/**
 * detectEvalDrift — compare train vs held-out pass rates on a trial corpus.
 *
 * SLICE-100 (FEAT-183 S5a). Surfaces when the held-out split's pass-rate
 * diverges from the train split's by more than the configured threshold —
 * a sign that the optimizer is overfitting to the train cases. Default
 * threshold (0.10 = 10 pp) is intentionally generous; calibration is
 * deferred to SLICE-104 with real soak data.
 *
 * Inputs:
 *   - trials: full corpus (both splits present, each trial's EvalCase has
 *     a `held_out: boolean` flag — but the trial schema doesn't carry the
 *     flag, so callers pass two arrays instead via `splitTrials`).
 *   - Use `detectEvalDriftFromSplits` when caller already has the split.
 *   - Use `detectEvalDrift` when caller has only a pass-rate for held-out
 *     (e.g. live held-out evaluation runs separately).
 */
import type { Trial } from "../types/trial.ts";
export interface DriftReport {
    /** True when |trainPassRate - heldOutPassRate| > threshold. */
    drift: boolean;
    /** Signed delta in PERCENTAGE POINTS (heldOut - train). Positive means held-out is better. */
    deltaPp: number;
    /** Pass rate computed across train trials, 0..1. */
    trainPassRate: number;
    /** Pass rate computed across held-out trials, 0..1. (Or the value passed in if using
     * the simple `detectEvalDrift(trials, heldOutPass)` signature.) */
    heldOutPassRate: number;
    /** Count of trials in each split. */
    trainCount: number;
    heldOutCount: number;
    /** Effective threshold used for the drift decision (defaults to 0.10). */
    threshold: number;
}
export interface DetectDriftOpts {
    /** Drift threshold in absolute fraction (e.g. 0.10 = 10 percentage points). Default 0.10. */
    threshold?: number;
    /** Minimum trial count per split below which `drift` is forced to `false` (insufficient
     * sample). Default: 5. */
    minSampleSize?: number;
}
/**
 * Detect drift when caller supplies a held-out pass-rate directly (e.g. measured by
 * an external held-out evaluation step). `trials` here is treated as the train split.
 */
export declare function detectEvalDrift(trials: Trial[], heldOutPassRate: number, opts?: DetectDriftOpts): DriftReport;
/**
 * Detect drift when caller supplies both splits as arrays.
 */
export declare function detectEvalDriftFromSplits(train: Trial[], heldOut: Trial[], opts?: DetectDriftOpts): DriftReport;
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