We couldn’t guarantee that. The post message is just an event the iframe fires at any time that we’d listen to. I suppose we could check if it’s onscreen when doing it - or perhaps adjust scrolling to accommodate the new height. That might work even if it’s offscreen.
Being on screen, or waiting a couple of seconds after initial load, would both be fine requirements for us. It’s interactivity we care about, the initial size is predictable enough. But of course, as you’ve pointed out, it can’t be tied to click events, since the interactions are inherently asynchronous.
Any conclusions, or anything I can do to help move things forward?