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>
Every host.env setting and PUNKTFUNK_* environment variable — compositor, video, input, gamepads, tuning — and how to use them.
The host reads its settings from ~/.config/punktfunk/host.env (a simple KEY=value file, #
starts a comment; keys are case-sensitive — punktfunk_compositor sets nothing, use the exact
uppercase names). On Windows the service reads %ProgramData%\punktfunk\host.env instead. Your
setup guide gives you a starting host.env for your desktop; this page is the
full reference for every setting.
You rarely need most of these. The host auto-detects the compositor, input backend, and
encoder from your live session — a box that flips between Steam Gaming Mode and a KDE/GNOME desktop
is followed automatically. The PUNKTFUNK_* knobs below are mostly optional overrides for
forcing a specific backend, tuning performance, or debugging. The starter host.env for your
platform sets only the few you actually need.
Session anchors
Leave these unset on a normal setup. Running as a systemctl --user service the host inherits
the correct XDG_RUNTIME_DIR from systemd, derives the session bus from it, and rewrites
WAYLAND_DISPLAY / XDG_CURRENT_DESKTOP / XDG_RUNTIME_DIR / DBUS_SESSION_BUS_ADDRESS on every
connect to follow the active session (Gaming ↔ Desktop) — a value written here can only be
redundant or stale.
Setting
When to set it
XDG_RUNTIME_DIR
Only when the host runs outside a user service (ssh, cron): /run/user/<your uid> — check id -u. A copy-pasted 1000 on a box where that isn't your uid points the host at another user's (nonexistent) PipeWire/D-Bus, and everything fails (audio Creation failed, no capture, clients report the host unreachable).
DBUS_SESSION_BUS_ADDRESS
Same cases only: unix:path=/run/user/<your uid>/bus. Otherwise derived automatically.
WAYLAND_DISPLAY
Only the dedicated headless-KDE appliance (wayland-kde, set by its shipped host.env.kde).
Which backend creates the virtual display. wlroots is sway/River; hyprland is its own backend. Leave unset. Setting it pins the backend and turns session-following off — per connect and mid-stream, so a Desktop ↔ Gaming switch kills the stream instead of being followed. For CI/tests and dedicated single-session appliances only.
PUNKTFUNK_VIDEO_SOURCE
virtual · portal
virtual creates a per-client display at the client's exact mode (the normal choice). portal captures an existing monitor instead.
PUNKTFUNK_ZEROCOPY
1 · 0(default on)
GPU zero-copy capture→encode (dmabuf → CUDA → NVENC, or D3D11 on Windows). On by default — no need to set it; it falls back to a CPU path automatically. Set 0 to force the CPU path. One exception: Windows Intel/QSV keeps the CPU path by default until zero-copy is validated on Intel hardware — set 1 to try it there.
PUNKTFUNK_INPUT_BACKEND
libei · gamescope · wlr · uinput
How input is injected. libei for GNOME/KDE, gamescope for Bazzite/gamescope, wlr for Sway/wlroots and Hyprland. Auto-detected with the compositor.
Encoder backend. auto (default) detects the GPU vendor: NVIDIA→NVENC, AMD→VAAPI/AMF, Intel→VAAPI/QSV. software (aliases sw/openh264) is the GPU-less H.264 path on both platforms — on Windows auto falls back to it when no GPU is found; on Linux it is explicit-only (auto never picks it).
PUNKTFUNK_RENDER_NODE
path
Linux DRM render node for zero-copy (default /dev/dri/renderD128). Set on multi-GPU boxes to pick the right GPU.
Resolution and refresh are not set here — the client chooses them. When a device connects,
the host creates a virtual display at that device's resolution and refresh rate. A 1080p60 laptop and
a 1440p120 desktop each get their own. (With Moonlight, set the mode in Moonlight; the native clients
let you pick a mode or default to the device's display.)
gamescope / session following (Linux, Bazzite/SteamOS)
Two mutually-exclusive models for a Steam/gamescope box. See Steam / gamescope for
the full picture (and Bazzite for that distro's specifics).
