diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/UtilitiesTests/TokenizerTests.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/UtilitiesTests/TokenizerTests.cs
new file mode 100644
index 000000000..4e417c13a
--- /dev/null
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/UtilitiesTests/TokenizerTests.cs
@@ -0,0 +1,26 @@
+using Microsoft.Teams.AI.AI.Tokenizers;
+
+namespace Microsoft.Teams.AI.Tests.UtilitiesTests
+{
+    public class TokenizerTests
+    {
+        public static IEnumerable<object[]> TokenizersObjects()
+        {
+            yield return new object[] { new GPTTokenizer() };
+            yield return new object[] { new GPTTokenizer("gpt-4") };
+        }
+
+
+        [Theory]
+        [MemberData(nameof(TokenizersObjects))]
+        public void ValidateResults(ITokenizer tokenizer)
+        {
+            string text = "Hello, World";
+            Assert.NotNull(tokenizer);
+            IReadOnlyList<int> tokens = tokenizer.Encode(text);
+
+            Assert.Equal(new int[] { 9906, 11, 4435 }, tokens);
+            Assert.Equal(text, tokenizer.Decode(tokens));
+        }
+    }
+}
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/DataSources/TextDataSource.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/DataSources/TextDataSource.cs
index 84f5a9827..0709d882e 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/DataSources/TextDataSource.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/DataSources/TextDataSource.cs
@@ -16,7 +16,7 @@ public class TextDataSource : IDataSource
         public string Name { get; }
 
         private readonly string _text;
-        private List<int> _tokens = new();
+        private IReadOnlyList<int> _tokens = new List<int>();
 
         /// <summary>
         /// Creates instance of `TextDataSource`
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/ActionAugmentationSection.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/ActionAugmentationSection.cs
index aceee66f1..64274532a 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/ActionAugmentationSection.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/ActionAugmentationSection.cs
@@ -18,7 +18,7 @@ public class ActionAugmentationSection : PromptSection
         public readonly Dictionary<string, ChatCompletionAction> Actions;
 
         private readonly string _text;
-        private List<int>? _tokens;
+        private IReadOnlyList<int>? _tokens;
 
         private class ActionMap
         {
@@ -64,7 +64,7 @@ public override async Task<RenderedPromptSection<List<ChatMessage>>> RenderAsMes
                 this._tokens = tokenizer.Encode(this._text);
             }
 
-            List<int> tokens = this._tokens;
+            IReadOnlyList<int> tokens = this._tokens;
             bool tooLong = false;
 
             if (this._tokens.Count > maxTokens)
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/GroupSection.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/GroupSection.cs
index 07d85d7bd..a94285f3b 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/GroupSection.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/GroupSection.cs
@@ -59,7 +59,7 @@ public override async Task<RenderedPromptSection<string>> RenderAsTextAsync(ITur
             // truncate
             if (this.Tokens > 1 && length > this.Tokens)
             {
-                List<int> encoded = tokenizer.Encode(text);
+                IReadOnlyList<int> encoded = tokenizer.Encode(text);
                 text = tokenizer.Decode(encoded.Take(this.Tokens).ToList());
                 length = this.Tokens;
             }
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/PromptSection.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/PromptSection.cs
index ecd9c5452..438010b5d 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/PromptSection.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Prompts/Sections/PromptSection.cs
@@ -124,7 +124,7 @@ public virtual async Task<RenderedPromptSection<string>> RenderAsTextAsync(ITurn
             // truncate
             if (this.Tokens > 1 && length > this.Tokens)
             {
-                List<int> encoded = tokenizer.Encode(text);
+                IReadOnlyList<int> encoded = tokenizer.Encode(text);
                 text = tokenizer.Decode(encoded.Take(this.Tokens).ToList());
                 length = this.Tokens;
             }
@@ -148,7 +148,7 @@ protected RenderedPromptSection<List<ChatMessage>> TruncateMessages(List<ChatMes
             foreach (ChatMessage message in messages)
             {
                 string text = this.GetMessageText(message);
-                List<int> encoded = tokenizer.Encode(text);
+                IReadOnlyList<int> encoded = tokenizer.Encode(text);
 
                 if (len + encoded.Count > budget)
                 {
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/GPTTokenizer.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/GPTTokenizer.cs
index 9f8eae27a..f24a07993 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/GPTTokenizer.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/GPTTokenizer.cs
@@ -1,4 +1,4 @@
-using SharpToken;
+using Microsoft.ML.Tokenizers;
 
 namespace Microsoft.Teams.AI.AI.Tokenizers
 {
@@ -7,52 +7,37 @@ namespace Microsoft.Teams.AI.AI.Tokenizers
     /// </summary>
     public class GPTTokenizer : ITokenizer
     {
-        private readonly GptEncoding _encoding;
+        private readonly Tokenizer _encoding;
 
