diff --git a/cereal/custom.capnp b/cereal/custom.capnp
index 1f14636bdd..908dee7d56 100644
--- a/cereal/custom.capnp
+++ b/cereal/custom.capnp
@@ -14,6 +14,7 @@ using Car = import "car.capnp";
 
 struct StarPilotCarControl @0x81c2f05a394cf4af {
   hudControl @0 :HUDControl;
+  steeringLimitInfo @1 :SteeringLimitInfo;
 
   struct HUDControl {
     audibleAlert @0 :AudibleAlert;
@@ -49,6 +50,16 @@ struct StarPilotCarControl @0x81c2f05a394cf4af {
       uwu @22;
     }
   }
+
+  struct SteeringLimitInfo {
+    valid @0 :Bool;
+    modelLimitErrorDeg @1 :Float32;
+    resumeLimitErrorDeg @2 :Float32;
+    cooperativeLimitErrorDeg @3 :Float32;
+    cooperativeOffsetDeg @4 :Float32;
+    monoTime @5 :UInt64;
+    combinedLimitErrorDeg @6 :Float32;
+  }
 }
 
 struct StarPilotCarParams @0xaedffd8f31e7b55d {
diff --git a/cereal/libcereal.a b/cereal/libcereal.a
index 9bdac9f8d1..a242c1f0f8 100644
Binary files a/cereal/libcereal.a and b/cereal/libcereal.a differ
diff --git a/opendbc_repo/opendbc/car/car.capnp b/opendbc_repo/opendbc/car/car.capnp
index bf205202d1..a0d3fad8a4 100644
--- a/opendbc_repo/opendbc/car/car.capnp
+++ b/opendbc_repo/opendbc/car/car.capnp
@@ -375,17 +375,6 @@ struct CarControl {
     torqueOutputCan @8: Float32;   # value sent over can to the car
     speed @6: Float32;  # m/s
     lateralControlMode @9: LateralControlMode;
-    steeringLimitInfo @10 :SteeringLimitInfo;
-
-    struct SteeringLimitInfo {
-      valid @0 :Bool;
-      modelLimitErrorDeg @1 :Float32;
-      resumeLimitErrorDeg @2 :Float32;
-      cooperativeLimitErrorDeg @3 :Float32;
-      cooperativeOffsetDeg @4 :Float32;
-      monoTime @5 :UInt64;
-      combinedLimitErrorDeg @6 :Float32;
-    }
 
     enum LongControlState @0xe40f3a917d908282{
       off @0;
diff --git a/opendbc_repo/opendbc/car/tesla/carcontroller.py b/opendbc_repo/opendbc/car/tesla/carcontroller.py
index d4aab08077..c29a836fba 100644
--- a/opendbc_repo/opendbc/car/tesla/carcontroller.py
+++ b/opendbc_repo/opendbc/car/tesla/carcontroller.py
@@ -49,15 +49,16 @@ class CarController(CarControllerBase):
     self.steering_limit_mono_time = 0
     self.combined_limit_error_deg = 0.0
 
-  def _write_steering_limit_info(self, actuators):
-    info = actuators.steeringLimitInfo
-    info.valid = self.steering_limit_info_valid
-    info.modelLimitErrorDeg = self.model_limit_error_deg
-    info.resumeLimitErrorDeg = self.resume_limit_error_deg
-    info.cooperativeLimitErrorDeg = self.cooperative_limit_error_deg
-    info.cooperativeOffsetDeg = self.cooperative_offset_deg
-    info.monoTime = self.steering_limit_mono_time
-    info.combinedLimitErrorDeg = self.combined_limit_error_deg
+  def get_steering_limit_info(self) -> dict[str, bool | float | int]:
+    return {
+      "valid": self.steering_limit_info_valid,
+      "modelLimitErrorDeg": self.model_limit_error_deg,
+      "resumeLimitErrorDeg": self.resume_limit_error_deg,
+      "cooperativeLimitErrorDeg": self.cooperative_limit_error_deg,
+      "cooperativeOffsetDeg": self.cooperative_offset_deg,
+      "monoTime": self.steering_limit_mono_time,
+      "combinedLimitErrorDeg": self.combined_limit_error_deg,
+    }
 
   def update(self, CC, CS, now_nanos, starpilot_toggles):
     if self.CP.carFingerprint == CAR.TESLA_MODEL_S_PREAP:
@@ -125,7 +126,6 @@ class CarController(CarControllerBase):
     # TODO: HUD control
     new_actuators = actuators.as_builder()
     new_actuators.steeringAngleDeg = self.apply_angle_command_last
-    self._write_steering_limit_info(new_actuators)
 
     self.frame += 1
     return new_actuators, can_sends
@@ -168,7 +168,6 @@ class CarController(CarControllerBase):
 
     new_actuators = actuators.as_builder()
     new_actuators.steeringAngleDeg = self.apply_angle_last
-    self._write_steering_limit_info(new_actuators)
 
     self.frame += 1
     return new_actuators, can_sends
diff --git a/opendbc_repo/opendbc/car/tesla/tests/test_coop_steering_limit_info.py b/opendbc_repo/opendbc/car/tesla/tests/test_coop_steering_limit_info.py
index 05ea35da2d..3515401f50 100644
--- a/opendbc_repo/opendbc/car/tesla/tests/test_coop_steering_limit_info.py
+++ b/opendbc_repo/opendbc/car/tesla/tests/test_coop_steering_limit_info.py
@@ -5,11 +5,13 @@ from types import SimpleNamespace
 
 import pytest
 
+import cereal.messaging as messaging
+
 from cereal import car
 from opendbc.car import gen_empty_fingerprint
 from opendbc.car.tesla.carcontroller import CarController
 from opendbc.car.tesla.interface import CarInterface
-from opendbc.car.tesla.values import CAR, DBC, TeslaSafetyFlags
+from opendbc.car.tesla.values import CAR, DBC
 
