.NET: [Bug]: DurableAIAgentProxy is not compatible with MapAGUI

[kpobb1989]

Description

I'm trying to build a ASP.NET Core front door with Durable Task Scheduler behind it for long-running operations and AG-UI.

But according to the source code, the DurableAIAgentProxy does not support streaming; however, MapAGUI uses SSE and requires streaming.

I also opened the dicussion : #5900

Code Sample

// Program.cs
using Microsoft.Agents.AI;
using Microsoft.Agents.AI.DurableTask;
using Microsoft.Agents.AI.Hosting.AGUI.AspNetCore;
using Microsoft.Extensions.AI;
using OpenAI;
using System.ClientModel;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAGUI();

string dtsConnection = builder.Configuration["DurableTask:ConnectionString"]
    ?? "Endpoint=http://dts-emulator:8080;TaskHub=default;Authentication=None";

var openAIClient = new OpenAIClient(
    new ApiKeyCredential("ollama"),
    new OpenAIClientOptions { Endpoint = new Uri("http://localhost:11434/v1") });

IChatClient chatClient = openAIClient
    .GetChatClient("gemma4:26b-nvfp4")
    .AsIChatClient();

builder.Services.AddSingleton(chatClient);

AIAgent agent = chatClient.AsAIAgent(
    name: "OllamaAgent",
    instructions: "You are a helpful assistant.");

builder.Services.ConfigureDurableAgents(
    options =>
    {
        options.DefaultTimeToLive = TimeSpan.FromDays(7);
        options.AddAIAgent(agent);
    },
    workerBuilder: b => b.UseDurableTaskScheduler(dtsConnection),
    clientBuilder: b => b.UseDurableTaskScheduler(dtsConnection));

var app = builder.Build();

AIAgent durableAgent = agent.AsDurableAgentProxy(app.Services);

// DurableAgent throws NotSupportedException("Streaming is not supported for durable agents.") at the runtime
app.MapAGUI("/chat", durableAgent);

await app.RunAsync();

Error Messages / Stack Traces

Package Versions

Microsoft.Agents.AI: 1.6.2, Microsoft.Agents.AI.Hosting.AGUI.AspNetCore: 1.6.2-preview.260521.1, Microsoft.Agents.AI.DurableTask: 1.6.2-preview.260521.1

.NET Version

.NET 10

Additional Context

No response

[github-actions]

🤖 Automated triage reproduction notes (agent-authored — trust but verify)

Agent analysis

Repro: DurableAIAgentProxy.RunCoreStreamingAsync() in dotnet/src/Microsoft.Agents.AI.DurableTask/DurableAIAgentProxy.cs:99 unconditionally throws NotSupportedException when streaming is attempted; AGUIEndpointRouteBuilderExtensions.MapAGUI() in dotnet/src/Microsoft.Agents.AI.Hosting.AGUI.AspNetCore/AGUIEndpointRouteBuilderExtensions.cs:122 always calls RunStreamingAsync with non-streaming fallback. Minimal repro: instantiate DurableAIAgentProxy and call RunStreamingAsync with any messages — the NotSupportedException is thrown immediately upon enumeration.

• Failing test: dotnet/tests/Microsoft.Agents.AI.DurableTask.UnitTests/DurableAIAgentProxyStreamingTests.cs
• Files examined: dotnet/src/Microsoft.Agents.AI.DurableTask/DurableAIAgentProxy.cs, dotnet/src/Microsoft.Agents.AI.Hosting.AGUI.AspNetCore/AGUIEndpointRouteBuilderExtensions.cs, dotnet/src/Microsoft.Agents.AI.Hosting/AIHostAgent.cs, dotnet/src/Microsoft.Agents.AI.Abstractions/AIAgent.cs, dotnet/src/Microsoft.Agents.AI.DurableTask/AIAgentExtensions.cs, dotnet/src/Microsoft.Agents.AI.DurableTask/IDurableAgentClient.cs
• Tests run: dotnet/tests/Microsoft.Agents.AI.DurableTask.UnitTests/DurableAIAgentProxyStreamingTests.cs
• Reported version: 1.6.2