Add launcher coordinator IPC and startup reservation

Introduce a launcher coordinator to reserve startup ownership and prevent duplicate host launches. Adds a NamedPipe-based IPC server/client (LauncherCoordinatorIpcServer/Client), coordinator messages/models, and PublicShellStatus/activation types for richer shell reporting. Enhances StartupAttemptRecord and StartupAttemptRegistry to track coordinator pid/pipe, heartbeat, reserved-before-host-start, and public IPC status, plus new reservation/heartbeat APIs and takeover logic. Wire coordinator into App and LauncherFlowCoordinator to attach secondary launchers, publish coordinator status, probe existing hosts, and include more detailed launch result details. Also adds unit tests and docs describing coordinator and startup visuals behavior.

LanMountainDesktop.Launcher/Services/Ipc/LauncherCoordinatorIpcClient.cs

@@ -0,0 +1,111 @@
+using System.IO.Pipes;
+using System.Text;
+using System.Text.Json;
+using LanMountainDesktop.Launcher.Models;
+
+namespace LanMountainDesktop.Launcher.Services.Ipc;
+
+internal sealed class LauncherCoordinatorIpcClient
+{
+    private const int LengthPrefixSize = 4;
+    private const int MaxPayloadLength = 1024 * 1024;
+
+    public async Task<LauncherCoordinatorResponse?> SendAsync(
+        string pipeName,
+        LauncherCoordinatorRequest request,
+        TimeSpan timeout)
+    {
+        if (string.IsNullOrWhiteSpace(pipeName))
+        {
+            return null;
+        }
+
+        using var timeoutCts = new CancellationTokenSource(timeout);
+        try
+        {
+            await using var client = new NamedPipeClientStream(
+                ".",
+                pipeName,
+                PipeDirection.InOut,
+                PipeOptions.Asynchronous);
+
+            await client.ConnectAsync(timeoutCts.Token).ConfigureAwait(false);
+            await WriteRequestAsync(client, request, timeoutCts.Token).ConfigureAwait(false);
+            return await ReadResponseAsync(client, timeoutCts.Token).ConfigureAwait(false);
+        }
+        catch (OperationCanceledException)
+        {
+            return null;
+        }
+        catch (TimeoutException)
+        {
+            return null;
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"Failed to send launcher coordinator IPC request: {ex.Message}");
+            return null;
+        }
+    }
+
+    private static async Task WriteRequestAsync(
+        Stream stream,
+        LauncherCoordinatorRequest request,
+        CancellationToken cancellationToken)
+    {
+        var json = JsonSerializer.Serialize(request, AppJsonContext.Default.LauncherCoordinatorRequest);
+        var payload = Encoding.UTF8.GetBytes(json);
+        await stream.WriteAsync(BitConverter.GetBytes(payload.Length), cancellationToken).ConfigureAwait(false);
+        await stream.WriteAsync(payload, cancellationToken).ConfigureAwait(false);
+        await stream.FlushAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    private static async Task<LauncherCoordinatorResponse?> ReadResponseAsync(
+        Stream stream,
+        CancellationToken cancellationToken)
+    {
+        var lengthBuffer = new byte[LengthPrefixSize];
+        if (!await ReadExactAsync(stream, lengthBuffer, cancellationToken).ConfigureAwait(false))
+        {
+            return null;
+        }
+
+        var payloadLength = BitConverter.ToInt32(lengthBuffer, 0);
+        if (payloadLength <= 0 || payloadLength > MaxPayloadLength)
+        {
+            return null;
+        }
+
+        var payload = new byte[payloadLength];
+        if (!await ReadExactAsync(stream, payload, cancellationToken).ConfigureAwait(false))
+        {
+            return null;
+        }
+
+        return JsonSerializer.Deserialize(
+            Encoding.UTF8.GetString(payload),
+            AppJsonContext.Default.LauncherCoordinatorResponse);
+    }
+
+    private static async Task<bool> ReadExactAsync(
+        Stream stream,
+        byte[] buffer,
+        CancellationToken cancellationToken)
+    {
+        var totalRead = 0;
+        while (totalRead < buffer.Length)
+        {
+            var read = await stream
+                .ReadAsync(buffer.AsMemory(totalRead, buffer.Length - totalRead), cancellationToken)
+                .ConfigureAwait(false);
+            if (read == 0)
+            {
+                return false;
+            }
+
+            totalRead += read;
+        }
+
+        return true;
+    }
+}

