Edge Functions only accept a function as the default export. Please also accept a Fetchable one, an object or class instance with a fetch(request, ...extra) method:
// works today
export default async (request, context) => new Response("ok");
// this fails at load
export default { fetch: async (request, context) => new Response("ok") };
That shape is what the ecosystem settled on (Cloudflare Workers, Deno, Bun, Hono, Elysia, Nitro), and Deno Deploy, which Edge Functions run on, already supports it. Today a framework whose app carries fetch needs a Netlify-specific line instead of being exported directly.
Suggested: when the default export isn’t callable but has a fetch function, call that, bound to the export, with the same arguments. Purely additive, since a callable default stays preferred.