I added a bit more information about Bun compatibility:
> While Bun is supported and Bun does support the `using` keyword, it's runtime automatically creates a polyfill for it whenever Function.toString() is called. This transpiled code relies on specific internal globals made available in the context where the function is serialized. Because the worker runs in a different isolated context where these globals are not registered, code with `using` will fail to execute.
> While Bun is supported and Bun does support the `using` keyword, it's runtime automatically creates a polyfill for it whenever Function.toString() is called. This transpiled code relies on specific internal globals made available in the context where the function is serialized. Because the worker runs in a different isolated context where these globals are not registered, code with `using` will fail to execute.