From Pathfinder Lost Omens Character Guide, which isn't enabled.

Ward Casting

FEAT 10

Activity reaction

Prerequisites Spellmaster Dedication; Steady Spellcasting

Trigger You attempt a flat check for Steady Spellcasting, but you haven't rolled yet.

You carefully ward your spell by drawing from a mantle of magical energy you prepared to protect your casting, increasing your chance of retaining the spell. You reduce the DC of the flat check for Steady Spellcasting from 15 to 10.

Pathfinder Lost Omens Character GuideOGL