Deleting a show someone was half-way through

The question: my cleanup tool deleted a series someone in the house was still watching. How do I stop that happening?

This is the single most expensive mistake a media-library cleanup can make, and it is almost always the same cause: the tool asked one source about who had watched what. Plex's own history can be off. Tautulli can have been down for the week that mattered. Trakt only reports at series level, so it cannot tell you somebody is four episodes into season three.

What Kustos does

• Watch state is merged from Plex history, Tautulli, Trakt and Simkl into one picture per person. A gap in one source cannot drop a title somebody is still watching, because the others still carry it. See Watch state is merged from several sources.
• Per person, not per server. A cleanup rule can require that everybody who has started a show has finished it, rather than asking whether the server-wide view says watched.
• Per episode where the source supports it. Movies work on any single source. TV per-season needs a per-episode source — Plex history, if you have it enabled, or Tautulli. Trakt alone reports at series level only, and Kustos says so rather than quietly answering from it.
• An unreadable source reports "unsupported", never "not watched." This is the part that matters most: guessing "nobody watched it" when a source is down is what releases a whole library at once.
• Dry run first, always. See Dry run first, always.

Where Kustos does not help. It cannot invent history that no source recorded. If somebody watched a show on a device that scrobbled nowhere, no tool can know. What Kustos can do is refuse to treat that silence as proof.