[dotnet] Duplicate user role message send to agent

[kimmywork]

What happened?

Duplicate message send to an agent for after initialize and get reply from one.

Here is the request generated by AutoGen and I observed via LM Studio logs.

2024-12-17 12:47:07  [INFO]
Received POST request to /v1/chat/completions with body: {
  "messages": [
    {
      "role": "system",
      "content": "You are a student that answer question from teacher",
      "name": "student"
    },
    {
      "role": "assistant",
      "content": "Hey teacher, please create math question for me.",
      "name": "student"
    },
    {
      "role": "user",
      "content": "Here's a simple addition problem for you:\n\nIf I have 2 blocks and my friend gives me 1 more block, how many blocks do I have now?\n\nWhat is your answer?",
      "name": "teacher"
    },
    {
      "role": "user",
      "content": "Here's a simple addition problem for you:\n\nIf I have 2 blocks and my friend gives me 1 more block, how many blocks do I have now?\n\nWhat is your answer?",
      "name": "teacher"
    }
  ],
  "model": "llama-3.2-3b-instruct"
}

What did you expect to happen?

There only should be 1 user role in the messages list.

How can we reproduce it (as minimally and precisely as possible)?

Run Following C# code (from one of the examples).

var config = new LMStudioConfig("localhost", 1234);


var teacher = new AssistantAgent(
    name: "teacher",
    systemMessage: @"You are a teacher that create pre-school math question for student and check answer.
If the answer is correct, you stop the conversation by saying [COMPLETE].
If the answer is wrong, you ask student to fix it.",
    llmConfig: new ConversableAgentConfig {
            Temperature = 0.0f,
            ConfigList = [config]
    }
).RegisterPrintMessage();

var student = new AssistantAgent(
    name: "student",
    systemMessage: "You are a student that answer question from teacher",
    llmConfig: new ConversableAgentConfig {
            Temperature = 0.0f,
            ConfigList = [config]
    }
).RegisterPrintMessage();

var conversation = await student.InitiateChatAsync(
    receiver: teacher,
    message: "Hey teacher, please create math question for me.",
    maxRound: 10);

AutoGen version

55e157c

Which package was this bug in

Other

Model used

llama-3.2-3b-instruct

Python version

N/A

Operating system

macOS

Any additional info you think would be helpful for fixing this bug

I found one possible solution, by update GroupChatExtension.cs line 64 in AutoGen.Core package to avoid this duplication.

if (!chatHistory.Contains(lastMessage)) {
    chatHistory = chatHistory.Append(lastMessage);
}

Just a suggestion.