Field report, Nobara + 0.20.0: switching into Game Mode mid-stream
disconnects the client and the box never lights up again. His journal has
the whole mechanism, ten seconds apart:
12:34:18.9 freed Steam: stopped the display manager for this stream
12:34:29.0 systemd[1685]: Stopping punktfunk-host.service
Stopping the display manager ends the user's last login session. The
packaged host is a `systemd --user` unit, so logind then stops
user@1000.service once UserStopDelaySec elapses — 10s by default on Nobara
— and takes the host with it. The stream dies, the scheduled restore never
runs, and the display manager stays down with nothing left to restart it:
a black box that needs a VT to recover. Exactly the two symptoms reported,
and the intermittency is just whether an active Gaming Mode session was
there to trigger the takeover at all.
It never showed on the repro VM because lingering was enabled there for the
earlier sessionless tests (`Linger=yes` — confirmed on the VM today), which
is precisely the thing that breaks the dependency: logind keeps the user
manager alive with no session. Our KDE/GNOME/Arch setup guides already ask
for it; his box, following the KDE route, did not have it.
So the takeover now ensures lingering BEFORE it touches the display
manager: `loginctl enable-linger` directly (allow_active in logind's own
policy — verified working unprivileged on Nobara), else the packaged helper
gains a `linger` verb that enables it for PKEXEC_UID alone, never a
caller-named user. If neither works the takeover is refused with an
actionable error and managed degrades to attach — mirroring the box's own
session is strictly better than a screen that needs a VT. Hosts that cannot
be reached this way (root, a system unit) skip the check: the cgroup test
is a pure `cgroup_under_user_manager` with a unit test, matched against the
real shapes on a Nobara box (`user@1000.service/app.slice/...` vs a
`session-N.scope`).
Also documents the requirement in the gamescope guide's Nobara section.
Checked on Linux: clippy -D warnings, 78 tests, rustfmt; helper verified
with `sh -n`, and the linger enable/disable round-trip run live on the
Nobara VM.
Field report (Nobara, 0.19.2): entering Game Mode mid-stream left the monitor
on and the stream mirroring at the desktop's resolution. Root cause: the
DM-flavor takeover needs privilege to stop plasmalogin, the polkit rule is a
docs-only manual step nobody installs, so every managed entry silently
degraded to ATTACH — and with a physical display connected the attach path
mirrors the box's own session at its own mode.
Ship the privilege with the packages instead: a root helper
(libexec/punktfunk/pf-dm-helper, verbs stop|restore) behind its own polkit
action (io.unom.punktfunk.dm-helper, allow_any — the same mechanism Nobara's
os-session-select uses, and the helper derives the DM unit from the
display-manager.service symlink itself so callers never name a unit across
the privilege boundary). The host tries the plain system-bus verbs first
(root / operator rule still take precedence), then pkexec's the helper; the
restore paths (idle restore + in-stream desktop-switch honor) use the same
ladder so a takeover that needed the helper can always be undone by it.
Packaged in rpm/deb/arch (Arch under /usr/lib/punktfunk with the policy's
exec.path annotation rewritten; the host probes both layouts). Nix is left
out deliberately: store paths can't match the probe, NixOS keeps the manual
rule. Docs updated — the rule snippet stays as the scoped alternative.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
First on-glass test of the DM-flavor takeover confirmed the black-screen
fix, but exposed that the managed model could not switch back: Steam's
in-stream session-select is a silent no-op while the display manager is
stopped (every config-write branch in os-session-select requires the DM
to be running), so the capture loss it causes just relaunched game mode.
The user pass of the switch script does leave one durable trace — the
~/.config/steamos-session-select sentinel, written before any DM check.
The managed launch now baselines its mtime; a capture loss with the
sentinel advanced reads as the switch request and is honored by
replaying the switch with the DM up: restore the display manager, run
the distro's own os-session-select (its internal pkexec is authorized
allow_any by the distro policy, so it works from the host's sessionless
context), then stop the autologin game-mode unit so Relogin lands in
the newly selected desktop. The capture-loss re-detection then follows
KWin as it comes up; a 120 s post-honor grace stops the rebuild loop
from racing the booting desktop back into game mode (superseded early
if the box's own game-mode unit reappears — the desktop→game leg stays
fast). The baseline is re-recorded on crash-restore so a pre-existing
sentinel never reads as a fresh request. Every verb in the sequence was
live-validated on the Nobara repro VM.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Field report (Nobara 43 HTPC): switching the host to Steam Game Mode
mid-stream permanently black-screened the box. Live-proven root cause on
a Nobara repro VM: our takeover masks the box's gamescope-session-plus
unit, plasmalogin's Relogin=true then fails its session Exec repeatedly
and trips systemd's start limit within ~1 s — the display manager dies,
and our restore verb (unmask + user start) cannot bring a seatless
gamescope back. Only 'reset-failed + restart' of the DM recovers.
The takeover is now display-manager-flavor-aware:
- SDDM (Bazzite/SteamOS) keeps the proven mask+SIGKILL path unchanged.
