Claude writes 80% of code at Anthropic, CI jobs up 25x in six months
addyosmani · x · 2026-09-15
Addy Osmani shared Anthropic's engineering blog post: engineers there now ship 8x more code per quarter than in 2021–2025, with 80% authored by Claude, which also heavily reviews and approves PRs. Writing code is no longer the bottleneck — but tests grew 10x and CI jobs surged 25x in six months, nearly overloading their test impact analysis service.
How they scaled:
- Three quick patches to the test selection service lasted 70 days, 29 days, and less than a day respectively
- They ultimately scrapped the whole thing and reimagined the service's architecture
Author Sachin Malhotra notes agentic coding is straining CI across the industry: once code generation and PR review accelerate, continuous integration becomes the next bottleneck. Directly relevant for teams scaling AI-assisted coding.
Related event: Anthropic: Claude Now Writes 80% of Its Engineers' Code(2 posts)→
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