By ByteBot
Anthropic bought Stainless in May and shut it down. That sounds dry until you realize Stainless was the SDK factory behind OpenAI, Google DeepMind, Perplexity, and Cloudflare’s own developer libraries. Every API update those teams shipped previously triggered automatic SDK regeneration across Python, TypeScript, Go, and more. As of September 1, that automation is gone. On September 21, Cloudflare open-sourced Forge — a CI pipeline that generates SDKs, CLIs, docs, and MCP servers from an OpenAPI spec, under Apache 2.0, with no Cloudflare dependency required.
What Forge Actually Does
Forge is a plugin pipeline with four stages: resolve, overlay, transform, finalize. You give it an OpenAPI 3.x spec. It hands back whichever surfaces you configure: SDKs in nine languages, a CLI, API reference documentation, and — critically for 2026 — MCP servers. Transformers chain, meaning one spec can produce a TypeScript SDK and an MCP server in the same CI run.
Installation is one command:
pnpm add @cloudflare/forgeForge already powers Cloudflare’s new cf CLI — an agentic command-line tool covering 3,000+ Cloudflare API operations (Wrangler covered about 280). The cf CLI supports natural-language command discovery and is built explicitly for AI agent tooling. It is the first production output from Forge, and it shipped the same week.
The MCP Angle Is the Real Story
SDK generation has existed for years. What makes Forge interesting in September 2026 is the MCP server transformer. AI agents — Claude, Copilot Autopilot, and every other tool that calls external APIs — do so through MCP. If your API does not have an MCP server, agents cannot use it natively. Before Forge, generating and maintaining an MCP server alongside your REST API was a manual, error-prone extra step. Forge automates it: your MCP server regenerates on every spec change, in CI, with the same preview build workflow as your TypeScript SDK.
“AI agents raise the stakes since stale or incomplete SDKs can cause an agent to misunderstand what a service can do.”
Dane Knecht, Cloudflare CTO
What Happened to Stainless
Stainless was a New York startup that offered managed, automated SDK generation. Most AI labs and many API-first companies relied on it. Anthropic acquired Stainless for $300M+ in May 2026. The same day, Stainless announced it was winding down all hosted products. New signups closed immediately. The platform shut completely on September 1.
Former Stainless users now need a replacement. The realistic options are Speakeasy (managed, closest like-for-like), Scalar (reads stainless.yml directly, has a migration guide), Fern (now owned by Postman), OpenAPI Generator (Apache 2.0, 80+ language generators, no MCP), and Forge. Of these, Forge is the only Apache 2.0 tool that generates MCP servers.
Why the License Matters
Apache 2.0 means you can run Forge on your own infrastructure, fork it, and modify it without paying anyone. Speakeasy, Fern, and APIMatic are commercial. OpenAPI Generator is open source but community-maintained and does not yet support MCP output. Forge sits in the middle: backed by Cloudflare’s engineering team, open source, and self-hostable by design.
For teams that were on Stainless: if you want managed and do not mind vendor lock-in, Speakeasy is the path of least resistance. If you want open source control and plan to add MCP server generation anyway, Forge is the better default today.
The repository is at github.com/cloudflare/forge. The full context on the Stainless acquisition and what it broke is worth reading before you choose a migration path.
