Introduction Frontend applications have grown from simple pages into complex systems with dozens of independent modules, shared state, real‑time updates, and rich user interactions. As the complexity increases, one question becomes critical: how do different parts of the application communicate with each other? The classic answers in modern frameworks are well known: Pass data down via props ( @Input in Angular, props in React) and bubble events up ( @Output , callbacks). Inject shared services (singletons) that act as a bridge between unrelated components. Use a global store (Redux, NgRx, Zustand) for everything. Each of these approaches works, but each also introduces a certain kind of coupling – a hidden dependency that makes code harder to change, test, and reason about.…