Desktop: rebuild the hosts board once the typing in the find box pauses, not once a letter

src/DodoSSH.Client.App/Views/HetznerImportScreen.axaml

@@ -253,8 +253,20 @@
               </Grid>
             </Border>
 
-            <ScrollViewer Grid.Row="1">
-              <ItemsControl ItemsSource="{Binding Rows}" Margin="12,8">
+            <!-- Virtualised, for an inventory of hundreds of machines: see the transfer queue's own note. -->
+            <ItemsControl Grid.Row="1" ItemsSource="{Binding Rows}">
+              <ItemsControl.Template>
+                <ControlTemplate>
+                  <ScrollViewer>
+                    <ItemsPresenter Name="PART_ItemsPresenter" ItemsPanel="{TemplateBinding ItemsPanel}" Margin="12,8" />
+                  </ScrollViewer>
+                </ControlTemplate>
+              </ItemsControl.Template>
+              <ItemsControl.ItemsPanel>
+                <ItemsPanelTemplate>
+                  <VirtualizingStackPanel />
+                </ItemsPanelTemplate>
+              </ItemsControl.ItemsPanel>
                 <ItemsControl.ItemTemplate>
                   <DataTemplate x:DataType="vm:HetznerRowViewModel">
                     <Border Classes="importrow" CornerRadius="8">
@@ -290,8 +302,7 @@
                     </Border>
                   </DataTemplate>
                 </ItemsControl.ItemTemplate>
-              </ItemsControl>
-            </ScrollViewer>
+            </ItemsControl>
 
           </Grid>
         </Border>

src/DodoSSH.Client.App/Views/HostsScreen.axaml

@@ -230,9 +230,13 @@
 
         Ctrl+K is named on it because the palette is the other way to reach a host by typing, and somebody
         who has found this box should know about the one that also connects on Enter.
+
+        One way, and passed back by the code-behind once the typing pauses: every change to the filter
+        rebuilds the board's sections and their cards, and a name typed at speed used to do that once a
+        letter. The view model still filters the moment it is told. See HostsScreen.OnFilterTyped.
       -->
       <Border Grid.Row="1" Margin="26,0,26,16">
-        <TextBox x:Name="HostFilter" Text="{Binding HostFilter}" Height="40" CornerRadius="10"
+        <TextBox x:Name="HostFilter" Text="{Binding HostFilter, Mode=OneWay}" Height="40" CornerRadius="10"
                  FontFamily="{StaticResource MonoFont}"
                  PlaceholderText="Find a host by name, address or note…   ·   Ctrl+K searches and connects" />
       </Border>

src/DodoSSH.Client.App/Views/HostsScreen.axaml.cs

@@ -106,6 +106,48 @@ internal sealed partial class HostsScreen : UserControl
         Board.AddHandler(ContextRequestedEvent, OnContextRequested, RoutingStrategies.Tunnel);
 
         WireTheBand();
+
+        HostFilter.TextChanged += OnFilterTyped;
+    }
+
+    /// <summary>How long the find box waits for the typing to pause before the board is rebuilt.</summary>
+    private static readonly TimeSpan FilterPause = TimeSpan.FromMilliseconds(150);
+
+    /// <summary>The wait itself, replaceable so a test can say when a pause is over rather than sleep through one.</summary>
+    internal Func<TimeSpan, Task> Pause { get; set; } = static span => Task.Delay(span);
+
+    /// <summary>How many times the find box has changed, so a wait can tell it is no longer the latest.</summary>
+    private int typed;
+
+    /// <summary>Hands the find box's text to the vault once the typing pauses.</summary>
+    /// <remarks>
+    /// <para>
+    /// Every change to the filter rebuilds the board's sections and every card in them, and a name typed at
+    /// speed used to do that once a letter. Now it is done once, with the whole of what was typed.
+    /// </para>
+    /// <para>
+    /// A wait rather than a binding delay, and on the dispatcher's own queue: the box is bound one way, so a
+    /// filter the vault sets itself — cleared, or restored — still lands in the box at once, and the
+    /// change it makes to the box comes back here as the same text, which changes nothing.
+    /// </para>
+    /// </remarks>
+    private void OnFilterTyped(object? sender, TextChangedEventArgs e) =>
+        _ = PassTheFilterOnAsync(HostFilter.Text ?? string.Empty, ++typed);
+
+    private async Task PassTheFilterOnAsync(string text, int keystroke)
+    {
+        await Pause(FilterPause).ConfigureAwait(true);
+
+        // A later letter has its own wait, and it is the one that speaks.
+        if (keystroke != typed)
+        {
+            return;
+        }
+
+        if (Vault is { } vault && !string.Equals(vault.HostFilter, text, StringComparison.Ordinal))
+        {
+            vault.HostFilter = text;
+        }
     }
 
