Valve is expanding beyond its well-known Proton compatibility layer with two new system-level tools for SteamOS, designed to bring more games to its upcoming Steam Frame headset. The additions—FEX and Lepton—extend SteamOS's reach into Arm-based hardware and Android software, addressing gaps that Proton alone cannot cover and signalling Valve's ambitions for SteamOS beyond traditional PC-style devices.

FEX is Valve's port of the open-source fex-emu project, which emulates x86 processor instructions on Arm chipsets and has been quietly funded by Valve since 2018; the company sees it as a foundation for bringing SteamOS to a wider range of Arm-based devices in future. Lepton, meanwhile, builds on the Waydroid project to let standard Android APKs run on SteamOS, which is particularly important for the Steam Frame since many standalone VR titles were originally built for Android-based Quest headsets—VR.org found that 52 of the first 120 "Great on Frame" games rely on Lepton rather than native Windows, Mac or Linux builds.