Sam and Ryan discuss the new features in React 19 that will specifically benefit developers building single-page applications. They talk about how Suspense and Transitions let developers "teach" React about when their apps are in a loading or a pending state, how Client Actions improve upon using events in React 18 to handle data mutations, and how Actions enable React Components to automatically render and discard optimistic updates without any knowledge of the application's data layer. They also discuss several new Hooks like useOptimistic, useFormStatus, useActionState, and useOptimistic.