/**
 * PKCE utilities using Web Crypto API.
 * Works in both Node.js 20+ and browsers.
 * [WHO]: generatePKCE
 * [FROM]: no external imports
 * [TO]: Consumed by core/lib/ai/src/utils/oauth/anthropic.ts, core/lib/ai/src/utils/oauth/google-antigravity.ts, core/lib/ai/src/utils/oauth/google-gemini-cli.ts, core/lib/ai/src/utils/oauth/openai-codex.ts
 * [HERE]: core/lib/ai/src/utils/oauth/pkce.ts - owned by core/lib/ai/AGENT.md
 */
/**
 * Generate PKCE code verifier and challenge.
 * Uses Web Crypto API for cross-platform compatibility.
 */
export declare function generatePKCE(): Promise<{
    verifier: string;
    challenge: string;
}>;