/**
 * Structured error payloads — and the sanitiser that makes them safe to send.
 *
 * An error body used to be `{ error: { code, message } }`, so any data the UI
 * needed had to be smuggled into the message: apps ended up parsing
 * `Checks failed: A, B` to find out which checks failed. `details` gives that
 * data a place of its own.
 *
 * It is written by the server and read by the client verbatim, which makes it a
 * channel — so it is bounded on every axis before it leaves:
 *
 *  - **Plain data only.** Strings, finite numbers, booleans, `null`, arrays and
 *    plain objects. A `Date` becomes its ISO string. Everything else is dropped:
 *    functions, symbols, `undefined`, BigInt, `NaN`/`Infinity`, and every exotic
 *    object — `Error` (a stack is an internal), `Map`/`Set`/`RegExp`, typed
 *    arrays, and class instances (an ORM row would otherwise walk out through an
 *    error body). Dropping rather than rejecting keeps a serialisation slip from
 *    turning a handled 422 into a 500.
 *  - **Acyclic and shallow.** A cycle is dropped where it closes;
 *    nesting past {@link MAX_ERROR_DETAILS_DEPTH} is dropped.
 *  - **Small.** Over {@link MAX_ERROR_DETAILS_BYTES} of serialised JSON the
 *    whole payload is dropped, so an error can never become an exfiltration or
 *    amplification channel.
 *  - **Opt-in.** Only errors explicitly constructed with `details` have any. An
 *    unexpected exception still becomes the neutral 500 with nothing attached.
 */
/** A structured error payload: plain JSON data, keyed by name. */
export type ErrorDetails = Record<string, unknown>;
/** Largest `details` payload sent to a client, in bytes of serialised JSON. */
export declare const MAX_ERROR_DETAILS_BYTES = 4096;
/** Deepest array/object nesting kept; anything below it is dropped. */
export declare const MAX_ERROR_DETAILS_DEPTH = 8;
/**
 * Makes a client-safe copy of a structured error payload, or returns
 * `undefined` when there is nothing safe to send (see the rules at the top of
 * this module). Never throws, and never returns the caller's own object.
 */
export declare function sanitizeErrorDetails(details: unknown): ErrorDetails | undefined;