diff --git a/python/packages/core/agent_framework/openai/_chat_client.py b/python/packages/core/agent_framework/openai/_chat_client.py
index 0214c8df20..0562e68f3e 100644
--- a/python/packages/core/agent_framework/openai/_chat_client.py
+++ b/python/packages/core/agent_framework/openai/_chat_client.py
@@ -327,7 +327,9 @@ def _prepare_options(self, messages: Sequence[Message], options: Mapping[str, An
             messages = prepend_instructions_to_messages(list(messages), instructions, role="system")
 
         # Start with a copy of options
-        run_options = {k: v for k, v in options.items() if v is not None and k not in {"instructions", "tools"}}
+        run_options = {
+            k: v for k, v in options.items() if v is not None and k not in {"instructions", "tools", "conversation_id"}
+        }
 
         # messages
         if messages and "messages" not in run_options:
diff --git a/python/packages/core/tests/azure/test_azure_chat_client.py b/python/packages/core/tests/azure/test_azure_chat_client.py
index 3e88504493..b6809d097d 100644
--- a/python/packages/core/tests/azure/test_azure_chat_client.py
+++ b/python/packages/core/tests/azure/test_azure_chat_client.py
@@ -626,6 +626,73 @@ async def test_streaming_with_none_delta(
     assert any(msg.contents for msg in results)
 
 
+@patch.object(AsyncChatCompletions, "create", new_callable=AsyncMock)
+async def test_cmc_with_conversation_id(
+    mock_create: AsyncMock,
+    azure_openai_unit_test_env: dict[str, str],
+    chat_history: list[Message],
+    mock_chat_completion_response: ChatCompletion,
+) -> None:
+    """Test that conversation_id is excluded from the completions create call."""
+    mock_create.return_value = mock_chat_completion_response
+    chat_history.append(Message(text="hello world", role="user"))
+
+    azure_chat_client = AzureOpenAIChatClient()
+    await azure_chat_client.get_response(
+        messages=chat_history,
+        options={"conversation_id": "12345"},
+    )
+
+    call_kwargs = mock_create.call_args.kwargs
+    assert "conversation_id" not in call_kwargs
+
+
+@patch.object(AsyncChatCompletions, "create", new_callable=AsyncMock)
+async def test_cmc_streaming_with_conversation_id(
+    mock_create: AsyncMock,
+    azure_openai_unit_test_env: dict[str, str],
+    chat_history: list[Message],
+    mock_streaming_chat_completion_response: AsyncStream[ChatCompletionChunk],
+) -> None:
+    """Test that conversation_id is excluded from the streaming completions create call."""
+    mock_create.return_value = mock_streaming_chat_completion_response
+    chat_history.append(Message(text="hello world", role="user"))
+
+    azure_chat_client = AzureOpenAIChatClient()
+    async for _ in azure_chat_client.get_response(
+        messages=chat_history,
+        options={"conversation_id": "12345"},
+        stream=True,
+    ):
+        pass
+
+    call_kwargs = mock_create.call_args.kwargs
+    assert "conversation_id" not in call_kwargs
+
+
+@patch.object(AsyncChatCompletions, "create", new_callable=AsyncMock)
+async def test_cmc_agent_with_service_session_id(
+    mock_create: AsyncMock,
+    azure_openai_unit_test_env: dict[str, str],
+    mock_chat_completion_response: ChatCompletion,
+) -> None:
+    """Test that agent.run() with a session containing service_session_id works correctly."""
+    mock_create.return_value = mock_chat_completion_response
+
+    azure_chat_client = AzureOpenAIChatClient()
+    agent = azure_chat_client.as_agent(
+        name="TestAgent",
+        instructions="You are a helpful assistant.",
+    )
+
+    session = agent.get_session(service_session_id="12345")
+    response = await agent.run("hello", session=session)
+
+    assert response is not None
+    call_kwargs = mock_create.call_args.kwargs
+    assert "conversation_id" not in call_kwargs
+
+
 @tool(approval_mode="never_require")
 def get_story_text() -> str:
     """Returns a story about Emily and David."""
diff --git a/python/packages/core/tests/openai/test_openai_chat_client.py b/python/packages/core/tests/openai/test_openai_chat_client.py
index 58faac42a3..04321b0883 100644
--- a/python/packages/core/tests/openai/test_openai_chat_client.py
+++ b/python/packages/core/tests/openai/test_openai_chat_client.py
@@ -1161,6 +1161,21 @@ def test_prepare_options_removes_parallel_tool_calls_when_no_tools(openai_unit_t
     assert "parallel_tool_calls" not in prepared_options
 
 
+def test_prepare_options_excludes_conversation_id(openai_unit_test_env: dict[str, str]) -> None:
+    """Test that conversation_id is excluded from prepared options for chat completions."""
+    client = OpenAIChatClient()
+
+    messages = [Message(role="user", text="test")]
+    options = {"conversation_id": "12345", "temperature": 0.7}
+
+    prepared_options = client._prepare_options(messages, options)
+
+    # conversation_id is not a valid parameter for AsyncCompletions.create()
+    assert "conversation_id" not in prepared_options
+    # Other options should still be present
+    assert prepared_options["temperature"] == 0.7
+
+
 async def test_streaming_exception_handling(openai_unit_test_env: dict[str, str]) -> None:
     """Test that streaming errors are properly handled."""
     client = OpenAIChatClient()