diff --git a/Capnp.Net.Runtime/TypeIdAttribute.cs b/Capnp.Net.Runtime/TypeIdAttribute.cs
new file mode 100644
index 0000000..098dd03
--- /dev/null
+++ b/Capnp.Net.Runtime/TypeIdAttribute.cs
@@ -0,0 +1,27 @@
+using System;
+
+namespace Capnp
+{
+    /// <summary>
+    /// Annotates an enum, class or interface with its schema type identifier.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Enum | AttributeTargets.Class |AttributeTargets.Interface, AllowMultiple = false, Inherited = false)]
+    public class TypeIdAttribute : Attribute
+    {
+        /// <summary>
+        /// Constructs this attribute.
+        /// </summary>
+        /// <param name="typeId">The 64-bit type identifier from the schema file.</param>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="typeId"/> is zero.</exception>
+        public TypeIdAttribute(ulong typeId)
+        {
+            if (typeId == 0) throw new ArgumentOutOfRangeException(nameof(typeId), "The value cannot be zero.");
+            Id = typeId;
+        }
+
+        /// <summary>
+        /// The schema type identifier.
+        /// </summary>
+        public ulong Id { get; }
+    }
+}
diff --git a/capnpc-csharp.tests/Embedded Resources/test.cs b/capnpc-csharp.tests/Embedded Resources/test.cs
index d20da0b..5db5225 100644
--- a/capnpc-csharp.tests/Embedded Resources/test.cs	
+++ b/capnpc-csharp.tests/Embedded Resources/test.cs	
@@ -7,6 +7,7 @@ using System.Threading.Tasks;
 
 namespace Capnproto_test.Capnp.Test
 {
+    [TypeId(0x9c8e9318b29d9cd3UL)]
     public enum TestEnum : ushort
     {
         foo,
@@ -19,8 +20,10 @@ namespace Capnproto_test.Capnp.Test
         garply
     }
 
+    [TypeId(0xa0a8f314b80b63fdUL)]
     public class TestAllTypes : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xa0a8f314b80b63fdUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -542,8 +545,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xeb3f9ebe98c73cb6UL)]
     public class TestDefaults : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xeb3f9ebe98c73cb6UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -1112,8 +1117,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xe3da5a2ccd28c0d8UL)]
     public class TestAnyPointer : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xe3da5a2ccd28c0d8UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -1170,8 +1177,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xf49850f63c2bfa59UL)]
     public class TestAnyOthers : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xf49850f63c2bfa59UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -1258,8 +1267,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xa9d5f8efe770022bUL)]
     public class TestOutOfOrder : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xa9d5f8efe770022bUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -1436,8 +1447,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xf47697362233ce52UL)]
     public class TestUnion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xf47697362233ce52UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -1654,8 +1667,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xfc76a82eecb7a718UL)]
         public class @union0 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xfc76a82eecb7a718UL;
             public enum WHICH : ushort
             {
                 U0f0s0 = 0,
@@ -2072,8 +2087,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xee0a6b99b7dc7ab2UL)]
         public class @union1 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xee0a6b99b7dc7ab2UL;
             public enum WHICH : ushort
             {
                 U1f0s0 = 0,
@@ -2652,8 +2669,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xafc5fd419f0d66d4UL)]
         public class @union2 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xafc5fd419f0d66d4UL;
             public enum WHICH : ushort
             {
                 U2f0s1 = 0,
@@ -2865,8 +2884,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa2fb022ec7f30053UL)]
         public class @union3 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa2fb022ec7f30053UL;
             public enum WHICH : ushort
             {
                 U3f0s1 = 0,
@@ -3079,8 +3100,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x9e2e784c915329b6UL)]
     public class TestUnnamedUnion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x9e2e784c915329b6UL;
         public enum WHICH : ushort
         {
             Foo = 0,
@@ -3258,8 +3281,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x89a9494f1b900f22UL)]
     public class TestUnionInUnion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x89a9494f1b900f22UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -3314,8 +3339,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xd005f6c63707670cUL)]
         public class @outer : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xd005f6c63707670cUL;
             public enum WHICH : ushort
             {
                 Inner = 0,
@@ -3444,8 +3471,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xff9ce111c6f8e5dbUL)]
             public class @inner : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xff9ce111c6f8e5dbUL;
                 public enum WHICH : ushort
                 {
                     Foo = 0,
@@ -3578,8 +3607,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xdc841556134c3103UL)]
     public class TestGroups : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xdc841556134c3103UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -3634,8 +3665,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xe22ae74ff9113268UL)]
         public class @groups : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xe22ae74ff9113268UL;
             public enum WHICH : ushort
             {
                 Foo = 0,
@@ -3789,8 +3822,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xf5fcba89c0c1196fUL)]
             public class @foo : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xf5fcba89c0c1196fUL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -3876,8 +3911,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xf0fa30304066a4b3UL)]
             public class @baz : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xf0fa30304066a4b3UL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -3963,8 +4000,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xb727c0d0091a001dUL)]
             public class @bar : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xb727c0d0091a001dUL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -4052,8 +4091,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xf77ed6f7454eec40UL)]
     public class TestInterleavedGroups : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xf77ed6f7454eec40UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -4122,8 +4163,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc7485a3516c7d3c8UL)]
         public class @group1 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc7485a3516c7d3c8UL;
             public enum WHICH : ushort
             {
                 Qux = 0,
@@ -4325,8 +4368,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xdb0afd413f4a313aUL)]
             public class @corge : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xdb0afd413f4a313aUL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -4428,8 +4473,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xcc85a335569990e9UL)]
         public class @group2 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xcc85a335569990e9UL;
             public enum WHICH : ushort
             {
                 Qux = 0,
@@ -4631,8 +4678,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xa017f0366827ee37UL)]
             public class @corge : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xa017f0366827ee37UL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -4735,8 +4784,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x94f7e0b103b4b718UL)]
     public class TestUnionDefaults : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x94f7e0b103b4b718UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -4854,8 +4905,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xd9f2b5941a343bcdUL)]
     public class TestNestedTypes : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xd9f2b5941a343bcdUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -4943,14 +4996,17 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xb651d2fba42056d4UL)]
         public enum NestedEnum : ushort
         {
             foo,
             bar
         }
 
