.NET: [Bug]: InMemoryChatHistoryProvider used even when service stores history (OpenAI Responses)

[ArturDorochowicz]

Description

I'm trying to use MAF against OpenAI Responses API, i.e. a service that stores history. I'm seeing InMemoryChatHistoryProvider storing messages in the session.

My understanding was that in this case the in memory provider should "disengage" and the session should only store the conversation/response id. I must be doing something wrong, because this fundamental scenario appears to be broken.

Code Sample

This test fails on the last assert (hasInMemoryHistory is true):

using System.ClientModel.Primitives;
using Azure.Identity;
using Microsoft.Agents.AI;
using OpenAI;
using OpenAI.Responses;
using Xunit;

namespace MafBug.Tests;

#pragma warning disable OPENAI001

public sealed class InMemoryChatHistoryProviderBugTests
{
    const string Endpoint = "https://xxx.services.ai.azure.com/openai/v1";
    const string Model = "gpt-5-mini";

    [Fact]
    public async Task ResponsesApi_DoesNotPopulateInMemoryChatHistoryProvider()
    {
        var cancellationToken = TestContext.Current.CancellationToken;

        var openai = new OpenAIClient(
            new BearerTokenPolicy(new DefaultAzureCredential(), scope: "https://ai.azure.com/.default"),
            new OpenAIClientOptions { Endpoint = new Uri(Endpoint) });
        var responsesClient = openai.GetResponsesClient();

        var agent = responsesClient.AsAIAgent(
            model: Model,
            instructions: "You are a helpful assistant. Respond with very short answers.",
            name: "ResponsesAgent");

        var session = await agent.CreateSessionAsync(cancellationToken);

        var r1 = await agent.RunAsync("Hi", session, cancellationToken: cancellationToken);

        var typedSession = Assert.IsType<ChatClientAgentSession>(session);
        Assert.False(
            string.IsNullOrWhiteSpace(typedSession.ConversationId),
            "ChatClientAgentSession.ConversationId is empty.");

        var hasInMemoryHistory = session.TryGetInMemoryChatHistory(out var inMemoryMessages);
        var storedCount = inMemoryMessages?.Count ?? 0;

        Assert.False(
            hasInMemoryHistory,
            $"BUG: InMemoryChatHistoryProvider stored {storedCount} message(s) in " +
            $"the session even though the OpenAI Responses API is storing " +
            $"conversation '{typedSession.ConversationId}' server-side. ");
    }
}

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

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Azure.Identity" Version="1.21.0" />
    <PackageReference Include="Microsoft.Agents.AI" Version="1.7.0" />
    <PackageReference Include="Microsoft.Agents.AI.OpenAI" Version="1.7.0" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.5.1" />
    <PackageReference Include="xunit.v3" Version="3.2.2" />
    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5" />
  </ItemGroup>

</Project>

Error Messages / Stack Traces

Package Versions

1.7.0, also checked 1.6.2

.NET Version

.net10

Additional Context

No response

[github-actions]

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

Agent analysis

Repro: ChatClientAgent.RunAsync() in dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs stores messages via InMemoryChatHistoryProvider even when the service returns a ConversationId. Two defects: (1) UpdateSessionConversationId (line 818) checks _agentOptions?.ChatHistoryProvider which is null for the default provider, skipping conflict detection; (2) ResolveChatHistoryProvider (line 979) checks chatOptions?.ConversationId which is never updated post-service-call, so it returns the InMemory provider to NotifyProvidersOfNewMessagesAtEndOfRunAsync (line 255). Minimal repro: create ChatClientAgent with no explicit ChatHistoryProvider, mock the IChatClient to return ChatResponse with ConversationId set, call RunAsync, observe session.TryGetInMemoryChatHistory returns true with 2 messages.

• Failing test: dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgent_Issue6120_InMemoryHistoryConflictTests.cs
• Files examined: dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs, dotnet/src/Microsoft.Agents.AI.Abstractions/InMemoryChatHistoryProvider.cs, dotnet/src/Microsoft.Agents.AI.OpenAI/Extensions/OpenAIResponseClientExtensions.cs, dotnet/src/Microsoft.Agents.AI.Abstractions/AgentSessionExtensions.cs, dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgentOptions.cs, dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgent_ChatHistoryManagementTests.cs, dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClientAgentTestHelper.cs
• Tests run: dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgent_Issue6120_InMemoryHistoryConflictTests.cs
• Reported version: 1.7.0
• Current version: 1.7.0