LanMountainDesktop.Launcher/Services/Ipc/LauncherCoordinatorIpcServer.cs

@@ -0,0 +1,235 @@
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+using System.IO.Pipes;
+using LanMountainDesktop.Launcher.Models;
+
+namespace LanMountainDesktop.Launcher.Services.Ipc;
+
+internal sealed class LauncherCoordinatorIpcServer : IDisposable
+{
+    private const int LengthPrefixSize = 4;
+    private const int MaxPayloadLength = 1024 * 1024;
+    private readonly string _pipeName;
+    private readonly Func<LauncherCoordinatorRequest, LauncherCoordinatorStatus, Task<LauncherCoordinatorResponse>> _requestHandler;
+    private readonly Action<LauncherCoordinatorStatus> _heartbeatHandler;
+    private readonly CancellationTokenSource _cts = new();
+    private readonly object _statusGate = new();
+    private LauncherCoordinatorStatus _status;
+    private Task? _listenTask;
+    private Task? _heartbeatTask;
+
+    public LauncherCoordinatorIpcServer(
+        string pipeName,
+        LauncherCoordinatorStatus initialStatus,
+        Func<LauncherCoordinatorRequest, LauncherCoordinatorStatus, Task<LauncherCoordinatorResponse>> requestHandler,
+        Action<LauncherCoordinatorStatus> heartbeatHandler)
+    {
+        _pipeName = pipeName;
+        _status = initialStatus;
+        _requestHandler = requestHandler;
+        _heartbeatHandler = heartbeatHandler;
+    }
+
+    public static string CreatePipeName()
+    {
+        var seed = $"{Environment.UserName}:{Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData)}";
+        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(seed.ToLowerInvariant()));
+        return $"LanMountainDesktop_Launcher_Coordinator_{Convert.ToHexString(bytes[..8])}";
+    }
+
+    public void Start()
+    {
+        _listenTask ??= Task.Run(ListenLoopAsync);
+        _heartbeatTask ??= Task.Run(HeartbeatLoopAsync);
+    }
+
+    public LauncherCoordinatorStatus GetStatus()
+    {
+        lock (_statusGate)
+        {
+            return _status;
+        }
+    }
+
+    public void UpdateStatus(LauncherCoordinatorStatus status)
+    {
+        lock (_statusGate)
+        {
+            _status = status;
+        }
+    }
+
+    public void Dispose()
+    {
+        _cts.Cancel();
+
+        try
+        {
+            _listenTask?.Wait(TimeSpan.FromSeconds(1));
+            _heartbeatTask?.Wait(TimeSpan.FromSeconds(1));
+        }
+        catch
+        {
+        }
+
+        _cts.Dispose();
+    }
+
+    private async Task ListenLoopAsync()
+    {
+        while (!_cts.IsCancellationRequested)
+        {
+            NamedPipeServerStream? server = null;
+            try
+            {
+                server = new NamedPipeServerStream(
+                    _pipeName,
+                    PipeDirection.InOut,
+                    8,
+                    PipeTransmissionMode.Byte,
+                    PipeOptions.Asynchronous);
+
+                await server.WaitForConnectionAsync(_cts.Token).ConfigureAwait(false);
+                var connectedServer = server;
+                _ = Task.Run(() => HandleConnectionAsync(connectedServer, _cts.Token), _cts.Token);
+                server = null;
+            }
+            catch (OperationCanceledException)
+            {
+                break;
+            }
+            catch (Exception ex)
+            {
+                Logger.Warn($"Launcher coordinator IPC listener failed: {ex.Message}");
+                try
+                {
+                    await Task.Delay(250, _cts.Token).ConfigureAwait(false);
+                }
+                catch (OperationCanceledException)
+                {
+                    break;
+                }
+            }
+            finally
+            {
+                server?.Dispose();
+            }
+        }
+    }
+
+    private async Task HeartbeatLoopAsync()
+    {
+        while (!_cts.IsCancellationRequested)
+        {
+            try
+            {
+                _heartbeatHandler(GetStatus());
+                await Task.Delay(TimeSpan.FromSeconds(2), _cts.Token).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException)
+            {
+                break;
+            }
+            catch (Exception ex)
+            {
+                Logger.Warn($"Launcher coordinator heartbeat failed: {ex.Message}");
+            }
+        }
+    }
+
+    private async Task HandleConnectionAsync(NamedPipeServerStream server, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var request = await ReadRequestAsync(server, cancellationToken).ConfigureAwait(false);
+            var status = GetStatus();
+            var response = request is null
+                ? new LauncherCoordinatorResponse
+                {
+                    Accepted = false,
+                    Code = "invalid_request",
+                    Message = "Launcher coordinator request was invalid.",
+                    Status = status
+                }
+                : await _requestHandler(request, status).ConfigureAwait(false);
+
+            await WriteResponseAsync(server, response, cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"Launcher coordinator IPC request failed: {ex.Message}");
+        }
+        finally
+        {
+            try
+            {
+                server.Dispose();
+            }
+            catch
+            {
+            }
+        }
+    }
+
+    private static async Task<LauncherCoordinatorRequest?> ReadRequestAsync(
+        Stream stream,
+        CancellationToken cancellationToken)
+    {
+        var lengthBuffer = new byte[LengthPrefixSize];
+        if (!await ReadExactAsync(stream, lengthBuffer, cancellationToken).ConfigureAwait(false))
+        {
+            return null;
+        }
+
+        var payloadLength = BitConverter.ToInt32(lengthBuffer, 0);
+        if (payloadLength <= 0 || payloadLength > MaxPayloadLength)
+        {
+            return null;
+        }
+
+        var payload = new byte[payloadLength];
+        if (!await ReadExactAsync(stream, payload, cancellationToken).ConfigureAwait(false))
+        {
+            return null;
+        }
+
+        return JsonSerializer.Deserialize(
+            Encoding.UTF8.GetString(payload),
+            AppJsonContext.Default.LauncherCoordinatorRequest);
+    }
+
+    private static async Task WriteResponseAsync(
+        Stream stream,
+        LauncherCoordinatorResponse response,
+        CancellationToken cancellationToken)
+    {
+        var json = JsonSerializer.Serialize(response, AppJsonContext.Default.LauncherCoordinatorResponse);
+        var payload = Encoding.UTF8.GetBytes(json);
+        await stream.WriteAsync(BitConverter.GetBytes(payload.Length), cancellationToken).ConfigureAwait(false);
+        await stream.WriteAsync(payload, cancellationToken).ConfigureAwait(false);
+        await stream.FlushAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    private static async Task<bool> ReadExactAsync(
+        Stream stream,
+        byte[] buffer,
+        CancellationToken cancellationToken)
+    {
+        var totalRead = 0;
+        while (totalRead < buffer.Length)
+        {
+            var read = await stream
+                .ReadAsync(buffer.AsMemory(totalRead, buffer.Length - totalRead), cancellationToken)
+                .ConfigureAwait(false);
+            if (read == 0)
+            {
+                return false;
+            }
+
+            totalRead += read;
+        }
+
+        return true;
+    }
+}

