Anthropic Acquires Stainless, the SDK Startup That Powered Its Rivals
Anthropic acquires Stainless in a move that pulls a critical piece of AI developer infrastructure away from its biggest competitors. The Claude maker announced the deal on Monday, though it did not disclose financial terms. The Information had reported last week that the acquisition was in the works, with a price tag of more than $300 million. Stainless is backed by Sequoia Capital and Andreessen Horowitz.
Founded in 2022 by Alex Rattray, a former Stripe engineer, Stainless built software that takes API specifications and automatically generates production-ready software development kits, or SDKs, across multiple programming languages including Python, TypeScript, Go, Kotlin, and Java. The real draw was that the platform kept those SDKs updated as APIs evolved, eliminating the manual overhead that had long frustrated developer teams.
That capability made Stainless a go-to tool across the AI industry. OpenAI, Google, Cloudflare, Replicate, and Runway were all among its customers and so was Anthropic itself, which relied on Stainless to power every official Anthropic SDK since the earliest days of its API.
Now that the deal is closed, those competitors will have to find another solution. Anthropic says it will wind down all hosted Stainless products, including the SDK generator. Existing customers will keep ownership of SDKs they have already generated and can modify them as they see fit, but the platform will no longer be available to outside companies going forward.
Rattray, who announced the news in a press release on Anthropic’s website, said he started Stainless because SDKs deserved the same level of care as the APIs they wrap. Noting that Anthropic was among the first teams to believe in that vision, he said bringing the two teams together was an easy decision.
For Anthropic, the acquisition is as much a competitive play as it is a talent and technology grab. By absorbing Stainless entirely, the company ensures that a tool that once served the whole industry will now serve only one.
