Google Antigravity vs OpenAI Codex CLIComparisonUpdated 2026-03-18
SUMMARY
Google Antigravity (IDE) uses markdown configuration while OpenAI Codex CLI (CLI) uses markdown. They differ on 3 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.
FEATURE COMPARISON
| Feature | Google Antigravity | OpenAI Codex CLI |
|---|---|---|
| Config format | markdown | markdown |
| Hierarchy support | ✓ | ✓ |
| Global config | ✗ | ✓ |
| Project config | ✓ | ✓ |
| Subdirectory scoping | ✓ | ✓ |
| File inclusion / imports | ✗ | ✗ |
| Ignore file | ✗ | .codexignore |
| IDE integration | ✓ | CLI |
| Schema / structure | Free-form (Markdown) | Free-form (Markdown) |
| Git committed | ✓ | ✓ |
| Encoding | UTF-8 | UTF-8 |
FILE MAPPING
SIDE-BY-SIDE CODE SAMPLES
Google Antigravity
AGENTS.md
markdown
# Project Instructions
## Architecture
- Monorepo with apps/ and packages/ directories
- Each app is a standalone Next.js deployment
- Shared packages use TypeScript project references
## Code Standards
- TypeScript strict mode everywhere
- Use Zod for runtime validation at API boundaries
- Prefer server components; use "use client" only when needed
- All database queries go through the data-access layer
## Testing
- Unit tests with Vitest for business logic
- Integration tests for API routes
- E2E tests with Playwright for critical user flows
## Deployment
- Preview deployments on every PR
- Production deploys from main branch only
- Environment variables managed via .env.local (never committed)
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
Google Antigravity: Not supported. OpenAI Codex CLI: Supported.
Google Antigravity: Not supported. OpenAI Codex CLI: .codexignore.
Google Antigravity: Supported. OpenAI Codex CLI: CLI.
WHICH SHOULD I USE?
Choose based on your IDE/CLI preference. If you use Google Antigravity, 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
SEE ALSO
Tool pages:
agentconfig.ing2026-03-18COMPARE(1)