diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..d9b922a
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,4 @@
+## 2024-06-07 - Memoize callbacks passed to Excalidraw
+
+**Learning:** Due to the exceptionally high rendering cost of the `@excalidraw/excalidraw` canvas, always ensure all callbacks passed to it (e.g., `onExcalidrawAPI`) are strictly memoized using `useCallback`. Passing inline functions as props breaks prop stability for `React.memo` and causes severe UI input lag caused by full canvas re-renders when parent states change.
+**Action:** When working with `<Excalidraw>` or its wrapper components like `<EditorCanvas>`, always extract inline callback functions (like `onExcalidrawAPI={(api) => { ... }}`) into `useCallback` hooks before passing them down.
diff --git a/src/client/App.tsx b/src/client/App.tsx
index 33ddb41..40151b2 100644
--- a/src/client/App.tsx
+++ b/src/client/App.tsx
@@ -307,6 +307,13 @@ function PrivateApp() {
     [],
   );
 
+  // ⚡ Bolt: Memoize the Excalidraw API callback to prevent EditorCanvas from re-rendering
+  // Excalidraw has exceptionally high rendering cost, so we must maintain prop stability
+  // for EditorCanvas's React.memo to avoid severe UI input lag on any parent state change.
+  const handleExcalidrawAPI = useCallback((api: ExcalidrawImperativeAPI) => {
+    excalidrawApiRef.current = api;
+  }, []);
+
   return (
     <div className="app-shell" ref={appShellRef}>
       {toastMessage && (
@@ -332,9 +339,7 @@ function PrivateApp() {
           onSceneChange={handleSceneChange}
           onSelectionStateChange={handleCodeBlockSelectionChange}
           onEditorActivity={scheduleThemeTokenSync}
-          onExcalidrawAPI={(api) => {
-            excalidrawApiRef.current = api;
-          }}
+          onExcalidrawAPI={handleExcalidrawAPI}
           renderEmbeddable={renderCodeBlockEmbeddable}
         />
         <CodeBlockSidebar