Anthropic replaces Git with in-house Scion

What happened: Anthropic detailed Scion, an in-house version control system it built and used to migrate its monorepo entirely off Git in five months. As Claude wrote more code, merges climbed from roughly 2,500 a day in May 2026 to more than 30,000 a day by September, and source control became the bottleneck. Scion assumes clients are always online, does commits and merges on the server, stores work as changesets in a write-ahead log and avoids packing objects into packfiles. A team of seven built it alongside the review surface Antique and a new code search tool.

Context: Anthropic points to Google’s Piper and Meta’s Sapling as prior art for large-scale monorepo version control. It stresses that Scion is not a general Git replacement and likely will not be offered as a product, and that it plans to publish some of the ideas it used to reason about scaling Git servers.

Why it matters: It is a concrete case of agent-scale development breaking tools built for humans typing code. If AI keeps writing a larger share of commits, more teams will hit the same wall, and version control is only the first piece of infrastructure to feel the strain.

(Original source: Anthropic)