diff --git a/config/shop.php b/config/shop.php
index 630431d..7fc1ef9 100644
--- a/config/shop.php
+++ b/config/shop.php
@@ -10,10 +10,13 @@ return [
         'product_action_runs' => 'product_action_runs',
         'product_attributes' => 'product_attributes',
         'product_categories' => 'product_categories',
+        'product_relations' => 'product_relations',
         'product_prices' => 'product_prices',
         'product_purchases' => 'product_purchases',
+        'product_actions' => 'product_actions',
         'product_stocks' => 'product_stocks',
         'products' => 'products',
+        'cart_discounts' => 'cart_discounts',
     ],
 
     // Model classes (allow overriding in main instance)
diff --git a/src/Enums/ProductRelationType.php b/src/Enums/ProductRelationType.php
new file mode 100644
index 0000000..868dd89
--- /dev/null
+++ b/src/Enums/ProductRelationType.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Blax\Shop\Enums;
+
+enum ProductRelationType: string
+{
+    case RELATED = 'related';
+    case UPSELL = 'upsell';
+    case CROSS_SELL = 'cross-sell';
+    case VARIATION = 'variation';
+    case DOWNSELL = 'downsell';
+    case ADD_ON = 'add-on';
+    case BUNDLE = 'bundle';
+    case SINGLE = 'single';
+
+
+    public function label(): string
+    {
+        return match ($this) {
+            self::RELATED => 'Related',
+            self::UPSELL => 'Upsell',
+            self::CROSS_SELL => 'Cross-sell',
+            self::VARIATION => 'Variation',
+            self::DOWNSELL => 'Downsell',
+            self::ADD_ON => 'Add-on',
+            self::BUNDLE => 'Bundle',
+            self::SINGLE => 'Single',
+        };
+    }
+}
diff --git a/src/Models/Product.php b/src/Models/Product.php
index ec7a4c8..3867aaf 100644
--- a/src/Models/Product.php
+++ b/src/Models/Product.php
@@ -13,18 +13,18 @@ use Blax\Shop\Enums\StockStatus;
 use Blax\Shop\Enums\StockType;
 use Blax\Shop\Traits\HasCategories;
 use Blax\Shop\Traits\HasPrices;
+use Blax\Shop\Traits\HasProductRelations;
 use Blax\Shop\Traits\HasStocks;
 use Illuminate\Database\Eloquent\Concerns\HasUuids;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
-use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Support\Facades\Cache;
 
 class Product extends Model implements Purchasable, Cartable
 {
-    use HasFactory, HasUuids, HasMetaTranslation, HasStocks, HasPrices, HasCategories;
+    use HasFactory, HasUuids, HasMetaTranslation, HasStocks, HasPrices, HasCategories, HasProductRelations;
 
     protected $fillable = [
         'slug',
@@ -204,26 +204,6 @@ class Product extends Model implements Purchasable, Cartable
         );
     }
 
-    public function relatedProducts(): BelongsToMany
-    {
-        return $this->belongsToMany(
-            self::class,
-            'product_relations',
-            'product_id',
-            'related_product_id'
-        )->withPivot('type')->withTimestamps();
-    }
-
-    public function upsells(): BelongsToMany
-    {
-        return $this->relatedProducts()->wherePivot('type', 'upsell');
-    }
-
-    public function crossSells(): BelongsToMany
-    {
-        return $this->relatedProducts()->wherePivot('type', 'cross-sell');
-    }
-
     public function scopeVisible($query)
     {
         return $query->where('is_visible', true)
diff --git a/src/Traits/HasCategories.php b/src/Traits/HasCategories.php
index 050c35e..d937d44 100644
--- a/src/Traits/HasCategories.php
+++ b/src/Traits/HasCategories.php
@@ -3,10 +3,15 @@
 namespace Blax\Shop\Traits;
 
 use Blax\Shop\Models\ProductCategory;
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Collection;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 
 trait HasCategories
 {
+    /**
+     * Categories assigned to the model.
+     */
     public function categories(): BelongsToMany
     {
         return $this->belongsToMany(
@@ -15,18 +20,30 @@ trait HasCategories
         );
     }
 