+        [TypeId(0x82cd03a53b29d76bUL)]
         public class NestedStruct : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x82cd03a53b29d76bUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5023,6 +5079,7 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xcfa0d546993a3df3UL)]
             public enum NestedEnum : ushort
             {
                 baz,
@@ -5032,8 +5089,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xe78aac389e77b065UL)]
     public class TestUsing : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xe78aac389e77b065UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -5107,8 +5166,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xe41885c94393277eUL)]
     public class TestLists : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xe41885c94393277eUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -5299,8 +5360,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8412c03b75b2cfeeUL)]
         public class Struct0 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8412c03b75b2cfeeUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5342,8 +5405,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xe0fe5870b141ad69UL)]
         public class Struct1 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xe0fe5870b141ad69UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5400,8 +5465,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa6411a353090145bUL)]
         public class Struct8 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa6411a353090145bUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5458,8 +5525,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa8abf7a82928986cUL)]
         public class Struct16 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa8abf7a82928986cUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5516,8 +5585,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xad7beedc4ed30742UL)]
         public class Struct32 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xad7beedc4ed30742UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5574,8 +5645,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xef9a34f2ff7cc646UL)]
         public class Struct64 : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xef9a34f2ff7cc646UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5632,8 +5705,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc6abf1b0329e6227UL)]
         public class StructP : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc6abf1b0329e6227UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5690,8 +5765,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x943a234ca336b16aUL)]
         public class Struct0c : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x943a234ca336b16aUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5748,8 +5825,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8991bc0e74a594cdUL)]
         public class Struct1c : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8991bc0e74a594cdUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5821,8 +5900,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xed267416528c7a24UL)]
         public class Struct8c : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xed267416528c7a24UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5894,8 +5975,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9978837b037d58e6UL)]
         public class Struct16c : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9978837b037d58e6UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -5967,8 +6050,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xed5fa940f54a7904UL)]
         public class Struct32c : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xed5fa940f54a7904UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -6040,8 +6125,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xbc743778f2597c7dUL)]
         public class Struct64c : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xbc743778f2597c7dUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -6113,8 +6200,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc2e364a40182013dUL)]
         public class StructPc : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc2e364a40182013dUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -6187,8 +6276,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x92fc29a80f3ddd5cUL)]
     public class TestFieldZeroIsBit : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x92fc29a80f3ddd5cUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -6277,8 +6368,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xa851ad32cbc2ffeaUL)]
     public class TestListDefaults : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xa851ad32cbc2ffeaUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -6359,8 +6452,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xa76e3c9bb7fd56d3UL)]
     public class TestLateUnion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xa76e3c9bb7fd56d3UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -6474,8 +6569,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x807280a2901aa079UL)]
         public class @theUnion : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x807280a2901aa079UL;
             public enum WHICH : ushort
             {
                 Qux = 0,
@@ -6633,8 +6730,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc1973984dee98e3aUL)]
         public class @anotherUnion : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc1973984dee98e3aUL;
             public enum WHICH : ushort
             {
                 Qux = 0,
@@ -6793,8 +6892,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x95b30dd14e01dda8UL)]
     public class TestOldVersion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x95b30dd14e01dda8UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -6881,8 +6982,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x8ed75a7469f04ce3UL)]
     public class TestNewVersion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x8ed75a7469f04ce3UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -7001,8 +7104,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xbd5fe16e5170c492UL)]
     public class TestOldUnionVersion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xbd5fe16e5170c492UL;
         public enum WHICH : ushort
         {
             A = 0,
@@ -7115,8 +7220,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xc7e4c513a975492bUL)]
     public class TestNewUnionVersion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xc7e4c513a975492bUL;
         public enum WHICH : ushort
         {
             A = 0,
@@ -7246,8 +7353,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x86232c1de4513e84UL)]
         public class @a : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x86232c1de4513e84UL;
             public enum WHICH : ushort
             {
                 A0 = 0,
@@ -7360,8 +7469,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xfaf781ef89a00e39UL)]
     public class TestStructUnion : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xfaf781ef89a00e39UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -7416,8 +7527,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x992edc677bef5a3cUL)]
         public class @un : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x992edc677bef5a3cUL;
             public enum WHICH : ushort
             {
                 Struct = 0,
@@ -7548,8 +7661,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9daec9823f171085UL)]
         public class SomeStruct : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9daec9823f171085UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -7622,8 +7737,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xdec497819d097c3cUL)]
     public class TestPrintInlineStructs : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xdec497819d097c3cUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -7694,8 +7811,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8e4936003708dac2UL)]
         public class InlineStruct : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8e4936003708dac2UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -7768,8 +7887,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x91afd4a864dbb030UL)]
     public class TestWholeFloatDefault : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x91afd4a864dbb030UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -7843,8 +7964,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x9d5b8cd8de9922ebUL)]
     public class TestGenerics<TFoo, TBar> : ICapnpSerializable where TFoo : class where TBar : class
     {
+        public const UInt64 TypeId = 0x9d5b8cd8de9922ebUL;
         public enum WHICH : ushort
         {
             Uv = 0,
@@ -8001,8 +8124,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xb46a779beaf3384eUL)]
         public class @ug : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb46a779beaf3384eUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -8058,8 +8183,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xf6a841117e19ac73UL)]
         public class Inner : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xf6a841117e19ac73UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -8131,8 +8258,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa9ab42b118d6d435UL)]
         public class Inner2<TBaz> : ICapnpSerializable where TBaz : class
         {
+            public const UInt64 TypeId = 0xa9ab42b118d6d435UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -8233,8 +8362,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xb6a0829c762b06f3UL)]
             public class DeepNest<TQux> : ICapnpSerializable where TQux : class
             {
+                public const UInt64 TypeId = 0xb6a0829c762b06f3UL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -8335,7 +8466,7 @@ namespace Capnproto_test.Capnp.Test
                     }
                 }
 
