/**
 * Stop hammering a server that is not answering.
 *
 * ── The behaviour this replaces ───────────────────────────────────────────
 * Every walk tried every configured target, in full, forever. A target that was
 * down did not merely fail — it failed SLOWLY, once per session, inside the same
 * serial walk as the healthy one: connect timeout, three retries with 2s/8s/30s
 * backoff, then the next session. One measured log carried 1,772 `fetch failed`
 * and 3,526 HTTP 429 and was still producing them at 26–38 per hour, days later.
 *
 * The cost lands on the wrong target. Because targets are walked in sequence, a
 * dead LAN box delays every ship to the healthy SaaS host behind it, and the
 * whole walk's completion — which is what the ledger, the health file and the
 * progress report all wait on.
 *
 * ── The rule ─────────────────────────────────────────────────────────────
 * Consecutive whole-walk failures trip the breaker. It stays open for a
 * doubling cooldown, capped, and one success closes it completely.
 *
 * Deliberately counted per WALK, not per request. A single walk already retries
 * internally and obeys Retry-After; failing individual requests are normal
 * operation and must not trip anything. What "the target is down" actually looks
 * like is a whole walk failing, repeatedly.
 *
 * Process-lifetime only, and that is the right lifetime: a restart is exactly
 * when you want to retry a target you gave up on. Nothing is persisted.
 *
 * A tripped breaker is never silent. It is reported to the health file so the
 * user hears "this server is being skipped" instead of watching a target quietly
 * never sync.
 */
/** Consecutive failed walks before a target is skipped. */
export declare const TRIP_AFTER_FAILURES: number;
/** First cooldown, doubled per subsequent failure. */
export declare const BASE_COOLDOWN_MS: number;
/** Ceiling, so a target is always retried eventually. */
export declare const MAX_COOLDOWN_MS: number;
/** Test seam. */
export declare function _resetBreakers(): void;
/** Cooldown for the Nth consecutive failure, doubling and capped. */
export declare function cooldownFor(failures: number): number;
export interface BreakerVerdict {
    /** True when this target should be skipped right now. */
    open: boolean;
    /** Milliseconds until the next attempt. 0 when closed. */
    retryInMs: number;
    failures: number;
    lastError: string;
    /**
     * True only for the failure that OPENS a new incident.
     *
     * A tripped breaker re-opens on every attempt until a success clears it, so a
     * caller that reports "tripped" on each open verdict counts elapsed time, not
     * incidents. One device reported 823 trips for ONE LAN box that was switched
     * off — 96 a day, for as long as the box stayed off — and the fleet panel read
     * that back as if 823 separate things had gone wrong.
     *
     * `failures` is the number to read for "how bad is it"; this flag is the one
     * to count.
     */
    tripped: boolean;
}
/** Should this target be skipped? */
export declare function breakerState(serverUrl: string, now?: number): BreakerVerdict;
/** A walk against this target completed. Clear everything. */
export declare function noteTargetSuccess(serverUrl: string): void;
/**
 * A walk against this target failed. Returns the verdict for the NEXT attempt,
 * so the caller can report "skipping for 4m" in the same breath as the failure.
 */
export declare function noteTargetFailure(serverUrl: string, error: string, now?: number): BreakerVerdict;
/** One line for the log, or null when there is nothing to say. */
export declare function breakerNotice(serverUrl: string, v: BreakerVerdict): string | null;
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