diff --git a/src/mudlib/gmcp.py b/src/mudlib/gmcp.py
index 1bf22f6..4654d30 100644
--- a/src/mudlib/gmcp.py
+++ b/src/mudlib/gmcp.py
@@ -13,6 +13,8 @@ log = logging.getLogger(__name__)
 
 def send_char_vitals(player: Player) -> None:
     """Send Char.Vitals — pl, max_pl, stamina, max_stamina."""
+    if not player.gmcp_enabled:
+        return
     player.send_gmcp(
         "Char.Vitals",
         {
@@ -26,6 +28,8 @@ def send_char_vitals(player: Player) -> None:
 
 def send_char_status(player: Player) -> None:
     """Send Char.Status — flying, resting, mode, in_combat."""
+    if not player.gmcp_enabled:
+        return
     player.send_gmcp(
         "Char.Status",
         {
@@ -39,6 +43,8 @@ def send_char_status(player: Player) -> None:
 
 def send_room_info(player: Player) -> None:
     """Send Room.Info — zone, coordinates, terrain, exits."""
+    if not player.gmcp_enabled:
+        return
     from mudlib.zone import Zone
 
     zone = player.location
@@ -78,6 +84,8 @@ def send_room_info(player: Player) -> None:
 
 def send_map_data(player: Player) -> None:
     """Send Room.Map — terrain viewport around player for client rendering."""
+    if not player.gmcp_enabled:
+        return
     from mudlib.zone import Zone
 
     zone = player.location
@@ -108,6 +116,8 @@ def send_map_data(player: Player) -> None:
 
 def send_msdp_vitals(player: Player) -> None:
     """Send MSDP variable updates for real-time gauges."""
+    if not player.msdp_enabled:
+        return
     player.send_msdp(
         {
             "HEALTH": str(round(player.pl, 1)),
diff --git a/src/mudlib/player.py b/src/mudlib/player.py
index bcf5003..558e0b0 100644
--- a/src/mudlib/player.py
+++ b/src/mudlib/player.py
@@ -5,6 +5,8 @@ from __future__ import annotations
 from dataclasses import dataclass, field
 from typing import TYPE_CHECKING, Any
 
+from telnetlib3 import GMCP, MSDP
+
 from mudlib.caps import ClientCaps
 from mudlib.entity import Entity
 
@@ -54,6 +56,26 @@ class Player(Entity):
         if self.writer is not None:
             self.writer.send_msdp(variables)
 
+    @property
+    def gmcp_enabled(self) -> bool:
+        """Whether this client has GMCP negotiated."""
+        if self.writer is None:
+            return False
+        return bool(
+            self.writer.local_option.enabled(GMCP)
+            or self.writer.remote_option.enabled(GMCP)
+        )
+
+    @property
+    def msdp_enabled(self) -> bool:
+        """Whether this client has MSDP negotiated."""
+        if self.writer is None:
+            return False
+        return bool(
+            self.writer.local_option.enabled(MSDP)
+            or self.writer.remote_option.enabled(MSDP)
+        )
+
 
 # Global registry of connected players
 players: dict[str, Player] = {}
diff --git a/src/mudlib/server.py b/src/mudlib/server.py
index 5c16329..64503d0 100644
--- a/src/mudlib/server.py
+++ b/src/mudlib/server.py
@@ -9,6 +9,8 @@ import tomllib
 from typing import cast
 
 import telnetlib3
+from telnetlib3 import GMCP, MSDP, WILL
+from telnetlib3.server import TelnetServer
 from telnetlib3.server_shell import readline2
 
 import mudlib.combat.commands
@@ -224,6 +226,17 @@ async def handle_login(
             return {"success": False, "player_data": None}
 
 
+class MudTelnetServer(TelnetServer):
+    """Telnet server that offers GMCP and MSDP during negotiation."""
+
+    def begin_advanced_negotiation(self) -> None:
+        """Offer GMCP and MSDP alongside the standard options."""
+        super().begin_advanced_negotiation()
+        assert self.writer is not None
+        self.writer.iac(WILL, GMCP)
+        self.writer.iac(WILL, MSDP)
+
+
 async def shell(
     reader: telnetlib3.TelnetReader | telnetlib3.TelnetReaderUnicode,
     writer: telnetlib3.TelnetWriter | telnetlib3.TelnetWriterUnicode,
@@ -527,7 +540,11 @@ async def run_server() -> None:
     # MUD clients like tintin++ reject CHARSET immediately via MTTS, but
     # telnetlib3 still waits for the full timeout. 0.5s is plenty.
     server = await telnetlib3.create_server(
-        host=HOST, port=PORT, shell=shell, connect_maxwait=0.5
+        host=HOST,
+        port=PORT,
+        shell=shell,
+        connect_maxwait=0.5,
+        protocol_factory=MudTelnetServer,
     )
     log.info("listening on %s:%d", HOST, PORT)
 
diff --git a/tests/test_embedded_if.py b/tests/test_embedded_if.py
index caea6f9..315bae4 100644
--- a/tests/test_embedded_if.py
+++ b/tests/test_embedded_if.py
@@ -17,6 +17,15 @@ requires_zork = pytest.mark.skipif(not ZORK_PATH.exists(), reason="zork1.z3 not
 
