Valve architect Pierre-Loup Griffais revealed in an interview this week that the company is funding the FEX emulator project and building an Arm-native version of Proton. The move is a deliberate effort to make the entire Steam catalog available on Arm-powered devices without forcing developers to ship separate builds.

What Valve Just Confirmed

Valve has been quietly bankrolling the FEX open-source project — a usermode x86-to-Arm64 emulator for Linux — for several years. Now the company is going public with its plan to marry that emulator with Proton, the compatibility layer that powers game playback on the Steam Deck, to create an Arm-ready SteamOS. In the coming months and years, this stack will allow gamers to pick up an Arm handheld, set-top box, or even a VR headset and play the same Windows games they already own.

The technical blueprint is straightforward: Proton, which translates Windows APIs to Linux equivalents and Direct3D to Vulkan, will be compiled natively for Arm. When a user launches an x86 Windows game, FEX sits underneath Proton and converts the game’s machine code from x86 to Arm64 using just-in-time translation. Because all of Valve’s own code runs natively, only the original game binaries incur emulation overhead — a design that Griffais claims keeps the performance penalty minimal.

Griffais stressed that Valve doesn’t want developers to spend time porting games to Arm. “We think that porting work is essentially wasted work when it comes to the value of the library,” he said, according to Thurrott.com. So the goal is to remove the CPU architecture as a compatibility barrier.

Which Games Will Work — and Which Won't

For the vast majority of single-player titles and many multiplayer games, the Proton+FEX combo should deliver a console-like “just works” experience. But there are critical exceptions.

Games that rely on kernel-mode anti-cheat drivers (e.g., Easy Anti-Cheat, BattlEye, Ricochet) or tight DRM schemes remain a question mark. While Proton itself has made substantial progress with anti-cheat vendors on x86 Linux, the added layer of CPU emulation introduces new variables. Some anti-cheat solutions may not function correctly in a translated environment, and publishers must opt-in to enable support. Launchers from third-party stores (Ubisoft Connect, EA App) can also introduce friction, though Valve continues to improve integration.

Performance is another unknown. JIT translation of x86 code to Arm64 is efficient, but CPU-bound titles that lean heavily on AVX or other advanced instructions may suffer. Microsoft’s Prism emulator on Windows 11 Arm has added hardware-accelerated AVX and AVX2 support for Qualcomm’s Snapdragon X chips; FEX currently lacks such SoC-specific optimizations. Independent benchmarks for real-world gaming over extended play sessions are nonexistent, so power users should treat Valve’s performance claims as directional until proven.

Valve will almost certainly introduce a verification program — similar to Steam Deck Verified — that labels games based on their Arm Proton+FEX compatibility. That database will become the go-to resource for armchair analysts.

The Emulation Layer: A Technical Primer

It helps to understand what happens when you click “Play” on a Steam game under this new stack.

  1. SteamOS on Arm boots and loads the Arm-native Proton runtime.
  2. Proton sets up a Windows-compatible environment, redirecting API calls and mapping graphics through DXVK/VKD3D to Vulkan.
  3. If the game binary is x86, FEX intercepts the launch and begins JIT-compiling the game’s code into Arm64 instructions. Translated blocks are cached to avoid repeated work.
  4. The game runs as though it were on a native Windows PC, unaware of the CPU emulation beneath it.

This approach differs from Microsoft’s Prism emulator, which is integrated into the Windows kernel. Prism emulates the entire x86/x64 process within Windows, including Windows libraries, whereas Valve’s model keeps the surrounding OS and Proton libraries native. The practical upshot is that translation work is concentrated on the game logic itself, not the entire software stack.

FEX is an open-source project hosted on GitHub, with a community that has already used it to run Windows games on Arm Linux devices via Wine. Valve’s funding accelerates that development and ensures it is optimized for SteamOS.

From Steam Deck to Arm Handhelds: How We Got Here

Valve’s journey to Arm began with the Steam Deck’s runaway success. The Deck proved that a compatibility layer could turn a Linux handheld into a viable PC gaming machine, eliminating the chicken-and-egg problem that had bedeviled Steam Machines a decade ago. As Arm silicon — spearheaded by Apple’s M-series and Qualcomm’s Snapdragon X — started demonstrating serious performance at low power, Valve saw an opportunity to broaden its hardware ecosystem.

The company had been funding FEX and other Arm tools since at least 2021, but kept the work low-profile. Now with partners like Lenovo shipping Arm-based laptops and rumors of a new Valve “Steam Machine” console swirling, the timing is right to go public. Griffais noted that the Arm build of SteamOS is essentially the same Arch Linux codebase, using the same updater and runtime — just compiled for Arm64. That architectural continuity means Valve can iterate quickly without forking the OS.

What Gamers Should Do Right Now

If you’re excited about the prospect of an Arm-powered Steam Deck successor or a living-room SteamOS console, here’s a practical checklist:

  • Review your library’s anti-cheat and DRM dependencies. ProtonDB is a good starting point, though Arm-specific data won’t appear until devices ship.
  • For the titles you can’t live without (e.g., Call of Duty, Destiny 2), keep a Windows PC or dual-boot setup as a fallback.
  • If you have access to an Arm Linux device (such as a Snapdragon X laptop running Ubuntu), you can experiment with FEX+Wine today to gauge performance on your favorite games. Community guides are available.
  • Wait for thorough, third-party performance reviews. Pay attention to frame-pacing, 1% lows, and thermal behavior over hour-long sessions — not just peak FPS.
  • Look for Valve’s hardware announcements: any official Arm device will likely ship with a verified game list, warranty support, and a mature software stack, making it a safer bet than a DIY Arm experiment.

For Developers and OEMs

Game developers can start testing their titles on Proton+FEX as early as now using community builds. Valve’s message is clear: you don’t need to lift a finger to support Arm if your game runs under the translation layer. However, for performance-critical or anti-cheat-heavy titles, planning an Arm-native build — perhaps using Arm64EC on Windows or a native Linux Arm binary — could pay off. Open communication with anti-cheat vendors about Proton on Arm is critical.

OEMs and system integrators should engage with Valve to obtain validated SteamOS Arm images and driver stacks. Kernel drivers (Wi-Fi, sound, GPU) must be robust and mainlined where possible to avoid fragmentation. Valve’s track record with the Steam Deck shows that a tight partnership between hardware and software yields a polished experience; Arm devices that ignore this lesson will frustrate users.

Outlook: When Will Arm SteamOS Devices Arrive?

Valve hasn’t announced a shipping date, but the pieces are falling into place. The company’s work on FEX and Proton for Arm coincides with a wave of powerful Arm SoCs from Qualcomm, MediaTek, and others. A “Steam Deck 2” with an Arm chip is plausible by 2026, and a dedicated Steam Machine console could appear even sooner. Independent benchmarks and anti-cheat vendor support will make or break the platform over the next 12 months.

If the Proton+FEX stack delivers on its promise, PC gaming will no longer be shackled to x86. That’s a future where you can buy an ultra-light Arm laptop, a handheld, or a set-top box and play the same library you’ve accumulated over decades. Valve’s quiet bet is finally public, and the next chapter of SteamOS is being written in Arm code.