bitbaum · catomean · Aug 29, 2026 · Aug 29, 2026
diff --git a/__tests__/unit/cat/nudge-language-ignores-currency.test.ts b/__tests__/unit/cat/nudge-language-ignores-currency.test.ts
@@ -0,0 +1,40 @@
+/**
+ * Nudge language used to be inferred from currency: no `profile.language` plus
+ * a CHF preference meant German. CHF is this platform's DEFAULT fiat, so that
+ * describes every account that never chose anything — and the founder, whose
+ * interface is English, opened his dashboard to a column of German nudge cards
+ * ("Lass „bitcoin" für dich arbeiten", "Biete „Handgemachte Keramiktasse" als
+ * Produkt an").
+ *
+ * A default is not a preference, and a currency is not a language — Switzerland
+ * has four national languages. This is the same category error `@/utils/locale`
+ * was written to end one layer down.
+ */
+
+import { resolveNudgeLanguage, NUDGE_COPY } from '@/services/cat/nudge-copy';
+
+describe('nudge language', () => {
+  it('does not read a language out of the currency', () => {
+    for (const currency of ['CHF', 'EUR', 'USD', 'chf', null, undefined]) {
+      expect(resolveNudgeLanguage({ language: null, currency })).toBe('en');
+    }
+  });
+
+  it('defaults to the language the interface actually speaks', () => {
+    expect(resolveNudgeLanguage(null)).toBe('en');
+    expect(resolveNudgeLanguage(undefined)).toBe('en');
+    expect(resolveNudgeLanguage({})).toBe('en');
+    expect(resolveNudgeLanguage({ language: '', currency: 'CHF' })).toBe('en');
+  });
+
+  it('still honours an explicit choice, whatever the currency says', () => {
+    expect(resolveNudgeLanguage({ language: 'de', currency: 'USD' })).toBe('de');
+    expect(resolveNudgeLanguage({ language: 'de-CH', currency: 'USD' })).toBe('de');
+    expect(resolveNudgeLanguage({ language: 'en', currency: 'CHF' })).toBe('en');
+  });
+
+  it('keeps a copy table for every language it can return', () => {
+    expect(Object.keys(NUDGE_COPY).sort()).toEqual(['de', 'en']);
+    expect(NUDGE_COPY.en.languageName).toBe('English');
+  });
+});
diff --git a/src/services/cat/nudge-copy.ts b/src/services/cat/nudge-copy.ts
@@ -2,9 +2,9 @@
  * Nudge copy SSOT — every user-facing nudge string, per language.
  *
  * One language per user: the language is resolved ONCE from the user's profile
- * (profile.language, falling back to a preferred-currency heuristic) and every
- * nudge — deterministic templates AND LLM-written reasons — uses it. Mixed
- * English/German cards on one dashboard were a founder-verified trust bug.
+ * (profile.language, and nothing else) and every nudge — deterministic
+ * templates AND LLM-written reasons — uses it. Mixed English/German cards on
+ * one dashboard were a founder-verified trust bug.
  */
 
 import { ENTITY_REGISTRY, type EntityType } from '@/config/entity-registry';
@@ -13,23 +13,35 @@ export type NudgeLanguage = 'en' | 'de';
 
 /**
  * Resolve the ONE language all nudges for this user are written in.
- * profile.language is authoritative; with no explicit language, an explicit
- * CHF currency preference (Swiss-focused platform) implies German. Default English.
+ *
+ * `profile.language` — an explicit choice — is the only input. Currency is NOT
+ * a language signal, and reading it as one is why a founder with an English
+ * interface got a dashboard of German nudge cards: CHF is this platform's
+ * DEFAULT fiat (see config/currencies), so "prefers CHF" is what every account
+ * that never chose anything looks like. A default is not a preference. And
+ * Switzerland has four national languages, so even a deliberate CHF would not
+ * imply German.
+ *
+ * It is the same category error `@/utils/locale` was written to end one layer
+ * down — there it was "the language of the interface is not the language of
+ * your operating system"; here it is "…is not the currency you get paid in".
+ *
+ * Note the practical consequence: no surface in this app writes
+ * `profile.language` (the sole write is a mapper default of 'en'), and the
+ * interface ships `<html lang="en">` with no translations. So 'de' is
+ * currently unreachable, and NUDGE_COPY.de waits for real i18n rather than
+ * being selected by a heuristic nobody opted into. That is deliberate — German
+ * nudge cards inside an English interface are the mixed-language dashboard
+ * this file's header calls a trust bug, just at a larger grain.
  */
 export function resolveNudgeLanguage(
+  // `currency` stays in the accepted shape because callers pass a whole
+  // profile — and because a regression test has to be able to hand this
+  // function the exact CHF-shaped profile that used to come back German.
   profile: { language?: string | null; currency?: string | null } | null | undefined
 ): NudgeLanguage {
   const lang = (profile?.language ?? '').toLowerCase();
-  if (lang.startsWith('de')) {
-    return 'de';
-  }
-  if (lang.startsWith('en')) {
-    return 'en';
-  }
-  if ((profile?.currency ?? '').toUpperCase() === 'CHF') {
-    return 'de';
-  }
-  return 'en';
+  return lang.startsWith('de') ? 'de' : 'en';
 }
 
 interface CopyBlock {