Larian Studios Forums Baldur's Gate III Baldur's Gate III - Technical & Gameplay Problems Free Weapon Set Switching / Shield AC

The way it currently works in the game is that you are free to switch weapons back and forth until you make your attack and NOT after it.
So no, you can't do a range attack and then switch to melee to get a free AoO on top.

Which would be a reasonable compromise as far as I'm concerned, if not for the bullshit of the shield giving you a +2 even when you are equipping a ranged weapon, currently, which is fairly stupid.