It led with `--mgmt-bind 127.0.0.1`, a rare cause, and never mentioned the one
fact that actually explains the symptom: the library rides the management API on
a different port (47990) than the QUIC stream plane (9777), so it can fail while
streaming to the same host works. Field triage of exactly that case spent hours
on the stream path before anyone questioned the port.
Leads with that now, and names browser-testing the port as the fast split between
"unreachable" and anything client-side.
enricobuehler
bae8742e48