diff --git a/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs b/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs
index 6a9a03d..712f89a 100644
--- a/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs
+++ b/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs
@@ -501,6 +501,27 @@ public sealed class ParticipantViewModel : ObservableObject
                 IsEnabled = true;
             }
         }
+        catch (InvalidOperationException)
+        {
+            // Race window: participant left the meeting between when the operator
+            // clicked Enable/Disable and when the engine resolved the ID. The
+            // controller throws InvalidOperationException with a "not currently
+            // visible on the network" message in this case. Surface it as a soft
+            // warning toast rather than letting it escape into the dispatcher's
+            // unhandled-exception channel (which fires a fatal crash dialog).
+            //
+            // Leave IsEnabled at its current value — the engine refused the state
+            // change, so the VM should reflect the actual engine state.
+            _toast?.Warn($"{DisplayName} just left the meeting");
+        }
+        catch (Exception ex)
+        {
+            // Defensive catch-all for any other engine-side failure (port bind
+            // race, pipeline factory throw, etc.). Same reasoning as above —
+            // an exception from an operator click should never tear down the
+            // dispatcher.
+            _toast?.Warn($"Couldn't toggle ISO for {DisplayName}: {ex.Message}");
+        }
         finally
         {
             IsProcessing = false;