptionalString()));
+    joiner.add("duration=" + java.util.Arrays.toString(getDuration()));
+    joiner.add("optionalDuration=" + java.util.Arrays.toString(getOptionalDuration()));
+    joiner.add("concreteTestType=" + java.util.Arrays.toString(getConcreteTestType()));
+    joiner.add(
+        "optionalConcreteTestType=" + java.util.Arrays.toString(getOptionalConcreteTestType()));
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5017")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.StructureWithOptionalFields,
+        new StructureField[] {
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "Duration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalDuration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              true)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithOptionalArrayFields> {
+    @Override
+    public Class<StructWithOptionalArrayFields> getType() {
+      return StructWithOptionalArrayFields.class;
+    }
+
+    @Override
+    public StructWithOptionalArrayFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Integer[] int32;
+      final Integer[] optionalInt32;
+      final String[] string;
+      final String[] optionalString;
+      final Double[] duration;
+      final Double[] optionalDuration;
+      final ConcreteTestType[] concreteTestType;
+      final ConcreteTestType[] optionalConcreteTestType;
+      final long encodingMask = decoder.decodeUInt32("EncodingMask").longValue();
+      int32 = decoder.decodeInt32Array("Int32");
+      if ((encodingMask & (1L << 0)) != 0) {
+        optionalInt32 = decoder.decodeInt32Array("OptionalInt32");
+      } else {
+        optionalInt32 = null;
+      }
+      string = decoder.decodeStringArray("String");
+      if ((encodingMask & (1L << 1)) != 0) {
+        optionalString = decoder.decodeStringArray("OptionalString");
+      } else {
+        optionalString = null;
+      }
+      duration = decoder.decodeDoubleArray("Duration");
+      if ((encodingMask & (1L << 2)) != 0) {
+        optionalDuration = decoder.decodeDoubleArray("OptionalDuration");
+      } else {
+        optionalDuration = null;
+      }
+      concreteTestType =
+          (ConcreteTestType[])
+              decoder.decodeStructArray("ConcreteTestType", ConcreteTestType.TYPE_ID);
+      if ((encodingMask & (1L << 3)) != 0) {
+        optionalConcreteTestType =
+            (ConcreteTestType[])
+                decoder.decodeStructArray("OptionalConcreteTestType", ConcreteTestType.TYPE_ID);
+      } else {
+        optionalConcreteTestType = null;
+      }
+      return new StructWithOptionalArrayFields(
+          int32,
+          optionalInt32,
+          string,
+          optionalString,
+          duration,
+          optionalDuration,
+          concreteTestType,
+          optionalConcreteTestType);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithOptionalArrayFields value) {
+      long encodingMask = 0L;
+      if (value.getOptionalInt32() != null) {
+        encodingMask |= (1L << 0);
+      }
+      if (value.getOptionalString() != null) {
+        encodingMask |= (1L << 1);
+      }
+      if (value.getOptionalDuration() != null) {
+        encodingMask |= (1L << 2);
+      }
+      if (value.getOptionalConcreteTestType() != null) {
+        encodingMask |= (1L << 3);
+      }
+      encoder.encodeUInt32("EncodingMask", Unsigned.uint(encodingMask));
+      encoder.encodeInt32Array("Int32", value.getInt32());
+      if (value.getOptionalInt32() != null) {
+        encoder.encodeInt32Array("OptionalInt32", value.getOptionalInt32());
+      }
+      encoder.encodeStringArray("String", value.getString());
+      if (value.getOptionalString() != null) {
+        encoder.encodeStringArray("OptionalString", value.getOptionalString());
+      }
+      encoder.encodeDoubleArray("Duration", value.getDuration());
+      if (value.getOptionalDuration() != null) {
+        encoder.encodeDoubleArray("OptionalDuration", value.getOptionalDuration());
+      }
+      encoder.encodeStructArray(
+          "ConcreteTestType", value.getConcreteTestType(), ConcreteTestType.TYPE_ID);
+      if (value.getOptionalConcreteTestType() != null) {
+        encoder.encodeStructArray(
+            "OptionalConcreteTestType",
+            value.getOptionalConcreteTestType(),
+            ConcreteTestType.TYPE_ID);
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalMatrixFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalMatrixFields.java
new file mode 100644
index 000000000..b419a3bfd
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalMatrixFields.java
@@ -0,0 +1,355 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithOptionalMatrixFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3035");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5059");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5061");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5060");
+
+  private final @Nullable Matrix int32;
+
+  private final @Nullable Matrix optionalInt32;
+
+  private final @Nullable Matrix string;
+
+  private final @Nullable Matrix optionalString;
+
+  private final @Nullable Matrix duration;
+
+  private final @Nullable Matrix optionalDuration;
+
+  private final @Nullable Matrix concreteTestType;
+
+  private final @Nullable Matrix optionalConcreteTestType;
+
+  public StructWithOptionalMatrixFields(
+      @Nullable Matrix int32,
+      @Nullable Matrix optionalInt32,
+      @Nullable Matrix string,
+      @Nullable Matrix optionalString,
+      @Nullable Matrix duration,
+      @Nullable Matrix optionalDuration,
+      @Nullable Matrix concreteTestType,
+      @Nullable Matrix optionalConcreteTestType) {
+    this.int32 = int32;
+    this.optionalInt32 = optionalInt32;
+    this.string = string;
+    this.optionalString = optionalString;
+    this.duration = duration;
+    this.optionalDuration = optionalDuration;
+    this.concreteTestType = concreteTestType;
+    this.optionalConcreteTestType = optionalConcreteTestType;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public @Nullable Matrix getInt32() {
+    return int32;
+  }
+
+  public @Nullable Matrix getOptionalInt32() {
+    return optionalInt32;
+  }
+
+  public @Nullable Matrix getString() {
+    return string;
+  }
+
+  public @Nullable Matrix getOptionalString() {
+    return optionalString;
+  }
+
+  public @Nullable Matrix getDuration() {
