/**
 * WebTransport (HTTP/3) lane primitive.
 *
 * Standalone client for the platform's WebTransport endpoint, which carries
 * the same session as the WebSocket lane.
 * Browser-native `WebTransport` API; no polyfill ships with the SDK.
 *
 * Browser support as of 2026-05:
 *   - Chromium 97+ (stable)
 *   - Firefox 125+ (stable)
 *   - Safari Technology Preview only (no stable release yet)
 *   - Node 22+ has experimental WebTransport behind a flag
 *
 * v1 surface is intentionally narrow: this exposes the bytes lane only,
 * caller decodes protobuf. Full `init({ transport: 'webtransport' })`
 * MessagingClient integration lands later, mirroring the SSE roadmap.
 *
 * @example
 * ```ts
 * import { WebTransportTransport } from '@droponair/sdk-js';
 * const wt = new WebTransportTransport({
 *   httpUrl: 'https://sdk.droponair.com',
 *   getJwt: async () => myJwt,
 * });
 * wt.onFrame((bytes) => { ... protobuf decode ... });
 * await wt.connect();
 * await wt.sendEnvelope(envelopeBytes);
 * ```
 */
export interface WebTransportTransportOptions {
    /** Base URL of the platform's REST API. The WT endpoint is derived as
     *  `<httpUrl>/v1/transport/wt?token=<jwt>`. */
    httpUrl: string;
    /** Returns a fresh JWT. Called once per connect. */
    getJwt: () => Promise<string>;
}
export type WTFrameHandler = (frame: Uint8Array) => void;
export type WTStateHandler = (state: 'connecting' | 'open' | 'closed' | 'error') => void;
export declare class WebTransportTransport {
    private readonly httpUrl;
    private readonly getJwt;
    private session;
    private stream;
    private writer;
    private reader;
    private frameHandler;
    private stateHandler;
    private readLoopAbort;
    constructor(options: WebTransportTransportOptions);
    /** Subscribe to incoming protobuf frames. Replaces any previous handler. */
    onFrame(handler: WTFrameHandler): void;
    /** Subscribe to lifecycle state changes. Replaces any previous handler. */
    onState(handler: WTStateHandler): void;
    /** Open the WebTransport session + a single bidirectional stream. */
    connect(): Promise<void>;
    /** Write a single protobuf Envelope to the bidirectional stream. */
    sendEnvelope(envelopeBytes: Uint8Array): Promise<void>;
    /** Close the session. Idempotent. */
    close(): void;
    private startReadLoop;
}