/**
 * GCP Application Default Credentials Provider
 *
 * Handles GCP authentication using Application Default Credentials.
 * Supports service account credentials and ADC resolution.
 */
import { AuthProvider, AuthResult, GCPADCConfig } from './index.js';
export declare class GCPADCProvider implements AuthProvider<GCPADCConfig> {
    readonly type: "gcp_adc";
    authenticate(config: GCPADCConfig): Promise<AuthResult>;
    refresh(config: GCPADCConfig): Promise<AuthResult>;
    clear(config: GCPADCConfig): Promise<void>;
    validate(config: GCPADCConfig): Promise<boolean>;
    /**
     * Get GCP access token from various sources
     */
    private getAccessToken;
    /**
     * Get token from gcloud CLI
     */
    private getTokenFromGcloud;
    /**
     * Get token from GCP metadata server
     */
    private getTokenFromMetadataServer;
    private getCacheKey;
}