Use this skill when reviewing, diagnosing, restructuring, or rewriting Svelte 5 / SvelteKit frontend code, especially when bugs or complexity stem from weak architecture, poor state ownership, reactivity problems, bad component boundaries, or accumulated technical debt. This skill is diagnosis-first, skeptical, and findings-first. It should question the current solution shape before fixing it, and it may recommend or drive a parallel clean rewrite when the status quo is no longer a good foundation.