diff --git a/frontend/scripts/check-i18n.js b/frontend/scripts/check-i18n.js
index d255eafcd..5ecb21309 100644
--- a/frontend/scripts/check-i18n.js
+++ b/frontend/scripts/check-i18n.js
@@ -19,6 +19,7 @@ import { fileURLToPath, pathToFileURL } from 'node:url';
 import { ENGLISH_FALLBACK_KEYS } from '../src/lib/locales/adminOperationsFallback.js';
 import { mergeInto } from '../src/lib/locales/createLocale.js';
 import { DATE_FORMAT_KEYS, DATE_FORMATS } from '../src/lib/locales/dateFormats.js';
+import { findMixedKeyQuoting } from './locale-key-quoting.js';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const LOCALES_DIR = join(__dirname, '..', 'src', 'lib', 'locales');
@@ -515,6 +516,36 @@ async function main() {
   }
   console.log('');
 
+  // --- Check 6: Locale key quoting ---
+  console.log('  --- Locale key quoting ---');
+  const localeSourceFiles = [];
+  for (const locale of localeDirs) {
+    const localeDir = join(LOCALES_DIR, locale);
+    const files = (await readdir(localeDir)).filter((f) => f.endsWith('.js') && f !== 'index.js');
+    for (const file of files) {
+      localeSourceFiles.push({
+        file: `src/lib/locales/${locale}/${file}`,
+        content: await readFile(join(localeDir, file), 'utf-8'),
+      });
+    }
+  }
+
+  const quotingProblems = findMixedKeyQuoting(localeSourceFiles);
+  let quotingErrors = 0;
+  if (quotingProblems.length > 0) {
+    for (const { file, unquoted } of quotingProblems) {
+      console.log(`  ✗ ${file}: unquoted key(s) in a quoted-key file`);
+      for (const { line, key } of unquoted) {
+        console.log(`      line ${line}: ${key}`);
+      }
+      quotingErrors += unquoted.length;
+    }
+    exitCode = 1;
+  } else {
+    console.log('  ✓ No mixed key quoting in locale files');
+  }
+  console.log('');
+
   // --- Summary ---
   if (requiredMissing > 0 || totalExtra > 0) {
     exitCode = 1;
@@ -532,13 +563,17 @@ async function main() {
     if (placeholderErrors > 0) issues.push(`${placeholderErrors} placeholder mismatch(es)`);
     if (carryoverTotal > 0) issues.push(`${carryoverTotal} suspected carryover(s)`);
     if (dateFormatErrors > 0) issues.push(`${dateFormatErrors} date format coverage error(s)`);
+    if (quotingErrors > 0)
+      issues.push(`${quotingErrors} unquoted key(s) in quoted-key locale file(s)`);
     console.log(`  ${issues.join(', ')}`);
     console.log('');
     process.exit(1);
   }
 }
 
-main().catch((err) => {
-  console.error(err);
-  process.exit(1);
-});
+if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
+  main().catch((err) => {
+    console.error(err);
+    process.exit(1);
+  });
+}
diff --git a/frontend/scripts/locale-key-quoting.js b/frontend/scripts/locale-key-quoting.js
new file mode 100644
index 000000000..affdfa752
--- /dev/null
+++ b/frontend/scripts/locale-key-quoting.js
@@ -0,0 +1,40 @@
+// The machine-translated catalogs quote every object key. Quoting an
+// identifier key is never required in JavaScript, so a file that quotes some
+// identifier keys and leaves others bare is a hand-edit or regeneration
+// artifact. Keys that are not valid identifiers (e.g. "field-mappings") must
+// stay quoted and do not signal the file's convention.
+const QUOTED_IDENTIFIER_KEY_PATTERN = /^\s*"([A-Za-z_$][A-Za-z0-9_$]*)":\s*(['"`])/;
+const UNQUOTED_IDENTIFIER_KEY_PATTERN = /^\s*([A-Za-z_$][A-Za-z0-9_$]*):\s*(['"`])/;
+
+/**
+ * Finds locale files that mix quoted and unquoted object keys. Files that
+ * quote their keys are expected to quote all of them.
