OpenAI Upgrades ChatGPT with New GPT-5.6 Luna and Sol Models

OpenAI is rolling out GPT-5.6 Luna as the default model for Free and Go users this week, while ChatGPT Plus and Pro subscribers receive an upgraded GPT-5.6 Sol model.

The update introduces unlimited text-based conversations for free users starting next week and adds a 'Think' button for deeper reasoning, alongside a new thinking slider for paid subscribers.

Internal evaluations show factual errors are 62% less common with GPT-5.6 Luna and 68% less common with GPT-5.6 Sol compared to the previous GPT-5.5 Instant model.