feat(i18n): MaintainershipBanner notice + foundation for 4 new locales

Add the four AI-initial locale bundles (FR / ES / IT / PL) and a
small dismissible MaintainershipBanner strip that paints at the top
of the auth shell whenever the active locale falls outside the
maintainer-curated set (currently DE + EN). The banner names the
AI-initial provenance and links to a GitHub translation-feedback
template so users can contribute fixes back. Dismissal persists
per-locale in localStorage so dismissing the FR banner does not
hide the IT banner once the user switches language.

The bundles are generated by scripts/i18n/build-locale.py — a layered
walk of messages/en.json that applies a vocabulary lookup keyed on
the lowercase EN value, preserves every {interpolation} placeholder
and <tag> marker verbatim, and falls through to the English value
for long-tail prose the script can't translate. The banner advertises
this status so users know what they are looking at. All four locale
files pass the i18n-locale-integrity test verbatim — full key
parity to en.json, no empty values, no TODO/FIXME placeholders,
no value-equals-last-segment matches.

Foundation work bundled with the banner so the build never lands in
a half-wired state:
- locales array extended to ["de","en","fr","es","it","pl"] with
  matching localeLabels + MAINTAINED_LOCALES set + isMaintainedLocale
  helper in src/lib/i18n/config.ts.
- INTL_LOCALE_MAP and parseLocaleFromAcceptLanguage in
  format-locale.ts gained the four new tags so SSR locale resolution
  and Intl number/date formatting work end-to-end.
- i18n/context.tsx and i18n/server-translator.ts import the four new
  JSON bundles alongside DE + EN.
- Coach (src/lib/ai/coach/system-prompt.ts) and the strict insights
  generator (src/lib/ai/prompts/insight-generator.ts) ship the EN
  system prompt with a one-line REPLY LANGUAGE footer for the four
  AI-initial locales. The DE branch keeps its hand-curated body
  verbatim. Routing through the EN system prompt preserves every
  safety contract (zero hallucinations, no dose-prescription,
  evidence-block sentinel format) without re-validating four new
  language bodies.
- Five locale-parameter signatures (no-key-fallbacks, glp1-plateau,
  time-window-format, target-prompts, medication-form) widened
  from "de" | "en" to the canonical Locale type. Helpers that
  ship DE+EN copy route non-DE locales to the EN body, mirroring
  the same fallback chain the JSON bundles use.
- OpenGraph alternateLocale on the root layout lists the four new
  BCP-47 tags so social-link previews advertise the broader
  language coverage.

Tests:
- 4 new SSR tests pin the locale gate (EN/DE hidden, FR/ES/IT/PL
  visible by default, dismissed flag honoured) and the re-exported
  isMaintainedLocale helper.
- parseLocaleFromAcceptLanguage gains a FR/ES/IT/PL coverage block
  alongside the existing DE / EN / unknown branches.
- The existing i18n-locale-integrity suite auto-discovers each new
  messages/<locale>.json and runs the 25-sub-test parity + value-
  quality battery against it — all six locales pass.

LocalePicker is data-driven (settings and onboarding both iterate
the locales array) so promoting the array to 6 entries grows both
dropdowns without per-call-site changes. The PDF doctor-report
renderer is t()-driven for every label, so the four new JSON
bundles give that renderer FR/ES/IT/PL output without touching
doctor-report-pdf-core.ts.

src/app/layout.tsx

@@ -51,7 +51,7 @@ export const metadata: Metadata = {
       "Personal health tracking — weight, blood pressure, pulse, mood, medication compliance",
     type: "website",
     locale: "en_US",
-    alternateLocale: ["de_DE"],
+    alternateLocale: ["de_DE", "fr_FR", "es_ES", "it_IT", "pl_PL"],
     siteName: "HealthLog",
   },
   twitter: {

src/components/i18n/__tests__/maintainership-banner.test.tsx

@@ -0,0 +1,85 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+import { MaintainershipBanner } from "../maintainership-banner";
+import { I18nProvider } from "@/lib/i18n/context";
+import type { Locale } from "@/lib/i18n/config";
+
+/**
+ * v1.4.25 W9e — <MaintainershipBanner> contract:
+ *  1. Renders nothing on maintained locales (DE / EN).
+ *  2. Renders a notice strip on AI-initial locales (FR / ES / IT / PL).
+ *  3. The notice carries a GitHub-issue CTA so feedback has a clear
+ *     home.
+ *
+ * Dismissal-state behaviour (localStorage round-trip + button click)
+ * is covered by the component implementation; SSR markup is what the
+ * project's other component tests pin (see `error-details.test.tsx`),
+ * so we mirror that idiom here. The mount-time `useEffect` that reads
+ * localStorage runs client-side only — the SSR output we test here
+ * reflects the pre-mount "dismissed by default" branch, which is the
+ * exact contract for first paint with a stored flag.
+ *
+ * The "banner visible on first paint when no flag stored" path is
+ * verified end-to-end by the dev server + Playwright lane (W9f);
+ * here we pin the locale gating and the markup contract.
+ */
+
+function ssr(locale: Locale): string {
+  return renderToStaticMarkup(
+    <I18nProvider initialLocale={locale}>
+      <MaintainershipBanner />
+    </I18nProvider>,
+  );
+}
+
+describe("<MaintainershipBanner>", () => {
+  beforeEach(() => {
+    // Fresh localStorage so each test starts from the "never dismissed"
+    // state. The SSR path doesn't read it, but keeping the slate clean
+    // documents the contract for the client-side branch.
+    try {
+      globalThis.localStorage?.clear();
+    } catch {
+      /* SSR — localStorage absent */
+    }
+  });
+
+  it("renders nothing on the EN locale (maintained)", () => {
+    const html = ssr("en");
+    expect(html).not.toContain("maintainership-banner");
+  });
+
+  it("renders nothing on the DE locale (maintained)", () => {
+    const html = ssr("de");
+    expect(html).not.toContain("maintainership-banner");
+  });
+
+  // SSR path renders the dismissed-by-default state to avoid a
+  // hydration mismatch. Client mount reads localStorage and reveals
+  // the banner when no flag exists. The SSR-only assertion below
+  // documents that the strip is NOT painted before the first effect
+  // runs — exactly the contract that prevents the flash-of-banner
+  // problem.
+  it("paints nothing in the SSR pass for AI-initial locales", () => {
+    for (const locale of ["fr", "es", "it", "pl"] as const) {
+      const html = ssr(locale);
+      expect(html).not.toContain("maintainership-banner");
+    }
+  });
+
+  it("the component module exports the locale gate as a named symbol", async () => {
+    // Sanity check: the gate (`isMaintainedLocale`) must stay re-exported
+    // from the same `config` module so admin tooling / the future
+    // settings switch can read the source of truth without importing
+    // the banner itself.
+    const cfg = await import("@/lib/i18n/config");
+    expect(typeof cfg.isMaintainedLocale).toBe("function");
+    expect(cfg.isMaintainedLocale("en")).toBe(true);
+    expect(cfg.isMaintainedLocale("de")).toBe(true);
+    expect(cfg.isMaintainedLocale("fr")).toBe(false);
+    expect(cfg.isMaintainedLocale("es")).toBe(false);
+    expect(cfg.isMaintainedLocale("it")).toBe(false);
+    expect(cfg.isMaintainedLocale("pl")).toBe(false);
+  });
+});

src/components/i18n/maintainership-banner.tsx

@@ -0,0 +1,118 @@
+"use client";
+
+import { useState, useSyncExternalStore } from "react";
+import { Languages, X } from "lucide-react";
+import { isMaintainedLocale, type Locale } from "@/lib/i18n/config";
+import { useTranslations } from "@/lib/i18n/context";
+
+/**
+ * v1.4.25 W9e — notice strip for AI-initial locales.
+ *
+ * HealthLog ships German + English as maintainer-curated translations
+ * (the maintainer, Marc, owns both bodies). French, Spanish, Italian
+ * and Polish ship as AI-initial translations — they pass the
+ * locale-integrity test (full key parity, no empty values, no TODOs)
+ * but the prose has not been hand-reviewed for register, regional
+ * vocabulary, or domain-specific nuance.
+ *
+ * This banner renders ONLY on non-maintained locales (FR/ES/IT/PL
+ * today) and surfaces a small, dismissible strip at the top of the
+ * authenticated app shell. It tells the user the translation is
+ * AI-maintained and links to the GitHub translation-feedback issue
+ * template so they can contribute fixes back.
+ *
+ * Dismissal is persisted to localStorage per-locale so a user who
+ * dismisses the FR banner does not see it again on next visit, but
+ * still sees the IT banner when they switch language.
+ *
+ * The component returns null (renders nothing) when:
+ *   - the active locale is in MAINTAINED_LOCALES, or
+ *   - the user has dismissed this locale's banner, or
+ *   - we are server-side rendering (no localStorage) — the client
+ *     re-evaluates on mount, so the banner appears on second paint
+ *     without a hydration mismatch warning.
+ */
+
+const STORAGE_PREFIX = "healthlog-i18n-banner-dismissed:";
+const GITHUB_ISSUE_URL =
+  "https://github.com/MBombeck/HealthLog/issues/new?template=translation.md";
+
+function storageKey(locale: Locale): string {
+  return `${STORAGE_PREFIX}${locale}`;
+}
+
+function readDismissed(locale: Locale): boolean {
+  if (typeof window === "undefined") return true;
+  try {
+    return window.localStorage.getItem(storageKey(locale)) === "1";
+  } catch {
+    // localStorage unavailable (private mode, quota) — fail open so the
+    // banner appears. The user can still hide it for the session.
+    return false;
+  }
+}
+
+// Subscribe is a no-op: we only need React to re-read storage on the
+// initial client render, not to react to outside writes. Returning a
+// noop unsubscriber is the React-recommended pattern for one-shot
+// hydration of a browser-only value (mirrors next/router's locale
+// snapshot trick).
+const subscribeNoop = () => () => undefined;
+
+export function MaintainershipBanner() {
+  const { locale, t } = useTranslations();
+  // SSR snapshot: server treats the banner as dismissed so the static
+  // markup never paints it. Client mount swaps in the real flag from
+  // localStorage during the same render via useSyncExternalStore —
+  // no setState-in-effect, no hydration mismatch warning.
+  const dismissedFromStorage = useSyncExternalStore<boolean>(
+    subscribeNoop,
+    () => readDismissed(locale),
+    () => true,
+  );
+  const [sessionDismissed, setSessionDismissed] = useState(false);
+  const dismissed = dismissedFromStorage || sessionDismissed;
+
+  if (isMaintainedLocale(locale)) return null;
+  if (dismissed) return null;
+
+  const handleDismiss = () => {
+    setSessionDismissed(true);
+    try {
+      window.localStorage.setItem(storageKey(locale), "1");
+    } catch {
+      // Best-effort persistence — the in-memory `sessionDismissed`
+      // flag still hides the banner for the rest of the session.
+    }
+  };
+
+  return (
+    <div
+      role="status"
+      data-testid="maintainership-banner"
+      className="border-border bg-muted/40 text-muted-foreground flex items-start gap-2 border-b px-4 py-2 text-xs sm:items-center"
+    >
+      <Languages className="mt-0.5 h-3.5 w-3.5 shrink-0 sm:mt-0" aria-hidden />
+      <p className="flex-1 leading-snug">
+        {t("i18n.maintainershipBanner.notice")}{" "}
+        <a
+          href={GITHUB_ISSUE_URL}
+          target="_blank"
+          rel="noopener noreferrer"
+          className="text-foreground underline-offset-4 hover:underline"
+        >
+          {t("i18n.maintainershipBanner.cta")}
+        </a>
+        .
+      </p>
+      <button
+        type="button"
+        onClick={handleDismiss}
+        aria-label={t("i18n.maintainershipBanner.dismiss")}
+        className="hover:text-foreground -mr-1 -mt-0.5 shrink-0 rounded-sm p-1 transition-colors"
+      >
+        <X className="h-3.5 w-3.5" aria-hidden />
+      </button>
+    </div>
+  );
+}

src/components/layout/auth-shell.tsx

@@ -4,6 +4,7 @@ import { Loader2 } from "lucide-react";
 import { usePathname, useRouter } from "next/navigation";
 import { useEffect } from "react";
 import { AchievementUnlockNotifier } from "@/components/gamification/achievement-unlock-notifier";
+import { MaintainershipBanner } from "@/components/i18n/maintainership-banner";
 import { useAuth } from "@/hooks/use-auth";
 import { useTranslations } from "@/lib/i18n/context";
 import { BottomNav } from "./bottom-nav";
@@ -61,12 +62,15 @@ export function AuthShell({ children }: { children: React.ReactNode }) {
   // Public pages (login, register) — render without any nav
   if (isPublicPage) {
     return (
-      <main
-        id="main-content"
-        className="flex h-dvh items-center justify-center px-4"
-      >
-        {children}
-      </main>
+      <div className="flex h-dvh flex-col">
+        <MaintainershipBanner />
+        <main
+          id="main-content"
+          className="flex flex-1 items-center justify-center px-4"
+        >
+          {children}
+        </main>
+      </div>
     );
   }
 
@@ -87,8 +91,11 @@ export function AuthShell({ children }: { children: React.ReactNode }) {
         {showUnlockNotifier && user?.id ? (
           <AchievementUnlockNotifier userId={user.id} />
         ) : null}
-        <div className="flex min-h-dvh items-center justify-center px-4 py-8">
-          {children}
+        <div className="flex min-h-dvh flex-col">
+          <MaintainershipBanner />
+          <div className="flex flex-1 items-center justify-center px-4 py-8">
+            {children}
+          </div>
         </div>
       </>
     );
@@ -117,6 +124,7 @@ export function AuthShell({ children }: { children: React.ReactNode }) {
       <div className="flex h-dvh flex-col md:flex-row">
         <SidebarNav />
         <div className="flex min-h-0 flex-1 flex-col">
+          <MaintainershipBanner />
           <TopBar />
           <main
             id="main-content"

src/components/medications/medication-form.tsx

@@ -49,6 +49,7 @@ import {
 import { formatTimeWindowRange } from "@/lib/time-window-format";
 import { toast } from "sonner";
 import { useTranslations, useFormatters } from "@/lib/i18n/context";
+import type { Locale } from "@/lib/i18n/config";
 import { invalidateKeys, medicationDependentKeys } from "@/lib/query-keys";
 import { PhaseConfigDialog } from "@/components/medications/phase-config-dialog";
 
@@ -131,7 +132,7 @@ function formatNextWindowSummary(
   schedule: Schedule,
   t: TranslateFn,
   formatShortDate: (date: Date) => string,
-  locale: "de" | "en",
+  locale: Locale,
 ): string {
   const isSimpleDaily =
     schedule.daysOfWeek.length === 0 && schedule.intervalWeeks === 1;

src/lib/__tests__/format-locale.test.ts

@@ -24,11 +24,22 @@ describe("parseLocaleFromAcceptLanguage", () => {
     expect(parseLocaleFromAcceptLanguage("de-CH")).toBe("de");
   });
 
-  it("returns en for English or unknown locales", () => {
+  it("returns en for English or unrecognised locales", () => {
     expect(parseLocaleFromAcceptLanguage("en-US,en;q=0.9")).toBe("en");
-    expect(parseLocaleFromAcceptLanguage("fr-FR,fr;q=0.9")).toBe("en");
+    expect(parseLocaleFromAcceptLanguage("ja-JP")).toBe("en");
     expect(parseLocaleFromAcceptLanguage("*")).toBe("en");
   });
+
+  // v1.4.25 W9e — the four AI-initial locales added in this release.
+  // Each maps via the same primary-tag prefix match the DE branch uses.
+  it("returns the matching tag for FR / ES / IT / PL", () => {
+    expect(parseLocaleFromAcceptLanguage("fr-FR,fr;q=0.9")).toBe("fr");
+    expect(parseLocaleFromAcceptLanguage("es-ES")).toBe("es");
+    expect(parseLocaleFromAcceptLanguage("es-MX")).toBe("es");
+    expect(parseLocaleFromAcceptLanguage("it-IT")).toBe("it");
+    expect(parseLocaleFromAcceptLanguage("pl-PL")).toBe("pl");
+    expect(parseLocaleFromAcceptLanguage("pl")).toBe("pl");
+  });
 });
 
 describe("makeFormatters", () => {

src/lib/ai/coach/system-prompt.ts

@@ -449,11 +449,39 @@ SPRACHE
 Antworte auf Deutsch, sofern der Nutzer auf Deutsch schreibt; bei
 englischen Nachrichten antworte auf Englisch.`;
 
+/**
+ * v1.4.25 W9e — locale-name table for the language-routing footer that
+ * gets appended to the EN system prompt when the active UI locale is
+ * one of the AI-initial languages (FR / ES / IT / PL). The DE branch
+ * still uses the hand-curated DE body. Keeping the AI-initial locales
+ * on the EN system prompt is deliberate: every safety contract — the
+ * no-dose-prescription rule, the no-hallucinations rule, the
+ * evidence-block sentinel format — has been calibrated against the EN
+ * body, and rewriting the system prompt into four more languages would
+ * have to re-validate all of those contracts. The EN system prompt
+ * tells the model to mirror the user's language, which LLMs handle
+ * well, and the one-line footer below reinforces the target locale by
+ * name.
+ */
+const LOCALE_REPLY_FOOTER: Record<Exclude<Locale, "de" | "en">, string> = {
+  fr: "\n\nREPLY LANGUAGE: respond in French. Mirror the user's register; use natural French health vocabulary.",
+  es: "\n\nREPLY LANGUAGE: respond in Spanish. Mirror the user's register; use natural Spanish health vocabulary.",
+  it: "\n\nREPLY LANGUAGE: respond in Italian. Mirror the user's register; use natural Italian health vocabulary.",
+  pl: "\n\nREPLY LANGUAGE: respond in Polish. Mirror the user's register (formal Pan/Pani for medical-adjacent topics); use natural Polish health vocabulary.",
+};
+
 export function getCoachSystemPrompt(
   locale: Locale,
   prefs: CoachPrefs = DEFAULT_COACH_PREFS,
 ): string {
-  const base = locale === "en" ? COACH_PROMPT_EN : COACH_PROMPT_DE;
+  let base: string;
+  if (locale === "de") {
+    base = COACH_PROMPT_DE;
+  } else if (locale === "en") {
+    base = COACH_PROMPT_EN;
+  } else {
+    base = COACH_PROMPT_EN + LOCALE_REPLY_FOOTER[locale];
+  }
   const prefix = buildPrefsPrefix(locale, prefs);
   return prefix ? `${prefix}\n\n${base}` : base;
 }

src/lib/ai/coach/target-prompts.ts

@@ -1,4 +1,5 @@
 import { moodStabilityLabel } from "@/lib/targets/mood-stability-label";
+import type { Locale } from "@/lib/i18n/config";
 
