diff --git a/src/domain/session/leftpanel/LeftPanelViewModel.js b/src/domain/session/leftpanel/LeftPanelViewModel.js
index 9e37a05e..04d8c2a5 100644
--- a/src/domain/session/leftpanel/LeftPanelViewModel.js
+++ b/src/domain/session/leftpanel/LeftPanelViewModel.js
@@ -43,7 +43,7 @@ export class LeftPanelViewModel extends ViewModel {
     }
 
     _mapTileViewModels(list) {
-        return new MappedList(list, (roomOrInvite, emitChange) => {
+        const mapper = (roomOrInvite, emitChange) => {
             let vm;
             if (roomOrInvite === null) {
                 vm = new PlaceholderRoomTileViewModel(this.childOptions({room: null, emitChange}));
@@ -64,7 +64,11 @@ export class LeftPanelViewModel extends ViewModel {
                 }
             }
             return vm;
-        });
+        };
+        const updater = (tileViewModel, noIdea, roomOrInvite) => {
+            return mapper(roomOrInvite);
+        }
+        return new MappedList(list, mapper, updater);
     }
 
     _updateCurrentVM(vm) {
diff --git a/src/matrix/Sync3ObservableList.ts b/src/matrix/Sync3ObservableList.ts
index 70028a08..25921597 100644
--- a/src/matrix/Sync3ObservableList.ts
+++ b/src/matrix/Sync3ObservableList.ts
@@ -17,12 +17,14 @@ limitations under the License.
 import * as assert from "assert";
 import { BaseObservableList } from "../observable/list/BaseObservableList";
 import { ObservableMap } from "../observable/map/ObservableMap.js";
+import { SubscriptionHandle } from "../observable/BaseObservable";
 import { Room } from "./room/Room.js";
 
 // subset of Sync3 functions used in this list; interfaced out for testing
 interface ISync {
     count(): number;
     roomAtIndex(i: number): string
+    indexOfRoom(roomId: string): number
 }
 
 /**
@@ -31,6 +33,7 @@ interface ISync {
 export class Sync3ObservableList extends BaseObservableList<Room | null> {
     sync: ISync;
     rooms: ObservableMap;
+    subscription: SubscriptionHandle | null;
 
     /**
      * Construct an observable list that produces Rooms within the sliding window of Sync3 responses
@@ -41,9 +44,40 @@ export class Sync3ObservableList extends BaseObservableList<Room | null> {
     constructor(sync3: ISync, rooms: ObservableMap) {
         super();
         this.sync = sync3;
+        this.subscription = null;
         this.rooms = rooms;
     }
 
+    onSubscribeFirst() {
+        this.subscription = this.rooms.subscribe(this);
+    }
+
+    onUnsubscribeLast() {
+        if (!this.subscription) {
+            return;
+        }
+        this.subscription();
+        this.subscription = null;
+    }
+
+    onAdd(index, entry) {
+        let i = this.sync.indexOfRoom(entry.id);
+        this.emitUpdate(i, entry); // we always emit updates as we have num_joined_rooms entries (placeholders)
+    }
+
+    onUpdate(index, entry, params) {
+        let i = this.sync.indexOfRoom(entry.id);
+        if (i === -1) {
+            return;
+        }
+        this.emitUpdate(i, entry); // we always emit updates as we have num_joined_rooms entries (placeholders)
+    }
+
+    onRemove(index, entry) {
+        let i = this.sync.indexOfRoom(entry.id);
+        this.emitUpdate(i, entry); // we always emit updates as we have num_joined_rooms entries (placeholders)
+    }
+
     get length(): number {
         return this.sync.count();
     }
@@ -120,6 +154,15 @@ export function tests() {
                 roomAtIndex: (i: number): string => {
                     return indexToRoomId[i];
                 },
+                indexOfRoom(roomId: string): number {
+                    for (let i of Object.keys(indexToRoomId)) {
+                        let r = indexToRoomId[i];
+                        if (r === roomId) {
+                            return Number(i);
+                        }
+                    }
+                    return -1;
+                }
             };
 
             makeRooms(100).forEach((r) => {
diff --git a/src/observable/list/BaseMappedList.ts b/src/observable/list/BaseMappedList.ts
index 4e3d05e0..6794d1a7 100644
--- a/src/observable/list/BaseMappedList.ts
+++ b/src/observable/list/BaseMappedList.ts
@@ -15,21 +15,21 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableList} from "./BaseObservableList";
-import {findAndUpdateInArray} from "./common";
+import { BaseObservableList } from "./BaseObservableList";
+import { findAndUpdateInArray } from "./common";
 
