Mir, Canonical’s replacement for the X window system, will not make it into the next version of the Ubuntu desktop.

Canonical initially planned to turn Mir on by default in Ubuntu 13.10, the version shipped in October 2013, but it was dropped due to compatibility problems in multi-monitor setups. It’s especially important not to add any buggy technologies to 14.04, the version coming in April 2014, because that is a Long-Term Support (LTS) edition that Canonical must maintain for five years. Mir itself seems to be working fine, but there are problems with XMir, an X11 compatibility layer that ensures Mir can work with applications built for X.”We will only bring Mir into 14.04 if we can be assured that we’re not going to have any support issues,” Ubuntu Community Manager Jono Bacon told Ars last month.

It now appears Mir won’t make it into the next edition. “It was affirmed today that Ubuntu 14.04 LTS will still be shipping with the stable and proven Unity 7 experience, which is designed around using an X.Org Server with Compiz,” Phoronix’s Michael Larabel wrote today. “It doesn’t appear they will try for using XMir by default in this next Long-Term Support release with Unity 7. It was also said today that point releases to Ubuntu 14.04 LTS will not be adding in Mir or Unity 8.”