ArcSwap Documentation

ArcSwap is the yield terminal for stablecoins on Arc — earn tokenized U.S. Treasury yield via USYC, swap inside Arc, bridge USDC across chains with CCTP, and provide liquidity. This guide will get you from zero to your first deposit in under five minutes.

Introduction

ArcSwap is a non-custodial frontend that brings together four primitives on the Arc Layer 1 blockchain into a single interface: a tokenized Treasury vault (Hashnote USYC), an automated market maker (Uniswap V2), Circle's cross-chain transfer protocol (CCTP V2), and a liquidity pool dashboard.

You always retain custody. ArcSwap never holds your funds, never has a backend that can pause your access, and the entire frontend is open-source and pinned to IPFS so the build you load is the build that was published.

Who is it for?

• Stablecoin holders who want yield on idle USDC without leaving the dollar.
• Arc-native traders swapping USDC ↔ EURC ↔ USYC inside the L1.
• Cross-chain users bridging USDC between Arc, Ethereum, Base, and other CCTP chains.
• Liquidity providers earning swap fees by adding to USDC/EURC and USDC/USYC pools.

Quick start

From a fresh browser to your first vault deposit in five steps.

1. Install a wallet. MetaMask, Rabby, or Coinbase Wallet — any EVM-compatible browser wallet works. See Supported wallets.
2. Add Arc Testnet. Visit arcswap.net/trade, click Connect, and approve the network add. Or add manually using the network info below.
3. Get testnet USDC. Use the Circle faucet to drip USDC onto your address. Arc uses USDC as native gas, so the faucet covers both spending and gas.
4. Open the Vault. Go to arcswap.net/vault, enter an amount of USDC, and click Deposit. You'll receive USYC tokens accruing daily.
5. That's it. Your USYC balance accrues yield based on the underlying U.S. Treasury bills. You can redeem any time during U.S. Treasury market hours.

Wallet setup

ArcSwap connects to your browser wallet via the standard EIP-1193 provider (i.e. window.ethereum). No accounts, no passwords, no centralized auth.

Adding Arc Testnet manually

If your wallet doesn't auto-prompt, add the network using these parameters:

Get testnet USDC

Arc Testnet uses USDC as the native gas token. You need USDC for both transactions and for whatever you want to do (deposit, swap, bridge). One faucet call covers both.

1. Visit faucet.circle.com.
2. Select Arc Testnet from the network dropdown.
3. Paste your wallet address and request — typically delivers within 30 seconds.
4. Faucet limit is per-day per-address. Come back tomorrow if you need more.

USYC Vault

The USYC Vault wraps Hashnote's U.S. Yield Coin (USYC), a tokenized money market fund backed 1:1 by short-duration U.S. Treasury bills and cash. Depositing USDC mints USYC at the live navigator-published NAV. Redeeming USYC burns it for USDC at the same NAV.

How the yield works

• The fund holds short-dated T-bills (typically 1-month and 3-month).
• As bills mature and roll, interest accrues to the fund's NAV.
• USYC's price-per-share rises by approximately the daily yield, divided across each accrual day.
• Currently targeting ~4.85% APY (varies with the U.S. Treasury rate environment).

Depositing

1. Connect wallet, ensure you're on Arc Testnet with USDC balance.
2. Open /vault, enter USDC amount.
3. First deposit triggers an approval tx (one-time per token, gives the vault permission to pull USDC).
4. Second tx is the deposit itself — you receive USYC tokens to your wallet.

Redeeming

Redemptions are processed at the next NAV strike during U.S. Treasury market hours. Outside hours, the request queues until market open.

Swap & Bridge

The /trade page combines two flows: an in-Arc AMM swap (USDC ↔ EURC ↔ USYC) and a cross-chain CCTP bridge for USDC.

Swap inside Arc

Swaps route through Uniswap V2 deployed by the Arc Foundation. The router computes the best direct or 2-hop path, you approve and execute. Slippage default is 0.5% (configurable).

Bridge across chains (CCTP)

CCTP (Cross-Chain Transfer Protocol) is Circle's burn-and-mint mechanism. Native USDC is destroyed on the source chain and freshly minted on the destination — no wrapped tokens, no liquidity pools, no bridge custodian.

1. Choose source chain (Arc Testnet) and destination chain (Ethereum Sepolia, Base Sepolia, etc.).
2. Enter USDC amount and recipient address.
3. First transaction: burn USDC on Arc.
4. Wait for Circle's IRIS attestation API (~10–20 minutes on testnet).
5. Second transaction: mint USDC on the destination chain. ArcSwap submits this for you when ready.

Liquidity Pools

The /pool page lets you provide liquidity to Uniswap V2 pairs on Arc and earn swap fees (0.25% per trade in the Arc fork). Currently surfaced pairs:

• USDC / EURC — stablecoin FX pair
• USDC / USYC — yield-bearing vs cash pair

Adding liquidity

1. Pick a pair, enter amounts (the second amount auto-fills based on current ratio).
2. Approve both tokens (one-time per token).
3. Click Add Liquidity — you receive LP tokens representing your share of the pool.

Removing liquidity

Burn your LP tokens to redeem the underlying USDC/EURC at the current pool ratio. Accumulated fees are baked into the redeemed amounts.

Points

The /point page shows your activity across vault deposits, swaps, bridges, and LP positions. Points are non-transferable and have no monetary value during testnet — they are an indicator of engagement and may inform future incentive programs.

