feat(app): Game Tuner screen + Home tile; move it out of Custom (UI pass)

ImPanick · claude · ImPanick · commit 43280c562a10 · 2026-05-31T13:31:40.000-08:00
Per owner: Game Tuning is its own top-level feature, not a Custom category. - Home: a new Game Tuner mode tile (⚙ cog) next to Custom Editor — the row is now four tiles (Recovery / Lazy Max / Custom / Game Tuner) and all four navigate. Game Tuning was removed from the Custom editor sidebar. - GameTunerViewModel / GameTunerView: reads the client's Engine.ini and lists each tunable. Toggles disable an effect; numbers show a toggle + a slider AND a free-text number box, both bound to the same value which CLAMPS to the setting's stable-max (typing 99999 in the box snaps back to the cap). Apply (behind a confirm dialog) writes Engine.ini via the Core service — backed up + atomic; restart Icarus to take effect. - Wiring: ShellViewModel GameTunerKey + resolve; HomeViewModel OpenGameTunerCommand; MainWindow DataTemplate GameTunerViewModel→GameTunerView; DI registers GameTuningCatalog + GameTuningService + GameTunerViewModel (validated by ValidateOnBuild). Caveat shown in the confirm + GAME-TUNING.md: these are standard UE cvars; Icarus may ignore/ clamp some — live verification (GT-6) is owner-run. Verified: dotnet build -c Debug and -c Release 0/0, dotnet test 230/230, dotnet format clean, governance-lint clean, smoke launch renders + the full DI graph (incl. GameTunerViewModel) validates at startup. Click-through QA is owner-run. Agent: claude-code/2.1.149 Consulted: AGENTS.md, .agent/CONSTITUTION.md#III,#V, .agent/CODE_STYLE.md#3,#7, docs/GAME-TUNING.md, docs/IUUT-PROJECT-DOCUMENTATION.md#20, docs/UI-DESIGN-CONCEPT.md Co-Authored-By: Claude <noreply@anthropic.com>
diff --git a/docs/IMPLEMENTATION-PLAN.md b/docs/IMPLEMENTATION-PLAN.md
@@ -32,13 +32,16 @@ SHA-1 load check passes) + `MountsModel`/`MountEditService` + **`FlagsFileCodec`
 - **Done:** navigation **shell** (in-window page swap — `INavigationService`/`ShellViewModel`,
   Home extracted to `Views/HomeView`, DataTemplate page rendering, Back/Home nav bar); the
   **Recovery screen** (wired to `RecoveryPlanner`/`RecoveryService`/`RecoveryAdvisor`: pick save →
-  Scan → per-file plan + advisories → confirm → Repair → report); and the **Custom editor shell**
-  (`CustomViewModel`/`CustomView`: profile selector + category sidebar → editor panel, incl. a new
-  **Game Tuning** category per owner request). All three tiles on Home now navigate. DI uses
-  `ValidateOnBuild` (whole graph validated at startup). Owner-run visual QA pending.
+  Scan → per-file plan + advisories → confirm → Repair → report); the **Custom editor shell**
+  (`CustomViewModel`/`CustomView`: profile selector + category sidebar → editor panel); and the
+  **Game Tuner** — its own Home tile (⚙, next to Custom; moved OUT of the Custom sidebar) backed by
+  the **Phase 7 Game Tuning Core, pulled forward** (`EngineIni` codec + `GameTuningCatalog` w/
+  stable-max caps + `GameTuningService`). `GameTunerView`: per setting a toggle, or toggle + slider +
+  **free-text number box clamped to the stable max**, applied to Engine.ini (backed up, atomic).
+  **All four Home tiles navigate.** DI uses `ValidateOnBuild`. Owner-run visual QA pending.
 - **Remaining UI:** wire the Custom **category editors** to their (already-built) Core services
   (Account/Characters/Accolades-Bestiary/Stash/…), Settings, Advanced/Raw viewer, Troubleshooting
-  modal, Game Tuning tab content, and a **polish pass**.
+  modal, and a **polish pass**. (Game Tuner is functional; GT-6 live-cvar verification still owner-run.)
