Ceki, the more important part of my question was: how is ContextSelectorStaticBinder used now in Logback? Is it guaranteed that the existing SLF4J provider will call ContextSelectorStaticBinder.init() Or is this just a class that is sitting there now unused for the moment?

In my preliminary tests, even with Logback 1.4.x as the SLF4J implementation, ContextSelectorStaticBinder.getSingleton().getContextSelector() is returning null. So can you confirm that ContextSelectorStaticBinder is currently unused and not configured when SLF4J 2.x is used?