KDE Plasma (KWin)

Configure a Slipstream host on KDE Plasma. The host uses KDE's KWin compositor to create a per-client virtual display, captured zero-copy on the GPU (NVIDIA, AMD and Intel alike). This page assumes the package is already installed, see Ubuntu, Fedora, Arch, or the Bazzite appliance.

New here? Read Security & Safe Use first, a streaming host is remote control of the machine, so keep it on a trusted LAN or VPN and require pairing.

host.env

The host auto-detects your KWin session on every connect, including a box that switches between the Plasma desktop and Steam Game Mode, so the starter ~/.config/slipstream/host.env is one line:

# ~/.config/slipstream/host.env  (keys are case-sensitive)
SLIPSTREAM_VIDEO_SOURCE=virtual
# GPU zero-copy capture->encode (dmabuf -> CUDA/NVENC on NVIDIA, dmabuf -> Vulkan Video or VAAPI on
# AMD/Intel) is ON by default; auto-falls back to CPU. Set SLIPSTREAM_ZEROCOPY=0 to force CPU.

Don't set SLIPSTREAM_COMPOSITOR, WAYLAND_DISPLAY, or XDG_CURRENT_DESKTOP here. Pinning the compositor turns auto-detection off, per connect and mid-stream, so a switch to Game Mode then kills the stream instead of being followed, and stale session values point the host at dead sockets. Forcing a backend is for CI and dedicated appliances (the headless session below ships a host.env.kde that pins on purpose).

If the box switches between the desktop and Game Mode, also enable lingering, the host is a user service, and without linger the logout moment of a session switch tears it (and PipeWire) down mid-stream:

sudo loginctl enable-linger "$USER"

See the Configuration reference for every option.

Use a Wayland session

KDE must run on Wayland, not X11, pick the Wayland session from the picker on the login screen. The virtual-display path is Wayland-only and will not come up under X11.

On a normal Plasma login KWin drives your real hardware, and any Plasma 6 release can create the virtual output, what it needs is the screencast grant below, not a particular version. The headless session further down is the exception: it runs kwin_wayland --virtual, and that backend only learned to create virtual outputs in KWin 6.5.6, so an appliance box needs 6.5.6 or newer. Check with:

kwin_wayland --version

Streaming the interactive desktop

To stream a logged-in Plasma desktop (rather than a headless session, below), KWin has to hand the host its restricted screencast protocol. The host package ships an io.slipstream.Host.desktop file whose X-KDE-Wayland-Interfaces grants exactly that on a normal interactive session (least-privilege, the same mechanism krfb/krdp use). After a fresh install, log out and back into the Desktop session once so KWin re-reads the grant.

Input needs no extra setup. That same .desktop file also grants org_kde_kwin_fake_input, so the host injects keyboard, mouse and touch straight into KWin, no portal, and no "Allow remote control?" dialog for a headless box to answer, on every distro. All a fresh install needs is the log out and back in above, so KWin re-reads the grant.

The old RemoteDesktop-portal grant only matters now if you force the libei input backend (SLIPSTREAM_INPUT_BACKEND=libei), that one injects through the RemoteDesktop portal, and on KDE it is also what a portal capture (SLIPSTREAM_VIDEO_SOURCE=portal) is anchored to, so the capture inherits the same grant. To seed it, Fedora and Bazzite ship a one-shot helper (run once as the streaming user, no root); the .deb and Arch packages don't include that wrapper, so copy the shipped kde-authorized file into the portal store by hand instead (the share dir is /usr/share/slipstream-host on Ubuntu, /usr/share/slipstream on Arch) and log out and back in:

bash /usr/share/slipstream/bazzite/kde-desktop-setup.sh    # Fedora / Bazzite

mkdir -p ~/.local/share/flatpak/db                        # Ubuntu / Arch
cp /usr/share/slipstream*/headless/kde-authorized ~/.local/share/flatpak/db/kde-authorized

A login-less appliance skips all of this, its headless session (below) needs none of these grants.

Start the host

With host.env in place, start the host from inside your Plasma session:

systemctl --user enable --now slipstream-host
journalctl --user -u slipstream-host -f   # watch it come up and print its identity fingerprint

This unit runs serve --gamestream, so it serves stock Moonlight clients as well as the native ones. For a native-only host, see What the unit starts.

A desktop-login host should also follow your session's lifetime, or restarting Plasma leaves the host wired to a compositor that is gone, it keeps answering, and every session after that fails at capture. Add the drop-in from Restart the host with your desktop. Skip it on the headless appliance route below.

Then bring up The Web Console to arm pairing and connect a client. To start at boot, including fully headless, see the headless session below or Running as a Service.

Persistent per-client scaling

KWin round-trips per-client display scale: it names each session's virtual output per client, so a scale you set for one client (150 %, 125 %, ...) is reapplied on that client's next connect. See Virtual displays.

Headless session

For a login-less appliance, a box that streams at boot with no graphical login, the host brings up a dedicated headless KWin session rather than relying on an interactive one. It runs its own kwin --virtual session (shipped as the slipstream-kde-session.service unit) with permission checks relaxed, so it needs none of the interactive grants above.

mkdir -p ~/.config/slipstream
cp /usr/share/slipstream/host.env.kde ~/.config/slipstream/host.env   # Ubuntu: /usr/share/slipstream-host/host.env.kde

systemctl --user daemon-reload
systemctl --user enable --now slipstream-kde-session slipstream-host
sudo loginctl enable-linger "$USER"

The session unit brings up headless KWin; the host unit follows it and starts listening. See Running as a Service for the full headless setup.

Troubleshooting

• KWin isn't handing over the screencast protocol: run slipstream-host probe-compositor from inside the session. It exits 0 only when KWin is up and advertising the grant to the host, and prints the reason when it isn't, after a fresh install that is usually just the missing log out and back in. On the headless appliance session, also check kwin_wayland --version is ≥ 6.5.6.
• Black screen / no picture: confirm you're on a Wayland session (not X11) and, on NVIDIA, that the GL userspace is installed. More in Troubleshooting.

To bring the console up and pair, see The Web Console.