/**
 * @license
 * Copyright 2026 Qwen
 * SPDX-License-Identifier: Apache-2.0
 */
/**
 * Bounded single-consumer push queue backing an adaptor's event stream.
 *
 * The orchestrator's pump is the sole consumer and may drop and
 * resubscribe (backoff); a new subscribe takes the queue over and ends
 * the previous iterator — events buffered between subscriptions are
 * retained, so a resubscribing pump can never lose a turn_complete.
 *
 * Overflow policy: drop the oldest `progress` events first (they are
 * advisory), else the oldest event, and count the drops so tests can
 * pin the behavior.
 */
export interface AsyncEventQueueOptions {
    capacity?: number;
    onDrop?: (dropped: number) => void;
}
export declare class AsyncEventQueue<T> {
    private readonly capacity;
    private readonly onDrop?;
    private buffered;
    private waiters;
    private ended;
    constructor(options?: AsyncEventQueueOptions);
    push(item: T): void;
    end(): void;
    subscribe(options?: {
        signal?: AbortSignal;
    }): AsyncIterable<T>;
    get size(): number;
    private evictOne;
    private abortedIterable;
}