func global() async -> Int { return await withCheckedContinuation { c in DispatchQueue.global().async { c.resume(returning: 42) } } } @MainActor final class Foo { func start() { Task { let x = await global() print(x, Thread.isMainThread) // 42 true Task { let x = await global() print(x, Thread.isMainThread) // 42 true } } } } これは引き継がれてそうです