Fix batch item lookup to match by sequence_number field

get_batch_item now searches for the item whose sequence_number field
matches the requested number, instead of using array position. Falls
back to index-based lookup for data without sequence_number fields.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

json_loader.py

@@ -21,11 +21,15 @@ def to_int(val: Any) -> int:
         return 0
 
 def get_batch_item(data: dict[str, Any], sequence_number: int) -> dict[str, Any]:
-    """Resolve batch item by sequence_number, clamping to valid range."""
+    """Resolve batch item by sequence_number field, falling back to array index."""
     if KEY_BATCH_DATA in data and isinstance(data[KEY_BATCH_DATA], list) and len(data[KEY_BATCH_DATA]) > 0:
+        # Search by sequence_number field first
+        for item in data[KEY_BATCH_DATA]:
+            if int(item.get("sequence_number", 0)) == sequence_number:
+                return item
+        # Fallback to array index
         idx = max(0, min(sequence_number - 1, len(data[KEY_BATCH_DATA]) - 1))
-        if sequence_number - 1 != idx:
-            logger.warning(f"Sequence {sequence_number} out of range (1-{len(data[KEY_BATCH_DATA])}), clamped to {idx + 1}")
+        logger.warning(f"No item with sequence_number={sequence_number}, falling back to index {idx}")
         return data[KEY_BATCH_DATA][idx]
     return data
 

tests/test_json_loader.py

@@ -31,7 +31,16 @@ class TestToInt:
 
 
 class TestGetBatchItem:
-    def test_valid_index(self):
+    def test_lookup_by_sequence_number_field(self):
+        data = {"batch_data": [
+            {"sequence_number": 1, "a": "first"},
+            {"sequence_number": 5, "a": "fifth"},
+            {"sequence_number": 3, "a": "third"},
+        ]}
+        assert get_batch_item(data, 5) == {"sequence_number": 5, "a": "fifth"}
+        assert get_batch_item(data, 3) == {"sequence_number": 3, "a": "third"}
+
+    def test_fallback_to_index(self):
         data = {"batch_data": [{"a": 1}, {"a": 2}, {"a": 3}]}
         assert get_batch_item(data, 2) == {"a": 2}