Hi @mwirtz,
Sessions and Threads are different things, using the old C API every “session” had its own thread for the lifetime of the session. For the REST API this has been changed so that TM1 holds a list of “sessions” separate to the threads and then shares the threads between the sessions. This new model only impacts REST API connections and should help when scaling to many thousands of users.
Pulse is getting information through the old C API but it should be similar to what you receive see when querying the Threads collection in the REST API.