+ *
+ * @param {Array<{file: string, content: string}>} files
+ * @returns {Array<{file: string, unquoted: Array<{line: number, key: string}>}>}
+ */
+export function findMixedKeyQuoting(files) {
+  const problems = [];
+
+  for (const { file, content } of files) {
+    const unquoted = [];
+    let quoted = 0;
+
+    content.split('\n').forEach((line, index) => {
+      if (QUOTED_IDENTIFIER_KEY_PATTERN.test(line)) {
+        quoted += 1;
+        return;
+      }
+      const match = line.match(UNQUOTED_IDENTIFIER_KEY_PATTERN);
+      if (match) {
+        unquoted.push({ line: index + 1, key: match[1] });
+      }
+    });
+
+    if (quoted > 0 && unquoted.length > 0) {
+      problems.push({ file, unquoted });
+    }
+  }
+
+  return problems;
+}
diff --git a/frontend/src/lib/locales/ar/supplemental.js b/frontend/src/lib/locales/ar/supplemental.js
index 8b67f71e1..59fa5cb3e 100644
--- a/frontend/src/lib/locales/ar/supplemental.js
+++ b/frontend/src/lib/locales/ar/supplemental.js
@@ -209,10 +209,10 @@ export default {
     "orSignInWithEmail": "أو قم بتسجيل الدخول باستخدام البريد الإلكتروني",
     "profileAndSecurity": "الملف الشخصي والأمان",
     "profileTitle": "الملف الشخصي",
-    languageTitle: "اللغة",
-    languageSubtitle: "اختر لغة هذه البوابة والرسائل التي تصلك.",
-    languageLabel: "اللغة",
-    languageSaved: "تم تحديث اللغة",
+    "languageTitle": "اللغة",
+    "languageSubtitle": "اختر لغة هذه البوابة والرسائل التي تصلك.",
+    "languageLabel": "اللغة",
+    "languageSaved": "تم تحديث اللغة",
     "profileSubtitle": "إدارة كيفية تسجيل الدخول إلى هذه البوابة.",
     "profileSection": "الحساب",
     "passkeysTitle": "مفاتيح المرور",
diff --git a/frontend/src/lib/locales/de/supplemental.js b/frontend/src/lib/locales/de/supplemental.js
index 3355e8180..522750d21 100644
--- a/frontend/src/lib/locales/de/supplemental.js
+++ b/frontend/src/lib/locales/de/supplemental.js
@@ -170,10 +170,10 @@ export default {
     "orSignInWithEmail": "oder melden Sie sich mit E-Mail an",
     "profileAndSecurity": "Profil und Sicherheit",
     "profileTitle": "Profil",
-    languageTitle: "Sprache",
-    languageSubtitle: "Wählen Sie die Sprache für dieses Portal und die E-Mails, die Sie erhalten.",
-    languageLabel: "Sprache",
-    languageSaved: "Sprache aktualisiert",
+    "languageTitle": "Sprache",
+    "languageSubtitle": "Wählen Sie die Sprache für dieses Portal und die E-Mails, die Sie erhalten.",
+    "languageLabel": "Sprache",
+    "languageSaved": "Sprache aktualisiert",
     "profileSubtitle": "Verwalten Sie, wie Sie sich bei diesem Portal anmelden.",
     "profileSection": "Konto",
     "passkeysTitle": "Passkeys",
diff --git a/frontend/src/lib/locales/es/supplemental.js b/frontend/src/lib/locales/es/supplemental.js
index 28f164ce9..5fdf86556 100644
--- a/frontend/src/lib/locales/es/supplemental.js
+++ b/frontend/src/lib/locales/es/supplemental.js
@@ -209,10 +209,10 @@ export default {
     "orSignInWithEmail": "o inicie sesión con el correo electrónico",
     "profileAndSecurity": "Perfil y seguridad",
     "profileTitle": "Perfil",
-    languageTitle: "Idioma",
-    languageSubtitle: "Elige el idioma de este portal y de los correos que recibes.",
-    languageLabel: "Idioma",
-    languageSaved: "Idioma actualizado",
+    "languageTitle": "Idioma",
+    "languageSubtitle": "Elige el idioma de este portal y de los correos que recibes.",
+    "languageLabel": "Idioma",
+    "languageSaved": "Idioma actualizado",
     "profileSubtitle": "Administre cómo inicia sesión en este portal.",
     "profileSection": "Cuenta",
     "passkeysTitle": "Claves de acceso",
diff --git a/frontend/src/lib/locales/ko/admin.js b/frontend/src/lib/locales/ko/admin.js
