diff --git a/scripts/patch-mdbook-theme.sh b/scripts/patch-mdbook-theme.sh
index d6c8653a5..75e76c1dd 100755
--- a/scripts/patch-mdbook-theme.sh
+++ b/scripts/patch-mdbook-theme.sh
@@ -1,34 +1,66 @@
 #!/bin/bash
 # Patch mdbook theme to add language selector and utility links
-# Usage: patch-mdbook-theme.sh <coreutils-docs-dir> [current-lang]
+# Usage: patch-mdbook-theme.sh <coreutils-docs-dir> <coreutils-l10n-dir>
 
 set -euo pipefail
 
-DOCS_DIR="${1:?Usage: $0 <coreutils-docs-dir> [current-lang]}"
-CURRENT_LANG="${2:-en}"
+DOCS_DIR="${1:?Usage: $0 <coreutils-docs-dir> <coreutils-l10n-dir>}"
+L10N_DIR="${2:?Usage: $0 <coreutils-docs-dir> <coreutils-l10n-dir>}"
 
 HEAD_HBS="$DOCS_DIR/theme/head.hbs"
 
-# Append language selector and utility links to head.hbs
+# Language display names (ftl filename -> display name)
+declare -A LANG_NAMES=(
+  [en-US]="English"
+  [ar]="العربية" [ast]="Asturianu" [ca]="Català" [cs]="Čeština"
+  [da]="Dansk" [de]="Deutsch" [eo]="Esperanto" [es-ES]="Español"
+  [fi]="Suomi" [fr-FR]="Français" [he]="עברית" [id]="Bahasa Indonesia"
+  [it]="Italiano" [ja]="日本語" [kab]="Taqbaylit" [ko]="한국어"
+  [nb-NO]="Norsk Bokmål" [ne]="नेपाली" [pl]="Polski" [pt]="Português"
+  [pt-BR]="Português (Brasil)" [ru]="Русский" [sv]="Svenska"
+  [tr]="Türkçe" [uk]="Українська" [vi]="Tiếng Việt"
+  [zh-Hans]="中文 (简体)" [zh-Hant]="中文 (繁體)"
+)
+
+# ftl filename -> URL lang code (used in /coreutils/docs-{code}/)
+declare -A FTL_TO_URL=(
+  [en-US]="en" [fr-FR]="fr" [es-ES]="es" [zh-Hans]="zh" [zh-Hant]="zh-Hant"
+  [pt-BR]="pt-BR" [nb-NO]="nb-NO"
+)
+# For others, the ftl name IS the URL code (ar, de, it, ja, etc.)
+
+# Scan l10n repo to find which locales have translations
+# Use a representative utility (ls) to find available locales
+LANGS_JSON="['en', 'English']"
+for ftl in "$L10N_DIR"/src/uu/ls/locales/*.ftl; do
+  [ -f "$ftl" ] || continue
+  ftl_name=$(basename "$ftl" .ftl)
+  [ "$ftl_name" = "en-US" ] && continue
+
+  display="${LANG_NAMES[$ftl_name]:-$ftl_name}"
+  url_code="${FTL_TO_URL[$ftl_name]:-$ftl_name}"
+  LANGS_JSON="$LANGS_JSON, ['$url_code', '$display']"
+done
+
+# Append styles and JS to head.hbs
 cat >> "$HEAD_HBS" << 'ENDSTYLE'
 <style>
-    .util-bar {
+    .util-links {
         display: flex;
-        justify-content: flex-end;
-        gap: 15px;
+        gap: 12px;
         align-items: center;
-        font-size: 0.85em;
-        margin-bottom: 10px;
+        font-size: 0.75em;
     }
-    .util-bar a {
+    .util-links a {
         color: var(--links);
         text-decoration: none;
     }
-    .util-bar a:hover {
+    .util-links a:hover {
         text-decoration: underline;
     }
     .lang-selector {
         position: relative;
+        display: inline-block;
     }
     .lang-selector select {
         appearance: none;
@@ -36,81 +68,89 @@ cat >> "$HEAD_HBS" << 'ENDSTYLE'
         color: var(--fg);
         border: 1px solid var(--table-border-color);
         border-radius: 4px;
-        padding: 4px 24px 4px 8px;
-        font-size: 0.85em;
+        padding: 2px 20px 2px 6px;
+        font-size: 1em;
         cursor: pointer;
     }
     .lang-selector::after {
         content: "▾";
         position: absolute;
-        right: 8px;
+        right: 6px;
         top: 50%;
         transform: translateY(-50%);
         pointer-events: none;
         color: var(--fg);
+        font-size: 0.8em;
     }
 </style>
 ENDSTYLE
-
-# Add JavaScript for language switching and utility bar injection
-cat >> "$HEAD_HBS" << ENDSCRIPT
+cat >> "$HEAD_HBS" << 'ENDSCRIPT'
 <script>
 document.addEventListener('DOMContentLoaded', function() {
-    // Only add util-bar on utility pages
     var path = window.location.pathname;
-    var match = path.match(/\/coreutils\/docs(?:-([a-z]{2}(?:-[A-Z]{2})?))?\/utils\/(\w+)\.html/);
+    // Match both deployed (/coreutils/docs[-lang]/utils/X.html) and local (book[-lang]/utils/X.html)
+    var match = path.match(/\/(?:coreutils\/)?docs(?:-([a-z]{2}(?:-[A-Z]{2})?))?\/utils\/(\w+)\.html/)
+             || path.match(/\/book(?:-([a-z]{2}(?:-[A-Z]{2})?))?\/utils\/(\w+)\.html/);
     if (!match) return;
 
