fix

frontend/src/preview/DocumentViewerPanel.tsx

@@ -1,4 +1,5 @@
 import React, {
+  Children,
   useCallback,
   useEffect,
   useMemo,
@@ -432,13 +433,7 @@ const DocumentViewerPanel: React.FC<DocumentViewerPanelProps> = ({
   const headerLeadingButtons = isSidebarVariant
     ? [collapseButton, maximizeButton].filter(Boolean)
     : [sidebarToggle, closeButton].filter(Boolean);
-  const headerLeadingContent = headerLeadingButtons.length
-    ? (
-        <>
-          {headerLeadingButtons}
-        </>
-      )
-    : null;
+  const headerLeadingContent = headerLeadingButtons.length ? Children.toArray(headerLeadingButtons) : null;
 
   const resizeHandle = isSidebarVariant ? (
     <button

frontend/src/preview/PdfViewer.tsx

@@ -82,8 +82,8 @@ const resolvePdfWasmBaseUrl = (): string => {
 
 const PdfViewer = ({ src, title, className, viewportRef }: PdfViewerProps): JSX.Element => {
   const containerRef = useRef<HTMLDivElement>(null);
-  const [viewportWidth, setViewportWidth] = useState(() => window.innerWidth);
-  const [viewportHeight, setViewportHeight] = useState(() => window.innerHeight);
+  const [viewportWidth, setViewportWidth] = useState(0);
+  const [viewportHeight, setViewportHeight] = useState(0);
   const [renderWidth, setRenderWidth] = useState(0);
   const [status, setStatus] = useState<RenderStatus>('idle');
   const [errorMessage, setErrorMessage] = useState<string | null>(null);