/**
 * What the comparison cannot see: a field one log measured and the other did
 * not.
 *
 * `--against` names the dollars that moved. It cannot name the findings that
 * *stopped being measurable*, and those look identical to good news. A log
 * where `session` was on 98% of calls and is now on 4% has not fixed its
 * conversation growth; it has stopped recording the field that would show it,
 * and every session-shaped finding in this report is now silent for a reason
 * that has nothing to do with the bill.
 *
 * The distinction this module exists to keep: **a finding that vanished
 * because it was fixed and a finding that vanished because the log went blind
 * are opposite facts.** Nothing else in the comparison can tell them apart —
 * the dollars are the same either way. Coverage can, and only coverage can.
 *
 * Shares, not counts: two logs of different lengths cannot be compared by how
 * many records carried a field. A log twice the size with the same share
 * measured exactly as well.
 */
import type { FieldCoverage } from './usage.js';
/** The fields a comparison can go blind on, with what each one unlocks. */
export declare const COVERAGE_FIELDS: readonly ['label', 'session', 'ts', 'stopReason'];
export type CoverageField = (typeof COVERAGE_FIELDS)[number];
export interface CoverageDrift {
    field: CoverageField;
    /** Share of parsed records carrying it in the previous log, 0–1. */
    was: number;
    /** Share in this log, 0–1. */
    now: number;
    /** `now - was`. Negative means the log went blinder. */
    delta: number;
}
/**
 * The threshold, stated here and repeated in every rendering's copy.
 *
 * A fifth of the records is enough to change which findings appear at all —
 * `sessionCosts` needs five conversations, `modelMixDrift` needs four dated
 * days — while smaller wobbles are the ordinary variation of a week's traffic
 * and reporting them would teach a reader to skip the section.
 */
export declare const COVERAGE_DRIFT_MIN = 0.2;
/**
 * Fields whose coverage moved by at least `minDelta`, biggest move first.
 *
 * Both directions are reported. A field that *appeared* matters too: findings
 * this report can make that the previous one could not are not a regression
 * in the bill, and a reader comparing two reports needs to know the second one
 * was simply able to see more.
 *
 * A log with no parsed records has no shares — an empty array, never zeroes,
 * because "0% carried a session" and "there was nothing to carry one" are the
 * distinction this whole file is about.
 */
export declare function coverageDrift(previous: FieldCoverage, current: FieldCoverage, options?: {
    minDelta?: number;
}): CoverageDrift[];
//# sourceMappingURL=coverage-drift.d.ts.map