diff --git a/docs/open.md b/docs/open.md
index 2e57bcdf..5cc8d5df 100644
--- a/docs/open.md
+++ b/docs/open.md
@@ -140,19 +140,21 @@ verifiziert**:
 
 ## Offene Verifikation (2026-08-05, Environment Checks / SystemCheckPage)
 
-**Voraussetzung, bevor irgendeiner der Punkte unten geprüft werden kann:** die Branches
-`claudedo/06aca9b3afec4b939f59b627bfe21737` (Checks + SystemCheckPage) und
-`claudedo/40272c0bb3b14562b59c022d09c382b6` (ExecutableResolver-Wiring in
-`ClaudeDo.Worker`) müssen erst gemerged werden — sie lagen bei dieser Abschluss-Session
-noch nicht auf `main`. Build/Test-Nachweis unten stammt aus einer lokalen Scratch-Integration
-beider Branches, nicht aus `main` selbst. Details → `installer-preflight` in
-`docs/explore-notes/README.md` und den neuen Abschnitt „Environment Checks" in
-`src/ClaudeDo.Installer/CLAUDE.md`.
+Checks + SystemCheckPage (`claudedo/06aca9b3…`) und das ExecutableResolver-Wiring im Worker
+(`claudedo/40272c0b…`) sind seit 2026-08-06 auf `main` gemerged; die frühere „erst mergen"-
+Voraussetzung ist erledigt. Details → `installer-preflight` in `docs/explore-notes/README.md`
+und der Abschnitt „Environment Checks" in `src/ClaudeDo.Installer/CLAUDE.md`.
 
-**Update 2026-08-06:** der „Claude Help Me"-Button ist jetzt implementiert
-(`Core/ClaudeHelpLauncher.cs` + `SystemCheckPageViewModel`/-View), gebaut + unit-getestet
-(`ClaudeDo.Installer.Tests`/`ClaudeDo.Localization.Tests` grün). Die Diagnose-Sektion
-(Config-Modus/`SettingsWindow`) bleibt **nicht implementiert** — eigener Folge-Task.
+**Update (2026-08-06):** beide Folge-Features sind jetzt implementiert und auf `main`.
+
+- Diagnose-Sektion (Config-Modus/`SettingsWindow`): `Pages/DiagnosePage/` + geteilte
+  `Checks/CheckListViewModel.cs`/`Checks/CheckListView.xaml` (auch von `SystemCheckPage`
+  genutzt, keine zweite Implementierung). Unit-getestet
+  (`tests/ClaudeDo.Installer.Tests/Pages/DiagnosePage/DiagnosePageViewModelTests.cs`).
+- „Claude Help Me"-Button: `Core/ClaudeHelpLauncher.cs` + `SystemCheckPageViewModel`/-View,
+  unit-getestet (`tests/ClaudeDo.Installer.Tests/Core/ClaudeHelpLauncherTests.cs`).
+
+Beides **nicht visuell verifiziert**:
 
 - [x] Help-Me-Button ist deaktiviert, wenn `claude-cli` nicht `Ok` ist oder `claude-auth`
       `Failed` ist (bleibt aktiv bei `Unknown`), mit erklärendem Tooltip — unit-getestet.
@@ -160,12 +162,16 @@ beider Branches, nicht aus `main` selbst. Details → `installer-preflight` in
       Session hat den Diagnose-Report gelesen — **nicht verifiziert** (der eigentliche
       Terminal-Start/`wt.exe`-Zusammenspiel und die Session-Qualität sind nur über die
       injizierte `IProcessLauncher`-Fake getestet, nie mit einem echten Terminal/CLI).
-- [ ] Diagnose-Sektion im Config-Modus zeigt die echten installierten Pfade/Ports, und der
-      laufende Worker auf 47821 gilt nicht als Konflikt — **nicht umsetzbar, Feature existiert
-      nicht.**
+- [ ] Platzierung des Help-Me-Buttons: er sitzt seit dem Merge der Diagnose-Sektion in einer
+      **eigenen Zeile unter** dem geteilten Check-Listen-Footer (der reservierte Slot *im*
+      Footer entfiel mit der Extraktion nach `CheckListView.xaml`). Optisch prüfen, ob das
+      so bleiben soll oder ob der Button in den geteilten Footer gehört.
+- [ ] Diagnose-Sektion im Config-Modus: Öffnen von SettingsWindow löst keinen Prüflauf aus, Klick
+      auf „Erneut prüfen" schon; zeigt die echten installierten Pfade/Ports (nicht die
+      InstallContext-Defaults), und der laufende Worker auf dem konfigurierten SignalR-Port gilt
+      nicht als Konflikt — **unit-verifiziert, visueller Durchlauf noch offen.**
 
-Sobald die beiden Branches oben gemerged sind, sind folgende Punkte real prüfbar (gebaut +
-unit-getestet gegen die Scratch-Integration, aber **nicht visuell verifiziert**):
+Weitere Punkte, gebaut + unit-getestet auf `main`, aber **nicht visuell verifiziert**:
 
 - [ ] SystemCheckPage: Layout, Icon-/Farbwirkung der vier Status (Ok grün / Warnung orange /
       Fehler rot / Unbekannt grau — `StatusGreenBrush`/`StatusOrangeBrush`/`StatusRedBrush`/
diff --git a/src/ClaudeDo.Installer/App.xaml.cs b/src/ClaudeDo.Installer/App.xaml.cs
index 4cb440fd..8465d71c 100644
--- a/src/ClaudeDo.Installer/App.xaml.cs
+++ b/src/ClaudeDo.Installer/App.xaml.cs
@@ -11,6 +11,7 @@ using ClaudeDo.Installer.Core.Interfaces;
 using ClaudeDo.Installer.Localization;
 using ClaudeDo.Localization;
 using ClaudeDo.Releases;
+using ClaudeDo.Installer.Pages.DiagnosePage;
 using ClaudeDo.Installer.Pages.InstallPage;
 using ClaudeDo.Installer.Pages.PathsPage;
 using ClaudeDo.Installer.Pages.ServicePage;
@@ -155,6 +156,10 @@ public partial class App : Application
         sc.AddSingleton<IInstallerPage, ServicePageViewModel>();
         sc.AddSingleton<IInstallerPage, UiSettingsPageViewModel>();
         sc.AddSingleton<IInstallerPage, InstallPageViewModel>();
+        sc.AddSingleton<IInstallerPage>(sp => new DiagnosePageViewModel(
+            sp.GetRequiredService<InstallContext>(),
+            sp.GetRequiredService<Func<EnvironmentCheckService>>(),
+            InstallerWorkerConfig.Load));
 
