What problem does it solve? Hard bugs and performance regressions resist casual code reading; without a reproducible signal, debugging devolves into guessing. This Skill enforces a disciplined six-phase diagnosis loop that builds a tight pass/fail feedback loop first, then reproduces, minimizes, hypothesizes, instruments, fixes, and cleans up. ## Core Features & Use Cases - Feedback loop construction: Ten ranked strategies for building a red-capable repro, from failing tests and curl scripts to headless browser runs, trace replay, fuzz loops, and git bisect harnesses. - Structured hypothesis testing: Generates 3-5 ranked falsifiable hypotheses, then instruments with tagged debug logs or debugger breakpoints, changing one variable at a time. - Regression testing and post-mortem: Writes the regression test before the fix at a correct seam, removes all debug instrumentation, and records the confirmed root cause in the commit message. - Use Case: A user reports that an export endpoint intermittently returns stale data in production. The Skill guides building a replay harness from a captured request, minimizing the repro, ranking hypotheses, and landing a fix with a regression test. ## Quick Start Ask the agent to diagnose the bug where the export endpoint intermittently returns stale data and have it build a reproducible failing test before proposing any fix.
