Federico Ulfo
Anthropic built Scion, an internal source-control system, after its monorepo grew from roughly 2,500 daily merged changes in May to over 30,000 in September 2026. Seven engineers migrated the repository and built supporting tools in five months.
Scion assumes connected clients. Servers handle commits, merges, and history queries, while clients retrieve only needed files. Immutable objects and tiered caches reduce repeated checkout work.
Anthropic reports a 200-fold reduction in source-control CPU and memory requirements, checkout speeds roughly 100 times faster, and a 25% CI CPU-capacity saving. These measurements describe its own workload.
The migration also changed engineering work: people guide architecture and review intent, while Claude implements changes. Testing increasingly happens after merging and before deployment.
Scion targets unusually large repositories. Anthropic is sharing its design rather than offering a general Git replacement.
Anthropic — Redesigning source control for agent-scale development
