I use ChatGPT Enterprise at work and Claude.AI (Free) and both have the concept of Projects to group related conversations so the model can learn from them and give better responses. You can also add files, documents, etc. to the project for better context
Yes, I see the Custom Assistant feature but that only allows for a system prompt, not upload of files for context. This article shows how to use it effectively for long running research projects.
This seems like a fundamental feature in modern AI assistants that's sorely missing in Kagi offering.
https://help.openai.com/en/articles/10169521-projects-in-chatgpt
https://support.claude.com/en/articles/9517075-what-are-projects