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May 18, 2026 • Kirsten Korosec

Anthropic Acquires Stainless SDK Automation Platform

Anthropic Acquires Stainless SDK Automation Platform Anthropic Acquires Stainless SDK Automation Platform Anthropic Acquires Stainless SDK Automation Platform

Anthropic Acquires Stainless: The Dev Tools Startup Used by OpenAI, Google, and Cloudflare

Anthropic announced Monday it has acquired Stainless, a startup founded by former Stripe engineer Alex Rattray whose software is widely used by rival AI labs, including OpenAI and Google.

Deal Overview

  • Terms undisclosed, but The Information reported the acquisition price exceeded $300 million
  • Backed by: Sequoia Capital and Andreessen Horowitz
  • Founded: 2022 in New York
  • Strategic Impact: Removes key infrastructure supplier from competitors' hands

What Stainless Does

Stainless rose to prominence for automating the creation and maintenance of software development kits (SDKs) — the libraries developers use to interact with APIs.

Core Technology

  • Takes API specifications and converts them into production-ready SDKs
  • Supports multiple programming languages: Python, TypeScript, Kotlin, Go, and Java
  • Automatically updates SDKs as APIs change
  • Eliminates time-consuming manual maintenance

Why It Matters for AI Agents

The technology is particularly valuable for companies building AI agents that can connect to external software and complete tasks on behalf of users. Stainless's SDK tools provide an easy way to build and maintain those connections.

Impact on the Market

Customer Base Affected:

  • OpenAI
  • Google
  • Replicate
  • Runway
  • Cloudflare

Product Sunset

Anthropic will wind down all hosted Stainless products, including its SDK generator. However:

  • Existing customers retain full ownership of SDKs generated to date
  • Customers have full rights to modify and extend their existing SDKs
  • Going forward, tools will be Anthropic-exclusive

Founder's Perspective

Alex Rattray, Stainless Founder:

"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."

Strategic Significance

According to Anthropic, Stainless software has powered the generation of every official Anthropic SDK since the earliest days of its API.

The acquisition positions Anthropic with exclusive access to SDK automation tools while cutting off this infrastructure from competitors in the AI race.