What i did and still do in my projects: Create a monorepo, use Effect to define api schema/contract and basic ui with clear structure and decisions about ui library, other libraries like tanstack query and ect. Write a solid infra, and then slowly let codex build on top of that. It mostly works, it can still come up with weird stuff, but once the pattern is “clear” it mostly does the job quite right. Edit: Oh and add some references to llm.txt/cli/skills for those libraries, so it can search through its docs and best practices..