fix: fall back to opening Device Hub when the devices:// URL scheme is unavailable

MiniSim/Service/AppleUtils.swift

@@ -3,6 +3,7 @@ import AppKit
 class AppleUtils {
   static var shell: ShellProtocol = Shell()
   static var workspace: NSWorkspace = .shared
+  static var fileExists: (String) -> Bool = { FileManager.default.fileExists(atPath: $0) }
 
   static func clearDerivedData(
     completionQueue: DispatchQueue = .main,
@@ -24,22 +25,90 @@ class AppleUtils {
     }
   }
 
-  static func launchSimulatorApp(uuid: String) throws {
-    let isSimulatorRunning = workspace.runningApplications
-      .contains { $0.bundleIdentifier == "com.apple.iphonesimulator" }
-
-    if !isSimulatorRunning {
-      guard let activeDeveloperDir = try? shell.execute(
-        command: DeviceConstants.ProcessPaths.xcodeSelect.rawValue,
-        arguments: ["-p"]
-      )
-        .trimmingCharacters(in: .whitespacesAndNewlines) else {
-        throw DeviceError.xcodeError
+  /// Xcode 27 removed `Contents/Developer/Applications` and replaced Simulator.app
+  /// with Device Hub, which ships next to Instruments in `Contents/Applications`.
+  /// Returns the GUI app to launch, or nil when neither is installed.
+  static func simulatorApp(developerDir: String) -> (path: String, isDeviceHub: Bool)? {
+    let simulator = "\(developerDir)/Applications/\(DeviceConstants.BundleURL.simulator.rawValue)"
+    if fileExists(simulator) {
+      return (simulator, false)
+    }
+
+    let deviceHub = URL(fileURLWithPath: developerDir)
+      .deletingLastPathComponent()
+      .appendingPathComponent("Applications")
+      .appendingPathComponent(DeviceConstants.BundleURL.deviceHub.rawValue)
+      .path
+    if fileExists(deviceHub) {
+      return (deviceHub, true)
+    }
+
+    return nil
+  }
+
+  /// Device Hub registers the `devices://` URL scheme. Opening this link launches it
+  /// if needed and shows that device's own window, which is how a specific device is
+  /// targeted on Xcode 27+ (`-CurrentDeviceUDID` is ignored by Device Hub).
+  /// The call is idempotent: repeating it re-focuses the existing window.
+  static func deviceHubDeepLink(uuid: String) -> String {
+    "devices://device/open?id=\(uuid)"
+  }
+
+  /// Ensures the simulator GUI is running and showing `uuid`.
+  /// Returns true when Device Hub handled it, meaning the device window is already
+  /// focused and no accessibility fallback is needed.
+  @discardableResult
+  static func launchSimulatorApp(uuid: String) throws -> Bool {
+    guard let activeDeveloperDir = try? shell.execute(
+      command: DeviceConstants.ProcessPaths.xcodeSelect.rawValue,
+      arguments: ["-p"]
+    )
+      .trimmingCharacters(in: .whitespacesAndNewlines),
+      let app = simulatorApp(developerDir: activeDeveloperDir) else {
+      throw DeviceError.xcodeError
+    }
+
+    if app.isDeviceHub {
+      // Always fired, even when Device Hub is already up: it is what switches the
+      // focused device, so an early return here would strand the user on the
+      // previously opened one. An unknown uuid is a safe no-op.
+      if uuid.isEmpty {
+        try shell.execute(
+          command: DeviceConstants.ProcessPaths.open.rawValue,
+          arguments: ["-a", app.path]
+        )
+      } else {
+        do {
+          try shell.execute(
+            command: DeviceConstants.ProcessPaths.open.rawValue,
+            arguments: [deviceHubDeepLink(uuid: uuid)]
+          )
+        } catch {
+          // LaunchServices may not know Device Hub's devices:// scheme yet on
+          // fresh Xcode installs, which makes `open devices://…` fail. Opening
+          // the app itself still works; the user just picks the device manually.
+          try shell.execute(
+            command: DeviceConstants.ProcessPaths.open.rawValue,
+            arguments: ["-a", app.path]
+          )
+        }
       }
-      try shell.execute(
-        command: "\(activeDeveloperDir)/Applications/Simulator.app/Contents/MacOS/Simulator",
-        arguments: ["--args", "-CurrentDeviceUDID", uuid]
-      )
+      return true
     }
+
+    // Simulator.app ignores -CurrentDeviceUDID once running, so only launch it once.
+    // Deliberately not checking SimulatorTrampoline here: it lingers after the GUI
+    // quits, so treating it as "running" would suppress the launch entirely.
+    let isSimulatorRunning = workspace.runningApplications
+      .contains { $0.bundleIdentifier == DeviceConstants.BundleID.simulator.rawValue }
+
+    guard !isSimulatorRunning else { return false }
+
+    // Launch through LaunchServices rather than exec'ing the binary.
+    try shell.execute(
+      command: DeviceConstants.ProcessPaths.open.rawValue,
+      arguments: ["-a", app.path, "--args", "-CurrentDeviceUDID", uuid]
+    )
+    return false
   }
 }

MiniSim/Service/DeviceConstants.swift

@@ -7,10 +7,17 @@ enum DeviceConstants {
   enum ProcessPaths: String {
     case xcrun = "/usr/bin/xcrun"
     case xcodeSelect = "/usr/bin/xcode-select"
+    case open = "/usr/bin/open"
   }
 
   enum BundleURL: String {
     case emulator = "qemu-system-aarch64"
     case simulator = "Simulator.app"
+    case deviceHub = "DeviceHub.app"
+  }
+
+  enum BundleID: String {
+    case simulator = "com.apple.iphonesimulator"
+    case deviceHub = "com.apple.dt.Devices"
   }
 }

MiniSim/Service/DeviceService.swift

@@ -33,12 +33,16 @@ extension DeviceServiceCommon {
   func focusDevice() {
     Thread.assertBackgroundThread()
 
-    let runningApps = NSWorkspace.shared.runningApplications.filter { $0.activationPolicy == .regular }
-
     if let uuid = device.identifier, device.platform == .ios {
-      try? AppleUtils.launchSimulatorApp(uuid: uuid)
+      // On Xcode 27+ the devices:// deep link opens and raises that device's own
+      // Device Hub window, so the accessibility pass below has nothing left to do.
+      if (try? AppleUtils.launchSimulatorApp(uuid: uuid)) == true {
+        return
+      }
     }
 
+    let runningApps = NSWorkspace.shared.runningApplications.filter { $0.activationPolicy == .regular }
+
     for app in runningApps {
       guard
         let bundleURL = app.bundleURL?.absoluteString,

MiniSimTests/AppleUtilsTests.swift

@@ -37,6 +37,7 @@ class AppleUtilsTests: XCTestCase {
 
   override func tearDown() {
     shellStub.tearDown()
+    AppleUtils.fileExists = { FileManager.default.fileExists(atPath: $0) }
     super.tearDown()
   }
 
@@ -78,30 +79,146 @@ class AppleUtilsTests: XCTestCase {
     waitForExpectations(timeout: 5, handler: nil)
   }
 
+  private func stubXcodeSelect(developerDir: String = "/Applications/Xcode.app/Contents/Developer") {
+    shellStub.mockedExecute = { command, _, _ in
+      if command == DeviceConstants.ProcessPaths.xcodeSelect.rawValue {
+        return developerDir
+      }
+      return ""
+    }
+  }
+
   func testLaunchSimulatorAppWhenNotRunning() {
     let uuid = "test-uuid"
     mockWorkspace.mockRunningApplications = [] // Simulator not running
+    stubXcodeSelect()
+    // Xcode 26 and earlier: Simulator.app is present.
+    AppleUtils.fileExists = { $0.hasSuffix("Developer/Applications/Simulator.app") }
+
+    XCTAssertFalse(try AppleUtils.launchSimulatorApp(uuid: uuid))
+
+    XCTAssertEqual(shellStub.lastExecutedCommand, DeviceConstants.ProcessPaths.open.rawValue)
+    XCTAssertEqual(shellStub.lastPassedArguments, [
+      "-a",
+      "/Applications/Xcode.app/Contents/Developer/Applications/Simulator.app",
+      "--args",
+      "-CurrentDeviceUDID",
+      uuid
+    ])
+  }
 
-    shellStub.mockedExecute = { command, _, _ in
+  func testLaunchSimulatorAppIgnoresLingeringTrampolineOnLegacyXcode() {
+    let uuid = "test-uuid"
+    // SimulatorTrampoline keeps running after Simulator.app quits, so it must not
+    // count as "the simulator app is already running".
+    mockWorkspace.mockRunningApplications = [
+      MockNSRunningApplication(bundleIdentifier: "com.apple.CoreSimulator.SimulatorTrampoline")
+    ]
+    stubXcodeSelect()
+    AppleUtils.fileExists = { $0.hasSuffix("Developer/Applications/Simulator.app") }
+
+    XCTAssertFalse(try AppleUtils.launchSimulatorApp(uuid: uuid))
+
+    XCTAssertEqual(shellStub.lastExecutedCommand, DeviceConstants.ProcessPaths.open.rawValue)
+  }
+
+  private func stubDeviceHubOnly() {
+    // Xcode 27 removed Simulator.app; only Device Hub exists.
+    AppleUtils.fileExists = { $0.hasSuffix("Contents/Applications/DeviceHub.app") }
+  }
+
+  func testLaunchSimulatorAppUsesDeepLinkOnXcode27() {
+    let uuid = "test-uuid"
+    mockWorkspace.mockRunningApplications = []
+    stubXcodeSelect()
+    stubDeviceHubOnly()
+
+    XCTAssertTrue(try AppleUtils.launchSimulatorApp(uuid: uuid))
+
+    // Device Hub ignores -CurrentDeviceUDID; the devices:// link targets the device.
+    XCTAssertEqual(shellStub.lastExecutedCommand, DeviceConstants.ProcessPaths.open.rawValue)
+    XCTAssertEqual(shellStub.lastPassedArguments, ["devices://device/open?id=\(uuid)"])
+  }
+
+  func testLaunchSimulatorAppFallsBackToOpeningDeviceHubWhenDeepLinkFails() {
+    let uuid = "test-uuid"
+    mockWorkspace.mockRunningApplications = []
+    stubDeviceHubOnly()
+    // Fresh Xcode installs may not have Device Hub's devices:// scheme in the
+    // LaunchServices database yet, so `open devices://…` exits non-zero.
+    shellStub.mockedExecute = { command, arguments, _ in
       if command == DeviceConstants.ProcessPaths.xcodeSelect.rawValue {
         return "/Applications/Xcode.app/Contents/Developer"
       }
+      if command == DeviceConstants.ProcessPaths.open.rawValue,
+         arguments.first?.hasPrefix("devices://") == true {
+        throw NSError(domain: "TestError", code: 1)
+      }
       return ""
     }
 