 - **Polish backlog (owner-noted, screenshots 2026-05-31):** general "not great"/spacing pass; the
   **Recovery header title+subtitle overlap** (two TextBlocks stacked in one grid cell — split into
   rows); revisit glass contrast/typography. Take note, don't act mid-feature.
diff --git a/src/IUUT.App/App.xaml.cs b/src/IUUT.App/App.xaml.cs
@@ -3,6 +3,7 @@
 using IUUT.App.ViewModels;
 using IUUT.Core.Abstractions;
 using IUUT.Core.Catalog;
+using IUUT.Core.GameTuning;
 using IUUT.Core.Io;
 using IUUT.Core.Recovery;
 using IUUT.Core.Services;
@@ -72,12 +73,17 @@ private static ServiceProvider ConfigureServices()
         services.AddSingleton<RecoveryAdvisor>();
         services.AddSingleton<RecoveryService>();
 
+        // --- Game Tuning (Engine.ini, master §20.1) ---------------------------
+        services.AddSingleton<GameTuningCatalog>();
+        services.AddSingleton<GameTuningService>();
+
         // --- UI shell + pages -------------------------------------------------
         services.AddSingleton<ShellViewModel>();
         services.AddSingleton<INavigationService>(sp => sp.GetRequiredService<ShellViewModel>());
         services.AddSingleton<HomeViewModel>();
         services.AddSingleton<RecoveryViewModel>();
         services.AddSingleton<CustomViewModel>();
+        services.AddSingleton<GameTunerViewModel>();
         services.AddSingleton<MainWindow>();
 
         // ValidateOnBuild constructs every registration at startup, so a broken DI graph
diff --git a/src/IUUT.App/MainWindow.xaml b/src/IUUT.App/MainWindow.xaml
@@ -34,6 +34,9 @@
         <DataTemplate DataType="{x:Type vm:CustomViewModel}">
             <views:CustomView />
         </DataTemplate>
+        <DataTemplate DataType="{x:Type vm:GameTunerViewModel}">
+            <views:GameTunerView />
+        </DataTemplate>
     </ui:FluentWindow.Resources>
 
     <Grid>
diff --git a/src/IUUT.App/ViewModels/CustomViewModel.cs b/src/IUUT.App/ViewModels/CustomViewModel.cs
@@ -155,13 +155,6 @@ private static IReadOnlyList<CustomCategory> BuildCategories() =>
             Status = "Core ready — FlagsFileCodec.",
         },
         new()
-        {
-            Glyph = "⚙",
-            Label = "Game Tuning",
-            Description = "Engine.ini performance/visual cvar toggles — \"Buff FPS\", fog/volumetrics, quality scalars, FPS + net.",
-            Status = "Future — Phase 7 (docs/GAME-TUNING.md). Bundled/sideloaded, offline; not yet built.",
-        },
-        new()
         {
             Glyph = "🧾",
             Label = "Advanced / Raw",
diff --git a/src/IUUT.App/ViewModels/GameTunerViewModel.cs b/src/IUUT.App/ViewModels/GameTunerViewModel.cs
@@ -0,0 +1,116 @@
+using System.Collections.ObjectModel;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using IUUT.Core.GameTuning;
+using IUUT.Core.Services;
+
+namespace IUUT.App.ViewModels;
+
+/// <summary>
+/// The Game Tuner page (master §20.1, docs/GAME-TUNING.md): reads the client's Engine.ini, shows
+/// each tunable as a toggle (or toggle + slider/number box for numbers), and applies the changes.
+/// Writes only Engine.ini (never save files), backed up + atomic via the Core service.
