fix(launcher): require executable Linux hosts

.github/workflows/headless-portability.yml

@@ -135,6 +135,13 @@ jobs:
           dotnet run --project src/AcDream.Headless/AcDream.Headless.csproj -c Release -- validate --config headless-k0.json
           if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
 
+      - name: Verify Linux headless host executable permission
+        if: runner.os == 'Linux'
+        shell: bash
+        run: |
+          set -euo pipefail
+          test -x src/AcDream.Headless/bin/Release/net10.0/acdream-headless
+
   portable-launcher:
     strategy:
       fail-fast: false

src/AcDream.Launcher.Core/Orchestration/LauncherExecutableSet.cs

@@ -12,12 +12,14 @@ namespace AcDream.Launcher.Core.Orchestration;
 public sealed class LauncherExecutableSet
 {
     private readonly Func<string, bool> _fileExists;
+    private readonly Func<string, bool> _hasUnixExecutePermission;
 
     public LauncherExecutableSet(
         string graphicalHostPath,
         string headlessHostPath,
         string? workingDirectory = null,
-        Func<string, bool>? fileExists = null)
+        Func<string, bool>? fileExists = null,
+        Func<string, bool>? hasUnixExecutePermission = null)
     {
         ArgumentException.ThrowIfNullOrWhiteSpace(graphicalHostPath);
         ArgumentException.ThrowIfNullOrWhiteSpace(headlessHostPath);
@@ -25,6 +27,8 @@ public sealed class LauncherExecutableSet
         HeadlessHostPath = headlessHostPath;
         WorkingDirectory = workingDirectory;
         _fileExists = fileExists ?? File.Exists;
+        _hasUnixExecutePermission =
+            hasUnixExecutePermission ?? HasUnixExecutePermission;
     }
 
     public string GraphicalHostPath { get; }
@@ -38,17 +42,25 @@ public sealed class LauncherExecutableSet
         string path = mode == LaunchMode.Headless
             ? HeadlessHostPath
             : GraphicalHostPath;
-        if (_fileExists(path))
-        {
-            return LauncherCapability.Available;
-        }
-
         string host = mode == LaunchMode.Headless
             ? "headless host"
             : "graphical client";
-        return LauncherCapability.Unavailable(
-            $"The co-deployed {host} is missing at '{path}'. Reinstall or update "
-            + "the client before launching.");
+        if (!_fileExists(path))
+        {
+            return LauncherCapability.Unavailable(
+                $"The co-deployed {host} is missing at '{path}'. Reinstall or update "
+                + "the client before launching.");
+        }
+
+        if (OperatingSystem.IsLinux() && !_hasUnixExecutePermission(path))
+        {
+            return LauncherCapability.Unavailable(
+                $"The co-deployed {host} at '{path}' exists but is not executable. "
+                + "Restore its executable permission (for example, chmod +x) or "
+                + "reinstall/update the client before launching.");
+        }
+
+        return LauncherCapability.Available;
     }
 
     public LauncherProcessSpec CreatePlaySpec(
@@ -99,4 +111,27 @@ public sealed class LauncherExecutableSet
                 capability.Reason ?? "The selected launcher host is unavailable.");
         }
     }
+
+    private static bool HasUnixExecutePermission(string path)
+    {
+        if (!OperatingSystem.IsLinux())
+        {
+            return true;
+        }
+
+        try
+        {
+            const UnixFileMode executeBits =
+                UnixFileMode.UserExecute
+                | UnixFileMode.GroupExecute
+                | UnixFileMode.OtherExecute;
+            return (File.GetUnixFileMode(path) & executeBits) != 0;
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            // Fail closed if the file vanished or its metadata cannot be read
+            // after the existence check. The next capability refresh retries.
+            return false;
+        }
+    }
 }

tests/AcDream.Launcher.Core.Tests/Orchestration/LauncherExecutableSetTests.cs

@@ -27,6 +27,8 @@ public sealed class LauncherExecutableSetTests : IDisposable
         string headless = Path.Combine(_root, "acdream-headless" + suffix);
         File.WriteAllText(graphical, string.Empty);
         File.WriteAllText(headless, string.Empty);
+        MakeExecutableOnLinux(graphical);
+        MakeExecutableOnLinux(headless);
 
         LauncherExecutableSet set = LauncherExecutableSet.FromDirectory(_root);
 
