feat(headless): establish portable Linux host boundary

Add the presentation-free acdream-headless executable, strict no-connect configuration validation, dependency and assembly guards, and a Windows/Ubuntu CI lane that builds and tests only the portable runtime closure.

Co-authored-by: Codex <noreply@openai.com>

.github/workflows/headless-portability.yml

@@ -0,0 +1,97 @@
+name: Headless portability
+
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/headless-portability.yml"
+      - "AcDream.slnx"
+      - "src/AcDream.Core/**"
+      - "src/AcDream.Core.Net/**"
+      - "src/AcDream.Content/**"
+      - "src/AcDream.Plugin.Abstractions/**"
+      - "src/AcDream.Runtime/**"
+      - "src/AcDream.Headless/**"
+      - "tests/AcDream.Core.Tests/**"
+      - "tests/AcDream.Core.Net.Tests/**"
+      - "tests/AcDream.Content.Tests/**"
+      - "tests/AcDream.Runtime.Tests/**"
+      - "tests/AcDream.Headless.Tests/**"
+  push:
+    paths:
+      - ".github/workflows/headless-portability.yml"
+      - "AcDream.slnx"
+      - "src/AcDream.Core/**"
+      - "src/AcDream.Core.Net/**"
+      - "src/AcDream.Content/**"
+      - "src/AcDream.Plugin.Abstractions/**"
+      - "src/AcDream.Runtime/**"
+      - "src/AcDream.Headless/**"
+      - "tests/AcDream.Core.Tests/**"
+      - "tests/AcDream.Core.Net.Tests/**"
+      - "tests/AcDream.Content.Tests/**"
+      - "tests/AcDream.Runtime.Tests/**"
+      - "tests/AcDream.Headless.Tests/**"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  portable-headless:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [windows-latest, ubuntu-latest]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Install .NET 10
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "10.0.x"
+
+      - name: Build presentation-free closure
+        shell: pwsh
+        run: |
+          $projects = @(
+            "src/AcDream.Plugin.Abstractions/AcDream.Plugin.Abstractions.csproj",
+            "src/AcDream.Core/AcDream.Core.csproj",
+            "src/AcDream.Core.Net/AcDream.Core.Net.csproj",
+            "src/AcDream.Content/AcDream.Content.csproj",
+            "src/AcDream.Runtime/AcDream.Runtime.csproj",
+            "src/AcDream.Headless/AcDream.Headless.csproj"
+          )
+          foreach ($project in $projects) {
+            dotnet build $project -c Release
+            if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+          }
+
+      # AcDream.Core.Tests still contains historical App integration fixtures,
+      # so it is deliberately not a member of this no-App restore lane. Core is
+      # built directly above and exercised through every portable downstream
+      # test project below; the complete solution lane retains Core.Tests.
+      - name: Test presentation-free closure
+        shell: pwsh
+        run: |
+          $projects = @(
+            "tests/AcDream.Core.Net.Tests/AcDream.Core.Net.Tests.csproj",
+            "tests/AcDream.Content.Tests/AcDream.Content.Tests.csproj",
+            "tests/AcDream.Runtime.Tests/AcDream.Runtime.Tests.csproj",
+            "tests/AcDream.Headless.Tests/AcDream.Headless.Tests.csproj"
+          )
+          foreach ($project in $projects) {
+            dotnet test $project -c Release
+            if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+          }
+
+      - name: Verify CLI without connecting
+        shell: pwsh
+        run: |
+          dotnet run --project src/AcDream.Headless/AcDream.Headless.csproj -c Release -- --help
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+          Set-Content -LiteralPath headless-k0.json -Value '{"version":1,"sessions":[]}'
+          dotnet run --project src/AcDream.Headless/AcDream.Headless.csproj -c Release -- validate --config headless-k0.json
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }

AcDream.slnx

@@ -6,6 +6,7 @@
     <Project Path="src/AcDream.Content/AcDream.Content.csproj" />
     <Project Path="src/AcDream.Core/AcDream.Core.csproj" />
     <Project Path="src/AcDream.Core.Net/AcDream.Core.Net.csproj" />
+    <Project Path="src/AcDream.Headless/AcDream.Headless.csproj" />
     <Project Path="src/AcDream.Plugin.Abstractions/AcDream.Plugin.Abstractions.csproj" />
     <Project Path="src/AcDream.Plugins.Smoke/AcDream.Plugins.Smoke.csproj" />
     <Project Path="src/AcDream.Runtime/AcDream.Runtime.csproj" />
@@ -23,6 +24,7 @@
     <Project Path="tests/AcDream.Core.Tests.Fixtures.HelloPlugin/AcDream.Core.Tests.Fixtures.HelloPlugin.csproj" />
     <Project Path="tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj" />
     <Project Path="tests/AcDream.Core.Net.Tests/AcDream.Core.Net.Tests.csproj" />
+    <Project Path="tests/AcDream.Headless.Tests/AcDream.Headless.Tests.csproj" />
     <Project Path="tests/AcDream.Runtime.Tests/AcDream.Runtime.Tests.csproj" />
     <Project Path="tests/AcDream.UI.Abstractions.Tests/AcDream.UI.Abstractions.Tests.csproj" />
   </Folder>

src/AcDream.Headless/AcDream.Headless.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <AssemblyName>acdream-headless</AssemblyName>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <LangVersion>latest</LangVersion>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="AcDream.Headless.Tests" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- The production headless process enters through the same Runtime root
+         as the graphical client. Presentation, UI, native-window, GL, and
+         audio projects are forbidden here and enforced by tests. -->
+    <ProjectReference Include="..\AcDream.Runtime\AcDream.Runtime.csproj" />
+  </ItemGroup>
+</Project>

src/AcDream.Headless/Configuration/HeadlessConfiguration.cs

@@ -0,0 +1,18 @@
+using System.Text.Json.Serialization;
+
+namespace AcDream.Headless.Configuration;
+
+internal sealed class HeadlessConfiguration
+{
+    [JsonRequired]
+    public int Version { get; init; }
+
+    [JsonRequired]
+    public List<HeadlessSessionDescriptor?> Sessions { get; init; } = [];
+}
+
+internal sealed class HeadlessSessionDescriptor
+{
+    [JsonRequired]
+    public string Id { get; init; } = string.Empty;
+}

src/AcDream.Headless/Configuration/HeadlessConfigurationException.cs

@@ -0,0 +1,9 @@
+namespace AcDream.Headless.Configuration;
+
+internal sealed class HeadlessConfigurationException : Exception
+{
+    internal HeadlessConfigurationException(string message)
+        : base(message)
+    {
+    }
+}

src/AcDream.Headless/Configuration/HeadlessConfigurationLoader.cs

@@ -0,0 +1,68 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AcDream.Headless.Configuration;
+
+internal static class HeadlessConfigurationLoader
+{
+    private const int CurrentVersion = 1;
+
+    private static readonly JsonSerializerOptions Options = new()
+    {
+        AllowTrailingCommas = false,
+        PropertyNameCaseInsensitive = false,
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        ReadCommentHandling = JsonCommentHandling.Disallow,
+        UnmappedMemberHandling = JsonUnmappedMemberHandling.Disallow,
+    };
+
+    internal static HeadlessConfiguration Load(string path)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(path);
+
+        string fullPath = Path.GetFullPath(path);
+        using FileStream stream = File.OpenRead(fullPath);
+        HeadlessConfiguration? configuration =
+            JsonSerializer.Deserialize<HeadlessConfiguration>(
+                stream,
+                Options);
+
+        if (configuration is null)
+        {
+            throw new HeadlessConfigurationException(
+                "The configuration document is empty.");
+        }
+
+        if (configuration.Version != CurrentVersion)
+        {
+            throw new HeadlessConfigurationException(
+                $"Unsupported configuration version {configuration.Version}; "
+                + $"expected {CurrentVersion}.");
+        }
+
+        if (configuration.Sessions is null)
+        {
+            throw new HeadlessConfigurationException(
+                "sessions must be an array.");
+        }
+
+        var sessionIds = new HashSet<string>(StringComparer.Ordinal);
+        foreach (HeadlessSessionDescriptor? session in configuration.Sessions)
+        {
+            if (session is null
+                || string.IsNullOrWhiteSpace(session.Id))
+            {
+                throw new HeadlessConfigurationException(
+                    "Every session requires a non-empty id.");
+            }
+
+            if (!sessionIds.Add(session.Id))
+            {
+                throw new HeadlessConfigurationException(
+                    $"Duplicate session id '{session.Id}'.");
+            }
+        }
+
+        return configuration;
+    }
+}

src/AcDream.Headless/HeadlessAssemblyMarker.cs

@@ -0,0 +1,6 @@
+namespace AcDream.Headless;
+
+/// <summary>
+/// Identifies the presentation-free production host assembly.
+/// </summary>
+internal static class HeadlessAssemblyMarker;

