Anthropic Completes Five-Month Migration From Git to In-House Scion System
Anthropic says its developers built Scion, a version control system that cuts checkout times from minutes to seconds and frees 25% of CI CPU capacity.
Anthropic developed an in-house version control system called Scion and completed its migration away from Git over five months, according to the company. Anthropic announced the switch on its company blog on 13 October, as reported by digitaltoday.co.kr.
Scion does not clone entire repositories. The server handles history lookup, commits and merges, while clients fetch only the data they need. All Scion features are exposed as APIs, allowing many operations without a local repository. According to Anthropic, the infrastructure footprint shrank to 1/200 of the previous Git mirror infrastructure in CPU and memory terms. Checkout times dropped from minutes to seconds, and 25% of CPU capacity was freed in CI alone.
Scion and the code review tool Antique were built by seven people. Anthropic said Claude Mythos preview rewrote the first version of the Git-to-Scion data migration pipeline, cutting memory use to 1/20 and making it four times faster.
Pressure on Git
Anthropic said merged code changes per day grew from about 2,500 in May 2026 to more than 30,000 in September 2026. The main branch history alone approached 100GB, and code checkouts for continuous integration reached about 25 million per day. Anthropic operated hundreds of Git mirrors before hitting their limits, and said such a system would previously have taken years to develop.
Anthropic stated Scion cannot replace Git as a general-purpose system. The company added that it will work with GitHub, GitLab and the open-source community, expecting similar problems to become common within 6 to 12 months.
Quick answers
What is Anthropic's Scion?
Scion is an in-house version control system built by Anthropic that replaces Git for its internal development. It does not clone entire repositories; the server handles history lookup, commits and merges while clients fetch only needed data, and all features are exposed as APIs.
How long did Anthropic's migration from Git to Scion take?
Anthropic completed the migration over five months and announced it on its company blog on 13 October.
How much did Scion reduce Anthropic's infrastructure?
The infrastructure footprint shrank to 1/200 of the previous Git mirror infrastructure in CPU and memory terms, checkout times dropped from minutes to seconds, and 25% of CPU capacity was freed in CI alone.