diff --git a/openpilot/common/params_keys.h b/openpilot/common/params_keys.h
index 111099fce9..4d8ffb64eb 100644
--- a/openpilot/common/params_keys.h
+++ b/openpilot/common/params_keys.h
@@ -195,11 +195,10 @@ inline static std::unordered_map<std::string, ParamKeyAttributes> keys = {
 
     // Model Manager params
     {"ModelManager_ActiveBundle", {PERSISTENT, JSON}},
-    {"ModelManager_ActiveJson", {CLEAR_ON_MANAGER_START, STRING}},
-    {"ModelManager_PrevBundle", {PERSISTENT, JSON}},
-    {"ModelManager_PrevBundle_USBGPU", {PERSISTENT, JSON}},
+    {"ModelManager_ActiveBundleUSBGPU", {PERSISTENT, JSON}},
+    {"ModelManager_ActiveJson", {CLEAR_ON_MANAGER_START, JSON}},
     {"ModelManager_ClearCache", {CLEAR_ON_MANAGER_START, BOOL}},
-    {"ModelManager_DownloadIndex", {CLEAR_ON_MANAGER_START | CLEAR_ON_ONROAD_TRANSITION, INT}},
+    {"ModelManager_DownloadRef", {CLEAR_ON_MANAGER_START | CLEAR_ON_ONROAD_TRANSITION, STRING}},
     {"ModelManager_Favs", {PERSISTENT | BACKUP, STRING}},
     {"ModelManager_LastSyncTime", {CLEAR_ON_MANAGER_START | CLEAR_ON_OFFROAD_TRANSITION, INT, "0"}},
     {"ModelManager_LastSyncTime_USBGPU", {CLEAR_ON_MANAGER_START | CLEAR_ON_OFFROAD_TRANSITION, INT, "0"}},
diff --git a/openpilot/selfdrive/ui/layouts/sidebar.py b/openpilot/selfdrive/ui/layouts/sidebar.py
index f950edaa46..5429a35851 100644
--- a/openpilot/selfdrive/ui/layouts/sidebar.py
+++ b/openpilot/selfdrive/ui/layouts/sidebar.py
@@ -168,9 +168,16 @@ class Sidebar(Widget, SidebarSP):
     # Home/Flag button
     flag_pressed = mouse_down and rl.check_collision_point_rec(mouse_pos, HOME_BTN)
     button_img = self._flag_img if ui_state.started else self._home_img
+    button_pos = rl.Vector2(HOME_BTN.x, HOME_BTN.y)
+    icon_opacity = 1.0
+
+    if gui_app.sunnypilot_ui():
+      button_img, button_pos, icon_opacity = SidebarSP._get_home_icon(self, button_img)
 
     tint = Colors.BUTTON_PRESSED if (ui_state.started and flag_pressed) else Colors.BUTTON_NORMAL
-    rl.draw_texture_ex(button_img, rl.Vector2(HOME_BTN.x, HOME_BTN.y), 0.0, 1.0, tint)
+    if icon_opacity < 1.0:
+      tint = rl.Color(tint[0], tint[1], tint[2], int(255 * icon_opacity))
+    rl.draw_texture_ex(button_img, button_pos, 0.0, 1.0, tint)
 
     # Microphone button
     if self._recording_audio:
diff --git a/openpilot/selfdrive/ui/mici/layouts/home.py b/openpilot/selfdrive/ui/mici/layouts/home.py
index ff8d350e08..fd74979404 100644
--- a/openpilot/selfdrive/ui/mici/layouts/home.py
+++ b/openpilot/selfdrive/ui/mici/layouts/home.py
@@ -248,8 +248,11 @@ class MiciHomeLayout(Widget):
 
     # ***** Center-aligned bottom section icons *****
     self._experimental_icon.set_visible(ui_state.experimental_mode)
-    self._egpu_icon.set_visible(ui_state.sm["deviceState"].chestnutPresent and ui_state.usbgpu_compiled)
-    self._egpu_icon_gray.set_visible(ui_state.sm["deviceState"].chestnutPresent and not ui_state.usbgpu_compiled)
+    if gui_app.sunnypilot_ui():
+      self._set_egpu_visibility()
+    else:
+      self._egpu_icon.set_visible(ui_state.sm["deviceState"].chestnutPresent and ui_state.usbgpu_compiled)
+      self._egpu_icon_gray.set_visible(ui_state.sm["deviceState"].chestnutPresent and not ui_state.usbgpu_compiled)
     self._mic_icon.set_visible(ui_state.recording_audio)
     self._body_icon.set_visible(bool(ui_state.is_body))
 
diff --git a/openpilot/selfdrive/ui/sunnypilot/layouts/settings/models.py b/openpilot/selfdrive/ui/sunnypilot/layouts/settings/models.py
index e4a6bea6e0..93668014f6 100644
--- a/openpilot/selfdrive/ui/sunnypilot/layouts/settings/models.py
+++ b/openpilot/selfdrive/ui/sunnypilot/layouts/settings/models.py
@@ -11,6 +11,8 @@ import pyray as rl
 
 from openpilot.cereal import custom
 from openpilot.sunnypilot.models.default_model import get_default_model
+from openpilot.sunnypilot.models.fetcher import ModelFetcher
+from openpilot.sunnypilot.models.helpers import ACTIVE_BUNDLE_KEYS
 from openpilot.common.constants import CV
 from openpilot.selfdrive.ui.ui_state import device, ui_state
 from openpilot.system.ui.lib.multilang import tr
@@ -68,7 +70,7 @@ class ModelsLayout(Widget):
       callback=self._clear_cache
     )
 
-    self.cancel_download_item = button_item(tr("Cancel Download"), tr("Cancel"), "", lambda: ui_state.params.remove("ModelManager_DownloadIndex"))
+    self.cancel_download_item = button_item(tr("Cancel Download"), tr("Cancel"), "", lambda: ui_state.params.remove("ModelManager_DownloadRef"))
 
     self.lane_turn_value_control = option_item_sp(tr("Adjust Lane Turn Speed"), "LaneTurnValue", 500, 2000,
                                                   tr("Set the maximum speed for lane turn desires. Default is 19 mph."),
@@ -146,7 +148,7 @@ class ModelsLayout(Widget):
     if not bundle:
       return
 
-    self.cancel_download_item.set_visible(bool(self.model_manager.selectedBundle) and ui_state.params.get("ModelManager_DownloadIndex") is not None)
+    self.cancel_download_item.set_visible(bool(self.model_manager.selectedBundle) and ui_state.params.get("ModelManager_DownloadRef") is not None)
 
     if (current_time := time.monotonic()) - self.last_cache_calc_time > 0.5:
       self.last_cache_calc_time = current_time
@@ -187,9 +189,10 @@ class ModelsLayout(Widget):
       return
     selected_ref = self.model_dialog.selection_ref
     if selected_ref == "Default":
-      ui_state.params.remove("ModelManager_ActiveBundle")
+      source = ModelFetcher.active_source(ui_state.sm["deviceState"].chestnutPresent)
+      ui_state.params.remove(ACTIVE_BUNDLE_KEYS[source])
     elif selected_bundle := next((bundle for bundle in self.model_manager.availableBundles if bundle.ref == selected_ref), None):
-      ui_state.params.put("ModelManager_DownloadIndex", selected_bundle.index)
+      ui_state.params.put("ModelManager_DownloadRef", selected_bundle.ref)
     self.model_dialog = None
 
   @staticmethod
@@ -227,7 +230,7 @@ class ModelsLayout(Widget):
     advanced_controls: bool = ui_state.params.get_bool("ShowAdvancedControls")
     turn_desire: bool = ui_state.params.get_bool("LaneTurnDesire")
     live_delay: bool = ui_state.params.get_bool("LagdToggle")
-    camera_offset: bool = ui_state.params.get("ModelManager_ActiveBundle") is not None
+    camera_offset: bool = ui_state.active_bundle is not None
 
     self.lane_turn_desire_toggle.action_item.set_state(turn_desire)
     self.lane_turn_value_control.set_visible(turn_desire and advanced_controls)
@@ -241,8 +244,9 @@ class ModelsLayout(Widget):
     self._update_lagd_description(live_delay)
     self.model_manager = ui_state.sm["modelManagerSP"]
     self._handle_bundle_download_progress()
-    default_label = f"{get_default_model()} (Default)"
-    active_name = self.model_manager.activeBundle.displayName if self.model_manager and self.model_manager.activeBundle.ref else default_label
+    # read the slot through ui_state, not modelManagerSP: the manager republishes a
+    # tick after a chestnut change, and the stale bundle flashes the wrong model
+    active_name = (ui_state.active_bundle or {}).get("displayName") or f"{get_default_model()} (Default)"
     self.current_model_item.action_item.set_value(active_name)
 
     if not ui_state.is_offroad():
diff --git a/openpilot/selfdrive/ui/sunnypilot/layouts/sidebar.py b/openpilot/selfdrive/ui/sunnypilot/layouts/sidebar.py
index 79bb15dbb8..7c74c48469 100644
--- a/openpilot/selfdrive/ui/sunnypilot/layouts/sidebar.py
+++ b/openpilot/selfdrive/ui/sunnypilot/layouts/sidebar.py
@@ -4,11 +4,14 @@ Copyright (c) 2021-, Haibin Wen, sunnypilot, and a number of other contributors.
 This file is part of sunnypilot and is licensed under the MIT License.
 See the LICENSE.md file in the root directory for more details.
 """
+import math
+
 import pyray as rl
 import time
 from dataclasses import dataclass
 from openpilot.selfdrive.ui.ui_state import ui_state
 from openpilot.sunnypilot.sunnylink.api import UNREGISTERED_SUNNYLINK_DONGLE_ID
+from openpilot.system.ui.lib.application import gui_app
 from openpilot.system.ui.lib.multilang import tr_noop
 
 
@@ -18,6 +21,9 @@ METRIC_MARGIN = 30
 METRIC_START_Y = 300
 HOME_BTN = rl.Rectangle(60, 860, 180, 180)
 