+    return duration;
+  }
+
+  public @Nullable Matrix getOptionalDuration() {
+    return optionalDuration;
+  }
+
+  public @Nullable Matrix getConcreteTestType() {
+    return concreteTestType;
+  }
+
+  public @Nullable Matrix getOptionalConcreteTestType() {
+    return optionalConcreteTestType;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithOptionalMatrixFields that = (StructWithOptionalMatrixFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getInt32(), that.getInt32());
+    eqb.append(getOptionalInt32(), that.getOptionalInt32());
+    eqb.append(getString(), that.getString());
+    eqb.append(getOptionalString(), that.getOptionalString());
+    eqb.append(getDuration(), that.getDuration());
+    eqb.append(getOptionalDuration(), that.getOptionalDuration());
+    eqb.append(getConcreteTestType(), that.getConcreteTestType());
+    eqb.append(getOptionalConcreteTestType(), that.getOptionalConcreteTestType());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getInt32());
+    hcb.append(getOptionalInt32());
+    hcb.append(getString());
+    hcb.append(getOptionalString());
+    hcb.append(getDuration());
+    hcb.append(getOptionalDuration());
+    hcb.append(getConcreteTestType());
+    hcb.append(getOptionalConcreteTestType());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithOptionalMatrixFields.class.getSimpleName() + "[", "]");
+    joiner.add("int32=" + getInt32());
+    joiner.add("optionalInt32=" + getOptionalInt32());
+    joiner.add("string=" + getString());
+    joiner.add("optionalString=" + getOptionalString());
+    joiner.add("duration=" + getDuration());
+    joiner.add("optionalDuration=" + getOptionalDuration());
+    joiner.add("concreteTestType=" + getConcreteTestType());
+    joiner.add("optionalConcreteTestType=" + getOptionalConcreteTestType());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5059")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.StructureWithOptionalFields,
+        new StructureField[] {
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "Duration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalDuration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              true)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithOptionalMatrixFields> {
+    @Override
+    public Class<StructWithOptionalMatrixFields> getType() {
+      return StructWithOptionalMatrixFields.class;
+    }
+
+    @Override
+    public StructWithOptionalMatrixFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Matrix int32;
+      final Matrix optionalInt32;
+      final Matrix string;
+      final Matrix optionalString;
+      final Matrix duration;
+      final Matrix optionalDuration;
+      final Matrix concreteTestType;
+      final Matrix optionalConcreteTestType;
+      final long encodingMask = decoder.decodeUInt32("EncodingMask").longValue();
+      int32 = decoder.decodeMatrix("Int32", BuiltinDataType.Int32);
+      if ((encodingMask & (1L << 0)) != 0) {
+        optionalInt32 = decoder.decodeMatrix("OptionalInt32", BuiltinDataType.Int32);
+      } else {
+        optionalInt32 = null;
+      }
+      string = decoder.decodeMatrix("String", BuiltinDataType.String);
+      if ((encodingMask & (1L << 1)) != 0) {
+        optionalString = decoder.decodeMatrix("OptionalString", BuiltinDataType.String);
+      } else {
+        optionalString = null;
+      }
+      duration = decoder.decodeMatrix("Duration", BuiltinDataType.Double);
+      if ((encodingMask & (1L << 2)) != 0) {
+        optionalDuration = decoder.decodeMatrix("OptionalDuration", BuiltinDataType.Double);
+      } else {
+        optionalDuration = null;
+      }
+      concreteTestType =
+          (Matrix) decoder.decodeStructMatrix("ConcreteTestType", ConcreteTestType.TYPE_ID);
+      if ((encodingMask & (1L << 3)) != 0) {
+        optionalConcreteTestType =
+            (Matrix)
+                decoder.decodeStructMatrix("OptionalConcreteTestType", ConcreteTestType.TYPE_ID);
+      } else {
+        optionalConcreteTestType = null;
+      }
+      return new StructWithOptionalMatrixFields(
+          int32,
+          optionalInt32,
+          string,
+          optionalString,
+          duration,
+          optionalDuration,
+          concreteTestType,
+          optionalConcreteTestType);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithOptionalMatrixFields value) {
+      long encodingMask = 0L;
+      if (value.getOptionalInt32() != null) {
+        encodingMask |= (1L << 0);
+      }
+      if (value.getOptionalString() != null) {
+        encodingMask |= (1L << 1);
+      }
+      if (value.getOptionalDuration() != null) {
+        encodingMask |= (1L << 2);
+      }
+      if (value.getOptionalConcreteTestType() != null) {
+        encodingMask |= (1L << 3);
+      }
+      encoder.encodeUInt32("EncodingMask", Unsigned.uint(encodingMask));
+      encoder.encodeMatrix("Int32", value.getInt32());
+      if (value.getOptionalInt32() != null) {
+        encoder.encodeMatrix("OptionalInt32", value.getOptionalInt32());
+      }
+      encoder.encodeMatrix("String", value.getString());
+      if (value.getOptionalString() != null) {
+        encoder.encodeMatrix("OptionalString", value.getOptionalString());
+      }
+      encoder.encodeMatrix("Duration", value.getDuration());
+      if (value.getOptionalDuration() != null) {
+        encoder.encodeMatrix("OptionalDuration", value.getOptionalDuration());
+      }
+      encoder.encodeStructMatrix(
+          "ConcreteTestType", value.getConcreteTestType(), ConcreteTestType.TYPE_ID);
+      if (value.getOptionalConcreteTestType() != null) {
+        encoder.encodeStructMatrix(
+            "OptionalConcreteTestType",
+            value.getOptionalConcreteTestType(),
+            ConcreteTestType.TYPE_ID);
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalScalarFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalScalarFields.java
new file mode 100644
index 000000000..68f6ded77
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithOptionalScalarFields.java
@@ -0,0 +1,353 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithOptionalScalarFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3016");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5011");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5013");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5012");
