diff --git a/python/packages/kagent-adk/src/kagent/adk/_agent_executor.py b/python/packages/kagent-adk/src/kagent/adk/_agent_executor.py
index 9c265c72e..7feed7552 100644
--- a/python/packages/kagent-adk/src/kagent/adk/_agent_executor.py
+++ b/python/packages/kagent-adk/src/kagent/adk/_agent_executor.py
@@ -33,6 +33,7 @@
     set_kagent_span_attributes,
 )
 
+from ._context import clear_user_id, set_user_id
 from .converters.event_converter import convert_event_to_a2a_events
 from .converters.request_converter import convert_a2a_request_to_adk_run_args
 
@@ -235,14 +236,23 @@ async def _handle_request(
             )
         )
 
-        task_result_aggregator = TaskResultAggregator()
-        async with Aclosing(runner.run_async(**run_args)) as agen:
-            async for adk_event in agen:
-                for a2a_event in convert_event_to_a2a_events(
-                    adk_event, invocation_context, context.task_id, context.context_id
-                ):
-                    task_result_aggregator.process_event(a2a_event)
-                    await event_queue.enqueue_event(a2a_event)
+        # Set user_id in context for passthrough to LLM providers
+        user_id = run_args.get("user_id")
+        if user_id:
+            set_user_id(user_id)
+
+        try:
+            task_result_aggregator = TaskResultAggregator()
+            async with Aclosing(runner.run_async(**run_args)) as agen:
+                async for adk_event in agen:
+                    for a2a_event in convert_event_to_a2a_events(
+                        adk_event, invocation_context, context.task_id, context.context_id
+                    ):
+                        task_result_aggregator.process_event(a2a_event)
+                        await event_queue.enqueue_event(a2a_event)
+        finally:
+            # Clear user_id from context to avoid leaking between requests
+            clear_user_id()
 
         # publish the task result event - this is final
         if (
diff --git a/python/packages/kagent-adk/src/kagent/adk/_context.py b/python/packages/kagent-adk/src/kagent/adk/_context.py
new file mode 100644
index 000000000..850a63771
--- /dev/null
+++ b/python/packages/kagent-adk/src/kagent/adk/_context.py
@@ -0,0 +1,29 @@
+"""Context variable module for passing user_id through async call chains."""
+
+from contextvars import ContextVar
+from typing import Optional
+
+_user_id_context: ContextVar[Optional[str]] = ContextVar("user_id", default=None)
+
+
+def set_user_id(user_id: str) -> None:
+    """Set the user_id in the current async context.
+
+    Args:
+        user_id: The user identifier to store in context.
+    """
+    _user_id_context.set(user_id)
+
+
+def get_user_id() -> Optional[str]:
+    """Get the user_id from the current async context.
+
+    Returns:
+        The user_id if set, None otherwise.
+    """
+    return _user_id_context.get()
+
+
+def clear_user_id() -> None:
+    """Clear the user_id from the current async context."""
+    _user_id_context.set(None)
diff --git a/python/packages/kagent-adk/src/kagent/adk/models/_openai.py b/python/packages/kagent-adk/src/kagent/adk/models/_openai.py
index 30fda6e9b..84e84a1cb 100644
--- a/python/packages/kagent-adk/src/kagent/adk/models/_openai.py
+++ b/python/packages/kagent-adk/src/kagent/adk/models/_openai.py
@@ -32,6 +32,7 @@
 from openai.types.shared_params import FunctionDefinition, FunctionParameters
 from pydantic import Field
 
+from .._context import get_user_id
 from ._ssl import create_ssl_context
 
 if TYPE_CHECKING:
@@ -394,6 +395,11 @@ async def generate_content_async(
             "messages": messages,
         }
 
+        # Add user parameter for usage tracking if user_id is available in context
+        user_id = get_user_id()
+        if user_id and user_id.strip():  # Only add if non-empty and non-whitespace
+            kwargs["user"] = user_id
+
         if self.frequency_penalty is not None:
             kwargs["frequency_penalty"] = self.frequency_penalty
         if self.max_tokens:
diff --git a/python/packages/kagent-adk/tests/unittests/models/test_openai.py b/python/packages/kagent-adk/tests/unittests/models/test_openai.py
index 67683b80d..9b700a137 100644
--- a/python/packages/kagent-adk/tests/unittests/models/test_openai.py
+++ b/python/packages/kagent-adk/tests/unittests/models/test_openai.py
@@ -21,6 +21,7 @@
 from google.genai.types import Content, Part
 from openai.types.chat.chat_completion_tool_param import ChatCompletionToolParam
 