-export type Mapper<F,T> = (value: F) => T
-export type Updater<F,T> = (mappedValue: T, params: any, value: F) => void;
+export type Mapper<F, T> = (value: F) => T
+export type Updater<F, T> = (mappedValue: T, params: any, value: F) => void;
 
-export class BaseMappedList<F,T,R = T> extends BaseObservableList<T> {
+export class BaseMappedList<F, T, R = T> extends BaseObservableList<T> {
     protected _sourceList: BaseObservableList<F>;
     protected _sourceUnsubscribe: (() => void) | null = null;
-    _mapper: Mapper<F,R>;
-    _updater?: Updater<F,T>;
+    _mapper: Mapper<F, R>;
+    _updater?: Updater<F, T>;
     _removeCallback?: (value: T) => void;
     _mappedValues: T[] | null = null;
 
-    constructor(sourceList: BaseObservableList<F>, mapper: Mapper<F,R>, updater?: Updater<F,T>, removeCallback?: (value: T) => void) {
+    constructor(sourceList: BaseObservableList<F>, mapper: Mapper<F, R>, updater?: Updater<F, T>, removeCallback?: (value: T) => void) {
         super();
         this._sourceList = sourceList;
         this._mapper = mapper;
@@ -50,12 +50,12 @@ export class BaseMappedList<F,T,R = T> extends BaseObservableList<T> {
     }
 }
 
-export function runAdd<F,T,R>(list: BaseMappedList<F,T,R>, index: number, mappedValue: T): void {
+export function runAdd<F, T, R>(list: BaseMappedList<F, T, R>, index: number, mappedValue: T): void {
     list._mappedValues!.splice(index, 0, mappedValue);
     list.emitAdd(index, mappedValue);
 }
 
-export function runUpdate<F,T,R>(list: BaseMappedList<F,T,R>, index: number, value: F, params: any): void {
+export function runUpdate<F, T, R>(list: BaseMappedList<F, T, R>, index: number, value: F, params: any): void {
     const mappedValue = list._mappedValues![index];
     if (list._updater) {
         list._updater(mappedValue, params, value);
@@ -63,7 +63,7 @@ export function runUpdate<F,T,R>(list: BaseMappedList<F,T,R>, index: number, val
     list.emitUpdate(index, mappedValue, params);
 }
 
-export function runRemove<F,T,R>(list: BaseMappedList<F,T,R>, index: number): void {
+export function runRemove<F, T, R>(list: BaseMappedList<F, T, R>, index: number): void {
     const mappedValue = list._mappedValues![index];
     list._mappedValues!.splice(index, 1);
     if (list._removeCallback) {
@@ -72,14 +72,14 @@ export function runRemove<F,T,R>(list: BaseMappedList<F,T,R>, index: number): vo
     list.emitRemove(index, mappedValue);
 }
 
-export function runMove<F,T,R>(list: BaseMappedList<F,T,R>, fromIdx: number, toIdx: number): void {
+export function runMove<F, T, R>(list: BaseMappedList<F, T, R>, fromIdx: number, toIdx: number): void {
     const mappedValue = list._mappedValues![fromIdx];
     list._mappedValues!.splice(fromIdx, 1);
     list._mappedValues!.splice(toIdx, 0, mappedValue);
     list.emitMove(fromIdx, toIdx, mappedValue);
 }
 
-export function runReset<F,T,R>(list: BaseMappedList<F,T,R>): void {
+export function runReset<F, T, R>(list: BaseMappedList<F, T, R>): void {
     list._mappedValues = [];
     list.emitReset();
 }
diff --git a/src/observable/list/ConcatList.ts b/src/observable/list/ConcatList.ts
index 5822468a..7d9676c9 100644
--- a/src/observable/list/ConcatList.ts
+++ b/src/observable/list/ConcatList.ts
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableList, IListObserver} from "./BaseObservableList";
+import { BaseObservableList, IListObserver } from "./BaseObservableList";
 
 export class ConcatList<T> extends BaseObservableList<T> implements IListObserver<T> {
     protected _sourceLists: BaseObservableList<T>[];
@@ -50,7 +50,7 @@ export class ConcatList<T> extends BaseObservableList<T> implements IListObserve
         // reset, and 
         this.emitReset();
         let idx = 0;
-        for(const item of this) {
+        for (const item of this) {
             this.emitAdd(idx, item);
             idx += 1;
         }
@@ -106,8 +106,8 @@ export class ConcatList<T> extends BaseObservableList<T> implements IListObserve
     }
 }
 
-import {ObservableArray} from "./ObservableArray";
-import {defaultObserverWith} from "./BaseObservableList";
+import { ObservableArray } from "./ObservableArray";
+import { defaultObserverWith } from "./BaseObservableList";
 export async function tests() {
     return {
         test_length(assert) {