OpenAI Codex

Setup

To use Codex, you can connect your ChatGPT Subscription or provide an API key. We recommend using your your ChatGPT account to use Codex as part of your Plus, Pro, Team, Edu, or Enterprise plan.

You can configure this in the settings page.

Available Models

• GPT-5-Codex
• GPT-5

Each of these models also have different levels of reasoning: low, medium, high. Using low will favor speed and fewer tokens, while high favors more thorough reasoning.

GPT-5-Codex is a version of GPT-5 further optimized for agentic coding in Codex. GPT-5-Codex was trained with a focus on real-world software engineering work; it's equally proficient at quick, interactive sessions and at independently powering through long, complex tasks. Its code review capability can catch critical bugs before they ship.

Limitations

Codex only supports command-based MCP servers.