What problem does it solve? Hard bugs and performance regressions stall when developers jump straight to guessing fixes without a reliable reproduction. This Skill enforces a disciplined six-phase loop — build a feedback loop, reproduce, hypothesise, instrument, fix with regression test, and clean up — so root causes are found systematically instead of by luck. ## Core Features & Use Cases - Feedback loop construction: Ten ranked strategies for building a deterministic pass/fail signal, from failing tests and curl scripts to headless browser replays, fuzz loops, and git bisect harnesses. - Ranked falsifiable hypotheses: Generates 3-5 hypotheses with explicit predictions before testing, and checkpoints them with the user to leverage domain knowledge. - Tagged instrumentation and cleanup: Every debug log gets a unique [DEBUG-...] prefix so removal is a single grep, and a post-mortem checklist captures the confirmed root cause. - Use Case: A user reports that an export endpoint intermittently returns corrupted data. The Skill guides building a 100-iteration loop to raise the reproduction rate, ranking hypotheses about concurrency vs serialization, instrumenting the boundary, and landing a regression test at the correct seam. ## Quick Start Ask the agent to diagnose the bug where the export button intermittently throws an error, and have it build a reproduction loop before proposing any fix.
