.NET: [Bug]: Following the Aspire DevUI Readme results in `Error: CLIENT_ERROR: Agent 'agentservice' not found.`

[hansmbakker]

Description

I followed https://github.com/microsoft/agent-framework/blob/939d4d01537339ea023272c42a5a7999f4eada8a/dotnet/src/Aspire.Hosting.AgentFramework.DevUI/README.md:

• created new Aspire solution using aspire new aspire-starter
• added DevUI code and nuget package to apphost
• removed generated frontend project
• replaced generated backend project by agent service setup from Readme
• I added Microsoft.Agents.AI.DevUI to the AppHost project as a workaround for .NET: [Bug]: Following the Aspire DevUI Readme results in 404 Not Found #5779

DevUI is correctly served now, but when sending a chat message to the agent, DevUI shows an error that it cannot find the agent service which is configured as a reference from Aspire.

Code Sample

AppHost.cs:

var builder = DistributedApplication.CreateBuilder(args);

var agentService = builder.AddProject<Projects.Handoff_AgentService>("agentservice")
    .WithHttpHealthCheck("/health");

var apiKey = builder.AddParameter("github-models-key",
    value: "github_pat_mysecret",
    secret: true);

var openai = builder.AddOpenAI("openai")
                    .WithApiKey(apiKey)
                    .WithEndpoint("https://models.github.ai/inference");

var devui = builder.AddDevUI("devui")
    .WithAgentService(agentService)
    .WaitFor(agentService);

builder.Build().Run();

AgentService Program.cs:

using Microsoft.Agents.AI.Hosting;

var builder = WebApplication.CreateBuilder(args);

// Add service defaults & Aspire client integrations.
builder.AddServiceDefaults();

// Add services to the container.
builder.Services.AddProblemDetails();

// Learn more about configuring OpenAPI at https://aka.ms/aspnet/openapi
builder.Services.AddOpenApi();

builder.AddOpenAIClient(connectionName: "openai");

// In the agent service's Program.cs
builder.AddAIAgent("writer", "You write short stories.");
builder.Services.AddOpenAIResponses();
builder.Services.AddOpenAIConversations();

var app = builder.Build();

app.MapOpenAIResponses();
app.MapOpenAIConversations();

// Configure the HTTP request pipeline.
app.UseExceptionHandler();

if (app.Environment.IsDevelopment())
{
    app.MapOpenApi();
}

app.MapDefaultEndpoints();

app.Run();

Error Messages / Stack Traces

In DevUI:

Error: CLIENT_ERROR: Agent 'agentservice' not found.

In Aspire:

{
  "resourceLogs": [
    {
      "scopeLogs": [
        {
          "scope": {
            "name": "Microsoft.Agents.AI.Hosting.OpenAI.Responses.HostedAgentResponseExecutor"
          },
          "logRecords": [
            {
              "timeUnixNano": "1778594930358264300",
              "severityNumber": 13,
              "severityText": "Warning",
              "body": {
                "stringValue": "Failed to resolve agent with name 'agentservice'"
              },
              "attributes": [
                {
                  "key": "AgentName",
                  "value": {
                    "stringValue": "agentservice"
                  }
                },
                {
                  "key": "ConnectionId",
                  "value": {
                    "stringValue": "0HNLG5VKSTDLF"
                  }
                },
                {
                  "key": "RequestId",
                  "value": {
                    "stringValue": "0HNLG5VKSTDLF:00000005"
                  }
                },
                {
                  "key": "RequestPath",
                  "value": {
                    "stringValue": "/v1/responses"
                  }
                },
                {
                  "key": "aspire.log_id",
                  "value": {
                    "stringValue": "16"
                  }
                }
              ],
              "flags": 1,
              "traceId": "53e9c743ba33b0a17c08371ceafe5bd6",
              "spanId": "6fd00178f7ac3f1d"
            }
          ]
        }
      ],
      "resource": {
        "attributes": [
          {
            "key": "service.name",
            "value": {
              "stringValue": "agentservice"
            }
          },
          {
            "key": "service.instance.id",
            "value": {
              "stringValue": "efrsgtzt"
            }
          },
          {
            "key": "telemetry.sdk.language",
            "value": {
              "stringValue": "dotnet"
            }
          },
          {
            "key": "telemetry.sdk.name",
            "value": {
              "stringValue": "opentelemetry"
            }
          },
          {
            "key": "telemetry.sdk.version",
            "value": {
              "stringValue": "1.15.3"
            }
          }
        ]
      }
    }
  ]
}

