Debug: Root Cause First

The most common debugging failure is patching the symptom. This skill forces a reproduce → hypothesize → prove → fix loop.

1. Reproduce

• Get the exact failing command (test, script, request). Run it yourself and capture the full output.
• If it doesn't reproduce, stop and gather info: environment, versions (node -v, python --version, lockfile), input data, env vars. Don't fix what you can't see.
• Make the reproduction as small and fast as possible (a single test, pytest path::test_name -x, npx vitest run file -t "name").

2. Read the error properly