100% open (there is no mirror repo that I'm aware of). There's certainly internal discussion, particularly when some members of the team don't want to be "seen

100% open (there is no mirror repo that I'm aware of). There's certainly internal discussion, particularly when some members of the team don't want to be "seen in public", but this isn't like other projects where it's sync'ed from a hidden internal repo. Disclaimer: while I work at Google on Cloud, and know the K8s folks, I've never even committed any changes.