Fix cart retrieval to prefer unmerged carts (and clarify active scope grouping)

packages/core/src/Managers/CartSessionManager.php

@@ -136,7 +136,7 @@ protected function fetchOrCreate(bool $create = false, bool $estimateShipping =
         );
 
         if (! $cartId && $user = $this->authManager->user()) {
-            $cartId = $user->carts()->active()->first()?->id;
+            $cartId = $user->carts()->unmerged()->active()->latest('id')->value('id');
         }
 
         if (! $cartId) {

packages/core/src/Models/Cart.php

@@ -256,8 +256,12 @@ public function orders(): HasMany
 
     public function scopeActive(Builder $query): Builder
     {
-        return $query->whereDoesntHave('orders')->orWhereHas('orders', function ($query) {
-            return $query->whereNull('placed_at');
+        return $query->where(function ($q) {
+            $q
+                ->whereDoesntHave('orders')
+                ->orWhereHas('orders', function ($sub) {
+                    $sub->whereNull('placed_at');
+            });
         });
     }
 

tests/core/Unit/Models/CartTest.php

@@ -1163,3 +1163,83 @@
         )->toBe($newOrder->id);
 
 });
+
+test('active scope correctly filters unmerged carts and isolates users', function () {
+    setAuthUserConfig();
+
+    $currency = Currency::factory()->create();
+    $channel  = Channel::factory()->create();
+
+    $userA = StubUser::factory()->create();
+    $userB = StubUser::factory()->create();
+
+    $otherUsersCart = Cart::factory()->create([
+        'user_id'     => $userB->id,
+        'currency_id' => $currency->id,
+        'channel_id'  => $channel->id,
+    ]);
+
+    $expectedCart  = Cart::factory()->create([
+        'user_id'     => $userA->id,
+        'currency_id' => $currency->id,
+        'channel_id'  => $channel->id,
+        'merged_id'   => null,
+    ]);
+
+    $mergedCart = Cart::factory()->create([
+        'user_id'     => $userA->id,
+        'currency_id' => $currency->id,
+        'channel_id'  => $channel->id,
+        'merged_id'   => $expectedCart->id,
+    ]);
+
+    $cartId = $userA->carts()
+        ->unmerged()
+        ->active()
+        ->latest('id')
+        ->value('id');
+
+    expect($cartId)->toBe($expectedCart->id)
+        ->and($cartId)->not->toBe($otherUsersCart->id)
+        ->and($cartId)->not->toBe($mergedCart->id);
+});
+
+test('cart session manager prefers the latest unmerged cart for an authenticated user', function () {
+    setAuthUserConfig();
+
+    $currency = Currency::factory()->create();
+    $channel  = Channel::factory()->create();
+    $user     = StubUser::factory()->create();
+
+    $older = Cart::factory()->create([
+        'user_id'     => $user->id,
+        'merged_id'   => null,
+        'currency_id' => $currency->id,
+        'channel_id'  => $channel->id,
+    ]);
+
+    $expectedCart = Cart::factory()->create([
+        'user_id'     => $user->id,
+        'merged_id'   => null,
+        'currency_id' => $currency->id,
+        'channel_id'  => $channel->id,
+    ]);
+
+    $mergedCart = Cart::factory()->create([
+        'user_id'     => $user->id,
+        'merged_id'   => $expectedCart->id,
+        'currency_id' => $currency->id,
+        'channel_id'  => $channel->id,
+    ]);
+
+    $this->actingAs($user);
+
+    $manager = app(\Lunar\Managers\CartSessionManager::class);
+    $foundCart = $manager->current();
+
+    expect($foundCart)->not->toBeNull()
+        ->and($foundCart->id)->toBe($expectedCart->id)
+        ->and($foundCart->id)->not->toBe($older->id)
+        ->and($foundCart->id)->not->toBe($mergedCart->id)
+        ->and($foundCart->merged_id)->toBeNull();
+});