Arc Network

Arc is a purpose-built Layer 1 blockchain optimized for stablecoin-denominated finance. Its three defining design choices:

• Stable fees — gas paid in USDC, so transaction costs are predictable in USD terms regardless of any token's price action.
• Sub-second deterministic finality — no chain reorgs; once a tx is finalized it cannot revert.
• Opt-in privacy — confidential transfers and selective disclosure for regulated use cases.

Arc is fully EVM-compatible: existing Solidity contracts, Hardhat / Foundry / Viem tooling all work without modification. Learn more at docs.arc.network.

USYC explained

USYC (U.S. Yield Coin) is an ERC-20 token issued by Hashnote representing shares of the Hashnote International Short Duration Yield Fund SP, a regulated money market fund holding short-dated U.S. Treasury bills and overnight repurchase agreements.

Key properties

Risks

• Issuer risk — Hashnote operates the fund. Their compliance, custody, and operational integrity matter.
• Smart contract risk — the USYC token contract and Teller contract have been audited but no audit eliminates risk.
• Market hours — redemptions queue outside market hours. In a panic, you can't exit instantly.
• Yield variability — the ~4.85% target tracks short-term U.S. Treasury rates and will move with the federal funds rate.

CCTP bridging

Cross-Chain Transfer Protocol is Circle's official bridge for USDC. Unlike lock-and-mint bridges (which create wrapped tokens backed by frozen liquidity), CCTP burns native USDC on the source chain and mints native USDC on the destination — every USDC stays "real USDC" all the way.

Why this matters

• No wrapped USDC variants (no USDC.e, no axlUSDC).
• No bridge TVL to drain — there's no pool of locked tokens for an attacker to target.
• Issuer-attested: only Circle's signed attestation can authorize the mint.

Trade-offs

• Latency — typically 10–20 minutes on testnet, 13–19 minutes on mainnet (Circle waits for source-chain finality).
• Two transactions — burn + mint, both paid by the user (gas on each chain).
• Limited chain coverage — only chains Circle supports (Ethereum, Base, Arbitrum, OP, Polygon PoS, Avalanche C-chain, Solana, Arc, etc.).

USDC as gas

Most chains use a volatile native token for gas (ETH, MATIC, AVAX). Arc uses USDC. The practical effect:

• Gas costs are predictable in USD terms — a transfer that costs $0.001 today costs $0.001 tomorrow, regardless of any token's price action.
• You don't need to maintain a "gas reserve" in a separate token. The same USDC you trade with pays for the trade.
• Internally, gas USDC has 18 decimals (to match standard EVM gas math), distinct from the 6-decimal ERC-20 USDC. The frontend handles the conversion.

Network info

Contract addresses

All contracts ArcSwap interacts with on Arc Testnet (chainId 5042002):

ArcSwap does not own or operate any smart contracts. The frontend calls into protocols operated by Hashnote, Circle, and the Arc Foundation.

Supported wallets

Any browser wallet that injects an EIP-1193 provider works. Tested:

• MetaMask — most common, widest compat
• Rabby — recommended for active DeFi users (better tx simulation, multi-chain UX)
• Coinbase Wallet — works via injected or extension
• Frame — desktop-native, supports hardware wallets
• Ledger / Trezor — through MetaMask, Rabby, or Frame

Mobile wallets via WalletConnect are not yet integrated. See Changelog for the roadmap.

Security

ArcSwap takes a defense-in-depth approach. Highlights:

• Non-custodial — no funds ever flow through ArcSwap-controlled addresses.
• Open source — the entire frontend is published; you can verify the code matches the served build.
• IPFS + ENS — production builds are content-addressed and pinned to multiple providers; ENS contenthash is updated only via multi-sig.
• CSP + SRI — Content-Security-Policy locks down script origins; Subresource Integrity hashes pin every CDN script.
• No hidden tracking — no analytics, no third-party scripts beyond what's required to render.

Found a vulnerability? Report it via SECURITY.md — bug bounty rewards from $100 (low) to $50,000 (critical), depending on impact.

FAQ

Why does USYC sometimes show 0% accrual?

U.S. Treasury markets are closed on weekends and U.S. bank holidays. During those windows the fund's NAV is fixed and your token quantity is unchanged, so the displayed APY rounds to zero. Yield resumes on the next U.S. business day.

Why is my CCTP bridge taking 20 minutes?

Circle waits for source-chain finality before issuing the attestation that authorizes the destination mint. On Arc this is sub-second; on Ethereum Sepolia it can take 13+ minutes (waiting for two epochs of beacon-chain finality). The total time is dominated by the slowest chain involved.

Can I lose money in the USYC vault?

In theory, yes — money market funds can technically "break the buck" if their underlying assets default. In practice, U.S. Treasury bills are the lowest-default-risk asset in global finance. Risks are detailed in the USYC explained section.

Does ArcSwap have its own token?

No. ArcSwap is a frontend, not a protocol. There is no ASWP token, no airdrop campaign, no governance token sale. Anyone telling you otherwise is running a scam.

When mainnet?

Arc mainnet is governed by the Arc Foundation; ArcSwap will deploy on mainnet shortly after Arc launches. See our roadmap for current milestones.

Changelog

v0.9.x — Arc Testnet

• 2026-04-25 — Documentation site published.
• 2026-04-25 — Security baseline: CSP, SRI, host security headers, vulnerability disclosure policy.
• 2026-04-22 — Vault page UX refresh; "How USYC works" section restructured for narrow viewports.
• 2026-04-20 — Homepage repositioned as Yield Terminal for Stablecoins.

Upcoming

• WalletConnect / Reown AppKit integration for mobile wallet support.
• Circle Gateway via Unified Balance Kit — deposit USYC from any supported chain.
• Status page at status.arcswap.net.
• Multi-sig governance for ENS contenthash and treasury.