fix: reduce iCloud CalDAV connections to prevent rate limiting

- Apple/Synology: batch fetch events with single client login instead of N separate connections
- Apple: add client cache (5min TTL) to reuse authenticated DAVClient across operations
- Apple: add retry with backoff for transient ConnectTimeoutError/SSL failures
- Increase cache stale threshold from 2min to 15min
- Increase background sync interval from 2min to 15min
- Throttle tab-focus sync to at most once per 5min

v1.75.2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "my-weekly-todo-list",
-  "version": "1.75.1",
+  "version": "1.75.2",
   "description": "A web-based weekly task management application that organizes to-dos and calendar events in a single, intuitive weekly view",
   "main": "index.js",
   "scripts": {

src/components/WeeklyView.tsx

@@ -2976,16 +2976,21 @@ export default function WeeklyView() {
                     console.error("[SYNC] Calendar sync error:", e);
                 }
             },
-            2 * 60 * 1000,
+            15 * 60 * 1000, // 15 min — avoid iCloud rate limiting
         );
         return () => clearInterval(interval);
     }, [session, fetchCalendarEvents]);
 
     // Sync when tab regains focus (catches external changes in other apps)
+    // Throttled: at most once per 5 minutes to avoid iCloud rate limiting
+    const lastFocusSyncRef = useRef(0);
     useEffect(() => {
         if (!session) return;
         const handleVisibility = () => {
             if (!document.hidden) {
+                const now = Date.now();
+                if (now - lastFocusSyncRef.current < 5 * 60 * 1000) return; // throttle
+                lastFocusSyncRef.current = now;
                 fetchCalendarEvents();
                 fetchTasks();
             }

src/lib/apple-calendar.ts

@@ -195,16 +195,72 @@ const createClient = (email: string, appSpecificPassword: string) => {
   });
 };
 
+/**
+ * Client cache: reuse authenticated DAVClient instances to avoid repeated login/fetchCalendars
+ * calls that trigger iCloud rate limiting. Cache entries expire after 5 minutes.
+ */
+interface CachedClient {
+  client: DAVClient;
+  calendars: any[];
+  createdAt: number;
+}
+const clientCache = new Map<string, CachedClient>();
+const CLIENT_CACHE_TTL = 5 * 60 * 1000; // 5 minutes
+
+async function getOrCreateClient(email: string, appSpecificPassword: string): Promise<{ client: DAVClient; calendars: any[] }> {
+  const cacheKey = `${email}:${appSpecificPassword.slice(0, 4)}`;
+  const cached = clientCache.get(cacheKey);
+
+  if (cached && (Date.now() - cached.createdAt) < CLIENT_CACHE_TTL) {
+    return { client: cached.client, calendars: cached.calendars };
+  }
+
+  const client = createClient(email, appSpecificPassword);
+  await client.login();
+  const calendars = await client.fetchCalendars();
+
+  clientCache.set(cacheKey, { client, calendars, createdAt: Date.now() });
+  return { client, calendars };
+}
+
+/**
+ * Retry wrapper for iCloud operations that may fail due to rate limiting / timeouts.
+ */
+async function withRetry<T>(fn: () => Promise<T>, maxRetries = 2, label = 'operation'): Promise<T> {
+  for (let attempt = 0; attempt <= maxRetries; attempt++) {
+    try {
+      return await fn();
+    } catch (err: any) {
+      const isTimeout = err?.cause?.code === 'UND_ERR_CONNECT_TIMEOUT' ||
+        err?.message?.includes('ConnectTimeout') ||
+        err?.message?.includes('fetch failed') ||
+        err?.message?.includes('SocketError') ||
+        err?.message?.includes('SSL');
+
+      if (isTimeout && attempt < maxRetries) {
+        const delay = (attempt + 1) * 3000; // 3s, 6s
+        console.warn(`[APPLE CALENDAR] ${label} attempt ${attempt + 1} failed (timeout), retrying in ${delay}ms...`);
+        // Invalidate client cache on timeout — connection may be stale
+        clientCache.clear();
+        await new Promise(resolve => setTimeout(resolve, delay));
+        continue;
+      }
+      throw err;
+    }
+  }
+  throw new Error('Unreachable');
+}
+
 /**
  * Validate credentials by attempting to fetch calendars
  * @returns List of found calendars if successful
  */
 export const validateCredentials = async (email: string, appSpecificPassword: string): Promise<AppleCalendar[]> => {
   try {
-    const client = createClient(email, appSpecificPassword);
-    await client.login();
-
-    const calendars = await client.fetchCalendars();
+    const { calendars } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'validateCredentials'
+    );
 
