diff --git a/src/Microsoft.ML.Tokenizers/Model/BPETokenizer.cs b/src/Microsoft.ML.Tokenizers/Model/BPETokenizer.cs
index 6b6ec7a234..405676c0de 100644
--- a/src/Microsoft.ML.Tokenizers/Model/BPETokenizer.cs
+++ b/src/Microsoft.ML.Tokenizers/Model/BPETokenizer.cs
@@ -757,11 +757,10 @@ public OperationStatus Decode(IEnumerable<int> ids, Span<char> destination, bool
         /// Read the given files to extract the vocab and merges
         internal static async ValueTask<(Dictionary<StringSpanOrdinalKey, int>?, Vec<(string, string)>)> ReadModelDataAsync(Stream vocab, Stream? merges, bool useAsync, CancellationToken cancellationToken = default)
         {
-            JsonSerializerOptions options = new() { Converters = { StringSpanOrdinalKeyConverter.Instance } };
+            Dictionary<StringSpanOrdinalKey, int>? dic = useAsync
+                                                         ? await JsonSerializer.DeserializeAsync(vocab, ModelSourceGenerationContext.Default.DictionaryStringSpanOrdinalKeyInt32, cancellationToken).ConfigureAwait(false)
+                                                         : JsonSerializer.Deserialize(vocab, ModelSourceGenerationContext.Default.DictionaryStringSpanOrdinalKeyInt32);
 
-            Dictionary<StringSpanOrdinalKey, int>? dic = useAsync ?
-                                                    await JsonSerializer.DeserializeAsync<Dictionary<StringSpanOrdinalKey, int>>(vocab, options, cancellationToken).ConfigureAwait(false) as Dictionary<StringSpanOrdinalKey, int> :
-                                                    JsonSerializer.Deserialize<Dictionary<StringSpanOrdinalKey, int>>(vocab, options) as Dictionary<StringSpanOrdinalKey, int>;
             var m = useAsync ?
                     await ConvertMergesToHashmapAsync(merges, useAsync, cancellationToken).ConfigureAwait(false) :
                     ConvertMergesToHashmapAsync(merges, useAsync).GetAwaiter().GetResult();
diff --git a/src/Microsoft.ML.Tokenizers/Model/CodeGenTokenizer.cs b/src/Microsoft.ML.Tokenizers/Model/CodeGenTokenizer.cs
index c1fd6bb1ca..a8b4577ea5 100644
--- a/src/Microsoft.ML.Tokenizers/Model/CodeGenTokenizer.cs
+++ b/src/Microsoft.ML.Tokenizers/Model/CodeGenTokenizer.cs
@@ -1764,11 +1764,10 @@ void TryMerge(int left, int right, ReadOnlySpan<char> textSpan)
 
