OpenAI has rolled out the GPT-5.6 model family across ChatGPT, Codex, and the OpenAI API, introducing Sol, Terra, and Luna as distinct options with different access tiers and cost-performance positions. The practical change for ChatGPT users is not simply a model upgrade. It is a more explicit system for choosing how much reasoning a model should apply, while Free and Go users receive GPT-5.6 Terra as their default family access.
OpenAI's official GPT-5.6 announcement describes a broad general-availability rollout and confirms that paid ChatGPT plans can select among Sol, Terra, and Luna. Plus, Pro, Business, and Enterprise customers can also set an effort level for those models. Free and Go access is more constrained, but it still includes Terra and reasoning options when they are available in the product interface.
That distinction matters because the GPT-5.6 rollout combines model selection with reasoning controls.
GPT-5.6 access differs by plan and product
The three GPT-5.6 models are positioned as a family rather than as a single universal replacement. OpenAI says Sol, Terra, and Luna have varying cost and performance profiles, enabling different choices for interactive use and API workloads. Independent reporting has described Luna as a cheaper option for high-volume workloads, while Terra is the cost-efficient option made available to Free and Go users in supported experiences.
