How to switch Codex to the GPT-6.1 Terra model

OpenAI released GPT-6.1 Terra in ChatGPT Work and Codex on October 26. It's available on Plus, Pro, Business, Enterprise and Edu plans and isn't offered in Chat. OpenAI's models page describes Terra as a fast, efficient model for writing, understanding images and screens, and computer use (it suggests GPT-6.1 Sol for repeated, long-running work when cost matters and Astra for the most demanding work).

1. Terra requires Codex CLI 0.159.0 or later. Check your version and update if needed.

codex --version
npm install -g @openai/codex@0.164.0

1. Start Codex with Terra.

codex -m gpt-6.1-terra

In a session that's already running, switch with /model. From 0.164.0 you can pass the name inline, as in /model gpt-6.1-terra.

1. The same option works for non-interactive runs.

codex exec -m gpt-6.1-terra "Review these dashboard screenshots and summarize what changed"

To use Terra by default, set it in your config file.

# ~/.codex/config.toml
model = "gpt-6.1-terra"

In the desktop app and ChatGPT Work on the web, open Advanced and pick it from the model list. Work on mobile supports it too. The models page lists Work and Codex in the desktop app, ChatGPT Work on the web and the Codex CLI as places to use Terra; the IDE extension isn't on that list. Enterprise access depends on workspace availability and administrator controls.