GPT-5.6 Sol and Luna in ChatGPT

ChatGPT's chat experience gets an updated GPT-5.6 Sol for paid users and unlimited GPT-5.6 Luna chats for free users.

Plus and Pro get a slider in ChatGPT on web, mobile, and desktop that sets how much thought the model puts into each answer
The same updated GPT-5.6 Sol now powers both Instant and deeper reasoning for paid users, so tone and behavior stay consistent instead of switching between two models
In OpenAI's internal evaluation on financial, medical, and legal prompts, responses containing at least one factual error were about 68% less common with the updated Sol than with GPT-5.5 Instant
Free and Go users move to GPT-5.6 Luna as the default this week, with unlimited text chats and a Think button for harder questions starting next week
Limits still apply to file uploads, images, and other tools on the free tier, and the updated Sol runs only in ChatGPT chat, not in Work or Codex