diff --git a/.python-version b/.python-version
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--- /dev/null
+++ b/.python-version
@@ -0,0 +1 @@
+venv
diff --git a/backend/apps/accounts/tests/test_phone_auth_request_contract.py b/backend/apps/accounts/tests/test_phone_auth_request_contract.py
new file mode 100644
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+++ b/backend/apps/accounts/tests/test_phone_auth_request_contract.py
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+from unittest.mock import patch
+
+import pytest
+from django.test import override_settings
+from django.urls import reverse
+
+from apps.accounts.models import OtpPurpose, PhoneOTP, User
+
+
+@pytest.mark.django_db
+@override_settings(OTP_PROVIDER="console")
+def test_phone_auth_request_creates_customer_for_new_phone(client):
+    with patch("apps.accounts.services.otp.generate_code", return_value="123456"):
+        response = client.post(
+            reverse("phone_auth_request"),
+            {
+                "phone_number": "0512345678",
+                "channel": "sms",
+                "first_name": "Sara",
+                "last_name": "Ali",
+                "email": "sara@example.com",
+            },
+            content_type="application/json",
+        )
+
+    assert response.status_code == 201
+    data = response.json()
+    assert "request_id" in data
+    assert "expires_at" in data
+
+    user = User.objects.get(phone_number="+966512345678")
+    assert user.role == "customer"
+    assert user.is_phone_verified is False
+
+    otp = PhoneOTP.objects.get(id=data["request_id"])
+    assert otp.phone_number == "+966512345678"
+    assert otp.purpose == OtpPurpose.AUTH
+
+
+@pytest.mark.django_db
+@override_settings(OTP_PROVIDER="console")
+def test_phone_auth_request_existing_phone_no_duplicate_user(client):
+    User.objects.create_user(
+        phone_number="+966512345678",
+        email="existing@example.com",
+        first_name="Existing",
+    )
+
+    before_count = User.objects.filter(phone_number="+966512345678").count()
+
+    with patch("apps.accounts.services.otp.generate_code", return_value="123456"):
+        response = client.post(
+            reverse("phone_auth_request"),
+            {"phone_number": "0512345678", "channel": "sms"},
+            content_type="application/json",
+        )
+
+    assert response.status_code == 201
+    assert User.objects.filter(phone_number="+966512345678").count() == before_count
+    assert PhoneOTP.objects.filter(phone_number="+966512345678").count() == 1
+
+
+@pytest.mark.django_db
+@override_settings(OTP_PROVIDER="console")
+def test_phone_auth_request_rejects_email_already_used(client):
+    User.objects.create_user(
+        phone_number="+966500000001",
+        email="taken@example.com",
+    )
+
+    response = client.post(
+        reverse("phone_auth_request"),
+        {
+            "phone_number": "0512345678",
+            "channel": "sms",
+            "email": "taken@example.com",
+        },
+        content_type="application/json",
+    )
+
+    assert response.status_code == 400
+    assert "detail" in response.json()
+    assert User.objects.filter(phone_number="+966512345678").count() == 0
+    assert PhoneOTP.objects.filter(phone_number="+966512345678").count() == 0
+
+
+@pytest.mark.django_db
+def test_phone_auth_request_invalid_phone_localized_en(client):
+    response = client.post(
+        reverse("phone_auth_request"),
+        {"phone_number": "123", "channel": "sms"},
+        content_type="application/json",
+        HTTP_ACCEPT_LANGUAGE="en",
+    )
+
+    assert response.status_code == 400
+    assert response.json()["phone_number"][0] == "Phone number must be in E.164 format or a valid Saudi mobile"
+
+
+@pytest.mark.django_db
+def test_phone_auth_request_invalid_phone_localized_ar(client):
+    response = client.post(
+        reverse("phone_auth_request"),
+        {"phone_number": "123", "channel": "sms"},
+        content_type="application/json",
+        HTTP_ACCEPT_LANGUAGE="ar-sa",
+    )
+
+    assert response.status_code == 400
+    assert response.json()["phone_number"][0] == "يجب أن يكون رقم الهاتف بصيغة E.164 أو رقم جوال سعودي صالح"
+
+
+@pytest.mark.django_db
+@override_settings(
+    OTP_PROVIDER="console",
+    OTP_MAX_PER_WINDOW=5,
+    OTP_WINDOW_MINUTES=15,
+    OTP_RESEND_COOLDOWN_SECONDS=60,
+)
+def test_phone_auth_request_cooldown_returns_retry_after(client):
+    with patch("apps.accounts.services.otp.generate_code", return_value="123456"):
+        first = client.post(
+            reverse("phone_auth_request"),
+            {"phone_number": "0512345678", "channel": "sms"},
+            content_type="application/json",
+        )
+        assert first.status_code == 201
+
+        second = client.post(
+            reverse("phone_auth_request"),
+            {"phone_number": "0512345678", "channel": "sms"},
+            content_type="application/json",
+        )
+
+    assert second.status_code == 429
+    data = second.json()
+    assert "detail" in data
+    assert data["retry_after_seconds"] > 0
+
+
+@pytest.mark.django_db
+@override_settings(
+    OTP_PROVIDER="console",
+    OTP_MAX_PER_WINDOW=1,
+    OTP_WINDOW_MINUTES=15,
+    OTP_RESEND_COOLDOWN_SECONDS=0,
+)
+def test_phone_auth_request_rate_limit_returns_retry_after(client):
+    with patch("apps.accounts.services.otp.generate_code", return_value="123456"):
+        first = client.post(
+            reverse("phone_auth_request"),
+            {"phone_number": "0512345678", "channel": "sms"},
+            content_type="application/json",
+        )
+        assert first.status_code == 201
+
+        second = client.post(
+            reverse("phone_auth_request"),
+            {"phone_number": "0512345678", "channel": "sms"},
+            content_type="application/json",
+        )
+
+    assert second.status_code == 429
+    data = second.json()
+    assert "detail" in data
+    assert data["retry_after_seconds"] > 0