diff --git a/src/domain/session/SessionViewModel.js b/src/domain/session/SessionViewModel.js
index 6aee0d8d..5c405a3f 100644
--- a/src/domain/session/SessionViewModel.js
+++ b/src/domain/session/SessionViewModel.js
@@ -39,7 +39,8 @@ export class SessionViewModel extends ViewModel {
         })));
         this._leftPanelViewModel = this.track(new LeftPanelViewModel(this.childOptions({
             invites: this._sessionContainer.session.invites,
-            rooms: this._sessionContainer.session.rooms
+            rooms: this._sessionContainer.session.rooms,
+            compareFn: this._sessionContainer.sync.compare.bind(this._sessionContainer.sync),
         })));
         this._settingsViewModel = null;
         this._roomViewModelObservable = null;
diff --git a/src/domain/session/leftpanel/LeftPanelViewModel.js b/src/domain/session/leftpanel/LeftPanelViewModel.js
index f38471ac..036efb27 100644
--- a/src/domain/session/leftpanel/LeftPanelViewModel.js
+++ b/src/domain/session/leftpanel/LeftPanelViewModel.js
@@ -26,7 +26,7 @@ import { PlaceholderRoomTileViewModel } from "./PlaceholderRoomTileViewModel.js"
 export class LeftPanelViewModel extends ViewModel {
     constructor(options) {
         super(options);
-        const {rooms, invites} = options;
+        const {rooms, invites, compareFn} = options;
         this._tileViewModelsMap = this._mapTileViewModels(rooms, invites);
         this._tileViewModelsFilterMap = new ApplyMap(this._tileViewModelsMap);
         this._tileViewModels = this._tileViewModelsFilterMap.sortValues((a, b) => a.compare(b));
@@ -34,6 +34,7 @@ export class LeftPanelViewModel extends ViewModel {
         this._setupNavigation();
         this._closeUrl = this.urlCreator.urlForSegment("session");
         this._settingsUrl = this.urlCreator.urlForSegment("settings");
+        this._compareFn = compareFn;
     }
 
     _mapTileViewModels(rooms, invites) {
@@ -45,7 +46,11 @@ export class LeftPanelViewModel extends ViewModel {
             } else if (roomOrInvite.isPlaceholder) {
                 vm = new PlaceholderRoomTileViewModel(this.childOptions({room: roomOrInvite, emitChange}));
             } else {
-                vm = new RoomTileViewModel(this.childOptions({room: roomOrInvite, emitChange}));
+                vm = new RoomTileViewModel(this.childOptions({
+                    room: roomOrInvite,
+                    compareFn: this._compareFn,
+                    emitChange,
+                }));
             }
             const isOpen = this.navigation.path.get("room")?.value === roomOrInvite.id;
             if (isOpen) {
diff --git a/src/domain/session/leftpanel/RoomTileViewModel.js b/src/domain/session/leftpanel/RoomTileViewModel.js
index db380f5d..f35619e2 100644
--- a/src/domain/session/leftpanel/RoomTileViewModel.js
+++ b/src/domain/session/leftpanel/RoomTileViewModel.js
@@ -20,9 +20,10 @@ import {BaseTileViewModel} from "./BaseTileViewModel.js";
 export class RoomTileViewModel extends BaseTileViewModel {
     constructor(options) {
         super(options);
-        const {room} = options;
+        const {room, compareFn} = options;
         this._room = room;
         this._url = this.urlCreator.openRoomActionUrl(this._room.id);
+        this._compareFn = compareFn;
     }
 
     get kind() {
@@ -34,6 +35,8 @@ export class RoomTileViewModel extends BaseTileViewModel {
     }
 
     compare(other) {
+        return this._compareFn(this._room.id, other._room.id);
+        
         const parentComparison = super.compare(other);
         if (parentComparison !== 0) {
             return parentComparison;
diff --git a/src/matrix/Sync3.ts b/src/matrix/Sync3.ts
index 4e6a90dd..21e3e9f7 100644
--- a/src/matrix/Sync3.ts
+++ b/src/matrix/Sync3.ts
@@ -97,8 +97,11 @@ interface RoomResponse {
 };
 
 type IndexToRoomId = {
-    [index: string]: string;
+    [index: number]: string;
 };
+type RoomIdToIndex = {
+    [roomId: string]: number;
+}
 
 export class Sync3 {
     private hsApi: HomeServerApi;
@@ -110,6 +113,7 @@ export class Sync3 {
     // sync v3 specific: contains the sliding window ranges to request
     private ranges: number[][];
     private roomIndexToRoomId: IndexToRoomId;
+    private roomIdToRoomIndex: RoomIdToIndex;
 
     public error?: any;
     public status: ObservableValue<SyncStatus>;
@@ -126,6 +130,7 @@ export class Sync3 {
         // Hydrogen only has 1 list currently (no DM section) so we only need 1 range
         this.ranges = [[0, 99]];
         this.roomIndexToRoomId = {};
+        this.roomIdToRoomIndex = {};
         console.log("session", session);
         console.log("storage", storage);
     }
@@ -152,6 +157,21 @@ export class Sync3 {
         }
     }
 
+    compare(roomIdA: string, roomIdB: string) {
+        if (roomIdA === roomIdB) {
+            return 0;
+        }
+        const indexA = this.roomIdToRoomIndex[roomIdA];
+        const indexB = this.roomIdToRoomIndex[roomIdB];
+        if (indexA === undefined || indexB === undefined) {
+            console.error("sync3 cannot compare: missing indices for rooms", roomIdA, roomIdB, indexA, indexB);
+        }
+        if (indexA < indexB) {
+            return -1;
+        }
+        return 1;
+    }
+
     // The purpose of this function is to do repeated /sync calls and call processResponse. It doesn't
     // know or care how to handle the response, it only cares about the position and retries.
     private async syncLoop(pos?: number) {
@@ -298,6 +318,14 @@ export class Sync3 {
             }
             await syncTxn.complete(log);
 
+            // atomically move all the rooms to their new positions
+            this.roomIndexToRoomId = indexToRoom;
+            this.roomIdToRoomIndex = {};
+            Object.keys(indexToRoom).forEach((indexStr) => {
+                const index = Number(indexStr);
+                this.roomIdToRoomIndex[indexToRoom[index]] = index;
+            });
+
             // update in-memory structs
             // this.session.afterSync(); // ???
 
@@ -317,10 +345,6 @@ export class Sync3 {
                 }
             }), []);
         });
-
-
-        // instantly move all the rooms to their new positions
-        this.roomIndexToRoomId = indexToRoom;
     }
 
     // The purpose of this function is to process the response `ops` array by modifying the current
diff --git a/src/placeholder-rooms.html b/src/placeholder-rooms.html
index b97f6031..8056df73 100644
--- a/src/placeholder-rooms.html
+++ b/src/placeholder-rooms.html
@@ -104,6 +104,7 @@
                     navigation: navigation,
                     urlCreator: urlRouter,
                     platform: platform,
+                    compareFn: syncer.compare.bind(syncer),
                 });
                 leftPanel.loadRoomRange = async (range) => {
                     // pretend to load something