@@ -64,4 +66,78 @@ public sealed class LauncherExecutableSetTests : IDisposable
         Assert.Throws<LauncherOperationException>(() =>
             set.CreateProbeSpec("session.json"));
     }
+
+    [Fact]
+    public void LinuxRequiresExecutePermissionForBothCoDeployedHosts()
+    {
+        if (!OperatingSystem.IsLinux())
+        {
+            return;
+        }
+
+        Directory.CreateDirectory(_root);
+        string graphical = Path.Combine(_root, "AcDream.App");
+        string headless = Path.Combine(_root, "acdream-headless");
+        File.WriteAllText(graphical, string.Empty);
+        File.WriteAllText(headless, string.Empty);
+        UnixFileMode notExecutable = UnixFileMode.UserRead | UnixFileMode.UserWrite
+            | UnixFileMode.GroupRead | UnixFileMode.OtherRead;
+        File.SetUnixFileMode(graphical, notExecutable);
+        File.SetUnixFileMode(headless, notExecutable);
+        LauncherExecutableSet set = LauncherExecutableSet.FromDirectory(_root);
+
+        LauncherCapability gui = set.GetAvailability(LaunchMode.Gui);
+        LauncherCapability headlessCapability =
+            set.GetAvailability(LaunchMode.Headless);
+
+        Assert.False(gui.IsAvailable);
+        Assert.Contains("not executable", gui.Reason, StringComparison.Ordinal);
+        Assert.Contains("chmod +x", gui.Reason, StringComparison.Ordinal);
+        Assert.False(headlessCapability.IsAvailable);
+        Assert.Contains("not executable", headlessCapability.Reason, StringComparison.Ordinal);
+        Assert.Throws<LauncherOperationException>(() =>
+            set.CreatePlaySpec(LaunchMode.GuiSelect, "session.json"));
+        Assert.Throws<LauncherOperationException>(() =>
+            set.CreateProbeSpec("session.json"));
+
+        MakeExecutableOnLinux(graphical);
+        MakeExecutableOnLinux(headless);
+
+        Assert.True(set.GetAvailability(LaunchMode.GuiSelect).IsAvailable);
+        Assert.True(set.GetAvailability(LaunchMode.Headless).IsAvailable);
+    }
+
+    [Fact]
+    public void WindowsPreservesExistenceOnlyAvailability()
+    {
+        if (!OperatingSystem.IsWindows())
+        {
+            return;
+        }
+
+        var set = new LauncherExecutableSet(
+            "graphical.exe",
+            "headless.exe",
+            fileExists: _ => true,
+            hasUnixExecutePermission: _ => false);
+
+        Assert.True(set.GetAvailability(LaunchMode.Gui).IsAvailable);
+        Assert.True(set.GetAvailability(LaunchMode.Headless).IsAvailable);
+    }
+
+    private static void MakeExecutableOnLinux(string path)
+    {
+        if (OperatingSystem.IsLinux())
+        {
+            File.SetUnixFileMode(
+                path,
+                UnixFileMode.UserRead
+                | UnixFileMode.UserWrite
+                | UnixFileMode.UserExecute
+                | UnixFileMode.GroupRead
+                | UnixFileMode.GroupExecute
+                | UnixFileMode.OtherRead
+                | UnixFileMode.OtherExecute);
+        }
+    }
 }

tests/AcDream.Launcher.Core.Tests/Orchestration/LauncherOrchestratorTests.cs

@@ -518,7 +518,8 @@ public sealed class LauncherOrchestratorTests : IDisposable
             executables ?? new LauncherExecutableSet(
                 "gui-host",
                 "headless-host",
-                fileExists: _ => true),
+                fileExists: _ => true,
+                hasUnixExecutePermission: _ => true),
             new LauncherInstallRecord("dats", "pak"),
             platform ?? WindowsCapabilities(),
             configService,

tests/AcDream.Launcher.Tests/LauncherProjectBoundaryTests.cs

@@ -116,6 +116,11 @@ public sealed class LauncherProjectBoundaryTests
         Assert.Contains("-getProperty:SelfContained", workflow, StringComparison.Ordinal);
         Assert.Contains("DOTNET_ROOT", workflow, StringComparison.Ordinal);
         Assert.Contains("--verify-publish", workflow, StringComparison.Ordinal);
+        Assert.Contains(
+            "test -x src/AcDream.Headless/bin/Release/net10.0/acdream-headless",
+            workflow,
+            StringComparison.Ordinal);
+        Assert.Contains("test -x \"$root/AcDream.App\"", workflow, StringComparison.Ordinal);
     }
 
     private static string EvaluateProperty(string projectPath, string property)