diff --git a/tests/Feature/Billing/CreditPackWebhookHandlerTest.php b/tests/Feature/Billing/CreditPackWebhookHandlerTest.php
index e55ebb5..f7abe93 100644
--- a/tests/Feature/Billing/CreditPackWebhookHandlerTest.php
+++ b/tests/Feature/Billing/CreditPackWebhookHandlerTest.php
@@ -27,3 +27,54 @@
 
     expect(app(CreditLedger::class)->balance($user))->toBe($balanceBefore + 500);
 });
+
+it('does not grant credits twice for duplicate credit pack checkout event', function () {
+    config()->set('billing.credit_packs.small.stripe_price_id', 'price_small');
+
+    $user = User::factory()->create();
+    $balanceBefore = app(CreditLedger::class)->balance($user);
+
+    $event = fakeStripeCheckoutCompletedEvent([
+        'event_id' => 'evt_duplicate_1',
+        'checkout_session_id' => 'cs_duplicate_1',
+        'user_id' => $user->id,
+        'pack_key' => 'small',
+        'pack_credits' => 500,
+        'price_id' => 'price_small',
+    ]);
+
+    app(CreditPackWebhookHandler::class)->handleCheckoutSessionCompleted($event);
+    app(CreditPackWebhookHandler::class)->handleCheckoutSessionCompleted($event);
+
+    expect(app(CreditLedger::class)->balance($user))->toBe($balanceBefore + 500);
+});
+
+it('does not grant credits twice for same checkout session with different event ids', function () {
+    config()->set('billing.credit_packs.small.stripe_price_id', 'price_small');
+
+    $user = User::factory()->create();
+    $balanceBefore = app(CreditLedger::class)->balance($user);
+
+    $event1 = fakeStripeCheckoutCompletedEvent([
+        'event_id' => 'evt_dup_a',
+        'checkout_session_id' => 'cs_same_session',
+        'user_id' => $user->id,
+        'pack_key' => 'small',
+        'pack_credits' => 500,
+        'price_id' => 'price_small',
+    ]);
+
+    $event2 = fakeStripeCheckoutCompletedEvent([
+        'event_id' => 'evt_dup_b',
+        'checkout_session_id' => 'cs_same_session',
+        'user_id' => $user->id,
+        'pack_key' => 'small',
+        'pack_credits' => 500,
+        'price_id' => 'price_small',
+    ]);
+
+    app(CreditPackWebhookHandler::class)->handleCheckoutSessionCompleted($event1);
+    app(CreditPackWebhookHandler::class)->handleCheckoutSessionCompleted($event2);
+
+    expect(app(CreditLedger::class)->balance($user))->toBe($balanceBefore + 500);
+});