Anthropic's Scion: A New Era in AI-Driven Source Control

Anthropic has developed Scion, an in-house version control system, to handle the unprecedented scale of code changes driven by AI. The company’s transition from git to Scion was necessitated by rapid growth, with code merges increasing from 2,500 to over 30,000 per day. Scion was designed with the assumption that clients are always online, leveraging a server that answers queries about file history and blame, creating commits, and performing merges and rebases. The system emphasizes horizontal scalability, making commits cheap, incremental, and lock-free, and treats the working copy as optional and sparse by design.