diff --git a/dotnet/src/Agents/Core/ChatCompletionAgent.cs b/dotnet/src/Agents/Core/ChatCompletionAgent.cs
index 56c8712ab50f..1975027630ba 100644
--- a/dotnet/src/Agents/Core/ChatCompletionAgent.cs
+++ b/dotnet/src/Agents/Core/ChatCompletionAgent.cs
@@ -391,6 +391,7 @@ private async IAsyncEnumerable<StreamingChatMessageContent> InternalInvokeStream
 
         this.Logger.LogAgentChatServiceInvokedStreamingAgent(nameof(InvokeAsync), this.Id, agentName, serviceType);
 
+        int messageIndex = messageCount;
         AuthorRole? role = null;
         StringBuilder builder = new();
         await foreach (StreamingChatMessageContent message in messages.ConfigureAwait(false))
@@ -401,18 +402,18 @@ private async IAsyncEnumerable<StreamingChatMessageContent> InternalInvokeStream
 
             builder.Append(message.ToString());
 
-            yield return message;
-        }
+            // Capture mutated messages related function calling / tools
+            for (; messageIndex < chat.Count; messageIndex++)
+            {
+                ChatMessageContent chatMessage = chat[messageIndex];
 
-        // Capture mutated messages related function calling / tools
-        for (int messageIndex = messageCount; messageIndex < chat.Count; messageIndex++)
-        {
-            ChatMessageContent message = chat[messageIndex];
+                chatMessage.AuthorName = this.Name;
 
-            message.AuthorName = this.Name;
+                await onNewMessage(chatMessage).ConfigureAwait(false);
+                history.Add(chatMessage);
+            }
 
-            await onNewMessage(message).ConfigureAwait(false);
-            history.Add(message);
+            yield return message;
         }
 
         // Do not duplicate terminated function result to history