Zuckerberg Is Writing Code Again. With Claude Code.

TL;DR: Mark Zuckerberg shipped 3 diffs to Meta's monorepo last month, his first code in 20 years. He's a heavy user of Claude Code CLI. One of his diffs got 200+ approvals from engineers who wanted to say they reviewed the CEO's code. He's not the only one. Garry Tan at Y Combinator is doing the same thing. The pattern is clear: AI coding tools are pulling founders back into the codebase. What happened? Gergely Orosz at The Pragmatic Engineer reported this week that Mark Zuckerberg is back to writing code. Three diffs landed in Meta's monorepo in March 2026. His tool of choice: Claude Code CLI , Anthropic's terminal-based AI coding assistant. 1 To put the scale in perspective: Meta's monorepo now has close to 100 million diffs . Back in 2006, the entire Facebook codebase had fewer than 10,000. 1 Zuckerberg's last meaningful code contributions were in 2006. That's a 20-year gap. The fact that he's back, and using an AI tool to do it, says something about where we are. The 2010 diff that