diff --git a/openpilot/starpilot/speed_limits/vision/model.py b/openpilot/starpilot/speed_limits/vision/model.py
index edf8e13c3d..26b27b7c4c 100644
--- a/openpilot/starpilot/speed_limits/vision/model.py
+++ b/openpilot/starpilot/speed_limits/vision/model.py
@@ -784,6 +784,26 @@ class VisionModelCore:
     best_score = 0.0
     best_retry_conflict = False
     rejected_advisory_boxes: list[tuple[int, int, int, int]] = []
+    classification_cache = {}
+    cached_bytes = 0
+
+    def classify_crop(crop):
+      nonlocal cached_bytes
+      if crop.nbytes > 1_048_576:
+        return self._classify_speed_limit_from_model(crop)
+      key = (id(getattr(self, "classifier_net", None)), self.CLASSIFIER_SHA256,
+             getattr(self, "classifier_input_size", self.CLASSIFIER_SIZE),
+             getattr(self, "classifier_logits_layer", None), getattr(self, "speed_enabled", True),
+             crop.dtype.str, crop.shape, crop.strides, crop.tobytes())
+      if key in classification_cache:
+        result, self.last_classifier_advisory_rejected, self.last_classifier_reject_dominant = classification_cache[key]
+        return result
+      result = self._classify_speed_limit_from_model(crop)
+      if cached_bytes + crop.nbytes <= 1_048_576:
+        classification_cache[key] = (result, self.last_classifier_advisory_rejected,
+                                    self.last_classifier_reject_dominant)
+        cached_bytes += crop.nbytes
+      return result
 
     for proposal_confidence, class_id, (x1, y1, x2, y2) in self._collect_detector_classifier_proposals(frame_bgr):
       if class_id == 1:
@@ -837,7 +857,7 @@ class VisionModelCore:
             continue
 
           for school_crop, crop_weight in self._iter_school_zone_read_crops(sign_crop):
-            read_result = self._classify_speed_limit_from_model(school_crop)
+            read_result = classify_crop(school_crop)
             if read_result is None:
               continue
 
