Anthropic's engineering post says its monorepo history alone is almost 100 GB, with a compressed working copy above 25 GB and roughly 25 million CI checkouts a day. At its peak it ran several hundred internal git mirrors. Scion assumes clients such as agents and CI jobs are always online, puts history, blame, merges and rebases on the server, and exposes every query through an API. The company migrated the monorepo in five months and also shipped a review tool called Antique, code search and a source-control permissions system. Caches hold hit rates above 99%, and CI gained 25% CPU capacity. Scion is not being released. Anthropic says it diverges too far from git to offer broadly, and suggests git platforms adopt server-side ideas instead. It credits Google's Piper and Meta's Sapling as prior art, and says Claude both created the bottleneck and helped build the fix. For builders, the signal is where agent-heavy teams hit limits first: merges, builds and CI rather than code generation. Anthropic expects other companies to meet the same pressure within six to 12 months.