SUMMARY
OpenAI Codex CLI (CLI) uses markdown configuration while Firebase Studio (Platform) uses text. They differ on 7 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.
FEATURE COMPARISON
| Feature | OpenAI Codex CLI | Firebase Studio |
|---|---|---|
| Config format | markdown | text |
| Hierarchy support | ✓ | ✗ |
| Global config | ✓ | ✗ |
| Project config | ✓ | ✓ |
| Subdirectory scoping | ✓ | ✗ |
| File inclusion / imports | ✗ | ✗ |
| Ignore file | .codexignore | ✗ |
| IDE integration | CLI | Platform |
| Schema / structure | Free-form (Markdown) | unknown |
| Git committed | ✓ | ✓ |
| Encoding | UTF-8 | UTF-8 |
FILE MAPPING
| Purpose | OpenAI Codex CLI | Firebase Studio |
|---|---|---|
| Settings / configuration | ~/.codex/config.toml | .idx/dev.nix |
KEY DIFFERENCES
OpenAI Codex CLI: markdown. Firebase Studio: text.
OpenAI Codex CLI: Supported. Firebase Studio: Not supported.
OpenAI Codex CLI: Supported. Firebase Studio: Not supported.
OpenAI Codex CLI: Supported. Firebase Studio: Not supported.
OpenAI Codex CLI: .codexignore. Firebase Studio: Not supported.
OpenAI Codex CLI: CLI. Firebase Studio: Platform.
OpenAI Codex CLI: Free-form (Markdown). Firebase Studio: unknown.
WHICH SHOULD I USE?
Choose based on your IDE/CLI preference. If you use OpenAI Codex CLI, configure AGENTS.md. If you use Firebase Studio, configure .idx/dev.nix. Many projects include config files for multiple tools so each team member can use their preferred editor.
PORTABILITY TIP
# Maintain a single source of truth:
cp AI-INSTRUCTIONS.md CLAUDE.md
cp AI-INSTRUCTIONS.md .cursorrules
cp AI-INSTRUCTIONS.md AGENTS.md