As stable as, say, golang's standard library.
Sure, it needs upfront thinking and commitment, but it's not that difficult and might be well worth it.
In the case of coreutils, the problem space is fairly simple and well-understood, so it should be quite easy to commit to a stable interface. Even for something exceptionally complex like a web browser, I'd expect most components to be easily kept backwards-compatible in terms of public api.
> As stable as, say, golang's standard library. Sure, it needs upfront thinking and commitment, but it's not that difficult and might be well worth it.
That's actually far less stable than is needed for core utils.
In the case of coreutils, the problem space is fairly simple and well-understood, so it should be quite easy to commit to a stable interface. Even for something exceptionally complex like a web browser, I'd expect most components to be easily kept backwards-compatible in terms of public api.