     /// <summary>The band's own wiring, and the two keys that go with a set.</summary>

src/DodoSSH.Client.App/Views/ImportScreen.axaml

@@ -131,8 +131,20 @@
           </Grid>
         </Border>
 
-        <ScrollViewer Grid.Row="1">
-          <ItemsControl ItemsSource="{Binding Rows}" Margin="12,8">
+        <!-- Virtualised, for an inventory of hundreds of machines: see the transfer queue's own note. -->
+        <ItemsControl Grid.Row="1" ItemsSource="{Binding Rows}">
+          <ItemsControl.Template>
+            <ControlTemplate>
+              <ScrollViewer>
+                <ItemsPresenter Name="PART_ItemsPresenter" ItemsPanel="{TemplateBinding ItemsPanel}" Margin="12,8" />
+              </ScrollViewer>
+            </ControlTemplate>
+          </ItemsControl.Template>
+          <ItemsControl.ItemsPanel>
+            <ItemsPanelTemplate>
+              <VirtualizingStackPanel />
+            </ItemsPanelTemplate>
+          </ItemsControl.ItemsPanel>
             <ItemsControl.ItemTemplate>
               <DataTemplate x:DataType="vm:ImportRowViewModel">
                 <Border Classes="importrow" CornerRadius="8">
@@ -161,8 +173,7 @@
                 </Border>
               </DataTemplate>
             </ItemsControl.ItemTemplate>
-          </ItemsControl>
-        </ScrollViewer>
+        </ItemsControl>
 
       </Grid>
     </Border>

src/DodoSSH.Client.App/Views/TransfersScreen.axaml

@@ -1190,8 +1190,24 @@
                      Text="{Binding Status}" IsVisible="{Binding IsConnected}" />
         </Grid>
 
-        <ScrollViewer Grid.Row="2">
-          <ItemsControl ItemsSource="{Binding Transfers}">
+        <!--
+          Virtualised: a folder download queues a row per file, and a stack panel inside an outer scroller
+          laid out and drew every one of them, thousands deep. The scroller is the control's own so the panel
+          knows the viewport it has to fill and realises only those rows.
+        -->
+        <ItemsControl Grid.Row="2" ItemsSource="{Binding Transfers}">
+            <ItemsControl.Template>
+              <ControlTemplate>
+                <ScrollViewer>
+                  <ItemsPresenter Name="PART_ItemsPresenter" ItemsPanel="{TemplateBinding ItemsPanel}" />
+                </ScrollViewer>
+              </ControlTemplate>
+            </ItemsControl.Template>
+            <ItemsControl.ItemsPanel>
+              <ItemsPanelTemplate>
+                <VirtualizingStackPanel />
+              </ItemsPanelTemplate>
+            </ItemsControl.ItemsPanel>
             <ItemsControl.ItemTemplate>
               <DataTemplate x:DataType="vm:TransferRowViewModel">
                 <!--
@@ -1239,7 +1255,6 @@
               </DataTemplate>
             </ItemsControl.ItemTemplate>
           </ItemsControl>
-        </ScrollViewer>
 
         <Button Grid.Row="3" Classes="ghost" Content="CLEAR FINISHED" Margin="0,10,0,0"
                 HorizontalAlignment="Left" Command="{Binding ClearCompletedCommand}" />

