Why Git wasn't enough
Anthropic hit the limits of its existing source control infrastructure after the rate of changes to its codebase rose roughly twelvefold in six months. According to the company, it averaged around 2,500 code changes merged per day in May 2026; by September that figure had passed 30,000.
Scion and Antique
To handle the load, the company built its own source control system as an alternative to Git. The system is called Scion and amounts to a redesign of centralized source control. On the review side, Anthropic uses a new system called Antique.
The scale of the numbers
According to Anthropic, the history of its main branch alone is almost 100 GB, and a compressed working copy is over 25 GB. The company performs on the order of 25 million code checkouts per day, before counting developer environments, agent sandboxes and research jobs. Fetched naively, that would mean over 600 PB of Git traffic per day.
Seven people, five months
The new system was built by a team of seven people, and the migration from Git was completed in five months. The team used adversarial review, pitting AI models against each other to find flaws, while experienced engineers steered the models away from over-engineering the system in response to hypothetical concerns.