LanMountainDesktop.Launcher/Services/LauncherFlowCoordinator.cs

@@ -1,6 +1,7 @@
 using System.Diagnostics;
 using Avalonia.Threading;
 using LanMountainDesktop.Launcher.Models;
+using LanMountainDesktop.Launcher.Services.Ipc;
 using LanMountainDesktop.Launcher.Views;
 using LanMountainDesktop.Shared.Contracts.Launcher;
 using LanMountainDesktop.Shared.IPC;
@@ -31,6 +32,7 @@ internal sealed class LauncherFlowCoordinator
     private readonly UpdateEngineService _updateEngine;
     private readonly PluginInstallerService _pluginInstallerService;
     private readonly StartupAttemptRegistry _startupAttemptRegistry;
+    private readonly LauncherCoordinatorIpcServer? _coordinatorIpcServer;
     private readonly IReadOnlyList<IOobeStep> _oobeSteps;
 
     public LauncherFlowCoordinator(
@@ -38,17 +40,25 @@ internal sealed class LauncherFlowCoordinator
         DeploymentLocator deploymentLocator,
         OobeStateService oobeStateService,
         UpdateEngineService updateEngine,
-        PluginInstallerService pluginInstallerService)
+        PluginInstallerService pluginInstallerService,
+        StartupAttemptRegistry? startupAttemptRegistry = null,
+        LauncherCoordinatorIpcServer? coordinatorIpcServer = null)
     {
         _context = context;
         _deploymentLocator = deploymentLocator;
         _oobeStateService = oobeStateService;
         _updateEngine = updateEngine;
         _pluginInstallerService = pluginInstallerService;
-        _startupAttemptRegistry = new StartupAttemptRegistry();
+        _startupAttemptRegistry = startupAttemptRegistry ?? new StartupAttemptRegistry();
+        _coordinatorIpcServer = coordinatorIpcServer;
         _oobeSteps = [new WelcomeOobeStep(_oobeStateService, _context)];
     }
 
