Anthropic Replaces Git with Custom Source Control System Scion to Handle 30k Daily Code Merges

Background

Anthropic has replaced Git with a homegrown source control system called Scion.

The Need for Scion

In May 2026, Anthropic averaged roughly 2,500 merged code changes per day. By September 2026, that figure had climbed past 30,000 merges per day.

The Rise of Claude

The company attributes the surge to the growing capabilities of its Claude models. Claude increasingly handles coding tasks on its own, which means code is being produced at a rate that looks less like a team of engineers and more like a factory floor.

Designing Scion

Seven engineers, five months Rather than patch the old setup, Anthropic built a new one. A team of just seven engineers designed Scion and completed the full migration of the company's monorepo in five months.

Key Features of Scion

Scion borrows design ideas from two systems built by companies that faced similar scale problems: Google's Piper and Meta's Sapling.

Performance Improvements

Scion uses always-online clients, meaning the developer's tools stay connected to central servers rather than holding a full independent copy of everything. Scion also moves commits and merges to the server side. CI job completion times dropped from minutes to seconds under Scion.

Benefits and Challenges

Scion reaches cache hit rates above 99%. Its CPU and memory footprint is 200 times smaller than the Git mirror infrastructure it replaced.

What This Means for Software Teams

There are risks too. Moving away from Git means leaving behind a massive ecosystem of compatible tools, integrations, and developer familiarity. Custom infrastructure also requires ongoing maintenance, and its long-term costs are harder to predict than its launch-day benchmarks.