A request that cannot be routed now says so

When a request could not be routed onward — because the hub it had to travel through was in the middle of shutting down, or because it was caught bouncing between hubs with nowhere to land — the failure was thrown away instead of being sent back. Nothing was broken and nothing was busy; the caller simply waited for an answer that no longer existed. In the browser that looked like a page or a panel that spins indefinitely.

Those failures are now reported. The caller gets a real error naming what went wrong, and where the cause is a hub restarting, it is reported as temporary so anything that can recover on its own — a live view, an open document — reconnects instead of giving up.