Worker talking to worker service with itty-router

I'm trying to get worker-a to talk to worker-b service, the worker-b service is deployed and I'm serving up the worker-a via

wrangler dev

wrangler dev

wrangler dev

wrangler dev

From worker-a:

...
router.get('/apps', async(request, env) => {
  return await env.API.fetch(request.clone())
})

...
router.get('/apps', async(request, env) => {
  return await env.API.fetch(request.clone())
})

...
router.get('/apps', async(request, env) => {
  return await env.API.fetch(request.clone())
})

...
router.get('/apps', async(request, env) => {
  return await env.API.fetch(request.clone())
})

From worker-b service:

router.get('/apps', async(request, env) => {
  return new Response('Hello')
})

router.get('/apps', async(request, env) => {
  return new Response('Hello')
})

router.get('/apps', async(request, env) => {
  return new Response('Hello')
})

router.get('/apps', async(request, env) => {
  return new Response('Hello')
})

But I just get

internal error {
  stack: Error: internal error,
  message: internal error
}

internal error {
  stack: Error: internal error,
  message: internal error
}

internal error {
  stack: Error: internal error,
  message: internal error
}

internal error {
  stack: Error: internal error,
  message: internal error
}

Is there a way to point to my local served worker service to debug what's going wrong?