Redesigning source control at Anthropic

Anthropic's code changes surged from 2,500 per day in May 2026 to over 30,000 daily by September, indicating a significant increase in development workload. This growth strained their existing source control infrastructure, leading them to create Scion, an in-house version control system. Scion was built to address the challenges of managing a massive monorepo in the cloud, where clients are always online.

Unlike Git, which operates on a decentralized model, Scion was designed with a server-centric architecture, allowing clients to fetch data as needed instead of maintaining a complete local copy. This design decision helped reduce the massive data traffic generated by daily code checkouts and cut down on storage requirements. Scion's client-server model enabled horizontal scalability, eliminating the need for multiple Git mirrors and streamlining operations.

By exposing source control queries as APIs, Scion opened up new possibilities for internal tools, such as automated bisecting and reverting pipelines, which previously relied on local repositories. The system's design embraced the unique characteristics of AGI-driven development, where remote agents can autonomously iterate and optimize code at unprecedented speeds.