+EGPU_ICON_WIDTH = 180
+EGPU_ICON_HEIGHT = 133
+
 
 # Color scheme
 class Colors:
@@ -53,6 +59,10 @@ class MetricData:
 class SidebarSP:
   def __init__(self):
     self._sunnylink_status = MetricData(tr_noop("SUNNYLINK"), tr_noop("OFFLINE"), Colors.WARNING)
+    self._egpu_green_img = gui_app.texture("icons_mici/egpu_green.png", EGPU_ICON_WIDTH, EGPU_ICON_HEIGHT)
+    self._egpu_default_img = gui_app.texture("icons_mici/egpu.png", EGPU_ICON_WIDTH, EGPU_ICON_HEIGHT)
+    self._egpu_orange_img = gui_app.texture("icons_mici/egpu_orange.png", EGPU_ICON_WIDTH, EGPU_ICON_HEIGHT)
+    self._egpu_gray_img = gui_app.texture("icons_mici/egpu_gray.png", EGPU_ICON_WIDTH, EGPU_ICON_HEIGHT)
 
   def _update_sunnylink_status(self):
     if not ui_state.params.get_bool("SunnylinkEnabled"):
@@ -78,6 +88,29 @@ class SidebarSP:
 
     self._sunnylink_status.update(tr_noop("SUNNYLINK"), status, color)
 
+  def _get_home_icon(self, default_img: rl.Texture) -> tuple[rl.Texture, rl.Vector2, float]:
+    default_pos = rl.Vector2(HOME_BTN.x, HOME_BTN.y)
+    if not ui_state.sm["deviceState"].chestnutPresent:
+      return default_img, default_pos, 1.0
+
+    big_model_selected = ui_state.usbgpu_compiled or ui_state.model_runner_tinygrad
+    big_model_failed = ui_state.started and ui_state.big_model_failed
+    loading = ui_state.usbgpu_loading or (big_model_selected and ui_state.started and ui_state.usbgpu_active is None)
+
+    if loading:
+      icon = self._egpu_default_img
+      opacity = 0.35 + 0.65 * (0.5 - 0.5 * math.cos(rl.get_time() * 6.0))
+    elif big_model_selected and big_model_failed:
+      icon, opacity = self._egpu_orange_img, 1.0
+    elif big_model_selected:
+      icon, opacity = self._egpu_green_img, 1.0
+    else:
+      icon, opacity = self._egpu_gray_img, 1.0
+
+    x = HOME_BTN.x + (HOME_BTN.width - icon.width) / 2
+    y = HOME_BTN.y + (HOME_BTN.height - icon.height) / 2
+    return icon, rl.Vector2(x, y), opacity
+
   def _draw_metrics_w_sunnylink(self, rect: rl.Rectangle, _temp, _panda, _connect):
     metrics = [_temp, _panda, _connect, self._sunnylink_status]
     start_y = int(rect.y) + METRIC_START_Y
diff --git a/openpilot/selfdrive/ui/sunnypilot/mici/layouts/home.py b/openpilot/selfdrive/ui/sunnypilot/mici/layouts/home.py
index d29e579c52..b261373947 100644
--- a/openpilot/selfdrive/ui/sunnypilot/mici/layouts/home.py
+++ b/openpilot/selfdrive/ui/sunnypilot/mici/layouts/home.py
@@ -4,8 +4,14 @@ Copyright (c) 2021-, Haibin Wen, sunnypilot, and a number of other contributors.
 This file is part of sunnypilot and is licensed under the MIT License.
 See the LICENSE.md file in the root directory for more details.
 """
+import math
+
+import pyray as rl
+
 from openpilot.selfdrive.ui.mici.layouts.home import MiciHomeLayout
+from openpilot.selfdrive.ui.ui_state import ui_state
 from openpilot.system.ui.lib.application import FontWeight
+from openpilot.system.ui.widgets.icon_widget import IconWidget
 from openpilot.system.ui.widgets.label import UnifiedLabel
 
 
@@ -13,3 +19,35 @@ class MiciHomeLayoutSP(MiciHomeLayout):
   def __init__(self):
     super().__init__()
     self._openpilot_label = UnifiedLabel("sunnypilot", font_size=88, font_weight=FontWeight.AUDIOWIDE, max_width=480, wrap_text=False)
+    self._egpu_icon_default = IconWidget("icons_mici/egpu.png", (50, 37))
+    self._egpu_icon_default.set_visible(False)
+    self._egpu_icon_orange = IconWidget("icons_mici/egpu_orange.png", (50, 37))
+    self._egpu_icon_orange.set_visible(False)
+    gray_idx = self._status_bar_layout.widgets.index(self._egpu_icon_gray)
+    self._status_bar_layout.widgets.insert(gray_idx + 1, self._egpu_icon_default)
+    self._status_bar_layout.widgets.insert(gray_idx + 2, self._egpu_icon_orange)
+
+  def _set_egpu_visibility(self):
+    chestnut = ui_state.sm["deviceState"].chestnutPresent
+    if not chestnut:
+      self._egpu_icon.set_visible(False)
+      self._egpu_icon_default.set_visible(False)
+      self._egpu_icon_orange.set_visible(False)
+      self._egpu_icon_gray.set_visible(False)
+      return
+
+    big_model_selected = ui_state.usbgpu_compiled or ui_state.model_runner_tinygrad
+    big_model_failed = ui_state.started and ui_state.big_model_failed
+    loading = ui_state.usbgpu_loading or (big_model_selected and ui_state.started and ui_state.usbgpu_active is None)
+
+    if loading:
+      self._egpu_icon_default._opacity = 0.35 + 0.65 * (0.5 - 0.5 * math.cos(rl.get_time() * 6.0))
+      self._egpu_icon_default.set_visible(True)
+      self._egpu_icon.set_visible(False)
+      self._egpu_icon_orange.set_visible(False)
+      self._egpu_icon_gray.set_visible(False)
+    else:
+      self._egpu_icon_default.set_visible(False)
+      self._egpu_icon.set_visible(big_model_selected and not big_model_failed)
+      self._egpu_icon_orange.set_visible(big_model_selected and big_model_failed)
+      self._egpu_icon_gray.set_visible(not big_model_selected)
diff --git a/openpilot/selfdrive/ui/sunnypilot/mici/layouts/models.py b/openpilot/selfdrive/ui/sunnypilot/mici/layouts/models.py
index 6eff456559..87073d531f 100644
--- a/openpilot/selfdrive/ui/sunnypilot/mici/layouts/models.py
+++ b/openpilot/selfdrive/ui/sunnypilot/mici/layouts/models.py
@@ -8,6 +8,8 @@ import pyray as rl
 
 from openpilot.cereal import custom
 from openpilot.sunnypilot.models.default_model import get_default_model
+from openpilot.sunnypilot.models.fetcher import ModelFetcher
+from openpilot.sunnypilot.models.helpers import ACTIVE_BUNDLE_KEYS
 from openpilot.selfdrive.ui.mici.widgets.button import BigButton
 from openpilot.selfdrive.ui.sunnypilot.layouts.settings.models import ModelsLayout
 from openpilot.selfdrive.ui.ui_state import ui_state, device
@@ -60,7 +62,7 @@ class ModelsLayoutMici(NavScroller):
     self.select_model_btn.set_click_callback(self._show_folders)
 
     self.cancel_download_btn = BigButton(tr("cancel download"))
-    self.cancel_download_btn.set_click_callback(lambda: ui_state.params.remove("ModelManager_DownloadIndex"))
+    self.cancel_download_btn.set_click_callback(lambda: ui_state.params.remove("ModelManager_DownloadRef"))
 
     self.main_items = [self.current_model_info, self.select_model_btn, self.cancel_download_btn]
     self._scroller.add_widgets(self.main_items)
@@ -113,11 +115,12 @@ class ModelsLayoutMici(NavScroller):
     gui_app.pop_widgets_to(self)
 
   def _select_model(self, bundle):
-    ui_state.params.put("ModelManager_DownloadIndex", bundle.index)
+    ui_state.params.put("ModelManager_DownloadRef", bundle.ref)
     self._pop_to_main()
 
   def _select_default(self):
-    ui_state.params.remove("ModelManager_ActiveBundle")
+    source = ModelFetcher.active_source(ui_state.sm["deviceState"].chestnutPresent)
+    ui_state.params.remove(ACTIVE_BUNDLE_KEYS[source])
     self._pop_to_main()
 
   def _select_folder(self, folder_name):
@@ -162,8 +165,9 @@ class ModelsLayoutMici(NavScroller):
     self._was_downloading = is_downloading
 
     self.current_model_info.current_model_header.set_text(tr("active model"))
-    default_model_text = f"{get_default_model()} (Default)".lower()
-    model_text = manager.activeBundle.displayName.lower() if manager.activeBundle.ref else default_model_text
+    # read the slot through ui_state, not modelManagerSP: the manager republishes a
+    # tick after a chestnut change, and the stale bundle flashes the wrong model
+    model_text = ((ui_state.active_bundle or {}).get("displayName") or f"{get_default_model()} (Default)").lower()
     self.current_model_info.current_model_text.set_text(model_text)
     self.current_model_info.info_header.set_text(tr("cache size"))
     self.current_model_info.info_text.set_text(f"{ModelsLayout.calculate_cache_size():.2f} MB")
diff --git a/openpilot/selfdrive/ui/sunnypilot/mici/onroad/hud_renderer.py b/openpilot/selfdrive/ui/sunnypilot/mici/onroad/hud_renderer.py
index 9d39d01727..ad75f7e969 100644
--- a/openpilot/selfdrive/ui/sunnypilot/mici/onroad/hud_renderer.py
+++ b/openpilot/selfdrive/ui/sunnypilot/mici/onroad/hud_renderer.py
@@ -7,6 +7,7 @@ See the LICENSE.md file in the root directory for more details.
 import pyray as rl
 
 from openpilot.selfdrive.ui.mici.onroad.hud_renderer import HudRenderer
+from openpilot.selfdrive.ui.ui_state import ui_state
 from openpilot.selfdrive.ui.sunnypilot.onroad.blind_spot_indicators import BlindSpotIndicators
 