+
+  private final @Nullable String string;
+
+  private final @Nullable String optionalString;
+
+  private final Integer int32;
+
+  private final @Nullable Integer optionalInt32;
+
+  private final Double duration;
+
+  private final @Nullable Double optionalDuration;
+
+  private final ConcreteTestType concreteTestType;
+
+  private final @Nullable ConcreteTestType optionalConcreteTestType;
+
+  public StructWithOptionalScalarFields(
+      @Nullable String string,
+      @Nullable String optionalString,
+      Integer int32,
+      @Nullable Integer optionalInt32,
+      Double duration,
+      @Nullable Double optionalDuration,
+      ConcreteTestType concreteTestType,
+      @Nullable ConcreteTestType optionalConcreteTestType) {
+    this.string = string;
+    this.optionalString = optionalString;
+    this.int32 = int32;
+    this.optionalInt32 = optionalInt32;
+    this.duration = duration;
+    this.optionalDuration = optionalDuration;
+    this.concreteTestType = concreteTestType;
+    this.optionalConcreteTestType = optionalConcreteTestType;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public @Nullable String getString() {
+    return string;
+  }
+
+  public @Nullable String getOptionalString() {
+    return optionalString;
+  }
+
+  public Integer getInt32() {
+    return int32;
+  }
+
+  public @Nullable Integer getOptionalInt32() {
+    return optionalInt32;
+  }
+
+  public Double getDuration() {
+    return duration;
+  }
+
+  public @Nullable Double getOptionalDuration() {
+    return optionalDuration;
+  }
+
+  public ConcreteTestType getConcreteTestType() {
+    return concreteTestType;
+  }
+
+  public @Nullable ConcreteTestType getOptionalConcreteTestType() {
+    return optionalConcreteTestType;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithOptionalScalarFields that = (StructWithOptionalScalarFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getString(), that.getString());
+    eqb.append(getOptionalString(), that.getOptionalString());
+    eqb.append(getInt32(), that.getInt32());
+    eqb.append(getOptionalInt32(), that.getOptionalInt32());
+    eqb.append(getDuration(), that.getDuration());
+    eqb.append(getOptionalDuration(), that.getOptionalDuration());
+    eqb.append(getConcreteTestType(), that.getConcreteTestType());
+    eqb.append(getOptionalConcreteTestType(), that.getOptionalConcreteTestType());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getString());
+    hcb.append(getOptionalString());
+    hcb.append(getInt32());
+    hcb.append(getOptionalInt32());
+    hcb.append(getDuration());
+    hcb.append(getOptionalDuration());
+    hcb.append(getConcreteTestType());
+    hcb.append(getOptionalConcreteTestType());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithOptionalScalarFields.class.getSimpleName() + "[", "]");
+    joiner.add("string='" + getString() + "'");
+    joiner.add("optionalString='" + getOptionalString() + "'");
+    joiner.add("int32=" + getInt32());
+    joiner.add("optionalInt32=" + getOptionalInt32());
+    joiner.add("duration=" + getDuration());
+    joiner.add("optionalDuration=" + getOptionalDuration());
+    joiner.add("concreteTestType=" + getConcreteTestType());
+    joiner.add("optionalConcreteTestType=" + getOptionalConcreteTestType());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5011")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.StructureWithOptionalFields,
+        new StructureField[] {
+          new StructureField(
+              "String",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalString",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 12),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "Int32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalInt32",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 6),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "Duration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalDuration",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 290),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true),
+          new StructureField(
+              "ConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "OptionalConcreteTestType",
+              LocalizedText.NULL_VALUE,
+              ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3006")
+                  .toNodeId(namespaceTable)
+                  .orElseThrow(),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              true)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithOptionalScalarFields> {
+    @Override
+    public Class<StructWithOptionalScalarFields> getType() {
+      return StructWithOptionalScalarFields.class;
+    }
+
+    @Override
+    public StructWithOptionalScalarFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final String string;
+      final String optionalString;
+      final Integer int32;
+      final Integer optionalInt32;
+      final Double duration;
+      final Double optionalDuration;
+      final ConcreteTestType concreteTestType;
+      final ConcreteTestType optionalConcreteTestType;
+      final long encodingMask = decoder.decodeUInt32("EncodingMask").longValue();
+      string = decoder.decodeString("String");
+      if ((encodingMask & (1L << 0)) != 0) {
+        optionalString = decoder.decodeString("OptionalString");
+      } else {
+        optionalString = null;
+      }
+      int32 = decoder.decodeInt32("Int32");
+      if ((encodingMask & (1L << 1)) != 0) {
+        optionalInt32 = decoder.decodeInt32("OptionalInt32");
+      } else {
+        optionalInt32 = null;
+      }
+      duration = decoder.decodeDouble("Duration");
+      if ((encodingMask & (1L << 2)) != 0) {
+        optionalDuration = decoder.decodeDouble("OptionalDuration");
+      } else {
+        optionalDuration = null;
+      }
+      concreteTestType =
+          (ConcreteTestType) decoder.decodeStruct("ConcreteTestType", ConcreteTestType.TYPE_ID);
+      if ((encodingMask & (1L << 3)) != 0) {
+        optionalConcreteTestType =
+            (ConcreteTestType)
+                decoder.decodeStruct("OptionalConcreteTestType", ConcreteTestType.TYPE_ID);
+      } else {
+        optionalConcreteTestType = null;
+      }
+      return new StructWithOptionalScalarFields(
+          string,
+          optionalString,
+          int32,
+          optionalInt32,
+          duration,
