Anthropic replaces Git with its own source control system

Anthropic described building Scion, a replacement for Git as the version-control system behind its main code repository, after the volume of code its own Claude agents were writing outgrew what Git’s distributed, offline-first design could handle. The company said its daily rate of merged changes rose from roughly 2,500 to more than 30,000 between May and September 2026, as coding agents — which it noted are “always online by definition” — took over more of the work.

Git stores a full copy of a repository’s history on every machine that clones it; Anthropic said its main branch history had grown to nearly 100GB, with a compressed working copy exceeding 25GB, and that daily automated checkouts for continuous-integration testing had reached 25 million. Workarounds — internal mirrors, sparse checkouts, promisor remotes — required several hundred git mirrors running at once and became harder to operate as the merge rate climbed.

Scion instead keeps data on a central server that clients fetch from on demand, rather than cloning the whole history locally, an approach Anthropic said drew on techniques from Google’s internal tool Piper and Meta’s Sapling, in particular the data model used by Sapling’s Mononoke backend. The company reported the new system cut its infrastructure footprint by roughly 200 times compared with git mirroring and sped up checkouts from minutes to seconds. Commentator Steve Newman noted that the project was itself substantially built by AI agents, in under five months — illustrating, he wrote, how AI’s advantage over human engineers lies less in raw intelligence than in sheer speed.