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OpenAI · Codex CLI · IDE extension · ChatGPT desktop app

OpenAI Codex rules files explained

Which instruction files OpenAI Codex reads (AGENTS.md), where to put them, and how to convert from other agents.

Files Codex reads

  • AGENTS.md

AGENTS.md: Yes (AGENTS.md originated here).

Skills folders: .codex/skills/

Who reads what

AgentRules filesAGENTS.md
ClaudeCLAUDE.md, .claude/rules/*.mdOnly when no CLAUDE.md exists (per research notes, Oct 2026; verify)
CodexAGENTS.mdYes (AGENTS.md originated here)
Cursor.cursor/rules/*.mdc, AGENTS.md, .cursorrules (legacy)Yes
Copilot.github/copilot-instructions.md, .github/instructions/*.instructions.md, AGENTS.mdYes
AntigravityGEMINI.md, AGENTS.mdYes (per research notes; verify)
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