The Client Sessions are used by the Muse Proxy Web Contexts which perform authentication in order to store the client authentication status to that Web Context, as well as other user metadata.
When a request comes to Muse Proxy (as a web server) without a Client Session cookie, a Client Session ID will be generated for it and sent back for storage in the browser in the form of a HTTP cookie. The name of the cookie is 'MuseClientSessionID'. The Client Session cookie is returned to the Client only for the requests which require an authentication context. If a Client has performed only requests for free or public resources (e.g. static files: *.css, *.js, images etc), no Client Session cookie will be returned in the response.