Anthropic has acquired Stainless, a developer tools startup founded by former Stripe engineer Alex Rattray, in a deal reportedly valued at over $300 million.

 

Stainless became well known in the AI ecosystem for automating the creation and maintenance of SDKs — the software libraries developers use to connect applications with APIs. Its technology has been widely adopted by major AI companies including OpenAI, Google, Cloudflare, Runway, and Replicate.

 

The startup’s platform helped developers generate production-ready SDKs across multiple programming languages such as Python, TypeScript, Go, Java, and Kotlin, while automatically updating them as APIs evolved. This removed a major engineering burden for fast-growing AI companies building agentic AI systems and developer platforms.

 

With this acquisition, Anthropic gains deeper control over a critical layer of AI developer infrastructure. The company also confirmed it will phase out Stainless’s hosted products, meaning the tools will no longer be available to competitors in the same way.

 

Interestingly, Anthropic revealed that Stainless technology has powered every official Anthropic SDK since the early days of its API platform — making this acquisition both strategic and deeply aligned with its developer ecosystem vision.

 

Another strong signal that the AI infrastructure race is accelerating rapidly.