Building with programmable money on Arc using App Kit I Corey Cooper

Sun, Aug 2, 2026, 12:00 AM

In this workshop at ETHGlobal New York 2026, Corey Cooper from Circle demonstrates building with programmable money on Arc using App Kit. Arc is Circle's L1 EVM-compatible blockchain, currently in testnet and launching soon, with around $15,000 in bounties for hackers. He frames the problem: as Circle expanded USDC across many chains, it wanted to give developers an SDK for multi-chain flows rather than Arc alone, since money often on-ramps into Arc and then moves out to other ecosystems. App Kit is a TypeScript SDK that bundles Circle's protocols (CCTP for bridging and Gateway for unified balances) and digital assets (USDC, EURC, USYC, and cbBTC for Arc), eliminating fragmentation across tooling, wallets, and services while letting developers reach EVM and non-EVM chains. It also has built-in monetization: by passing a parameter with a wallet address and basis points, developers take a cut of any orchestrated flow, paid out instantly via Circle's smart contracts, and it ships with Circle's own RPC and wallet adapters. Corey walks through the common flows App Kit simplifies: bridging (for example, a neobank onramping a customer from Base to Arc in one click via CCTP), payouts and invoicing across chains in under five lines of code, swaps across currencies and assets for onchain FX or buying cbBTC, unified balances via Circle Gateway (deposit into a gateway contract for a virtual balance spendable instantly on any supported chain, cut from around 300 lines of code to five), and simple sends using the built-in Circle RPC. A cross-chain send from Arc to Solana is roughly four lines. He runs a live demo, depositing $5 USDC into his Arc gateway balance and doing a payout to a Base address with subsecond finality. He then introduces the Circle Agent Stack, a CLI that drops into any agent harness to give self-custodial wallets, OTP authentication, and App Kit functionality plus Circle's nano payments protocol for gas-free x402 transactions. Using a tool called Proceeds, he wraps a mock API (a Nike EYBL high school basketball stats endpoint, a nod to his past as a scout) with x402 and nano payment support, then has Claude call it, recognize nano payments, pay $1 USDC from his gateway balance, and return the league's top five scorers with a scouting report. He closes on Q&A, noting Arc mainnet is coming soon and that the use cases exciting him most seamlessly bridge offchain and onchain without educating the user, citing Cash App's USDC integration. 00:00 Introduction 00:11 What Is Arc and the Bounties 00:39 The Tools Circle Built for Developers 01:08 The Problem: Building for Multi-Chain Flows 01:36 Why the World Will Be Multi-Chain 02:09 Reducing Fragmentation With CCTP and Gateway 02:51 What Is App Kit 03:32 Shipping Patterns Fast With Built-In Monetization 04:09 Powered by Circle Smart Contracts 04:38 Bring Your Own Wallet or Use Circle's 05:15 Common Flow: Bridging for Neobanks 05:40 Common Flow: Payouts and Invoicing 05:59 Common Flow: Swaps and Onchain FX 07:40 How the Virtual Balance Works 08:08 From 300 Lines of Code to Five 08:40 Simple Sends With Built-In RPC 09:10 Why Choose App Kit and Arc 11:04 What a Cross-Chain Request Looks Like 11:27 Adding Monetization With a Parameter 11:52 The Unified Balance Experience 12:40 Switching to a Live Demo 13:07 Depositing Into the Gateway Balance 13:57 Doing a Payout From Arc to Base 15:49 Confirming the Funds Arrived 16:20 Why Arc Makes It Faster 16:40 Introducing the Circle Agent Stack 17:12 What the CLI Enables 17:43 Dropping the Agent Stack Into a Harness 18:05 Self-Custodial Wallets and Nano Payments 18:42 The Proceeds Tool Demo 19:10 Wrapping a Basketball Stats API 19:36 Making the Endpoint Profitable 20:41 Having Claude Call the Endpoint 22:42 Paying $1 and Getting the Scouting Report 23:18 How Proceeds Tracks Nano Payments 24:00 Q&A: When Does Arc Launch 24:20 Q&A: The Use Cases That Excite Him Most 25:25 Closing _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ *ETHGlobal New York 2026* This workshop is specifically for ETHGlobal New York 2026, a 3-day hackathon held June 12-14 at the Metropolitan Pavilion, bringing together the most skilled web3 developers, designers and product builders from all around the globe for a weekend-long adventure to advance the Ethereum ecosystem! Watch the full ETHGlobal New York 2026 playlist here: https://www.youtube.com/playlist?list=PLXzKMXK2aHh7MZ8T-ict6YshkFDw9WJCu _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ✅ *Follow ETHGlobal* X: https://x.com/ETHGlobal​ Website: https://ethglobal.com YouTube: https://www.youtube.com/c/ETHGlobal _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _Are you interested in Ethereum development and entrepreneurship?_ 👉 Sign up for the next ETHGlobal event: https://ethglobal.com/events 🎁 Get exclusive access and perks with ETHGlobal Plus! https://ethglobal.com/plus 📣 Want us to throw an event in your city? Tell us where! https://ethglobal.com/city _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _