diff --git a/tests/unit/test_auth_bind_wechat_sync.py b/tests/unit/test_auth_bind_wechat_sync.py
new file mode 100755
index 000000000..e11a41e7f
--- /dev/null
+++ b/tests/unit/test_auth_bind_wechat_sync.py
@@ -0,0 +1,738 @@
+"""Auth bind_contact + wechat_sync use cases unit tests.
+
+Covers BindContactUseCase, SendVerificationCodeUseCase, WechatSyncUseCase.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from datetime import datetime, timedelta, timezone
+from unittest.mock import MagicMock
+
+from packages.application.auth.bind_contact_use_case import (
+    BindContactRequest,
+    BindContactResponse,
+    BindContactUseCase,
+    SendVerificationCodeRequest,
+    SendVerificationCodeResponse,
+    SendVerificationCodeUseCase,
+)
+from packages.application.auth.wechat_sync_use_case import (
+    WechatSyncRequest,
+    WechatSyncResponse,
+    WechatSyncUseCase,
+)
+
+# ── Test helpers ─────────────────────────────────────────
+
+
+@dataclass
+class FakeUser:
+    id: str = "user-123"
+    email: str = "test@example.com"
+    display_name: str = "Test User"
+    username: str = "testuser"
+    password_hash: str = ""
+    email_verified: bool = False
+    phone: str = ""
+    phone_verified: bool = False
+    binding_completed_at: datetime | None = None
+    last_login_at: datetime | None = None
+    last_login_ip: str | None = None
+    wechat_openid: str | None = None
+    wechat_unionid: str | None = None
+    email_verification_token: str | None = None
+    password_reset_token: str | None = None
+    password_reset_expires_at: datetime | None = None
+    created_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
+
+
+class FakeUserRepository:
+    def __init__(self, user=None):
+        self._user = user
+        self.saved_user = None
+        self.save_called = 0
+
+    def find_by_id(self, user_id):
+        if self._user and self._user.id == user_id:
+            return self._user
+        return None
+
+    def find_by_email(self, email):
+        if self._user and self._user.email == email:
+            return self._user
+        return None
+
+    def find_by_phone(self, phone):
+        if self._user and self._user.phone == phone:
+            return self._user
+        return None
+
+    def find_by_username(self, username):
+        if self._user and self._user.username == username:
+            return self._user
+        return None
+
+    def find_by_wechat_openid(self, openid):
+        if self._user and self._user.wechat_openid == openid:
+            return self._user
+        return None
+
+    def find_by_wechat_unionid(self, unionid):
+        if self._user and self._user.wechat_unionid == unionid:
+            return self._user
+        return None
+
+    def save(self, user):
+        self.saved_user = user
+        self.save_called += 1
+        self._user = user
+        return user
+
+
+class FakeVerificationCode:
+    def __init__(self, code="123456", created_at=None, expires_at=None):
+        self.code = code
+        self.created_at = created_at or datetime.now(timezone.utc)
+        self.expires_at = expires_at or (datetime.now(timezone.utc) + timedelta(minutes=5))
+
+
+class FakeVerificationCodeService:
+    def __init__(self, verify_success=True, verify_error=None, generate_code="123456"):
+        self._verify_success = verify_success
+        self._verify_error = verify_error
+        self._generate_code = generate_code
+        self.verified = []
+        self.generated = []
+
+    def verify(self, recipient, code_type, code_value):
+        self.verified.append(
+            {
+                "recipient": recipient,
+                "code_type": code_type,
+                "code_value": code_value,
+            }
+        )
+        return self._verify_success, self._verify_error
+
+    def generate(self, recipient, code_type):
+        self.generated.append({"recipient": recipient, "code_type": code_type})
+        return FakeVerificationCode(code=self._generate_code), None
+
+
+class FakeSessionStore:
+    def __init__(self):
+        self.saved_sessions = []
+
+    def save_session(self, **kwargs):
+        self.saved_sessions.append(kwargs)
+        return True
+
+
+class FakeSmsService:
+    def __init__(self):
+        self.sent = []
+
+    def send_verification_code(self, phone, code):
+        self.sent.append({"phone": phone, "code": code})
+
+
+class FakeEmailService:
+    def __init__(self):
+        self.sent = []
+
+    def send_email(self, to, subject, body):
+        self.sent.append({"to": to, "subject": subject, "body": body})
+
+
+# ── BindContactUseCase tests ────────────────────────────
+
+
+class TestBindContactUseCase:
+    def _make_use_case(self, user_repo=None, verify_svc=None):
+        return BindContactUseCase(
+            user_repository=user_repo or FakeUserRepository(),
+            verification_code_service=verify_svc or FakeVerificationCodeService(),
+        )
+
+    def test_bind_phone_success(self):
+        user = FakeUser(id="user-1", phone="", phone_verified=False)
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=True)
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(
+            user_id="user-1",
+            phone="13800138000",
+            phone_code="123456",
+        )
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert isinstance(response, BindContactResponse)
+        assert response.user.phone == "13800138000"
+        assert response.user.phone_verified is True
+
+        # verification was called
+        assert len(verify_svc.verified) == 1
+        assert verify_svc.verified[0]["recipient"] == "13800138000"
+
+    def test_bind_email_success(self):
+        user = FakeUser(id="user-1", email="old@example.com", email_verified=False)
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=True)
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(
+            user_id="user-1",
+            email="new@example.com",
+            email_code="123456",
+        )
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert response.user.email == "new@example.com"
+        assert response.user.email_verified is True
+        assert len(verify_svc.verified) == 1
+
+    def test_bind_both_phone_and_email(self):
+        user = FakeUser(id="user-1", phone="", phone_verified=False, email_verified=False)
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=True)
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(
+            user_id="user-1",
+            phone="13800138000",
+            phone_code="123456",
+            email="new@example.com",
+            email_code="123456",
+        )
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert response.user.phone == "13800138000"
+        assert response.user.phone_verified is True
+        assert response.user.email == "new@example.com"
+        assert response.user.email_verified is True
+        assert response.user.binding_completed_at is not None
+        assert len(verify_svc.verified) == 2
+
+    def test_binding_complete_with_real_email(self):
+        """Both phone and email verified, real email (not wechat.local) → binding completed."""
+        user = FakeUser(
+            id="user-1",
+            email="",
+            phone="",
+            phone_verified=False,
+            email_verified=False,
+        )
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=True)
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(
+            user_id="user-1",
+            phone="13800138000",
+            phone_code="123456",
+            email="user@real.com",
+            email_code="123456",
+        )
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response.user.binding_completed_at is not None
+        assert response.to_dict()["user"]["binding_complete"] is True
+
+    def test_binding_not_complete_with_wechat_email(self):
+        """WeChat placeholder email doesn't count for binding completion."""
+        user = FakeUser(
+            id="user-1",
+            email="abc@wechat.local",
+            email_verified=True,
+            phone="",
+            phone_verified=False,
+        )
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=True)
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(
+            user_id="user-1",
+            phone="13800138000",
+            phone_code="123456",
+        )
+        response, error = use_case.execute(req)
+
+        assert error is None
+        # wechat.local email doesn't count
+        assert response.user.binding_completed_at is None
+        assert response.to_dict()["user"]["binding_complete"] is False
+
+    def test_no_phone_no_email_returns_error(self):
+        repo = FakeUserRepository()
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = BindContactRequest(user_id="user-1")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "至少填写手机号或邮箱" in error
+
+    def test_user_not_found(self):
+        repo = FakeUserRepository()  # no user
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = BindContactRequest(user_id="nonexistent", phone="13800138000", phone_code="123")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "用户不存在" in error
+
+    def test_invalid_phone_format(self):
+        user = FakeUser(id="user-1")
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = BindContactRequest(user_id="user-1", phone="123", phone_code="123456")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert error is not None
+
+    def test_invalid_email_format(self):
+        user = FakeUser(id="user-1")
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = BindContactRequest(user_id="user-1", email="not-an-email", email_code="123456")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert error is not None
+
+    def test_phone_missing_code(self):
+        user = FakeUser(id="user-1")
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = BindContactRequest(user_id="user-1", phone="13800138000")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "请输入手机验证码" in error
+
+    def test_email_missing_code(self):
+        user = FakeUser(id="user-1")
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = BindContactRequest(user_id="user-1", email="a@b.com")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "请输入邮箱验证码" in error
+
+    def test_phone_already_bound_to_other_user(self):
+        other_user = FakeUser(id="user-2", phone="13800138000")
+        current_user = FakeUser(id="user-1", phone="")
+        # repo only finds "other" user for phone lookup
+        repo = FakeUserRepository(user=other_user)
+        # But we also need find_by_id to find the current user
+        # Our simple repo can only hold one user. Let's use MagicMock instead.
+        repo = MagicMock()
+        repo.find_by_id.return_value = current_user
+        repo.find_by_phone.return_value = other_user
+
+        verify_svc = FakeVerificationCodeService()
+        use_case = BindContactUseCase(user_repository=repo, verification_code_service=verify_svc)
+
+        req = BindContactRequest(user_id="user-1", phone="13800138000", phone_code="123456")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "已被其他账号绑定" in error
+
+    def test_email_already_bound_to_other_user(self):
+        current_user = FakeUser(id="user-1", email="old@example.com")
+        other_user = FakeUser(id="user-2", email="new@example.com")
+
+        repo = MagicMock()
+        repo.find_by_id.return_value = current_user
+        repo.find_by_email.return_value = other_user
+
+        verify_svc = FakeVerificationCodeService()
+        use_case = BindContactUseCase(user_repository=repo, verification_code_service=verify_svc)
+
+        req = BindContactRequest(user_id="user-1", email="new@example.com", email_code="123456")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "已被其他账号绑定" in error
+
+    def test_phone_verification_failed(self):
+        user = FakeUser(id="user-1", phone="")
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=False, verify_error="验证码错误或已过期")
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(user_id="user-1", phone="13800138000", phone_code="wrong")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "手机验证码错误" in error
+
+    def test_email_verification_failed(self):
+        user = FakeUser(id="user-1")
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=False, verify_error="验证码错误")
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(user_id="user-1", email="a@b.com", email_code="wrong")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "邮箱验证码错误" in error
+
+    def test_bind_same_phone_to_self_ok(self):
+        """Binding the same phone to the same user should work (no conflict)."""
+        user = FakeUser(id="user-1", phone="13800138000", phone_verified=False)
+        repo = FakeUserRepository(user=user)
+        verify_svc = FakeVerificationCodeService(verify_success=True)
+        use_case = self._make_use_case(user_repo=repo, verify_svc=verify_svc)
+
+        req = BindContactRequest(user_id="user-1", phone="13800138000", phone_code="123456")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+
+    def test_exception_handling(self):
+        repo = MagicMock()
+        repo.find_by_id.side_effect = RuntimeError("DB down")
+        verify_svc = FakeVerificationCodeService()
+        use_case = BindContactUseCase(user_repository=repo, verification_code_service=verify_svc)
+
+        req = BindContactRequest(user_id="user-1", phone="13800138000", phone_code="123")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "绑定失败" in error
+
+
+# ── SendVerificationCodeUseCase tests ───────────────────
+
+
+class TestSendVerificationCodeUseCase:
+    def test_send_phone_code_success(self):
+        verify_svc = FakeVerificationCodeService(generate_code="654321")
+        sms_svc = FakeSmsService()
+        use_case = SendVerificationCodeUseCase(
+            verification_code_service=verify_svc,
+            sms_service=sms_svc,
+        )
+
+        req = SendVerificationCodeRequest(target="phone", value="13800138000", purpose="bind")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert isinstance(response, SendVerificationCodeResponse)
+        assert response.expires_in > 0
+        assert response.resend_after == 60
+
+        assert len(verify_svc.generated) == 1
+        assert verify_svc.generated[0]["code_type"] == "phone_bind"
+
+        # SMS was sent
+        assert len(sms_svc.sent) == 1
+        assert sms_svc.sent[0]["phone"] == "13800138000"
+        assert sms_svc.sent[0]["code"] == "654321"
+
+    def test_send_email_code_success(self):
+        verify_svc = FakeVerificationCodeService(generate_code="111222")
+        email_svc = FakeEmailService()
+        use_case = SendVerificationCodeUseCase(
+            verification_code_service=verify_svc,
+            email_service=email_svc,
+        )
+
+        req = SendVerificationCodeRequest(target="email", value="test@example.com", purpose="bind")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+
+        assert len(verify_svc.generated) == 1
+        assert verify_svc.generated[0]["code_type"] == "email_bind"
+
+        assert len(email_svc.sent) == 1
+        assert email_svc.sent[0]["to"] == "test@example.com"
+        assert "111222" in email_svc.sent[0]["body"]
+
+    def test_invalid_phone_format(self):
+        verify_svc = FakeVerificationCodeService()
+        use_case = SendVerificationCodeUseCase(verification_code_service=verify_svc)
+
+        req = SendVerificationCodeRequest(target="phone", value="123", purpose="bind")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert error is not None
+
+    def test_invalid_email_format(self):
+        verify_svc = FakeVerificationCodeService()
+        use_case = SendVerificationCodeUseCase(verification_code_service=verify_svc)
+
+        req = SendVerificationCodeRequest(target="email", value="not-email", purpose="bind")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert error is not None
+
+    def test_unsupported_target_type(self):
+        verify_svc = FakeVerificationCodeService()
+        use_case = SendVerificationCodeUseCase(verification_code_service=verify_svc)
+
+        req = SendVerificationCodeRequest(target="carrier_pigeon", value="hello", purpose="bind")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "不支持的目标类型" in error
+
+    def test_email_recipient_lowercased(self):
+        verify_svc = FakeVerificationCodeService()
+        email_svc = FakeEmailService()
+        use_case = SendVerificationCodeUseCase(
+            verification_code_service=verify_svc,
+            email_service=email_svc,
+        )
+
+        req = SendVerificationCodeRequest(target="email", value="TEST@Example.COM", purpose="login")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        # recipient should be lowercased
+        assert verify_svc.generated[0]["recipient"] == "test@example.com"
+
+    def test_no_sms_service_phone_still_returns_success(self):
+        """If no SMS service is configured, code is generated but not sent."""
+        verify_svc = FakeVerificationCodeService()
+        use_case = SendVerificationCodeUseCase(verification_code_service=verify_svc)
+
+        req = SendVerificationCodeRequest(target="phone", value="13800138000", purpose="login")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        # code was generated
+        assert len(verify_svc.generated) == 1
+
+    def test_exception_handling(self):
+        verify_svc = MagicMock()
+        verify_svc.generate.side_effect = RuntimeError("Redis down")
+        use_case = SendVerificationCodeUseCase(verification_code_service=verify_svc)
+
+        req = SendVerificationCodeRequest(target="email", value="a@b.com", purpose="bind")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "发送失败" in error
+
+    def test_to_dict_returns_correct_fields(self):
+        resp = SendVerificationCodeResponse(expires_in=300, resend_after=60)
+        d = resp.to_dict()
+        assert d["expires_in"] == 300
+        assert d["resend_after"] == 60
+
+
+# ── WechatSyncUseCase tests ─────────────────────────────
+
+
+class TestWechatSyncUseCase:
+    def _make_use_case(self, user_repo=None, session_store=None, secret_key="test-secret-key-for-jwt"):
+        return WechatSyncUseCase(
+            user_repository=user_repo or FakeUserRepository(),
+            session_store=session_store or FakeSessionStore(),
+            jwt_secret_key=secret_key,
+        )
+
+    def test_existing_user_login_by_openid(self):
+        user = FakeUser(
+            id="user-1",
+            wechat_openid="openid-abc",
+            display_name="WeChat User",
+        )
+        repo = FakeUserRepository(user=user)
+        store = FakeSessionStore()
+        use_case = self._make_use_case(user_repo=repo, session_store=store)
+
+        req = WechatSyncRequest(openid="openid-abc")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert isinstance(response, WechatSyncResponse)
+        assert response.user_id == "user-1"
+        assert response.is_new_user is False
+        assert response.access_token
+        assert response.refresh_token
+
+        # session created
+        assert len(store.saved_sessions) == 1
+        session = store.saved_sessions[0]
+        assert session["user_id"] == "user-1"
+        assert "wechat_" in session["device_info"]
+
+        # last login updated
+        assert repo.saved_user.last_login_at is not None
+        assert repo.saved_user.last_login_ip == "bff_gateway"
+
+    def test_existing_user_by_unionid_binds_openid(self):
+        user = FakeUser(
+            id="user-1",
+            wechat_openid=None,  # no openid
+            wechat_unionid="unionid-xyz",
+            display_name="Existing User",
+        )
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = WechatSyncRequest(openid="openid-new", unionid="unionid-xyz")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert response.user_id == "user-1"
+        assert response.is_new_user is False
