diff --git a/Libraries/Esiur/Data/Codec.cs b/Libraries/Esiur/Data/Codec.cs
index 0b3bc77..b030e09 100644
--- a/Libraries/Esiur/Data/Codec.cs
+++ b/Libraries/Esiur/Data/Codec.cs
@@ -102,6 +102,8 @@ public static class Codec
     static AsyncParser[] TypedAsyncParsers = new AsyncParser[]
     {
         DataDeserializer.TypedParserAsync,
+        DataDeserializer.TypeDefInfoParserAsync,
+        DataDeserializer.TruParserAsync,
     };
 
     static AsyncParser[] ExtendedAsyncParsers = new AsyncParser[]
@@ -168,6 +170,8 @@ public static class Codec
     static SyncParser[] TypedParsers = new SyncParser[]
     {
         DataDeserializer.TypedParser,
+        DataDeserializer.TypeDefInfoParser,
+        DataDeserializer.TruParser,
         //DataDeserializer.RecordParser,
         //DataDeserializer.TypedListParser,
         //DataDeserializer.TypedMapParser,
@@ -541,7 +545,15 @@ public static class Codec
         type = valueOrSource.GetType();
 
 
-        if (Composers.ContainsKey(type))
+        if (valueOrSource is Tru)
+        {
+            return DataSerializer.TruComposer(valueOrSource, warehouse, connection);
+        }
+        else if (valueOrSource is Types.TypeDefInfo)
+        {
+            return DataSerializer.TypeDefComposer(valueOrSource, warehouse, connection);
+        }
+        else if (Composers.ContainsKey(type))
         {
             return Composers[type](valueOrSource, warehouse, connection);
         }
@@ -555,6 +567,10 @@ public static class Codec
             {
                 return DataSerializer.RecordComposer(valueOrSource, warehouse, connection);
             }
+            else if (valueOrSource is IndexedStructure)
+            {
+                return DataSerializer.StructureComposer(valueOrSource, warehouse, connection);
+            }
             else if (type.IsGenericType)
             {
                 var genericType = type.GetGenericTypeDefinition();
@@ -636,6 +652,43 @@ public static class Codec
         return tdu.Composed;
     }
 
+    /// <summary>
+    /// Encodes a local indexed structure. This is equivalent to <see cref="Compose"/>, but
+    /// makes the expected structure type explicit at call sites such as TypeDef and authentication.
+    /// </summary>
+    public static byte[] ComposeIndexedType<T>(T value, Warehouse warehouse, EpConnection connection)
+        where T : IndexedStructure
+        => Compose(value, warehouse, connection);
+
+    /// <summary>
+    /// Parses one indexed structure and returns both the consumed byte count and typed value.
+    /// Unknown indexes are ignored and missing indexes retain their CLR defaults.
+    /// </summary>
+    public static (uint Size, T Value) ParseIndexedType<T>(byte[] data, uint offset, Warehouse warehouse)
+        where T : IndexedStructure
+    {
+        var (size, value) = ParseSync(data, offset, warehouse);
+        return (size, value is T typed ? typed : IndexedStructureCodec.FromMap<T>(value));
+    }
+
+    /// <summary>
+    /// Parses an already framed TDU as an indexed structure.
+    /// </summary>
+    public static T ParseIndexedType<T>(PlainTdu tdu, Warehouse warehouse)
+        where T : IndexedStructure
+    {
+        var value = ParseSync(tdu, warehouse);
+        return value is T typed ? typed : IndexedStructureCodec.FromMap<T>(value);
+    }
+
+    /// <summary>
+    /// Converts an indexed map already decoded by the codec to a typed structure without
+    /// reparsing any wire data.
+    /// </summary>
+    public static T ParseIndexedType<T>(object indexedMap)
+        where T : IndexedStructure
+        => indexedMap is T typed ? typed : IndexedStructureCodec.FromMap<T>(indexedMap);
+
     public static bool IsAnonymous(Type type)
     {
         // Detect anonymous types
diff --git a/Libraries/Esiur/Data/DataDeserializer.cs b/Libraries/Esiur/Data/DataDeserializer.cs
index 9e93c2d..01ecb73 100644
--- a/Libraries/Esiur/Data/DataDeserializer.cs
+++ b/Libraries/Esiur/Data/DataDeserializer.cs
@@ -11,14 +11,57 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
+using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices.ComTypes;
 using System.Text;
+using System.Threading;
 
 namespace Esiur.Data;
 
 public static class DataDeserializer
 {
+    internal static readonly AsyncLocal<ulong[]> TypeDefRequestSequence = new();
+
+    public static async AsyncReply<object> TypeDefInfoParserAsync(
+        ParsedTdu tdu, EpConnection connection, uint[] requestSequence)
+    {
+        var parsed = await Codec.ParseAsync(tdu.Data, tdu.PayloadOffset, connection, requestSequence);
+        if (parsed.Size != tdu.PayloadLength)
+            throw new InvalidDataException("The TypeDef payload contains trailing or incomplete data.");
+
+        return IndexedStructureCodec.FromMap<Types.TypeDefInfo>(parsed.Value);
+    }
+
+    public static object TypeDefInfoParser(ParsedTdu tdu, Warehouse warehouse)
+    {
+        var (size, value) = Codec.ParseSync(tdu.Data, tdu.PayloadOffset, warehouse);
+        if (size != tdu.PayloadLength)
+            throw new InvalidDataException("The TypeDef payload contains trailing or incomplete data.");
+
+        return IndexedStructureCodec.FromMap<Types.TypeDefInfo>(value);
+    }
+
+    public static async AsyncReply<object> TruParserAsync(
+        ParsedTdu tdu, EpConnection connection, uint[] requestSequence)
+    {
+        var parsed = await Tru.ParseAsync(tdu.Data, tdu.PayloadOffset, connection,
+                                          TypeDefRequestSequence.Value);
+        if (parsed.Size != tdu.PayloadLength)
+            throw new InvalidDataException("The TRU payload contains trailing or incomplete data.");
+
+        return parsed.Value;
+    }
+
+    public static object TruParser(ParsedTdu tdu, Warehouse warehouse)
+    {
+        var parsed = Tru.Parse(tdu.Data, tdu.PayloadOffset, warehouse);
+        if (parsed.Size != tdu.PayloadLength)
+            throw new InvalidDataException("The TRU payload contains trailing or incomplete data.");
+
+        return parsed.Value;
+    }
+
     public static object NullParserAsync(ParsedTdu tdu, EpConnection connection, uint[] requestSequence)
     {
         return null;
@@ -445,6 +488,7 @@ public static class DataDeserializer
             {
                 current.Class = previous.Value.Class;
                 current.Identifier = previous.Value.Identifier;
+                current.Index = previous.Value.Index;
                 current.Metadata = previous.Value.Metadata;
             }
             else if (current.Identifier == TduIdentifier.TypeOfTarget)
@@ -596,6 +640,7 @@ public static class DataDeserializer
             {
                 current.Class = previous.Value.Class;
                 current.Identifier = previous.Value.Identifier;
+                current.Index = previous.Value.Index;
                 current.Metadata = previous.Value.Metadata;
             }
             else if (current.Identifier == TduIdentifier.TypeOfTarget)
@@ -908,6 +953,7 @@ public static class DataDeserializer
             {
                 current.Class = previous.Value.Class;
                 current.Identifier = previous.Value.Identifier;
+                current.Index = previous.Value.Index;
                 current.Metadata = previous.Value.Metadata;
             }
 
@@ -959,6 +1005,7 @@ public static class DataDeserializer
             {
                 current.Class = previous.Value.Class;
                 current.Identifier = previous.Value.Identifier;
+                current.Index = previous.Value.Index;
                 current.Metadata = previous.Value.Metadata;
             }
 
@@ -1163,6 +1210,7 @@ public static class DataDeserializer
                     {
                         current.Class = previous.Value.Class;
                         current.Identifier = previous.Value.Identifier;
+                        current.Index = previous.Value.Index;
                         current.Metadata = previous.Value.Metadata;
                     }
                     else if (current.Identifier == TduIdentifier.TypeOfTarget)
@@ -1271,6 +1319,7 @@ public static class DataDeserializer
                                 {
                                     current.Class = previous.Value.Class;
                                     current.Identifier = previous.Value.Identifier;
+                                    current.Index = previous.Value.Index;
                                     current.Metadata = previous.Value.Metadata;
                                 }
                             }
@@ -1624,6 +1673,7 @@ public static class DataDeserializer
                     {
                         current.Class = previous.Value.Class;
                         current.Identifier = previous.Value.Identifier;
+                        current.Index = previous.Value.Index;
                         current.Metadata = previous.Value.Metadata;
                     }
                     else if (current.Identifier == TduIdentifier.TypeOfTarget)
diff --git a/Libraries/Esiur/Data/DataSerializer.cs b/Libraries/Esiur/Data/DataSerializer.cs
index 8a160c1..7fbecb1 100644
--- a/Libraries/Esiur/Data/DataSerializer.cs
+++ b/Libraries/Esiur/Data/DataSerializer.cs
@@ -567,9 +567,13 @@ public static class DataSerializer
             {
                 var tdu = Codec.ComposeInternal(i, warehouse, connection);
 
