Use codex.toml (or configurable filename) instead of generic config.toml

What variant of Codex are you using?

CLI (also affects shared config behavior used by IDE/App)

What feature would you like to see?

I’d like Codex to stop using the generic filename config.toml and move to a clearer Codex-specific name: codex.toml.

Today, project-scoped config lives in .codex/config.toml and user config in ~/.codex/config.toml. The filename is very generic and easy to confuse with other tools, especially in repos that already contain multiple config.toml files.

Proposed direction:

1. Prefer codex.toml as the canonical config filename.
2. Support existing config.toml during a transition window.
3. Emit a non-blocking warning when loading config.toml if codex.toml is absent.
4. Eventually deprecate config.toml (or keep as fallback indefinitely if needed).

Possible resolution paths:

• Minimal change: keep directories as-is, just rename filenames:
• ~/.codex/config.toml -> ~/.codex/codex.toml
• .codex/config.toml -> .codex/codex.toml
• Better long-term flexibility: add a configurable config filename/path override (this may overlap with #7971).

Why this helps:

• Better discoverability: codex.toml is self-identifying.
• Fewer naming collisions/confusion with other tools.
• Easier onboarding and docs readability (users instantly know the file belongs to Codex).

Additional information

I saw #7971 (config path configurability) was completed, which is related, but this request is specifically about the default filename semantics and discoverability.

Environment (for context):

• Codex CLI: 0.98.0
• Platform: macOS v26.2