Python: .NET: [Bug]: DevUI returning 401 code execution_error

Description

When running a very basic agent against a new Foundry project model I get this when running the agent from DevUI:

The same agent works with devUI using Python, it also works from .NET when not using devUI

Code Sample

AIProjectClient aiProjectClient = new(new Uri(endpoint), new DefaultAzureCredential());
var chatclient = aiProjectClient.GetAzureOpenAIChatClient().AsIChatClient();

await aiProjectClient.CreateAIAgentAsync("WeatherAgent", new AgentVersionCreationOptions(new PromptAgentDefinition(model: deploymentName) { Instructions = "You are a weather expert. You provide accurate weather predications at the requested location" }));

builder.Services.AddChatClient(chatclient);

// Register sample agents with tools
builder.AddAIAgent(name: "WeatherAgent", instructions: null);

builder.Services.AddOpenAIResponses();
builder.Services.AddOpenAIConversations();

Error Messages / Stack Traces

Package Versions

Microsoft.Agents.AI, AzureAI, DevUI version 1.0.0-preview.260212.1

.NET Version

.NET 10

Additional Context

No response