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

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
// appHttpControllersAdminAdminController.php

namespace AppHttpControllersAdmin;

use AppHttpControllersController;
use IlluminateHttpRequest;

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

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

User Dashboard Controller

<?php
// appHttpControllersDashboardController.php

namespace AppHttpControllers;

use IlluminateHttpRequest;

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
// appHttpControllersAuthAuthenticatedSessionController.php

namespace AppHttpControllersAuth;

use AppHttpControllersController;
use AppHttpRequestsAuthLoginRequest;
use IlluminateHttpRedirectResponse;
use IlluminateHttpRequest;
use IlluminateSupportFacadesAuth;
use IlluminateViewView;

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
// appModelsUser.php

namespace AppModels;

use IlluminateDatabaseEloquentFactoriesHasFactory;
use IlluminateFoundationAuthUser as Authenticatable;
use IlluminateNotificationsNotifiable;
use LaravelSanctumHasApiTokens;

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
// appHttpKernel.php

namespace AppHttp;

use IlluminateFoundationHttpKernel as HttpKernel;

class Kernel extends HttpKernel
{
    protected $middleware = [
        IlluminateHttpMiddlewareTrustProxies::class,
        IlluminateHttpMiddlewareHandleCors::class,
        IlluminateFoundationHttpMiddlewarePreventRequestsDuringMaintenance::class,
        IlluminateHttpMiddlewareValidatePostSize::class,
        AppHttpMiddlewareTrimStrings::class,
        IlluminateFoundationHttpMiddlewareConvertEmptyStringsToNull::class,
    ];

    protected $middlewareGroups = [
        'web' => [
            AppHttpMiddlewareEncryptCookies::class,
            IlluminateCookieMiddlewareAddQueuedCookiesToResponse::class,
            IlluminateSessionMiddlewareStartSession::class,
            IlluminateViewMiddlewareShareErrorsFromSession::class,
            AppHttpMiddlewareVerifyCsrfToken::class,
            IlluminateRoutingMiddlewareSubstituteBindings::class,
        ],

        'api' => [
            IlluminateRoutingMiddlewareThrottleRequests::class . ':api',
            IlluminateRoutingMiddlewareSubstituteBindings::class,
        ],
    ];

    protected $middlewareAliases = [
        'auth' => AppHttpMiddlewareAuthenticate::class,
        'auth.basic' => IlluminateAuthMiddlewareAuthenticateWithBasicAuth::class,
        'cache.headers' => IlluminateHttpMiddlewareSetCacheHeaders::class,
        'can' => IlluminateAuthMiddlewareAuthorize::class,
        'guest' => AppHttpMiddlewareRedirectIfAuthenticated::class,
        'password.confirm' => IlluminateAuthMiddlewareRequirePassword::class,
        'signed' => IlluminateRoutingMiddlewareValidateSignature::class,
        'throttle' => IlluminateRoutingMiddlewareThrottleRequests::class,
        'verified' => IlluminateAuthMiddlewareEnsureEmailIsVerified::class,
        'admin' => AppHttpMiddlewareAdminMiddleware::class,
    ];
}

Routes

<?php
// routes/web.php

use AppHttpControllersAdminAdminController;
use AppHttpControllersDashboardController;
use IlluminateSupportFacadesRoute;

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.