OpenAI is rolling out significant updates to ChatGPT across all user tiers. Free and Go users will get a new default model replacing GPT-5.5, along with a "Think" button that enables higher reasoning power for complex questions. Next week, these users will gain access to unlimited text chats and the new Think button, though separate limits will remain for files, images, voice, and image generation.
Plus and Pro users are receiving the upgraded GPT-5.6 Sol model today, designed for quick tasks like questions, web research, advice, planning, writing, and decision-making. This is separate from the GPT-5.6 Sol used for Codex and Work, which remains unchanged. These users also get a thinking slider to adjust how much cognitive effort the model applies based on query complexity.
OpenAI's internal evaluations show meaningful accuracy improvements: GPT-5.6 Luna produces 62% fewer factual errors compared to GPT-5.5-Instant, while GPT-5.6 Sol reduces errors by 68%.