-                var currentTru = Tru.FromType(i?.GetType(), warehouse);
+                // Structures are deliberately schema-less and therefore have no TRU of their
+                // own; their composed value is a typed byte/dynamic map.
+                var currentTru = IndexedStructureCodec.ContainsStructure(i?.GetType())
+                    ? null
+                    : Tru.FromType(i?.GetType(), warehouse);
 
-                if (tdu.Class == TduClass.Typed && tru.Match(currentTru))
+                if (tdu.Class == TduClass.Typed && currentTru != null && tru.Match(currentTru))
                 {
                     var d = tdu.Composed.Clip(tdu.ContentOffset,
                         (uint)tdu.Composed.Length - tdu.ContentOffset);
@@ -605,6 +609,12 @@ public static class DataSerializer
     {
         var elementTru = Tru.FromType(type, warehouse);
 
+        // Local structures and other schema-less CLR types intentionally have no TRU.
+        // Preserve them as a dynamic list; the indexed binder reconstructs the requested
+        // collection type after parsing.
+        if (elementTru == null)
+            return ListComposer(value, warehouse, connection);
+
         byte[] composed = TypedArrayComposer(value, elementTru, warehouse, connection);
 
         if (composed == null)
@@ -859,6 +869,38 @@ public static class DataSerializer
         return new Tdu(TduIdentifier.Map, rt.ToArray(), (uint)rt.Count, null, null);
     }
 
+    /// <summary>
+    /// Composes an indexed CLR structure using the compatible Map&lt;byte, object&gt; wire shape.
+    /// </summary>
+    public static Tdu StructureComposer(object value, Warehouse warehouse, EpConnection connection)
+    {
+        if (value == null)
+            return new Tdu(TduIdentifier.Null, Array.Empty<byte>(), 0, null, null);
+
+        var map = IndexedStructureCodec.ToMap((IndexedStructure)value);
+        return TypedMapComposer(map, typeof(byte), typeof(object), warehouse, connection);
+    }
+
+    /// <summary>
+    /// Carries a TRU as a self-framed value, allowing it to appear in dynamic structure fields.
+    /// </summary>
+    public static Tdu TruComposer(object value, Warehouse warehouse, EpConnection connection)
+    {
+        var data = ((Tru)value).Compose(connection);
+        return new Tdu(TduIdentifier.TRU, data, (ulong)data.Length, null, connection);
+    }
+
+    /// <summary>
+    /// Carries a TypeDefInfo in the dedicated TypeDef slot. Its payload remains an indexed
+    /// structure so new fields can be added without changing this outer framing.
+    /// </summary>
+    public static Tdu TypeDefComposer(object value, Warehouse warehouse, EpConnection connection)
+    {
+        var structure = StructureComposer(value, warehouse, connection);
+        return new Tdu(TduIdentifier.TypeDef, structure.Composed,
+                       (ulong)structure.Composed.Length, null, connection);
+    }
+
     public static unsafe Tdu UUIDComposer(object value, Warehouse warehouse, EpConnection connection)
     {
         return new Tdu(TduIdentifier.UUID, ((Uuid)value).Data, 16, null, null);
diff --git a/Libraries/Esiur/Data/IndexAttribute.cs b/Libraries/Esiur/Data/IndexAttribute.cs
new file mode 100644
index 0000000..c72666d
--- /dev/null
+++ b/Libraries/Esiur/Data/IndexAttribute.cs
@@ -0,0 +1,29 @@
+using System;
+
+namespace Esiur.Data;
+
+/// <summary>
+/// Assigns a stable wire index to a field or property of a <see cref="IndexedStructure"/>.
+/// </summary>
+[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field,
+                AllowMultiple = false, Inherited = true)]
+public sealed class IndexAttribute : Attribute
+{
+    /// <summary>
+    /// Gets or sets the byte-sized index used on the wire.
+    /// </summary>
+    public byte Index { get; set; }
+
+    public IndexAttribute()
+    {
+    }
+
+    public IndexAttribute(int index)
+    {
+        if (index < byte.MinValue || index > byte.MaxValue)
+            throw new ArgumentOutOfRangeException(nameof(index),
+                "A structure index must be between 0 and 255.");
+
+        Index = (byte)index;
+    }
+}
diff --git a/Libraries/Esiur/Data/IndexedStructure.cs b/Libraries/Esiur/Data/IndexedStructure.cs
new file mode 100644
index 0000000..1d3ee2a
--- /dev/null
+++ b/Libraries/Esiur/Data/IndexedStructure.cs
@@ -0,0 +1,21 @@
+#nullable enable
+using System;
+using System.Collections;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+
+namespace Esiur.Data;
+
+/// <summary>
+/// Base class for local, schema-less types whose members are identified by byte indexes.
+/// Structures use the same wire representation as <c>Map&lt;byte, object&gt;</c>, but can be
+/// composed and parsed directly as CLR types through <see cref="Codec"/>.
+/// </summary>
+public abstract class IndexedStructure
+{
+
+}
+
diff --git a/Libraries/Esiur/Data/IndexedStructureCodec.cs b/Libraries/Esiur/Data/IndexedStructureCodec.cs
new file mode 100644
index 0000000..a7871c6
--- /dev/null
+++ b/Libraries/Esiur/Data/IndexedStructureCodec.cs
@@ -0,0 +1,276 @@
+using System;
+using System.Collections;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Text;
+
+namespace Esiur.Data
+{
+    internal static class IndexedStructureCodec
+    {
+        private sealed class IndexedMember
+        {
+            public byte Index { get; }
+            public string Name { get; }
+            public Type Type { get; }
+            public Func<object, object?> Get { get; }
+            public Action<object, object?> Set { get; }
+
+            public IndexedMember(byte index, PropertyInfo property)
+            {
+                Index = index;
+                Name = property.Name;
+                Type = property.PropertyType;
+                Get = property.GetValue;
+                Set = property.SetValue;
+            }
+
+            public IndexedMember(byte index, FieldInfo field)
+            {
+                Index = index;
+                Name = field.Name;
+                Type = field.FieldType;
+                Get = field.GetValue;
+                Set = field.SetValue;
+            }
+        }
+
+        private static readonly ConcurrentDictionary<Type, IndexedMember[]> Members = new();
+
+        internal static Map<byte, object?> ToMap(IndexedStructure value)
+        {
+            if (value is null)
+                throw new ArgumentNullException(nameof(value));
+
+            var map = new Map<byte, object?>();
+            foreach (var member in GetMembers(value.GetType()))
+            {
+                var memberValue = member.Get(value);
+                if (memberValue is not null)
+                    map[member.Index] = PrepareForComposition(memberValue);
+            }
+
+            return map;
+        }
+
+        internal static T FromMap<T>(object value) where T : IndexedStructure
+            => (T)FromMap(value, typeof(T));
+
+        internal static object FromMap(object value, Type targetType)
+        {
+            if (!typeof(IndexedStructure).IsAssignableFrom(targetType))
+                throw new ArgumentException($"{targetType.FullName} does not inherit {nameof(IndexedStructure)}.",
+                                            nameof(targetType));
+
+            if (value is not IDictionary map)
+                throw new InvalidDataException(
+                    $"Cannot parse {targetType.FullName}: expected an indexed map but received {value?.GetType().FullName ?? "null"}.");
+
+            object instance;
+            try
+            {
+                instance = Activator.CreateInstance(targetType, true)!;
+            }
+            catch (Exception ex)
+            {
+                throw new InvalidOperationException(
+                    $"Structure type {targetType.FullName} must have a parameterless constructor.", ex);
+            }
+
+            var members = GetMembers(targetType).ToDictionary(x => x.Index);
+            foreach (DictionaryEntry entry in map)
+            {
+                byte index;
+                try
+                {
+                    index = Convert.ToByte(entry.Key);
+                }
+                catch (Exception ex)
+                {
+                    throw new InvalidDataException("A structure field index is not a byte value.", ex);
+                }
+
+                // Sparse structures are version tolerant: fields unknown to this CLR type are ignored.
+                if (!members.TryGetValue(index, out var member))
+                    continue;
+
+                try
+                {
+                    member.Set(instance, ConvertValue(entry.Value, member.Type));
+                }
+                catch (Exception ex) when (ex is not InvalidDataException)
+                {
+                    throw new InvalidDataException(
+                        $"Could not assign structure field {targetType.Name}.{member.Name} (index {index}).", ex);
+                }
+            }
+
+            return instance;
+        }
+
+        private static IndexedMember[] GetMembers(Type type)
+            => Members.GetOrAdd(type, DiscoverMembers);
+
+        private static IndexedMember[] DiscoverMembers(Type type)
+        {
+            if (!typeof(IndexedStructure).IsAssignableFrom(type))
+                throw new InvalidOperationException($"{type.FullName} does not inherit {nameof(IndexedStructure)}.");
+
+            var members = new List<IndexedMember>();
+            const BindingFlags flags = BindingFlags.Instance | BindingFlags.Public;
+
+            foreach (var property in type.GetProperties(flags))
+            {
+                var attribute = property.GetCustomAttribute<IndexAttribute>(true);
+                if (attribute is null)
+                    continue;
+
+                if (!property.CanRead || !property.CanWrite || property.GetIndexParameters().Length != 0)
+                    throw new InvalidOperationException(
+                        $"Indexed property {type.FullName}.{property.Name} must be a readable, writable, non-indexer property.");
+
+                members.Add(new IndexedMember(attribute.Index, property));
+            }
+
+            foreach (var field in type.GetFields(flags))
+            {
+                var attribute = field.GetCustomAttribute<IndexAttribute>(true);
+                if (attribute is null)
+                    continue;
+
+                if (field.IsInitOnly || field.IsLiteral)
+                    throw new InvalidOperationException(
+                        $"Indexed field {type.FullName}.{field.Name} must be writable.");
+
+                members.Add(new IndexedMember(attribute.Index, field));
+            }
+
+            var duplicate = members.GroupBy(x => x.Index).FirstOrDefault(x => x.Count() > 1);
+            if (duplicate is not null)
+                throw new InvalidOperationException(
+                    $"Structure type {type.FullName} uses index {duplicate.Key} more than once.");
+
+            return members.OrderBy(x => x.Index).ToArray();
+        }
+
+        private static object? PrepareForComposition(object? value)
+        {
+            if (value is IndexedStructure structure)
+                return ToMap(structure);
+
+            // Protocol-owned enums are values, not distributed enum TypeDefs. Carry their
+            // underlying integer so an indexed structure has no warehouse-registration dependency.
+            if (value is Enum enumValue)
+                return Convert.ChangeType(enumValue, Enum.GetUnderlyingType(enumValue.GetType()));
+
+            // A collection containing structures cannot advertise the local CLR structure type
+            // through TRU. Encode it as a dynamic list and recursively turn its items into maps.
+            if (value is IEnumerable sequence && value is not string && value is not byte[] && value is not IDictionary)
+            {
+                var items = sequence.Cast<object?>().ToArray();
+                if (items.Any(x => x is IndexedStructure || ContainsStructure(x?.GetType())))
+                    return items.Select(PrepareForComposition).ToArray();
+            }
+
+            return value;
+        }
+
+        internal static bool ContainsStructure(Type? type)
+        {
+            if (type is null)
+                return false;
+            if (typeof(IndexedStructure).IsAssignableFrom(type))
+                return true;
+            if (type.IsArray)
+                return ContainsStructure(type.GetElementType());
+            if (type.IsGenericType)
+                return type.GetGenericArguments().Any(ContainsStructure);
+            return false;
+        }
+
+        private static object? ConvertValue(object? value, Type targetType)
+        {
+            if (value is null)
+            {
+                if (targetType.IsValueType && Nullable.GetUnderlyingType(targetType) is null)
+                    return Activator.CreateInstance(targetType);
+                return null;
+            }
+
+            if (targetType.IsInstanceOfType(value))
+                return value;
+
+            var underlyingType = Nullable.GetUnderlyingType(targetType) ?? targetType;
+
+            if (typeof(IndexedStructure).IsAssignableFrom(underlyingType))
+                return FromMap(value, underlyingType);
+
+            if (targetType.IsArray && value is IEnumerable arraySource)
+            {
+                var elementType = targetType.GetElementType()!;
+                var values = arraySource.Cast<object?>().Select(x => ConvertValue(x, elementType)).ToArray();
+                var array = Array.CreateInstance(elementType, values.Length);
+                for (var i = 0; i < values.Length; i++)
+                    array.SetValue(values[i], i);
+                return array;
+            }
+
+            if (TryGetListElementType(targetType, out var listElementType) && value is IEnumerable listSource)
+            {
+                var concreteType = targetType.IsInterface || targetType.IsAbstract
+                    ? typeof(List<>).MakeGenericType(listElementType)
+                    : targetType;
+                var list = (IList)Activator.CreateInstance(concreteType)!;
+                foreach (var item in listSource)
+                    list.Add(ConvertValue(item, listElementType));
+                return list;
+            }
+
+            if (TryGetMapTypes(targetType, out var keyType, out var valueType) && value is IDictionary sourceMap)
+            {
+                var concreteType = targetType.IsInterface || targetType.IsAbstract
+                    ? typeof(Dictionary<,>).MakeGenericType(keyType, valueType)
+                    : targetType;
+                var targetMap = (IDictionary)Activator.CreateInstance(concreteType)!;
+                foreach (DictionaryEntry item in sourceMap)
+                    targetMap.Add(ConvertValue(item.Key, keyType), ConvertValue(item.Value, valueType));
+                return targetMap;
+            }
+
+            return RuntimeCaster.Cast(value, targetType);
+        }
+
+        private static bool TryGetListElementType(Type type, out Type elementType)
+        {
+            var candidate = type.IsGenericType &&
+                            (type.GetGenericTypeDefinition() == typeof(List<>) ||
+                             type.GetGenericTypeDefinition() == typeof(IList<>) ||
+                             type.GetGenericTypeDefinition() == typeof(ICollection<>) ||
+                             type.GetGenericTypeDefinition() == typeof(IEnumerable<>))
+                ? type
+                : type.GetInterfaces().FirstOrDefault(x => x.IsGenericType &&
+                    x.GetGenericTypeDefinition() == typeof(IList<>));
+
+            elementType = candidate?.GetGenericArguments()[0] ?? typeof(object);
+            return candidate is not null;
+        }
+
+        private static bool TryGetMapTypes(Type type, out Type keyType, out Type valueType)
+        {
+            var candidate = type.IsGenericType &&
+                            (type.GetGenericTypeDefinition() == typeof(Map<,>) ||
+                             type.GetGenericTypeDefinition() == typeof(Dictionary<,>) ||
+                             type.GetGenericTypeDefinition() == typeof(IDictionary<,>))
+                ? type
+                : type.GetInterfaces().FirstOrDefault(x => x.IsGenericType &&
+                    x.GetGenericTypeDefinition() == typeof(IDictionary<,>));
+
+            var arguments = candidate?.GetGenericArguments();
+            keyType = arguments?[0] ?? typeof(object);
+            valueType = arguments?[1] ?? typeof(object);
+            return candidate is not null;
+        }
+    }
+
+}
diff --git a/Libraries/Esiur/Data/ParsedTdu.cs b/Libraries/Esiur/Data/ParsedTdu.cs
index 101bbba..26986bb 100644
--- a/Libraries/Esiur/Data/ParsedTdu.cs
+++ b/Libraries/Esiur/Data/ParsedTdu.cs
@@ -75,7 +75,7 @@ namespace Esiur.Data
                     Ends = ends
                 };
             }
-            else if (cls == TduClass.Typed)
+            else if ((h & 0xC7) == 0x80) //  cls == TduClass = Typed & Identifier = Typed
             {
                 ulong cll = (ulong)(h >> 3) & 0x7;
 
