The startup that built SDK tooling for OpenAI, Google, and Cloudflare now belongs to their biggest competitor. Anthropic has acquired Stainless, a New York-based developer tools company, with all hosted products shutting down as part of the deal.
Stainless's core product automated SDK generation - that means it took an API specification and automatically created the code libraries (in Python, TypeScript, Go, Ruby, and other languages) that developers use to connect to an API without writing all the connection logic themselves. Maintaining those libraries across multiple languages manually is slow and error-prone, so Anthropic, OpenAI, Google, and Cloudflare all used Stainless to generate and keep client libraries in sync with their evolving APIs.
The acquisition creates an obvious conflict: Anthropic now owns infrastructure that previously served its direct competitors. Those companies will need to rebuild what Stainless provided or find a replacement vendor. With hosted products winding down entirely, this reads as an acqui-hire - Anthropic wanted the engineering team and their technical approach, not a going business.
Deal terms weren't disclosed. Stainless had raised venture funding including backing from Y Combinator before the deal closed.
For developers who depended on Stainless's hosted SDK generation service, the clock is ticking to migrate. For Anthropic, the move fits a pattern of investing in developer-facing infrastructure. Claudee Code](/tools/claude-code/) and the Claude API are competing hard against OpenAI and Google for developer adoption, and SDK quality is one of the real friction points that determines whether a developer picks one API over another.