.NET: [Bug]: builder.AddWorkflow(“some-name”) triggers error `System.InvalidOperationException: The workflow factory returned workflow with name '', but the expected name is 'some-name'.`

[hansmbakker]

Description

I created an Agent Service in .NET Aspire by creating an ASP.NET Core API project with OpenAI endpoints and by registering agents and a workflow exposed as agent.

I followed https://learn.microsoft.com/en-us/agent-framework/get-started/hosting?pivots=programming-language-csharp#core-hosting-library for the steps regarding the dependency injection registration.

I registered my workflow as an agent according to the examples on that page.

AgentWorkflowBuilder.CreateHandoffBuilderWith(agent) does not allow specifying a name, but apparently builder.AddWorkflow(name, delegate) checks for the configured name.

The Name property of Workflow is get-only (it can only be set during via init) and there is no setter.

Code Sample

builder.AddWorkflow("travel-booking-workflow", (sp, key) =>
         {
             var hotelAgent = sp.GetRequiredKeyedService<AIAgent>("HotelReservationAgent");
             var rideAgent = sp.GetRequiredKeyedService<AIAgent>("TransportationAgent");
             var travelAgent = sp.GetRequiredKeyedService<AIAgent>("TravelConciergeAgent");
#pragma warning disable MAAIW001 // This demo is specifically to show handoffs
             return AgentWorkflowBuilder
                .CreateHandoffBuilderWith(travelAgent)
                .WithHandoff(travelAgent, rideAgent, "Book a ride to the concert")
                .WithHandoff(travelAgent, hotelAgent, "Book a hotel room")
                .WithHandoffs(rideAgent, [travelAgent, hotelAgent])
                .WithHandoffs(hotelAgent, [travelAgent, rideAgent])
                .EnableReturnToPrevious()
                .Build();
#pragma warning restore MAAIW001
         }).AddAsAIAgent(agentName);

Error Messages / Stack Traces

> System.InvalidOperationException: The workflow factory returned workflow with name '', but the expected name is 'travel-booking-workflow'.

Package Versions

Microsoft.Agents.AI: 1.5.0

.NET Version

.NET 10.0

Additional Context

This issue was already posted before in several issues, and seems to have been ignored after #1885 was marked Closed without being fully fixed.

[github-actions]

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

Agent analysis

The bug is in HandoffWorkflowBuilderCore.Build() at dotnet/src/Microsoft.Agents.AI.Workflows/HandoffWorkflowBuilder.cs:301-335 — it creates a WorkflowBuilder (line 305) but never calls builder.WithName(), so the resulting Workflow.Name is null. When AddWorkflow() in dotnet/src/Microsoft.Agents.AI.Hosting/HostApplicationBuilderWorkflowExtensions.cs:41 checks workflow.Name against the registered key, it throws InvalidOperationException. Minimal repro: register via builder.AddWorkflow("any-name", (sp, key) => AgentWorkflowBuilder.CreateHandoffBuilderWith(agent).Build()) and resolve the keyed Workflow service.

• Failing test: dotnet/tests/Microsoft.Agents.AI.Hosting.UnitTests/Issue5791_HandoffWorkflowNameTest.cs
• Files examined: dotnet/src/Microsoft.Agents.AI.Hosting/HostApplicationBuilderWorkflowExtensions.cs, dotnet/src/Microsoft.Agents.AI.Workflows/HandoffWorkflowBuilder.cs, dotnet/src/Microsoft.Agents.AI.Workflows/AgentWorkflowBuilder.cs, dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowBuilder.cs, dotnet/src/Microsoft.Agents.AI.Workflows/Workflow.cs, dotnet/tests/Microsoft.Agents.AI.Hosting.UnitTests/HostApplicationBuilderWorkflowExtensionsTests.cs
• Tests run: dotnet/tests/Microsoft.Agents.AI.Hosting.UnitTests/Issue5791_HandoffWorkflowNameTest.cs
• Reported version: 1.5.0

[hansmbakker]

There is a workaround available from https://elbruno.com/2026/01/14/trick-to-fix-devui-workflow-errors-in-microsoft-agent-framework/ using reflection:

Create a workflow.SetName(name) extension method:

using Microsoft.Agents.AI.Workflows;
using System.Reflection;
 
namespace ChatApp20.Web.Extensions;
 
public static class WorkflowExtensions
{
    public static T SetName<T>(this T workflow, string name) where T : class
    {
        InvokeSetWorkflowName(workflow, name);
        return workflow;
    }
 
    private static void InvokeSetWorkflowName<T>(T workflow, string name) where T : class
    {
        var type = workflow.GetType();
 
        var nameProperty = type.GetProperty("Name", BindingFlags.Public | BindingFlags.Instance);
 
        if (nameProperty != null)
        {
            var backingField = type.GetField("<Name>k__BackingField",
                BindingFlags.NonPublic | BindingFlags.Instance);
 
            if (backingField != null)
            {
                backingField.SetValue(workflow, name);
            }
            else if (nameProperty.CanWrite)
            {
                nameProperty.SetValue(workflow, name);
            }
        }
    }
}

Use it inside the method that returns the workflow for builder.AddWorkflow(name, workflowFactory):

builder.AddWorkflow("HandoffWorkflow", (sp, key) => {
  var workflow = AgentWorkflowBuilder.CreateHandoffBuilderWith(routerAgent)
    .WithHandoff(routerAgent, technicalAgent)
    .WithHandoff(routerAgent, businessAgent)
    .WithHandoff(routerAgent, creativeAgent)
    .WithHandoff(routerAgent, researchAgent)
    .WithHandoff(routerAgent, writerAgent)
    .Build();
 
  workflow.SetName("HandOffWorkflow");
 
  return workflow;
});