import type { Passthrough } from '../types';
export type MergedPassthrough<TBody = Record<string, unknown>> = {
    body: TBody;
    headers: Record<string, string>;
    query: Record<string, string>;
};
export declare function mergePassthrough<TBody extends Record<string, unknown>>(connectorBody: TBody, connectorHeaders?: Record<string, string>, passthrough?: Passthrough, connectorQuery?: Record<string, string>): MergedPassthrough<TBody>;
/**
 * Merge `override` headers over `base` headers where `override` ALWAYS wins,
 * case-insensitively — used where connector-signed headers (SES SigV4: Host,
 * X-Amz-Date, X-Amz-Content-Sha256, Authorization, X-Amz-Security-Token) are
 * applied on top of already-merged passthrough headers. A case-variant of a
 * signed header carried in `base` (e.g. a passthrough lowercase `authorization`)
 * is removed so it cannot produce a comma-joined duplicate with the signed
 * `Authorization`. Returns a plain object (not a `Headers` instance) so callers
 * that pass it straight to `fetch` keep their existing wire shape.
 */
export declare function mergeHeaders(base: Record<string, string>, override: Record<string, string>): Record<string, string>;
/**
 * Recursively merge plain objects, `source` winning at the leaves. Arrays and
 * non-plain values replace rather than merge; `undefined` in `source` is
 * skipped so it never erases a connector-set value.
 */
export declare function deepMergeBody(target: Record<string, unknown>, source: Record<string, unknown>): Record<string, unknown>;