Could you maybe make use of Simon Willsons [LLM lib/app](https://github.com/simonw/llm)? It has great LLM support (just pass in the model to use) and records everything by default.
The one feature missing from LLM core for this right now is serving models over an HTTP OpenAI-compatible local server. There's a plugin you can try for that here though: https://github.com/irthomasthomas/llm-model-gateway
