Each section covers the upgrade from the previous LTS release, the section on 2.401.1 covers the upgrade from 2.387.3.
No notable changes requiring upgrade notes.
No notable changes requiring upgrade notes.
A custom JavaScript library, jenkins-js-modules has been removed from Jenkins core.
Users of the OWASP Dependency Track plugin must upgrade to 4.3.1 or newer.
Users of the ServiceNow CI/CD plugin must upgrade to 2.1 or newer.
The default connection mode for the Java command line interface client is now -webSocket.
You can specify -http to continue to use the former default (for example because you are running Jenkins in a servlet container other than the recommended built-in Jetty, or because you are running an unusual reverse proxy which does not support WebSocket). You can also continue to specify -ssh to use SSH transport (for example because you prefer to authenticate with a private key rather than an API token), or use a native SSH client.
If you use the Jenkins CLI but cannot make WebSocket connections to the Jenkins controller, you will now need to pass the -http or -ssh option if you were not already doing so.