# Stainless and Voxgig, compared

> The generator behind many of the best-known AI SDKs. Its hosted product is winding down. Stainless generated the official client libraries for OpenAI, Anthropic, Cloudflare and several hundred other providers, and set the quality bar this whole field now aims at. Anthropic acquired it in May 2026 and is winding down the hosted generator. Published by Voxgig, which makes one of the two tools. Facts checked 7 September 2026.

**Status.** Anthropic announced on 18 May 2026 that it had acquired Stainless and would wind down all hosted Stainless products, including the SDK generator. New signups, projects and SDKs stopped the same day. Stainless says customers keep the SDKs generated to date and full rights to modify and extend them, and points existing customers at a transition page.

## What it is

Stainless was a commercial SDK generation service. Its output is the most widely read generated code in the industry: the official OpenAI, Anthropic and Cloudflare client libraries, Meta's Llama Stack, Groq, Cerebras, LangChain and several hundred other providers. Most people who have used a modern AI API in Python or TypeScript have used a Stainless-generated SDK without knowing it.

The targets were TypeScript, Python, Go, Java, Kotlin, Ruby, C#, PHP and Terraform. Generated SDKs were licensed Apache 2.0 to the customer.

The design idea that made it work was a configuration layer sitting between the OpenAPI description and the output. The spec said what the API was. A separate Stainless config said what the library should feel like: resource naming, method names, pagination style, model names, which endpoints were promoted and which were hidden.

What that buys you is the ability to fix an SDK without touching the API description, and to keep the library's shape stable when the spec churns. It is the single most copied idea in this field. Voxgig's semantic model is a different answer to the same problem: rather than a config that adjusts the output, the model is a type-safe description of entities and operations that every surface is generated from.

## Facts

- Made by: Stainless, acquired by Anthropic in May 2026
- Status: Hosted products winding down
- Licence: Generator proprietary. Generated SDKs Apache 2.0
- Language targets: 9, including Terraform
- Site: stainless.com (https://www.stainless.com)

## What Stainless does that Voxgig does not

### Output quality as the entire product

Read the openai or anthropic Python and TypeScript libraries. They read as though a careful person wrote them, and they are generated. Streaming, typed errors, request IDs, automatic pagination, retries with idempotency, per-language conventions honoured rather than approximated. Those repositories are public, and they are the most detailed available reference for what generated output can look like.

### The config layer, separated from the spec

Keeping library shape out of the API description is the right instinct, and it is why Stainless output looks designed rather than transcribed. It also makes the config an artefact that has to be maintained and understood, and it was proprietary. Both halves are relevant when evaluating any successor.

### MCP servers and docs from the same config

Stainless did not stop at SDKs. Its plans counted SDKs, documentation sites and Model Context Protocol servers as the same kind of thing, all generated from one API description and one config, and it led its own marketing on the MCP output rather than treating it as an add-on. That is the same bet Voxgig makes with its six surfaces, made independently, and it is the part of the product most worth copying: an MCP server hand-written beside a generated SDK drifts on the next release, and one generated from the same source cannot.

### It set the conventions the field now works to

Standardised streaming, cursor and page-based auto-pagination, typed error hierarchies, and retry-with-idempotency across every language target, at a point when most of this field had none of them. A large part of what customers now expect from any SDK generator, Voxgig included, was normalised here first.

## Side by side

| | Stainless | Voxgig |
| --- | --- | --- |
| Status | Hosted products winding down since 18 May 2026. No new projects | Actively developed |
| Licence | Generator proprietary. Generated SDKs Apache 2.0 to the customer | Generator MIT. Generated SDKs are yours |
| Language targets | 9, including Terraform | 22 bundled language targets, more from packages |
| MCP server | Yes, while it was sold | Yes |
| Where the shape was decided | A proprietary config layer over the spec | A type-safe semantic model, in your repo |
| Where generation ran | The vendor's platform | Your machine |
| Regeneration after the vendor leaves | Not available | Runs from your repo with no account |

## Choose Stainless when

- For new work you cannot: the hosted generator stopped taking projects on 18 May 2026.
- If you are an existing customer, the SDKs you have generated still work and you still own them. Nothing is revoked, nothing phones home, and there is no deadline on the code itself. Read the transition guidance before you do anything drastic.
- If your API is stable and your SDKs are finished, freezing them and maintaining them by hand is a perfectly reasonable plan. It is not the plan a generator vendor would suggest, and for a slow-moving API it is sometimes the cheapest one.

## Choose Voxgig when

- You want regeneration back, running from your own repository, with no account and no vendor in the path. That is the specific failure mode you have just lived through, and it is the one Voxgig is built to not have.
- You want the generator itself readable and forkable, so a future acquisition is somebody else's problem rather than yours.
- You want an MCP server generated beside the SDK from the same model, which is where a lot of Stainless-shaped API businesses are heading anyway.

## Limits of this comparison

- Every generator makes different naming, module layout and pagination decisions. Moving a published SDK from one to another changes your customers' code. Any move needs a major version and a migration note rather than a patch release. That applies to a move to Voxgig as much as to any other tool.
- This page is published by a vendor whose product competes for the same customers. The primary facts are in Anthropic's and Stainless's own announcements, linked below.
- Anthropic's statements are the authority on what happens next to Stainless customers. Anything here is a summary of them as of 7 September 2026.

Corrections go to info@voxgig.com. A correction changes the page and moves its checked date.

## First-party sources

- [Stainless's announcement](https://www.stainless.com/blog/stainless-is-joining-anthropic)
- [stainless.com](https://www.stainless.com)
- [The openai-python library, generated by Stainless](https://github.com/openai/openai-python)

## The other comparisons

- [All SDK generator comparisons](https://voxgig.com/sdk/comparisons): the index, the method, and the wider field.
- [OpenAPI Generator](https://voxgig.com/sdk/comparisons/openapi-generator): The community generator most APIs have shipped an SDK from at least once.
- [Speakeasy](https://voxgig.com/sdk/comparisons/speakeasy): Commercial SDK generation with the widest non-SDK output in this comparison.
- [Fern](https://voxgig.com/sdk/comparisons/fern): SDKs and a documentation site from one definition. Part of Postman since January 2026.
- [APIMatic](https://voxgig.com/sdk/comparisons/apimatic): The longest-running commercial generator here, and the only one that converts between description formats.
- [liblab](https://voxgig.com/sdk/comparisons/liblab): SDK generation shaped as a release pipeline. Part of Postman since November 2025.
- [Kiota](https://voxgig.com/sdk/comparisons/kiota): Microsoft's client generator, built so you do not need a separate SDK per API.
- [Hey API](https://voxgig.com/sdk/comparisons/hey-api): The TypeScript ecosystem's generator. One language, done properly.
- [Voxgig SDK Generator](https://voxgig.com/sdk)