i18n: community translations for new languages (Spanish, German, French, ...) -- contributors welcome

[hoangsonww]

Summary

The dashboard currently ships 3 languages: English (en), Chinese (zh), Vietnamese (vi). I'd love to support more — Spanish, German, French, Japanese, Portuguese, etc. — but I'm only fluent in English, Vietnamese, and Chinese, so I can't author or vouch for the correctness of other languages myself.

This is an open call for community contributors. If you're fluent in a language we don't support yet, please add it! One language per PR is ideal.

The bar: same standard as the existing languages

A new language is only useful if it's correct, comprehensive, and complete. That means:

• Full coverage — all ~1,452 translation keys across 15 namespaces must be present in the new locale. No missing keys, no silent fall-back to English in the UI. (For reference, en has 1,452 leaf strings today; zh/vi are at 1,446 — a small pre-existing drift new locales should not copy; match en exactly.)
• Correctness — a fluent/native speaker must review every namespace. AI tools (incl. Claude) are fine for a first pass and are encouraged to move fast, but a human who actually speaks the language must verify the output before it's merged. Machine translation alone is not acceptable — UI microcopy, button labels, pluralization, and domain terms break in subtle ways that only a speaker catches.
• Consistency with our conventions — keep technical identifiers and the "Agent" terminology untranslated the way zh/vi already do (there's a test that enforces this). Don't translate interpolation variables or placeholders — {{count}}, {{name}}, <code>…</code>, etc. must stay intact. Match tone/length so the UI doesn't overflow.

What "adding a language <xx>" actually involves

Please read docs/I18N.md first — it documents the architecture (i18next + react-i18next, detection order, namespaces). Concretely, a complete PR touches:

1. client/src/i18n/locales/<xx>/*.json — translate all 15 namespaces:
   activity, alerts, analytics, ccConfig, common, dashboard, errors, kanban, nav, run, sessions, settings, splash, updates, workflows.
   Largest are workflows (411), settings (269), ccConfig (227), common (163), run (141). Keep the exact key structure as en.
2. client/src/i18n/index.ts — import each <ns>_<xx> bundle, add to resources, and add "<xx>" to supportedLngs.
3. client/src/i18n/format.ts — wire locale-aware date/number/model-name formatting for the new locale.
4. client/src/i18n/__tests__/i18n.test.ts — extend the assertions to cover <xx> (key parity vs en, "Agent" left untranslated, non-explicit tag like es-ES → es). Bonus: a real parity test that fails on any missing key would help all locales.
5. README-<XX>.md — a full translation of README.md (we keep README-VN.md / README-CN.md as standalone files; add the language switcher link at the top like the others).
6. wiki/ — add <xx> entries to wiki/i18n-content.js following .claude/rules/wiki-i18n.md, then bump the cache: CACHE_NAME in wiki/sw.js and the i18n-content.js?v= query in wiki/index.html.
7. docs/I18N.md — add the language to "Supported languages" and the supportedLngs list.

Acceptance criteria

• All 15 namespaces present in client/src/i18n/locales/<xx>/ with the same keys as en (no missing, no extra)
• Registered in index.ts (resources + supportedLngs) and format.ts
• npm run test:client passes, including the i18n test extended for <xx>
• Interpolation placeholders and <code>/identifiers/"Agent" terminology preserved
• README-<XX>.md added; switcher links updated across README variants
• Wiki i18n-content.js updated per the wiki-i18n rule + cache version bumped
• docs/I18N.md updated
• PR states who reviewed the translation and their fluency (self/native/professional). If AI-assisted, say which tool and confirm a fluent human verified it.

Notes for contributors

• One language per PR keeps review tractable.
• If you can only do part (e.g. the client UI but not the README/wiki), open a draft PR and say so — partial-but-correct beats complete-but-wrong, and others can build on it.
• Not sure where to start? The client locales/<xx>/*.json files are the highest-impact piece. Copy en/ as the scaffold and translate in place.
• Questions welcome in this thread. 🙏

Filed as a standing community task — comment to claim a language so we don't duplicate effort.

[hoangsonww]

Remember that when adding a new localization (i.e. language) to the project, please ensure the following:

1. Comprehensive translation across the app.
2. Add your new language + its translations to the wiki page as well (under wiki/index.html).