diff --git a/python/packages/core/agent_framework/azure/_responses_client.py b/python/packages/core/agent_framework/azure/_responses_client.py
index b5b0ca1b5e..2debbd7b21 100644
--- a/python/packages/core/agent_framework/azure/_responses_client.py
+++ b/python/packages/core/agent_framework/azure/_responses_client.py
@@ -180,7 +180,7 @@ class MyOptions(AzureOpenAIResponsesOptions, total=False):
                 client: AzureOpenAIResponsesClient[MyOptions] = AzureOpenAIResponsesClient()
                 response = await client.get_response("Hello", options={"my_custom_option": "value"})
         """
-        if model_id := kwargs.pop("model_id", None) and not deployment_name:
+        if (model_id := kwargs.pop("model_id", None)) and not deployment_name:
             deployment_name = str(model_id)
 
         # Project client path: create OpenAI client from an Azure AI Foundry project
diff --git a/python/packages/core/tests/azure/test_azure_responses_client.py b/python/packages/core/tests/azure/test_azure_responses_client.py
index 4e9b25ca6a..37efff16ca 100644
--- a/python/packages/core/tests/azure/test_azure_responses_client.py
+++ b/python/packages/core/tests/azure/test_azure_responses_client.py
@@ -90,6 +90,29 @@ def test_init_model_id_constructor(azure_openai_unit_test_env: dict[str, str]) -
     assert isinstance(azure_responses_client, SupportsChatGetResponse)
 
 
+def test_init_model_id_kwarg(azure_openai_unit_test_env: dict[str, str]) -> None:
+    """Test that model_id kwarg correctly sets the deployment name (issue #4299)."""
+    azure_responses_client = AzureOpenAIResponsesClient(model_id="gpt-4o")
+
+    assert azure_responses_client.model_id == "gpt-4o"
+    assert isinstance(azure_responses_client, SupportsChatGetResponse)
+
+
+def test_init_model_id_kwarg_does_not_override_deployment_name(azure_openai_unit_test_env: dict[str, str]) -> None:
+    """Test that deployment_name takes precedence over model_id kwarg (issue #4299)."""
+    azure_responses_client = AzureOpenAIResponsesClient(deployment_name="my-deployment", model_id="gpt-4o")
+
+    assert azure_responses_client.model_id == "my-deployment"
+    assert isinstance(azure_responses_client, SupportsChatGetResponse)
+
+
+def test_init_model_id_kwarg_none(azure_openai_unit_test_env: dict[str, str]) -> None:
+    """Test that model_id=None does not override the env-var deployment name."""
+    azure_responses_client = AzureOpenAIResponsesClient(model_id=None)
+
+    assert azure_responses_client.model_id == azure_openai_unit_test_env["AZURE_OPENAI_RESPONSES_DEPLOYMENT_NAME"]
+
+
 def test_init_with_default_header(azure_openai_unit_test_env: dict[str, str]) -> None:
     default_headers = {"X-Unit-Test": "test-guid"}