An architect wants to stabilize a high-risk COBOL subsystem before planning full extraction. Which refactoring pattern is most appropriate as an initial step?

Think of it like working hands-on with IBM mainframe systems — the answer here is 'Extract Service, to immediately move the subsystem into a new deployment unit'. Encapsulate is the lower-risk first step that introduces a stable interface around the subsystem without moving it, allowing the team to validate the interface contract before committing to full extra. On real mainframe exams, this concept comes up repeatedly so make sure you have it locked in.