Stainless
The SDK generator behind OpenAI, Anthropic, and Google's official client libraries.
Retired
Stainless appears to be discontinued or shut down — acquired by Anthropic May 2026; hosted products sunset Sep 2026 This page is kept as an archive record and is excluded from search engines.
About
Stainless was the quiet infrastructure behind much of the AI industry's developer experience: founded in 2022 by former Stripe engineer Alex Rattray, its compiler turned API specifications into production-ready SDKs across Python, TypeScript, Kotlin, Go, and Java — automatically kept in sync as APIs changed. It powered every official Anthropic SDK since the Claude API's early days, plus OpenAI's, Google's, Cloudflare's, Runway's, and Replicate's client libraries. The company raised a $25M Series A led by a16z with Sequoia participating.
The honest caveat, and it is a big one: Anthropic acquired Stainless in May 2026 for a reported $300M+ and is winding down all hosted products — the platform was scheduled to sunset on September 1, 2026, with the technology going Anthropic-only. Do not adopt Stainless for new projects. It earns its place here as the tool that defined the category and the cautionary tale about building on venture-backed dev infrastructure: have an exit plan. Speakeasy and Fern are the living alternatives.
What it can do
- Spec-to-SDK compilation across 5+ languages
- Automatic SDK updates as APIs evolve
- Custom code overlays surviving regeneration
- Powered Anthropic, OpenAI, Google, and Cloudflare SDKs
Setup
Not recommended for new adoption — the hosted platform is being wound down post-acquisition. Existing customers retain full rights to SDKs generated to date.
Prerequisites
None — historical entry. Evaluate Speakeasy or Fern instead.
Use cases
Works with
Trust score — 6/10
Scored 6/10 (metrics tier, metrics-v1). Evidence: Verified via vendor site/docs/GitHub and reputable coverage, wave 46; Trending score 65/100 from researcher assessment.
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.