Setting
Values
Meaning
PUNKTFUNK_GAMESCOPE_ATTACH
1
Attach model: the box owns its gamescope session on its own display (you switch Gaming ↔ Desktop with the Steam UI); the host just 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 resolution — Game Mode on the virtual screen — restoring the box on idle.
PUNKTFUNK_GAMESCOPE_SESSION
steam
The host owns a gamescope-session-plus (Steam) session at the client's mode (headless appliance; no physical session running).
PUNKTFUNK_GAMESCOPE_NODE
auto · node id
Discover + 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 the backend in place, no reconnect). On by default on Bazzite/SteamOS; set 0 to disable.
Compositor-specific (Linux)
See your desktop page (KDE, GNOME) for when to set these.
Managing virtual displays — keep-alive after disconnect, exclusive vs. extend, and (on
Windows/KDE) persistent per-client scaling — now has its own settings surface in the web console
and display-settings.json. See Virtual displays. The two
*_VIRTUAL_PRIMARY knobs and PUNKTFUNK_MONITOR_LINGER_MS below still work but are superseded by
it (a settings file wins over them).
Setting
Values
Meaning
PUNKTFUNK_KWIN_VIRTUAL_PRIMARY
1
Make the streamed per-session output the sole desktop so plasmashell + windows render on it (not on the headless bootstrap output). Set by the KDE appliance host.env. Superseded by the console's Topology setting.
PUNKTFUNK_MUTTER_VIRTUAL_PRIMARY
1
GNOME/Mutter equivalent of the above.
Session recovery (Linux)
Setting
Values
Meaning
PUNKTFUNK_RECOVER_SESSION_CMD
command
Operator hook fired (debounced) when a client connects while no graphical session is live for the host's user — the state a compositor crash leaves behind (gnome-shell SIGSEGV → GDM greeter, whose auto-login is once-per-boot). Typically sudo -n systemctl restart gdm with a matching NOPASSWD sudoers rule, or systemctl restart display-manager under a polkit rule; with auto-login enabled the restart brings the desktop back and the client's automatic retry lands in it. Unset/empty = disabled (the default).
PUNKTFUNK_ON_CONNECT_CMD
command
Fired (detached) when a client connects, on either plane — the event JSON on stdin plus PF_EVENT_* env vars. The zero-config little sibling of hooks.json, which adds filters, webhooks, and debounce.
PUNKTFUNK_ON_DISCONNECT_CMD
command
The client.disconnected counterpart of PUNKTFUNK_ON_CONNECT_CMD (its PF_EVENT_REASON is quit, timeout, or error).
Video quality
Setting
Values
Meaning
PUNKTFUNK_FEC_PCT
N (percent)
Forward-error-correction redundancy for lossy links (the default is sensible for a normal LAN). Higher = more loss-resilient, more bandwidth.
PUNKTFUNK_10BIT
1 · 0(default on)
HEVC Main10 / HDR. On by default — the host permits 10-bit; a session goes 10-bit only when the client advertises it (behind the client's HDR setting). Set 0 to force 8-bit. Windows host, plus the Linux GNOME 50+ GameStream desktop mirror (PUNKTFUNK_VIDEO_SOURCE=portal, mirrored monitor in HDR mode — check with punktfunk-host hdr-probe). Linux virtual displays (native protocol, GameStream default) stay 8-bit: Mutter's virtual-monitor screencast is SDR-only upstream.
PUNKTFUNK_444
1 · 0(default on)
Full-chroma HEVC 4:4:4 (Range Extensions) — sharper text/desktop, no chroma loss. On by default on the host; the client's own 4:4:4 setting (default off) is the real switch. Set 0 to force 4:2:0. punktfunk/1 native only (Moonlight stays 4:2:0), HEVC-only, honored only when the client advertises 4:4:4 and the GPU supports it (probed; NVENC is the validated path — VAAPI/AMF/QSV decline). Independent of 10-bit.
