Update app.py

app.py

@@ -722,6 +722,7 @@ CRITICAL RULES:
 5.  **SINGLE JSON OUTPUT:** Print exactly ONE JSON object at the end of your script. Do not print debug statements or multiple JSON objects.
 6.  **VALID JSON STRUCTURE:** The output MUST be a dictionary/object, not an array or primitive value.
 7.  **SAFE DATA JOINING:** When joining/merging dataframes or looking up values across dataframes, ALWAYS check if matches exist before accessing with `.iloc[0]`. Use `.merge()` with `how='left'` or check `len(filtered_df) > 0` before accessing rows. Never assume keys will match exactly between dataframes.
+8.  **CONSISTENT COLUMN NAMES:** After aggregation or renaming, always use the NEW column names in subsequent operations. Track renamed columns carefully - if you rename 'Zone' to 'zone', use 'zone' everywhere after.
 
 --- USER'S SCENARIO ---
 {user_scenario}