 
@@ -21,6 +22,8 @@ class HudRendererSP(HudRenderer):
 
   def _render(self, rect: rl.Rectangle) -> None:
     super()._render(rect)
+    if ui_state.usbgpu and not ui_state.usbgpu_compiled and ui_state.model_runner_tinygrad:
+      self._draw_model_source(rect)
     self.blind_spot_indicators.render(rect)
 
   def _has_blind_spot_detected(self) -> bool:
diff --git a/openpilot/selfdrive/ui/sunnypilot/ui_state.py b/openpilot/selfdrive/ui/sunnypilot/ui_state.py
index 602830a4db..9bed533d3f 100644
--- a/openpilot/selfdrive/ui/sunnypilot/ui_state.py
+++ b/openpilot/selfdrive/ui/sunnypilot/ui_state.py
@@ -10,6 +10,7 @@ from openpilot.cereal import messaging, log, custom
 from opendbc.car.structs import car
 from openpilot.common.params import Params
 from openpilot.selfdrive.ui.sunnypilot.layouts.settings.display import OnroadBrightness
+from openpilot.sunnypilot.models.helpers import ACTIVE_BUNDLE_KEYS, get_active_source
 from openpilot.sunnypilot.sunnylink.sunnylink_state import SunnylinkState
 from openpilot.system.ui.lib.application import gui_app
 from openpilot.system.ui.sunnypilot.widgets.screen_saver import ScreenSaverSP
@@ -43,6 +44,7 @@ class UIStateSP:
     self.screensaver_enabled: bool = False
 
     self.active_bundle = None
+    self.model_runner_tinygrad: bool = False
     self.blindspot: bool = False
     self.chevron_metrics = None
     self.custom_interactive_timeout: int = 0
@@ -150,7 +152,10 @@ class UIStateSP:
       self.has_icbm = self.CP_SP.intelligentCruiseButtonManagementAvailable and self.params.get_bool("IntelligentCruiseButtonManagement")
 
     self._enforce_constraints()
-    self.active_bundle = self.params.get("ModelManager_ActiveBundle")
+    source = get_active_source(usbgpu=self.usbgpu, usbgpu_active=self.usbgpu_active,
+                               usbgpu_loading=self.usbgpu_loading, offroad=self.is_offroad())
+    self.active_bundle = self.params.get(ACTIVE_BUNDLE_KEYS[source])
+    self.model_runner_tinygrad = self.active_bundle is not None and self.active_bundle.get("runner") == "tinygrad"
     self.blindspot = self.params.get_bool("BlindSpot")
     self.chevron_metrics = self.params.get("ChevronInfo")
     self.custom_interactive_timeout = self.params.get("InteractivityTimeout", return_default=True)
diff --git a/openpilot/selfdrive/ui/ui_state.py b/openpilot/selfdrive/ui/ui_state.py
index e0aca74ff2..7e2a2494ea 100644
--- a/openpilot/selfdrive/ui/ui_state.py
+++ b/openpilot/selfdrive/ui/ui_state.py
@@ -112,6 +112,15 @@ class UIState(UIStateSP):
   def add_on_body_changed_callbacks(self, callback: Callable[[], None]):
     self._on_body_changed_callbacks.append(callback)
 
+  @property
+  def big_model_failed(self) -> bool:
+    # Mirrors the onroad HUD's four-condition check so sidebar and home icons reflect the same failure states
+    return (self.usbgpu_active is False or
+            not self.sm['deviceState'].chestnutPresent or
+            (self.usbgpu_active is True and self.sm.recv_frame['modelV2'] > self.started_frame and
+             not self.sm.alive['modelV2']) or
+            (self.usbgpu_active is None and self.sm.recv_frame['modelV2'] > self.started_frame))
+
   @property
   def engaged(self) -> bool:
     return self.started and (self.sm["selfdriveState"].enabled or self.sm["selfdriveStateSP"].mads.enabled)
diff --git a/openpilot/sunnypilot/modeld_v2/modeld.py b/openpilot/sunnypilot/modeld_v2/modeld.py
index 9f3d709537..d180012279 100755
--- a/openpilot/sunnypilot/modeld_v2/modeld.py
+++ b/openpilot/sunnypilot/modeld_v2/modeld.py
@@ -91,7 +91,7 @@ class ModelState(ModelStateBase):
     if env_pkl and os.path.exists(env_pkl):
       model_bundle = None
     else:
-      model_bundle = get_active_bundle()
+      model_bundle = get_active_bundle(usbgpu=usbgpu)
     self.generation = model_bundle.generation if model_bundle is not None else None
     overrides = {override.key: override.value for override in model_bundle.overrides} if model_bundle else {}
 
diff --git a/openpilot/sunnypilot/modeld_v2/tests/helpers.py b/openpilot/sunnypilot/modeld_v2/tests/helpers.py
index ee59e82785..6e66bf771a 100644
--- a/openpilot/sunnypilot/modeld_v2/tests/helpers.py
+++ b/openpilot/sunnypilot/modeld_v2/tests/helpers.py
@@ -190,8 +190,8 @@ def tmp_path():
 
 def patch_modeld(monkeypatch):
   def _patch(bundle):
-    monkeypatch.setattr(helpers, 'get_active_bundle', lambda params=None: bundle)
-    monkeypatch.setattr(modeld_module, 'get_active_bundle', lambda params=None: bundle)
+    monkeypatch.setattr(helpers, 'get_active_bundle', lambda params=None, *, usbgpu=None: bundle)
+    monkeypatch.setattr(modeld_module, 'get_active_bundle', lambda params=None, *, usbgpu=None: bundle)
 
   return _patch
 
diff --git a/openpilot/sunnypilot/modeld_v2/tests/test_combined_pkl_loader.py b/openpilot/sunnypilot/modeld_v2/tests/test_combined_pkl_loader.py
index 3396649a1d..ccd8cbc7f3 100644
--- a/openpilot/sunnypilot/modeld_v2/tests/test_combined_pkl_loader.py
+++ b/openpilot/sunnypilot/modeld_v2/tests/test_combined_pkl_loader.py
@@ -59,8 +59,8 @@ class TestFindDrivingPkl(OpenpilotTestCase):
 class TestModelStateCombinedInit(OpenpilotTestCase):
   def test_asserts_when_no_pkl(self, monkeypatch):
     bundle = DummyBundle(models=[], is_20hz=True)
-    monkeypatch.setattr(helpers, 'get_active_bundle', lambda params=None: bundle)
-    monkeypatch.setattr(modeld_module, 'get_active_bundle', lambda params=None: bundle)
+    monkeypatch.setattr(helpers, 'get_active_bundle', lambda params=None, *, usbgpu=None: bundle)
+    monkeypatch.setattr(modeld_module, 'get_active_bundle', lambda params=None, *, usbgpu=None: bundle)
     with self.assertRaisesRegex(AssertionError, "No driving pkl found"):
       ModelState(cam_w=CAM_W, cam_h=CAM_H)
 
diff --git a/openpilot/sunnypilot/models/fetcher.py b/openpilot/sunnypilot/models/fetcher.py
index c9e86edd0c..1bbfb02f70 100644
--- a/openpilot/sunnypilot/models/fetcher.py
+++ b/openpilot/sunnypilot/models/fetcher.py
@@ -141,41 +141,50 @@ class ModelFetcher:
   MODEL_URL = "https://raw.githubusercontent.com/sunnypilot/sunnypilot-models/refs/heads/gh-pages/docs/driving_models_v21.json"
   MODEL_URL_USBGPU = "https://raw.githubusercontent.com/sunnypilot/sunnypilot-models/refs/heads/gh-pages/docs/driving_models_usbgpu_v22.json"
 
+  MODEL_SOURCES = {
+    "qcom": (MODEL_URL, ""),
+    "usbgpu": (MODEL_URL_USBGPU, "_USBGPU"),
+  }
+
   def __init__(self, params: Params):
     self.params = params
     self.model_parser = ModelParser()
-    self._is_usbgpu: bool | None = None
-    self.model_cache = ModelCache(params)
-    self.model_url = self.MODEL_URL
+    self.model_caches = {
+      source: ModelCache(params, suffix=suffix)
+      for source, (_, suffix) in self.MODEL_SOURCES.items()
+    }
+    self._refetched: set[str] = set()
+    self.params.put("ModelManager_ActiveJson", {
+      "qcom": self.MODEL_URL,
+      "usbgpu": self.MODEL_URL_USBGPU,
+    }, block=True)
 
-  def _update_model_source(self, chestnut_present: bool) -> None:
-    """Updates what json to use based on chestnut hardware presence via deviceState"""
-    is_usbgpu = chestnut_present
-    if is_usbgpu != self._is_usbgpu:
-      self._is_usbgpu = is_usbgpu
-      self.model_cache = ModelCache(self.params, suffix="_USBGPU" if is_usbgpu else "")
-      self.model_url = self.MODEL_URL_USBGPU if is_usbgpu else self.MODEL_URL
-      self.params.put("ModelManager_ActiveJson", self.model_url, block=True)
+  @staticmethod
+  def active_source(chestnut_present: bool) -> str:
+    return "usbgpu" if chestnut_present else "qcom"
 
-  def _fetch_and_cache_models(self) -> list[custom.ModelManagerSP.ModelBundle] | None:
+  def _fetch_and_cache_models(self, source: str) -> list[custom.ModelManagerSP.ModelBundle] | None:
     """Fetches fresh model data from remote and updates cache.
     Returns None on transport errors. Raises on 404 and other fatal HTTP errors.
     """
+    model_url, _ = self.MODEL_SOURCES[source]
     try:
-      response = requests.get(self.model_url, timeout=10)
+      response = requests.get(model_url, timeout=10)
 
       # Explicitly handle 404 differently
       if response.status_code == 404:
-        cloudlog.error(f"Models URL returned 404 Not Found: {self.model_url}")
-        raise HTTPError(f"404 Not Found: {self.model_url}", response=response)
+        cloudlog.error(f"Models URL returned 404 Not Found: {model_url}")
+        raise HTTPError(f"404 Not Found: {model_url}", response=response)
 
