/**
 * hosting/headers — one lower-casing of one header bag, shared by every door.
 *
 * A six-line helper gets its own file for the reason every other shared piece
 * in this folder does: two copies of it is how the request door and the
 * conversation door end up disagreeing about whether a header the caller sent
 * as `X-Session-Id` is present, and that disagreement would surface as one door
 * seeing a session the other cannot.
 */
/// <reference types="node" />
import type { IncomingMessage } from 'node:http';
/**
 * Header names lower-cased, repeated values joined — the shape every wire reads
 * from, so no wire ever has to guess at casing.
 */
export declare function lowerCasedHeaders(headers: IncomingMessage['headers']): Record<string, string>;