Last verified 2026-09-21 by ReviewGamers Editorial
Valve moved SteamOS 3.9 into its Preview channel on 29 August 2026 and followed with 3.9.1 on 14 September. The headline items are a Linux 7.2 kernel, KDE Plasma 6.7.3 for Desktop Mode and the first groundwork for hibernation. This is what changed, according to Valve’s own release notes and GamingOnLinux’s reproduction of them, and whether a Steam Deck owner should opt in.
What the Preview channel is
SteamOS ships on three channels. Stable is what a Deck runs out of the box. Beta gets fixes earlier. Preview is where major version work lands first, and Valve’s 3.9.0 post is explicit that it is for people willing to hit bugs and report them through Valve’s bug tracker. You switch under Settings > System > System Update Channel. If you stay on Stable you will see none of this until 3.9 graduates.
Desktop Mode moves from Plasma 6.4.3 to 6.7.3
The most visible change is in Desktop Mode. Valve’s 29 August notes list a jump from KDE Plasma 6.4.3 to 6.7.3, sitting on an updated Arch Linux base. Two smaller desktop changes come with it: the Desktop Mode lock screen can now be explicitly enabled, and there is a bootloader compatibility update. Valve’s post does not enumerate Plasma’s own feature changes, so this article does not either.
Kernel: Linux 7.2
GamingOnLinux’s quotation of the full patch notes records the kernel rebase to Linux 7.2, up from the 6.16 LTS series the site says 3.8 uses. Alongside it, the notes list improved graphics support when SteamOS runs as a virtual-machine guest, and a rename of the steamos- command-line scripts to holo-, with aliases kept so existing scripts do not break. That last item only matters if you use the terminal in Desktop Mode.
Hibernation: preliminary, and not in Game Mode yet
This is the item most people are waiting on, and it is not usable yet. The notes quoted by GamingOnLinux describe preliminary hibernation support that is not yet exposed in the Game Mode interface. In other words the plumbing is in, the switch is not. Valve has not given a timeline for surfacing it, and none should be assumed.
WiFi backend: wpa_supplicant for new installs
A quieter change with a gotcha. New SteamOS installs default to the wpa_supplicant WiFi backend. Existing installs stay on iwd unless you change the backend yourself in Developer Settings. So an upgraded Deck and a freshly imaged Deck can behave differently on the same network, which is worth remembering if you are comparing notes with someone else or troubleshooting a connection.
SteamOS 3.9.1 Preview (14 September)
Valve’s 3.9.1 post is a fix list with four entries:
- a system crash when launching Forza Horizon 6 on the Lenovo Legion Go 2 is fixed
- frame limits that produced lower frame rates than intended on certain external displays are fixed, which is the one docked Deck owners should care about
- suspend and resume on systems with RDNA1 or RDNA2 dedicated GPUs is fixed, relevant to SteamOS on desktop hardware rather than the Deck itself
- a startup regression that hid the boot logo is fixed
Meanwhile on Beta: 3.8.27
Valve’s 3.8.27 Beta notes, also dated 14 September, fix a rare issue where fan speed reverted to BIOS control until the next reboot. That fix is on the 3.8 line, so Preview users are on a different track.
Should you opt in?
Not unless you want to test. Nothing in 3.9 is a must-have today: the Plasma upgrade only shows in Desktop Mode, hibernation is not reachable from Game Mode, and the kernel change is invisible in normal use. Stable users lose nothing by waiting. No performance figures are published in Valve’s notes, and none are offered here.
One item to flag as not yet confirmed: a Steam Deck HQ headline referenced HDMI 2.1 support in connection with this release, but that did not appear in the release notes captured for this article, so it is not treated as part of 3.9.
For what is running well or badly on the Deck this month, read our Onimusha: Way of the Sword Steam Deck guide and the explainer on why WARDOGS is Unsupported, or browse the Steam Deck hub.