 
 BASELINE_SHA = "a80064be4fdf4b8765a5e9dec44d8a5c266f48a8"
@@ -62,21 +64,25 @@ def run_frame(controller, requested_angle=0.0, torque=0.0, speed=15.0, measured_
   )
 
 
+def get_limit_info(controller):
+  return SimpleNamespace(**controller.get_steering_limit_info())
+
+
 def legacy_actuator_dict(actuators):
-  values = actuators.to_dict()
-  values.pop("steeringLimitInfo", None)
-  return values
+  return actuators.to_dict()
 
 
 def test_steering_limit_info_defaults_to_invalid():
-  actuators = car.CarControl.Actuators.new_message()
+  controller = make_controller()
 
-  assert not actuators.steeringLimitInfo.valid
+  info = get_limit_info(controller)
+  assert not info.valid
+  assert info.monoTime == 0
 
 
-def test_steering_limit_info_round_trips_through_car_output():
-  output = car.CarOutput.new_message()
-  info = output.actuatorsOutput.steeringLimitInfo
+def test_steering_limit_info_round_trips_through_custom_message():
+  message = messaging.new_message("starpilotCarControl", valid=True)
+  info = message.starpilotCarControl.steeringLimitInfo
   info.valid = True
   info.modelLimitErrorDeg = 1.25
   info.resumeLimitErrorDeg = 0.5
@@ -85,25 +91,25 @@ def test_steering_limit_info_round_trips_through_car_output():
   info.monoTime = 1_234_567_890
   info.combinedLimitErrorDeg = 3.75
 
-  with car.CarOutput.from_bytes(output.to_bytes()) as restored:
-    restored_info = restored.actuatorsOutput.steeringLimitInfo
-    assert restored_info.valid
-    assert restored_info.modelLimitErrorDeg == 1.25
-    assert restored_info.resumeLimitErrorDeg == 0.5
-    assert restored_info.cooperativeLimitErrorDeg == 2.0
-    assert restored_info.cooperativeOffsetDeg == -4.5
-    assert restored_info.monoTime == 1_234_567_890
-    assert restored_info.combinedLimitErrorDeg == 3.75
+  restored = messaging.log_from_bytes(message.to_bytes())
+  restored_info = restored.starpilotCarControl.steeringLimitInfo
+  assert restored_info.valid
+  assert restored_info.modelLimitErrorDeg == 1.25
+  assert restored_info.resumeLimitErrorDeg == 0.5
+  assert restored_info.cooperativeLimitErrorDeg == 2.0
+  assert restored_info.cooperativeOffsetDeg == -4.5
+  assert restored_info.monoTime == 1_234_567_890
+  assert restored_info.combinedLimitErrorDeg == 3.75
 
 
-def test_active_cooperative_controller_publishes_r_n_a_t_f_diagnostics():
+def test_active_cooperative_controller_reports_diagnostics():
   controller = make_controller()
   requested_angle = 20.0
   now_nanos = 1_234_567_890
 
   actuators, _ = run_frame(controller, requested_angle, torque=0.9, measured_angle=0.0, now_nanos=now_nanos)
 
-  info = actuators.steeringLimitInfo
+  info = get_limit_info(controller)
   assert info.valid
   assert info.monoTime == now_nanos
   assert info.modelLimitErrorDeg == pytest.approx(abs(requested_angle - controller.apply_angle_last), abs=1e-5)
@@ -129,7 +135,7 @@ def test_cooperative_offset_alone_does_not_become_limiter_error():
     actuators, _ = run_frame(controller, torque=0.9, now_nanos=1_000_000_000 + frame * 10_000_000)
 
   assert actuators is not None
-  info = actuators.steeringLimitInfo
+  info = get_limit_info(controller)
   assert info.valid
   assert info.cooperativeOffsetDeg > 2.5
   assert info.modelLimitErrorDeg < 2.5
@@ -145,7 +151,7 @@ def test_combined_error_keeps_two_same_direction_small_limits_visible():
 
   actuators, _ = run_frame(controller, -2.5, torque=-1.5, speed=12.5, measured_angle=0.0)
 
-  info = actuators.steeringLimitInfo
+  info = get_limit_info(controller)
   assert info.modelLimitErrorDeg == pytest.approx(1.5045133, abs=1e-5)
   assert info.resumeLimitErrorDeg == pytest.approx(0.0, abs=1e-5)
   assert info.cooperativeLimitErrorDeg == pytest.approx(1.5045133, abs=1e-5)
@@ -158,26 +164,26 @@ def test_combined_error_keeps_two_same_direction_small_limits_visible():
 def test_intervening_100hz_frame_retains_matching_50hz_sample():
   controller = make_controller()
   first, _ = run_frame(controller, 8.0, torque=0.9, now_nanos=1_000_000_000)
-  first_info = first.steeringLimitInfo.to_dict()
+  first_info = controller.get_steering_limit_info()
 
   second, _ = run_frame(controller, -40.0, torque=-1.5, now_nanos=1_010_000_000)
 
