diff --git a/src/lib/ai/prompts/base-system.ts b/src/lib/ai/prompts/base-system.ts
index 8140acaa4..6f16d1576 100644
--- a/src/lib/ai/prompts/base-system.ts
+++ b/src/lib/ai/prompts/base-system.ts
@@ -11,6 +11,19 @@ import {
   forbiddenFiller,
   formattingContract,
 } from "./shared-contracts";
+import {
+  instructionLocale,
+  targetLanguageName,
+  withOutputLanguage,
+} from "./output-language";
+
+/**
+ * Placeholder for the reply language inside the English output clause.
+ *
+ * Kept as a token (rather than a template literal in the section array) so the
+ * section array stays a plain data structure the parity tests can iterate.
+ */
+const OUTPUT_LANGUAGE_TOKEN = "{{OUTPUT_LANGUAGE}}";
 
 /**
  * Version of the per-metric assessment base prompt + its signal contract.
@@ -42,8 +55,13 @@ import {
  * rotation. This activates the dormant "do NOT open with the number" branch so
  * the per-metric card reads as warm as the overview. Clause ORDER only —
  * grounding, non-diagnostic framing, and every safety contract are unchanged.
+ * 6.2.0 — output language: French, Spanish, Italian and Polish readers used to
+ * fall to the German instruction body, whose output clause asks for German
+ * prose. They now compose the English body with their language named in the
+ * output clause and the locale's own reply-language directive appended last.
+ * The German and English prompts are byte-identical to 6.1.0 (test-pinned).
  */
-export const PROMPT_VERSION = "6.1.0" as const;
+export const PROMPT_VERSION = "6.2.0" as const;
 
 /**
  * Base system prompt for the per-metric Insights *assessment* cards.
@@ -245,16 +263,30 @@ Synthese statt Aufzählung: die Geschichte dessen, was die Daten bedeuten, zähl
   },
   {
     id: "output",
-    en: `OUTPUT FORMAT: Reply with valid JSON only, in exactly this schema. The "summary" field holds the complete assessment in English: 1-3 short paragraphs of 1-3 sentences each, separated by a blank line written as \\n\\n INSIDE the JSON string. A steady one-liner stays a single paragraph:
+    // The language name is interpolated so a locale riding the English
+    // instruction body still asks for prose in the reader's own language. For
+    // `en` it renders "English" — byte-identical to the pre-6.2.0 literal.
+    en: `OUTPUT FORMAT: Reply with valid JSON only, in exactly this schema. The "summary" field holds the complete assessment in ${OUTPUT_LANGUAGE_TOKEN}: 1-3 short paragraphs of 1-3 sentences each, separated by a blank line written as \\n\\n INSIDE the JSON string. A steady one-liner stays a single paragraph:
 { "summary": "..." }`,
     de: `AUSGABEFORMAT: Antworte ausschließlich mit validem JSON in genau diesem Schema. Das Feld "summary" enthält die komplette Einschätzung auf Deutsch: 1-3 kurze Absätze mit je 1-3 Sätzen, getrennt durch eine Leerzeile als \\n\\n INNERHALB des JSON-Strings. Ein stabiler Einzeiler bleibt EIN Absatz:
 { "summary": "..." }`,
   },
 ];
 
-/** The locale text fragments are joined by a blank line, in section order. */
-function composeAssessmentPrompt(locale: "en" | "de"): string {
-  return ASSESSMENT_SECTIONS.map((s) => s[locale]).join("\n\n");
+/**
+ * The locale text fragments are joined by a blank line, in section order.
+ *
+ * `languageName` fills the output clause's language token on the English body.
+ * The German body names its language natively and carries no token, so the
+ * replacement is a no-op there.
+ */
+function composeAssessmentPrompt(
+  instructionBody: "en" | "de",
+  languageName: string,
+): string {
+  return ASSESSMENT_SECTIONS.map((s) =>
+    s[instructionBody].split(OUTPUT_LANGUAGE_TOKEN).join(languageName),
+  ).join("\n\n");
 }
 
