Maintains capability vision documents in `.codestable/requirements/` with three modes: draft for future capabilities, backfill for undocumented existing ones, and update for changes. Gets triggered during feature design to capture vision, or during acceptance to upgrade draft requirements to current status once implemented. The docs answer "what capability and why" in plain language, not "how to build it" (that's architecture's job). Enforces single file per run because AI loves to batch generate requirements nobody reviews. The pitch field has to work as marketing copy, user stories need concrete scenarios, and you're not allowed to stuff implementation details in. Watch out for the temptation to write PRD-style field dumps or explain like you're teaching a class.
npx skills add https://github.com/liuzhengdongfortest/codestable --skill cs-req