[GUI] add game library watcher & remove rescan button (#678)

src/SharpEmu.GUI/GameEntry.cs

@@ -8,6 +8,15 @@ using Avalonia.Media.Imaging;
 
 namespace SharpEmu.GUI;
 
+[Flags]
+internal enum GameEntryChanges
+{
+    None = 0,
+    Metadata = 1,
+    Cover = 2,
+    Background = 4,
+}
+
 public sealed class GameEntry : INotifyPropertyChanged
 {
     // Placeholder gradients for games without cover art, picked
@@ -27,29 +36,39 @@ public sealed class GameEntry : INotifyPropertyChanged
     private Bitmap? _cover;
     private IBrush? _placeholderBrush;
     private long _sizeBytes;
+    private string _name;
+    private string? _titleId;
+    private string? _version;
+    private string? _coverPath;
+    private string? _backgroundPath;
+    private string _initials;
+    private FileStamp _coverStamp;
+    private FileStamp _backgroundStamp;
 
     public GameEntry(
         string name, string? titleId, string? version, string path, long sizeBytes,
         string? coverPath, string? backgroundPath)
     {
-        Name = name;
-        TitleId = titleId;
-        Version = version;
+        _name = name;
+        _titleId = titleId;
+        _version = version;
         Path = path;
         _sizeBytes = sizeBytes;
-        CoverPath = coverPath;
-        BackgroundPath = backgroundPath;
-        Initials = ComputeInitials(name);
+        _coverPath = coverPath;
+        _backgroundPath = backgroundPath;
+        _initials = ComputeInitials(name);
+        _coverStamp = FileStamp.Read(coverPath);
+        _backgroundStamp = FileStamp.Read(backgroundPath);
     }
 
     public event PropertyChangedEventHandler? PropertyChanged;
 
-    public string Name { get; }
+    public string Name => _name;
 
-    public string? TitleId { get; }
+    public string? TitleId => _titleId;
 
     /// <summary>Content version from sce_sys/param.json, e.g. "01.000.000".</summary>
-    public string? Version { get; }
+    public string? Version => _version;
 
     public string Path { get; }
 
@@ -75,10 +94,10 @@ public sealed class GameEntry : INotifyPropertyChanged
     }
 
     /// <summary>Path to the cover art image shipped with the game, if found.</summary>
-    public string? CoverPath { get; }
+    public string? CoverPath => _coverPath;
 
     /// <summary>Path to the key art (pic0/pic1) shipped with the game, if found.</summary>
-    public string? BackgroundPath { get; }
+    public string? BackgroundPath => _backgroundPath;
 
     /// <summary>
     /// Decoded key art used as the window backdrop while this game is
@@ -86,7 +105,7 @@ public sealed class GameEntry : INotifyPropertyChanged
     /// </summary>
     public Bitmap? Background { get; set; }
 
-    public string Initials { get; }
+    public string Initials => _initials;
 
     // Built lazily: brushes are AvaloniaObjects that must be created on the
     // UI thread, while GameEntry itself is constructed on the scan thread.
@@ -121,6 +140,74 @@ public sealed class GameEntry : INotifyPropertyChanged
     /// <summary>Formatted install size badge shown in the launch bar.</summary>
     public string SizeText => FormatSize(SizeBytes);
 
+    /// <summary>
+    /// Applies a fresh filesystem scan to this presentation object so its
+    /// ListBox container and selection remain stable
+    /// </summary>
+    internal GameEntryChanges UpdateFrom(GameEntry scanned)
+    {
+        if (!Path.Equals(scanned.Path, GameLibraryPath.Comparison))
+        {
+            throw new ArgumentException("Only matching game paths can be reconciled", nameof(scanned));
+        }
+
+        var changes = GameEntryChanges.None;
+        if (!string.Equals(_name, scanned.Name, StringComparison.Ordinal))
+        {
+            _name = scanned.Name;
+            _initials = ComputeInitials(scanned.Name);
+            _placeholderBrush = null;
+            RaisePropertyChanged(nameof(Name));
+            RaisePropertyChanged(nameof(Initials));
+            RaisePropertyChanged(nameof(PlaceholderBrush));
+            changes |= GameEntryChanges.Metadata;
+        }
+
+        if (!string.Equals(_titleId, scanned.TitleId, StringComparison.Ordinal))
+        {
+            _titleId = scanned.TitleId;
+            RaisePropertyChanged(nameof(TitleId));
+            RaisePropertyChanged(nameof(HasTitleId));
+            changes |= GameEntryChanges.Metadata;
+        }
+
+        if (!string.Equals(_version, scanned.Version, StringComparison.Ordinal))
+        {
+            _version = scanned.Version;
+            RaisePropertyChanged(nameof(Version));
+            RaisePropertyChanged(nameof(VersionText));
+            RaisePropertyChanged(nameof(HasVersion));
+            changes |= GameEntryChanges.Metadata;
+        }
+
+        if (!string.Equals(_coverPath, scanned.CoverPath, StringComparison.Ordinal)
+            || _coverStamp != scanned._coverStamp)
+        {
+            _coverPath = scanned.CoverPath;
+            _coverStamp = scanned._coverStamp;
+            var previousCover = Cover;
+            Cover = null;
+            previousCover?.Dispose();
+            changes |= GameEntryChanges.Cover;
+        }
+
+        if (!string.Equals(_backgroundPath, scanned.BackgroundPath, StringComparison.Ordinal)
+            || _backgroundStamp != scanned._backgroundStamp)
+        {
+            _backgroundPath = scanned.BackgroundPath;
+            _backgroundStamp = scanned._backgroundStamp;
+            var previousBackground = Background;
+            Background = null;
+            previousBackground?.Dispose();
+            changes |= GameEntryChanges.Background;
+        }
+
+        return changes;
+    }
+
+    private void RaisePropertyChanged(string propertyName) =>
+        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+
     private static string ComputeInitials(string name)
     {
         var initials = name
@@ -164,4 +251,29 @@ public sealed class GameEntry : INotifyPropertyChanged
             _ => $"{bytes} B",
         };
     }
+
+    private readonly record struct FileStamp(long Length, long LastWriteTimeUtcTicks)
+    {
+        public static FileStamp Read(string? path)
+        {
+            if (path is null)
+            {
+                return default;
+            }
+
+            try
+            {
+                var file = new FileInfo(path);
+                return file.Exists
+                    ? new FileStamp(file.Length, file.LastWriteTimeUtc.Ticks)
+                    : default;
+            }
+            catch (Exception exception) when (
+                exception is IOException
+                    or UnauthorizedAccessException)
+            {
+                return default;
+            }
+        }
+    }
 }

