Running a 4K Sonarr or Radarr alongside your main one

The question: I have a second Sonarr for 4K. How do I get titles into it without doing it by hand?

What Kustos does

• Both instances are connected as their own cards, and Kustos usually finds them for you. See Applications → Sonarr / Radarr instances.
• A rule promotes a title. Add to another instance takes a title that matches your conditions and adds it to the second one, with that instance's own quality profile and root folder. See Arr Rules.
• Tags can be kept in step between the two — append, mirror, or un-mark-only — so a tag you use to drive something on the main instance does not go stale on the 4K one.
• "Already on another instance" is a condition, so a rule can act on what one instance holds and the other does not.
• Artwork follows the title, not the instance. A poster, background or season poster set on a title reaches every Plex copy of it: both libraries when the 4K copy lives in its own Plex library, and every copy when 4K and HD sit unstacked in one library. You dress a title once.
• Searching only the season somebody is on is a setting, and it exists for exactly this case: most seasons of an older show simply do not exist in 2160p, so a 4K instance that searches every gap asks indexers for releases nothing has ever checked for.

A warning that applies to any multi-instance setup. An unreadable instance reports unsupported rather than answering "not there". That is deliberate: a rule keyed on "already on the 4K instance" would otherwise match your entire library the moment that instance went down.

Where Kustos does not help. It does not install or configure Sonarr and Radarr for you from nothing on every platform, and it does not solve the parts of a dual-instance setup that are genuinely about your disks — root folders, remote path mappings, and whether both instances can see the same storage. Those are yours to get right, and Kustos works with whatever you decide.