What problem does it solve? Fixing a bug by reading code first produces a plausible theory instead of the real fault, and fixes without reproduction cannot be proven to work. This Skill enforces a disciplined debugging workflow: reproduce the fault before reading code, turn the reproduction into a failing test, prove the cause with measurement, and sweep for the same defect shape elsewhere. ## Core Features & Use Cases - Reproduction-first diagnosis: Shrink the fault to the smallest input that still shows it, reproduce on the original platform, and treat failure to reproduce as a reportable finding rather than a licence to guess. - Failing-test-first fixing: Write the test before the fix, watch it go red, read the failure message, and place the test at the layer where the fault is still visible as data. - Cause proof and shape sweep: Measure instead of guessing after two hypotheses, calibrate new instruments against known answers, and grep for the fault's shape across src/, scripts/, e2e/, and docs. - Use Case: A Telegram bot truncates player names in a stats poster. Reproduce the truncation, write a spec asserting on the SVG string (not the rasterized PNG), watch it fail, fix the cause, then sweep for other render calls missing the same guard. ## Quick Start Ask the assistant to use the fix-a-bug skill to investigate and fix a reported defect, starting from a minimal reproduction and a failing test.
