diff --git a/tests/Feature/Api/V1/ApiHappyPathTest.php b/tests/Feature/Api/V1/ApiHappyPathTest.php
new file mode 100644
index 0000000..28e8869
--- /dev/null
+++ b/tests/Feature/Api/V1/ApiHappyPathTest.php
@@ -0,0 +1,93 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Contracts\Billing\CreditLedger;
+use App\Enums\Plan;
+use App\Models\User;
+use App\Services\Api\ApiKeyGenerator;
+use Illuminate\Http\UploadedFile;
+use Illuminate\Support\Facades\Queue;
+use Illuminate\Support\Facades\Storage;
+
+it('runs full api conversion happy path', function () {
+    Storage::fake('local');
+    Queue::fake();
+
+    $user = User::factory()->create(['plan' => Plan::Pro]);
+    $token = app(ApiKeyGenerator::class)->create($user, 'API')->plainToken;
+
+    // 1. Upload file
+    $uploadResponse = $this->withToken($token)
+        ->postJson('/api/v1/files', [
+            'file' => UploadedFile::fake()->image('image.png', 100, 100),
+        ])
+        ->assertCreated();
+
+    $fileId = $uploadResponse->json('data.id');
+    expect($fileId)->toBeInt();
+
+    // 2. Get target formats
+    $this->withToken($token)
+        ->getJson("/api/v1/files/{$fileId}/targets")
+        ->assertOk()
+        ->assertJsonFragment(['target_format' => 'jpg']);
+
+    // 3. Estimate conversion cost
+    $estimateResponse = $this->withToken($token)
+        ->postJson('/api/v1/conversions/estimate', [
+            'file_id' => $fileId,
+            'target_format' => 'jpg',
+            'options' => [],
+        ])
+        ->assertOk();
+
+    expect($estimateResponse->json('data.amount'))->toBeGreaterThan(0);
+    expect($estimateResponse->json('data.has_enough_credits'))->toBeTrue();
+    $this->assertDatabaseCount('conversion_jobs', 0);
+
+    // 4. Create conversion job
+    $conversionResponse = $this->withToken($token)
+        ->postJson('/api/v1/conversions', [
+            'file_id' => $fileId,
+            'target_format' => 'jpg',
+            'options' => [],
+        ])
+        ->assertCreated();
+
+    $conversionId = $conversionResponse->json('data.id');
+    expect($conversionId)->toBeInt();
+    expect($conversionResponse->json('data.status'))->toBe('queued');
+
+    // 5. Check conversion status
+    $this->withToken($token)
+        ->getJson("/api/v1/conversions/{$conversionId}")
+        ->assertOk()
+        ->assertJsonPath('data.id', $conversionId)
+        ->assertJsonPath('data.status', 'queued');
+
+    $this->assertDatabaseHas('conversion_jobs', [
+        'id' => $conversionId,
+        'status' => 'queued',
+    ]);
+});
+
+it('api key authentication is required for all business endpoints', function () {
+    $this->getJson('/api/v1/converters')->assertUnauthorized();
+    $this->postJson('/api/v1/files')->assertUnauthorized();
+    $this->postJson('/api/v1/conversions/estimate')->assertUnauthorized();
+    $this->postJson('/api/v1/conversions')->assertUnauthorized();
+    $this->getJson('/api/v1/credits/balance')->assertUnauthorized();
+});
+
+it('returns credits balance during happy path', function () {
+    $user = User::factory()->create(['plan' => Plan::Pro]);
+    $balance = app(CreditLedger::class)->balance($user);
+    $token = app(ApiKeyGenerator::class)->create($user, 'API')->plainToken;
+
+    $this->withToken($token)
+        ->getJson('/api/v1/credits/balance')
+        ->assertOk()
+        ->assertJsonPath('data.balance', $balance)
+        ->assertJsonPath('data.unit', 'credits');
+});