OpenAI expands GPT-6 lineup with cheaper, more reliable Sol and Luna models

OpenAI has expanded its GPT-6 generation with updated versions of its smaller Sol and Luna models, positioning them as more efficient and affordable alternatives following the launch of the flagship GPT-6 Astra earlier this month.

Sol is designed for complex tasks such as coding, while Luna targets high-volume clerical work including document summarization, information extraction, and quick questions. OpenAI said API access to the 6-series Sol and Luna will cost half as much as the 5.6 series, attributing the price cut to improvements in caching and inference.

The company also said the new models produce more factually accurate answers and have a lower coding error rate. OpenAI's internal factuality evaluation, based on de-identified real-world conversations, shows GPT-6 Sol makes about half as many mistakes as its predecessor, reaching Astra-level reliability at much lower cost.

The updated models are now available in ChatGPT Work and Codex for most paid accounts and in the ChatGPT API, with Luna coming to the desktop app and Free and Go users. OpenAI expects to roll them out to the ChatGPT app and website gradually throughout the day.