# Valve's new compatibility layers for SteamOS

> Beyond Proton, two new tools help run Windows and Android games on Linux-based Steam devices.
- Title: Valve's new compatibility layers for SteamOS · Ars Technica
- Summary: Beyond Proton, two new tools help run Windows and Android games on Linux-based Steam devices. Valve is using FEX to run x86 games on Arm processors and…
- Keywords: valve, steamos, steam deck, steam frame, proton, fex, lepton, arm processors, android, compatibility layers, vr headsets, quest
- Source: Ars Technica — https://arstechnica.com/gaming/2026/09/not-just-proton-getting-to-know-valves-new-steamos-compatibility-layers
- Published: 2026-09-16T20:23:16+00:00
- Read time: 1 min
- Topics: valve, steamos, steam deck, steam frame, proton, fex, lepton, arm processors, android, compatibility layers, vr headsets, quest
## Two new compatibility layers
Valve is using FEX and Lepton to get more games running on the Steam Frame VR headset. These join Proton, which already runs Windows games on Linux.
## FEX emulates x86 on Arm
FEX is based on fex-emu, an open source project that emulates x86 processor instructions on Arm chips. It includes a binary recompiler and code caching to minimize stuttering.
## Valve funded FEX for years
Valve has funded FEX lead developer Ryan Houdek since it was just a prototype. The company anticipated nearly a decade of work would be needed before it was ready.

> They trusted me with the responsibility of designing and frameworking the project in a way that it can work long-term
## SteamOS coming to more Arm devices
With FEX ready, Valve is exploring SteamOS for other Arm devices. The goal is letting gamers use Arm hardware without leaving part of their game library behind.

> I have to leave a portion of my catalog behind if I'm even considering it.
## Lepton runs Android apps
Lepton expands the Waydroid project to get Android APKs running on SteamOS. This is key for Steam Frame, since many VR titles were designed for Android-based Quest headsets.
## 52 Frame games use Lepton
Of the first 120 games marked 'Great on Frame', 52 run as Android executables via Lepton. Three Steam games now lack any Windows, Mac, or Linux builds entirely.

> They're really VR developers who want to publish their VR content, and they're porting a mobile VR title
## Could other Android apps come?
Valve hasn't ruled out generic Android apps on Steam through Lepton. But the company says it's focused on games, not broader app support.

> We've never disinvited people from doing that
## Key takeaway

Valve is using FEX to run x86 games on Arm processors and Lepton to run Android VR apps on SteamOS, expanding what can run on Steam devices.