diff --git a/src/mudlib/player.py b/src/mudlib/player.py
index 42ca584..7806250 100644
--- a/src/mudlib/player.py
+++ b/src/mudlib/player.py
@@ -10,6 +10,7 @@ from mudlib.entity import Entity
 
 if TYPE_CHECKING:
     from mudlib.editor import Editor
+    from mudlib.if_session import IFSession
 
 
 @dataclass
@@ -22,6 +23,7 @@ class Player(Entity):
     mode_stack: list[str] = field(default_factory=lambda: ["normal"])
     caps: ClientCaps = field(default_factory=lambda: ClientCaps(ansi=True))
     editor: Editor | None = None
+    if_session: IFSession | None = None
 
     @property
     def mode(self) -> str:
diff --git a/src/mudlib/server.py b/src/mudlib/server.py
index 6d80a95..a62cdcd 100644
--- a/src/mudlib/server.py
+++ b/src/mudlib/server.py
@@ -312,6 +312,8 @@ async def shell(
             # Show appropriate prompt based on mode
             if player.mode == "editor" and player.editor:
                 _writer.write(f"  {player.editor.cursor + 1}> ")
+            elif player.mode == "if" and player.if_session:
+                _writer.write("> ")
             else:
                 _writer.write("mud> ")
             await _writer.drain()
@@ -321,7 +323,7 @@ async def shell(
                 break
 
             command = inp.strip()
-            if not command and player.mode != "editor":
+            if not command and player.mode not in ("editor", "if"):
                 continue
 
             # Handle editor mode
@@ -332,6 +334,16 @@ async def shell(
                 if response.done:
                     player.editor = None
                     player.mode_stack.pop()
+            # Handle IF mode
+            elif player.mode == "if" and player.if_session:
+                response = await player.if_session.handle_input(command)
+                if response.output:
+                    await player.send(response.output)
+                if response.done:
+                    await player.if_session.stop()
+                    player.if_session = None
+                    player.mode_stack.pop()
+                    await player.send("you leave the terminal.\r\n")
             else:
                 # Dispatch normal command
                 await mudlib.commands.dispatch(player, command)
diff --git a/tests/test_if_mode.py b/tests/test_if_mode.py
new file mode 100644
index 0000000..9b708af
--- /dev/null
+++ b/tests/test_if_mode.py
@@ -0,0 +1,121 @@
+"""Tests for IF mode integration with player model and server shell."""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from mudlib.if_session import IFResponse, IFSession
+from mudlib.player import Player
+
+
+@pytest.fixture
+def mock_writer():
+    writer = MagicMock()
+    writer.write = MagicMock()
+    writer.drain = AsyncMock()
+    return writer
+
+
+@pytest.fixture
+def mock_reader():
+    return MagicMock()
+
+
+@pytest.fixture
+def player(mock_reader, mock_writer):
+    return Player(name="TestPlayer", x=5, y=5, reader=mock_reader, writer=mock_writer)
+
+
+def test_player_has_if_session_attribute(player):
+    """Player has if_session attribute that defaults to None."""
+    assert hasattr(player, "if_session")
+    assert player.if_session is None
+
+
+def test_player_if_session_can_be_set(player):
+    """Player.if_session can be set to an IFSession instance."""
+    session = IFSession(player, "/path/to/story.z5", "story")
+    player.if_session = session
+    assert player.if_session == session
+
+
+@pytest.mark.asyncio
+async def test_if_mode_routes_input_to_if_session(player):
+    """When mode is 'if' and if_session is set, input routes to if_session.handle_input."""
+    # Create a mock IF session
+    mock_session = MagicMock()
+    mock_session.handle_input = AsyncMock(
+        return_value=IFResponse(output="You see a room.\r\n", done=False)
+    )
+
+    player.if_session = mock_session
+    player.mode_stack.append("if")
+
+    # Simulate input routing (what shell loop should do)
+    if player.mode == "if" and player.if_session:
+        response = await player.if_session.handle_input("look")
+        assert response.output == "You see a room.\r\n"
+        assert response.done is False
+
+    mock_session.handle_input.assert_called_once_with("look")
+
+
+@pytest.mark.asyncio
+async def test_if_mode_done_clears_session_and_pops_mode(player):
+    """When handle_input returns done=True, mode pops and if_session is cleared."""
+    # Create a mock IF session that returns done=True
+    mock_session = MagicMock()
+    mock_session.handle_input = AsyncMock(
+        return_value=IFResponse(output="Goodbye.\r\n", done=True)
+    )
+    mock_session.stop = AsyncMock()
+
+    player.if_session = mock_session
+    player.mode_stack.append("if")
+
+    # Simulate shell loop handling done response
+    if player.mode == "if" and player.if_session:
+        response = await player.if_session.handle_input("::quit")
+        if response.done:
+            await player.if_session.stop()
+            player.if_session = None
+            player.mode_stack.pop()
+
+    assert player.mode == "normal"
+    assert player.if_session is None
+    mock_session.stop.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_mode_stack_push_and_pop_for_if(player):
+    """Test mode stack mechanics for IF mode."""
+    assert player.mode_stack == ["normal"]
+    assert player.mode == "normal"
+
+    # Enter IF mode
+    player.mode_stack.append("if")
+    assert player.mode == "if"
+    assert player.mode_stack == ["normal", "if"]
+
+    # Exit IF mode
+    player.mode_stack.pop()
+    assert player.mode == "normal"
+    assert player.mode_stack == ["normal"]
+
+
+@pytest.mark.asyncio
+async def test_empty_input_allowed_in_if_mode(player):
+    """Test that empty input is allowed in IF mode (some IF games accept blank input)."""
+    # Create a mock IF session
+    mock_session = MagicMock()
+    mock_session.handle_input = AsyncMock(
+        return_value=IFResponse(output="Time passes.\r\n", done=False)
+    )
+
+    player.if_session = mock_session
+    player.mode_stack.append("if")
+
+    # Empty input should still be passed to IF session
+    response = await player.if_session.handle_input("")
+    assert response.output == "Time passes.\r\n"
+    mock_session.handle_input.assert_called_once_with("")