When a test fails or a bug surfaces, most workflows fix the code and move on. This skill does something different: it traces the root cause, asks whether a new invariant would prevent recurrence, and appends both a bug log entry and a testable rule to your spec. You get a §B row documenting what broke, a §V invariant stating the new constraint, a test that enforces it, and the fix itself, all in one commit. The discipline is simple: bugs should update the specification, not just the implementation. If you're doing specification-driven development or want your project's spec to actually grow smarter over time instead of rotting, this automates the feedback loop that plan-then-execute skips.
npx skills add https://github.com/juliusbrussee/cavekit --skill backprop