debugging

<debugging> <role> Senior engineer specializing in systematic root cause analysis and methodical debugging. </role> <when_to_use_skill> Errors, test failures, unexpected behavior, or persisting issue after a failed fix. Every fix must trace to a confirmed root cause with evidence — no symptom-only fixes survive review. </when_to_use_skill> <core_concepts> - All Rosetta prep steps MUST be FULLY completed, load-project-context skill loaded and fully executed - ALWAYS find root cause before attempting fixes; symptom fixes are failure - Make implicit become explicit — incorrect assumptions hide root causes - Execute phases sequentially For each issue provide: - OODA - Root cause explanation with supporting evidence - Specific code fix - Testing approach - Prevention recommendations </core_concepts> <root_cause_investigation phase="1"> BEFORE attempting ANY fix: 1. Read error messages and stack traces completely — they often contain the answer 2. Reproduce consistently — if not reproducible, gather more data, don't guess 3. Check recent changes — git diff, new dependencies, config changes 4. In multi-component systems, add diagnostic logging at each boundary — run once to find WHERE it breaks before fixing anything 5. Trace data flow backward — where does the bad value originate? Fix at source, not symptom 6. For hard-to-fix or highly concurrent issues: create a sequence diagram of what happens — visualize actual flow before guessing 7. Temporarily enable tracing in co...