diff --git a/frontend/src/components/admin/UserDetailSection.tsx b/frontend/src/components/admin/UserDetailSection.tsx
index 51261a4..26ab578 100644
--- a/frontend/src/components/admin/UserDetailSection.tsx
+++ b/frontend/src/components/admin/UserDetailSection.tsx
@@ -1,10 +1,10 @@
-import { X, User, ShieldCheck, Loader2 } from 'lucide-react';
+import { X, User, ShieldCheck, Share2, Loader2 } from 'lucide-react';
 import { toast } from 'sonner';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
 import { Select } from '@/components/ui/select';
 import { Button } from '@/components/ui/button';
 import { Skeleton } from '@/components/ui/skeleton';
-import { useAdminUserDetail, useUpdateRole, getErrorMessage } from '@/hooks/useAdmin';
+import { useAdminUserDetail, useAdminSharingStats, useUpdateRole, getErrorMessage } from '@/hooks/useAdmin';
 import { getRelativeTime } from '@/lib/date-utils';
 import { cn } from '@/lib/utils';
 import type { UserRole } from '@/types';
@@ -57,6 +57,7 @@ function MfaBadge({ enabled, pending }: { enabled: boolean; pending: boolean })
 export default function UserDetailSection({ userId, onClose }: UserDetailSectionProps) {
   const { data: user, isLoading, error } = useAdminUserDetail(userId);
   const updateRole = useUpdateRole();
+  const { data: sharingStats } = useAdminSharingStats(userId);
 
   const handleRoleChange = async (newRole: UserRole) => {
     if (!user || newRole === user.role) return;
@@ -218,6 +219,24 @@ export default function UserDetailSection({ userId, onClose }: UserDetailSection
           />
         </CardContent>
       </Card>
+
+      {/* Sharing Stats */}
+      <Card className="col-span-1">
+        <CardHeader className="pb-3">
+          <div className="flex items-center gap-2">
+            <div className="p-1.5 rounded-md bg-accent/10">
+              <Share2 className="h-3.5 w-3.5 text-accent" />
+            </div>
+            <CardTitle className="text-sm">Sharing</CardTitle>
+          </div>
+        </CardHeader>
+        <CardContent className="pt-0 space-y-0.5">
+          <DetailRow label="Calendars Shared" value={String(sharingStats?.shared_calendars_owned ?? 0)} />
+          <DetailRow label="Member Of" value={String(sharingStats?.calendars_member_of ?? 0)} />
+          <DetailRow label="Invites Sent" value={String(sharingStats?.pending_invites_sent ?? 0)} />
+          <DetailRow label="Invites Received" value={String(sharingStats?.pending_invites_received ?? 0)} />
+        </CardContent>
+      </Card>
     </div>
   );
 }
diff --git a/frontend/src/components/calendar/CalendarPage.tsx b/frontend/src/components/calendar/CalendarPage.tsx
index 51b15b2..cf5ad2a 100644
--- a/frontend/src/components/calendar/CalendarPage.tsx
+++ b/frontend/src/components/calendar/CalendarPage.tsx
@@ -42,7 +42,7 @@ export default function CalendarPage() {
   const [createDefaults, setCreateDefaults] = useState<CreateDefaults | null>(null);
 
   const { settings } = useSettings();
-  const { data: calendars = [], sharedData } = useCalendars();
+  const { data: calendars = [], sharedData, allCalendarIds } = useCalendars({ pollingEnabled: true });
   const [visibleSharedIds, setVisibleSharedIds] = useState<Set<number>>(new Set());
   const calendarContainerRef = useRef<HTMLDivElement>(null);
 
@@ -99,6 +99,15 @@ export default function CalendarPage() {
 
   const panelOpen = panelMode !== 'closed';
 
+  // Track desktop breakpoint to prevent dual EventDetailPanel mount
+  const [isDesktop, setIsDesktop] = useState(() => window.matchMedia('(min-width: 1024px)').matches);
+  useEffect(() => {
+    const mql = window.matchMedia('(min-width: 1024px)');
+    const handler = (e: MediaQueryListEvent) => setIsDesktop(e.matches);
+    mql.addEventListener('change', handler);
+    return () => mql.removeEventListener('change', handler);
+  }, []);
+
   // Continuously resize calendar during panel open/close CSS transition
   useEffect(() => {
     let rafId: number;
@@ -150,6 +159,15 @@ export default function CalendarPage() {
   const selectedEventPermission = selectedEvent ? permissionMap.get(selectedEvent.calendar_id) ?? null : null;
   const selectedEventIsShared = selectedEvent ? permissionMap.has(selectedEvent.calendar_id) && permissionMap.get(selectedEvent.calendar_id) !== 'owner' : false;
 
