.NET: [Bug]: An internal server error occurred on Microsoft.Agents.AI.Foundry.Hosting `1.10.0-preview.260610.1`

[tsubakimoto]

Description

Simple agent sample is not working using Microsoft.Agents.AI.Foundry.Hosting 1.10.0-preview.260610.1.

Code Sample

based this sample.
https://github.com/microsoft-foundry/foundry-samples/tree/main/samples/csharp/hosted-agents/agent-framework/simple-agent


<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <RootNamespace>SimpleAgent</RootNamespace>
    <AssemblyName>simple-agent</AssemblyName>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <NoWarn>$(NoWarn);NU1903;NU1605</NoWarn>
    <UserSecretsId>61a81a17-2b41-40be-a519-da32c302b7a0</UserSecretsId>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Agents.AI.Foundry.Hosting" Version="1.10.0-preview.260610.1" />
    <PackageReference Include="Azure.AI.Projects" Version="2.1.0-beta.1" />
    <PackageReference Include="DotNetEnv" Version="3.1.1" />
  </ItemGroup>

</Project>



// Copyright (c) Microsoft. All rights reserved.

using Azure.AI.AgentServer.Core;
using Azure.AI.Projects;
using Azure.Identity;
using DotNetEnv;
using Microsoft.Agents.AI;
using Microsoft.Agents.AI.Foundry.Hosting;

Env.TraversePath().Load();

var projectEndpoint = new Uri(Environment.GetEnvironmentVariable("FOUNDRY_PROJECT_ENDPOINT")
    ?? throw new InvalidOperationException("FOUNDRY_PROJECT_ENDPOINT environment variable is not set."));
var deployment = Environment.GetEnvironmentVariable("AZURE_AI_MODEL_DEPLOYMENT_NAME") ?? "gpt-4o";

AIAgent agent = new AIProjectClient(projectEndpoint, new DefaultAzureCredential())
    .AsAIAgent(
        model: deployment,
        instructions: """
            You are a helpful AI assistant hosted as a Foundry Hosted Agent.
            You can help with a wide range of tasks including answering questions,
            providing explanations, brainstorming ideas, and offering guidance.
            Be concise, clear, and helpful in your responses.
            """,
        name: "simple-agent",
        description: "A simple general-purpose AI assistant");

var builder = AgentHost.CreateBuilder(args);
builder.Services.AddFoundryResponses(agent);
builder.RegisterProtocol("responses", endpoints => endpoints.MapFoundryResponses());

var app = builder.Build();
app.Run();

