predict error

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Describe the bug
log show:[2026-03-09 05:21:04,764] [ml.models::_get_predictions_from_ml_backend::297] [ERROR] Error occurred: 500 Server Error: INTERNAL SERVER ERROR for url: http://localhost:9090/predict

payload={'tasks': [{'id': 11, 'data': {'uid': 25001, 'id': 42807, 'stars': 0,
                                             'review': 'One is a good first effort by a novice director. Good acting, excellent special effects and cameos by Cleveland news celebrities make this a relatively painless way to spend a couple hours. The weak points were the script and editing which made the story confusing in some parts and overly simplistic in others. Tomeric shows that he has the technical skill to make a reasonable science fiction movie- it will be interesting to see what he can do with a decent script in a more challenging genre like comedy or drama.',
                                             'type': 'Train', 'filename': './train/unsup/42807_0.txt',
                                             'url': 'http://www.imdb.com/title/tt0227189/usercomments'}, 'meta': {},
                          'created_at': '2026-03-03T07:00:34.363732Z', 'updated_at': '2026-03-03T07:00:34.363744Z',
                          'is_labeled': False, 'overlap': 1, 'inner_id': 2, 'total_annotations': 0,
                          'cancelled_annotations': 0, 'total_predictions': 0, 'comment_count': 0,
                          'unresolved_comment_count': 0, 'last_comment_updated_at': None, 'project': 10,
                          'updated_by': None, 'file_upload': 24, 'comment_authors': [], 'annotations': [],
                          'predictions': []}], 'project': '10.1772520650',
               'label_config': '<View>\n  <Text name="text" value="$review"/>\n  <View style="box-shadow: 2px 2px 5px #999;                padding: 20px; margin-top: 2em;                border-radius: 5px;">\n    <Header value="Choose text sentiment"/>\n    <Choices name="sentiment" toName="text" choice="single" showInLine="true">\n      <Choice value="Positive"/>\n      <Choice value="Negative"/>\n      <Choice value="Neutral"/>\n    </Choices>\n  </View>\n</View><!-- {\n  "data": {"text": "This is a great 3D movie that delivers everything almost right in your face."}\n} -->',
               'params': {'login': None, 'password': None, 'context': None}}

    req = requests.post("http://localhost:9090/predict", json=payload)
    print(req.json())
#{'detail': "ValueError: No control tag of type TextArea and object tag of type ('Image', 'Text', 'HyperText', 'Paragraphs') found in label config", 'request': {}, 'result': {'traceback': 'Traceback (most recent call last):\n  File "/usr/local/lib/python3.12/site-packages/label_studio_ml/exceptions.py", line 39, in exception_f\n    return f(*args, **kwargs)\n           ^^^^^^^^^^^^^^^^^^\n  File "/usr/local/lib/python3.12/site-packages/label_studio_ml/api.py", line 69, in _predict\n    response = model.predict(tasks, context=context, **params)\n               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File "/app/model.py", line 284, in predict\n    prompt_tag, object_tag = self._find_prompt_tags()\n                             ^^^^^^^^^^^^^^^^^^^^^^^^\n  File "/app/model.py", line 219, in _find_prompt_tags\n    prompt_from_name, prompt_to_name, value = li.get_first_tag_occurence(\n                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File "/usr/local/lib/python3.12/site-packages/label_studio_sdk/label_interface/interface.py", line 1324, in get_first_tag_occurence\n    raise ValueError(\nValueError: No control tag of type TextArea and object tag of type (\'Image\', \'Text\', \'HyperText\', \'Paragraphs\') found in label config\n'}, 'status': 500}

[2026-03-09 06:43:04,785] [DEBUG] [label_studio_ml.api::log_response_info::193] Response body: b'{"detail":"ValueError: No control tag of type TextArea and object tag of type ('Image', 'Text', 'HyperText', 'Paragraphs') found in label config","request":{},"result":{"traceback":"Traceback (most recent call last):\n File \"/usr/local/lib/python3.12/site-packages/label_studio_ml/exceptions.py\", line 39, in exception_f\n return f(*args, **kwargs)\n ^^^^^^^^^^^^^^^^^^\n File \"/usr/local/lib/python3.12/site-packages/label_studio_ml/api.py\", line 69, in _predict\n response = model.predict(tasks, context=context, **params)\n ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n File \"/app/model.py\", line 284, in predict\n prompt_tag, object_tag = self._find_prompt_tags()\n ^^^^^^^^^^^^^^^^^^^^^^^^\n File \"/app/model.py\", line 219, in _find_prompt_tags\n prompt_from_name, prompt_to_name, value = li.get_first_tag_occurence(\n ^^^^^^^^^^^^^^^^^^^^^^^^^^^\n File \"/usr/local/lib/python3.12/site-packages/label_studio_sdk/label_interface/interface.py\", line 1324, in get_first_tag_occurence\n raise ValueError(\nValueError: No control tag of type TextArea and object tag of type ('Image', 'Text', 'HyperText', 'Paragraphs') found in label config\n"},"status":500}\n'

[heidi-humansignal]

Hello,

Thank you for contacting Label Studio,

The /predict request is reaching your ML backend, but the backend code you’re running expects a different labeling configuration than the one you’re sending.
Your payload’s label_config is a text classification config:

• <Text name="text" value="$review"/>
• <Choices name="sentiment" toName="text" ...> ... </Choices>

But the ML backend crashes with:
ValueError: No control tag of type TextArea and object tag of type ('Image', 'Text', 'HyperText', 'Paragraphs') found in label config
That error means the backend’s model.py is trying to locate a <TextArea> control tag (typically used as a “prompt” input) via the Label Studio SDK label interface parser, and it cannot find one. it’s a mismatch between the backend you’re using and the project labeling interface you configured.

Could you please double-check the project labeling interface ?
Best Regards!

Comment by Oussama Assili
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