fix: handle degenerate bbox and unhandled exceptions in inspection frame endpoint

Cast bbox coordinates to int in crop_frame to prevent numpy float indexing errors.
Add error handling for ValueError/OSError in the /inspect/frame endpoint to return
422 instead of 500 when frame extraction or cropping fails.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

inspection/frames.py

@@ -77,7 +77,7 @@ def crop_frame(
     Returns:
         Cropped HxWx3 BGR numpy array.
     """
-    x1, y1, x2, y2 = bbox
+    x1, y1, x2, y2 = int(bbox[0]), int(bbox[1]), int(bbox[2]), int(bbox[3])
     if x2 <= x1 or y2 <= y1:
         raise ValueError(
             f"Invalid bbox: [{x1}, {y1}, {x2}, {y2}] — must have x2 > x1 and y2 > y1"

inspection/router.py

@@ -99,7 +99,10 @@ async def get_frame(
     _validate_frame_idx(input_path, frame_idx)
 
     # Extract frame in thread pool (cv2 seek can block)
-    frame = await asyncio.to_thread(extract_frame, input_path, frame_idx)
+    try:
+        frame = await asyncio.to_thread(extract_frame, input_path, frame_idx)
+    except (ValueError, OSError) as exc:
+        raise HTTPException(status_code=422, detail=str(exc))
 
     # Optionally crop to track bbox
     if track_id is not None:
@@ -110,7 +113,18 @@ async def get_frame(
         instance_id = _parse_track_id(track_id)
         target = _find_track(tracks, instance_id, track_id)
         if target and "bbox" in target:
-            frame = crop_frame(frame, target["bbox"], padding=padding)
+            bbox = target["bbox"]
+            # Validate bbox is non-degenerate before cropping
+            x1, y1, x2, y2 = [int(c) for c in bbox]
+            if x2 <= x1 or y2 <= y1:
+                raise HTTPException(
+                    status_code=422,
+                    detail=f"Track {track_id} has a degenerate bbox [{x1},{y1},{x2},{y2}] at frame {frame_idx}.",
+                )
+            try:
+                frame = crop_frame(frame, [x1, y1, x2, y2], padding=padding)
+            except ValueError as exc:
+                raise HTTPException(status_code=422, detail=str(exc))
         else:
             raise HTTPException(
                 status_code=404,