Claude Code vs Codex CLI: Terminal AI Agents Compared

Both Claude Code and Codex CLI are terminal-first AI coding agents, but they differ in model provider, skill format, and development philosophy.

Open Source vs Proprietary

Codex CLI is fully open source, allowing developers to inspect, modify, and contribute to the tool itself. Claude Code is proprietary, though its skill ecosystem (SKILL.md files) is open and community-driven.

Skills & Configuration

Claude Code uses SKILL.md for skills, CLAUDE.md for project configuration, and supports hooks and rules for automation. Codex CLI uses AGENTS.md and a plugin system. Many skills work across both platforms with minor format adaptations.

Model Quality

Claude Code uses Anthropic's Claude models (Sonnet, Opus), known for strong reasoning and code generation. Codex CLI uses OpenAI's models (GPT-4o, o3), which are also highly capable. Both are among the best for coding tasks.

Pricing

Claude Code: Pro $20/month, Max $100-200/month. Codex CLI: Included with ChatGPT Plus ($20/month) or uses API credits.

Ecosystem & Community

Claude Code has a larger skill ecosystem (14,000+ skills) and more mature community tooling. Codex CLI's open-source nature attracts contributors who build plugins and integrations.

Verdict

Choose Claude Code for the largest skill ecosystem and mature agentic workflows. Choose Codex CLI if you value open source, want OpenAI model access, or already pay for ChatGPT Plus.