.NET: [Docmentation]: Unclear how to show reasoning in AG-UI

Description

I created several agents and exposed them using MapAGUIServer.

AG-UI and CopilotKit have support for reasoning messages but Agent Framework does not seem to send them to the frontend.

Update: it turns out that setting the Reasoning property in ChatOptions of HarnessAgents makes this work.
Please interpret this issue as a documentation issue instead of a bug.

Code Sample

I used e.g. a HarnessAgent, both with and without BackgroundAgents, and I used gpt-5.6-luna as LLM

return sp.GetRequiredService<IChatClient>().AsHarnessAgent(new HarnessAgentOptions
        {
            Name = name,
            HarnessInstructions = Instructions,
            ChatOptions = new ChatOptions { Tools = tools },
            AIContextProviders = contextProviders,
            BackgroundAgents = SpecialistAgents.ResolveAll(registry),
            // Keeps the harness re-invoking itself turn-over-turn until every delegated background task reaches a
            // terminal state.
            LoopEvaluators = [new BackgroundTaskCompletionLoopEvaluator()],
            LoopAgentOptions = new LoopAgentOptions { MaxIterations = 10 },
            DisableWebSearch = true,
            OpenTelemetrySourceName = GenAiSourceNames.Agents,
        });

Error Messages / Stack Traces

There is no error, it is just that the REASONING_* messages are not sent to the frontend

Package Versions

Microsoft.Agents.AI.Hosting.AGUI.AspNetCore: 1.21.0-preview.260911.1, Microsoft.Agents.AI.Harness: 1.21.0, Aspire.Azure.AI.OpenAI: 13.5.4-preview.1.26464.4

.NET Version

.NET 10

Additional Context

No response