While the prospect of Steam games running on your phone is a tantalising one (and an Arm-based Steam Deck, a bizarre thought), what's probably more likely here is testing for Wind

Valve is bridging its x86 library with ARM framework support for possible Steam games on mobile. The focus on ARM64 hints at expanded cross-platform support for SteamOS. Speculation includes Steam games on mobile and the potential development of Valve's standalone VR headset.

Proton is Valve's solution for running many Windows games seamlessly on the Linux-based SteamOS. The leaked code shows Valve testing this ARM64 version with a wide

Valve are likely up to something hardware-related again, report NotebookCheck. Their next chunk of plastic and wires – following the Valve Index, Steam Deck and Steam Deck OLED – could swap PC gaming’s favoured x86 architecture for ARM, the type of processor favoured by the Nintendo Switch, Macs, and mobile phones.

Valve may be developing an ARM64 version of Proton for Linux gaming. Hundreds of games, like Left 4 Dead, have been tested for compatibility using a new 64-bit layer. The potential for ARM64-based portable consoles opens exciting new possibilities.

It looks like Valve is working on bringing the Steam Deck's "special sauce" for Windows games on Linux to Snapdragon and other ARM devices.

Valve’s Proton software makes it possible to play many Windows PC games on computers running Linux-based operating system, including Valve’s own Steam Deck handheld gaming PC. So far Proton has only been available for PCs with Intel or AMD processors based on x86_64 architecture,

Valve appear to have some pretty ambitious future plans for Steam, as we've seen recently a leak (and not for the first time) that Valve has plans for ARM64 and Android support on Linux.