My question is a generalization of this one: Can you interrupt an action with a Ready Action?
When you ready an action in Pathfinder, the readied player jumps in an instant before the trigger happens (emphasis mine):
Readying an Action
You can ready a standard action, a move action, a swift action, or a free action. To do so, specify the action you will take and the conditions under which you will take it. Then, anytime before your next action, you may take the readied action in response to that condition. The action occurs just before the action that triggers it. If the triggered action is part of another character's activities, you interrupt the other character. Assuming he is still capable of doing so, he continues his actions once you complete your readied action. Your initiative result changes. For the rest of the encounter, your initiative result is the count on which you took the readied action, and you act immediately ahead of the character whose action triggered your readied action.
Are actions atomic (in the computer science sense)?
For each of the different kinds of actions in Pathfinder (Standard, Move, Full-round, Swift, Immediate, Free, and any others you can think of), can one character perform their readied action in the middle of another character's action?
Examples by intuition:
- It makes sense in the question linked above for a readied action to interrupt a move action (e.g. wolf wants to move past me, so I ready myself to sidestep when the wolf comes within 5').
- It makes sense that a person could ready themselves to shoot an arrow when an NPC attempts to light a torch (full-round action).
- It doesn't make sense to interrupt an immediate action (e.g. person says a word, ceace concentrating on a spell, etc.).