There has been no apparent change in the medium. Developers are still writing out their code in a programming language, inputting that code into a compiler, and see another representation of that program come out on the other side. Just like we've been doing since the early days of using digital switching. Whether or not a compiler is built using an LLM is just an implementation detail.
It does appear that the REPL has grown in popularity where in the past was used sparingly, but I don't really think a small difference in input method is a change in medium. I don't consider the introduction of punchcards to have been a change in medium over when switches were switched by hand either. It is still actuating the same mechanical switches.
Today's programming languages are way better than the ones we had even a few years ago. Like night and day difference. I suspect that is where your threshold idea is coming from. But, like, today's mechanical saws are way better than the early mechanical saws but I don't think we would normally consider a woodworker to be an artisan just because he's using a primitive deathtrap instead of a modern sawstop. Perhaps I'm out of touch with the kids today, but I expect an artisan woodworker is normally considered one that uses hand tools — that being a different medium from mechanized tools which do the work in a completely different way, not just an earlier version of the same thing.
Computing saw as similar medium shift from, as it pertains to programming, mechanical switching to digital switching. And I posit that is the threshold.
But we've yet to leave the digital switching realm. We still write our programs the same way we did 50 years ago. The compilers have gotten way, way, way more featureful and smarter, but it is still the same old story: You write a program in a language the computer can interpret, feed it to a compiler (or layers of compilers), and out comes something the machine can execute.