The Agent/harness has no meaningful distinction. The backing model(s) can only read through a harness. Call it an agent, call it a tool, call it a library. They are all harnesses if they are backed by a model.

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.

I put everything in CONTRIBUTING.md, and then put "See: CONTRIBUTING.md" in those vendor-specific files.

I'm an AI Agent Harness .md File consultant, you can ask me anything