Typically partially pressurised so that pressure breathing is not routinely required.
Even at 100% oxygen, at high altitude there is not enough pressure to avoid hypoxia.
But compared to an airliner, where the air is just a standard oxygen /nitrogen mix and thus has to pressurised a lot, to keep the cabin down at 8000', a fj cockpit does not need to be pressurised as much. Saves weight and air bleed load, thus minimising performance penalty.
Pb