-  assert second.steeringLimitInfo.to_dict() == first_info
-  assert second.steeringLimitInfo.monoTime == 1_000_000_000
+  assert controller.get_steering_limit_info() == first_info
+  assert controller.get_steering_limit_info()["monoTime"] == 1_000_000_000
 
 
 def test_inactive_interval_clears_sample_until_next_steering_update():
   controller = make_controller()
   active, _ = run_frame(controller, 8.0, torque=0.9, now_nanos=1_000_000_000)
-  assert active.steeringLimitInfo.valid
+  assert get_limit_info(controller).valid
 
   inactive, _ = run_frame(controller, 8.0, torque=0.9, lat_active=False, now_nanos=1_010_000_000)
-  assert not inactive.steeringLimitInfo.valid
-  assert inactive.steeringLimitInfo.monoTime == 0
+  assert not get_limit_info(controller).valid
+  assert get_limit_info(controller).monoTime == 0
 
   resumed, _ = run_frame(controller, 8.0, torque=0.9, now_nanos=1_020_000_000)
-  assert resumed.steeringLimitInfo.valid
-  assert resumed.steeringLimitInfo.monoTime == 1_020_000_000
+  assert get_limit_info(controller).valid
+  assert get_limit_info(controller).monoTime == 1_020_000_000
 
 
 @pytest.mark.parametrize(("candidate", "cooperative", "steering_disengage"), (
@@ -190,8 +196,9 @@ def test_diagnostics_invalid_when_not_in_supported_active_path(candidate, cooper
 
   actuators, _ = run_frame(controller, torque=1.5, steering_disengage=steering_disengage)
 
-  assert not actuators.steeringLimitInfo.valid
-  assert actuators.steeringLimitInfo.monoTime == 0
+  info = get_limit_info(controller)
+  assert not info.valid
+  assert info.monoTime == 0
 
 
 def test_actual_actuators_and_steering_can_match_pinned_baseline_fixture():
diff --git a/selfdrive/car/card.py b/selfdrive/car/card.py
index 2e83ce373d..9e2d1a4e8d 100644
--- a/selfdrive/car/card.py
+++ b/selfdrive/car/card.py
@@ -43,6 +43,22 @@ REDNECK_DECREASE_LOOKAHEAD_POINTS = 10
 SLC_SOURCE_NONE = "None"
 EventName = log.OnroadEvent.EventName
 
+
+def _build_starpilot_car_control(steering_limit_info: dict[str, bool | float | int] | None, valid: bool):
+  message = messaging.new_message('starpilotCarControl')
+  message.valid = valid
+  if steering_limit_info is not None:
+    info = message.starpilotCarControl.steeringLimitInfo
+    info.valid = bool(steering_limit_info.get("valid", False))
+    info.modelLimitErrorDeg = float(steering_limit_info.get("modelLimitErrorDeg", 0.0))
+    info.resumeLimitErrorDeg = float(steering_limit_info.get("resumeLimitErrorDeg", 0.0))
+    info.cooperativeLimitErrorDeg = float(steering_limit_info.get("cooperativeLimitErrorDeg", 0.0))
+    info.cooperativeOffsetDeg = float(steering_limit_info.get("cooperativeOffsetDeg", 0.0))
+    info.monoTime = int(steering_limit_info.get("monoTime", 0))
+    info.combinedLimitErrorDeg = float(steering_limit_info.get("combinedLimitErrorDeg", 0.0))
+  return message
+
+
 # forward
 carlog.addHandler(ForwardingHandler(cloudlog))
 
@@ -86,7 +102,7 @@ class Car:
   def __init__(self, CI=None, RI=None) -> None:
     self.can_sock = messaging.sub_sock('can', timeout=20)
     self.sm = messaging.SubMaster(['pandaStates', 'carControl', 'onroadEvents', 'radarState', 'longitudinalPlan'])
-    self.pm = messaging.PubMaster(['sendcan', 'carState', 'carParams', 'carOutput', 'liveTracks'])
+    self.pm = messaging.PubMaster(['sendcan', 'carState', 'carParams', 'carOutput', 'liveTracks', 'starpilotCarControl'])
     self.gps_pm = None
 
     self.can_rcv_cum_timeout_counter = 0
@@ -99,6 +115,7 @@ class Car:
     self.initialized_prev = False
 
     self.last_actuators_output = structs.CarControl.Actuators()
+    self.last_steering_limit_info: dict[str, bool | float | int] | None = None
 
     self.params = Params()
     self.params_memory = Params(memory=True)
@@ -396,6 +413,12 @@ class Car:
     co_send.carOutput.actuatorsOutput = self.last_actuators_output
     self.pm.send('carOutput', co_send)
 
+    starpilot_control_send = _build_starpilot_car_control(
+      self.last_steering_limit_info,
+      CS.canValid and self.sm.all_checks(['carControl']),
+    )
+    self.pm.send('starpilotCarControl', starpilot_control_send)
+
     # kick off controlsd step while we actuate the latest carControl packet
     cs_send = messaging.new_message('carState')
     cs_send.valid = CS.canValid
@@ -450,6 +473,8 @@ class Car:
         self.CI.CC.update_live_params(live_params.roll, live_params.angleOffsetDeg,
                                       live_params.stiffnessFactor, live_params.steerRatio)
       self.last_actuators_output, can_sends = self.CI.apply(CC, now_nanos, self.starpilot_toggles)
+      get_steering_limit_info = getattr(self.CI.CC, "get_steering_limit_info", None)
+      self.last_steering_limit_info = get_steering_limit_info() if get_steering_limit_info is not None else None
       self.pm.send('sendcan', can_list_to_can_capnp(can_sends, msgtype='sendcan', valid=CS.canValid))
 
