redirect on error

import { createAPIFileRoute } from '@tanstack/react-start/api'
import { fetchRequestHandler } from '@trpc/server/adapters/fetch'
import { redirect } from '@tanstack/react-router'
import { appRouter } from '~/integrations/trpc/router'
import { createTRPCContext } from '~/integrations/trpc/config'

function handler({ request }: { request: Request }) {
  return fetchRequestHandler({
    req: request,
    router: appRouter,
    endpoint: '/api/trpc',
    createContext: () => createTRPCContext({ request }),
    onError: ({ error }) => {
      if (error.code === 'UNAUTHORIZED') {
        throw redirect({ to: '/auth/sign-in' })
      }
    },
  })
}

export const APIRoute = createAPIFileRoute('/api/trpc/$')({
  GET: handler,
  POST: handler,
})

if (error.code === 'UNAUTHORIZED') {
       // here
      throw redirect({ to: '/auth/sign-in' })
}