This update is for the SteamOS Beta and Preview channels, and includes new features that are still being tested. You can opt into this in Settings > System > System Update Channel.
These notes contain all changes since the current stable SteamOS 3.8 release, with the changes added since the previous 3.9 preview releases noted below
New in SteamOS 3.9.4
General
Fixed an issue causing firmware updates to occasionally fail to apply on Steam Machine
Fixed a bug wherein changing the timezone could prevent switching to Desktop Mode until a reboot
Fixed a regression from previous 3.9 releases that caused some apps to run behind Steam's loading screen, such as A Plague Tale: Innocence
Fixed a regression from previous 3.9 releases that caused screenshots to be taken at 720p even when the display and game resolution are at a higher resolution
Reduced incidence of audio clicks on 3.5mm output with sensitive earphones/speakers
Security and stability updates
Developer
SteamOS 3.9
General
Updated Arch Linux base
Updated Desktop Mode from Plasma 6.4.3 to Plasma 6.7.3
Improved support for Steam Frame wireless adapter
Fixed a bug causing hidden WiFi networks to fail to connect on the first attempt
Fixed Steam Remote Play not working on Steam Machine when booting with no external display connected
Fixed "Disable Frame Limiter" toggle not working when VRR is enabled
Fixed the frame limiter incorrectly applying to VR titles when streaming from Steam Machine to Steam Frame
Fixed loss of input if a launcher window is accidentally dragged around in Game Mode
Fixed an issue causing frame limits to result in lower than intended FPS on certain external displays
Fixed issues with suspend/resume on systems with RDNA1 or RDNA2 based dedicated GPUs
Fixed audio issues on hotplug of certain monitors in a multi-monitor setup
Fixed a system crash when launching Forza Horizon 6 on Legion Go 2
Added preliminary support for Legion Go 2 brightness control
Fixed an issue causing certain games (incl. ELDEN RING and DARK SOULS™ III) to fail to run on recent Panther Lake Intel CPUs
Fixed performance issues in STAR WARS: Galactic Racer on resume from suspend on Steam Machine
Fixed an issue that could lead to GPU errors in The Crew Motorfest
Worked around a firmware issue on some ASUS devices causing excessive fan speed upon waking from sleep
Fixed boot screen corruption on Intel PTL+ devices
Security and stability updates
Misc
Updated the bootloader to improve compatibility with certain motherboards
The Desktop Mode lockscreen is no longer prevented from being explicitly enabled in settings (but remains off by default)
Fixed logging in to Desktop Mode via RDP with system users when enabled
Developer
Switched WiFi backend to wpa_supplicant by default for new installations, improving compatibility with various WiFi networks
Enhanced wpa_supplicant to support fast WiFi reconnect on resume from sleep, previously only available in the iwd backend
Known issue: Existing installations will continue to use iwd unless manually enabled in Developer Settings
Linux kernel rebased on Linux 7.2
Added preliminary support for hibernation, not yet exposed in Game Mode UI
Various scripts and packages have been renamed from `steamos-` to `holo-`, with aliases to the former names where appropriate
Improved support for running SteamOS as a VM guest with accelerated graphics (virtio-gpu, venus)
Updated included renderdoc version
Reintroduced support for Android binder IPC
