/**
 * AWS SigV4 v4 signing — single platform-agnostic implementation.
 *
 * Pure function — given a request + credentials + region + service + clock,
 * produces the same request with an `Authorization` header attached. Uses
 * Web Crypto (`crypto.subtle`) which works in browsers, extension service
 * workers, extension offscreen documents, and Node 22+ (where it lives on
 * `globalThis.crypto`).
 *
 * Consumed via `@slicc/shared-ts` by the webapp/extension mount backends and
 * the node-server sign-and-forward handlers. Verified against the canonical
 * AWS SigV4 v4 test vectors in `packages/shared-ts/tests/sigv4.test.ts`.
 */
export interface SigV4Request {
    method: 'GET' | 'PUT' | 'POST' | 'DELETE' | 'HEAD';
    url: URL;
    headers: Record<string, string>;
    body?: Uint8Array;
}
export interface SigV4Credentials {
    accessKeyId: string;
    secretAccessKey: string;
    sessionToken?: string;
}
export declare function signSigV4(req: SigV4Request, creds: SigV4Credentials, region: string, service?: string, now?: Date): Promise<SigV4Request>;
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