         // Steps — execution order matters for the FreshInstall pipeline (IEnumerable<IInstallStep>).
         // Double-registered as both IInstallStep and concrete type so the Update pipeline
diff --git a/src/ClaudeDo.Installer/CLAUDE.md b/src/ClaudeDo.Installer/CLAUDE.md
index 59118972..9a02c039 100644
--- a/src/ClaudeDo.Installer/CLAUDE.md
+++ b/src/ClaudeDo.Installer/CLAUDE.md
@@ -128,12 +128,6 @@ The Apps & Features uninstall string and "Rerun Installer" both point at `<Insta
 
 ## Environment Checks
 
-> **Merge status (2026-08-06): `Checks/`, `SystemCheckPage`, `ExecutableResolver`, and the
-> "Claude Help Me" button below are on this branch.** The 2026-08-05 note about two unmerged
-> task branches applied to an earlier state; the "Claude Help Me" button follow-up has since
-> landed (see below). The Config-mode Diagnose section in `SettingsWindow` is still **not**
-> implemented — see `docs/open.md`.
-
 `Checks/` holds one `IEnvironmentCheck` per concern, run in parallel by `EnvironmentCheckService.RunAllAsync`:
 
 | Check | Severity | What it verifies |
@@ -156,6 +150,10 @@ regardless of severity (an indeterminate result — e.g. the CLI not found, so v
 can't be checked — must not strand the user; the underlying `Error`-severity check for the CLI
 itself, `ClaudeCliCheck`, is what blocks in that case).
 
+The check-row rendering and the check-run logic (busy state, summary text, Recheck command) live
+in one place — `Checks/CheckListViewModel.cs` + `Checks/CheckListView.xaml` — composed by every
+page that hosts a check list, not duplicated per page.
+
 `SystemCheckPage` (`Pages/SystemCheckPage/`) hosts the check list in the **FreshInstall** wizard
 only, registered via `PageResolver` at `Order = 1` (directly after `WelcomePage`); `WizardViewModel`
 filters it back out in `Update` mode along with Paths/Service/UiSettings. Checks run automatically
@@ -164,8 +162,8 @@ on page entry (`LoadAsync`, guarded against double-entry). "Next" is disabled vi
 subscribes to `PropertyChanged` on the current page so a live recheck can flip it back. A "Recheck"
 button re-runs `EnvironmentCheckService.RunAllAsync` (disabled while already running).
 
-**"Claude Help Me" button** (`Core/ClaudeHelpLauncher.cs`) — a second footer button next to
-"Recheck", enabled only when `claude-cli` is `Ok` and `claude-auth` is not `Failed` (`Unknown`
+**"Claude Help Me" button** (`Core/ClaudeHelpLauncher.cs`) — a second button below the shared
+check-list footer, enabled only when `claude-cli` is `Ok` and `claude-auth` is not `Failed` (`Unknown`
 stays enabled — an indeterminate login state shouldn't block the one feature that could help
 diagnose it). `BuildReportAsync` renders all check results (Id/Severity/Status/Message table,
 plus the full `Detail` of any `Failed` check) and system info (OS, `dotnet --list-runtimes`,
@@ -175,7 +173,15 @@ user) and deliberately excludes credentials/tokens/env-var dumps. `LaunchTermina
 `wt.exe -d %TEMP% cmd.exe /k <claude> <prompt>` (or `cmd.exe /k <claude> <prompt>` if `wt.exe`
 isn't resolvable) via the injectable `IProcessLauncher`, pointing the initial prompt at that
 report file. Errors from either step surface as `ClaudeHelpError` on the page, never an
-exception.
+exception. It reads the last report via `CheckListViewModel.LastReport`, so it re-evaluates on
+every check run.
 