@@ -206,7 +206,7 @@ namespace Esiur.Data
                     Ends = ends
                 };
             }
-            else if (cls == TduClass.Typed)
+            else if ((h & 0xC7) == 0x80) // else if (cls == TduClass.Typed)
             {
                 ulong cll = (ulong)(h >> 3) & 0x7;
 
@@ -395,7 +395,7 @@ namespace Esiur.Data
                     Ends = ends
                 };
             }
-            else if (cls == TduClass.Typed)
+            else if ((h & 0xC7) == 0x80) // (cls == TduClass.Typed)
             {
                 ulong cll = (ulong)(h >> 3) & 0x7;
 
diff --git a/Libraries/Esiur/Data/PlainTdu.cs b/Libraries/Esiur/Data/PlainTdu.cs
index 05cc3e2..3667e21 100644
--- a/Libraries/Esiur/Data/PlainTdu.cs
+++ b/Libraries/Esiur/Data/PlainTdu.cs
@@ -75,7 +75,7 @@ namespace Esiur.Data
                     Ends = ends
                 };
             }
-            else if (cls == TduClass.Typed)
+            else if ((h & 0xC7) == 0x80) // else if (cls == TduClass.Typed)
             {
                 ulong cll = (ulong)(h >> 3) & 0x7;
 
diff --git a/Libraries/Esiur/Data/Tdu.cs b/Libraries/Esiur/Data/Tdu.cs
index 4418482..5908526 100644
--- a/Libraries/Esiur/Data/Tdu.cs
+++ b/Libraries/Esiur/Data/Tdu.cs
@@ -81,7 +81,8 @@ public struct Tdu
                 Composed = DC.Combine(new byte[] { (byte)Identifier }, 0, 1, data, 0, (uint)length);
         }
         else if (Class == TduClass.Dynamic
-            || Class == TduClass.Extension)
+            || Class == TduClass.Extension
+            || (Class == TduClass.Typed && Identifier != TduIdentifier.Typed))
         {
 
             if (length == 0)
@@ -287,6 +288,14 @@ public struct Tdu
         if (Class != TduClass.Typed || with.Class != TduClass.Typed)
             return false;
 