+    public static string ResolveSuccessPolicyKey(CommandContext context)
+    {
+        return new StartupSuccessTracker(context).PolicyKey;
+    }
+
     public async Task<LauncherResult> RunAsync(SplashWindow? existingSplashWindow = null)
     {
         try
@@ -98,6 +108,44 @@ internal sealed class LauncherFlowCoordinator
             var softTimeoutShown = false;
             var attachedToExistingAttempt = false;
             StartupAttemptRecord? trackedAttempt = null;
+            PublicShellStatus? shellStatus = null;
+
+            void PublishCoordinatorStatus(bool? hostProcessAliveOverride = null, bool completed = false, bool succeeded = false)
+            {
+                if (_coordinatorIpcServer is null)
+                {
+                    return;
+                }
+
+                trackedAttempt = _startupAttemptRegistry.GetOwnedAttempt() ?? trackedAttempt;
+                var hostPid = trackedAttempt?.HostPid ?? 0;
+                var hostProcessAlive = hostProcessAliveOverride ??
+                                       (hostPid > 0 && TryGetLiveProcess(hostPid, out _));
+                var status = new LauncherCoordinatorStatus
+                {
+                    AttemptId = trackedAttempt?.AttemptId ?? string.Empty,
+                    CoordinatorPid = Environment.ProcessId,
+                    HostPid = hostPid,
+                    HostProcessAlive = hostProcessAlive,
+                    LaunchSource = trackedAttempt?.LaunchSource ?? _context.LaunchSource,
+                    SuccessPolicy = trackedAttempt?.SuccessPolicy ?? startupSuccessTracker.PolicyKey,
+                    LastObservedStage = lastStage,
+                    LastObservedMessage = lastStageMessage,
+                    PublicIpcConnected = ipcConnected,
+                    State = trackedAttempt?.State.ToString() ?? StartupAttemptState.Pending.ToString(),
+                    SoftTimeoutShown = softTimeoutShown,
+                    Completed = completed,
+                    Succeeded = succeeded,
+                    ShellStatus = shellStatus,
+                    UpdatedAtUtc = DateTimeOffset.UtcNow
+                };
+
+                _coordinatorIpcServer.UpdateStatus(status);
+                _startupAttemptRegistry.UpdateOwnedCoordinatorHeartbeat(status);
+            }
+
+            trackedAttempt = _startupAttemptRegistry.GetOwnedAttempt();
+            PublishCoordinatorStatus();
 
             var loadingState = new LoadingStateMessage();
             EventHandler? splashClosedHandler = null;
@@ -135,6 +183,7 @@ internal sealed class LauncherFlowCoordinator
                         reporter.Report(MapStartupStageToSplashStage(message.Stage), message.Message ?? message.Stage.ToString());
                         loadingDetailsWindow?.UpdateLoadingState(loadingState);
                         _startupAttemptRegistry.UpdateOwnedStage(message.Stage, message.Message, ipcConnected: true);
+                        PublishCoordinatorStatus();
 
                         if (startupSuccessTracker.TryResolve(message.Stage, out var successState))
                         {
@@ -171,6 +220,51 @@ internal sealed class LauncherFlowCoordinator
 
             try
             {
+                if (ShouldProbeExistingHostBeforeLaunch(_context))
+                {
+                    var existingActivation = await TryActivateExistingHostWithStatusAsync(ipcClient, TimeSpan.FromMilliseconds(900))
+                        .ConfigureAwait(false);
+                    if (existingActivation is not null)
+                    {
+                        ipcConnected = true;
+                        shellStatus = existingActivation.Status;
+                        lastStage = existingActivation.Accepted
+                            ? StartupStage.ActivationRedirected
+                            : StartupStage.ActivationFailed;
+                        lastStageMessage = existingActivation.Message;
+                        if (existingActivation.Accepted)
+                        {
+                            _startupAttemptRegistry.MarkOwnedSucceeded(lastStage, lastStageMessage);
+                        }
+                        else
+                        {
+                            _startupAttemptRegistry.MarkOwnedFailed(lastStage, lastStageMessage);
+                        }
+
+                        PublishCoordinatorStatus(
+                            hostProcessAliveOverride: true,
+                            completed: true,
+                            succeeded: existingActivation.Accepted);
+                        windowsClosingByCoordinator = true;
+                        await CloseWindowsAsync(splashWindow, loadingDetailsWindow).ConfigureAwait(false);
+                        return BuildResult(
+                            success: existingActivation.Accepted,
+                            stage: "launch",
+                            code: existingActivation.Accepted ? "existing_host_activated" : "existing_host_activation_failed",
+                            message: existingActivation.Message,
+                            details: MergeDetails(
+                                launcherContextDetails,
+                                new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
+                                {
+                                    ["publicIpcConnected"] = "true",
+                                    ["existingHostPid"] = existingActivation.Status.ProcessId.ToString(),
+                                    ["existingShellState"] = existingActivation.Status.ShellState,
+                                    ["existingTrayState"] = existingActivation.Status.Tray.State,
+                                    ["existingTaskbarUsable"] = existingActivation.Status.Taskbar.IsUsable.ToString()
+                                }));
+                    }
+                }
+
                 reporter.Report("update", "Checking updates...");
                 var updateResult = await _updateEngine.ApplyPendingUpdateAsync().ConfigureAwait(false);
                 if (!updateResult.Success)
@@ -212,6 +306,7 @@ internal sealed class LauncherFlowCoordinator
                         ? "Attached to the existing startup attempt."
                         : attachableAttempt.LastObservedMessage;
                     reporter.Report(MapStartupStageToSplashStage(lastStage), lastStageMessage);
+                    PublishCoordinatorStatus(hostProcessAliveOverride: true);
 
