GPT-5.6 Luna 80% cheaper, GPT-5.6 Terra 20% cheaper; Fast mode replaces Priority

Starting July 30, GPT-5.6 Luna costs 80% less, while GPT-5.6 Terra costs 20% less. See pricing details.

We're also introducing Fast mode in the API, which replaces our Priority Processing offering. For GPT-5.6 Sol, Fast mode now delivers up to 2.5× faster speeds than standard processing at twice the price. This change is backward compatible: requests tagged priority will automatically use Fast mode.