/** What the library was doing when counting failed. */
export type UsageFaultOperation = 
/** Reading a window (a cap, a rate limit, the spend ceiling). */
"read"
/** Recording usage. A dropped event is usage counted by nothing. */
 | "write"
/** Resolving the meter or the scope customer a read/write needs. */
 | "resolve";
/** What the library DID as a result — the part that decides whether a customer
 *  was over-served, under-served, or unaffected. */
export type UsageFaultOutcome = 
/** Reported 0. The window does not apply: nothing is refused. */
"counted-zero"
/** Reported the last value read successfully. Stale, but bounded and sane. */
 | "used-last-known"
/** Refused: the call was denied because usage could not be established. */
 | "refused"
/** The event was not recorded. That usage is now uncountable, permanently. */
 | "dropped";
export interface UsageFault {
    operation: UsageFaultOperation;
    outcome: UsageFaultOutcome;
    error: unknown;
    orgId?: string;
    /** `org` / `k:<kind>` / `u:<memberId>` when the fault belongs to one. */
    scope?: string;
    /** The value served instead, when one was. */
    served?: number;
}
export type UsageFaultHandler = (fault: UsageFault) => void;
/**
 * Be told when a usage read or write fails, and what was served instead.
 *
 * ```ts
 * onUsageFault((f) => {
 *   if (f.outcome === "counted-zero") metrics.increment("billing.uncounted");
 *   logger.error({ ...f }, "usage counting degraded");
 * });
 * ```
 *
 * Returns an unsubscribe function. Registering ANY handler silences the built-in
 * console warning, on the assumption that a deployment which asked to be told has
 * somewhere better to put it.
 */
export declare function onUsageFault(handler: UsageFaultHandler): () => void;
/** Test seam: drop every handler, and the once-per-process de-duplication. */
export declare function resetUsageFaults(): void;
export declare function reportUsageFault(fault: UsageFault): void;
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