ChatGPT Free gets GPT-6 Luna, but only in the desktop app

OpenAI released two more models in the GPT-6 family on Tuesday. GPT-6 Sol and GPT-6 Luna follow GPT-6 Astra, which arrived in early September, and are designed to bring much of what Astra can do to faster, cheaper models. For anyone using ChatGPT without a paid plan, one line in the announcement matters most. Free and Go users can access GPT-6 Luna, but only in the desktop app.

OpenAI mentions no access for those plans on the web or in the mobile apps. The same restriction applied to Astra on ChatGPT Plus. The release notes state that in ChatGPT, "the models are available in Work and Codex, but not Chat." Notebookcheck explained earlier how Plus subscribers find GPT-6 Astra in Work, and the desktop app route is the same here.

What free users keep in Chat

Nothing changes in the chat window for now. Free and Go users still get GPT-5.6 Luna there, which OpenAI made the default for both plans in August, along with unlimited text chats and a Think button for harder questions. GPT-6 Luna in the desktop app comes with no such promise. OpenAI has not published a usage limit for it, neither a number nor a statement that it is unlimited, so nobody knows yet how far the allowance goes.

Sol for Plus, Pro and Business

Paying subscribers get both models, also in Work and Codex. That covers Plus, Pro, Business, Enterprise and Edu. OpenAI suggests Sol for complex coding and agentic workflows and Luna for focused, high-volume tasks. By OpenAI's own measurements, Sol makes about half as many factual mistakes as GPT-5.6 Sol, while Luna at higher effort settings matches GPT-5.6 Sol at roughly one-hundredth of the cost. None of these figures have been independently verified yet.

In Chat, Plus stays where it was, with GPT-5.6 Sol as the top option. Since mid-September, ChatGPT Plus no longer switches to Thinking on its own. Pro, Business and Enterprise users still get Astra in Chat, where it runs as GPT-6 Pro. On Enterprise plans, Sol and Luna only appear once an administrator turns them on.

Half price for developers

Both models are already live in the API at half the price of their predecessors. Sol costs $2 per million input tokens and $10 per million output tokens, and Luna costs $0.10 and $0.50. Cached input is billed at a 90% discount. In ChatGPT, OpenAI rolled out the models gradually over the course of Tuesday and advised users who could not see them yet to try again later. The company has still not said when they will come to the regular chat window.