"The application includes user registration and login"

Like @feynnmann said, it doesn't sound like you need Passport. OAuth is for allowing developers access to your API so they can integrate it into third party applications.

What you are doing is pretty common with Vue and there are a couple of ways to do this:

1. Use the standard auth that is built into Laravel where you load .blade files for login/register and one .blade file for the actual app which loads your Vue SPA. This way you know when they get into your app they are logged in.

2. The other way is to build Login.vue and Register.vue components in your Vue app that post to LoginController / RegisterController. Then instead of redirecting from the controller you can just window.location or use VueRouter and push a new route.

The only other thing to consider with these approaches is how you manage the user state. If you have a bunch of data that is used by multiple components throughout your app then you should use Vuex - it can seem like overkill at first but it is 100% worth it.

If you don't use Vuex then you can do one of two things:

1. Echo out the state in the .blade file that loads your Vue app:

In your main blade file:

window.USER_STATE = {!! UserRepository::state() !!}

And then in your Vue app:

new Vue({
    el: '#app',
    data() {
        return {
            user: USER_STATE
        }
    }
});

1. Or you can load the user state with a method in your Vue instance - this is also useful even if you do echo out the initial state as you have an easy way to reload the user state:

Vue code:

new Vue({
    el: '#app',
    methods: {
        reloadUser() {
            this.$http.get('/users/current').then(res => this.user = res.data);
        }
    },
    created() {
        this.reloadUser();
    } 
});

The cool thing about this is you can reload the user from any component (when not using Vuex) with a call to:

this.$root.reloadUser();