square · blakemcanally · Jul 23, 2026 · Jul 23, 2026 · Jul 23, 2026 · Jul 23, 2026
@@ -1,5 +1,7 @@
 [tools]
-tuist = "4.23.0"
+# 4.27.0+ is required to parse swift-tools-version 6.0 package manifests
+# (older versions fail decoding the manifest's build-settings format).
+tuist = "4.27.0"
 swiftformat = "0.54.2"
 
 [settings]

@@ -1,4 +1,4 @@
-// swift-tools-version:5.9
+// swift-tools-version:6.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import CompilerPluginSupport
@@ -209,7 +209,7 @@ let package = Package(
             path: "ViewEnvironmentUI/Sources"
         ),
     ],
-    swiftLanguageVersions: [.v5]
+    swiftLanguageModes: [.v5]
 )
 
 // MARK: Helpers
@@ -222,8 +222,14 @@ extension PackageDescription.Product {
     }
 }
 
+let swift6Targets: Set<String> = ["Workflow"]
+
 for target in package.targets {
     var settings = target.swiftSettings ?? []
-    settings.append(.enableExperimentalFeature("StrictConcurrency=targeted"))
+    if swift6Targets.contains(target.name) {
+        settings.append(.swiftLanguageMode(.v6))
+    } else {
+        settings.append(.enableExperimentalFeature("StrictConcurrency=targeted"))
+    }
     target.swiftSettings = settings
 }
@@ -55,6 +55,7 @@ extension AsyncWorkerWorkflow {
 extension AsyncWorkerWorkflow {
     typealias Rendering = MessageScreen
 
+    @MainActor
     func render(state: AsyncWorkerWorkflow.State, context: RenderContext<AsyncWorkerWorkflow>) -> Rendering {
         NetworkRequestWorker()
             .mapOutput { result in

@@ -133,6 +133,7 @@ struct RefreshWorker: Worker {
 extension DemoWorkflow {
     typealias Rendering = DemoScreen
 
+    @MainActor
     func render(state: DemoWorkflow.State, context: RenderContext<DemoWorkflow>) -> Rendering {
         let color: UIColor = switch state.colorState {
         case .red:

@@ -61,6 +61,7 @@ extension RootWorkflow {
 extension RootWorkflow {
     typealias Rendering = CrossFadeScreen
 
+    @MainActor
     func render(state: RootWorkflow.State, context: RenderContext<RootWorkflow>) -> Rendering {
         switch state {
         case .welcome:

@@ -64,6 +64,7 @@ extension WelcomeWorkflow {
 extension WelcomeWorkflow {
     typealias Rendering = WelcomeScreen
 
+    @MainActor
     func render(state: WelcomeWorkflow.State, context: RenderContext<WelcomeWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
         return WelcomeScreen(

@@ -63,6 +63,7 @@ extension DemoWorkflow {
     private static let colors: [UIColor] = [.red, .blue, .green, .yellow]
     private static let complimentaryColors: [UIColor] = [.blue, .green, .yellow, .purple]
 
+    @MainActor
     func render(state: State, context: RenderContext<DemoWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
 
@@ -75,6 +76,7 @@ extension DemoWorkflow {
         )
     }
 
+    @MainActor
     private func leadingScreenFor(state: State, context: RenderContext<DemoWorkflow>) -> AnyScreen {
         let sink = context.makeSink(of: Action.self)
 

@@ -165,6 +165,7 @@ extension AuthenticationWorkflow {
 extension AuthenticationWorkflow {
     typealias Rendering = AlertContainerScreen<ModalContainerScreen<BackStackScreen<AnyScreen>>>
 
+    @MainActor
     func render(state: AuthenticationWorkflow.State, context: RenderContext<AuthenticationWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
 
@@ -235,6 +236,7 @@ extension AuthenticationWorkflow {
         )
     }
 
+    @MainActor
     private func twoFactorScreen(error: AuthenticationService.AuthenticationError?, intermediateSession: String, sink: Sink<Action>) -> BackStackScreen<AnyScreen>.Item {
         let title: String = if let authenticationError = error {
             authenticationError.localizedDescription

@@ -71,6 +71,7 @@ extension LoginWorkflow {
 extension LoginWorkflow {
     typealias Rendering = LoginScreen
 
+    @MainActor
     func render(state: LoginWorkflow.State, context: RenderContext<LoginWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
 

@@ -77,6 +77,7 @@ extension ConfirmQuitWorkflow {
 extension ConfirmQuitWorkflow {
     typealias Rendering = (ConfirmQuitScreen, Alert?)
 
