Mark Zuckerberg Returns to Writing Code After Two Decades, Submits Diffs and Uses Claude Code Heavily

Mark Zuckerberg has returned to writing code for the first time in roughly two decades, submitting three diffs to Meta's internal monorepo and becoming a heavy user of Anthropic's Claude Code CLI tool, The Pragmatic Engineer reported, citing sources familiar with the matter. Zuckerberg joins a small but visible trend of technology executives and company founders returning to hands-on engineering work, accelerated by the availability of AI coding assistants that can dramatically compress the ramp-up time for executives who have been away from active coding. The use of Claude Code by Zuckerberg is notable given that Meta has its own AI infrastructure and Llama model family. It signals a degree of practical deference to Anthropic's developer tooling even at the highest levels of a competing AI organization. Claude Code has gained significant traction among professional developers for its ability to understand and work within complex existing codebases. Y Combinator president Garry Tan was also cited as part of the trend, with industry leader participation in hands-on coding returning amid the AI coding assistant wave. For Zuckerberg, the return to coding carries symbolic weight. He built early versions of Facebook himself before stepping back from day-to-day engineering as Meta grew. His re-engagement comes as he has publicly described 2025 and 2026 as transformative years for AI at Meta, with the company deploying AI agents internally and integrating AI across its product portfolio.