Anthropic Builds Scion to Replace Git After Merges Hit 30,000/Day
TL;DR
- Daily merges at Anthropic grew from 2,500 in May to over 30,000 by September, a 12x surge driven by Claude-generated code.
- Scion's server-centric design cut CPU and memory requirements 200x versus the prior Git mirroring setup; CI checkouts dropped from minutes to seconds.
- Seven engineers built Scion and migrated Anthropic's full monorepo in five months, using Claude itself to write much of the system.
Anthropic has replaced Git in its monorepo with Scion, a custom version-control system built by seven engineers in roughly five months, and the company says it will not be open-sourced. In a post on its engineering blog, the company reports that daily merges on the repo climbed from "around 2,500 code changes merged per day" in May 2026 to "over 30,000 per day" by September, a jump it attributes largely to agents writing code.
The framing is that Git's distributed design cracked under agent-scale load. "The properties that make git excellent for distributed, offline work were actively undermining our ability to scale as the repo grew," the post reads. The main-branch history alone runs to almost 100 GB, the compressed working copy sits above 25 GB, and CI pulls roughly 25 million checkouts per day on its own.
Scion is built around an always-online client-server model with regional caches, with each tier running at over 99% cache hit rate. Anthropic claims the new infrastructure runs with a 200x smaller CPU and memory footprint than its previous Git-mirroring setup, and that "CI and research jobs check out code two orders of magnitude faster (in seconds rather than minutes)." A companion code-review tool, Antique, was built in parallel. This is one of 344 Anthropic items our tracker has logged in the last 90 days.
The post also credits Claude for part of the system itself. On the Git-to-Scion ingestion pipeline, the engineers write: "We asked it to rewrite the whole thing, and with no further instructions, it produced a version that consumed 20x less memory and was 4x faster."
Anthropic is explicit that the tool is not for general release. "Scion is by no means a suitable replacement for git for general use," the post says, and the company instead urges the Git community to adopt compatible server-side improvements, better RPCs, and improved negotiation protocols for agent-scale workloads.
What others are reporting
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The Register Read →
Frames this as a self-inflicted crisis: Anthropic created the problem (Claude generating massive code) and used Claude to fix it, repositioning humans as safety gatekeepers.
We don't expect this rate of growth to slow down anytime soon; the latent demand for merging code is practically infinite.
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AlphaSignal Read →
Positions Scion as a blueprint for organizations facing agent-scale throughput, detailing the engineering solutions: sparse checkouts, server-side operations, CDN-like caching.
Daily merges grew from 2,500 in May to over 30,000 in September, driven by Claude writing most of the code.
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GIGAZINE Read →
Emphasizes the broader infrastructure bottleneck shift: AI has moved the constraint from coding to developer tooling, with the industry expected to hit the same wall within 6-12 months.
Git's mechanism, which requires a complete copy for each client, became a factor that hindered scaling.
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Crypto Briefing Read →
Leads with efficiency numbers (200x smaller infrastructure footprint) and frames agent-driven code volume as the primary forcing function for tooling reinvention across the industry.
Scion's CPU and memory requirements are 200 times smaller than those of its previous Git mirroring infrastructure.
Shared on Bluesky by 4 AI experts
Originally reported by anthropic.com
Read the original article →Original headline: Anthropic Open-Sources Scion, a Git Replacement Built by Seven Engineers With Claude in Five Months