OpenAI Codex (CLI)

OpenAI's coding agent across CLI, IDE extension, web and cloud.

Best for: Developers already on ChatGPT plans who want a terminal/cloud agent.
Open source: yes (CLI) · Licence: Apache-2.0 (checked on GitHub 2026-10-16) · GitHub
Pricing: Included in ChatGPT plans: Free $0, Go $8/mo, Plus $20/mo (CLI, IDE, cloud), Pro from $100/mo ($100/$200/$500); Business/Enterprise; or an API key at API rates. (source: official page, checked 2026-10-16)
Other CLI agents: Aider, goose, Gemini CLI, Warp

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Pricing is copied from each tool's official page on the date shown and left out where we couldn't read it; prices change. Licences were checked on GitHub; 'unconfirmed' means not verified. No affiliate links.