Steam ARM64 on Termux/X11

Run Valve's conventional native ARM64 Linux Steam client on an unrooted Samsung Galaxy Tab S9+ using Termux, Debian PRoot, Termux:X11/KDE, Mesa Turnip, official Proton 11 ARM64, and its bundled FEX/DXVK stack.

Current status

• Native ARM64 Steam launches, authenticates, renders its UI, and downloads games.
• Turnip provides Vulkan acceleration on the Snapdragon/Adreno GPU.
• Official Proton 11 ARM64 and Steam Linux Runtime 4 ARM64 are registered and launch through the correct ARM64 paths.
• Superflight runs fullscreen through FEX, Wine, DXVK, and Turnip with working PulseAudio output.
• An optional microSD library keeps Windows game depots external while Proton, runtimes, active downloads, and per-game compatdata remain on internal F2FS. Kingsway runs fullscreen with audio through this split route.
• Burnout remains experimental; its detailed EA, FEX, and DXVK investigation is kept in docs/TECHNICAL_LOG.md, not duplicated here.

What changed

Recompiled PRoot

Stock PRoot was not sufficient for Steam and Pressure Vessel. The repository rebuild applies narrowly scoped fixes for:

• glibc robust-list calls blocked by Android seccomp;
• System V semaphore operations and waiter wakeups used by Steam;
• Pressure Vessel's .l2s metadata, bind mounts, pivot sequence, and shared /tmp behavior;
• the private /proc/net route view required by Wine's Windows networking APIs.

The source is pinned and rebuilt by:

scripts/build-proot.sh

The build is stamped with the source commit, ordered patch-set hash, source-diff hash, and binary hash. The exact patches live under patches/.

Hardened the Steam launcher

bin/steam-arm now prepares a completely user-local runtime:

• private Debian/glibc, D-Bus, Mesa/Turnip, and Steam paths;
• ARM64 compatibility-tool registration and traditional Steam SDK symlinks;
• stable software-rendered CEF while games retain Vulkan acceleration;
• Android loopback/network compatibility shims;
• canonical PulseAudio TCP setup;
• bounded session logs, /dev/null guards for runaway CEF logs, and a 1 GiB free-space floor.

It does not replace global library paths or modify the existing KDE/Mesa setup.

Tuned Superflight

scripts/configure-superflight-performance.py applies a backup-first, atomic Unity profile: fullscreen 1280x720, quality zero, and antialiasing, motion blur, post-processing, and shadows disabled.

The game initially pinned all 72 observed Unity/DXVK threads to CPUs 0-3. On this tablet those are the lower-capacity cores. The guarded scripts/set-superflight-affinity.py validates the game/App ID and the measured CPU topology before moving all game threads to CPUs 4-7. In the same menu scene, observed game CPU use fell from about 157% to 97%, and play felt noticeably smoother. This affinity is process-local and must currently be applied after each launch.

Reproduce

Read docs/PROPRIETARY_AND_BINARY_INPUTS.md for the required external Steam, Proton, runtime, and Mesa payloads. They are not stored in this repository.

scripts/inventory.sh
scripts/build-proot.sh
scripts/prepare-arm64-runtime-shadow.sh
scripts/install-project-files.sh
scripts/verify-gpu.sh
~/bin/steam-arm

In Steam, explicitly force Superflight (App ID 732430) to use Proton 11.0 (ARM64), and set this launch option for audio:

PULSE_SERVER=tcp:127.0.0.1:4713 %command%

With Steam and Wine stopped, apply the graphics profile:

scripts/configure-superflight-performance.py --base "$HOME/steam-arm64"
scripts/configure-superflight-performance.py --base "$HOME/steam-arm64" --check

After Superflight starts, apply and verify the confirmed live affinity:

scripts/set-superflight-affinity.py
scripts/set-superflight-affinity.py --check

With Steam fully stopped, prepare and register the removable Windows-game library before the next Steam start:

bin/steam-arm64-removable-library.py --base "$HOME/steam-arm64" prepare
bin/steam-arm64-removable-library.py --base "$HOME/steam-arm64" register
scripts/install-project-files.sh

register makes a byte-verified backup before atomically adding the library to Steam's libraryfolders.vdf, and refuses to run while Steam or Wine is active. Use this library only for Windows game depots. The launcher keeps Steam's steamapps control metadata internal, binds only steamapps/common to the card, and uses dedicated internal compatdata and active-download directories. Android's portable-storage FUSE does not implement the file locks Steam needs for manifests or patch state. The launcher fails early if the card is absent or the layout is unsafe.

WINE_CPU_TOPOLOGY=4:4,5,6,7 is a candidate for making the affinity persistent, but it is intentionally not presented as confirmed until a clean launch proves the same per-thread masks and performance.

Validate the repository

for test_file in scripts/test-*.py; do
    PYTHONDONTWRITEBYTECODE=1 python3 "$test_file" || exit
done

The retained tests cover the launcher log guard, PulseAudio preparation, Pressure Vessel route injection, Superflight settings, and affinity validation.

Key paths

• bin/steam-arm — production launcher.
• patches/ — reproducible PRoot patch series.
• config/steam-arm64-compatibilitytools.vdf.in — official ARM64 Proton/runtime registration.
• scripts/ — builds, installation, probes, and game tuning.
• docs/TECHNICAL_LOG.md — full chronological evidence and unresolved diagnostics.
• docs/ARCHITECTURE.md — component boundaries.

Observed platform

• Samsung Galaxy Tab S9+, Snapdragon 8 Gen 2 / Adreno 740
• Debian 13 under Termux PRoot
• ARM64 Steam build 1785799196
• Mesa Turnip 26.2.0-devel (git-9452d1daec)
• PRoot base commit a89b3732ec6ae1db674510f0843b2f3db54d0a2f

No root, bootloader unlock, custom kernel, flash, chroot, or global Mesa/library replacement is required.