I find that for dev workflows (even outside firefox containers) to not mix up badly, you end up needing to split localhost anyway - so for example, binding to specific IPs inside 127.0.0.1/8 (it's a whole /8, you're usually not running out of that), or, depending on how badly you need ::1/IPv6 bindings, service.localhost6 or service.localhost6.localdomain6 style names instead of just localhost.