GPT-6 Sol and Luna: OpenAI halves AI prices

What's new

On September 22, 2026, OpenAI released two new models: GPT-6 Sol and GPT-6 Luna. They are updated versions of the GPT-5.6 series and build on the same technology as the more expensive flagship model GPT-6 Astra, which came out earlier this year.

What's clever

Sol is the powerful model, built for difficult tasks such as programming and technical analysis. Luna is the fast and cheap little sibling, which is good for large volumes of simple tasks, such as summarizing texts, answering questions or pulling information out of documents. Both models can handle up to about 1 million tokens (pieces of text) in one conversation, equivalent to several thousand pages of text, so they can work with very long documents at a time. OpenAI says Sol makes significantly fewer mistakes: in tests of programming tasks, the so-called "deception rate" (how often the model gives a wrong answer it believes is correct) fell from 10.4 to 1.3 percent compared with its predecessor.

Cheaper or better?

Both models cost about 50 percent less than the previous versions, and the prices are fixed with no expiration date. Sol costs $2 per million input tokens and $10 per million output tokens, the same as Anthropic's Claude Sonnet 5, but about half of Claude Opus 5.5. Luna is even cheaper at $0.10 for input and $0.50 for output, which according to VentureBeat is about 87 percent below Google's Gemini 3.8 Flash on output prices (Google's prices do rise after New Year, however). OpenAI says Luna can match the older Sol model's reliability at just one-hundredth of the price.

What it's good at

Sol is the choice if you need something complicated coded or heavy analyses done, where quality matters most. Luna fits everyday tasks such as reading and summarizing emails, finding answers in documents or responding to customer inquiries quickly and cheaply. The models are rolling out via the API and to paying ChatGPT users (Plus, Pro, Business, Enterprise and Edu), while Luna will also be freely available in the desktop app for Free and Go users. For now, the new models do not work in the regular chat mode in ChatGPT, only via the API and in the Work and Codex tools.