-**Not implemented:** a Diagnose section in `SettingsWindow` (Config mode) that re-runs the same
-checks against the installed configuration — still speced as a follow-up, no code yet.
+`DiagnosePage` (`Pages/DiagnosePage/`) hosts the same `CheckListView` in `SettingsWindow` (Config
+mode only, `ShowInSettings = true` / `ShowInWizard = false`, `Order = 5` — after UiSettings).
+Nothing here blocks navigation and checks do **not** auto-run on load — only on a "Recheck" click.
+Unlike the wizard, its `InstallContext` is built from the **installed** configuration
+(`InstallerWorkerConfig.Load()` for `ClaudeBin`/`SignalRPort`, the shared `InstallContext` for
+`InstallDirectory`/`ExternalMcpPort`), refreshed on every `LoadAsync()` — not the wizard-default
+`InstallContext` the DI container hands out, which is only populated once a page's `ApplyAsync`
+(i.e. Save) runs. `DiagnosePage` intentionally has **no** "Claude Help Me" button — that one is
+wizard-only.
diff --git a/src/ClaudeDo.Installer/Checks/CheckListView.xaml b/src/ClaudeDo.Installer/Checks/CheckListView.xaml
new file mode 100644
index 00000000..7d44db53
--- /dev/null
+++ b/src/ClaudeDo.Installer/Checks/CheckListView.xaml
@@ -0,0 +1,91 @@
+<UserControl x:Class="ClaudeDo.Installer.Checks.CheckListView"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:local="clr-namespace:ClaudeDo.Installer.Checks"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
+             d:DataContext="{d:DesignInstance local:CheckListViewModel}"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d">
+
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="*"/>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="Auto"/>
+        </Grid.RowDefinitions>
+
+        <!-- Check list -->
+        <ScrollViewer Grid.Row="0" VerticalScrollBarVisibility="Auto">
+            <ItemsControl ItemsSource="{Binding Rows}">
+                <ItemsControl.ItemTemplate>
+                    <DataTemplate DataType="{x:Type local:CheckRowViewModel}">
+                        <Border Margin="0,0,0,6" Padding="10,8"
+                                Background="{StaticResource IslandBgBrush}"
+                                BorderBrush="{StaticResource BorderSubtleBrush}"
+                                BorderThickness="1" CornerRadius="4">
+                            <StackPanel>
+                                <Grid>
+                                    <Grid.ColumnDefinitions>
+                                        <ColumnDefinition Width="Auto"/>
+                                        <ColumnDefinition Width="*"/>
+                                    </Grid.ColumnDefinitions>
+
+                                    <Ellipse Grid.Column="0" Width="10" Height="10" Margin="0,0,10,0"
+                                             VerticalAlignment="Top"
+                                             Fill="{Binding StatusBrush}"/>
+
+                                    <StackPanel Grid.Column="1">
+                                        <TextBlock Text="{Binding Title}" FontSize="13" FontWeight="SemiBold"/>
+                                        <TextBlock Text="{Binding Message}" FontSize="12"
+                                                   Foreground="{StaticResource TextSecondaryBrush}"
+                                                   TextWrapping="Wrap" Margin="0,2,0,0"/>
+
+                                        <TextBlock Text="{Binding Hint}" FontSize="11"
+                                                   Foreground="{StaticResource TextMutedBrush}"
+                                                   TextWrapping="Wrap" Margin="0,4,0,0"
+                                                   Visibility="{Binding Hint, Converter={StaticResource NullToCollapsedConverter}}"/>
+
+                                        <Button Content="{Binding HelpUrl}"
+                                                HorizontalAlignment="Left" Margin="-16,4,0,0"
+                                                Background="Transparent" BorderThickness="0"
+                                                Foreground="{StaticResource AccentLightBrush}"
+                                                Cursor="Hand"
+                                                Command="{Binding DataContext.OpenHelpUrlCommand, RelativeSource={RelativeSource AncestorType=ItemsControl}}"
+                                                CommandParameter="{Binding HelpUrl}"
+                                                Visibility="{Binding HelpUrl, Converter={StaticResource NullToCollapsedConverter}}"/>
+                                    </StackPanel>
+                                </Grid>
+                            </StackPanel>
+                        </Border>
+                    </DataTemplate>
+                </ItemsControl.ItemTemplate>
+            </ItemsControl>
+        </ScrollViewer>
+
+        <!-- Progress + summary -->
+        <StackPanel Grid.Row="1" Margin="0,8,0,0">
+            <ProgressBar IsIndeterminate="True" Margin="0,0,0,8"
+                         Visibility="{Binding IsRunning, Converter={StaticResource BoolToVisConverter}}"/>
+            <TextBlock Text="{Binding Summary}" FontSize="12" TextWrapping="Wrap"
+                       Foreground="{StaticResource TextSecondaryBrush}">
+                <TextBlock.Style>
+                    <Style TargetType="TextBlock">
+                        <Style.Triggers>
+                            <DataTrigger Binding="{Binding HasBlockingError}" Value="True">
+                                <Setter Property="Foreground" Value="{StaticResource ErrorBrush}"/>
+                            </DataTrigger>
+                        </Style.Triggers>
+                    </Style>
+                </TextBlock.Style>
+            </TextBlock>
+        </StackPanel>
+
+        <!-- Footer -->
+        <StackPanel Grid.Row="2" Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,12,0,0">
+            <!-- Reserved space: a "Claude Help Me" button lands here in a follow-up task. -->
+            <Button Content="{loc:Tr installer.systemCheck.recheck}"
+                    Command="{Binding RunChecksCommand}"/>
+        </StackPanel>
+    </Grid>
+</UserControl>
diff --git a/src/ClaudeDo.Installer/Checks/CheckListView.xaml.cs b/src/ClaudeDo.Installer/Checks/CheckListView.xaml.cs
new file mode 100644
index 00000000..345a2145
--- /dev/null
+++ b/src/ClaudeDo.Installer/Checks/CheckListView.xaml.cs
@@ -0,0 +1,8 @@
+using System.Windows.Controls;
+
+namespace ClaudeDo.Installer.Checks;
+
+public partial class CheckListView : UserControl
+{
+    public CheckListView() => InitializeComponent();
+}
diff --git a/src/ClaudeDo.Installer/Checks/CheckListViewModel.cs b/src/ClaudeDo.Installer/Checks/CheckListViewModel.cs
new file mode 100644
index 00000000..c782c6e6
--- /dev/null
+++ b/src/ClaudeDo.Installer/Checks/CheckListViewModel.cs
@@ -0,0 +1,139 @@
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Windows;
+using System.Windows.Media;
+using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+
+namespace ClaudeDo.Installer.Checks;
+
+public sealed class CheckRowViewModel
+{
+    public CheckRowViewModel(CheckResult result)
+    {
+        var loc = TrExtension.Localizer;
+        Status = result.Status;
+        Severity = result.Severity;
+        Title = loc?[result.TitleKey] ?? result.TitleKey;
+        Message = result.Message;
+        Hint = result.HintKey is not null ? loc?[result.HintKey] ?? result.HintKey : null;
+        HelpUrl = result.HelpUrl;
+        StatusBrush = ResolveBrush(Status, Severity);
+    }
+
+    public CheckStatus Status { get; }
+    public CheckSeverity Severity { get; }
+    public string Title { get; }
+    public string Message { get; }
+    public string? Hint { get; }
+    public string? HelpUrl { get; }
+    public Brush StatusBrush { get; }
+
+    private static Brush ResolveBrush(CheckStatus status, CheckSeverity severity)
+    {
+        var key = status switch
+        {
+            CheckStatus.Ok => "StatusGreenBrush",
+            CheckStatus.Unknown => "StatusGrayBrush",
+            CheckStatus.Failed when severity == CheckSeverity.Error => "StatusRedBrush",
+            CheckStatus.Failed => "StatusOrangeBrush",
+            _ => "StatusGrayBrush",
+        };
+        return Application.Current?.Resources[key] as Brush ?? Brushes.Gray;
+    }
+}
+
+/// <summary>
+/// Shared presentation logic for the environment check list: running the check pass, tracking