     // Filter to VEVENT-only calendars — exclude VTODO (Reminders) collections
     const eventCalendars = calendars.filter(cal => {
@@ -246,10 +302,10 @@ export const getUpcomingEvents = async (
   timeMax: string
 ): Promise<AppleCalendarEvent[]> => {
   try {
-    const client = createClient(email, appSpecificPassword);
-    await client.login();
-
-    const calendars = await client.fetchCalendars();
+    const { client, calendars } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'getUpcomingEvents'
+    );
     const targetCalendar = calendars.find(c => c.url === calendarUrl);
 
     if (!targetCalendar) {
@@ -411,6 +467,180 @@ export const getUpcomingEvents = async (
   }
 };
 
+/**
+ * Batch fetch events from multiple calendars with a single login.
+ * Avoids creating a new client/login per calendar (which causes iCloud rate-limiting).
+ */
+export const getUpcomingEventsBatch = async (
+  email: string,
+  appSpecificPassword: string,
+  calendarUrls: string[],
+  timeMin: string,
+  timeMax: string
+): Promise<Map<string, AppleCalendarEvent[]>> => {
+  const results = new Map<string, AppleCalendarEvent[]>();
+  if (calendarUrls.length === 0) return results;
+
+  try {
+    const { client, calendars } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'getUpcomingEventsBatch'
+    );
+
+    for (const calendarUrl of calendarUrls) {
+      try {
+        const targetCalendar = calendars.find(c => c.url === calendarUrl);
+        if (!targetCalendar) {
+          console.log(`[APPLE CALENDAR] Calendar not found: ${calendarUrl}`);
+          results.set(calendarUrl, []);
+          continue;
+        }
+
+        const events = await client.fetchCalendarObjects({
+          calendar: targetCalendar,
+          timeRange: {
+            start: new Date(timeMin).toISOString(),
+            end: new Date(timeMax).toISOString(),
+          },
+        });
+
+        const parsedEvents: AppleCalendarEvent[] = [];
+        const minTime = new Date(timeMin).getTime();
+        const maxTime = new Date(timeMax).getTime();
+
+        events.forEach(eventObj => {
+          const data = (eventObj as any).data;
+          if (!data) return;
+          try {
+            const jcalData = ICAL.parse(data);
+            const comp = new ICAL.Component(jcalData);
+            const vevents = comp.getAllSubcomponents('vevent');
+            const baseEvents: any[] = [];
+            const exceptions: Map<string, any[]> = new Map();
+
+            vevents.forEach((vevent: any) => {
+              const recurrenceId = vevent.getFirstPropertyValue('recurrence-id');
+              if (recurrenceId) {
+                const event = new ICAL.Event(vevent);
+                const uid = event.uid;
+                if (!exceptions.has(uid)) exceptions.set(uid, []);
+                exceptions.get(uid)!.push(vevent);
+              } else {
+                baseEvents.push(vevent);
+              }
+            });
+
+            baseEvents.forEach((vevent: any) => {
+              const event = new ICAL.Event(vevent);
+              const rrule = vevent.getFirstPropertyValue('rrule');
+
+              if (rrule) {
+                const uid = event.uid;
+                const exceptionVevents = exceptions.get(uid) || [];
+                const exceptionDates = new Set<string>();
+                const isAllDayRecurring = event.startDate.isDate === true;
+
+                exceptionVevents.forEach((exVevent: any) => {
+                  const exEvent = new ICAL.Event(exVevent);
+                  const exDtStartProp = exVevent.getFirstProperty('dtstart');
+                  const exTzid = exDtStartProp?.getParameter('tzid') as string | undefined;
+                  const recId = exVevent.getFirstPropertyValue('recurrence-id');
+                  if (recId) exceptionDates.add(icalTimeToUtcDate(recId, exTzid).toISOString());
+
+                  const exStart = icalTimeToUtcDate(exEvent.startDate, exTzid);
+                  const exEnd = icalTimeToUtcDate(exEvent.endDate, exTzid);
+                  const exIsAllDay = exEvent.startDate.isDate === true;
+
+                  if (exEnd.getTime() >= minTime && exStart.getTime() <= maxTime) {
+                    parsedEvents.push({
+                      id: `caldav::${eventObj.url}::${exEvent.uid}::${exStart.toISOString()}`,
+                      title: exEvent.summary || 'Untitled Event',
+                      startDate: exIsAllDay ? formatDateToLocalISO(exStart) : exStart.toISOString(),
+                      endDate: exIsAllDay ? formatDateToLocalISO(exEnd) : exEnd.toISOString(),
+                      description: exEvent.description,
+                      location: exEvent.location,
