Anthropic said it replaced Git with an in-house version control system called Scion, migrating its entire monorepo over five months with a seven-person team, according to a post on the company's engineering blog.
Daily code merges grew from 2,500 in May to more than 30,000 by September, Anthropic said, as its monorepo expanded to nearly 100 gigabytes of history. The company wrote that maintaining "several hundred internal git mirrors" strained infrastructure and made basic operations like diff and blame slow on partial clones.
Git assumes a client holds a complete local copy of a repository for offline work, Anthropic said, but its engineering is now done almost entirely by always-online coding agents and continuous integration jobs. "The properties that make git excellent for distributed, offline work were actively undermining our ability to scale," the company wrote.
Scion fetches data on demand from a server rather than storing a full repository locally, records changes as content-addressed changesets instead of full snapshots, and uses tiered caching that Anthropic said hits its cache more than 99% of the time. The result is infrastructure Anthropic says is 200 times smaller than its previous git mirrors, with CI checkouts about two orders of magnitude faster.
A version control system built around agents that never go offline is a specific bet on how software gets written now. Teams running high volumes of autonomous coding agents against a large monorepo are hitting the same git bottlenecks Anthropic describes, and Scion is a concrete design to study even though it is not open source.