Hi! We’ve had a regression with post-cache edge functions that was resolved last friday, 6:30am UTC.
The /.netlify/internal/ef-cache path is, as you correctly assumed, an internal thing and shouldn’t be shown to edge functions users - but through a bug in a deployment, this wasn’t hidden from users correctly. We’ve since fixed the bug.
Here’s a related forums post that we kept up-to-date: New error in edge function when calling response.text()