Stainless
Acquired by Anthropic; SDK generator closed to new signups (2026).
Overview
Stainless generated production-grade, idiomatic SDKs from an OpenAPI spec across nine languages until Anthropic acquired it for $300M+ in May 2026 and wound the hosted platform down. Existing customers keep the SDKs they generated; new signups are closed.
Pricing
Pricing shown for reference only. These figures reflect RECATOOLS research as of 31 Aug 2026 and may be out of date or incomplete. This is not financial or purchasing advice — always confirm the current price on the provider’s official website before making any decision.
- Up to 5 generators (SDKs, docs, MCP)
- 25 endpoints, 5 seats
- 100 preview builds/mo
- Email support
- Unlimited generators
- Free for qualifying FOSS projects
- Existing customers keep their SDKs
- SOC 2 compliance reports
- Custom contract terms
Use cases
What you can produce with Stainless
- Production-ready, idiomatic SDKs in up to 9 languages from one OpenAPI spec
- Automated package publishing to npm, PyPI, Maven, RubyGems, and other registries
- Auto-generated documentation site with custom domain and AI chat support
- CLI tool and MCP server generation alongside client libraries
- Changelog generation and GitHub PR workflow for every API spec change
- Unit test scaffolding and streaming/webhook/async handling built into generated SDKs
- Terraform provider generation for infrastructure-as-code API integrations
ASEAN Perspective
Stainless in Southeast Asia
Stainless had no dedicated APAC presence, pricing in local currencies, or documented ASEAN customer base, though its generated SDKs — especially the OpenAI and Anthropic Python and TypeScript clients — are widely used by Southeast Asian AI developers daily. The service's abrupt shutdown in May 2026 disproportionately affects smaller APAC API teams that relied on its free tier or affordable Starter plan, as the leading alternatives (Speakeasy, Fern) carry higher entry-level pricing. APAC teams exploring SDK automation should evaluate Speakeasy or the open-source Stainful fork as migration paths.
Note: Stainless was acquired by Anthropic; the hosted product has been closed to new customers since May 2026.
Stainless earned real trust before the acquisition: OpenAI, Anthropic, Meta, Google, Cloudflare and Groq all shipped their official SDKs through its compiler, which turned an OpenAPI spec into idiomatic TypeScript, Python, Go, Java, Kotlin, Ruby, PHP, C#, and Terraform clients complete with retries, pagination, and docs sites. HN commenters who'd used it described the SDK output as reliable and low-maintenance, not just fast to ship. Then Anthropic bought the company for $300M+ in May 2026 and wound the hosted product down the same week — new signups, projects, and SDK generation stopped immediately, though existing customers keep full rights to what they'd already generated. The Stainless team is now inside Anthropic's Claude Platform group. Bottom line: outstanding engineering, but as of mid-2026 it's not a product you can buy — evaluate Speakeasy or Fern instead.
What people say
You can't sign up for Stainless anymore. That's the headline: Anthropic acquired the company for north of $300 million in May 2026 and wound down the hosted SDK generator the same week, cutting off new signups, new projects, and new SDK generation entirely. It's a strange note to end on for a product that, by every account, was very good.
What it did was turn an OpenAPI spec into genuinely idiomatic client code — TypeScript, Python, Go, Java, Kotlin, Ruby, PHP, C#, Terraform — complete with retries, pagination, streaming, typed models, changelogs, and hosted docs. OpenAI, Anthropic, Meta, Google, Cloudflare, Groq, and Runway all shipped their official SDKs through it, about as strong a trust signal as a dev-tools company gets. On Hacker News, engineers who'd used the Node and Python generators described the output as reliable and low-maintenance, not merely fast to ship.
The acquisition news landed badly with exactly the audience Stainless had built: an announcement noting hundreds of companies relied on Stainless, followed within the same breath by a shutdown notice, reads to a lot of developers like a cautionary tale about depending on a small vendor for critical plumbing. Existing customers keep full ownership of what they'd already generated and can self-serve locally via CLI, but the managed workflow — auto-updates, hosted docs, CI integration — is gone unless Anthropic revives it inside Claude's platform tooling.
If you're picking an SDK generator today, look at Speakeasy or Fern instead — Stainless isn't one of the options anymore, however good it used to be.
Summary of public user & expert reviews, compiled by RECATOOLS.
Notable facts
- Stainless SDKs are downloaded tens of millions of times every week by developers worldwide — making it invisible infrastructure inside virtually every major AI app.
- Anthropic paid over $300 million for a company that had roughly $1 million in annual recurring revenue at the time of its seed round in April 2024 — a 300x+ revenue multiple reflecting strategic, not financial, value.
- The acquisition created an awkward situation: Anthropic now owns the tool that OpenAI and Google used to maintain their official developer libraries.
- Stainless used a custom YAML config layer (stainless.yml) between OpenAPI specs and generated code — a design decision that enabled fine-grained control but also locked customers into the platform's toolchain.
Frequently asked questions
About this listing
This entry was compiled from publicly available data including Stainless's official website, press releases, documentation, and reputable third-party publications. RECATOOLS is not affiliated with Stainless unless explicitly stated.
Third-party AI tools update their pricing, features, availability, and policies frequently. Information here may be outdated by the time you read this — we make reasonable efforts to keep listings current, but cannot guarantee absolute accuracy.
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