ReadonlychannelReadonlyendpointThe resolved input endpoint feeding the channel, or null when the channel is
unpatched (its last source was removed — the head is fed by nothing).
ReadonlysourceThe registered source id the channel references, or null for a raw endpoint.
Readonlytype
Broadcast after a crosspoint write (PATCH /patch/input/{kind}/{index}): a channel's current source assignment — either the registered source id it now references, or the raw endpoint it reads (for an implicit source). So every client converges on the source → channel crosspoint state.