Is 30% of Microsoft's code AI-generated?

Summary

A few months back, news outlets were reporting that Satya Nadella claimed 30% of the code in Microsoft's repositories was AI-generated. This fueled the hype around tools like Copilot and Cursor. If Microsoft's developers were now "vibe coding," everyone should embrace the method. I have to admit, for a moment I felt like I was being left behind. When it comes to adopting new technology, I typically choose the slow and careful approach. But suddenly, it seemed like the world was moving on without me. Here's the thing though, I use Copilot. I use Cursor at work as well. But I can't honestly claim that 30% of my code is AI-generated. For every function an AI generates for me, I spend enough time tweaking and adapting it to our specific use case that I might as well claim authorship. Is that what Microsoft employees are doing? Or are they simply writing prompts or a set of instructions, then letting the LLM write the code, generate the tests, and make the commits entirely on its own? So I went back to reread what Satya actually said: I'd say maybe 20%, 30% of the code that is inside of our repos today and some of our projects are probably all written by software. Fair enough. But then I watched the video where he actually said it. Interestingly, it was Zuckerberg who asked the question. What you hear in the interview is a whole lot of "maybe," "probably," "something like". Not the confidence portrayed in the written headlines. But here's what I really want to know. How are they tracking this? Are developers labeling all AI-generated code as such? Is there some distinct signature that marks it? How can you even tell when code is AI-generated? Unlike a written article where we can identify clear patterns, telltale phrasing, word choices that deviate from an author's typical style, code doesn't come with obvious fingerprints. For example, there's no way to tell when a senior developer on my team uses AI. Why? Because they don't commit code they haven't thoroughly reviewed ...