I just read Anthropic’s post on how they replaced git with their own source control system, called Scion. Here are the main points:
- Scion assumes agents are always online. The server does most of the work, and the clients are mostly agents.
- They built it because daily merges went from about 2,500 in May to over 30,000 in September, mostly from AI agents. Git was built for people working offline with a full copy of the repo, and that stopped working at their scale.
- Each client only downloads the files it actually needs, instead of the full 100 GB repo. It’s like streaming on Spotify instead of downloading a whole music library.
- Clients can ask the server questions through an API without cloning anything, which saves time and storage.
- They learned from other companies’ version control tools, like Google’s Piper and Meta’s Sapling.
- Seven engineers built it in five months, and Claude wrote most of the code.
- The engineers focused on design decisions, reviewed the intent of each change instead of every line, and often had to tell Claude no when it over-engineered things.
New on our Engineering blog: Creating in-house source control.
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.
Here, we share how we built a new version control system—and fully migrated our monorepo from git—in five months:
anthropic.com/engineering/re…