Anthropic builds custom source control system Scion to handle massive code change velocity

Anthropic developed Scion, a custom source control alternative to Git, to manage a dramatic increase in code changes, rising from an average of 2,500 merged changes per day in May 2026 to over 30,000 per day by September. The new system was built by a seven-person team over five months, addressing issues like a 100 GB main branch history and reducing potential daily Git traffic from over 600 PB to a much lower level; Scion intentionally lacks offline support because Claude, a heavy user, is always online.