Anthropic redesigned their source control system to support a large increase in code changes, from 2,500 to 30,000 merges per day, by building an in-house version control system called Scion. Scion is designed to work with always-online agents and jobs, and it uses a client-server architecture with a server that answers questions about file history and blame. The new system has improved performance and scalability, reducing the infrastructure footprint by 200x and speeding up code checkouts by two orders of magnitude. This change was necessary due to the rapid growth of their monorepo, which was straining their previous git-based system.