[sapatmohit]

Summary

First part of #1008, split as suggested in the assignment comment: next-intl without i18n routing, locale resolution, <html lang>, the three message files with a key-parity test, and the sidebar. The sign-in form and the two language switchers follow in a second PR.

next-intl 4.14.9 (latest at the time of writing). Its peer range includes next ^16.0.0, and it runs on the repo's Next 16.4.2: build and the full e2e suite pass.

Changes

• src/i18n/config.ts: supported locales (en, de, it) and the resolution order: amcp_locale cookie if it holds a supported locale, then the best Accept-Language match by quality (de-AT → de), then en. An unknown cookie value is ignored.
• src/i18n/request.ts: next-intl request config. Non-English messages are laid over en.json, so a key missing in de/it shows the English text, never the raw key.
• next.config.ts: createNextIntlPlugin, inside the existing Sentry wrapper. No middleware and no locale prefixes, so proxy.ts, the rewrites and ?redirect= links are unchanged.
• app/layout.tsx: <html lang> follows the resolved locale; messages are passed once through NextIntlClientProvider around Providers. The layout was already force-dynamic, so reading the cookie per request adds nothing.
• messages/{en,de,it}.json: nav.* (group titles, items, Settings, Switch workspace, Log out, the Workspace fallback, the Star on GitHub button).
• lib/navigation.ts: each NAV group and item gets an id used as its message key. The English label stays because the command palette searches it; translating the palette is out of scope here.
• app-sidebar.tsx and github-star-button.tsx: hard-coded strings replaced with useTranslations('nav'). Hrefs and the active-item logic are untouched.
• .github/CONTRIBUTING.md: a short "Translating the UI" section.

next-intl 4.14 brings its own dependencies (@swc/core, @parcel/watcher, @formatjs/*), which is most of the package-lock.json diff. @parcel/watcher moves from dev-only to a runtime dependency because of that.

Self-hosted vs Cloud: identical. Frontend only, no backend, database or ee/ change. The language is a per-browser cookie, so members of one workspace can use different languages.

Translations

German and Italian aren't my native languages, so please review those strings. I followed the tone of content/guides/de (Sie, "Connectors", "Marktplatz", "Audit-Log") and content/guides/it (tu, "Connettori", "Impostazioni"). Two translations were shortened to fit the 248px sidebar without truncation: "Stern auf GitHub" / "Stella su GitHub", and "Setup e onboarding".

	Light	Dark
German
Italian

Type

• New feature

Testing

New tests/e2e/i18n.spec.ts (7 tests): de-DE renders the sidebar in German with lang="de", it-IT in Italian, fr-FR falls back to English; the amcp_locale cookie wins over Accept-Language; an unsupported cookie value is ignored; de.json and it.json have exactly the keys of en.json.

Commands and results:

Directory	Command	Result
packages/frontend	npm run lint	0 errors, 52 warnings (same 52 as main)
packages/frontend	npx tsc --noEmit -p tsconfig.json	pass
packages/frontend	npm run build	pass
packages/frontend	npm run test:e2e	264 passed, incl. the 7 new ones and login-redirect-*
packages/backend	npm test	22,422 passed, 5 failed

The 5 backend failures are baseline: the same 5 fail on a clean main checkout (database.engine.hana.spec.ts ×2, mcp-endpoint.controller.spec.ts ×2, first-success.service.spec.ts ×1). This PR doesn't touch the backend.

Also checked manually against a local backend: switching amcp_locale between en, de and it and reloading, navigating through the sidebar, the workspace menu, and log out.

• Added/updated tests
• Tested manually

Checklist

• My code follows the existing code style
• I have tested my changes locally
• I have updated documentation (if applicable)
• All existing tests pass (npm test): frontend yes; backend has the 5 baseline failures above
• This PR has a descriptive title

packages/frontend/AGENTS.md was rewritten by next dev locally and is left out, as AGENTS.md asks.

Related Issues

Part of #1008

[github-actions]

👋 Welcome, @sapatmohit, and thanks for opening your first PR on AnythingMCP!

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[github-actions]

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[sapatmohit]

I have read the CLA Document and I hereby sign the CLA