English UI flashes before hydration with non-English locales

[314systems]

Describe the bug

When using a non-English locale, the UI briefly renders in English during page reload before the client-side hydration completes.

Additional context

2026-06-13.15.08.12.mov

Logs

[houtan-rocky]

The English flash can't be removed server-side here (locale-sensitive routes are prerendered/ISR and the locale lives in localStorage).
(To make a reload paint the right language with no flash, the language must already be in the response the CDN hands back)
are we willing to putting locale into the CDN cache key ? @trueberryless

and it will need prefix_except_default
https://i18n.nuxtjs.org/docs/guide#prefix_except_default

[gameroman]

I thinks this is not planned: #275