Function call_output 

async fn call_output(
    state: &TransportState,
    key: &SessionSlot,
    call_id: &str,
) -> CallOutput

A call’s own output, read from the transport’s held copy of its seat.

The frame that names the file is a ChatAppended row the fold has already applied, so the held conversation is where the read resolves it; a seat this transport holds nothing for has no conversation to name one.

Both the copy’s lock and the file read block, so they run off the connection’s loop the way every other conversation read here does.