                     if (startupSuccessTracker.TryResolve(lastStage, out var attachedSuccessState))
                     {
@@ -318,12 +413,19 @@ internal sealed class LauncherFlowCoordinator
 
                 if (!attachedToExistingAttempt)
                 {
-                    trackedAttempt = _startupAttemptRegistry.StartOwnedAttempt(
-                        launchOutcome.Process.Id,
-                        _context.LaunchSource,
-                        startupSuccessTracker.PolicyKey,
-                        lastStage,
-                        lastStageMessage);
+                    var reservedAttempt = _startupAttemptRegistry.GetOwnedAttempt();
+                    trackedAttempt = reservedAttempt is { ReservedBeforeHostStart: true }
+                        ? _startupAttemptRegistry.AssignOwnedHostProcess(
+                            launchOutcome.Process.Id,
+                            lastStage,
+                            lastStageMessage)
+                        : _startupAttemptRegistry.StartOwnedAttempt(
+                            launchOutcome.Process.Id,
+                            _context.LaunchSource,
+                            startupSuccessTracker.PolicyKey,
+                            lastStage,
+                            lastStageMessage);
+                    PublishCoordinatorStatus(hostProcessAliveOverride: true);
                 }
 
                 var connected = await TryConnectToPublicIpcAsync(ipcClient, TimeSpan.FromSeconds(5)).ConfigureAwait(false);
@@ -335,6 +437,8 @@ internal sealed class LauncherFlowCoordinator
                 {
                     ipcConnected = true;
                     _startupAttemptRegistry.MarkOwnedIpcConnected();
+                    shellStatus = await TryGetPublicShellStatusAsync(ipcClient).ConfigureAwait(false);
+                    PublishCoordinatorStatus(hostProcessAliveOverride: true);
                 }
 
                 Dictionary<string, string> ComposeLaunchDetails(bool hostProcessAlive, bool recoveryActivationAttempted = false)
@@ -368,6 +472,7 @@ internal sealed class LauncherFlowCoordinator
                         var successState = await successTcs.Task.ConfigureAwait(false);
                         windowsClosingByCoordinator = true;
                         _startupAttemptRegistry.MarkOwnedSucceeded(successState.Stage, successState.Message);
+                        PublishCoordinatorStatus(!launchOutcome.Process.HasExited, completed: true, succeeded: true);
                         await CloseWindowsAsync(splashWindow, loadingDetailsWindow).ConfigureAwait(false);
                         return BuildResult(
                             success: true,
@@ -392,6 +497,7 @@ internal sealed class LauncherFlowCoordinator
                         if (exitCode == HostExitCodes.SecondaryActivationSucceeded)
                         {
                             _startupAttemptRegistry.MarkOwnedSucceeded(StartupStage.ActivationRedirected, "Host redirected activation to the existing desktop instance.");
+                            PublishCoordinatorStatus(hostProcessAliveOverride: false, completed: true, succeeded: true);
                             await CloseWindowsAsync(splashWindow, loadingDetailsWindow).ConfigureAwait(false);
                             return BuildResult(
                                 success: true,
@@ -407,6 +513,7 @@ internal sealed class LauncherFlowCoordinator
                         }
 
                         _startupAttemptRegistry.MarkOwnedFailed(lastStage, activationFailureReason);
+                        PublishCoordinatorStatus(hostProcessAliveOverride: false, completed: true, succeeded: false);
                         await CloseWindowsAsync(splashWindow, loadingDetailsWindow).ConfigureAwait(false);
                         return BuildResult(
                             success: false,
@@ -435,6 +542,8 @@ internal sealed class LauncherFlowCoordinator
                         {
                             ipcConnected = true;
                             _startupAttemptRegistry.MarkOwnedIpcConnected();
+                            shellStatus = await TryGetPublicShellStatusAsync(ipcClient).ConfigureAwait(false);
+                            PublishCoordinatorStatus(hostProcessAliveOverride: true);
                         }
 
                         nextReconnectAttemptAt = DateTimeOffset.UtcNow.AddSeconds(5);
@@ -453,6 +562,7 @@ internal sealed class LauncherFlowCoordinator
                             SoftTimeoutDetailsMessage,
                             trackedAttempt?.StartedAtUtc ?? startedAt);
                         loadingDetailsWindow?.UpdateLoadingState(loadingState);
+                        PublishCoordinatorStatus(hostProcessAliveOverride: !launchOutcome.Process.HasExited);
                     }
 
                     if (now >= hardTimeoutAt)
@@ -491,6 +601,8 @@ internal sealed class LauncherFlowCoordinator
                     {
                         ipcConnected = true;
                         _startupAttemptRegistry.MarkOwnedIpcConnected();
+                        shellStatus = await TryGetPublicShellStatusAsync(ipcClient).ConfigureAwait(false);
+                        PublishCoordinatorStatus(hostProcessAliveOverride: true);
                     }
                 }
 
