Codex — Rules

File format

Markdown

Discovery path

AGENTS.md

Global install path

~/.codex

Syllago install method

Symlink, Direct copy

Symlink support

Yes

Features

How each feature converts to syllago's canonical format. See format conversion for what these statuses mean.

Fields

Native frontmatter or config fields this provider exposes. The first column is the provider's own field name; the canonical key column links to syllago's cross-provider equivalent.

Provider field	Conversion	Canonical key	Summary
project_doc_fallback_filenames	TranslatedConversion type: TranslatedActively mapped to the target provider’s equivalent field during conversion.Learn more →	—	Native rules filename is AGENTS.md, with configurable fallback list via config.toml project_doc_fallback_filenames.
project_doc_max_bytes	DroppedConversion type: DroppedCan’t be meaningfully preserved. Removed from the output with a portability warning.Learn more →	—	Configurable byte cap on AGENTS.md reads via config.toml project_doc_max_bytes; prevents oversized rules files from blowing the context window.
features.child_agents_md	Not portableConversion type: Not portableUnique to this provider — can’t be carried across providers.Learn more →	—	When features.child_agents_md is enabled, Codex emits scope/precedence guidance and combines AGENTS.md files across a directory hierarchy.

Other features

Behaviors, conventions, and capabilities that aren't tied to a single named field — things like path-based activation, discovery rules, and lifecycle behavior.

Feature	Conversion	Summary
cross_provider_recognition	TranslatedConversion type: TranslatedActively mapped to the target provider’s equivalent field during conversion.Learn more →	agents_md_filename: Codex reads AGENTS.md files using the standard filename used by multiple providers
hierarchical_loading	TranslatedConversion type: TranslatedActively mapped to the target provider’s equivalent field during conversion.Learn more →	hierarchical_agents_md: Codex loads AGENTS.md from subdirectories with defined precedence (deeper overrides higher)

Sources

Source
https://raw.githubusercontent.com/openai/codex/main/docs/agents_md.md
https://raw.githubusercontent.com/openai/codex/main/AGENTS.md