Use a --isolated flag instead of the setting

The setting is silently ignored by a dt that does not know it, which
would leak one launch's environment into another. An unknown flag fails
the launch instead, the caller decides per launch, and nothing has to be
read from settings.json before the broker election.

Author: irvingoujAtDevolution

README.md

@@ -88,12 +88,13 @@ settings file. On Windows, `WT_PARENT_WINDOW_HANDLE` embeds the window as a
 child of that HWND. `alwaysShowTabs: false` hides the tab row when only one
 tab is open.
 
-`"compatibility.isolatedMode": true` (from Windows Terminal 1.22 and earlier)
-makes each launch its own process: it neither forwards to a running instance
-nor becomes the broker for later launches, so every window keeps its own
-environment, `WT_PARENT_WINDOW_HANDLE`, and settings directory. `-w` targeting
-of other windows is unavailable, and persisted layouts are neither restored
-nor saved.
+`dt --isolated` (or `Devolutions.Terminal.exe --isolated`) runs the launch in
+its own process: it neither forwards to a running instance nor becomes the
+broker for later launches, so every window keeps its own environment,
+`WT_PARENT_WINDOW_HANDLE`, and settings directory. `-w` targeting of other
+windows is unavailable, and persisted layouts are neither restored nor saved.
+It is the per-launch equivalent of Windows Terminal's
+`compatibility.isolatedMode` setting, which Windows Terminal 1.23 removed.
 
 Set `"experimental.terminalEngine": "ghostty"` to use the pinned
 `libghostty-vt` engine globally. A profile can override it with `"builtin"` or

src/Devolutions.Terminal.App/Models/TerminalLayoutStateStore.cs

@@ -11,11 +11,8 @@ preference is not null &&
          preference.Equals("persistedLayoutAndContent", StringComparison.OrdinalIgnoreCase));
 
     // Matches Windows Terminal: an isolated process never restores or saves the shared window layouts.
-    public static bool ShouldUsePersistedLayout(AppSettings settings)
-    {
-        ArgumentNullException.ThrowIfNull(settings);
-        return !settings.IsolatedMode && IsPersistedLayoutPreference(settings.FirstWindowPreference);
-    }
+    public static bool ShouldUsePersistedLayout(string? firstWindowPreference, bool isolated) =>
+        !isolated && IsPersistedLayoutPreference(firstWindowPreference);
 
     public static WindowLayoutState? ReadWindowState(ApplicationStateStore store, int windowId)
     {

src/Devolutions.Terminal.App/Views/MainWindow.axaml.cs

@@ -77,6 +77,7 @@ public partial class MainWindow :
     private readonly Func<GlobalSummonArgs, ValueTask<WindowActionResult>>? _summonRequested;
     private readonly Action<AppSettings>? _settingsChanged;
     private readonly ISystemMenuService _systemMenuService;
+    private readonly bool _isolated;
     private readonly TaskCompletionSource<TerminalWindowActivationResult> _initialActivationCompletion =
         new(TaskCreationOptions.RunContinuationsAsynchronously);
     private readonly DispatcherTimer _notificationTimer;
@@ -102,10 +103,12 @@ public MainWindow(
         Action<string>? workspaceRequested = null,
         Func<GlobalSummonArgs, ValueTask<WindowActionResult>>? summonRequested = null,
         Action<AppSettings>? settingsChanged = null,
-        ISystemMenuService? systemMenuService = null)
+        ISystemMenuService? systemMenuService = null,
+        bool isolated = false)
     {
         WindowId = windowId;
         WindowName = windowName;
+        _isolated = isolated;
         _initialActivation = initialActivation;
         _newWindowRequested = newWindowRequested;
         _tabTearOffRequested = tabTearOffRequested;
@@ -3647,7 +3650,7 @@ private void PersistWorkspace(TerminalWindowLayoutDescriptor layout)
     };
 
     private bool UsesPersistedLayout =>
-        TerminalLayoutStateStore.ShouldUsePersistedLayout(_settings);
+        TerminalLayoutStateStore.ShouldUsePersistedLayout(_settings.FirstWindowPreference, _isolated);
 
