Anthropic announced on Monday that it has acquired Stainless, a startup that developed tools for automatically generating software development kits used by leading AI companies. The acquisition, valued at more than $300 million according to reports, brings a key infrastructure supplier under Anthropic’s ownership while ending the independent operation of Stainless’s hosted products, including its SDK generator.

Customers who have already created SDKs through Stainless will retain full ownership of those tools and can continue to modify them freely. The New York‑based company, founded in 2022, gained prominence by turning API specifications into ready‑to‑use SDKs across languages such as Python, TypeScript, Kotlin, Go, and Java, automatically updating them as APIs evolve.

The technology is especially valuable to firms building AI agents that must connect to external services, a capability that Anthropic, OpenAI, Google, Cloudflare and others rely on. With the deal, those SDK generation capabilities will now be exclusive to Anthropic, giving it tighter control over a critical part of the AI development stack.

Alex Rattray, founder of Stainless, said the merger aligns with the original vision of giving SDKs the same level of care as the APIs they wrap, and he sees joining Anthropic as a natural next step for the team and its developers.