Advice needed: Chat history with custom agents using DelegatingAIAgent

[Dazfl]

I'm looking for some advice regarding chat history and calling sub-agents from a custom agent.

If I have a custom agent define using the DelegatingAIAgent, that makes a call to a sub-agent ...

internal sealed MyAgent(AIAgent innerAgent) : DelegatingAIAgent(innerAgent)
{
   ...
   public override asyn Task<AgentResponseUpdate> RunCoreStreamingAsync(IEnumerable<ChatMessage> messages, ...)
   {
      ...
      var subAgentResponse = await subAgent.RunAsync(query);
      ...
   }
}

... and if there is some back and forth with a user (clarifying questions, etc), what is the best way for the subAgent to keep track of the conversation?

• Is it as simple as sending the full chat history (IEnumerable<ChatMessage>) to the subAgent?
• Should the subAgent have chat memory configured and then I just pass in the last message?
• Would OpenAI Responses be better here instead of Chat Completions?

I know this is probably a case of 'there is no one solution', but I'm just interested to see how others have handled this scenario.

[chetantoshniwal]

Refer to handoff orchestration pattern MAF supports https://github.com/microsoft/agent-framework/tree/main/dotnet/samples/03-workflows/Orchestration/Handoff seems like a good fit for your use-case

[Denis Samatov (denis-samatov)]

There should be one clear owner of conversation state. Do not both pass the complete parent history and load the same turns again from a persistent sub-agent session.

For a stateless/short-lived delegation, pass the selected context explicitly and do not retain a sub-agent session:

List<ChatMessage> subMessages = parentMessages
    .Where(IsRelevantToSubAgent)
    .ToList();

AgentResponse result = await subAgent.RunAsync(
    subMessages,
    session: null,
    cancellationToken: cancellationToken);

For a long-lived specialist, create and persist its own AgentSession, associate it with the parent conversation, and pass only the new turn or handoff delta:

AgentResponse result = await subAgent.RunAsync(
    newMessages,
    subSession,
    cancellationToken: cancellationToken);

Using the named cancellationToken argument matters: the RunAsync overload is (messages, session, options, cancellationToken), so RunAsync(subMessages, subSession, cancellationToken) would try to pass a CancellationToken as AgentRunOptions and does not compile.

Responses versus Chat Completions does not decide this ownership question. Choose the provider API for its transport/tool semantics, but make the history boundary explicit, persist parent/sub-session IDs together when stateful, cap delegated context, and test that clarification turns are not duplicated.