.NET: [Bug]: ChatClientAgent throws when using ChatHistoryProvider with Azure OpenAI Responses API and store=false

[luismanez]

Description

When using Microsoft.Agents.AI with Azure OpenAI Responses API through AsIChatClient(), ChatClientAgent throws if a ChatHistoryProvider is configured, even when the request is explicitly stateless (store=false / StoredOutputEnabled = false).

The exception is:

Only ConversationId or ChatHistoryProvider may be used, but not both. The service returned a conversation id indicating server-side chat history management, but the agent has a ChatHistoryProvider configured.

From captured HTTP traffic:

• the request is sent with "store": false
• the final JSON response does not contain a conversation field
• the final JSON response has "previous_response_id": null

This suggests the issue is not caused by Azure OpenAI returning a real conversation id. Instead, it appears that somewhere in the adapter chain, a non-null ConversationId is surfaced to ChatClientAgent, causing MAF to incorrectly assume server-side history management.

From source inspection, ChatClientAgent throws whenever the adapted ChatResponse / ChatResponseUpdate contains a non-null ConversationId, regardless of whether the underlying provider is actually using a real server-side conversation.

Relevant MAF code:

• RunCoreStreamingAsync(...) combines updates via ToChatResponse() and then calls UpdateSessionConversationId(...)
• RunCoreAsync(...) also calls UpdateSessionConversationId(...)
• UpdateSessionConversationId(...) throws if both ConversationId and ChatHistoryProvider are present

This is especially problematic for Azure OpenAI Responses scenarios where the caller explicitly wants to manage history client-side with ChatHistoryProvider.

Code Sample

using Azure;
using Azure.AI.OpenAI;
using Microsoft.Agents.AI;
using Microsoft.Extensions.AI;
using OpenAI.Responses;

string endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT")!;
string apiKey = Environment.GetEnvironmentVariable("AZURE_OPENAI_API_KEY")!;
string deployment = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT")!;

var azureClient = new AzureOpenAIClient(
    new Uri(endpoint),
    new AzureKeyCredential(apiKey));

var responsesClient = azureClient.GetResponsesClient(deployment);

IChatClient chatClient = responsesClient.AsIChatClient();

var agent = new ChatClientAgent(
    chatClient,
    new ChatClientAgentOptions
    {
        Name = "ReproAgent",
        ChatOptions = new ChatOptions
        {
            Instructions = "You are a helpful assistant.",
            RawRepresentationFactory = _ => new CreateResponseOptions
            {
                StoredOutputEnabled = false
            }
        },
        ChatHistoryProvider = new InMemoryChatHistoryProvider()
    });

AgentSession session = await agent.CreateSessionAsync();

// Non-streaming
var response = await agent.RunAsync("Say hello.", session);

// Streaming
await foreach (var update in agent.RunStreamingAsync("Say hello.", session))
{
    Console.Write(update.Text);
}


## Captured HTTP Request


{
  "model": "gpt-4.1-mini",
  "input": [
    {
      "type": "message",
      "role": "user",
      "content": [
        {
          "type": "input_text",
          "text": "How would you define Zava business in just 5 words?"
        }
      ]
    }
  ],
  "stream": true,
  "store": false
}


## Captured HTTP Response


{
  "id": "resp_0c09e9748364cb3c0169c573ecf76881909672744ee7074f94",
  "object": "response",
  "status": "completed",
  "model": "gpt-4.1-mini",
  "output": [
    {
      "type": "message",
      "role": "assistant",
      "status": "completed",
      "content": [
        {
          "type": "output_text",
          "text": "..."
        }
      ]
    }
  ],
  "previous_response_id": null,
  "store": false
}


Notably, there is no `conversation` field in the response.

Error Messages / Stack Traces

Only ConversationId or ChatHistoryProvider may be used, but not both. The service returned a conversation id indicating server-side chat history management, but the agent has a ChatHistoryProvider configured.

   at Microsoft.Agents.AI.ChatClientAgent.UpdateSessionConversationId(ChatClientAgentSession session, String responseConversationId, CancellationToken cancellationToken)
   at Microsoft.Agents.AI.ChatClientAgent.<RunCoreStreamingAsync>d__29.MoveNext()
   at Microsoft.Agents.AI.ChatClientAgent.<RunCoreStreamingAsync>d__29.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.MoveNext()
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.MoveNext()
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)

Package Versions

Microsoft.Agents.AI 1.0.0-rc3, Microsoft.Extensions.AI 10.3.0, Microsoft.Agents.AI.OpenAI 1.0.0-rc3

.NET Version

.NET 10

Additional Context

A few observations that may help narrow this down:

1. This reproduces with Azure OpenAI Responses API.
2. The outgoing request explicitly includes "store": false.
3. The final HTTP response does not contain a conversation field.
4. The final HTTP response has "previous_response_id": null.
5. MAF throws only because ChatClientAgent receives a non-null ConversationId from the adapted ChatResponse / ChatResponseUpdate.
6. This appears to happen even though the underlying HTTP response does not contain a real server-managed conversation id.

Potentially relevant MAF source:

• dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
• dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs

Behavioral expectation:

• If ChatHistoryProvider is configured and the request is stateless (store=false), ChatClientAgent should not treat the returned value as a real server-side conversation id and should not throw.

Actual behavior:

• ChatClientAgent throws as if the provider were managing server-side history, even though the Responses request/response indicates a stateless flow.

Note

I am aware that the underlying adapter stack may be mapping Responses semantics into ConversationId in a way that is broader than a true server-managed conversation. Even so, from the MAF side this currently makes ChatHistoryProvider unusable for this scenario, despite the request being explicitly stateless.

[luismanez]

@stephentoub we might need your thoughts here, as this is closely related to Microsoft.Extensions.AI