diff --git a/scripts/consolidate-private-calendars.ts b/scripts/consolidate-private-calendars.ts
new file mode 100644
index 0000000..3ca55dc
--- /dev/null
+++ b/scripts/consolidate-private-calendars.ts
@@ -0,0 +1,196 @@
+#!/usr/bin/env ts-node
+
+/**
+ * Script to consolidate duplicate "Privée" calendars
+ * - Identifies the calendar to keep (with active sync and most events)
+ * - Migrates events from duplicate calendars to the one to keep
+ * - Deletes duplicate calendars and their sync configs
+ */
+
+import { PrismaClient } from '@prisma/client';
+
+const prisma = new PrismaClient();
+
+async function consolidatePrivateCalendars() {
+  try {
+    console.log('🔍 Searching for duplicate "Privée" calendars...\n');
+
+    // Find all calendars named "Privée"
+    const privateCalendars = await prisma.calendar.findMany({
+      where: {
+        name: 'Privée',
+      },
+      include: {
+        syncConfig: {
+          include: {
+            mailCredential: true,
+          },
+        },
+        _count: {
+          select: {
+            events: true,
+          },
+        },
+      },
+    });
+
+    console.log(`Found ${privateCalendars.length} calendars named "Privée"\n`);
+
+    if (privateCalendars.length <= 1) {
+      console.log('✅ No duplicates found. Nothing to consolidate.\n');
+      return;
+    }
+
+    // Find the calendar to keep:
+    // 1. Has active sync (syncEnabled = true)
+    // 2. Has the most events
+    // 3. Most recent
+    const calendarsToSort = [...privateCalendars];
+    calendarsToSort.sort((a, b) => {
+      // Priority 1: Active sync
+      const aHasActiveSync = a.syncConfig?.syncEnabled === true;
+      const bHasActiveSync = b.syncConfig?.syncEnabled === true;
+      if (aHasActiveSync && !bHasActiveSync) return -1;
+      if (!aHasActiveSync && bHasActiveSync) return 1;
+
+      // Priority 2: Most events
+      const aEventCount = a._count.events;
+      const bEventCount = b._count.events;
+      if (aEventCount !== bEventCount) {
+        return bEventCount - aEventCount; // Descending
+      }
+
+      // Priority 3: Most recent
+      return b.createdAt.getTime() - a.createdAt.getTime(); // Descending
+    });
+
+    const calendarToKeep = calendarsToSort[0];
+    const calendarsToDelete = calendarsToSort.slice(1);
+
+    console.log('📋 Calendar to KEEP:');
+    console.log(`   ID: ${calendarToKeep.id}`);
+    console.log(`   Events: ${calendarToKeep._count.events}`);
+    console.log(`   Sync enabled: ${calendarToKeep.syncConfig?.syncEnabled || false}`);
+    console.log(`   Provider: ${calendarToKeep.syncConfig?.provider || 'none'}`);
+    console.log(`   Created: ${calendarToKeep.createdAt}\n`);
+
+    console.log(`🗑️  Calendars to DELETE (${calendarsToDelete.length}):`);
+    for (const cal of calendarsToDelete) {
+      console.log(`   ID: ${cal.id}`);
+      console.log(`   Events: ${cal._count.events}`);
+      console.log(`   Sync enabled: ${cal.syncConfig?.syncEnabled || false}`);
+      console.log(`   Created: ${cal.createdAt}\n`);
+    }
+
+    // Migrate events from calendars to delete to the calendar to keep
+    let totalMigrated = 0;
+    for (const calToDelete of calendarsToDelete) {
+      const eventsToMigrate = await prisma.event.findMany({
+        where: {
+          calendarId: calToDelete.id,
+        },
+      });
+
+      console.log(`📦 Migrating ${eventsToMigrate.length} events from calendar ${calToDelete.id}...`);
+
+      for (const event of eventsToMigrate) {
+        // Check if event with same externalEventId already exists in target calendar
+        const externalId = (event as any).externalEventId;
+        
+        if (externalId) {
+          // Check if event with this externalEventId already exists in target calendar
+          const existingEvent = await prisma.event.findFirst({
+            where: {
+              calendarId: calendarToKeep.id,
+              externalEventId: externalId,
+            },
+          });
+
+          if (existingEvent) {
+            console.log(`   ⚠️  Skipping event "${event.title}" - already exists in target calendar (externalEventId: ${externalId.substring(0, 50)}...)`);
+            // Delete the duplicate event
+            await prisma.event.delete({
+              where: { id: event.id },
+            });
+            continue;
+          }
+        } else {
+          // For events without externalEventId, check by title + date
+          const existingEvent = await prisma.event.findFirst({
+            where: {
+              calendarId: calendarToKeep.id,
+              title: event.title,
+              start: event.start,
+            },
+          });
+
+          if (existingEvent) {
+            console.log(`   ⚠️  Skipping event "${event.title}" - already exists in target calendar (title + date match)`);
+            // Delete the duplicate event
+            await prisma.event.delete({
+              where: { id: event.id },
+            });
+            continue;
+          }
+        }
+
+        // Migrate event to target calendar
+        try {
+          await prisma.event.update({
+            where: { id: event.id },
+            data: {
+              calendarId: calendarToKeep.id,
+            },
+          });
+          totalMigrated++;
+          console.log(`   ✅ Migrated: "${event.title}"`);
+        } catch (error) {
+          console.error(`   ❌ Error migrating event "${event.title}":`, error);
+        }
+      }
+    }
+
+    console.log(`\n✅ Migrated ${totalMigrated} events to calendar ${calendarToKeep.id}\n`);
+
+    // Delete duplicate calendars and their sync configs
+    for (const calToDelete of calendarsToDelete) {
+      console.log(`🗑️  Deleting calendar ${calToDelete.id}...`);
+
+      // Delete sync config if exists
+      if (calToDelete.syncConfig) {
+        await prisma.calendarSync.delete({
+          where: { id: calToDelete.syncConfig.id },
+        });
+        console.log(`   ✅ Deleted sync config ${calToDelete.syncConfig.id}`);
+      }
+
+      // Delete calendar (events are already migrated or deleted)
+      await prisma.calendar.delete({
+        where: { id: calToDelete.id },
+      });
+      console.log(`   ✅ Deleted calendar ${calToDelete.id}`);
+    }
+
+    console.log(`\n✅ Consolidation completed!`);
+    console.log(`   Kept: 1 calendar (${calendarToKeep.id})`);
+    console.log(`   Deleted: ${calendarsToDelete.length} duplicate calendars`);
+    console.log(`   Migrated: ${totalMigrated} events\n`);
+
+  } catch (error) {
+    console.error('❌ Error consolidating calendars:', error);
+    throw error;
+  } finally {
+    await prisma.$disconnect();
+  }
+}
+
+// Run the script
+consolidatePrivateCalendars()
+  .then(() => {
+    console.log('✅ Script completed successfully');
+    process.exit(0);
+  })
+  .catch((error) => {
+    console.error('❌ Script failed:', error);
+    process.exit(1);
+  });
diff --git a/scripts/explore-calendar-duplicates.sql b/scripts/explore-calendar-duplicates.sql
new file mode 100644
index 0000000..f1e4f26
--- /dev/null
+++ b/scripts/explore-calendar-duplicates.sql
@@ -0,0 +1,150 @@
+-- ============================================
+-- Script d'exploration des duplications de calendriers et événements
+-- ============================================
+
+-- 1. Lister tous les calendriers "Privée" avec leurs détails
+SELECT 
+    c.id,
+    c.name,
+    c.color,
+    c.description,
+    c."userId",
+    c."missionId",
+    c."createdAt",
+    c."updatedAt",
+    cs.id as "syncConfigId",
+    cs.provider,
+    cs."externalCalendarId",
+    cs."syncEnabled",
+    cs."lastSyncAt",
+    mc.email as "mailCredentialEmail",
+    (SELECT COUNT(*) FROM "Event" e WHERE e."calendarId" = c.id) as "eventCount"
