At the moment brXM expects the SERVERID cookie to contain URL-valid characters only and passes the value on to an SPA as server-id query parameter. For instance it does not encode a pipe character ("|") but it should because not all (SPA) webservers accept that.

SPA SDK

Note it should also be tested with the SPA SDK as the SPA proxies the received serverid from a query param back as header param (and nginx should in that case work with the server id header to achieve stickiness)