diff --git a/backend/app/jobs/notifications.py b/backend/app/jobs/notifications.py
index ca15d2f..7798f0c 100644
--- a/backend/app/jobs/notifications.py
+++ b/backend/app/jobs/notifications.py
@@ -21,6 +21,7 @@ from app.models.notification import Notification as AppNotification
 from app.models.reminder import Reminder
 from app.models.calendar_event import CalendarEvent
 from app.models.calendar import Calendar
+from app.models.event_lock import EventLock
 from app.models.todo import Todo
 from app.models.project import Project
 from app.models.ntfy_sent import NtfySent
@@ -300,6 +301,18 @@ async def _purge_resolved_requests(db: AsyncSession) -> None:
     await db.commit()
 
 
+
+async def _purge_expired_locks(db: AsyncSession) -> None:
+    """Remove non-permanent event locks that have expired."""
+    await db.execute(
+        delete(EventLock).where(
+            EventLock.is_permanent == False,  # noqa: E712
+            EventLock.expires_at < datetime.now(),
+        )
+    )
+    await db.commit()
+
+
 # ── Entry point ───────────────────────────────────────────────────────────────
 
 async def run_notification_dispatch() -> None:
@@ -343,6 +356,7 @@ async def run_notification_dispatch() -> None:
             await _purge_expired_sessions(db)
             await _purge_old_notifications(db)
             await _purge_resolved_requests(db)
+            await _purge_expired_locks(db)
 
     except Exception:
         # Broad catch: job failure must never crash the scheduler or the app
diff --git a/backend/app/routers/calendars.py b/backend/app/routers/calendars.py
index 2e324a7..7dec7fc 100644
--- a/backend/app/routers/calendars.py
+++ b/backend/app/routers/calendars.py
@@ -1,11 +1,12 @@
 from fastapi import APIRouter, Depends, HTTPException, Path
 from sqlalchemy.ext.asyncio import AsyncSession
-from sqlalchemy import select, update
+from sqlalchemy import func, select, update
 from typing import List
 
 from app.database import get_db
 from app.models.calendar import Calendar
 from app.models.calendar_event import CalendarEvent
+from app.models.calendar_member import CalendarMember
 from app.schemas.calendar import CalendarCreate, CalendarUpdate, CalendarResponse
 from app.routers.auth import get_current_user
 from app.models.user import User
@@ -23,7 +24,28 @@ async def get_calendars(
         .where(Calendar.user_id == current_user.id)
         .order_by(Calendar.is_default.desc(), Calendar.name.asc())
     )
-    return result.scalars().all()
+    calendars = result.scalars().all()
+
+    # Populate member_count for shared calendars
+    cal_ids = [c.id for c in calendars if c.is_shared]
+    count_map: dict[int, int] = {}
+    if cal_ids:
+        counts = await db.execute(
+            select(CalendarMember.calendar_id, func.count())
+            .where(
+                CalendarMember.calendar_id.in_(cal_ids),
+                CalendarMember.status == "accepted",
+            )
+            .group_by(CalendarMember.calendar_id)
+        )
+        count_map = dict(counts.all())
+
+    return [
+        CalendarResponse.model_validate(c, from_attributes=True).model_copy(
+            update={"member_count": count_map.get(c.id, 0)}
+        )
+        for c in calendars
+    ]
 
 
 @router.post("/", response_model=CalendarResponse, status_code=201)
diff --git a/backend/app/routers/shared_calendars.py b/backend/app/routers/shared_calendars.py
index 3ad07ba..f84edb7 100644
--- a/backend/app/routers/shared_calendars.py
+++ b/backend/app/routers/shared_calendars.py
@@ -4,7 +4,7 @@ Shared calendars router — invites, membership, locks, sync.
 All endpoints live under /api/shared-calendars.
 """
 import logging
-from datetime import datetime
+from datetime import datetime, timedelta
 from typing import Optional
 
 from fastapi import APIRouter, Depends, HTTPException, Path, Query, Request
@@ -60,7 +60,7 @@ def _build_member_response(member: CalendarMember) -> dict:
         "calendar_id": member.calendar_id,
         "user_id": member.user_id,
         "umbral_name": member.user.umbral_name if member.user else "",
-        "preferred_name": None,
+        "preferred_name": member.user.preferred_name if member.user else None,
         "permission": member.permission,
         "can_add_others": member.can_add_others,
         "local_color": member.local_color,
@@ -462,8 +462,10 @@ async def update_member(
     if not update_data:
         raise HTTPException(status_code=400, detail="No fields to update")
 
-    for key, value in update_data.items():
-        setattr(member, key, value)
+    if "permission" in update_data:
+        member.permission = update_data["permission"]
+    if "can_add_others" in update_data:
+        member.can_add_others = update_data["can_add_others"]
 
     await log_audit_event(
         db,
@@ -581,6 +583,11 @@ async def sync_shared_calendars(
     """Sync events and member changes since a given timestamp. Cap 500 events."""
     MAX_EVENTS = 500
 