+                      url: exVevent.getFirstPropertyValue('url')?.toString() || undefined,
+                      recurringEventId: exEvent.uid,
+                      isRecurring: true,
+                      ...extractExtendedProps(exVevent),
+                    });
+                  }
+                });
+
+                try {
+                  const dtStartProp = vevent.getFirstProperty('dtstart');
+                  const dtStartTzid = dtStartProp?.getParameter('tzid') as string | undefined;
+                  const startUtc = icalTimeToUtcDate(event.startDate, dtStartTzid);
+                  const endUtc = icalTimeToUtcDate(event.endDate, dtStartTzid);
+                  const duration = endUtc.getTime() - startUtc.getTime();
+                  const iter = event.iterator();
+                  let next;
+                  let safetyCount = 0;
+
+                  while ((next = iter.next()) && safetyCount < 500) {
+                    safetyCount++;
+                    const occStart = icalTimeToUtcDate(next, dtStartTzid);
+                    const occEnd = new Date(occStart.getTime() + duration);
+                    if (occStart.getTime() > maxTime) break;
+                    if (occEnd.getTime() < minTime) continue;
+                    if (exceptionDates.has(occStart.toISOString())) continue;
+
+                    parsedEvents.push({
+                      id: `caldav::${eventObj.url}::${event.uid}::${occStart.toISOString()}`,
+                      title: event.summary || 'Untitled Event',
+                      startDate: isAllDayRecurring ? formatDateToLocalISO(occStart) : occStart.toISOString(),
+                      endDate: isAllDayRecurring ? formatDateToLocalISO(occEnd) : occEnd.toISOString(),
+                      description: event.description,
+                      location: event.location,
+                      url: vevent.getFirstPropertyValue('url')?.toString() || undefined,
+                      recurringEventId: event.uid,
+                      isRecurring: true,
+                      ...extractExtendedProps(vevent),
+                    });
+                  }
+                } catch (expandErr: any) {
+                  console.error(`[APPLE CALENDAR] Error expanding recurrence for "${event.summary}":`, expandErr);
+                }
+              } else {
+                const nrDtStartProp = vevent.getFirstProperty('dtstart');
+                const nrTzid = nrDtStartProp?.getParameter('tzid') as string | undefined;
+                const start = icalTimeToUtcDate(event.startDate, nrTzid);
+                const end = icalTimeToUtcDate(event.endDate, nrTzid);
+                const isAllDay = event.startDate.isDate === true;
+                if (end.getTime() < minTime || start.getTime() > maxTime) return;
+
+                parsedEvents.push({
+                  id: `caldav::${eventObj.url}::${event.uid || 'unknown'}`,
+                  title: event.summary || 'Untitled Event',
+                  startDate: isAllDay ? formatDateToLocalISO(start) : start.toISOString(),
+                  endDate: isAllDay ? formatDateToLocalISO(end) : end.toISOString(),
+                  description: event.description,
+                  location: event.location,
+                  url: vevent.getFirstPropertyValue('url')?.toString() || undefined,
+                  ...extractExtendedProps(vevent),
+                });
+              }
+            });
+          } catch (parseErr: any) {
+            console.error(`[APPLE CALENDAR] Error parsing event data for calendar ${calendarUrl}:`, parseErr);
+          }
+        });
+
+        results.set(calendarUrl, parsedEvents);
+        console.log(`[APPLE CALENDAR] Batch: ${parsedEvents.length} events from ${calendarUrl.split('/').pop()}`);
+      } catch (calErr: any) {
+        console.error(`[APPLE CALENDAR] Batch error for ${calendarUrl}:`, calErr.message || calErr);
+        results.set(calendarUrl, []);
+      }
+    }
+  } catch (error: any) {
+    console.error(`[APPLE CALENDAR] Batch login/init failed:`, error.message || error);
+    calendarUrls.forEach(url => results.set(url, []));
+  }
+
+  return results;
+};
+
 /**
  * Create a new event in the specified calendar
  */
@@ -439,10 +669,10 @@ export const createEvent = async (
   }
 ): Promise<AppleCalendarEvent> => {
   try {
-    const client = createClient(email, appSpecificPassword);
-    await client.login();
-
-    const calendars = await client.fetchCalendars();
+    const { client, calendars } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'createEvent'
+    );
     const targetCalendar = calendars.find(c => c.url === calendarUrl);
 
