A frontend build can look correct and still feel wrong. This usually happens when the team receives finished designs but not finished interaction decisions. The design handoff might include: screens components spacing rules design tokens responsive layouts prototype links That is useful, but it is not always enough to build a product that feels clear. The frontend still needs answers to questions like: What happens before data loads? What happens if data is empty? What should the user see after an error? Which state is optimistic and which state waits for confirmation? When should the route change? What should be handled by the component, the server action, the API, or the CMS? What copy explains uncertainty? I think of this as interaction architecture. It sits between UX and implementation. It defines the behavior that makes the interface usable after the visual design is done. Example: a multi-step lead form A Figma file might show each step clearly.…