Can't deploy Vite/Nodejs app

I have a frontend and backend and I'm trying to deploy it as one repo however there is an error with my vercel.json. The build fails saying my runtime is not a valid version. here is my vercel.json

{
    "version": 2,
    "functions": {
      "backend/api/**/*.ts": {
        "runtime": "edge"
      }
    },
    "rewrites": [
      { "source": "/api/(.*)", "destination": "/backend/api/$1" },
      { "source": "/(.*)", "destination": "/frontend/$1" }
    ]
  }