     if (!targetCalendar) {
@@ -629,8 +859,10 @@ export const updateEvent = async (
   }
 ): Promise<AppleCalendarEvent> => {
   try {
-    const client = createClient(email, appSpecificPassword);
-    await client.login();
+    const { client, calendars } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'updateEvent'
+    );
 
     let targetObject: any = null;
 
@@ -648,7 +880,6 @@ export const updateEvent = async (
       }
     } else {
       // Legacy fallback: O(n) scan for old-format IDs
-      const calendars = await client.fetchCalendars();
       const targetCalendar = calendars.find(c => c.url === calendarUrl);
 
       if (!targetCalendar) {
@@ -880,8 +1111,10 @@ export const deleteRecurringInstance = async (
   deleteMode: string
 ): Promise<void> => {
   try {
-    const client = createClient(email, appSpecificPassword);
-    await client.login();
+    const { client } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'deleteRecurringInstance'
+    );
 
     // Parse the caldav ID to get objectUrl and occurrence date
     const parts = eventId.split('::');
@@ -1040,8 +1273,10 @@ export const deleteEvent = async (
   eventId: string
 ): Promise<void> => {
   try {
-    const client = createClient(email, appSpecificPassword);
-    await client.login();
+    const { client, calendars } = await withRetry(
+      () => getOrCreateClient(email, appSpecificPassword),
+      2, 'deleteEvent'
+    );
 
     // Try O(1) path first with new caldav:: ID format
     const parsed = parseCaldavId(eventId);
@@ -1055,7 +1290,6 @@ export const deleteEvent = async (
     }
 
     // Legacy fallback: O(n) scan for old-format IDs
-    const calendars = await client.fetchCalendars();
     const targetCalendar = calendars.find(c => c.url === calendarUrl);
 
     if (!targetCalendar) {

src/lib/calendar-cache.ts

@@ -4,7 +4,7 @@
 import { prisma } from './prisma';
 import { getCalendarEvents, CalendarEvent, CalendarConnection } from './calendar-events';
 
-const STALE_THRESHOLD_MS = 2 * 60 * 1000; // 2 minutes — keep in sync with external changes
+const STALE_THRESHOLD_MS = 15 * 60 * 1000; // 15 minutes — avoid iCloud rate limiting
 
 /**
  * Get the Monday (start of ISO week) for a given date.

src/lib/calendar-events.ts

@@ -1,7 +1,7 @@
 import { GoogleCalendarEvent, getUserCalendars as getGoogleCalendars, getUpcomingEvents as getGoogleEvents, initializeOAuth as initializeGoogleOAuth } from './google-calendar';
-import { AppleCalendarEvent, getUserCalendars as getAppleCalendars, getUpcomingEvents as getAppleEvents } from './apple-calendar';
+import { AppleCalendarEvent, getUserCalendars as getAppleCalendars, getUpcomingEvents as getAppleEvents, getUpcomingEventsBatch as getAppleEventsBatch } from './apple-calendar';
 import { getUpcomingEvents as getOutlookEvents, refreshAccessToken as refreshOutlookTokenAPI, createEvent as createOutlookEvent, updateEvent as updateOutlookEvent, deleteEvent as deleteOutlookEvent } from './outlook-calendar';
-import { getUserCalendars as getSynologyCalendars, getUpcomingEvents as getSynologyEvents } from './synology-calendar';
+import { getUserCalendars as getSynologyCalendars, getUpcomingEvents as getSynologyEvents, getUpcomingEventsBatch as getSynologyEventsBatch } from './synology-calendar';
 import { getUpcomingEvents as getNotionEvents, refreshAccessToken as refreshNotionToken } from './notion-calendar';
 import { PrismaClient } from '@prisma/client';
 
