Observed live on a Deck host: the user switched Game Mode → Desktop, KDE came
up in 0.8 s — and the capture-loss rebuild's FIRST detection ran inside that
gap, still said Gaming, and its gamescope re-acquire restarted
gamescope-session.target. On SteamOS that steals the seat: the user was
yanked out of the KDE session they had just chosen, the two session managers
fought (job canceled / dependency failed), no gamescope node appeared within
30 s, and the stream died at the 40 s rebuild budget.
A rebuild probe acting on possibly-stale detection must never stop, relaunch,
or take over box sessions. New pf_vdisplay::rebuild_probe_scope (RAII,
counted): while held, the gamescope managed/takeover create paths only attach
to a live node and fail fast otherwise — no stop_autologin_sessions, no
session-plus relaunch, no gamescope-session.target restart. The capture-loss
loop holds it for the first 4 s after a loss (the detection-ambiguity
window); after that, destructive rebuilds are allowed again, so a genuine
switch INTO Game Mode still gets its headless takeover. Probe failures are
instant, so the loop now paces itself at ~2 Hz instead of spinning.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
333c8979e9