diff --git a/app/Models/Mod.php b/app/Models/Mod.php
index badebf9..36a5ca5 100644
--- a/app/Models/Mod.php
+++ b/app/Models/Mod.php
@@ -16,6 +16,8 @@ use Illuminate\Support\Str;
 use Laravel\Scout\Searchable;
 
 /**
+ * @property int $id
+ * @property string $name
  * @property string $slug
  */
 class Mod extends Model
diff --git a/app/Models/ModDependency.php b/app/Models/ModDependency.php
new file mode 100644
index 0000000..f4eb842
--- /dev/null
+++ b/app/Models/ModDependency.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+/**
+ * @property int $id
+ * @property int $mod_version_id
+ * @property int $dependency_mod_id
+ * @property string $version_constraint
+ * @property int|null $resolved_version_id
+ */
+class ModDependency extends Model
+{
+    /**
+     * The relationship between a mod dependency and mod version.
+     */
+    public function modVersion(): BelongsTo
+    {
+        return $this->belongsTo(ModVersion::class);
+    }
+
+    /**
+     * The relationship between a mod dependency and mod.
+     */
+    public function dependencyMod(): BelongsTo
+    {
+        return $this->belongsTo(Mod::class, 'dependency_mod_id');
+    }
+
+    /**
+     * The relationship between a mod dependency and resolved mod version.
+     */
+    public function resolvedVersion(): BelongsTo
+    {
+        return $this->belongsTo(ModVersion::class, 'resolved_version_id');
+    }
+}
diff --git a/app/Models/ModVersion.php b/app/Models/ModVersion.php
index a167039..e14a254 100644
--- a/app/Models/ModVersion.php
+++ b/app/Models/ModVersion.php
@@ -6,8 +6,14 @@ use App\Models\Scopes\DisabledScope;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
 
+/**
+ * @property int $id
+ * @property int $mod_id
+ * @property string $version
+ */
 class ModVersion extends Model
 {
     use HasFactory, SoftDeletes;
@@ -22,6 +28,14 @@ class ModVersion extends Model
         return $this->belongsTo(Mod::class);
     }
 
+    /**
+     * The relationship between a mod version and its dependencies.
+     */
+    public function dependencies(): HasMany
+    {
+        return $this->hasMany(ModDependency::class);
+    }
+
     public function sptVersion(): BelongsTo
     {
         return $this->belongsTo(SptVersion::class);
diff --git a/app/Observers/ModDependencyObserver.php b/app/Observers/ModDependencyObserver.php
new file mode 100644
index 0000000..2d6eeff
--- /dev/null
+++ b/app/Observers/ModDependencyObserver.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Observers;
+
+use App\Models\ModDependency;
+use App\Models\ModVersion;
+use App\Services\ModVersionService;
+
+class ModDependencyObserver
+{
+    protected ModVersionService $modVersionService;
+
+    public function __construct(ModVersionService $modVersionService)
+    {
+        $this->modVersionService = $modVersionService;
+    }
+
+    public function saved(ModDependency $modDependency): void
+    {
+        $modVersion = ModVersion::find($modDependency->mod_version_id);
+        if ($modVersion) {
+            $this->modVersionService->resolveDependencies($modVersion);
+        }
+    }
+
+    public function deleted(ModDependency $modDependency): void
+    {
+        $modVersion = ModVersion::find($modDependency->mod_version_id);
+        if ($modVersion) {
+            $this->modVersionService->resolveDependencies($modVersion);
+        }
+    }
+}
diff --git a/app/Observers/ModVersionObserver.php b/app/Observers/ModVersionObserver.php
new file mode 100644
index 0000000..4d4195a
--- /dev/null
+++ b/app/Observers/ModVersionObserver.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Observers;
+
+use App\Models\ModDependency;
+use App\Models\ModVersion;
+use App\Services\ModVersionService;
+
+class ModVersionObserver
+{
+    protected ModVersionService $modVersionService;
+
+    public function __construct(ModVersionService $modVersionService)
+    {
+        $this->modVersionService = $modVersionService;
+    }
+
+    public function saved(ModVersion $modVersion): void
+    {
+        $dependencies = ModDependency::where('resolved_version_id', $modVersion->id)->get();
+        foreach ($dependencies as $dependency) {
+            $this->modVersionService->resolveDependencies($dependency->modVersion);
+        }
+    }
+
+    public function deleted(ModVersion $modVersion): void
+    {
+        $dependencies = ModDependency::where('resolved_version_id', $modVersion->id)->get();
+        foreach ($dependencies as $dependency) {
+            $this->modVersionService->resolveDependencies($dependency->modVersion);
+        }
+    }
+}
diff --git a/app/Providers/AppServiceProvider.php b/app/Providers/AppServiceProvider.php
index dd2a10a..86eacd5 100644
--- a/app/Providers/AppServiceProvider.php
+++ b/app/Providers/AppServiceProvider.php
@@ -2,7 +2,11 @@
 
