Sessions are configurable in eZ Publish 5 by defining the
session_name setting under your siteaccess group configuration in your
Here's a usage example:
For better integration between 5.x (symfony based) kernel and legacy (4.x) kernel, injection is used to inject settings, session and current siteaccess from 5.x into legacy using an event: kernel.event_subscriber
When eZ Publish legacy (4.x kernel and extensions) are running via the new eZ Publish 5 kernel, then the Symfony session is injected into it and all session related settings in legacy is ignored.
For more details on how to configure sessions in your eZ Publish 5 setup, please refer to the documentation of Symfony HTTP Fundation component.