+          optionalDuration,
+          concreteTestType,
+          optionalConcreteTestType);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithOptionalScalarFields value) {
+      long encodingMask = 0L;
+      if (value.getOptionalString() != null) {
+        encodingMask |= (1L << 0);
+      }
+      if (value.getOptionalInt32() != null) {
+        encodingMask |= (1L << 1);
+      }
+      if (value.getOptionalDuration() != null) {
+        encodingMask |= (1L << 2);
+      }
+      if (value.getOptionalConcreteTestType() != null) {
+        encodingMask |= (1L << 3);
+      }
+      encoder.encodeUInt32("EncodingMask", Unsigned.uint(encodingMask));
+      encoder.encodeString("String", value.getString());
+      if (value.getOptionalString() != null) {
+        encoder.encodeString("OptionalString", value.getOptionalString());
+      }
+      encoder.encodeInt32("Int32", value.getInt32());
+      if (value.getOptionalInt32() != null) {
+        encoder.encodeInt32("OptionalInt32", value.getOptionalInt32());
+      }
+      encoder.encodeDouble("Duration", value.getDuration());
+      if (value.getOptionalDuration() != null) {
+        encoder.encodeDouble("OptionalDuration", value.getOptionalDuration());
+      }
+      encoder.encodeStruct(
+          "ConcreteTestType", value.getConcreteTestType(), ConcreteTestType.TYPE_ID);
+      if (value.getOptionalConcreteTestType() != null) {
+        encoder.encodeStruct(
+            "OptionalConcreteTestType",
+            value.getOptionalConcreteTestType(),
+            ConcreteTestType.TYPE_ID);
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureArrayFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureArrayFields.java
new file mode 100644
index 000000000..520fa4166
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureArrayFields.java
@@ -0,0 +1,185 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithStructureArrayFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3029");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5053");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5055");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5054");
+
+  private final ExtensionObject @Nullable [] struct1;
+
+  private final ExtensionObject @Nullable [] struct2;
+
+  private final ExtensionObject @Nullable [] struct3;
+
+  public StructWithStructureArrayFields(
+      ExtensionObject @Nullable [] struct1,
+      ExtensionObject @Nullable [] struct2,
+      ExtensionObject @Nullable [] struct3) {
+    this.struct1 = struct1;
+    this.struct2 = struct2;
+    this.struct3 = struct3;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public ExtensionObject @Nullable [] getStruct1() {
+    return struct1;
+  }
+
+  public ExtensionObject @Nullable [] getStruct2() {
+    return struct2;
+  }
+
+  public ExtensionObject @Nullable [] getStruct3() {
+    return struct3;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithStructureArrayFields that = (StructWithStructureArrayFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getStruct1(), that.getStruct1());
+    eqb.append(getStruct2(), that.getStruct2());
+    eqb.append(getStruct3(), that.getStruct3());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getStruct1());
+    hcb.append(getStruct2());
+    hcb.append(getStruct3());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithStructureArrayFields.class.getSimpleName() + "[", "]");
+    joiner.add("struct1=" + java.util.Arrays.toString(getStruct1()));
+    joiner.add("struct2=" + java.util.Arrays.toString(getStruct2()));
+    joiner.add("struct3=" + java.util.Arrays.toString(getStruct3()));
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5053")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Struct1",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Struct2",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Struct3",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithStructureArrayFields> {
+    @Override
+    public Class<StructWithStructureArrayFields> getType() {
+      return StructWithStructureArrayFields.class;
+    }
+
+    @Override
+    public StructWithStructureArrayFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final ExtensionObject[] struct1;
+      final ExtensionObject[] struct2;
+      final ExtensionObject[] struct3;
+      struct1 = decoder.decodeExtensionObjectArray("Struct1");
+      struct2 = decoder.decodeExtensionObjectArray("Struct2");
+      struct3 = decoder.decodeExtensionObjectArray("Struct3");
+      return new StructWithStructureArrayFields(struct1, struct2, struct3);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithStructureArrayFields value) {
+      encoder.encodeExtensionObjectArray("Struct1", value.getStruct1());
+      encoder.encodeExtensionObjectArray("Struct2", value.getStruct2());
+      encoder.encodeExtensionObjectArray("Struct3", value.getStruct3());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureMatrixFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureMatrixFields.java
new file mode 100644
index 000000000..427eb9e6f
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureMatrixFields.java
@@ -0,0 +1,184 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+import org.jspecify.annotations.Nullable;
+
+public class StructWithStructureMatrixFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3032");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5056");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5058");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5057");
+
+  private final @Nullable Matrix struct1;
+
+  private final @Nullable Matrix struct2;
+
+  private final @Nullable Matrix struct3;
+
+  public StructWithStructureMatrixFields(
+      @Nullable Matrix struct1, @Nullable Matrix struct2, @Nullable Matrix struct3) {
+    this.struct1 = struct1;
+    this.struct2 = struct2;
+    this.struct3 = struct3;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public @Nullable Matrix getStruct1() {
+    return struct1;
+  }
+
+  public @Nullable Matrix getStruct2() {
+    return struct2;
+  }
+
+  public @Nullable Matrix getStruct3() {
+    return struct3;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithStructureMatrixFields that = (StructWithStructureMatrixFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getStruct1(), that.getStruct1());
+    eqb.append(getStruct2(), that.getStruct2());
