[Feature]: Simplified Chinese (zh-CN) localization for web, desktop and mobile apps

[Shunamxiao]

Before submitting

• I searched existing issues. I am aware that [Feature]: Community-led Simplified Chinese localization with a minimal i18n foundation #4082 (Community-led Simplified Chinese localization) already exists and is open, and that [Feature]: Add Chinese (zh-CN) localization / i18n support #1463 was closed by maintainers citing capacity. This issue is intentionally filed as an additional community signal for the same need, with verified repository status below that [Feature]: Community-led Simplified Chinese localization with a minimal i18n foundation #4082 did not include. Please close it as a duplicate if that is preferred.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/web, apps/desktop, native (Android / iOS)

Problem or use case

T3 Code's interface is English-only across the web app, the desktop app, and the mobile apps. Verified against the current main tree: the repository has no i18n infrastructure at all, no locale files, no translation catalogs, and UI strings are hardcoded in components.

For Chinese-speaking developers, English-only UI raises the barrier to using and contributing to the project, especially for settings, permission prompts, error messages, and unfamiliar agent terminology. Chinese-speaking developers are a large part of the global developer community, and mobile usage in particular is common among this group, which makes the lack of localization in the Android/iOS apps more visible.

A previous request (#1463) was closed because maintainers did not have capacity for i18n at the time. This issue re-raises the need with a small, community-friendly scope in mind, and acknowledges the maintenance-cost concern.

Proposed solution

Introduce a lightweight localization foundation and add Simplified Chinese (zh-CN) as the first additional locale, ideally covering web, desktop, and mobile surfaces:

1. Keep English as the default and source locale.
2. Extract only core user-facing strings into locale files, starting with navigation, common buttons and actions, settings labels, dialogs and menus, and common status/error messages.
3. Add a zh-CN translation file for those strings.
4. Provide a language setting, persisted locally, with automatic browser/system locale detection as an optional first-run default.
5. Fall back to English for any missing key.
6. Add a CI check that fails on missing or structurally inconsistent translation keys.
7. Include a short contributor guide for adding or updating translations.

Why this matters

• A localized core interface makes T3 Code usable and understandable for a large Chinese-speaking audience that is comfortable with programming but not with an English-only product UI.
• A minimal i18n foundation makes future community-contributed locales possible without asking maintainers to do the translation work themselves.
• The project already has meaningful adoption signals from Chinese-speaking users (see [Feature]: Add Chinese (zh-CN) localization / i18n support #1463, [Feature]: Community-led Simplified Chinese localization with a minimal i18n foundation #4082, and discussion activity), and the mobile apps are a primary entry point for this audience.

Smallest useful scope

First version covers only the core application shell and the most frequently used UI text:

• navigation;
• common buttons and actions;
• settings labels;
• dialogs and menus;
• common status and error messages.

English stays the default. Documentation, marketing pages, uncommon screens, and additional locales are out of scope for the initial PR.

Alternatives considered

• Browser/OS auto-translation: inconsistent quality, poor handling of dialogs, dynamic content, technical terminology, and desktop/mobile contexts.
• A separate Chinese fork: diverges from upstream quickly and duplicates maintenance work.
• Translating documentation only: helps onboarding but does not address day-to-day use of the application itself.
• Hardcoding Chinese in components: does not scale and makes maintenance harder.

Risks or tradeoffs

i18n introduces ongoing maintenance: every new or changed UI string needs a translation entry. Mitigations:

• English as the reliable fallback;
• structurally consistent locale files;
• CI checks for missing keys;
• documented translation workflow;
• starting with a deliberately small set of core strings.

There is also a small architectural and bundle-size cost, which is why the foundation should stay minimal.

Examples or references

• Current open request: [Feature]: Community-led Simplified Chinese localization with a minimal i18n foundation #4082
• Earlier closed request: [Feature]: Add Chinese (zh-CN) localization / i18n support #1463
• Maintainer capacity response: [Feature]: Add Chinese (zh-CN) localization / i18n support #1463 (comment)

Contribution

• I would be open to helping implement this.

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中文摘要:本 issue 请求为 T3 Code 增加简体中文(zh-CN)界面支持,并搭建轻量多语言(i18n)基础。我已核实当前代码库没有任何 i18n 基础设施。已知存在开放中的 #4082 与本需求相同,本 issue 作为额外的社区需求信号提交,同时覆盖 Web、桌面与移动端 App。若维护者认为重复,可关闭。