microsoft/autogen · error · ArgumentException

Invalid message type

Error message

Invalid message type

What it means

Error "Invalid message type" thrown in microsoft/autogen.

Source

Thrown at dotnet/src/AutoGen.AzureAIInference/Agent/ChatCompletionsClientAgent.cs:124

    public async IAsyncEnumerable<IMessage> GenerateStreamingReplyAsync(
        IEnumerable<IMessage> messages,
        GenerateReplyOptions? options = null,
        [EnumeratorCancellation] CancellationToken cancellationToken = default)
    {
        var settings = this.CreateChatCompletionsOptions(options, messages);
        var response = await this.chatCompletionsClient.CompleteStreamingAsync(settings, cancellationToken);
        await foreach (var update in response.WithCancellation(cancellationToken))
        {
            yield return new MessageEnvelope<StreamingChatCompletionsUpdate>(update, from: this.Name);
        }
    }

    private ChatCompletionsOptions CreateChatCompletionsOptions(GenerateReplyOptions? options, IEnumerable<IMessage> messages)
    {
        var oaiMessages = messages.Select(m => m switch
        {
            IMessage<ChatRequestMessage> chatRequestMessage => chatRequestMessage.Content,
            _ => throw new ArgumentException("Invalid message type")
        });

        // add system message if there's no system message in messages
        if (!oaiMessages.Any(m => m is ChatRequestSystemMessage))
        {
            oaiMessages = new[] { new ChatRequestSystemMessage(systemMessage) }.Concat(oaiMessages);
        }

        // clone the options by serializing and deserializing
        var json = JsonSerializer.Serialize(this.options);
        var settings = JsonSerializer.Deserialize<ChatCompletionsOptions>(json) ?? throw new InvalidOperationException("Failed to clone options");

        foreach (var m in oaiMessages)
        {
            settings.Messages.Add(m);
        }

        settings.Temperature = options?.Temperature ?? settings.Temperature;

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Pass only TextMessage, ImageMessage, MultiModalMessage, or ToolCallMessage

Example fix

Convert the message to a supported IMessage type before invoking the agent

When it happens

Trigger: Thrown at dotnet/src/AutoGen.AzureAIInference/Agent/ChatCompletionsClientAgent.cs:124 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/1139b0bf0a839a54. Report an issue: GitHub.