-                [Proxy(typeof(DeepNestInterfaceProxy<>)), Skeleton(typeof(DeepNestInterfaceSkeleton<>))]
+                [TypeId(0x8839ed86c9794287UL), Proxy(typeof(DeepNestInterfaceProxy<>)), Skeleton(typeof(DeepNestInterfaceSkeleton<>))]
                 public interface IDeepNestInterface<TQuux> : IDisposable
                 {
                     Task Call(CancellationToken cancellationToken_ = default);
@@ -8374,8 +8505,10 @@ namespace Capnproto_test.Capnp.Test
                 public static class DeepNestInterface<TQuux>
                     where TQuux : class
                 {
+                    [TypeId(0xb84eecc799437049UL)]
                     public class Params_call : ICapnpSerializable
                     {
+                        public const UInt64 TypeId = 0xb84eecc799437049UL;
                         void ICapnpSerializable.Deserialize(DeserializerState arg_)
                         {
                             var reader = READER.create(arg_);
@@ -8417,8 +8550,10 @@ namespace Capnproto_test.Capnp.Test
                         }
                     }
 
+                    [TypeId(0xe080f0fc54614f6fUL)]
                     public class Result_call : ICapnpSerializable
                     {
+                        public const UInt64 TypeId = 0xe080f0fc54614f6fUL;
                         void ICapnpSerializable.Deserialize(DeserializerState arg_)
                         {
                             var reader = READER.create(arg_);
@@ -8463,7 +8598,7 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
-        [Proxy(typeof(InterfaceProxy<>)), Skeleton(typeof(InterfaceSkeleton<>))]
+        [TypeId(0xc9e749e8dd54da5cUL), Proxy(typeof(InterfaceProxy<>)), Skeleton(typeof(InterfaceSkeleton<>))]
         public interface IInterface<TQux> : IDisposable
         {
             Task<(TQux, Capnproto_test.Capnp.Test.TestGenerics<Capnproto_test.Capnp.Test.TestAllTypes, Capnproto_test.Capnp.Test.TestAnyPointer>)> Call(Capnproto_test.Capnp.Test.TestGenerics<TFoo, TBar>.Inner2<string> arg_, CancellationToken cancellationToken_ = default);
@@ -8510,8 +8645,10 @@ namespace Capnproto_test.Capnp.Test
         public static class Interface<TQux>
             where TQux : class
         {
+            [TypeId(0xa5b46224e33581adUL)]
             public class Result_call : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xa5b46224e33581adUL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -8584,8 +8721,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8e656edfb45ba6cfUL)]
         public class UseAliases : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8e656edfb45ba6cfUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -8718,8 +8857,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xa9b2b1f52dde845dUL)]
     public class TestGenericsWrapper<TFoo, TBar> : ICapnpSerializable where TFoo : class where TBar : class
     {
+        public const UInt64 TypeId = 0xa9b2b1f52dde845dUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -8776,8 +8917,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xf28f83667a557a04UL)]
     public class TestGenericsWrapper2 : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xf28f83667a557a04UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -8834,7 +8977,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestImplicitMethodParamsProxy)), Skeleton(typeof(TestImplicitMethodParamsSkeleton))]
+    [TypeId(0x8b9717a3f8d85a9aUL), Proxy(typeof(TestImplicitMethodParamsProxy)), Skeleton(typeof(TestImplicitMethodParamsSkeleton))]
     public interface ITestImplicitMethodParams : IDisposable
     {
         Task<Capnproto_test.Capnp.Test.TestGenerics<TT, TU>> Call<TT, TU>(TT foo, TU bar, CancellationToken cancellationToken_ = default)
@@ -8885,8 +9028,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestImplicitMethodParams
     {
+        [TypeId(0xf83f8caf54bdc486UL)]
         public class Params_call<TT, TU> : ICapnpSerializable where TT : class where TU : class
         {
+            public const UInt64 TypeId = 0xf83f8caf54bdc486UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -8959,7 +9104,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestImplicitMethodParamsInGenericProxy<>)), Skeleton(typeof(TestImplicitMethodParamsInGenericSkeleton<>))]
+    [TypeId(0xdf9ccdeb81a704c9UL), Proxy(typeof(TestImplicitMethodParamsInGenericProxy<>)), Skeleton(typeof(TestImplicitMethodParamsInGenericSkeleton<>))]
     public interface ITestImplicitMethodParamsInGeneric<TV> : IDisposable
     {
         Task<Capnproto_test.Capnp.Test.TestGenerics<TT, TU>> Call<TT, TU>(TT foo, TU bar, CancellationToken cancellationToken_ = default)
@@ -9011,8 +9156,10 @@ namespace Capnproto_test.Capnp.Test
     public static class TestImplicitMethodParamsInGeneric<TV>
         where TV : class
     {
+        [TypeId(0x9aab8e25c808d71eUL)]
         public class Params_call<TT, TU> : ICapnpSerializable where TT : class where TU : class
         {
+            public const UInt64 TypeId = 0x9aab8e25c808d71eUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -9085,8 +9232,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xa54870440e919063UL)]
     public class TestGenericsUnion<TFoo, TBar> : ICapnpSerializable where TFoo : class where TBar : class
     {
+        public const UInt64 TypeId = 0xa54870440e919063UL;
         public enum WHICH : ushort
         {
             Foo = 0,
@@ -9218,8 +9367,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x9427b2a71030338fUL)]
     public class TestUseGenerics : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x9427b2a71030338fUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -9667,8 +9818,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xc5598844441096dcUL)]
     public class TestEmptyStruct : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xc5598844441096dcUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -9710,8 +9863,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xabed745cd8c92095UL)]
     public class TestConstants : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xabed745cd8c92095UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -9753,8 +9908,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xddc280dbee9c99b3UL)]
     public class TestAnyPointerConstants : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xddc280dbee9c99b3UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -9856,7 +10013,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestInterfaceProxy)), Skeleton(typeof(TestInterfaceSkeleton))]
+    [TypeId(0x88eb12a0e0af92b2UL), Proxy(typeof(TestInterfaceProxy)), Skeleton(typeof(TestInterfaceSkeleton))]
     public interface ITestInterface : IDisposable
     {
         Task<string> Foo(uint i, bool j, CancellationToken cancellationToken_ = default);
@@ -9940,8 +10097,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestInterface
     {
+        [TypeId(0xb874edc0d559b391UL)]
         public class Params_foo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb874edc0d559b391UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10013,8 +10172,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xb04fcaddab714ba4UL)]
         public class Result_foo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb04fcaddab714ba4UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10071,8 +10232,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xd044893357b42568UL)]
         public class Params_bar : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xd044893357b42568UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10114,8 +10277,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9bf141df4247d52fUL)]
         public class Result_bar : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9bf141df4247d52fUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10157,8 +10322,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xd9ac8abb2a91cfbcUL)]
         public class Params_baz : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xd9ac8abb2a91cfbcUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10215,8 +10382,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9b99d14f2f375b2dUL)]
         public class Result_baz : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9b99d14f2f375b2dUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10259,7 +10428,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestExtendsProxy)), Skeleton(typeof(TestExtendsSkeleton))]
+    [TypeId(0xe4e9bac98670b748UL), Proxy(typeof(TestExtendsProxy)), Skeleton(typeof(TestExtendsSkeleton))]
     public interface ITestExtends : Capnproto_test.Capnp.Test.ITestInterface
     {
         Task Qux(CancellationToken cancellationToken_ = default);
@@ -10371,8 +10540,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestExtends
     {
+        [TypeId(0x83a4bc5471363f17UL)]
         public class Params_qux : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x83a4bc5471363f17UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10414,8 +10585,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8e4b3d1a3e2753ddUL)]
         public class Result_qux : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8e4b3d1a3e2753ddUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10457,8 +10630,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xacf67532a7e7bad9UL)]
         public class Result_corge : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xacf67532a7e7bad9UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10500,8 +10675,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xf3b834e851ea8af6UL)]
         public class Params_grault : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xf3b834e851ea8af6UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10544,7 +10721,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestExtends2Proxy)), Skeleton(typeof(TestExtends2Skeleton))]
+    [TypeId(0x98d7e0ef61488783UL), Proxy(typeof(TestExtends2Proxy)), Skeleton(typeof(TestExtends2Skeleton))]
     public interface ITestExtends2 : Capnproto_test.Capnp.Test.ITestExtends
     {
     }
@@ -10626,7 +10803,7 @@ namespace Capnproto_test.Capnp.Test
         public override ulong InterfaceId => 11013518732491786115UL;
     }
 
