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Field-diagnosed on Nobara (fc44, canary g13179011), where Game Mode became unstartable and the box was handed to plasma. #144's bind works — the patched build genuinely reaches a session script that hardcodes /usr/bin/gamescope — but a mount namespace in a systemd USER unit is also a USER namespace, and only this uid is mapped in it. Measured on the box: on disk / in a unit without the bind : drwxrwxrwt 2 0 0 /tmp/.X11-unix in a unit WITH the bind : drwxrwxrwt 2 65534 65534 /tmp/.X11-unix uid_map inside : 1000 1000 1 wlroots checks that /tmp/.X11-unix is "owned by root or us", sees nobody, and refuses: wlserver: [xwayland/sockets.c:100] /tmp/.X11-unix not owned by root or us wlserver: [xwayland/sockets.c:217] No display available in the first 33 -> SIGSEGV in run_pipewire Three ~10 s failures then feed chimeraos' short-session tracker, session-plus stops even trying, and steamos-session-select rewrites the user's session to plasma. So the symptom an operator reports is "thrown onto KDE and I can't get back" — two removes from the cause. Two further bugs found while fixing it, each worse than the one reported: * THE BIND WAS ARMED EVERYWHERE. The condition was only `gamescope_bin() != /usr/bin/gamescope`, so every box with punktfunk-gamescope installed took a namespace it has no use for — Bazzite, SteamOS-likes, the Deck. The blast radius was every gamescope box, not just the hardcoded-path ones the mechanism exists for. Now the host READS the session script and arms only where it never mentions GAMESCOPE_BIN and names /usr/bin/gamescope outright; everything else is bit-for-bit pre-#144, no namespace at all. An unreadable script does not arm. * THE DROP-IN OUTLIVED ITS SOURCES. It was written to ~/.config/systemd/user/ on the TEMPLATE, so it also applied to the box's OWN autologin unit at every boot — while both paths it binds live in tmpfs. After a reboot the drop-in survives and its sources do not, and BindReadOnlyPaths= with a missing source fails the unit outright. THAT is why the field symptom survived a reboot. It now lives in $XDG_RUNTIME_DIR (dies with the login session), removal covers both the runtime and the legacy $HOME path, and restore_takeover_on_startup does that removal unconditionally at host start — which is the upgrade path for every box already running canary g13179011. Without it, updating the host would not un-brick them. * A bind was armed even when gamescope_bin() fell back to the bare name "gamescope". The wrapper execs `gamescope` through PATH inside the unit — onto the path we just bound the wrapper over. Fork bomb. Refused ahead of even the operator's force. Where the bind IS armed it now carries its own compensation: a user-owned $XDG_RUNTIME_DIR/punktfunk-x11 bound read-WRITE over /tmp/.X11-unix (Xwayland creates the socket there), so the ownership check sees "us". Skipped when that directory is already ours or absent — neither is the hazard. Stale sockets are pruned by connect-test so a SIGKILLed session cannot walk the 33 display slots away. And rather than trust that reasoning, the host now ASKS THE BOX before arming: it runs the field reproduction with the real property set — `systemd-run --user --wait --collect --property=<the same args> -- stat -c %u /tmp/.X11-unix` — and arms only if the answer is our uid. Anything else (65534, a rejected property, no user manager, a blown 10 s budget) means no bind, and the session runs stock gamescope: no HDR, no in-node cursor, but it STARTS. A runtime backstop disarms and relaunches if a session launched with the bind armed produces no node in its window, latching one-way per process. The XFixes-cursor concern that argued against relocating the socket does not hold: the only host-side X client is spawned under `plan.gamescope_cursor`, which is `gamescope && !gamescope_composites_cursor()`, and our shipped +pfhdr4 build is patch level 4 — so on the very route where the bind arms, that reader is never constructed.