Root Cause Tracing

Overview

Bugs often surface deep in a stack trace—far away from the code that actually caused them. This skill teaches you to walk the chain backward until you reach the true trigger, then reinforce defenses so the issue cannot recur.

Core principle: Never patch just the symptom. Follow the evidence upstream and fix the source.

When to Use

• Error occurs deep inside execution (nested call stack, worker, async task).
• Stack trace is long or unhelpful; unclear where invalid data originated.
• Behavior differs across tests/runs and you need to identify the polluting test.
• You suspect earlier code (setup, beforeEach, fixtures) seeded bad state.

Decision flow:

Bug surfaces deep? → yes → Can you trace back? → yes → Trace to original trigger → Add defense-in-depth → Done
                                          ↘ no → Temporary symptom fix (last resort)