Redesigning Source Control at Anthropic

Anthropic built Scion, a custom in-house version control system, to replace Git after their code merge rate exploded from 2,500 to over 30,000 changes per day due to AI-assisted development with Claude. The migration was completed in five months and was necessary because Git's decentralized design became a bottleneck—their monorepo history alone reached nearly 100 GB, and the company was performing 25 million daily code checkouts that would have generated over 600 PB of traffic using Git naively.