GPT-5.6 in the API (Generally Available)

The GPT-5.6 family from OpenAI is out of limited preview and open to all API developers in three tiers.

Sol is the flagship tier, strongest at coding, knowledge work, cybersecurity, and science
Terra matches GPT-5.5 performance at lower cost, and Luna is the fastest and cheapest tier for high-volume tasks
Per million input and output tokens: Sol costs $5 and $30, Terra costs $2.50 and $15, Luna costs $1 and $6
The number marks the model generation, while Sol, Terra, and Luna mark capability tiers that can each advance on their own schedule
The same models now sit behind ChatGPT and Codex, not only the API