When you Cast a Spell on a willing target, you may use your Short action to impose a contingency on that spell. Name a condition. The instant that condition becomes true, the spell takes effect on the target. You must make your normal spellcasting roll when Casting the Spell, with any attendant possibilities of Good Things or Bad Things determined before the spell takes effect. If the target already has a contingent spell on them, the prior contingent spell ends without triggering.

The spell's duration does not begin until the condition becomes true and the spell takes effect. The spell affects only the initial target, even if it normally has an area of effect. The Unweave spell can remove the contingent spell if it is cast on the target and the caster of the Unweave is aware of the contingent spell.