diff --git a/apps/desktop/src/main.tsx b/apps/desktop/src/main.tsx
index 159270c01664..343816b8e024 100644
--- a/apps/desktop/src/main.tsx
+++ b/apps/desktop/src/main.tsx
@@ -31,7 +31,16 @@ if (new URLSearchParams(window.location.search).get('win') === 'overlay') {
           <I18nProvider>
             <ThemeProvider>
               <HapticsProvider>
-                <HashRouter>
+                {/* useTransitions={false}: react-router v7's HashRouter wraps every
+                    route state update in React.startTransition() by default. In
+                    React 19's concurrent renderer, transitions are non-urgent — React
+                    can yield mid-render and resume later. When the app is under load
+                    (streaming token deltas, gateway events, store updates), those
+                    higher-priority updates keep interrupting the transition, starving
+                    the route change commit. The session sidebar highlight + main pane
+                    both freeze for seconds despite the main thread being free.
+                    Disabling transitions makes navigate() commit at default priority. */}
+                <HashRouter useTransitions={false}>
                   <App />
                 </HashRouter>
               </HapticsProvider>