diff --git a/core/themes/olivero/js/messages.es6.js b/core/themes/olivero/js/messages.es6.js
index cf1fdd8dba..7b63bb3c5e 100644
--- a/core/themes/olivero/js/messages.es6.js
+++ b/core/themes/olivero/js/messages.es6.js
@@ -3,7 +3,7 @@
  * Messages.
  */
 
-((Drupal) => {
+((Drupal, once) => {
   /**
    * Adds close button to the message.
    *
@@ -28,8 +28,6 @@
     closeBtnWrapper.appendChild(closeBtn);
     closeBtn.appendChild(closeBtnText);
 
-    message.classList.add('messages-processed');
-
     closeBtn.addEventListener('click', () => {
       message.classList.add('hidden');
     });
@@ -58,7 +56,7 @@
 
     messageWrapper.setAttribute(
       'class',
-      `messages-list__item messages messages--${type} messages-processed`,
+      `messages-list__item messages messages--${type}`,
     );
     messageWrapper.setAttribute(
       'role',
@@ -114,13 +112,7 @@
    */
   Drupal.behaviors.messages = {
     attach(context) {
-      const messages = context.querySelectorAll(
-        '.messages:not(.messages-processed)',
-      );
-
-      messages.forEach((message) => {
-        closeMessage(message);
-      });
+      once('olivero-messages', '.messages', context).forEach(closeMessage);
     },
   };
-})(Drupal);
+})(Drupal, once);
diff --git a/core/themes/olivero/js/messages.js b/core/themes/olivero/js/messages.js
index aadb74b614..fc465e1ec2 100644
--- a/core/themes/olivero/js/messages.js
+++ b/core/themes/olivero/js/messages.js
@@ -5,7 +5,7 @@
 * @preserve
 **/
 
-(function (Drupal) {
+(function (Drupal, once) {
   var closeMessage = function closeMessage(message) {
     var messageContainer = message.querySelector('.messages__container');
     var closeBtnWrapper = document.createElement('div');
@@ -19,7 +19,6 @@
     messageContainer.appendChild(closeBtnWrapper);
     closeBtnWrapper.appendChild(closeBtn);
     closeBtn.appendChild(closeBtnText);
-    message.classList.add('messages-processed');
     closeBtn.addEventListener('click', function () {
       message.classList.add('hidden');
     });
@@ -31,7 +30,7 @@
         id = _ref2.id;
     var messagesTypes = Drupal.Message.getMessageTypeLabels();
     var messageWrapper = document.createElement('div');
-    messageWrapper.setAttribute('class', "messages-list__item messages messages--".concat(type, " messages-processed"));
+    messageWrapper.setAttribute('class', "messages-list__item messages messages--".concat(type));
     messageWrapper.setAttribute('role', type === 'error' || type === 'warning' ? 'alert' : 'status');
     messageWrapper.setAttribute('aria-labelledby', "".concat(id, "-title"));
     messageWrapper.setAttribute('data-drupal-message-id', id);
@@ -63,10 +62,7 @@
 
   Drupal.behaviors.messages = {
     attach: function attach(context) {
-      var messages = context.querySelectorAll('.messages:not(.messages-processed)');
-      messages.forEach(function (message) {
-        closeMessage(message);
-      });
+      once('olivero-messages', '.messages', context).forEach(closeMessage);
     }
   };
-})(Drupal);
\ No newline at end of file
+})(Drupal, once);
\ No newline at end of file
diff --git a/core/themes/olivero/js/navigation.es6.js b/core/themes/olivero/js/navigation.es6.js
index fe79681038..50d10bddda 100644
--- a/core/themes/olivero/js/navigation.es6.js
+++ b/core/themes/olivero/js/navigation.es6.js
@@ -1,4 +1,4 @@
-((Drupal) => {
+((Drupal, once) => {
   /**
    * Checks if navWrapper contains "is-active" class.
    * @param {object} navWrapper
@@ -103,13 +103,15 @@
    * Initialize the navigation JS.
    */
   Drupal.behaviors.oliveroNavigation = {
-    attach(context, settings) {
+    attach(context) {
       const navWrapperId = 'header-nav';
-      const navWrapper = context.querySelector(
-        `#${navWrapperId}:not(.${navWrapperId}-processed)`,
-      );
+      const navWrapper = once(
+        'olivero-navigation',
+        `#${navWrapperId}`,
+        context,
+      ).shift();
+
       if (navWrapper) {
-        navWrapper.classList.add(`${navWrapperId}-processed`);
         const { olivero } = Drupal;
         const navButton = context.querySelector('.mobile-nav-button');
         const body = context.querySelector('body');
@@ -122,7 +124,6 @@
           focusableNavElements[focusableNavElements.length - 1];
 
