Redesigning Source Control at Anthropic

Anthropic built a custom source control system called Scion to replace Git after their code change rate exploded from 2,500 merges per day in May 2026 to over 30,000 by September, driven largely by rapid model development. The new centralized system, inspired by Google's Piper and Meta's Sapling, was developed by seven engineers over five months and handles extreme scale requirements including 100 GB of main branch history and 25 million daily code checkouts for CI. Anthropic prioritized online performance over offline support since Claude, their heaviest user, is necessarily always connected.