       # Raise for any other 4xx/5xx
       response.raise_for_status()
 
       json_data = response.json()
-      self.model_cache.set(json_data)
-      cloudlog.debug("Successfully updated models cache")
-      return self.model_parser.parse_models(json_data)
+      parsed = self.model_parser.parse_models(json_data)
+      if parsed:
+        self.model_caches[source].set(json_data)
+        cloudlog.debug(f"Successfully updated models cache for {source}")
+      return parsed
 
     except ConnectionError as e:
       cloudlog.warning(f"DNS/connection error while fetching models: {e}")
@@ -188,16 +197,40 @@ class ModelFetcher:
 
     return None
 
-  def get_available_bundles(self, chestnut_present: bool = False) -> list[custom.ModelManagerSP.ModelBundle]:
-    """Gets the list of available models, with smart cache handling"""
-    self._update_model_source(chestnut_present)
-    cached_data, is_expired = self.model_cache.get()
+  @staticmethod
+  def _cache_matches_source(source: str, cached_data: dict) -> bool:
+    bundles = cached_data.get("bundles", [])
+    if source == "usbgpu":
+      return any(bundle.get("is_big") is True for bundle in bundles)
+    return not any(bundle.get("is_big") is True for bundle in bundles)
+
+  def get_bundles_for_source(self, source: str) -> list[custom.ModelManagerSP.ModelBundle]:
+    if source not in self.MODEL_SOURCES:
+      cloudlog.warning(f"Unknown model source: {source}")
+      return []
+
+    cached_data, is_expired = self.model_caches[source].get()
 
     if cached_data and not is_expired:
-      cloudlog.debug("Using valid cached models data")
-      return self.model_parser.parse_models(cached_data)
+      # a source is refetched over a mismatch at most once per process: if the fresh
+      # manifest still mismatches, the URL is authoritative and the cache is trusted
+      if self._cache_matches_source(source, cached_data) or source in self._refetched:
+        try:
+          parsed = self.model_parser.parse_models(cached_data)
+        except Exception:
+          cloudlog.warning(f"Failed to parse cached models for {source}; refetching", exc_info=True)
+        else:
+          if parsed:
+            cloudlog.debug(f"Using valid cached models data for source {source}")
+            return parsed
+          # a source-matching cache that yields no valid bundles is stale (e.g. an old
+          # manifest version) - do not trust it, refetch so the source is repopulated
+          cloudlog.warning(f"Cached models for {source} have no valid bundles; refetching")
+      else:
+        self._refetched.add(source)
+        cloudlog.warning(f"Cached models for {source} not valid; refetching once")
 
-    fetched_bundles = self._fetch_and_cache_models()
+    fetched_bundles = self._fetch_and_cache_models(source)
     if fetched_bundles is not None:
       return fetched_bundles
 
@@ -205,14 +238,33 @@ class ModelFetcher:
       cloudlog.warning("Failed to fetch fresh data and no cache available")
 
     cloudlog.warning("Failed to fetch fresh data. Using expired cache as fallback")
-    return self.model_parser.parse_models(cached_data)
+    try:
+      return self.model_parser.parse_models(cached_data)
+    except Exception:
+      return []
+
+
+def get_cached_bundles(params: Params, source: str) -> list[custom.ModelManagerSP.ModelBundle]:
+
+  if source not in ModelFetcher.MODEL_SOURCES:
+    cloudlog.warning(f"Unknown model source: {source}")
+    return []
+  _, suffix = ModelFetcher.MODEL_SOURCES[source]
+  cached_data = params.get(f"ModelManager_ModelsCache{suffix}")
+  if not cached_data:
+    return []
+  try:
+    return ModelParser.parse_models(cached_data)
+  except Exception as e:
+    cloudlog.warning(f"Failed to parse cached models for source {source}: {e}")
+    return []
 
 
 if __name__ == "__main__":
   from openpilot.selfdrive.modeld.helpers import usbgpu_present
   params = Params()
   model_fetcher = ModelFetcher(params)
-  bundles = model_fetcher.get_available_bundles(chestnut_present=usbgpu_present())
+  bundles = model_fetcher.get_bundles_for_source(ModelFetcher.active_source(usbgpu_present()))
   for bundle in bundles:
     for model in bundle.models:
       model_overrides = {override.key: override.value for override in bundle.overrides}
diff --git a/openpilot/sunnypilot/models/helpers.py b/openpilot/sunnypilot/models/helpers.py
index e33cc445d1..707b86f722 100644
--- a/openpilot/sunnypilot/models/helpers.py
+++ b/openpilot/sunnypilot/models/helpers.py
@@ -16,6 +16,7 @@ from openpilot.common.params import Params
 from openpilot.common.swaglog import cloudlog
 from openpilot.sunnypilot.models.constants import Meta, MetaSimPose, MetaTombRaider
 from openpilot.common.hardware.hw import Paths
+from openpilot.selfdrive.modeld.helpers import usbgpu_present
 
 # SET ME TO THE EXACT JSON VERSION WE SET IN SUNNYPILOT_MODELS REPO
 REQUIRED_JSON_VERSION = 18
@@ -24,6 +25,12 @@ CUSTOM_MODEL_PATH = Paths.model_root()
 METADATA_PATH = Path(__file__).parent / '../models/supercombo_metadata.pkl'
 ModelManager = custom.ModelManagerSP
 
+ACTIVE_BUNDLE_KEYS = {
+  "qcom": "ModelManager_ActiveBundle",
+  "usbgpu": "ModelManager_ActiveBundleUSBGPU",
+}
+_LAST_VALIDATED_RAW: dict[str, dict | None] = {}
+
 
 def _compute_hash(file_path: str) -> str | None:
   from openpilot.common.file_chunker import open_file_chunked
@@ -97,55 +104,81 @@ def _bundle_needs_reset(active_bundle: custom.ModelManagerSP.ModelBundle, availa
       return True
     if active_bundle.minimumSelectorVersion != matching_bundle.minimumSelectorVersion:
       return True
-    if active_bundle.runner.raw != matching_bundle.runner.raw:
+    if active_bundle.runner != matching_bundle.runner:
       return True
     if set(_bundle_artifacts(active_bundle)) != set(_bundle_artifacts(matching_bundle)):
       return True
 
-  # missing files trigger re-download, not selection reset
-  return False
+  return not _bundle_is_valid_locally(active_bundle)
 
 
-def _prev_bundle_key(is_usbgpu: bool) -> str:
-  return "ModelManager_PrevBundle_USBGPU" if is_usbgpu else "ModelManager_PrevBundle"
-
-
-def validate_active_bundle(params: Params, available_bundles: list[custom.ModelManagerSP.ModelBundle] | None = None,
-                           is_usbgpu: bool = False) -> None:
-  raw_bundle = params.get("ModelManager_ActiveBundle")
-  if not raw_bundle:
-    prev = params.get(_prev_bundle_key(is_usbgpu))
-    if prev and (prev_bundle := get_active_bundle(params, raw_bundle_dict=prev)) is not None:
-      if not _bundle_needs_reset(prev_bundle, available_bundles):
-        params.put("ModelManager_ActiveBundle", prev, block=True)
-    return
-
-  active_bundle = get_active_bundle(params, raw_bundle_dict=raw_bundle)
-  if active_bundle is None or _bundle_needs_reset(active_bundle, available_bundles):
-    cloudlog.warning("Active model bundle invalid; resetting to default")
-    params.put(_prev_bundle_key(not is_usbgpu), raw_bundle, block=True)
-
-    prev = params.get(_prev_bundle_key(is_usbgpu))
-    if prev and (prev_bundle := get_active_bundle(params, raw_bundle_dict=prev)) is not None:
-      if not _bundle_needs_reset(prev_bundle, available_bundles):
-        params.put("ModelManager_ActiveBundle", prev, block=True)
-        return
-
-    params.remove("ModelManager_ActiveBundle")
-    params.put("ModelRunnerTypeCache", int(custom.ModelManagerSP.Runner.stock), block=True)
-
-
-def get_active_bundle(params: Params | None = None, raw_bundle_dict: dict | bytes | None = None) -> "custom.ModelManagerSP.ModelBundle | None":
-  params = params or Params()
+def _parse_active_bundle(raw_bundle) -> "custom.ModelManagerSP.ModelBundle | None":
   try:
-    active_bundle_dict = raw_bundle_dict if raw_bundle_dict is not None else (params.get("ModelManager_ActiveBundle") or {})
-    if isinstance(active_bundle_dict, dict) and active_bundle_dict and is_bundle_version_compatible(active_bundle_dict):
-      return custom.ModelManagerSP.ModelBundle(**active_bundle_dict)
+    if isinstance(raw_bundle, dict) and raw_bundle and is_bundle_version_compatible(raw_bundle):
+      return custom.ModelManagerSP.ModelBundle(**raw_bundle)
   except Exception:
     pass
   return None
 
 
+def get_selected_bundle(params: Params | None = None, source: str = "qcom") -> "custom.ModelManagerSP.ModelBundle | None":
+  params = params or Params()
+  return _parse_active_bundle(params.get(ACTIVE_BUNDLE_KEYS[source]))
+
+
+def get_active_source(usbgpu: bool | None = None, usbgpu_active: bool | None = None,
+                      usbgpu_loading: bool | None = None, offroad: bool | None = None) -> str:
+  if usbgpu is None:
+    usbgpu = usbgpu_present()
+  state_valid = usbgpu_active is not None or usbgpu_loading is not None or offroad is not None
+  big_active = usbgpu and (not state_valid or usbgpu_active or usbgpu_loading or offroad)
+  return "usbgpu" if big_active else "qcom"
+
+
+def get_active_bundle(params: Params | None = None, *, usbgpu: bool | None = None) -> "custom.ModelManagerSP.ModelBundle | None":
+  # no cross-slot fallback: an empty active slot means the hardware default, which
+  # only stock modeld can run - modeld_v2 requires a real bundle
+  params = params or Params()
+  return get_selected_bundle(params, get_active_source(usbgpu=usbgpu))
+
+
+def resolve_bundle_by_ref(
+  ref: str, source_bundles: dict[str, list[custom.ModelManagerSP.ModelBundle]],
+) -> "tuple[custom.ModelManagerSP.ModelBundle, str] | None":
+  for source, bundles in source_bundles.items():
+    for bundle in bundles:
+      if bundle.ref == ref:
+        return bundle, source
+  return None
+
+
+def _validate_active_bundle(params: Params, source: str, available_bundles: list[custom.ModelManagerSP.ModelBundle] | None = None) -> None:
+  global _LAST_VALIDATED_RAW
+
+  key = ACTIVE_BUNDLE_KEYS[source]
+  raw_bundle = params.get(key)
+  if not raw_bundle:
+    return
+
+  if _LAST_VALIDATED_RAW.get(key) == raw_bundle:
+    return
+
+  active_bundle = _parse_active_bundle(raw_bundle)
+  if active_bundle is None or _bundle_needs_reset(active_bundle, available_bundles):
+    cloudlog.warning(f"Active model bundle invalid for {source}; resetting to default")
+    params.remove(key)
+    _LAST_VALIDATED_RAW[key] = None
+  else:
+    _LAST_VALIDATED_RAW[key] = raw_bundle
+
+
+def validate_active_bundles(params: Params, source_bundles: dict[str, list[custom.ModelManagerSP.ModelBundle]]) -> None:
+  # an empty list means the fetch failed, not that the catalog dropped the bundle
+  for source, bundles in source_bundles.items():
+    _validate_active_bundle(params, source, bundles or None)
+  get_active_model_runner(params, force_check=True)
+
+
 def get_active_model_runner(params: Params | None = None, force_check: bool = False) -> int:
   params = params or Params()
   cached_runner_type = params.get("ModelRunnerTypeCache")
diff --git a/openpilot/sunnypilot/models/manager.py b/openpilot/sunnypilot/models/manager.py
index e47cf7536c..2405566d55 100644
--- a/openpilot/sunnypilot/models/manager.py
+++ b/openpilot/sunnypilot/models/manager.py
@@ -17,7 +17,8 @@ from openpilot.common.hardware.hw import Paths
 
