OpenAI is removing text chat limits across ChatGPT and switching free and Go users to GPT-5.6 Luna as the default model, replacing GPT-5.5. The change lands the week after the service crossed 1 billion weekly users.
Free and Go users also get a new think button that unlocks higher reasoning power for complex questions. OpenAI says separate caps still apply to files, images, voice, and image generation.
Plus and Pro subscribers receive an upgraded GPT-5.6 Sol tuned for quick tasks like web research, planning, and writing, alongside a thinking slider that adjusts how much effort the model puts into an answer. OpenAI notes this version differs from the GPT-5.6 Sol used in Codex and Work, which stays unchanged.
Internal evaluations put factual errors 62 percent lower for Luna and 68 percent lower for the updated Sol compared with GPT-5.5-Instant.
The new Sol is available to paid tiers immediately, while the free and Go changes roll out this week. Unlimited text chats and the think button arrive next week.
