/**
 * Per-host concurrency limiter using semaphores.
 * Maps API hostnames to max concurrent request slots.
 */
/** Default per-host concurrency limits based on API rate limits */
export declare const DEFAULT_HOST_LIMITS: Record<string, number>;
/** GitHub unauthenticated rate limit is much lower (60/hr vs 5000/hr) */
export declare const GITHUB_UNAUTH_LIMIT = 2;
/** Default download concurrency (CDN, not API) */
export declare const DOWNLOAD_CONCURRENCY = 5;
/** Map source types to their API hostnames */
export declare const SOURCE_TYPE_HOSTS: Record<string, string>;
export declare class HostSemaphore {
    private active;
    private limits;
    private queues;
    private defaultLimit;
    constructor(hostLimits: Record<string, number>, defaultLimit?: number);
    private getHost;
    private getLimit;
    getActiveCount(host: string): number;
    acquire(url: string): Promise<void>;
    release(url: string): void;
    run<T>(url: string, fn: () => Promise<T>): Promise<T>;
}
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