Anthropic Acquires Stainless: AI Giant Strengthens Dev Tools Control with Major Startup Deal

Artificial intelligence company Anthropic has officially acquired the developer tools startup Stainless, a company whose software is already widely used across the AI industry, including by rivals like OpenAI, Google, and Cloudflare. The move signals a strategic push by Anthropic to strengthen control over critical AI infrastructure tools that power modern application development.

While financial details were not officially disclosed, reports from The Information suggest that Anthropic was in advanced talks to acquire Stainless for over $300 million. The startup is backed by major venture capital firms including Sequoia Capital and Andreessen Horowitz, making it one of the more significant infrastructure deals in the AI space this year.

Stainless, founded in 2022 by former Stripe engineer Alex Rattray, built its reputation around automating the creation of software development kits (SDKs). These SDKs help developers connect applications to APIs, and Stainless made the process faster by automatically generating and maintaining them across programming languages like Python, Go, Java, Kotlin, and TypeScript. Its tools became especially important for AI companies building agents that need to interact with external systems.

As part of the acquisition, Anthropic confirmed it will shut down Stainless’s hosted products, including its SDK generator service. However, existing customers will still retain ownership of any SDKs they have already generated and can modify them freely. The shift effectively removes a widely used infrastructure tool from open availability, raising its strategic importance within Anthropic’s ecosystem while limiting access for competitors.

In a statement, founder Alex Rattray said Stainless was built to ensure SDKs receive the same level of care as the APIs they support, and noted that partnering with Anthropic allows the team to continue their mission at a larger scale. Anthropic also revealed that Stainless technology has powered its own SDKs from the earliest days of its API, highlighting how deeply integrated the startup already was within its operations.

SOURCE: Techcrunch