diff --git a/openpilot/starpilot/aol/tests/test_vehicle_policy_cache.py b/openpilot/starpilot/aol/tests/test_vehicle_policy_cache.py
new file mode 100644
index 0000000000..3912ee2285
--- /dev/null
+++ b/openpilot/starpilot/aol/tests/test_vehicle_policy_cache.py
@@ -0,0 +1,232 @@
+"""Exact CarParams snapshots may cache policy; live authority remains current."""
+
+from dataclasses import FrozenInstanceError
+from types import SimpleNamespace
+from unittest.mock import Mock, patch
+import warnings
+
+import pytest
+from capnp import KjException
+
+from opendbc.car import gen_empty_fingerprint, structs
+from opendbc.car.car_helpers import interfaces
+from opendbc.car.ford.values import CAR as FORD
+from opendbc.car.gm.values import CAR as GM
+from opendbc.car.honda.values import CAR as HONDA
+from opendbc.car.hyundai.values import CAR as HYUNDAI
+from opendbc.car.mazda.values import CAR as MAZDA
+from opendbc.car.tesla.fingerprints import FINGERPRINTS as TESLA_FINGERPRINTS
+from opendbc.car.tesla.values import CAR as TESLA
+from opendbc.car.toyota.values import CAR as TOYOTA
+from openpilot.starpilot.aol import vehicle
+
+
+@pytest.fixture(autouse=True)
+def clear_policy_cache():
+  vehicle._policy_for_bytes.cache_clear()
+  yield
+  vehicle._policy_for_bytes.cache_clear()
+
+
+def profile(brand):
+  """Factory inputs from each port's existing positive admission fixtures."""
+  models = {'honda': HONDA.HONDA_CIVIC_BOSCH, 'hyundai': HYUNDAI.HYUNDAI_SONATA,
+            'gm': GM.CHEVROLET_BOLT_CC_2018_2021, 'ford': FORD.FORD_ESCAPE_MK4,
+            'mazda': MAZDA.MAZDA_CX5_2022, 'tesla': TESLA.TESLA_MODEL_S_PREAP,
+            'toyota': TOYOTA.TOYOTA_COROLLA_TSS2}
+  fp = gen_empty_fingerprint()
+  if brand == 'gm':
+    fp[0][0x201] = 6
+    fp[2].update({0x320: 8, 0x180: 4})
+  elif brand == 'ford':
+    fp[0][0x5A] = 8
+    fp[2].update({0x3D6: 8, 0x186: 8})
+  elif brand == 'tesla':
+    fp[0] = dict(TESLA_FINGERPRINTS[models[brand]][0])
+  return interfaces[models[brand]].get_params(models[brand], fp, [], brand == 'honda', False, False)
+
+
+def assert_equivalent(cp):
+  expected = vehicle._policy_for_uncached(cp)
+  assert vehicle.policy_for(cp) == expected
+  assert vehicle.policy_for(cp.as_reader()) == expected
+  return expected
+
+
+@pytest.mark.parametrize('brand', ('honda', 'hyundai', 'gm', 'ford', 'mazda', 'tesla', 'toyota'))
+def test_actual_port_profile_and_startup_marking_match(brand):
+  cp = profile(brand)
+  initial = assert_equivalent(cp)
+  assert initial.intent_supported, brand
+  cp.safetyConfigs[-1].safetyParam |= initial.safety_param_addition
+  cp.alternativeExperience |= initial.alternative_experience_addition
+  marked = assert_equivalent(cp)
+  assert marked.intent_supported and marked.runtime_supported
+  assert vehicle.native_matches_cp(cp, int(cp.safetyConfigs[-1].safetyModel.raw), cp.safetyConfigs[-1].safetyParam)
+
+
+@pytest.mark.parametrize('control', ('torque', 'pid', 'angle'))
+def test_controller_variants_match(control):
+  cp = profile('toyota')
+  cp.steerControlType = 'angle' if control == 'angle' else 'torque'
+  cp.lateralTuning.init('pid' if control == 'pid' else 'torque')
+  assert_equivalent(cp)
+
+
+@pytest.mark.parametrize('field', ('brand', 'carFingerprint', 'flags', 'passive', 'notCar', 'dashcamOnly',
+                                  'pcmCruise', 'openpilotLongitudinalControl', 'alternativeExperience',
+                                  'safetyParam', 'safetyModel', 'safetyConfigs', 'lateralTuning', 'carVin'))