src/DodoSSH.Client.Shell/ViewModels/ReplaceableCollection.cs

@@ -0,0 +1,44 @@
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
+
+namespace DodoSSH.Client.Shell.ViewModels;
+
+/// <summary>
+/// An observable list whose whole contents can be swapped and announced once.
+/// </summary>
+/// <remarks>
+/// <para>
+/// For the lists rebuilt wholesale from the vault. They used to be emptied with <c>Clear</c> and refilled an
+/// <c>Add</c> at a time, which announced every row separately — and two other view models listen to the host
+/// list and redo their own work on every announcement: the transfers screen refilled its host picker, and the
+/// shell walked every host against every tab. A reload of n hosts was n of each, so roughly n² rows touched;
+/// three hundred hosts came to some ninety thousand notifications per reload.
+/// </para>
+/// <para>
+/// One <see cref="NotifyCollectionChangedAction.Reset"/> instead, which is also exactly what <c>Clear</c> has
+/// always said first, so a listener that coped with the old sequence copes with this. Nothing listening to
+/// these lists reads the items an announcement carries; they all re-read the list.
+/// </para>
+/// </remarks>
+internal sealed class ReplaceableCollection<T> : ObservableCollection<T>
+{
+    /// <summary>Makes <paramref name="items"/> the whole of the list, and says so once.</summary>
+    internal void ReplaceAll(IEnumerable<T> items)
+    {
+        ArgumentNullException.ThrowIfNull(items);
+
+        CheckReentrancy();
+
+        Items.Clear();
+
+        foreach (var item in items)
+        {
+            Items.Add(item);
+        }
+
+        OnPropertyChanged(new PropertyChangedEventArgs(nameof(Count)));
+        OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
+        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+    }
+}

src/DodoSSH.Client.Shell/ViewModels/TransfersViewModel.cs

@@ -867,14 +867,14 @@ internal sealed partial class TransfersViewModel : ObservableObject, IAsyncDispo
     /// not this object's to clear. The rows are shared: they carry the decrypted host, and copying that would
     /// be a second decrypted copy of a secret for no gain.
     /// </remarks>
-    internal ObservableCollection<HostRowViewModel> Hosts { get; } = [];
+    internal ReplaceableCollection<HostRowViewModel> Hosts { get; } = [];
 
     [ObservableProperty]
     private HostRowViewModel? selectedHost;
 
     /// <summary>The buckets that can be browsed, which is the vault's list.</summary>
     /// <inheritdoc cref="Hosts" path="/remarks" />
-    internal ObservableCollection<ObjectStoreRowViewModel> Buckets { get; } = [];
+    internal ReplaceableCollection<ObjectStoreRowViewModel> Buckets { get; } = [];
 
     [ObservableProperty]
     private ObjectStoreRowViewModel? selectedBucket;
@@ -3986,7 +3986,21 @@ internal sealed partial class TransfersViewModel : ObservableObject, IAsyncDispo
         }
     }
 
-    private void OnVaultListChanged(object? sender, NotifyCollectionChangedEventArgs e) => RefreshHosts();
+    /// <remarks>
+    /// Only the picker the list feeds. Refilling both on either list's change made every reload refill the host
+    /// picker once for the hosts and again for the buckets.
+    /// </remarks>
+    private void OnVaultListChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        if (vault is { } open && ReferenceEquals(sender, open.ObjectStores))
+        {
+            RefreshPickers(hosts: false, buckets: true);
+        }
+        else
+        {
+            RefreshPickers(hosts: true, buckets: false);
+        }
+    }
 
     /// <summary>
     /// Rebuilds both pickers from the vault's lists.
@@ -4004,34 +4018,34 @@ internal sealed partial class TransfersViewModel : ObservableObject, IAsyncDispo
     /// connected to.
     /// </para>
     /// </remarks>
-    private void RefreshHosts()
+    private void RefreshHosts() => RefreshPickers(hosts: true, buckets: true);
+
+    private void RefreshPickers(bool hosts, bool buckets)
     {
         refreshingPickers = true;
 
         try
         {
-            Hosts.Clear();
-
             if (vault is not { } open)
             {
+                Hosts.ReplaceAll([]);
                 return;
             }
 
-            foreach (var row in open.Hosts)
+            if (hosts)
             {
-                Hosts.Add(row);
+                Hosts.ReplaceAll(open.Hosts);
+
+                SelectedHost = Hosts.FirstOrDefault(row => row.EntityId == chosenHost) ?? Hosts.FirstOrDefault();
             }
 
-            SelectedHost = Hosts.FirstOrDefault(row => row.EntityId == chosenHost) ?? Hosts.FirstOrDefault();
-
-            Buckets.Clear();
-
-            foreach (var row in open.ObjectStores)
+            if (buckets)
             {
-                Buckets.Add(row);
-            }
+                Buckets.ReplaceAll(open.ObjectStores);
 