+    eqb.append(getStruct3(), that.getStruct3());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getStruct1());
+    hcb.append(getStruct2());
+    hcb.append(getStruct3());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithStructureMatrixFields.class.getSimpleName() + "[", "]");
+    joiner.add("struct1=" + getStruct1());
+    joiner.add("struct2=" + getStruct2());
+    joiner.add("struct3=" + getStruct3());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5056")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Struct1",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Struct2",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Struct3",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithStructureMatrixFields> {
+    @Override
+    public Class<StructWithStructureMatrixFields> getType() {
+      return StructWithStructureMatrixFields.class;
+    }
+
+    @Override
+    public StructWithStructureMatrixFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final Matrix struct1;
+      final Matrix struct2;
+      final Matrix struct3;
+      struct1 = decoder.decodeMatrix("Struct1", BuiltinDataType.ExtensionObject);
+      struct2 = decoder.decodeMatrix("Struct2", BuiltinDataType.ExtensionObject);
+      struct3 = decoder.decodeMatrix("Struct3", BuiltinDataType.ExtensionObject);
+      return new StructWithStructureMatrixFields(struct1, struct2, struct3);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithStructureMatrixFields value) {
+      encoder.encodeMatrix("Struct1", value.getStruct1());
+      encoder.encodeMatrix("Struct2", value.getStruct2());
+      encoder.encodeMatrix("Struct3", value.getStruct3());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureScalarFields.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureScalarFields.java
new file mode 100644
index 000000000..9b006c506
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/StructWithStructureScalarFields.java
@@ -0,0 +1,182 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import java.util.StringJoiner;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.UaStructuredType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExtensionObject;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.Structure;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.util.codegen.EqualsBuilder;
+import org.eclipse.milo.opcua.stack.core.util.codegen.HashCodeBuilder;
+
+public class StructWithStructureScalarFields extends Structure implements UaStructuredType {
+  public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3026");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5050");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5052");
+
+  public static final ExpandedNodeId XML_ENCODING_ID = ExpandedNodeId.parse("ns=1;i=5051");
+
+  private final ExtensionObject struct1;
+
+  private final ExtensionObject struct2;
+
+  private final ExtensionObject struct3;
+
+  public StructWithStructureScalarFields(
+      ExtensionObject struct1, ExtensionObject struct2, ExtensionObject struct3) {
+    this.struct1 = struct1;
+    this.struct2 = struct2;
+    this.struct3 = struct3;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TYPE_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public ExtensionObject getStruct1() {
+    return struct1;
+  }
+
+  public ExtensionObject getStruct2() {
+    return struct2;
+  }
+
+  public ExtensionObject getStruct3() {
+    return struct3;
+  }
+
+  @Override
+  public boolean equals(Object object) {
+    if (this == object) {
+      return true;
+    } else if (object == null || getClass() != object.getClass()) {
+      return false;
+    }
+    StructWithStructureScalarFields that = (StructWithStructureScalarFields) object;
+    var eqb = new EqualsBuilder();
+    eqb.append(getStruct1(), that.getStruct1());
+    eqb.append(getStruct2(), that.getStruct2());
+    eqb.append(getStruct3(), that.getStruct3());
+    return eqb.build();
+  }
+
+  @Override
+  public int hashCode() {
+    var hcb = new HashCodeBuilder();
+    hcb.append(getStruct1());
+    hcb.append(getStruct2());
+    hcb.append(getStruct3());
+    return hcb.build();
+  }
+
+  @Override
+  public String toString() {
+    var joiner =
+        new StringJoiner(", ", StructWithStructureScalarFields.class.getSimpleName() + "[", "]");
+    joiner.add("struct1=" + getStruct1());
+    joiner.add("struct2=" + getStruct2());
+    joiner.add("struct3=" + getStruct3());
+    return joiner.toString();
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5050")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=22")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Structure,
+        new StructureField[] {
+          new StructureField(
+              "Struct1",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Struct2",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Struct3",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 22),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<StructWithStructureScalarFields> {
+    @Override
+    public Class<StructWithStructureScalarFields> getType() {
+      return StructWithStructureScalarFields.class;
+    }
+
+    @Override
+    public StructWithStructureScalarFields decodeType(EncodingContext context, UaDecoder decoder) {
+      final ExtensionObject struct1;
+      final ExtensionObject struct2;
+      final ExtensionObject struct3;
+      struct1 = decoder.decodeExtensionObject("Struct1");
+      struct2 = decoder.decodeExtensionObject("Struct2");
+      struct3 = decoder.decodeExtensionObject("Struct3");
+      return new StructWithStructureScalarFields(struct1, struct2, struct3);
+    }
+
+    @Override
+    public void encodeType(
+        EncodingContext context, UaEncoder encoder, StructWithStructureScalarFields value) {
+      encoder.encodeExtensionObject("Struct1", value.getStruct1());
+      encoder.encodeExtensionObject("Struct2", value.getStruct2());
+      encoder.encodeExtensionObject("Struct3", value.getStruct3());
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/TestEnumType.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/TestEnumType.java
new file mode 100644
index 000000000..f9d927d41
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/TestEnumType.java
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import org.eclipse.milo.opcua.stack.core.types.UaEnumeratedType;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.structured.EnumDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.EnumField;
