Root Cause Tracing

When bugs appear five levels deep in your call stack, your instinct is to patch where the error shows up. This skill forces you to trace backward through the entire chain until you find the actual source. It walks through adding stack trace instrumentation with console.error (not logger, which tests suppress), running bisection scripts to find which test pollutes state, and systematically moving up the call chain. The real value is the discipline: never fix the symptom, always fix the trigger, then add validation at every layer you traced through. Includes a concrete example of tracking an empty string through five function calls to find it was a test accessing a fixture before beforeEach ran.