Anthropic acquired Stainless, the SDK platform used by OpenAI and Google, for $300 million

Anthropic announced the acquisition of Stainless, a New York-based startup founded in 2022 by Alex Rattey, a former Stripe platform engineer. The deal exceeded $300 million, though Anthropic officially did not disclose exact terms. This event demonstrates the growing importance of development tools in the AI company ecosystem.

What is Stainless and why is it needed

Stainless specializes in automating the creation and updating of Software Development Kits (SDKs) — libraries that developers use to integrate with APIs. The platform transforms API specifications into production-ready SDKs in several programming languages: Python, TypeScript, Kotlin, Go, and Java. Stainless's key differentiator from competitors is automation of updates. When an API changes, the Stainless generator synchronizes changes across all supported SDKs, freeing developers from the need to manually maintain multiple versions of the library. This saves weeks of engineer work, especially during active development.

Why Anthropic is buying right now

The strategic importance of the deal is obvious: Anthropic itself has used Stainless SDKs since its early API development days and fully relied on this platform to support its official SDKs. By acquiring the company, Anthropic not only secures its own needs but also removes a key infrastructure provider from the hands of direct competitors, including OpenAI, Google, and Cloudflare, who actively used Stainless for their integrations. This is particularly important in the context of exponential AI agent development. Modern intelligent agents must seamlessly connect to thousands of different services and platforms — from payment systems to CRMs, from cloud storage to specialized tools. Each requires a reliable, up-to-date, and well-documented SDK.

"SDKs deserve the same care as the APIs they wrap," said

Alex Rattey, expressing enthusiasm about joining teams with Anthropic, a platform where his work takes on maximum significance.

What will close and what will remain

Anthropic will discontinue support for all Stainless hosted products, including the cloud SDK generator, which previously operated as SaaS. However, existing platform customers will not lose their SDKs — they remain in full user ownership with all rights to modify and extend the code.

• All Stainless cloud services will be discontinued in the coming months
• Existing SDKs remain in customer ownership with full rights
• Developers will be able to freely modify and maintain their code
• Legacy SDKs will continue to work without changes
• Customers do not require immediate migration

What this means for the industry

The acquisition signals that developer infrastructure is becoming a strategic asset in the AI race. When OpenAI, Google, and Cloudflare chose Stainless, it was a niche tool. Now Anthropic demonstrates that such competencies must be held internally: no dependence on anyone in critical parts of the development chain. Expect other major AI companies to follow the same path, consolidating critical infrastructure within their organizations.