+import org.jspecify.annotations.Nullable;
+
+public enum TestEnumType implements UaEnumeratedType {
+  A(0),
+
+  B(1),
+
+  C(2);
+
+  private final int value;
+
+  TestEnumType(int value) {
+    this.value = value;
+  }
+
+  @Override
+  public int getValue() {
+    return value;
+  }
+
+  @Override
+  public ExpandedNodeId getTypeId() {
+    return TypeInfo.TYPE_ID;
+  }
+
+  public static @Nullable TestEnumType from(int value) {
+    switch (value) {
+      case 0:
+        return A;
+      case 1:
+        return B;
+      case 2:
+        return C;
+      default:
+        return null;
+    }
+  }
+
+  public static EnumDefinition definition() {
+    return new EnumDefinition(
+        new EnumField[] {
+          new EnumField(0L, LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE, "A"),
+          new EnumField(1L, LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE, "B"),
+          new EnumField(2L, LocalizedText.NULL_VALUE, LocalizedText.NULL_VALUE, "C")
+        });
+  }
+
+  public static final class TypeInfo {
+    public static final ExpandedNodeId TYPE_ID = ExpandedNodeId.parse("ns=1;i=3011");
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfArray.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfArray.java
new file mode 100644
index 000000000..8f1afc5a0
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfArray.java
@@ -0,0 +1,237 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.StatusCodes;
+import org.eclipse.milo.opcua.stack.core.UaSerializationException;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.types.structured.Union;
+
+public class UnionOfArray extends Union {
+  public static final ExpandedNodeId TYPE_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3023");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5032");
+
+  public static final ExpandedNodeId XML_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5033");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5034");
+
+  private final Type type;
+
+  private final Object value;
+
+  private UnionOfArray(Type type, Object value) {
+    this.type = type;
+    this.value = value;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Boolean[] asBoolean() {
+    return (Boolean[]) value;
+  }
+
+  public Byte[] asSByte() {
+    return (Byte[]) value;
+  }
+
+  public UByte[] asByte() {
+    return (UByte[]) value;
+  }
+
+  public Boolean[] getBoolean() {
+    return (Boolean[]) value;
+  }
+
+  public Byte[] getSByte() {
+    return (Byte[]) value;
+  }
+
+  public UByte[] getByte() {
+    return (UByte[]) value;
+  }
+
+  public boolean isBoolean() {
+    return type == Type.Boolean;
+  }
+
+  public boolean isSByte() {
+    return type == Type.SByte;
+  }
+
+  public boolean isByte() {
+    return type == Type.Byte;
+  }
+
+  @Override
+  public String toString() {
+    return switch (type) {
+      case NULL -> "UnionOfArray[null]";
+      case Boolean -> "UnionOfArray[Boolean=" + value + "]";
+      case SByte -> "UnionOfArray[SByte=" + value + "]";
+      case Byte -> "UnionOfArray[Byte=" + value + "]";
+    };
+  }
+
+  public static UnionOfArray ofNull() {
+    return new UnionOfArray(Type.NULL, null);
+  }
+
+  public static UnionOfArray ofBoolean(Boolean[] value) {
+    return new UnionOfArray(Type.Boolean, value);
+  }
+
+  public static UnionOfArray ofSByte(Byte[] value) {
+    return new UnionOfArray(Type.SByte, value);
+  }
+
+  public static UnionOfArray ofByte(UByte[] value) {
+    return new UnionOfArray(Type.Byte, value);
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5032")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=12756")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Union,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              1,
+              new UInteger[] {UInteger.valueOf(3)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  enum Type {
+    NULL,
+
+    Boolean,
+
+    SByte,
+
+    Byte
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<UnionOfArray> {
+    @Override
+    public Class<UnionOfArray> getType() {
+      return UnionOfArray.class;
+    }
+
+    @Override
+    public UnionOfArray decodeType(EncodingContext context, UaDecoder decoder) {
+      UInteger switchValue = decoder.decodeUInt32("SwitchField");
+      switch (switchValue.intValue()) {
+        case 0:
+          return UnionOfArray.ofNull();
+        case 1:
+          {
+            final Boolean[] _boolean;
+            _boolean = decoder.decodeBooleanArray("Boolean");
+            return UnionOfArray.ofBoolean(_boolean);
+          }
+        case 2:
+          {
+            final Byte[] sByte;
+            sByte = decoder.decodeSByteArray("SByte");
+            return UnionOfArray.ofSByte(sByte);
+          }
+        case 3:
+          {
+            final UByte[] _byte;
+            _byte = decoder.decodeByteArray("Byte");
+            return UnionOfArray.ofByte(_byte);
+          }
+        default:
+          throw new UaSerializationException(
+              StatusCodes.Bad_DecodingError, "unknown field in Union UnionOfArray: " + switchValue);
+      }
+    }
+
+    @Override
+    public void encodeType(EncodingContext context, UaEncoder encoder, UnionOfArray value) {
+      encoder.encodeUInt32("SwitchField", Unsigned.uint(value.type.ordinal()));
+      switch (value.type) {
+        case NULL:
+          break;
+        case Boolean:
+          {
+            encoder.encodeBooleanArray("Boolean", value.getBoolean());
+            break;
+          }
+        case SByte:
+          {
+            encoder.encodeSByteArray("SByte", value.getSByte());
+            break;
+          }
+        case Byte:
+          {
+            encoder.encodeByteArray("Byte", value.getByte());
+            break;
+          }
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfMatrix.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfMatrix.java
new file mode 100644
index 000000000..7ba81b058
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfMatrix.java
@@ -0,0 +1,239 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.StatusCodes;
+import org.eclipse.milo.opcua.stack.core.UaSerializationException;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.Matrix;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.types.structured.Union;
