punktfunk/docs-site/content/docs/gamescope.md

title, description

title	description
Steam / gamescope	Configure a gamescope/Steam host — attach vs managed, session following, and limits.

gamescope is the compositor behind Steam Gaming Mode — the couch/handheld game UI on Bazzite, SteamOS, or any distro running a gamescope session. The host auto-detects gamescope from your live session, so you rarely need to set anything here. It also follows a Gaming ↔ Desktop switch mid-stream — flip between Gaming Mode and the desktop with Steam's normal UI and the host re-targets whatever's running without a reconnect.

This page covers the gamescope-specific choices. To get a host running on an appliance box, start from the install guide for your OS: Bazzite or SteamOS (Host).

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.

Attach vs managed

There are two mutually-exclusive models for a gamescope box; pick one. With nothing set, a box that has gamescope session infrastructure (Bazzite, SteamOS, Nobara) gets managed; the Bazzite template ships with attach chosen instead.

• Attach (PUNKTFUNK_GAMESCOPE_ATTACH=1) — the box owns its gamescope session and decides Gaming vs Desktop via the normal Steam UI. Game Mode stays on the box's own (physical) display; the host attaches to whatever's live and never tears it down, so switching Desktop ↔ Game is rock-solid and disconnecting leaves the box where it was. When the box is headless (no display connected) and the session is its own autologin unit, the host restarts it at the client's resolution on a mismatch; a box driving a physical display — and any foreign or bare gamescope — is streamed at its own mode.
• Managed (the infra-detected default; force with PUNKTFUNK_GAMESCOPE_MANAGED=1) — the host takes the box's gamescope session over and relaunches it headless at the client's exact resolution and refresh — Game Mode runs on the virtual screen, physical displays drop out of it — restoring the box on idle after disconnect.

Nobara and other autologin display managers

The managed takeover has to stop the box's Gaming Mode session to free Steam. How it does that depends on the display manager driving the autologin:

• SDDM (Bazzite, SteamOS): handled automatically — no setup.

• plasmalogin (Nobara) and other display managers: the host must stop the display manager itself for the length of the stream and restart it afterwards, which needs privilege. The packages ship that privilege: a root helper (/usr/libexec/punktfunk/pf-dm-helper) behind its own polkit action (io.unom.punktfunk.dm-helper), invoked automatically when the plain systemctl verbs are denied — no setup. The helper only stops/restores the unit the display-manager.service symlink points at, the same class of local-seat operation these distros already authorize for their own session switcher (Nobara's os-session-select).

  Installed from a tarball, or prefer not to ship the allow_any action? Remove the .policy file and use a polkit rule scoped to your user instead (adjust the unit and user names to your box) — the host tries the plain verbs first, so the rule takes precedence:

  // /etc/polkit-1/rules.d/49-punktfunk-dm.rules
  polkit.addRule(function(action, subject) {
      if (action.id == "org.freedesktop.systemd1.manage-units" &&
          action.lookup("unit") == "plasmalogin.service" &&
          subject.user == "YOUR_USER") {
          return polkit.Result.YES;
      }
  });
  

  With no privilege path at all the host degrades safely: it attaches to the live Gaming Mode session instead (Game Mode stays on the box's display at the box's own resolution, mirrored to the client — if your monitor stays on and the stream runs at the desktop's resolution, this is what happened; check the host log for "managed takeover unavailable"). If the display-manager restart ever loses its privilege mid-restore, PUNKTFUNK_RECOVER_SESSION_CMD (see Configuration) is fired as the fallback.

  With the takeover authorized the in-stream session switch round-trips in managed mode: Steam's "Switch to Desktop" inside the streamed Game Mode returns the box to its desktop session and the stream follows it there; the desktop's "Return to Gaming Mode" switches it forward again.

Session following

PUNKTFUNK_SESSION_WATCH follows a Gaming ↔ Desktop switch mid-stream — the host rebuilds the backend in place, with no reconnect. It is on by default on Bazzite/SteamOS; set 0 to disable. One host service covers both faces of the box: it streams Gaming Mode over gamescope and the desktop over its own compositor, and re-targets whichever is live on each switch.

Start the host

On an appliance box (Bazzite, SteamOS) the install guide already enables the host service for you. On any other distro running a gamescope session, just start it — the host auto-detects the live gamescope session and picks the model for it:

systemctl --user enable --now punktfunk-host

Then bring up The Web Console to arm pairing.

gamescope knobs

The gamescope-specific settings in host.env. Leave them unset to auto-detect; set one only to force a model. See the full Configuration reference for every other knob.

Setting	Values	Meaning
PUNKTFUNK_GAMESCOPE_ATTACH	1	Attach model: the box owns its gamescope session (on its own display); the host captures whatever's live and never tears it down. On a headless box the box-owned autologin session is restarted at the client's resolution on a mismatch; a box driving a physical display, and any foreign/bare gamescope, streams at its own mode.
PUNKTFUNK_GAMESCOPE_MANAGED	1	Managed model (the default where session infra is detected): the host takes the box's gamescope over and relaunches it headless at the client's exact mode, restoring on idle.
PUNKTFUNK_GAMESCOPE_SESSION	steam	The host owns a gamescope-session-plus (Steam) session at the client's mode — a headless appliance with no physical session running.
PUNKTFUNK_GAMESCOPE_NODE	auto · node id	Discover and capture a running gamescope's PipeWire node at a fixed mode. Do not combine with SESSION.
PUNKTFUNK_GAMESCOPE_APP	command	For an ad-hoc bare-gamescope session, the nested command to run (e.g. vkcube).
PUNKTFUNK_SESSION_WATCH	1 · 0	Follow a Gaming ↔ Desktop switch mid-stream (rebuild in place, no reconnect). On by default on Bazzite/SteamOS; set 0 to disable.

Known limits

These apply to the Gaming Mode (gamescope) path only; the desktop path is unaffected.

• gamescope 3.16.22 or newer is required. Older versions can deadlock during capture. Bazzite's and SteamOS's current gamescope is fine; this only bites if you've pinned an old one.
• The mouse cursor isn't included in the captured image — a gamescope limitation for now.
• Touch arrives as a single-finger pointer. gamescope's virtual input device has no touchscreen, so the host maps a client's touchscreen to an absolute pointer: taps click exactly where you touch and drags work, but multi-touch gestures (pinch) aren't available in Gaming Mode. The desktop path has full multi-touch.
• HDR isn't supported on the gamescope path — gamescope's capture output is 8-bit. SDR streams normally.

To stream the KDE Plasma desktop of a Steam box instead, see KDE Plasma. To bring up the web console and pair a client, see The Web Console.