Alloy

Alloy powers https://typespec.io/, which Microsoft it seems is using to generate new OpenAPI sdks for Azure, among other things!

Looks like a great DSL, similar to https://smithy.io/, but more extensible, not tied to Java, and built with Typescript in mind.

Alloy itself seems like a delightful way to do codegen, and there have been talks mentioning Stripe uses a custom React render target just like this to generate their famously readable SDKs and code examples across all languages.