Setting the mode is still persisted but only on a build level. The reason being this change JENKINS-29899. The cookie's path contains the build number and does not affect the display of any other builds of the job.

It would be nice to switch the mode of all console logs of a Job in general. Setting the path of the cookie to the Job URL would do the trick. An option in the Job configuration to set the default display would of course also be fine.

The intention of JENKINS-29899 was to store the cookies at the Jenkins instance level. It sets the cookie path to rootURL and this works as expected for URLs like http://example.com/jenkins.

However, when running from the top-level URL (e.g. http://example.com), the rootURL is empty, so the browser stores the cookies on the current path.

Code changed in jenkins
User: Steven Brown
Path:
src/main/resources/hudson/plugins/timestamper/annotator/TimestampAnnotatorFactory/script.js
http://jenkins-ci.org/commit/timestamper-plugin/26f6fdb2d47f88e1fe8afd454407fc5283eaeb6b
Log:
[FIXED JENKINS-32074] When rootURL is empty, store cookies at '/'

When Jenkins is running from the top-level URL, the rootURL variable is an empty
string. In this case, store the cookies at '/' instead of rootURL.

Prior to this change, the cookies were created with an empty path, and the
browser defaults to storing them at the build URL. These cookies will now be
deleted because they would override the cookies stored at the Jenkins URL.

Bug introduced by JENKINS-29899.

Released with Timestamper 1.7.3. Thanks for your investigative work, Timo.