Anthropic says its daily merged code changes rose from roughly 2,500 in May 2026 to more than 30,000 by September. Source control became its biggest development bottleneck, prompting the company to replace Git for its monorepo.
In an engineering disclosure published on October 13, Anthropic describes Scion, an internal version-control system designed for clients that are almost all agents or automated jobs already online. They don’t need an independent copy of the repository capable of answering every question offline.
A seven-person team built Scion, a related code-review tool called Antique, and supporting infrastructure, then completed the migration in five months, according to Anthropic. The lesson for other companies is how much infrastructure can change when automated clients become the dominant consumers of source control, not that they should abandon Git.
The Bottleneck Was Repeated Access, Not Just Repository Size
Anthropic’s monorepo had become expensive to distribute. Its main-branch history approached 100 GB, while a compressed working copy exceeded 25 GB.
CI performed approximately 25 million checkouts daily, before counting developer environments, agent sandboxes, or research jobs. Repeatedly making a large repository available to short-lived clients was the central scaling problem.
The company estimates that naively fetching those working copies would generate more than 600 petabytes of Git traffic per day. That is a hypothetical calculation, not a measurement of actual traffic. Anthropic already used shallow clones, sparse checkouts, promisor remotes, internal mirrors, and repository snapshots stored in blob storage to avoid such waste.
Those measures bought time. At peak, however, Anthropic operated several hundred Git mirrors. As merge volume increased, repository snapshots fell further behind the latest main-branch revision between refreshes. Keeping history-dependent operations such as diff and blame working correctly with partial clones also required increasing care.
Scion followed extensive use of Git’s existing mechanisms and infrastructure workarounds under an unusually large automated workload. It wasn’t Anthropic’s first response to a slow clone.
The company’s account describes a mismatch between distributed repository mechanics and centralized, high-volume consumption. It doesn’t establish that Git is unsuitable for ordinary development.
Scion Moves Repository Intelligence to the Server
Git’s distributed design lets a conventional clone operate as a self-contained repository. Developers can inspect history, create commits, and perform many operations without contacting a central service.