+    # Cap since to 7 days ago to prevent unbounded scans
+    floor = datetime.now() - timedelta(days=7)
+    if since < floor:
+        since = floor
+
     cal_id_list: list[int] = []
     if calendar_ids:
         for part in calendar_ids.split(","):
diff --git a/backend/app/schemas/shared_calendar.py b/backend/app/schemas/shared_calendar.py
index 5b5420f..453aaa2 100644
--- a/backend/app/schemas/shared_calendar.py
+++ b/backend/app/schemas/shared_calendar.py
@@ -34,9 +34,6 @@ class UpdateLocalColorRequest(BaseModel):
         return v
 
 
-class ConvertToSharedRequest(BaseModel):
-    model_config = ConfigDict(extra="forbid")
-
 
 class CalendarMemberResponse(BaseModel):
     model_config = ConfigDict(from_attributes=True)
diff --git a/frontend/src/components/calendar/CalendarForm.tsx b/frontend/src/components/calendar/CalendarForm.tsx
index 1a17e18..3040b93 100644
--- a/frontend/src/components/calendar/CalendarForm.tsx
+++ b/frontend/src/components/calendar/CalendarForm.tsx
@@ -14,7 +14,6 @@ import {
 import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';
 import { Button } from '@/components/ui/button';
-import { Switch } from '@/components/ui/switch';
 import PermissionToggle from './PermissionToggle';
 import { useConnections } from '@/hooks/useConnections';
 import { useSharedCalendars } from '@/hooks/useSharedCalendars';
@@ -35,7 +34,6 @@ export default function CalendarForm({ calendar, onClose }: CalendarFormProps) {
   const queryClient = useQueryClient();
   const [name, setName] = useState(calendar?.name || '');
   const [color, setColor] = useState(calendar?.color || '#3b82f6');
-  const [isShared, setIsShared] = useState(calendar?.is_shared ?? false);
 
   const [pendingInvite, setPendingInvite] = useState<{ conn: Connection; permission: CalendarPermission } | null>(null);
 
@@ -131,7 +129,7 @@ export default function CalendarForm({ calendar, onClose }: CalendarFormProps) {
 
   return (
     <Dialog open={true} onOpenChange={onClose}>
-      <DialogContent className={isShared && showSharing ? 'max-w-3xl' : undefined}>
+      <DialogContent className={calendar?.is_shared && showSharing ? 'max-w-3xl' : undefined}>
         <DialogClose onClick={onClose} />
         <DialogHeader>
           <DialogTitle>{calendar ? 'Edit Calendar' : 'New Calendar'}</DialogTitle>
@@ -170,15 +168,7 @@ export default function CalendarForm({ calendar, onClose }: CalendarFormProps) {
 
           {showSharing && (
             <>
-              <div className="flex items-center justify-between py-3 border-t border-border">
-                <Label className="mb-0">Share this calendar</Label>
-                <Switch
-                  checked={isShared}
-                  onCheckedChange={setIsShared}
-                />
-              </div>
-
-              {isShared && (
+              {calendar?.is_shared && (
                 <div className="space-y-3">
                   <div className="flex items-center justify-between">
                     <Label className="mb-0">Members</Label>
diff --git a/frontend/src/components/calendar/CalendarPage.tsx b/frontend/src/components/calendar/CalendarPage.tsx
index 3f0543a..dab78d2 100644
--- a/frontend/src/components/calendar/CalendarPage.tsx
+++ b/frontend/src/components/calendar/CalendarPage.tsx
@@ -9,6 +9,7 @@ import interactionPlugin from '@fullcalendar/interaction';
 import type { EventClickArg, DateSelectArg, EventDropArg, DatesSetArg } from '@fullcalendar/core';
 import { ChevronLeft, ChevronRight, Plus, Search } from 'lucide-react';
 import api, { getErrorMessage } from '@/lib/api';
+import axios from 'axios';
 import type { CalendarEvent, EventTemplate, Location as LocationType, CalendarPermission } from '@/types';
 import { useCalendars } from '@/hooks/useCalendars';
 import { useSettings } from '@/hooks/useSettings';
@@ -244,7 +245,11 @@ export default function CalendarPage() {
     onError: (error, variables) => {
       variables.revert();
       queryClient.invalidateQueries({ queryKey: ['calendar-events'] });
-      toast.error(getErrorMessage(error, 'Failed to update event'));
+      if (axios.isAxiosError(error) && error.response?.status === 423) {
+        toast.error('Event is locked by another user');
+      } else {
+        toast.error(getErrorMessage(error, 'Failed to update event'));
+      }
     },
   });
 
diff --git a/frontend/src/hooks/useEventLock.ts b/frontend/src/hooks/useEventLock.ts
index 3495773..8df39f5 100644
--- a/frontend/src/hooks/useEventLock.ts
+++ b/frontend/src/hooks/useEventLock.ts
@@ -44,7 +44,7 @@ export function useEventLock(eventId: number | null) {
     } catch {
       // Fire-and-forget on release errors
     }
-  }, []);
+  }, [releaseMutation]);
 
   // Auto-release on unmount or eventId change
   useEffect(() => {