Aeo Troubleshooting

Use when debugging a failure, reading a stack trace, reproducing a flaky or intermittent bug, isolating a regression, or running a root cause analysis. Hypothesis-driven debugging with a recorded experiment at every step: reproduce, read the whole error, form and test one hypothesis at a time, isolate by binary search over code and commits (git bisect), inputs, environment, and dependencies, then trace the root cause with 5 Whys and a fault tree. Also covers stack-trace anatomy, an error-pattern lookup table, and a debugger, profiler, and network tools reference.

Use when diagnosing a dependency conflict or version mismatch, a diamond dependency, an environment issue, a PATH problem, a permission error, an environment variable that is not taking effect, a CORS error, a DNS failure, a timeout, an async bug, a concurrency problem, a race condition, a deadlock, an unhandled promise rejection, or a memory leak. Every pattern is listed with its symptoms, causes, and fixes, so a recognized failure can be matched and closed quickly. A catalogue of known failures; for an unknown failure that needs a hypothesis-driven investigation, use systematic-debugging.