+        // Dedicated typed-class values (TypeDef/TRU) carry no metadata. Their identifier
+        // completely describes the outer type and is sufficient for continuation encoding.
+        if (Identifier != TduIdentifier.Typed)
+            return true;
+
+        if (Metadata == null || with.Metadata == null)
+            return false;
+
         if (!Metadata.Match(with.Metadata))
             return false;
 
diff --git a/Libraries/Esiur/Data/TduIdentifier.cs b/Libraries/Esiur/Data/TduIdentifier.cs
index 9a608a1..d387358 100644
--- a/Libraries/Esiur/Data/TduIdentifier.cs
+++ b/Libraries/Esiur/Data/TduIdentifier.cs
@@ -51,16 +51,11 @@ namespace Esiur.Data
         MapList = 0x47,
 
         Typed = 0x80,
+        TypeDef = 0x81,
+        TRU = 0x82,
 
-        //Record = 0x80,
-        //TypedList = 0x81,
-        //TypedMap = 0x82,
-        //TypedTuple = 0x83,
-        //TypedEnum = 0x84,
-        //TypedConstant = 0x85,
 
         TypeContinuation = 0xC0,
         TypeOfTarget = 0xC1,
-        TypeDef = 0xC2,
     }
 }
diff --git a/Libraries/Esiur/Data/Types/ArgumentDefInfo.cs b/Libraries/Esiur/Data/Types/ArgumentDefInfo.cs
new file mode 100644
index 0000000..e073388
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/ArgumentDefInfo.cs
@@ -0,0 +1,15 @@
+#nullable enable
+
+namespace Esiur.Data.Types;
+
+/// <summary>
+/// Indexed function-argument definition carried inside <see cref="FunctionDefInfo"/>.
+/// </summary>
+public class ArgumentDefInfo : MemberDefInfo
+{
+    [Index((int)ArgumentDefField.ValueType)]
+    public Tru ValueType { get; set; } = null!;
+
+    [Index((int)ArgumentDefField.DefaultValue)]
+    public object? DefaultValue { get; set; }
+}
diff --git a/Libraries/Esiur/Data/Types/ConstantDefInfo.cs b/Libraries/Esiur/Data/Types/ConstantDefInfo.cs
new file mode 100644
index 0000000..ef2cfdc
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/ConstantDefInfo.cs
@@ -0,0 +1,12 @@
+#nullable enable
+
+namespace Esiur.Data.Types;
+
+public class ConstantDefInfo : MemberDefInfo
+{
+    [Index((int)ConstantDefField.ValueType)]
+    public Tru ValueType { get; set; } = null!;
+
+    [Index((int)ConstantDefField.Value)]
+    public object? Value { get; set; }
+}
diff --git a/Libraries/Esiur/Data/Types/EventDef.cs b/Libraries/Esiur/Data/Types/EventDef.cs
index a6ec2c5..2710e72 100644
--- a/Libraries/Esiur/Data/Types/EventDef.cs
+++ b/Libraries/Esiur/Data/Types/EventDef.cs
@@ -28,12 +28,51 @@ public class EventDef : MemberDef
 
     public bool AutoDelivered { get; set; }
 
+    // Compatibility for existing subscription paths while callers migrate to AutoDelivered.
+    public bool Subscribable
+    {
+        get => !AutoDelivered;
+        set => AutoDelivered = !value;
+    }
+
     public bool Deprecated { get; set; }
 
     public EventInfo EventInfo { get; set; }
 
     public Tru ArgumentType { get; set; }
 
+    public static async AsyncReply<ParseResult<EventDef>> ParseAsync(
+        byte[] data, uint offset, byte index, bool inherited,
+        EpConnection connection, ulong[] requestSequence)
+    {
+        var originalOffset = offset;
+        var hasAnnotations = (data[offset] & 0x10) != 0;
+        var subscribable = (data[offset++] & 0x08) != 0;
+        var name = data.GetString(offset + 1, data[offset]);
+        offset += (uint)data[offset] + 1;
+
+        var argumentType = await Tru.ParseAsync(data, offset, connection, requestSequence);
+        offset += argumentType.Size;
+
+        Map<string, string> annotations = null;
+        if (hasAnnotations)
+        {
+            var (size, value) = Codec.ParseSync(data, offset, null);
+            annotations = value as Map<string, string>;
+            offset += size;
+        }
+
+        return new ParseResult<EventDef>(new EventDef
+        {
+            Index = index,
+            Name = name,
+            Inherited = inherited,
+            ArgumentType = argumentType.Value,
+            Subscribable = subscribable,
+            Annotations = annotations,
+        }, offset - originalOffset);
+    }
+
     
 
     //public static async AsyncReply<ParseResult<EventDef>> ParseAsync(byte[] data, uint offset, byte index, bool inherited, EpConnection connection, ulong[] requestSequence)
diff --git a/Libraries/Esiur/Data/Types/EventDefInfo.cs b/Libraries/Esiur/Data/Types/EventDefInfo.cs
new file mode 100644
index 0000000..c4974b8
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/EventDefInfo.cs
@@ -0,0 +1,19 @@
+#nullable enable
+
+namespace Esiur.Data.Types;
+
+public class EventDefInfo : MemberDefInfo
+{
+    [Index((int)EventDefField.ArgumentType)]
+    public Tru ArgumentType { get; set; } = null!;
+
+    [Index((int)EventDefField.ArgumentName)]
+    public string? ArgumentName { get; set; }
+
+    [Index((int)EventDefField.OrderingControl)]
+    public OrderingControl OrderingControl { get; set; }
+
+    // Kept byte-sized until the protocol defines a HistoryControl enum.
+    [Index((int)EventDefField.HistoryControl)]
+    public byte HistoryControl { get; set; }
+}
diff --git a/Libraries/Esiur/Data/Types/FunctionDef.cs b/Libraries/Esiur/Data/Types/FunctionDef.cs
index ae2015d..cdeda32 100644
--- a/Libraries/Esiur/Data/Types/FunctionDef.cs
+++ b/Libraries/Esiur/Data/Types/FunctionDef.cs
@@ -46,49 +46,38 @@ public class FunctionDef : MemberDef
         set;
     }
 
-
-    public static async AsyncReply<ParseResult<FunctionDef>> ParseAsync(byte[] data, uint offset, byte index, bool inherited, EpConnection connection, ulong[] requestSequence)
+    public static async AsyncReply<ParseResult<FunctionDef>> ParseAsync(
+        byte[] data, uint offset, byte index, bool inherited,
+        EpConnection connection, ulong[] requestSequence)
     {
-
-        var oOffset = offset;
-
-        var isStatic = ((data[offset] & 0x4) == 0x4);
-        var hasAnnotation = ((data[offset++] & 0x10) == 0x10);
-
+        var originalOffset = offset;
+        var isStatic = (data[offset] & 0x04) != 0;
+        var hasAnnotations = (data[offset++] & 0x10) != 0;
         var name = data.GetString(offset + 1, data[offset]);
         offset += (uint)data[offset] + 1;
 
-        //Console.WriteLine("Parsing functionDef " + name);
-
-        // return type
         var returnType = await Tru.ParseAsync(data, offset, connection, requestSequence);
         offset += returnType.Size;
-            
-        // arguments count
-        var argsCount = data[offset++];
-        List<ArgumentDef> arguments = new();
 
-        for (var a = 0; a < argsCount; a++)
+        var argumentCount = data[offset++];
+        var arguments = new List<ArgumentDef>(argumentCount);
+        for (var argumentIndex = 0; argumentIndex < argumentCount; argumentIndex++)
         {
-            var argType = await ArgumentDef.ParseAsync(data, offset, a, connection, requestSequence);
-            arguments.Add(argType.Value);
-            offset += argType.Size;
+            var argument = await ArgumentDef.ParseAsync(
+                data, offset, argumentIndex, connection, requestSequence);
+            arguments.Add(argument.Value);
+            offset += argument.Size;
         }
 
         Map<string, string> annotations = null;
-
-        // arguments
-        if (hasAnnotation) // Annotation ?
+        if (hasAnnotations)
         {
-            var (len, anns) = Codec.ParseSync(data, offset, null);
-
-            if (anns is Map<string, string> map)
-                annotations = map;
-
-            offset += len;
+            var (size, value) = Codec.ParseSync(data, offset, null);
+            annotations = value as Map<string, string>;
+            offset += size;
         }
 
-        return new ParseResult<FunctionDef>( new FunctionDef()
+        return new ParseResult<FunctionDef>(new FunctionDef
         {
             Index = index,
             Name = name,
@@ -97,35 +86,89 @@ public class FunctionDef : MemberDef
             Inherited = inherited,
             Annotations = annotations,
             ReturnType = returnType.Value,
-        }, offset - oOffset);
+        }, offset - originalOffset);
     }
 
