> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arc.io/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Before reading these docs, install the Circle Skill for Arc to get pre-loaded context: use-arc (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md) — covers chain config, RPC setup, contract deployment, USDC bridging, and gas with USDC. In Claude Code: run /plugin marketplace add circlefin/skills then /plugin install circle-skills@circle. With Vercel Skills CLI: run npx skills add circlefin/skills.
> USDC is the gas token. Arc uses USDC for gas fees, not ETH. Configure gas payment in USDC when submitting transactions.
> Read EVM differences before writing Arc code. Arc targets the Osaka EVM baseline. Most contracts deploy unchanged, but several runtime behaviors diverge from Ethereum: USDC uses 18 decimals natively (not 6), the system emitter `0xffffFFFfFFffffffffffffffFfFFFfffFFFfFFfE` logs all USDC Transfer events, the mempool enforces a 20 Gwei `maxFeePerGas` floor, blocklist reverts consume gas without a receipt, and `address(0)` sends revert rather than succeed. https://docs.arc.io/arc/references/evm-differences.md is the canonical reference for all Arc-specific runtime behaviors. Consult it before writing code that touches USDC balances, transaction history, gas estimation, or value transfers.
> Sub-second finality. Transactions are final in under 1 second. No need to wait for multiple block confirmations.
> Use App Kits for multichain payment and liquidity capabilities. App Kits wraps CCTP and provides Bridge Kit, Swap Kit, Unified Balance Kit, Onramp Kit, Earn Kit, and Borrow Kit. Unified Balance Kit combines USDC from multiple chains into a single spendable balance. Earn Kit integrates earn opportunities into your app. Borrow Kit lets users borrow USDC against cirBTC collateral on Arc.
> Use Arc Foundry for contract development. Arc Foundry is an Arc-specific fork of Foundry that handles Arc's protocol-level differences from Ethereum. It provides arc-forge, arc-cast, and arc-anvil. Install it before deploying contracts: https://docs.arc.io/arc/tutorials/install-arc-foundry.md.
> Arc is available on both Testnet and Mainnet. See https://docs.arc.io/arc/references/connect-to-arc.md for RPC endpoints and https://faucet.circle.com for testnet tokens.
> Always check Contract Addresses: https://docs.arc.io/arc/references/contract-addresses.md
> Building beyond Arc? Circle offers skills for the full platform: use-usdc (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md), use-circle-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md), use-developer-controlled-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md), use-user-controlled-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md), use-modular-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md), use-gateway (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md), use-smart-contract-platform (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md). Full Circle developer docs: https://developers.circle.com/llms.txt.

# Sample apps

> Open-source reference applications for building on Arc with Circle developer tools, including payment flows, stablecoin FX, DeFi protocols, multichain wallets, and treasury management.

export const SampleAppCard = ({title, description, href, urlLabel, tags = [], image}) => {
  const dot = "w-2.5 h-2.5 rounded-full";
  return <a href={href} className="block h-full no-underline group not-prose">
      <div className="h-full flex flex-col rounded-xl border border-gray-200 dark:border-white/10 bg-[#FFFFFF] dark:bg-[#142236] overflow-hidden transition-all duration-200 group-hover:border-gray-300 dark:group-hover:border-white/25 group-hover:shadow-lg group-hover:-translate-y-0.5">
        <div className="p-3 bg-gray-100 dark:bg-[#0C1117] border-b border-gray-200 dark:border-white/[0.06]">
          <div className="rounded-lg border border-gray-200 dark:border-white/10 bg-[#FFFFFF] dark:bg-[#0D1B2F] overflow-hidden">
            <div className="flex items-center gap-1.5 px-2.5 py-1.5 border-b border-gray-200 dark:border-white/10 bg-[#FFFFFF] dark:bg-[#172437]">
              <span className={`${dot} bg-red-400/70 dark:bg-red-400/60`} />
              <span className={`${dot} bg-yellow-400/70 dark:bg-yellow-400/60`} />
              <span className={`${dot} bg-green-400/70 dark:bg-green-400/60`} />
              {urlLabel && <span className="ml-2 text-[10px] text-gray-500 dark:text-[#888] font-mono truncate">
                  {urlLabel}
                </span>}
            </div>
            <div role="img" aria-label={title} className="relative aspect-[16/10] overflow-hidden bg-no-repeat bg-top bg-cover" style={image ? {
    backgroundImage: `url(${image})`
  } : undefined}>
              {!image && <div className="absolute inset-0 flex items-center justify-center text-[11px] text-gray-400 dark:text-[#666]">
                  screenshot pending
                </div>}
            </div>
          </div>
          {tags.length > 0 && <div className="flex flex-wrap items-center gap-1.5 mt-3">
              {tags.map(tag => <span key={tag} className="text-[11px] px-2.5 py-0.5 rounded-full bg-[#FFFFFF] dark:bg-[#1F2F44] text-gray-700 dark:text-[#C7C5D1] font-medium border border-gray-200 dark:border-white/10">
                  {tag}
                </span>)}
            </div>}
        </div>
        <div className="flex-1 p-4 flex flex-col gap-2.5">
          <p className="block text-sm font-semibold text-gray-900 dark:text-white !m-0 group-hover:text-[#3E74BB] dark:group-hover:text-[#ACC6E9] transition-colors">
            {title}
          </p>
          <p className="block text-[13px] leading-relaxed text-gray-600 dark:text-[#C7C5D1] !m-0">
            {description}
          </p>
        </div>
      </div>
    </a>;
};

