@olympionex - fyi, these days snapd allows snaps to create/use a snap-specific directory in /run/snap.<snap name>/ and any commands within the snap are able to access those files. That should cover many use cases. For snap-to-snap communication, that can either be done via the content interface or implementing an application specific interface, like with mir, udisks2, etc. It really depends on the situation. You may want to start a new topic if this doesn’t meet your needs and can discuss paths forward.
/me notes that /var/run is typically a symlink to /run these days