After some initial implementation we found out that the "instanceId" which is delivered on the lifecycle event "instance_add" seems to be different from the "src" parameter which is later on send by the plugin instance.
It is a bit confusing because in this questions https://dev.coyoapp.com/discuss/6000b682c87152001e71e0de it is said that these should be the same. But we definitely get different ids which is leading to extra implementation work, because the requests have to be mapped to the plugin object created/persisted beforehand in the lifecyle event "instance_add". Right now we do an extra window.postMessage with sub "init" to get the "instanceId" from the "scr" parameter.
Would it not be simpler if src == instanceId?