src/SharpEmu.GUI/GameLibraryPath.cs

@@ -0,0 +1,17 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.GUI;
+
+internal static class GameLibraryPath
+{
+    public static StringComparer Comparer { get; } =
+        OperatingSystem.IsWindows() || OperatingSystem.IsMacOS()
+            ? StringComparer.OrdinalIgnoreCase
+            : StringComparer.Ordinal;
+
+    public static StringComparison Comparison { get; } =
+        OperatingSystem.IsWindows() || OperatingSystem.IsMacOS()
+            ? StringComparison.OrdinalIgnoreCase
+            : StringComparison.Ordinal;
+}

src/SharpEmu.GUI/GameLibraryReconciler.cs

@@ -0,0 +1,98 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.GUI;
+
+internal sealed record GameLibraryReconciliation(
+    IReadOnlyList<GameEntry> Games,
+    IReadOnlyList<GameEntry> CoversToLoad,
+    IReadOnlySet<GameEntry> BackgroundsChanged);
+
+/// <summary>
+/// Applies filesystem scan results while preserving presentation object
+/// identity for games that remain in the library
+/// </summary>
+internal static class GameLibraryReconciler
+{
+    public static GameLibraryReconciliation Reconcile(
+        IReadOnlyList<GameEntry> current,
+        IReadOnlyList<GameEntry> scanned)
+    {
+        var existingByPath = current.ToDictionary(game => game.Path, GameLibraryPath.Comparer);
+        var merged = new List<GameEntry>(scanned.Count);
+        var coversToLoad = new List<GameEntry>();
+        var backgroundsChanged = new HashSet<GameEntry>();
+
+        foreach (var scannedGame in scanned)
+        {
+            if (!existingByPath.TryGetValue(scannedGame.Path, out var existing))
+            {
+                merged.Add(scannedGame);
+                if (scannedGame.CoverPath is not null)
+                {
+                    coversToLoad.Add(scannedGame);
+                }
+
+                continue;
+            }
+
+            var changes = existing.UpdateFrom(scannedGame);
+            merged.Add(existing);
+            if ((changes & GameEntryChanges.Cover) != 0 && existing.CoverPath is not null)
+            {
+                coversToLoad.Add(existing);
+            }
+
+            if ((changes & GameEntryChanges.Background) != 0)
+            {
+                backgroundsChanged.Add(existing);
+            }
+        }
+
+        return new GameLibraryReconciliation(merged, coversToLoad, backgroundsChanged);
+    }
+
+    /// <summary>
+    /// Reorders, inserts and removes only the items needed to reach the desired
+    /// visible sequence
+    /// </summary>
+    public static void ReconcileVisibleGames(
+        IList<GameEntry> visible,
+        IReadOnlyList<GameEntry> desired)
+    {
+        for (var index = 0; index < desired.Count; index++)
+        {
+            var game = desired[index];
+            if (index < visible.Count && ReferenceEquals(visible[index], game))
+            {
+                continue;
+            }
+
+            var existingIndex = -1;
+            for (var candidate = index + 1; candidate < visible.Count; candidate++)
+            {
+                if (ReferenceEquals(visible[candidate], game))
+                {
+                    existingIndex = candidate;
+                    break;
+                }
+            }
+
+            if (existingIndex >= 0)
+            {
+                var existing = visible[existingIndex];
+                visible.RemoveAt(existingIndex);
+                visible.Insert(index, existing);
+            }
+            else
+            {
+                visible.Insert(index, game);
+            }
+        }
+
+        while (visible.Count > desired.Count)
+        {
+            visible.RemoveAt(visible.Count - 1);
+        }
+    }
+}