-            SelectedBucket = Buckets.FirstOrDefault(row => row.EntityId == chosenBucket) ?? Buckets.FirstOrDefault();
+                SelectedBucket =
+                    Buckets.FirstOrDefault(row => row.EntityId == chosenBucket) ?? Buckets.FirstOrDefault();
+            }
         }
         finally
         {

src/DodoSSH.Client.Shell/ViewModels/VaultViewModel.cs

@@ -1663,7 +1663,7 @@ internal sealed partial class VaultViewModel(
     /// host key list checks itself against, so a filter applied here would change what the application can
     /// do rather than what it shows. <see cref="VisibleHosts"/> is the filtered view.
     /// </remarks>
-    internal ObservableCollection<HostRowViewModel> Hosts { get; } = [];
+    internal ReplaceableCollection<HostRowViewModel> Hosts { get; } = [];
 
     /// <summary>The hosts the grid is showing: one level of the group tree, narrowed by the box.</summary>
     /// <remarks>
@@ -1677,7 +1677,7 @@ internal sealed partial class VaultViewModel(
     /// alone: the phone draws <see cref="SidebarRows"/>, which is the same hosts flattened under headings.
     /// </para>
     /// </remarks>
-    internal ObservableCollection<HostRowViewModel> VisibleHosts { get; } = [];
+    internal ReplaceableCollection<HostRowViewModel> VisibleHosts { get; } = [];
 
     /// <summary>Whether the grid has anything to draw.</summary>
     /// <remarks>
@@ -1891,7 +1891,7 @@ internal sealed partial class VaultViewModel(
     /// groupless keychain is one flat grid and nothing above it.
     /// </para>
     /// </remarks>
-    internal ObservableCollection<HostSectionViewModel> HostSections { get; } = [];
+    internal ReplaceableCollection<HostSectionViewModel> HostSections { get; } = [];
 
     /// <summary>Every host on the board, in the order its cards are drawn — every section, one after another.</summary>
     /// <remarks>
@@ -2003,7 +2003,7 @@ internal sealed partial class VaultViewModel(
     internal ObservableCollection<CredentialRowViewModel> Credentials { get; } = [];
 
     /// <summary>The buckets to show, unpushed local state included.</summary>
-    internal ObservableCollection<ObjectStoreRowViewModel> ObjectStores { get; } = [];
+    internal ReplaceableCollection<ObjectStoreRowViewModel> ObjectStores { get; } = [];
 
     /// <summary>The tags to show, with the number of hosts wearing each.</summary>
     /// <remarks>
@@ -4714,18 +4714,14 @@ internal sealed partial class VaultViewModel(
 
         var (rows, unreadable) = await FetchHostRowsAsync(cancellationToken).ConfigureAwait(true);
 
-        Hosts.Clear();
-
         // Grouped by vault, with the one new items go into first, then by name inside each. Two vaults can
         // hold a host with the same label and both are shown: which vault it is in is what tells them
-        // apart, which is why the row carries the name rather than the list deduplicating.
-        foreach (var host in rows
+        // apart, which is why the row carries the name rather than the list deduplicating. Swapped in whole,
+        // and announced once: see ReplaceableCollection for what a row at a time cost.
+        Hosts.ReplaceAll(rows
             .OrderByDescending(row => row.VaultId == session.ActiveVaultId)
             .ThenBy(row => row.VaultName, StringComparer.CurrentCulture)
-            .ThenBy(row => row.Label, StringComparer.CurrentCulture))
-        {
-            Hosts.Add(host);
-        }
+            .ThenBy(row => row.Label, StringComparer.CurrentCulture));
 
         SelectedHost = SelectionAfterReload(selectedId);
         ApplyTheChosenHosts();
@@ -4816,13 +4812,9 @@ internal sealed partial class VaultViewModel(
 
         var selectedId = SelectedObjectStore?.EntityId;
 
-        ObjectStores.Clear();
-
-        foreach (var store in listing.Items
-            .OrderBy(store => store.Secret.Label, StringComparer.CurrentCulture))
-        {
-            ObjectStores.Add(new ObjectStoreRowViewModel(store));
-        }
+        ObjectStores.ReplaceAll(listing.Items
+            .OrderBy(store => store.Secret.Label, StringComparer.CurrentCulture)
+            .Select(store => new ObjectStoreRowViewModel(store)));
 
