Anthropic detailed the move in a blog post on Tuesday, describing a five-month migration to Scion, a centralized monorepo system that in some ways resembles Subversion rather than Git's distributed architecture. The company said its main branch is about 100 GB, with a compressed working copy more than a quarter of that size, and that it performs about 25 million code checkouts per day for continuous integration alone. Fetched naively, it said, that would mean more than 600 PB of Git traffic per day.
"In May 2026, Anthropic averaged around 2,500 code changes merged per day; as of September, we merged over 30,000 per day," the company said. "We don't expect this rate of growth to slow down anytime soon; the latent demand for merging code is practically infinite, and every bottleneck we remove immediately leads to a further increase in the amount of code we produce."
Anthropic is not the first organisation to hit the limits of Git. Google uses its own Piper monorepo system, Microsoft built Virtual File System for Git, and Meta developed Sapling. GitHub, which is owned by Microsoft, said in April that recent availability problems were linked to the exponential growth in pull requests and commits. Academic researchers have also noted the flood of AI-generated code.
According to Anthropic, Scion was designed with AI agents in mind. The client leaves most of the work to the server, source control queries are exposed through an API, and the unit of work is a "changeset" stored in a write-ahead log rather than a Git commit pointing to a tree. Claude also helped build related tools, including Antique, a code review interface, a code search tool, and a source control IAM system. Work on Scion began in January, and when the Claude Mythos Preview became available internally, the model rewrote an early Git-to-Scion ingestion pipeline that used 20 times less memory and ran four times faster.
Anthropic acknowledged that the decentralized approach embodied by Git remains the right one for most code repositories. But at the company's scale, engineers found it impractical. Developers who worked on Scion, the company said, agree that Claude writes better code than they do, but they keep a role as reviewers: "Very often, we found that the role of the engineers was to tell Claude 'no,'"