What are OpenAI’s GPT-6 Sol and Luna, and which one should you use?

Sol and Luna bring GPT-6 capability to lower-cost everyday work; Astra is the step-up option for unusually long, autonomous computer tasks.

Sol and Luna are the lower-cost members of OpenAI’s GPT-6 family, launched September 22 and positioned below the flagship GPT-6 Astra. The practical split is workload, not prestige: start with Sol or Luna for drafting, summaries, routine analysis, coding help, and jobs where many inexpensive attempts matter more than one marathon run. Move to Astra when an agent must keep a very long project in view, operate a computer across many steps, or recover from complications with less hand-holding.

Astra arrived September 3 with an approximately 1.05-million-token context window, full computer use, and OpenAI’s first “Critical” cybersecurity-capability rating—power that calls for tighter permissions and human checkpoints. Whatever the model, verify facts and code before acting. Access is rolling out gradually, so the names may not appear in every account or API region at once.