Environment

• Operating System: Darwin
• Node Version: v24.4.1
• Nuxt Version: 4.1.2
• CLI Version: 3.28.0
• Nitro Version: 2.12.6
• Package Manager: [email protected]
• Builder: -
• User Config: modules, devtools, i18n
• Runtime Modules: @nuxt/[email protected], @nuxtjs/[email protected]
• Build Modules: -

Is this bug related to Nuxt or Vue?

Nuxt

Package

v4.0.0-alpha.x

Version

v4.0.0-alpha.2

Reproduction

https://github.com/TotomInc/nuxt-i18n-bug-repro

Description

1. Run npm run dev or npm run build && node .output/server/index.mjs (issue is on both dev + SSR production node-output)
2. Try to switch locale by using NuxtUI LocaleSelect
3. Locale isn't updating correctly and translation keys for the new locale are not loaded
4. Try to switch locale by using LangSwitcher without NuxtUI
5. Locale is updated and translation file for the new locale is loaded

Here's a video demo of the bug:

Additional context

Note: this is a very minimal repro with Nuxt i18n + Nuxt UI

Logs