-    [Proxy(typeof(TestPipelineProxy)), Skeleton(typeof(TestPipelineSkeleton))]
+    [TypeId(0xa5a404caa61d4cd0UL), Proxy(typeof(TestPipelineProxy)), Skeleton(typeof(TestPipelineSkeleton))]
     public interface ITestPipeline : IDisposable
     {
         Task<(string, Capnproto_test.Capnp.Test.TestPipeline.Box)> GetCap(uint n, Capnproto_test.Capnp.Test.ITestInterface inCap, CancellationToken cancellationToken_ = default);
@@ -10740,8 +10917,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestPipeline
     {
+        [TypeId(0xb0b29e51db0e26b1UL)]
         public class Box : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb0b29e51db0e26b1UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10798,8 +10977,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9442ad5a1d2c8acbUL)]
         public class AnyBox : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9442ad5a1d2c8acbUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10856,8 +11037,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc7e8df5096257034UL)]
         public class Params_getCap : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc7e8df5096257034UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -10929,8 +11112,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xb2442a9e0ba28fdfUL)]
         public class Result_getCap : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb2442a9e0ba28fdfUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11002,8 +11187,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa604ee63cf37819fUL)]
         public class Params_testPointers : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa604ee63cf37819fUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11090,8 +11277,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8eda54756c6070d6UL)]
         public class Result_testPointers : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8eda54756c6070d6UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11133,8 +11322,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xf8e36b53ab093d4eUL)]
         public class Params_getAnyCap : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xf8e36b53ab093d4eUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11206,8 +11397,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xbf44b4c94c26ef79UL)]
         public class Result_getAnyCap : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xbf44b4c94c26ef79UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11280,7 +11473,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestCallOrderProxy)), Skeleton(typeof(TestCallOrderSkeleton))]
+    [TypeId(0xa0e77035bdff0051UL), Proxy(typeof(TestCallOrderProxy)), Skeleton(typeof(TestCallOrderSkeleton))]
     public interface ITestCallOrder : IDisposable
     {
         Task<uint> GetCallSequence(uint expected, CancellationToken cancellationToken_ = default);
@@ -11325,8 +11518,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestCallOrder
     {
+        [TypeId(0x8f1e8cd56ceb74dcUL)]
         public class Params_getCallSequence : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8f1e8cd56ceb74dcUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11383,8 +11578,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xdedbb6bf3810eab7UL)]
         public class Result_getCallSequence : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xdedbb6bf3810eab7UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11442,7 +11639,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestTailCalleeProxy)), Skeleton(typeof(TestTailCalleeSkeleton))]
+    [TypeId(0xddd699207eb8e23bUL), Proxy(typeof(TestTailCalleeProxy)), Skeleton(typeof(TestTailCalleeSkeleton))]
     public interface ITestTailCallee : IDisposable
     {
         Task<Capnproto_test.Capnp.Test.TestTailCallee.TailResult> Foo(int i, string t, CancellationToken cancellationToken_ = default);
@@ -11499,8 +11696,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestTailCallee
     {
+        [TypeId(0xa9ed2e5a9fd53d19UL)]
         public class TailResult : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa9ed2e5a9fd53d19UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11587,8 +11786,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc5e1efc325614957UL)]
         public class Params_foo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc5e1efc325614957UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11661,7 +11862,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestTailCallerProxy)), Skeleton(typeof(TestTailCallerSkeleton))]
+    [TypeId(0x870bf40110ce3035UL), Proxy(typeof(TestTailCallerProxy)), Skeleton(typeof(TestTailCallerSkeleton))]
     public interface ITestTailCaller : IDisposable
     {
         Task<Capnproto_test.Capnp.Test.TestTailCallee.TailResult> Foo(int i, Capnproto_test.Capnp.Test.ITestTailCallee callee, CancellationToken cancellationToken_ = default);
@@ -11713,8 +11914,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestTailCaller
     {
+        [TypeId(0xb07a279515dc8ac5UL)]
         public class Params_foo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb07a279515dc8ac5UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -11787,7 +11990,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestHandleProxy)), Skeleton(typeof(TestHandleSkeleton))]
+    [TypeId(0xa38e5efe41e53a15UL), Proxy(typeof(TestHandleProxy)), Skeleton(typeof(TestHandleSkeleton))]
     public interface ITestHandle : IDisposable
     {
     }
@@ -11806,7 +12009,7 @@ namespace Capnproto_test.Capnp.Test
         public override ulong InterfaceId => 11785461720995412501UL;
     }
 
-    [Proxy(typeof(TestMoreStuffProxy)), Skeleton(typeof(TestMoreStuffSkeleton))]
+    [TypeId(0xddc70bf9784133cfUL), Proxy(typeof(TestMoreStuffProxy)), Skeleton(typeof(TestMoreStuffSkeleton))]
     public interface ITestMoreStuff : Capnproto_test.Capnp.Test.ITestCallOrder
     {
         Task<string> CallFoo(Capnproto_test.Capnp.Test.ITestInterface cap, CancellationToken cancellationToken_ = default);
@@ -12198,8 +12401,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestMoreStuff
     {
+        [TypeId(0x931ba418da60f6e4UL)]
         public class Params_callFoo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x931ba418da60f6e4UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12256,8 +12461,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9a28970beccecdd0UL)]
         public class Result_callFoo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9a28970beccecdd0UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12314,8 +12521,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xfabc700c2ebe6378UL)]
         public class Params_callFooWhenResolved : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xfabc700c2ebe6378UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12372,8 +12581,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa54ce1e9aa822f90UL)]