@@ -908,7 +928,7 @@ class VisionModelCore:
         if face_filter is not None and face_filter.reject_once((proposal_confidence, class_id, (x1, y1, x2, y2))):
           self.latest_detector_proposal = None
           return None
-        model_read = self._classify_speed_limit_from_model(sign_crop)
+        model_read = classify_crop(sign_crop)
         if not any((expand_left, expand_top, expand_right, expand_bottom)):
           primary_reject_dominant = bool(
             not raw_is_regulatory and getattr(self, "last_classifier_reject_dominant", False)
diff --git a/openpilot/starpilot/speed_limits/vision/tests/test_classifier_reuse.py b/openpilot/starpilot/speed_limits/vision/tests/test_classifier_reuse.py
new file mode 100644
index 0000000000..d6cc6d37f0
--- /dev/null
+++ b/openpilot/starpilot/speed_limits/vision/tests/test_classifier_reuse.py
@@ -0,0 +1,159 @@
+import ast
+from collections import deque
+import dataclasses
+import inspect
+import textwrap
+import types
+import unittest
+
+import numpy as np
+
+from openpilot.starpilot.speed_limits.vision import model
+
+
+def uncached_reference():
+  tree = ast.parse(textwrap.dedent(inspect.getsource(model.VisionModelCore._detect_sign_from_detector_classifier)))
+  class Calls(ast.NodeTransformer):
+    replaced = 0
+    def visit_Call(self, node):
+      self.generic_visit(node)
+      if isinstance(node.func, ast.Name) and node.func.id == 'classify_crop':
+        node.func = ast.Attribute(value=ast.Name(id='self', ctx=ast.Load()),
+                                  attr='_classify_speed_limit_from_model', ctx=ast.Load())
+        self.replaced += 1
+      return node
+  calls = Calls()
+  tree = calls.visit(tree)
+  assert calls.replaced == 2
+  namespace = dict(vars(model))
+  exec(compile(ast.fix_missing_locations(tree), '<uncached numeric oracle>', 'exec'), namespace)
+  return namespace['_detect_sign_from_detector_classifier']
+
+
+def fixture(frame, proposals, mode='counted_reject', uncached=False, after_read=None):
+  core = model.VisionModelCore.__new__(model.VisionModelCore)
+  core.calls = []
+  core.last_classifier_forward_count = 0
+  core.latest_detector_proposal = None
+  core.history = deque()
+  core.classifier_net = object()
+  core.classifier_input_size = 128
+  core.classifier_logits_layer = None
+  core.speed_enabled = True
+  core.last_classifier_advisory_rejected = False
+  core.last_classifier_reject_dominant = False
+  core._collect_detector_classifier_proposals = lambda _: proposals
+  core._is_regulatory_speed_sign = lambda crop: mode == 'counted_reject' or bool(int(crop.sum()) % 3)
+  def reader(crop):
+    import hashlib
+    digest = hashlib.sha256(crop.tobytes()).hexdigest()
+    core.calls.append((digest, crop.shape))
+    core.last_classifier_forward_count += 1
+    value = int(digest[:8], 16)
+    core.last_classifier_advisory_rejected = bool(value % 7 == 0)
+    core.last_classifier_reject_dominant = bool(value % 5 == 0)
+    if mode == 'counted_reject':
+      core.last_classifier_advisory_rejected = core.last_classifier_reject_dominant = False
+    if after_read is not None:
+      after_read(core, len(core.calls))
+    if mode == 'school_fallback':
+      return 45, .9
+    if mode in ('reject', 'counted_reject'):
+      return None
+    if mode == 'accepted':
+      return 25, .94
+    if value % 4 == 0:
+      return None
+    return [20, 25, 35, 45][value % 4], .6 + (value % 39) / 100
+  core._classify_speed_limit_from_model = reader
+  if uncached:
+    core._detect_sign_from_detector_classifier = types.MethodType(uncached_reference(), core)
+  return core
+
+
+def result(core, frame):
+  detection = core._detect_sign_from_detector_classifier(frame)
+  assert core.last_classifier_forward_count == len(core.calls)
+  return (dataclasses.asdict(detection) if detection else None,
+          dataclasses.asdict(core.latest_detector_proposal) if core.latest_detector_proposal else None,
+          core.last_classifier_advisory_rejected, core.last_classifier_reject_dominant)
+
+
+class TestClassifierReuse(unittest.TestCase):
+  def test_school_fallback_preserves_votes_and_both_flags(self):
+    frame = np.random.default_rng(5).integers(0, 256, (200, 240, 3), dtype=np.uint8)
+    proposals = [(.9, 2, (85, 22, 160, 122))]
+    original = fixture(frame, proposals, 'school_fallback', uncached=True)
+    reused = fixture(frame, proposals, 'school_fallback')
+    self.assertEqual(result(original, frame), result(reused, frame))
+    self.assertEqual((len(original.calls), len(reused.calls)), (11, 10))
+    self.assertEqual(original.calls[0], original.calls[-1])
+
+  def test_none_and_flags_reused_without_counting_a_new_read(self):
+    frame = np.random.default_rng(6).integers(0, 256, (200, 240, 3), dtype=np.uint8)
+    proposals = [(.9, 0, (85, 22, 160, 122)), (.8, 0, (85, 22, 160, 122))]
+    original = fixture(frame, proposals, uncached=True)
+    reused = fixture(frame, proposals)
+    self.assertEqual(result(original, frame), result(reused, frame))
+    self.assertEqual((len(original.calls), len(reused.calls)), (6, 3))
+    reused.reset()
+    result(reused, frame)
+    self.assertEqual(len(reused.calls), 6)
+
+  def test_failure_does_not_leave_cross_invocation_cache(self):
+    frame = np.zeros((200, 240, 3), np.uint8)
+    def fail_second(_, count):
+      if count == 2:
+        raise ValueError('reader failure')
+    core = fixture(frame, [(.9, 0, (85, 22, 160, 122))], after_read=fail_second)
+    with self.assertRaisesRegex(ValueError, 'reader failure'):
+      result(core, frame)
+    self.assertEqual(len(core.calls), 2)
+    result(core, frame)
+    self.assertEqual(len(core.calls), 5)
+
+  def test_model_request_and_mode_changes_invalidate_reuse(self):
+    frame = np.random.default_rng(8).integers(0, 256, (200, 240, 3), dtype=np.uint8)
+    proposals = [(.9, 0, (85, 22, 160, 122)), (.8, 0, (85, 22, 160, 122))]
+    changes = {'classifier_net': object(), 'classifier_input_size': 129,
+               'classifier_logits_layer': 'different request', 'speed_enabled': False,
+               'CLASSIFIER_SHA256': '0' * 64}
+    for key, value in changes.items():
+      with self.subTest(key=key):
+        def change(core, count):
+          if count == 3:
+            setattr(core, key, value)
+        core = fixture(frame, proposals, after_read=change)
+        result(core, frame)
+        self.assertEqual(len(core.calls), 6)
+
+  def test_same_view_with_changed_pixels_is_not_reused(self):
+    frame = np.random.default_rng(9).integers(0, 256, (200, 240, 3), dtype=np.uint8)
+    proposals = [(.9, 0, (85, 22, 160, 122)), (.8, 0, (85, 22, 160, 122))]
+    def change(_, count):
+      if count == 3:
+        frame[:] ^= 255
+    core = fixture(frame, proposals, after_read=change)
+    result(core, frame)
+    self.assertEqual(len(core.calls), 6)
+
+  def test_memory_budget_falls_back_without_dropping_decisions(self):
+    frame = np.zeros((1000, 1000, 3), np.uint8)
+    proposals = [(.9, 0, (500, 100, 850, 450)), (.8, 0, (500, 100, 850, 450))]
+    original = fixture(frame, proposals, uncached=True)
+    reused = fixture(frame, proposals)
+    self.assertEqual(result(original, frame), result(reused, frame))
+    self.assertEqual(len(original.calls), 6)
+    self.assertGreater(len(reused.calls), 3)
+    self.assertLessEqual(len(reused.calls), 6)
+
+  def test_oversize_crops_use_original_reader(self):
+    frame = np.zeros((1600, 1600, 3), np.uint8)
+    proposals = [(.9, 0, (600, 100, 1400, 900)), (.8, 0, (600, 100, 1400, 900))]
+    core = fixture(frame, proposals)
+    result(core, frame)
+    self.assertEqual(len(core.calls), 6)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/prebuilt.json b/prebuilt.json
index a2c9411086..3e43f958e2 100644
--- a/prebuilt.json
+++ b/prebuilt.json
@@ -1 +1 @@
-{"protected_inventory_sha256": "c48237da6a4ac8e70dbfcdecc8d3683fbae6b69e5543254105f5d34307f3bd5b", "schema_version": 1}
+{"protected_inventory_sha256": "634cdb0998641b505e1f24b4fb715965c778b355de58ecfb7cf292b5616941e2", "schema_version": 1}