type RuntimeFallbackReason = "model-not-found" | "context-exceeded";
type RuntimeFallbackEvent = {
    event: {
        type: string;
        properties?: unknown;
    };
};
type RuntimeFallbackDependencies = {
    defaultFallbackChain?: string[];
    getCurrentModel?: (sessionID: string) => string | undefined;
    getAvailableModels?: (sessionID: string) => Set<string>;
    setCurrentModel?: (sessionID: string, model: string) => void | Promise<void>;
    onFallbackApplied?: (input: {
        sessionID: string;
        previousModel: string;
        nextModel: string;
        reason: RuntimeFallbackReason;
    }) => void | Promise<void>;
};
export declare function createRuntimeFallbackHandler(deps?: RuntimeFallbackDependencies): ({ event }: RuntimeFallbackEvent) => Promise<void>;
export {};