diff --git a/pyproject.toml b/pyproject.toml
index 28174475..fd556aea 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "sap-cloud-sdk"
-version = "0.45.2"
+version = "0.45.3"
 description = "SAP Cloud SDK for Python"
 readme = "README.md"
 license = "Apache-2.0"
diff --git a/src/sap_cloud_sdk/agentgateway/_lob.py b/src/sap_cloud_sdk/agentgateway/_lob.py
index 0c46124c..6a199b82 100644
--- a/src/sap_cloud_sdk/agentgateway/_lob.py
+++ b/src/sap_cloud_sdk/agentgateway/_lob.py
@@ -151,7 +151,12 @@ def get_ias_client_id_lob() -> str:
     )
     if not dest:
         raise AgentGatewaySDKError(f"IAS destination '{dest_name}' not found")
-    return dest.properties.get("clientId", "")
+    client_id = dest.properties.get("clientId", "")
+    if not client_id:
+        raise AgentGatewaySDKError(
+            f"IAS destination '{dest_name}' does not contain a 'clientId' property"
+        )
+    return client_id
 
 
 async def fetch_system_auth(
diff --git a/src/sap_cloud_sdk/agentgateway/agw_client.py b/src/sap_cloud_sdk/agentgateway/agw_client.py
index 6ee67458..6f353de6 100644
--- a/src/sap_cloud_sdk/agentgateway/agw_client.py
+++ b/src/sap_cloud_sdk/agentgateway/agw_client.py
@@ -347,6 +347,10 @@ def get_ias_client_id(self) -> str:
                     "Customer agent credentials detected at '%s'", credentials_path
                 )
                 credentials = load_customer_credentials(credentials_path)
+                if not credentials.client_id:
+                    raise AgentGatewaySDKError(
+                        "Customer agent credentials file does not contain a 'client_id'"
+                    )
                 return credentials.client_id
 
             # LoB flow — read clientId from the IAS destination properties
diff --git a/tests/agentgateway/unit/test_agw_client.py b/tests/agentgateway/unit/test_agw_client.py
index 714c3ec9..207deb9d 100644
--- a/tests/agentgateway/unit/test_agw_client.py
+++ b/tests/agentgateway/unit/test_agw_client.py
@@ -1209,6 +1209,17 @@ def test_customer_raises_on_load_failure(self):
             with pytest.raises(AgentGatewaySDKError, match="Could not resolve IAS client ID"):
                 create_client().get_ias_client_id()
 
+    def test_customer_raises_when_client_id_empty(self):
+        mock_creds = MagicMock()
+        mock_creds.client_id = ""
+
+        with (
+            patch(_DETECT_CREDS_PATCH, return_value="/etc/ums/credentials/credentials"),
+            patch(_LOAD_CREDS_PATCH, return_value=mock_creds),
+        ):
+            with pytest.raises(AgentGatewaySDKError, match="client_id"):
+                create_client().get_ias_client_id()
+
     # --- LoB flow ---
 
     @_NO_CUSTOMER_CREDS
@@ -1225,11 +1236,10 @@ def test_lob_raises_when_destination_not_found(self, _mock_detect):
                 create_client(tenant_subdomain="my-tenant").get_ias_client_id()
 
     @_NO_CUSTOMER_CREDS
-    def test_lob_returns_empty_string_when_property_absent(self, _mock_detect):
-        with patch(_GET_IAS_CLIENT_ID_LOB_PATCH, return_value=""):
-            result = create_client(tenant_subdomain="my-tenant").get_ias_client_id()
-
-        assert result == ""
+    def test_lob_raises_when_client_id_property_absent(self, _mock_detect):
+        with patch(_GET_IAS_CLIENT_ID_LOB_PATCH, side_effect=AgentGatewaySDKError("does not contain a 'clientId' property")):
+            with pytest.raises(AgentGatewaySDKError, match="clientId"):
+                create_client(tenant_subdomain="my-tenant").get_ias_client_id()
 
     @_NO_CUSTOMER_CREDS
     def test_lob_raises_on_exception(self, _mock_detect):
diff --git a/tests/agentgateway/unit/test_lob.py b/tests/agentgateway/unit/test_lob.py
index 6d972b8d..98c6ce02 100644
--- a/tests/agentgateway/unit/test_lob.py
+++ b/tests/agentgateway/unit/test_lob.py
@@ -1252,7 +1252,7 @@ def test_raises_when_destination_not_found(self):
             with pytest.raises(AgentGatewaySDKError, match="sap-managed-runtime-ias-eu10"):
                 get_ias_client_id_lob()
 
-    def test_returns_empty_string_when_property_absent(self):
+    def test_raises_when_client_id_property_absent(self):
         mock_dest = MagicMock()
         mock_dest.properties = {}
         mock_dest_client = MagicMock()
@@ -1262,9 +1262,8 @@ def test_returns_empty_string_when_property_absent(self):
             patch("sap_cloud_sdk.agentgateway._lob._ias_dest_name", return_value="sap-managed-runtime-ias-eu10"),
             patch("sap_cloud_sdk.agentgateway._lob.create_destination_client", return_value=mock_dest_client),
         ):
-            result = get_ias_client_id_lob()
-
-        assert result == ""
+            with pytest.raises(AgentGatewaySDKError, match="clientId"):
+                get_ias_client_id_lob()
 
     def test_raises_when_landscape_env_not_set(self):
         with patch("sap_cloud_sdk.agentgateway._lob._ias_dest_name", side_effect=EnvironmentError("APPFND_CONHOS_LANDSCAPE not set")):