debugging-and-error-recovery

Reproduce the failure reliably first, 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 that fails without the fix and verifying the full suite passes.

Run git bisect start, mark the current commit as bad and a known working commit as good, then test each midpoint checkout. You can automate it with git bisect run followed by your focused test command.

Classify it as timing-dependent, environment-dependent, state-dependent, or truly random. Add timestamps and logging around the suspected area, compare environments, check for leaked shared state, and set up alerts for the error signature.

Symptom fixes mask the underlying defect, so the bug resurfaces elsewhere and compounds with later changes. Asking why the failure happens until reaching the actual cause produces a durable fix that a regression test can guard.

Add instrumentation when you cannot localize a failure or the issue is intermittent, and remove it once the bug is fixed and guarded by tests. Keep permanent logging only for error boundaries, API error context, and key performance metrics.