What problem does it solve? Hard bugs and performance regressions resist casual debugging: staring at code rarely finds the cause. This Skill enforces a disciplined six-phase loop — build a feedback loop, reproduce, hypothesise, instrument, fix with a regression test, and clean up — so bugs are found systematically instead of by luck. ## Core Features & Use Cases - Feedback-loop construction: Ten ranked strategies for building a fast, deterministic pass/fail signal, from failing tests and curl scripts to headless browser runs, bisection harnesses, and differential loops. - Falsifiable hypothesis ranking: Generates 3–5 ranked hypotheses with explicit predictions before any testing, avoiding single-hypothesis anchoring. - Tagged instrumentation and cleanup: Every debug log gets a unique [DEBUG-xxxx] prefix so cleanup is a single grep, and the post-mortem phase records the confirmed root cause in the commit message. - Use Case: A user reports that an export button intermittently throws an error. The Skill builds a reproduction loop (using the included human-in-the-loop bash template if needed), reproduces the failure, tests ranked hypotheses one variable at a time, and lands a fix guarded by a regression test. ## Quick Start Ask the agent to diagnose the bug you are experiencing and describe the exact symptom, error message, or performance regression you observed.