Last week, OpenAI released three GPT-5.6 models—Sol, Terra, and Luna—and introduced ChatGPT Work, an agent for longer multi-step tasks, inside its newly unified ChatGPT app. Sol is the flagship model, available only to Plus, Pro, Business, and Enterprise users. Terra balances speed and power, while Luna is designed for speed. Free and $8 Go users get Terra only inside ChatGPT Work and Codex. Eligible paid users can pair Sol, Terra, or Luna with different reasoning settings, which determine how much thinking ChatGPT does and how quickly usage limits are reached. Per one million input/output tokens, Luna costs $1/$6, Terra costs $2.50/$15, and Sol costs $5/$30. Developer Simon Willison found that identical prompts can cost .71 cents or 48.55 cents depending on model and effort. The new desktop app folds Codex, chat, and Work into one place, and ChatGPT Work is also available inside the mobile app. The Codex desktop app is not going anywhere, per OpenAI engineering lead Thibault Sottiaux.