       self.CC_prev = CC
diff --git a/selfdrive/car/tests/test_starpilot_car_control.py b/selfdrive/car/tests/test_starpilot_car_control.py
new file mode 100644
index 0000000000..9bf54b12bc
--- /dev/null
+++ b/selfdrive/car/tests/test_starpilot_car_control.py
@@ -0,0 +1,30 @@
+import cereal.messaging as messaging
+
+from cereal import car
+from openpilot.selfdrive.car.card import _build_starpilot_car_control
+
+
+def test_steering_diagnostics_use_reserved_custom_message():
+  values = {
+    "valid": True,
+    "modelLimitErrorDeg": 1.25,
+    "resumeLimitErrorDeg": 0.5,
+    "cooperativeLimitErrorDeg": 2.0,
+    "cooperativeOffsetDeg": -4.5,
+    "monoTime": 1_234_567_890,
+    "combinedLimitErrorDeg": 3.75,
+  }
+
+  message = _build_starpilot_car_control(values, True)
+  restored = messaging.log_from_bytes(message.to_bytes())
+  info = restored.starpilotCarControl.steeringLimitInfo
+
+  assert restored.valid
+  for field, value in values.items():
+    assert getattr(info, field) == value
+
+
+def test_stock_car_output_has_no_fork_specific_fields():
+  actuators = car.CarOutput.new_message().actuatorsOutput
+
+  assert "steeringLimitInfo" not in actuators.to_dict()
diff --git a/selfdrive/controls/controlsd.py b/selfdrive/controls/controlsd.py
index 94363186d4..0fdf7c97cb 100644
--- a/selfdrive/controls/controlsd.py
+++ b/selfdrive/controls/controlsd.py
@@ -390,6 +390,7 @@ class Controls:
 
     self.sm = messaging.SubMaster(['liveDelay', 'liveParameters', 'liveTorqueParameters', 'modelV2', 'selfdriveState',
                                    'liveCalibration', 'livePose', 'longitudinalPlan', 'lateralManeuverPlan', 'carState', 'carOutput',
+                                   'starpilotCarControl',
                                    'driverMonitoringState', 'onroadEvents', 'driverAssistance', 'radarState'], poll='selfdriveState')
     self.pm = messaging.PubMaster(['carControl', 'controlsState', 'starpilotLateralState'])
 
@@ -884,7 +885,7 @@ class Controls:
         )
         now_nanos = self.sm.logMonoTime['selfdriveState'] if REPLAY else time.monotonic_ns()
         self.steer_limited_by_safety = is_angle_steering_limited(
-          self.CP, CC.actuators.steeringAngleDeg, CO, output_healthy, now_nanos,
+          self.CP, CC.actuators.steeringAngleDeg, CO, self.sm['starpilotCarControl'], output_healthy, now_nanos,
         )
       else:
         self.steer_limited_by_safety = abs(CC.actuators.torque - CO.actuatorsOutput.torque) > 1e-2
diff --git a/selfdrive/controls/lib/steering_saturation.py b/selfdrive/controls/lib/steering_saturation.py
index 827527a3a4..b2da8b04cf 100644
--- a/selfdrive/controls/lib/steering_saturation.py
+++ b/selfdrive/controls/lib/steering_saturation.py
@@ -3,8 +3,7 @@ import math
 from opendbc.car.tesla.values import CAR, TeslaSafetyFlags
 
 
-# TODO This is speed dependent
-STEER_ANGLE_SATURATION_THRESHOLD = 2.5  # Degrees
+STEER_ANGLE_SATURATION_THRESHOLD = 2.5
 _MAX_STEERING_LIMIT_INFO_AGE_NANOS = 100_000_000
 
 
@@ -13,7 +12,8 @@ def _legacy_angle_steering_limited(requested_angle: float, car_output) -> bool:
     STEER_ANGLE_SATURATION_THRESHOLD
 
 
-def is_angle_steering_limited(CP, requested_angle: float, car_output, output_healthy: bool, now_nanos: int) -> bool:
+def is_angle_steering_limited(CP, requested_angle: float, car_output, starpilot_car_control,
+                              output_healthy: bool, now_nanos: int) -> bool:
   legacy_limited = _legacy_angle_steering_limited(requested_angle, car_output)
 
   try:
@@ -24,7 +24,10 @@ def is_angle_steering_limited(CP, requested_angle: float, car_output, output_hea
     if CP.carFingerprint != CAR.TESLA_MODEL_3 or not cooperative_enabled or not output_healthy:
       return legacy_limited
 
-    info = car_output.actuatorsOutput.steeringLimitInfo
+    if not starpilot_car_control.valid:
+      return legacy_limited
+
+    info = starpilot_car_control.starpilotCarControl.steeringLimitInfo
     errors = (
       info.modelLimitErrorDeg,
       info.resumeLimitErrorDeg,
diff --git a/selfdrive/controls/tests/test_steering_saturation.py b/selfdrive/controls/tests/test_steering_saturation.py
index 520b74e614..c7425c79b8 100644
--- a/selfdrive/controls/tests/test_steering_saturation.py
+++ b/selfdrive/controls/tests/test_steering_saturation.py
@@ -1,5 +1,6 @@
 import math
 