 @dataclass
 class MockWriter:
+    def __post_init__(self):
+        # Mock option negotiation state
+        from unittest.mock import MagicMock
+
+        self.local_option = MagicMock()
+        self.local_option.enabled = MagicMock(return_value=False)
+        self.remote_option = MagicMock()
+        self.remote_option.enabled = MagicMock(return_value=False)
+
     def write(self, data):
         pass
 
diff --git a/tests/test_gmcp.py b/tests/test_gmcp.py
index f163300..fa5aafb 100644
--- a/tests/test_gmcp.py
+++ b/tests/test_gmcp.py
@@ -47,6 +47,11 @@ def mock_writer():
     writer.drain = AsyncMock()
     writer.send_gmcp = MagicMock()
     writer.send_msdp = MagicMock()
+    # Option negotiation state (for gmcp_enabled/msdp_enabled checks)
+    writer.local_option = MagicMock()
+    writer.local_option.enabled = MagicMock(return_value=True)
+    writer.remote_option = MagicMock()
+    writer.remote_option.enabled = MagicMock(return_value=True)
     return writer
 
 
@@ -502,3 +507,58 @@ async def test_char_status_sent_on_rest_complete(player):
     ]
     assert len(status_calls) == 1
     assert status_calls[0][0][1]["resting"] is False
+
+
+def test_msdp_vitals_skipped_when_not_negotiated(player):
+    """Test send_msdp_vitals skips when MSDP is not negotiated."""
+    player.writer.local_option.enabled.return_value = False
+    player.writer.remote_option.enabled.return_value = False
+
+    send_msdp_vitals(player)
+
+    player.writer.send_msdp.assert_not_called()
+
+
+def test_msdp_enabled_property(player):
+    """Test msdp_enabled reflects negotiation state."""
+    player.writer.local_option.enabled.return_value = False
+    player.writer.remote_option.enabled.return_value = False
+    assert not player.msdp_enabled
+
+    player.writer.local_option.enabled.return_value = True
+    assert player.msdp_enabled
+
+
+def test_gmcp_enabled_property(player):
+    """Test gmcp_enabled reflects negotiation state."""
+    player.writer.local_option.enabled.return_value = False
+    player.writer.remote_option.enabled.return_value = False
+    assert not player.gmcp_enabled
+
+    player.writer.remote_option.enabled.return_value = True
+    assert player.gmcp_enabled
+
+
+def test_msdp_enabled_no_writer():
+    """Test msdp_enabled with no writer returns False."""
+    p = Player(name="NoWriter", writer=None)
+    assert not p.msdp_enabled
+
+
+def test_gmcp_enabled_no_writer():
+    """Test gmcp_enabled with no writer returns False."""
+    p = Player(name="NoWriter", writer=None)
+    assert not p.gmcp_enabled
+
+
+def test_gmcp_sends_skipped_when_not_negotiated(player):
+    """Test all GMCP send functions skip when GMCP is not negotiated."""
+    player.writer.local_option.enabled.return_value = False
+    player.writer.remote_option.enabled.return_value = False
+
+    send_char_vitals(player)
+    send_char_status(player)
+    send_room_info(player)
+    send_map_data(player)
+
+    player.writer.send_gmcp.assert_not_called()
diff --git a/tests/test_paint_mode.py b/tests/test_paint_mode.py
index 1b7e3eb..5a3761e 100644
--- a/tests/test_paint_mode.py
+++ b/tests/test_paint_mode.py
@@ -35,6 +35,13 @@ class MockWriter:
 
     def __init__(self):
         self.messages = []
+        # Mock option negotiation state
+        from unittest.mock import MagicMock
+
+        self.local_option = MagicMock()
+        self.local_option.enabled = MagicMock(return_value=False)
+        self.remote_option = MagicMock()
+        self.remote_option.enabled = MagicMock(return_value=False)
 
     def write(self, message: str):
         self.messages.append(message)