@@ -506,6 +618,8 @@ internal sealed class LauncherFlowCoordinator
                     {
                         windowsClosingByCoordinator = true;
                         _startupAttemptRegistry.MarkOwnedSucceeded(recoveryOutcome.Stage, recoveryOutcome.Message);
+                        shellStatus = await TryGetPublicShellStatusAsync(ipcClient).ConfigureAwait(false);
+                        PublishCoordinatorStatus(!launchOutcome.Process.HasExited, completed: true, succeeded: true);
                         await CloseWindowsAsync(splashWindow, loadingDetailsWindow).ConfigureAwait(false);
                         return BuildResult(
                             success: true,
@@ -520,6 +634,7 @@ internal sealed class LauncherFlowCoordinator
 
                 windowsClosingByCoordinator = true;
                 _startupAttemptRegistry.MarkOwnedFailed(lastStage, activationFailureReason);
+                PublishCoordinatorStatus(!launchOutcome.Process.HasExited, completed: true, succeeded: false);
                 await CloseWindowsAsync(splashWindow, loadingDetailsWindow).ConfigureAwait(false);
                 return BuildResult(
                     success: false,
@@ -1200,6 +1315,11 @@ internal sealed class LauncherFlowCoordinator
         LanMountainDesktopIpcClient ipcClient,
         TimeSpan timeout)
     {
+        if (ipcClient.IsConnected)
+        {
+            return true;
+        }
+
         var connectTask = ipcClient.ConnectAsync();
         var completedTask = await Task.WhenAny(connectTask, Task.Delay(timeout)).ConfigureAwait(false);
         if (completedTask != connectTask)
@@ -1211,6 +1331,59 @@ internal sealed class LauncherFlowCoordinator
         return true;
     }
 
+    private static bool ShouldProbeExistingHostBeforeLaunch(CommandContext context)
+    {
+        if (!string.Equals(context.Command, "launch", StringComparison.OrdinalIgnoreCase))
+        {
+            return false;
+        }
+
+        if (context.IsPreviewCommand || context.IsMaintenanceCommand)
+        {
+            return false;
+        }
+
+        return !string.Equals(context.LaunchSource, "restart", StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static async Task<PublicShellActivationResult?> TryActivateExistingHostWithStatusAsync(
+        LanMountainDesktopIpcClient ipcClient,
+        TimeSpan timeout)
+    {
+        try
+        {
+            var connected = ipcClient.IsConnected ||
+                            await TryConnectToPublicIpcAsync(ipcClient, timeout).ConfigureAwait(false);
+            if (!connected)
+            {
+                return null;
+            }
+
+            var shellProxy = ipcClient.CreateProxy<IPublicShellControlService>();
+            return await shellProxy.ActivateMainWindowWithStatusAsync().ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"Existing host activation probe failed: {ex.Message}");
+            return null;
+        }
+    }
+
+    private static async Task<PublicShellStatus?> TryGetPublicShellStatusAsync(
+        LanMountainDesktopIpcClient ipcClient)
+    {
+        try
+        {
+            var shellProxy = ipcClient.CreateProxy<IPublicShellControlService>();
+            return await shellProxy.GetShellStatusAsync().ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"Failed to query public shell status: {ex.Message}");
+            return null;
+        }
+    }
+
     private static async Task<StartupSuccessState?> TryRecoverWithPublicActivationAsync(
         LanMountainDesktopIpcClient ipcClient,
         Process hostProcess,
@@ -1305,8 +1478,14 @@ internal sealed class LauncherFlowCoordinator
             details["startupAttemptState"] = trackedAttempt.State.ToString();
             details["startupAttemptStartedAtUtc"] = trackedAttempt.StartedAtUtc.ToString("O");
             details["startupAttemptUpdatedAtUtc"] = trackedAttempt.UpdatedAtUtc.ToString("O");
+            details["startupAttemptHeartbeatAtUtc"] = trackedAttempt.HeartbeatAtUtc.ToString("O");
             details["successPolicy"] = trackedAttempt.SuccessPolicy;
             details["hostPid"] = trackedAttempt.HostPid.ToString();
+            details["coordinatorPid"] = trackedAttempt.CoordinatorPid.ToString();
+            details["coordinatorPipeName"] = trackedAttempt.CoordinatorPipeName;
+            details["reservedBeforeHostStart"] = trackedAttempt.ReservedBeforeHostStart.ToString();
+            details["publicIpcConnected"] = trackedAttempt.PublicIpcConnected.ToString();
+            details["shellStatus"] = trackedAttempt.ShellStatus;
         }
 
         return details;

