Most teams rely on interviews and surveys, then realize later they asked the wrong questions. This session shows how to add synthetic users and structured role play into your workflow so you can iterate research and design decisions in hours, not weeks. We will cover a practical loop that combines persona hypotheses, agent prompts, red team scenarios, and rehearsal style walkthroughs to stress test flows, content, and edge cases. You will see how to calibrate synthetic users with real data, when to trust them, when to ignore them, and how to translate simulated conversations into clear product decisions. You will leave with templates, a facilitation guide, and a checklist for bringing this into your next sprint.