Grilling relentlessly questions the user about a plan, decision, or idea to stress-test their thinking and reach a shared understanding. It maps the session as a design tree where decisions branch out, organized into rounds of questioning based on settled prerequisites. The agent provides recommended answers, discovers environment facts using sub-agents rather than asking the user, and continues until the design tree frontier is completely empty. Reach for it when the user wants to thoroughly pressure-test their ideas or uses grill trigger phrases.