-    public byte[] Compose(EpConnection connection)
-    {
 
-        var name = DC.ToBytes(Name);
+    //public static async AsyncReply<ParseResult<FunctionDef>> ParseAsync(byte[] data, uint offset, byte index, bool inherited, EpConnection connection, ulong[] requestSequence)
+    //{
 
-        var bl = new BinaryList()
-                .AddUInt8((byte)name.Length)
-                .AddUInt8Array(name)
-                .AddUInt8Array(ReturnType.Compose(connection))
-                .AddUInt8((byte)Arguments.Length);
+    //    var oOffset = offset;
 
-        for (var i = 0; i < Arguments.Length; i++)
-            bl.AddUInt8Array(Arguments[i].Compose(connection));
+    //    var isStatic = ((data[offset] & 0x4) == 0x4);
+    //    var hasAnnotation = ((data[offset++] & 0x10) == 0x10);
+
+    //    var name = data.GetString(offset + 1, data[offset]);
+    //    offset += (uint)data[offset] + 1;
+
+    //    //Console.WriteLine("Parsing functionDef " + name);
+
+    //    // return type
+    //    var returnType = await Tru.ParseAsync(data, offset, connection, requestSequence);
+    //    offset += returnType.Size;
+
+    //    // arguments count
+    //    var argsCount = data[offset++];
+    //    List<ArgumentDef> arguments = new();
+
+    //    for (var a = 0; a < argsCount; a++)
+    //    {
+    //        var argType = await ArgumentDef.ParseAsync(data, offset, a, connection, requestSequence);
+    //        arguments.Add(argType.Value);
+    //        offset += argType.Size;
+    //    }
+
+    //    Map<string, string> annotations = null;
+
+    //    // arguments
+    //    if (hasAnnotation) // Annotation ?
+    //    {
+    //        var (len, anns) = Codec.ParseSync(data, offset, null);
+
+    //        if (anns is Map<string, string> map)
+    //            annotations = map;
+
+    //        offset += len;
+    //    }
+
+    //    return new ParseResult<FunctionDef>( new FunctionDef()
+    //    {
+    //        Index = index,
+    //        Name = name,
+    //        Arguments = arguments.ToArray(),
+    //        IsStatic = isStatic,
+    //        Inherited = inherited,
+    //        Annotations = annotations,
+    //        ReturnType = returnType.Value,
+    //    }, offset - oOffset);
+    //}
+
+    //public byte[] Compose(EpConnection connection)
+    //{
+
+    //    var name = DC.ToBytes(Name);
+
+    //    var bl = new BinaryList()
+    //            .AddUInt8((byte)name.Length)
+    //            .AddUInt8Array(name)
+    //            .AddUInt8Array(ReturnType.Compose(connection))
+    //            .AddUInt8((byte)Arguments.Length);
+
+    //    for (var i = 0; i < Arguments.Length; i++)
+    //        bl.AddUInt8Array(Arguments[i].Compose(connection));
 
 
-        if (Annotations != null)
-        {
-            var exp = Codec.Compose(Annotations, connection.Instance.Warehouse , connection);// DC.ToBytes(Annotation);
-            bl.AddUInt8Array(exp);
-            bl.InsertUInt8(0, (byte)((Inherited ? (byte)0x90 : (byte)0x10) | (IsStatic ? 0x4 : 0)));
-        }
-        else
-            bl.InsertUInt8(0, (byte)((Inherited ? (byte)0x80 : (byte)0x0) | (IsStatic ? 0x4 : 0)));
+    //    if (Annotations != null)
+    //    {
+    //        var exp = Codec.Compose(Annotations, connection.Instance.Warehouse , connection);// DC.ToBytes(Annotation);
+    //        bl.AddUInt8Array(exp);
+    //        bl.InsertUInt8(0, (byte)((Inherited ? (byte)0x90 : (byte)0x10) | (IsStatic ? 0x4 : 0)));
+    //    }
+    //    else
+    //        bl.InsertUInt8(0, (byte)((Inherited ? (byte)0x80 : (byte)0x0) | (IsStatic ? 0x4 : 0)));
 
-        return bl.ToArray();
-    }
+    //    return bl.ToArray();
+    //}
 
 
     public static FunctionDef MakeFunctionDef(Warehouse warehouse, Type type, MethodInfo mi, byte index, string name, TypeDef schema)
diff --git a/Libraries/Esiur/Data/Types/FunctionDefInfo.cs b/Libraries/Esiur/Data/Types/FunctionDefInfo.cs
new file mode 100644
index 0000000..4e429c6
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/FunctionDefInfo.cs
@@ -0,0 +1,16 @@
+#nullable enable
+using System.Collections.Generic;
+
+namespace Esiur.Data.Types;
+
+public class FunctionDefInfo : MemberDefInfo
+{
+    [Index((int)FunctionDefField.Arguments)]
+    public List<ArgumentDefInfo>? Arguments { get; set; }
+
+    [Index((int)FunctionDefField.ReturnType)]
+    public Tru ReturnType { get; set; } = null!;
+
+    [Index((int)FunctionDefField.StreamMode)]
+    public StreamMode StreamMode { get; set; }
+}
diff --git a/Libraries/Esiur/Data/Types/MemberDefInfo.cs b/Libraries/Esiur/Data/Types/MemberDefInfo.cs
new file mode 100644
index 0000000..e075640
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/MemberDefInfo.cs
@@ -0,0 +1,71 @@
+#nullable enable
+using System.Collections.Generic;
+
+namespace Esiur.Data.Types;
+
+/// <summary>
+/// Wire representation shared by all TypeDef members.
+/// </summary>
+public class MemberDefInfo : IndexedStructure
+{
+    [Index((int)MemberDefField.Index)]
+    public byte Index { get; set; }
+
+    [Index((int)MemberDefField.Name)]
+    public string Name { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Raw member-specific flags. Interpret this as PropertyDefFlags, FunctionDefFlags,
+    /// EventDefFlags, ConstantDefFlags, or ArgumentDefFlags according to the concrete type.
+    /// </summary>
+    [Index((int)MemberDefField.Flags)]
+    public byte Flags { get; set; }
+
+    [Index((int)MemberDefField.Description)]
+    public string? Description { get; set; }
+
+    [Index((int)MemberDefField.Usage)]
+    public string? Usage { get; set; }
+
+    [Index((int)MemberDefField.Examples)]
+    public List<object>? Examples { get; set; }
+
+    [Index((int)MemberDefField.Tags)]
+    public List<string>? Tags { get; set; }
+
+    [Index((int)MemberDefField.Unit)]
+    public string? Unit { get; set; }
+
+    [Index((int)MemberDefField.Minimum)]
+    public object? Minimum { get; set; }
+
+    [Index((int)MemberDefField.Maximum)]
+    public object? Maximum { get; set; }
+
+    [Index((int)MemberDefField.AllowedValues)]
+    public List<object>? AllowedValues { get; set; }
+
+    [Index((int)MemberDefField.Pattern)]
+    public string? Pattern { get; set; }
+
+    [Index((int)MemberDefField.Format)]
+    public string? Format { get; set; }
+
+    [Index((int)MemberDefField.Preconditions)]
+    public List<string>? Preconditions { get; set; }
+
+    [Index((int)MemberDefField.Postconditions)]
+    public List<string>? Postconditions { get; set; }
+
+    [Index((int)MemberDefField.Effects)]
+    public OperationEffects Effects { get; set; }
+
+    [Index((int)MemberDefField.Warnings)]
+    public List<string>? Warnings { get; set; }
+
+    [Index((int)MemberDefField.RelatedMembers)]
+    public List<byte>? RelatedMembers { get; set; }
+
+    [Index((int)MemberDefField.DeprecationMessage)]
+    public string? DeprecationMessage { get; set; }
+}
diff --git a/Libraries/Esiur/Data/Types/PropertyDef.cs b/Libraries/Esiur/Data/Types/PropertyDef.cs
index 930277a..feabe22 100644
--- a/Libraries/Esiur/Data/Types/PropertyDef.cs
+++ b/Libraries/Esiur/Data/Types/PropertyDef.cs
@@ -44,11 +44,58 @@ public class PropertyDef : MemberDef
 
     public bool ReadOnly { get; set; }
 
+    // Compatibility for code still consuming the previous permission model.
+    public PropertyPermission Permission
+    {
+        get => ReadOnly ? PropertyPermission.Read : PropertyPermission.ReadWrite;
+        set => ReadOnly = value == PropertyPermission.Read;
+    }
+
     public bool Constant { get; set; }
     //public bool IsNullable { get; set; }
 
     public bool Historical { get; set; }
 
+    public bool HasHistory
+    {
+        get => Historical;
+        set => Historical = value;
+    }
+
+    public static async AsyncReply<ParseResult<PropertyDef>> ParseAsync(
+        byte[] data, uint offset, byte index, bool inherited,
+        EpConnection connection, ulong[] requestSequence)
+    {
+        var originalOffset = offset;
+        var hasAnnotations = (data[offset] & 0x08) != 0;
+        var hasHistory = (data[offset] & 0x01) != 0;
+        var permission = (PropertyPermission)((data[offset++] >> 1) & 0x03);
+        var name = data.GetString(offset + 1, data[offset]);
+        offset += (uint)data[offset] + 1;
+
+        var valueType = await Tru.ParseAsync(data, offset, connection, requestSequence);
+        offset += valueType.Size;
+
+        Map<string, string> annotations = null;
+        if (hasAnnotations)
+        {
+            var (size, value) = Codec.ParseSync(data, offset, null);
+            annotations = value as Map<string, string>;
+            offset += size;
+        }
+
+        return new ParseResult<PropertyDef>(new PropertyDef
+        {
+            Index = index,
+            Name = name,
+            Inherited = inherited,
+            Permission = permission,
+            HasHistory = hasHistory,
+            ValueType = valueType.Value,
+            Annotations = annotations,
+        }, offset - originalOffset);
+    }
+
     /*
     public PropertyType Mode
     {
@@ -273,6 +320,15 @@ public class PropertyDef : MemberDef
  
