useScriptGoogleTagManager onBeforeGtmStart callback not triggered when GTM ID is set via nuxt.config

[DanLDU]

🐛 The bug

When using the useScriptGoogleTagManager composable in a Nuxt 4 project with the GTM ID defined in nuxt.config, the onBeforeGtmStart callback is not triggered.

Example (Doesn't work):

// nuxt.config:
scripts: {
    registry: {
      googleTagManager: {
        id: "GTM-XXXXXX",
      },
    },
  }

//component: 
const { proxy } = useScriptGoogleTagManager({
  onBeforeGtmStart: (gtag) => {
    gtag('consent', 'default', {
      ad_user_data: 'denied',
      ad_personalization: 'denied',
      ad_storage: 'granted',
      analytics_storage: 'denied',
      wait_for_update: 500,
    });
  },
});

However, if the GTM ID is passed directly as an argument to useScriptGoogleTagManager, the callback works as expected.
Example (It works):

const { proxy } = useScriptGoogleTagManager({
  id: 'GTM-XXXXXXXX',
  onBeforeGtmStart: (gtag) => {
    gtag('consent', 'default', {
      ad_user_data: 'denied',
      ad_personalization: 'denied',
      ad_storage: 'granted',
      analytics_storage: 'denied',
      wait_for_update: 500,
    });
  },
});

🛠️ To reproduce

https://stackblitz.com/edit/nuxt-starter-zwdg7pfn?file=package.json,nuxt.config.ts,pages%2Findex.vue

🌈 Expected behavior

When the GTM ID is set via the Nuxt config, the onBeforeGtmStart hook passed to useScriptGoogleTagManager should be called before the GTM script starts, just as it does when passing the ID directly.

https://scripts.nuxt.com/scripts/tracking/google-tag-manager#configuring-gtm-before-it-starts

ℹ️ Additional context

Versions:

• Nuxt 4.1.2
• Nuxt Scripts 0.12.1

Using the nuxt scripts module's useScriptGoogleTagManager

The difference seems to be related to the GTM ID source (config vs argument)

[harlan-zw]

Thanks for the issue. The solution will likely look like support for configuring the gtag instructions in nuxt.config as the gtag would have already loaded when you're using the composable afterwards.