+  // Close panel if shared calendar was removed while viewing
+  useEffect(() => {
+    if (!selectedEvent || allCalendarIds.size === 0) return;
+    if (!allCalendarIds.has(selectedEvent.calendar_id)) {
+      handlePanelClose();
+      toast.info('This calendar is no longer available');
+    }
+  }, [allCalendarIds, selectedEvent]);
+
   // Escape key closes detail panel
   useEffect(() => {
     if (!panelOpen) return;
@@ -497,29 +515,27 @@ export default function CalendarPage() {
           </div>
 
           {/* Detail panel (desktop) */}
-          <div
-            className={`overflow-hidden transition-all duration-300 ease-[cubic-bezier(0.16,1,0.3,1)] ${
-              panelOpen ? 'hidden lg:block lg:w-[45%]' : 'w-0 opacity-0'
-            }`}
-          >
-            <EventDetailPanel
-              event={panelMode === 'view' ? selectedEvent : null}
-              isCreating={panelMode === 'create'}
-              createDefaults={createDefaults}
-              onClose={handlePanelClose}
-              onSaved={handlePanelClose}
-              locationName={selectedEvent?.location_id ? locationMap.get(selectedEvent.location_id) : undefined}
-              myPermission={selectedEventPermission}
-              isSharedEvent={selectedEventIsShared}
-            />
-          </div>
+          {panelOpen && isDesktop && (
+            <div className="overflow-hidden transition-all duration-300 ease-[cubic-bezier(0.16,1,0.3,1)] w-[45%]">
+              <EventDetailPanel
+                event={panelMode === 'view' ? selectedEvent : null}
+                isCreating={panelMode === 'create'}
+                createDefaults={createDefaults}
+                onClose={handlePanelClose}
+                onSaved={handlePanelClose}
+                locationName={selectedEvent?.location_id ? locationMap.get(selectedEvent.location_id) : undefined}
+                myPermission={selectedEventPermission}
+                isSharedEvent={selectedEventIsShared}
+              />
+            </div>
+          )}
         </div>
       </div>
 
       {/* Mobile detail panel overlay */}
-      {panelOpen && (
+      {panelOpen && !isDesktop && (
         <div
-          className="lg:hidden fixed inset-0 z-50 bg-background/80 backdrop-blur-sm"
+          className="fixed inset-0 z-50 bg-background/80 backdrop-blur-sm"
           onClick={handlePanelClose}
         >
           <div
diff --git a/frontend/src/hooks/useAdmin.ts b/frontend/src/hooks/useAdmin.ts
index ac0cb52..8a394fa 100644
--- a/frontend/src/hooks/useAdmin.ts
+++ b/frontend/src/hooks/useAdmin.ts
@@ -61,6 +61,24 @@ export function useAdminUserDetail(userId: number | null) {
   });
 }
 
+interface SharingStats {
+  shared_calendars_owned: number;
+  calendars_member_of: number;
+  pending_invites_sent: number;
+  pending_invites_received: number;
+}
+
+export function useAdminSharingStats(userId: number | null) {
+  return useQuery<SharingStats>({
+    queryKey: ['admin', 'users', userId, 'sharing-stats'],
+    queryFn: async () => {
+      const { data } = await api.get<SharingStats>(`/admin/users/${userId}/sharing-stats`);
+      return data;
+    },
+    enabled: userId !== null,
+  });
+}
+
 export function useAdminDashboard() {
   return useQuery<AdminDashboardData>({
     queryKey: ['admin', 'dashboard'],
diff --git a/frontend/src/hooks/useCalendars.ts b/frontend/src/hooks/useCalendars.ts
index 825de5e..7bbfd3f 100644
--- a/frontend/src/hooks/useCalendars.ts
+++ b/frontend/src/hooks/useCalendars.ts
@@ -3,7 +3,11 @@ import { useQuery } from '@tanstack/react-query';
 import api from '@/lib/api';
 import type { Calendar, SharedCalendarMembership } from '@/types';
 
-export function useCalendars() {
+interface UseCalendarsOptions {
+  pollingEnabled?: boolean;
+}
+
+export function useCalendars({ pollingEnabled = false }: UseCalendarsOptions = {}) {
   const ownedQuery = useQuery({
     queryKey: ['calendars'],
     queryFn: async () => {
@@ -18,7 +22,7 @@ export function useCalendars() {
       const { data } = await api.get<SharedCalendarMembership[]>('/shared-calendars');
       return data;
     },
-    refetchInterval: 5_000,
+    refetchInterval: pollingEnabled ? 5_000 : false,
     staleTime: 3_000,
   });