The problem described over there https://stackoverflow.com/questions/31205287/encoding-servlets-with-utf-8-on-wildfly still exists with the latest release. I had to explicitly set UTF-8 as default encoding to make resteasy properly decode form submissions and not decode UTF-8 as latin-1 (at least it looks a lot like that to me).

On top of that, persisting session ids to file store (without using <distributable/> in web.xml) tends to lose the session store when reloading the (unmanaged) webapp too fast during development.