/**
 * One-time ERC-20 `approve(Permit2, amount)` helper for the `upto` scheme.
 *
 * The Permit2 contract must be allowed to pull the payer's USDC before any
 * `PermitWitnessTransferFrom` signature is settle-able on-chain. Each payer
 * needs to do this exactly once per (token, chain).
 *
 * `ethers` is imported lazily so that browsers / serverless functions that
 * only sign (and never broadcast) don't pull it into their bundle. Install
 * `ethers@^6` to use this helper.
 */
/** Approval result. `skipped: true` means the allowance was already sufficient. */
export interface ApprovePermit2Result {
    skipped: boolean;
    txHash?: string;
    allowanceBefore: string;
    allowanceAfter: string;
}
export interface ApprovePermit2Options {
    /** HTTP(S) RPC endpoint for the target EVM chain. */
    rpcUrl: string;
    /** Hex private key (with or without `0x` prefix). */
    privateKey: string;
    /** ERC-20 token contract (USDC on Base is `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). */
    tokenAddress: string;
    /** Allowance to set. Defaults to `2**256 - 1` (the Uniswap/x402 convention). */
    amount?: bigint;
    /** Override Permit2 address (defaults to the canonical CREATE2 deployment). */
    permit2Address?: string;
}
/**
 * Submit a one-time `ERC20.approve(Permit2, amount)` transaction.
 *
 * Idempotent: if the existing allowance already meets or exceeds `amount`,
 * no transaction is broadcast and `skipped: true` is returned.
 */
export declare function approvePermit2(opts: ApprovePermit2Options): Promise<ApprovePermit2Result>;