/**
 * Async counting semaphore with FIFO fairness for global concurrency control.
 *
 * Module-level singleton shared across all groups.
 * Supports AbortSignal for timeout/shutdown cancellation.
 */
export declare class AsyncSemaphore {
    private permits;
    readonly maxPermits: number;
    private readonly queue;
    private disposed;
    constructor(maxPermits?: number);
    /**
     * Acquire a permit. Resolves immediately if available,
     * otherwise FIFO-queues until a permit is released.
     *
     * Rejects if:
     * - The semaphore has been disposed
     * - The provided AbortSignal fires while queued
     */
    acquire(signal?: AbortSignal): Promise<void>;
    /**
     * Release a permit. Wakes the oldest queued waiter (FIFO)
     * or increments the available permit count.
     */
    release(): void;
    /**
     * Dispose the semaphore: reject all queued waiters and prevent
     * future acquisitions. Called on server shutdown.
     */
    dispose(): void;
    /** Number of permits currently available. */
    get available(): number;
    /** Number of waiters currently queued. */
    get waiting(): number;
    /** Whether the semaphore has been disposed. */
    get isDisposed(): boolean;
    /** Reset for testing. */
    resetForTesting(): void;
}
export declare const concurrencySemaphore: AsyncSemaphore;
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