class CostRouterError(Exception):
    """Base exception for CostRouter."""


class NoModelForTierError(CostRouterError):
    """No model configured for the requested tier."""


class ScreenerError(CostRouterError):
    """Error during the screening/classification step."""


class AllModelsFailedError(CostRouterError):
    """All models (including fallbacks) failed to produce a response."""