     private void TryPersistCurrentLayout(TerminalWindowLayoutDescriptor layout)
     {

src/Devolutions.Terminal.Cli/CliContracts.cs

@@ -24,7 +24,8 @@ public sealed record CliInvocation(
     CliLaunchMode LaunchMode,
     int? SavedLayout,
     IReadOnlyList<ActionAndArgs> Actions,
-    CliSaveRequest? SaveRequest = null);
+    CliSaveRequest? SaveRequest = null,
+    bool Isolated = false);
 
 public sealed record CliParseResult(
     int ExitCode,

src/Devolutions.Terminal.Cli/CliParser.cs

@@ -118,6 +118,7 @@ private static CliParseResult ParseCore(
         int? rows = null;
         int? savedLayout = null;
         var launchMode = CliLaunchMode.Default;
+        var isolated = false;
         CliSaveRequest? save = null;
 
         for (var segmentIndex = 0; segmentIndex < segments.Count; segmentIndex++)
@@ -135,7 +136,8 @@ private static CliParseResult ParseCore(
                     ref columns,
                     ref rows,
                     ref savedLayout,
-                    ref launchMode);
+                    ref launchMode,
+                    ref isolated);
             }
 
             var command = index < segment.Count && Commands.Contains(segment[index])
@@ -215,7 +217,8 @@ save is null &&
             launchMode,
             savedLayout,
             actions,
-            save);
+            save,
+            isolated);
         return new(0, string.Empty, false, invocation);
     }
 
@@ -228,7 +231,8 @@ private static void ParseRootOptions(
         ref int? columns,
         ref int? rows,
         ref int? savedLayout,
-        ref CliLaunchMode launchMode)
+        ref CliLaunchMode launchMode,
+        ref bool isolated)
     {
         while (index < args.Count)
         {
@@ -269,6 +273,10 @@ private static void ParseRootOptions(
                     launchMode |= CliLaunchMode.Focus;
                     index++;
                     break;
+                case "--isolated":
+                    isolated = true;
+                    index++;
+                    break;
                 default:
                     if (option.StartsWith('-') &&
                         option.Length > 2 &&
@@ -696,6 +704,7 @@ internal static class CommandLineSchema
           -M, --maximized        Launch maximized
           -F, --fullscreen       Launch fullscreen
           -f, --focus            Hide the title bar
+          --isolated             Own process: never join or serve other launches
 
         Commands:
           new-tab, nt   split-pane, sp   focus-tab, ft   move-focus, mf
@@ -708,6 +717,7 @@ public static RootCommand Create()
         root.Options.Add(new Option<string>("--window") { Description = "Target window." });
         root.Options.Add(new Option<string>("--pos") { Description = "Window position." });
         root.Options.Add(new Option<string>("--size") { Description = "Terminal size." });
+        root.Options.Add(new Option<bool>("--isolated") { Description = "Run in its own process." });
         foreach (var (name, alias) in new[]
                  {
                      ("new-tab", "nt"),

src/Devolutions.Terminal.Cli/Program.cs

@@ -1,6 +1,5 @@
 using System.Diagnostics;
 using Devolutions.Terminal.Broker;
-using Devolutions.Terminal.Settings;
 
 namespace Devolutions.Terminal.Cli;
 
@@ -18,8 +17,8 @@ public static async Task<int> Main(string[] args)
         }
 
         var invocation = parsed.Invocation!;
-        var response = SettingsService.IsIsolatedModeEnabled()
-            ? BrokerResponse.Unavailable("Isolated mode does not use the broker.")
+        var response = invocation.Isolated
+            ? BrokerResponse.Unavailable("Isolated launches do not use the broker.")
             : await new BrokerClient().SendAsync(
                 invocation.TargetWindow,
                 CliInvocationSerializer.Serialize(invocation)).ConfigureAwait(false);

src/Devolutions.Terminal.Settings/Models.cs

@@ -131,7 +131,6 @@ public sealed class AppSettings
     public bool AlwaysShowNotificationIcon { get; set; }
     public List<string> DisabledProfileSources { get; set; } = [];
     public bool AllowHeadless { get; set; }
-    public bool IsolatedMode { get; set; }
     public bool EnableColorSelection { get; set; }
 
