diff --git a/Anthropic.SDK.Tests/Anthropic.SDK.Tests.csproj b/Anthropic.SDK.Tests/Anthropic.SDK.Tests.csproj
index 7649e1b..4fcf4c9 100644
--- a/Anthropic.SDK.Tests/Anthropic.SDK.Tests.csproj
+++ b/Anthropic.SDK.Tests/Anthropic.SDK.Tests.csproj
@@ -35,7 +35,7 @@
   <ItemGroup>
     <PackageReference Include="Google.Cloud.AIPlatform.V1" Version="3.24.0" />
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="8.0.0" />
-    <PackageReference Include="Microsoft.Extensions.AI" Version="9.9.0" />
+    <PackageReference Include="Microsoft.Extensions.AI" Version="9.9.1" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.0.0" />
diff --git a/Anthropic.SDK.Tests/Messages.ChatClient.cs b/Anthropic.SDK.Tests/Messages.ChatClient.cs
index 524c80b..5bf5158 100644
--- a/Anthropic.SDK.Tests/Messages.ChatClient.cs
+++ b/Anthropic.SDK.Tests/Messages.ChatClient.cs
@@ -155,7 +155,7 @@ public async Task TestThinkingStreamingRedactedConversation()
 
             messages.AddMessages(updates);
 
-            Assert.IsTrue(messages.Last().Contents.OfType<Extensions.MEAI.RedactedThinkingContent>().Any());
+            Assert.IsTrue(messages.Last().Contents.OfType<TextReasoningContent>().Any(c => c.ProtectedData is not null));
 
             messages.Add(new ChatMessage(ChatRole.User, "how many letters are in the word strawberry?"));
 
diff --git a/Anthropic.SDK.Tests/VertexAI.ChatClient.cs b/Anthropic.SDK.Tests/VertexAI.ChatClient.cs
index d237b27..a62d2d4 100644
--- a/Anthropic.SDK.Tests/VertexAI.ChatClient.cs
+++ b/Anthropic.SDK.Tests/VertexAI.ChatClient.cs
@@ -261,7 +261,7 @@ public async Task TestThinkingStreamingRedactedConversation()
 
             messages.AddMessages(updates);
 
-            Assert.IsTrue(messages.Last().Contents.OfType<Extensions.MEAI.RedactedThinkingContent>().Any());
+            Assert.IsTrue(messages.Last().Contents.OfType<TextReasoningContent>().Any(c => c.ProtectedData is not null));
 
             messages.Add(new ChatMessage(ChatRole.User, "how many letters are in the word strawberry?"));
 
diff --git a/Anthropic.SDK/Anthropic.SDK.csproj b/Anthropic.SDK/Anthropic.SDK.csproj
index cd49dff..c246de1 100644
--- a/Anthropic.SDK/Anthropic.SDK.csproj
+++ b/Anthropic.SDK/Anthropic.SDK.csproj
@@ -36,7 +36,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.AI.Abstractions" Version="9.9.0" />
+    <PackageReference Include="Microsoft.Extensions.AI.Abstractions" Version="9.9.1" />
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="8.0.0" />
   </ItemGroup>
 
diff --git a/Anthropic.SDK/Extensions/MEAI.cs b/Anthropic.SDK/Extensions/MEAI.cs
deleted file mode 100644
index 1b7dec4..0000000
--- a/Anthropic.SDK/Extensions/MEAI.cs
+++ /dev/null
@@ -1,15 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Anthropic.SDK.Extensions.MEAI
-{
-    public sealed class RedactedThinkingContent : Microsoft.Extensions.AI.AIContent
-    {
-        public RedactedThinkingContent(string data)
-        {
-            Data = data;
-        }
-        public string Data { get; set; }
-    }
-}
diff --git a/Anthropic.SDK/Messaging/ChatClientHelper.cs b/Anthropic.SDK/Messaging/ChatClientHelper.cs
index 405d006..648d783 100644
--- a/Anthropic.SDK/Messaging/ChatClientHelper.cs
+++ b/Anthropic.SDK/Messaging/ChatClientHelper.cs
@@ -173,16 +173,19 @@ public static MessageParameters CreateMessageParameters(IChatClient client, IEnu
                                 });
                                 break;
 
