The answer is definitely not "no", but as far as I'm aware we haven't found any particular cases where that level of formalism and that specific style of arrang

The answer is definitely not "no", but as far as I'm aware we haven't found any particular cases where that level of formalism and that specific style of arrangement would help. In an open source world where multiple shipping operating systems are based on (different snapshots of) the same core code and interfaces, it seems much more valuable to try and push straight to Committed interfaces (public, stable, documented) where we can. There are plenty of cases where people use Uncommitted interfaces today in things that they layer on top in appliances and so on, but mostly it's expected that those people are paying attention to what's being worked on and integrated. When folks pull new changes from illumos-gate into their release engineering branches or soft forks, they're generally doing that explicitly and testing that things still work for them. Also, unlike the distributions (who ship artefacts to users) it doesn't really make much sense for us to version illumos itself. This makes it a bit harder to reason about when it would be acceptable to renege on an interface contract, etc. In general we try to move things to Committed over time, and then generally try very hard never to break or remove those things after that point.