         SelectedObjectStore = ObjectStores.FirstOrDefault(row => row.EntityId == selectedId);
 
@@ -5388,12 +5380,7 @@ internal sealed partial class VaultViewModel(
         // a walk up the group tree, and this is the map that walk is made against.
         var parents = EffectiveParents();
 
-        VisibleHosts.Clear();
-
-        foreach (var host in Hosts.Where(host => Matches(host, parents)))
-        {
-            VisibleHosts.Add(host);
-        }
+        VisibleHosts.ReplaceAll(Hosts.Where(host => Matches(host, parents)));
 
         RebuildSidebarRows();
 
@@ -5403,7 +5390,7 @@ internal sealed partial class VaultViewModel(
         // property directly, and a host that is not on screen is not one any of them should act on.
         SelectedHost = selected is not null && VisibleHosts.Contains(selected) ? selected : null;
 
-        // After the host selection, not before: this mirrors it, and the ListBox's own answer to the Clear()
+        // After the host selection, not before: this mirrors it, and the ListBox's own answer to the reset
         // above is a null that has to be overwritten rather than read.
         SelectedSidebarRow = SelectedHost;
 
@@ -5473,12 +5460,7 @@ internal sealed partial class VaultViewModel(
     /// </remarks>
     private void RebuildHostSections()
     {
-        HostSections.Clear();
-
-        foreach (var built in BuildHostSections())
-        {
-            HostSections.Add(built);
-        }
+        HostSections.ReplaceAll(BuildHostSections());
 
         // Computed rather than stored, and none of the four has a change notification of its own — the same
         // arrangement RebuildVisibleHosts holds for HasVisibleHosts and NoVisibleHostsMessage, and for the

tests/DodoSSH.Client.App.Layout.Tests/HostGridTests.cs

@@ -520,6 +520,53 @@ public sealed class HostGridTests : IAsyncLifetime
         });
     }
 
+    /// <remarks>
+    /// Every change to the filter rebuilds the board's sections and every card in them, and a name typed at
+    /// speed used to do that once a letter. The box now tells the vault once the typing pauses — and then
+    /// exactly once, with the whole of what was typed.
+    /// </remarks>
+    [Fact]
+    public async Task TypingIntoTheFindBox_RebuildsTheBoardOnceThePauseComes_NotOnceALetter()
+    {
+        await OnTheBoardAsync((screen, _) =>
+        {
+            // Each letter's wait, ended by hand: the pause is real time in the application, and this says
+            // when it is over instead of sleeping through it.
+            var pauses = new List<TaskCompletionSource>();
+
+            screen.Pause = _ =>
+            {
+                var pause = new TaskCompletionSource();
+                pauses.Add(pause);
+                return pause.Task;
+            };
+
+            var rebuilds = 0;
+            vault.HostSections.CollectionChanged += (_, _) => rebuilds++;
+
+            var box = screen.FindControl<TextBox>("HostFilter").ShouldNotBeNull();
+
+            box.Text = "p";
+            box.Text = "pr";
+            box.Text = "pro";
+            Dispatcher.UIThread.RunJobs();
+
+            vault.HostFilter.ShouldBeNullOrEmpty("nothing has reached the vault while the typing goes on");
+            rebuilds.ShouldBe(0);
+
+            foreach (var pause in pauses)
+            {
+                pause.SetResult();
+            }
+
+            Dispatcher.UIThread.RunJobs();
+
+            vault.HostFilter.ShouldBe("pro");
+            rebuilds.ShouldBe(1, "only the last letter's wait passes the text on");
+            vault.VisibleHosts.ShouldHaveSingleItem().Label.ShouldBe("prod-db");
+        });
+    }
+
     // ---- Helpers ----
 
     private static void RightClick(Visual card, Visual window)

tests/DodoSSH.Client.App.Layout.Tests/ScreenLayoutTests.cs

@@ -1386,6 +1386,48 @@ public sealed class ScreenLayoutTests : IAsyncLifetime
         await MeasureTransfersAsync(faults => faults.ShouldBeEmpty());
     }
 
