debugging-and-error-recovery

Start by reproducing the failure reliably, then localize which layer is failing, reduce to a minimal failing case, and fix the root cause rather than the symptom. Finish by adding a regression test and verifying the full suite passes.

Use git bisect: mark the current commit as bad and a known-working commit as good, then let git checkout midpoint commits while you run the failing test at each step. You can automate it with git bisect run plus your test command.

Classify it as timing-dependent, environment-dependent, state-dependent, or truly random. Add timestamps or artificial delays for race conditions, compare environments and data, check for leaked shared state, or add defensive logging and alerting until it recurs.

Symptom fixes mask the underlying defect, so the bug resurfaces elsewhere and compounds with later changes. Asking why repeatedly until you reach the actual cause ensures the fix holds and the regression test guards the right behavior.

Remove instrumentation once the bug is fixed and a regression test guards against recurrence, especially logs useful only during development or containing sensitive data. Keep permanent instrumentation like error boundaries, API error logging, and performance metrics.