GPT-5.6 Terra Pro
OpenAI · released Jul 9, 2026
| size | mid-sized, not disclosed by the manufacturer |
| context window | 1,050,000 tokens |
| longest response | 128,000 tokens |
| knowledge cutoff | February 2026 |
| open weights | no |
| API price | $2 per million input tokens, $12 per million output tokens |
| input and output | text and images in, text out |
Manufacturer data (model page, announcement, pricing), verified Sep 25, 2026.
Where we tested it
The silence test
TaskThe model had to stay quiet for a moment; the correct reply had zero characters.
It stayed silent in four of six tries, every time in English. In Czech it once wrote an ellipsis, and to the request for a moment of quiet it replied “OK.”
You'll find the size band and figures for other models on the Tested models page.