Overview
- OpenAI updated ChatGPT on Thursday by deploying a Chat-optimized GPT-5.6 Sol to Plus and Pro users and beginning a rollout of GPT-5.6 Luna to Free and Go accounts with unlimited text chats and a new Think button scheduled for next week.
- Plus and Pro subscribers get a reasoning slider that lets them trade speed for deeper, slower answers while the Chat-optimized Sol delivers more focused replies and tighter formatting for everyday conversations.
- Free and Go users will default to GPT-5.6 Luna and can tap a Think button to request extra reasoning on hard questions, but non-text features such as file uploads, image generation, voice, and other tools will still face usage limits.
- OpenAI says internal tests on financial, medical, and legal prompts show Sol reduced responses with factual errors by about 68% and Luna by about 62% versus GPT-5.5 Instant, though the company has not published the full prompts or reproduction details.
- The Sol update applies only to the Chat experience and does not change the Sol variants used by Codex or ChatGPT Work, and the move comes as ChatGPT serves over one billion weekly users, raising operational and governance implications for safety and abuse protections.