+import cereal.messaging as messaging
 import pytest
 
 from cereal import car
@@ -33,39 +34,44 @@ def make_case(candidate=CAR.TESLA_MODEL_3, cooperative_enabled=True):
 
   output = car.CarOutput.new_message()
   output.actuatorsOutput.steeringAngleDeg = OUTPUT_ANGLE
-  info = output.actuatorsOutput.steeringLimitInfo
+
+  diagnostics = messaging.new_message("starpilotCarControl", valid=True)
+  info = diagnostics.starpilotCarControl.steeringLimitInfo
   info.valid = True
   info.monoTime = SAMPLE_TIME_NANOS
   info.cooperativeOffsetDeg = 5.5
-  return cp, output
+  return cp, output, diagnostics
 
 
-def detect(cp, output, requested_angle=REQUESTED_ANGLE, output_healthy=True, now_nanos=FRESH_TIME_NANOS):
-  return is_angle_steering_limited(cp.as_reader(), requested_angle, output.as_reader(), output_healthy, now_nanos)
+def detect(cp, output, diagnostics, requested_angle=REQUESTED_ANGLE,
+           output_healthy=True, now_nanos=FRESH_TIME_NANOS):
+  return is_angle_steering_limited(
+    cp.as_reader(), requested_angle, output.as_reader(), diagnostics.as_reader(), output_healthy, now_nanos,
+  )
 
 
 def test_light_offset_does_not_count_as_limiting():
-  cp, output = make_case()
+  cp, output, diagnostics = make_case()
 
-  assert not detect(cp, output)
+  assert not detect(cp, output, diagnostics)
 
 
 @pytest.mark.parametrize("field", ERROR_FIELDS)
 def test_each_genuine_limit_is_visible_during_cooperation(field):
-  cp, output = make_case()
-  setattr(output.actuatorsOutput.steeringLimitInfo, field, 3.0)
+  cp, output, diagnostics = make_case()
+  setattr(diagnostics.starpilotCarControl.steeringLimitInfo, field, 3.0)
 
-  assert detect(cp, output)
+  assert detect(cp, output, diagnostics)
 
 
 def test_combined_small_limits_remain_visible():
-  cp, output = make_case()
-  info = output.actuatorsOutput.steeringLimitInfo
+  cp, output, diagnostics = make_case()
+  info = diagnostics.starpilotCarControl.steeringLimitInfo
   info.modelLimitErrorDeg = 1.5
   info.cooperativeLimitErrorDeg = 1.5
   info.combinedLimitErrorDeg = 3.0
 
-  assert detect(cp, output)
+  assert detect(cp, output, diagnostics)
 
 
 @pytest.mark.parametrize(("error", "expected"), (
@@ -73,24 +79,24 @@ def test_combined_small_limits_remain_visible():
   (NEXT_FLOAT32_AFTER_2_5, True),
 ))
 def test_diagnostic_threshold_is_strictly_greater(error, expected):
-  cp, output = make_case()
-  output.actuatorsOutput.steeringLimitInfo.modelLimitErrorDeg = error
+  cp, output, diagnostics = make_case()
+  diagnostics.starpilotCarControl.steeringLimitInfo.modelLimitErrorDeg = error
 
-  assert detect(cp, output) is expected
+  assert detect(cp, output, diagnostics) is expected
 
 
 @pytest.mark.parametrize("age_nanos", (0, MAX_DIAGNOSTIC_AGE_NANOS))
 def test_diagnostic_age_bounds_are_inclusive(age_nanos):
-  cp, output = make_case()
+  cp, output, diagnostics = make_case()
 
-  assert not detect(cp, output, now_nanos=SAMPLE_TIME_NANOS + age_nanos)
+  assert not detect(cp, output, diagnostics, now_nanos=SAMPLE_TIME_NANOS + age_nanos)
 
 
 def test_signed_cooperative_offset_is_valid_data():
-  cp, output = make_case()
-  output.actuatorsOutput.steeringLimitInfo.cooperativeOffsetDeg = -5.5
+  cp, output, diagnostics = make_case()
+  diagnostics.starpilotCarControl.steeringLimitInfo.cooperativeOffsetDeg = -5.5
 
-  assert not detect(cp, output)
+  assert not detect(cp, output, diagnostics)
 
 
 @pytest.mark.parametrize("scenario", (
@@ -104,29 +110,28 @@ def test_signed_cooperative_offset_is_valid_data():
   "cooperative_mode_disabled",
 ))
 def test_unusable_diagnostics_keep_legacy_warning(scenario):
-  cp, output = make_case()
+  cp, output, diagnostics = make_case()
   output_healthy = True
   now_nanos = FRESH_TIME_NANOS
 
   if scenario == "default_message":
-    output = car.CarOutput.new_message()
-    output.actuatorsOutput.steeringAngleDeg = OUTPUT_ANGLE
+    diagnostics = messaging.new_message("starpilotCarControl")
   elif scenario == "invalid_flag":
-    output.actuatorsOutput.steeringLimitInfo.valid = False
+    diagnostics.starpilotCarControl.steeringLimitInfo.valid = False
   elif scenario == "zero_timestamp":
-    output.actuatorsOutput.steeringLimitInfo.monoTime = 0
+    diagnostics.starpilotCarControl.steeringLimitInfo.monoTime = 0
   elif scenario == "future_timestamp":
-    output.actuatorsOutput.steeringLimitInfo.monoTime = now_nanos + 1
+    diagnostics.starpilotCarControl.steeringLimitInfo.monoTime = now_nanos + 1
   elif scenario == "stale_timestamp":
-    output.actuatorsOutput.steeringLimitInfo.monoTime = now_nanos - MAX_DIAGNOSTIC_AGE_NANOS - 1
+    diagnostics.starpilotCarControl.steeringLimitInfo.monoTime = now_nanos - MAX_DIAGNOSTIC_AGE_NANOS - 1
   elif scenario == "unhealthy_output":
     output_healthy = False
   elif scenario == "unsupported_model":
-    cp, output = make_case(CAR.TESLA_MODEL_Y)
+    cp, output, diagnostics = make_case(CAR.TESLA_MODEL_Y)
   elif scenario == "cooperative_mode_disabled":
-    cp, output = make_case(cooperative_enabled=False)
+    cp, output, diagnostics = make_case(cooperative_enabled=False)
 
