On a 24-inch 1920×1200 monitor, a useful configuration is to tile two windows side-by-side, e.g. web browser and code editor or terminal. In this configuration, the web browser gets a 960px width.

Jenkins uses @media max-width queries, and it has a breakpoint at 970px below which it decides the screen is too narrow to fit a 320px sidebar and the main content together. It then widens the sidebar to the whole page width, and moves main content below. This is a very unfriendly layout, because the “above the fold” page content is identical on every Jenkins page.

I think the sidebar could be shrunk down to 200px without much affecting the UX, allowing the two-column breakpoint to be moved to 850px or so.