GPT-6 Sol and Luna Explained: Pricing, Where to Use Them, and Which to Pick vs Astra Low (Light)
OpenAI released GPT-6 Sol and GPT-6 Luna on September 22, 2026 (US time). Sol is priced at 1/5 of Astra ($2 input / $10 output) and Luna at 1/100 ($0.10 input / $0.50 output), and both are available in ChatGPT Work and Codex on Plus, Pro, Business, Enterprise and Edu, and in the API. Free and Go get Luna only, in the desktop app. Neither model was in regular Chat at launch, but since October 7 GPT-6 in Chat runs on Sol for Plus, Pro, Business and Enterprise, and since October 8 on Luna for Free and Go. GPT-5.6 remains available during the transition period. Written for people who currently use Astra at low (shown as Light in the app), this article separates its sources by publisher: the official use-case guidance (Sol at Medium, Luna at High, Astra from Light) and how it differs from the app's default preset (Sol Light); OpenAI's AutomationBench result where Sol xhigh beat Astra low; the values in Artificial Analysis's comparisons (42% for Astra low vs 19% for Sol medium on Terminal-Bench 4.0, but 59% vs 58% on business workflows); and AI Arte's small-scale test (every setting passed the short tasks, which is no basis for a ranking). It also explains why unit-price ratios don't carry over directly to the total cost of a job or to how much a subscription covers, and where the decision turns: Sol medium for everyday work, Sol low or Luna high for short, easy-to-verify jobs, and Astra for hard design work and important reviews.