     // Per-window settings.

src/Devolutions.Terminal.Settings/SettingsLoader.cs

@@ -19,7 +19,6 @@ public static class SettingsLoader
 {
     private const string OriginKey = "$terminalOrigin";
     private const string SourceKey = "$terminalSource";
-    private const string IsolatedModeKey = "compatibility.isolatedMode";
 
     private static readonly JsonDocumentOptions DocumentOptions = new()
     {
@@ -34,27 +33,6 @@ public static string ReadEmbeddedDefaults()
     public static string ReadEmbeddedUserDefaults()
         => ReadEmbeddedResource("Devolutions.Terminal.Settings.userDefaults.json");
 
-    /// <summary>
-    /// Reads only <c>compatibility.isolatedMode</c> from a user settings document, so startup can
-    /// decide whether to use the broker before loading the full settings.
-    /// </summary>
-    public static bool ReadIsolatedMode(string? userJson)
-    {
-        if (string.IsNullOrWhiteSpace(userJson))
-        {
-            return false;
-        }
-
-        try
-        {
-            return Bool(JsonNode.Parse(userJson, documentOptions: DocumentOptions) as JsonObject, IsolatedModeKey);
-        }
-        catch (JsonException)
-        {
-            return false;
-        }
-    }
-
     private static string ReadEmbeddedResource(string name)
     {
         using var stream = typeof(SettingsLoader).Assembly.GetManifestResourceStream(name);
@@ -342,7 +320,6 @@ private static AppSettings Resolve(
             AlwaysShowNotificationIcon = Bool(root, "alwaysShowNotificationIcon"),
             DisabledProfileSources = StringList(root["disabledProfileSources"]),
             AllowHeadless = Bool(root, "compatibility.allowHeadless"),
-            IsolatedMode = Bool(root, IsolatedModeKey),
             EnableColorSelection = Bool(root, "experimental.enableColorSelection"),
             DefaultProfile = String(root, "defaultProfile"),
             InitialCols = Int(root, "initialCols", 80, minimum: 1),
@@ -1158,7 +1135,6 @@ private static bool GuidsEqual(string? left, string? right) =>
         ["alwaysShowNotificationIcon"] = settings.AlwaysShowNotificationIcon,
         ["disabledProfileSources"] = StringArray(settings.DisabledProfileSources),
         ["compatibility.allowHeadless"] = settings.AllowHeadless,
-        [IsolatedModeKey] = settings.IsolatedMode,
         ["experimental.enableColorSelection"] = settings.EnableColorSelection,
         ["defaultProfile"] = settings.DefaultProfile,
         ["initialCols"] = settings.InitialCols,

src/Devolutions.Terminal.Settings/SettingsService.cs

@@ -149,22 +149,6 @@ public static void Save(AppSettings settings)
     public static AppSettings CreateDefault() =>
         SettingsLoader.Load(SettingsLoader.ReadEmbeddedDefaults());
 
-    public static bool IsIsolatedModeEnabled() => IsIsolatedModeEnabled(SettingsPath);
-
-    public static bool IsIsolatedModeEnabled(string settingsPath)
-    {
-        ArgumentException.ThrowIfNullOrWhiteSpace(settingsPath);
-        try
-        {
-            return File.Exists(settingsPath) &&
-                SettingsLoader.ReadIsolatedMode(File.ReadAllText(settingsPath, Encoding.UTF8));
-        }
-        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
-        {
-            return false;
-        }
-    }
-
     public static ApplicationStateStore LoadApplicationState() =>
         new(Path.GetDirectoryName(Path.GetFullPath(StatePath))!);
 

src/Devolutions.Terminal/App.axaml.cs

@@ -30,7 +30,10 @@ public override void OnFrameworkInitializationCompleted()
         if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
         {
             _desktop = desktop;
-            _router = new TerminalWindowRouter(desktop, ConfigureWindow);
+            _router = new TerminalWindowRouter(
+                desktop,
+                ConfigureWindow,
+                isolated: InitialInvocation?.Isolated ?? false);
             BrokerHandler?.SetHandler(_router);
             if (OperatingSystem.IsMacOS())
             {