+    @MainActor
     func render(state: ConfirmQuitWorkflow.State, context: RenderContext<ConfirmQuitWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
         var alert: Alert?

@@ -86,6 +86,7 @@ extension RunGameWorkflow {
 extension RunGameWorkflow {
     typealias Rendering = AlertContainerScreen<ModalContainerScreen<BackStackScreen<AnyScreen>>>
 
+    @MainActor
     func render(state: RunGameWorkflow.State, context: RenderContext<RunGameWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
         var modals: [ModalContainerScreenModal] = []
@@ -160,6 +161,7 @@ extension RunGameWorkflow {
         return AlertContainerScreen(baseScreen: modalContainerScreen, alert: alert)
     }
 
+    @MainActor
     private func newGameScreen(sink: Sink<Action>, playerX: String, playerO: String) -> NewGameScreen {
         NewGameScreen(
             playerX: playerX,

@@ -85,6 +85,7 @@ extension TakeTurnsWorkflow {
 extension TakeTurnsWorkflow {
     typealias Rendering = GamePlayScreen
 
+    @MainActor
     func render(state: TakeTurnsWorkflow.State, context: RenderContext<TakeTurnsWorkflow>) -> Rendering {
         let sink = context.makeSink(of: Action.self)
 

@@ -67,6 +67,7 @@ extension MainWorkflow {
 extension MainWorkflow {
     typealias Rendering = AlertContainerScreen<ModalContainerScreen<BackStackScreen<AnyScreen>>>
 
+    @MainActor
     func render(state: MainWorkflow.State, context: RenderContext<MainWorkflow>) -> Rendering {
         switch state {
         case .authenticating:

@@ -21,6 +21,7 @@ import XCTest
 
 @testable import TicTacToe
 
+@MainActor
 class AuthenticationWorkflowTests: XCTestCase {
     // MARK: Action Tests
 

@@ -20,6 +20,7 @@ import XCTest
 
 @testable import TicTacToe
 
+@MainActor
 class ConfirmQuitWorkflowTests: XCTestCase {
     // MARK: Action Tests
 

@@ -20,6 +20,7 @@ import XCTest
 
 @testable import TicTacToe
 
+@MainActor
 class LoginWorkflowTests: XCTestCase {
     // MARK: Action Tests
 

@@ -22,6 +22,7 @@ import XCTest
 
 @testable import TicTacToe
 
+@MainActor
 class MainWorkflowTests: XCTestCase {
     // MARK: Action Tests
 

@@ -21,6 +21,7 @@ import XCTest
 
 @testable import TicTacToe
 
+@MainActor
 class RunGameWorkflowTests: XCTestCase {
     // MARK: Action Tests
 

@@ -20,6 +20,7 @@ import XCTest
 
 @testable import TicTacToe
 
+@MainActor
 class TakeTurnsWorkflowTests: XCTestCase {
     // MARK: Action Tests
 

@@ -80,6 +80,7 @@ extension WelcomeWorkflow {
 extension WelcomeWorkflow {
     typealias Rendering = WelcomeScreen
 
+    @MainActor
     func render(state: WelcomeWorkflow.State, context: RenderContext<WelcomeWorkflow>) -> Rendering {
         // Create a "sink" of type `Action`. A sink is what we use to send actions to the workflow.
         let sink = context.makeSink(of: Action.self)

@@ -90,6 +90,7 @@ extension RootWorkflow {
 extension RootWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>
 