LanMountainDesktop.Launcher/Services/StartupAttemptRegistry.cs

@@ -9,6 +9,7 @@ namespace LanMountainDesktop.Launcher.Services;
 
 internal sealed class StartupAttemptRegistry
 {
+    private static readonly TimeSpan CoordinatorHeartbeatTimeout = TimeSpan.FromSeconds(10);
     private static readonly JsonSerializerOptions SerializerOptions = new()
     {
         WriteIndented = true
@@ -45,12 +46,14 @@ internal sealed class StartupAttemptRegistry
         {
             AttemptId = Guid.NewGuid().ToString("N"),
             HostPid = hostPid,
+            CoordinatorPid = Environment.ProcessId,
             LaunchSource = launchSource,
             SuccessPolicy = successPolicy,
             LastObservedStage = stage,
             LastObservedMessage = message ?? string.Empty,
             StartedAtUtc = DateTimeOffset.UtcNow,
             UpdatedAtUtc = DateTimeOffset.UtcNow,
+            HeartbeatAtUtc = DateTimeOffset.UtcNow,
             State = StartupAttemptState.Pending
         };
 
@@ -63,6 +66,148 @@ internal sealed class StartupAttemptRegistry
         return Clone(record);
     }
 
+    public bool TryReserveCoordinator(
+        string launchSource,
+        string successPolicy,
+        string coordinatorPipeName,
+        out StartupAttemptRecord reservedAttempt,
+        out StartupAttemptRecord? activeCoordinatorAttempt)
+    {
+        StartupAttemptRecord? reserved = null;
+        StartupAttemptRecord? active = null;
+
+        ExecuteWithLock(() =>
+        {
+            var existing = LoadUnsafe();
+            if (existing is not null && IsCoordinatorLive(existing))
+            {
+                active = Clone(existing);
+                return;
+            }
+
+            if (existing is not null && IsRecoverableCoordinatorAttempt(existing))
+            {
+                existing.CoordinatorPid = Environment.ProcessId;
+                existing.CoordinatorPipeName = coordinatorPipeName;
+                existing.HeartbeatAtUtc = DateTimeOffset.UtcNow;
+                existing.UpdatedAtUtc = DateTimeOffset.UtcNow;
+                if (existing.HostPid <= 0)
+                {
+                    existing.ReservedBeforeHostStart = true;
+                }
+
+                if (existing.State == StartupAttemptState.DetachedWaiting)
+                {
+                    existing.State = StartupAttemptState.SoftTimeout;
+                }
+
+                _ownedAttemptId = existing.AttemptId;
+                SaveUnsafe(existing);
+                reserved = Clone(existing);
+                return;
+            }
+
+            var now = DateTimeOffset.UtcNow;
+            var record = new StartupAttemptRecord
+            {
+                AttemptId = Guid.NewGuid().ToString("N"),
+                HostPid = 0,
+                CoordinatorPid = Environment.ProcessId,
+                CoordinatorPipeName = coordinatorPipeName,
+                LaunchSource = launchSource,
+                SuccessPolicy = successPolicy,
+                LastObservedStage = StartupStage.Initializing,
+                LastObservedMessage = "Launcher coordinator reserved startup ownership.",
+                StartedAtUtc = now,
+                UpdatedAtUtc = now,
+                HeartbeatAtUtc = now,
+                ReservedBeforeHostStart = true,
+                State = StartupAttemptState.Pending
+            };
+
+            _ownedAttemptId = record.AttemptId;
+            SaveUnsafe(record);
+            reserved = Clone(record);
+        });
+
+        reservedAttempt = reserved ?? new StartupAttemptRecord();
+        activeCoordinatorAttempt = active;
+        return reserved is not null;
+    }
+
+    public StartupAttemptRecord? GetOwnedAttempt()
+    {
+        StartupAttemptRecord? result = null;
+        if (string.IsNullOrWhiteSpace(_ownedAttemptId))
+        {
+            return null;
+        }
+
+        ExecuteWithLock(() =>
+        {
+            var record = LoadUnsafe();
+            if (record is not null && string.Equals(record.AttemptId, _ownedAttemptId, StringComparison.Ordinal))
+            {
+                result = Clone(record);
+            }
+        });
+
+        return result;
+    }
+
+    public StartupAttemptRecord? TryGetLiveCoordinatorAttempt()
+    {
+        StartupAttemptRecord? result = null;
+        ExecuteWithLock(() =>
+        {
+            var record = LoadUnsafe();
+            if (record is not null && IsCoordinatorLive(record))
+            {
+                result = Clone(record);
+            }
+        });
+
+        return result;
+    }
+
+    public StartupAttemptRecord? TryGetLatestAttempt()
+    {
+        StartupAttemptRecord? result = null;
+        ExecuteWithLock(() =>
+        {
+            var record = LoadUnsafe();
+            if (record is not null)
+            {
+                result = Clone(record);
+            }
+        });
+
+        return result;
+    }
+
+    public StartupAttemptRecord AssignOwnedHostProcess(
+        int hostPid,
+        StartupStage stage,
+        string? message)
+    {
+        StartupAttemptRecord? result = null;
+        UpdateOwned(record =>
+        {
+            record.HostPid = hostPid;
+            record.LastObservedStage = stage;
+            record.LastObservedMessage = message ?? record.LastObservedMessage;
+            record.ReservedBeforeHostStart = false;
+            result = Clone(record);
+        });
+
+        return result ?? StartOwnedAttempt(
+            hostPid,
+            string.Empty,
+            string.Empty,
+            stage,
+            message);
+    }
+
     public bool AdoptAttempt(string attemptId)
     {
         if (string.IsNullOrWhiteSpace(attemptId))
@@ -120,7 +265,11 @@ internal sealed class StartupAttemptRegistry
 
