One command shows which AGENTS.md files Codex actually loaded

At session start Codex reads ~/.codex/AGENTS.md (global), then the project root, then each folder down to where you launched, and concatenates them. Closer files come later and win; an AGENTS.override.md replaces AGENTS.md in its folder. Past 32 KiB combined, the rest is dropped. When you're not sure what went in, the official docs give you this:

codex --ask-for-approval never "Summarize the current instructions."

To check that a subfolder's override replaces the broader rules, run it from that folder.

codex --cd services/payments "Summarize the current instructions."

To raise the cap or accept other file names:

# ~/.codex/config.toml
project_doc_max_bytes = 65536
project_doc_fallback_filenames = ["TEAM_GUIDE.md", ".agents.md"]