Anthropic Builds Scion to Replace Git After Daily Merges Hit 30,000
Anthropic built Scion, an in-house Git alternative, after daily merges jumped from 2,500 to 30,000. It isn't intended as a general-purpose Git replacement.
Anthropic says it has replaced Git for its own monorepo. In an engineering post published October 13, 2026, the company says it built an in-house version control system called Scion after merged code changes went from around 2,500 per day in May to more than 30,000 per day by September.
A team of seven people built Scion, a code review tool called Antique, and about half a dozen related systems. The full migration took five months, according to the post.
The load numbers are the story. Anthropic says it runs on the order of 25 million CI checkouts a day, which would be over 600 PB of Git traffic if fetched naively. At its peak it operated several hundred internal Git mirrors. The company says Scion's footprint is now 200x smaller in CPU and memory than that mirror setup, CI and research checkouts are two orders of magnitude faster (seconds instead of minutes), and CI alone gained 25% in CPU capacity.
Don't plan your weekend around it. Anthropic says Scion is "by no means a suitable replacement for git for general use" and needs its own code review, code search and CI. The post announces no release. Simon Willison wrote that it sounds like "a reinvention of centralized source control along the lines of Subversion." On Hacker News, engineer Nick G said offline support was skipped because Claude is the heaviest user and is necessarily online.
My take: this is an infrastructure story, not an installation invitation. It's a good postmortem on what happens when your biggest committer never sleeps. File it under "read, don't install."
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Sources
- Redesigning source control at Anthropic, anthropic.com
- Redesigning source control at Anthropic, Simon Willison’s Weblog
Meanwhile at the anchor desk
Thirty thousand merges a day, a seven-person team, five months, and a whole new source control empire built in-house. That is what a company looks like when it is truly in a hurry, darling.
The 200x figure is measured against Anthropic's previous Git mirroring setup, not against Git as such, and the post gives no outside benchmark. Also, "Subversion" is the most polite way of saying "we went back to a central server."