+/// busy/summary state, and the row collection. Composed (not subclassed) by every page that
+/// hosts a check list — <see cref="Pages.SystemCheckPage.SystemCheckPageViewModel"/> and
+/// <see cref="Pages.DiagnosePage.DiagnosePageViewModel"/> — so the run logic exists exactly once.
+/// </summary>
+public partial class CheckListViewModel : ObservableObject
+{
+    private readonly InstallContext _context;
+    private readonly Func<EnvironmentCheckService> _checkServiceFactory;
+
+    public ObservableCollection<CheckRowViewModel> Rows { get; } = [];
+
+    /// <summary>Report of the most recent run, null before the first one. Hosts that need the raw
+    /// results (the wizard's "Claude Help Me" button) read it instead of running the checks again.</summary>
+    public EnvironmentCheckReport? LastReport { get; private set; }
+
+    [ObservableProperty] private bool _isRunning;
+    [ObservableProperty] private bool _hasRun;
+    [ObservableProperty] private bool _hasBlockingError;
+    [ObservableProperty] private string _summary = string.Empty;
+
+    public CheckListViewModel(InstallContext context, Func<EnvironmentCheckService> checkServiceFactory)
+    {
+        _context = context;
+        _checkServiceFactory = checkServiceFactory;
+    }
+
+    partial void OnIsRunningChanged(bool value) => RunChecksCommand.NotifyCanExecuteChanged();
+
+    [RelayCommand(CanExecute = nameof(CanRunChecks))]
+    private async Task RunChecksAsync()
+    {
+        if (IsRunning) return;
+
+        IsRunning = true;
+        Summary = TrExtension.Localizer?["installer.systemCheck.summary.running"] ?? "Checking your system…";
+
+        try
+        {
+            var service = _checkServiceFactory();
+            var report = await service.RunAllAsync(_context, CancellationToken.None);
+
+            Rows.Clear();
+            foreach (var result in report.Results)
+                Rows.Add(new CheckRowViewModel(result));
+
+            LastReport = report;
+            OnPropertyChanged(nameof(LastReport));
+            HasBlockingError = report.HasBlockingError;
+            Summary = BuildSummary(report);
+            HasRun = true;
+        }
+        finally
+        {
+            IsRunning = false;
+        }
+    }
+
+    private bool CanRunChecks() => !IsRunning;
+
+    private static string BuildSummary(EnvironmentCheckReport report)
+    {
+        var loc = TrExtension.Localizer;
+
+        var blocking = report.Results
+            .Where(r => r.Severity == CheckSeverity.Error && r.Status == CheckStatus.Failed)
+            .ToList();
+        if (blocking.Count > 0)
+        {
+            var names = string.Join(", ", blocking.Select(r => loc?[r.TitleKey] ?? r.TitleKey));
+            return loc?.Get("installer.systemCheck.summary.blocking", blocking.Count, names)
+                   ?? $"{blocking.Count} problem(s) must be fixed: {names}";
+        }
+
+        var warnings = report.Results.Count(r => r.Severity == CheckSeverity.Warning && r.Status == CheckStatus.Failed);
+        if (warnings > 0)
+        {
+            return loc?.Get("installer.systemCheck.summary.warnings", warnings)
+                   ?? $"{warnings} warning(s) found.";
+        }
+
+        return loc?["installer.systemCheck.summary.ok"] ?? "Everything looks good.";
+    }
+
+    [RelayCommand]
+    private static void OpenHelpUrl(string? url)
+    {
+        if (string.IsNullOrEmpty(url)) return;
+        Process.Start(new ProcessStartInfo(url) { UseShellExecute = true });
+    }
+}
diff --git a/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageView.xaml b/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageView.xaml
new file mode 100644
index 00000000..f8f7b7c0
--- /dev/null
+++ b/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageView.xaml
@@ -0,0 +1,27 @@
+<UserControl x:Class="ClaudeDo.Installer.Pages.DiagnosePage.DiagnosePageView"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.DiagnosePage"
+             xmlns:checks="clr-namespace:ClaudeDo.Installer.Checks"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
+             d:DataContext="{d:DesignInstance local:DiagnosePageViewModel}"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d">
+
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="*"/>
+        </Grid.RowDefinitions>
+
+        <!-- Header -->
+        <StackPanel Grid.Row="0" Margin="0,0,0,16">
+            <TextBlock Text="{loc:Tr installer.diagnose.title}" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
+            <TextBlock Text="{loc:Tr installer.diagnose.subtitle}"
+                       Foreground="{StaticResource TextSecondaryBrush}" TextWrapping="Wrap"/>
+        </StackPanel>
+
+        <checks:CheckListView Grid.Row="1" DataContext="{Binding Checks}"/>
+    </Grid>
+</UserControl>
diff --git a/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageView.xaml.cs b/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageView.xaml.cs
new file mode 100644
index 00000000..a99c423f
--- /dev/null
+++ b/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageView.xaml.cs
@@ -0,0 +1,8 @@
+using System.Windows.Controls;
+
+namespace ClaudeDo.Installer.Pages.DiagnosePage;
+
+public partial class DiagnosePageView : UserControl
+{
+    public DiagnosePageView() => InitializeComponent();
+}
diff --git a/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageViewModel.cs b/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageViewModel.cs
new file mode 100644
index 00000000..699d119c
--- /dev/null
+++ b/src/ClaudeDo.Installer/Pages/DiagnosePage/DiagnosePageViewModel.cs
@@ -0,0 +1,50 @@
+using System.Windows.Controls;
+using ClaudeDo.Installer.Checks;
+using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace ClaudeDo.Installer.Pages.DiagnosePage;
+
+/// <summary>
+/// Re-runs the same environment checks as the wizard's SystemCheckPage, but against the
+/// installed configuration (worker.config.json + the detected install directory) instead of
+/// wizard defaults, and nothing here blocks navigation or auto-runs on load.
+/// </summary>
+public partial class DiagnosePageViewModel : ObservableObject, IInstallerPage
+{
+    private readonly InstallContext _sharedContext;
+    private readonly Func<InstallerWorkerConfig> _loadWorkerConfig;
+    private readonly InstallContext _installedContext = new();
+    private DiagnosePageView? _view;
+
+    public string Title => TrExtension.Localizer?["installer.diagnose.title"] ?? "Diagnose";
+    public string Icon => "";
+    public int Order => 5;
+    public bool ShowInWizard => false;
+    public bool ShowInSettings => true;
+    public UserControl View => _view ??= new DiagnosePageView { DataContext = this };
+
+    public CheckListViewModel Checks { get; }
+
+    public DiagnosePageViewModel(InstallContext sharedContext, Func<EnvironmentCheckService> checkServiceFactory, Func<InstallerWorkerConfig> loadWorkerConfig)
+    {
+        _sharedContext = sharedContext;
+        _loadWorkerConfig = loadWorkerConfig;
+        Checks = new CheckListViewModel(_installedContext, checkServiceFactory);
+    }
+
+    public Task LoadAsync()
+    {
+        var cfg = _loadWorkerConfig();
+        _installedContext.InstallDirectory = _sharedContext.InstallDirectory;
+        _installedContext.ClaudeBin = cfg.ClaudeBin;
+        _installedContext.SignalRPort = cfg.SignalRPort;
+        _installedContext.ExternalMcpPort = _sharedContext.ExternalMcpPort;
+        return Task.CompletedTask;
+    }
+
+    public Task ApplyAsync() => Task.CompletedTask;
+
+    public bool Validate() => true;
+}
diff --git a/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageView.xaml b/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageView.xaml
index 642b8180..ca3b4314 100644
--- a/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageView.xaml
+++ b/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageView.xaml
@@ -2,6 +2,7 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.SystemCheckPage"
+             xmlns:checks="clr-namespace:ClaudeDo.Installer.Checks"
              xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
              d:DataContext="{d:DesignInstance local:SystemCheckPageViewModel}"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
@@ -13,7 +14,6 @@
             <RowDefinition Height="Auto"/>
             <RowDefinition Height="*"/>
             <RowDefinition Height="Auto"/>
-            <RowDefinition Height="Auto"/>
         </Grid.RowDefinitions>
 
