/**
 * Midstream-aware federation transport loader (ADR-120, Step 2).
 *
 * Extends the agentic-flow `loadQuicTransport` loader pattern with a
 * preferred branch that probes `midstreamer` first. When `midstreamer`
 * ships real QUIC (currently the WASM build is a counter-tracking
 * stub per ADR-119), this loader picks it up automatically without
 * any change to consumer plugins.
 *
 * Resolution order:
 *
 *   1. If `MIDSTREAMER_QUIC_NATIVE=1` AND the `midstreamer` module
 *      exposes a real `QuicMultistream`-derived `AgentTransport`,
 *      use it. (Today: probes fail closed and we fall through.)
 *
 *   2. Otherwise: defer to agentic-flow's existing loader, which
 *      itself respects `AGENTIC_FLOW_QUIC_NATIVE=1` (ADR-108) and
 *      falls back to WebSocket (ADR-104) otherwise.
 *
 * The loader is opt-in: callers must explicitly invoke
 * `loadFederationTransport()` instead of `loadQuicTransport()`.
 * Behavior is identical to `loadQuicTransport()` until upstream
 * `midstreamer` ships its real QUIC build AND the operator sets the
 * env flag — so this change is safe to land before any of that
 * happens.
 *
 * Re-exports the `AgentTransport` / `AgentMessage` / `QuicTransportConfig`
 * surface from agentic-flow so consumers only import from one place.
 */
export interface AgentMessage {
    id: string;
    type: 'task' | 'result' | 'status' | 'coordination' | 'heartbeat' | string;
    payload: unknown;
    metadata?: Record<string, unknown>;
    [key: string]: unknown;
}
export interface AgentTransport {
    send: (address: string, message: AgentMessage) => Promise<void>;
    onMessage: (handler: (address: string, message: AgentMessage) => void) => void;
    listen?: (port: number, host?: string) => Promise<void>;
    close?: () => Promise<void> | void;
    [key: string]: unknown;
}
export interface QuicTransportConfig {
    port?: number;
    host?: string;
    serverName?: string;
    [key: string]: unknown;
}
/** Result envelope describing which backend the loader picked. */
export interface LoadedFederationTransport {
    /** The live transport. Send/receive against this. */
    transport: AgentTransport;
    /** Which loader branch resolved. Useful for logs/metrics. */
    source: 'midstreamer-native' | 'agentic-flow-loader' | 'websocket-fallback';
    /** Free-form note when a probe failed (helps explain a fallback). */
    fallbackReason?: string;
}
/**
 * Top-level loader for federation transport. Identical signature to
 * agentic-flow's `loadQuicTransport`, but with the midstreamer-first
 * preference. Use this from `plugins/ruflo-federation` in place of
 * the bare `loadQuicTransport`.
 *
 * Failure mode: if midstreamer is requested but rejects (stub, init
 * error, missing package), this function falls through to the
 * agentic-flow loader. If current agentic-flow does not export its
 * historical loader subpath, the plugin-owned WebSocket fallback is
 * used directly (ADR-104, #2618).
 */
export declare function loadFederationTransport(config?: QuicTransportConfig): Promise<LoadedFederationTransport>;
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