diff --git a/routes/web.php b/routes/web.php
index 000558adc..9060ed139 100644
--- a/routes/web.php
+++ b/routes/web.php
@@ -496,7 +496,7 @@ Route::domain(config('pixelfed.domain.app'))->middleware(['localization'])->grou
 
     // Laravel 13's Horizon no longer redirects the base path to its dashboard,
     // so /horizon 404s by default. Redirect admins from /horizon to /horizon/dashboard.
-    Route::redirect('horizon', 'horizon/dashboard')->middleware('admin');
+    Route::redirect('horizon', '/horizon/dashboard')->middleware('admin');
 
     Route::redirect('groups/', '/groups/home');
     Route::redirect('groups/home', '/groups/feed');
diff --git a/tests/Feature/Admin/HorizonRedirectTest.php b/tests/Feature/Admin/HorizonRedirectTest.php
new file mode 100644
index 000000000..416fcb108
--- /dev/null
+++ b/tests/Feature/Admin/HorizonRedirectTest.php
@@ -0,0 +1,57 @@
+<?php
+
+use App\Models\User;
+use Illuminate\Foundation\Testing\LazilyRefreshDatabase;
+
+uses(LazilyRefreshDatabase::class);
+
+/*
+|--------------------------------------------------------------------------
+| /horizon base-path redirect
+|--------------------------------------------------------------------------
+|
+| Laravel 13's Horizon no longer redirects its base path, so routes/web.php
+| adds an admin-only redirect from /horizon to the dashboard. The destination
+| must be ABSOLUTE (leading slash): a relative "horizon/dashboard" Location is
+| resolved by the browser against a trailing-slash request path /horizon/ to
+| /horizon/horizon/dashboard (a doubled path served as HTTP 200 by Horizon's
+| SPA catch-all), silently missing the dashboard.
+|
+*/
+
+it('redirects an admin from /horizon to an absolute /horizon/dashboard', function () {
+    $admin = User::factory()->admin()->create();
+    $admin->refresh();
+
+    $response = $this->actingAs($admin)->get('/horizon');
+
+    $response->assertRedirect('/horizon/dashboard');
+
+    // The Location header must be absolute so a trailing-slash request cannot
+    // resolve it into a doubled /horizon/horizon/dashboard path.
+    expect($response->headers->get('Location'))->toEndWith('/horizon/dashboard');
+    expect(parse_url($response->headers->get('Location'), PHP_URL_PATH))
+        ->toBe('/horizon/dashboard');
+});
+
+it('redirects with an absolute Location for a trailing-slash /horizon/ request', function () {
+    $admin = User::factory()->admin()->create();
+    $admin->refresh();
+
+    $response = $this->actingAs($admin)->get('/horizon/');
+
+    // Regardless of the trailing slash, the redirect path is the absolute
+    // dashboard path, never a relative reference that would double up.
+    expect(parse_url($response->headers->get('Location'), PHP_URL_PATH))
+        ->toBe('/horizon/dashboard');
+});
+
+it('does not allow a non-admin to use the /horizon redirect', function () {
+    $user = User::factory()->create(['is_admin' => false]);
+    $user->refresh();
+
+    // The admin middleware bounces non-admins to the app root, not the dashboard.
+    $this->actingAs($user)
+        ->get('/horizon')
+        ->assertRedirect(config('app.url'));
+});