OpenAI has launched GPT-6 Sol and GPT-6 Luna, lower-cost members of its GPT-6 family that it trained with similar methods to its flagship GPT-6 Astra, the company said on 22 September 2026.
API prices are $2 per million input tokens and $10 per million output tokens for Sol, and $0.10 and $0.50 for Luna, which OpenAI said is 50% cheaper than GPT-5.6 promotional pricing. It also said improved prompt caching delivers higher cache hit rates by default, with discounts of 90% on cached input.
OpenAI claimed that on AutomationBench, a test of business workflows across apps, Sol at xhigh effort outperforms Claude Opus 5 at max effort at 9% of the cost per task. These are vendor-reported results.
Both models are available in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu users, and in the API as gpt-6-sol and gpt-6-luna. Free and Go users can access Luna in the desktop app. OpenAI said Astra remains its best model.