AI stackHarnesses

OpenAI Codex

Harness · terminal agent

The jobOpenAI's coding agent: open-source CLI, IDE extension, apps and cloud tasksVisit developers.openai.com

Best forChatGPT subscribers who want an open-source terminal agent plus cloud tasks

Skip ifYou want Claude, Gemini or open models, or tab completion as your main workflow

Verified Oct 5, 20263 sourcesLive

See all 8 alternatives to OpenAI Codex

OpenAI Codex also appears in Alternatives to GitHub Copilot, Alternatives to Cursor, Alternatives to Claude Code

Editor notes

The OpenAI counterpart to Claude Code. The CLI is open source, the models are OpenAI's only. It comes with ChatGPT plans (Free covers quick tasks) or bills per token on an API key, so cost follows the account you already have. A natural pick if ChatGPT is already your main AI account.

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

Summary

Codex is OpenAI's software engineering agent. The open-source Codex CLI runs locally in your terminal, and the same agent is available in an IDE extension, the ChatGPT desktop/web apps and as cloud tasks. It is included in ChatGPT plans or can be billed by API key at API rates.

Key details

Surface	CLIIDE extensiondesktopweb/cloudiOS
Platforms	macoslinuxwindowsweb
BYOK (Bring Your Own Key)	Yes (OpenAI API key only)
MCP Support	✓ Yes
Agent Skills Support	✓ Yes
Open Source	✓ Yes(Apache-2.0)

Installation

Terminal

curl -fsSL https://chatgpt.com/codex/install.sh | sh

Alternative installation methods:

npm install -g @openai/codex

brew install --cask codex

Repository

Pricing

From the vendor's pricing pageVerified Oct 5, 2026

Plan	Price	Basis
Free	Free
Go	$8/mo	Billed monthly
Plus	$20/mo	Billed monthly
Pro	$100/mo	Billed monthly
Business	$25/mo per seat	Per seat, billed monthly
API key	Price pending

Sources

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