Crosschain Usdc Balance Gateway

---
name: crosschain-usdc-balance-gateway
description: "Unified crosschain USDC balance via Circle Gateway + Circle Programmable Wallets. Deposit USDC on any supported chain, check your unified balance, and instantly mint USDC on any destination chain in <500ms — no bridging, no raw private keys."
category: "Finance & Crypto"
author: community
version: "1.1.0"
icon: coins
---

# Nexwave Gateway — Unified Crosschain USDC for OpenClaw Agents

## What This Skill Does

Circle Gateway gives you a **single unified USDC balance** that is instantly accessible on any supported chain in under 500 milliseconds. Instead of holding separate USDC balances on Ethereum, Base, Avalanche, etc., you deposit USDC into Gateway on any chain and can mint it out on any other chain — instantly.

This is fundamentally different from bridging. There are no liquidity pools, no bridge operators, no 15-minute waits. Gateway uses a deposit → sign burn intent → receive attestation → mint flow that executes in <500ms.

## Supported Chains (Testnet)

| Chain | Domain ID | USDC Address |
|---|---|---|
| Ethereum Sepolia | 0 | `0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238` |
| Base Sepolia | 6 | `0x036CbD53842c5426634e7929541eC2318f3dCF7e` |
| Arc Testnet | 26 | `0x3600000000000000000000000000000000000000` |

**Note:** Arc is Circle's purpose-built L1 blockchain where USDC is the native gas token. No separate gas token needed — USDC covers everything. Arc has the fastest Gateway finality at ~0.5 seconds.

**Gateway Contracts (same address on all EVM chains):**
- Gateway Wallet: `0x0077777d7EBA4688BDeF3E311b846F25870A19B9`
- Gateway Minter: `0x0022222ABE238Cc2C7Bb1f21003F0a260052475B`

**Gateway API (testnet):** `https://gateway-api-testnet.circle.com/v1`

## Prerequisites

1. Circle Developer Account with API key and entity secret (https://console.circle.com)
2. The `circle-wallet` skill installed (`clawhub install eltontay/circle-wallet`) with a wallet set containing wallets on ETH-SEPOLIA, BASE-SEPOLIA, and ARC-TESTNET
3. Testnet USDC from https://faucet.circle.com (20 USDC per address per chain, every 2 hours)
4. Testnet ETH for gas on Sepolia/Base Sepolia (use Google's Sepolia faucet). On Arc, USDC is the native gas token — same faucet covers everything.
5. Node.js installed with the `viem`, `dotenv`, and `@circle-fin/developer-controlled-wallets` packages

## How To Use This Skill

### Step 1: Setup the Project

Run the setup script to initialize the project with all dependencies:

```bash
cd /path/to/nexwave-gateway && bash setup.sh
```

This creates a `gateway-app/` directory with all necessary files pre-configured.

### Step 2: Check Gateway Info and Your Balance

```bash
cd gateway-app && node check-balance.js
```

This queries the Gateway API for supported chains and shows your unified USDC balance across all chains.

### Step 3: Deposit USDC into Gateway

```bash
node deposit.js
```

This deposits USDC into the Gateway Wallet contract on Ethereum Sepolia and Arc Testnet. After deposit and chain finality, your unified balance is credited. Arc finalizes in ~0.5 seconds; Ethereum may take up to 20 minutes.

### Step 4: Transfer USDC Crosschain Instantly

```bash
node transfer.js
```

This creates burn intents, signs them via Circle Programmable Wallets (MPC — no raw private keys), submits them to the Gateway API for attestation, and mints USDC on Base Sepolia. The attestation response typically arrives in <500ms.

## Key Concepts

**Unified Balance:** After depositing USDC into Gateway on any chain, the Gateway system credits your address with a unified balance. This balance is not locked to any specific chain — it can be accessed on any supported chain.

**Burn Intent:** To withdraw from your unified balance to a specific chain, you sign a "burn intent" — an EIP-712 typed data structure specifying the source chain, destination chain, amount, and recipient. Signing is done securely via Circle's MPC Programmable Wallets (no raw private keys). Gateway verifies your balance is sufficient and returns a signed attestation.

**Circle Programmable Wallets:** Instead of raw private keys in `.env` files, this skill uses Circle's developer-controlled wallets backed by multi-party computation (MPC). The private key is never exposed — signing happens server-side via Circle's API. This makes the skill safe for agent use without risk of key exfiltration.

**Attestation:** The Gateway API's signed proof that authorizes minting on the destination chain. You submit this attestation to the Gateway Minter contract on the destination chain to receive USDC.

**Fees:** 0.5 basis points (0.005%) during the early access period (through June 30, 2026). Plus base gas fees for on-chain transactions.

## Flow Diagram

```
Agent deposits USDC on Chain A
        │
        ▼
Gateway Wallet Contract (approve + deposit)
        │
        ▼
Wait for chain finality → Unified balance credited
        │
        ▼
Agent signs burn intent (EIP-712 via Circle MPC Wallets)
        │
        ▼
Submit to Gateway API ──► Attestation returned (<500ms)
        │
        ▼
Submit attestation to Gateway Minter on Chain B
        │
        ▼
USDC minted on Chain B for recipient
```

## Agent Use Cases

- **Multi-chain arbitrage:** Access USDC on any chain instantly to capture price differences
- **Cross-chain payments:** Pay for services on any chain from a single balance
- **Treasury management:** Consolidate USDC from multiple chains into one balance
- **Agent-to-agent commerce:** Accept payment on one chain, spend on another without delays
- **Capital efficiency:** No need to pre-position USDC across chains

## Troubleshooting

- **"Insufficient balance"**: Wait for chain finality after depositing. Ethereum takes ~20 min, Arc is ~0.5 seconds.
- **"Gateway deposit not yet picked up"**: The Gateway API waits for block confirmations. Be patient on Ethereum.
- **Gas errors**: On Ethereum/Base you need testnet ETH for gas. On Arc, USDC is the gas token — same faucet covers everything.
- **Faucet limits**: You can get 20 USDC per address per chain every 2 hours from faucet.circle.com.

## References

- Circle Gateway Docs: https://developers.circle.com/gateway
- Circle Programmable Wallets: https://developers.circle.com/wallets
- Circle Wallet Skill (ClawHub): https://clawhub.ai/eltontay/circle-wallet
- Arc Testnet Docs: https://docs.arc.network
- Gateway Quickstart: https://developers.circle.com/gateway/quickstarts/unified-balance-evm
- Full Quickstart Code: https://github.com/circlefin/evm-gateway-contracts/tree/master/quickstart
- Circle Faucet: https://faucet.circle.com
- Gateway API Reference: https://gateway-api-testnet.circle.com/v1/info