Preview Feature — Requires --enable-preview at compile and runtime. The API stabilized significantly from Java 21 through 24 and will be finalized in a future release. The Unstructured Concurrency Problem When you submit tasks to an ExecutorService, the tasks are logically related but structurally unconnected — the executor doesn’t know they belong together: // Unstructured concurrency — looks simple, hides serious problems ExecutorService executor = Executors.newCachedThreadPool(); Future<Order> orderFuture = executor.