GPT-5.6 Sol, Terra and Luna open to everyone with tiered API pricing

OpenAI is opening its newest model family to everyone. Sol, Terra and Luna, the three tiers of GPT-5.6, go publicly available on Thursday, July 9, 2026.

A new naming system

OpenAI unveiled GPT-5.6 on June 26, 2026, and with it a new way of naming models. The number marks the generation, while Sol, Terra and Luna mark durable capability tiers that will persist across generations:

• Sol is the flagship and most capable model
• Terra is a strong lower-cost option
• Luna is the fastest and most cost-efficient

The idea is that you pick a tier once and carry it forward, rather than relearning the lineup with every release.

From limited preview to public launch

The rollout has been unusually staged. After the June announcement, GPT-5.6 ran in a limited preview open only to trusted partners, accessible through the API and Codex. The public launch on July 9 opens all three tiers to everyone.

Reported API pricing per million tokens puts Sol at $5 input / $30 output, Terra at $2.50 / $15, and Luna at $1 / $6. That gives the family a 5x price spread between the flagship and the featherweight, which is the practical point of the tier system: match the model to the task and pay accordingly.

Why the tiers matter

The interesting choice here is not any single model but the structure. Flagship models grab benchmarks, but most production workloads do not need the most capable option on every call. A stable three-tier lineup with predictable pricing makes it easier for teams to route work: Sol for the hard problems, Terra for the balanced middle, Luna for high-volume, latency-sensitive tasks.

For developers, the question on launch day is simple: which tier do you reach for first, the flagship Sol or the fast and cheap Luna? Thursday is when everyone finds out what the answer is in practice.