         private static Dictionary<StringSpanOrdinalKey, (int, string)> GetVocabulary(Stream vocabularyStream)
         {
-            Dictionary<StringSpanOrdinalKey, (int, string)>? vocab;
+            Vocabulary? vocab;
             try
             {
-                JsonSerializerOptions options = new() { Converters = { StringSpanOrdinalKeyCustomConverter.Instance } };
-                vocab = JsonSerializer.Deserialize<Dictionary<StringSpanOrdinalKey, (int, string)>>(vocabularyStream, options) as Dictionary<StringSpanOrdinalKey, (int, string)>;
+                vocab = JsonSerializer.Deserialize(vocabularyStream, ModelSourceGenerationContext.Default.Vocabulary);
             }
             catch (Exception e)
             {
diff --git a/src/Microsoft.ML.Tokenizers/Model/EnglishRobertaTokenizer.cs b/src/Microsoft.ML.Tokenizers/Model/EnglishRobertaTokenizer.cs
index 85f921ff0f..4557508c73 100644
--- a/src/Microsoft.ML.Tokenizers/Model/EnglishRobertaTokenizer.cs
+++ b/src/Microsoft.ML.Tokenizers/Model/EnglishRobertaTokenizer.cs
@@ -169,8 +169,7 @@ private static Dictionary<StringSpanOrdinalKey, int> GetVocabulary(Stream vocabu
             Dictionary<StringSpanOrdinalKey, int>? vocab;
             try
             {
-                JsonSerializerOptions options = new() { Converters = { StringSpanOrdinalKeyConverter.Instance } };
-                vocab = JsonSerializer.Deserialize<Dictionary<StringSpanOrdinalKey, int>>(vocabularyStream, options) as Dictionary<StringSpanOrdinalKey, int>;
+                vocab = JsonSerializer.Deserialize(vocabularyStream, ModelSourceGenerationContext.Default.DictionaryStringSpanOrdinalKeyInt32);
             }
             catch (Exception e)
             {
diff --git a/src/Microsoft.ML.Tokenizers/Model/ModelSourceGenerationContext.cs b/src/Microsoft.ML.Tokenizers/Model/ModelSourceGenerationContext.cs
new file mode 100644
index 0000000000..e3075d92e5
--- /dev/null
+++ b/src/Microsoft.ML.Tokenizers/Model/ModelSourceGenerationContext.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace Microsoft.ML.Tokenizers;
+
+[JsonSerializable(typeof(Dictionary<StringSpanOrdinalKey, int>))]
+[JsonSerializable(typeof(Vocabulary))]
+internal partial class ModelSourceGenerationContext : JsonSerializerContext;
diff --git a/src/Microsoft.ML.Tokenizers/Utils/StringSpanOrdinalKey.cs b/src/Microsoft.ML.Tokenizers/Utils/StringSpanOrdinalKey.cs
index 69f8c31b85..0ae599381e 100644
--- a/src/Microsoft.ML.Tokenizers/Utils/StringSpanOrdinalKey.cs
+++ b/src/Microsoft.ML.Tokenizers/Utils/StringSpanOrdinalKey.cs
@@ -15,6 +15,7 @@ namespace Microsoft.ML.Tokenizers
     /// This should only be used with a Ptr/Length for querying. For storing in a dictionary, this should
     /// always be used with a string.
     /// </remarks>
+    [JsonConverter(typeof(StringSpanOrdinalKeyConverter))]
     internal readonly unsafe struct StringSpanOrdinalKey : IEquatable<StringSpanOrdinalKey>
     {
         public readonly char* Ptr;
@@ -124,12 +125,14 @@ internal void Set(string k, TValue v)
         }
     }
 
+    [JsonConverter(typeof(VocabularyConverter))]
+    internal sealed class Vocabulary : Dictionary<StringSpanOrdinalKey, (int, string)>;
+
     /// <summary>
     /// Custom JSON converter for <see cref="StringSpanOrdinalKey"/>.
     /// </summary>
     internal sealed class StringSpanOrdinalKeyConverter : JsonConverter<StringSpanOrdinalKey>
     {
-        public static StringSpanOrdinalKeyConverter Instance { get; } = new StringSpanOrdinalKeyConverter();
         public override StringSpanOrdinalKey ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) =>
             new StringSpanOrdinalKey(reader.GetString()!);
 
@@ -140,13 +143,11 @@ public override void WriteAsPropertyName(Utf8JsonWriter writer, StringSpanOrdina
         public override void Write(Utf8JsonWriter writer, StringSpanOrdinalKey value, JsonSerializerOptions options) => writer.WriteStringValue(value.Data!);
     }
 
-    internal class StringSpanOrdinalKeyCustomConverter : JsonConverter<Dictionary<StringSpanOrdinalKey, (int, string)>>
+    internal class VocabularyConverter : JsonConverter<Vocabulary>
     {
-        public static StringSpanOrdinalKeyCustomConverter Instance { get; } = new StringSpanOrdinalKeyCustomConverter();
-
-        public override Dictionary<StringSpanOrdinalKey, (int, string)> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        public override Vocabulary Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
-            var dictionary = new Dictionary<StringSpanOrdinalKey, (int, string)>();
+            var dictionary = new Vocabulary();
             while (reader.Read())
             {
                 if (reader.TokenType == JsonTokenType.EndObject)
@@ -165,7 +166,7 @@ internal class StringSpanOrdinalKeyCustomConverter : JsonConverter<Dictionary<St
             throw new JsonException("Invalid JSON.");
         }
 
-        public override void Write(Utf8JsonWriter writer, Dictionary<StringSpanOrdinalKey, (int, string)> value, JsonSerializerOptions options) => throw new NotImplementedException();
+        public override void Write(Utf8JsonWriter writer, Vocabulary value, JsonSerializerOptions options) => throw new NotImplementedException();
     }
 
     /// <summary>