Find what a change could break somewhere else before it ships, beyond the diff, and prove the one fact it's safe because of by running real code instead of writing it up. Use for 'blast radius of X', 'what could this break', or reviewing a small diff you don't trust. DO NOT use for explaining how existing code works (use how instead) or investigating why it was built that way (use why instead). Triggers: blast radius of X, what could this break, is this change safe, review this diff, what am I missing in this change.