diff --git a/frontend/src/components/calendar/EventDetailPanel.tsx b/frontend/src/components/calendar/EventDetailPanel.tsx
index b656fbe..8362a1f 100644
--- a/frontend/src/components/calendar/EventDetailPanel.tsx
+++ b/frontend/src/components/calendar/EventDetailPanel.tsx
@@ -264,6 +264,7 @@ export default function EventDetailPanel({
   const [locationSearch, setLocationSearch] = useState('');
 
   // Poll lock status in view mode for shared events (Stream A: real-time lock awareness)
+  // lockInfo is only set from the 423 error path; poll data (viewLockQuery.data) is used directly.
   const viewLockQuery = useQuery({
     queryKey: ['event-lock', event?.id],
     queryFn: async () => {
@@ -274,18 +275,22 @@ export default function EventDetailPanel({
     },
     enabled: !!isSharedEvent && !!event && typeof event.id === 'number' && !isEditing && !isCreating,
     refetchInterval: 5_000,
+    refetchIntervalInBackground: true,
+    refetchOnMount: 'always',
   });
 
-  // Show/hide lock banner proactively in view mode (poll data always authoritative)
+  // Clear 423-error lockInfo when poll confirms lock is gone
   useEffect(() => {
-    if (!viewLockQuery.data) return;
-    if (viewLockQuery.data.locked) {
-      setLockInfo(viewLockQuery.data);
-    } else {
+    if (viewLockQuery.data && !viewLockQuery.data.locked) {
       setLockInfo(null);
     }
   }, [viewLockQuery.data]);
 
+  // Derived: authoritative lock state — poll data wins, 423 error lockInfo as fallback
+  const activeLockInfo: EventLockInfo | null =
+    (viewLockQuery.data?.locked ? viewLockQuery.data : null) ??
+    (lockInfo?.locked ? lockInfo : null);
+
   const isRecurring = !!(event?.is_recurring || event?.parent_event_id);
 
   // Permission helpers
@@ -580,8 +585,8 @@ export default function EventDetailPanel({
                         size="icon"
                         className="h-7 w-7"
                         onClick={handleEditStart}
-                        disabled={isAcquiringLock || !!(lockInfo && lockInfo.locked)}
-                        title={lockInfo && lockInfo.locked ? `Locked by ${lockInfo.locked_by_name || 'another user'}` : 'Edit event'}
+                        disabled={isAcquiringLock || !!activeLockInfo}
+                        title={activeLockInfo ? `Locked by ${activeLockInfo.locked_by_name || 'another user'}` : 'Edit event'}
                       >
                         {isAcquiringLock ? <Loader2 className="h-3.5 w-3.5 animate-spin" /> : <Pencil className="h-3.5 w-3.5" />}
                       </Button>
@@ -629,12 +634,12 @@ export default function EventDetailPanel({
 
       {/* Body */}
       <div className="flex-1 overflow-y-auto px-5 py-4 space-y-3">
-        {/* Lock banner */}
-        {lockInfo && lockInfo.locked && (
+        {/* Lock banner — shown when activeLockInfo reports a lock (poll-authoritative) */}
+        {activeLockInfo && (
           <EventLockBanner
-            lockedByName={lockInfo.locked_by_name || 'another user'}
-            expiresAt={lockInfo.expires_at}
-            isPermanent={lockInfo.is_permanent}
+            lockedByName={activeLockInfo.locked_by_name || 'another user'}
+            expiresAt={activeLockInfo.expires_at}
+            isPermanent={activeLockInfo.is_permanent}
           />
         )}