OpenBB-finance/OpenBB · error · ValueError

Failed to convert chart to JSON

Error message

Failed to convert chart to JSON

What it means

Thrown by the OmniWidgetResponseModel Pydantic model_validator when the content is detected as a plotly Figure (duck-typed by class name) but calling Figure.to_json() raises. The widget response pipeline serializes charts to JSON for the frontend; any exception during plotly serialization is wrapped in this ValueError.

Source

Thrown at openbb_platform/extensions/platform_api/openbb_platform_api/response_models.py:239

            )

        # If parameter was supplied, assume the data is formatted correctly.
        if content and parse_as:
            data_format = {
                "data_type": "object",
                "parse_as": parse_as,
            }
            values.data_format = data_format
            del values.parse_as

            return values

        if content.__class__.__name__ == "Figure":
            values.parse_as = "chart"
            try:
                content = content.to_json()
            except Exception as e:
                raise ValueError("Failed to convert chart to JSON") from e
            values.content = content
        elif isinstance(content, dict) and "layout" in content and "data" in content:
            values.parse_as = "chart"
        elif isinstance(content, list) and all(
            isinstance(item, dict) for item in content
        ):
            values.parse_as = "table"
        elif isinstance(content, pd.DataFrame):
            values.parse_as = "table"
            try:
                content = json.loads(content.to_json(orient="records"))
            except Exception as e:
                raise ValueError("Failed to convert DataFrame to JSON") from e
            values.content = content
        elif isinstance(content, dict) and all(
            isinstance(v, list) for v in content.values()
        ):
            values.parse_as = "table"

View on GitHub (pinned to 3e071fcc2c)

Solutions

1. Verify the object is a plotly.graph_objs.Figure (or plotly FigureWidget), not a matplotlib.figure.Figure.
2. Test fig.to_json() standalone in a REPL to surface the underlying exception chained via __cause__.
3. Pre-convert the Figure yourself with json.loads(fig.to_json()) and pass the resulting dict, or pass parse_as='chart' with the already-serialized dict {'data':..., 'layout':...}.
4. Sanitize the Figure before passing it: cast Timestamp indices to strings and replace non-serializable values.

Example fix

# before
resp = OmniWidgetResponseModel(content=matplotlib_fig)  # wrong Figure class

# after
import plotly.graph_objects as go
fig = go.Figure(...)  # plotly Figure
resp = OmniWidgetResponseModel(content=fig)

from plotly.graph_objs import Figure
if not isinstance(content, Figure):
    raise TypeError("content must be a plotly Figure, dict, or list of records")
content = json.loads(content.to_json())  # fail early, before the model validator

def is_plotly_figure(obj) -> bool:
    return obj.__class__.__name__ == "Figure" and hasattr(obj, "to_json")

try:
    resp = OmniWidgetResponseModel(content=fig)
except ValueError as e:
    if "chart to JSON" in str(e) and e.__cause__:
        logger.error("plotly serialization failed: %s", e.__cause__)
    raise

When it happens

Trigger: Constructing OmniWidgetResponseModel(content=<plotly Figure object>) where the Figure contains objects plotly cannot serialize (e.g. custom dtypes, NaN-heavy data, non-JSON-serializable custom trace attributes, or a numpy array inside hovertemplate data), or where 'Figure' is a different class that also has a failing to_json().

Common situations: Passing a matplotlib figure (also named Figure) instead of a plotly one; a Figure built from a DataFrame with Timestamp/TimestampTZ indices or Decimal values that plotly's JSON encoder rejects; plotly version changes that alter to_json behavior.

Related errors

• Failed to convert DataFrame to JSON
• Failed to convert dictionary of lists to list of records
• At least one extension type must be selected.
• Incorrect email or password
• Charting is not installed. Please install `openbb-charting`.

AI-assisted analysis of OpenBB-finance/OpenBB@3e071fcc2c (2026-08-14). Data as JSON: /api/errors/6c92b8a8f6cf66dc. Report an issue: GitHub.