Verified live on a SteamOS 3.8.14→3.8.16 update: the A/B partset switch
rebuilds /etc and drops everything not on Valve's keep list — the udev
rule (uhid access: virtual pads silently degrade to Xbox 360), the
vhci-hcd autoload (native Deck pad transport), and the UDP buffer sysctl
(back to 208 KB → stutter). Valve's sanctioned extension point is a
drop-in under /etc/atomic-update.conf.d/ — itself on the stock keep
list, so it self-preserves. install.sh §4 and update.sh now register
scripts/punktfunk-atomic-keep.conf there.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