         public class Result_callFooWhenResolved : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa54ce1e9aa822f90UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12430,8 +12641,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x94fe60465c95182bUL)]
         public class Params_neverReturn : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x94fe60465c95182bUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12488,8 +12701,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xdef4e5fa6999c5dcUL)]
         public class Result_neverReturn : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xdef4e5fa6999c5dcUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12546,8 +12761,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xfe7c8fbb769d8e58UL)]
         public class Params_hold : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xfe7c8fbb769d8e58UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12604,8 +12821,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xf839fb1374d003c9UL)]
         public class Result_hold : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xf839fb1374d003c9UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12647,8 +12866,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xf8c5e5ef1edf83beUL)]
         public class Params_callHeld : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xf8c5e5ef1edf83beUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12690,8 +12911,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xe59935f160ac7578UL)]
         public class Result_callHeld : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xe59935f160ac7578UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12748,8 +12971,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xfeffc025fce317e3UL)]
         public class Params_getHeld : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xfeffc025fce317e3UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12791,8 +13016,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xef4e146185af67ceUL)]
         public class Result_getHeld : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xef4e146185af67ceUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12849,8 +13076,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc07526f7e2e533b9UL)]
         public class Params_echo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc07526f7e2e533b9UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12907,8 +13136,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa6224536593d5b92UL)]
         public class Result_echo : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa6224536593d5b92UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -12965,8 +13196,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa1cc32d87f3edeb1UL)]
         public class Params_expectCancel : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa1cc32d87f3edeb1UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13023,8 +13256,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8a3eba1758c0916eUL)]
         public class Result_expectCancel : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8a3eba1758c0916eUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13066,8 +13301,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x99160a25fa50fbf1UL)]
         public class Params_methodWithDefaults : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x99160a25fa50fbf1UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13156,8 +13393,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9c7e066f845a6c56UL)]
         public class Result_methodWithDefaults : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9c7e066f845a6c56UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13230,8 +13469,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xead024a301a092a1UL)]
         public class Params_getHandle : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xead024a301a092a1UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13273,8 +13514,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc3490d75420a1fe8UL)]
         public class Result_getHandle : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc3490d75420a1fe8UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13331,8 +13574,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xd8493f0e175d61f2UL)]
         public class Params_getNull : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xd8493f0e175d61f2UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13374,8 +13619,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xe6955d8ef1023671UL)]
         public class Result_getNull : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xe6955d8ef1023671UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13432,8 +13679,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x805df436f55dd07aUL)]
         public class Params_getEnormousString : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x805df436f55dd07aUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13475,8 +13724,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x860e7512dc3925b0UL)]
         public class Result_getEnormousString : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x860e7512dc3925b0UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13533,8 +13784,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xfb92899aeb0ee74fUL)]
         public class Params_methodWithNullDefault : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xfb92899aeb0ee74fUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13606,8 +13859,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8467348247305cf7UL)]
         public class Result_methodWithNullDefault : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8467348247305cf7UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -13650,7 +13905,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestMembraneProxy)), Skeleton(typeof(TestMembraneSkeleton))]
+    [TypeId(0xc07d8dcd80a69c0cUL), Proxy(typeof(TestMembraneProxy)), Skeleton(typeof(TestMembraneSkeleton))]
     public interface ITestMembrane : IDisposable
     {
         Task<Capnproto_test.Capnp.Test.TestMembrane.IThing> MakeThing(CancellationToken cancellationToken_ = default);
@@ -13806,7 +14061,7 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestMembrane
     {
-        [Proxy(typeof(ThingProxy)), Skeleton(typeof(ThingSkeleton))]
+        [TypeId(0x9352e4e41f173917UL), Proxy(typeof(ThingProxy)), Skeleton(typeof(ThingSkeleton))]
         public interface IThing : IDisposable
         {
             Task<Capnproto_test.Capnp.Test.TestMembrane.Result> PassThrough(CancellationToken cancellationToken_ = default);
@@ -13873,8 +14128,10 @@ namespace Capnproto_test.Capnp.Test
 
