Comment by freedomben

Having experimented with soft-linking AGENTS.md into CLAUDE.md and GEMINI.md, this lines up well with my experience. I now just let each time maintain it's own files and don't try to combine them. If it's something like my custom "## Agent Instructions" then I just copy-pasta and it's not been hard, and since that section is mostly identical I just treat AGENTS.md as the canonical and copy/paste any changes over to the others.