- plasmalogin/unknown DMs never mask: with privilege (root or an
operator polkit rule scoped to the DM unit — documented) the host
stops the DM for the stream and restores it with reset-failed +
restart (PUNKTFUNK_RECOVER_SESSION_CMD as fallback), recorded in the
persisted takeover state so a host crash still restores; without
privilege the managed takeover degrades to ATTACH and mirrors the
box's live Game Mode instead of destabilizing the seat. Both legs of
the privileged cycle live-verified on the repro VM (headless managed
session works with zero login sessions; render nodes are 0666).
A loaded-but-inactive leftover instance never triggers the DM stop.
Companion fixes from the same triage:
- ensure_box_gamescope_mode gains the attach-only rebuild-probe guard
both managed paths already had (stale post-capture-loss detection
restarted the box's unit), and no longer re-modes a box that drives a
physical display — attach mirrors on-glass; re-mode is the
headless-box model.
- Capture-loss rebuilds targeting gamescope get a 100 s budget: the
40 s budget expired inside the first 45 s Steam-cold-start launch
attempt, a guaranteed single-shot failure.
- A PUNKTFUNK_COMPOSITOR pin now WARNs once per capture loss when the
live session no longer matches it (the pin disables
session-following — the reporter's original stream-death trigger).
- A managed session that took nothing over (client gamescope pin beside
a live desktop) is stopped on disconnect instead of being orphaned
forever.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Field triage (Nobara, Discord): the kde.md starter host.env told desktop
users to set PUNKTFUNK_COMPOSITOR=kwin, which PINS the backend — detect()
short-circuits and the capture-loss rebuild never re-detects — so a
mid-stream switch to Game Mode killed the stream instead of following it.
A follow-up hardcoded XDG_RUNTIME_DIR=/run/user/1000 anchor broke PipeWire
for any non-1000 uid (pw audio connect: Creation failed).
Revamp across every starter/example/reference:
- Desktop starters (kde/gnome/hyprland/sway) shrink to
PUNKTFUNK_VIDEO_SOURCE=virtual + an explicit warning that pinning
disables session-following; forcing a backend is CI/appliance-only.
- host.env.example: rewritten around auto-detection; anchors demoted to a
commented ssh/cron-only block with the uid trap spelled out; the
gamescope ATTACH/MANAGED knobs documented (previously missing);
case-sensitivity called out.
- packaging/bazzite/host.env + README: drop the uid-1000 anchors (a
systemctl --user service inherits/derives them); README's stale
PUNKTFUNK_COMPOSITOR=gamescope-era template synced to the real one.
- packaging/kde/host.env: loud APPLIANCE-ONLY header (it pins on purpose).
- configuration.md: session-anchors section inverted to "leave unset",
compositor row states the pin consequence, case-sensitivity note.
- troubleshooting.md: new "session fails right after editing host.env"
section (case, wrong-uid anchors, stale pin, restart-to-apply).
- gamescope.md/bazzite.md: attach/managed descriptions match current
behavior (managed is the infra-detected default; attach re-modes a
box-owned session to the client's resolution).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
- rebuild-check.sh + punktfunk-rebuild-check.service (enabled, ordered
Before=punktfunk-host): ldd-probes the host binary at session start —
milliseconds when healthy, a full update.sh rebuild only when a
SteamOS update actually broke its library links. update.sh restarts
go --no-block so the check → update.sh → restart chain can't deadlock
against the unit ordering. update.sh retrofits the unit.
- installer summary: web console is https (the unit serves TLS).
- docs: steamos-host.md (runner in the build step, keep-list + auto
rebuild = updates survive hands-free), gamescope.md (Gaming Mode
touch = single-finger pointer, exact taps, no multi-touch),
plugins.mdx (SteamOS runner note), scripts/steamdeck/README.md
(rebuild-check, runner payload, keep list, honest packaging
trade-off + the CI-prebuilt future direction).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Split the docs' single distro×desktop axis (ubuntu-gnome / ubuntu-kde / fedora-kde) into two,
which deduplicates the shared mechanics and scales to distros that run several desktops (Arch):
- Install the host — per distro/OS (ubuntu, fedora, arch, bazzite, steamos-host, windows-host):
GPU driver + package + input group, then a canonical "Configure your desktop" funnel.
- Configure your desktop — per compositor (kde, gnome, gamescope, sway): host.env, compositor
quirks, the headless session, and starting the host.
New shared web-console page (enable · login password · arm pairing) removes the console/password
block that was copy-pasted across all seven host pages. Merged ubuntu-gnome + ubuntu-kde into
ubuntu; renamed fedora-kde to fedora; kept bazzite and steamos-host as dedicated appliance guides
(trimmed of duplication). Moved the KWin headless session, the GNOME EGL/lock traps, and the
gamescope attach/managed model out of the distro pages onto their compositor pages.
Fixed while restructuring: distro-specific paths on kde (kde-desktop-setup.sh is Fedora/Bazzite-only;
the .deb ships host.env.kde under /usr/share/punktfunk-host), the interactive "start the host" step
that was lost in the merge, sway over-claiming Hyprland, and a pre-existing broken anchor in
how-it-works.
Removal of the three old pages was captured by the preceding commit b28ddfc (a concurrent commit
swept up the staged git-rm); the net docs tree is correct. Fumadocs build + internal link/anchor
check green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
