Target class [admin] does not exist Problem in Laravel Version 11.36.1 and php version 6.2.12

Question

I am trying to create a login system where both admin and users can log in using the same form. The problem is when I log in with admin credentials, the URL redirects correctly to admin/dashboard, but I see the error:

Target class [admin] does not exist

Here is the relevant code:

Admin Controller

<?php
// app\Http\Controllers\Admin\AdminController.php

namespace App\Http\Controllers\Admin;

use App\Http\Controllers\Controller;
use Illuminate\Http\Request;

class AdminController extends Controller
{
    public function __construct()
    {
        $this->middleware('admin');
    }

    public function dashboard()
    {
        return view('admin.dashboard');
    }
}

User Dashboard Controller

<?php
// app\Http\Controllers\DashboardController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class DashboardController extends Controller
{
    public function __construct()
    {
        $this->middleware('auth');
    }

    public function index()
    {
        $user = auth()->user();
        $recentOrders = $user->cartItems()
            ->with('product')
            ->latest()
            ->take(5)
            ->get();

        return view('dashboard', compact('recentOrders'));
    }
}

Authenticated Session Controller

<?php
// app\Http\Controllers\Auth\AuthenticatedSessionController.php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use App\Http\Requests\Auth\LoginRequest;
use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;
use Illuminate\View\View;

class AuthenticatedSessionController extends Controller
{
    public function create(): View
    {
        return view('auth.login');
    }

    public function store(LoginRequest $request)
    {
        $request->authenticate();
        $request->session()->regenerate();

        if (Auth::user()->isAdmin()) {
            return redirect()->intended(route('admin.dashboard'));
        }

        return redirect()->intended(route('dashboard'));
    }

    public function destroy(Request $request): RedirectResponse
    {
        Auth::guard('web')->logout();

        $request->session()->invalidate();

        $request->session()->regenerateToken();

        return redirect('/');
    }
}

User Model

<?php
// app\Models\User.php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Foundation\Auth\User as Authenticatable;
use Illuminate\Notifications\Notifiable;
use Laravel\Sanctum\HasApiTokens;

class User extends Authenticatable
{
    use HasFactory, Notifiable;

    protected $fillable = [
        'name',
        'email',
        'password',
        'is_admin',
    ];

    protected $hidden = [
        'password',
        'remember_token',
    ];

    protected $casts = [
        'email_verified_at' => 'datetime',
        'password' => 'hashed',
        'is_admin' => 'boolean',
    ];

    public function cartItems()
    {
        return $this->hasMany(CartItem::class);
    }

    public function isAdmin()
    {
        return $this->is_admin;
    }
}

Kernel Middleware

<?php
// app\Http\Kernel.php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    protected $middleware = [
        \Illuminate\Http\Middleware\TrustProxies::class,
        \Illuminate\Http\Middleware\HandleCors::class,
        \Illuminate\Foundation\Http\Middleware\PreventRequestsDuringMaintenance::class,
        \Illuminate\Http\Middleware\ValidatePostSize::class,
        \App\Http\Middleware\TrimStrings::class,
        \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
    ];

    protected $middlewareGroups = [
        'web' => [
            \App\Http\Middleware\EncryptCookies::class,
            \Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
            \Illuminate\Session\Middleware\StartSession::class,
            \Illuminate\View\Middleware\ShareErrorsFromSession::class,
            \App\Http\Middleware\VerifyCsrfToken::class,
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],

        'api' => [
            \Illuminate\Routing\Middleware\ThrottleRequests::class . ':api',
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],
    ];

    protected $middlewareAliases = [
        'auth' => \App\Http\Middleware\Authenticate::class,
        'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
        'cache.headers' => \Illuminate\Http\Middleware\SetCacheHeaders::class,
        'can' => \Illuminate\Auth\Middleware\Authorize::class,
        'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,
        'password.confirm' => \Illuminate\Auth\Middleware\RequirePassword::class,
        'signed' => \Illuminate\Routing\Middleware\ValidateSignature::class,
        'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,
        'verified' => \Illuminate\Auth\Middleware\EnsureEmailIsVerified::class,
        'admin' => \App\Http\Middleware\AdminMiddleware::class,
    ];
}

Routes

<?php
// routes/web.php

use App\Http\Controllers\Admin\AdminController;
use App\Http\Controllers\DashboardController;
use Illuminate\Support\Facades\Route;

Route::get('/', [HomeController::class, 'index'])->name('home');

require __DIR__.'/auth.php';

Route::middleware(['auth'])->group(function () {
    Route::get('/dashboard', [DashboardController::class, 'index'])->name('dashboard');
});

Route::middleware(['auth', 'admin'])->group(function () {
    Route::get('/admin/dashboard', [AdminController::class, 'dashboard'])->name('admin.dashboard');
});

I’ve confirmed that the middleware and route definitions seem fine. What am I missing here? How can I fix the Target class [admin] does not exist error?

Any help or guidance would be greatly appreciated!

I am tired to find out where the problem is occur.