 namespace App\Providers;
 
+use App\Models\ModDependency;
+use App\Models\ModVersion;
 use App\Models\User;
+use App\Observers\ModDependencyObserver;
+use App\Observers\ModVersionObserver;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Support\Facades\Gate;
 use Illuminate\Support\ServiceProvider;
@@ -25,6 +29,10 @@ class AppServiceProvider extends ServiceProvider
         // Allow mass assignment for all models. Be careful!
         Model::unguard();
 
+        // Register observers.
+        ModVersion::observe(ModVersionObserver::class);
+        ModDependency::observe(ModDependencyObserver::class);
+
         // This gate determines who can access the Pulse dashboard.
         Gate::define('viewPulse', function (User $user) {
             return $user->isAdmin();
diff --git a/app/Services/ModVersionService.php b/app/Services/ModVersionService.php
new file mode 100644
index 0000000..68d6bb8
--- /dev/null
+++ b/app/Services/ModVersionService.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace App\Services;
+
+use App\Models\ModVersion;
+use Composer\Semver\Semver;
+use Illuminate\Support\Facades\Log;
+
+class ModVersionService
+{
+    // TODO: This works, but it needs to be refactored. It's too big and does too much.
+    public function resolveDependencies(ModVersion $modVersion): array
+    {
+        $resolvedVersions = [];
+
+        try {
+            // Eager load dependencies with related mod versions
+            $dependencies = $modVersion->dependencies()->with(['dependencyMod.versions'])->get();
+
+            foreach ($dependencies as $dependency) {
+                $dependencyMod = $dependency->dependencyMod;
+
+                // Ensure dependencyMod exists and has versions
+                if (! $dependencyMod || $dependencyMod->versions->isEmpty()) {
+                    if ($dependency->resolved_version_id !== null) {
+                        $dependency->updateQuietly(['resolved_version_id' => null]);
+                    }
+                    $resolvedVersions[$dependency->id] = null;
+
+                    continue;
+                }
+
+                // Get available versions in the form ['version' => 'id']
+                $availableVersions = $dependencyMod->versions->pluck('id', 'version')->toArray();
+
+                // Find the latest version that satisfies the constraint
+                $satisfyingVersions = Semver::satisfiedBy(array_keys($availableVersions), $dependency->version_constraint);
+
+                // Get the first element's id from satisfyingVersions
+                $latestVersionId = $satisfyingVersions ? $availableVersions[reset($satisfyingVersions)] : null;
+
+                // Update the resolved version ID in the ModDependency record
+                if ($dependency->resolved_version_id !== $latestVersionId) {
+                    $dependency->updateQuietly(['resolved_version_id' => $latestVersionId]);
+                }
+
+                // Add the resolved ModVersion to the array (or null if not found)
+                $resolvedVersions[$dependency->id] = $latestVersionId ? ModVersion::find($latestVersionId) : null;
+            }
+        } catch (\Exception $e) {
+            Log::error('Error resolving dependencies for ModVersion: '.$modVersion->id, [
+                'exception' => $e->getMessage(),
+                'mod_version_id' => $modVersion->id,
+            ]);
+        }
+
+        return $resolvedVersions;
+    }
+}
diff --git a/composer.json b/composer.json
index 453b984..3933260 100644
--- a/composer.json
