diff --git a/src/views/tinode-web.jsx b/src/views/tinode-web.jsx
index 1c95690e..643d5680 100644
--- a/src/views/tinode-web.jsx
+++ b/src/views/tinode-web.jsx
@@ -800,7 +800,18 @@ class TinodeWeb extends React.Component {
       // Topic for MessagesView selector.
       let topicName = hash.path[1] || null;
       if (topicName != this.state.topicSelected) {
-        if (!Tinode.topicType(topicName)) {
+        // A syntactically valid topic name is not enough on its own: mobilePanel='topic-view' only
+        // ever pairs correctly with MessagesView actually being allowed to render, which requires
+        // !chapterOneActive (i.e. this.tinode.isAuthenticated()) -- see tinode-web.jsx's render().
+        // Without this check, opening (or being redirected/deep-linked to) a #/<topic> URL while
+        // logged out set mobilePanel to 'topic-view' anyway; on mobile that made *both* the
+        // SidepanelView gate (`mobilePanel=='sidepanel'`) and the MessagesView gate
+        // (`!chapterOneActive`) false at once, so neither rendered -- a permanently blank white
+        // screen (app-container empty, no thrown error) that a hash change alone couldn't recover
+        // from, only a full reload. Reproduced live: logging out, then setting location.hash to a
+        // real group's `#/<topic>` URL. Falling back to the same "invalid topic" branch already used
+        // for a malformed name reuses a path already proven safe with topicName=null.
+        if (!Tinode.topicType(topicName) || !this.tinode.isAuthenticated()) {
           // Clear invalid topic name and hide messages view on mobile.
           topicName = null;
           newState.mobilePanel = 'sidepanel';