Why Form Callbacks Break Portability and How Declarative Trees Fix It

Most form libraries manage state within a single application using callbacks for validation and conditional logic, but these cannot be serialized or shared across systems. When a form must be rendered by multiple clients, generated by a visual builder, or validated independently on a server, its logic must travel with its structure. Encoding behavior as plain strings or embedded expressions introduces parsing risks, versioning issues, and potential security concerns. A closed declarative expression tree — representing conditions and effects as pure JSON data — solves this by making form logic serializable, inspectable, and executable across different runtimes. This approach treats a form as a true cross-system contract rather than application-specific component state.