Bazzite (and SteamOS-like hosts) run Steam Big Picture inside their OWN
gamescope-session-plus session. Nesting a second gamescope+Steam can't work — the
second Steam sees the first and exits, taking the nested gamescope down with it
(crash in its exit handlers), killing both video and input. The robust model is to
let punktfunk OWN that session: run gamescope-session-plus headless at the client's
resolution (full Steam Deck UI polish: MangoApp, VRR, controller config) and have
the host ATTACH to it rather than spawn its own.
The video half already existed (PUNKTFUNK_GAMESCOPE_NODE=<id> attaches to a
PipeWire node). This finishes it:
- PUNKTFUNK_GAMESCOPE_NODE=auto discovers the gamescope Video/Source node, so the
(dynamic) node id needn't be hand-wired.
- The attach path now also points the libei injector at the running session's EIS
socket: find_gamescope_eis_socket() scans XDG_RUNTIME_DIR for gamescope-<N>-ei,
connect()-probes each (stale dead-session sockets refuse), and writes the newest
live one to the relay file the injector reads. So input reaches the attached
session with zero manual config.
scripts/punktfunk-steam-session.service: a systemd --user unit that runs
gamescope-session-plus headless at a configured resolution, with the one-time
headless-appliance setup (linger + multi-user.target) documented inline.
Validated live on bazzite (RTX 4090): the full Steam Big Picture session streams
(1499 frames, p50 ~1ms) with mouse/keyboard injected into it (device resumed, all
caps, emitted=true), node + EIS socket both auto-detected.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