-    XCTAssertNoThrow(try AppleUtils.launchSimulatorApp(uuid: uuid))
+    XCTAssertTrue(try AppleUtils.launchSimulatorApp(uuid: uuid))
 
-    XCTAssertEqual(shellStub.lastExecutedCommand, "/Applications/Xcode.app/Contents/Developer/Applications/Simulator.app/Contents/MacOS/Simulator")
-    XCTAssertEqual(shellStub.lastPassedArguments, ["--args", "-CurrentDeviceUDID", uuid])
+    XCTAssertEqual(shellStub.lastExecutedCommand, DeviceConstants.ProcessPaths.open.rawValue)
+    XCTAssertEqual(shellStub.lastPassedArguments, [
+      "-a",
+      "/Applications/Xcode.app/Contents/Applications/DeviceHub.app"
+    ])
   }
 
-  func testLaunchSimulatorAppWhenAlreadyRunning() {
-    let uuid = "test-uuid"
-    mockWorkspace.mockRunningApplications = [MockNSRunningApplication(bundleIdentifier: "com.apple.iphonesimulator")]
+  func testLaunchSimulatorAppDeepLinksEvenWhenDeviceHubAlreadyRunning() {
+    let uuid = "other-uuid"
+    // Device Hub already showing some other device: the deep link is what switches
+    // focus, so it must still fire rather than returning early.
+    mockWorkspace.mockRunningApplications = [
+      MockNSRunningApplication(bundleIdentifier: DeviceConstants.BundleID.deviceHub.rawValue)
+    ]
+    stubXcodeSelect()
+    stubDeviceHubOnly()
 
-    XCTAssertNoThrow(try AppleUtils.launchSimulatorApp(uuid: uuid))
+    XCTAssertTrue(try AppleUtils.launchSimulatorApp(uuid: uuid))
 
-    XCTAssertTrue(shellStub.lastExecutedCommand.isEmpty, "Should not execute any command when simulator is already running")
+    XCTAssertEqual(shellStub.lastPassedArguments, ["devices://device/open?id=\(uuid)"])
+  }
+
+  func testLaunchSimulatorAppOpensDeviceHubWithoutDeepLinkWhenUuidIsEmpty() {
+    mockWorkspace.mockRunningApplications = []
+    stubXcodeSelect()
+    stubDeviceHubOnly()
+
+    XCTAssertTrue(try AppleUtils.launchSimulatorApp(uuid: ""))
+
+    XCTAssertEqual(shellStub.lastPassedArguments, [
+      "-a",
+      "/Applications/Xcode.app/Contents/Applications/DeviceHub.app"
+    ])
+  }
+
+  func testLaunchSimulatorAppThrowsWhenNoSimulatorAppInstalled() {
+    mockWorkspace.mockRunningApplications = []
+    stubXcodeSelect()
+    AppleUtils.fileExists = { _ in false }
+
+    XCTAssertThrowsError(try AppleUtils.launchSimulatorApp(uuid: "test-uuid")) { error in
+      XCTAssertEqual(error as? DeviceError, DeviceError.xcodeError)
+    }
+  }
+
+  func testLaunchSimulatorAppWhenAlreadyRunning() {
+    let uuid = "test-uuid"
+    mockWorkspace.mockRunningApplications = [
+      MockNSRunningApplication(bundleIdentifier: DeviceConstants.BundleID.simulator.rawValue)
+    ]
+    stubXcodeSelect()
+    AppleUtils.fileExists = { $0.hasSuffix("Developer/Applications/Simulator.app") }
+
+    XCTAssertFalse(try AppleUtils.launchSimulatorApp(uuid: uuid))
+
+    XCTAssertEqual(
+      shellStub.lastExecutedCommand,
+      DeviceConstants.ProcessPaths.xcodeSelect.rawValue,
+      "Should resolve the app but never re-open Simulator.app when it is already running"
+    )
   }
 
   func testLaunchSimulatorAppWithXcodeError() {