 from openpilot.cereal import messaging, custom
 from openpilot.sunnypilot.models.fetcher import ModelFetcher
-from openpilot.sunnypilot.models.helpers import get_active_bundle, validate_active_bundle, verify_file
+from openpilot.sunnypilot.models.helpers import (ACTIVE_BUNDLE_KEYS, get_active_bundle, get_selected_bundle,
+                                                  resolve_bundle_by_ref, validate_active_bundles, verify_file)
 
 # (connect, read) seconds. read is per-request inactivity, not a total cap
 DOWNLOAD_TIMEOUT = (30, 30)
@@ -31,9 +32,11 @@ class ModelManagerSP:
     self.model_fetcher = ModelFetcher(self.params)
     self.pm = messaging.PubMaster(["modelManagerSP"])
     self.sm = messaging.SubMaster(["deviceState"])
+    self.chestnut_present = False
     self.available_models: list[custom.ModelManagerSP.ModelBundle] = []
+    self.source_models: dict[str, list[custom.ModelManagerSP.ModelBundle]] = {}
     self.selected_bundle: custom.ModelManagerSP.ModelBundle = None
-    self.active_bundle: custom.ModelManagerSP.ModelBundle = get_active_bundle(self.params)
+    self.active_bundle: custom.ModelManagerSP.ModelBundle = get_active_bundle(self.params, usbgpu=self.chestnut_present)
     self._chunk_size = 128 * 1000  # 128 KB chunks
     self._download_start_times: dict[str, float] = {}  # Track start time per model
 
@@ -77,7 +80,7 @@ class ModelManagerSP:
           f.write(chunk)
           bytes_downloaded += len(chunk)
 
-          if self.params.get("ModelManager_DownloadIndex") is None:
+          if self.params.get("ModelManager_DownloadRef") is None:
             raise Exception("Download cancelled")
 
           if total_size > 0:
@@ -115,7 +118,7 @@ class ModelManagerSP:
             for data in response.iter_content(chunk_size=self._chunk_size):
               f.write(data)
               chunk_downloaded += len(data)
-              if self.params.get("ModelManager_DownloadIndex") is None:
+              if self.params.get("ModelManager_DownloadRef") is None:
                 raise Exception("Download cancelled")
               intra = chunk_downloaded / max(chunk_size, 1)
               progress = min(99.0, ((i + intra) / num_chunks) * 100)
@@ -217,8 +220,7 @@ class ModelManagerSP:
     model_manager_state.availableBundles = self.available_models
     self.pm.send('modelManagerSP', msg)
 
-  async def _download_bundle(self, model_bundle: custom.ModelManagerSP.ModelBundle, destination_path: str) -> None:
-    """Downloads all models in a bundle"""
+  async def _download_bundle(self, model_bundle: custom.ModelManagerSP.ModelBundle, destination_path: str, source: str) -> None:
     self.selected_bundle = model_bundle
     self.selected_bundle.status = custom.ModelManagerSP.DownloadStatus.downloading
     for model in self.selected_bundle.models:
@@ -240,10 +242,9 @@ class ModelManagerSP:
           seen_artifacts.add(artifact.fileName)
           await self._process_artifact(artifact, destination_path)
 
-      self.active_bundle = self.selected_bundle
-      self.active_bundle.status = custom.ModelManagerSP.DownloadStatus.downloaded
-      self.params.put("ModelManager_ActiveBundle", self.active_bundle.to_dict(), block=True)
-      self.selected_bundle = None
+      self.selected_bundle.status = custom.ModelManagerSP.DownloadStatus.downloaded
+      self.params.put(ACTIVE_BUNDLE_KEYS[source], model_bundle.to_dict(), block=True)
+      self.active_bundle = get_active_bundle(self.params, usbgpu=self.chestnut_present)
 
     except Exception:
       if self.selected_bundle is not None:
@@ -253,37 +254,32 @@ class ModelManagerSP:
     finally:
       self._report_status()
 
-  def download(self, model_bundle: custom.ModelManagerSP.ModelBundle, destination_path: str) -> None:
+  def download(self, model_bundle: custom.ModelManagerSP.ModelBundle, destination_path: str, source: str) -> None:
     """Main entry point for downloading a model bundle"""
-    asyncio.run(self._download_bundle(model_bundle, destination_path))
-
-  BOOT_SETTLE_TICKS = 10  # seconds at 1 Hz before validating active bundle
+    asyncio.run(self._download_bundle(model_bundle, destination_path, source))
 
   def main_thread(self) -> None:
     """Main thread for model management"""
     rk = Ratekeeper(1, print_delay_threshold=None)
-    boot_ticks = 0
 
     while True:
       try:
         self.sm.update(0)
-        chestnut_present = self.sm['deviceState'].chestnutPresent
-        self.available_models = self.model_fetcher.get_available_bundles(chestnut_present)
-        if boot_ticks >= self.BOOT_SETTLE_TICKS:
-          validate_active_bundle(self.params, self.available_models, is_usbgpu=chestnut_present)
-        boot_ticks = min(boot_ticks + 1, self.BOOT_SETTLE_TICKS)
-        self.active_bundle = get_active_bundle(self.params)
+        self.chestnut_present = self.sm['deviceState'].chestnutPresent
+        self.source_models = {source: self.model_fetcher.get_bundles_for_source(source) for source in ModelFetcher.MODEL_SOURCES}
+        self.available_models = self.source_models[ModelFetcher.active_source(self.chestnut_present)]
+        validate_active_bundles(self.params, self.source_models)
+        self.active_bundle = get_active_bundle(self.params, usbgpu=self.chestnut_present)
 
-        if (index_to_download := self.params.get("ModelManager_DownloadIndex")) is not None:
-          if self.active_bundle and self.active_bundle.index == index_to_download:
-            self.params.remove("ModelManager_DownloadIndex")
-          elif model_to_download := next((model for model in self.available_models if model.index == index_to_download), None):
+        if (ref_to_download := self.params.get("ModelManager_DownloadRef")) is not None:
+          if resolved := resolve_bundle_by_ref(ref_to_download, self.source_models):
+            model_to_download, source = resolved
             try:
-              self.download(model_to_download, Paths.model_root())
+              self.download(model_to_download, Paths.model_root(), source)
             except Exception as e:
               cloudlog.exception(e)
             finally:
-              self.params.remove("ModelManager_DownloadIndex")
+              self.params.remove("ModelManager_DownloadRef")
               self.selected_bundle = None
 
         if self.params.get("ModelManager_ClearCache"):
@@ -302,12 +298,14 @@ class ModelManagerSP:
     Clears the model cache directory of all files except those in the active model bundle.
     """
 
-    # Get list of files used by active model bundle
+    # Get list of files used by both slots' selected bundles (either may become
+    # the truly active bundle depending on hardware availability)
     active_files = []
-    if self.active_bundle is not None: # When the default model is active
-      for model in self.active_bundle.models:
-        if hasattr(model, 'artifact') and model.artifact.fileName:
-          active_files.append(model.artifact.fileName)
+    for source in ACTIVE_BUNDLE_KEYS:
+      if selected_bundle := get_selected_bundle(self.params, source):
+        for model in selected_bundle.models:
+          if model.artifact.fileName:
+            active_files.append(model.artifact.fileName)
 
     # Remove all files except active ones (including their chunk files)
     model_dir = Paths.model_root()
diff --git a/openpilot/sunnypilot/models/tests/test_manager_download.py b/openpilot/sunnypilot/models/tests/test_manager_download.py
index 67fb9023af..d74deb03e6 100644
--- a/openpilot/sunnypilot/models/tests/test_manager_download.py
+++ b/openpilot/sunnypilot/models/tests/test_manager_download.py
@@ -11,6 +11,7 @@ import http.server
 import os
 import tempfile
 import threading
+import time
 import unittest
 from typing import Any
 from unittest import mock
@@ -23,6 +24,10 @@ from openpilot.common.test import OpenpilotTestCase
 from openpilot.common.file_chunker import get_chunk_name, get_manifest_path
 from openpilot.selfdrive.test.helpers import http_server_context
 from openpilot.sunnypilot.models import manager as manager_module
+from openpilot.sunnypilot.models.fetcher import ModelFetcher, get_cached_bundles
+from openpilot.sunnypilot.models import helpers
+from openpilot.sunnypilot.models.helpers import (get_active_bundle, get_active_source, get_selected_bundle,
+                                                  resolve_bundle_by_ref, validate_active_bundles)
 from openpilot.sunnypilot.models.manager import ModelManagerSP
 
 CHUNK_BODIES = [b'A' * 5000, b'B' * 5000, b'C' * 3000]
@@ -103,6 +108,7 @@ class ManagerDownloadTestBase(OpenpilotTestCase):
     self.manager.selected_bundle = None
     self.manager.active_bundle = None
     self.manager.available_models = []
+    self.manager.chestnut_present = False
     self.manager._chunk_size = 1024
     self.manager._download_start_times = {}
 
