fix

frontend/src/desktop/DesktopWorkspace.tsx

@@ -408,9 +408,21 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
 
     commitSize();
 
-    const observer = new ResizeObserver(commitSize);
+    let rafId: number | null = null;
+    const observer = new ResizeObserver(() => {
+      if (rafId != null) return;
+      rafId = requestAnimationFrame(() => {
+        rafId = null;
+        commitSize();
+      });
+    });
     observer.observe(container);
-    return () => observer.disconnect();
+    return () => {
+      observer.disconnect();
+      if (rafId != null) {
+        cancelAnimationFrame(rafId);
+      }
+    };
   }, [engine]);
 
   const resolvePreviewDimensions = useCallback(

frontend/src/documents/DocumentsManager.ts

@@ -15,6 +15,8 @@ class DocumentsManager<T extends ManagedDocument = ManagedDocument> {
 
   private listeners: Set<() => void>;
 
+  private emitScheduled: boolean;
+
   constructor(
     fetchDocument?: FetchDocument,
   ) {
@@ -22,10 +24,18 @@ class DocumentsManager<T extends ManagedDocument = ManagedDocument> {
     this.fetcher = fetchDocument;
     this.inflight = new Map();
     this.listeners = new Set();
+    this.emitScheduled = false;
   }
 
   private emit() {
+    if (this.emitScheduled) {
+      return;
+    }
+    this.emitScheduled = true;
+    setTimeout(() => {
+      this.emitScheduled = false;
       this.listeners.forEach((fn) => fn());
+    }, 0);
   }
 
   subscribe(listener: () => void) {

frontend/src/preview/DocumentViewerPanel.tsx

@@ -1,5 +1,4 @@
 import React, {
-  Children,
   useCallback,
   useEffect,
   useMemo,
@@ -431,9 +430,15 @@ const DocumentViewerPanel: React.FC<DocumentViewerPanelProps> = ({
     : null;
 
   const headerLeadingButtons = isSidebarVariant
-    ? [collapseButton, maximizeButton].filter(Boolean)
+    ? [
-    : [sidebarToggle, closeButton].filter(Boolean);
+        collapseButton ? <React.Fragment key="collapse-button">{collapseButton}</React.Fragment> : null,
-  const headerLeadingContent = headerLeadingButtons.length ? Children.toArray(headerLeadingButtons) : null;
+        maximizeButton ? <React.Fragment key="maximize-button">{maximizeButton}</React.Fragment> : null,
+      ].filter(Boolean)
+    : [
+        sidebarToggle ? <React.Fragment key="sidebar-toggle">{sidebarToggle}</React.Fragment> : null,
+        closeButton ? <React.Fragment key="close-button">{closeButton}</React.Fragment> : null,
+      ].filter(Boolean);
+  const headerLeadingContent = headerLeadingButtons.length ? headerLeadingButtons : null;
 
   const resizeHandle = isSidebarVariant ? (
     <button