How to Install / Upgrade: Improving GPT‑5.6 Sol in ChatGPT—and expanding access to GPT-5.6 Luna for free users

ChatGPT is rolling out an improved GPT-5.6 Sol with better accuracy and consistency, and it is expanding access so free users can use GPT-5.6 Luna for unlimited everyday chats.

To get the update, open ChatGPT in the web app or mobile app while signed in. Switch the model selector to GPT-5.6 Sol when you want the improved model, or choose GPT-5.6 Luna for everyday chatting. Free users should select GPT-5.6 Luna in the same model menu; no separate download or install is required beyond an up-to-date ChatGPT client and a normal sign-in.

If Sol or Luna does not appear in the model list, refresh the page or fully quit and reopen the app, then confirm you are signed into the right account. Verify the change by starting a new chat, checking that the selector shows GPT-5.6 Sol or GPT-5.6 Luna, and confirming free-tier chats with Luna are available without a paid upgrade for everyday use.