Implicit model binding fails when using {locale} prefix in routes

Question

I'm working on a multilingual Laravel 12 app. All my routes are grouped under a {locale} prefix, like this:

Route::prefix('{locale}')
 ->group(function () {
 Route::get('/activities/{activity}', [ActivityController::class, 'show'])
 ->name('activities.show');
 });

In my Localization middleware, I set the locale and define URL defaults:

<?php
namespace App\Http\Middleware;
use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\App;
use Illuminate\Support\Facades\URL;
use Symfony\Component\HttpFoundation\Response;
/**
 * Middleware to set the application's locale based on URL parameter, user preference or session.
 */
class Localization
{
 /**
 * Handle an incoming request and set the locale.
 *
 * @param Request $request The incoming HTTP request instance.
 * @param Closure(Request): Response $next The next middleware to call.
 */
 public function handle(Request $request, Closure $next): Response
 {
 $locale = $request->route('locale')
 ?? optional(auth()->user())->language
 ?? session('locale', config('app.locale'));
 if (! array_key_exists($locale, config('app.available_locales'))) {
 $locale = config('app.locale');
 }
 App::setLocale($locale);
 URL::defaults(['locale' => $locale]);
 session()->put('locale', $locale);
 return $next($request);
 }
}

I am getting this error with my controllers:

TypeError: App\Http\Controllers\ActivityController::show(): Argument #1 ($activity) must be of type App\Models\Activity, string given

My controller looks like this:

 /**
 * Display the details for a given activity.
 */
 public function show(Activity $activity): View
 {
 abort_unless($activity->isPublished(), 404);
 return view('activities.show', [
 'activity' => $activity,
 'title' => $activity->title,
 ]);
 }

If I manually add Request $request or string $locale before $activity, it works - but I'd really prefer not to have to include $locale or $request in every controller action.

Middleware priority is correct: Localization runs before SubstituteBindings.

return Application::configure(basePath: dirname(__DIR__))
 ->withRouting(
 web: __DIR__.'/../routes/web.php',
 commands: __DIR__.'/../routes/console.php',
 health: '/up',
 )
 ->withMiddleware(function (Middleware $middleware): void {
 // Add Localization middleware to web group
 $middleware->web(append: [
 Localization::class,
 ]);
 
 // Prioritize Localization middleware before SubstituteBindings
 $middleware->prependToPriorityList(
 before: SubstituteBindings::class,
 prepend: Localization::class,
 );
 })

Is there a clean way to keep my {locale} route prefix and make implicit model binding work without adding $locale or $request to every controller method?

Is this a known limitation or am I missing something subtle?

Here is my LanguageController for better insight:

/**
 * Controller handling the application language switching.
 */
class LanguageController extends Controller
{
 /**
 * Switch the application language.
 *
 * Handles changing the application language for both authenticated
 * and unauthenticated users. For authenticated users, it also updates their
 * language preference in the database.
 *
 * @param Request $request The HTTP request containing the locale.
 * @return RedirectResponse Redirects back to the previous page with the new locale.
 */
 public function switch(Request $request): RedirectResponse
 {
 $validated = $request->validate([
 'locale' => ['required','string', Rule::in(array_keys(config('app.available_locales')))],
 ]);
 $newLocale = $validated['locale'];
 session()->put('locale', $newLocale);
 $prev = url()->previous();
 $uri = Uri::of($prev);
 $segments = collect(explode('/', ltrim($uri->path(), '/')));
 $available = array_keys(config('app.available_locales'));
 if ($segments->isNotEmpty() && in_array($segments->first(), $available, true)) {
 $segments[0] = $newLocale;
 } else {
 $segments->prepend($newLocale);
 }
 $newPath = '/'.$segments->implode('/');
 $target = (string) $uri->withPath($newPath);
 return redirect()->to($target);
 }
}

• rozsazoltan: I removed the general "best way" part from your question because without it, your problem is much more focused, and it would be a pity for the post to get closed because of that. There's no such thing as "the best" or "recommended" way - it always depends on the project, goals, and many other factors. When you ask questions like that, you'll often get a wide range of scattered answers that don't necessarily address your original problem.