seems to be a regression because this worked before. I sat with @joshlong and we managed to get it working again by adding the following hints:

  class Hints implements RuntimeHintsRegistrar {

    @Override
    public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
        for (var t : Set.of(com.google.protobuf.Value.class,
                com.google.protobuf.Value.Builder.class,
                com.google.protobuf.Struct.class)) {
            hints.reflection().registerType(t, MemberCategory.values());
        }
    }
}

Comment From: ThomasVitale

Fixed in https://github.com/spring-projects/spring-ai/pull/1266