RxJS Subjects in the Angular Signals Era: Obsolete or Still Powerful?

For years, Angular developers lived in a world powered by RxJS . Streams, subscriptions, operators, Subjects — if you wanted reactive behavior in Angular, RxJS was the way. Then Angular introduced Signals , a new reactivity model that promised something developers had been craving: Simpler state management with less boilerplate. Suddenly, many Angular developers began asking: Do we still need RxJS Subjects? Are Signals replacing RxJS? Should we rewrite everything? Before we panic-delete our Subject imports, let's understand what actually changed . A Quick Mental Model Think of it like this: Signals are like a spreadsheet cell. When a value changes, everything depending on it updates automatically. RxJS is like a pipeline of events. Data flows through operators, transformations, and async processes. Both are reactive — but they solve different problems . The Old Angular Pattern: RxJS Everywhere Before Signals, developers often used BehaviorSubject even for simple component state. Exampl