         <!-- Header -->
@@ -23,85 +23,17 @@
                        Foreground="{StaticResource TextSecondaryBrush}" TextWrapping="Wrap"/>
         </StackPanel>
 
-        <!-- Check list -->
-        <ScrollViewer Grid.Row="1" VerticalScrollBarVisibility="Auto">
-            <ItemsControl ItemsSource="{Binding Rows}">
-                <ItemsControl.ItemTemplate>
-                    <DataTemplate DataType="{x:Type local:CheckRowViewModel}">
-                        <Border Margin="0,0,0,6" Padding="10,8"
-                                Background="{StaticResource IslandBgBrush}"
-                                BorderBrush="{StaticResource BorderSubtleBrush}"
-                                BorderThickness="1" CornerRadius="4">
-                            <StackPanel>
-                                <Grid>
-                                    <Grid.ColumnDefinitions>
-                                        <ColumnDefinition Width="Auto"/>
-                                        <ColumnDefinition Width="*"/>
-                                    </Grid.ColumnDefinitions>
+        <checks:CheckListView Grid.Row="1" DataContext="{Binding Checks}"/>
 
-                                    <Ellipse Grid.Column="0" Width="10" Height="10" Margin="0,0,10,0"
-                                             VerticalAlignment="Top"
-                                             Fill="{Binding StatusBrush}"/>
-
-                                    <StackPanel Grid.Column="1">
-                                        <TextBlock Text="{Binding Title}" FontSize="13" FontWeight="SemiBold"/>
-                                        <TextBlock Text="{Binding Message}" FontSize="12"
-                                                   Foreground="{StaticResource TextSecondaryBrush}"
-                                                   TextWrapping="Wrap" Margin="0,2,0,0"/>
-
-                                        <TextBlock Text="{Binding Hint}" FontSize="11"
-                                                   Foreground="{StaticResource TextMutedBrush}"
-                                                   TextWrapping="Wrap" Margin="0,4,0,0"
-                                                   Visibility="{Binding Hint, Converter={StaticResource NullToCollapsedConverter}}"/>
-
-                                        <Button Content="{Binding HelpUrl}"
-                                                HorizontalAlignment="Left" Margin="-16,4,0,0"
-                                                Background="Transparent" BorderThickness="0"
-                                                Foreground="{StaticResource AccentLightBrush}"
-                                                Cursor="Hand"
-                                                Command="{Binding DataContext.OpenHelpUrlCommand, RelativeSource={RelativeSource AncestorType=ItemsControl}}"
-                                                CommandParameter="{Binding HelpUrl}"
-                                                Visibility="{Binding HelpUrl, Converter={StaticResource NullToCollapsedConverter}}"/>
-                                    </StackPanel>
-                                </Grid>
-                            </StackPanel>
-                        </Border>
-                    </DataTemplate>
-                </ItemsControl.ItemTemplate>
-            </ItemsControl>
-        </ScrollViewer>
-
-        <!-- Progress + summary -->
+        <!-- Wizard-only footer: "Claude Help Me" (the Recheck button lives in the shared list) -->
         <StackPanel Grid.Row="2" Margin="0,8,0,0">
-            <ProgressBar IsIndeterminate="True" Margin="0,0,0,8"
-                         Visibility="{Binding IsRunning, Converter={StaticResource BoolToVisConverter}}"/>
-            <TextBlock Text="{Binding Summary}" FontSize="12" TextWrapping="Wrap"
-                       Foreground="{StaticResource TextSecondaryBrush}">
-                <TextBlock.Style>
-                    <Style TargetType="TextBlock">
-                        <Style.Triggers>
-                            <DataTrigger Binding="{Binding HasBlockingError}" Value="True">
-                                <Setter Property="Foreground" Value="{StaticResource ErrorBrush}"/>
-                            </DataTrigger>
-                        </Style.Triggers>
-                    </Style>
-                </TextBlock.Style>
-            </TextBlock>
-        </StackPanel>
-
-        <!-- Footer -->
-        <StackPanel Grid.Row="3" Margin="0,12,0,0">
             <TextBlock Text="{Binding ClaudeHelpError}" FontSize="12" TextWrapping="Wrap"
                        Foreground="{StaticResource ErrorBrush}" Margin="0,0,0,8"
                        Visibility="{Binding ClaudeHelpError, Converter={StaticResource NullToCollapsedConverter}}"/>
-            <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
-                <Button Content="{loc:Tr installer.systemCheck.claudeHelp.button}"
-                        ToolTip="{Binding ClaudeHelpTooltip}"
-                        Command="{Binding StartClaudeHelpCommand}"
-                        Margin="0,0,8,0"/>
-                <Button Content="{loc:Tr installer.systemCheck.recheck}"
-                        Command="{Binding RunChecksCommand}"/>
-            </StackPanel>
+            <Button Content="{loc:Tr installer.systemCheck.claudeHelp.button}"
+                    HorizontalAlignment="Right"
+                    ToolTip="{Binding ClaudeHelpTooltip}"
+                    Command="{Binding StartClaudeHelpCommand}"/>
         </StackPanel>
     </Grid>
 </UserControl>
diff --git a/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageViewModel.cs b/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageViewModel.cs
index 8e46a910..ea305b58 100644
--- a/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageViewModel.cs
+++ b/src/ClaudeDo.Installer/Pages/SystemCheckPage/SystemCheckPageViewModel.cs
@@ -1,8 +1,5 @@
 using System.Collections.ObjectModel;
-using System.Diagnostics;
-using System.Windows;
 using System.Windows.Controls;
-using System.Windows.Media;
 using ClaudeDo.Installer.Checks;
 using ClaudeDo.Installer.Core;
 using ClaudeDo.Installer.Localization;
@@ -11,73 +8,40 @@ using CommunityToolkit.Mvvm.Input;
 
 namespace ClaudeDo.Installer.Pages.SystemCheckPage;
 