-  assert detect(cp, output, output_healthy=output_healthy, now_nanos=now_nanos)
+  assert detect(cp, output, diagnostics, output_healthy=output_healthy, now_nanos=now_nanos)
 
 
 @pytest.mark.parametrize(("requested_angle", "expected"), (
@@ -134,10 +139,10 @@ def test_unusable_diagnostics_keep_legacy_warning(scenario):
   (OUTPUT_ANGLE - NEXT_FLOAT32_AFTER_2_5, True),
 ))
 def test_fallback_preserves_legacy_strict_threshold(requested_angle, expected):
-  cp, output = make_case()
-  output.actuatorsOutput.steeringLimitInfo.valid = False
+  cp, output, diagnostics = make_case()
+  diagnostics.starpilotCarControl.steeringLimitInfo.valid = False
 
-  assert detect(cp, output, requested_angle=requested_angle) is expected
+  assert detect(cp, output, diagnostics, requested_angle=requested_angle) is expected
 
 
 @pytest.mark.parametrize("field", NUMERIC_FIELDS)
@@ -147,15 +152,15 @@ def test_fallback_preserves_legacy_strict_threshold(requested_angle, expected):
   (-math.inf, OUTPUT_ANGLE, False),
 ))
 def test_nonfinite_diagnostic_values_use_legacy_fallback(field, bad_value, requested_angle, legacy_result):
-  cp, output = make_case()
-  setattr(output.actuatorsOutput.steeringLimitInfo, field, bad_value)
+  cp, output, diagnostics = make_case()
+  setattr(diagnostics.starpilotCarControl.steeringLimitInfo, field, bad_value)
 
-  assert detect(cp, output, requested_angle=requested_angle) is legacy_result
+  assert detect(cp, output, diagnostics, requested_angle=requested_angle) is legacy_result
 
 
 @pytest.mark.parametrize("field", ERROR_FIELDS)
 def test_negative_error_values_use_legacy_fallback(field):
-  cp, output = make_case()
-  setattr(output.actuatorsOutput.steeringLimitInfo, field, -0.1)
+  cp, output, diagnostics = make_case()
+  setattr(diagnostics.starpilotCarControl.steeringLimitInfo, field, -0.1)
 
-  assert detect(cp, output)
+  assert detect(cp, output, diagnostics)
diff --git a/selfdrive/controls/tests/test_steering_saturation_publish.py b/selfdrive/controls/tests/test_steering_saturation_publish.py
index 0c46e77947..0d7623483d 100644
--- a/selfdrive/controls/tests/test_steering_saturation_publish.py
+++ b/selfdrive/controls/tests/test_steering_saturation_publish.py
@@ -1,5 +1,6 @@
 from types import SimpleNamespace
 
+import cereal.messaging as messaging
 import pytest
 
 from cereal import car, custom, log
@@ -27,7 +28,7 @@ class CapturePubMaster:
 
 
 class PublishSubMaster:
-  def __init__(self, car_output, selfdrive_time_nanos, output_healthy=True):
+  def __init__(self, car_output, starpilot_car_control, selfdrive_time_nanos, output_healthy=True):
     car_state = car.CarState.new_message()
     car_state.canValid = True
 
@@ -43,6 +44,7 @@ class PublishSubMaster:
       "starpilotCarState": custom.StarPilotCarState.new_message().as_reader(),
       "selfdriveState": selfdrive_state.as_reader(),
       "carOutput": car_output.as_reader(),
+      "starpilotCarControl": starpilot_car_control.as_reader(),
       "driverAssistance": log.DriverAssistance.new_message().as_reader(),
       "driverMonitoringState": log.DriverMonitoringState.new_message().as_reader(),
     }
@@ -69,19 +71,24 @@ def make_car_params():
 def make_car_output(real_limit_error=0.0):
   output = car.CarOutput.new_message()
   output.actuatorsOutput.steeringAngleDeg = OUTPUT_ANGLE
-  info = output.actuatorsOutput.steeringLimitInfo
+  return output
+
+
+def make_starpilot_car_control(real_limit_error=0.0):
+  message = messaging.new_message("starpilotCarControl", valid=True)
+  info = message.starpilotCarControl.steeringLimitInfo
   info.valid = True
   info.monoTime = SAMPLE_TIME_NANOS
   info.cooperativeOffsetDeg = 5.5
   info.modelLimitErrorDeg = real_limit_error
   info.combinedLimitErrorDeg = real_limit_error
-  return output
+  return message
 
