import type { MCPHttpSseTransportConfig, MCPJsonRpcMessage, MCPTransport, MCPTransportSendOptions } from '../../types/connector/index.js';
import { type Logger } from '../../utils/logger.js';
export declare class HttpSseTransport implements MCPTransport {
    private readonly config;
    private messageHandlers;
    private closeHandlers;
    private errorHandlers;
    private connected;
    private abortController;
    private generation;
    private activeSends;
    private sseUrl;
    private postUrl;
    private log;
    private readonly timeoutMs;
    /** Defaults to the ambient global `fetch`; never read again once captured. */
    private readonly fetchImpl;
    constructor(config: MCPHttpSseTransportConfig, log?: Logger);
    connect(): Promise<void>;
    close(): Promise<void>;
    /**
     * Drop every registered handler.
     *
     * `onMessage`/`onClose`/`onError` append, and `MCPClient.connect()` calls
     * all three every time — and is reachable again after `disconnect()`. So
     * without this each reconnect duplicated the set, and after n cycles one
     * inbound message dispatched to n handlers, n-1 of them closures over dead
     * sessions that kept their old client state alive.
     */
    private clearHandlers;
    send(message: MCPJsonRpcMessage, options?: MCPTransportSendOptions): Promise<void>;
    onMessage(handler: (message: MCPJsonRpcMessage) => void): void;
    onClose(handler: () => void): void;
    onError(handler: (error: Error) => void): void;
    isConnected(): boolean;
    /**
     * `extra` comes from `MCPTransportSendOptions.headers` — the client's
     * per-send authority — and is merged over this transport's own static
     * config headers so a caller's value wins on a collision. See
     * {@link StreamableHttpTransport}'s method of the same name, which this
     * mirrors; the HTTP-SSE POST had no equivalent merge until now, so a
     * per-request header or bearer token silently never reached the wire.
     */
    private buildHeaders;
    private beginSend;
    private assertCurrent;
    private isCurrent;
    private startSSE;
    private listenSSE;
}
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