# 0003. Bilingual UI (zh-CN / en)

> All UI strings and aria-labels are hardcoded Chinese. No i18n library.

Source: https://kcq.nebutra.com/docs/architecture/adr/0003-bilingual-ui


* Status: Accepted
* Date: 2026-10-09
* Deciders: tseka

Context [#context]

All UI strings and aria-labels are hardcoded Chinese. No i18n library.

Decision [#decision]

* Support `zh-CN` and `en` across the landing page and the app.
* Library: `vue-i18n` (composition API, typed message schema).
* Default locale `en`. Resolution: explicit user choice (persisted) → `navigator.languages` best match → `en`. Public pages use path locales (`/home` en as `x-default`, `/zh/home`).
* `<html lang>` follows the active locale.
* Message keys are namespaced by feature. Brand name (ADR 0001) is not translated.
* `/home` locale variants are crawlable (`hreflang`).

Consequences [#consequences]

* Every new user-visible string goes through `t()`; enforced by lint on `.vue` templates.
* Migration is incremental per feature; Chinese is the source locale during migration.