OpenAI Releases Updated GPT-6 Sol and Luna Models at Half the Price of Previous Generation

OpenAI announced in September 2026 the release of updated versions of its GPT-6 Sol and Luna models, expanding the GPT-6 generation that began earlier in the month with the launch of GPT-6 Astra.

Sol is designed for complex tasks such as coding, while Luna targets high-volume clerical work — summarizing documents, extracting information, and answering quick questions. Both new models are now available in ChatGPT Work and Codex for most paid accounts and through the ChatGPT API. Luna is also available in the desktop app and for Free and Go users, with a gradual rollout to the broader ChatGPT app and website expected throughout the day of launch.

The most significant change is pricing. OpenAI says the GPT-6 Sol and Luna models will be available at half the cost of the previous 5.6 series, a reduction the company attributes to improvements in caching and inference.

OpenAI also claims improved factual accuracy and lower coding error rates. According to the company’s announcement, GPT-6 Sol makes roughly half as many mistakes as its predecessor on an internal factuality evaluation based on real-world conversations where users flagged model errors — placing it at what OpenAI describes as “Astra-level reliability.”

The release comes amid intensifying competition with Anthropic. OpenAI claims GPT-6 Sol and Luna outperform Anthropic’s top models, including Fable and Opus. Notably, Anthropic released a new version of Opus 5.5 just 90 minutes before OpenAI’s announcement.

For users and developers, the price reduction alongside claimed accuracy gains could make the GPT-6 series a more practical option for high-volume applications — though independent evaluations of the performance claims have yet to emerge.