GPT-5.6 Sol

<p>GPT-5.6 Sol is the flagship of OpenAI’s GPT-5.6 series, alongside Terra (balanced) and Luna (fast). API pricing is $5 per million input tokens and $30 per million output tokens, with explicit cache breakpoints and a 30-minute minimum cache life.</p><p>On 13 August 2026 OpenAI and Cerebras previewed <strong>Ultrafast</strong>, a service tier that runs Sol at up to 750 output tokens per second — roughly 14x standard speed — with no claimed quality loss. Ultrafast launched first in the OpenAI API and is limited to a selected group of customers while capacity grows. OpenAI already sells a Fast Mode at about 2.5x speed for roughly double the price, making Ultrafast a third speed tier.</p>