On Monday, Anthropic announced its acquisition of startup Stainless in a deal reportedly valued at over $300 million. Founded by former Stripe engineer Alex Rattray in 2022, Stainless has received investment from Sequoia Capital and Andreessen Horowitz. Its SDK auto-generation tool is widely adopted across the AI industry, serving clients including OpenAI, Google, Replicate, Runway, and Cloudflare. An SDK (Software Development Kit) serves as the foundational library developers use to call APIs. Stainless's technology automatically converts API specifications into multi-language SDKs supporting Python, TypeScript, Go, Java, and others, while updating them seamlessly whenever an API changes—eliminating the tedious burden of manual maintenance. For parties building AI Agents, this represents critical infrastructure connecting external software. However, post-acquisition, this infrastructure will belong exclusively to Anthropic. The company stated it would shut down all Stainless-hosted services, including its SDK generator. Existing customers may retain their generated SDKs and freely modify or extend them. According to Anthropic, Stainless provided SDK support for its APIs from early on, with nearly all official Anthropic SDKs originally built using that platform. In the announcement, Rattray said, "Anthropic was one of our earliest collaborating teams. Seeing everything developers have built on Claude made merging teams an easy decision." Implicitly, shared infrastructure once offered among partners now marks the end of exclusivity under single ownership.