+    @MainActor
     func render(state: RootWorkflow.State, context: RenderContext<RootWorkflow>) -> Rendering {
         // Create a sink to handle the back action from the TodoListWorkflow to log out.
         let sink = context.makeSink(of: Action.self)

@@ -87,6 +87,7 @@ extension WelcomeWorkflow {
 extension WelcomeWorkflow {
     typealias Rendering = WelcomeScreen
 
+    @MainActor
     func render(state: WelcomeWorkflow.State, context: RenderContext<WelcomeWorkflow>) -> Rendering {
         // Create a "sink" of type `Action`. A sink is what we use to send actions to the workflow.
         let sink = context.makeSink(of: Action.self)

@@ -88,6 +88,7 @@ extension RootWorkflow {
 extension RootWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>
 
+    @MainActor
     func render(state: RootWorkflow.State, context: RenderContext<RootWorkflow>) -> Rendering {
         // Delete the `let sink = context.makeSink(of: ...) as we no longer need a sink.
 

@@ -109,6 +109,7 @@ extension TodoEditWorkflow {
 extension TodoEditWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>.Item
 
+    @MainActor
     func render(state: TodoEditWorkflow.State, context: RenderContext<TodoEditWorkflow>) -> Rendering {
         // The sink is used to send actions back to this workflow.
         let sink = context.makeSink(of: Action.self)

@@ -120,6 +120,7 @@ extension TodoListWorkflow {
 extension TodoListWorkflow {
     typealias Rendering = [BackStackScreen<AnyScreen>.Item]
 
+    @MainActor
     func render(state: TodoListWorkflow.State, context: RenderContext<TodoListWorkflow>) -> Rendering {
         // Define a sink to be able to send actions.
         let sink = context.makeSink(of: Action.self)

@@ -87,6 +87,7 @@ extension WelcomeWorkflow {
 extension WelcomeWorkflow {
     typealias Rendering = WelcomeScreen
 
+    @MainActor
     func render(state: WelcomeWorkflow.State, context: RenderContext<WelcomeWorkflow>) -> Rendering {
         // Create a "sink" of type `Action`. A sink is what we use to send actions to the workflow.
         let sink = context.makeSink(of: Action.self)

@@ -90,6 +90,7 @@ extension RootWorkflow {
 extension RootWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>
 
+    @MainActor
     func render(state: RootWorkflow.State, context: RenderContext<RootWorkflow>) -> Rendering {
         // Our list of back stack items. Will always include the "WelcomeScreen".
         var backStackItems: [BackStackScreen<AnyScreen>.Item] = []

@@ -109,6 +109,7 @@ extension TodoEditWorkflow {
 extension TodoEditWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>.Item
 
+    @MainActor
     func render(state: TodoEditWorkflow.State, context: RenderContext<TodoEditWorkflow>) -> Rendering {
         // The sink is used to send actions back to this workflow.
         let sink = context.makeSink(of: Action.self)

@@ -97,6 +97,7 @@ extension TodoListWorkflow {
 extension TodoListWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>.Item
 
+    @MainActor
     func render(state: TodoListWorkflow.State, context: RenderContext<TodoListWorkflow>) -> Rendering {
         // Define a sink to be able to send actions.
         let sink = context.makeSink(of: Action.self)

@@ -139,6 +139,7 @@ extension TodoWorkflow {
 extension TodoWorkflow {
     typealias Rendering = [BackStackScreen<AnyScreen>.Item]
 
+    @MainActor
     func render(state: TodoWorkflow.State, context: RenderContext<TodoWorkflow>) -> Rendering {
         let todoListItem = TodoListWorkflow(name: name, todos: state.todos)
             .mapOutput { output -> ListAction in

@@ -87,6 +87,7 @@ extension WelcomeWorkflow {
 extension WelcomeWorkflow {
     typealias Rendering = WelcomeScreen
 
+    @MainActor
     func render(state: WelcomeWorkflow.State, context: RenderContext<WelcomeWorkflow>) -> Rendering {
         // Create a "sink" of type `Action`. A sink is what we use to send actions to the workflow.
         let sink = context.makeSink(of: Action.self)

