Next.js route handler auth return type conflicts

[SongDerrick]

What is the improvement or update you wish to see?

import { auth } from "auth"

export const GET = auth((req) => {
  if (req.auth) {
    return Response.json({ data: "Protected data" })
  }

  return Response.json({ message: "Not authenticated" }, { status: 401 })
}) as any // TODO: Fix `auth()` return type

This code is from next-auth-example template.

without explicit type casting as any, type error occurs

such as

Type error: Route "app/api/protected/route.ts" has an invalid export:
  "unknown" is not a valid POST return type:
    Expected "void | Response | Promise<void | Response>", got "unknown".

For my case, I handled with explicit type casting by createing new type and interface to deal with it.

app/api/sample/route.ts

interface AuthRequest extends Request {
  auth?: any
}

type NextAuthAPIRouteHandler = (req: Request) => Promise<
  NextResponse<
    | {
        error: string
      }
    | {
        ok: boolean
      }
  >
>


export const POST = auth(async function POST(request: AuthRequest) {
  if (!request.auth) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }
  try {
    await businessLogic()
    return NextResponse.json({ ok: true }, { status: 200 })
  } catch (error) {
    return NextResponse.json(
      { ok: false, error: 'Sending Data Failed' },
      { status: 500 }
    )
  }
}) as NextAuthAPIRouteHandler

Therefore, there must be docs fixed since there is no explanations about explicit type casting.
Build Error always occurs without it, so i think it needs to be fixed.
Thanks.

Is there any context that might help us understand?

Reproduction environment

  System:
    OS: macOS 14.6.1
    CPU: (8) arm64 Apple M2
    Memory: 85.50 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.0.0 
    npm: 10.5.1 
    pnpm: 9.6.0 
  Browsers:
    Chrome: 128.0.6613.113
    Safari: 17.6

Does the docs page already exist? Please link to it.

https://authjs.dev/getting-started/session-management/protecting

[SongDerrick]

Created PR regarding this issues #11729

[github-actions]

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[fprl]

Any update on this one? I see that the PR got closed

[SongDerrick]

i havent got any response

[krizpoon]

Have the same issue with version 5.0.0-beta.25 + NextJS 15.0.1. Need to cast handlers as any.