From ed08d4152bba56144764dbd1bec3f4408c76fd27 Mon Sep 17 00:00:00 2001
From: Josh Hawkins <32435876+hawkeye217@users.noreply.github.com>
Date: Fri, 22 May 2026 08:48:19 -0500
Subject: [PATCH] discard tracked-object state when detect resolution changes
 mid-session

When detect resolution changes mid-session every tracked object we hold
was localized against the old pixel grid. Their boxes no longer
correspond to anything in the new frame, and the `end` callback that
fires when their IDs disappear from the new detect process's detections
publishes those stale boxes to consumers (LPR, snapshot crop) that slice
the new frame and crash on empty arrays. Drop the tracked-object state
on a shape change so no stale boxes ever cross the CameraState boundary.

Belt-and-suspenders: also drop any incoming batch whose boxes exceed the
current detect resolution. These are in-flight queue entries from the
pre-recycle detect process that beat the new detect process to the
queue; processing them would re-introduce stale-resolution tracked
objects we just dropped above. The per-camera detect process clamps
legitimate boxes to detect.width-1 / detect.height-1, so any coord
beyond that is unambiguously stale.
---
 frigate/camera/state.py | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/frigate/camera/state.py b/frigate/camera/state.py
index dc44e7a88e..f0cf553e52 100644
--- a/frigate/camera/state.py
+++ b/frigate/camera/state.py
@@ -45,6 +45,7 @@ class CameraState:
         self.frame_cache: dict[float, dict[str, Any]] = {}
         self.zone_objects: defaultdict[str, list[Any]] = defaultdict(list)
         self._current_frame = np.zeros(self.camera_config.frame_shape_yuv, np.uint8)
+        self._last_frame_shape: tuple[int, int] = self.camera_config.frame_shape_yuv
         self.current_frame_lock = threading.Lock()
         self.current_frame_time = 0.0
         self.motion_boxes: list[tuple[int, int, int, int]] = []
@@ -311,6 +312,31 @@ class CameraState:
         motion_boxes: list[tuple[int, int, int, int]],
         regions: list[tuple[int, int, int, int]],
     ) -> None:
+        # detect resolution changed — drop tracked state so old-grid
+        # boxes don't leak through end-callbacks
+        current_shape = self.camera_config.frame_shape_yuv
+        if current_shape != self._last_frame_shape:
+            logger.debug(
+                f"{self.name}: detect resolution changed {self._last_frame_shape} -> {current_shape}, dropping tracked state"
+            )
+            with self.current_frame_lock:
+                self.tracked_objects.clear()
+                self.motion_boxes = []
+                self.regions = []
+            self._last_frame_shape = current_shape
+
+        # drop in-flight batches from the pre-recycle detect process
+        # whose boxes exceed the current detect resolution
+        detect = self.camera_config.detect
+        if detect.width is not None and detect.height is not None:
+            for obj in current_detections.values():
+                box = obj.get("box")
+                if box and (box[2] > detect.width or box[3] > detect.height):
+                    logger.debug(
+                        f"{self.name}: dropping stale-resolution detection batch (box {box} exceeds {detect.width}x{detect.height})"
+                    )
+                    return
+
         current_frame = self.frame_manager.get(
             frame_name, self.camera_config.frame_shape_yuv
         )