+++ b/composer.json
@@ -9,6 +9,7 @@
         "ext-curl": "*",
         "ext-intl": "*",
         "aws/aws-sdk-php": "^3.314",
+        "composer/semver": "^3.4",
         "filament/filament": "^3.2",
         "http-interop/http-factory-guzzle": "^1.2",
         "laravel/framework": "^11.11",
diff --git a/composer.lock b/composer.lock
index ec1e5e9..49786cc 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "93542851cf4f8ca963cbb447d144300e",
+    "content-hash": "920d8caa63c8b0da280a78c05d5983a8",
     "packages": [
         {
             "name": "anourvalar/eloquent-serialize",
@@ -620,6 +620,87 @@
             ],
             "time": "2023-12-20T15:40:13+00:00"
         },
+        {
+            "name": "composer/semver",
+            "version": "3.4.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/composer/semver.git",
+                "reference": "c51258e759afdb17f1fd1fe83bc12baaef6309d6"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/composer/semver/zipball/c51258e759afdb17f1fd1fe83bc12baaef6309d6",
+                "reference": "c51258e759afdb17f1fd1fe83bc12baaef6309d6",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.3.2 || ^7.0 || ^8.0"
+            },
+            "require-dev": {
+                "phpstan/phpstan": "^1.4",
+                "symfony/phpunit-bridge": "^4.2 || ^5"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "3.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Composer\\Semver\\": "src"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nils Adermann",
+                    "email": "naderman@naderman.de",
+                    "homepage": "http://www.naderman.de"
+                },
+                {
+                    "name": "Jordi Boggiano",
+                    "email": "j.boggiano@seld.be",
+                    "homepage": "http://seld.be"
+                },
+                {
+                    "name": "Rob Bast",
+                    "email": "rob.bast@gmail.com",
+                    "homepage": "http://robbast.nl"
+                }
+            ],
+            "description": "Semver library that offers utilities, version constraint parsing and validation.",
+            "keywords": [
+                "semantic",
+                "semver",
+                "validation",
+                "versioning"
+            ],
+            "support": {
+                "irc": "ircs://irc.libera.chat:6697/composer",
+                "issues": "https://github.com/composer/semver/issues",
+                "source": "https://github.com/composer/semver/tree/3.4.2"
+            },
+            "funding": [
+                {
+                    "url": "https://packagist.com",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/composer",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/composer/composer",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2024-07-12T11:35:52+00:00"
+        },
         {
             "name": "danharrin/date-format-converter",
             "version": "v0.3.1",
diff --git a/database/factories/ModFactory.php b/database/factories/ModFactory.php
index aef197b..f7699dc 100644
--- a/database/factories/ModFactory.php
+++ b/database/factories/ModFactory.php
@@ -30,12 +30,21 @@ class ModFactory extends Factory
             'featured' => fake()->boolean(),
             'contains_ai_content' => fake()->boolean(),
             'contains_ads' => fake()->boolean(),
-            'disabled' => fake()->boolean(),
             'created_at' => now(),
             'updated_at' => now(),
         ];
     }
 
