Alex Rattray’s Stainless is joining Anthropic as the devtools startup winds down hosted products
Alex Rattray’s SDK-generator startup will wind down hosted products; The Information reported talks above $300M as Anthropic folds a key supplier into its stack.
By Ryan Merket ·
Why it matters
A neutral SDK supplier used by several top labs is becoming first-party at one of them. That reshapes the devtools landscape around AI APIs, pushing rivals to in-source or find alternatives and giving Anthropic more control over how developers build on Claude. For founders, it is a reminder that distribution into platform incumbents can be both the fastest path to scale and the trigger for consolidation.
Alex Rattray, a former Stripe engineer and founder of Stainless, is selling his New York devtools startup to Anthropic, which confirmed the acquisition in a TechCrunch report. Stainless built an SDK generator used by heavyweight customers including OpenAI, Google, and Cloudflare, according to TechCrunch.
Rattray spun up Stainless in 2022 and quickly found demand among API-first teams that wanted production-grade SDKs without hand-coding every client library. That early traction, plus backing from Sequoia Capital and Andreessen Horowitz cited by TechCrunch, put a small devtools shop in the middle of the AI platform wars.
What is changing for customers
Anthropic told TechCrunch it will wind down all hosted Stainless products, including the SDK generator. Existing customers keep the SDKs they have generated to date, with full rights to modify and extend them. The companies did not disclose timing details in the TechCrunch piece, and terms were not announced. The Information reported last week that Anthropic was in talks to acquire Stainless for more than $300 million.
For teams that depended on Stainless as a service, the near-term task is inventory: identify which products and client libraries trace back to Stainless output, decide whether to maintain them in-house, and plan a migration path for any pipelines that relied on the hosted generator.
Why Anthropic wants this
Anthropic is leaning hard into developer experience around Claude, from enterprise features to a coding agent in the terminal called Claude Code. Folding Stainless into Anthropic looks like a move to own more of the SDK toolchain that touches how developers call models, manage versions, and ship integrations. It also removes a neutral supplier that was serving rivals, which could matter as model providers race to tighten their ecosystems.
The fit is strategic: Anthropic pitches Claude as a workspace for complex professional work and has been adding integrations across the stack. Owning world-class SDK generation tech could translate into faster, better-maintained client libraries and tighter workflows for Claude users.
Founder lens
This outcome underscores how much leverage a focused devtools founder can have in a platform wave. Rattray built Stainless for a specific pain point that every API company feels, found adoption inside marquee AI labs, and turned that wedge into an exit to a foundation model provider that needs great DX to compete. Stainless will wind down as a standalone service, but its core ideas are likely to live on inside Anthropic’s developer stack.
The competitive angle
Taking Stainless out of market forces OpenAI, Google, Cloudflare, and other customers to make choices: maintain existing SDKs themselves, retool around other generators or frameworks, or invest more in in-house tooling. For the broader ecosystem, it is another data point in the consolidation of AI infrastructure around model vendors and their first-party tooling.