diff --git a/crates/ui-egui/src/app/playback.rs b/crates/ui-egui/src/app/playback.rs
index 73e765ff7..c959829cd 100644
--- a/crates/ui-egui/src/app/playback.rs
+++ b/crates/ui-egui/src/app/playback.rs
@@ -144,6 +144,10 @@ impl SlideApp {
         let visible = show::viewport_visible(ctx);
         let Some(doc) = self.session.active().map(|d| d.doc.clone()) else { return };
         let Some(show) = self.show.as_mut() else { return };
+        if show.presenter_grid && self.services.presenter.as_ref().is_some_and(|host| !host.is_open()) {
+            // A web popup closed with its grid open must not hold auto-advance while this tab is hidden (#1866).
+            show.presenter_grid = false;
+        }
         if visible {
             // A visible logic-only pass (`run_logic`) carries the last full frame's input time.
             // Anchoring that stale time to `now` would move the hidden clock backwards if the
diff --git a/crates/ui-egui/src/presenter.rs b/crates/ui-egui/src/presenter.rs
index 5d99e63c8..a58878830 100644
--- a/crates/ui-egui/src/presenter.rs
+++ b/crates/ui-egui/src/presenter.rs
@@ -175,6 +175,10 @@ impl View {
                 .collect::<Vec<_>>()
         });
         for (key, modifiers) in keys {
+            if snapshot.grid && matches!(key, egui::Key::Space | egui::Key::Enter) {
+                // A focused thumbnail takes these to choose its slide; the show ignores them while the grid is open.
+                continue;
+            }
             // Consume once before widgets see Space/Enter, avoiding a second button activation.
             ui.input_mut(|i| i.consume_key(modifiers, key));
             commands.push(Command::Key {
@@ -525,6 +529,9 @@ mod tests {
         h.get_by_label("3").click();
         h.run_steps(2);
         assert_eq!(h.state().2, vec![Command::Goto { slide: 2 }]);
+        h.key_press(egui::Key::Enter);
+        h.run_steps(2);
+        assert!(!h.state().2.iter().any(|c| matches!(c, Command::Key { .. })), "Enter is left to the focused thumbnail");
     }
 
     #[test]