Arc Relay Bridge

A cross-chain USDC bridge built on Circle's CCTP V2, deployable to Arc Testnet. Burn USDC on a source chain and natively mint it on the destination — no wrapped tokens, no liquidity pools.

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Features

• Native USDC bridging via Circle CCTP V2 — 1:1, no slippage, no wrapped tokens
• ERC-4337 gasless burn (Beta) — bridge without native tokens using our USDC Paymaster
• Gasless mint relay — skip the wallet-switch step on arrival for a 1 USDC relay fee
• 4-step progress UI — Approve → Burn → Attest → Mint with real-time status
• Session resume — interrupted bridges can be resumed from the burn transaction hash
• Multi-chain — Arc Testnet ↔ Ethereum Sepolia, Base Sepolia, Avalanche Fuji

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Supported Chains

Chain	CCTP Domain	Chain ID	minFinalityThreshold
Arc Testnet	26	5042002	2000 (finalized)
Ethereum Sepolia	0	11155111	1000 (safe, ~1–3 min)
Base Sepolia	6	84532	1000 (safe, ~1–3 min)
Avalanche Fuji	1	43113	1000 (safe, ~1–3 min)

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Contract Addresses

All CCTP V2 contracts are deployed at the same address on every chain.

Contract	Address
TokenMessenger (CCTP V2)	0x8FE6B999Dc680CcFDD5Bf7EB0974218be2542DAA
MessageTransmitter (CCTP V2)	0xE737e5cEBEEBa77EFE34D4aa090756590b1CE275

Chain	USDC Address
Arc Testnet	0x3600000000000000000000000000000000000000
Ethereum Sepolia	0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238
Base Sepolia	0x036CbD53842c5426634e7929541eC2318f3dCF7e
Avalanche Fuji	0x5425890298aed601595a70AB815c96711a31Bc65

Paymaster v5 (ERC-4337 v0.7)

Deployed 2026-06-01. Compiled with evmVersion: "paris" for Arc/Fuji compatibility.

Chain	Address
Arc Testnet	0xfD06D288d481515a986DF28030AF013De290D76C
Ethereum Sepolia	0xC9E9ba0bfE58FA438B8B6f2182d3ADA3669F9Eb4
Base Sepolia	0xe355E9dCdEAB37eA8fd81b9457Ad2C56d3eE9055
Avalanche Fuji	0x7C75A75B59b63871e1Bb47fA63e541F0e5975f93

FeeRouter v2

Deployed 2026-05-23. Hardened: immutable addresses, reentrancy lock, zero-recipient guard.

Chain	Address
Arc Testnet	0x8256a1e1f8971448b49dA0F55b8A1BB6557eA8FC
Ethereum Sepolia	0x5B1F511ed4dF76f369671BF1c4aCF0dD84CC0804
Base Sepolia	0x8d4B57eD464df10414Dde3ADC2E403a01ebc50d8
Avalanche Fuji	0x64D160b7E91e78e52dFc0e8829640E32A919164C

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Quick Start

pnpm install
pnpm --filter @workspace/arc-bridge run dev   # bridge frontend
pnpm run typecheck                             # full typecheck
pnpm run build                                 # build all packages

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Architecture

The bridge is frontend-only — all logic runs client-side via ethers.js + MetaMask.

User EOA (MetaMask)
    │
    ├─ Standard bridge
    │     └─ approve → depositForBurn → poll Iris API → receiveMessage
    │
    └─ ERC-4337 gasless
          ├─ Smart account (SimpleAccount, same address on every chain)
          │     └─ approve + depositForBurn (batched UserOp)
          ├─ Paymaster gas vault (USDC replaces native tokens for gas)
          └─ Pimlico bundler → EntryPoint v0.7

Key decisions

• CCTP V2 only — 7-param depositForBurn (selector 0x8e0250ee). V1 selector reverts.
• Arc USDC uses 6 decimals via ERC-20 interface (native representation is 18 dec for gas only).
• Gasless USDC source — the smart account's own wallet. The Paymaster gas vault covers gas fees only, not the bridge amount.
• entryPoint is constant — keeps single-slot 0x60a0 init; 2-immutable 0x60c0 silently reverts on Arc/Base/Fuji.
• No nonReentrant on validatePaymasterUserOp — ERC-7562 forbids global storage writes for unstaked paymasters.

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Stack

Layer	Technology
Frontend	React 19 + Vite + Tailwind CSS + shadcn/ui
Web3	ethers.js v6
ERC-4337	permissionless v0.3.6 + viem v2.51.3
Bundler	Pimlico (testnet)
Protocol	Circle CCTP V2
Attestation	Circle Iris API (sandbox)
Monorepo	pnpm workspaces + Node.js 24 + TypeScript 5.9

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Documentation

File	Description
Overview	Product overview and bridge flow
User Guide	Step-by-step usage and ERC-4337 setup
Paymaster	Paymaster architecture, flow, deployment
Technical Reference	Addresses, ABIs, RPCs
Development	Local setup, scripts, gotchas
Changelog	Release history and bug fixes

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Known Gotchas

• ALL chains use CCTP V2 — V1 4-param selector will revert.
• Arc USDC is a special system address — always use ERC-20 interface (6 dec).
• Arc explorer: https://testnet.arcscan.app — previous URLs are dead.
• Sepolia RPC: use publicnode.com — rpc.sepolia.org is unreliable.
• Paymaster gas vault ≠ smart account wallet — the vault covers gas, not the bridge amount.
• Base Sepolia gasless needs a one-time gas vault deposit before first bridge.

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Links

• Circle Faucet (testnet USDC)
• Arc Docs
• CCTP Docs
• Arc Testnet Explorer
• Sepolia Etherscan
• Base Sepolia Explorer
• Fuji Explorer