-public sealed class CheckRowViewModel
-{
-    public CheckRowViewModel(CheckResult result)
-    {
-        var loc = TrExtension.Localizer;
-        Status = result.Status;
-        Severity = result.Severity;
-        Title = loc?[result.TitleKey] ?? result.TitleKey;
-        Message = result.Message;
-        Hint = result.HintKey is not null ? loc?[result.HintKey] ?? result.HintKey : null;
-        HelpUrl = result.HelpUrl;
-        StatusBrush = ResolveBrush(Status, Severity);
-    }
-
-    public CheckStatus Status { get; }
-    public CheckSeverity Severity { get; }
-    public string Title { get; }
-    public string Message { get; }
-    public string? Hint { get; }
-    public string? HelpUrl { get; }
-    public Brush StatusBrush { get; }
-
-    private static Brush ResolveBrush(CheckStatus status, CheckSeverity severity)
-    {
-        var key = status switch
-        {
-            CheckStatus.Ok => "StatusGreenBrush",
-            CheckStatus.Unknown => "StatusGrayBrush",
-            CheckStatus.Failed when severity == CheckSeverity.Error => "StatusRedBrush",
-            CheckStatus.Failed => "StatusOrangeBrush",
-            _ => "StatusGrayBrush",
-        };
-        return Application.Current?.Resources[key] as Brush ?? Brushes.Gray;
-    }
-}
-
 public partial class SystemCheckPageViewModel : ObservableObject, IInstallerPage
 {
     private readonly InstallContext _context;
-    private readonly Func<EnvironmentCheckService> _checkServiceFactory;
     private readonly ClaudeHelpLauncher _claudeHelpLauncher;
     private SystemCheckPageView? _view;
     private bool _hasStarted;
-    private EnvironmentCheckReport? _lastReport;
 
     public string Title => TrExtension.Localizer?["installer.systemCheck.title"] ?? "System Check";
-    public string Icon => "";
+    public string Icon => "";
     public int Order => 1;
     public bool ShowInWizard => true;
     public bool ShowInSettings => false;
     public UserControl View => _view ??= new SystemCheckPageView { DataContext = this };
 
-    public ObservableCollection<CheckRowViewModel> Rows { get; } = [];
+    public CheckListViewModel Checks { get; }
+
+    // Pass-through to the shared check-run logic — kept so this page's UI/tests can bind
+    // directly on it, matching the pre-extraction API.
+    public ObservableCollection<CheckRowViewModel> Rows => Checks.Rows;
+    public bool IsRunning => Checks.IsRunning;
+    public bool HasRun => Checks.HasRun;
+    public bool HasBlockingError => Checks.HasBlockingError;
+    public string Summary => Checks.Summary;
+    public IAsyncRelayCommand RunChecksCommand => Checks.RunChecksCommand;
+
+    public bool BlocksNavigation => Checks.IsRunning || Checks.HasBlockingError;
 
-    [ObservableProperty] private bool _isRunning;
-    [ObservableProperty] private bool _hasRun;
-    [ObservableProperty] private bool _hasBlockingError;
-    [ObservableProperty] private string _summary = string.Empty;
     [ObservableProperty] private string? _claudeHelpError;
 
-    public bool BlocksNavigation => IsRunning || HasBlockingError;
-
     public bool ClaudeCliOk =>
-        _lastReport?.Results.FirstOrDefault(r => r.Id == ClaudeCliCheck.CheckId)?.Status == CheckStatus.Ok;
+        Checks.LastReport?.Results.FirstOrDefault(r => r.Id == ClaudeCliCheck.CheckId)?.Status == CheckStatus.Ok;
 
     public bool ClaudeAuthFailed =>
-        _lastReport?.Results.FirstOrDefault(r => r.Id == ClaudeAuthCheck.CheckId)?.Status == CheckStatus.Failed;
+        Checks.LastReport?.Results.FirstOrDefault(r => r.Id == ClaudeAuthCheck.CheckId)?.Status == CheckStatus.Failed;
 
     public bool CanStartClaudeHelp => ClaudeCliOk && !ClaudeAuthFailed;
 
@@ -101,24 +65,28 @@ public partial class SystemCheckPageViewModel : ObservableObject, IInstallerPage
         ClaudeHelpLauncher claudeHelpLauncher)
     {
         _context = context;
-        _checkServiceFactory = checkServiceFactory;
         _claudeHelpLauncher = claudeHelpLauncher;
+        Checks = new CheckListViewModel(context, checkServiceFactory);
+        // The wizard listens for PropertyChanged on this page to re-evaluate "Next" — bubble
+        // any change from the composed check list up so a live recheck can flip it back, and so
+        // the Claude-Help gating re-reads the fresh report.
+        Checks.PropertyChanged += (_, _) =>
+        {
+            OnPropertyChanged(nameof(BlocksNavigation));
+            OnPropertyChanged(nameof(ClaudeCliOk));
+            OnPropertyChanged(nameof(ClaudeAuthFailed));
+            OnPropertyChanged(nameof(CanStartClaudeHelp));
+            OnPropertyChanged(nameof(ClaudeHelpTooltip));
+            StartClaudeHelpCommand.NotifyCanExecuteChanged();
+        };
     }
 
