diff --git a/klausur-service/backend/page_crop.py b/klausur-service/backend/page_crop.py
index 1356fdd..108e095 100644
--- a/klausur-service/backend/page_crop.py
+++ b/klausur-service/backend/page_crop.py
@@ -535,19 +535,30 @@ def _detect_gutter_continuity(
     if region_w <= 2 * margin + 10:
         return None
 
-    # Scan from edge inward to find where frac drops below transition threshold
+    # Find the peak of dark fraction (gutter center).
+    # For right gutters the peak is near the edge; for left gutters
+    # (V-shaped spine shadow) the peak may be well inside the region.
     transition_thresh = 0.50
+    peak_frac = float(np.max(frac_smooth[margin:region_w - margin]))
+
+    if peak_frac < 0.70:
+        logger.debug(
+            "%s gutter: peak dark fraction %.2f < 0.70", side.capitalize(), peak_frac,
+        )
+        return None
+
+    peak_x = int(np.argmax(frac_smooth[margin:region_w - margin])) + margin
     gutter_inner = None  # local x in search_region
 
     if side == "right":
-        # Scan from right edge (region_w - 1) inward (toward 0)
-        for x in range(region_w - 1 - margin, margin, -1):
+        # Scan from peak toward the page center (leftward)
+        for x in range(peak_x, margin, -1):
             if frac_smooth[x] < transition_thresh:
-                gutter_inner = x + 1  # crop just past the transition
+                gutter_inner = x + 1
                 break
     else:
-        # Scan from left edge (0) inward (toward region_w)
-        for x in range(margin, region_w - margin):
+        # Scan from peak toward the page center (rightward)
+        for x in range(peak_x, region_w - margin):
             if frac_smooth[x] < transition_thresh:
                 gutter_inner = x - 1
                 break