Suppose I have a hacker. Enemy moves his own hacker close by ( no LOS on the whole thing, to simplify). I think he is inside my ZoC or that he will be and declare a hacking attack. Then he moves again. When we measure things, after the first move he was outside of my ZoC. After the second, he was inside. Does he get attacked, or was the ARO lost because it was invalid at the moment it was declared ( even if it became valid later on the order)?
Due to All At Once rule, target is in range because they were in range at some point during the order.
You need to ARO at your first opportunity, but you can't expend an ARO that hasn't been generated. So what happened is this: 3. Your opponent moved to just outside ZOC 4. You didn't get an ARO, so you simply told your opponent your intention if you did get an ARO 5. Your opponent moved inside ZOC 6. Now you got an ARO, which you used to hack The opposite case is explicitly covered in the FAQ 3. Your opponent moves inside ZOC 4. You decline to ARO because you think it's outside ZOC 5. Your oppenent moves again 6. You attempt to declare an ARO, but can't because you missed your first opportunity The way to deal with this gracefully is to be explicit and consistent: "I think this guy has an ARO, so he'll hack. Oh, now I definitely have an ARO it's the same hack." Edit: or what @Mahtamori said as a simpler explanation.