Environment

• Operating System: Darwin
• Node Version: v22.17.0
• Nuxt Version: 3.17.7
• CLI Version: 3.26.4
• Nitro Version: 2.12.4
• Package Manager: pnpm@10.12.1
• Builder: -
• User Config: compatibilityDate, devtools, extends
• Runtime Modules: -
• Build Modules: -

Reproduction

https://stackblitz.com/edit/github-1zim1ccd?file=project/app/plugins/example.ts,layer/types/foo.ts,project/types/index.d.ts

Describe the bug

Once I migrated my projects to v4, I noticed that all my type augmentations stopped working.

Let's assume that there is a composable, which has some options:

// layer/app/composables/useFoo.ts
export function useFoo(option: keyof FooOptions) {}

// layer/types/foo.ts
export interface FooOptions {
    'from-layer': any
}

and the options are augmented in a project extending the layer, where the composable comes from:

// project/types/index.d.ts
declare module '@layer-foo/types/foo' {
    interface FooOptions {
        'from-project': any
    }
}

export {}

In v3, both options were accepted:

However, in v4, only the base interface is considered:

Additional context

The v4 projects are using the new default tsconfig

{
  // https://nuxt.com/docs/guide/concepts/typescript
  "files": [],
  "references": [
    {
      "path": "./.nuxt/tsconfig.app.json"
    },
    {
      "path": "./.nuxt/tsconfig.server.json"
    },
    {
      "path": "./.nuxt/tsconfig.shared.json"
    },
    {
      "path": "./.nuxt/tsconfig.node.json"
    }
  ]
}

Logs