Span/log attributes a failure declares for tracing: failure.code plus whatever its factory's trace mapper (see define) explicitly allowlisted from data. A failure whose factory declared no mapper yields the code alone — unmapped payload fields never leave the process, which is what makes redaction (passwords, tokens) the default rather than a discipline.

Keyed by code, so it also works on failures that crossed a realm or a fromJSON revive.

import * as Failure from './failure.ts';

const AuthFailed = Failure.define(
  'AuthFailed',
  (d: { status: number; password: string }) => `auth rejected: HTTP ${d.status}`,
  { trace: (d) => ({ 'auth.status': d.status }) },
);

Failure.attributes(AuthFailed({ status: 401, password: 'hunter2' }));
// { 'failure.code': 'AuthFailed', 'auth.status': 401 } — the password cannot leak: never mapped