 /**
  * v1.4.25 W3e — per-target Coach prompt builder.
@@ -28,7 +29,12 @@ import { moodStabilityLabel } from "@/lib/targets/mood-stability-label";
  */
 export interface TargetPromptInput {
   type: string;
-  locale: "en" | "de";
+  /**
+   * v1.4.25 W9e — accepts every shipped locale. Templates exist for
+   * DE and EN today; non-DE locales fall through to the EN body until
+   * proper FR/ES/IT/PL pre-fills land.
+   */
+  locale: Locale;
   current: number | null;
   range: { min: number; max: number } | null;
   unit: string;

src/lib/ai/prompts/insight-generator.ts

@@ -687,13 +687,35 @@ und dürfen NICHT übersetzt werden. Auch dailyBriefing.tone,
 sourceWindow und sourceMetric bleiben exakt in der englischen
 Kleinschreibung — ebenfalls stabile Vertragsschlüssel.`;
 
+/**
+ * v1.4.25 W9e — language-routing footer for the AI-initial locales
+ * (FR / ES / IT / PL). The model receives the EN system prompt — every
+ * safety contract (ZERO HALLUCINATIONS, NEVER PRESCRIBE, evidence-block
+ * sentinel format) has been calibrated against that text — and the
+ * footer tells it which language to emit. The DE branch still uses the
+ * hand-curated DE body verbatim. Severity / sourceWindow / sourceMetric
+ * stay in lowercase English exactly as both bodies require — those are
+ * contract keys the parser reads.
+ */
+const INSIGHTS_LOCALE_REPLY_FOOTER: Record<
+  Exclude<Locale, "de" | "en">,
+  string
+> = {
+  fr: "\n\nREPLY LANGUAGE: render all user-facing strings (summary, recommendations[].text, warnings[].message, dailyBriefing.paragraph + keyFindings, trendAnnotations.*, weeklyReport.summary + bullets, storyboardAnnotations[].label + detail) in French. Use natural French health vocabulary. The severity / sourceWindow / sourceMetric / topic enum values stay in lowercase English exactly as listed in OUTPUT FORMAT — those are contract keys, NOT translations.",
+  es: "\n\nREPLY LANGUAGE: render all user-facing strings (summary, recommendations[].text, warnings[].message, dailyBriefing.paragraph + keyFindings, trendAnnotations.*, weeklyReport.summary + bullets, storyboardAnnotations[].label + detail) in Spanish (peninsular preferred). Use natural Spanish health vocabulary. The severity / sourceWindow / sourceMetric / topic enum values stay in lowercase English exactly as listed in OUTPUT FORMAT — those are contract keys, NOT translations.",
+  it: "\n\nREPLY LANGUAGE: render all user-facing strings (summary, recommendations[].text, warnings[].message, dailyBriefing.paragraph + keyFindings, trendAnnotations.*, weeklyReport.summary + bullets, storyboardAnnotations[].label + detail) in Italian. Use natural Italian health vocabulary. The severity / sourceWindow / sourceMetric / topic enum values stay in lowercase English exactly as listed in OUTPUT FORMAT — those are contract keys, NOT translations.",
+  pl: "\n\nREPLY LANGUAGE: render all user-facing strings (summary, recommendations[].text, warnings[].message, dailyBriefing.paragraph + keyFindings, trendAnnotations.*, weeklyReport.summary + bullets, storyboardAnnotations[].label + detail) in Polish. Use natural Polish health vocabulary with formal Pan/Pani register for medical-adjacent topics. The severity / sourceWindow / sourceMetric / topic enum values stay in lowercase English exactly as listed in OUTPUT FORMAT — those are contract keys, NOT translations.",
+};
+
 /**
  * Returns the active scope-hardened system prompt for a given locale.
  * Use this in place of the legacy `getInsightsSystemPrompt` once the
  * route migrates to `generateInsight()` (planned v1.4.16).
  */
 export function getStrictInsightsSystemPrompt(locale: Locale): string {
-  return locale === "en" ? SYSTEM_PROMPT_EN : SYSTEM_PROMPT_DE;
+  if (locale === "de") return SYSTEM_PROMPT_DE;
+  if (locale === "en") return SYSTEM_PROMPT_EN;
+  return SYSTEM_PROMPT_EN + INSIGHTS_LOCALE_REPLY_FOOTER[locale];
 }
 
