diff --git a/examples/companion_radio/main.cpp b/examples/companion_radio/main.cpp
index 9f3f9924..ffd1a4b8 100644
--- a/examples/companion_radio/main.cpp
+++ b/examples/companion_radio/main.cpp
@@ -466,6 +466,22 @@ extern "C" EMSCRIPTEN_KEEPALIVE int sim_test_set_timezone_hours(int hours) {
   return 1;
 }
 
+// auto_off_secs (NodePrefs.h) defaults to 15 -- a real device's screen
+// (and, if auto_lock is also set, the UI itself) turns off/locks 15s
+// after the last input, real power-saving behaviour a battery-powered
+// board actually needs. UITask::autoOffMillis() (ui-new/UITask.h) treats
+// 0 as "never" and skips the whole turnOff()/auto_lock branch in
+// UITask::loop() entirely -- there's no separate flag to touch. A demo
+// running on a visitor's screen has no battery to save and no reason to
+// go dark or lock itself while they're reading it.
+extern "C" EMSCRIPTEN_KEEPALIVE int sim_test_disable_screen_timeout() {
+  if (!g_sim_ready) return 0;
+  NodePrefs* prefs = the_mesh.getNodePrefs();
+  if (!prefs) return 0;
+  prefs->auto_off_secs = 0;
+  return 1;
+}
+
 #ifdef DISPLAY_CLASS
 // Jumps the on-device UI straight to the DM thread with the first known
 // ADV_TYPE_CHAT contact (UITask::openContactDM() -- the exact same real