source?
edit: it seems asking for a source it frowned uppon in this site. And it seems there's no source.
I don’t know about hosting it internally but a an Apple focused podcast I listen to (Accidental Tech Podcast) has mentioned numerous times in the last few months they’re using Claude heavily. And they know Apple insiders.
I don't believe it's published anywhere, but it's common knowledge to Apple engineers. I can second the poster's assertion that they run Claude internally.