         public static class Thing
         {
+            [TypeId(0xff9bdcd05085d786UL)]
             public class Params_passThrough : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xff9bdcd05085d786UL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -13916,8 +14173,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xee94bed3615ee745UL)]
             public class Params_intercept : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xee94bed3615ee745UL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -13960,8 +14219,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xb0c6163faf291965UL)]
         public class Result : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb0c6163faf291965UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14018,8 +14279,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xd8ac2acc3ece6556UL)]
         public class Params_makeThing : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xd8ac2acc3ece6556UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14061,8 +14324,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xe5d4904814ccbf29UL)]
         public class Result_makeThing : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xe5d4904814ccbf29UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14119,8 +14384,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x945d9f634a6a29daUL)]
         public class Params_callPassThrough : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x945d9f634a6a29daUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14192,8 +14459,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8749aac3375c5c71UL)]
         public class Params_callIntercept : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8749aac3375c5c71UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14265,8 +14534,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x869a1b7ab34b42c9UL)]
         public class Params_loopback : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x869a1b7ab34b42c9UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14323,8 +14594,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xecd19398fd88ab5cUL)]
         public class Result_loopback : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xecd19398fd88ab5cUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14381,8 +14654,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x8f6bb30cc62917ffUL)]
         public class Params_waitForever : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8f6bb30cc62917ffUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14424,8 +14699,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc343a4907280be01UL)]
         public class Result_waitForever : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc343a4907280be01UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14468,8 +14745,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x949449ad7c11fa5cUL)]
     public class TestContainMembrane : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x949449ad7c11fa5cUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -14541,8 +14820,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xdd2b66a791a279f0UL)]
     public class TestTransferCap : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xdd2b66a791a279f0UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -14598,8 +14879,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc7263e8f88844abcUL)]
         public class Element : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc7263e8f88844abcUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14672,7 +14955,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestKeywordMethodsProxy)), Skeleton(typeof(TestKeywordMethodsSkeleton))]
+    [TypeId(0x9ae342d394247cfcUL), Proxy(typeof(TestKeywordMethodsProxy)), Skeleton(typeof(TestKeywordMethodsSkeleton))]
     public interface ITestKeywordMethods : IDisposable
     {
         Task Delete(CancellationToken cancellationToken_ = default);
@@ -14767,8 +15050,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestKeywordMethods
     {
+        [TypeId(0xca3a89cdeb6bd6b7UL)]
         public class Params_delete : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xca3a89cdeb6bd6b7UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14810,8 +15095,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xeeb5843598307592UL)]
         public class Result_delete : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xeeb5843598307592UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14853,8 +15140,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x9cf5a8313c5db036UL)]
         public class Params_class : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x9cf5a8313c5db036UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14896,8 +15185,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc0253868ac12e7d8UL)]
         public class Result_class : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc0253868ac12e7d8UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14939,8 +15230,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xa4a08763833c7757UL)]
         public class Params_void : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xa4a08763833c7757UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -14982,8 +15275,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xde82773089c0aeabUL)]
         public class Result_void : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xde82773089c0aeabUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -15025,8 +15320,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x99817360625e8ca3UL)]
         public class Params_return : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x99817360625e8ca3UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -15068,8 +15365,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xb70872e07eaa992fUL)]
         public class Result_return : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xb70872e07eaa992fUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -15112,7 +15411,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestAuthenticatedBootstrapProxy<>)), Skeleton(typeof(TestAuthenticatedBootstrapSkeleton<>))]
+    [TypeId(0xea72cc77253798cdUL), Proxy(typeof(TestAuthenticatedBootstrapProxy<>)), Skeleton(typeof(TestAuthenticatedBootstrapSkeleton<>))]
     public interface ITestAuthenticatedBootstrap<TVatId> : IDisposable
     {
         Task<TVatId> GetCallerId(CancellationToken cancellationToken_ = default);
@@ -15161,8 +15460,10 @@ namespace Capnproto_test.Capnp.Test
     public static class TestAuthenticatedBootstrap<TVatId>
         where TVatId : class
     {
+        [TypeId(0x8ec30e2451f1cffeUL)]
         public class Params_getCallerId : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x8ec30e2451f1cffeUL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -15204,8 +15505,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xc71cf776034a3e67UL)]
         public class Result_getCallerId : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc71cf776034a3e67UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -15263,8 +15566,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xceba982cb629f6c2UL)]
     public class TestSturdyRef : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xceba982cb629f6c2UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15336,8 +15641,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xe02d3bbe1010e342UL)]
     public class TestSturdyRefHostId : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xe02d3bbe1010e342UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15394,8 +15701,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xaeb2ad168e2f5697UL)]
     public class TestSturdyRefObjectId : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xaeb2ad168e2f5697UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15451,6 +15760,7 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xef428f2f67c4d439UL)]
         public enum Tag : ushort
         {
             testInterface,
@@ -15462,8 +15772,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0x9e5c574772b1d462UL)]
     public class TestProvisionId : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0x9e5c574772b1d462UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15505,8 +15817,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xea2fb7dca9cdbdeaUL)]
     public class TestRecipientId : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xea2fb7dca9cdbdeaUL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15548,8 +15862,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xa805157b98b65469UL)]
     public class TestThirdPartyCapId : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xa805157b98b65469UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15591,8 +15907,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xf4c58a8ebcd0f600UL)]
     public class TestJoinResult : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xf4c58a8ebcd0f600UL;
         void ICapnpSerializable.Deserialize(DeserializerState arg_)
         {
             var reader = READER.create(arg_);
@@ -15634,8 +15952,10 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
+    [TypeId(0xd1fd8e9caf2a5d58UL)]
     public class TestNameAnnotation : ICapnpSerializable
     {
+        public const UInt64 TypeId = 0xd1fd8e9caf2a5d58UL;
         public enum WHICH : ushort
         {
             BadFieldName = 0,
@@ -15796,8 +16116,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0x89d9d1626b34017cUL)]
         public class @badlyNamedUnion : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0x89d9d1626b34017cUL;
             public enum WHICH : ushort
             {
                 BadlyNamedGroup = 0,
@@ -15926,8 +16248,10 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xc3594bce5b24b722UL)]
             public class @badlyNamedGroup : ICapnpSerializable
             {
+                public const UInt64 TypeId = 0xc3594bce5b24b722UL;
                 void ICapnpSerializable.Deserialize(DeserializerState arg_)
                 {
                     var reader = READER.create(arg_);
@@ -15969,6 +16293,7 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xf610d1deb4c9e84aUL)]
         public enum BadlyNamedEnum : ushort
         {
             foo,
@@ -15976,8 +16301,10 @@ namespace Capnproto_test.Capnp.Test
             baz
         }
 