         /// <summary>
-        /// Creates an instance of `GPTTokenizer` using the `cl100k_base` encoding by default
+        /// Creates an instance of `GPTTokenizer` using "gpt-4" model name by default which is using the `cl100k_base` encoding
         /// </summary>
-        public GPTTokenizer()
-        {
-            this._encoding = GptEncoding.GetEncoding("cl100k_base");
-        }
+        public GPTTokenizer() => _encoding = Tokenizer.CreateTiktokenForModel("gpt-4");
 
         /// <summary>
         /// Creates an instance of `GPTTokenizer`
         /// </summary>
         /// <param name="encoding">encoding to use</param>
-        public GPTTokenizer(GptEncoding encoding)
-        {
-            this._encoding = encoding;
-        }
+        public GPTTokenizer(Tokenizer encoding) => this._encoding = encoding;
 
         /// <summary>
         /// Creates an instance of `GPTTokenizer`
         /// </summary>
         /// <param name="model">model to encode/decode for</param>
-        public GPTTokenizer(string model)
-        {
-            this._encoding = GptEncoding.GetEncodingForModel(model);
-        }
+        public GPTTokenizer(string model) => this._encoding = Tokenizer.CreateTiktokenForModel(model);
 
         /// <summary>
         /// Encode
         /// </summary>
         /// <param name="text">text to encode</param>
         /// <returns>encoded tokens</returns>
-        public List<int> Encode(string text)
-        {
-            return this._encoding.Encode(text);
-        }
+        public IReadOnlyList<int> Encode(string text) => this._encoding.EncodeToIds(text);
 
         /// <summary>
         /// Decode
         /// </summary>
         /// <param name="tokens">tokens to decode</param>
         /// <returns>decoded text</returns>
-        public string Decode(List<int> tokens)
-        {
-            return this._encoding.Decode(tokens);
-        }
+        public string Decode(IEnumerable<int> tokens) => this._encoding.Decode(tokens)!;
     }
 }
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/ITokenizer.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/ITokenizer.cs
index abd29985b..a7a230cb6 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/ITokenizer.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/AI/Tokenizers/ITokenizer.cs
@@ -10,13 +10,13 @@ public interface ITokenizer
         /// </summary>
         /// <param name="text">text to encode</param>
         /// <returns>encoded bytes</returns>
-        public List<int> Encode(string text);
+        public IReadOnlyList<int> Encode(string text);
 
         /// <summary>
         /// Decode
         /// </summary>
         /// <param name="tokens">tokens to decode</param>
         /// <returns>decoded string</returns>
-        public string Decode(List<int> tokens);
+        public string Decode(IEnumerable<int> tokens);
     }
 }
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Authentication/OAuthAuthentication.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Authentication/OAuthAuthentication.cs
index 732101aac..70a48e087 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Authentication/OAuthAuthentication.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Authentication/OAuthAuthentication.cs
@@ -3,7 +3,6 @@
 using Microsoft.Teams.AI.Exceptions;
 using Microsoft.Teams.AI.State;
 using System.Runtime.CompilerServices;
-using System.Threading;
 
 [assembly: InternalsVisibleTo("Microsoft.Teams.AI.Tests")]
 namespace Microsoft.Teams.AI
@@ -133,6 +132,9 @@ public async Task SignOutUserAsync(ITurnContext context, TState state, Cancellat
             await UserTokenClientWrapper.SignoutUserAsync(context, _settings.ConnectionName, cancellationToken);
         }
 
+        /// <summary>
+        /// Get user token
+        /// </summary>
         protected virtual async Task<TokenResponse> GetUserToken(ITurnContext context, string connectionName, CancellationToken cancellationToken = default)
         {
             return await UserTokenClientWrapper.GetUserTokenAsync(context, connectionName, "", cancellationToken);
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Microsoft.Teams.AI.csproj b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Microsoft.Teams.AI.csproj
index 90551ddc2..8f5ec700a 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Microsoft.Teams.AI.csproj
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Microsoft.Teams.AI.csproj
@@ -45,7 +45,7 @@
     <PackageReference Include="Microsoft.Bot.Builder.Integration.AspNet.Core" Version="4.21.1" />
     <PackageReference Include="Microsoft.Identity.Client" Version="4.59.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
-    <PackageReference Include="SharpToken" Version="1.2.17" />
+    <PackageReference Include="Microsoft.ML.Tokenizers" Version="0.22.0-preview.24179.1" />
     <PackageReference Include="System.Text.Json" Version="7.0.4" />
   </ItemGroup>
 
diff --git a/dotnet/packages/Microsoft.TeamsAI/nuget.config b/dotnet/packages/Microsoft.TeamsAI/nuget.config
new file mode 100644
index 000000000..45a49fc03
--- /dev/null
+++ b/dotnet/packages/Microsoft.TeamsAI/nuget.config
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <add key="dotnet-local-feed" value=" https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-libraries/nuget/v3/index.json" />
+    <add key="nuget" value="https://api.nuget.org/v3/index.json" />
+  </packageSources>
+</configuration>