+/// </summary>
+public sealed class GameTunerViewModel : ObservableObject
+{
+    private readonly GameTuningService _service;
+    private readonly GameTuningCatalog _catalog;
+
+    private string _saveRoot;
+    private bool _isBusy;
+    private string _statusMessage = "Reads the game's Engine.ini.";
+
+    /// <summary>Creates the Game Tuner over the tuning service + catalog.</summary>
+    public GameTunerViewModel(GameTuningService service, GameTuningCatalog catalog)
+    {
+        ArgumentNullException.ThrowIfNull(service);
+        ArgumentNullException.ThrowIfNull(catalog);
+        _service = service;
+        _catalog = catalog;
+        _saveRoot = SaveDiscoveryService.ResolveDefaultSaveRoot();
+
+        Settings = [];
+        LoadCommand = new RelayCommand(Load);
+    }
+
+    /// <summary>The tunable settings.</summary>
+    public ObservableCollection<GameTuningSettingViewModel> Settings { get; }
+
+    /// <summary>(Re)reads Engine.ini.</summary>
+    public IRelayCommand LoadCommand { get; }
+
+    /// <summary>The Icarus save root (Engine.ini is under <c>Config\WindowsNoEditor\</c>).</summary>
+    public string SaveRoot
+    {
+        get => _saveRoot;
+        set => SetProperty(ref _saveRoot, value);
+    }
+
+    /// <summary>The resolved Engine.ini path (for display).</summary>
+    public string EngineIniPath => GameTuningService.ResolveEngineIniPath(SaveRoot);
+
+    /// <summary>True while applying.</summary>
+    public bool IsBusy
+    {
+        get => _isBusy;
+        private set => SetProperty(ref _isBusy, value);
+    }
+
+    /// <summary>Status-bar message.</summary>
+    public string StatusMessage
+    {
+        get => _statusMessage;
+        private set => SetProperty(ref _statusMessage, value);
+    }
+
+    /// <summary>Reads the current Engine.ini state into the settings list.</summary>
+    public void Load()
+    {
+        try
+        {
+            Settings.Clear();
+            foreach (var state in _service.ReadCurrent(SaveRoot, _catalog))
+            {
+                Settings.Add(new GameTuningSettingViewModel(state));
+            }
+
+            StatusMessage = $"{Settings.Count(s => s.Enabled)} of {Settings.Count} settings active · {EngineIniPath}";
+        }
+#pragma warning disable CA1031 // UI boundary: surface, never crash.
+        catch (Exception ex)
+        {
+            StatusMessage = $"Could not read Engine.ini: {ex.Message}";
+        }
+#pragma warning restore CA1031
+    }
+
+    /// <summary>Applies the settings to Engine.ini (call after a user confirm), then refreshes.</summary>
+    public async Task ApplyAsync()
+    {
+        if (IsBusy)
+        {
+            return;
+        }
+
+        IsBusy = true;
+        try
+        {
+            var ok = await _service.ApplyAsync(SaveRoot, Settings.Select(s => s.State).ToList());
+            StatusMessage = ok
+                ? "Applied to Engine.ini — restart Icarus for the changes to take effect."
+                : "Apply failed; the original Engine.ini is unchanged.";
+        }
+#pragma warning disable CA1031 // UI boundary: surface, never crash.
+        catch (Exception ex)
+        {
+            StatusMessage = $"Apply failed: {ex.Message}";
+        }
+#pragma warning restore CA1031
+        finally
+        {
+            IsBusy = false;
+        }
+
+        Load();
+    }
+}
diff --git a/src/IUUT.App/ViewModels/GameTuningSettingViewModel.cs b/src/IUUT.App/ViewModels/GameTuningSettingViewModel.cs
@@ -0,0 +1,73 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using IUUT.Core.GameTuning;
+
+namespace IUUT.App.ViewModels;
+
+/// <summary>
+/// Binding-shape for one tunable Engine.ini setting. <see cref="Value"/> clamps to the setting's
+/// stable maximum, so both the slider and the free-text number box stay within the safe cap.
+/// </summary>
+public sealed class GameTuningSettingViewModel : ObservableObject
+{
+    private readonly GameTuningState _state;
+
+    /// <summary>Wraps a tuning state.</summary>
+    public GameTuningSettingViewModel(GameTuningState state)
+    {
+        ArgumentNullException.ThrowIfNull(state);
+        _state = state;
+    }
+
+    /// <summary>The underlying state (passed back to the service on apply).</summary>
+    public GameTuningState State => _state;
+
+    /// <summary>Setting label.</summary>
+    public string Label => _state.Setting.Label;
+
+    /// <summary>Setting description.</summary>
+    public string Description => _state.Setting.Description;
+
