Proton is an open-source compatibility layer developed by Valve for running modern Windows-exclusive Steam games on Linux.

Pierre-Loup Griffais, employee of Valve announced Proton 4.11, based on Wine 4.11. Among the usual variety of functional fixes, as well as a new Vulkan-based D3D9 implementation, it also includes a significant amount of work on reducing CPU overhead for multithreaded games.