+def test_mutable_builder_and_alias_reader_never_reuse_a_prior_snapshot(field):
+  cp = profile('toyota')
+  alias = cp.as_reader()
+  accepted = vehicle.policy_for(cp)
+  assert accepted.intent_supported
+  before_key = vehicle._car_params_bytes(cp)
+  before = vehicle._policy_for_bytes.cache_info()
+  if field == 'safetyParam':
+    cp.safetyConfigs[0].safetyParam ^= 1
+  elif field == 'safetyModel':
+    cp.safetyConfigs[0].safetyModel = 'noOutput'
+  elif field == 'safetyConfigs':
+    cp.safetyConfigs = []
+  elif field == 'lateralTuning':
+    cp.lateralTuning.init('pid')
+  elif field in ('passive', 'notCar', 'dashcamOnly', 'pcmCruise', 'openpilotLongitudinalControl'):
+    setattr(cp, field, not getattr(cp, field))
+  else:
+    setattr(cp, field, {'brand': 'unregistered', 'carFingerprint': 'unregistered', 'flags': int(cp.flags) ^ 1,
+                        'alternativeExperience': 1, 'carVin': 'CACHE-MUTATION'}[field])
+  assert vehicle._car_params_bytes(cp) != before_key
+  expected = vehicle._policy_for_uncached(cp)
+  assert vehicle.policy_for(cp) == vehicle.policy_for(alias) == expected
+  after = vehicle._policy_for_bytes.cache_info()
+  assert after.misses == before.misses + 1
+  assert after.hits == before.hits + 1
+  if field in ('brand', 'carFingerprint', 'passive', 'notCar', 'dashcamOnly', 'safetyModel', 'safetyConfigs'):
+    assert not expected.intent_supported
+
+
+def test_duck_types_and_schema_spoofs_bypass_serialization_untouched(monkeypatch):
+  sentinel = vehicle.AolVehiclePolicy(settings_supported=True)
+  owner = SimpleNamespace(policy_for=Mock(return_value=sentinel))
+  monkeypatch.setitem(vehicle._PORTS, 'cache-test', owner)
+  for schema in (None, structs.CarParams.schema):
+    cp = SimpleNamespace(brand='cache-test', schema=schema, to_bytes=Mock(side_effect=AssertionError),
+                         copy=Mock(side_effect=AssertionError), as_builder=Mock(side_effect=AssertionError))
+    assert vehicle._car_params_bytes(cp) is None
+    assert vehicle.policy_for(cp) is sentinel
+    owner.policy_for.assert_called_with(cp)
+    cp.to_bytes.assert_not_called()
+    cp.copy.assert_not_called()
+    cp.as_builder.assert_not_called()
+
+  class HostileMeta(type):
+    def __eq__(cls, other):
+      raise AssertionError('Unknown type equality must not run')
+
+  class Unknown(metaclass=HostileMeta):
+    brand = 'cache-test'
+
+    @property
+    def schema(self):
+      raise AssertionError('Unknown schema must not be read')
+
+  assert vehicle._car_params_bytes(Unknown()) is None
+  assert vehicle.policy_for(Unknown()) is sentinel
+  assert vehicle._policy_for_bytes.cache_info().misses == 0
+
+
+def outcome(call, cp):
+  try:
+    return ('result', call(cp))
+  except Exception as exc:
+    return ('exception', type(exc), str(exc))
+
+
+def test_malformed_wrong_schema_and_original_exceptions_are_preserved(monkeypatch):
+  wrong = structs.CarState(canValid=True)
+  for cp in (None, b'not a CarParams message', object(), SimpleNamespace(brand=[]), wrong, wrong.as_reader()):
+    assert vehicle._car_params_bytes(cp) is None
+    assert outcome(vehicle.policy_for, cp) == outcome(vehicle._policy_for_uncached, cp)
+  owner = SimpleNamespace(policy_for=Mock(side_effect=RuntimeError('original dispatcher exception')))
+  monkeypatch.setitem(vehicle._PORTS, 'cache-test', owner)
+  cp = SimpleNamespace(brand='cache-test')
+  assert outcome(vehicle.policy_for, cp) == outcome(vehicle._policy_for_uncached, cp)
+  with pytest.raises((ValueError, KjException)):
+    vehicle._policy_for_bytes(b'not a CarParams message')
