Anthropic built Scion as code-change volume surged
Anthropic says it developed Scion, a custom alternative to Git, as its rate of merged code changes rose from about 2,500 per day in May 2026 to more than 30,000 per day by September. The migration from Git took five months and was carried out by a team of seven.
The company describes infrastructure pressures behind the redesign: its main branch history is nearly 100 GB, a compressed working copy exceeds 25 GB, and CI performs roughly 25 million checkouts a day. Anthropic says naive Git fetching at that volume would amount to more than 600 PB of traffic per day. Scion is a centralized source-control design, and the account notes that offline support was not prioritized because Claude, its heaviest user, needs to be online.
The report documents a response to Anthropic’s own scale; it does not establish that the same design or workload applies broadly across software teams. Source: https://simonwillison.net/2026/Oct/13/redesigning-source-control-at-anthropic