Anthropic acquires Stainless, an SDK tool used by OpenAI and Google

Anthropic announced the acquisition of Stainless, a New York-based startup founded in 2022 by former Stripe engineer Alex Rattray. Stainless automated the creation and maintenance of SDKs in languages like Python, TypeScript, Go, Java, and Kotlin from API specifications. The company’s tools were quietly used across the AI industry by major players including OpenAI, Google, Cloudflare, Runway, and Replicate. Anthropic itself relied on Stainless since the early days of its API. The deal is reportedly worth more than $300 million, though terms were not officially disclosed.

Anthropic confirmed it will wind down all hosted Stainless products, including the automated SDK generator. Existing customers retain rights to SDKs already generated, but the core engine will no longer be available to outsiders. This move immediately creates a dependency problem for rival model providers, who must now maintain frameworks manually or seek alternatives. The acquisition marks Anthropic’s fourth in six months, following purchases of Bun, Vercept, and Coefficient Bio. Industry analysts see this as part of a broader shift where AI labs compete on developer tooling and orchestration layers, with Anthropic’s head of platform engineering noting that “agents are only as useful as what they can connect to.”