Less than a year after CEO Satya Nadella said 30% of Microsoft's code is AI-written, company appoints an 'Engineering Quality Head;' and here's why that matters

Microsoft CEO Satya Nadella has created a brand new role at the company—an engineering quality head—and handed it to Charlie Bell, the executive who previously ran the Redmond giant's security division. The appointment, announced in an internal memo shared on Microsoft's blog on February 4, comes less than a year after Nadella publicly boasted that AI now writes up to 30 percent of the company's code.The timing raises an obvious question that Nadella's memo carefully avoids answering: why does Microsoft suddenly need someone dedicated to engineering quality?

AI-written code is surging, and so are the bugs

Back in April 2025, during a fireside chat with Meta CEO Mark Zuckerberg, Nadella said that 20 to 30 percent of code in Microsoft's repositories was "written by software." Microsoft CTO Kevin Scott went further, predicting that 95 percent of all code would be AI-generated by 2030. But speed and volume don't automatically mean quality. Research from GitClear found that code churn—the rate at which recently written code gets rewritten or deleted—roughly doubled after AI coding tools became widespread. Microsoft's own researchers published findings showing that developers miss around 40 percent more bugs when reviewing AI-generated code compared to human-written code.Meanwhile, Windows 11 has been having a rough run. January 2026 alone saw a security update that left business PCs unable to boot, a separate patch that broke shutdown functionality, and two emergency out-of-band fixes.

File Explorer remains sluggish, and a dark mode bug that Microsoft accidentally made worse while trying to fix it still hasn't been resolved. The company has even pulled engineers off new feature development to focus entirely on fixing reliability problems—an effort internally called "swarming"—expected to last several months.

Bell steps down from security, Google veteran Gallot steps in

Bell, who joined Microsoft in 2021 after 23 years at Amazon, will now work as an individual contributor focused on engineering quality, reporting directly to Nadella.

His replacement as security chief is Hayete Gallot, who spent 15 years at Microsoft before leaving for Google Cloud in 2024. Gallot returns as executive vice president for security.Nadella framed the move as a planned transition. "Charlie and I have been planning this transition for some time, given his desire to move from being an org leader to being an IC engineer," he wrote.

Copilot adoption remains underwhelming despite the AI push

The engineering quality push also arrives at a moment when Microsoft's AI bet isn't paying off the way investors hoped. Only 3.3 percent of Microsoft 365 and Office 365 users currently pay for Copilot. The company's stock is down significantly this year, and Azure's growth rate disappointed analysts during last week's earnings call. Microsoft has even started quietly scaling back Copilot integrations in apps like Notepad and Paint.Whether Bell's new role signals a genuine course correction or is simply damage control will depend on what actually ships in the months ahead.