+
+
+def test_serialization_and_decode_failure_fall_back_to_original_builder(monkeypatch):
+  cp = profile('toyota')
+  expected = vehicle._policy_for_uncached(cp)
+
+  class BrokenSchema:
+    @property
+    def schema(self):
+      raise RuntimeError('schema unavailable')
+
+  with monkeypatch.context() as broken:
+    broken.setattr(vehicle, 'CarParams', BrokenSchema())
+    assert vehicle._car_params_bytes(cp) is None
+    assert vehicle.policy_for(cp) == expected
+  decoder = SimpleNamespace(schema=structs.CarParams.schema, from_bytes=Mock(side_effect=RuntimeError('decode unavailable')))
+  monkeypatch.setattr(vehicle, 'CarParams', decoder)
+  with patch.object(vehicle, '_policy_for_uncached', wraps=vehicle._policy_for_uncached) as uncached:
+    assert vehicle.policy_for(cp) == expected
+    uncached.assert_called_once_with(cp)
+  decoder.from_bytes.assert_called_once()
+
+
+def test_original_builder_write_state_and_repeat_warning_are_unchanged():
+  cp = profile('toyota')
+  with warnings.catch_warnings(record=True) as caught:
+    warnings.simplefilter('always')
+    for _ in range(4):
+      assert_equivalent(cp)
+    assert not caught
+    cp.to_bytes()
+    assert not caught
+    cp.to_bytes()
+    assert any('already been written' in str(item.message) for item in caught)
+
+
+def test_lru_bound_oversize_bypass_and_frozen_result():
+  cp = profile('toyota')
+  for index in range(9):
+    cp.carVin = str(index)
+    assert_equivalent(cp)
+  info = vehicle._policy_for_bytes.cache_info()
+  assert info.maxsize == info.currsize == 8
+  cp.carVin = '0'
+  vehicle.policy_for(cp)
+  assert vehicle._policy_for_bytes.cache_info().misses == info.misses + 1
+  cp.carVin = 'v' * (64 * 1024)
+  before = vehicle._policy_for_bytes.cache_info()
+  assert vehicle._car_params_bytes(cp) is None
+  result = vehicle.policy_for(cp)
+  assert result == vehicle._policy_for_uncached(cp)
+  assert vehicle._policy_for_bytes.cache_info() == before
+  with pytest.raises(FrozenInstanceError):
+    result.__setattr__('intent_supported', False)
+
+
+def test_warm_policy_does_not_cache_current_state_or_native_permission():
+  cp = profile('mazda')
+  cp.alternativeExperience = 32
+  assert vehicle.policy_for(cp).ordinary_axis_ack_required
+  assert vehicle.policy_for(cp).intent_supported
+  cs = structs.CarState(canValid=True, canTimeout=False, gearShifter='drive', vEgo=20)
+  native = SimpleNamespace(safetyModel=int(cp.safetyConfigs[0].safetyModel.raw),
+                           safetyParam=cp.safetyConfigs[0].safetyParam, requestedLateral=True, lateralAllowed=True)
+  assert vehicle.ordinary_axis_request_allowed(cp, cs)
+  assert not vehicle.native_latch_rejected(cp, native, state=cs)
+  native.lateralAllowed = False
+  assert vehicle.native_latch_rejected(cp, native, state=cs)
+  cs.canValid = False
+  assert not vehicle.ordinary_axis_request_allowed(cp, cs)
+  cs.canValid, cs.steerFaultPermanent = True, True
+  assert not vehicle.ordinary_axis_request_allowed(cp, cs)
+  cs.steerFaultPermanent, cs.steerFaultTemporary = False, True
+  assert not vehicle.native_latch_rejected(cp, native, state=cs)
+  native.safetyParam ^= 1
+  assert not vehicle.native_matches_cp(cp, native.safetyModel, native.safetyParam)
diff --git a/openpilot/starpilot/aol/vehicle.py b/openpilot/starpilot/aol/vehicle.py
index 093c775ff0..b23708f3a5 100644
--- a/openpilot/starpilot/aol/vehicle.py
+++ b/openpilot/starpilot/aol/vehicle.py
@@ -1,5 +1,10 @@
 """Fail-closed dispatch to vehicle-owned AOL capabilities."""