+
+public class UnionOfMatrix extends Union {
+  public static final ExpandedNodeId TYPE_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3038");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5062");
+
+  public static final ExpandedNodeId XML_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5063");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5064");
+
+  private final Type type;
+
+  private final Object value;
+
+  private UnionOfMatrix(Type type, Object value) {
+    this.type = type;
+    this.value = value;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Matrix asBoolean() {
+    return (Matrix) value;
+  }
+
+  public Matrix asSByte() {
+    return (Matrix) value;
+  }
+
+  public Matrix asByte() {
+    return (Matrix) value;
+  }
+
+  public Matrix getBoolean() {
+    return (Matrix) value;
+  }
+
+  public Matrix getSByte() {
+    return (Matrix) value;
+  }
+
+  public Matrix getByte() {
+    return (Matrix) value;
+  }
+
+  public boolean isBoolean() {
+    return type == Type.Boolean;
+  }
+
+  public boolean isSByte() {
+    return type == Type.SByte;
+  }
+
+  public boolean isByte() {
+    return type == Type.Byte;
+  }
+
+  @Override
+  public String toString() {
+    return switch (type) {
+      case NULL -> "UnionOfMatrix[null]";
+      case Boolean -> "UnionOfMatrix[Boolean=" + value + "]";
+      case SByte -> "UnionOfMatrix[SByte=" + value + "]";
+      case Byte -> "UnionOfMatrix[Byte=" + value + "]";
+    };
+  }
+
+  public static UnionOfMatrix ofNull() {
+    return new UnionOfMatrix(Type.NULL, null);
+  }
+
+  public static UnionOfMatrix ofBoolean(Matrix value) {
+    return new UnionOfMatrix(Type.Boolean, value);
+  }
+
+  public static UnionOfMatrix ofSByte(Matrix value) {
+    return new UnionOfMatrix(Type.SByte, value);
+  }
+
+  public static UnionOfMatrix ofByte(Matrix value) {
+    return new UnionOfMatrix(Type.Byte, value);
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5062")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=12756")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Union,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              2,
+              new UInteger[] {UInteger.valueOf(2), UInteger.valueOf(2)},
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  enum Type {
+    NULL,
+
+    Boolean,
+
+    SByte,
+
+    Byte
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<UnionOfMatrix> {
+    @Override
+    public Class<UnionOfMatrix> getType() {
+      return UnionOfMatrix.class;
+    }
+
+    @Override
+    public UnionOfMatrix decodeType(EncodingContext context, UaDecoder decoder) {
+      UInteger switchValue = decoder.decodeUInt32("SwitchField");
+      switch (switchValue.intValue()) {
+        case 0:
+          return UnionOfMatrix.ofNull();
+        case 1:
+          {
+            final Matrix _boolean;
+            _boolean = decoder.decodeMatrix("Boolean", BuiltinDataType.Boolean);
+            return UnionOfMatrix.ofBoolean(_boolean);
+          }
+        case 2:
+          {
+            final Matrix sByte;
+            sByte = decoder.decodeMatrix("SByte", BuiltinDataType.SByte);
+            return UnionOfMatrix.ofSByte(sByte);
+          }
+        case 3:
+          {
+            final Matrix _byte;
+            _byte = decoder.decodeMatrix("Byte", BuiltinDataType.Byte);
+            return UnionOfMatrix.ofByte(_byte);
+          }
+        default:
+          throw new UaSerializationException(
+              StatusCodes.Bad_DecodingError,
+              "unknown field in Union UnionOfMatrix: " + switchValue);
+      }
+    }
+
+    @Override
+    public void encodeType(EncodingContext context, UaEncoder encoder, UnionOfMatrix value) {
+      encoder.encodeUInt32("SwitchField", Unsigned.uint(value.type.ordinal()));
+      switch (value.type) {
+        case NULL:
+          break;
+        case Boolean:
+          {
+            encoder.encodeMatrix("Boolean", value.getBoolean());
+            break;
+          }
+        case SByte:
+          {
+            encoder.encodeMatrix("SByte", value.getSByte());
+            break;
+          }
+        case Byte:
+          {
+            encoder.encodeMatrix("Byte", value.getByte());
+            break;
+          }
+      }
+    }
+  }
+}
diff --git a/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfScalar.java b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfScalar.java
new file mode 100644
index 000000000..f31370e1f
--- /dev/null
+++ b/opc-ua-sdk/sdk-core/src/test/java/org/eclipse/milo/opcua/test/types/UnionOfScalar.java
@@ -0,0 +1,238 @@
+/*
+ * Copyright (c) 2025 the Eclipse Milo Authors
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+package org.eclipse.milo.opcua.test.types;
+
+import org.eclipse.milo.opcua.stack.core.NamespaceTable;
+import org.eclipse.milo.opcua.stack.core.StatusCodes;
+import org.eclipse.milo.opcua.stack.core.UaSerializationException;
+import org.eclipse.milo.opcua.stack.core.encoding.EncodingContext;
+import org.eclipse.milo.opcua.stack.core.encoding.GenericDataTypeCodec;
+import org.eclipse.milo.opcua.stack.core.encoding.UaDecoder;
+import org.eclipse.milo.opcua.stack.core.encoding.UaEncoder;
+import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.LocalizedText;
+import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UByte;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.UInteger;
+import org.eclipse.milo.opcua.stack.core.types.builtin.unsigned.Unsigned;
+import org.eclipse.milo.opcua.stack.core.types.enumerated.StructureType;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureDefinition;
+import org.eclipse.milo.opcua.stack.core.types.structured.StructureField;
+import org.eclipse.milo.opcua.stack.core.types.structured.Union;
+
+public class UnionOfScalar extends Union {
+  public static final ExpandedNodeId TYPE_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=3020");
+
+  public static final ExpandedNodeId BINARY_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5029");
+
+  public static final ExpandedNodeId XML_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5030");
+
+  public static final ExpandedNodeId JSON_ENCODING_ID =
+      ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5031");
+
+  private final Type type;
+
+  private final Object value;
+
+  private UnionOfScalar(Type type, Object value) {
