BerriAI/litellm · error · ValueError

api_base is required

Error message

api_base is required

What it means

The base InteractionsAPIConfig get_complete_url raises ValueError when api_base is None. Interactions (OpenAI Responses-style agent/model interaction endpoints) require a concrete base URL; the default implementation just returns api_base, so a None value is rejected before the HTTP client would produce a nonsense request.

Source

Thrown at litellm/llms/base_llm/interactions/transformation.py:118

        stream: bool | None = None,
    ) -> str:
        """
        Get the complete URL for the interaction request.

        Per OpenAPI spec: POST /{api_version}/interactions

        Args:
            api_base: Base URL for the API
            model: The model name (for model interactions)
            agent: The agent name (for agent interactions)
            litellm_params: LiteLLM parameters
            stream: Whether this is a streaming request

        Returns:
            The complete URL for the request
        """
        if api_base is None:
            raise ValueError("api_base is required")
        return api_base

    @abstractmethod
    def transform_request(
        self,
        model: str | None,
        agent: str | None,
        input: InteractionInput | None,
        optional_params: InteractionsAPIOptionalRequestParams,
        litellm_params: GenericLiteLLMParams,
        headers: dict,
    ) -> dict:
        """
        Transform the input request into the provider's expected format.

        Per OpenAPI spec, the request body should be either:
        - CreateModelInteractionParams (with model)
        - CreateAgentInteractionParams (with agent)

View on GitHub (pinned to 6c2dcb801b)

Solutions

1. Pass api_base with the request (litellm_params={'api_base': ...}).
2. Set the matching provider env var (e.g. OPENAI_API_BASE).
3. Add api_base to the proxy model config used by interactions routes.
4. Provider authors: override get_complete_url in the InteractionsAPIConfig subclass with a sane default.

Example fix

# before
litellm.interactions(model='my-provider/agent-1', input='hi')  # api_base None

# after
litellm.interactions(model='my-provider/agent-1', input='hi', api_base='https://host/v1')

def validate_interactions_call(api_base: str | None) -> None:
    if api_base is None and not os.environ.get('OPENAI_API_BASE'):
        raise ConfigError('interactions API requires api_base')

try:
    litellm.interactions(...)
except ValueError as e:
    if 'api_base is required' in str(e):
        raise ConfigError('set api_base or OPENAI_API_BASE for interactions') from e
    raise

When it happens

Trigger: Calling the interactions API (litellm.interactions / proxy /v1/interactions routes) for a provider whose params contain no api_base: missing <PROVIDER>_API_BASE env, custom provider registered without a default base URL, or proxy model entry lacking api_base.

Common situations: Self-hosted OpenAI-compatible servers used for interactions without base URL configuration; new provider configs that only set transform_request; environment differences between local (env set) and CI/deploy (env missing).

Related errors

• api_base is required for Azure AI Studio. Please set the api
• api_base is required
• api_base is required
• api_base is required
• API base is required for OpenAI image variations

AI-assisted analysis of BerriAI/litellm@6c2dcb801b (2026-08-15). Data as JSON: /api/errors/fd31b5b362781ac8. Report an issue: GitHub.