A browser launched from ssh, systemd-run --scope, or set-environment does not get environment.d -- and on taimen that means Skia-GPU

scope: generic · severity: trap · confidence: proven · subsystem: graphics

Evidence

2026-09-02 taimen, webkit2gtk-6.0 2.52.6. Epiphany launched via systemd-run --user --scope ... epiphany from an ssh shell: /proc//environ had no WEBKIT_SKIA_ENABLE_CPU_RENDERING; YouTube’s like/dislike/bookmark/menu icons rendered as noise, the tab’s WebKitWebProcess held 877-912 MB of DRM memory (fdinfo), the scope hit MemoryHigh=1500M in 20 s and systemd-oomd killed it at +87 s (app.slice pressure 80.85% > 50% for 30 s). Same URL with the env passed explicitly on the command line: environ shows the flag, every icon clean, DRM 339 MB, scope 898 MB, swap 0, no oomd. systemctl --user set-environment WEBKIT_SKIA_USE_LINEAR_TILE_TEXTURES=1 before a –scope launch: web process dmabuf_fds=0 (flag never arrived); same flag on the command line: 167 dma-buf fds and 178 PRIME_HANDLE_TO_FD in strace.

~/.config/environment.d/*.conf reaches only what the user manager spawns. An icon tap (D-Bus activation), gtk-launch through the session bus, and systemd-run --user services get it. These do not:

• ssh phone 'setsid epiphany URL' – the ssh session’s environment;
• systemd-run --user --scope ... epiphany – a scope is your own fork, moved into a cgroup; it inherits your environment, not the manager’s;
• systemctl --user set-environment FOO=1 followed by either of the above – it changes the manager’s block, which those launches never read.

The launch looks right (real app-*.scope, powerhintd fires, mempressure finds it) and the browser comes up, so nothing complains. On taimen the missing variable is WEBKIT_SKIA_ENABLE_CPU_RENDERING=1, and without it WebKit paints with Skia-GPU on the a540 – the path panel-corruption-was-gpu-reset-wreckage-not-tearing condemned. Three symptoms follow and each was chased as its own bug before the environ check:

symptom	Skia-GPU (flag lost)	CPU rendering (flag present)
YouTube icons	like/dislike/bookmark/menu filled with noise	clean
tab WebProcess DRM memory	877-912 MB	339 MB
scope after 35 s, page idle	1211-1311 MB, swapping, oomd at +87 s	898 MB, swap 0, no oomd

Positive control, every arm: sudo tr '\0' '\n' < /proc/$(pgrep WebKitWebProc | tail -1)/environ | grep WEBKIT_. An arm whose variable is not in that output measured the default, whatever the launcher said. For flags that change allocation, add a second control that cannot lie: WEBKIT_SKIA_USE_LINEAR_TILE_TEXTURES=1 must show dma-buf fds in the web process (ls -l /proc/PID/fd | grep -c dmabuf); zero means it fell back.

How to launch for a measurement: pass the variables on the command line of the scope, e.g. systemd-run --user --scope -u app-gnome-org.gnome.Epiphany-$$.scope env WEBKIT_SKIA_ENABLE_CPU_RENDERING=1 ... epiphany URL, and read them back from environ. Also delete ~/.local/share/epiphany/session_state.xml between arms: every epiphany URL against a running instance adds a tab, an oomd kill keeps them all, and the next launch restores every one – sixteen YouTube tabs and eight web processes were “the memory ceiling” for three arms on 2026-09-02.