Why Git broke
The numbers Anthropic gave for its own code output explain the whole thing.
"In May, we merged around 2,500 code changes per day. In September, we merged more than 30,000 per day. As a result, we became bottlenecked by developer infrastructure built for human (rather than agent) scale," Anthropic said.
That's more than a tenfold jump in four months, and it happened because Claude is now doing the bulk of the coding. Git and the tooling stacked around it were made for people typing at human speed.
Push an AI agent through the same pipes at agent speed and they clog.
What Scion does differently
Scion is built for always-online agents like Claude. Git has every machine keep a full copy of the repository. Scion doesn't. It fetches data on demand instead, which is a better fit for agents that are constantly connected.
A team of seven engineers moved Anthropic's entire monorepo onto it over five months. According to the company's engineering blog, the switch cut infrastructure use by roughly 200 times, brought checkouts down to seconds, and added about 25% more CI capacity.
The humans mostly say 'no' now
With Claude handling most of the writing, the engineers' job has quietly changed shape. They spend more of their day reviewing what the agents produce and keeping it inside the rules, the company says, often telling Claude 'no' to make it behave.
The coding is increasingly the machine's work. The judgment about what ships is still the human's.
Why it matters
There's something telling about a company rebuilding one of the most basic pieces of software plumbing because its own AI outgrew it. Git isn't some niche tool. It's the thing almost every developer on earth uses, and Anthropic hit a wall with it inside a year of letting Claude loose on its codebase.
Most of these details come from Anthropic's own engineering blog, so they're the company's account of its setup rather than an outside audit. Even so, the direction is clear enough. When the code is mostly written by AI, the tools built for humans start to crack, and the firms closest to that shift are the first to feel it.