feat: allow customizing root id and tag

packages/nuxt/src/app/entry.ts

@@ -9,6 +9,8 @@ import '#build/css'
 import _plugins from '#build/plugins'
 // @ts-ignore
 import RootComponent from '#build/root-component.mjs'
+// @ts-ignore
+import { appRootId } from '#build/nuxt.config.mjs'
 
 if (!globalThis.$fetch) {
   // @ts-ignore
@@ -64,7 +66,7 @@ if (process.client) {
     try {
       await nuxt.hooks.callHook('app:created', vueApp)
       await nuxt.hooks.callHook('app:beforeMount', vueApp)
-      vueApp.mount('#__nuxt')
+      vueApp.mount('#' + appRootId)
       await nuxt.hooks.callHook('app:mounted', vueApp)
       await nextTick()
     } catch (err) {

packages/nuxt/src/core/nitro.ts

@@ -33,7 +33,9 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
     handlers: nuxt.options.serverHandlers,
     devHandlers: [],
     baseURL: nuxt.options.app.baseURL,
-    virtual: {},
+    virtual: {
+      '#internal/nuxt.config.mjs': () => nuxt.vfs['#build/nuxt.config']
+    },
     routeRules: {
       '/__nuxt_error': { cache: false }
     },

packages/nuxt/src/core/runtime/nitro/renderer.ts

@@ -8,7 +8,8 @@ import { renderToString as _renderToString } from 'vue/server-renderer'
 import { useRuntimeConfig, useNitroApp, defineRenderHandler, getRouteRules } from '#internal/nitro'
 // eslint-disable-next-line import/no-restricted-paths
 import type { NuxtApp, NuxtSSRContext } from '#app'
-
+// @ts-ignore
+import { appRootId, appRootTag } from '#internal/nuxt.config.mjs'
 // @ts-ignore
 import { buildAssetsURL, publicAssetsURL } from '#paths'
 
@@ -71,7 +72,7 @@ const getSSRRenderer = lazyCachedFunction(async () => {
     if (process.dev && process.env.NUXT_VITE_NODE_OPTIONS) {
       renderer.rendererContext.updateManifest(await getClientManifest())
     }
-    return `<div id="__nuxt">${html}</div>`
+    return `<${appRootTag} id="${appRootId}">${html}</${appRootTag}>`
   }
 
   return renderer
@@ -83,7 +84,7 @@ const getSPARenderer = lazyCachedFunction(async () => {
 
   const options = {
     manifest,
-    renderToString: () => '<div id="__nuxt"></div>',
+    renderToString: () => `<${appRootTag} id="${appRootId}"></${appRootTag}>`,
     buildAssetsURL
   }
   // Create SPA renderer and cache the result for all requests

packages/schema/src/config/app.ts

@@ -143,6 +143,17 @@ export default defineUntypedSchema({
      * @type {typeof import('../src/types/config').NuxtAppConfig['keepalive']}
      */
     keepalive: false,
+
+    /**
+     * Customize Nuxt root element id.
+     */
+    rootId: '__nuxt',
+
+    /**
+     * Customize Nuxt root element tag.
+     *
+     */
+    rootTag: 'div',
   },
 
   /**