To add a complicating factor, from this blogpost [1] GitHub say's "...if you provide private repository content as input to an AI Feature, we may use that input to improve AI features".

So I assume that if you were to supply a significant chunk of code to AI and ask for a code review, then your code could end up in the training data even though it wasn't written by AI (unless you know there's a manual opt-out option [2]).

[1] https://github.blog/changelog/2026-03-25-updates-to-our-priv... [2] https://github.com/settings/copilot/features