OpenAI is updating the language model behind ChatGPT for free and Go plans: the previous GPT-5.5 is being replaced with GPT-5.6 Luna. According to the company, a key outcome of this update is the removal of the message limit for text chats — after the roll-out, eligible users will be able to send an unlimited number of messages to the AI.
New features for free users
With GPT-5.6 Luna, users also receive a "Think" button. Pressing this button causes the model to deploy more reasoning capacity on complex queries. The company notes that limits and restrictions remain in place for file uploads, the use of images and audio, and for image generation.
For subscribers: GPT-5.6 Sol and a thinking slider
Plus and Pro subscribers receive access to an enhanced GPT-5.6 Sol model. OpenAI says Sol performs better on fast tasks such as answering questions, conducting web research, providing advice, planning, writing, and decision-making. ChatGPT Plus and Pro users also get a thinking slider that lets them set how much the model should deliberate on a given response; the slider is adjustable based on the complexity and number of steps required to solve a query.
Accuracy and rollout timing
OpenAI's internal measurements show that GPT-5.6 Luna produces 62 percent fewer factual errors compared with GPT-5.5-Instant, and GPT-5.6 Sol shows a 68 percent reduction. The company is deploying the update in the coming days, and users should start seeing the changes as soon as next week.
Why this matters
The change removes a practical constraint for free users by eliminating chat limits, while providing paying customers with a faster, more capable model and finer control over model deliberation. At the same time, multimodal usage limits remain, so file, image, and audio handling and image generation continue to be subject to the existing restrictions.