+    /**
+     * Indicate that the mod should be disabled.
+     */
+    public function disabled(): static
+    {
+        return $this->state(fn (array $attributes) => [
+            'disabled' => true,
+        ]);
+    }
+
     /**
      * Indicate that the mod should be soft-deleted.
      */
diff --git a/database/factories/ModVersionFactory.php b/database/factories/ModVersionFactory.php
index cb8b613..a282b4f 100644
--- a/database/factories/ModVersionFactory.php
+++ b/database/factories/ModVersionFactory.php
@@ -22,9 +22,18 @@ class ModVersionFactory extends Factory
             'spt_version_id' => SptVersion::factory(),
             'virus_total_link' => fake()->url(),
             'downloads' => fake()->randomNumber(),
-            'disabled' => fake()->boolean(),
             'created_at' => Carbon::now()->subDays(rand(0, 365))->subHours(rand(0, 23)),
             'updated_at' => Carbon::now()->subDays(rand(0, 365))->subHours(rand(0, 23)),
         ];
     }
+
+    /**
+     * Indicate that the mod version should be disabled.
+     */
+    public function disabled(): static
+    {
+        return $this->state(fn (array $attributes) => [
+            'disabled' => true,
+        ]);
+    }
 }
diff --git a/database/migrations/2024_07_25_161219_create_mod_dependencies.php b/database/migrations/2024_07_25_161219_create_mod_dependencies.php
new file mode 100644
index 0000000..8ba53bc
--- /dev/null
+++ b/database/migrations/2024_07_25_161219_create_mod_dependencies.php
@@ -0,0 +1,35 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('mod_dependencies', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('mod_version_id')
+                ->constrained('mod_versions')
+                ->cascadeOnDelete()
+                ->cascadeOnUpdate();
+            $table->foreignId('dependency_mod_id')
+                ->constrained('mods')
+                ->cascadeOnDelete()
+                ->cascadeOnUpdate();
+            $table->string('version_constraint'); // e.g., ^1.0.1
+            $table->foreignId('resolved_version_id')
+                ->nullable()
+                ->constrained('mod_versions')
+                ->nullOnDelete()
+                ->cascadeOnUpdate();
+            $table->timestamps();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('mod_dependencies');
+    }
+};
diff --git a/tests/Feature/ModDependencyTest.php b/tests/Feature/ModDependencyTest.php
new file mode 100644
index 0000000..5a99c23
--- /dev/null
+++ b/tests/Feature/ModDependencyTest.php
@@ -0,0 +1,236 @@
+<?php
+
+use App\Models\Mod;
+use App\Models\ModDependency;
+use App\Models\ModVersion;
+
+it('resolves mod version dependency when mod version is created', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    // Create versions for Mod A that depends on Mod B
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.1');
+});
+
+it('resolves mod version dependency when mod version is updated', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    $modBv3 = ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    // Create versions for Mod A that depends on Mod B
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.1');
+
+    // Update the mod B version
+    $modBv3->update(['version' => '1.1.2']);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.2');
+});
+
+it('resolves mod version dependency when mod version is deleted', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    $modBv3 = ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    // Create versions for Mod A that depends on Mod B
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.1');
+
+    // Update the mod B version
+    $modBv3->delete();
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.0');
+});
+
+it('resolves mod version dependency after semantic version constraint is updated', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.1']);
+
+    // Create versions for Mod A that depends on Mod B
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.1');
+
+    // Update the dependency version constraint
+    $modDependency->update(['version_constraint' => '^2.0.0']);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('2.0.1');
+});
+
+it('resolves mod version dependency with exact semantic version constraint', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    // Create versions for Mod A that depends on Mod B
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '1.1.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.0');
+});
+
+it('resolves mod version dependency with complex semantic version constraint', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.2.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.2.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    // Create versions for Mod A that depends on Mod B
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '>=1.0.0 <2.0.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.2.1');
+
+    $modDependency->update(['version_constraint' => '1.0.0 || >=1.1.0 <1.2.0']);
+
+    $modDependency->refresh();
+    expect($modDependency->resolvedVersion->version)->toBe('1.1.1');
+});
+
+it('resolves null when no mod versions are available', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create version for Mod A that has no resolvable dependency
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolved_version_id)->toBeNull();
+});
+
+it('resolves null when no mod versions match against semantic version constraint', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+
+    // Create versions for Mod B
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    // Create version for Mod A that has no resolvable dependency
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+    $modDependency = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '~1.2.0',
+    ]);
+
+    $modDependency->refresh();
+    expect($modDependency->resolved_version_id)->toBeNull();
+});
+
+it('resolves multiple dependencies', function () {
+    $modA = Mod::factory()->create(['name' => 'Mod A']);
+    $modB = Mod::factory()->create(['name' => 'Mod B']);
+    $modC = Mod::factory()->create(['name' => 'Mod C']);
+
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modB->id, 'version' => '2.0.0']);
+
+    ModVersion::factory()->create(['mod_id' => $modC->id, 'version' => '1.0.0']);
+    ModVersion::factory()->create(['mod_id' => $modC->id, 'version' => '1.1.0']);
+    ModVersion::factory()->create(['mod_id' => $modC->id, 'version' => '1.1.1']);
+    ModVersion::factory()->create(['mod_id' => $modC->id, 'version' => '2.0.0']);
+
+    // Creating a version for Mod A that depends on Mod B and Mod C
+    $modAv1 = ModVersion::factory()->create(['mod_id' => $modA->id, 'version' => '1.0.0']);
+
+    $modDependencyB = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modB->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+    $modDependencyC = ModDependency::create([
+        'mod_version_id' => $modAv1->id,
+        'dependency_mod_id' => $modC->id,
+        'version_constraint' => '^1.0.0',
+    ]);
+
+    $modDependencyB->refresh();
+    expect($modDependencyB->resolvedVersion->version)->toBe('1.1.1');
+
+    $modDependencyC->refresh();
+    expect($modDependencyC->resolvedVersion->version)->toBe('1.1.1');
+});