OpenAI · Model release
GPT-5.6 Sol, Terra, and Luna: what the three-tier release changes
OpenAI's July family is a tier decision before it is a model decision: Sol for difficult work, Terra for balance, and Luna for volume. Since 2026-09-22 GPT-6 Sol and Luna are the newer Sol/Luna options at lower rates; input and output savings differ by tier.
What changed
- The family splits capability and cost into three named tiers instead of one default choice.
- The July 30 price update made Terra and Luna materially cheaper for API workloads; Sol's list followed on 2026-08-21, cut from $5/$30 to $4/$20 (promotional at least through 2026-11-21).
- The right comparison is cost per successful task, not only the headline rate card.
- Superseded on 2026-09-22: GPT-6 Sol ($2/$10) and GPT-6 Luna ($0.10/$0.50) replace Sol and Luna. Terra has no GPT-6 successor but now costs more than GPT-6 Sol.
Best fit
- Mixed application workloads
- Agentic coding
- High-volume classification
What to be careful about
- OpenAI's public benchmark disclosure is narrower than the marketing surface.
- Specify the full model ID in production so routing does not silently move you to a more expensive tier.
Dataset snapshot: GPT-5.6 Sol is also represented in the checked comparison dataset. Prices and benchmark figures carry their own field dates.