I don't think this is a problem.  There is no precedent that socket files need to be randomised.  For example, if you run postgresql you may have a socket file `/tmp/.s.PGSQL.5432` (predictably the same on every run).  MySQL does something similar.

I remember that we discussed this months ago on IRC and I could not reproduce the threat scenario you suggested exists here.

Besides: with a random socket file name (that is created by the backend), how is the client supposed to know how to connect?  Well-known socket files are roughly equivalent to well-known ports.

I hold that this is no problem and doesn't need to be changed.