diff --git a/tests/unit/test_agent_controller.py b/tests/unit/test_agent_controller.py
index 02cb80b01a74..5913fd3bf992 100644
--- a/tests/unit/test_agent_controller.py
+++ b/tests/unit/test_agent_controller.py
@@ -1,5 +1,5 @@
 import asyncio
-from unittest.mock import ANY, AsyncMock, MagicMock
+from unittest.mock import ANY, AsyncMock, MagicMock, call
 from uuid import uuid4
 
 import pytest
@@ -16,6 +16,7 @@
     ChangeAgentStateAction,
     CmdRunAction,
     MessageAction,
+    PromptExtensionAction,
     SystemMessageAction,
 )
 from openhands.events.observation import (
@@ -750,6 +751,169 @@ async def test_prompt_manager_initialization(mock_agent, mock_event_stream):
     await controller.close()
 
 
+@pytest.mark.asyncio
+async def test_prompt_manager_extensions(mock_agent, mock_event_stream):
+    """Test that prompt extensions are properly added to event stream."""
+    # Mock the prompt manager and enable extensions
+    mock_agent.config.enable_prompt_extensions = True
+    mock_prompt_manager = MagicMock(spec=PromptManager)
+    mock_prompt_manager.get_system_message.return_value = "Test system message"
+
+    # Mock the prompt extension methods
+    def add_examples(msg):
+        msg.content[0].text = "Examples added: " + msg.content[0].text
+    mock_prompt_manager.add_examples_to_initial_message.side_effect = add_examples
+
+    def add_info(msg):
+        msg.content[0].text = "Info added: " + msg.content[0].text
+    mock_prompt_manager.add_info_to_initial_message.side_effect = add_info
+
+    def enhance(msg):
+        msg.content[0].text = "Enhanced: " + msg.content[0].text
+    mock_prompt_manager.enhance_message.side_effect = enhance
+
+    mock_agent.get_prompt_manager.return_value = mock_prompt_manager
+
+    # Create controller
+    controller = AgentController(
+        agent=mock_agent,
+        event_stream=mock_event_stream,
+        max_iterations=10,
+        sid='test',
+        confirmation_mode=False,
+        headless_mode=True,
+    )
+
+    # Send a user message
+    message_action = MessageAction(content="Test message")
+    message_action._source = EventSource.USER
+    await controller._on_event(message_action)
+
+    # Get all calls to add_event
+    actual_calls = mock_event_stream.add_event.call_args_list
+
+    # Verify that system message was added
+    assert any(
+        isinstance(args[0], SystemMessageAction) and args[0].content == "Test system message"
+        for args, _ in actual_calls
+    )
+
+    # Verify that prompt extensions were added
+    expected_extensions = [
+        ("Examples added: Test message", "examples"),
+        ("Info added: Examples added: Test message", "info"),
+        ("Enhanced: Info added: Examples added: Test message", "enhance"),
+    ]
+    for content, ext_type in expected_extensions:
+        assert any(
+            isinstance(args[0], PromptExtensionAction)
+            and args[0].content == content
+            and args[0].extension_type == ext_type
+            for args, _ in actual_calls
+        ), f"Missing extension: {ext_type}"
+
+
+
+    await controller.close()
+
+
+@pytest.mark.asyncio
+async def test_prompt_manager_extensions_disabled(mock_agent, mock_event_stream):
+    """Test that prompt extensions are not added when disabled."""
+    # Mock the prompt manager but disable extensions
+    mock_agent.config.enable_prompt_extensions = False
+    mock_prompt_manager = MagicMock(spec=PromptManager)
+    mock_prompt_manager.get_system_message.return_value = "Test system message"
+    mock_agent.get_prompt_manager.return_value = mock_prompt_manager
+
+    # Create controller
+    controller = AgentController(
+        agent=mock_agent,
+        event_stream=mock_event_stream,
+        max_iterations=10,
+        sid='test',
+        confirmation_mode=False,
+        headless_mode=True,
+    )
+
+    # Send a user message
+    message_action = MessageAction(content="Test message")
+    message_action._source = EventSource.USER
+    await controller._on_event(message_action)
+
+    # Get all calls to add_event
+    actual_calls = mock_event_stream.add_event.call_args_list
+
+    # Verify that system message was added
+    assert any(
+        isinstance(args[0], SystemMessageAction) and args[0].content == "Test system message"
+        for args, _ in actual_calls
+    )
+
+    # Verify that no prompt extensions were added
+    assert not any(
+        isinstance(args[0], PromptExtensionAction)
+        for args, _ in actual_calls
+    )
+
+    # Verify that extension methods were not called
+    mock_prompt_manager.add_examples_to_initial_message.assert_not_called()
+    mock_prompt_manager.add_info_to_initial_message.assert_not_called()
+    mock_prompt_manager.enhance_message.assert_not_called()
+
+    await controller.close()
+
+
+@pytest.mark.asyncio
+async def test_prompt_manager_extensions_delegate(mock_agent, mock_event_stream):
+    """Test that prompt extensions are not added for delegate controllers."""
+    # Mock the prompt manager
+    mock_prompt_manager = MagicMock(spec=PromptManager)
+    mock_prompt_manager.get_system_message.return_value = "Test system message"
+    mock_agent.get_prompt_manager.return_value = mock_prompt_manager
+
+    # Create delegate controller
+    controller = AgentController(
+        agent=mock_agent,
+        event_stream=mock_event_stream,
+        max_iterations=10,
+        sid='test',
+        confirmation_mode=False,
+        headless_mode=True,
+        is_delegate=True,  # This should prevent system message and extensions
+    )
+
+    # Send a user message
+    message_action = MessageAction(content="Test message")
+    message_action._source = EventSource.USER
+    await controller._on_event(message_action)
+
+    # Get all calls to add_event
+    actual_calls = mock_event_stream.add_event.call_args_list
+
+    # Verify that only the original message was added (plus state changes)
+    print("Message action:", message_action)
+    print("Actual calls:", actual_calls)
+    assert any(
+        args[0] == message_action and args[1] == EventSource.USER
+        for args, _ in actual_calls
+    )
+
+    # Verify that no system message or prompt extensions were added
+    assert not any(
+        isinstance(args[0], SystemMessageAction) or isinstance(args[0], PromptExtensionAction)
+        for args, _ in actual_calls
+    )
+
+    # Verify that system message and extension methods were not called
+    mock_prompt_manager.get_system_message.assert_not_called()
+    mock_prompt_manager.add_examples_to_initial_message.assert_not_called()
+    mock_prompt_manager.add_info_to_initial_message.assert_not_called()
+    mock_prompt_manager.enhance_message.assert_not_called()
+
+    await controller.close()
+
+
 @pytest.mark.asyncio
 async def test_prompt_manager_not_initialized(mock_agent, mock_event_stream):
     """Test that no system message is sent if prompt manager is not initialized."""