/**
 * Event-loop lag monitor — attribution for "the first call took seconds".
 *
 * Why this exists rather than a fix: the 2026-08-25 audit measured, over 268
 * real `labels` calls, a mean server time of 5.6 s, while the FTS query those
 * calls run takes 6–11 ms in isolation. Narrowing it further: the first call
 * after the handshake took 1,215–1,336 ms, the SAME call 8 s later took 18 ms,
 * and the tool's own phase timer reported 0.0 s for a call the client saw take
 * 1.3 s. So the time was not inside the tool — requests were queueing behind
 * synchronous work on the single Node event loop. `node:sqlite` is synchronous
 * by design and this server opens a 2.5 GB symbol index and a 630 MB label
 * index, so that is the shape of the suspect.
 *
 * What could NOT be reproduced: measured from outside on this VM with a WARM
 * OS file cache, the loop is barely blocked — three ~140 ms stalls in the first
 * 5.5 s, 415 ms of blocking in total across 25 s, on top of a 1,749 ms
 * `initialize`. The corpus averages come from cold caches, which cannot be
 * recreated on demand without disturbing the machine.
 *
 * Rather than invent a fix for blocking that cannot currently be measured, this
 * leaves the measurement in the server. Turn it on with DEBUG_LOGGING and the
 * next investigation gets attribution — which phase, how long — instead of the
 * inference above. Off by default; the timer is unref'd, so it never keeps the
 * process alive, and it does no work beyond a subtraction per tick.
 */
/** Start sampling. No-op when already running, or when debug logging is off. */
export declare function startLoopLagMonitor(startedAt?: number): void;
/** Stop sampling. Safe to call when never started. */
export declare function stopLoopLagMonitor(): void;
/** What the monitor has seen so far — for a diagnostics dump or a test. */
export declare function getLoopLagStats(): {
    stallCount: number;
    worstLagMs: number;
    totalLagMs: number;
};
/** Test seam — the counters are process-wide. */
export declare function resetLoopLagStats(): void;
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