Move Ghostty rendering into a dedicated worker process

Packages/macOS/CmuxGhosttyRenderService/Package.swift

@@ -0,0 +1,119 @@
+// swift-tools-version: 6.0
+
+import Foundation
+import PackageDescription
+
+let packageDirectory = URL(fileURLWithPath: #filePath).deletingLastPathComponent()
+let ghosttyArchivePath = packageDirectory
+    .appendingPathComponent(
+        "../../../GhosttyKit.xcframework/macos-arm64_x86_64/ghostty-internal.a"
+    )
+    .standardizedFileURL
+    .path
+
+let package = Package(
+    name: "CmuxGhosttyRenderService",
+    platforms: [
+        .macOS(.v14),
+    ],
+    products: [
+        .library(
+            name: "CmuxGhosttyRenderClient",
+            targets: ["CmuxGhosttyRenderClient"]
+        ),
+        .library(
+            name: "CmuxGhosttyRenderWorker",
+            targets: ["CmuxGhosttyRenderWorker"]
+        ),
+        .executable(
+            name: "cmux-ghostty-render-fixture",
+            targets: ["cmux-ghostty-render-fixture"]
+        ),
+        .executable(
+            name: "cmux-ghostty-render-worker-test-host",
+            targets: ["cmux-ghostty-render-worker-test-host"]
+        ),
+    ],
+    dependencies: [
+        .package(path: "../CmuxTerminalRenderTransport"),
+    ],
+    targets: [
+        .target(
+            name: "CmuxGhosttyRenderClient",
+            dependencies: [
+                .product(
+                    name: "CmuxTerminalRenderTransport",
+                    package: "CmuxTerminalRenderTransport"
+                ),
+            ],
+            swiftSettings: [
+                .swiftLanguageMode(.v6),
+                .enableUpcomingFeature("ExistentialAny"),
+                .enableUpcomingFeature("InternalImportsByDefault"),
+            ]
+        ),
+        .systemLibrary(
+            name: "CmuxGhosttyRenderWorkerGhosttyKit",
+            path: "Sources/GhosttyKit"
+        ),
+        .target(
+            name: "CmuxGhosttyRenderWorker",
+            dependencies: [
+                .product(
+                    name: "CmuxTerminalRenderTransport",
+                    package: "CmuxTerminalRenderTransport"
+                ),
+                "CmuxGhosttyRenderWorkerGhosttyKit",
+            ],
+            swiftSettings: [
+                .swiftLanguageMode(.v6),
+                .enableUpcomingFeature("ExistentialAny"),
+                .enableUpcomingFeature("InternalImportsByDefault"),
+            ],
+            linkerSettings: [
+                // The Ghostty XCFramework's macOS archive lacks SwiftPM's
+                // required `lib` prefix. Import its headers through the local
+                // shim target and link the same archive explicitly.
+                .unsafeFlags([ghosttyArchivePath]),
+                .linkedLibrary("c++"),
+                .linkedFramework("Metal"),
+                .linkedFramework("QuartzCore"),
+                .linkedFramework("IOSurface"),
+                .linkedFramework("UniformTypeIdentifiers"),
+                .linkedFramework("Carbon"),
+            ]
+        ),
+        .executableTarget(
+            name: "cmux-ghostty-render-fixture",
+            dependencies: [
+                .product(
+                    name: "CmuxTerminalRenderTransport",
+                    package: "CmuxTerminalRenderTransport"
+                ),
+            ],
+            swiftSettings: [
+                .swiftLanguageMode(.v6),
+            ]
+        ),
+        .executableTarget(
+            name: "cmux-ghostty-render-worker-test-host",
+            dependencies: ["CmuxGhosttyRenderWorker"],
+            swiftSettings: [
+                .swiftLanguageMode(.v6),
+            ]
+        ),
+        .testTarget(
+            name: "CmuxGhosttyRenderClientTests",
+            dependencies: [
+                "CmuxGhosttyRenderClient",
+                "cmux-ghostty-render-fixture",
+                "cmux-ghostty-render-worker-test-host",
+            ],
+            swiftSettings: [
+                .swiftLanguageMode(.v6),
+                .enableUpcomingFeature("ExistentialAny"),
+                .enableUpcomingFeature("InternalImportsByDefault"),
+            ]
+        ),
+    ]
+)

Packages/macOS/CmuxGhosttyRenderService/Sources/CmuxGhosttyRenderClient/GhosttyRenderCommandSink.swift

@@ -0,0 +1,41 @@
+public import CmuxTerminalRenderTransport
+internal import Dispatch
+
+/// Thread-safe, totally ordered ingress for terminal renderer commands.
+///
+/// Ghostty PTY output arrives on I/O threads while AppKit mutations arrive on
+/// the main actor. Both enter this one serial queue before the client actor
+/// consumes them, preventing unstructured Tasks from reordering output,
+/// resize, focus, and pointer changes.
+public final class GhosttyRenderCommandSink: @unchecked Sendable {
+    private let queue = DispatchQueue(
+        label: "dev.cmux.ghostty-render.command-outbox",
+        qos: .userInitiated
+    )
+    private let continuation: AsyncStream<TerminalRenderWorkerCommand>.Continuation
+    let stream: AsyncStream<TerminalRenderWorkerCommand>
+
+    init() {
+        let pair = AsyncStream.makeStream(
+            of: TerminalRenderWorkerCommand.self,
+            bufferingPolicy: .unbounded
+        )
+        self.stream = pair.stream
+        self.continuation = pair.continuation
+    }
+
+    /// Adds one command to the global worker ordering lane without blocking
+    /// the caller on process I/O.
+    public func enqueue(_ command: TerminalRenderWorkerCommand) {
+        queue.async { [continuation] in
+            continuation.yield(command)
+        }
+    }
+
+    /// Ends the ordering lane during client shutdown.
+    func finish() {
+        queue.async { [continuation] in
+            continuation.finish()
+        }
+    }
+}