diff --git a/src/AcDream.Launcher.Core/Orchestration/LauncherExecutableSet.cs b/src/AcDream.Launcher.Core/Orchestration/LauncherExecutableSet.cs
index 4add2816..8014ff20 100644
--- a/src/AcDream.Launcher.Core/Orchestration/LauncherExecutableSet.cs
+++ b/src/AcDream.Launcher.Core/Orchestration/LauncherExecutableSet.cs
@@ -100,7 +100,14 @@ public sealed class LauncherExecutableSet
         return mode == LaunchMode.Headless
             ? new LauncherProcessSpec(
                 paths.HeadlessHostPath,
-                ["--config", configFilePath],
+                // "run" is REQUIRED and positional: HeadlessCommandLine.Parse
+                // reads arguments[0] as the command and accepts only
+                // "validate" or "run". Passing "--config" first made every
+                // launcher-started headless session die instantly with
+                // "Invalid command. Run --help for usage." (exit 64) — the
+                // graphical host takes a bare "--session-config", and this
+                // sibling call was written to match it.
+                ["run", "--config", configFilePath],
                 paths.WorkingDirectory,
                 StderrLogPath: stderrLogPath)
             : new LauncherProcessSpec(
@@ -119,7 +126,11 @@ public sealed class LauncherExecutableSet
         ExecutablePaths paths = RequireAvailable(LaunchMode.Headless);
         return new LauncherProcessSpec(
             paths.HeadlessHostPath,
-            ["--config", configFilePath],
+            // Same grammar as CreatePlaySpec's headless arm — see its comment.
+            // A probe is an ordinary "run" whose session config carries
+            // mode: "probe"; the difference is in the document, not the
+            // command line.
+            ["run", "--config", configFilePath],
             paths.WorkingDirectory,
             StderrLogPath: stderrLogPath);
     }
diff --git a/src/AcDream.Launcher/MainWindow.axaml b/src/AcDream.Launcher/MainWindow.axaml
index bb638338..ab945311 100644
--- a/src/AcDream.Launcher/MainWindow.axaml
+++ b/src/AcDream.Launcher/MainWindow.axaml
@@ -193,20 +193,18 @@
               <Border Background="#213044" CornerRadius="6" Padding="12">
                 <StackPanel Spacing="10">
                   <TextBlock Text="Launch" Classes="section" />
-                  <!-- LU5: one obvious action. Play enters the world AS THE
-                       SELECTED CHARACTER (LaunchMode.Gui composes a character
-                       selector, and the client skips its own select screen
-                       entirely when one is present). The other two stay as
-                       deliberate, secondary choices. -->
+                  <!-- LU7: choosing a character means choosing to play AS that
+                       character, so the only two things offered here are the
+                       two ways to be that character: in the game window, or
+                       headless. Character select is an ACCOUNT-level action —
+                       it deliberately picks no character — and lives on the
+                       account page only. -->
                   <StackPanel Orientation="Horizontal" Spacing="8">
                     <Button Content="Play"
                             Classes="primary"
                             MinWidth="110"
                             AutomationProperties.Name="Play as the selected character"
                             Command="{Binding LaunchGuiCommand}" />
-                    <Button Content="Character select"
-                            AutomationProperties.Name="Launch to the character select screen"
-                            Command="{Binding LaunchGuiSelectCommand}" />
                     <Button Content="Headless"
                             AutomationProperties.Name="Launch a headless session"
                             Command="{Binding LaunchHeadlessCommand}" />
diff --git a/src/AcDream.Launcher/ViewModels/LauncherWindowViewModel.cs b/src/AcDream.Launcher/ViewModels/LauncherWindowViewModel.cs
index 75ec841b..2a9ec928 100644
--- a/src/AcDream.Launcher/ViewModels/LauncherWindowViewModel.cs
+++ b/src/AcDream.Launcher/ViewModels/LauncherWindowViewModel.cs
@@ -71,9 +71,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
         LaunchGuiCommand = new AsyncRelayCommand(
             () => LaunchSelectedAsync(LaunchMode.Gui),
             () => CanLaunchGui);
-        LaunchGuiSelectCommand = new AsyncRelayCommand(
-            () => LaunchSelectedAsync(LaunchMode.GuiSelect),
-            () => CanLaunchGuiSelect);
         LaunchAccountGuiSelectCommand = new AsyncRelayCommand(
             LaunchSelectedAccountGuiSelectAsync,
             () => CanLaunchAccountGuiSelect);
@@ -119,7 +116,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
             {
                 OnPropertyChanged(nameof(CanProbe));
                 OnPropertyChanged(nameof(CanLaunchGui));
-                OnPropertyChanged(nameof(CanLaunchGuiSelect));
                 OnPropertyChanged(nameof(CanLaunchHeadless));
                 OnPropertyChanged(nameof(CanLaunchAccountGuiSelect));
                 OnPropertyChanged(nameof(ShowGuiLaunchDisabledReason));
@@ -224,8 +220,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
 
     public bool CanLaunchGui => CanLaunch(LaunchMode.Gui);
 