index febd54e7b..524f510aa 100644
--- a/frontend/src/lib/locales/ko/admin.js
+++ b/frontend/src/lib/locales/ko/admin.js
@@ -658,14 +658,14 @@ export default {
       "textBody": "일반 텍스트 본문",
       "adminNotes": "설명(관리자 메모)",
       "activeHint": "활성(해제하면 기본 내장 템플릿 사용)",
-      localeLabel: "언어",
-      defaultLocale: "기본(모든 언어)",
-      translationHint: "이 언어의 버전을 편집하고 있습니다. 다른 언어는 기본 템플릿을 사용합니다.",
-      translationSaved: "번역이 저장되었습니다",
-      translationDelete: "번역 삭제",
-      translationDeleted: "번역이 삭제되었습니다",
-      translationSaveFailed: "번역을 저장하지 못했습니다: {error}",
-      translationDeleteFailed: "번역을 삭제하지 못했습니다: {error}",
+      "localeLabel": "언어",
+      "defaultLocale": "기본(모든 언어)",
+      "translationHint": "이 언어의 버전을 편집하고 있습니다. 다른 언어는 기본 템플릿을 사용합니다.",
+      "translationSaved": "번역이 저장되었습니다",
+      "translationDelete": "번역 삭제",
+      "translationDeleted": "번역이 삭제되었습니다",
+      "translationSaveFailed": "번역을 저장하지 못했습니다: {error}",
+      "translationDeleteFailed": "번역을 삭제하지 못했습니다: {error}",
       "availableVariables": "사용 가능한 변수",
       "syntaxHint": "템플릿은 Go의 html/template 문법을 사용합니다. 값에는 {open} .Field {close}를, 반복에는 {open} range .Items {close}…{open} end {close}를 사용하세요.",
       "preview": "미리보기",
diff --git a/frontend/src/lib/locales/ko/channels.js b/frontend/src/lib/locales/ko/channels.js
index 85699eee1..042491718 100644
--- a/frontend/src/lib/locales/ko/channels.js
+++ b/frontend/src/lib/locales/ko/channels.js
@@ -434,10 +434,10 @@ export default {
     "orSignInWithEmail": "또는 이메일로 로그인",
     "profileAndSecurity": "프로필 및 보안",
     "profileTitle": "프로필",
-    languageTitle: "언어",
-    languageSubtitle: "이 포털과 받은 이메일에 사용할 언어를 선택하세요.",
-    languageLabel: "언어",
-    languageSaved: "언어가 업데이트되었습니다",
+    "languageTitle": "언어",
+    "languageSubtitle": "이 포털과 받은 이메일에 사용할 언어를 선택하세요.",
+    "languageLabel": "언어",
+    "languageSaved": "언어가 업데이트되었습니다",
     "profileSubtitle": "이 포털의 로그인 방식을 관리합니다.",
     "profileSection": "계정",
     "passkeysTitle": "패스키",
diff --git a/frontend/src/lib/locales/pt-BR/supplemental.js b/frontend/src/lib/locales/pt-BR/supplemental.js
index 6786e80ee..817cacfdd 100644
--- a/frontend/src/lib/locales/pt-BR/supplemental.js
+++ b/frontend/src/lib/locales/pt-BR/supplemental.js
@@ -209,10 +209,10 @@ export default {
     "orSignInWithEmail": "ou faça login com o e-mail",
     "profileAndSecurity": "Perfil e segurança",
     "profileTitle": "Perfil",
-    languageTitle: "Idioma",
-    languageSubtitle: "Escolha o idioma deste portal e dos e-mails que você recebe.",
-    languageLabel: "Idioma",
-    languageSaved: "Idioma atualizado",
+    "languageTitle": "Idioma",
+    "languageSubtitle": "Escolha o idioma deste portal e dos e-mails que você recebe.",
+    "languageLabel": "Idioma",
+    "languageSaved": "Idioma atualizado",
     "profileSubtitle": "Gerencie como você entra neste portal.",
     "profileSection": "Conta",
     "passkeysTitle": "Chaves de acesso",
diff --git a/frontend/src/lib/locales/zh-CN/supplemental.js b/frontend/src/lib/locales/zh-CN/supplemental.js
index 90cefb090..54ce4ccc3 100644
--- a/frontend/src/lib/locales/zh-CN/supplemental.js
+++ b/frontend/src/lib/locales/zh-CN/supplemental.js
@@ -210,10 +210,10 @@ export default {
     "orSignInWithEmail": "或使用电子邮件登录",
     "profileAndSecurity": "个人资料和安全",
     "profileTitle": "个人资料",
-    languageTitle: "语言",
-    languageSubtitle: "选择此门户和您收到的邮件的语言。",
-    languageLabel: "语言",
-    languageSaved: "语言已更新",
+    "languageTitle": "语言",
+    "languageSubtitle": "选择此门户和您收到的邮件的语言。",
+    "languageLabel": "语言",
+    "languageSaved": "语言已更新",
     "profileSubtitle": "管理您登录此门户的方式。",
     "profileSection": "帐户",
     "passkeysTitle": "通行密钥",