Augment Code vs OpenAI Codex CLI

Augment Code vs OpenAI Codex CLIComparisonUpdated 2026-03-16

SUMMARY

Augment Code (IDE) uses markdown configuration while OpenAI Codex CLI (CLI) uses markdown. They differ on 2 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.

FEATURE COMPARISON

Feature	Augment Code	OpenAI Codex CLI	Notes
Config format	markdown	markdown
Hierarchy support	✓	✓	Whether config files can be placed at multiple directory levels
Global config	✓	✓	User-wide configuration outside any project
Project config	✓	✓
Subdirectory scoping	✓	✓	Config files in subdirectories that apply only to that subtree
File inclusion / imports	✗	✗	Ability to include or reference other files from config
Ignore file	✗	.codexignore
IDE integration	✓	CLI
Schema / structure	Free-form (Markdown)	Free-form (Markdown)	Whether config uses structured schema or free-form content
Git committed	✓	✓	Whether primary config files are intended to be version-controlled
Encoding	UTF-8	UTF-8

FILE MAPPING

Purpose	Augment Code	OpenAI Codex CLI
Project instructions	AGENTS.md	AGENTS.md
Project instructions	.augment-guidelines.md	AGENTS.override.md

SIDE-BY-SIDE CODE SAMPLES

Augment Code

AGENTS.md

markdown

# Project Rules

## Architecture
- Clean architecture with domain, application, and infrastructure layers
- Domain models must not import from infrastructure
- Use dependency injection for all services

## Code Style
- TypeScript strict mode, no implicit any
- Use Result<T, E> for error handling in domain layer
- Prefer composition over inheritance
- Maximum 3 parameters per function; use options objects for more

## Testing
- Unit tests for domain logic (no mocking frameworks)
- Integration tests for API endpoints
- E2E tests for critical user journeys with Playwright

## Dependencies
- Do not add new dependencies without discussing first
- Prefer standard library over third-party for simple tasks

OpenAI Codex CLI

AGENTS.md

markdown

# AGENTS.md

## Project Overview

This is a Next.js 14 e-commerce application using the App Router,
Server Components, and Drizzle ORM with PostgreSQL.

## Code Conventions

- Use TypeScript strict mode throughout
- Prefer Server Components; use "use client" only when necessary
- Name files with kebab-case: `product-card.tsx`, not `ProductCard.tsx`
- Co-locate tests: `product-card.test.tsx` next to `product-card.tsx`

## Architecture

- `app/`           — Next.js App Router pages and layouts
- `components/`    — Shared UI components
- `lib/`           — Utilities, database client, auth helpers
- `actions/`       — Server Actions for mutations

## Testing

- Use Vitest for unit tests, Playwright for E2E
- Mock database calls using `lib/test-utils.ts` helpers
- Every new component needs at least one test

## Build Commands

```bash
pnpm dev          # Start dev server
pnpm build        # Production build
pnpm test         # Run Vitest
pnpm test:e2e     # Run Playwright
pnpm lint         # ESLint check
```

KEY DIFFERENCES

1. Ignore file

Augment Code: Not supported. OpenAI Codex CLI: .codexignore.

2. IDE integration

Augment Code: Supported. OpenAI Codex CLI: CLI.

WHICH SHOULD I USE?

Recommendation

Choose based on your IDE/CLI preference. If you use Augment Code, configure AGENTS.md. If you use OpenAI Codex CLI, configure AGENTS.md. Many projects include config files for multiple tools so each team member can use their preferred editor.

PORTABILITY TIP

sync-instructions.sh

bash

# Maintain a single source of truth:
cp AI-INSTRUCTIONS.md CLAUDE.md
cp AI-INSTRUCTIONS.md .cursorrules
cp AI-INSTRUCTIONS.md AGENTS.md