     }
 
+    public static PropertyDef MakePropertyDef(
+        Warehouse warehouse, Type type, PropertyInfo pi, string name, byte index,
+        PropertyPermission permission, TypeDef typeDef)
+    {
+        var definition = MakePropertyDef(warehouse, type, pi, name, index, typeDef);
+        definition.Permission = permission;
+        return definition;
+    }
+
 
     public static string GetTypeAnnotationName(Type type)
     {
diff --git a/Libraries/Esiur/Data/Types/PropertyDefInfo.cs b/Libraries/Esiur/Data/Types/PropertyDefInfo.cs
new file mode 100644
index 0000000..8413730
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/PropertyDefInfo.cs
@@ -0,0 +1,19 @@
+#nullable enable
+
+namespace Esiur.Data.Types;
+
+public class PropertyDefInfo : MemberDefInfo
+{
+    [Index((int)PropertyDefField.ValueType)]
+    public Tru ValueType { get; set; } = null!;
+
+    [Index((int)PropertyDefField.OrderingControl)]
+    public OrderingControl OrderingControl { get; set; }
+
+    // Kept byte-sized until the protocol defines a HistoryControl enum.
+    [Index((int)PropertyDefField.HistoryControl)]
+    public byte HistoryControl { get; set; }
+
+    [Index((int)PropertyDefField.DefaultValue)]
+    public object? DefaultValue { get; set; }
+}
diff --git a/Libraries/Esiur/Data/Types/RemoteTypeDef.cs b/Libraries/Esiur/Data/Types/RemoteTypeDef.cs
index 2e7d34d..6e6fc5a 100644
--- a/Libraries/Esiur/Data/Types/RemoteTypeDef.cs
+++ b/Libraries/Esiur/Data/Types/RemoteTypeDef.cs
@@ -44,6 +44,26 @@ public class RemoteTypeDef:TypeDef
     {
         uint ends = offset + contentLength;
 
+        if (((byte)data[offset] & 0xC7) == (byte)TduIdentifier.TypeDef)
+        {
+            var previousSequence = DataDeserializer.TypeDefRequestSequence.Value;
+            try
+            {
+                DataDeserializer.TypeDefRequestSequence.Value = requestSequence;
+                var parsed = await Codec.ParseAsync(data, offset, connection, null);
+                if (parsed.Size != contentLength || parsed.Value is not TypeDefInfo info)
+                    throw new Exception("Invalid TypeDefInfo payload.");
+
+                ApplyInfo(od, domain, data, offset, contentLength, info);
+                CompleteRegistration(od, connection);
+                return od;
+            }
+            finally
+            {
+                DataDeserializer.TypeDefRequestSequence.Value = previousSequence;
+            }
+        }
+
         uint oOffset = offset;
 
         // start parsing...
@@ -161,5 +181,139 @@ public class RemoteTypeDef:TypeDef
 
         return od;
     }
+
+    private static void ApplyInfo(RemoteTypeDef definition, string domain, byte[] data,
+                                  uint offset, uint contentLength, TypeDefInfo info)
+    {
+        definition._domain = domain;
+        definition._content = data.Clip(offset, contentLength);
+        definition._typeId = info.Id;
+        definition._parentTypeId = info.Parent;
+        definition._typeName = string.IsNullOrEmpty(info.Namespace)
+            ? info.Name
+            : $"{info.Namespace}.{info.Name}";
+        definition._typeDefKind = info.Kind;
+        definition._version = info.Version;
+        definition.Annotations = info.Annotations;
+
+        definition._properties.Clear();
+        definition._functions.Clear();
+        definition._events.Clear();
+        definition._constants.Clear();
+
+        if (info.Properties != null)
+            definition._properties.AddRange(info.Properties.Select(x => ToProperty(definition, x)));
+        if (info.Functions != null)
+            definition._functions.AddRange(info.Functions.Select(x => ToFunction(definition, x)));
+        if (info.Events != null)
+            definition._events.AddRange(info.Events.Select(x => ToEvent(definition, x)));
+        if (info.Constants != null)
+            definition._constants.AddRange(info.Constants.Select(x => ToConstant(definition, x)));
+    }
+
+    private static T ApplyMember<T>(RemoteTypeDef definition, MemberDefInfo info, T member)
+        where T : MemberDef
+    {
+        member.Definition = definition;
+        member.Index = info.Index;
+        member.Name = info.Name;
+        member.Inherited = (info.Flags & (byte)MemberDefFlags.Inherited) != 0;
+        member.Description = info.Description;
+        member.Usage = info.Usage;
+        member.Examples = info.Examples;
+        member.Tags = info.Tags;
+        member.Unit = info.Unit;
+        member.Minimum = info.Minimum;
+        member.Maximum = info.Maximum;
+        member.AllowedValues = info.AllowedValues;
+        member.Pattern = info.Pattern;
+        member.Format = info.Format;
+        member.Preconditions = info.Preconditions;
+        member.Postconditions = info.Postconditions;
+        member.Effects = info.Effects;
+        member.Warnings = info.Warnings;
+        member.RelatedMembers = info.RelatedMembers;
+        member.DeprecationMessage = info.DeprecationMessage;
+        return member;
+    }
+
+    private static PropertyDef ToProperty(RemoteTypeDef definition, PropertyDefInfo info)
+    {
+        var flags = (PropertyDefFlags)info.Flags;
+        return ApplyMember(definition, info, new PropertyDef
+        {
+            ValueType = info.ValueType,
+            ReadOnly = flags.HasFlag(PropertyDefFlags.ReadOnly),
+            Constant = flags.HasFlag(PropertyDefFlags.Constant),
+            Historical = flags.HasFlag(PropertyDefFlags.Historical) || info.HistoryControl != 0,
+        });
+    }
+
+    private static FunctionDef ToFunction(RemoteTypeDef definition, FunctionDefInfo info)
+    {
+        var flags = (FunctionDefFlags)info.Flags;
+        return ApplyMember(definition, info, new FunctionDef
+        {
+            ReturnType = info.ReturnType,
+            StreamMode = info.StreamMode,
+            IsStatic = flags.HasFlag(FunctionDefFlags.Static),
+            ReadOnly = flags.HasFlag(FunctionDefFlags.ReadOnly),
+            Idempotent = flags.HasFlag(FunctionDefFlags.Idempotent),
+            Cancellable = flags.HasFlag(FunctionDefFlags.Cancellable),
+            Deprecated = flags.HasFlag(FunctionDefFlags.Deprecated),
+            Arguments = info.Arguments?.Select(ToArgument).ToArray() ?? Array.Empty<ArgumentDef>(),
+        });
+    }
+
+    private static ArgumentDef ToArgument(ArgumentDefInfo info)
+    {
+        var flags = (ArgumentDefFlags)info.Flags;
+        return new ArgumentDef
+        {
+            Index = info.Index,
+            Name = info.Name,
+            Optional = flags.HasFlag(ArgumentDefFlags.Optional),
+            Type = info.ValueType,
+            DefaultValue = info.DefaultValue,
+        };
+    }
+
+    private static EventDef ToEvent(RemoteTypeDef definition, EventDefInfo info)
+    {
+        var flags = (EventDefFlags)info.Flags;
+        return ApplyMember(definition, info, new EventDef
+        {
+            ArgumentType = info.ArgumentType,
+            AutoDelivered = flags.HasFlag(EventDefFlags.AutoDelivered),
+            Deprecated = flags.HasFlag(EventDefFlags.Deprecated),
+        });
+    }
+
+    private static ConstantDef ToConstant(RemoteTypeDef definition, ConstantDefInfo info)
+        => ApplyMember(definition, info, new ConstantDef
+        {
+            ValueType = info.ValueType,
+            Value = info.Value,
+        });
+
+    private static void CompleteRegistration(RemoteTypeDef definition, EpConnection connection)
+    {
+        definition._proxyType = connection.Instance?.Warehouse?.TryGetProxyType(
+            definition.Kind, definition.Domain, definition.Name);
+
+        if (definition._proxyType != null)
+        {
+            foreach (var property in definition.Properties)
+                property.PropertyInfo = definition._proxyType.GetProperty(property.Name);
+            foreach (var function in definition.Functions)
+                function.MethodInfo = definition._proxyType.GetMethod(function.Name);
+            foreach (var eventDefinition in definition.Events)
+                eventDefinition.EventInfo = definition._proxyType.GetEvent(eventDefinition.Name);
+            foreach (var constant in definition.Constants)
+                constant.FieldInfo = definition._proxyType.GetField(constant.Name);
+        }
+
+        connection.Instance?.Warehouse?.TryRegisterRemoteTypeDef(connection.RemoteDomain, definition);
+    }
 }
 
diff --git a/Libraries/Esiur/Data/Types/TypeDef.cs b/Libraries/Esiur/Data/Types/TypeDef.cs
index fe54274..6e5b75c 100644
--- a/Libraries/Esiur/Data/Types/TypeDef.cs
+++ b/Libraries/Esiur/Data/Types/TypeDef.cs
@@ -46,6 +46,8 @@ public class TypeDef
 
     public TypeDefKind Kind => _typeDefKind;
 