+FROM "Calendar" c
+LEFT JOIN "CalendarSync" cs ON cs."calendarId" = c.id
+LEFT JOIN "MailCredentials" mc ON mc.id = cs."mailCredentialId"
+WHERE c.name = 'Privée'
+ORDER BY c."createdAt" DESC;
+
+-- 2. Voir tous les événements "Vendredi saint" avec leurs calendriers
+SELECT 
+    e.id,
+    e.title,
+    e."calendarId",
+    c.name as "calendarName",
+    e."externalEventId",
+    e.start,
+    e.end,
+    e."isAllDay",
+    e."createdAt",
+    e."updatedAt"
+FROM "Event" e
+JOIN "Calendar" c ON c.id = e."calendarId"
+WHERE e.title = 'Vendredi saint'
+ORDER BY e.start, c.name;
+
+-- 3. Identifier les événements en double par externalEventId (même événement dans plusieurs calendriers)
+SELECT 
+    e."externalEventId",
+    e.title,
+    COUNT(*) as "occurrenceCount",
+    STRING_AGG(DISTINCT c.id::text, ', ') as "calendarIds",
+    STRING_AGG(DISTINCT c.name, ', ') as "calendarNames",
+    MIN(e.start) as "earliestStart",
+    MAX(e.start) as "latestStart"
+FROM "Event" e
+JOIN "Calendar" c ON c.id = e."calendarId"
+WHERE e."externalEventId" IS NOT NULL
+  AND e."externalEventId" != ''
+GROUP BY e."externalEventId", e.title
+HAVING COUNT(*) > 1
+ORDER BY "occurrenceCount" DESC, e.title;
+
+-- 4. Voir les détails complets des événements en double
+SELECT 
+    e.id,
+    e.title,
+    e."externalEventId",
+    e."calendarId",
+    c.name as "calendarName",
+    c."userId",
+    e.start,
+    e.end,
+    e."isAllDay",
+    e."createdAt",
+    e."updatedAt"
+FROM "Event" e
+JOIN "Calendar" c ON c.id = e."calendarId"
+WHERE e."externalEventId" IN (
+    SELECT "externalEventId"
+    FROM "Event"
+    WHERE "externalEventId" IS NOT NULL
+      AND "externalEventId" != ''
+    GROUP BY "externalEventId"
+    HAVING COUNT(*) > 1
+)
+ORDER BY e."externalEventId", e."calendarId", e.start;
+
+-- 5. Compter les événements par calendrier "Privée"
+SELECT 
+    c.id as "calendarId",
+    c.name,
+    COUNT(e.id) as "totalEvents",
+    COUNT(CASE WHEN e."externalEventId" IS NOT NULL THEN 1 END) as "eventsWithExternalId",
+    COUNT(CASE WHEN e."externalEventId" IS NULL THEN 1 END) as "eventsWithoutExternalId"
+FROM "Calendar" c
+LEFT JOIN "Event" e ON e."calendarId" = c.id
+WHERE c.name = 'Privée'
+GROUP BY c.id, c.name
+ORDER BY "totalEvents" DESC;
+
+-- 6. Voir les événements "TEST de connaissances" (celui qui apparaît en double dans les logs)
+SELECT 
+    e.id,
+    e.title,
+    e."externalEventId",
+    e."calendarId",
+    c.name as "calendarName",
+    e.start,
+    e.end,
+    e."createdAt"
+FROM "Event" e
+JOIN "Calendar" c ON c.id = e."calendarId"
+WHERE e.title LIKE '%TEST de connaissances%'
+   OR e."externalEventId" = 'AAMkADg2NjBjMDUwLTJlMzYtNDBlZi1iNzE4LTA5YWFiYTdhMWJmYwBGAAAAAABiHJmWOydNSY0OtAePspbBBwBWDBinTymARZbnqCRYQq7IAAAAAAENAABWDBinTymARZbnqCRYQq7IAAMGtqjeAAA='
+ORDER BY e."calendarId", e.start;
+
+-- 7. Lister tous les CalendarSync pour les calendriers "Privée"
+SELECT 
+    cs.id,
+    cs."calendarId",
+    c.name as "calendarName",
+    cs.provider,
+    cs."externalCalendarId",
+    cs."syncEnabled",
+    cs."lastSyncAt",
+    cs."syncFrequency",
+    cs."lastSyncError",
+    mc.email as "mailCredentialEmail"
+FROM "CalendarSync" cs
+JOIN "Calendar" c ON c.id = cs."calendarId"
+LEFT JOIN "MailCredentials" mc ON mc.id = cs."mailCredentialId"
+WHERE c.name = 'Privée'
+ORDER BY cs."createdAt" DESC;
+
+-- 8. Trouver les événements sans externalEventId dans les calendriers Microsoft
+SELECT 
+    e.id,
+    e.title,
+    e."calendarId",
+    c.name as "calendarName",
+    e.start,
+    e.end,
+    e."createdAt",
+    cs.provider
+FROM "Event" e
+JOIN "Calendar" c ON c.id = e."calendarId"
+LEFT JOIN "CalendarSync" cs ON cs."calendarId" = c.id
+WHERE c.name = 'Privée'
+  AND (e."externalEventId" IS NULL OR e."externalEventId" = '')
+  AND cs.provider = 'microsoft'
+ORDER BY e.start DESC;