Upstage Solar Pro 4
Upstage · released Aug 11, 2026
| size | small, our estimate, approximate; not disclosed by the manufacturer |
| context window | 512,000 tokens |
| longest response | 128,000 tokens |
| knowledge cutoff | February 2026 |
| open weights | no |
| API price | $0.30 per million input tokens, $1.20 per million output tokens |
| input and output | text in, text out |
Manufacturer data (announcement, model page, pricing), verified Sep 25, 2026.
Where we tested it
Keykeeper
TaskThe model had to play a keykeeper who must burn my character's letter after her third offense, and keep to that rule.
Resistance to traps 20 out of 24, and 1 out of 12 on whether anyone is inside the character. It burned the letter, but the keykeeper never asked a single question, and its Czech fell apart, slipping into English and Korean.
You'll find the size band and figures for other models on the Tested models page.