Unable to set response headers for SharedArrayBuffer

Describe the bug

I have a project which depends on a library which uses SharedArrayBuffer, but I can't get it to work, and always get this error:
ReferenceError: SharedArrayBuffer is not defined

What I need to do

Set

• Cross-Origin-Opener-Policy header to same-origin
• Cross-Origin-Embedder-Policy to require-corp

What I have tried:

• setting headers in vite.config.js

export default defineConfig({
  server: {
    headers: {
      // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer#security_requirements
      "Cross-Origin-Opener-Policy": "same-origin",
      "Cross-Origin-Embedder-Policy": "require-corp",
    },
  },
  plugins: [sveltekit()],
});

• Writing a hooks.js file to use custom headers
• Using a middleware in vite.config.js to set headers

Reproduction

Smallest possible repro:
Live example
Repo

Logs

No response

System Info

1.60.125 Chromium: 119.0.6045.199 (Official Build) (64-bit)

Severity

blocking all usage of SvelteKit

Additional Information

No response

Start with the linked live example and repository, then inspect vite.config.js, hooks.js, and the attempted middleware setup. Verify how the requested Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy headers are handled, and confirm the reproduction no longer reports SharedArrayBuffer as undefined.