diff --git a/frontend/src/preview/DocumentViewerPanel.jsx b/frontend/src/preview/DocumentViewerPanel.jsx
index 6b2bfce..c7480c3 100644
--- a/frontend/src/preview/DocumentViewerPanel.jsx
+++ b/frontend/src/preview/DocumentViewerPanel.jsx
@@ -98,6 +98,17 @@ const getSidebarWidthFromRoot = () => {
   return Number.isFinite(parsed) ? parsed : null;
 };
 
+const shouldSuppressSidebarForDetailWidth = (detailWidth) => {
+  if (!isBrowser || !Number.isFinite(detailWidth)) {
+    return false;
+  }
+  const sidebarWidth = getSidebarWidthFromRoot() || 0;
+  const minMainContentWidth = window.innerWidth / 3;
+  const occupiedWidth = detailWidth + sidebarWidth;
+  const availableWidth = window.innerWidth - occupiedWidth;
+  return availableWidth < minMainContentWidth;
+};
+
 export const createDocumentViewerHeaderActions = ({
   document,
   actionState,
@@ -343,15 +354,7 @@ const DocumentViewerPanel = ({
       const panelWidth = pendingWidthRef.current
         ?? detailPanelWidth
         ?? panelRef.current?.getBoundingClientRect().width;
-      const sidebarWidth = getSidebarWidthFromRoot();
-      if (!Number.isFinite(panelWidth)) {
-        setSidebarSuppressed(false);
-        return;
-      }
-      const minMainContentWidth = (window.innerWidth * 2) / 5;
-      const occupiedWidth = panelWidth + (Number.isFinite(sidebarWidth) ? sidebarWidth : 0);
-      const availableWidth = window.innerWidth - occupiedWidth;
-      setSidebarSuppressed(availableWidth < minMainContentWidth);
+      setSidebarSuppressed(shouldSuppressSidebarForDetailWidth(panelWidth));
     };
 
     updateSuppression();
@@ -414,8 +417,8 @@ const DocumentViewerPanel = ({
       if (clamped != null) {
         pendingWidthRef.current = clamped;
         applyDetailPanelWidth(clamped);
-        if (isSidebarVariant && isBrowser) {
-          setSidebarSuppressed(clamped > window.innerWidth / 2);
+        if (isSidebarVariant) {
+          setSidebarSuppressed(shouldSuppressSidebarForDetailWidth(clamped));
         }
       }
     };