diff --git a/buggy.py b/buggy.py
--- a/buggy.py
+++ b/buggy.py
@@ -7,7 +7,7 @@ def merge_sorted(left: List[int], right: List[int]) -> List[int]:
     i, j = 0, 0
     while i < len(left) and j < len(right):
-        if left[i] >= right[j]:  # Bug: should be <= for stable ascending merge
+        if left[i] <= right[j]:
             result.append(left[i])
             i += 1
         else:
