/** numerator/denominator, or null on a zero denominator (undefined, never a silent 0). */
export declare function ratio(numerator: number, denominator: number): number | null;
/** Percent render for a scorecard cell; null → "n/a". */
export declare function pct(value: number | null): string;
/**
 * Which way a metric has to move to count as a regression.
 * - `lower-is-better` (hallucination RATE): regressed when the current value RISES.
 * - `higher-is-better` (cache-hit RATIO): regressed when the current value FALLS.
 */
export type RegressionDirection = "higher-is-better" | "lower-is-better";
/**
 * The single gate predicate both oracles draw from: did `current` regress against
 * `baseline`, in the given direction? `epsilon` absorbs floating-point noise so a
 * byte-identical re-run never trips.
 *
 * - A `null` current value carries no signal and cannot regress.
 * - A `null` baseline is treated as 0 — the floor a ratio cannot drop below
 *   (`higher-is-better` never trips), and the floor any positive rate exceeds
 *   (`lower-is-better` trips on any positive current).
 */
export declare function valueRegressed(current: number | null, baseline: number | null | undefined, direction: RegressionDirection, epsilon?: number): boolean;
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