PUNKTFUNK_CHACHA20
1 · 0(default on)
ChaCha20-Poly1305 session encryption for clients without hardware AES (old ARM TVs, e.g. webOS), lifting their ~100 Mbps software-AES decrypt ceiling. On by default on the host; a session uses it only when the client requests it — everyone else stays on AES-GCM. Purely a performance choice (both ciphers are full-strength); set 0 to force AES-GCM for all sessions.
PUNKTFUNK_PYROWAVE_MAX_MBPS
N (Mbps)
Cap the PyroWave Automatic bitrate pin, for a host on a link that the open-loop pin can outrun (e.g. 4:4:4 + HDR at 5120×1440@240 pins ~5.3 Gbps, over a 5GbE link). Unset = no cap. Only affects Automatic (bitrate 0) PyroWave sessions; an explicit client bitrate bypasses it.
PUNKTFUNK_DSCP
1
Opt-in DSCP / SO_PRIORITY QoS tagging on the media sockets. No-op on the wire on Windows without a qWAVE policy.
PUNKTFUNK_OH264_THREADS / PUNKTFUNK_OH264_GOP
N
Software (openh264) encoder tuning: encode threads (default 2 — latency over throughput) and GOP length (default 0 = encoder-auto). Only relevant with PUNKTFUNK_ENCODER=software.
The virtual pad the host creates. Usually auto-resolved from the client's physical controller — set this only to force a type. xbox360 (XInput) is the universal fallback. dualsenseedge gives the client's back paddles native buttons; switchpro gives Nintendo-family pads correct glyphs/layout + gyro. steamcontroller2 (the 2026 Steam Controller) is passed through as-is — the host presents a real SC2 (28DE:1302) that Steam Input drives directly, mirroring the physical pad's raw reports (Linux only). DualSense (Edge)/DualShock 4 work on Linux (UHID) and Windows (UMDF); the Steam Deck pad too (Windows via the promoted UMDF identity); Switch Pro and the classic Steam Controller need Linux UHID. Unsupported choices fold to Xbox 360.
PUNKTFUNK_STEAM_GADGET
1 · 0
Force the raw USB-gadget virtual Steam Deck on/off. On by default on SteamOS, off elsewhere. Lets Steam promote the virtual Deck to full Steam Input.
Audio / microphone
Setting
Values
Meaning
PUNKTFUNK_AUDIO_GAIN
float (default 1.0)
Linear gain applied to capture — bump it for a quiet source.
PUNKTFUNK_MIC_DEVICE
name substring
(Windows) Target mic-uplink device by friendly-name substring (first match wins).
PUNKTFUNK_NO_MIC_INSTALL
set
(Windows) Skip installing the virtual-mic driver (e.g. when the host runs as SYSTEM).
Windows host
Setting
Values
Meaning
PUNKTFUNK_VDISPLAY
pf
Virtual-display backend. The bundled pf-vdisplay IddCx driver is the only backend now — informational; leave as pf.
PUNKTFUNK_SECURE_DDA
1
Capture the secure desktop (UAC / lock / login) so the stream survives those transitions.
PUNKTFUNK_MONITOR_LINGER_MS
ms (default 10000)
Defer tearing a per-client virtual display down after disconnect. A reconnect inside the window preempts it and creates a fresh one (a reused IddCx swap-chain is dead); the stable per-client monitor id keeps Windows' saved display config applying either way. Superseded by the console's Keep alive setting — see Virtual displays.
PUNKTFUNK_RENDER_ADAPTER
description substring
Multi-GPU boxes only: force the NVENC/capture GPU by adapter Description substring (e.g. 4090). Leave unset on single-GPU machines.
PUNKTFUNK_HOST_CMD
e.g. serve --gamestream
The host subcommand the service launches. Default serve --gamestream; use serve for a secure native-only host.
Network & discovery
Setting
Values
Meaning
PUNKTFUNK_MDNS
1 · 0(default on)
mDNS adverts (native + GameStream). 0 skips them (same as --no-mdns) — for networks/containers where multicast doesn't work; add the host by address in the client instead.