+    /// <remarks>
+    /// A folder download queues a row per file. The queue was a plain stack inside an outer scroller, which
+    /// measured and drew every row however deep — so the number of rows built here is the claim, not the
+    /// layout: a few screens' worth out of two thousand.
+    /// </remarks>
+    [Fact]
+    public async Task ADeepQueue_BuildsOnlyTheRowsOnScreen()
+    {
+        transfers.IsConnected = true;
+
+        for (var file = 0; file < 2000; file++)
+        {
+            Enqueue(TransferDirection.Download, $"asset-{file:0000}.png", 4096, 0, TransferState.Queued);
+        }
+
+        await LayoutHarness.OnTheUiThreadAsync(
+            () =>
+            {
+                var screen = new TransfersScreen { DataContext = transfers };
+
+                var window = LayoutHarness.HostAtMinimumSize(
+                    screen,
+                    LayoutHarness.SessionScreenWidth(transfers.IsConnected),
+                    LayoutHarness.SessionScreenHeight);
+
+                try
+                {
+                    var built = screen.GetVisualDescendants()
+                        .OfType<ProgressBar>()
+                        .Count(bar => bar.Classes.Contains("transferbar"));
+
+                    built.ShouldBeGreaterThan(0, "the rows on screen are still drawn");
+                    built.ShouldBeLessThan(200, "the rest of the two thousand are not");
+                }
+                finally
+                {
+                    window.Close();
+                }
+            },
+            Token);
+    }
+
     /// <remarks>
     /// The edit strip, which shares the questions' Grid row and is the tallest thing that can be in it: a
     /// heading, a path, a scrolling log of saves, the conflict card and a button. Its log is bounded for the
@@ -1632,11 +1674,24 @@ public sealed class ScreenLayoutTests : IAsyncLifetime
 
                 try
                 {
-                    var words = screen.GetVisualDescendants()
-                        .OfType<TextBlock>()
-                        .Where(text => text.Classes.Contains("transferstatus"))
-                        .Select(text => text.Text ?? string.Empty)
-                        .ToList();
+                    // Row by row, scrolled to: the queue is virtualised, so a row off the bottom of the strip is
+                    // not built until it is scrolled to — see ADeepQueue_BuildsOnlyTheRowsOnScreen.
+                    var queue = screen.GetVisualDescendants().OfType<ItemsControl>()
+                        .First(control => ReferenceEquals(control.ItemsSource, transfers.Transfers));
+
+                    var words = new List<string>();
+
+                    for (var row = 0; row < expected.Length; row++)
+                    {
+                        queue.ScrollIntoView(row);
+                        window.UpdateLayout();
+
+                        words.Add(queue.ContainerFromIndex(row).ShouldNotBeNull()
+                            .GetVisualDescendants()
+                            .OfType<TextBlock>()
+                            .Single(text => text.Classes.Contains("transferstatus"))
+                            .Text ?? string.Empty);
+                    }
 
                     words.ShouldBe(expected);
                 }

tests/DodoSSH.Client.App.Tests/ShellFlowTests.cs

@@ -669,6 +669,38 @@ public sealed partial class ShellFlowTests : IAsyncLifetime
         shell.StatusMessage.ShouldBe("Locked.");
     }
 
+    /// <remarks>
+    /// A reload used to empty the host list and refill it a row at a time, announcing each — and the transfers
+    /// screen refilled its own picker, announcing each of those, on every one of them. Three hundred hosts came
+    /// to some ninety thousand notifications. Counted here as announcements reaching the two lists, which is
+    /// what the transfers screen and the board both answer.
+    /// </remarks>
+    [Fact]
+    public async Task ReloadingTheHosts_AnnouncesTheListOnce_NotOncePerHost()
+    {
+        await UnlockedAsync();
+        var vault = shell.Vault!;
+
+        foreach (var label in new[] { "prod-db", "prod-web", "stage-web", "dev-box" })
+        {
+            await AddHostAsync(vault, label);
+        }
+
+        var vaultAnnouncements = 0;
+        var pickerAnnouncements = 0;
+
+        vault.Hosts.CollectionChanged += (_, _) => vaultAnnouncements++;
+        shell.Transfers.Hosts.CollectionChanged += (_, _) => pickerAnnouncements++;
+
+        await vault.LoadAsync(Token);
+
+        vault.Hosts.Count.ShouldBe(4);
+        shell.Transfers.Hosts.Count.ShouldBe(4);
+
+        vaultAnnouncements.ShouldBe(1);
+        pickerAnnouncements.ShouldBe(1);
+    }
+
     [Fact]
     public async Task AnAutomaticPass_SaysNothingWhenThereIsNothingToDo()
     {