+
+        # openid was bound
+        assert repo.saved_user.wechat_openid == "openid-new"
+
+    def test_new_user_creation(self):
+        repo = FakeUserRepository()  # no existing user
+        store = FakeSessionStore()
+        use_case = self._make_use_case(user_repo=repo, session_store=store)
+
+        req = WechatSyncRequest(
+            openid="openid-new123",
+            nickname="微信昵称",
+            avatar_url="https://example.com/avatar.png",
+        )
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response is not None
+        assert response.is_new_user is True
+        assert response.nickname == "微信昵称"
+        assert response.user_id
+        assert len(response.user_id) == 32  # uuid4 hex
+
+        # user was saved
+        assert repo.saved_user is not None
+        assert repo.saved_user.wechat_openid == "openid-new123"
+        assert repo.saved_user.email_verified is True
+        assert "wechat.local" in repo.saved_user.email
+        assert repo.saved_user.username.startswith("wx_")
+        assert repo.saved_user.display_name == "微信昵称"
+
+    def test_empty_openid_returns_error(self):
+        use_case = self._make_use_case()
+        req = WechatSyncRequest(openid="")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "openid is required" in error
+
+    def test_default_nickname_when_empty(self):
+        repo = FakeUserRepository()
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = WechatSyncRequest(openid="openid-1", nickname="")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response.is_new_user is True
+        assert response.nickname == "微信用户"
+
+    def test_username_uniqueness_suffix(self):
+        """When username already exists, a numeric suffix is added."""
+        # First user with same openid prefix
+        existing = FakeUser(username="wx_openidnew123_")
+        repo = FakeUserRepository(user=existing)
+
+        # Our simple FakeUserRepository only holds one user.
+        # Use MagicMock for more control.
+        repo = MagicMock()
+        repo.find_by_wechat_openid.return_value = None
+        repo.find_by_wechat_unionid.return_value = None
+        # first find_by_username returns a user (conflict), second time None (unique)
+        call_count = {"n": 0}
+
+        def mock_find_by_username(username):
+            call_count["n"] += 1
+            if call_count["n"] == 1:
+                return FakeUser(username=username)  # conflict
+            return None  # unique on second try
+
+        repo.find_by_username.side_effect = mock_find_by_username
+        repo.save = MagicMock(side_effect=lambda u: u)
+
+        use_case = WechatSyncUseCase(
+            user_repository=repo,
+            session_store=FakeSessionStore(),
+            jwt_secret_key="test-secret",
+        )
+
+        req = WechatSyncRequest(openid="openid-new123", nickname="Test")
+        response, error = use_case.execute(req)
+
+        assert error is None
+        assert response.is_new_user is True
+        # username should have _1 suffix
+        saved_user = repo.save.call_args[0][0]
+        assert saved_user.username.endswith("_1")
+
+    def test_to_dict_has_token_alias_for_compat(self):
+        user = FakeUser(id="u-1", wechat_openid="oid-1", display_name="Name")
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = WechatSyncRequest(openid="oid-1")
+        response, _ = use_case.execute(req)
+
+        d = response.to_dict()
+        assert d["access_token"] == d["token"]  # compat alias
+        assert d["is_new_user"] is False
+        assert d["user"]["id"] == "u-1"
+        assert d["user_info"]["display_name"] == "Name"
+
+    def test_access_token_has_correct_claims(self):
+        import jwt as pyjwt
+
+        user = FakeUser(id="user-99", wechat_openid="oid-99")
+        repo = FakeUserRepository(user=user)
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = WechatSyncRequest(openid="oid-99")
+        response, _ = use_case.execute(req)
+
+        payload = pyjwt.decode(response.access_token, "test-secret-key-for-jwt", algorithms=["HS256"])
+        assert payload["sub"] == "user-99"
+        assert payload["type"] == "user_auth"
+        assert "sid" in payload
+        assert "exp" in payload
+
+    def test_exception_handling(self):
+        repo = MagicMock()
+        repo.find_by_wechat_openid.side_effect = RuntimeError("DB down")
+        use_case = self._make_use_case(user_repo=repo)
+
+        req = WechatSyncRequest(openid="abc")
+        response, error = use_case.execute(req)
+
+        assert response is None
+        assert "Internal error" in error