+    /// <summary>Whether this is a numeric setting (shows the slider + number box).</summary>
+    public bool IsNumber => _state.Setting.Kind == GameTuningKind.Number;
+
+    /// <summary>Slider minimum.</summary>
+    public double Minimum => _state.Setting.Min;
+
+    /// <summary>Slider maximum — the stable cap.</summary>
+    public double Maximum => _state.Setting.StableMax;
+
+    /// <summary>Slider step.</summary>
+    public double Step => _state.Setting.Step;
+
+    /// <summary>Optional unit suffix.</summary>
+    public string Unit => _state.Setting.Unit ?? "";
+
+    /// <summary>Whether IUUT manages this cvar (on → written; off → removed/game default).</summary>
+    public bool Enabled
+    {
+        get => _state.Enabled;
+        set
+        {
+            if (_state.Enabled != value)
+            {
+                _state.Enabled = value;
+                OnPropertyChanged();
+            }
+        }
+    }
+
+    /// <summary>The numeric value, clamped to [<see cref="Minimum"/>, <see cref="Maximum"/>] (the stable cap).</summary>
+    public double Value
+    {
+        get => _state.Value;
+        set
+        {
+            var clamped = Math.Clamp(value, Minimum, Maximum);
+            if (Math.Abs(_state.Value - clamped) > double.Epsilon)
+            {
+                _state.Value = clamped;
+                OnPropertyChanged();
+            }
+        }
+    }
+}
diff --git a/src/IUUT.App/ViewModels/HomeViewModel.cs b/src/IUUT.App/ViewModels/HomeViewModel.cs
@@ -41,6 +41,7 @@ public HomeViewModel(HomeService home, LazyMaxApplyService apply, INavigationSer
         LoadCommand = new AsyncRelayCommand(LoadAsync);
         OpenRecoveryCommand = new RelayCommand(() => _navigation.NavigateTo(ShellViewModel.RecoveryKey));
         OpenCustomCommand = new RelayCommand(() => _navigation.NavigateTo(ShellViewModel.CustomKey));
+        OpenGameTunerCommand = new RelayCommand(() => _navigation.NavigateTo(ShellViewModel.GameTunerKey));
     }
 
     /// <summary>Discovered save profiles for the dropdown.</summary>
@@ -55,6 +56,9 @@ public HomeViewModel(HomeService home, LazyMaxApplyService apply, INavigationSer
     /// <summary>Opens the Custom editor page.</summary>
     public IRelayCommand OpenCustomCommand { get; }
 
+    /// <summary>Opens the Game Tuner (Engine.ini) page.</summary>
+    public IRelayCommand OpenGameTunerCommand { get; }
+
     /// <summary>The save root being scanned (editable; Browse updates it).</summary>
     public string SaveRoot
     {
diff --git a/src/IUUT.App/ViewModels/ShellViewModel.cs b/src/IUUT.App/ViewModels/ShellViewModel.cs
@@ -21,6 +21,9 @@ public sealed class ShellViewModel : ObservableObject, INavigationService
     /// <summary>The Custom editor page key.</summary>
     public const string CustomKey = "Custom";
 
+    /// <summary>The Game Tuner page key.</summary>
+    public const string GameTunerKey = "GameTuner";
+
     private readonly IServiceProvider _services;
     private readonly Stack<string> _back = new();
 
@@ -95,6 +98,7 @@ private void SetPage(string key)
         HomeKey => _services.GetRequiredService<HomeViewModel>(),
         RecoveryKey => _services.GetRequiredService<RecoveryViewModel>(),
         CustomKey => _services.GetRequiredService<CustomViewModel>(),
+        GameTunerKey => _services.GetRequiredService<GameTunerViewModel>(),
         _ => throw new ArgumentOutOfRangeException(nameof(key), key, "Unknown page key."),
     };
 }
diff --git a/src/IUUT.App/Views/GameTunerView.xaml b/src/IUUT.App/Views/GameTunerView.xaml
@@ -0,0 +1,96 @@
+<UserControl x:Class="IUUT.App.Views.GameTunerView"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d">
+
+    <!-- Game Tuner (master §20.1, docs/GAME-TUNING.md). DataContext = GameTunerViewModel. -->
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+            <RowDefinition Height="Auto" />
+        </Grid.RowDefinitions>
+
+        <!-- Header -->
+        <Border Grid.Row="0" Style="{StaticResource GlassCard}" Padding="16">
+            <Grid>
+                <Grid.ColumnDefinitions>
+                    <ColumnDefinition Width="*" />
+                    <ColumnDefinition Width="Auto" />
+                </Grid.ColumnDefinitions>
+                <StackPanel Grid.Column="0">
+                    <TextBlock Text="⚙  Game Tuner" Style="{StaticResource TitleText}" />
+                    <TextBlock Text="Engine.ini performance &amp; visual tweaks — toggle effects off, set quality/FPS. Standard Unreal cvars; restart Icarus to apply. A backup is taken before any write."