     public void MarkOwnedIpcConnected()
     {
-        UpdateOwned(record => record.IpcConnected = true);
+        UpdateOwned(record =>
+        {
+            record.IpcConnected = true;
+            record.PublicIpcConnected = true;
+        });
     }
 
     public void UpdateOwnedStage(StartupStage stage, string? message, bool ipcConnected)
@@ -132,10 +281,25 @@ internal sealed class StartupAttemptRegistry
             if (ipcConnected)
             {
                 record.IpcConnected = true;
+                record.PublicIpcConnected = true;
             }
         });
     }
 
+    public void UpdateOwnedCoordinatorHeartbeat(LauncherCoordinatorStatus status)
+    {
+        UpdateOwned(record =>
+        {
+            record.CoordinatorPid = Environment.ProcessId;
+            record.HeartbeatAtUtc = DateTimeOffset.UtcNow;
+            record.LastObservedStage = status.LastObservedStage;
+            record.LastObservedMessage = status.LastObservedMessage;
+            record.IpcConnected = status.PublicIpcConnected;
+            record.PublicIpcConnected = status.PublicIpcConnected;
+            record.ShellStatus = status.ShellStatus?.ShellState ?? status.State;
+        });
+    }
+
     public void MarkOwnedSoftTimeout(string? message)
     {
         UpdateOwned(record =>
@@ -267,6 +431,38 @@ internal sealed class StartupAttemptRegistry
         return TryGetLiveProcess(record.HostPid, out _);
     }
 
+    private static bool IsRecoverableCoordinatorAttempt(StartupAttemptRecord record)
+    {
+        if (record.State is not (StartupAttemptState.Pending or StartupAttemptState.SoftTimeout or StartupAttemptState.DetachedWaiting))
+        {
+            return false;
+        }
+
+        if (record.HostPid <= 0)
+        {
+            return true;
+        }
+
+        return TryGetLiveProcess(record.HostPid, out _);
+    }
+
+    private static bool IsCoordinatorLive(StartupAttemptRecord record)
+    {
+        if (record.State is not (StartupAttemptState.Pending or StartupAttemptState.SoftTimeout or StartupAttemptState.DetachedWaiting))
+        {
+            return false;
+        }
+
+        if (record.CoordinatorPid <= 0 ||
+            string.IsNullOrWhiteSpace(record.CoordinatorPipeName) ||
+            DateTimeOffset.UtcNow - record.HeartbeatAtUtc > CoordinatorHeartbeatTimeout)
+        {
+            return false;
+        }
+
+        return TryGetLiveProcess(record.CoordinatorPid, out _);
+    }
+
     private static bool TryGetLiveProcess(int processId, out Process? process)
     {
         process = null;
@@ -300,13 +496,19 @@ internal sealed class StartupAttemptRegistry
         {
             AttemptId = record.AttemptId,
             HostPid = record.HostPid,
+            CoordinatorPid = record.CoordinatorPid,
+            CoordinatorPipeName = record.CoordinatorPipeName,
             StartedAtUtc = record.StartedAtUtc,
             UpdatedAtUtc = record.UpdatedAtUtc,
+            HeartbeatAtUtc = record.HeartbeatAtUtc,
             LaunchSource = record.LaunchSource,
             SuccessPolicy = record.SuccessPolicy,
             LastObservedStage = record.LastObservedStage,
             LastObservedMessage = record.LastObservedMessage,
             IpcConnected = record.IpcConnected,
+            PublicIpcConnected = record.PublicIpcConnected,
+            ShellStatus = record.ShellStatus,
+            ReservedBeforeHostStart = record.ReservedBeforeHostStart,
             State = record.State
         };
     }