Package Versions

• Aspire.Hosting.AgentFramework.DevUI: 1.5.0-preview.260507.1
• other Microsoft.Agents.AI.*: 1.5.0

.NET Version

10.0

Additional Context

No response

[github-actions]

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

Agent analysis

Repro: AgentFrameworkBuilderExtensions.WithAgentService() in dotnet/src/Aspire.Hosting.AgentFramework.DevUI/AgentFrameworkBuilderExtensions.cs:178 defaults agents to [new AgentEntityInfo(resource.Name)] when no agents param is provided, causing the aggregator to send entity_id=resourceName to the backend, which cannot resolve it because the agent was registered under a different name via AddAIAgent(). Minimal repro: register agent "writer" with AddAIAgent, then POST /v1/responses with metadata.entity_id="agentservice" (the resource name) — returns 400 "not found". Fix should either change the default to require explicit agent names, or update the README example to always pass the agents parameter.

• Failing test: dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/DevUIAspireAgentNameMismatchTests.cs
• Files examined: dotnet/src/Aspire.Hosting.AgentFramework.DevUI/AgentFrameworkBuilderExtensions.cs, dotnet/src/Aspire.Hosting.AgentFramework.DevUI/DevUIAggregatorHostedService.cs, dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/Responses/HostedAgentResponseExecutor.cs, dotnet/src/Aspire.Hosting.AgentFramework.DevUI/AgentServiceAnnotation.cs, dotnet/src/Aspire.Hosting.AgentFramework.DevUI/AgentEntityInfo.cs, dotnet/src/Aspire.Hosting.AgentFramework.DevUI/README.md
• Tests run: dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/DevUIAspireAgentNameMismatchTests.cs
• Reported version: 1.5.0

[hansmbakker]

What helped

Changing .WithAgentService(...) call to the code below helped:

var devui = builder.AddDevUI("devui")
    .WithAgentService(agentService, agents: [new("writer", "Writes short stories")])
    .WaitFor(agentService);

Working code

AppHost

var builder = DistributedApplication.CreateBuilder(args);

var apiKey = builder.AddParameter("github-models-key",
    value: "github_pat_mysecret",
    secret: true);

var openai = builder.AddOpenAI("openai")
                    .WithApiKey(apiKey)
                    .WithEndpoint("https://models.github.ai/inference");

var agentService = builder.AddProject<Projects.Handoff_AgentService>("agentservice")
        .WithReference(openai)
        .WithHttpHealthCheck("/health");

var devui = builder.AddDevUI("devui")
    .WithAgentService(agentService, agents: [new("writer", "Writes short stories")])
    .WaitFor(agentService);

builder.Build().Run();

AgentService Program.cs

using Microsoft.Agents.AI.Hosting;

var builder = WebApplication.CreateBuilder(args);

// Add service defaults & Aspire client integrations.
builder.AddServiceDefaults();

// Add services to the container.
builder.Services.AddProblemDetails();

// Learn more about configuring OpenAPI at https://aka.ms/aspnet/openapi
builder.Services.AddOpenApi();

builder.AddOpenAIClient(connectionName: "openai")
        .AddChatClient("openai/gpt-5-mini");

// In the agent service's Program.cs
builder.AddAIAgent("agentservice", "You write short stories.");
builder.Services.AddOpenAIResponses();
builder.Services.AddOpenAIConversations();

var app = builder.Build();

app.MapOpenAIResponses();
app.MapOpenAIConversations();

// Configure the HTTP request pipeline.
app.UseExceptionHandler();

if (app.Environment.IsDevelopment())
{
    app.MapOpenApi();
}

app.MapDefaultEndpoints();

app.Run();

Why the sample was not clear

This was not clear from Usage example section in the README - there, the AppHost and Program.cs are incompatible with each other:

• The writerAgent aspire component is named writer-agent and the agent is named writer.
• The .WithAgentService call does not specify the agent name to use, so it falls back to the name if the Aspire component, which is not the same.