+        [TypeId(0xbe406b6341d52284UL)]
         public class NestedStruct : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xbe406b6341d52284UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -16048,6 +16375,7 @@ namespace Capnproto_test.Capnp.Test
                 }
             }
 
+            [TypeId(0xf6cb3f9c7a4322e0UL)]
             public enum DeeplyNestedEnum : ushort
             {
                 quux,
@@ -16057,7 +16385,7 @@ namespace Capnproto_test.Capnp.Test
         }
     }
 
-    [Proxy(typeof(TestNameAnnotationInterfaceProxy)), Skeleton(typeof(TestNameAnnotationInterfaceSkeleton))]
+    [TypeId(0xd112a69d31ed918bUL), Proxy(typeof(TestNameAnnotationInterfaceProxy)), Skeleton(typeof(TestNameAnnotationInterfaceSkeleton))]
     public interface ITestNameAnnotationInterface : IDisposable
     {
         Task BadlyNamedMethod(byte badlyNamedParam, CancellationToken cancellationToken_ = default);
@@ -16096,8 +16424,10 @@ namespace Capnproto_test.Capnp.Test
 
     public static class TestNameAnnotationInterface
     {
+        [TypeId(0xc12efc3b075adfe9UL)]
         public class Params_badlyNamedMethod : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xc12efc3b075adfe9UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
@@ -16154,8 +16484,10 @@ namespace Capnproto_test.Capnp.Test
             }
         }
 
+        [TypeId(0xdcc3cdb4b28f6c86UL)]
         public class Result_badlyNamedMethod : ICapnpSerializable
         {
+            public const UInt64 TypeId = 0xdcc3cdb4b28f6c86UL;
             void ICapnpSerializable.Deserialize(DeserializerState arg_)
             {
                 var reader = READER.create(arg_);
diff --git a/capnpc-csharp/Generator/CodeGenerator.cs b/capnpc-csharp/Generator/CodeGenerator.cs
index e401b3a..d5e41c7 100644
--- a/capnpc-csharp/Generator/CodeGenerator.cs
+++ b/capnpc-csharp/Generator/CodeGenerator.cs
@@ -71,6 +71,9 @@
                     .AddConstraintClauses(MakeTypeParameterConstraints(def).ToArray());
             }
 
