GPT-6.1 Terra is not available on the free plan. When OpenAI launched this fast, low-cost model on October 26, 2026, it opened it only to five paid plans: Plus, Pro, Business, Enterprise, and Edu. The Free and Go plans are not on the list. Free users who want a no-cost model from the same generation can look for GPT-6 Luna in the desktop app, the lightweight model prepared for the Free and Go plans.
Who can use it, and who cannot
Only five plans are on the list; the Free and Go plans are not. This table makes it clear at a glance:
| Your plan | Can you use Terra? |
|---|---|
| Free, Go | No — use GPT-6 Luna instead |
| Plus, Pro, Business | Yes, in Work and Codex |
| Enterprise, Edu | Yes, but an administrator must enable it first |
There is one more condition behind every yes in the table: Terra only appears in ChatGPT Work and Codex. It is not in the regular chat window.
Three steps to switch when you cannot find it
Once you have confirmed your plan is on the list, follow these three steps. First, open the ChatGPT desktop app and go to Work or Codex — do not stay in the regular chat window. Second, click the model menu above the input box and choose Advanced. Third, pick GPT-6.1 Terra from the list. Command-line users can upgrade Codex CLI to 0.159.0 or later and specify the model with codex -m gpt-6.1-terra. If it still does not show up, the gradual rollout probably has not reached your account yet; check again after a while.
Three pitfalls to watch out for
First, buying Plus does not give you API access. A subscription only covers Work and Codex usage inside the app; API calls are billed separately by usage. The model name is gpt-6.1-terra: $1 per million input tokens, $0.05 per million cached input tokens, and $5 per million output tokens. Second, Enterprise and Edu accounts need an administrator to enable it first — upgrading on your own will not make it appear. Third, prices rise when a single input exceeds 272,000 tokens, so split large files into smaller pieces before sending them.
