Anthropic acquires Stainless, the dev tools startup powering OpenAI and Google

Anthropic announced Monday that it has acquired Stainless, a startup founded by former Stripe engineer Alex Rattray whose software development tools are widely used by rival AI labs, including OpenAI and Google. The deal, whose terms were not disclosed, was reported last week by The Information to be valued at more than $300 million. Stainless is backed by Sequoia Capital and Andreessen Horowitz.

A strategic infrastructure play

The acquisition removes a key piece of infrastructure from the hands of Anthropic’s competitors. The company told Bitcoin World that it will wind down all hosted Stainless products, including its SDK generator. An Anthropic spokesperson confirmed that existing Stainless customers will retain ownership of the SDKs they have generated and will have full rights to modify and extend them.

Stainless, founded in 2022 and based in New York, rose to prominence in the AI industry by automating the creation and maintenance of software development kits (SDKs) — the libraries developers use to interact with APIs. Rattray’s software takes API specifications and turns them into production-ready SDKs across multiple programming languages, including Python, TypeScript, Kotlin, Go, and Java. The platform automatically updates SDKs as APIs change, eliminating the time-consuming manual maintenance process.

Why this matters for the AI ecosystem

The technology is particularly valuable for companies building AI agents that connect to external software and complete tasks on behalf of users. Stainless’s SDK tools simplify building and maintaining those connections. Going forward, however, the tools will be exclusive to Anthropic.

According to Anthropic, Stainless software has powered the generation of every official Anthropic SDK since the earliest days of its API. Rattray said in a press release, “I started Stainless because SDKs deserve as much care as the APIs they wrap. Anthropic was one of the first teams to bet on this with us. We have been watching what developers have built on Claude over the last few years, which made bringing our teams together an easy decision.”

Implications for competitors

The deal means that OpenAI, Google, Cloudflare, Replicate, Runway, and other companies that relied on Stainless will now need to find alternative solutions or build their own SDK generation tools. This shift could slow development cycles for some AI products that depend on frequent API updates.

Industry analysts view the acquisition as part of a broader trend where leading AI labs are vertically integrating key tools to gain competitive advantages. By owning the SDK pipeline, Anthropic can ensure tighter integration between its API and the developer experience, potentially attracting more third-party developers to build on Claude.

Conclusion

Anthropic’s acquisition of Stainless for over $300 million is a strategic move that strengthens its developer infrastructure while depriving rivals of a widely used tool. The deal underscores the growing importance of developer tooling in the AI arms race and signals that Anthropic is willing to invest heavily in controlling its technical stack. For the broader AI ecosystem, it raises questions about how dependent startups should become on third-party infrastructure that could be acquired by a competitor.

FAQs

Q1: What does Stainless do?
Stainless automates the creation and maintenance of software development kits (SDKs) for APIs. It converts API specifications into production-ready SDKs in multiple programming languages and automatically updates them as APIs change.

Q2: How much did Anthropic pay for Stainless?
Anthropic did not disclose the terms, but The Information reported the deal was valued at more than $300 million.

Q3: Will existing Stainless customers lose access?
Anthropic will wind down all hosted Stainless products, including the SDK generator. However, existing customers will retain ownership of the SDKs they have generated and have full rights to modify and extend them.