There has to be a second PR approver. There's no way a company as large this can allow an individual the ability to push to production without a secondary person involved.
When there's at least two people involved you can then start to look at more systematic factors that go beyond any single human mistake.
When both the submitter and approver miss that there's no changelog entry for a PR does that mean a checklist is needed? Should the changelog be automated with the commit message which can be improved for external consumption?
I'd find it very hard to believe that this high profile change just happened to be the only change missing from the changelog.
Bugs are always going to happen but housekeeping like writing something to a changelog when a commit is merged can be quality assured.
I don't know, this is a company that is pushing the narrative of software engineers becoming obsolete. Why do you think they would have respect for Software Engineering processes. As few as they are concerned, a few coders working in isolation with Claude Code is all that you need. (pun unintended)
If there really is no PR reviewer and no separate QA what is Anthropic even doing. I have respect for someone owning their mistake but as others have mentioned it reveals what may be a systemic issue.