src/SharpEmu.GUI/GameLibraryWatcher.cs

@@ -0,0 +1,147 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.GUI;
+
+/// <summary>
+/// Watches configured game folders and collapses filesystem bursts into one
+/// library refresh request
+/// </summary>
+internal sealed class GameLibraryWatcher : IDisposable
+{
+    private static readonly TimeSpan DefaultDebounceInterval = TimeSpan.FromMilliseconds(600);
+
+    private readonly object _sync = new();
+    private readonly TimeSpan _debounceInterval;
+    private readonly List<FileSystemWatcher> _watchers = [];
+    private Timer? _debounceTimer;
+    private bool _disposed;
+
+    internal GameLibraryWatcher(TimeSpan? debounceInterval = null)
+    {
+        _debounceInterval = debounceInterval ?? DefaultDebounceInterval;
+    }
+
+    public event EventHandler? RefreshRequested;
+
+    /// <summary>
+    /// Replaces the watched roots with the current configured game folders
+    /// </summary>
+    public void Watch(IReadOnlyList<string> folders)
+    {
+        lock (_sync)
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            foreach (var watcher in _watchers)
+            {
+                watcher.Dispose();
+            }
+
+            _watchers.Clear();
+            _debounceTimer?.Change(Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
+            foreach (var folder in folders.Distinct(GameLibraryPath.Comparer))
+            {
+                if (string.IsNullOrWhiteSpace(folder) || !Directory.Exists(folder))
+                {
+                    continue;
+                }
+
+                try
+                {
+                    var watcher = new FileSystemWatcher(folder)
+                    {
+                        IncludeSubdirectories = true,
+                        NotifyFilter = NotifyFilters.FileName
+                                       | NotifyFilters.DirectoryName
+                                       | NotifyFilters.LastWrite
+                                       | NotifyFilters.Size,
+                    };
+                    watcher.Created += OnFileSystemChanged;
+                    watcher.Changed += OnFileSystemChanged;
+                    watcher.Deleted += OnFileSystemChanged;
+                    watcher.Renamed += OnFileSystemChanged;
+                    watcher.Error += OnWatcherError;
+                    watcher.EnableRaisingEvents = true;
+                    _watchers.Add(watcher);
+                }
+                catch (Exception exception) when (
+                    exception is ArgumentException
+                        or IOException
+                        or UnauthorizedAccessException)
+                {
+                    Console.Error.WriteLine(
+                        $"[GUI][WARN] Could not watch game folder '{folder}': {exception.Message}");
+                }
+            }
+        }
+    }
+
+    private void OnFileSystemChanged(object sender, FileSystemEventArgs args)
+        => ScheduleRefresh();
+
+    private void OnWatcherError(object sender, ErrorEventArgs args)
+    {
+        Console.Error.WriteLine(
+            $"[GUI][WARN] Game library watcher reported an error: {args.GetException().Message}");
+        ScheduleRefresh();
+    }
+
+    private void ScheduleRefresh()
+    {
+        lock (_sync)
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            if (_debounceTimer is null)
+            {
+                _debounceTimer = new Timer(
+                    static state => ((GameLibraryWatcher)state!).RaiseRefreshRequested(),
+                    this,
+                    _debounceInterval,
+                    Timeout.InfiniteTimeSpan);
+            }
+            else
+            {
+                _debounceTimer.Change(_debounceInterval, Timeout.InfiniteTimeSpan);
+            }
+        }
+    }
+
+    private void RaiseRefreshRequested()
+    {
+        lock (_sync)
+        {
+            if (_disposed)
+            {
+                return;
+            }
+        }
+
+        RefreshRequested?.Invoke(this, EventArgs.Empty);
+    }
+
+    public void Dispose()
+    {
+        lock (_sync)
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            _disposed = true;
+            _debounceTimer?.Dispose();
+            _debounceTimer = null;
+            foreach (var watcher in _watchers)
+            {
+                watcher.Dispose();
+            }
+
+            _watchers.Clear();
+        }
+    }
+}

src/SharpEmu.GUI/Languages/ar.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "ابحث في المكتبة...",
   "Library.AddFolder": "＋ إضافة مجلد",
-  "Library.Rescan": "⟳ إعادة الفحص",
   "Library.OpenFile": "فتح ملف...",
 
   "Library.Context.Launch": "تشغيل",

src/SharpEmu.GUI/Languages/br.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Pesquisar na biblioteca…",
   "Library.AddFolder": "＋ Adicionar pasta",
-  "Library.Rescan": "⟳ Atualizar biblioteca",
   "Library.OpenFile": "Abrir arquivo…",
 
