How to persist user context or memory in a thread in assistants api?

I have user context like name, age, and designation.
I also have some memories like he likes playing badminton.
I want to pass this information to each thread that user creates, so that AI can personalize responses.
Firstly I passed it as a first message (it didn’t work as when user has sent some messages, it goes out of the context window).
Second, I tried including it after every user message, but that caused unnecessary token usage, and if memory gets little long, the AI responses deteriorate.
If we use text file upload and API performs RAG, it won’t be retrieved that often and I want user context to always be in context window.
How can we achieve above?