Anthropic acquires dev tools startup used by OpenAI

Anthropic said on May 18 that it had acquired Stainless, a New York startup that builds software for generating developer tools from API specifications. The deal gives Anthropic control of a company whose products were used by Anthropic itself as well as OpenAI, Google, Cloudflare and other API providers, according to Anthropic, Stainless and earlier Stainless marketing materials. (anthropic.com) Anthropic did not disclose terms. The Information had reported last week that Anthropic was in talks to buy Stainless for more than $300 million. The transaction adds another developer-infrastructure asset to Anthropic’s product stack as the company pushes deeper into coding, agents and API tooling. (stainless.com) Anthropic said Stainless had powered the generation of every official Anthropic SDK since the earliest days of its API, while Stainless said its products were built to improve developer experience and connections between agents and external systems. ### Which startup did Anthropic buy, and what does it make? Stainless was founded in 2022 and turns an API specification into software development kits, command-line tools and related developer interfaces, according to Anthropic and Stainless. (anthropic.com) Anthropic said the company’s tools generate SDKs across languages including TypeScript, Python, Go, Java and Kotlin, and keep those libraries updated as APIs change. Stainless described itself on its website as a provider of “best-in-class interfaces for developers and agents,” with products for SDKs, documentation and MCP servers derived from OpenAPI specifications. Its site said it was trusted by Anthropic, Cloudflare, Google, OpenAI and others. (anthropic.com) ### Why was Stainless relevant beyond Anthropic? OpenAI, Cloudflare and Meta were named by Stainless in earlier company materials as users of its SDK-generation software, and TechCrunch reported that Google, Replicate and Runway were among the companies using the platform. That made Stainless a shared infrastructure supplier across several AI and developer-platform companies. (anthropic.com) Alex Rattray, Stainless’ founder and chief executive, said in Anthropic’s announcement that he started the company because “SDKs deserve as much care as the APIs they wrap.” In a separate Stainless post, the company said it was joining Anthropic “to accelerate our mission to improve developer experience and improve the connections between agents and systems.” (stainless.com) ### What did Anthropic say about how it already used the tools? Anthropic said Stainless had powered every official Anthropic SDK since the earliest days of its API. TechCrunch, citing Anthropic, reported that the software was integrated into Anthropic’s developer stack and used in parts of its internal code pipeline for automation. (stainless.com) Anthropic has been expanding its developer-facing products this year. The company’s Claude Code product page says its coding agent works in terminals, IDEs, desktop apps and Slack, and Anthropic has recently announced deals and product updates tied to Claude Code, developer APIs and tool use. (anthropic.com) ### What changes now for Stainless customers? Anthropic told TechCrunch it would wind down all hosted Stainless products, including the SDK generator. An Anthropic spokesperson said customers would still own the SDKs they had already generated and would keep the rights to modify and extend them. (anthropic.com) Stainless said on May 18 that its team would join Anthropic’s Claude Platform team. The company did not say in its post that existing hosted products would continue independently after the acquisition. ### Where does this fit in Anthropic’s recent dealmaking? (claude.com) Anthropic’s May 18 newsroom post lists Stainless as the company’s latest acquisition. Anthropic has also announced other product and infrastructure moves in recent months, including acquisitions tied to Claude Code and computer-use capabilities, plus a compute partnership with SpaceX announced on May 6. The next public source for details is Anthropic’s own announcement page and Stainless’ May 18 blog post, which name the joining team and the product areas involved. (techcrunch.com) Neither company has published deal terms in those posts. (anthropic.com 1) (anthropic.com 2) (stainless.com)