Update interface.py

interface.py

@@ -32,6 +32,7 @@ def create_sample_data():
 def load_messages_from_file(file_obj):
     """
     Read uploaded CSV or Excel file and convert to JSON string of message dicts.
+    Handles pandas Timestamp conversion to strings.
     """
     ext = os.path.splitext(file_obj.name)[1].lower()
     try:
@@ -44,8 +45,17 @@ def load_messages_from_file(file_obj):
     except Exception as e:
         return {'error': f'Failed to read file: {e}'}
 
-    messages_data = df.to_dict(orient='records')
-    return json.dumps(messages_data)
+    # Convert DataFrame to list of dicts
+    records = df.to_dict(orient='records')
+    # Serialize pandas Timestamps to ISO strings
+    for rec in records:
+        for key, val in rec.items():
+            if hasattr(val, 'isoformat'):
+                try:
+                    rec[key] = val.isoformat()
+                except Exception:
+                    rec[key] = str(val)
+    return json.dumps(records)
 
 
 def analyze_uploaded_file(file_obj):