   "Library.Context.Launch": "Jogar",

src/SharpEmu.GUI/Languages/de.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Bibliothek durchsuchen…",
   "Library.AddFolder": "＋ Spielordner hinzufügen",
-  "Library.Rescan": "⟳ Neu scannen",
   "Library.OpenFile": "Datei öffnen…",
 
   "Library.Context.Launch": "Starten",

src/SharpEmu.GUI/Languages/dk.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Søg i biblioteket…",
   "Library.AddFolder": "＋ Tilføj mappe",
-  "Library.Rescan": "⟳ Genindlæs",
   "Library.OpenFile": "Åbn fil…",
 
   "Library.Context.Launch": "Start",

src/SharpEmu.GUI/Languages/en.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Search library…",
   "Library.AddFolder": "＋ Add folder",
-  "Library.Rescan": "⟳ Rescan",
   "Library.OpenFile": "Open file…",
 
   "Library.Context.Launch": "Launch",

src/SharpEmu.GUI/Languages/es.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Buscar en la biblioteca…",
   "Library.AddFolder": "＋ Añadir carpeta",
-  "Library.Rescan": "⟳ Volver a escanear",
   "Library.OpenFile": "Abrir archivo…",
 
   "Library.Context.Launch": "Iniciar",

src/SharpEmu.GUI/Languages/fr.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Rechercher dans la bibliothèque…",
   "Library.AddFolder": "＋ Ajouter un dossier",
-  "Library.Rescan": "⟳ Analyser à nouveau",
   "Library.OpenFile": "Ouvrir un fichier…",
 
   "Library.Context.Launch": "Lancer",

src/SharpEmu.GUI/Languages/hu.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Keresés a könyvtárban",
   "Library.AddFolder": "＋ Mappa hozzáadása",
-  "Library.Rescan": "⟳ Újrakeresés",
   "Library.OpenFile": "Fájl megnyitása…",
 
   "Library.Context.Launch": "Inditás",

src/SharpEmu.GUI/Languages/it.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Cerca nella libreria…",
   "Library.AddFolder": "＋ Aggiungi cartella",
-  "Library.Rescan": "⟳ Riscansiona",
   "Library.OpenFile": "Apri file…",
 
   "Library.Context.Launch": "Avvia",

src/SharpEmu.GUI/Languages/ja.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "ライブラリを検索…",
   "Library.AddFolder": "＋ フォルダーを追加",
-  "Library.Rescan": "⟳ 再スキャン",
   "Library.OpenFile": "ファイルを開く…",
 
   "Library.Context.Launch": "起動",

src/SharpEmu.GUI/Languages/ko.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "라이브러리 검색…",
   "Library.AddFolder": "＋ 폴더 추가",
-  "Library.Rescan": "⟳ 다시 스캔",
   "Library.OpenFile": "파일 열기…",
 
   "Library.Context.Launch": "실행",

src/SharpEmu.GUI/Languages/nl.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Zoeken in bibliotheek…",
   "Library.AddFolder": "＋ Map toevoegen",
-  "Library.Rescan": "⟳ Opnieuw scannen",
   "Library.OpenFile": "Bestand openen…",
 
   "Library.Context.Launch": "Starten",

src/SharpEmu.GUI/Languages/pt.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Pesquisar biblioteca…",
   "Library.AddFolder": "＋ Adicionar pasta",
-  "Library.Rescan": "⟳ Reanalisar",
   "Library.OpenFile": "Abrir ficheiro…",
 
   "Library.Context.Launch": "Iniciar",

src/SharpEmu.GUI/Languages/ru.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Поиск…",
   "Library.AddFolder": "＋ Добавить папку",
-  "Library.Rescan": "⟳ Сканировать",
   "Library.OpenFile": "Открыть файл…",
 
   "Library.Context.Launch": "Запустить",

src/SharpEmu.GUI/Languages/tr.json

@@ -8,7 +8,6 @@
 
   "Library.SearchWatermark": "Kütüphanede ara…",
   "Library.AddFolder": "＋ Klasör ekle",
-  "Library.Rescan": "⟳ Yeniden tara",
   "Library.OpenFile": "Dosya aç…",
 
   "Library.Context.Launch": "Başlat",

src/SharpEmu.GUI/MainWindow.axaml

@@ -80,7 +80,6 @@ SPDX-License-Identifier: GPL-2.0-or-later
                     VerticalAlignment="Center">
           <TextBox x:Name="SearchBox" PlaceholderText="Search library…" Width="240" VerticalAlignment="Center" />
           <Button x:Name="AddFolderButton" Classes="ghost" Content="＋ Add folder" VerticalAlignment="Center" />
-          <Button x:Name="RescanButton" Classes="ghost" Content="⟳ Rescan" VerticalAlignment="Center" />
           <Button x:Name="OpenFileButton" Classes="ghost" Content="Open file…" VerticalAlignment="Center" />
         </StackPanel>
       </Grid>