src/AcDream.Headless/HeadlessEntryPoint.cs

@@ -0,0 +1,82 @@
+using AcDream.Headless.Configuration;
+
+namespace AcDream.Headless;
+
+internal static class HeadlessEntryPoint
+{
+    private const string HelpText =
+        """
+        acdream-headless
+
+        Usage:
+          acdream-headless --help
+          acdream-headless validate --config <path>
+
+        Commands:
+          validate   Validate a versioned headless configuration without connecting.
+
+        Secrets are never accepted on the command line.
+        """;
+
+    internal static int Run(
+        IReadOnlyList<string> arguments,
+        TextWriter output,
+        TextWriter error)
+    {
+        ArgumentNullException.ThrowIfNull(arguments);
+        ArgumentNullException.ThrowIfNull(output);
+        ArgumentNullException.ThrowIfNull(error);
+
+        if (arguments.Count == 0
+            || IsHelp(arguments[0]))
+        {
+            output.WriteLine(HelpText);
+            return (int)HeadlessExitCode.Success;
+        }
+
+        if (!string.Equals(
+                arguments[0],
+                "validate",
+                StringComparison.Ordinal))
+        {
+            error.WriteLine("Unknown command. Run --help for usage.");
+            return (int)HeadlessExitCode.UsageError;
+        }
+
+        if (arguments.Count != 3
+            || !string.Equals(
+                arguments[1],
+                "--config",
+                StringComparison.Ordinal))
+        {
+            error.WriteLine(
+                "validate requires exactly: --config <path>");
+            return (int)HeadlessExitCode.UsageError;
+        }
+
+        try
+        {
+            HeadlessConfiguration configuration =
+                HeadlessConfigurationLoader.Load(arguments[2]);
+            output.WriteLine(
+                $"Configuration valid: version {configuration.Version}, "
+                + $"{configuration.Sessions.Count} session(s).");
+            return (int)HeadlessExitCode.Success;
+        }
+        catch (Exception exception)
+            when (exception is IOException
+                or UnauthorizedAccessException
+                or ArgumentException
+                or NotSupportedException
+                or System.Text.Json.JsonException
+                or HeadlessConfigurationException)
+        {
+            error.WriteLine($"Configuration invalid: {exception.Message}");
+            return (int)HeadlessExitCode.ConfigurationError;
+        }
+    }
+
+    private static bool IsHelp(string argument) =>
+        string.Equals(argument, "--help", StringComparison.Ordinal)
+        || string.Equals(argument, "-h", StringComparison.Ordinal);
+}

src/AcDream.Headless/HeadlessExitCode.cs

@@ -0,0 +1,8 @@
+namespace AcDream.Headless;
+
+internal enum HeadlessExitCode
+{
+    Success = 0,
+    UsageError = 2,
+    ConfigurationError = 3,
+}

src/AcDream.Headless/Program.cs

@@ -0,0 +1,3 @@
+using AcDream.Headless;
+
+return HeadlessEntryPoint.Run(args, Console.Out, Console.Error);

tests/AcDream.Headless.Tests/AcDream.Headless.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <LangVersion>latest</LangVersion>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\AcDream.Headless\AcDream.Headless.csproj" />
+  </ItemGroup>
+</Project>

tests/AcDream.Headless.Tests/HeadlessDependencyBoundaryTests.cs

@@ -0,0 +1,134 @@
+using System.Text.Json;
+using System.Xml.Linq;
+using System.Runtime.CompilerServices;
+
+namespace AcDream.Headless.Tests;
+
+public sealed class HeadlessDependencyBoundaryTests
+{
+    private static readonly string[] ForbiddenDependencyPrefixes =
+    [
+        "AcDream.App",
+        "AcDream.UI.",
+        "Silk.NET",
+        "OpenAL",
+        "Arch",
+        "ImGui",
+    ];
+
+    [Fact]
+    public void HeadlessAssemblyReferencesOnlyTheRuntimeProject()
+    {
+        string repositoryRoot = FindRepositoryRoot();
+        string projectPath = Path.Combine(
+            repositoryRoot,
+            "src",
+            "AcDream.Headless",
+            "AcDream.Headless.csproj");
+        var project = XDocument.Load(projectPath);
+        string projectDirectory = Path.GetDirectoryName(projectPath)!;
+
+        string[] actual = project
+            .Descendants("ProjectReference")
+            .Select(reference => reference.Attribute("Include")?.Value)
+            .Where(static include => !string.IsNullOrWhiteSpace(include))
+            .Select(include => Path.GetFullPath(Path.Combine(
+                projectDirectory,
+                include!.Replace(
+                    '\\',
+                    Path.DirectorySeparatorChar))))
+            .ToArray();
+        string expected = Path.Combine(
+            repositoryRoot,
+            "src",
+            "AcDream.Runtime",
+            "AcDream.Runtime.csproj");
+
+        Assert.Equal([expected], actual);
+        Assert.Empty(project.Descendants("PackageReference"));
+    }
+
+    [Fact]
+    public void HeadlessDependencyClosureHasNoPresentationOrBackendLibraries()
+    {
+        string depsPath = Path.ChangeExtension(
+            typeof(HeadlessDependencyBoundaryTests).Assembly.Location,
+            ".deps.json");
+
+        using JsonDocument document =
+            JsonDocument.Parse(File.ReadAllText(depsPath));
+        string[] libraries = document.RootElement
+            .GetProperty("libraries")
+            .EnumerateObject()
+            .Select(static library => LibraryName(library.Name))
+            .ToArray();
+
+        Assert.DoesNotContain(libraries, IsForbidden);
+    }
+
+    [Fact]
+    public void HelpPathLoadsNoPresentationOrBackendAssembly()
+    {
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+        Assert.Equal(
+            0,
+            HeadlessEntryPoint.Run(["--help"], output, error));
+
+        string[] loaded = AppDomain.CurrentDomain
+            .GetAssemblies()
+            .Select(static assembly =>
+                assembly.GetName().Name ?? string.Empty)
+            .ToArray();
+
+        Assert.DoesNotContain(loaded, IsForbidden);
+    }
+
+    private static string FindRepositoryRoot(
+        [CallerFilePath] string sourcePath = "")
+    {
+        string[] starts =
+        {
+            Path.GetDirectoryName(sourcePath) ?? string.Empty,
+            Directory.GetCurrentDirectory(),
+            AppContext.BaseDirectory,
+        };
+        foreach (string start in starts)
+        {
+            if (string.IsNullOrEmpty(start))
+            {
+                continue;
+            }
+
+            DirectoryInfo? directory = new(start);
+            while (directory is not null)
+            {
+                if (File.Exists(Path.Combine(
+                        directory.FullName,
+                        "AcDream.slnx")))
+                {
+                    return directory.FullName;
+                }
+
+                directory = directory.Parent;
+            }
+        }
+
+        throw new DirectoryNotFoundException(
+            "Could not find AcDream.slnx above the working or output directory.");
+    }
+
+    private static string LibraryName(string libraryIdentity)
+    {
+        int separatorIndex = libraryIdentity.IndexOf('/');
+        return separatorIndex < 0
+            ? libraryIdentity
+            : libraryIdentity[..separatorIndex];
+    }
+
+    private static bool IsForbidden(string assemblyName) =>
+        ForbiddenDependencyPrefixes.Any(prefix =>
+            assemblyName.StartsWith(
+                prefix,
+                StringComparison.OrdinalIgnoreCase));
+}

