Anthropic acquires Stainless, integrating the SDK generation platform that has produced every official Claude client library since the first API releases

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First they came for openclaw and I did not do anything Then they came for opencode and I did not do anything

Anthropic is acquiring @stainlessapi, an SDK and MCP server platform that has powered every Anthropic SDK since the earliest days of our API.

Read more: https://www.anthropic.com/news/anthropic-acquires-stainless

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Gergely Orosz@GergelyOrosz

“Can you not use AI to build an SDK?”

The answer, it turns out, is “no.” This is why Anthropic, OpenAI and Meta all use a dedicated tool (until now: Stainless) to *generate* their SDKs.

SDKs need to be consistent and reliable. It’s two things LLMs are bad at! So.

The Pragmatic Engineer@Pragmatic_Eng

Anthropic acquired and is shutting down Stainless, a startup also used by OpenAI and Meta to generate their SDKs. So, will OpenAI and Meta rewrite their SDK using AI agents? Unlikely.

We covered why, and also Stainless alternatives in our deepdive:

https://newsletter.pragmaticengineer.com/p/building-great-sdks

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Gergely Orosz@GergelyOrosz

Such a strange take.

1. This was an acquihire of a string eng team. Super common for this outcome to happen

2. Out of all companies, OpenAI should have the least problem rewriting an SDK generation tool using eg Codex.

3. They probably won’t do #2 but use a competing vendor!

Larsen Cundric@larsencc

Be Anthropic:

- compete with OpenAI - OpenAI uses Stainless for their SDK - acquire Stainless - shut it down

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Jennifer Li@JenniferHli

Huge congratulations to @RattrayAlex and the @StainlessAPI team on the acquisition by @AnthropicAI.

From our earliest conversations, what stood out about Stainless was the clarity of the mission: make APIs feel effortless for developers, by turning API design into great SDKs, docs, and tooling by default. It sounds simple until you appreciate how much craft sits behind it. True to its name, Stainless polished every detail developers only notice when they’re missing: type safety, idiomatic clients, versioning, reliability, to create an experience that just works.

That kind of infrastructure compounds. As AI becomes more programmable and more deeply embedded in every product, the interface between developers and models matters enormously. Stainless built one of the defining developer infrastructure companies for that world.

Proud to have been part of the journey, and excited to see what the team builds next with Anthropic. Congrats Alex, Mark, Daniella, Alex A, Mirole and the entire Stainless team!!

Anthropic@AnthropicAI

Anthropic is acquiring @stainlessapi, an SDK and MCP server platform that has powered every Anthropic SDK since the earliest days of our API.

Read more: https://www.anthropic.com/news/anthropic-acquires-stainless

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Jerry Liu@jerryjliu0

very happy for you

do we have to maintain our SDKs manually again

Stainless@StainlessAPI

We're thrilled to announce that Stainless is joining @AnthropicAI! Stainless was founded to make software better for everyone, and we're honored to continue that mission on the Anthropic team. Check out the announcement blog post for more: https://www.stainless.com/blog/stainless-is-joining-anthropic/

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Dan Shipper 📧@danshipper

Amazing!!

So proud of @RattrayAlex and honored to be a tiny investor

Anthropic@AnthropicAI

Anthropic is acquiring @stainlessapi, an SDK and MCP server platform that has powered every Anthropic SDK since the earliest days of our API.

Read more: https://www.anthropic.com/news/anthropic-acquires-stainless

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Rohan Paul@rohanpaul_ai

Anthropic just acquired Stainless to make Claude agents better at reaching real software systems through cleaner SDKs, CLIs, and MCP servers.

Shows again that better connectivity infrastructure will matter as much as better model intelligence once companies start asking agents to perform actual work.

Stainless has generated every official Anthropic SDK since the early Claude API days, which means Anthropic is buying a toolchain that already sits inside its developer platform.

Anthropic@AnthropicAI

Anthropic is acquiring @stainlessapi, an SDK and MCP server platform that has powered every Anthropic SDK since the earliest days of our API.

Read more: https://www.anthropic.com/news/anthropic-acquires-stainless

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Sarah Wang@sarahdingwang

Congrats @RattrayAlex , @StainlessAPI and @AnthropicAI! The mission of making APIs effortless for developers (and agents) is more important than ever

And big congrats to my amazing partner @JenniferHli who is on what I believe will be a generational run 🐐

Jennifer Li@JenniferHli

Huge congratulations to @RattrayAlex and the @StainlessAPI team on the acquisition by @AnthropicAI.

From our earliest conversations, what stood out about Stainless was the clarity of the mission: make APIs feel effortless for developers, by turning API design into great SDKs, docs, and tooling by default. It sounds simple until you appreciate how much craft sits behind it. True to its name, Stainless polished every detail developers only notice when they’re missing: type safety, idiomatic clients, versioning, reliability, to create an experience that just works.

That kind of infrastructure compounds. As AI becomes more programmable and more deeply embedded in every product, the interface between developers and models matters enormously. Stainless built one of the defining developer infrastructure companies for that world.

Proud to have been part of the journey, and excited to see what the team builds next with Anthropic. Congrats Alex, Mark, Daniella, Alex A, Mirole and the entire Stainless team!!

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Gergely Orosz@GergelyOrosz

You can ofc use it to vibe code an SDK it just won’t be fun for devs or even agents to use!

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Gergely Orosz@GergelyOrosz

@Pragmatic_Eng Exactly.

Anthropic then moved off rapidly. It's not exactly an unsolvable problem. Every vendor you use is a risk, and if something happens to the vendor you react. Migrate / move off, this is not all that difficult... esp for world-class eng teams...

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Arnav Gupta@championswimmer

@GergelyOrosz OpenAI acquired Statsig which Anthropic and many of their competitors were using for agent/API telemetry as well.

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Jennifer Li@JenniferHli

Big thank you to my best partners @jeffreysilv and @stuffyokodraws on this journey as well. Couldn’t have done this without you! ❤️🙏🏻

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Tanishq (tk) 🌊@tanishqk

@jxnlco i wonder if they're gonna boot OpenAI from it

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Alex Plescan@alexplescan

@GergelyOrosz If this ends up with OpenAI moving their Go SDK off Stainless, that's a win in my book. The thing currently adds 11MB to my project's binary... nearly half the size of ALL my deps combined.

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Gergely Orosz@GergelyOrosz

@webguy @alexplescan Having talked to experts on building SDK the problem with vibe coding is consistency and reliability

A production-grade SDK cannot have varying conventions and it cannot NOT work…

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Đoc@ponzibaron

@jxnlco Next they came for goblinmode and I ended them.

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Vanar@Vanarchain

@rohanpaul_ai Great step. Better infrastructure always unlocks better real world AI use.

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Joel Haasnoot@webguy

@GergelyOrosz @alexplescan Sure. Tbh we rarely use SDKs. They in general are bloated, complicated, may not use the client library we want, etc. We often choose to just build the handful of HTTP calls we need to integrate ourselves. Yes, streaming is more complicated if that's needed, etc.

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Kirill Goldin@KirillGoldinBiz

@GergelyOrosz Interesting story about Stainless. But in general, one can build consistent and reliable SDK that does not rely on probabilistic models. But you can use AI as a tool while building it. Same as any other tools.

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Katelyn Lesse@katelyn_lesse

@danshipper @RattrayAlex 💙

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