It’s really on a case by case basis so it’s hard to give general advice, it’s what works for your team. You can 1) push back on the external library upgrade 2) upgrade B 3) delete B (all of these have the property of assuring your master branch only has one version of the external library running) 4) break B and make it incumbent on the team responsible for B to upgrade later 5) shade the external dependency and/or play other tricks to deploy multiple versions. I’ve known teams to do all of these depending on stage of the company, number of engineers, etc.