OpenAI Codex CLI vs Cursor | agentconfig.ing

OpenAI Codex CLI vs CursorComparisonUpdated 2026-03-16

SUMMARY

OpenAI Codex CLI (CLI) uses markdown configuration while Cursor (IDE) uses mdc. They differ on 4 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.

FEATURE COMPARISON

Feature	OpenAI Codex CLI	Cursor	Notes
Config format	markdown	mdc
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	.cursorignore
IDE integration	CLI	✓
Schema / structure	Free-form (Markdown)	Hybrid (MDC frontmatter + 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	OpenAI Codex CLI	Cursor
Ignore patterns	.codexignore	.cursorignore

SIDE-BY-SIDE CODE SAMPLES

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
```

Cursor

.cursor/rules/*.mdc

mdc

---
description: React component conventions and patterns
globs: "*.tsx"
alwaysApply: false
---

# React Component Rules

- Use functional components with explicit return types
- Define props interface directly above the component
- Export components as named exports, never default
- Use Tailwind CSS utility classes exclusively

KEY DIFFERENCES

1. Config format

OpenAI Codex CLI: markdown. Cursor: mdc.

2. Ignore file

OpenAI Codex CLI: .codexignore. Cursor: .cursorignore.

3. IDE integration

OpenAI Codex CLI: CLI. Cursor: Supported.

4. Schema / structure

OpenAI Codex CLI: Free-form (Markdown). Cursor: Hybrid (MDC frontmatter + Markdown).

WHICH SHOULD I USE?

Recommendation

Choose based on your IDE/CLI preference. If you use OpenAI Codex CLI, configure AGENTS.md. If you use Cursor, configure .cursorrules. 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