     var currentLang = match[1] || 'en';
     var utilName = match[2];
 
-    var bar = document.createElement('div');
-    bar.className = 'util-bar';
+    // Find the existing .additional div and append our links there
+    var additional = document.querySelector('.additional');
+    if (!additional) return;
+
+    var links = document.createElement('div');
+    links.className = 'util-links';
 
     // Source code link
     var srcLink = document.createElement('a');
     srcLink.href = 'https://github.com/uutils/coreutils/tree/main/src/uu/' + utilName;
-    srcLink.textContent = 'Source code';
+    srcLink.textContent = 'Source';
     srcLink.target = '_blank';
-    bar.appendChild(srcLink);
+    links.appendChild(srcLink);
 
     // Report issue link
     var issueLink = document.createElement('a');
     issueLink.href = 'https://github.com/uutils/coreutils/issues/new?title=' + utilName + ':%20&labels=bug';
-    issueLink.textContent = 'Report an issue';
+    issueLink.textContent = 'Report a bug';
     issueLink.target = '_blank';
-    bar.appendChild(issueLink);
+    links.appendChild(issueLink);
 
     // Language selector
     var langDiv = document.createElement('div');
     langDiv.className = 'lang-selector';
     var select = document.createElement('select');
-    var langs = {
-        'en': 'English', 'fr': 'Français', 'de': 'Deutsch', 'es': 'Español',
-        'it': 'Italiano', 'pt': 'Português', 'pt-BR': 'Português (BR)',
-        'ja': '日本語', 'ko': '한국어', 'ru': 'Русский', 'zh': '中文',
-        'uk': 'Українська', 'sv': 'Svenska', 'pl': 'Polski', 'tr': 'Türkçe'
-    };
-    for (var code in langs) {
+    var langs = LANGS_PLACEHOLDER;
+    langs.forEach(function(l) {
         var opt = document.createElement('option');
-        opt.value = code;
-        opt.textContent = langs[code];
-        if (code === currentLang) opt.selected = true;
+        opt.value = l[0];
+        opt.textContent = l[1];
+        if (l[0] === currentLang) opt.selected = true;
         select.appendChild(opt);
-    }
+    });
     select.addEventListener('change', function() {
         var newLang = this.value;
-        var suffix = newLang === 'en' ? '' : '-' + newLang;
-        window.location.href = '/coreutils/docs' + suffix + '/utils/' + utilName + '.html';
+        var curPath = window.location.pathname;
+        // Replace the directory segment right before /utils/:
+        // .../book[-lang]/utils/X.html or .../docs[-lang]/utils/X.html
+        var newPath = curPath.replace(
+            /\/(book|docs)(?:-[a-zA-Z]{2}(?:-[a-zA-Z]+)?)?\/utils\//,
+            function(m, base) {
+                return '/' + base + (newLang === 'en' ? '' : '-' + newLang) + '/utils/';
+            }
+        );
+        window.location.href = newPath;
     });
     langDiv.appendChild(select);
-    bar.appendChild(langDiv);
+    links.appendChild(langDiv);
 
-    // Insert bar at the top of the content
-    var main = document.querySelector('main');
-    if (main) main.insertBefore(bar, main.firstChild);
+    additional.appendChild(links);
 });
 </script>
 ENDSCRIPT
 
+# Inject the dynamically-built language list
+sed -i "s|LANGS_PLACEHOLDER|[${LANGS_JSON}]|" "$HEAD_HBS"
+
 echo "Patched $HEAD_HBS with language selector and utility links"