The problem is that we cannot pass an instance of File through the Form initialValues prop. It seems that the form internally clones the initialValues, and this process destroys the File instance, resulting in an empty JS object instead.
The current workaround is to clone the initialValues manually outside the Form component using the standard JS function
structuredClone.
const handleFormRef = useCallback<RefCallback<FormHandle>>(form => {
if (form) {
form.values = structuredClone(initialValues);
}
}, []);
<KendoForm ref={handleFormRef} />