Steam: native Linux build for the Steam Deck #202

Part of #142 · Milestone 3: Playable desktop build (Windows and Linux) · plan item 3.9

Size: M · Owner-only step: no · Blocks launch: yes

What

The spike (#158) ran the same build on the Deck two ways. Native Linux held 60 fps in every scene on Low and High; the Windows build through Proton dropped to about 50 fps in the late cellar on High (stage 3, every boss beaten, everything bought). Ship a Linux x64 build beside the Windows one, so the Deck (and Linux desktops) run it natively.

Decision / recommendation

Owner, 2026-10-27: native Linux for the Deck as well as Windows. Two depots from the same commit, one launch option per OS.

Done when

• The Linux build starts straight into the game in Game Mode on the Deck, with sound, and works offline
• Runs under Steam Linux Runtime 4.0 (steamrt4, the one Valve recommends for native games; Steamworks defaults to the old scout unless we pick it)
• Electron's Chrome sandbox settled: the spike passes --no-sandbox because its root-owned helper can't work from Steam's folder or its runtime container; keep the renderer sandboxed if the runtime allows it, otherwise write down why not
• Steamworks loads libsteam_api.so; Shift+Tab overlay tried natively (Steam: overlay #173)
• The Deck runs the native build by default (not Proton)
• Store page lists SteamOS + Linux with system requirements (Steam: store text and tags #153)

Sources

• https://partner.steamgames.com/doc/steamdeck/compat
• https://partner.steamgames.com/doc/store/application/platforms
• https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/blob/main/docs/slr-for-game-developers.md
• https://www.electronjs.org/docs/latest/tutorial/sandbox
• Spike results: Steam: Electron spike on its own branch #158

Plan page (owner only): https://claude.ai/artifact/Cf5SWQHzAKTy2uHCC1UQgw