Language
Spec: internationalisation.
The interface speaks English (en-US, the default), Spanish (es) and Canadian French (fr-CA). /locale shows the current language; /locale es switches and saves [ui] locale = "es". Codes are forgiving: es-ES, es_MX, spanish and español all work. The desktop app follows the system’s language by default and switches in Settings › Appearance, from the same catalogs.
Any other language (/locale ja) changes the language the model replies in, while the interface stays in English until someone adds a catalog. Code, paths, commands and tool output are never translated, and blitz doctor, --help and command-line errors stay in English so they can be shared in bug reports.
To add or correct a language, put a JSON catalog in ~/.blitz/locales/; see translating.