+from kagent.adk._context import clear_user_id, set_user_id
 from kagent.adk.models import OpenAI
 from kagent.adk.models._openai import _convert_tools_to_openai
 
@@ -338,6 +339,178 @@ async def mock_coro(*args, **kwargs):
         assert kwargs["max_tokens"] == 4096
 
 
+@pytest.mark.asyncio
+async def test_generate_content_async_with_user_passthrough(llm_request, generate_content_response):
+    """Test that user_id from context is passed as 'user' parameter to OpenAI API."""
+    openai_llm = OpenAI(model="gpt-3.5-turbo", type="openai", api_key="fake")
+
+    # Set user_id in context
+    test_user_id = "user@example.com"
+    set_user_id(test_user_id)
+
+    try:
+        with mock.patch.object(openai_llm, "_client") as mock_client:
+            # Create a mock coroutine that returns the generate_content_response.
+            async def mock_coro(*args, **kwargs):
+                return generate_content_response
+
+            # Assign the coroutine to the mocked method
+            mock_client.chat.completions.create.return_value = mock_coro()
+
+            _ = [resp async for resp in openai_llm.generate_content_async(llm_request, stream=False)]
+            mock_client.chat.completions.create.assert_called_once()
+            _, kwargs = mock_client.chat.completions.create.call_args
+            assert kwargs["user"] == test_user_id
+    finally:
+        clear_user_id()
+
+
+@pytest.mark.asyncio
+async def test_generate_content_async_without_user_passthrough(llm_request, generate_content_response):
+    """Test that 'user' parameter is not included when user_id is not in context."""
+    openai_llm = OpenAI(model="gpt-3.5-turbo", type="openai", api_key="fake")
+
+    # Ensure user_id is not in context
+    clear_user_id()
+
+    with mock.patch.object(openai_llm, "_client") as mock_client:
+        # Create a mock coroutine that returns the generate_content_response.
+        async def mock_coro(*args, **kwargs):
+            return generate_content_response
+
+        # Assign the coroutine to the mocked method
+        mock_client.chat.completions.create.return_value = mock_coro()
+
+        _ = [resp async for resp in openai_llm.generate_content_async(llm_request, stream=False)]
+        mock_client.chat.completions.create.assert_called_once()
+        _, kwargs = mock_client.chat.completions.create.call_args
+        assert "user" not in kwargs
+
+
+@pytest.mark.asyncio
+async def test_generate_content_async_streaming_with_user_passthrough(llm_request):
+    """Test that user_id from context is passed as 'user' parameter in streaming mode."""
+    openai_llm = OpenAI(model="gpt-3.5-turbo", type="openai", api_key="fake")
+
+    # Set user_id in context
+    test_user_id = "user@example.com"
+    set_user_id(test_user_id)
+
+    try:
+        with mock.patch.object(openai_llm, "_client") as mock_client:
+            # Create a mock async generator for streaming
+            async def mock_stream(*args, **kwargs):
+                class MockChunk:
+                    def __init__(self):
+                        class MockDelta:
+                            def __init__(self):
+                                self.content = "Hello"
+
+                        class MockChoice:
+                            def __init__(self):
+                                self.delta = MockDelta()
+                                self.finish_reason = "stop"
+
+                        self.choices = [MockChoice()]
+
+                yield MockChunk()
+
+            # Assign the async generator to the mocked method
+            mock_client.chat.completions.create.return_value = mock_stream()
+
+            _ = [resp async for resp in openai_llm.generate_content_async(llm_request, stream=True)]
+            mock_client.chat.completions.create.assert_called_once()
+            _, kwargs = mock_client.chat.completions.create.call_args
+            assert kwargs["user"] == test_user_id
+            assert kwargs["stream"] is True
+    finally:
+        clear_user_id()
+
+
+@pytest.mark.asyncio
+async def test_azure_openai_with_user_passthrough(llm_request, generate_content_response):
+    """Test that user_id from context is passed as 'user' parameter to Azure OpenAI API."""
+    from kagent.adk.models import AzureOpenAI
+
+    azure_llm = AzureOpenAI(
+        model="gpt-35-turbo",
+        type="azure_openai",
+        api_key="fake",
+        azure_endpoint="https://test.openai.azure.com",
+        api_version="2024-02-15-preview",
+    )
+
+    # Set user_id in context
+    test_user_id = "user@example.com"
+    set_user_id(test_user_id)
+
+    try:
+        with mock.patch.object(azure_llm, "_client") as mock_client:
+            # Create a mock coroutine that returns the generate_content_response.
+            async def mock_coro(*args, **kwargs):
+                return generate_content_response