@@ -397,21 +397,12 @@ export const getCalendarEvents = async (
         }
 
         // Get user calendars to identify which ones to fetch events from
-        // We can pass null/dummy client if getUserCalendars just calls validateCredentials which creates its own client
-        // Actually getUserCalendars in apple-calendar.ts (wrapper around validateCredentials) takes (email, password)
-        // But here it was imported as getAppleCalendars(appleClient, accessToken) which matched the old signature?
-
-        // Let's check apple-calendar.ts signature for getUserCalendars.
-        // It is: export const getUserCalendars = validateCredentials;
-        // validateCredentials: (email: string, appSpecificPassword: string)
-
         const freshCalendars = await getAppleCalendars(email, appPassword);
 
         // Use stored selection state if available, otherwise use all fresh calendars
         let calendars = freshCalendars;
         if (connection.calendars && Array.isArray(connection.calendars) && connection.calendars.length > 0) {
           const storedCalendars = connection.calendars as any[];
-          // Only fetch from calendars that are selected
           calendars = freshCalendars.filter(fc => {
             const stored = storedCalendars.find((sc: any) => sc.id === fc.id);
             return stored ? stored.selected !== false : true;
@@ -419,17 +410,18 @@ export const getCalendarEvents = async (
         }
         const calendarIds = calendars.map(c => c.id);
 
-        // Fetch events for each calendar
-        for (const calendarId of calendarIds) {
-          const calendarEvents = await getAppleEvents(
+        // Batch fetch: single login, single calendar list, then fetch all calendars
+        console.log(`[CALENDAR] Apple: batch fetching ${calendarIds.length} calendars with single connection`);
+        const batchResults = await getAppleEventsBatch(
           email,
           appPassword,
-            calendarId,
+          calendarIds,
           timeMin,
           timeMax
         );
 
-          console.log(`[CALENDAR] Fetched ${calendarEvents.length} events from calendar ${calendarId}`);
+        for (const [calendarId, calendarEvents] of batchResults) {
+          console.log(`[CALENDAR] Fetched ${calendarEvents.length} events from Apple calendar ${calendarId}`);
 
           events = events.concat(calendarEvents.map((event: any) => {
             const isDateOnly = (s: string) => s && !s.includes('T');
@@ -519,17 +511,18 @@ export const getCalendarEvents = async (
           continue;
         }
 
-        for (const calendarId of calendarIds) {
-          try {
-            const calendarEvents = await getSynologyEvents(
+        // Batch fetch: single login, single calendar list, then fetch all calendars
+        console.log(`[CALENDAR] Synology: batch fetching ${calendarIds.length} calendars with single connection`);
+        const batchResults = await getSynologyEventsBatch(
           serverUrl,
           username,
           password,
-              calendarId,
+          calendarIds,
           timeMin,
           timeMax
         );
 
+        for (const [calendarId, calendarEvents] of batchResults) {
           console.log(`[CALENDAR] Synology: fetched ${calendarEvents.length} events from calendar ${calendarId}`);
           const calendarData = calendars.find(c => c.id === calendarId);
           const freshCal = freshCalendars.find(c => c.id === calendarId);
@@ -564,23 +557,6 @@ export const getCalendarEvents = async (
               attachments: event.attachments as EventAttachment[] || undefined,
             };
           }));
-          } catch (calError: any) {
-            const msg = calError?.message || '';
-            if (msg.includes('not found') || msg.includes('Not found') || calError?.status === 404) {
-              console.warn(`[CALENDAR] Synology: calendar ${calendarId} not found, removing from stored list`);
-              calendars = calendars.filter((c: any) => c.id !== calendarId);
-              try {
-                await prisma.calendarConnection.update({
-                  where: { id: connection.id },
-                  data: { calendars: calendars },
-                });
-              } catch (dbErr) {
-                console.error('[CALENDAR] Synology: failed to prune calendar from DB:', dbErr);
-              }
-            } else {
-              console.error(`[CALENDAR] Synology: error fetching events from calendar ${calendarId}:`, calError);
-            }
-          }
         }
       } else if (connection.provider === 'outlook') {
         console.log('[CALENDAR] Processing Outlook connection:', connection.id);

src/lib/synology-calendar.ts

@@ -435,6 +435,196 @@ export const getUpcomingEvents = async (
   }
 };
 
+/**
+ * Batch fetch events from multiple Synology calendars using a single client/login.
+ * Avoids creating N separate connections for N calendars.
+ */
+export const getUpcomingEventsBatch = async (
+  serverUrl: string,
+  username: string,
+  password: string,
+  calendarUrls: string[],
+  timeMin: string,
+  timeMax: string
+): Promise<Map<string, SynologyCalendarEvent[]>> => {
+  const results = new Map<string, SynologyCalendarEvent[]>();
+  if (calendarUrls.length === 0) return results;
+
+  try {
+    const client = createClient(serverUrl, username, password);
+    await loginClient(client, serverUrl, username);
+    const calendars = await client.fetchCalendars();
+
+    const getPath = (url: string) => {
+      try { return new URL(url).pathname; } catch { return url; }
+    };
+
+    const minTime = new Date(timeMin).getTime();
+    const maxTime = new Date(timeMax).getTime();
+
+    for (const calendarUrl of calendarUrls) {
+      try {
+        const targetPath = getPath(calendarUrl);
+        const targetCalendar = calendars.find(c => getPath(c.url) === targetPath);
+        if (!targetCalendar) {
+          console.log(`[SYNOLOGY CALENDAR] Calendar not found: ${calendarUrl}`);
+          results.set(calendarUrl, []);
+          continue;
+        }
+
+        const events = await client.fetchCalendarObjects({
+          calendar: targetCalendar,
+          timeRange: {
+            start: new Date(timeMin).toISOString(),
+            end: new Date(timeMax).toISOString(),
+          },
+        });
+
+        const parsedEvents: SynologyCalendarEvent[] = [];
+
+        events.forEach(eventObj => {
+          const data = (eventObj as any).data;
+          if (!data) return;
+          try {
+            const jcalData = ICAL.parse(data);
+            const comp = new ICAL.Component(jcalData);
+            const vevents = comp.getAllSubcomponents('vevent');
+            const baseEvents: any[] = [];
+            const exceptions: Map<string, any[]> = new Map();
+
+            vevents.forEach((vevent: any) => {
+              const recurrenceId = vevent.getFirstPropertyValue('recurrence-id');
+              if (recurrenceId) {
+                const event = new ICAL.Event(vevent);
+                const uid = event.uid;
+                if (!exceptions.has(uid)) exceptions.set(uid, []);
+                exceptions.get(uid)!.push(vevent);
+              } else {
+                baseEvents.push(vevent);
+              }
+            });
+
+            baseEvents.forEach((vevent: any) => {
+              const event = new ICAL.Event(vevent);
+              const rrule = vevent.getFirstPropertyValue('rrule');
+
+              if (rrule) {
+                const uid = event.uid;
+                const exceptionVevents = exceptions.get(uid) || [];
+                const exceptionDates = new Set<string>();
+                const isAllDayRecurring = event.startDate.isDate === true;
+
+                exceptionVevents.forEach((exVevent: any) => {
+                  const exEvent = new ICAL.Event(exVevent);
+                  const exDtStartProp = exVevent.getFirstProperty('dtstart');
+                  const exTzid = exDtStartProp?.getParameter('tzid') as string | undefined;
+                  const recId = exVevent.getFirstPropertyValue('recurrence-id');
+                  if (recId) exceptionDates.add(icalTimeToUtcDate(recId, exTzid).toISOString());
+
+                  const exStart = icalTimeToUtcDate(exEvent.startDate, exTzid);
+                  const exEnd = icalTimeToUtcDate(exEvent.endDate, exTzid);
+                  const exIsAllDay = exEvent.startDate.isDate === true;
+
+                  if (exEnd.getTime() >= minTime && exStart.getTime() <= maxTime) {
+                    parsedEvents.push({
+                      id: `caldav::${eventObj.url}::${exEvent.uid}::${exStart.toISOString()}`,
+                      title: exEvent.summary || 'Untitled Event',
+                      startDate: exIsAllDay ? formatDateToLocalISO(exStart) : exStart.toISOString(),
+                      endDate: exIsAllDay ? formatDateToLocalISO(exEnd) : exEnd.toISOString(),
+                      description: exEvent.description,
+                      location: exEvent.location,
+                      url: exVevent.getFirstPropertyValue('url')?.toString() || undefined,
+                      recurringEventId: exEvent.uid,
+                      isRecurring: true,
+                      ...extractExtendedProps(exVevent),
+                    });
+                  }
+                });
+
+                try {
+                  const dtStartProp = vevent.getFirstProperty('dtstart');
+                  const dtStartTzid = dtStartProp?.getParameter('tzid') as string | undefined;
+                  const startUtc = icalTimeToUtcDate(event.startDate, dtStartTzid);
+                  const endUtc = icalTimeToUtcDate(event.endDate, dtStartTzid);
+                  const duration = endUtc.getTime() - startUtc.getTime();
+                  const iter = event.iterator();
+                  let next;
+                  let safetyCount = 0;
+
+                  while ((next = iter.next()) && safetyCount < 500) {
+                    safetyCount++;
+                    const occStart = icalTimeToUtcDate(next, dtStartTzid);
+                    const occEnd = new Date(occStart.getTime() + duration);
+
+                    if (occStart.getTime() > maxTime) break;
+                    if (occEnd.getTime() < minTime) continue;
+                    if (exceptionDates.has(occStart.toISOString())) continue;
+
+                    parsedEvents.push({
+                      id: `caldav::${eventObj.url}::${event.uid}::${occStart.toISOString()}`,
+                      title: event.summary || 'Untitled Event',
+                      startDate: isAllDayRecurring ? formatDateToLocalISO(occStart) : occStart.toISOString(),
+                      endDate: isAllDayRecurring ? formatDateToLocalISO(occStart) : occEnd.toISOString(),
+                      description: event.description,
+                      location: event.location,
+                      url: vevent.getFirstPropertyValue('url')?.toString() || undefined,
+                      recurringEventId: event.uid,
+                      isRecurring: true,
+                      ...extractExtendedProps(vevent),
+                    });
+                  }
+                } catch (expandErr: any) {
+                  console.error(`[SYNOLOGY CALENDAR] Error expanding recurrence for "${event.summary}":`, expandErr);
+                }
+              } else {
+                const nrDtStartProp = vevent.getFirstProperty('dtstart');
+                const nrTzid = nrDtStartProp?.getParameter('tzid') as string | undefined;
+                const start = icalTimeToUtcDate(event.startDate, nrTzid);
+                const end = icalTimeToUtcDate(event.endDate, nrTzid);
+                const isAllDay = event.startDate.isDate === true;
+
+                if (end.getTime() < minTime || start.getTime() > maxTime) return;
+
+                parsedEvents.push({
+                  id: `caldav::${eventObj.url}::${event.uid || 'unknown'}`,
+                  title: event.summary || 'Untitled Event',
+                  startDate: isAllDay ? formatDateToLocalISO(start) : start.toISOString(),
+                  endDate: isAllDay ? formatDateToLocalISO(end) : end.toISOString(),
+                  description: event.description,
+                  location: event.location,
+                  url: vevent.getFirstPropertyValue('url')?.toString() || undefined,
+                  ...extractExtendedProps(vevent),
+                });
+              }
+            });
+          } catch (parseErr: any) {
+            console.error(`[SYNOLOGY CALENDAR] Error parsing event data for calendar ${calendarUrl}:`, parseErr);
+          }
+        });
+
+        results.set(calendarUrl, parsedEvents);
+      } catch (calErr: any) {
+        const msg = calErr?.message || '';
+        const status = calErr?.response?.status || calErr?.status;
+        if (status === 404 || msg.includes('not found') || msg.includes('Calendar not found')) {
+          console.warn(`[SYNOLOGY CALENDAR] Calendar not found in batch: ${calendarUrl}`);
+          results.set(calendarUrl, []);
+        } else {
+          console.error(`[SYNOLOGY CALENDAR] Batch error for ${calendarUrl}:`, calErr);
+          results.set(calendarUrl, []);
+        }
+      }
+    }
+
+    return results;
+  } catch (error: any) {
+    console.error('[SYNOLOGY CALENDAR] Batch fetch failed:', error);
+    // Return empty results for all calendars
+    calendarUrls.forEach(url => results.set(url, []));
+    return results;
+  }
+};
+
 /**
  * Create a new event in the specified calendar
  */