@@ -249,6 +255,85 @@ class TestManagerDownload(ManagerDownloadTestBase):
         assert self.manager._download_start_times == {}
     self.run_with_server(body)
 
+  def test_download_ref_present_keeps_download_alive(self):
+    """A pending download request (DownloadRef set) must not be cancelled mid-transfer."""
+    def body():
+      artifact = self.make_artifact(chunked=True)
+      base_path = os.path.join(self.dest, artifact.fileName)
+      self.manager.params.get.side_effect = lambda key: b"ref" if key == "ModelManager_DownloadRef" else None
+      asyncio.run(self.manager._download_chunked(artifact.downloadUri.uri, base_path, artifact))
+      assert os.path.isfile(get_manifest_path(base_path))
+    self.run_with_server(body)
+
+  def test_cancellation_via_download_ref(self):
+    """Removing DownloadRef mid-transfer cancels the download."""
+    def body():
+      artifact = self.make_artifact(chunked=True)
+      base_path = os.path.join(self.dest, artifact.fileName)
+      checks = {"n": 0}
+
+      def get(key):
+        if key == "ModelManager_DownloadRef":
+          checks["n"] += 1
+          return b"ref" if checks["n"] <= 2 else None
+        return b"0"
+
+      self.manager.params.get.side_effect = get
+      with self.assertRaises(Exception) as ctx:
+        asyncio.run(self.manager._download_chunked(artifact.downloadUri.uri, base_path, artifact))
+      assert 'cancelled' in str(ctx.exception).lower()
+      assert not os.path.isfile(get_manifest_path(base_path))
+    self.run_with_server(body)
+
+  def _make_params_with_store(self):
+    params = mock.MagicMock()
+    store = {}
+
+    def get(key, *args, **kwargs):
+      return store.get(key, b"0")  # b"0" -> download not cancelled
+
+    def put(key, value, *args, **kwargs):
+      store[key] = value
+
+    params.get.side_effect = get
+    params.put.side_effect = put
+    return params, store
+
+  def test_download_writes_qcom_slot(self):
+    """A download resolved to the qcom source writes the qcom active bundle slot only."""
+    def body():
+      artifact = self.make_artifact(chunked=True)
+      self._bundle.ref = "test-ref"
+      self._bundle.minimumSelectorVersion = 18
+      params, store = self._make_params_with_store()
+      self.manager.params = params
+      asyncio.run(self.manager._download_bundle(self._bundle, self.dest, "qcom"))
+
+      assert "ModelManager_ActiveBundle" in store, "qcom download must write the qcom slot"
+      assert "ModelManager_ActiveBundleUSBGPU" not in store, "qcom download must not touch the usbgpu slot"
+      assert self.manager.selected_bundle.status == custom.ModelManagerSP.DownloadStatus.downloaded
+      assert self.manager.active_bundle is not None and self.manager.active_bundle.ref == "test-ref"
+      assert self.manager.active_bundle.status == custom.ModelManagerSP.DownloadStatus.downloaded
+      chunk_names = [get_chunk_name(artifact.fileName, i, len(artifact.chunks)) for i in range(len(artifact.chunks))]
+      missing = [c for c in chunk_names if not os.path.isfile(os.path.join(self.dest, c))]
+      assert missing == [], f"chunks missing from the cache: {missing}"
+    self.run_with_server(body)
+
+  def test_download_writes_usbgpu_slot(self):
+    """A download resolved to the usbgpu source writes the usbgpu active bundle slot only."""
+    def body():
+      self.make_artifact(chunked=True)
+      self._bundle.ref = "big-ref"
+      self._bundle.minimumSelectorVersion = 18
+      params, store = self._make_params_with_store()
+      self.manager.params = params
+      asyncio.run(self.manager._download_bundle(self._bundle, self.dest, "usbgpu"))
+
+      assert "ModelManager_ActiveBundleUSBGPU" in store, "usbgpu download must write the usbgpu slot"
+      assert "ModelManager_ActiveBundle" not in store, "usbgpu download must not touch the qcom slot"
+      assert self.manager.selected_bundle.status == custom.ModelManagerSP.DownloadStatus.downloaded
+    self.run_with_server(body)
+
 
 class TestManagerImports(OpenpilotTestCase):
   """Catches undeclared dependencies. aiohttp lived only in the AGNOS venv; 19.6 dropped
@@ -267,6 +352,352 @@ class TestManagerImports(OpenpilotTestCase):
     assert connect > 0 and read > 0, "requests defaults to no timeout; downloads would hang forever"
 