Error Messages / Stack Traces

info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 GET http://localhost:8088/agentdev/version - - -
info: Azure.AI.AgentServer.Core.Internal.InboundRequestLoggingMiddleware[1689694937]
      Inbound GET /agentdev/version starting (x-request-id: , x-ms-client-request-id: , trace-id: af83ce6b76f1d3f6e884e3d7e14c2e9a)
warn: Azure.AI.AgentServer.Core.Internal.InboundRequestLoggingMiddleware[601900377]
      Inbound GET /agentdev/version failed HTTP 404 in 0ms (x-request-id: , x-ms-client-request-id: , trace-id: af83ce6b76f1d3f6e884e3d7e14c2e9a)
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 GET http://localhost:8088/agentdev/version - 404 0 - 0.5652ms
info: Microsoft.AspNetCore.Hosting.Diagnostics[16]
      Request reached the end of the middleware pipeline without being handled by application code. Request path: GET http://localhost:8088/agentdev/version, Response status code: 404
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 POST http://localhost:8088/responses - application/json 169
info: Azure.AI.AgentServer.Core.Internal.InboundRequestLoggingMiddleware[1689694937]
      Inbound POST /responses starting (x-request-id: , x-ms-client-request-id: , trace-id: 3cdba48ca9f8c96364ed02edab0fe352)
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'HTTP: POST /responses'
info: Azure.AI.AgentServer.Responses.Internal.ResponseEndpointHandler[0]
      Creating response caresp_5180c2681e20c9e200t5EuoxZiuGLfYOkcoq2KkqqjSSOmWCMr: Streaming=True Background=False Store=True Model= ConversationId=20d742b4-dcc3-4c29-acaa-c70d9ad163ab PreviousResponseId=(null) HasUserIsolationKey=False HasChatIsolationKey=False
info: Azure.AI.AgentServer.Responses.Internal.ResponseEndpointHandler[0]
      SSE stream started for response caresp_5180c2681e20c9e200t5EuoxZiuGLfYOkcoq2KkqqjSSOmWCMr
info: Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator[0]
      Invoking handler AgentFrameworkResponseHandler for response caresp_5180c2681e20c9e200t5EuoxZiuGLfYOkcoq2KkqqjSSOmWCMr
fail: Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator[0]
      Handler failed for response caresp_5180c2681e20c9e200t5EuoxZiuGLfYOkcoq2KkqqjSSOmWCMr
      System.InvalidOperationException: The registered HostedSessionIsolationKeyProvider returned null for the current request. Ensure the Foundry platform is providing the x-agent-user-isolation-key and x-agent-chat-isolation-key headers, or register a custom provider that supplies fallback values for local development.
         at Microsoft.Agents.AI.Foundry.Hosting.AgentFrameworkResponseHandler.CreateAsync(CreateResponse request, ResponseContext context, CancellationToken cancellationToken)+MoveNext()
         at Microsoft.Agents.AI.Foundry.Hosting.AgentFrameworkResponseHandler.CreateAsync(CreateResponse request, ResponseContext context, CancellationToken cancellationToken)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.ProcessEventsAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, IAsyncObserver`1 publisher, CancellationToken ct)+MoveNext()
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.ProcessEventsAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, IAsyncObserver`1 publisher, CancellationToken ct)+MoveNext()
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.ProcessEventsAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, IAsyncObserver`1 publisher, CancellationToken ct)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.CreateStreamingAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, CancellationToken ct)+MoveNext()
warn: Azure.AI.AgentServer.Responses.Internal.ResponseEndpointHandler[0]
      SSE stream error for response caresp_5180c2681e20c9e200t5EuoxZiuGLfYOkcoq2KkqqjSSOmWCMr
      Azure.AI.AgentServer.Responses.ResponsesApiException: An internal server error occurred.
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.ThrowIfPreCreatedFailure(ResponseExecution execution)
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.CreateStreamingAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, CancellationToken ct)+MoveNext()
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.CreateStreamingAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, CancellationToken ct)+MoveNext()
         at Azure.AI.AgentServer.Responses.Internal.ResponseOrchestrator.CreateStreamingAsync(CreateResponse request, ResponseExecution execution, ResponseContext context, CancellationToken ct)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
         at Azure.AI.AgentServer.Responses.Internal.SseResult.ExecuteAsync(HttpContext httpContext)
         at Azure.AI.AgentServer.Responses.Internal.SseResult.ExecuteAsync(HttpContext httpContext)
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'HTTP: POST /responses'
info: Azure.AI.AgentServer.Core.Internal.InboundRequestLoggingMiddleware[194824245]
      Inbound POST /responses completed HTTP 200 in 5ms (x-request-id: , x-ms-client-request-id: , trace-id: 3cdba48ca9f8c96364ed02edab0fe352)
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 POST http://localhost:8088/responses - 200 - text/event-stream;+charset=utf-8 5.7099ms

Package Versions

Microsoft.Agents.AI.Foundry.Hosting: 1.10.0-preview.260610.1

.NET Version

.NET 10

Additional Context

Same error occurred from 1.6.2-preview.260521.1 to 1.10.0-preview.260610.1 .

[github-actions]

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

Agent analysis

Repro: AgentFrameworkResponseHandler.CreateAsync in dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/AgentFrameworkResponseHandler.cs (lines 79-88) throws InvalidOperationException when PlatformHostedSessionIsolationKeyProvider returns null, which always happens in local development because x-agent-user-isolation-key and x-agent-chat-isolation-key headers are absent. The fix should either make PlatformHostedSessionIsolationKeyProvider provide fallback values for local dev, or have AddFoundryResponses() in ServiceCollectionExtensions.cs auto-register a development-mode provider (similar to the existing DevTemporaryLocalSessionIsolationKeyProvider in samples). Minimal repro: call AddFoundryResponses(agent) then POST /responses without isolation headers.

• Failing test: none
• Files examined: dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/AgentFrameworkResponseHandler.cs, dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/PlatformHostedSessionIsolationKeyProvider.cs, dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/HostedSessionIsolationKeyProvider.cs, dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/ServiceCollectionExtensions.cs, dotnet/tests/Microsoft.Agents.AI.Foundry.Hosting.UnitTests/HostedSessionIdentityContextTests.cs, dotnet/samples/04-hosting/FoundryHostedAgents/responses/Hosted_Shared_Contributor_Setup/DevTemporaryLocalSessionIsolationKeyProvider.cs
• Tests run: Microsoft.Agents.AI.Foundry.Hosting.UnitTests (all tests pass including Handler_NullKeysFromProvider_ThrowsInvalidOperationAsync which confirms the exact bug path)
• Reported version: 1.10.0-preview.260610.1
• Current version: 1.10.0-preview