The librarian
The librarian reads your threads as they go and keeps your projects tidy. It files each thread in a project, making one when none fits, keeps each project's state up to date, adds a repo to a project's folders once its threads work there, and renames threads that have wandered off from their title (never one you named). It also looks after the Pocket cards threads filed.
It looks after a thread's first message and when a turn ends, then catches up at most every 20 minutes while the thread keeps going. A catch-up after only a quick reply is skipped without asking anything.
Each look is one short call to Haiku, Claude's small, cheap model, rather than the model your threads run on. It runs on one of your own Claude logins: the one with the most room in the pool picked under Runs on (the same pool that writes thread titles, also in Settings › Models), and it counts towards that login's usage like any other call. When every login in the pool is out of room it waits, and with only Codex logins it doesn't run at all. Threads in a private folder (Settings › Models) are never sent to it.
The Librarian view lists what it did and what it will look at next. Turn off Look at threads there to pause it; what's queued waits until you turn it back on. If it files a thread wrongly, take the thread out of the project and it won't put it back.