-    public function scopeByCategory($query, ProductCategory|string $category_or_id)
+    /**
+     * Scope: filter by a single category (id or slug).
+     *
+     * @param  Builder<static>  $query
+     */
+    public function scopeByCategory(Builder $query, ProductCategory|string $category_or_id): Builder
     {
         $categoryId = $category_or_id instanceof ProductCategory
             ? $category_or_id->id
             : $category_or_id;
 
-        return $query->whereHas('categories', function ($q) use ($categoryId) {
-            $q->where('id', $categoryId);
+        return $query->whereHas('categories', function (Builder $q) use ($categoryId) {
+            $q->where('id', $categoryId)
+                ->orWhere('slug', $categoryId);
         });
     }
 
-    public function scopeByCategories($query, array $category_ids)
+    /**
+     * Scope: filter by all provided categories.
+     *
+     * @param  Builder<static>  $query
+     * @param  array<int, ProductCategory|string>  $category_ids
+     */
+    public function scopeByCategories(Builder $query, array $category_ids): Builder
     {
         foreach ($category_ids as $category_id) {
             $query->byCategory($category_id);
@@ -35,18 +52,30 @@ trait HasCategories
         return $query;
     }
 
-    public function scopeWithoutCategory($query, ProductCategory|string $category_or_id)
+    /**
+     * Scope: exclude a single category (id or slug).
+     *
+     * @param  Builder<static>  $query
+     */
+    public function scopeWithoutCategory(Builder $query, ProductCategory|string $category_or_id): Builder
     {
         $categoryId = $category_or_id instanceof ProductCategory
             ? $category_or_id->id
             : $category_or_id;
 
-        return $query->whereDoesntHave('categories', function ($q) use ($categoryId) {
-            $q->where('id', $categoryId);
+        return $query->whereDoesntHave('categories', function (Builder $q) use ($categoryId) {
+            $q->where('id', $categoryId)
+                ->orWhere('slug', $categoryId);
         });
     }
 
-    public function scopeWithoutCategories($query, array $category_ids)
+    /**
+     * Scope: exclude any of the provided categories.
+     *
+     * @param  Builder<static>  $query
+     * @param  array<int, ProductCategory|string>  $category_ids
+     */
+    public function scopeWithoutCategories(Builder $query, array $category_ids): Builder
     {
         foreach ($category_ids as $category_id) {
             $query->withoutCategory($category_id);
@@ -55,11 +84,19 @@ trait HasCategories
         return $query;
     }
 
+    /**
+     * Attach a single category model.
+     */
     public function assignCategory(ProductCategory $category): void
     {
         $this->categories()->attach($category);
     }
 
+    /**
+     * Attach multiple category models.
+     *
+     * @param  array<int, ProductCategory>  $categories
+     */
     public function assignCategories(array $categories): void
     {
         foreach ($categories as $category) {
@@ -67,11 +104,19 @@ trait HasCategories
         }
     }
 
+    /**
+     * Detach a single category model.
+     */
     public function removeCategory(ProductCategory $category): void
     {
         $this->categories()->detach($category);
     }
 
+    /**
+     * Detach multiple category models.
+     *
+     * @param  array<int, ProductCategory>  $categories
+     */
     public function removeCategories(array $categories): void
     {
         foreach ($categories as $category) {
@@ -79,17 +124,30 @@ trait HasCategories
         }
     }
 
+    /**
+     * Sync categories by ids or models.
+     *
+     * @param  array<int, ProductCategory|int|string>  $categories
+     */
     public function syncCategories(array $categories): void
     {
         $this->categories()->sync($categories);
     }
 
+    /**
+     * Attach or create a category by name.
+     */
     public function assignCategoryByName(string $name): void
     {
         $category = config('shop.models.product_category')::firstOrCreate(['name' => $name]);
         $this->assignCategory($category);
     }
 
