in SLF4J-389, having slf4j simple provider caching System.out and System.err was though as a bug, annoying some people in their integration where they prefer not caching and benefitting from code changing System.out/err value to change slf4j simple output

In Maven, this cache is more seen as a feature, that prevents changing Maven output location in a plugin that would play with System.out/err for integrating some code: Maven is an open world, I didn't find such a plugin, but it may exist and the new not-caching slf4j simple would more been seen as a bug for us.

In fact, caching is not per se a bug: it's a feature that can be useful to disable (or the oposite, to enable when you want it)

Please add a configuration to enable/disable caching: I don't know if caching should be enabled by default or not, it depends on what you consider the default behaviour of slf4j simple provider for years