If the public API is changed in a not-backward-compatible way, I would suggest to release new ASDF system (bordeaux-threads2), and leave the old version available in quicklisp forever.
People who are ready to use new version, just add bordeaux-thread2 into their ASDF dependency. Others are able to use old version.
This is a good practice. And it costs nothing.
IMHO it's not a good practice and it does cost complexity/noise. you lose the clarity around the digital representation(s) of the identity of the library. there's only one b-t library, and the fact that it has changed in a way that made it incompatible with something else does not change its identity. but it's only the 0.02 of an outsider... -- attila Notice the erosion of your (digital) freedom, and do something about it! PGP: 2FA1 A9DC 9C1E BA25 A59C 963F 5D5F 45C7 DFCD 0A39 OTR XMPP: 8647EEAC EA30FEEF E1B55146 573E52EE 21B1FF06