saved
Redesigning source control at Anthropic
Hraness wrote this summary from a saved copy of the source. Quotations are taken word for word from the source.
gist
As agent-written merges grew from about 2,500 to over 30,000 a day, git became Anthropic's biggest development bottleneck. A seven-person team used Claude to build Scion, a server-centric version control system for always-online agents, and moved the monorepo off git in five months, cutting infrastructure 200x and checkout times from minutes to seconds.
ideas
- Agents are always online. Git's offline, every-clone-a-server design clashes with a monorepo near 100 GB of history and roughly 25 million CI checkouts a day.
- Put the server in charge. Scion stores changesets as file-level diffs in a write-ahead log, computes blame and history as recursive derived data, and serves immutable objects through tiered caches.
- Skip the checkout. Rich server APIs let CI and tools ask history questions directly, and sparse or virtualized checkouts fetch only what jobs read.
- Engineers now steer and say no. Claude wrote most code and found big optimizations; humans supplied design tradeoffs, reviewed intent, and reined in over-engineering.
- Rethink human-scale workflows. A global merge-queue lock no longer fits, so Anthropic leans on post-merge testing and urges git forges to adopt Scion's server-side ideas.
quotes
“if we designed source control with the fact that agents are always online in mind from the start, what would it look like?”
“Very often, we found that the role of the engineers was to tell Claude “no.””
“Scion is by no means a suitable replacement for git for general use.”