OpenAI announced it is removing limits on text-based chats for all ChatGPT users, a move that coincides with the service crossing 1 billion weekly active users. The free tier and the lower-cost Go tier will now be powered by the GPT-5.6 Luna model by default, replacing GPT-5.5. These users will also receive a new “Think” button that enables higher reasoning power for complex queries, though separate caps on files, images, voice, and image generation remain in place.

For Plus and Pro subscribers, OpenAI is rolling out an upgraded version of GPT-5.6 Sol tuned for quick tasks such as answering questions, web research, advice, planning, writing, and decision-making. The company says this model produces more compact and robust answers. Notably, this version is distinct from the GPT-5.6 Sol used for Codex and Work, which remains unchanged. Plus and Pro users also gain a thinking slider that lets them adjust how much computational effort the model puts into each response, allowing them to dial up or down based on query complexity.

OpenAI shared internal evaluation results comparing the new models with GPT-5.5-Instant: factual errors were 62% less common for GPT-5.6 Luna and 68% less common for the updated GPT-5.6 Sol. The upgraded Sol model is available to Plus and Pro users immediately, while the changes for Free and Go users—unlimited text chats and the Think button—will roll out during the current week and the following week.