OpenAI gives free ChatGPT users unlimited chats with GPT-5.6 Luna

OpenAI is expanding access to its GPT-5.6 models by giving free ChatGPT users unlimited text conversations with GPT-5.6 Luna and introducing new controls for deeper reasoning.

GPT-5.6 Luna will become the default model for Free and Go users this week, according to an announcement released Thursday. Unlimited text chats and a new Think button will begin rolling out to those users next week, subject to safeguards against abuse.

The Think button will allow free users to give GPT-5.6 Luna more time to process questions that require additional reasoning. OpenAI said limits will continue to apply to file uploads, image generation, and other tools despite the removal of limits on text conversations.

OpenAI is also updating GPT-5.6 Sol for Plus and Pro subscribers. The company said the revised model is designed to provide more focused answers, reduce unnecessary detail, and improve factual reliability when responding to questions involving dates, numbers, sources, rules, or assumptions.

Plus and Pro users will receive a new slider on ChatGPT’s web, mobile, and desktop applications that controls how much reasoning effort the model applies to each answer.

Users can select lower effort for quick questions or increase the setting for research, planning, writing, coding, and other complex tasks. OpenAI said the same GPT-5.6 Sol model will now power both immediate responses and deeper reasoning modes, creating a more consistent experience between them.

The updated GPT-5.6 Sol and its reasoning slider are available to Plus and Pro users beginning Thursday.

OpenAI said internal testing showed that answers containing at least one factual error were about 68% less common with GPT-5.6 Sol than with GPT-5.5 Instant across a set of financial, medical, and legal questions requiring detailed factual information.

GPT-5.6 Luna reduced the rate of responses containing factual errors by approximately 62% compared with GPT-5.5 Instant in the same evaluation.

The company said GPT-5.6 Sol is also intended to adjust the amount of detail based on the complexity of the user’s request. Quick questions should receive direct answers, while research and multistep assignments should produce fuller responses without obscuring the main recommendation.

OpenAI said ChatGPT is now used by 1 billion people each week for searches, planning, research, writing, advice, and complex decisions.

The latest changes apply specifically to the Chat experience inside ChatGPT. The versions of GPT-5.6 Sol used in ChatGPT Work and Codex are not being changed as part of the rollout.

OpenAI introduced the broader GPT-5.6 model family in July. The lineup includes Sol as its flagship model, Terra as its balanced model for everyday work, and Luna as its fastest and lowest cost option.

The company said it has also expanded safety training and evaluations for users believed to be under 18. These measures include additional restrictions involving romantic roleplay, dangerous activities, graphic violence, age restricted goods, sexual content, eating disorders, and body image risks.