diff --git a/openpilot/selfdrive/controls/lib/latcontrol_torque.py b/openpilot/selfdrive/controls/lib/latcontrol_torque.py
index 60eb1b9c54..2b07a370a6 100644
--- a/openpilot/selfdrive/controls/lib/latcontrol_torque.py
+++ b/openpilot/selfdrive/controls/lib/latcontrol_torque.py
@@ -12,6 +12,7 @@ from openpilot.common.filter_simple import FirstOrderFilter
 from openpilot.selfdrive.controls.lib.latcontrol import LatControl
 from openpilot.common.pid import PIDController
 from openpilot.starpilot.lateral.controller_selection import ControllerMode, default_selection, policy_for
+from openpilot.starpilot.lateral.torque_shaping import KP as STARPILOT_KP
 from openpilot.starpilot.lateral.torque_extension import apply_turn_assist, create_extension, create_turn_assist
 from openpilot.starpilot.flm import live as flm
 
@@ -62,6 +63,8 @@ class LatControlTorque(LatControl):
     self.jerk_filter = FirstOrderFilter(0.0, 1 / (2 * np.pi * LP_FILTER_CUTOFF_HZ), self.dt)
     self.turn_assist = create_turn_assist(CP, turn_assist)
     self.starpilot_extension = create_extension(self, CP, self.controller_mode, self.controller_policy, turn_assist=turn_assist)
+    if self.starpilot_extension is not None:
+      self.pid._k_p = [[0.0], [STARPILOT_KP]]
     self.flm_source = flm.GmLiveSource(CP, self.controller_mode)
     self.flm_surface = None
     from openpilot.starpilot.flm.runtime_adapter_registry import baseline_values
diff --git a/openpilot/starpilot/lateral/tests/test_effective_starpilot_gain.py b/openpilot/starpilot/lateral/tests/test_effective_starpilot_gain.py
new file mode 100644
index 0000000000..0320ef14d2
--- /dev/null
+++ b/openpilot/starpilot/lateral/tests/test_effective_starpilot_gain.py
@@ -0,0 +1,70 @@
+from types import SimpleNamespace
+
+import numpy as np
+import pytest
+
+from opendbc.car.car_helpers import interfaces
+from opendbc.car.hyundai.values import CAR
+from opendbc.car.gm.values import CAR as GM_CAR
+from opendbc.car.vehicle_model import VehicleModel
+from openpilot.cereal import log
+from openpilot.selfdrive.controls.lib.latcontrol_torque import LatControlTorque
+from openpilot.starpilot.lateral.controller_selection import ControllerMode, policy_for
+from openpilot.starpilot.lateral.gain_runtime import create_gain_owner, gain_basis
+from openpilot.starpilot.lateral.torque_settings import DOCUMENT_KEY, replace_gain, serialize_document
+
+
+def controller(car=CAR.KIA_EV6, mode=ControllerMode.STARPILOT):
+  cp = interfaces[car].get_non_essential_params(car)
+  return cp, LatControlTorque(cp.as_reader(), interfaces[car](cp), .01, controller_mode=mode)
+
+
+def test_every_starpilot_torque_profile_uses_effective_stable_gain():
+  checked = []
+  wrong = []
+  for car, interface in interfaces.items():
+    cp = interface.get_non_essential_params(car)
+    if cp.lateralTuning.which() != 'torque' or policy_for(cp) is None:
+      continue
+    before = cp.to_dict()
+    selected = LatControlTorque(cp.as_reader(), interface(cp), .01, controller_mode=ControllerMode.STARPILOT)
+    assert cp.to_dict() == before
+    checked.append(str(car))
+    for speed in (.3, 1., 2., 5., 10., 15., 30.):
+      actual = float(np.interp(speed, selected.pid._k_p[0], selected.pid._k_p[1]))
+      if actual != pytest.approx(.6):
+        wrong.append((str(car), speed, actual))
+  assert {'KIA_EV6', 'HYUNDAI_IONIQ_5', 'KIA_NIRO_EV_2ND_GEN'} <= set(checked)
+  assert not wrong, wrong
+
+
+def test_ev6_low_speed_proportional_term_matches_stable_effective_loop():
+  cp, selected = controller()
+  params = log.VehicleParameters.new_message(angleOffsetDeg=-.53, roll=.015)
+  state = SimpleNamespace(vEgo=2.3547, steeringAngleDeg=-38.1, steeringPressed=False)
+  vm = VehicleModel(cp)
+  for frame in range(100):
+    _, _, result = selected.update(frame > 5, state, vm, params, False, -.001, False, .3)
+    if result.active:
+      raw_error = result.desiredLateralAccel - result.actualLateralAccel
+      low_speed_factor = (np.interp(state.vEgo, [0., 10., 20., 30.], [12., 10.5, 8., 5.]) / state.vEgo) ** 2
+      assert result.p == pytest.approx(raw_error * (.6 + low_speed_factor), abs=1e-6)
+
+
+def test_preexisting_manual_gain_keeps_ownership_and_withdraws_to_stable(tmp_path):
+  cp, selected = controller(GM_CAR.CHEVROLET_BOLT_ACC_2022_2023)
+  basis = gain_basis(cp, selected)
+  raw = serialize_document(replace_gain({}, str(cp.carFingerprint), basis, 'custom', .7))
+  file = tmp_path / DOCUMENT_KEY
+  file.write_bytes(raw)
+  (tmp_path / "AdvancedLateralTune").write_bytes(b"1")
+  params = SimpleNamespace(get_param_path=lambda key: str(tmp_path / key))
+  owner = create_gain_owner(params, cp, selected)
+  assert owner is not None
+  assert selected.pid._k_p == [[0.], [.7]]
+  assert file.read_bytes() == raw
+  selected.pid.i = .123
+  file.unlink()
+  owner.refresh(now_ns=1_000_000_000)
+  assert selected.pid._k_p == [[0.], [.6]]
+  assert selected.pid.i == .123
diff --git a/prebuilt.json b/prebuilt.json
index a0c0a17d77..04ac3cc9b7 100644
--- a/prebuilt.json
+++ b/prebuilt.json
@@ -1 +1 @@
-{"protected_inventory_sha256": "0fbaa39f00cef954a60bf801f0a0d1981355394fbf5e4870f106bac14d219f2b", "schema_version": 1}
+{"protected_inventory_sha256": "525678c0d1155fc613717e32fcd31216bcdc0fc98c63b907e0fe5a02cb849db0", "schema_version": 1}