Nuxtjs Guideline: Lifecycle — Avoid side effects in script setup root. Description: Move side effects to lifecycle hooks. Do: Side effects in onMounted. Don't: setInterval in root script setup. Good Example: onMounted(() => { interval = setInterval(...) }). Bad Example: <script setup>setInterval(...)</script>. Severity: High. Docs: https://nuxt.com/docs/guide/concepts/nuxt-lifecycle.