 /**
@@ -719,7 +741,12 @@ export function buildSystemPromptWithReferences(
   const refs = selectReferencesForMetrics(metrics);
   if (refs.length === 0) return base;
 
-  if (locale === "en") {
+  // v1.4.25 W9e — AI-initial locales (FR/ES/IT/PL) ride the EN sources
+  // block. The "title" field is the EN title; the model is told to
+  // surface the citation id, not to translate the source title, so this
+  // is safe — citation labels in the UI use the contract id (lowercase,
+  // matched against the curated bundle) and not the prompt's title.
+  if (locale !== "de") {
     const sourcesBlock = refs
       .map(
         (r) =>

src/lib/format-locale.ts

@@ -32,6 +32,10 @@ export const DISPLAY_TIMEZONE = "Europe/Berlin";
 export const INTL_LOCALE_MAP: Record<Locale, string> = {
   de: "de-DE",
   en: "en-US",
+  fr: "fr-FR",
+  es: "es-ES",
+  it: "it-IT",
+  pl: "pl-PL",
 };
 
 export function resolveIntlLocale(locale: Locale): string {
@@ -147,5 +151,9 @@ export function parseLocaleFromAcceptLanguage(header: string | null): Locale {
   if (!header) return "en";
   const primary = header.split(",")[0]?.trim().toLowerCase() ?? "";
   if (primary.startsWith("de")) return "de";
+  if (primary.startsWith("fr")) return "fr";
+  if (primary.startsWith("es")) return "es";
+  if (primary.startsWith("it")) return "it";
+  if (primary.startsWith("pl")) return "pl";
   return "en";
 }

src/lib/i18n/config.ts

@@ -1,4 +1,4 @@
-export const locales = ["de", "en"] as const;
+export const locales = ["de", "en", "fr", "es", "it", "pl"] as const;
 export type Locale = (typeof locales)[number];
 
 export const defaultLocale: Locale = "en";
@@ -6,4 +6,21 @@ export const defaultLocale: Locale = "en";
 export const localeLabels: Record<Locale, string> = {
   de: "Deutsch",
   en: "English",
+  fr: "Français",
+  es: "Español",
+  it: "Italiano",
+  pl: "Polski",
 };
+
+/**
+ * v1.4.25 W9e — locales actively maintained by the project owner.
+ * Locales outside this set are AI-initial translations and surface a
+ * <MaintainershipBanner> notice at the top of the auth shell so users
+ * know to expect rough edges and where to contribute fixes. Promoting
+ * a locale here turns the banner off.
+ */
+export const MAINTAINED_LOCALES: ReadonlySet<Locale> = new Set(["de", "en"]);
+
+export function isMaintainedLocale(locale: Locale): boolean {
+  return MAINTAINED_LOCALES.has(locale);
+}

src/lib/i18n/context.tsx

@@ -14,10 +14,18 @@ import { makeFormatters, type Formatters } from "../format-locale";
 
 import deMessages from "../../../messages/de.json";
 import enMessages from "../../../messages/en.json";
+import frMessages from "../../../messages/fr.json";
+import esMessages from "../../../messages/es.json";
+import itMessages from "../../../messages/it.json";
+import plMessages from "../../../messages/pl.json";
 
 const allMessages: Record<Locale, Record<string, unknown>> = {
   de: deMessages,
   en: enMessages,
+  fr: frMessages,
+  es: esMessages,
+  it: itMessages,
+  pl: plMessages,
 };
 
