microsoft/autogen · error · InvalidOperationException

Invalid return message type {message.GetType().Name}

Error message

Invalid return message type {message.GetType().Name}

What it means

Error "Invalid return message type {message.GetType().Name}" thrown in microsoft/autogen.

Source

Thrown at dotnet/src/AutoGen.AzureAIInference/Middleware/AzureAIInferenceChatRequestMessageConnector.cs:98

                {
                    throw new InvalidOperationException($"Invalid streaming message type {reply.GetType().Name}");
                }
                else
                {
                    yield return reply;
                }
            }
        }
    }

    public IMessage PostProcessMessage(IMessage message)
    {
        return message switch
        {
            IMessage<ChatResponseMessage> m => PostProcessChatResponseMessage(m.Content, m.From),
            IMessage<ChatCompletions> m => PostProcessChatCompletions(m),
            _ when strictMode is false => message,
            _ => throw new InvalidOperationException($"Invalid return message type {message.GetType().Name}"),
        };
    }

    public IMessage? PostProcessStreamingMessage(IMessage<StreamingChatCompletionsUpdate> update, string? currentToolName)
    {
        if (update.Content.ContentUpdate is string contentUpdate && string.IsNullOrEmpty(contentUpdate) == false)
        {
            // text message
            return new TextMessageUpdate(Role.Assistant, contentUpdate, from: update.From);
        }
        else if (update.Content.FunctionName is string functionName)
        {
            return new ToolCallMessageUpdate(functionName, string.Empty, from: update.From);
        }
        else if (update.Content.FunctionArgumentsUpdate is string functionArgumentsUpdate && currentToolName is string)
        {
            return new ToolCallMessageUpdate(currentToolName, functionArgumentsUpdate, from: update.From);
        }

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Return a TextMessage or ToolCallMessage as the final reply

Example fix

Ensure the agent's final reply is a supported IMessage type

When it happens

Trigger: Thrown at dotnet/src/AutoGen.AzureAIInference/Middleware/AzureAIInferenceChatRequestMessageConnector.cs:98 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/d0ac5e9d5e67a028. Report an issue: GitHub.