Opportunity attacks are entirely automatic, which is a bit annoying since that means you have no choice not to make one; they don't pop-up like counterspell or projected ward do, they just happen as soon as an enemy tries to move away from you.
However Baldur's Gate 3 contains a metric buttload of custom status effects that prevent reactions; pretty much from late act 2 onwards if you get into any fight and got hit by anything you probably lost your reaction due to Dazed, Electrocuted, Mildly Perturbed, Slowed, etc.
Last edited by Haravikk; 17/08/23 09:03 AM.