Unexpected token S in JSON at position 0' Next auth - json

Question

A teammate and I are working developing an application portal. We have the same exact code, node version and environment variables but when he logs in, he gets this error. I am able to login perfectly without any error. He was also able to login last week so at one point it was working for him.
A lot of solutions I've read about are adding code that trims or stringifies the JSON response. But it makes no sense that it works for me as it is but he would need to add code to make his work. Does anyone know why this is happening? (He has a NEXTAUTH_URL in the .env as well).
[next-auth][error][CLIENT_FETCH_ERROR]
https://next-auth.js.org/errors#client_fetch_error invalid json response body at http://localhost:3000/api/auth/session reason: Unexpected token S in JSON at position 0 {
error: {
message: 'invalid json response body at http://localhost:3000/api/auth/session reason: Unexpected token S in JSON at position 0',
stack: 'FetchError: invalid json response body at http://localhost:3000/api/auth/session reason: Unexpected token S in JSON at position 0\n'

Answer 1

I had the same error with next-redux-wrapper. I was implementing the old version's set up. I had this causing error:
export const getServerSideProps = wrapper.getServerSideProps(
async ({ req, params, store }) => {
const session = await getSession({ req });
if (!session) {
return {
redirect: {
destination: "/login",
permanent: false,
},
};
}
await store.dispatch(getBookingDetails(req.headers.cookie, req, params.id));
}
);
I had to change it to:
// the way how I pass callback changed
export const getServerSideProps = wrapper.getServerSideProps(
(store) =>
async ({ req, params }) => {
....rest of the code
);

Answer 2

I recently encountered exactly the same problem but luckily managed to settle it.
The solution is to (1) NEXT_PUBLIC_SECRET is required in .env and (2) [...nextauth].ts added with secret: process.env.NEXT_PUBLIC_SECRET.
I have the following link to thank for the above solution.
Hope it works for you too.