/** Architectural layer that raised the error. */
export type AppErrorLayer = 'embedder' | 'parser' | 'vectordb' | 'config' | 'pdf-visual';
/** Nature of the failure, independent of layer. */
export type AppErrorKind = 'validation' | 'io' | 'config' | 'internal';
/**
 * Abstract base for every domain error. Stores the `layer`/`kind`
 * discriminants and the originating `cause`, leaving the concrete subclass to
 * own its public constructor signature and its `name`.
 */
export declare abstract class AppError extends Error {
    readonly layer: AppErrorLayer;
    readonly kind: AppErrorKind;
    readonly cause?: Error;
    protected constructor(message: string, layer: AppErrorLayer, kind: AppErrorKind, cause?: Error);
}
/** Type guard: narrows an unknown value to the shared error taxonomy. */
export declare function isAppError(value: unknown): value is AppError;
/**
 * Walks the `.cause` chain starting from `error`, returning errors in order
 * `[outer, cause, cause.cause, ...]`. The walk stops at the first link whose
 * `.cause` is not an `Error`. Self-referential chains are guarded against.
 */
export declare function getCauseChain(error: Error): Error[];
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