         init({
-          settings,
           olivero,
           navWrapperId,
           navWrapper,
@@ -135,4 +136,4 @@
       }
     },
   };
-})(Drupal);
+})(Drupal, once);
diff --git a/core/themes/olivero/js/navigation.js b/core/themes/olivero/js/navigation.js
index 1e07658f55..b6ea85a4f0 100644
--- a/core/themes/olivero/js/navigation.js
+++ b/core/themes/olivero/js/navigation.js
@@ -5,7 +5,7 @@
 * @preserve
 **/
 
-(function (Drupal) {
+(function (Drupal, once) {
   function isNavOpen(navWrapper) {
     return navWrapper.classList.contains('is-active');
   }
@@ -71,12 +71,11 @@
   }
 
   Drupal.behaviors.oliveroNavigation = {
-    attach: function attach(context, settings) {
+    attach: function attach(context) {
       var navWrapperId = 'header-nav';
-      var navWrapper = context.querySelector("#".concat(navWrapperId, ":not(.").concat(navWrapperId, "-processed)"));
+      var navWrapper = once('olivero-navigation', "#".concat(navWrapperId), context).shift();
 
       if (navWrapper) {
-        navWrapper.classList.add("".concat(navWrapperId, "-processed"));
         var olivero = Drupal.olivero;
         var navButton = context.querySelector('.mobile-nav-button');
         var body = context.querySelector('body');
@@ -85,7 +84,6 @@
         var firstFocusableEl = focusableNavElements[0];
         var lastFocusableEl = focusableNavElements[focusableNavElements.length - 1];
         init({
-          settings: settings,
           olivero: olivero,
           navWrapperId: navWrapperId,
           navWrapper: navWrapper,
@@ -98,4 +96,4 @@
       }
     }
   };
-})(Drupal);
\ No newline at end of file
+})(Drupal, once);
\ No newline at end of file
diff --git a/core/themes/olivero/js/tabs.es6.js b/core/themes/olivero/js/tabs.es6.js
index ce29438dea..b5c1232aa8 100644
--- a/core/themes/olivero/js/tabs.es6.js
+++ b/core/themes/olivero/js/tabs.es6.js
@@ -1,4 +1,4 @@
-((Drupal) => {
+((Drupal, once) => {
   function init(el) {
     const tabs = el.querySelector('.tabs');
     const expandedClass = 'is-expanded';
@@ -32,9 +32,7 @@
 
   Drupal.behaviors.tabs = {
     attach(context) {
-      context
-        .querySelectorAll('[data-drupal-nav-tabs]')
-        .forEach((el) => init(el));
+      once('olivero-tabs', '[data-drupal-nav-tabs]', context).forEach(init);
     },
   };
-})(Drupal);
+})(Drupal, once);
diff --git a/core/themes/olivero/js/tabs.js b/core/themes/olivero/js/tabs.js
index 9dda7c72f0..6932f9b405 100644
--- a/core/themes/olivero/js/tabs.js
+++ b/core/themes/olivero/js/tabs.js
@@ -5,7 +5,7 @@
 * @preserve
 **/
 
-(function (Drupal) {
+(function (Drupal, once) {
   function init(el) {
     var tabs = el.querySelector('.tabs');
     var expandedClass = 'is-expanded';
@@ -37,9 +37,7 @@
 
   Drupal.behaviors.tabs = {
     attach: function attach(context) {
-      context.querySelectorAll('[data-drupal-nav-tabs]').forEach(function (el) {
-        return init(el);
-      });
+      once('olivero-tabs', '[data-drupal-nav-tabs]', context).forEach(init);
     }
   };
-})(Drupal);
\ No newline at end of file
+})(Drupal, once);
\ No newline at end of file
diff --git a/core/themes/olivero/olivero.libraries.yml b/core/themes/olivero/olivero.libraries.yml
index 679f9e2caf..d2880457df 100644
--- a/core/themes/olivero/olivero.libraries.yml
+++ b/core/themes/olivero/olivero.libraries.yml
@@ -63,6 +63,7 @@ global-styling:
     js/second-level-navigation.js: {}
   dependencies:
     - core/drupal
+    - core/once
 
 book:
   css: