If you don't like CLAUDE.md, you can just add a memory/modify the plan agent to make an AGENTS.md. These aren't rigid systems. And, you don't have to tell it to look for an AGENTS.md, it'll just pick it up. First thing it does with /init is just look at what's already in the project folder. You should give CC a try!
works the other way as well, i have my opencode.jsonc which declares what model an agent should use, and it points at .claude/agents/ those agents each have their anthropic based model instead, almost feel like this broke in the past week though for just cc, hard to tell as cc keeps changing and i dont wanna update and learn more claude based nonsense again, if i wasn't locked into a year of pro or whatever, I would 100% be done using them entirely.