src/SharpEmu.GUI/MainWindow.axaml.cs

@@ -41,15 +41,9 @@ public partial class MainWindow : Window
     private static readonly IBrush WarningLineBrush = new SolidColorBrush(Color.Parse("#E8B341"));
     private static readonly IBrush ErrorLineBrush = new SolidColorBrush(Color.Parse("#F2777C"));
     private static readonly IBrush SuccessLineBrush = new SolidColorBrush(Color.Parse("#63D489"));
-    private static readonly StringComparer FilePathComparer = OperatingSystem.IsWindows()
-        ? StringComparer.OrdinalIgnoreCase
-        : StringComparer.Ordinal;
-    private static readonly StringComparison FilePathComparison = OperatingSystem.IsWindows()
-        ? StringComparison.OrdinalIgnoreCase
-        : StringComparison.Ordinal;
-
     private readonly List<GameEntry> _allGames = new();
     private readonly ObservableCollection<GameEntry> _visibleGames = new();
+    private readonly GameLibraryWatcher _libraryWatcher = new();
     private readonly AvaloniaList<LogLine> _consoleLines = new();
     private readonly List<LogLine> _allConsoleLines = new();
     private readonly ConcurrentQueue<(string Line, bool IsError)> _pendingLines = new();
@@ -85,8 +79,10 @@ public partial class MainWindow : Window
     private string? _runningGameName;
     private string? _runningGameTitleId;
     private long _runningSinceUnixSeconds;
+    private int _libraryScanGeneration;
     private int _detailLoadGeneration;
     private int _backdropGeneration;
+    private bool _isClosing;
 
     // Bundled key art shown whenever no game-specific backdrop applies; the
     // plain window color remains the fallback when the asset fails to load.
@@ -133,6 +129,7 @@ public partial class MainWindow : Window
         }
 
         GameList.ItemsSource = _visibleGames;
+        _libraryWatcher.RefreshRequested += OnLibraryRefreshRequested;
         ConsoleList.ItemsSource = _consoleLines;
         _consoleMirror = GuiConsoleMirror.Install((line, isError) =>
             _pendingLines.Enqueue((line, isError)));
@@ -173,7 +170,6 @@ public partial class MainWindow : Window
         ConsoleSearchBox.TextChanged += (_, _) => RefreshVisibleConsoleLines();
         AddFolderButton.Click += async (_, _) => await AddFolderAsync();
         EmptyAddFolderButton.Click += async (_, _) => await AddFolderAsync();
-        RescanButton.Click += async (_, _) => await RescanLibraryAsync();
         OpenFileButton.Click += async (_, _) => await OpenFileAsync();
         LaunchButton.Click += (_, _) => LaunchSelected();
         ClearLogButton.Click += (_, _) => { _consoleLines.Clear(); _allConsoleLines.Clear(); };
@@ -619,7 +615,6 @@ public partial class MainWindow : Window
 
         SearchBox.PlaceholderText = loc.Get("Library.SearchWatermark");
         AddFolderButton.Content = loc.Get("Library.AddFolder");
-        RescanButton.Content = loc.Get("Library.Rescan");
         OpenFileButton.Content = loc.Get("Library.OpenFile");
 
         CtxLaunch.Header = loc.Get("Library.Context.Launch");
@@ -798,6 +793,10 @@ public partial class MainWindow : Window
 
     private void OnWindowClosing()
     {
+        _isClosing = true;
+        Interlocked.Increment(ref _libraryScanGeneration);
+        Interlocked.Increment(ref _detailLoadGeneration);
+        _libraryWatcher.Dispose();
         _settings.Save();
         _consoleFlushTimer.Stop();
         _libraryBlurTimer.Stop();
@@ -1176,7 +1175,7 @@ public partial class MainWindow : Window
         }
 
         var changed = false;
-        if (!_settings.GameFolders.Contains(path, FilePathComparer))
+        if (!_settings.GameFolders.Contains(path, GameLibraryPath.Comparer))
         {
             _settings.GameFolders.Add(path);
             changed = true;
@@ -1186,7 +1185,7 @@ public partial class MainWindow : Window
         // games beneath it that were removed from the library earlier.
         var prefix = Path.TrimEndingDirectorySeparator(path) + Path.DirectorySeparatorChar;
         changed |= _settings.ExcludedGames.RemoveAll(excluded =>
-            excluded.StartsWith(prefix, FilePathComparison)) > 0;
+            excluded.StartsWith(prefix, GameLibraryPath.Comparison)) > 0;
 
         if (changed)
         {
@@ -1196,25 +1195,72 @@ public partial class MainWindow : Window
         await RescanLibraryAsync();
     }
 