-    partial void OnIsRunningChanged(bool value)
-    {
-        OnPropertyChanged(nameof(BlocksNavigation));
-        RunChecksCommand.NotifyCanExecuteChanged();
-    }
-
-    partial void OnHasBlockingErrorChanged(bool value) => OnPropertyChanged(nameof(BlocksNavigation));
-
     public Task LoadAsync()
     {
         if (!_hasStarted)
         {
             _hasStarted = true;
-            _ = RunChecksAsync();
+            _ = Checks.RunChecksCommand.ExecuteAsync(null);
         }
         return Task.CompletedTask;
     }
@@ -127,82 +95,17 @@ public partial class SystemCheckPageViewModel : ObservableObject, IInstallerPage
 
     public bool Validate() => !HasBlockingError;
 
-    [RelayCommand(CanExecute = nameof(CanRunChecks))]
-    private async Task RunChecksAsync()
-    {
-        if (IsRunning) return;
-
-        IsRunning = true;
-        Summary = TrExtension.Localizer?["installer.systemCheck.summary.running"] ?? "Checking your system…";
-
-        try
-        {
-            var service = _checkServiceFactory();
-            var report = await service.RunAllAsync(_context, CancellationToken.None);
-
-            Rows.Clear();
-            foreach (var result in report.Results)
-                Rows.Add(new CheckRowViewModel(result));
-
-            _lastReport = report;
-            HasBlockingError = report.HasBlockingError;
-            Summary = BuildSummary(report);
-            HasRun = true;
-
-            OnPropertyChanged(nameof(CanStartClaudeHelp));
-            OnPropertyChanged(nameof(ClaudeHelpTooltip));
-            StartClaudeHelpCommand.NotifyCanExecuteChanged();
-        }
-        finally
-        {
-            IsRunning = false;
-        }
-    }
-
-    private bool CanRunChecks() => !IsRunning;
-
     [RelayCommand(CanExecute = nameof(CanStartClaudeHelp))]
     private async Task StartClaudeHelpAsync()
     {
-        if (_lastReport is null) return;
+        if (Checks.LastReport is null) return;
 
         ClaudeHelpError = null;
-        var result = await _claudeHelpLauncher.LaunchAsync(_lastReport, _context, CancellationToken.None);
+        var result = await _claudeHelpLauncher.LaunchAsync(Checks.LastReport, _context, CancellationToken.None);
         if (!result.Success)
         {
             ClaudeHelpError = TrExtension.Localizer?.Get("installer.systemCheck.claudeHelp.error", result.ErrorMessage ?? "")
                               ?? $"Could not start the Claude session: {result.ErrorMessage}";
         }
     }
-
-    private static string BuildSummary(EnvironmentCheckReport report)
-    {
-        var loc = TrExtension.Localizer;
-
-        var blocking = report.Results
-            .Where(r => r.Severity == CheckSeverity.Error && r.Status == CheckStatus.Failed)
-            .ToList();
-        if (blocking.Count > 0)
-        {
-            var names = string.Join(", ", blocking.Select(r => loc?[r.TitleKey] ?? r.TitleKey));
-            return loc?.Get("installer.systemCheck.summary.blocking", blocking.Count, names)
-                   ?? $"{blocking.Count} problem(s) must be fixed: {names}";
-        }
-
-        var warnings = report.Results.Count(r => r.Severity == CheckSeverity.Warning && r.Status == CheckStatus.Failed);
-        if (warnings > 0)
-        {
-            return loc?.Get("installer.systemCheck.summary.warnings", warnings)
-                   ?? $"{warnings} warning(s) found.";
-        }
-
-        return loc?["installer.systemCheck.summary.ok"] ?? "Everything looks good.";
-    }
-
-    [RelayCommand]
-    private static void OpenHelpUrl(string? url)
-    {
-        if (string.IsNullOrEmpty(url)) return;
-        Process.Start(new ProcessStartInfo(url) { UseShellExecute = true });
-    }
 }
diff --git a/src/ClaudeDo.Localization/locales/de.json b/src/ClaudeDo.Localization/locales/de.json
index 0a0a1aac..f9d91991 100644
--- a/src/ClaudeDo.Localization/locales/de.json
+++ b/src/ClaudeDo.Localization/locales/de.json
@@ -540,6 +540,10 @@
       "subtitle": "Klicke auf Installieren, um ClaudeDo zu erstellen und bereitzustellen.",
       "launch": "ClaudeDo starten"
     },
+    "diagnose": {
+      "title": "Diagnose",
+      "subtitle": "Führt die Systemprüfungen erneut aus, gegen deine installierte Konfiguration."
+    },
     "settings": {
       "removeUserData": "Benutzerdaten entfernen (Aufgaben, Logs, Konfigurationen in ~/.todo-app)",
       "uninstall": "Deinstallieren",
diff --git a/src/ClaudeDo.Localization/locales/en.json b/src/ClaudeDo.Localization/locales/en.json
index 9100236c..d82e237a 100644
--- a/src/ClaudeDo.Localization/locales/en.json
+++ b/src/ClaudeDo.Localization/locales/en.json
@@ -540,6 +540,10 @@
       "subtitle": "Click Install to build and deploy ClaudeDo.",
       "launch": "Launch ClaudeDo"
     },
+    "diagnose": {
+      "title": "Diagnose",
+      "subtitle": "Re-run the environment checks against your installed configuration."
+    },
     "settings": {
       "removeUserData": "Remove user data (tasks, logs, configs in ~/.todo-app)",
       "uninstall": "Uninstall",
diff --git a/tests/ClaudeDo.Installer.Tests/PageResolverTests.cs b/tests/ClaudeDo.Installer.Tests/PageResolverTests.cs
index 1845d3fb..22614804 100644
--- a/tests/ClaudeDo.Installer.Tests/PageResolverTests.cs
+++ b/tests/ClaudeDo.Installer.Tests/PageResolverTests.cs
@@ -1,4 +1,6 @@
+using ClaudeDo.Installer.Checks;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Pages.DiagnosePage;
 using ClaudeDo.Installer.Pages.PathsPage;
 using ClaudeDo.Installer.Pages.ServicePage;
 using ClaudeDo.Installer.Pages.SystemCheckPage;
@@ -41,4 +43,33 @@ public class PageResolverTests
 
