import { Request, Response } from 'express';
export type Provider = 'openai' | 'anthropic' | 'gemini';
export interface SseRelayOptions {
    provider: Provider;
    tier: 'standard' | 'pro';
    cacheHeader?: string;
    similarity?: number;
    latencyMs?: number;
}
export declare class SseRelay {
    static simulateHit(res: Response, cachedResponse: any, opts: SseRelayOptions): Promise<void>;
    static relayMiss(req: Request, res: Response, upstreamBody: any, provider: Provider, opts: SseRelayOptions): Promise<void>;
    private static setSseHeaders;
    private static defaultModel;
    private static buildUpstreamRequest;
    private static buildChunkEvent;
    private static formatSSE;
    private static extractTextFromResponse;
}
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