PUNKTFUNK_DATA_PORT
port
Pin the per-session video data plane to a fixed UDP port and stream direct (no hole-punch) — open exactly that port in the host firewall. Same as serve --data-port; see Troubleshooting. Default: random port + hole-punch.
Auth, API & paths
Setting
Values
Meaning
PUNKTFUNK_MGMT_TOKEN
token
Bearer token for the management API. If unset it's auto-generated and persisted to ~/.config/punktfunk/mgmt-token (the bundled web console sources it). Set only to pin a specific token.
PUNKTFUNK_UI_PASSWORD
password
Web-console login password. Normally generated on first start and stored in ~/.config/punktfunk/web-password — see Forgot your Password?.
Leave these at their defaults unless you're chasing latency; see the troubleshooting
notes for context.
Setting
Values
Meaning
PUNKTFUNK_GSO
1 · 0
UDP Generic Segmentation Offload on the send path (coalesce a frame's packets into kernel super-buffers) — cuts send CPU ~30%, but its line-rate packet trains can cost delivered throughput on constrained links (measured on a 2.5GbE hop). Off by default until send pacing spaces the super-buffers; set 1 to opt in (auto-falls back to sendmmsg on kernels/paths without support).
PUNKTFUNK_SPLIT_ENCODE
0/disable · 1/auto · 2 · 3
NVENC N-way split-encode for very high pixel rates (5K@240). auto picks automatically above ~1 Gpix/s.
PUNKTFUNK_GPU_PRIORITY_CLASS
off · normal · high · realtime · auto
(Windows) GPU scheduling priority for capture/encode under a GPU-saturating game. Default auto (starts high, upgrades to realtime when it's safe — e.g. HAGS off); high pins the static pre-gate behaviour; realtime is the strongest lever but can freeze NVENC on some setups.
PUNKTFUNK_IDD_DEPTH
N (default 2)
(Windows) IDD-push pipeline depth. 1 cuts latency once GPU priority is raised; higher smooths a contended GPU.
Log verbosity. On Windows, logs land in %ProgramData%\punktfunk\logs\ (size-capped: a file over 10 MB is rotated to .old at the next service/host start, one generation kept).
PUNKTFUNK_FFMPEG_DEBUG
set
Verbose libavcodec/FFmpeg logging from the encoder.
PUNKTFUNK_VIDEO_DROP
N (percent)
Deliberately drop N% of video packets to exercise FEC recovery. Testing only.
Client-side (native clients)
A few knobs are read by the native clients, not the host:
Force the decode path. Default auto-selects hardware per vendor (Linux: VAAPI on Intel/AMD, Vulkan Video on NVIDIA and the Steam Deck; Windows: Vulkan Video on NVIDIA/AMD, D3D11VA on Intel and others) with a software fallback.
Bitrate
The client requests a bitrate; the host encodes to it. There's no host-side bitrate knob. To find a
good value:
Native clients (Apple, Linux, Windows, Android): use the built-in speed test (from a
host's menu). It measures your link, suggests a bitrate, and applies it.
Moonlight: set the bitrate in Moonlight's settings. Start moderate and raise it.
Multiple devices at once
The native punktfunk/1 host (serve) streams up to 4 sessions at once by default (an encoder
bound); further clients wait in the accept queue until a slot frees up. Each session gets its own
virtual display at the client's exact resolution, sharing the host's input/audio/mic services. The
limit isn't settable from serve's command line yet — punktfunk1-host, the standalone test host,
exposes it as --max-concurrent N (see the Host CLI reference).
Codec and FEC
Client and host negotiate the codec: HEVC (H.265) by default, AV1 for clients that
support it, and H.264 when the session runs on the GPU-less software encoder.
The native protocol adds forward error correction for lossy links — see PUNKTFUNK_FEC_PCT above.
enricobuehlerandClaude Fable 5
e35dad529b