diff --git a/js/activity.js b/js/activity.js
index 67b3c35fa0..a071d90b8c 100644
--- a/js/activity.js
+++ b/js/activity.js
@@ -7513,7 +7513,6 @@ class Activity {
             this.toolbar.renderJavaScriptIcon(toggleJSWindow);
             this.toolbar.renderLanguageSelectIcon(this.languageBox);
             this.toolbar.renderWrapIcon();
-
             initPalettes(this.palettes);
 
             if (this.planet !== undefined) {
@@ -7524,7 +7523,7 @@ class Activity {
 
             window.saveLocally = this.saveLocally;
 
-            initBasicProtoBlocks(this);
+            initCoreProtoBlocks(this);
 
             // Load any macros saved in local storage.
             // this.storage.macros = null;
@@ -7541,6 +7540,15 @@ class Activity {
                     processPluginData(this, this.pluginData, "localStorage:plugins")
                 );
             }
+            if ("requestIdleCallback" in window) {
+                requestIdleCallback(() => {
+                    initAdvancedProtoBlocks(this);
+                });
+            } else {
+                setTimeout(() => {
+                    initAdvancedProtoBlocks(this);
+                }, 100);
+            }
 
             // Load custom mode saved in local storage.
             const custommodeData = this.storage.custommode;
@@ -8191,7 +8199,8 @@ class Activity {
 
             // Reinitialize blocks
             if (this.blocks) {
-                initBasicProtoBlocks(this);
+                initCoreProtoBlocks(this);
+                initAdvancedProtoBlocks(this);
             }
 
             // Restore palette positions
diff --git a/js/basicblocks.js b/js/basicblocks.js
index 9e550facee..cb8d058090 100644
--- a/js/basicblocks.js
+++ b/js/basicblocks.js
@@ -81,8 +81,28 @@ const BACKWARDCOMPATIBILIYDICT = {
  * @param  {Object} blocks
  * @returns {void}
  */
-const initBasicProtoBlocks = activity => {
+const initCoreProtoBlocks = activity => {
     activity.blocks.palettes = activity.palettes;
+    setupFlowBlocks(activity);
+    setupNumberBlocks(activity);
+    setupActionBlocks(activity);
+    setupBoxesBlocks(activity);
+    setupBooleanBlocks(activity);
+
+    // Push protoblocks onto their palettes.
+    for (const protoblock in activity.blocks.protoBlockDict) {
+        if (activity.blocks.protoBlockDict[protoblock].palette != null) {
+            activity.blocks.protoBlockDict[protoblock].palette.add(
+                activity.blocks.protoBlockDict[protoblock]
+            );
+        }
+    }
+};
+
+/**
+ * Initialize advanced / heavy blocks (deferred).
+ */
+const initAdvancedProtoBlocks = activity => {
     setupRhythmBlockPaletteBlocks(activity);
     setupRhythmBlocks(activity);
     setupMeterBlocks(activity);
@@ -93,11 +113,6 @@ const initBasicProtoBlocks = activity => {
     setupVolumeBlocks(activity);
     setupDrumBlocks(activity);
     setupWidgetBlocks(activity);
-    setupFlowBlocks(activity);
-    setupNumberBlocks(activity);
-    setupActionBlocks(activity);
-    setupBoxesBlocks(activity);
-    setupBooleanBlocks(activity);
     setupHeapBlocks(activity);
     setupDictBlocks(activity);
     setupExtrasBlocks(activity);
@@ -108,7 +123,7 @@ const initBasicProtoBlocks = activity => {
     setupSensorsBlocks(activity);
     setupEnsembleBlocks(activity);
 
-    // Push protoblocks onto their palettes.
+    // Push newly added protoblocks onto palettes
     for (const protoblock in activity.blocks.protoBlockDict) {
         if (activity.blocks.protoBlockDict[protoblock].palette != null) {
             activity.blocks.protoBlockDict[protoblock].palette.add(
@@ -117,9 +132,17 @@ const initBasicProtoBlocks = activity => {
         }
     }
 };
+
+const initBasicProtoBlocks = activity => {
+    initCoreProtoBlocks(activity);
+    initAdvancedProtoBlocks(activity);
+};
+
 if (typeof module !== "undefined" && module.exports) {
     module.exports = {
         initBasicProtoBlocks,
+        initCoreProtoBlocks,
+        initAdvancedProtoBlocks,
         BACKWARDCOMPATIBILIYDICT
     };
 }
diff --git a/package.json b/package.json
index eb72cd3afa..eb7811b58b 100644
--- a/package.json
+++ b/package.json
@@ -56,7 +56,6 @@
     "http-server": "^14.1.1",
     "i18next": "^25.3.2",
     "i18next-http-backend": "^3.0.2",
-    "node": "^24.2.0",
     "postcss": "^8.5.6",
     "sass": "^1.97.2",
     "tone": "^15.1.22"