diff --git a/lib/hooks/peer-list-hooks.js b/lib/hooks/peer-list-hooks.js
--- a/lib/hooks/peer-list-hooks.js
+++ b/lib/hooks/peer-list-hooks.js
@@ -7,6 +7,7 @@
 import {
   getAllPeerDevices,
   getAllPeerUserIDAndDeviceIDs,
+  getPeersPrimaryDeviceIDs,
 } from '../selectors/user-selectors.js';
 import { IdentityClientContext } from '../shared/identity-client-context.js';
 import { usePeerToPeerCommunication } from '../tunnelbroker/peer-to-peer-context.js';
@@ -72,6 +73,7 @@
   const broadcastDeviceListUpdates = useBroadcastDeviceListUpdates();
 
   const allPeerDevices = useSelector(getAllPeerDevices);
+  const peerPrimaryDevices = useSelector(getPeersPrimaryDeviceIDs);
 
   return React.useCallback(
     async (userIDs: $ReadOnlyArray<string>, broadcastUpdates: ?boolean) => {
@@ -87,6 +89,25 @@
       if (Object.keys(deviceLists).length === 0) {
         return {};
       }
+
+      const primaryDeviceChangedUserIDs = userIDs.filter(userID => {
+        const prevPrimaryDeviceID = peerPrimaryDevices[userID];
+        const newPrimaryDeviceID = result.deviceLists[userID]?.devices[0];
+        return (
+          !!prevPrimaryDeviceID &&
+          !!newPrimaryDeviceID &&
+          newPrimaryDeviceID !== prevPrimaryDeviceID
+        );
+      });
+
+      if (primaryDeviceChangedUserIDs.length > 0) {
+        console.log(
+          'Primary device ID changed for users',
+          primaryDeviceChangedUserIDs,
+        );
+        // TODO: implement
+      }
+
       dispatch({
         type: setPeerDeviceListsActionType,
         payload: { deviceLists, usersPlatformDetails },
@@ -112,6 +133,7 @@
     },
     [
       allPeerDevices,
+      peerPrimaryDevices,
       broadcastDeviceListUpdates,
       dispatch,
       getDeviceListsForUsers,
diff --git a/lib/selectors/user-selectors.js b/lib/selectors/user-selectors.js
--- a/lib/selectors/user-selectors.js
+++ b/lib/selectors/user-selectors.js
@@ -328,6 +328,19 @@
     ),
 );
 
+const getPeersPrimaryDeviceIDs: (state: BaseAppState<>) => {
+  +[userID: string]: ?string,
+} = createSelector(
+  (state: BaseAppState<>) => state.auxUserStore.auxUserInfos,
+  (auxUserInfos: AuxUserInfos) =>
+    Object.fromEntries(
+      entries(auxUserInfos).map(([userID, { deviceList }]) => [
+        userID,
+        deviceList?.devices?.[0],
+      ]),
+    ),
+);
+
 const getOwnPrimaryDeviceID: (state: BaseAppState<>) => ?string =
   createSelector(
     (state: BaseAppState<>) => state.auxUserStore.auxUserInfos,
@@ -353,6 +366,7 @@
   getKeyserverDeviceID,
   getAllPeerDevices,
   getAllPeerUserIDAndDeviceIDs,
+  getPeersPrimaryDeviceIDs,
   getOwnPrimaryDeviceID,
   getOwnRawDeviceList,
 };