We noticed that branch names like PROJ-1234/some-feature don't work together with Blue Ocean.

Indirect navigation to the build in Blue Ocean works fine:

• Going to https://hostname/blue/organizations/jenkins/component-name/activity/
• Clicking one of the builds to go to https://hostname/blue/organizations/jenkins/component-name/detail/PROJ-1234%2Fsome-feature/5/pipeline correctly loads the build pipeline

Directly navigating to the build in Blue Ocean is broken (which also breaks the GitHub integration):

• Entering https://hostname/blue/organizations/jenkins/component-name/detail/PROJ-1234%2Fsome-feature/5/pipeline in my browser
• This triggers a HTTP 302 redirect to https://hostname/blue/organizations/jenkins/component-name/detail/PROJ-1234/some-feature/5/pipeline/
• A 404 page is served and I can't access my build.

Classic Jenkins works fine:

• Going to https://hostname/job/component-name/job/PROJ-1234%252Fsome-feature/5/ (either directly or through the classic Jenkins interface) is no issue

Indirectly navigating to a build in Blue Ocean and then clicking the classic Jenkins button is broken:

• The link embedded into that page is https://hostname/job/component-name/job/PROJ-1234%2Fsome-feature/5, which yields a 404
• Based on reverse engineering, https://hostname/job/component-name/job/PROJ-1234%252Fsome-feature/5/ should be the correct link

For confidentality reasons, I've replaced the hostname of our Jenkins with 'hostname', the name of the component with 'component-name' and the branch name with 'PROJ-1234/some-feature'.