GPT-6 Sol and Luna: OpenAI brings Astra's gains to cheaper models
September 22, 2026 · JICA LABS
On the same September 22 that Anthropic unveiled Claude Opus 5.5, OpenAI launched GPT-6 Sol and GPT-6 Luna, two models aimed at everyday work. They follow GPT-6 Astra, the series' large model.
Two models, two jobs
- GPT-6 Sol: the mid-tier model, with more reasoning ability, for day-to-day tasks. It costs $2 per million input tokens and $10 per million output tokens.
- GPT-6 Luna: the cheapest and fastest, built for high-volume responses. It costs $0.10 and $0.50 per million input and output tokens.
Both cost half as much as their 5.6 versions. OpenAI says Sol makes about half as many mistakes as GPT-5.6 Sol, thanks to the same training methods used on Astra to improve professional work, factuality, coding and computer use.
Comparisons with Claude
In the results OpenAI shared, Sol comes out ahead of Claude Opus 5 on some workflow and long-task benchmarks at a fraction of the cost, and roughly ties it on the OSWorld 2.0 computer-use test. Take these comparisons with caution: they are published by the company itself and are against Opus 5, not Opus 5.5, which launched the same day.
Availability
Sol and Luna are live in ChatGPT Work and Codex for most paid plans, and in the API. Luna also reaches Free and Go users through the desktop app. GitHub announced availability in its developer tools the same day.
The price race among the big AI labs has sped up: see also Claude Opus 5.5 and our pricing comparison with a calculator.