         Assert.False(page.ShowInSettings);
     }
+
+    [Fact]
+    public void DiagnosePage_is_shown_in_settings_but_not_in_the_wizard()
+    {
+        var context = new InstallContext();
+        var page = new DiagnosePageViewModel(context, () => throw new InvalidOperationException(), () => new InstallerWorkerConfig());
+
+        Assert.True(page.ShowInSettings);
+        Assert.False(page.ShowInWizard);
+    }
+
+    [Fact]
+    public void DiagnosePage_appears_in_the_settings_sidebar_after_the_other_settings_pages()
+    {
+        var context = new InstallContext();
+        var pages = new IInstallerPage[]
+        {
+            new PathsPageViewModel(context),
+            new ServicePageViewModel(context),
+            new UiSettingsPageViewModel(context),
+            new DiagnosePageViewModel(context, () => throw new InvalidOperationException(), () => new InstallerWorkerConfig()),
+        };
+
+        var resolver = new PageResolver(pages);
+        var settingsPages = resolver.SettingsPages.ToList();
+
+        Assert.Equal(4, settingsPages.Count);
+        Assert.IsType<DiagnosePageViewModel>(settingsPages[^1]);
+    }
 }
diff --git a/tests/ClaudeDo.Installer.Tests/Pages/DiagnosePage/DiagnosePageViewModelTests.cs b/tests/ClaudeDo.Installer.Tests/Pages/DiagnosePage/DiagnosePageViewModelTests.cs
new file mode 100644
index 00000000..ef759c61
--- /dev/null
+++ b/tests/ClaudeDo.Installer.Tests/Pages/DiagnosePage/DiagnosePageViewModelTests.cs
@@ -0,0 +1,125 @@
+using System.Net;
+using System.Net.Sockets;
+using ClaudeDo.Installer.Checks;
+using ClaudeDo.Installer.Checks.Interfaces;
+using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Tests.Pages.SystemCheckPage;
+using Vm = ClaudeDo.Installer.Pages.DiagnosePage.DiagnosePageViewModel;
+
+namespace ClaudeDo.Installer.Tests.Pages.DiagnosePage;
+
+public sealed class DiagnosePageViewModelTests
+{
+    private sealed class FakeOwnerResolver : IPortOwnerResolver
+    {
+        private readonly string? _owner;
+        public FakeOwnerResolver(string? owner) => _owner = owner;
+        public Task<string?> FindOwningProcessNameAsync(int port, CancellationToken ct) => Task.FromResult(_owner);
+    }
+
+    private static int GetFreePort()
+    {
+        var listener = new TcpListener(IPAddress.Loopback, 0);
+        listener.Start();
+        var port = ((IPEndPoint)listener.LocalEndpoint).Port;
+        listener.Stop();
+        return port;
+    }
+
+    [Fact]
+    public async Task Loading_the_page_does_not_run_checks()
+    {
+        var check = FakeEnvironmentCheck.Ok("a");
+        var vm = new Vm(
+            new InstallContext(),
+            () => new EnvironmentCheckService(new IEnvironmentCheck[] { check }),
+            () => new InstallerWorkerConfig());
+
+        await vm.LoadAsync();
+
+        Assert.Equal(0, check.CallCount);
+        Assert.False(vm.Checks.HasRun);
+        Assert.Empty(vm.Checks.Rows);
+    }
+
+    [Fact]
+    public async Task Clicking_check_runs_once_and_a_second_click_during_the_run_starts_no_new_run()
+    {
+        var gate = new TaskCompletionSource();
+        var slow = new FakeEnvironmentCheck("slow", CheckSeverity.Error, async (_, _) =>
+        {
+            await gate.Task;
+            return CheckResult.Ok("slow", CheckSeverity.Error, "checks.slow.title", "ok");
+        });
+
+        var factoryCalls = 0;
+        var vm = new Vm(
+            new InstallContext(),
+            () =>
+            {
+                factoryCalls++;
+                return new EnvironmentCheckService(new IEnvironmentCheck[] { slow });
+            },
+            () => new InstallerWorkerConfig());
+
+        await vm.LoadAsync();
+
+        var firstRun = vm.Checks.RunChecksCommand.ExecuteAsync(null);
+        Assert.True(vm.Checks.IsRunning);
+
+        await vm.Checks.RunChecksCommand.ExecuteAsync(null); // second click while the first run is still in flight
+
+        Assert.Equal(1, factoryCalls);
+        Assert.Equal(1, slow.CallCount);
+
+        gate.SetResult();
+        await firstRun;
+
+        Assert.False(vm.Checks.IsRunning);
+    }
+
+    [Fact]
+    public async Task Checks_run_against_the_installed_configuration_not_context_defaults()
+    {
+        InstallContext? capturedCtx = null;
+        var probe = new FakeEnvironmentCheck("probe", CheckSeverity.Warning, (ctx, _) =>
+        {
+            capturedCtx = ctx;
+            return Task.FromResult(CheckResult.Ok("probe", CheckSeverity.Warning, "checks.probe.title", "ok"));
+        });
+
+        var sharedContext = new InstallContext { InstallDirectory = @"C:\Program Files\ClaudeDo" };
+        var vm = new Vm(
+            sharedContext,
+            () => new EnvironmentCheckService(new IEnvironmentCheck[] { probe }),
+            () => new InstallerWorkerConfig { ClaudeBin = @"C:\installed\claude.exe", SignalRPort = 55555 });
+
+        await vm.LoadAsync();
+        await vm.Checks.RunChecksCommand.ExecuteAsync(null);
+
+        Assert.NotNull(capturedCtx);
+        Assert.Equal(@"C:\installed\claude.exe", capturedCtx!.ClaudeBin);
+        Assert.Equal(55555, capturedCtx.SignalRPort);
+        Assert.Equal(@"C:\Program Files\ClaudeDo", capturedCtx.InstallDirectory);
+    }
+
+    [Fact]
+    public async Task Worker_already_running_on_the_installed_signalr_port_reports_ok()
+    {
+        var port = GetFreePort();
+        using var occupying = new TcpListener(IPAddress.Loopback, port);
+        occupying.Start();
+
+        var sharedContext = new InstallContext { ExternalMcpPort = GetFreePort() };
+        var vm = new Vm(
+            sharedContext,
+            () => new EnvironmentCheckService(new IEnvironmentCheck[] { new PortCheck(new FakeOwnerResolver("ClaudeDo.Worker")) }),
+            () => new InstallerWorkerConfig { SignalRPort = port });
+
+        await vm.LoadAsync();
+        await vm.Checks.RunChecksCommand.ExecuteAsync(null);
+
+        var row = Assert.Single(vm.Checks.Rows);
+        Assert.Equal(CheckStatus.Ok, row.Status);
+    }
+}