-    public bool CanLaunchGuiSelect => CanLaunch(LaunchMode.GuiSelect);
-
     public bool CanLaunchHeadless => CanLaunch(LaunchMode.Headless);
 
     public bool CanLaunchAccountGuiSelect =>
@@ -287,8 +281,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
 
     public AsyncRelayCommand LaunchGuiCommand { get; }
 
-    public AsyncRelayCommand LaunchGuiSelectCommand { get; }
-
     public AsyncRelayCommand LaunchAccountGuiSelectCommand { get; }
 
     public AsyncRelayCommand LaunchHeadlessCommand { get; }
@@ -375,7 +367,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
         OnPropertyChanged(nameof(IsModalOpen));
         OnPropertyChanged(nameof(CanProbe));
         OnPropertyChanged(nameof(CanLaunchGui));
-        OnPropertyChanged(nameof(CanLaunchGuiSelect));
         OnPropertyChanged(nameof(CanLaunchHeadless));
         OnPropertyChanged(nameof(CanLaunchAccountGuiSelect));
         OnPropertyChanged(nameof(ShowGuiLaunchDisabledReason));
@@ -434,7 +425,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
         OnPropertyChanged(nameof(CanProbe));
         OnPropertyChanged(nameof(ProbeDisabledReason));
         OnPropertyChanged(nameof(CanLaunchGui));
-        OnPropertyChanged(nameof(CanLaunchGuiSelect));
         OnPropertyChanged(nameof(CanLaunchHeadless));
         OnPropertyChanged(nameof(CanLaunchAccountGuiSelect));
         OnPropertyChanged(nameof(AccountGuiSelectDisabledReason));
@@ -474,7 +464,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
         OnPropertyChanged(nameof(CanProbe));
         OnPropertyChanged(nameof(ProbeDisabledReason));
         OnPropertyChanged(nameof(CanLaunchGui));
-        OnPropertyChanged(nameof(CanLaunchGuiSelect));
         OnPropertyChanged(nameof(CanLaunchHeadless));
         OnPropertyChanged(nameof(CanLaunchAccountGuiSelect));
         OnPropertyChanged(nameof(AccountGuiSelectDisabledReason));
@@ -1062,7 +1051,6 @@ public sealed class LauncherWindowViewModel : ObservableObject, IDisposable
         SaveCharacterSettingsCommand.NotifyCanExecuteChanged();
         RefreshCharactersCommand.NotifyCanExecuteChanged();
         LaunchGuiCommand.NotifyCanExecuteChanged();
-        LaunchGuiSelectCommand.NotifyCanExecuteChanged();
         LaunchAccountGuiSelectCommand.NotifyCanExecuteChanged();
         LaunchHeadlessCommand.NotifyCanExecuteChanged();
         CancelOperationCommand.NotifyCanExecuteChanged();
diff --git a/tests/AcDream.Headless.Tests/LauncherHeadlessCommandLineContractTests.cs b/tests/AcDream.Headless.Tests/LauncherHeadlessCommandLineContractTests.cs
new file mode 100644
index 00000000..6ed44d9c
--- /dev/null
+++ b/tests/AcDream.Headless.Tests/LauncherHeadlessCommandLineContractTests.cs
@@ -0,0 +1,94 @@
+using AcDream.Headless.Configuration;
+using AcDream.Launcher.Core.Launching;
+using AcDream.Launcher.Core.Orchestration;
+using AcDream.Launcher.Core.Profiles;
+
+namespace AcDream.Headless.Tests;
+
+/// <summary>
+/// The launcher spawns the headless host; the headless host decides what a
+/// valid command line is. Nothing connected those two facts, and they drifted:
+/// the launcher passed <c>--config &lt;path&gt;</c> while
+/// <see cref="HeadlessCommandLine.Parse"/> reads <c>arguments[0]</c> as the
+/// command and accepts only <c>validate</c> or <c>run</c>. Every
+/// launcher-started headless session and every character refresh therefore died
+/// instantly with "Invalid command. Run --help for usage." — visible only as an
+/// exit code in a status file, which is why it survived a whole campaign.
+///
+/// <para>These tests are the missing connection: they take the argument vector
+/// the launcher will really use and hand it to the parser the host will really
