/**
 * Upstream WebSocket client for the proxy's renderer bridge.
 *
 * `new WebSocket(url)` cannot set request headers, so the bridge used to move
 * the tenant identity into the query string -- where the renderer, correctly,
 * refuses to read it. This client speaks the same handshake through
 * `WebSocketStream`, which does accept headers, so the bridge hop can carry the
 * exact identity headers every other proxied request carries.
 *
 * The surface is deliberately `WebSocket`-shaped (`readyState`, `send`,
 * `close`, `onopen`/`onmessage`/`onerror`/`onclose` receiving real DOM events)
 * so the bridge wiring in `main.ts` is unchanged by the transport swap.
 *
 * @module proxy/websocket-client
 */
export interface UpstreamWebSocketConnection {
    readonly readable: ReadableStream<string | Uint8Array>;
    readonly writable: WritableStream<string | Uint8Array>;
}
/** The subset of `WebSocketStream` this client depends on. */
export interface UpstreamWebSocketStream {
    readonly opened: Promise<UpstreamWebSocketConnection>;
    readonly closed: Promise<{
        closeCode?: number;
        reason?: string;
    }>;
    close(closeInfo?: {
        closeCode?: number;
        reason?: string;
    }): void;
}
export type UpstreamWebSocketStreamFactory = (url: string, init: {
    headers: [string, string][];
}) => UpstreamWebSocketStream;
/**
 * Resolve the runtime's `WebSocketStream`.
 *
 * Fails loudly rather than falling back to `new WebSocket(url)`: a silent
 * fallback would drop the identity headers again and reproduce the 502 this
 * client exists to fix. The proxy binary is compiled with `--unstable-net`.
 */
export declare function resolveUpstreamWebSocketStreamFactory(): UpstreamWebSocketStreamFactory;
/** A `WebSocket`-shaped client that presents request headers on connect. */
export declare class UpstreamWebSocket {
    #private;
    onopen: ((event: Event) => void) | null;
    onmessage: ((event: MessageEvent<string | Uint8Array>) => void) | null;
    onerror: ((event: Event) => void) | null;
    onclose: ((event: CloseEvent) => void) | null;
    constructor(url: URL | string, headers: Headers, factory: UpstreamWebSocketStreamFactory);
    get readyState(): number;
    send(data: string | ArrayBufferLike | ArrayBufferView | Blob): void;
    close(code?: number, reason?: string): void;
}
export declare function connectUpstreamWebSocket(url: URL | string, headers: Headers, factory?: UpstreamWebSocketStreamFactory): UpstreamWebSocket;
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