Signal-Driven Error Monitoring: Detecting and Debugging Reactive Failures in Angular

Angular Signals introduce a synchronous, localized reactivity model that can fail silently — computed values stop updating, effects loop infinitely, or mutations never trigger re-renders without any visible error. This post explains the three phases of the signal lifecycle (read, compute, notify), categorizes common reactive failure types, and presents lightweight instrumentation patterns to surface them. Practical utilities like `observeSignal()`, `traceComputed()`, and a `safeEffect()` wrapper are introduced with real component examples and a live StackBlitz demo. The core philosophy shifts from catching exceptions to observing lifecycles, with guiding principles around immutability, pure computations, and early instrumentation.