Signin callback error

[MatD1]

After attempting to enable JWT and following the docs, every time I attempt to sign in with Twitch it errors out and in the console it leaves a message saying.

[next-auth][error][OAUTH_CALLBACK_HANDLER_ERROR] 
https://next-auth.js.org/errors#oauth_callback_handler_error Unexpected token o in JSON at position 1 {
  message: 'Unexpected token o in JSON at position 1',
  stack: 'SyntaxError: Unexpected token o in JSON at position 1\n' +
    '    at JSON.parse (<anonymous>)\n' +
    '    at Object.encode (webpack-internal:///./node_modules/next-auth/jwt/index.js:57:65)\n' +
    '    at Object.callback (webpack-internal:///./node_modules/next-auth/server/routes/callback.js:116:43)\n' +
    '    at processTicksAndRejections (internal/process/task_queues.js:95:5)\n' +
    '    at async NextAuthHandler (webpack-internal:///./node_modules/next-auth/server/index.js:171:18)\n' +
    '    at async eval (webpack-internal:///./node_modules/next-auth/server/index.js:251:32)\n' +
    '    at async Object.apiResolver (/Users/mat/Documents/Coding/Random Apps/TwitchDash/twitchdash/node_modules/next/dist/server/api-utils.js:101:9)\n' +
    '    at async DevServer.handleApiRequest (/Users/mat/Documents/Coding/Random Apps/TwitchDash/twitchdash/node_modules/next/dist/server/next-server.js:770:9)\n' +
    '    at async Object.fn (/Users/mat/Documents/Coding/Random Apps/TwitchDash/twitchdash/node_modules/next/dist/server/next-server.js:661:37)\n' +
    '    at async Router.execute (/Users/mat/Documents/Coding/Random Apps/TwitchDash/twitchdash/node_modules/next/dist/server/router.js:205:32)',
  name: 'SyntaxError'
}

This is happening after I add the signing key and verificationoptions to the JWT option in [...nextauth].js If I remove them the error does not happen but ofcourse nextauth the complains that the jwt is using the auto generated signing key

// with the above mentioned items
import NextAuth from "next-auth";
import TwitchProvider from "next-auth/providers/twitch";

export default NextAuth({
    providers: [
      TwitchProvider({
        clientId: process.env.TWITCH_CLIENT_ID,
        clientSecret: process.env.TWITCH_SECRET,
      }),
    ],
    debug: true,
    secret: process.env.SECRET,
    session: {
        jwt: true,
    },
    jwt: {
        secret: process.env.SECRET,
        signingKey: { 
            kty:"oct",
            kid:"xxx",
            algz:"HS512",
            k:"xxx"
        },
        
        verificationOptions: {
            algorithms: ['HS512']
        },

      },
  });

// the signing key was grabbed with the code mentioned in the docs

//without the above mentioned options
import NextAuth from "next-auth";
import TwitchProvider from "next-auth/providers/twitch";

export default NextAuth({
    providers: [
      TwitchProvider({
        clientId: process.env.TWITCH_CLIENT_ID,
        clientSecret: process.env.TWITCH_SECRET,
      }),
    ],
    debug: true,
    secret: process.env.SECRET,
    session: {
        jwt: true,
    },
    jwt: {
        secret: process.env.SECRET,
      },
  });

[Wokkipannu]

The documentation seems to be wrong. Looking into the code, it expects you to give signinKey as a string which then gets parsed to JSON.
So your signinKey should look like

signinKey: '{"kty":"oct","kid":""xxx","alg":"HS512","k":"xxx"}'

[balazsorban44]

probably related https://github.com/nextauthjs/docs/issues/5