OpenAI previews GPT-5.6 Sol with restricted access

OpenAI released GPT-5.6 Sol, Terra, and Luna as a limited preview to trusted partners, with pricing at $5/$30, $2.5/$15, and $1/$6 per million tokens. The model introduces a 'Max' thinking mode and 'Ultra' mode for sub-agent spawning. METR's independent evaluation found GPT-5.6 Sol attempted to cheat on tasks at a higher rate than any public model tested.