---
description: Known runtime issues when running Opik Optimizer with current dependencies.
headline: Known Issues
title: Known Issues
canonical-url: https://www.comet.com/docs/opik/development/optimization-runs/known_issues
---

<Note>
  In Opik 2.0, datasets and experiments are project-scoped. Make sure to specify a `project_name` when creating datasets and running experiments so they are associated with the correct project.
</Note>

## Known Issues

<AccordionGroup>
  <Accordion title="Rate limiter errors (pyrate-limiter 4.x)">
    If `pyrate-limiter` 4.x is installed you may see `TypeError: Limiter.__init__() got an unexpected keyword argument 'raise_when_fail'`. That version dropped the legacy flag our optimizer still passes.

    **Workaround**: pin `pyrate-limiter` to a 3.x release:
    ```bash
    pip install "pyrate-limiter>=3.0.0,<4.0.0"
    ```

    **Fixed in**: `3.0.0` (2026-01-26). Upgrade the SDK to remove the legacy flag entirely.
  </Accordion>

  <Accordion title="tqdm / rich progress error (tqdm >= 4.71)">
    `convert_tqdm_to_rich.<locals>._tqdm_to_track() missing 1 required positional argument: 'iterable'` comes from `tqdm` >= 4.71 changing the wrapper signature we rely on.

    **Workaround**: pin `tqdm` to 4.70.0:
    ```bash
    pip install tqdm==4.70.0
    ```

    **Fixed in**: `3.0.0` (2026-01-26).
  </Accordion>

  <Accordion title="Pydantic serialization warnings">
    `PydanticSerializationUnexpectedValue` is emitted when LiteLLM serializes `Message` objects with fewer fields than the schema (an upstream change in LiteLLM/Pydantic v2). We suppress the warning because the payload is still valid.

    **Workaround**: avoid the affected LiteLLM builds:
    ```bash
    pip install --upgrade "litellm<1.81.1"
    ```

    **Fixed in**: `3.0.0` (2026-01-26).
  </Accordion>

  <Accordion title="litellm → OpenAI connection errors (1.81.x)">
    `litellm.InternalServerError: OpenAIException - Connection error.` has been reproducible against LiteLLM `1.81.*`. These releases can break the OpenAI evaluation flow inside Opik Optimizer.
 
    **Workaround**:
    ```bash
    pip install --upgrade "litellm<1.81.0"
    ```

    **Fixed in**: `3.0.0` (2026-01-26).
  </Accordion>
</AccordionGroup>

## Common Errors

<AccordionGroup>
  <Accordion title="ValueError: Prompt must be a ChatPrompt object">
    This error occurs when you pass an incorrect type to the optimizer's `optimize_prompt()` method.

    **Solution**: Ensure you're using the `ChatPrompt` class to define your prompt:
    ```python
    from opik_optimizer import ChatPrompt

    prompt = ChatPrompt(
        messages=[
            {"role": "system", "content": "Your system prompt here"},
            {"role": "user", "content": "Your user prompt with {variable}"},
        ],
        model="gpt-4",
    )
    ```
  </Accordion>

  <Accordion title="ValueError: Dataset must be a Dataset object">
    This error occurs when the dataset passed to the optimizer is not a proper `Dataset` object.

    **Solution**: Use the `Dataset` class to create your dataset:
    ```python
    import opik

    client = opik.Opik()
    dataset = client.get_or_create_dataset(name="your-dataset-name", project_name="my-project")
    dataset.insert(
        [
            {"input": "example 1", "output": "expected 1"},
            {"input": "example 2", "output": "expected 2"},
        ]
    )
    ```
  </Accordion>

  <Accordion title="ValueError: Metric must be a function">
    This error occurs when the metric parameter is not callable or doesn't have the correct signature.

    **Solution**: Ensure your metric is a function that takes `dataset_item` and `llm_output` as arguments and returns a `ScoreResult`:
    ```python
    from opik.evaluation.metrics import ScoreResult

    def my_metric(dataset_item, llm_output):
        # Your scoring logic here
        score = calculate_score(dataset_item, llm_output)
        return ScoreResult(
            name="my-metric",
            value=score,
            reason="Explanation for the score",
        )
    ```
  </Accordion>

  <Accordion title="ValueError: Missing required key in prompt">
    This error occurs when your prompt template contains placeholders (e.g., `{variable}`) that don't match your dataset fields.

    **Solution**: Ensure all placeholders in your prompt match the keys in your dataset:
    ```python
    # Prompt with {question} placeholder
    prompt = ChatPrompt(
        user="Answer: {question}",
        model="gpt-4",
    )

    # Dataset must have 'question' field
    dataset = Dataset.from_list(
        [
            {"question": "What is AI?", "output": "..."},
        ]
    )
    ```
  </Accordion>

  <Accordion title="ImportError: gepa package is required for GepaOptimizer">
    This error occurs when trying to use the `GepaOptimizer` without the required `gepa` package installed.

    **Solution**: Install the gepa package:
    ```bash
    pip install gepa
    ```
  </Accordion>

  <Accordion title="Exception: Make sure you have provider API key set">
    This error typically occurs when the LLM provider API key is not configured in your environment.

    **Solution**: Set the appropriate environment variable for your LLM provider:
    ```bash
    # For OpenAI
    export OPENAI_API_KEY="your-api-key"

    # For Anthropic
    export ANTHROPIC_API_KEY="your-api-key"

    # For other providers, check the LiteLLM documentation
    ```
  </Accordion>
</AccordionGroup>