Anthropic Replaced Git in Five Months as Merges Hit 30,000 a Day
Anthropic built its own version control system, Scion, and moved its monorepo off git in five months after merges per day grew past 30,000.
In May 2026, Anthropic averaged around 2,500 code changes merged per day; by September it merged over 30,000 daily, and source control had become its biggest development bottleneck. It built an in-house version control system called Scion and moved its monorepo off git in five months, shipping a code review surface, code search, source access control, and new ways of landing reviewed code. The same models that broke source control are what built its replacement.
Anthropic’s own framing beats the migration story: “The bottleneck, now, is all of the developer infrastructure built for human scale: source control, builds, and CI.” The company says the latent demand for merging code is practically infinite, and that removing a bottleneck immediately produces more code. I buy that. The merge rate is not a demand curve waiting to be met; it is a function of how wide the pipe is. Nothing about that curve looks like it turns over.
I run a forge on a homelab for a handful of repos, the web UI annoys me, and I have never once considered writing my own version control. That is the right call for nearly every team. Solving a tenfold jump in merges takes headcount and money; five months of in-house VCS, a review surface, and IAM is neither cheap nor small. My read: 30,000 is the number that matters, and Scion is the receipt.
The constraint moves downstream anyway. If writing code stops being the slow part, the queue that hurts is review, CI, and landing, the parts still designed around a human at the end. Anthropic says it is often the first to see where human-scale tooling strains, which tracks for a company writing this much software with its own models. Everyone else meets the same wall later, at smaller numbers, in CI minutes and review latency long before git is the problem, which is the part worth planning for.
Skip this if you merge a few hundred changes a week and the pipeline keeps up. Scion’s mechanics will not transfer to a small repo, and five months is better spent on the CI queue already in place. Picture 30,000 merges a day landing in one monorepo while a review surface holds the line. Then count merges per day in your own repo for one week. That count decides what to build; Anthropic’s 30,000 does not.