What problem does it solve? Hard bugs and performance regressions stall when developers stare at code without a reliable reproduction signal. This Skill enforces a disciplined six-phase loop — build a feedback loop, reproduce, hypothesise, instrument, fix, and clean up — so debugging becomes systematic instead of guesswork. ## Core Features & Use Cases - Feedback loop construction: Ten ranked strategies for building a deterministic pass/fail signal, from failing tests and curl scripts to Playwright traces, fuzz loops, and git bisect harnesses. - 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. - Use Case: A user reports that an export endpoint intermittently returns empty files. The Skill guides building a loop that replays the failing request 100 times, ranking hypotheses about race conditions, instrumenting the suspected boundary, and landing a regression test with the fix. ## Quick Start Ask the agent to diagnose the bug where the export endpoint intermittently returns empty files and follow the structured diagnosis loop.