OpenAI Launches GPT-6 Sol and Luna at Half the Price

OpenAI has expanded its GPT-6 generation with updated versions of its smaller Sol and Luna models, cutting API prices in half compared with the 5.6 series and claiming significant accuracy gains.

The release follows GPT-6 Astra, which launched earlier this month. OpenAI called Astra its most powerful and capable model yet and the "world's best model" for a variety of activities, including computer work and coding. The two new models extend that generation down OpenAI's tier hierarchy.

"GPT-6 Astra introduced a new generation of intelligence; these models extend its benefits by making that intelligence more efficient and accessible," the company writes.

Sol and Luna occupy different tiers in OpenAI's lineup. The first models in each series arrived earlier this year. Sol targets complex tasks like coding. OpenAI positions Luna for clerical work — "high-volume tasks with a clear goal, like summarizing documents, extracting information, or answering quick questions."

Price cut driven by caching and inference

The 6 series models will be available at half the cost of the 5.6 series of Sol and Luna. OpenAI attributes the price drop to improvements in caching and inference.

The company also claims its newest models produce more factually accurate answers and make fewer coding errors.

"On our internal factuality evaluation, which is based on de-identified real-world conversations where users flagged mistakes by our models, GPT-6 Sol makes about half as many mistakes as its predecessor, reaching Astra-level reliability at much lower cost," the announcement reads.

That framing matters for OpenAI's business. Cheaper, more reliable mid-tier models broaden the audience for Astra-generation intelligence beyond customers willing to pay premium rates — particularly relevant for high-volume enterprise workloads like document summarization, which Luna is built to serve.

Competitive jockeying with Anthropic

As is typical with OpenAI's releases, the company claims its newest offerings outshine those of its primary competitor, Anthropic. OpenAI repeatedly claims GPT-6 Sol and Luna handle tasks substantially better than Anthropic's top models, Fable and Opus.

The rivalry is running hot. Anthropic released a new version of Opus 5.5 just 90 minutes before OpenAI's release, reflecting the intense competition between the two companies.

Availability

The new versions of Sol and Luna are now available in ChatGPT Work and Codex for most paid accounts, and in the ChatGPT API. Luna is also available in the desktop app and for Free and Go users. OpenAI expects to roll out the models to ChatGPT — the app and website — gradually throughout the day.