BerriAI/litellm · error · NotImplementedError

LAR-1 routing only supports async routing. Enable async_only

Error message

LAR-1 routing only supports async routing. Enable async_only_mode on the router or use acompletion.

What it means

Raised by LAR1RoutingStrategy.get_available_deployment: the strategy only implements async deployment selection, and it was invoked on a sync routing path (router not in async_only_mode / non-acompletion call).

Source

Thrown at litellm/router_strategy/lar1_routing.py:177

    ) -> tuple[dict | None, bool]:
        if not deployments:
            return None, False

        for deployment in deployments:
            if not isinstance(deployment, dict):
                continue
            model_type = deployment.get("model_info", {}).get("type", "")
            if model_type == target_type:
                return deployment, True

        for deployment in deployments:
            if isinstance(deployment, dict):
                return deployment, False

        return None, False

    def get_available_deployment(self, *args, **kwargs):
        raise NotImplementedError(
            "LAR-1 routing only supports async routing. Enable async_only_mode on the router or use acompletion."
        )

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Enable async_only_mode on the router or call via acompletion.

When it happens

Trigger: Thrown at litellm/router_strategy/lar1_routing.py:177 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/8605b924d7149e92. Report an issue: GitHub.