 
+class TestResolveBundleByRef(OpenpilotTestCase):
+  """A ref resolves to (bundle, source) across both hardware manifests. Refs are
+  unique per manifest and never overlap across sources, so a ref maps to exactly
+  one slot. Shared by the manager's download flow and the settings UI."""
+
+  @staticmethod
+  def _bundle(ref: str):
+    bundle = custom.ModelManagerSP.ModelBundle.new_message()
+    bundle.ref = ref
+    return bundle
+
+  def test_qcom_ref_resolves_to_qcom_slot(self):
+    small = self._bundle("small")
+    assert resolve_bundle_by_ref("small", {"qcom": [small], "usbgpu": []}) == (small, "qcom")
+
+  def test_usbgpu_ref_resolves_to_usbgpu_slot(self):
+    big = self._bundle("big")
+    assert resolve_bundle_by_ref("big", {"qcom": [], "usbgpu": [big]}) == (big, "usbgpu")
+
+  def test_unknown_ref_returns_none(self):
+    source_bundles = {"qcom": [self._bundle("small")], "usbgpu": []}
+    assert resolve_bundle_by_ref("nope", source_bundles) is None
+
+
+def manifest_bundle(short_name: str, ref: str, index: int = 0, is_big: bool = False) -> dict:
+  """Minimal manifest bundle dict, version-compatible (no chunks to avoid disk side effects).
+  Big (usbgpu) bundles carry `is_big: true` in the manifest JSON."""
+  return {
+    "index": index,
+    "short_name": short_name,
+    "display_name": short_name.upper(),
+    "generation": 1,
+    "environment": "release",
+    "runner": "tinygrad",
+    "is_big": is_big,
+    "minimum_selector_version": "18",
+    "ref": ref,
+    "models": [{
+      "type": "supercombo",
+      "artifact": {
+        "file_name": f"{short_name}.pkl",
+        "download_uri": {"url": f"https://example.com/{short_name}.pkl", "sha256": "s"},
+      },
+    }],
+  }
+
+
+def fresh_sync_time() -> int:
+  return int(time.monotonic() * 1e9)
+
+
+class TestModelFetcherSources(OpenpilotTestCase):
+  """Both manifests are always maintained: get_bundles_for_source exposes either
+  source by name, and active_source picks which one matches the attached hardware."""
+
+  def _make_params(self, qcom_manifest, usbgpu_manifest):
+    params = mock.MagicMock()
+
+    def get(key):
+      if key == "ModelManager_ModelsCache":
+        return qcom_manifest
+      if key == "ModelManager_ModelsCache_USBGPU":
+        return usbgpu_manifest
+      if key in ("ModelManager_LastSyncTime", "ModelManager_LastSyncTime_USBGPU"):
+        return fresh_sync_time()
+      return None
+
+    params.get.side_effect = get
+    return params
+
+  def test_active_source_follows_chestnut_presence(self):
+    assert ModelFetcher.active_source(False) == "qcom"
+    assert ModelFetcher.active_source(True) == "usbgpu"
+
+  def test_get_bundles_for_source_returns_each_source(self):
+    params = self._make_params({"bundles": [manifest_bundle("small", "aaa")]},
+                               {"bundles": [manifest_bundle("big", "bbb", is_big=True)]})
+    fetcher = ModelFetcher(params)
+    assert [bundle.ref for bundle in fetcher.get_bundles_for_source("qcom")] == ["aaa"]
+    assert [bundle.ref for bundle in fetcher.get_bundles_for_source("usbgpu")] == ["bbb"]
+
+  def test_get_bundles_for_source_unknown(self):
+    assert ModelFetcher(mock.MagicMock()).get_bundles_for_source("bogus") == []
+
+  def test_get_cached_bundles_parses_source(self):
+    params = self._make_params({"bundles": [manifest_bundle("small", "aaa")]},
+                               {"bundles": [manifest_bundle("big", "bbb", is_big=True)]})
+    qcom_bundles = get_cached_bundles(params, "qcom")
+    usbgpu_bundles = get_cached_bundles(params, "usbgpu")
+    assert [b.ref for b in qcom_bundles] == ["aaa"]
+    assert [b.ref for b in usbgpu_bundles] == ["bbb"]
+    assert qcom_bundles[0].displayName == "SMALL"
+
+  def test_get_cached_bundles_empty_when_missing(self):
+    params = mock.MagicMock()
+    params.get.return_value = None
+    assert get_cached_bundles(params, "qcom") == []
+    assert get_cached_bundles(params, "usbgpu") == []
+
+  def test_get_cached_bundles_unknown_source(self):
+    assert get_cached_bundles(mock.MagicMock(), "bogus") == []
+
+  def test_active_json_has_both_urls(self):
+    params = mock.MagicMock()
+    ModelFetcher(params)
+    active_json_calls = [call for call in params.put.call_args_list if call.args[0] == "ModelManager_ActiveJson"]
+    assert active_json_calls, "expected ModelManager_ActiveJson to be written"
+    assert active_json_calls[-1].args[1] == {
+      "qcom": ModelFetcher.MODEL_URL,
+      "usbgpu": ModelFetcher.MODEL_URL_USBGPU,
+    }
+
+
+
+class TestSourceCacheIntegrity(OpenpilotTestCase):
+  """Each source's cached manifest must contain only that source's models; the
+  `is_big` flag in the JSON marks the big (usbgpu) models. A mismatched cache is
+  legacy data from before the per-source split (the active manifest was cached
+  under the unsuffixed key regardless of hardware) and is refetched. This
+  replaces the old one-time bundle migration."""
+
+  def _make_params(self, qcom_manifest, usbgpu_manifest):
+    params = mock.MagicMock()
+
+    def get(key):
+      if key == "ModelManager_ModelsCache":
+        return qcom_manifest
+      if key == "ModelManager_ModelsCache_USBGPU":
+        return usbgpu_manifest
+      if key in ("ModelManager_LastSyncTime", "ModelManager_LastSyncTime_USBGPU"):
+        return fresh_sync_time()
+      return None
+
+    params.get.side_effect = get
+    return params
+
+  def _fetched(self, *bundles):
+    return ModelFetcher(mock.MagicMock()).model_parser.parse_models({"bundles": list(bundles)})
+
+  def test_qcom_cache_with_big_models_is_refetched(self):
+    """Legacy: the unsuffixed cache holds the big manifest. is_big confirms it is
+    the wrong set for qcom, so a fresh fetch replaces it."""
+    params = self._make_params({"bundles": [manifest_bundle("big", "bbb", is_big=True)]},
+                               {"bundles": [manifest_bundle("big2", "ccc", is_big=True)]})
+    fetcher = ModelFetcher(params)
+    fetched = self._fetched(manifest_bundle("small", "aaa"))
+    with mock.patch.object(fetcher, "_fetch_and_cache_models", return_value=fetched):
+      bundles = fetcher.get_bundles_for_source("qcom")
+    assert [bundle.ref for bundle in bundles] == ["aaa"]
+
+  def test_usbgpu_cache_without_big_models_is_refetched(self):
+    params = self._make_params({"bundles": [manifest_bundle("small", "aaa")]},
+                               {"bundles": [manifest_bundle("big2", "ccc")]})
+    fetcher = ModelFetcher(params)
+    fetched = self._fetched(manifest_bundle("big", "bbb", is_big=True))
+    with mock.patch.object(fetcher, "_fetch_and_cache_models", return_value=fetched):
+      bundles = fetcher.get_bundles_for_source("usbgpu")
+    assert [bundle.ref for bundle in bundles] == ["bbb"]
+
+  def test_matching_caches_are_used_without_fetch(self):
+    params = self._make_params({"bundles": [manifest_bundle("small", "aaa")]},
+                               {"bundles": [manifest_bundle("big", "bbb", is_big=True)]})
+    fetcher = ModelFetcher(params)
+    with mock.patch.object(fetcher, "_fetch_and_cache_models", side_effect=AssertionError("cache should be used")):
+      assert [bundle.ref for bundle in fetcher.get_bundles_for_source("qcom")] == ["aaa"]
+      assert [bundle.ref for bundle in fetcher.get_bundles_for_source("usbgpu")] == ["bbb"]
+
+  def test_stale_version_cache_is_refetched(self):
+    """A source-matching cache whose bundles are all filtered by the selector version
+    check parses to zero valid bundles; it is stale (e.g. an old manifest) and must be
+    refetched instead of silently returning an empty list forever."""
+    stale = manifest_bundle("small", "aaa")
+    stale["minimum_selector_version"] = "16"
+    params = self._make_params({"bundles": [stale]},
+                               {"bundles": [manifest_bundle("big", "bbb", is_big=True)]})
+    fetcher = ModelFetcher(params)
+    fetched = self._fetched(manifest_bundle("small2", "ddd"))
+    with mock.patch.object(fetcher, "_fetch_and_cache_models", return_value=fetched) as fetch:
+      bundles = fetcher.get_bundles_for_source("qcom")
+    fetch.assert_called_once_with("qcom")
+    assert [bundle.ref for bundle in bundles] == ["ddd"]
+
+  def test_mismatched_refetch_happens_once(self):
+    """If the fresh manifest still fails the source check, the URL is authoritative:
+    trust it instead of refetching at 1 Hz forever."""
+    params = self._make_params({"bundles": [manifest_bundle("big", "bbb", is_big=True)]},
+                               {"bundles": [manifest_bundle("big2", "ccc", is_big=True)]})
+    fetcher = ModelFetcher(params)
+    fetched = self._fetched(manifest_bundle("big", "bbb", is_big=True))
+    with mock.patch.object(fetcher, "_fetch_and_cache_models", return_value=fetched) as fetch:
+      first = fetcher.get_bundles_for_source("qcom")
+      second = fetcher.get_bundles_for_source("qcom")
+    fetch.assert_called_once_with("qcom")
+    assert [bundle.ref for bundle in first] == ["bbb"]
+    assert [bundle.ref for bundle in second] == ["bbb"]
+
+  def test_corrupt_cache_is_refetched(self):
+    """A cache that fails to parse (e.g. truncated/foreign JSON) must trigger a
+    refetch instead of raising every loop and never recovering."""
+    corrupt = {"bundles": [{"short_name": "broken"}]}  # missing required fields
+    params = self._make_params(corrupt, {"bundles": [manifest_bundle("big", "bbb", is_big=True)]})
+    fetcher = ModelFetcher(params)
+    fetched = self._fetched(manifest_bundle("small", "aaa"))
+    with mock.patch.object(fetcher, "_fetch_and_cache_models", return_value=fetched) as fetch:
+      bundles = fetcher.get_bundles_for_source("qcom")
+    fetch.assert_called_once_with("qcom")
+    assert [bundle.ref for bundle in bundles] == ["aaa"]
+
+
+class TestActiveBundleValidation(OpenpilotTestCase):
+  """Validation is per-slot: a failed fetch (empty bundle list) must not reset a slot,
+  and resetting one slot must not stomp the runner cache derived from the other."""
+
+  def setUp(self):
+    super().setUp()
+    helpers._LAST_VALIDATED_RAW.clear()
+
+  @staticmethod
+  def _raw_bundle(ref: str, runner: int | None = None) -> dict:
+    bundle = custom.ModelManagerSP.ModelBundle.new_message()
+    bundle.ref = ref
+    bundle.minimumSelectorVersion = 18
+    if runner is not None:
+      bundle.runner = runner
+    return bundle.to_dict()
+
+  def _params(self, qcom=None, usbgpu=None):
+    params = mock.MagicMock()
+
+    def get(key, *args, **kwargs):
+      return {"ModelManager_ActiveBundle": qcom, "ModelManager_ActiveBundleUSBGPU": usbgpu}.get(key)
+
+    params.get.side_effect = get
+    return params
+
+  def test_empty_catalog_does_not_reset_slot(self):
+    params = self._params(qcom=self._raw_bundle("small"))
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=False):
+      validate_active_bundles(params, {"qcom": [], "usbgpu": []})
+    params.remove.assert_not_called()
+
+  def test_reset_recomputes_runner_from_surviving_slot(self):
+    tinygrad = int(custom.ModelManagerSP.Runner.tinygrad)
+    big_raw = self._raw_bundle("big", runner=tinygrad)
+    params = self._params(qcom=self._raw_bundle("gone"), usbgpu=big_raw)
+    catalog = {"qcom": [custom.ModelManagerSP.ModelBundle(**self._raw_bundle("other"))],
+               "usbgpu": [custom.ModelManagerSP.ModelBundle(**big_raw)]}
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=True):
+      validate_active_bundles(params, catalog)
+    params.remove.assert_called_once_with("ModelManager_ActiveBundle")
+    runner_puts = [call for call in params.put.call_args_list if call.args[0] == "ModelRunnerTypeCache"]
+    assert [call.args[1] for call in runner_puts] == [tinygrad]
+
+
+class TestActiveBundleSelection(OpenpilotTestCase):
+  """The effective active bundle is the active source's slot: usbgpu when a GPU is
+  present, qcom otherwise. An empty active slot means the hardware default (stock
+  runner), never the other slot's pick - modeld_v2 requires a real bundle."""
+
+  @staticmethod
+  def _raw_bundle(ref: str) -> dict:
+    bundle = custom.ModelManagerSP.ModelBundle.new_message()
+    bundle.ref = ref
+    bundle.minimumSelectorVersion = 18
+    return bundle.to_dict()
+
+  def _params(self, qcom=None, usbgpu=None):
+    params = mock.MagicMock()
+
+    def get(key, *args, **kwargs):
+      if key == "ModelManager_ActiveBundle":
+        return qcom
+      if key == "ModelManager_ActiveBundleUSBGPU":
+        return usbgpu
+      return None
+
+    params.get.side_effect = get
+    return params
+
+  def test_selected_bundle_is_per_slot(self):
+    params = self._params(qcom=self._raw_bundle("small"), usbgpu=self._raw_bundle("big"))
+    assert get_selected_bundle(params, "qcom").ref == "small"
+    assert get_selected_bundle(params, "usbgpu").ref == "big"
+
+  def test_no_gpu_uses_qcom_slot(self):
+    params = self._params(qcom=self._raw_bundle("small"), usbgpu=self._raw_bundle("big"))
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=False):
+      assert get_active_bundle(params).ref == "small"
+
+  def test_gpu_uses_usbgpu_slot(self):
+    params = self._params(qcom=self._raw_bundle("small"), usbgpu=self._raw_bundle("big"))
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=True):
+      assert get_active_bundle(params).ref == "big"
+
+  def test_gpu_without_big_selection_is_hardware_default(self):
+    params = self._params(qcom=self._raw_bundle("small"), usbgpu=None)
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=True):
+      assert get_active_bundle(params) is None
+
+
+class TestEffectiveSource(OpenpilotTestCase):
+  """One gate decides the active source. With no flags it is runtime truth (GPU
+  attached); display callers (mici) pass the ui_state flags, which additionally
+  require the big model to be loading, active, or the device offroad. The active
+  bundle is simply the selected bundle of that source."""
+
+  @staticmethod
+  def _raw_bundle(ref: str) -> dict:
+    bundle = custom.ModelManagerSP.ModelBundle.new_message()
+    bundle.ref = ref
+    bundle.minimumSelectorVersion = 18
+    return bundle.to_dict()
+
+  def test_runtime_no_gpu(self):
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=False):
+      assert get_active_source() == "qcom"
+
+  def test_runtime_gpu_present(self):
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=True):
+      assert get_active_source() == "usbgpu"
+
+  def test_display_offroad_gpu_present_shows_big(self):
+    assert get_active_source(usbgpu=True, usbgpu_active=False, usbgpu_loading=False, offroad=True) == "usbgpu"
+
+  def test_display_onroad_gpu_loading_shows_big(self):
+    assert get_active_source(usbgpu=True, usbgpu_active=False, usbgpu_loading=True, offroad=False) == "usbgpu"
+
+  def test_display_onroad_gpu_active_shows_big(self):
+    assert get_active_source(usbgpu=True, usbgpu_active=True, usbgpu_loading=False, offroad=False) == "usbgpu"
+
+  def test_display_onroad_gpu_idle_shows_small(self):
+    assert get_active_source(usbgpu=True, usbgpu_active=False, usbgpu_loading=False, offroad=False) == "qcom"
+
+  def test_display_active_none_is_idle(self):
+    assert get_active_source(usbgpu=True, usbgpu_active=None, usbgpu_loading=False, offroad=False) == "qcom"
+
+  def test_active_bundle_follows_source(self):
+    params = mock.MagicMock()
+    params.get.side_effect = lambda key: {"ModelManager_ActiveBundle": self._raw_bundle("small"),
+                                          "ModelManager_ActiveBundleUSBGPU": self._raw_bundle("big")}.get(key)
+    with mock.patch("openpilot.sunnypilot.models.helpers.usbgpu_present", return_value=False):
+      assert get_active_bundle(params).ref == "small"
+    assert get_selected_bundle(params, get_active_source(usbgpu=True, usbgpu_active=False,
+                                                         usbgpu_loading=False, offroad=True)).ref == "big"
+
+
 @unittest.skipUnless(os.environ.get('RUN_INTEGRATION_TESTS'), 'requires external network')
 class TestLiveModelManifest(OpenpilotTestCase):
   """Every artifact and chunk URL in the published manifest must resolve."""
diff --git a/openpilot/sunnypilot/models/tests/test_tinygrad_ref.py b/openpilot/sunnypilot/models/tests/test_tinygrad_ref.py
index fd389f93c0..d6d82dfb32 100644
--- a/openpilot/sunnypilot/models/tests/test_tinygrad_ref.py
+++ b/openpilot/sunnypilot/models/tests/test_tinygrad_ref.py
@@ -1,13 +1,11 @@
 import requests
 