-    private async Task RescanLibraryAsync()
+    private void OnLibraryRefreshRequested(object? sender, EventArgs args)
     {
+        Dispatcher.UIThread.Post(
+            () =>
+            {
+                if (!_isClosing)
+                {
+                    _ = RescanLibraryFromWatcherAsync();
+                }
+            },
+            DispatcherPriority.Background);
+    }
+
+    private async Task RescanLibraryFromWatcherAsync()
+    {
+        try
+        {
+            await RescanLibraryAsync(showProgress: false);
+        }
+        catch (Exception exception)
+        {
+            Console.Error.WriteLine(
+                $"[GUI][WARN] Automatic library refresh failed: {exception.Message}");
+        }
+    }
+
+    private async Task RescanLibraryAsync(bool showProgress = true)
+    {
+        Dispatcher.UIThread.VerifyAccess();
+
+        var scanGeneration = Interlocked.Increment(ref _libraryScanGeneration);
         var folders = _settings.GameFolders.ToArray();
-        var excluded = new HashSet<string>(_settings.ExcludedGames, FilePathComparer);
-        StatusBarRight.Text = Localization.Instance.Get("Status.ScanningLibrary");
-        EmptyState.IsVisible = false;
-        LoadingState.IsVisible = true;
+        var excluded = new HashSet<string>(_settings.ExcludedGames, GameLibraryPath.Comparer);
+        _libraryWatcher.Watch(folders);
+        var showLoadingState = showProgress && _allGames.Count == 0;
+        if (showProgress)
+        {
+            StatusBarRight.Text = Localization.Instance.Get("Status.ScanningLibrary");
+        }
+
+        if (showLoadingState)
+        {
+            EmptyState.IsVisible = false;
+            LoadingState.IsVisible = true;
+        }
 
         var games = await Task.Run(() => ScanFolders(folders, excluded));
+        if (_isClosing || scanGeneration != Volatile.Read(ref _libraryScanGeneration))
+        {
+            return;
+        }
 
+        Dispatcher.UIThread.VerifyAccess();
+        var reconciliation = GameLibraryReconciler.Reconcile(_allGames, games);
         _allGames.Clear();
-        _allGames.AddRange(games);
-        RefreshVisibleGames();
+        _allGames.AddRange(reconciliation.Games);
+        RefreshVisibleGames(reconciliation.BackgroundsChanged);
         LoadingState.IsVisible = false;
-        LoadGameDetailsInBackground(games);
+        LoadGameDetailsInBackground(reconciliation.CoversToLoad, reconciliation.Games);
         UpdateDiscordPresence();
-        StatusBarRight.Text = folders.Length == 0
-            ? Localization.Instance.Get("Status.AddFolderPrompt")
-            : Localization.Instance.Format("Status.LibraryScanned", games.Count, folders.Length);
+        if (showProgress)
+        {
+            StatusBarRight.Text = folders.Length == 0
+                ? Localization.Instance.Get("Status.AddFolderPrompt")
+                : Localization.Instance.Format("Status.LibraryScanned", games.Count, folders.Length);
+        }
     }
 
     /// <summary>
@@ -1222,44 +1268,57 @@ public partial class MainWindow : Window
     /// game's install folder size — posting results back as they become
     /// ready. A newer scan invalidates older loads.
     /// </summary>
-    private void LoadGameDetailsInBackground(IReadOnlyList<GameEntry> games)
+    private void LoadGameDetailsInBackground(
+        IReadOnlyList<GameEntry> coversToLoad,
+        IReadOnlyList<GameEntry> gamesToMeasure)
     {
         var generation = ++_detailLoadGeneration;
         _ = Task.Run(() =>
         {
             // Covers first: they are cheap and the most visible, so the grid
             // fills with art before the (potentially slow) size pass runs.
-            foreach (var game in games)
+            foreach (var game in coversToLoad)
             {
                 if (generation != _detailLoadGeneration)
                 {
                     return;
                 }
 
-                if (game.CoverPath is null)
+                var requestedCoverPath = game.CoverPath;
+                if (requestedCoverPath is null)
                 {
                     continue;
                 }
 
                 try
                 {
-                    using var stream = File.OpenRead(game.CoverPath);
+                    using var stream = File.OpenRead(requestedCoverPath);
                     var bitmap = Bitmap.DecodeToWidth(stream, 312);
                     Dispatcher.UIThread.Post(() =>
                     {
-                        if (generation == _detailLoadGeneration)
+                        if (generation == _detailLoadGeneration
+                            && _allGames.Contains(game)
+                            && string.Equals(
+                                game.CoverPath,
+                                requestedCoverPath,
+                                StringComparison.Ordinal))
                         {
                             game.Cover = bitmap;
                         }
+                        else
+                        {
+                            bitmap.Dispose();
+                        }
                     });
                 }
-                catch (Exception)
+                catch (Exception exception)
                 {
-                    // A missing or undecodable image keeps the placeholder.
+                    Console.Error.WriteLine(
+                        $"[GUI][WARN] Could not load cover '{requestedCoverPath}': {exception.Message}");
                 }
             }
 
