That sounds like your report source. What is that? Are you trying to use a foundset as report source? Then it won’t work like that, because you cannot send a JSFoundSet from client to server (headless client) over the wire. If you need to use a foundset, you will have to send something to the headless client that allows it to create/load that same foundset that you want (for example a bunch of primary keys to load or some query criteria).