 
+from functools import lru_cache
+
+from capnp.lib.capnp import _DynamicStructBuilder, _DynamicStructReader
+from opendbc.car.structs import CarParams
+
 from openpilot.starpilot.aol.policy import AolVehiclePolicy
 from openpilot.starpilot.aol.intent import AolCardIntent
 from openpilot.starpilot.car.honda import aol as honda
@@ -11,9 +16,11 @@ from openpilot.starpilot.car.tesla import aol as tesla
 from openpilot.starpilot.car.toyota import aol as toyota
 
 _PORTS = {'honda': honda, 'hyundai': hyundai, 'gm': gm, 'ford': ford, 'mazda': mazda, 'tesla': tesla, 'toyota': toyota}
+_POLICY_CACHE_SIZE = 8
+_POLICY_CACHE_MAX_BYTES = 64 * 1024
 
 
-def policy_for(CP) -> AolVehiclePolicy:
+def _policy_for_uncached(CP) -> AolVehiclePolicy:
   try:
     port = _PORTS.get(CP.brand)
     return port.policy_for(CP) if port is not None else AolVehiclePolicy()
@@ -21,6 +28,44 @@ def policy_for(CP) -> AolVehiclePolicy:
     return AolVehiclePolicy()
 
 
+def _car_params_bytes(CP) -> bytes | None:
+  # Unknown ducktypes keep the original dispatch behavior without serialization.
+  cp_type = type(CP)
+  if cp_type is not _DynamicStructBuilder and cp_type is not _DynamicStructReader:
+    return None
+  try:
+    if CP.schema != CarParams.schema:
+      return None
+    # Never serialize the original builder: to_bytes changes its write state.
+    snapshot = CP.copy() if cp_type is _DynamicStructBuilder else CP.as_builder()
+    if type(snapshot) is not _DynamicStructBuilder:
+      return None
+    key = snapshot.to_bytes()
+    return key if len(key) <= _POLICY_CACHE_MAX_BYTES else None
+  except Exception:
+    return None
+
+
+@lru_cache(maxsize=_POLICY_CACHE_SIZE)
+def _policy_for_bytes(key: bytes) -> AolVehiclePolicy:
+  # Evaluate the same immutable bytes as the key, never a mutable caller alias.
+  with CarParams.from_bytes(key) as CP:
+    if type(CP) is not _DynamicStructReader or CP.schema != CarParams.schema:
+      raise TypeError('Unsupported CarParams snapshot')
+    return _policy_for_uncached(CP)
+
+
+def policy_for(CP) -> AolVehiclePolicy:
+  key = _car_params_bytes(CP)
+  if key is not None:
+    try:
+      # Only the frozen static policy is reused. Live authority stays uncached.
+      return _policy_for_bytes(key)
+    except Exception:
+      pass
+  return _policy_for_uncached(CP)
+
+
 def native_profile_supported(model: int, param: int) -> bool:
   return any(port.native_profile_supported(model, param) for port in _PORTS.values())
 
diff --git a/prebuilt.json b/prebuilt.json
index c0dd89ddab..cbd114bc53 100644
--- a/prebuilt.json
+++ b/prebuilt.json
@@ -1,4 +1 @@
-{
-  "schema_version": 1,
-  "protected_inventory_sha256": "b567c57ef61d9e04942364f375a09b1465d1ce6dc5fe3e128782d2a7da622071"
-}
+{"protected_inventory_sha256": "ec474989597c90246eef09acaacab24b8bbf68c04b1271dbac521e005b84082a", "schema_version": 1}