+/// use. The two cannot drift again without failing here.</para>
+/// </summary>
+public sealed class LauncherHeadlessCommandLineContractTests : IDisposable
+{
+    private readonly string _root = Path.Combine(
+        Path.GetTempPath(),
+        "acdream-headless-cli-contract",
+        Guid.NewGuid().ToString("N"));
+
+    public LauncherHeadlessCommandLineContractTests()
+    {
+        // The spec builders refuse to name an executable that is not there, so
+        // the contract can only be exercised against files that exist.
+        Directory.CreateDirectory(AppDirectory);
+        string suffix = OperatingSystem.IsWindows() ? ".exe" : string.Empty;
+        File.WriteAllText(Path.Combine(AppDirectory, "AcDream.App" + suffix), "stub");
+        File.WriteAllText(Path.Combine(AppDirectory, "acdream-headless" + suffix), "stub");
+    }
+
+    public void Dispose()
+    {
+        if (Directory.Exists(_root))
+        {
+            Directory.Delete(_root, recursive: true);
+        }
+    }
+
+    [Fact]
+    public void ProbeArgumentsParseAsAHeadlessRunCommand()
+    {
+        LauncherProcessSpec spec = ExecutableSet().CreateProbeSpec(ConfigPath);
+
+        HeadlessCommandLine parsed = HeadlessCommandLine.Parse(spec.Arguments);
+
+        Assert.Equal("run", parsed.Command);
+        Assert.Equal(ConfigPath, parsed.ConfigurationPath);
+    }
+
+    [Fact]
+    public void HeadlessPlayArgumentsParseAsAHeadlessRunCommand()
+    {
+        LauncherProcessSpec spec = ExecutableSet()
+            .CreatePlaySpec(LaunchMode.Headless, ConfigPath);
+
+        HeadlessCommandLine parsed = HeadlessCommandLine.Parse(spec.Arguments);
+
+        Assert.Equal("run", parsed.Command);
+        Assert.Equal(ConfigPath, parsed.ConfigurationPath);
+    }
+
+    /// <summary>
+    /// The graphical host is a DIFFERENT program with a different grammar — it
+    /// takes a bare <c>--session-config</c> and has no command word. Copying
+    /// that shape onto the headless call is exactly the mistake this file
+    /// exists to prevent, so pin the difference rather than leaving it implied.
+    /// </summary>
+    [Theory]
+    [InlineData(LaunchMode.Gui)]
+    [InlineData(LaunchMode.GuiSelect)]
+    public void GraphicalArgumentsAreNotAHeadlessCommandLine(LaunchMode mode)
+    {
+        LauncherProcessSpec spec = ExecutableSet().CreatePlaySpec(mode, ConfigPath);
+
+        Assert.Equal(["--session-config", ConfigPath], spec.Arguments);
+        Assert.Throws<HeadlessCommandLineException>(
+            () => HeadlessCommandLine.Parse(spec.Arguments));
+    }
+
+    private string AppDirectory => Path.Combine(_root, "app");
+
+    private string ConfigPath => Path.Combine(_root, "session.json");
+
+    private LauncherExecutableSet ExecutableSet() =>
+        LauncherExecutableSet.FromDirectory(AppDirectory);
+}
diff --git a/tests/AcDream.Launcher.Tests/LauncherWindowViewModelTests.cs b/tests/AcDream.Launcher.Tests/LauncherWindowViewModelTests.cs
index d33d2603..2399e4d0 100644
--- a/tests/AcDream.Launcher.Tests/LauncherWindowViewModelTests.cs
+++ b/tests/AcDream.Launcher.Tests/LauncherWindowViewModelTests.cs
@@ -221,7 +221,10 @@ public sealed class LauncherWindowViewModelTests
 
         Assert.True(viewModel.ShowLinuxGraphicalNotice);
         Assert.False(viewModel.CanLaunchGui);
-        Assert.False(viewModel.CanLaunchGuiSelect);
+        // LU7: a selected character offers only Play and Headless. Character
+        // select is an account-level action and no longer has a per-character
+        // command to gate.
+        Assert.False(viewModel.CanLaunchAccountGuiSelect);
         Assert.True(viewModel.CanLaunchHeadless);
         Assert.Equal(
             LauncherPlatformCapabilities.LinuxGraphicalLaunchDisabledReason,