diff --git a/server/models/room.js b/server/models/room.js
index 275f102..afdd2d6 100644
--- a/server/models/room.js
+++ b/server/models/room.js
@@ -527,7 +527,9 @@ const collectPostgresChanges = (room) => {
   return {
     attempts,
     participantUserIds: [...participantUserIds],
-    replaceAttempts: !room.isNew && room.isModified('event'),
+    // An event switch starts a new attempt stream. The migration writer must
+    // mirror it without deleting attempts from the previous event.
+    syncAllAttempts: !room.isNew && room.isModified('event'),
     syncAllParticipants: room.isNew,
     syncRoomOwners: room.isNew || room.isModified('owner') || room.isModified('admin'),
   };
diff --git a/server/models/room.test.js b/server/models/room.test.js
index 0505c69..bf42ab0 100644
--- a/server/models/room.test.js
+++ b/server/models/room.test.js
@@ -407,13 +407,13 @@ describe('room security helpers', () => {
         syncAllResults: false,
       }],
       participantUserIds: ['1234'],
-      replaceAttempts: false,
+      syncAllAttempts: false,
       syncAllParticipants: false,
       syncRoomOwners: false,
     });
   });
 
-  it('replaces PostgreSQL attempts when the room event resets them', () => {
+  it('syncs the new PostgreSQL attempt stream when the room event resets it', () => {
     const room = RoomModel.hydrate({
       _id: '507f1f77bcf86cd799439011',
       name: 'Practice room',
@@ -439,7 +439,7 @@ describe('room security helpers', () => {
         syncAllResults: true,
       }],
       participantUserIds: [],
-      replaceAttempts: true,
+      syncAllAttempts: true,
       syncAllParticipants: false,
       syncRoomOwners: false,
     });
diff --git a/server/postgres/dualWrite.js b/server/postgres/dualWrite.js
index 32db886..42a0cf7 100644
--- a/server/postgres/dualWrite.js
+++ b/server/postgres/dualWrite.js
@@ -537,7 +537,7 @@ const syncAttemptResults = async (client, roomState, attemptState, attempt, user
 
 const writeRoomChanges = async (client, room, changes) => {
   const resultUserIds = new Set();
-  if (changes.replaceAttempts) {
+  if (changes.syncAllAttempts) {
     (room.attempts || []).forEach((attempt) => {
       resultEntries(attempt.results).forEach(([userId]) => resultUserIds.add(userId));
     });
@@ -563,8 +563,7 @@ const writeRoomChanges = async (client, room, changes) => {
     return null;
   }
 
-  if (changes.replaceAttempts) {
-    await client.query('DELETE FROM app.attempts WHERE room_id = $1', [roomState.roomId]);
+  if (changes.syncAllAttempts) {
     for (const [attemptIndex, attempt] of (room.attempts || []).entries()) {
       const attemptState = await upsertAttempt(client, room, roomState, attempt, attemptIndex);
       await syncAttemptResults(
diff --git a/server/postgres/dualWrite.test.js b/server/postgres/dualWrite.test.js
index 5a4ea80..6198edd 100644
--- a/server/postgres/dualWrite.test.js
+++ b/server/postgres/dualWrite.test.js
@@ -175,6 +175,48 @@ describe('PostgreSQL dual writer', () => {
       .toContain(12001);
   });
 
+  it('retains prior-event rows when an event switch starts a new attempt stream', async () => {
+    const updatedAt = new Date('2026-07-10T20:00:00.000Z');
+    const room = {
+      _id: '507f1f77bcf86cd799439011',
+      name: 'Practice room',
+      event: '222',
+      accessCode: 'room-access-code',
+      type: 'normal',
+      owner: user,
+      admin: user,
+      users: [user],
+      attempts: [{
+        id: 0,
+        scrambles: ['R U2 R\''],
+        results: new Map([['1234', {
+          time: 8000,
+          penalties: {},
+          createdAt: updatedAt,
+          updatedAt,
+        }]]),
+        createdAt: updatedAt,
+        updatedAt,
+      }],
+      createdAt: updatedAt,
+      updatedAt,
+    };
+
+    await mirrorRoomChanges(room, {
+      attempts: [],
+      participantUserIds: [],
+      syncAllAttempts: true,
+      syncAllParticipants: false,
+      syncRoomOwners: true,
+    });
+
+    const statements = client.query.mock.calls.map(([sql]) => sql);
+    expect(statements.some((sql) => sql.includes('DELETE FROM app.attempts'))).toBe(false);
+    expect(statements.some((sql) => sql.includes('DELETE FROM app.solves'))).toBe(false);
+    expect(statements.filter((sql) => sql.includes('INSERT INTO app.attempts'))).toHaveLength(1);
+    expect(statements.filter((sql) => sql.includes('INSERT INTO app.solves'))).toHaveLength(1);
+  });
+
   it('mirrors sanitized metric events and soft-deletes rooms', async () => {
     const occurredAt = new Date('2026-07-09T20:00:00.000Z');
     await mirrorMetricEvent({