In-server fetch to dev routes not working

Environment

Nitro version: 2.13.1
Node version: 20.19.1

import { defineEventHandler } from 'h3';

export default defineNitroConfig({
  compatibilityDate: '2025-03-01',
  srcDir: 'server',
  devHandlers: [
    {
      route: '/devTest',
      handler: defineEventHandler((event) => {
        return 'dev test response';
      }),
    },
  ],
});

Reproduction

Minimal reproduction in stackblitz

1. Define dev route in the nitro config.
2. Verify that the route is working when called directly.
3. Define normal route that calls the dev route -> Fails with error.

Describe the bug

The dev routes are not reachable from the normal routes. More info in the original issue I opened on nuxt repo.

Additional context

No response

Logs

Start with the nitro.config.ts setup and reproduce the behavior using the linked StackBlitz example, comparing direct requests to /devTest with requests made from a normal route. Trace how devHandlers are reached during in-server fetches; done means the normal route can reach /devTest as well as a direct request.