Declaring module 'nuxt/schema' makes 'ui' property required instead of optional

[fkwww27]

Environment

Operating system	Linux 6.6.87.2-microsoft-standard-WSL2
CPU	11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz (16 cores)
Node.js version	v22.22.2
nuxt/cli version	3.37.0
Package manager	npm@10.9.7
Nuxt version	4.5.1
Nitro version	2.13.4
Builder	vite@8.2.0
Config	compatibilityDate, css, devServer, devtools, modules
Modules	@nuxt/ui@4.10.0

Is this bug related to Nuxt or Vue?

Nuxt

Package

v4.x

Version

v.4.10.0

Reproduction

1. You need to add into app folder, file {anything}.d.ts.
2. Add the following code:

declare module "nuxt/schema" {
  interface AppConfigInput {}
}

export {};

3. Observe that the ui property in app.config.ts becomes required.

Description

Without a .d.ts file, the ui property is optional:

After adding a .d.ts file that augments nuxt/schema, the ui property becomes required:

Expected behavior

The ui property should remain optional after augmenting nuxt/schema.

Additional context

No response

Logs

[coderabbitai]

🔗 Related PRs

#6520 - fix(module): expose component theme keys in AppConfig type [merged]
#6531 - fix(module): merge custom variants into AppConfig type [merged]
#6686 - fix(useComponentProps): let app config defaultVariants override withDefaults [merged]
#6731 - feat(vue): support experimental.componentDetection [open]
#6777 - docs(installation): note vue-tsc build race with auto-import declarations [merged]

---

📝 Issue Planner

_{Check the box below or use the @coderabbitai plan command to generate an implementation plan and prompts that you can use with your favorite coding assistant.}

• Create Plan

---

🧪 Issue enrichment is currently in open beta.

You can configure auto-planning by selecting labels in the issue_enrichment configuration.

To disable automatic issue enrichment, add the following to your .coderabbit.yaml:

issue_enrichment:
  auto_enrich:
    enabled: false

💬 Have feedback or questions? Drop into our discord!