The mirror has had a management API since it was built, and the only thing
driving it was curl on the mirror's own machine. This is the other half: a
client, so the operations belong to whatever has a reason to perform them.
The mirror's refusals travel as their own sentence rather than a status code.
Putting the reason in the body was deliberate on the server side, and a client
that kept only the number would undo it — "the mirror said 400" sends somebody
to the wrong machine, "the source URL answered 404" sends them to the right one.
NextProtos is cleared for the same reason the mirror's server clears it. That
configuration is shaped for the agent stream, which pins h2; a transport
carrying a pinned protocol it is not set up to speak negotiates h2 and then
talks HTTP/1.1 over it, and fails with an error mentioning neither ALPN nor
the mirror.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