+    public int Version => _version;
+
     public EventDef GetEventDefByName(string eventName)
     {
         foreach (var i in _events)
@@ -151,7 +153,8 @@ public class TypeDef
 
     public virtual byte[] Compose(EpConnection connection)
     {
-        return null;
+        var warehouse = connection?.Instance?.Warehouse ?? Warehouse.Default;
+        return Codec.Compose(TypeDefInfo.FromTypeDef(this), warehouse, connection);
     }
 
    
diff --git a/Libraries/Esiur/Data/Types/TypeDefInfo.cs b/Libraries/Esiur/Data/Types/TypeDefInfo.cs
new file mode 100644
index 0000000..8a82bc2
--- /dev/null
+++ b/Libraries/Esiur/Data/Types/TypeDefInfo.cs
@@ -0,0 +1,168 @@
+#nullable enable
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Esiur.Data.Types;
+
+/// <summary>
+/// Indexed, transport-safe representation of a type definition.
+/// </summary>
+public class TypeDefInfo : IndexedStructure
+{
+    [Index((int)TypeDefField.Version)]
+    public int Version { get; set; }
+
+    [Index((int)TypeDefField.Id)]
+    public ulong Id { get; set; }
+
+    [Index((int)TypeDefField.Name)]
+    public string Name { get; set; } = string.Empty;
+
+    [Index((int)TypeDefField.Namespace)]
+    public string? Namespace { get; set; }
+
+    [Index((int)TypeDefField.Kind)]
+    public TypeDefKind Kind { get; set; }
+
+    [Index((int)TypeDefField.Parent)]
+    public ulong? Parent { get; set; }
+
+    [Index((int)TypeDefField.Properties)]
+    public List<PropertyDefInfo>? Properties { get; set; }
+
+    [Index((int)TypeDefField.Functions)]
+    public List<FunctionDefInfo>? Functions { get; set; }
+
+    [Index((int)TypeDefField.Events)]
+    public List<EventDefInfo>? Events { get; set; }
+
+    [Index((int)TypeDefField.Constants)]
+    public List<ConstantDefInfo>? Constants { get; set; }
+
+    [Index((int)TypeDefField.Usage)]
+    public string? Usage { get; set; }
+
+    [Index((int)TypeDefField.Description)]
+    public string? Description { get; set; }
+
+    [Index((int)TypeDefField.Example)]
+    public object? Example { get; set; }
+
+    [Index((int)TypeDefField.Category)]
+    public string? Category { get; set; }
+
+    [Index((int)TypeDefField.Since)]
+    public string? Since { get; set; }
+
+    [Index((int)TypeDefField.Annotations)]
+    public Map<string, string>? Annotations { get; set; }
+
+    public static TypeDefInfo FromTypeDef(TypeDef definition)
+    {
+        return new TypeDefInfo
+        {
+            Version = definition.Version,
+            Id = definition.Id,
+            Name = definition.Name,
+            Kind = definition.Kind,
+            Parent = definition.ParentTypeId,
+            Annotations = definition.Annotations,
+            Properties = definition.Properties.Select(FromProperty).ToList(),
+            Functions = definition.Functions.Select(FromFunction).ToList(),
+            Events = definition.Events.Select(FromEvent).ToList(),
+            Constants = definition.Constants.Select(FromConstant).ToList(),
+        };
+    }
+
+    private static T CopyMember<T>(MemberDef source, T target) where T : MemberDefInfo
+    {
+        target.Index = source.Index;
+        target.Name = source.Name;
+        target.Description = source.Description;
+        target.Usage = source.Usage;
+        target.Examples = source.Examples;
+        target.Tags = source.Tags;
+        target.Unit = source.Unit;
+        target.Minimum = source.Minimum;
+        target.Maximum = source.Maximum;
+        target.AllowedValues = source.AllowedValues;
+        target.Pattern = source.Pattern;
+        target.Format = source.Format;
+        target.Preconditions = source.Preconditions;
+        target.Postconditions = source.Postconditions;
+        target.Effects = source.Effects;
+        target.Warnings = source.Warnings;
+        target.RelatedMembers = source.RelatedMembers;
+        target.DeprecationMessage = source.DeprecationMessage;
+        return target;
+    }
+
+    private static PropertyDefInfo FromProperty(PropertyDef source)
+    {
+        var flags = source.Inherited ? PropertyDefFlags.Inherited : PropertyDefFlags.None;
+        if (source.ReadOnly) flags |= PropertyDefFlags.ReadOnly;
+        if (source.Constant) flags |= PropertyDefFlags.Constant;
+        if (source.Historical) flags |= PropertyDefFlags.Historical;
+
+        return CopyMember(source, new PropertyDefInfo
+        {
+            Flags = (byte)flags,
+            ValueType = source.ValueType,
+            HistoryControl = source.Historical ? (byte)1 : (byte)0,
+        });
+    }
+
+    private static FunctionDefInfo FromFunction(FunctionDef source)
+    {
+        var flags = source.Inherited ? FunctionDefFlags.Inherited : FunctionDefFlags.None;
+        if (source.Deprecated) flags |= FunctionDefFlags.Deprecated;
+        if (source.IsStatic) flags |= FunctionDefFlags.Static;
+        if (source.ReadOnly) flags |= FunctionDefFlags.ReadOnly;
+        if (source.Idempotent) flags |= FunctionDefFlags.Idempotent;
+        if (source.Cancellable) flags |= FunctionDefFlags.Cancellable;
+
+        return CopyMember(source, new FunctionDefInfo
+        {
+            Flags = (byte)flags,
+            ReturnType = source.ReturnType,
+            StreamMode = source.StreamMode,
+            Arguments = source.Arguments?.Select(FromArgument).ToList(),
+        });
+    }
+
+    private static ArgumentDefInfo FromArgument(ArgumentDef source)
+    {
+        return new ArgumentDefInfo
+        {
+            Index = checked((byte)source.Index),
+            Name = source.Name,
+            Flags = source.Optional ? (byte)ArgumentDefFlags.Optional : (byte)ArgumentDefFlags.None,
+            ValueType = source.Type,
+            DefaultValue = source.DefaultValue,
+        };
+    }
+
+    private static EventDefInfo FromEvent(EventDef source)
+    {
+        var flags = source.Inherited ? EventDefFlags.Inherited : EventDefFlags.None;
+        if (source.Deprecated) flags |= EventDefFlags.Deprecated;
+        if (source.AutoDelivered) flags |= EventDefFlags.AutoDelivered;
+
+        return CopyMember(source, new EventDefInfo
+        {
+            Flags = (byte)flags,
+            ArgumentType = source.ArgumentType,
+        });
+    }
+
+    private static ConstantDefInfo FromConstant(ConstantDef source)
+    {
+        var flags = source.Inherited ? ConstantDefFlags.Inherited : ConstantDefFlags.None;
+        return CopyMember(source, new ConstantDefInfo
+        {
+            Flags = (byte)flags,
+            ValueType = source.ValueType,
+            Value = source.Value,
+        });
+    }
+}
diff --git a/Libraries/Esiur/Resource/Attributes/StorageAttribute.cs b/Libraries/Esiur/Resource/Attributes/StorageAttribute.cs
deleted file mode 100644
index e608f27..0000000
--- a/Libraries/Esiur/Resource/Attributes/StorageAttribute.cs
+++ /dev/null
@@ -1,15 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Esiur.Resource;
-
-[AttributeUsage(AttributeTargets.Property)]
-public class StorageAttribute : Attribute
-{
-    public StorageMode Mode { get; set; }
-    public StorageAttribute(StorageMode mode)
-    {
-        Mode = mode;
-    }
-}
diff --git a/Libraries/Esiur/Resource/PropertyPermission.cs b/Libraries/Esiur/Resource/PropertyPermission.cs
index 2d72b06..3becb6f 100644
--- a/Libraries/Esiur/Resource/PropertyPermission.cs
+++ b/Libraries/Esiur/Resource/PropertyPermission.cs
@@ -4,10 +4,10 @@ using System.Text;
 
