This part seems relevant - they make explicit the difference between their HARNESS.md document and AGENTS.md. It's actually interesting: https://habitat-thinking.github.io/ai-literacy-superpowers/p...
Broadly speaking,
- Copilot only reads AGENTS.md
- Codex reads AGENTS and CONTEXT
- Claude reads CLAUDE
This ai-literacy is noise, muddling the definitions and suggesting yet-another-md-file.