WAIT UNTIL THEY HAVE MOTION OPEN. Everything that has to SEE a composition — inspect_composition, and anything touching their media — runs in their browser, so it needs the tab. Ask them to open the session link, then call this instead of asking them to tell you when it is ready. It returns as soon as the tab connects, or after about 25 seconds with tabConnected false — in which case call it again, or give up and say so. Do not spin on it: two or three waits, then tell them you are waiting and stop.