microsoft/autogen · error · FormatNotSupportedError

Unknown format `{value['format']}` for `{key}` in `{model_na

Error message

Unknown format `{value['format']}` for `{key}` in `{model_name}`

What it means

Error "Unknown format `{value['format']}` for `{key}` in `{model_name}`" thrown in microsoft/autogen.

Source

Thrown at python/packages/autogen-core/src/autogen_core/utils/_json_to_pydantic.py:288

                item_model_name = self._get_item_model_name(key, model_name)
                item_type = self._json_schema_to_model(item_schema, item_model_name, root_schema)
            else:
                item_type_name = item_schema.get("type")
                if item_type_name is None:
                    item_type = str
                elif item_type_name not in TYPE_MAPPING:
                    raise UnsupportedKeywordError(
                        f"Unsupported or missing item type `{item_type_name}` for array field `{key}` in `{model_name}`"
                    )
                else:
                    item_type = TYPE_MAPPING[item_type_name]

            base_type = conlist(item_type, **constraints) if constraints else List[item_type]  # type: ignore[valid-type]

        if "format" in value:
            format_type = FORMAT_MAPPING.get(value["format"])
            if format_type is None:
                raise FormatNotSupportedError(f"Unknown format `{value['format']}` for `{key}` in `{model_name}`")
            if not isinstance(format_type, type):
                return format_type
            if not issubclass(format_type, str):
                return format_type
            return format_type

        return base_type

    def _json_schema_to_model(
        self, schema: Dict[str, Any], model_name: str, root_schema: Dict[str, Any]
    ) -> Type[BaseModel]:
        if "allOf" in schema:
            merged: Dict[str, Any] = {"type": "object", "properties": {}, "required": []}
            for s in schema["allOf"]:
                part = self._resolve_ref(s["$ref"], root_schema) if "$ref" in s else s
                merged["properties"].update(part.get("properties", {}))
                merged["required"].extend(part.get("required", []))
            for k, v in schema.items():

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Use a recognized format or remove it

Example fix

Drop unknown 'format' or map it to a supported one

When it happens

Trigger: Thrown at python/packages/autogen-core/src/autogen_core/utils/_json_to_pydantic.py:288 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/a49fdeb56d7ae0d5. Report an issue: GitHub.