Go to Settings → AI and find Document Language.

The setting only becomes available once AI Resume or AI Cover Letter is switched on. There's nothing for it to apply to otherwise.

​Auto (match job posting): the default. Sprout writes each document in the language of the job posting itself. A German listing gets German documents, an English listing gets English ones. For most people applying across several countries, this is the right choice.

Or fix it to one language for every application:

Fixing the language is useful when a job market doesn't match the posting language (for example, applying to English-language listings in a country where you'd rather present in the local language).

You don't have to change your default to handle a one-off. When you regenerate a single resume or cover letter, you can pick a different language for that document alone. Your overall setting stays as it is.

Worth being clear about: Document Language only affects the resumes and cover letters Sprout generates. The Sprout app itself stays in English.

Changing this setting affects future applications. Documents that were already generated keep the language they were written in, and applications you've already submitted are unaffected.

If you want an existing document in a different language, regenerate it from the application and choose the language there.