[iOS][Android] Shell: Fix tab bar visibility and selection after first tab becomes invisible

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellItemRenderer.cs

@@ -456,7 +456,7 @@ _updateMenuItemSource is not null &&
 				}
 			}
 
-			if (DisplayedPage is null)
+			if (DisplayedPage is null && !_menuSetup)
 				return;
 
 			if (ShellItemController.ShowTabs)

src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemRenderer.cs

@@ -220,6 +220,9 @@ protected virtual void OnItemsCollectionChanged(object sender, NotifyCollectionC
 						RemoveRenderer(renderer);
 					}
 				}
+
+				// Recalculate IsInMoreTab for remaining renderers since tab positions shifted after removal.
+				UpdateIsInMoreTabForRenderers();
 			}
 
 			if (e.NewItems != null && e.NewItems.Count > 0)
@@ -324,6 +327,22 @@ void SetTabItemsEnabledState()
 			}
 		}
 
+		void UpdateIsInMoreTabForRenderers()
+		{
+			const int maxTabs = 5;
+			var currentViewControllers = ViewControllers;
+			if (currentViewControllers == null)
+				return;
+
+			bool willUseMore = currentViewControllers.Length > maxTabs;
+			for (int i = 0; i < currentViewControllers.Length; i++)
+			{
+				var renderer = RendererForViewController(currentViewControllers[i]);
+				if (renderer != null)
+					renderer.IsInMoreTab = willUseMore && i >= maxTabs - 1;
+			}
+		}
+
 		void CreateTabRenderers()
 		{
 			if (ShellItem.CurrentItem == null)

src/Controls/tests/TestCases.HostApp/Issues/Issue34343.cs

@@ -0,0 +1,146 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 34343, "TabBar displays wrong tabs after first tab becomes invisible", PlatformAffected.Android | PlatformAffected.iOS)]
+public class Issue34343 : Shell
+{
+	ContentPage _tab1Page;
+	public Issue34343()
+	{
+		Routing.RegisterRoute("Page51", typeof(Issue34343_Page51));
+
+		var tabBar = new TabBar();
+		var button = new Button
+		{
+			Text = "Hide Tab1 and Go to Tab5",
+			AutomationId = "HideAndNavigateButton",
+		};
+
+		_tab1Page = new ContentPage
+		{
+			Title = "Tab1",
+			Content = new VerticalStackLayout
+			{
+				Children = { button }
+			}
+		};
+
+		button.Clicked += async (s, e) =>
+		{
+			// Setting IsVisible = false on the page (as in the issue repro: "this.IsVisible = false")
+			_tab1Page.IsVisible = false;
+			await Shell.Current.GoToAsync("///Tab5");
+		};
+
+		var tab1Content = new ShellContent
+		{
+			Title = "Tab1",
+			Route = "Tab1",
+			Content = _tab1Page
+		};
+
+		var tab1 = new Tab { Title = "Tab1", AutomationId = "Tab1" };
+		tab1.Items.Add(tab1Content);
+		tabBar.Items.Add(tab1);
+
+		for (int i = 2; i <= 4; i++)
+		{
+			int tabNum = i;
+			var content = new ShellContent
+			{
+				Title = $"Tab{tabNum}",
+				Route = $"Tab{tabNum}",
+				ContentTemplate = new DataTemplate(() => new ContentPage
+				{
+					Title = $"Tab{tabNum}",
+					Content = new Label
+					{
+						Text = $"Tab{tabNum} Content",
+						AutomationId = $"Tab{tabNum}Content",
+						HorizontalOptions = LayoutOptions.Center,
+						VerticalOptions = LayoutOptions.Center
+					}
+				})
+			};
+			var tab = new Tab { Title = $"Tab{tabNum}", AutomationId = $"Tab{tabNum}" };
+			tab.Items.Add(content);
+			tabBar.Items.Add(tab);
+		}
+
+		// Tab 5 - has a button to navigate to Page51 (iOS repro: relative sub-page navigation)
+		var navigateToPage51Button = new Button
+		{
+			Text = "Navigate to Page51",
+			AutomationId = "NavigateToPage51Button",
+		};
+		navigateToPage51Button.Clicked += async (s, e) =>
+		{
+			await Shell.Current.GoToAsync("Page51");
+		};
+
+		var tab5Page = new ContentPage
+		{
+			Title = "Tab5",
+			Content = new VerticalStackLayout
+			{
+				VerticalOptions = LayoutOptions.Center,
+				Children =
+				{
+					new Label
+					{
+						Text = "Tab5 Content",
+						AutomationId = "Tab5Content",
+						HorizontalOptions = LayoutOptions.Center
+					},
+					navigateToPage51Button
+				}
+			}
+		};
+
+		var tab5Content = new ShellContent { Title = "Tab5", Route = "Tab5", Content = tab5Page };
+		var tab5 = new Tab { Title = "Tab5", AutomationId = "Tab5" };
+		tab5.Items.Add(tab5Content);
+		tabBar.Items.Add(tab5);
+
+		for (int i = 6; i <= 7; i++)
+		{
+			int tabNum = i;
+			var content = new ShellContent
+			{
+				Title = $"Tab{tabNum}",
+				Route = $"Tab{tabNum}",
+				ContentTemplate = new DataTemplate(() => new ContentPage
+				{
+					Title = $"Tab{tabNum}",
+					Content = new Label
+					{
+						Text = $"Tab{tabNum} Content",
+						AutomationId = $"Tab{tabNum}Content",
+						HorizontalOptions = LayoutOptions.Center,
+						VerticalOptions = LayoutOptions.Center
+					}
+				})
+			};
+			var tab = new Tab { Title = $"Tab{tabNum}", AutomationId = $"Tab{tabNum}" };
+			tab.Items.Add(content);
+			tabBar.Items.Add(tab);
+		}
+
+		Items.Add(tabBar);
+	}
+}
+
+// Sub-page navigated to from Tab5 (relative route "Page51")
+public class Issue34343_Page51 : ContentPage
+{
+	public Issue34343_Page51()
+	{
+		Title = "Page51";
+		Content = new Label
+		{
+			Text = "Page51 Content",
+			AutomationId = "Page51Content",
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue34343.cs

@@ -0,0 +1,37 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue34343 : _IssuesUITest
+{
+	public override string Issue => "TabBar displays wrong tabs after first tab becomes invisible";
+
+	public Issue34343(TestDevice device) : base(device) { }
+
+#if ANDROID
+	[Test]
+	[Category(UITestCategories.Shell)]
+	public void TabBarShouldDisplayCorrectTabsAfterFirstTabBecomesInvisible()
+	{
+		App.WaitForElement("HideAndNavigateButton");
+		App.Tap("HideAndNavigateButton");
+		App.WaitForElement("Tab5Content");
+		VerifyScreenshot();
+	}
+#endif
+
+#if IOS || MACCATALYST
+	[Test]
+	[Category(UITestCategories.Shell)]
+	public void SubPageNavigationShouldWorkAfterFirstTabBecomesInvisible()
+	{
+		App.WaitForElement("HideAndNavigateButton");
+		App.Tap("HideAndNavigateButton");
+		App.WaitForElement("Tab5Content");
+		App.Tap("NavigateToPage51Button");
+		VerifyScreenshot();
+	}
+#endif
+}