+    this.type = type;
+    this.value = value;
+  }
+
+  @Override
+  public ExpandedNodeId getBinaryEncodingId() {
+    return BINARY_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getJsonEncodingId() {
+    return JSON_ENCODING_ID;
+  }
+
+  @Override
+  public ExpandedNodeId getXmlEncodingId() {
+    return XML_ENCODING_ID;
+  }
+
+  public Boolean asBoolean() {
+    return (Boolean) value;
+  }
+
+  public Byte asSByte() {
+    return (Byte) value;
+  }
+
+  public UByte asByte() {
+    return (UByte) value;
+  }
+
+  public Boolean getBoolean() {
+    return (Boolean) value;
+  }
+
+  public Byte getSByte() {
+    return (Byte) value;
+  }
+
+  public UByte getByte() {
+    return (UByte) value;
+  }
+
+  public boolean isBoolean() {
+    return type == Type.Boolean;
+  }
+
+  public boolean isSByte() {
+    return type == Type.SByte;
+  }
+
+  public boolean isByte() {
+    return type == Type.Byte;
+  }
+
+  @Override
+  public String toString() {
+    return switch (type) {
+      case NULL -> "UnionOfScalar[null]";
+      case Boolean -> "UnionOfScalar[Boolean=" + value + "]";
+      case SByte -> "UnionOfScalar[SByte=" + value + "]";
+      case Byte -> "UnionOfScalar[Byte=" + value + "]";
+    };
+  }
+
+  public static UnionOfScalar ofNull() {
+    return new UnionOfScalar(Type.NULL, null);
+  }
+
+  public static UnionOfScalar ofBoolean(Boolean value) {
+    return new UnionOfScalar(Type.Boolean, value);
+  }
+
+  public static UnionOfScalar ofSByte(Byte value) {
+    return new UnionOfScalar(Type.SByte, value);
+  }
+
+  public static UnionOfScalar ofByte(UByte value) {
+    return new UnionOfScalar(Type.Byte, value);
+  }
+
+  public static StructureDefinition definition(NamespaceTable namespaceTable) {
+    return new StructureDefinition(
+        ExpandedNodeId.parse("nsu=https://github.com/eclipse/milo/DataTypeTest;i=5029")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        ExpandedNodeId.parse("nsu=http://opcfoundation.org/UA/;i=12756")
+            .toNodeId(namespaceTable)
+            .orElseThrow(),
+        StructureType.Union,
+        new StructureField[] {
+          new StructureField(
+              "Boolean",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 1),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "SByte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 2),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false),
+          new StructureField(
+              "Byte",
+              LocalizedText.NULL_VALUE,
+              new NodeId(0, 3),
+              -1,
+              null,
+              UInteger.valueOf(0),
+              false)
+        });
+  }
+
+  enum Type {
+    NULL,
+
+    Boolean,
+
+    SByte,
+
+    Byte
+  }
+
+  public static final class Codec extends GenericDataTypeCodec<UnionOfScalar> {
+    @Override
+    public Class<UnionOfScalar> getType() {
+      return UnionOfScalar.class;
+    }
+
+    @Override
+    public UnionOfScalar decodeType(EncodingContext context, UaDecoder decoder) {
+      UInteger switchValue = decoder.decodeUInt32("SwitchField");
+      switch (switchValue.intValue()) {
+        case 0:
+          return UnionOfScalar.ofNull();
+        case 1:
+          {
+            final Boolean _boolean;
+            _boolean = decoder.decodeBoolean("Boolean");
+            return UnionOfScalar.ofBoolean(_boolean);
+          }
+        case 2:
+          {
+            final Byte sByte;
+            sByte = decoder.decodeSByte("SByte");
+            return UnionOfScalar.ofSByte(sByte);
+          }
+        case 3:
+          {
+            final UByte _byte;
+            _byte = decoder.decodeByte("Byte");
+            return UnionOfScalar.ofByte(_byte);
+          }
+        default:
+          throw new UaSerializationException(
+              StatusCodes.Bad_DecodingError,
+              "unknown field in Union UnionOfScalar: " + switchValue);
+      }
+    }
+
+    @Override
+    public void encodeType(EncodingContext context, UaEncoder encoder, UnionOfScalar value) {
+      encoder.encodeUInt32("SwitchField", Unsigned.uint(value.type.ordinal()));
+      switch (value.type) {
+        case NULL:
+          break;
+        case Boolean:
+          {
+            encoder.encodeBoolean("Boolean", value.getBoolean());
+            break;
+          }
+        case SByte:
+          {
+            encoder.encodeSByte("SByte", value.getSByte());
+            break;
+          }
+        case Byte:
+          {
+            encoder.encodeByte("Byte", value.getByte());
+            break;
+          }
+      }
+    }
+  }
+}
diff --git a/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/types/builtin/Matrix.java b/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/types/builtin/Matrix.java
index 1afaf9462..5f5d5b2db 100644
--- a/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/types/builtin/Matrix.java
+++ b/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/types/builtin/Matrix.java
@@ -209,6 +209,7 @@ public String toString() {
     StringJoiner joiner =
         new StringJoiner(", ", Matrix.class.getSimpleName() + "{", "}")
             .add("builtinDataType=" + builtinDataType)
+            .add("dataType=" + dataTypeId.toParseableString())
             .add("dimensions=" + Arrays.toString(dimensions));
 
     Class<?> clazz = ArrayUtil.getType(flatArray);
diff --git a/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/types/builtin/MatrixTest.java b/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/types/builtin/MatrixTest.java
index 01c6c0ffb..6103facb6 100644
--- a/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/types/builtin/MatrixTest.java
+++ b/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/types/builtin/MatrixTest.java
@@ -74,10 +74,12 @@ void matrixEquals() {
   @Test
   void matrixToString() {
     assertEquals(
-        "Matrix{builtinDataType=Int32, dimensions=[2, 2], flatArray=[1, 2, 3, 4]}",
+        "Matrix{builtinDataType=Int32, "
+            + "dataType=ns=0;i=6, dimensions=[2, 2], flatArray=[1, 2, 3, 4]}",
         primitiveMatrix2d.toString());
     assertEquals(
-        "Matrix{builtinDataType=Int32, dimensions=[2, 2], flatArray=[1, 2, 3, 4]}",
+        "Matrix{builtinDataType=Int32, "
+            + "dataType=ns=0;i=6, dimensions=[2, 2], flatArray=[1, 2, 3, 4]}",
         boxedMatrix2d.toString());
   }