Installing & Updating
A plain build-and-install script handles vendored packages, triggered automatically by the same pacman upgrade that updates everything else.
Vendored AUR and custom packages are built with plain makepkg (as a dedicated unprivileged sobarch-build user, never as root) and installed with pacman -U, the same thing an AUR helper would do under the hood, just without the standing ability to build any AUR package unreviewed. The script fetches the current repository snapshot first, so it always sees the packages as they are now.
Installing one on demand
From the desktop: Super → Sobarch → Install Apps. This flattens every software profile's packages into one deduped list (not-yet-installed packages first, tagged with their profile and AUR where it applies; installed ones follow, marked installed) and installs whichever one you pick: official-repo packages via pacman, AUR/custom packages through the same sync mechanism described below. A failed AUR build points you to /var/log/sobarch/aur-sync.log.
Staying up to date
There's no separate timer for building vendored packages. A pacman hook fires after every transaction that upgrades a package (pacman -Syu, or any other upgrade), and starts the sync script as a detached systemd unit, sobarch-aur-sync. It's detached because pacman still holds its database lock while hooks run, so the sync has to wait for your upgrade to finish before it can install anything. The upgrade itself returns immediately; the sync carries on in the background and notifies you if something goes wrong.
The sync diffs the versions pinned in the repository against what's actually installed and rebuilds anything behind. It only ever touches vendored packages that are already installed, so it never installs a profile package you didn't pick. The hook is refused rather than stacked if a sync is already running, a hand-run sync waits for the lock instead of overlapping, and the hook does nothing inside a chroot or when the sync script's own pacman calls fire it again.
One gap is accepted on purpose: a pacman -Syu that upgrades nothing runs no transaction, so the hook doesn't fire. Vendored packages are then rechecked on the next real upgrade or the next Update System run.
For a one-click version of the whole thing, Super → Sobarch → Update System runs pacman -Syu, then the same sync, then your config merge, with progress notifications. Raw pacman -Syu keeps working unchanged. Update System also installs any "every install" package (see AUR & Custom Packages) that was added to the distro after your system was installed, since the background sync only updates what's already present.
Update notifications
A daily background check (a systemd user timer, first run ten minutes after login) notifies you when official-repo updates or a new sobarch-skel/sobarch-scripts are pending; click the notification to open Update System. It only looks, never installs, and re-notifies at most weekly for an unchanged backlog. If you set up rescue media, the same check also tells you when a newer Arch ISO than the one on the rescue partition is available, and clicking that notification opens the refresh prompt. A failed or offline check is treated as "unknown", never as "nothing to do".
From a terminal
sobarch aur-sync runs the same sync by hand (with no arguments it updates what's already installed; with package names it installs exactly those, from the vendored set only), and sobarch update does the full system update described above. See The sobarch Command for the full list.
When a build fails
If a vendored package fails to build or install during the automatic sync, you get a critical desktop notification listing which packages failed, since the hook runs without a terminal you'd necessarily be watching. The full output is in /var/log/sobarch/aur-sync.log and in the journal under sobarch-aur-sync.