We store a UUID in their browser and send that along so if they chatted before we un-archive their previous channel to give the Slack operator all the context.
Is there any way to get/set this UUID so I can allow the user to use the same channel if I have my own way of identifying them?
This is in the works. We will provide a way for you to "sign" a request with a userId, so we can guarantee you set the id, and not someone else.