 
-def make_controls(car_output, selfdrive_time_nanos, output_healthy=True):
+def make_controls(car_output, starpilot_car_control, selfdrive_time_nanos, output_healthy=True):
   controls = Controls.__new__(Controls)
   controls.CP = make_car_params()
-  controls.sm = PublishSubMaster(car_output, selfdrive_time_nanos, output_healthy)
+  controls.sm = PublishSubMaster(car_output, starpilot_car_control, selfdrive_time_nanos, output_healthy)
   controls.pm = CapturePubMaster()
   controls.curvature = 0.0
   controls.calibrated_pose = None
@@ -100,7 +107,9 @@ def run_publish(monkeypatch, replay, selfdrive_time_nanos, host_time_nanos=HOST_
                 output_healthy=True, real_limit_error=0.0):
   monkeypatch.setattr(controlsd, "REPLAY", replay, raising=False)
   monkeypatch.setattr(controlsd.time, "monotonic_ns", lambda: host_time_nanos)
-  controls = make_controls(make_car_output(real_limit_error), selfdrive_time_nanos, output_healthy)
+  controls = make_controls(
+    make_car_output(real_limit_error), make_starpilot_car_control(real_limit_error), selfdrive_time_nanos, output_healthy,
+  )
   cc = car.CarControl.new_message()
   cc.enabled = True
   cc.latActive = True
diff --git a/selfdrive/selfdrived/tests/test_tesla_coop_saturation_warning.py b/selfdrive/selfdrived/tests/test_tesla_coop_saturation_warning.py
index 24f9fb268d..60785f3240 100644
--- a/selfdrive/selfdrived/tests/test_tesla_coop_saturation_warning.py
+++ b/selfdrive/selfdrived/tests/test_tesla_coop_saturation_warning.py
@@ -53,6 +53,20 @@ def make_car_control(requested_angle, lat_active=True):
   return control
 
 
+def make_starpilot_car_control(controller):
+  message = messaging.new_message("starpilotCarControl", valid=True)
+  values = controller.get_steering_limit_info()
+  info = message.starpilotCarControl.steeringLimitInfo
+  info.valid = values["valid"]
+  info.modelLimitErrorDeg = values["modelLimitErrorDeg"]
+  info.resumeLimitErrorDeg = values["resumeLimitErrorDeg"]
+  info.cooperativeLimitErrorDeg = values["cooperativeLimitErrorDeg"]
+  info.cooperativeOffsetDeg = values["cooperativeOffsetDeg"]
+  info.monoTime = values["monoTime"]
+  info.combinedLimitErrorDeg = values["combinedLimitErrorDeg"]
+  return message
+
+
 def run_controller_frame(controller, requested_angle, torque, speed, measured_angle, frame,
                          lat_active=True, steering_disengage=False):
   now_nanos = START_NANOS + frame * 10_000_000
@@ -65,7 +79,8 @@ def run_controller_frame(controller, requested_angle, torque, speed, measured_an
   event = messaging.new_message("carOutput", valid=True)
   event.carOutput.actuatorsOutput = actuators
   restored = messaging.log_from_bytes(event.to_bytes())
-  return restored.carOutput, now_nanos
+  diagnostics = messaging.log_from_bytes(make_starpilot_car_control(controller).to_bytes())
+  return restored.carOutput, diagnostics, now_nanos
 
 
 def make_lateral_car_state(speed, measured_angle):
@@ -163,13 +178,13 @@ def test_recorded_light_torque_reproduction_no_longer_reaches_warning():
   output = None
   now_nanos = 0
   for frame in range(260):
-    output, now_nanos = run_controller_frame(
+    output, diagnostics, now_nanos = run_controller_frame(
       tesla_controller, REPRO_REQUESTED_ANGLE, REPRO_TORQUE, REPRO_SPEED, REPRO_MEASURED_ANGLE, frame,
     )
     if frame >= 210:
       legacy_limited = abs(REPRO_REQUESTED_ANGLE - output.actuatorsOutput.steeringAngleDeg) > 2.5
       corrected_limited = is_angle_steering_limited(
-        CP.as_reader(), REPRO_REQUESTED_ANGLE, output, True, now_nanos,
+        CP.as_reader(), REPRO_REQUESTED_ANGLE, output, diagnostics, True, now_nanos,
       )
       baseline_log = advance_angle_counter(
         baseline_counter, CP, lateral_state, legacy_limited, REPRO_DESIRED_CURVATURE,
@@ -178,7 +193,7 @@ def test_recorded_light_torque_reproduction_no_longer_reaches_warning():
         corrected_counter, CP, lateral_state, corrected_limited, REPRO_DESIRED_CURVATURE,
       )
 
-  info = output.actuatorsOutput.steeringLimitInfo
+  info = diagnostics.starpilotCarControl.steeringLimitInfo
   errors = (info.modelLimitErrorDeg, info.resumeLimitErrorDeg,
             info.cooperativeLimitErrorDeg, info.combinedLimitErrorDeg)
   assert info.valid
@@ -213,13 +228,13 @@ def test_persistent_real_model_limiting_with_light_torque_still_warns():
   angle_log = None
   output = None
   for frame in range(60):
-    output, now_nanos = run_controller_frame(
+    output, diagnostics, now_nanos = run_controller_frame(
       tesla_controller, requested_angle, REPRO_TORQUE, speed, 0.0, frame,
     )
-    limited = is_angle_steering_limited(CP.as_reader(), requested_angle, output, True, now_nanos)
+    limited = is_angle_steering_limited(CP.as_reader(), requested_angle, output, diagnostics, True, now_nanos)
     angle_log = advance_angle_counter(angle_counter, CP, lateral_state, limited, 0.01)
 