+    /**
+     * Attach or create categories by names.
+     *
+     * @param  array<int, string>  $names
+     */
     public function assignCategoriesByNames(array $names): void
     {
         foreach ($names as $name) {
@@ -97,16 +155,141 @@ trait HasCategories
         }
     }
 
-    public function asssignCategoryBySlug(string $slug): void
+    /**
+     * Attach or create a category by slug.
+     */
+    public function assignCategoryBySlug(string $slug): void
     {
         $category = config('shop.models.product_category')::firstOrCreate(['slug' => $slug]);
         $this->assignCategory($category);
     }
 
+    /**
+     * Attach or create categories by slugs.
+     *
+     * @param  array<int, string>  $slugs
+     */
     public function assignCategoriesBySlugs(array $slugs): void
     {
         foreach ($slugs as $slug) {
-            $this->asssignCategoryBySlug($slug);
+            $this->assignCategoryBySlug($slug);
         }
     }
+
+    /**
+     * Backward compatible alias with previous typo.
+     *
+     * @deprecated Use assignCategoryBySlug instead.
+     */
+    public function asssignCategoryBySlug(string $slug): void
+    {
+        $this->assignCategoryBySlug($slug);
+    }
+
+    /**
+     * Check if the model is linked to a category (id or slug).
+     */
+    public function hasCategory(ProductCategory|string $category_or_id): bool
+    {
+        $categoryId = $category_or_id instanceof ProductCategory
+            ? $category_or_id->id
+            : $category_or_id;
+
+        if ($this->relationLoaded('categories')) {
+            /** @var Collection<int, ProductCategory> $categories */
+            $categories = $this->categories;
+
+            return $categories->contains(function (ProductCategory $category) use ($categoryId) {
+                return $category->id === $categoryId || $category->slug === $categoryId;
+            });
+        }
+
+        return $this->categories()
+            ->where(function (Builder $q) use ($categoryId) {
+                $q->where('id', $categoryId)
+                    ->orWhere('slug', $categoryId);
+            })
+            ->exists();
+    }
+
+    /**
+     * Check if the model has any of the provided categories.
+     *
+     * @param  array<int, ProductCategory|string>  $category_ids
+     */
+    public function hasAnyCategory(array $category_ids): bool
+    {
+        if ($this->relationLoaded('categories')) {
+            /** @var Collection<int, ProductCategory> $categories */
+            $categories = $this->categories;
+            $ids = [];
+            $slugs = [];
+
+            foreach ($category_ids as $category) {
+                $ids[] = $category instanceof ProductCategory ? $category->id : $category;
+                $slugs[] = $category instanceof ProductCategory ? $category->slug : $category;
+            }
+
+            return $categories->contains(function (ProductCategory $category) use ($ids, $slugs) {
+                return in_array($category->id, $ids, true) || in_array($category->slug, $slugs, true);
+            });
+        }
+
+        $ids = [];
+        $slugs = [];
+
+        foreach ($category_ids as $category) {
+            $ids[] = $category instanceof ProductCategory ? $category->id : $category;
+            $slugs[] = $category instanceof ProductCategory ? $category->slug : $category;
+        }
+
+        return $this->categories()
+            ->where(function (Builder $q) use ($ids, $slugs) {
+                $q->whereIn('id', $ids)
+                    ->orWhereIn('slug', $slugs);
+            })
+            ->exists();
+    }
+
+    /**
+     * Check if the model has all of the provided categories.
+     *
+     * @param  array<int, ProductCategory|string>  $category_ids
+     */
+    public function hasAllCategories(array $category_ids): bool
+    {
+        if ($category_ids === []) {
+            return false;
+        }
+
+        if ($this->relationLoaded('categories')) {
+            /** @var Collection<int, ProductCategory> $categories */
+            $categories = $this->categories;
+
+            foreach ($category_ids as $category) {
+                if (! $this->hasCategory($category)) {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        $ids = [];
+        $slugs = [];
+
+        foreach ($category_ids as $category) {
+            $ids[] = $category instanceof ProductCategory ? $category->id : $category;
+            $slugs[] = $category instanceof ProductCategory ? $category->slug : $category;
+        }
+
+        $count = $this->categories()
+            ->where(function (Builder $q) use ($ids, $slugs) {
+                $q->whereIn('id', $ids)
+                    ->orWhereIn('slug', $slugs);
+            })
+            ->count();
+
+        return $count >= count($category_ids);
+    }
 }
diff --git a/src/Traits/HasProductRelations.php b/src/Traits/HasProductRelations.php
new file mode 100644
index 0000000..517f77b
--- /dev/null
+++ b/src/Traits/HasProductRelations.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Blax\Shop\Traits;
+
+use Blax\Shop\Enums\ProductRelationType;
+use Illuminate\Database\Eloquent\Relations\BelongsToMany;
+
+trait HasProductRelations
+{
+    public function productRelations(): BelongsToMany
+    {
+        return $this->belongsToMany(
+            self::class,
+            config('shop.tables.product_relations', 'product_relations'),
+            'product_id',
+            'related_product_id'
+        )->withPivot('type', 'sort_order')->withTimestamps();
+    }
+
+    public function relatedProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::RELATED);
+    }
+
+    public function variantProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::VARIATION);
+    }
+
+    public function upsellProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::UPSELL);
+    }
+
+    public function crossSellProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::CROSS_SELL);
+    }
+
+    public function downsellProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::DOWNSELL);
+    }
+
+    public function addOnProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::ADD_ON);
+    }
+
+    public function bundleProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::BUNDLE);
+    }
+
+    public function singleProducts(): BelongsToMany
+    {
+        return $this->relationsByType(ProductRelationType::SINGLE);
+    }
+
+    public function relationsByType(ProductRelationType|string $type): BelongsToMany
+    {
+        $typeValue = $type instanceof ProductRelationType ? $type->value : $type;
+
+        return $this->productRelations()->wherePivot('type', $typeValue);
+    }
+}
diff --git a/tests/Feature/ProductManagementTest.php b/tests/Feature/ProductManagementTest.php
index 7bcc667..da80b32 100644
--- a/tests/Feature/ProductManagementTest.php
+++ b/tests/Feature/ProductManagementTest.php
@@ -2,6 +2,7 @@
 
