export interface PKCECodes {
    codeVerifier: string;
    codeChallenge: string;
}
/**
 * Generate PKCE codes theo RFC 7636 cho OAuth 2.0.
 * Port từ CLIProxyAPI `internal/auth/claude/pkce.go`:
 *  - 96 random bytes → 128 ký tự base64url (no padding) làm verifier
 *  - SHA256 verifier → base64url (no padding) làm challenge
 */
export declare function generatePKCECodes(): PKCECodes;
export declare function generateRandomState(): string;