Cloudflare Open-Sources Forge After Stainless Shutdown Leaves Customers Stranded

Within a span of eleven days, two major technology companies have publicly committed to open-source SDK generation infrastructure. The catalyst: the sudden disappearance of Stainless, a proprietary service that both Cloudflare and Google had depended on for maintaining their software development kits.

Cloudflare unveiled Forge, a new open-source tool designed to take API specifications and automatically generate the SDKs, command-line interfaces, documentation and other components needed to interact with an API. The project operates under an Apache 2.0 license, allowing developers to run, modify and fork it without any obligation to Cloudflare.

In a blog post authored by Dimitri Mitropoulos, Matt Taylor and Samuel MacLeod, Cloudflare explained the philosophy behind the release: "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 company noted that Forge is still in early stages, currently generating output for the cf CLI, Cloudflare's unified command-line interface. The company plans to migrate its API documentation and SDKs to the system in the coming months.

The Stainless Acquisition and Its Fallout

Google's move came first, announced just eleven days before Cloudflare's Forge release. On September 17, Google revealed it had partnered with Speakeasy, an API tooling firm, to open-source the latter's OpenAPI code-generation suite under an AGPLv3 license. Google attributed the decision to a sudden service interruption when its SDK-generation provider was acquired and subsequently shut down operations.

Google's statement on the matter was blunt: "This sudden disruption highlighted that proprietary, closed-source generators create unacceptable platform risk. 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 company behind that disruption was Stainless. On May 18, Anthropic completed its acquisition of the SDK and MCP tooling company, after which Stainless announced plans to discontinue its products, including the SDK generator that had been essential for keeping client libraries synchronized with evolving APIs.

The shutdown affected a broad customer base that included OpenAI, Google and Cloudflare. While these organizations retained the SDKs that Stainless had previously generated, they lost access to the shared service that had enabled them to regenerate and refresh those SDKs as their APIs changed.

Cloudflare's Path to Building Forge

Cloudflare had already begun developing the foundational components that would eventually become Forge. In April, the company released a technical preview of cf, a new unified command-line interface intended to provide developers and AI agents with a consistent set of commands for accessing Cloudflare's products. At that time, Cloudflare had constructed a TypeScript-based schema and generation system designed to maintain alignment between CLI commands, configuration, bindings and other interfaces with its underlying API.

The initial preview was limited in scope, covering only a subset of Cloudflare's product offerings, though the company indicated it was already testing a version that would span its entire API surface. Forge represents the code-generation system that has evolved from this work, now responsible for producing the output that cf requires.

Tools like Forge eliminate the need for API providers to manually maintain separate SDKs, CLI command sets and documentation. When an API is modified, a single definition can be used to generate updated SDKs, CLI commands and documentation for the developers or agents that consume it.

Why Hosted Generators Fell Short

Cloudflare had relied on Stainless as one of several hosted generation services in production, but the company does not single it out by name. Instead, Cloudflare articulates the broader frustrations it encountered with the category of hosted generators.

Scale presented a significant challenge. Cloudflare now operates more than 3,500 API operations supported by hundreds of services maintained by distinct engineering teams. A generation system must accurately reflect changes across this expansive API landscape in the tools that customers use, without transforming every update into a company-wide coordination effort.

Cloudflare also wanted its engineers to preview how an API change would affect the resulting SDK, CLI and documentation before merging the underlying code. Additionally, the company sought a system that could extend beyond traditional SDKs to encompass MCP servers and Cap'n Web bindings, which enable applications to invoke remote services through Cloudflare's TypeScript-based RPC system as though they were local function calls.

External services proved inadequate for these requirements. Cloudflare reports that issues introduced in one part of its API could remain hidden until another team attempted a release, forcing engineers to trace failures through systems beyond their control and coordinate fixes across organizational and vendor boundaries.

The authors of the Forge announcement reflected on this experience: "We've tried several hosted products that attempt to solve this, and relied on some in production. None of them solved this problem for us, and some have shut down entirely."

The Case for Open Source

The Stainless shutdown provides substantial context for Cloudflare's decision to release Forge as open source. Stainless's generator was proprietary and operated as a hosted service, creating customer dependency on the company's continued operation. Forge's permissive Apache 2.0 license enables developers to operate it on their own infrastructure, modify it, or fork the project to continue using it independently of Cloudflare.

The emergence of AI agents amplifies the importance of this choice. AI agents increasingly depend on SDKs, CLIs and API bindings to comprehend what software can accomplish and how to interact with it. When those interfaces lag behind the underlying service, agents may operate from incomplete or outdated descriptions of available capabilities.

Cloudflare CTO Dane Knecht emphasized this concern when discussing why maintaining current interfaces has become more critical: "APIs have always been how software connects, but AI agents make the quality of SDKs, CLIs, and API bindings even more important. 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."

According to Knecht, Cloudflare determined that SDK and CLI generation had "become too important" to remain 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 stated.

Early Days Ahead

Forge still faces significant development work. The project remains in its early phase, with cf as its first production application. Cloudflare expects its API documentation and existing SDKs to transition to the system during the coming months. Several input formats and generation targets discussed in the announcement represent future development priorities.

The timing, however, sends a powerful signal. Within eleven days, Google and Cloudflare—both former Stainless customers—have publicly backed open-source SDK-generation infrastructure following the loss of the proprietary service they had relied upon. Google characterized that dependency as an "unacceptable platform risk." Cloudflare, through Forge, is now working to eliminate that same risk from its own technology stack.