 namespace Esiur.Resource
 {
-    //public enum PropertyPermission : byte
-    //{
-    //    ReadOnly = 0,
-    //    Write,
-    //    ReadWrite,
-    //}
+    public enum PropertyPermission : byte
+    {
+        Read = 1,
+        Write,
+        ReadWrite,
+    }
 }
diff --git a/Tests/Unit/IndexedStructureTests.cs b/Tests/Unit/IndexedStructureTests.cs
new file mode 100644
index 0000000..052148b
--- /dev/null
+++ b/Tests/Unit/IndexedStructureTests.cs
@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Generic;
+using Esiur.Data;
+using Esiur.Resource;
+
+namespace Esiur.Tests.Unit;
+
+public class IndexedStructureTests
+{
+    private sealed class ExampleInfo : IndexedStructure
+    {
+        [Index(1)]
+        public int Count { get; set; }
+
+        [Index(2)]
+        public string? Note { get; set; }
+    }
+
+    private sealed class MemberDefInfo : IndexedStructure
+    {
+        [Index(1)]
+        public string? Name { get; set; }
+
+        [Index(2)]
+        public ExampleInfo? Example { get; set; }
+
+        [Index(3)]
+        public List<ExampleInfo>? Examples { get; set; }
+    }
+
+    [Fact]
+    public void NestedStructure_RoundTripsDirectly()
+    {
+        var source = new MemberDefInfo
+        {
+            Name = "length",
+            Example = new ExampleInfo { Count = 3, Note = "nested" },
+            Examples = new List<ExampleInfo>
+            {
+                new() { Count = 4, Note = "first" },
+                new() { Count = 5, Note = "second" },
+            },
+        };
+
+        var bytes = Codec.ComposeIndexedType(source, Warehouse.Default, null);
+        var (_, raw) = Codec.ParseSync(bytes, 0, Warehouse.Default);
+        var (size, parsed) = Codec.ParseIndexedType<MemberDefInfo>(bytes, 0, Warehouse.Default);
+
+        Assert.Equal((uint)bytes.Length, size);
+        Assert.IsType<Map<byte, object>>(raw);
+        Assert.Equal("length", parsed.Name);
+        Assert.NotNull(parsed.Example);
+        Assert.Equal(3, parsed.Example.Count);
+        Assert.Equal("nested", parsed.Example.Note);
+        Assert.Equal(2, parsed.Examples!.Count);
+        Assert.Equal(5, parsed.Examples[1].Count);
+    }
+
+    [Fact]
+    public void UnknownIndexes_AreIgnored()
+    {
+        var map = new Map<byte, object>
+        {
+            [1] = "known",
+            [99] = "future field",
+        };
+
+        var parsed = Codec.ParseIndexedType<MemberDefInfo>(map);
+
+        Assert.Equal("known", parsed.Name);
+        Assert.Null(parsed.Example);
+    }
+
+    [Fact]
+    public void DuplicateIndexes_AreRejected()
+    {
+        var value = new InvalidStructure();
+        var error = Assert.Throws<InvalidOperationException>(() =>
+            Codec.ComposeIndexedType(value, Warehouse.Default, null));
+
+        Assert.Contains("index 1", error.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private sealed class InvalidStructure : IndexedStructure
+    {
+        [Index(1)] public int First { get; set; }
+        [Index(1)] public int Second { get; set; }
+    }
+}
diff --git a/Tests/Unit/TypeDefInfoSerializationTests.cs b/Tests/Unit/TypeDefInfoSerializationTests.cs
new file mode 100644
index 0000000..7e6f472
--- /dev/null
+++ b/Tests/Unit/TypeDefInfoSerializationTests.cs
@@ -0,0 +1,130 @@
+using System.Collections.Generic;
+using Esiur.Data;
+using Esiur.Data.Types;
+using Esiur.Resource;
+
+namespace Esiur.Tests.Unit;
+
+public class TypeDefInfoSerializationTests
+{
+    [Fact]
+    public void Tru_HasDedicatedTduAndRoundTrips()
+    {
+        Tru source = new TruPrimitive(TruIdentifier.String, true, typeof(string));
+
+        var bytes = Codec.Compose(source, Warehouse.Default, null);
+        var (size, value) = Codec.ParseSync(bytes, 0, Warehouse.Default);
+
+        Assert.Equal((byte)TduIdentifier.TRU, (byte)(bytes[0] & 0xC7));
+        Assert.Equal((uint)bytes.Length, size);
+        var parsed = Assert.IsAssignableFrom<Tru>(value);
+        Assert.Equal(TruIdentifier.String, parsed.Identifier);
+        Assert.True(parsed.Nullable);
+    }
+
+    [Fact]
+    public void ConsecutiveTrus_UseContinuationAndRoundTrip()
+    {
+        var source = new object[]
+        {
+            new TruPrimitive(TruIdentifier.String, false, typeof(string)),
+            new TruPrimitive(TruIdentifier.Int32, false, typeof(int)),
+        };
+
+        var bytes = Codec.Compose(source, Warehouse.Default, null);
+        var (_, value) = Codec.ParseSync(bytes, 0, Warehouse.Default);
+        var parsed = Assert.IsType<object[]>(value);
+
+        Assert.Equal(TruIdentifier.String, Assert.IsAssignableFrom<Tru>(parsed[0]).Identifier);
+        Assert.Equal(TruIdentifier.Int32, Assert.IsAssignableFrom<Tru>(parsed[1]).Identifier);
+    }
+
+    [Fact]
+    public void TypeDefInfo_WithNestedMembersAndTrus_RoundTrips()
+    {
+        var source = new TypeDefInfo
+        {
+            Version = 3,
+            Id = 42,
+            Name = "Widget",
+            Namespace = "Example.Models",
+            Kind = TypeDefKind.Resource,
+            Parent = 7,
+            Description = "A test resource",
+            Annotations = new Map<string, string> { ["audience"] = "test" },
+            Properties = new List<PropertyDefInfo>
+            {
+                new()
+                {
+                    Index = 1,
+                    Name = "Title",
+                    Flags = (byte)PropertyDefFlags.ReadOnly,
+                    ValueType = new TruPrimitive(TruIdentifier.String, false, typeof(string)),
+                    OrderingControl = OrderingControl.LatestOnly,
+                },
+            },
+            Functions = new List<FunctionDefInfo>
+            {
+                new()
+                {
+                    Index = 2,
+                    Name = "Find",
+                    Flags = (byte)FunctionDefFlags.Idempotent,
+                    ReturnType = new TruPrimitive(TruIdentifier.String, true, typeof(string)),
+                    Arguments = new List<ArgumentDefInfo>
+                    {
+                        new()
+                        {
+                            Index = 0,
+                            Name = "id",
+                            ValueType = new TruPrimitive(TruIdentifier.UInt64, false, typeof(ulong)),
+                        },
+                    },
+                },
+            },
+            Events = new List<EventDefInfo>
+            {
+                new()
+                {
+                    Index = 3,
+                    Name = "Changed",
+                    ArgumentName = "title",
+                    ArgumentType = new TruPrimitive(TruIdentifier.String, false, typeof(string)),
+                },
+            },
+            Constants = new List<ConstantDefInfo>
+            {
+                new()
+                {
+                    Index = 4,
+                    Name = "Maximum",
+                    ValueType = new TruPrimitive(TruIdentifier.Int32, false, typeof(int)),
+                    Value = 100,
+                },
+            },
+        };
+
+        var bytes = Codec.Compose(source, Warehouse.Default, null);
+        var (size, parsed) = Codec.ParseIndexedType<TypeDefInfo>(bytes, 0, Warehouse.Default);
+
+        Assert.Equal((byte)TduIdentifier.TypeDef, (byte)(bytes[0] & 0xC7));
+        Assert.Equal((uint)bytes.Length, size);
+        Assert.Equal(source.Id, parsed.Id);
+        Assert.Equal("Widget", parsed.Name);
+        Assert.Equal(TypeDefKind.Resource, parsed.Kind);
+        Assert.Equal("test", parsed.Annotations!["audience"]);
+
+        var property = Assert.Single(parsed.Properties!);
+        Assert.Equal("Title", property.Name);
+        Assert.Equal(TruIdentifier.String, property.ValueType.Identifier);
+        Assert.Equal(OrderingControl.LatestOnly, property.OrderingControl);
+
+        var function = Assert.Single(parsed.Functions!);
+        Assert.True(function.ReturnType.Nullable);
+        Assert.Equal(TruIdentifier.String, function.ReturnType.Identifier);
+        Assert.Equal(TruIdentifier.UInt64, Assert.Single(function.Arguments!).ValueType.Identifier);
+
+        Assert.Equal(TruIdentifier.String, Assert.Single(parsed.Events!).ArgumentType.Identifier);
+        Assert.Equal(100, Convert.ToInt32(Assert.Single(parsed.Constants!).Value));
+    }
+}