-                            case Microsoft.Extensions.AI.TextReasoningContent textReasoningContent:
-                                currentMessage.Content.Add(new Messaging.ThinkingContent()
+                            case Microsoft.Extensions.AI.TextReasoningContent reasoningContent:
+                                if (string.IsNullOrEmpty(reasoningContent.Text))
                                 {
-                                    Thinking = textReasoningContent.Text,
-                                    Signature = textReasoningContent.AdditionalProperties[nameof(ThinkingContent.Signature)]?.ToString()
-                                });
-                                break;
-
-                            case Anthropic.SDK.Extensions.MEAI.RedactedThinkingContent redactedThinkingContent:
-                                currentMessage.Content.Add(new Messaging.RedactedThinkingContent() { Data = redactedThinkingContent.Data });
+                                    currentMessage.Content.Add(new Messaging.RedactedThinkingContent() { Data = reasoningContent.ProtectedData });
+                                }
+                                else
+                                {
+                                    currentMessage.Content.Add(new Messaging.ThinkingContent()
+                                    {
+                                        Thinking = reasoningContent.Text,
+                                        Signature = reasoningContent.ProtectedData,
+                                    });
+                                }
                                 break;
 
                             case Microsoft.Extensions.AI.TextContent textContent:
@@ -256,15 +259,15 @@ public static List<AIContent> ProcessResponseContent(MessageResponse response)
                     case Messaging.ThinkingContent thinkingContent:
                         contents.Add(new Microsoft.Extensions.AI.TextReasoningContent(thinkingContent.Thinking)
                         {
-                            AdditionalProperties = new AdditionalPropertiesDictionary
-                            {
-                                [nameof(ThinkingContent.Signature)] = thinkingContent.Signature
-                            }
+                            ProtectedData = thinkingContent.Signature,
                         });
                         break;
 
                     case Messaging.RedactedThinkingContent redactedThinkingContent:
-                        contents.Add(new Anthropic.SDK.Extensions.MEAI.RedactedThinkingContent(redactedThinkingContent.Data));
+                        contents.Add(new Microsoft.Extensions.AI.TextReasoningContent(null)
+                        {
+                            ProtectedData = redactedThinkingContent.Data,
+                        });
                         break;
 
                     case TextContent tc:
diff --git a/Anthropic.SDK/Messaging/MessagesEndpoint.ChatClient.cs b/Anthropic.SDK/Messaging/MessagesEndpoint.ChatClient.cs
index e9a80b8..be87da2 100644
--- a/Anthropic.SDK/Messaging/MessagesEndpoint.ChatClient.cs
+++ b/Anthropic.SDK/Messaging/MessagesEndpoint.ChatClient.cs
@@ -104,7 +104,7 @@ async IAsyncEnumerable<ChatResponseUpdate> IChatClient.GetStreamingResponseAsync
 
             if (!string.IsNullOrEmpty(response.ContentBlock?.Data))
             {
-                update.Contents.Add(new SDK.Extensions.MEAI.RedactedThinkingContent(response.ContentBlock?.Data));
+                update.Contents.Add(new TextReasoningContent(null) { ProtectedData = response.ContentBlock.Data });
             }
             
             if (response.StreamStartMessage?.Usage is {} startStreamMessageUsage)
@@ -128,10 +128,7 @@ async IAsyncEnumerable<ChatResponseUpdate> IChatClient.GetStreamingResponseAsync
                 {
                     update.Contents.Add(new TextReasoningContent(thinking)
                     {
-                        AdditionalProperties = new AdditionalPropertiesDictionary
-                        {
-                            [nameof(ThinkingContent.Signature)] = response.Delta.Signature
-                        }
+                        ProtectedData = response.Delta.Signature,
                     });
                 }
 
diff --git a/Anthropic.SDK/Messaging/VertexAIMessagesEndpoint.ChatClient.cs b/Anthropic.SDK/Messaging/VertexAIMessagesEndpoint.ChatClient.cs
index 7073298..2981960 100644
--- a/Anthropic.SDK/Messaging/VertexAIMessagesEndpoint.ChatClient.cs
+++ b/Anthropic.SDK/Messaging/VertexAIMessagesEndpoint.ChatClient.cs
@@ -56,7 +56,7 @@ async IAsyncEnumerable<ChatResponseUpdate> IChatClient.GetStreamingResponseAsync
 
             if (!string.IsNullOrEmpty(response.ContentBlock?.Data))
             {
-                update.Contents.Add(new SDK.Extensions.MEAI.RedactedThinkingContent(response.ContentBlock?.Data));
+                update.Contents.Add(new TextReasoningContent(null) { ProtectedData = response.ContentBlock.Data });
             }
             
             if (response.StreamStartMessage?.Usage is {} startStreamMessageUsage)
@@ -80,10 +80,7 @@ async IAsyncEnumerable<ChatResponseUpdate> IChatClient.GetStreamingResponseAsync
                 {
                     update.Contents.Add(new Microsoft.Extensions.AI.TextReasoningContent(thinking)
                     {
-                        AdditionalProperties = new AdditionalPropertiesDictionary
-                        {
-                            [nameof(ThinkingContent.Signature)] = response.Delta.Signature
-                        }
+                        ProtectedData = response.Delta.Signature,
                     });
                 }