OpenAI is removing limits on text-based chats for all users on ChatGPT, which recently crossed the 1 billion weekly user mark, the company announced today.

The new GPT-5.6 Luna model will power this experience and will be the default model for Free and Go users, replacing GPT-5.5.

Both users will also get a new “Think” button that lets them select higher reasoning power for complex questions. OpenAI said that there will still be separate limits for files, images, voice, and image generation.

The update brings changes for Plus and Pro users as well. They’ll gain access to an upgraded GPT-5.6 Sol model that’s better for quick tasks such as questions, web research, advice, planning, writing, and making decisions. The company noted that this new model will give more compact and robust answers. (Notably, this is a separate version from GPT-5.6 Sol used for Codex and Work, which is unchanged.)

ChatGPT Plus and Pro users are also getting a thinking slider to adjust “how much” thought the model puts into an answer. They can tune the thinking slider based on complexity and steps involved in solving a query.

OpenAI said an internal evaluation found that, compared to GPT-5.5-Instant, factual errors were 62% less common for GPT-5.6 Luna and 68% less common for GPT-5.6 Sol.

The updated version of GPT-5.6 Sol is available to Plus and Pro users today, while the other changes for Free and Go users are arriving this week. Next week, users will gain access to unlimited text chats and the new Think button for harder questions.