tests/AcDream.Headless.Tests/HeadlessEntryPointTests.cs

@@ -0,0 +1,109 @@
+namespace AcDream.Headless.Tests;
+
+public sealed class HeadlessEntryPointTests
+{
+    [Theory]
+    [InlineData("--help")]
+    [InlineData("-h")]
+    public void HelpIsPresentationFreeAndSuccessful(string argument)
+    {
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+
+        int exitCode = HeadlessEntryPoint.Run(
+            [argument],
+            output,
+            error);
+
+        Assert.Equal(0, exitCode);
+        Assert.Contains("acdream-headless", output.ToString());
+        Assert.Contains("Secrets are never accepted", output.ToString());
+        Assert.Equal(string.Empty, error.ToString());
+    }
+
+    [Fact]
+    public void ValidateAcceptsStrictEmptyNoConnectConfiguration()
+    {
+        using var file = TemporaryConfiguration.Create(
+            """{"version":1,"sessions":[]}""");
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+
+        int exitCode = HeadlessEntryPoint.Run(
+            ["validate", "--config", file.Path],
+            output,
+            error);
+
+        Assert.Equal(0, exitCode);
+        Assert.Contains("0 session(s)", output.ToString());
+        Assert.Equal(string.Empty, error.ToString());
+    }
+
+    [Theory]
+    [InlineData("""{"version":2,"sessions":[]}""", "Unsupported configuration version")]
+    [InlineData("""{"version":1,"sessions":[],"password":"secret"}""", "could not be mapped")]
+    [InlineData("""{"version":1,"sessions":[{"id":"bot"},{"id":"bot"}]}""", "Duplicate session id")]
+    [InlineData("""{"version":1,"sessions":[null]}""", "non-empty id")]
+    [InlineData("""{"version":1}""", "required properties")]
+    public void ValidateRejectsInvalidOrSecretShapedConfiguration(
+        string json,
+        string expectedError)
+    {
+        using var file = TemporaryConfiguration.Create(json);
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+
+        int exitCode = HeadlessEntryPoint.Run(
+            ["validate", "--config", file.Path],
+            output,
+            error);
+
+        Assert.Equal(3, exitCode);
+        Assert.Contains(
+            expectedError,
+            error.ToString(),
+            StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("secret", error.ToString());
+        Assert.Equal(string.Empty, output.ToString());
+    }
+
+    [Fact]
+    public void UnknownCommandReturnsUsageError()
+    {
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+
+        int exitCode = HeadlessEntryPoint.Run(
+            ["connect", "--password", "secret"],
+            output,
+            error);
+
+        Assert.Equal(2, exitCode);
+        Assert.DoesNotContain("secret", error.ToString());
+        Assert.Equal(string.Empty, output.ToString());
+    }
+
+    private sealed class TemporaryConfiguration : IDisposable
+    {
+        private TemporaryConfiguration(string path)
+        {
+            Path = path;
+        }
+
+        internal string Path { get; }
+
+        internal static TemporaryConfiguration Create(string json)
+        {
+            string path = System.IO.Path.Combine(
+                System.IO.Path.GetTempPath(),
+                $"acdream-headless-{Guid.NewGuid():N}.json");
+            File.WriteAllText(path, json);
+            return new TemporaryConfiguration(path);
+        }
+
+        public void Dispose()
+        {
+            File.Delete(Path);
+        }
+    }
+}

tests/AcDream.Runtime.Tests/RuntimeDependencyBoundaryTests.cs

@@ -1,5 +1,6 @@
 using System.Text.Json;
 using System.Xml.Linq;
+using System.Runtime.CompilerServices;
 
 namespace AcDream.Runtime.Tests;
 
@@ -59,7 +60,11 @@ public sealed class RuntimeDependencyBoundaryTests
             .Descendants("ProjectReference")
             .Select(reference => reference.Attribute("Include")?.Value)
             .Where(static include => !string.IsNullOrWhiteSpace(include))
-            .Select(include => Path.GetFullPath(Path.Combine(projectDirectory, include!)))
+            .Select(include => Path.GetFullPath(Path.Combine(
+                projectDirectory,
+                include!.Replace(
+                    '\\',
+                    Path.DirectorySeparatorChar))))
             .Order(StringComparer.OrdinalIgnoreCase)
             .ToArray();
         var expectedReferences = new[]
@@ -94,21 +99,38 @@ public sealed class RuntimeDependencyBoundaryTests
         Assert.DoesNotContain(loadedAssemblies, IsForbidden);
     }
 
-    private static string FindRepositoryRoot()
+    private static string FindRepositoryRoot(
+        [CallerFilePath] string sourcePath = "")
     {
-        var directory = new DirectoryInfo(AppContext.BaseDirectory);
-        while (directory is not null)
+        string[] starts =
         {
-            if (File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
+            Path.GetDirectoryName(sourcePath) ?? string.Empty,
+            Directory.GetCurrentDirectory(),
+            AppContext.BaseDirectory,
+        };
+        foreach (string start in starts)
+        {
+            if (string.IsNullOrEmpty(start))
             {
-                return directory.FullName;
+                continue;
             }
 
-            directory = directory.Parent;
+            var directory = new DirectoryInfo(start);
+            while (directory is not null)
+            {
+                if (File.Exists(Path.Combine(
+                        directory.FullName,
+                        "AcDream.slnx")))
+                {
+                    return directory.FullName;
+                }
+
+                directory = directory.Parent;
+            }
         }
 
         throw new DirectoryNotFoundException(
-            $"Could not find AcDream.slnx above {AppContext.BaseDirectory}.");
+            "Could not find AcDream.slnx above the source, working, or output directory.");
     }
 
     private static string LibraryName(string libraryIdentity)