-  info = output.actuatorsOutput.steeringLimitInfo
+  info = diagnostics.starpilotCarControl.steeringLimitInfo
   assert info.valid
   assert info.modelLimitErrorDeg > 2.5
   assert info.combinedLimitErrorDeg > 2.5
@@ -238,18 +253,18 @@ def test_default_old_output_uses_legacy_warning_path():
   output_event = messaging.new_message("carOutput", valid=True)
   output_event.carOutput.actuatorsOutput.steeringAngleDeg = REPRO_MEASURED_ANGLE
   output = messaging.log_from_bytes(output_event.to_bytes()).carOutput
+  diagnostics = messaging.log_from_bytes(messaging.new_message("starpilotCarControl").to_bytes())
   lateral_state = make_lateral_car_state(REPRO_SPEED, REPRO_MEASURED_ANGLE)
   angle_counter = LatControlAngle(CP.as_reader(), None, DT_CTRL)
 
   for frame in range(50):
     limited = is_angle_steering_limited(
-      CP.as_reader(), REPRO_REQUESTED_ANGLE, output, True, START_NANOS + frame * 10_000_000,
+      CP.as_reader(), REPRO_REQUESTED_ANGLE, output, diagnostics, True, START_NANOS + frame * 10_000_000,
     )
     angle_log = advance_angle_counter(
       angle_counter, CP, lateral_state, limited, REPRO_DESIRED_CURVATURE,
     )
 
-  assert not output.actuatorsOutput.steeringLimitInfo.valid
   assert angle_log.saturated
   selfdrived = configure_selfdrived(CP)
   events, _ = run_selfdrived_warning_path(
@@ -265,15 +280,15 @@ def test_stale_real_offset_sample_uses_legacy_warning_path():
   angle_counter = LatControlAngle(CP.as_reader(), None, DT_CTRL)
 
   for frame in range(260):
-    output, now_nanos = run_controller_frame(
+    output, diagnostics, now_nanos = run_controller_frame(
       tesla_controller, REPRO_REQUESTED_ANGLE, REPRO_TORQUE, REPRO_SPEED, REPRO_MEASURED_ANGLE, frame,
     )
 
-  assert not is_angle_steering_limited(CP.as_reader(), REPRO_REQUESTED_ANGLE, output, True, now_nanos)
-  stale_now_nanos = output.actuatorsOutput.steeringLimitInfo.monoTime + 100_000_001
+  assert not is_angle_steering_limited(CP.as_reader(), REPRO_REQUESTED_ANGLE, output, diagnostics, True, now_nanos)
+  stale_now_nanos = diagnostics.starpilotCarControl.steeringLimitInfo.monoTime + 100_000_001
   for _ in range(50):
     limited = is_angle_steering_limited(
-      CP.as_reader(), REPRO_REQUESTED_ANGLE, output, True, stale_now_nanos,
+      CP.as_reader(), REPRO_REQUESTED_ANGLE, output, diagnostics, True, stale_now_nanos,
     )
     angle_log = advance_angle_counter(
       angle_counter, CP, lateral_state, limited, REPRO_DESIRED_CURVATURE,
@@ -291,24 +306,24 @@ def test_inactive_interval_clears_diagnostics_before_reengagement():
   CP = make_params()
   tesla_controller = CarController(DBC[CAR.TESLA_MODEL_3], CP)
 
-  active, _ = run_controller_frame(tesla_controller, 0.0, REPRO_TORQUE, REPRO_SPEED, 0.0, 0)
-  inactive, _ = run_controller_frame(
+  active, active_diagnostics, _ = run_controller_frame(tesla_controller, 0.0, REPRO_TORQUE, REPRO_SPEED, 0.0, 0)
+  inactive, inactive_diagnostics, _ = run_controller_frame(
     tesla_controller, 0.0, REPRO_TORQUE, REPRO_SPEED, 0.0, 1, lat_active=False,
   )
-  resumed, resumed_now = run_controller_frame(
+  resumed, resumed_diagnostics, resumed_now = run_controller_frame(
     tesla_controller, 0.0, REPRO_TORQUE, REPRO_SPEED, 0.0, 2,
   )
-  overridden, _ = run_controller_frame(
+  overridden, overridden_diagnostics, _ = run_controller_frame(
     tesla_controller, 0.0, REPRO_TORQUE, REPRO_SPEED, 0.0, 3, steering_disengage=True,
   )
 
-  assert active.actuatorsOutput.steeringLimitInfo.valid
-  assert not inactive.actuatorsOutput.steeringLimitInfo.valid
-  assert inactive.actuatorsOutput.steeringLimitInfo.monoTime == 0
-  assert resumed.actuatorsOutput.steeringLimitInfo.valid
-  assert resumed.actuatorsOutput.steeringLimitInfo.monoTime == resumed_now
-  assert not overridden.actuatorsOutput.steeringLimitInfo.valid
-  assert overridden.actuatorsOutput.steeringLimitInfo.monoTime == 0
+  assert active_diagnostics.starpilotCarControl.steeringLimitInfo.valid
+  assert not inactive_diagnostics.starpilotCarControl.steeringLimitInfo.valid
+  assert inactive_diagnostics.starpilotCarControl.steeringLimitInfo.monoTime == 0
+  assert resumed_diagnostics.starpilotCarControl.steeringLimitInfo.valid
+  assert resumed_diagnostics.starpilotCarControl.steeringLimitInfo.monoTime == resumed_now
+  assert not overridden_diagnostics.starpilotCarControl.steeringLimitInfo.valid
+  assert overridden_diagnostics.starpilotCarControl.steeringLimitInfo.monoTime == 0
 
 
 @pytest.mark.parametrize(("fault_field", "expected_event"), (