 namespace Blax\Shop\Tests\Feature;
 
+use Blax\Shop\Enums\ProductRelationType;
 use Blax\Shop\Enums\ProductStatus;
 use Blax\Shop\Enums\ProductType;
 use Blax\Shop\Models\Product;
@@ -157,11 +158,11 @@ class ProductManagementTest extends TestCase
         $product = Product::factory()->create();
         $relatedProduct = Product::factory()->create();
 
-        $product->relatedProducts()->attach($relatedProduct->id, [
-            'type' => 'related',
+        $product->productRelations()->attach($relatedProduct->id, [
+            'type' => ProductRelationType::RELATED->value,
         ]);
 
-        $this->assertTrue($product->relatedProducts->contains($relatedProduct));
+        $this->assertTrue($product->relatedProducts()->get()->contains($relatedProduct));
     }
 
     /** @test */
@@ -170,11 +171,11 @@ class ProductManagementTest extends TestCase
         $product = Product::factory()->create();
         $upsellProduct = Product::factory()->create();
 
-        $product->relatedProducts()->attach($upsellProduct->id, [
-            'type' => 'upsell',
+        $product->productRelations()->attach($upsellProduct->id, [
+            'type' => ProductRelationType::UPSELL->value,
         ]);
 
-        $this->assertTrue($product->upsells->contains($upsellProduct));
+        $this->assertTrue($product->upsellProducts()->get()->contains($upsellProduct));
     }
 
     /** @test */
@@ -183,11 +184,11 @@ class ProductManagementTest extends TestCase
         $product = Product::factory()->create();
         $crossSellProduct = Product::factory()->create();
 
