After launch, an engineer edited the production prompt to make a document assistant's tone warmer. A week later, finance notices that extracted invoice dates are wrong more often. Which missing lifecycle mechanism best explains how this reached production?

Answer: B — Gated change control, where every prompt change passes the regression eval before release, with rollback

(b) is right: iteration must run through change control; a regression eval covering extraction would have caught the drop before release, and rollback would limit the damage. (a) buys capability instead of process. (c) and (d) help communication and understanding but wouldn't have stopped an unevaluated change.