OpenAI debuts GPT-5.6 Sol, Terra, Luna in limited preview

On June 26, 2026, OpenAI began a limited preview of its GPT-5.6 model series in three tiers: Sol (flagship), Terra (balanced, matching GPT-5.5 at 2x lower cost) and Luna (fast and affordable). Notably, access is restricted to a small group of trusted partners at the US government's request — the first time the administration has preemptively asked a US AI company to limit a model's release.

Key points

• Three models: Sol for the hardest tasks (coding, security research); Terra for everyday work; Luna for high-volume tasks.
• API price per 1M tokens: Sol $5 in / $30 out; Terra $2.50 / $15; Luna $1 / $6.
• Government-requested limits: the White House Office of the National Cyber Director and OSTP asked OpenAI to restrict the rollout over the model's cyber capabilities; OpenAI says this should not be the long-term default.
• New features: a max reasoning effort and an ultra mode (using subagents); sets a new SOTA on Terminal-Bench 2.1 (coding).
• Safety: its most robust safeguard stack yet, with 700,000+ A100-equivalent GPU hours of automated red-teaming.
• Access: first via the API + Codex for select partners, with ChatGPT/general availability in the coming weeks; on Cerebras at up to 750 tokens/sec from July.