Little thought yet but related, figured if client host is dual stack, could separate "client over WAN via IPv<whatever> to reach relay" function from traffic routed into tor's cells for carriage to pop out other side, like a VPN for IP versions. Exits would have to tag their support of "exit v4 and/or v6 to clearnet" in consensus so circuits get built to a place that can actually ship the client's cells out to clearnet. Relays WAN function already offer inbound connection capabilities by their listed OR IP format in consensus, but not yet any outbound IP version, which client must also know from consensus and compute to reach next input. Building WAN paths is different from what is carried within. So that, it seems possible, if in consensus, to make WAN path like... v6 cells ==> client v6 - v6 guard v6 - v6 mid v4 - v4 exit v6 ==> v6 clearnet v4 cells ==> client v6 - v6 guard v6 - v6 mid v4 - v4 exit v4 ==> v4 clearnet Not quite sure why yet, or if theory correct.