DroidDeck/docs/development/arm64-steam-client.md

Native arm64 Steam client: channel and runtime

The default client is Valve's arm64 Linux build (steamrtarm64/steam). Valve does not support it, but publishes it on the Steam Deck client channels. droiddeck-steam-install installs it and droiddeck-session starts it with STEAM_RUNTIME=1.

Channel

• The default is steamdeck_publicbeta (manifest steam_client_steamdeck_publicbeta_linuxarm64). Valve also publishes steam_client_steamdeck_stable_linuxarm64.
• droiddeck-steam-install --channel prints the channel in use. The session passes that value as -clientbeta and writes it to package/beta. The two must match, or the client loops on rc 42.
• Setting: BL_STEAM_CHANNEL, otherwise ~/.config/droiddeck/steam-channel, set to beta or stable. A set channel never changes on its own.
• With no setting, the client falls back to steamdeck_stable automatically. It stays on stable (package/droiddeck-channel) until a setting says otherwise. The fallback happens:
  • when the client was started two more times without being shown after the start-failure repair (package/droiddeck-unconfirmed: two unconfirmed starts trigger a repair, which writes repaired; two more unconfirmed starts trigger the fallback);
  • when the beta manifest has no *_linuxarm64_linuxarm64 component. The install log then lists the manifest's block names, so a renamed or removed arm64 build can be seen.
• The x86-64 client keeps steamdeck_publicbeta (see x86-64-steam-client.md).

Steam Runtime container

Valve's 2026-10-15 beta made the x86 Linux client 64-bit and put it in a Steam Runtime container (pressure-vessel). The container needs unprivileged user and mount namespaces and a D-Bus session bus, which an Android app does not have. The x86-64 path already works around this. The arm64 client gets the same treatment if Valve containerizes it too:

• STEAM_STEAMRT_RECURSION_GUARD=1 is exported for both clients. It tells the client that it is already inside its container, so after an update it does not re-execute itself through pressure-vessel-wrap (bwrap).

• droiddeck-steamrt-shim <client dir> <shim dir> builds the shim when the client carries pv-runtime/steam-runtime-steamrt or a steam-runtime-check-requirements probe:

  • Valve's runtime is linked file by file;
  • the probe is replaced with exit 0;
  • its own steam-runtime-launch-client runs commands directly.

  For the arm64 client the session then starts it with STEAM_RUNTIME_STEAMRT and PATH pointing at ~/.droiddeck-steamrt-shim and logs "Valve containerized the arm64 Steam client". Without those files the shim is not built and the start is unchanged.

What Valve's manifests carry (checked 2026-10-22)

• steam_client_steamdeck_publicbeta_linuxarm64 (1792626604) and steam_client_steamdeck_stable_linuxarm64 (1792618285) have the same blocks. Three platforms share them:
  • *_linuxarm64_linuxarm64: the native client (steamrtarm64/, linuxarm64/). No pressure-vessel, no steam-runtime-check-requirements. These are the only platform blocks the installer keeps.
  • *_steamrt_linuxarm64: Valve's x86-64 SteamRT 3c client (steamrt64/steam is an x86-64 ELF) with steamrt64/pv-runtime/steam-runtime-steamrt (pressure-vessel, steam-runtime-check-requirements, steam-runtime-launch-client). This is the containerized client the 2026-10-15 beta made the default on x86. Valve ships it to arm64 hosts as well, presumably to run under FEX. The installer skips it.
  • bins_androidarm64_linuxarm64: androidarm64/libsteamclient.so, steamservice.so and friends.
• steam_client_steamdeck_publicbeta_ubuntu12 has stopped at 1792108788, while stable ubuntu12 follows stable (1792618285). On beta the 32-bit ubuntu12 client no longer gets updates.
• If a future manifest drops *_linuxarm64_linuxarm64, the installer logs the block list and moves to stable. If stable drops it too, the remaining option is the x86-64 client under FEX (x86-64-steam-client.md).