@@ -88,6 +88,7 @@ extension RootWorkflow {
 extension RootWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>
 
+    @MainActor
     func render(state: RootWorkflow.State, context: RenderContext<RootWorkflow>) -> Rendering {
         // Our list of back stack items. Will always include the "WelcomeScreen".
         var backStackItems: [BackStackScreen<AnyScreen>.Item] = []

@@ -109,6 +109,7 @@ extension TodoEditWorkflow {
 extension TodoEditWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>.Item
 
+    @MainActor
     func render(state: TodoEditWorkflow.State, context: RenderContext<TodoEditWorkflow>) -> Rendering {
         // The sink is used to send actions back to this workflow.
         let sink = context.makeSink(of: Action.self)

@@ -97,6 +97,7 @@ extension TodoListWorkflow {
 extension TodoListWorkflow {
     typealias Rendering = BackStackScreen<AnyScreen>.Item
 
+    @MainActor
     func render(state: TodoListWorkflow.State, context: RenderContext<TodoListWorkflow>) -> Rendering {
         // Define a sink to be able to send actions.
         let sink = context.makeSink(of: Action.self)

@@ -139,6 +139,7 @@ extension TodoWorkflow {
 extension TodoWorkflow {
     typealias Rendering = [BackStackScreen<AnyScreen>.Item]
 
+    @MainActor
     func render(state: TodoWorkflow.State, context: RenderContext<TodoWorkflow>) -> Rendering {
         let todoListItem = TodoListWorkflow(name: name, todos: state.todos)
             .mapOutput { output -> ListAction in

@@ -92,6 +92,7 @@ extension WelcomeWorkflow {
 extension WelcomeWorkflow {
     typealias Rendering = WelcomeScreen
 
+    @MainActor
     func render(state: WelcomeWorkflow.State, context: RenderContext<WelcomeWorkflow>) -> Rendering {
         // Create a "sink" of type `Action`. A sink is what we use to send actions to the workflow.
         let sink = context.makeSink(of: Action.self)

@@ -25,6 +25,7 @@ import XCTest
 // Import `WorkflowUI` as testable so that the wrappedScreen in `AnyScreen` can be accessed.
 @testable import WorkflowUI
 
+@MainActor
 class RootWorkflowTests: XCTestCase {
     func testWelcomeRendering() throws {
         RootWorkflow()

@@ -18,6 +18,7 @@ import WorkflowTesting
 import XCTest
 @testable import Tutorial5Complete
 
+@MainActor
 class TodoEditWorkflowTests: XCTestCase {
     func testAction() throws {
         TodoEditWorkflow.Action

@@ -18,6 +18,7 @@ import WorkflowTesting
 import XCTest
 @testable import Tutorial5Complete
 
+@MainActor
 class TodoListWorkflowTests: XCTestCase {
     func testActions() throws {
         TodoListWorkflow.Action

@@ -21,6 +21,7 @@ import WorkflowUI
 import XCTest
 @testable import Tutorial5Complete
 
+@MainActor
 class TodoWorkflowTests: XCTestCase {
     func testSelectingTodo() throws {
         let todos: [TodoModel] = [TodoModel(title: "Title", note: "Note")]

@@ -18,6 +18,7 @@ import WorkflowTesting
 import XCTest
 @testable import Tutorial5Complete
 
+@MainActor
 class WelcomeWorkflowTests: XCTestCase {
     func testNameUpdates() throws {
         WelcomeWorkflow.Action

@@ -49,6 +49,7 @@ extension DemoWorkflow {
 extension DemoWorkflow {
     typealias Rendering = DemoScreen
 
+    @MainActor
     func render(state: DemoWorkflow.State, context: RenderContext<DemoWorkflow>) -> Rendering {
         // Combine-based worker example
         DemoWorker()

@@ -11,6 +11,7 @@ import WorkflowTesting
 import XCTest
 @testable import WorkflowCombineSampleApp
 
+@MainActor
 class DemoWorkflowTests: XCTestCase {
     func test_demoWorkflow_publishesNewDate() {
         let expectedDate = Date(timeIntervalSince1970: 0)