Anthropic acquires Stainless, the SDK infrastructure used by OpenAI and Google

Strategic consolidation of AI infrastructure

Anthropic announced on May 18 that it has acquired Stainless, the New York-based developer tools startup founded in 2022 by former Stripe engineer Alex Rattray. According to The Information, the deal values Stainless at more than $300 million, though Anthropic declined to publicly disclose terms. The acquisition brings under Anthropic’s roof a critical piece of infrastructure currently relied upon by rival AI companies including OpenAI, Google, Cloudflare, Replicate, and Runway.

Stainless has become essential to the emerging AI agent ecosystem because it automates a historically manual and error-prone process: generating and maintaining software development kits (SDKs) that allow external applications to interact with APIs. According to TechCrunch, the platform converts API specifications into production-ready code across five major programming languages—Python, TypeScript, Kotlin, Go, and Java—and automatically synchronizes SDK implementations whenever the underlying API changes. This automation eliminates weeks of engineering effort for teams building integrations.

From shared infrastructure to proprietary advantage

The significance of this acquisition lies in transforming a shared vendor tool into competitive property. Anthropic stated that Stainless software has powered the generation of every official Claude SDK since the company’s API launch. Now, the company will wind down all hosted Stainless products, including the SDK generator platform itself. According to Anthropic’s statement to TechCrunch, existing customers retain full ownership and modification rights to SDKs they have already generated—but cannot continue using Stainless’s platform for future development.

This move eliminates a dependency for Anthropic while raising friction for competitors who relied on Stainless as a common tool. OpenAI and Google, which have built their own expansive API ecosystems, will need to develop or acquire alternative SDK maintenance infrastructure or redirect engineering resources to in-house solutions.

Alex Rattray, Stainless’s founder, framed the acquisition as a natural fit, stating in a press release that “Anthropic was one of the first teams to bet on this with us,” and cited developers’ adoption of Claude as motivation for joining the company rather than remaining independent. The startup was backed by Sequoia Capital and Andreessen Horowitz, prominent venture firms with deep ties across the AI industry.

Why This Matters

Anthropic is addressing a genuine infrastructure gap: as AI agents become more sophisticated, the ability to safely and quickly integrate external APIs becomes a bottleneck. By internalizing SDK generation, Anthropic reduces friction in its own platform while raising costs for competitors relying on third-party tooling. For teams currently using Stainless—particularly those building competitive AI products—this acquisition signals the need to prioritize API integration infrastructure within their own engineering roadmaps. The move also reflects a broader consolidation trend in AI infrastructure, where companies are vertically integrating previously commoditized layers rather than relying on shared vendor ecosystems.