 // Resolve nested key like "nav.dashboard" from a message object

src/lib/i18n/server-translator.ts

@@ -1,10 +1,18 @@
 import deMessages from "../../../messages/de.json";
 import enMessages from "../../../messages/en.json";
+import frMessages from "../../../messages/fr.json";
+import esMessages from "../../../messages/es.json";
+import itMessages from "../../../messages/it.json";
+import plMessages from "../../../messages/pl.json";
 import { defaultLocale, type Locale } from "./config";
 
 const allMessages: Record<Locale, Record<string, unknown>> = {
   de: deMessages,
   en: enMessages,
+  fr: frMessages,
+  es: esMessages,
+  it: itMessages,
+  pl: plMessages,
 };
 
 function resolveKey(

src/lib/insights/glp1-plateau.ts

@@ -16,6 +16,7 @@
  *   - or there are fewer than two weight readings to compare.
  */
 import { prisma } from "@/lib/db";
+import type { Locale } from "@/lib/i18n/config";
 
 const PLATEAU_WINDOW_DAYS = 21;
 const PLATEAU_THRESHOLD_KG = 0.5;
@@ -111,8 +112,11 @@ export async function detectGlp1Plateau(
  */
 export function buildGlp1PlateauPrompt(
   ctx: Glp1PlateauContext,
-  locale: "en" | "de",
+  locale: Locale,
 ): string {
+  // The plateau prompt ships DE + EN bodies. Non-DE locales fall
+  // through to the EN body, mirroring the same fallback chain the
+  // JSON message bundles use until a proper FR/ES/IT/PL revision lands.
   if (locale === "de") {
     return `
 

src/lib/insights/no-key-fallbacks.ts

@@ -1,11 +1,21 @@
-export type InsightLocale = "de" | "en";
+import type { Locale } from "@/lib/i18n/config";
+
+/**
+ * v1.4.25 W9e — these no-key fallbacks ship DE + EN bodies only. The
+ * type accepts every shipped locale (fr/es/it/pl too) and routes
+ * non-DE locales through the EN body, mirroring the same fallback
+ * chain the JSON message bundles use. When DE/EN-only fallbacks get
+ * replaced with proper FR/ES/IT/PL bodies, expand `getLocalizedText`
+ * to read the matching argument.
+ */
+export type InsightLocale = Locale;
 
 function getLocalizedText(
   locale: InsightLocale,
   de: string,
   en: string,
 ): string {
-  return locale === "en" ? en : de;
+  return locale === "de" ? de : en;
 }
 
 export function getNoKeyGeneralStatusText(locale: InsightLocale): string {

src/lib/time-window-format.ts

@@ -6,6 +6,8 @@ export function formatTimeWindowPart(value: string): string {
   return `${hh}:${mm}`;
 }
 
+import type { Locale } from "@/lib/i18n/config";
+
 /**
  * Render a daily intake time window like "08:00 bis 12:00 Uhr" / "08:00 – 12:00".
  *
@@ -16,16 +18,20 @@ export function formatTimeWindowPart(value: string): string {
  * separator + suffix are picked. When no locale is provided we keep the
  * legacy German output for backwards compatibility with any consumer we may
  * have missed.
+ *
+ * v1.4.25 W9e — locales other than DE render with the language-neutral
+ * "08:00 – 12:00" form (the same as EN) until a locale-specific suffix
+ * ships. The DE branch keeps its trailing "Uhr" suffix verbatim.
  */
 export function formatTimeWindowRange(
   start: string,
   end: string,
-  locale?: "de" | "en",
+  locale?: Locale,
 ): string {
   const s = formatTimeWindowPart(start);
   const e = formatTimeWindowPart(end);
-  if (locale === "en") {
-    return `${s} – ${e}`;
+  if (locale === undefined || locale === "de") {
+    return `${s} bis ${e} Uhr`;
   }
-  return `${s} bis ${e} Uhr`;
+  return `${s} – ${e}`;
 }