Valve has released the SteamOS 3.9 preview, moving Desktop Mode to KDE Plasma 6.7.3 and the underlying kernel to Linux 7.2. The SteamOS 3.9 preview notes cover Steam Deck, Steam Machine, and other SteamOS devices, and follow a smaller patch that had already landed on the beta branch to fix assorted Desktop Mode and gaming-mode bugs.
What the SteamOS 3.9 preview changes
The headline move is the Desktop Mode upgrade. KDE Plasma jumps from 6.4.3 to 6.7.3, a gap of three point releases, which brings Krunner’s search function up to date, adds clipboard pinning, and improves handling for drawing tablets, according to TechPowerUp’s breakdown of the changelog. SteamOS has historically shipped an older, tested build of Plasma that lags behind KDE’s own release cadence, so a three-point jump in one preview is a bigger step than the version’s naming suggests. None of it touches Gaming Mode directly, but it matters to anyone who drops into Desktop Mode to manage files, install software outside the Steam client, or plug in a tablet for streaming and content work.
The kernel update carries its own list, and it applies regardless of whether Desktop Mode is ever opened. Linux 7.2 brings performance improvements for Intel’s Arc B390 graphics silicon, and adds USB4Stream, a kernel-level feature for sharing data directly between two USB4-connected devices without routing through a separate protocol stack. That is useful for anyone connecting a Steam Machine or Deck to a dock or another USB4 device and wanting a direct data path rather than a workaround.
Why the coverage split by a day
Phoronix had the preview reported first. By teqpost’s arithmetic, comparing the two outlets’ publish times, TechPowerUp’s writeup landed roughly 18.7 hours later. Phoronix’s initial report focused on the move to Plasma and the kernel bump; the fuller breakdown, including the exact KDE version delta and the specific kernel features, only showed up once TechPowerUp published. That gap is a reminder that the two pieces of coverage are summaries of the same source material, not independent findings, so anyone wanting the complete list without waiting on either outlet’s framing is better off starting with Valve’s own preview notes, which carry the full changelog Valve is actually shipping.
SteamOS previews are opt-in and land on the beta branch before Valve rolls changes out more broadly. Given that pattern, expect 3.9 to spend time collecting feedback from Deck and Steam Machine owners running it before Valve promotes it to the stable channel.
