Best practice for handling per-user chat history with DI in agent-based REST APIs

[ahmar-husain]

I’m working on an agent-based system where a REST endpoint invokes an AI agent, and subsequent requests for the same user need to be context-aware by leveraging stored conversation history.

Current Design

• I have implemented a custom ChatHistoryProvider backed by Redis to store and retrieve chat history per user.
• I created an AgentFactory that returns an AI agent instance.
• The factory is registered with scoped lifetime in DI.

Challenge

• I ended up using a factory pattern to pass userId during agent creation.
• This makes the design feel a bit forced and less aligned with standard DI practices.
• On every new request, a new agent instance is created via the factory ,The conversation history is then rehydrated from Redis for that user/session

What I’m Trying to Understand

• Is This the recommended pattern for handling runtime values like userId in services such as chat history providers?
• Is this stateless agent per request + history rehydration the expected/recommended pattern in agent-based systems?
• Or should an agent instance be long-lived per conversation/session (e.g., cached or stored), instead of recreated on each request?

Take a loot at my redis history provider and factory class below

RedisChatHistoryProvider.txt
ShipmentAgentFactory.txt

Additional Context (Current Invocation Pattern)

From my REST endpoint, this is how I’m currently invoking the agent:

     var agent = agentFactory.Create(userInput, conversationId);
     var session = await agent.CreateSessionAsync();
     var response = await agent.RunAsync<ContainerAgentResponse>(userInput, session);
     return JsonSerializer.Deserialize<ContainerAgentResponse>(response.Text)!;