-            foreach (var game in games)
+            foreach (var game in gamesToMeasure)
             {
                 if (generation != _detailLoadGeneration)
                 {
@@ -1271,7 +1330,7 @@ public partial class MainWindow : Window
                 {
                     Dispatcher.UIThread.Post(() =>
                     {
-                        if (generation == _detailLoadGeneration)
+                        if (generation == _detailLoadGeneration && _allGames.Contains(game))
                         {
                             game.SizeBytes = size;
                         }
@@ -1306,9 +1365,10 @@ public partial class MainWindow : Window
                 total += file.Length;
             }
         }
-        catch (Exception)
+        catch (Exception exception)
         {
-            // Fall back to whatever was accumulated so far.
+            Console.Error.WriteLine(
+                $"[GUI][WARN] Could not measure game folder '{directory}': {exception.Message}");
         }
 
         return total;
@@ -1317,7 +1377,7 @@ public partial class MainWindow : Window
     private static List<GameEntry> ScanFolders(IReadOnlyList<string> folders, IReadOnlySet<string> excludedPaths)
     {
         var games = new List<GameEntry>();
-        var seen = new HashSet<string>(FilePathComparer);
+        var seen = new HashSet<string>(GameLibraryPath.Comparer);
         var enumeration = new EnumerationOptions
         {
             IgnoreInaccessible = true,
@@ -1347,8 +1407,10 @@ public partial class MainWindow : Window
                     {
                         size = new FileInfo(fullPath).Length;
                     }
-                    catch (IOException)
+                    catch (IOException exception)
                     {
+                        Console.Error.WriteLine(
+                            $"[GUI][WARN] Could not inspect executable '{fullPath}': {exception.Message}");
                     }
 
                     var (title, titleId, version) = TryReadParamJson(fullPath);
@@ -1357,9 +1419,10 @@ public partial class MainWindow : Window
                         FindCoverFor(fullPath), FindBackgroundFor(fullPath)));
                 }
             }
-            catch (Exception)
+            catch (Exception exception)
             {
-                // Skip folders that fail to enumerate.
+                Console.Error.WriteLine(
+                    $"[GUI][WARN] Could not scan game folder '{folder}': {exception.Message}");
             }
         }
 
@@ -1600,24 +1663,26 @@ public partial class MainWindow : Window
             return;
         }
 
-        if (!_settings.ExcludedGames.Contains(game.Path, FilePathComparer))
+        if (!_settings.ExcludedGames.Contains(game.Path, GameLibraryPath.Comparer))
         {
             _settings.ExcludedGames.Add(game.Path);
             _settings.Save();
         }
 
-        _allGames.RemoveAll(g => string.Equals(g.Path, game.Path, FilePathComparison));
+        _allGames.RemoveAll(g =>
+            string.Equals(g.Path, game.Path, GameLibraryPath.Comparison));
         GameList.SelectedItem = null;
         RefreshVisibleGames();
         StatusBarRight.Text = Localization.Instance.Format("Status.RemovedFromLibrary", game.Name);
     }
 
-    private void RefreshVisibleGames()
+    private void RefreshVisibleGames(IReadOnlySet<GameEntry>? backgroundsChanged = null)
     {
         var query = SearchBox.Text?.Trim() ?? string.Empty;
-        var selectedPath = (GameList.SelectedItem as GameEntry)?.Path;
+        var selectedBefore = GameList.SelectedItem as GameEntry;
+        var selectedPath = selectedBefore?.Path;
+        var desired = new List<GameEntry>(_allGames.Count);
 
-        _visibleGames.Clear();
         foreach (var game in _allGames)
         {
             if (query.Length == 0 ||
@@ -1625,21 +1690,37 @@ public partial class MainWindow : Window
                 game.Path.Contains(query, StringComparison.OrdinalIgnoreCase) ||
                 (game.TitleId?.Contains(query, StringComparison.OrdinalIgnoreCase) ?? false))
             {
-                _visibleGames.Add(game);
+                desired.Add(game);
             }
         }
 
-        if (selectedPath is not null &&
-            _visibleGames.FirstOrDefault(g => g.Path.Equals(selectedPath, FilePathComparison))
-                is { } reselected)
+        GameLibraryReconciler.ReconcileVisibleGames(_visibleGames, desired);
+
+        var selectedAfter = selectedPath is null
+            ? null
+            : _visibleGames.FirstOrDefault(game =>
+                game.Path.Equals(selectedPath, GameLibraryPath.Comparison));
+        if (!ReferenceEquals(GameList.SelectedItem, selectedAfter))
         {
-            GameList.SelectedItem = reselected;
+            GameList.SelectedItem = selectedAfter;
         }
 
         EmptyState.IsVisible = _visibleGames.Count == 0;
         UpdateEmptyStateTexts();
 
-        UpdateSelectedGame();
+        if (!ReferenceEquals(selectedBefore, selectedAfter))
+        {
+            UpdateSelectedGame();
+        }
+        else
+        {
+            UpdateSelectedGameTexts();
+            UpdateRunButtons();
+            if (selectedAfter is not null && backgroundsChanged?.Contains(selectedAfter) == true)
+            {
+                _ = UpdateBackdropAsync(selectedAfter);
+            }
+        }
     }
 
