Anthropic Builds Scion to Replace Git After Merge Volume Jumped Twelvefold

Anthropic has built its own version control system, Scion, to replace Git for its internal monorepo. The company described the project in an engineering blog post published around 13 October 2026. Coverage that followed, including reports by Officechai and El Solitario, says the daily volume of merged code rose from about 2,500 changes in May to more than 30,000 by September. That growth is what pushed the company past what Git could handle.

Anthropic Scion moves the source of truth to the server.

Scion keeps the server as the single source of truth. Clients fetch only the files they need, and the server handles history, blame, merges and rebases. Checkouts are sparse by default. El Solitario says the design assumes clients are usually online and are mostly agents or automated jobs, and that it draws on ideas from Google's Piper and Meta's Sapling.

Why the old setup broke down.

Officechai reports that Claude's coding output overwhelmed the existing infrastructure, so the switch became unavoidable. Before the change, Anthropic ran several hundred Git mirrors and seed snapshots to cope with the load. Running a standard full clone for each of its roughly 25 million daily CI checkouts would have meant more than 600 petabytes of traffic per day, according to El Solitario's account of the company's arithmetic.

Anthropic's performance claims are large. It says Scion's infrastructure footprint is about 200 times smaller than the old Git mirroring setup, measured in CPU and memory. Continuous integration and research jobs now check out code in seconds rather than minutes, and CI alone freed about 25 percent of CPU capacity across the fleet. The main branch history is close to 100 GB, and a compressed working copy is more than 25 GB. These figures come from Anthropic's own account as reported. No outside party has tested them.

Seven engineers built Scion over about five months. The same team also produced Antique, a code review tool, a code search system and a permissions layer for the monorepo. The coverage does not say how the team was organised or who led it.

Several questions remain open. Anthropic has not said whether Scion will be released as open source, and the reporting found no public code repository. Officechai argues that the system is impractical for most companies, because it needs its own review, search and CI stack to work. The storage format, the protocol details and how the central server handles failover are not described in the coverage reviewed.

For most teams, the practical lesson is simpler. Measure how long your own checkouts take and how much history each job downloads. Sparse checkouts are already available in standard Git, and a clear picture of your load comes before any decision about replacing your tools. If you need to read API output from your own repository host, the free JSON formatter at /en/json-formatter can make it easier to scan.