+            topDecl = topDecl.AddMembers(CommonSnippetGen.MakeTypeIdConst(def.Id, _names));
+            topDecl = topDecl.WithAttributeLists(CommonSnippetGen.MakeTypeIdAttributeLists(def.Id));
+
             if (def.UnionInfo != null)
             {
                 topDecl = topDecl.AddMembers(_commonGen.MakeUnionSelectorEnum(def));
diff --git a/capnpc-csharp/Generator/CommonSnippetGen.cs b/capnpc-csharp/Generator/CommonSnippetGen.cs
index 2e1797d..e2058a6 100644
--- a/capnpc-csharp/Generator/CommonSnippetGen.cs
+++ b/capnpc-csharp/Generator/CommonSnippetGen.cs
@@ -52,6 +52,7 @@ namespace CapnpC.Generator
         public EnumDeclarationSyntax MakeEnum(TypeDefinition def)
         {
             var decl = EnumDeclaration(def.Name)
+                .WithAttributeLists(MakeTypeIdAttributeLists(def.Id))
                 .AddModifiers(Public)
                 .AddBaseListTypes(SimpleBaseType(Type<ushort>()));
 
@@ -89,5 +90,38 @@ namespace CapnpC.Generator
             }
         }
 
+        static LiteralExpressionSyntax HexLiteral(ulong id) =>
+            LiteralExpression(
+                SyntaxKind.NumericLiteralExpression,
+                Literal($"0x{id:x}UL", id));
+
+        public static FieldDeclarationSyntax MakeTypeIdConst(ulong id, GenNames names) =>
+            FieldDeclaration(
+                VariableDeclaration(
+                    IdentifierName("UInt64"))
+                .WithVariables(
+                    SingletonSeparatedList<VariableDeclaratorSyntax>(
+                        VariableDeclarator(names.TypeIdField.Identifier)
+                        .WithInitializer(
+                            EqualsValueClause(HexLiteral(id))))))
+                .WithModifiers(
+                    TokenList(
+                        new[]{
+                            Token(SyntaxKind.PublicKeyword),
+                            Token(SyntaxKind.ConstKeyword)}));
+
+        public static AttributeSyntax MakeTypeIdAttribute(ulong id) =>
+            Attribute(
+                IdentifierName("TypeId"))
+            .WithArgumentList(
+                AttributeArgumentList(
+                    SingletonSeparatedList<AttributeArgumentSyntax>(
+                        AttributeArgument(HexLiteral(id)))));
+
+        public static SyntaxList<AttributeListSyntax> MakeTypeIdAttributeLists(ulong id) =>
+            SingletonList<AttributeListSyntax>(
+                AttributeList(
+                    SingletonSeparatedList<AttributeSyntax>(
+                        CommonSnippetGen.MakeTypeIdAttribute(id))));
     }
 }
diff --git a/capnpc-csharp/Generator/GenNames.cs b/capnpc-csharp/Generator/GenNames.cs
index f842413..e4620d0 100644
--- a/capnpc-csharp/Generator/GenNames.cs
+++ b/capnpc-csharp/Generator/GenNames.cs
@@ -63,6 +63,7 @@ namespace CapnpC.Generator
         public string MemberAccessPathNameFormat { get; }
         public Name TaskParameter { get; }
         public Name EagerMethod { get; }
+        public Name TypeIdField { get; }
 
         public GenNames(GeneratorOptions options)
         {
@@ -98,6 +99,7 @@ namespace CapnpC.Generator
             MemberAccessPathNameFormat = options.MemberAccessPathNameFormat;
             TaskParameter = new Name(options.TaskParameterName);
             EagerMethod = new Name(options.EagerMethodName);
+            TypeIdField = new Name(options.TypeIdFieldName);
         }
 
         public Name MakeTypeName(TypeDefinition def, NameUsage usage = NameUsage.Default)
diff --git a/capnpc-csharp/Generator/GeneratorOptions.cs b/capnpc-csharp/Generator/GeneratorOptions.cs
index 76faf93..58a0d80 100644
--- a/capnpc-csharp/Generator/GeneratorOptions.cs
+++ b/capnpc-csharp/Generator/GeneratorOptions.cs
@@ -38,5 +38,6 @@ namespace CapnpC.Generator
         public string MemberAccessPathNameFormat { get; set; } = "Path_{0}_{1}";
         public string TaskParameterName { get; set; } = "task";
         public string EagerMethodName { get; set; } = "Eager";
+        public string TypeIdFieldName { get; set; } = "TypeId";
     }
 }
diff --git a/capnpc-csharp/Generator/InterfaceSnippetGen.cs b/capnpc-csharp/Generator/InterfaceSnippetGen.cs
index f0adfaa..d6769f5 100644
--- a/capnpc-csharp/Generator/InterfaceSnippetGen.cs
+++ b/capnpc-csharp/Generator/InterfaceSnippetGen.cs
@@ -97,6 +97,7 @@ namespace CapnpC.Generator
                 .AddAttributeLists(
                     AttributeList()
                         .AddAttributes(
+                            CommonSnippetGen.MakeTypeIdAttribute(type.Id),
                             Attribute(IdentifierName("Proxy"))
                                 .AddArgumentListArguments(
                                     AttributeArgument(