OpenAI has released a major update for ChatGPT today. Free users now have the default model switched to GPT-5.6Luna, and the Chat mode no longer has text conversation limits, allowing unlimited usage. This feature will be rolled out to all free users this week.
Plus and Pro users also received upgrades. The GPT-5.6Sol in Chat has undergone specialized optimization, and the official stated that it shows significant improvements in factual accuracy and answer quality. Altman posted on X platform: "5.6Sol performs much better in chats, and free users can also have unlimited text chats!"
OpenAI stated that 1 billion people per week use ChatGPT for quick Q&A, web search, planning, research, consulting, and complex decision-making. This GPT-5.6Sol update is designed to cover the entire range of these usages. The updated model provides more focused responses, adjusting the level of detail based on the question, avoiding unnecessary formatting, and offering helpful corrections when simply agreeing without value. For Plus and Pro users, the same model powers both instant answers and deep reasoning, providing a more consistent experience.
In particular, for quick questions, the model provides direct answers with necessary context; for complex tasks such as multi-step planning, research, or writing, it gives more complete responses while keeping the core recommendations clear. In the comparison examples shown by OpenAI, GPT-5.5Instant lists all information like rain, wind, and temperature in a cycling consultation scenario, while GPT-5.6Sol first answers the user's real concern, identifies wind as the main influencing factor instead of rain, keeps only the details needed by the cyclist, and even directly generates a weather forecast sheet.
There are also significant improvements in hallucinations. Internal assessments by OpenAI show that the proportion of at least one factual error in financial, medical, and legal prompts decreased by about 62% for GPT-5.6Luna compared to GPT-5.5Instant, and by about 68% for GPT-5.6Sol.
Subscribers also received UI experience updates. After the release of the three 5.6 models, users had to select the model and inference strength simultaneously, which was complicated. Now, the Chat interface introduces the same slider feature used in Codex. Plus and Pro users can adjust the model's thinking volume on the web, mobile, and desktop versions—keep it in fast mode for daily questions, and increase the slider when planning, researching, writing, coding, or making decisions.
Free users now have full access to GPT-5.6Luna, with unlimited text chatting. However, features such as image generation and file uploads still have limits. Since Luna is not a universal model, OpenAI has added a new "Think" button to handle complex issues.
Notably, this GPT-5.6Sol update is limited to the ChatGPT chat experience, and the GPT-5.6Sol version used in Work and Codex is not included in this update.
