/**
 * Zero-dependency concurrency limiter.
 *
 * Motivation: `doDeepSearch` previously ran every search-angle in parallel
 * via `Promise.allSettled`. For `maxRounds = 8` that means 8 simultaneous
 * upstream requests against a single BYOK provider, which (a) blows past
 * Brave's 1 req/s free-tier limit and (b) fans out paid Tavily/Exa calls
 * faster than the user wanted when they asked for "deep" research.
 *
 * `createLimiter(N)` returns a `run(fn)` wrapper that never executes more
 * than N callbacks at the same time. Callers keep their existing
 * `Promise.allSettled` + `.map` shape — only the body is wrapped.
 *
 * Semantics match p-limit: in-flight count is capped, queued work is
 * dispatched FIFO as slots free up, a callback that throws still frees
 * its slot.
 */
export interface Limiter {
    <T>(fn: () => Promise<T>): Promise<T>;
    readonly activeCount: number;
    readonly pendingCount: number;
    readonly concurrency: number;
}
export declare function createLimiter(concurrency: number): Limiter;
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