I agree it’s grey-area, but I’d lean towards calling it a breaking change, as it’s not too hard to imagine setups that would rely on a particular stdout format

I agree it’s grey-area, but I’d lean towards calling it a breaking change, as it’s not too hard to imagine setups that would rely on a particular stdout format (e.g. some kind of log-parsing to generate an HTML report from an e2e test orchestration suite). But this is a major update, so breaking is fine anyway.