+
+            # Assign the coroutine to the mocked method
+            mock_client.chat.completions.create.return_value = mock_coro()
+
+            _ = [resp async for resp in azure_llm.generate_content_async(llm_request, stream=False)]
+            mock_client.chat.completions.create.assert_called_once()
+            _, kwargs = mock_client.chat.completions.create.call_args
+            assert kwargs["user"] == test_user_id
+    finally:
+        clear_user_id()
+
+
+@pytest.mark.asyncio
+async def test_generate_content_async_with_empty_user_id(llm_request, generate_content_response):
+    """Test that empty string user_id is not passed to OpenAI API."""
+    openai_llm = OpenAI(model="gpt-3.5-turbo", type="openai", api_key="fake")
+
+    # Set empty user_id in context
+    set_user_id("")
+
+    try:
+        with mock.patch.object(openai_llm, "_client") as mock_client:
+
+            async def mock_coro(*args, **kwargs):
+                return generate_content_response
+
+            mock_client.chat.completions.create.return_value = mock_coro()
+
+            _ = [resp async for resp in openai_llm.generate_content_async(llm_request, stream=False)]
+            mock_client.chat.completions.create.assert_called_once()
+            _, kwargs = mock_client.chat.completions.create.call_args
+            # Empty string should not be included (checked with .strip())
+            assert "user" not in kwargs
+    finally:
+        clear_user_id()
+
+
+@pytest.mark.asyncio
+async def test_generate_content_async_with_whitespace_only_user_id(llm_request, generate_content_response):
+    """Test that whitespace-only user_id is not passed to OpenAI API."""
+    openai_llm = OpenAI(model="gpt-3.5-turbo", type="openai", api_key="fake")
+
+    # Set whitespace-only user_id in context
+    set_user_id("   ")
+
+    try:
+        with mock.patch.object(openai_llm, "_client") as mock_client:
+
+            async def mock_coro(*args, **kwargs):
+                return generate_content_response
+
+            mock_client.chat.completions.create.return_value = mock_coro()
+
+            _ = [resp async for resp in openai_llm.generate_content_async(llm_request, stream=False)]
+            mock_client.chat.completions.create.assert_called_once()
+            _, kwargs = mock_client.chat.completions.create.call_args
+            # Whitespace-only string should not be included
+            assert "user" not in kwargs
+    finally:
+        clear_user_id()
+
+
 # ============================================================================
 # SSL/TLS Configuration Tests
 # ============================================================================
diff --git a/python/packages/kagent-adk/tests/unittests/test_context.py b/python/packages/kagent-adk/tests/unittests/test_context.py
new file mode 100644
index 000000000..765b975bb
--- /dev/null
+++ b/python/packages/kagent-adk/tests/unittests/test_context.py
@@ -0,0 +1,71 @@
+"""Unit tests for context variable module."""
+
+import pytest
+
+from kagent.adk._context import clear_user_id, get_user_id, set_user_id
+
+
+def test_get_user_id_default():
+    """Test that get_user_id returns None by default."""
+    # Ensure context is cleared
+    clear_user_id()
+    assert get_user_id() is None
+
+
+def test_set_and_get_user_id():
+    """Test setting and getting user_id."""
+    test_user_id = "user@example.com"
+    set_user_id(test_user_id)
+    try:
+        assert get_user_id() == test_user_id
+    finally:
+        clear_user_id()
+
+
+def test_clear_user_id():
+    """Test clearing user_id from context."""
+    test_user_id = "user@example.com"
+    set_user_id(test_user_id)
+    assert get_user_id() == test_user_id
+
+    clear_user_id()
+    assert get_user_id() is None
+
+
+def test_set_user_id_overwrites_previous():
+    """Test that setting user_id overwrites the previous value."""
+    set_user_id("user1@example.com")
+    try:
+        assert get_user_id() == "user1@example.com"
+
+        set_user_id("user2@example.com")
+        assert get_user_id() == "user2@example.com"
+    finally:
+        clear_user_id()
+
+
+@pytest.mark.asyncio
+async def test_context_isolation():
+    """Test that context variables are isolated per async task."""
+    import asyncio
+
+    async def task1():
+        set_user_id("user1@example.com")
+        await asyncio.sleep(0.01)
+        return get_user_id()
+
+    async def task2():
+        set_user_id("user2@example.com")
+        await asyncio.sleep(0.01)
+        return get_user_id()
+
+    # Run tasks concurrently
+    results = await asyncio.gather(task1(), task2())
+
+    # Each task should see its own user_id
+    assert results[0] == "user1@example.com"
+    assert results[1] == "user2@example.com"
+
+    # Main context should not have user_id set
+    clear_user_id()
+    assert get_user_id() is None