nextjs + next-auth v5 : missing secret, but it's in process.env

Question

I am getting this error, running locally a nextjs project, using next-auth v5

Unhandled Runtime Error MissingSecret: Missing secret, please set AUTH_SECRET or config.secret. Read more at https://errors.authjs.dev#missingsecret

But my .env file has (key changed)

AUTH_SECRET="srqoi/XynrMAjcjuMx6T5kGMXRAc+giSoSIxvpESUpA="

also, I can console.log my process.env file and I get, aside others,
this on server terminal/console { ... AUTH_SECRET: 'srqoi/XynrMAjcjuMx6T5kGMXRAc+giSoSIxvpESUpA=' }

but it's empty in the browser, when console.log is executed at runtime

what am I doing wrong ?

Context

I am getting the error at this line

export const { auth, signIn, signOut } = NextAuth(authConfig);

this is my authConfig

import { getUser } from "@/services/authService";
import type { NextAuthConfig } from "next-auth";
import Credentials from "next-auth/providers/credentials";
import { z } from "zod";
import dotenv from "dotenv";

dotenv.config();
console.dir(process.env);

export const authConfig = {
  pages: {
    signIn: "/login",
  },
  callbacks: {
    authorized({ auth, request: { nextUrl } }) {
      console.log("running auth/config.js -> callbacks.authorized");
      const isLoggedIn = !!auth?.user;
      const isOnDashboard = nextUrl.pathname.startsWith("/dashboard");
      if (isOnDashboard) {
        if (isLoggedIn) return true;
        return false; // Redirect unauthenticated users to login page
      } else if (isLoggedIn) {
        return Response.redirect(new URL("/dashboard", nextUrl));
      }
      return true;
    },
  },
  providers: [
    Credentials({
      async authorize(credentials) {
        console.log(
          "runnning auth/config.ts -> providers.Credentials.authorize - Received credentials:",
          credentials
        );

        const parsedCredentials = z
          .object({ email: z.string().email(), password: z.string().min(6) })
          .safeParse(credentials);

        if (parsedCredentials.success) {
          const { email, password } = parsedCredentials.data;
          const user = await getUser(email, password);
          if (!user) return null;
          return user;
        }

        console.log("Invalid credentials");
        return null;
      },
    }),
  ],
  secret: process.env.AUTH_SECRET,
} satisfies NextAuthConfig;

Answer 1

Resolved adding

'use server';

to my login form action solved ALL problems.

I suppose this forced my next-auth code to be run also only server side, so it's finding the .env and populating the process.env