Really test out the key

app/api/chat/route.ts

@@ -8,10 +8,12 @@ import { nanoid } from '@/lib/utils'
 export const runtime = 'edge'
 
 export async function POST(req: Request) {
+  if (process.env.VERCEL_ENV !== 'preview') {
     const session = await auth()
     if (session == null) {
       return new Response('Unauthorized', { status: 401 })
     }
+  }
 
   const json = await req.json()
   const { messages, previewToken } = json