-from openpilot.common.params import Params
 from openpilot.sunnypilot.models.tinygrad_ref import get_tinygrad_ref
 from openpilot.sunnypilot.models.fetcher import ModelFetcher
 from openpilot.common.test import OpenpilotTestCase
 
 def fetch_tinygrad_ref():
-  fetcher = ModelFetcher(Params())
-  response = requests.get(fetcher.model_url, timeout=10)
+  response = requests.get(ModelFetcher.MODEL_URL, timeout=10)
   response.raise_for_status()
   json_data = response.json()
   return json_data.get("tinygrad_ref")
diff --git a/openpilot/sunnypilot/sunnylink/statsd.py b/openpilot/sunnypilot/sunnylink/statsd.py
index 7e8faf6327..a221fc084f 100755
--- a/openpilot/sunnypilot/sunnylink/statsd.py
+++ b/openpilot/sunnypilot/sunnylink/statsd.py
@@ -65,6 +65,7 @@ def sp_stats(end_event):
     'MadsSteeringMode',
     'MadsUnifiedEngagementMode',
     'ModelManager_ActiveBundle',
+    'ModelManager_ActiveBundleUSBGPU',
     'ModelManager_Favs',
     'EnableSunnylinkUploader',
     'SunnylinkEnabled',
diff --git a/openpilot/sunnypilot/system/params_migration.py b/openpilot/sunnypilot/system/params_migration.py
index 130fd64310..f0f0d7248a 100644
--- a/openpilot/sunnypilot/system/params_migration.py
+++ b/openpilot/sunnypilot/system/params_migration.py
@@ -84,6 +84,21 @@ def _migrate_tesla_mads_screen_button(_params):
     cloudlog.exception(f"Error migrating TeslaMadsScreenButton: {e}")
 
 
+def _migrate_model_bundle_slots(_params):
+  # Pre-split, a chestnut user's big-model selection lived in the single
+  # ActiveBundle. Seed both slots; validation drops whichever does not match
+  # its own manifest.
+  try:
+    if _params.get("ModelManager_ActiveBundleUSBGPU") is not None:
+      return
+    if (bundle := _params.get("ModelManager_ActiveBundle")) is None:
+      return
+    _params.put("ModelManager_ActiveBundleUSBGPU", bundle, block=True)
+    cloudlog.info("params_migration: seeded ModelManager_ActiveBundleUSBGPU from ModelManager_ActiveBundle")
+  except Exception as e:
+    cloudlog.exception(f"Error migrating model bundle slots: {e}")
+
+
 def run_migration(_params):
   # migrate OnroadScreenOffBrightness
   if _params.get("OnroadScreenOffBrightnessMigrated") != ONROAD_BRIGHTNESS_MIGRATION_VERSION:
@@ -120,3 +135,6 @@ def run_migration(_params):
 
   # seed TeslaMadsScreenButton for existing Tesla installs
   _migrate_tesla_mads_screen_button(_params)
+
+  # seed the usbgpu model slot from the pre-split single slot
+  _migrate_model_bundle_slots(_params)
diff --git a/openpilot/sunnypilot/system/tests/__init__.py b/openpilot/sunnypilot/system/tests/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/openpilot/sunnypilot/system/tests/test_params_migration.py b/openpilot/sunnypilot/system/tests/test_params_migration.py
new file mode 100644
index 0000000000..328a7a65af
--- /dev/null
+++ b/openpilot/sunnypilot/system/tests/test_params_migration.py
@@ -0,0 +1,36 @@
+"""
+Copyright (c) 2021-, Haibin Wen, sunnypilot, and a number of other contributors.
+
+This file is part of sunnypilot and is licensed under the MIT License.
+See the LICENSE.md file in the root directory for more details.
+"""
+
+from openpilot.common.params import Params
+from openpilot.common.test import OpenpilotTestCase
+from openpilot.sunnypilot.system.params_migration import _migrate_model_bundle_slots
+
+
+class TestModelBundleSlotMigration(OpenpilotTestCase):
+  """Pre-split, a chestnut user's big-model selection lived in the single ActiveBundle.
+  The migration seeds both slots; per-source validation later drops whichever does not
+  match its own manifest."""
+
+  def test_seeds_usbgpu_slot_from_active_bundle(self):
+    params = Params()
+    bundle = {"ref": "big", "minimumSelectorVersion": 18}
+    params.put("ModelManager_ActiveBundle", bundle, block=True)
+    _migrate_model_bundle_slots(params)
+    assert params.get("ModelManager_ActiveBundleUSBGPU") == bundle
+    assert params.get("ModelManager_ActiveBundle") == bundle
+
+  def test_noop_when_usbgpu_slot_already_set(self):
+    params = Params()
+    params.put("ModelManager_ActiveBundle", {"ref": "small"}, block=True)
+    params.put("ModelManager_ActiveBundleUSBGPU", {"ref": "big"}, block=True)
+    _migrate_model_bundle_slots(params)
+    assert params.get("ModelManager_ActiveBundleUSBGPU") == {"ref": "big"}
+
+  def test_noop_when_no_selection(self):
+    params = Params()
+    _migrate_model_bundle_slots(params)
+    assert params.get("ModelManager_ActiveBundleUSBGPU") is None
diff --git a/openpilot/system/ui/sunnypilot/lib/utils.py b/openpilot/system/ui/sunnypilot/lib/utils.py
index b9ed152aff..6ae30d13ae 100644
--- a/openpilot/system/ui/sunnypilot/lib/utils.py
+++ b/openpilot/system/ui/sunnypilot/lib/utils.py
@@ -8,12 +8,26 @@ from collections.abc import Callable
 
 import pyray as rl
 
-from openpilot.system.ui.lib.application import FontWeight
+from openpilot.system.ui.lib.application import gui_app, FontWeight
 from openpilot.system.ui.sunnypilot.lib.styles import style
 from openpilot.system.ui.sunnypilot.widgets.list_view import ButtonActionSP
-from openpilot.system.ui.widgets.label import UnifiedLabel
+from openpilot.system.ui.widgets.label import ScrollState, UnifiedLabel
 from openpilot.system.ui.widgets.list_view import BUTTON_WIDTH, BUTTON_HEIGHT, TEXT_PADDING, _resolve_value
 
+SCROLL_SPEED = 1.2  # stock is 0.8, boosted 50% to compensate for larger font (50 vs 32)
+SCROLL_REFERENCE_FPS = 60.
+
+
+class UnifiedLabelSP(UnifiedLabel):
+  # stock scroll formula (0.8 / 60 * fps) is inverted — pre-correct so speed is constant px/sec
+  def _render(self, _):
+    if self._needs_scroll and self._scroll_state == ScrollState.SCROLLING:
+      fps = gui_app.target_fps
+      wrong_step = 0.8 / SCROLL_REFERENCE_FPS * fps
+      correct_step = SCROLL_SPEED * SCROLL_REFERENCE_FPS / fps
+      self._scroll_offset -= (correct_step - wrong_step)
+    super()._render(_)
+
 
 class NoElideButtonAction(ButtonActionSP):
   def get_width_hint(self):
@@ -21,14 +35,12 @@ class NoElideButtonAction(ButtonActionSP):
 
 
 class ScrollingButtonAction(ButtonActionSP):
-  """ButtonActionSP whose value scrolls instead of eliding when it doesn't fit."""
-
   def __init__(self, text: str | Callable[[], str], width: int = style.BUTTON_ACTION_WIDTH,
                enabled: bool | Callable[[], bool] = True):
     super().__init__(text=text, width=width, enabled=enabled)
-    self._value_label = UnifiedLabel("", font_size=style.ITEM_TEXT_FONT_SIZE, font_weight=FontWeight.NORMAL,
-                                     text_color=self._value_color, scroll=True,
-                                     alignment_vertical=rl.GuiTextAlignmentVertical.TEXT_ALIGN_MIDDLE)
+    self._value_label = UnifiedLabelSP("", font_size=style.ITEM_TEXT_FONT_SIZE, font_weight=FontWeight.NORMAL,
+                                       text_color=self._value_color, scroll=True,
+                                       alignment_vertical=rl.GuiTextAlignmentVertical.TEXT_ALIGN_MIDDLE)
 
   def set_value(self, value: str | Callable[[], str], color: rl.Color = style.ITEM_TEXT_VALUE_COLOR):
     if self.value != _resolve_value(value, ""):