+                               Style="{StaticResource MutedText}" TextWrapping="Wrap" Margin="0,4,0,0" />
+                    <TextBlock Text="{Binding EngineIniPath}" Style="{StaticResource MonoText}" Margin="0,6,0,0" TextTrimming="CharacterEllipsis" />
+                </StackPanel>
+                <Button Grid.Column="1" Content="Reload" Command="{Binding LoadCommand}" VerticalAlignment="Top" Padding="14,4" />
+            </Grid>
+        </Border>
+
+        <!-- Settings list -->
+        <Border Grid.Row="1" Style="{StaticResource GlassCard}" Padding="12" Margin="0,12,0,0">
+            <ScrollViewer VerticalScrollBarVisibility="Auto">
+                <ItemsControl ItemsSource="{Binding Settings}">
+                    <ItemsControl.ItemTemplate>
+                        <DataTemplate>
+                            <Border Margin="0,0,0,8" Padding="14,10" CornerRadius="4"
+                                    Background="{StaticResource DataBackdropBrush}"
+                                    BorderBrush="{StaticResource GlassStrokeBrush}" BorderThickness="1">
+                                <Grid>
+                                    <Grid.ColumnDefinitions>
+                                        <ColumnDefinition Width="*" />
+                                        <ColumnDefinition Width="Auto" />
+                                        <ColumnDefinition Width="Auto" />
+                                    </Grid.ColumnDefinitions>
+
+                                    <StackPanel Grid.Column="0" VerticalAlignment="Center" Margin="0,0,12,0">
+                                        <TextBlock Text="{Binding Label}" Style="{StaticResource BodyText}" />
+                                        <TextBlock Text="{Binding Description}" Style="{StaticResource MutedText}" TextWrapping="Wrap" Margin="0,2,0,0" />
+                                    </StackPanel>
+
+                                    <CheckBox Grid.Column="1" IsChecked="{Binding Enabled, Mode=TwoWay}" VerticalAlignment="Center" Margin="0,0,16,0" />
+
+                                    <StackPanel Grid.Column="2" Orientation="Horizontal" VerticalAlignment="Center">
+                                        <StackPanel.Style>
+                                            <Style TargetType="StackPanel">
+                                                <Setter Property="Visibility" Value="Visible" />
+                                                <Style.Triggers>
+                                                    <DataTrigger Binding="{Binding IsNumber}" Value="False">
+                                                        <Setter Property="Visibility" Value="Collapsed" />
+                                                    </DataTrigger>
+                                                </Style.Triggers>
+                                            </Style>
+                                        </StackPanel.Style>
+                                        <Slider Width="150" VerticalAlignment="Center"
+                                                Minimum="{Binding Minimum}" Maximum="{Binding Maximum}"
+                                                Value="{Binding Value, Mode=TwoWay}"
+                                                TickFrequency="{Binding Step}" IsSnapToTickEnabled="True"
+                                                IsEnabled="{Binding Enabled}" />
+                                        <TextBox Width="62" Margin="10,0,4,0" VerticalAlignment="Center"
+                                                 Text="{Binding Value, Mode=TwoWay, UpdateSourceTrigger=LostFocus}"
+                                                 IsEnabled="{Binding Enabled}" />
+                                        <TextBlock Text="{Binding Unit}" Style="{StaticResource MutedText}" VerticalAlignment="Center" />
+                                    </StackPanel>
+                                </Grid>
+                            </Border>
+                        </DataTemplate>
+                    </ItemsControl.ItemTemplate>
+                </ItemsControl>
+            </ScrollViewer>
+        </Border>
+
+        <!-- Status + apply -->
+        <Grid Grid.Row="2" Margin="0,12,0,0">
+            <Grid.ColumnDefinitions>
+                <ColumnDefinition Width="*" />
+                <ColumnDefinition Width="Auto" />
+            </Grid.ColumnDefinitions>
+            <TextBlock Grid.Column="0" Text="{Binding StatusMessage}" Style="{StaticResource MutedText}"
+                       VerticalAlignment="Center" TextWrapping="Wrap" Margin="0,0,12,0" />
+            <Button Grid.Column="1" Content="⚙  Apply to Engine.ini" Click="OnApply" Padding="18,8" FontWeight="SemiBold" />
+        </Grid>
+    </Grid>
+</UserControl>
diff --git a/src/IUUT.App/Views/GameTunerView.xaml.cs b/src/IUUT.App/Views/GameTunerView.xaml.cs
diff --git a/src/IUUT.App/Views/HomeView.xaml b/src/IUUT.App/Views/HomeView.xaml
