Anthropic bought Stainless and shuttered its SDK generator. Cloudflare open-sourced Forge instead.
Cloudflare has announced an open source tool that takes an API definition and automatically produces the SDKs, command-line tools, documentation, and other interfaces used to interact with it.
Forge, as it’s called, is available under an Apache 2.0 license, and can be run and modified privately without paying Cloudflare a dime. In a blog post published on Monday by Dimitri Mitropoulos, Matt Taylor, and Samuel MacLeod, Cloudflare notes that the project is still early: it already generates the output required for Cloudflare’s cf CLI, its unified command-line interface for working across the Cloudflare platform, with the company’s API documentation and SDKs due to move over in the coming months.
“We believe that building tools for APIs is a core part of the Internet, and you should be able to do that without needing a SaaS product.”
“We believe that building tools for APIs is a core part of the Internet, and you should be able to do that without needing a SaaS product,” the authors write.
When your SDK generator disappears
Cloudflare’s announcement comes just 11 days after Google made a somewhat similar move, revealing it had partnered with API tooling company Speakeasy to open-source the latter’s OpenAPI code-generation suite under an AGPLv3 license.
In a blog post published September 17, Google said its decision was prompted by the sudden loss of its SDK-generation service, after the provider was acquired and “abruptly announced its shutdown.” This happened just as Google was preparing to launch a new API.
“This sudden disruption highlighted that proprietary, closed-source generators create unacceptable platform risk.”
“This sudden disruption highlighted that proprietary, closed-source generators create unacceptable platform risk,” the company wrote. “If the industry relies on OpenAPI to define interfaces, the tooling to compile those interfaces into client libraries, CLIs, and agent tools should be open infrastructure.”
The provider Google was referring to was Stainless. Anthropic acquired the SDK and MCP tooling company on May 18, after which Stainless said it would wind down its products, including the SDK generator used to keep client libraries updated as APIs changed.
As The New Stack reported at the time, the closure affected a swathe of customers including OpenAI, Google and Cloudflare. While those companies retained the SDKs Stainless had already generated for them, they lost the shared service they had relied on to regenerate and update those SDKs as their APIs evolved.
Cloudflare, for its part, had already begun building some of the machinery that would become Forge. In April, the company released a technical preview of cf, a new unified command-line interface intended to eventually expose Cloudflare’s products through a consistent set of commands for developers and AI agents. At the time, Cloudflare said it had created a new TypeScript-based schema and generation system to keep CLI commands, configuration, bindings and other interfaces in sync with its API.
That earlier preview was limited — cf initially covered only a small subset of Cloudflare products — although the company said it was already testing a version spanning its entire API surface. Forge is the code-generation system that has emerged from that work and now generates the output required by cf.
Tools such as Forge save API providers from having to maintain each SDK, CLI command set and documentation surface separately by hand. When the underlying API changes, the same definition can be used to produce updated SDKs, CLI commands and documentation for the developers — or agents — consuming it.
Why Cloudflare built its own generator
While Stainless was one of the hosted generation products Cloudflare had relied on in production, Cloudflare doesn’t name it specifically, instead spelling out why Cloudflare had become dissatisfied with the broader category of hosted generators.
Part of the problem is sheer volume: Cloudflare says it now has more than 3,500 API operations, backed by hundreds of services maintained by different engineering teams. A generator therefore has to keep changes across that sprawling API estate accurately reflected in the tools customers use, without turning every update into a coordination exercise across the company.
Cloudflare also wanted engineers to see what an API change would do to the resulting SDK, CLI and documentation before the underlying code was merged. Moreover, it wanted the same system to reach beyond conventional SDKs into things such as MCP servers and Cap’n Web bindings, which allow applications to invoke remote services through Cloudflare’s TypeScript-based RPC system in much the same way they would call local functions.
That had proved difficult with external services. Cloudflare says problems introduced in one part of its API could surface only when another team later tried to release something, leaving engineers to trace the failure back through systems they did not fully control and then coordinate a fix across company and vendor boundaries.
“We’ve tried several hosted products that attempt to solve this, and relied on some in production,” the authors write. “None of them solved this problem for us, and some have shut down entirely.”
The open-source factor
And so the Stainless wind-down goes some way toward explaining why Cloudflare is making Forge open source. Stainless’s generator was proprietary and delivered as a hosted service, leaving customers dependent on the company continuing to operate it. Forge’s permissive Apache 2.0 license means developers can run it on their own infrastructure, modify it, or fork the project and continue using it independently of Cloudflare.
AI agents raise the stakes further, because they increasingly rely on SDKs, CLIs and API bindings to understand what software can do and how to interact with it. If those interfaces lag behind the underlying service, the agent may be working from an incomplete or outdated description of its capabilities.
That is the concern Cloudflare CTO Dane Knecht highlights when explaining why keeping those interfaces current matters more than ever today.
“APIs have always been how software connects, but AI agents make the quality of SDKs, CLIs, and API bindings even more important,” Knecht tells The New Stack over email. “If that layer is stale or incomplete, an agent doesn’t just have a worse developer experience, it can misunderstand what a service can do.”
Ultimately, Cloudflare created Forge because SDK and CLI generation has “become too important” to sit outside its internal development process.
“Cloudflare needed a pipeline our teams could run, test, and extend themselves, and we think other developers should have access to that same kind of open, vendor independent foundation,” Knecht says.
Forge still has plenty to prove, of course. The project is early, cf is its first production output, and Cloudflare says its API documentation and existing SDKs will move over during the coming months. Several of the input formats and generated targets it discusses are also future work.
But the timing is quite revealing. Within 11 days, Google and Cloudflare — both former Stainless customers — have publicly thrown their heft behind open source SDK-generation infrastructure after the disappearance of the proprietary service they had relied on. Google describes that dependency as an “unacceptable platform risk.” Cloudflare, with Forge, is now trying to remove the same risk from its own stack.
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