Anthropic has acquired Stainless, a New York-based developer tools startup founded by former Stripe engineer Alex Rattray, in a deal reported to be worth more than $300 million. The acquisition removes a critical piece of shared AI infrastructure from competitors, as Anthropic confirmed it will wind down all hosted Stainless products and restrict access exclusively to its own teams.
Founded in 2022 and backed by Sequoia Capital and Andreessen Horowitz, Stainless built software that automatically generates and maintains software development kits across languages including Python, TypeScript, Go, and Java — tools that OpenAI, Google, Cloudflare, and Runway have all relied upon to connect developers to their APIs.
Rattray described the decision as straightforward, noting that Anthropic had been among the earliest adopters of Stainless technology and that its SDKs have powered every official Anthropic API integration since launch. Existing customers retain full rights to SDKs already generated but will lose access to future hosted services.
