OpenAI Codex · tool · fg-0495

Codex does not read the repo's CLAUDE.md or other existing instruction files

Codex ignores rules that Claude Code follows from CLAUDE.md

Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100

Cause

In each directory Codex reads AGENTS.override.md, then AGENTS.md, and other names only when they are listed in project_doc_fallback_filenames. Fallback names are tried only where no AGENTS.md exists.

Fix

List the extra filenames in config.toml, or add an AGENTS.md that points to the shared file.

Apply

# ~/.codex/config.toml
project_doc_fallback_filenames = ["CLAUDE.md"]

Affects: Codex CLI, IDE extension, and ChatGPT desktop app, as of 2026-10

Sources

https://learn.chatgpt.com/docs/agent-configuration/agents-md

Have your agent know this before it fails

claude mcp add --transport http footgun https://getfootgun.com/api/mcp