     /// <summary>
@@ -1861,7 +1942,8 @@ public partial class MainWindow : Window
         }
 
         var resolvedTitleId = string.IsNullOrWhiteSpace(titleId)
-            ? _allGames.FirstOrDefault(game => game.Path.Equals(ebootPath, FilePathComparison))?.TitleId
+            ? _allGames.FirstOrDefault(game =>
+                game.Path.Equals(ebootPath, GameLibraryPath.Comparison))?.TitleId
             : titleId;
         var effective = EffectiveLaunchSettings.Resolve(_settings, PerGameSettings.Load(resolvedTitleId));
 

tests/SharpEmu.Libs.Tests/GUI/GameLibraryReconcilerTests.cs

@@ -0,0 +1,100 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Collections.ObjectModel;
+using SharpEmu.GUI;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.GUI;
+
+public sealed class GameLibraryReconcilerTests
+{
+    [Fact]
+    public void Reconcile_PreservesExistingEntriesAndAppliesMetadataChanges()
+    {
+        var retained = CreateGame("retained", name: "Old name", version: "01.000");
+        var removed = CreateGame("removed");
+        var scannedRetained = CreateGame(
+            "retained",
+            name: "New name",
+            version: "02.000");
+        var added = CreateGame("added");
+
+        var result = GameLibraryReconciler.Reconcile(
+            [retained, removed],
+            [scannedRetained, added]);
+
+        Assert.Equal(2, result.Games.Count);
+        Assert.Same(retained, result.Games[0]);
+        Assert.Same(added, result.Games[1]);
+        Assert.Equal("New name", retained.Name);
+        Assert.Equal("02.000", retained.Version);
+        Assert.DoesNotContain(removed, result.Games);
+    }
+
+    [Fact]
+    public void Reconcile_ChangedCoverAndBackgroundReloadsExistingEntry()
+    {
+        var retained = CreateGame(
+            "retained",
+            coverPath: AssetPath("old-cover.png"),
+            backgroundPath: AssetPath("old-background.png"));
+        var scanned = CreateGame(
+            "retained",
+            coverPath: AssetPath("new-cover.png"),
+            backgroundPath: AssetPath("new-background.png"));
+
+        var result = GameLibraryReconciler.Reconcile([retained], [scanned]);
+
+        Assert.Same(retained, Assert.Single(result.Games));
+        Assert.Same(retained, Assert.Single(result.CoversToLoad));
+        Assert.Contains(retained, result.BackgroundsChanged);
+        Assert.Equal(scanned.CoverPath, retained.CoverPath);
+        Assert.Equal(scanned.BackgroundPath, retained.BackgroundPath);
+    }
+
+    [Fact]
+    public void ReconcileVisibleGames_UsesMinimalIdentityPreservingChanges()
+    {
+        var first = CreateGame("first");
+        var second = CreateGame("second");
+        var removed = CreateGame("removed");
+        var added = CreateGame("added");
+        var visible = new ObservableCollection<GameEntry>
+        {
+            first,
+            second,
+            removed,
+        };
+
+        GameLibraryReconciler.ReconcileVisibleGames(
+            visible,
+            [second, first, added]);
+
+        Assert.Equal([second, first, added], visible);
+        Assert.Same(second, visible[0]);
+        Assert.Same(first, visible[1]);
+        Assert.Same(added, visible[2]);
+    }
+
+    private static GameEntry CreateGame(
+        string id,
+        string? name = null,
+        string? version = null,
+        string? coverPath = null,
+        string? backgroundPath = null)
+        => new(
+            name ?? id,
+            $"PPSA-{id}",
+            version,
+            GamePath(id),
+            1,
+            coverPath,
+            backgroundPath);
+
+    private static string GamePath(string id)
+        => Path.GetFullPath(Path.Combine("library-tests", id, "eboot.bin"));
+
+    private static string AssetPath(string name)
+        => Path.GetFullPath(Path.Combine("library-tests", "assets", name));
+}

tests/SharpEmu.Libs.Tests/GUI/GameLibraryWatcherTests.cs

@@ -0,0 +1,38 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.GUI;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.GUI;
+
+public sealed class GameLibraryWatcherTests
+{
+    [Fact]
+    public async Task Watch_FileCreation_RequestsRefresh()
+    {
+        var directory = Path.Combine(
+            Path.GetTempPath(),
+            $"sharpemu-library-watcher-{Guid.NewGuid():N}");
+        Directory.CreateDirectory(directory);
+
+        try
+        {
+            using var watcher = new GameLibraryWatcher(TimeSpan.FromMilliseconds(25));
+            var refreshRequested = new TaskCompletionSource(
+                TaskCreationOptions.RunContinuationsAsynchronously);
+            watcher.RefreshRequested += (_, _) => refreshRequested.TrySetResult();
+            watcher.Watch([directory]);
+
+            await File.WriteAllTextAsync(
+                Path.Combine(directory, "eboot.bin"),
+                "test");
+
+            await refreshRequested.Task.WaitAsync(TimeSpan.FromSeconds(5));
+        }
+        finally
+        {
+            Directory.Delete(directory, recursive: true);
+        }
+    }
+}