-        $product->relatedProducts()->attach($crossSellProduct->id, [
-            'type' => 'cross-sell',
+        $product->productRelations()->attach($crossSellProduct->id, [
+            'type' => ProductRelationType::CROSS_SELL->value,
         ]);
 
-        $this->assertTrue($product->crossSells->contains($crossSellProduct));
+        $this->assertTrue($product->crossSellProducts()->get()->contains($crossSellProduct));
     }
 
     /** @test */
diff --git a/tests/Unit/ProductRelationsTest.php b/tests/Unit/ProductRelationsTest.php
new file mode 100644
index 0000000..6810da3
--- /dev/null
+++ b/tests/Unit/ProductRelationsTest.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace Blax\Shop\Tests\Unit;
+
+use Blax\Shop\Enums\ProductRelationType;
+use Blax\Shop\Models\Product;
+use Blax\Shop\Tests\TestCase;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+class ProductRelationsTest extends TestCase
+{
+    use RefreshDatabase;
+
+    /** @test */
+    public function it_filters_relations_by_relation_type()
+    {
+        $product = Product::factory()->create();
+        $related = Product::factory()->create();
+        $upsell = Product::factory()->create();
+        $crossSell = Product::factory()->create();
+
+        $product->productRelations()->attach($related->id, [
+            'type' => ProductRelationType::RELATED->value,
+            'sort_order' => 1,
+        ]);
+
+        $product->productRelations()->attach($upsell->id, [
+            'type' => ProductRelationType::UPSELL->value,
+            'sort_order' => 2,
+        ]);
+
+        $product->productRelations()->attach($crossSell->id, [
+            'type' => ProductRelationType::CROSS_SELL->value,
+            'sort_order' => 3,
+        ]);
+
+        $this->assertTrue($product->relatedProducts()->get()->contains($related));
+        $this->assertTrue($product->upsellProducts()->get()->contains($upsell));
+        $this->assertTrue($product->crossSellProducts()->get()->contains($crossSell));
+
+        $this->assertSame(1, $product->relatedProducts()->first()->pivot->sort_order);
+    }
+
+    /** @test */
+    public function relations_by_type_accepts_enum_or_string()
+    {
+        $product = Product::factory()->create();
+        $related = Product::factory()->create();
+
+        $product->productRelations()->attach($related->id, [
+            'type' => ProductRelationType::RELATED->value,
+        ]);
+
+        $this->assertTrue($product->relationsByType(ProductRelationType::RELATED)->exists());
+        $this->assertTrue($product->relationsByType('related')->exists());
+    }
+
+    /** @test */
+    public function it_can_be_queried_by_specific_relation_types()
+    {
+        $withUpsell = Product::factory()->create();
+        $upsell = Product::factory()->create();
+        $withCrossSell = Product::factory()->create();
+        $crossSell = Product::factory()->create();
+        $unrelated = Product::factory()->create();
+
+        $withUpsell->productRelations()->attach($upsell->id, [
+            'type' => ProductRelationType::UPSELL->value,
+            'sort_order' => 1,
+        ]);
+
+        $withCrossSell->productRelations()->attach($crossSell->id, [
+            'type' => ProductRelationType::CROSS_SELL->value,
+            'sort_order' => 2,
+        ]);
+
+        $upsellMatch = Product::whereHas('upsellProducts', function ($query) use ($upsell) {
+            $query->whereKey($upsell->id);
+        })->get();
+
+        $crossSellMatch = Product::whereHas('crossSellProducts', function ($query) use ($crossSell) {
+            $query->whereKey($crossSell->id);
+        })->get();
+
+        $this->assertTrue($upsellMatch->contains($withUpsell));
+        $this->assertFalse($upsellMatch->contains($withCrossSell));
+        $this->assertFalse($upsellMatch->contains($unrelated));
+
+        $this->assertTrue($crossSellMatch->contains($withCrossSell));
+        $this->assertFalse($crossSellMatch->contains($withUpsell));
+        $this->assertFalse($crossSellMatch->contains($unrelated));
+    }
+}