Pinia

This is a TDD-focused Pinia implementation guide for building state stores in a JARVIS-style AI assistant UI. It's aimed at Nuxt apps with SSR where you need to manage system metrics, command queues, and user preferences without leaking state between requests. The workflow is opinionated: write tests first, implement stores with the composition API setup syntax, validate all inputs in actions, and never persist sensitive data. What's useful here is the concrete pattern for clamping metrics values, composing stores together, and the emphasis on TypeScript interfaces over loose objects. The examples are specific to a HUD dashboard scenario but the patterns translate to any stateful Nuxt application where SSR safety matters.