diff --git a/src/matrix/net/HomeServerApi.js b/src/matrix/net/HomeServerApi.js
index 308e71d9..91ffc97c 100644
--- a/src/matrix/net/HomeServerApi.js
+++ b/src/matrix/net/HomeServerApi.js
@@ -110,6 +110,10 @@ export class HomeServerApi {
         return this._get("/sync", {since, timeout, filter}, null, options);
     }
 
+    sync3(body, pos, timeout, options = null) {
+        return this._authedRequest("POST", this._url("/sync", "/_matrix/client/v3"), {timeout, pos}, body, options);
+    }
+
     // params is from, dir and optionally to, limit, filter.
     messages(roomId, params, options = null) {
         return this._get(`/rooms/${encodeURIComponent(roomId)}/messages`, params, null, options);
diff --git a/src/placeholder-rooms.html b/src/placeholder-rooms.html
index 5f0f305e..a4e7de46 100644
--- a/src/placeholder-rooms.html
+++ b/src/placeholder-rooms.html
@@ -11,6 +11,8 @@
         </style>
 	</head>
 	<body class="not-ie11">
+        <input id="tokeninput" type="password" placeholder="access_token"/>
+        <input id="tokensubmit" type="button" value="Start" />
         <div id="session-status" class="hydrogen" style="height: 500px;"></div>
         <script id="main" type="module">
             import {LeftPanelView} from "./platform/web/ui/session/leftpanel/LeftPanelView.js";
@@ -20,6 +22,8 @@
             import {parseUrlPath, stringifyPath} from "./domain/navigation/index.js";
             import {ObservableMap} from "./observable/index.js";
             import {History} from "./platform/web/dom/History.js";
+            import {HomeServerApi} from "./matrix/net/HomeServerApi.js";
+            import {xhrRequest} from "./platform/web/dom/request/xhr.js";
             const navigation = new Navigation(() => false);
             const rooms = new ObservableMap();
             for (let i = 0; i < 1000; i++) {
@@ -65,6 +69,41 @@
             };
             const view = new LeftPanelView(leftPanel);
             document.getElementById("session-status").appendChild(view.mount());
+
+
+            document.getElementById("tokensubmit").addEventListener("click", () => {
+                const accessToken = document.getElementById("tokeninput").value;
+                const sessionId = new Date().getTime() + "";
+                const hs = new HomeServerApi({
+                    homeserver: "http://localhost:8008",
+                    accessToken: accessToken,
+                    request: xhrRequest,
+                });
+
+                const loop = async () => {
+                    let pos;
+                    while (true) {
+                        let req = hs.sync3({
+                            session_id: sessionId,
+                            lists: [{
+                                rooms: [ [0,99] ],
+                                // TODO: only send these the first time.
+                                sort: ["by_highlight_count", "by_notification_count", "by_recency"],
+                                timeline_limit: 20,
+                                required_state: [
+                                    ["m.room.avatar", ""],
+                                ]
+                            }],
+                        }, pos, 10);
+                        const resp = await req.response();
+                        console.log(resp);
+                        pos = resp.pos;
+                        await sleep(100);
+                    }
+                }
+                loop();
+            });
+
         </script>
 	</body>
 </html>
