feat: add BasePay action provider — gasless USDC, batch pay, escrow, subscriptions on Base Mainnet

[osr21]

Summary

This PR adds BasePay as a community action provider for AgentKit, giving AI agents five USDC payment primitives on Base Mainnet with no additional dependencies.

Actions added

Action	Description
basepay_send_usdc	Direct USDC transfer (agent pays ETH gas)
basepay_send_usdc_gasless	EIP-3009 relay — no ETH needed by the agent
basepay_batch_pay_usdc	Pay up to 200 recipients atomically
basepay_create_escrow	Time-lock USDC for a beneficiary
basepay_subscribe	On-chain recurring USDC payment

How gasless works

The agent signs an EIP-3009 TransferWithAuthorization typed message (no on-chain tx). The BasePay relay submits it to USDC.transferWithAuthorization(), paying the ETH gas. This means agents can send USDC with zero ETH balance — a critical unlock for autonomous agent wallets.

Verified contracts (Base Mainnet)

Contract	Address
BatchPayV2	0xe40d…c68
EscrowV2	0x1eb2…499
SubscriptionManagerV2	0x1019…421

Usage

import { AgentKit } from "@coinbase/agentkit";
import { basePayActionProvider } from "./action-providers/basepay";

const agentKit = await AgentKit.from({
  walletProvider,
  actionProviders: [basePayActionProvider()],
});

Or via the standalone npm package:

npm install basepay-agentkit @coinbase/agentkit viem zod

import { basePayActionProvider } from "basepay-agentkit";

Self-hosting the relay

The relay is open-source (github.com/osr21/basepay) and requires only a funded EOA (ETH on Base) to operate. Configurable via basePayActionProvider({ relayUrl: "https://your-relay.example.com" }).

No new dependencies

The provider uses only packages already in the AgentKit dependency graph (viem, zod). The relay call uses native fetch.

---

Live dApp: https://base-pay.replit.app
npm package: https://www.npmjs.com/package/basepay-agentkit
Contracts + source: https://github.com/osr21/basepay

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2