 /**
@@ -272,5 +304,13 @@ export const ASSESSMENT_SECTION_PAIRS: readonly {
 }[] = ASSESSMENT_SECTIONS;
 
 export function getBaseSystemPrompt(locale: Locale): string {
-  return composeAssessmentPrompt(locale === "en" ? "en" : "de");
+  // German readers compose the German body; every other locale composes the
+  // English body and is told, in its own language, which language to write in.
+  // The former `locale === "en" ? "en" : "de"` sent French, Spanish, Italian
+  // and Polish readers a German prompt that asked for German prose.
+  const composed = composeAssessmentPrompt(
+    instructionLocale(locale),
+    targetLanguageName(locale),
+  );
+  return withOutputLanguage(composed, locale);
 }
diff --git a/src/lib/ai/prompts/output-language.ts b/src/lib/ai/prompts/output-language.ts
new file mode 100644
index 000000000..4ba920db4
--- /dev/null
+++ b/src/lib/ai/prompts/output-language.ts
@@ -0,0 +1,107 @@
+/**
+ * Output-language resolution for the assessment prompt family.
+ *
+ * The problem this solves: the prompt modules historically branched
+ * `locale === "en" ? EN_BODY : DE_BODY`. That binary is correct for a de/en
+ * product, but HealthLog ships six UI locales — so every fr/es/it/pl reader
+ * fell to the GERMAN instruction body, whose output clause explicitly asks for
+ * a German assessment. A French account therefore received German prose (on
+ * the surfaces that reached the prompts at all).
+ *
+ * The fix keeps ONE instruction body per prompt in the two languages that have
+ * a reviewed body (de, en) and names the reader's language in an explicit
+ * directive, rather than growing four more hand-maintained translations of
+ * every prompt. The directive text itself is NOT invented here: it is the
+ * `reply_language_directive` from `safety-contracts.<locale>.yaml`, written
+ * natively per locale and already carried in production by the native
+ * insights/briefing prompts (`native-prompts.ts:338,507`). This module only
+ * makes that same mechanism reachable from the assessment family.
+ *
+ * Polarity matters and is the whole point: the fallback for an unknown or
+ * non-German locale is ENGLISH, never German. `instructionLocale` is the
+ * single replacement for every scattered de-default binary.
+ */
+import type { Locale } from "@/lib/i18n/config";
+
+import { loadSafetyContracts } from "./safety-contracts";
+
+/**
+ * Which reviewed instruction body a locale composes.
+ *
+ * German for German readers (its body is reviewed and its register is the one
+ * the largest non-English audience reads); English for everyone else. The
+ * reader's actual language is then named by `outputLanguageDirective`.
+ */
+export function instructionLocale(locale: Locale): "de" | "en" {
+  return locale === "de" ? "de" : "en";
+}
+
+/**
+ * English name of the language the assessment must be WRITTEN in.
+ *
+ * English names because they are interpolated into the English instruction
+ * body; the directive that follows is in the reader's own language.
+ */
+export function targetLanguageName(locale: Locale): string {
+  switch (locale) {
+    case "de":
+      return "German";
+    case "fr":
+      return "French";
+    case "es":
+      return "Spanish";
+    case "it":
+      return "Italian";
+    case "pl":
+      return "Polish";
+    default:
+      return "English";
+  }
+}
+
+/**
+ * Fallback directive when the safety matrix cannot be loaded.
+ *
+ * The matrix read is a synchronous file read + schema parse that throws on a
+ * malformed or missing file. A prompt that silently loses its language
+ * directive would regress exactly the bug this module fixes, so fall back to a
+ * plain English instruction naming the language rather than to an empty
+ * string.
+ */
+function fallbackDirective(locale: Locale): string {
+  return `Write your reply in ${targetLanguageName(locale)}.`;
+}
+
+/**
+ * The terminal OUTPUT LANGUAGE section for a prompt, or `""` when the
+ * composed instruction body already carries the language natively.
+ *
+ * de and en compose their own reviewed body, whose output clause already names
+ * the language — appending a directive there would be redundant and would
+ * change two prompts that are deliberately byte-stable. The four locales that
+ * ride the English body get the directive, placed last so it is the most
+ * recent instruction the model reads.
+ */
+export function outputLanguageDirective(locale: Locale): string {
+  if (locale === "de" || locale === "en") return "";
+
+  let directive: string;
+  try {
+    directive = loadSafetyContracts(locale).reply_language_directive;
+  } catch {
+    directive = fallbackDirective(locale);
+  }
+
+  return `OUTPUT LANGUAGE: ${directive}`;
+}
+
+/**
+ * Append the directive to a composed prompt when one applies.
+ *
+ * Kept here so every adopting module joins it identically (blank-line
+ * separated, directive last) instead of each re-deriving the spacing.
+ */
+export function withOutputLanguage(prompt: string, locale: Locale): string {
+  const directive = outputLanguageDirective(locale);
+  return directive ? `${prompt}\n\n${directive}` : prompt;
+}