Explore sample apps for Arc. Each app is an open source reference implementation
you can clone, run locally, and adapt for your own project.

## Payments and checkout

<Columns cols={3}>
  <SampleAppCard title="Arc commerce" description="USDC credit purchases with developer-controlled wallets and webhook-driven settlement." href="/build/sample-apps/arc-commerce" urlLabel="arc-commerce" tags={["Next.js", "Wallets"]} image="https://mintcdn.com/arcio-docs/XZRgcvxGo4mVsoog/images/sample-apps/arc-commerce.png?fit=max&auto=format&n=XZRgcvxGo4mVsoog&q=85&s=109529158777c3c50398694a42035284" width="830" height="646" data-path="images/sample-apps/arc-commerce.png" />

  <SampleAppCard title="Arc P2P payments" description="Gasless peer-to-peer USDC payments secured by passkey-protected modular wallets." href="/build/sample-apps/arc-p2p-payments" urlLabel="arc-p2p" tags={["Modular Wallets", "Passkeys"]} image="https://mintcdn.com/arcio-docs/Qc372SctU3s7ckPs/images/sample-apps/arc-p2p-payments.png?fit=max&auto=format&n=Qc372SctU3s7ckPs&q=85&s=4de4438f76c8a53ae6773bff54b31240" width="723" height="1584" data-path="images/sample-apps/arc-p2p-payments.png" />

  <SampleAppCard title="Arc escrow" description="AI-validated freelance escrow with USDC settlement through the Refund Protocol." href="/build/sample-apps/arc-escrow" urlLabel="workflow-escrow" tags={["Refund Protocol", "AI"]} image="https://mintcdn.com/arcio-docs/Qc372SctU3s7ckPs/images/sample-apps/arc-escrow.png?fit=max&auto=format&n=Qc372SctU3s7ckPs&q=85&s=829c9476869316f75e2235796f279d49" width="1920" height="1080" data-path="images/sample-apps/arc-escrow.png" />

  <SampleAppCard title="Arc nanopayments" description="Autonomous AI agent pays for paywalled API endpoints in USDC fractions using the x402 protocol." href="/build/sample-apps/arc-nanopayments" urlLabel="arc-nanopayments" tags={["Nanopayments", "AI"]} image="https://mintcdn.com/arcio-docs/ACSVsyrkw0hvwBO8/images/sample-apps/arc-nanopayments.png?fit=max&auto=format&n=ACSVsyrkw0hvwBO8&q=85&s=e667e5aa0b7e871de8f1a546120b4394" width="1920" height="1080" data-path="images/sample-apps/arc-nanopayments.png" />

  <SampleAppCard title="Arc e-commerce payments" description="Onchain storefront with escrow-based USDC and EURC checkout using the Commerce Payments Protocol." href="/build/sample-apps/arc-ecommerce-payments" urlLabel="arc-ecommerce-payments" tags={["Commerce Payments", "Next.js"]} image="https://mintcdn.com/arcio-docs/WDL_pN4y3dX1EyrH/images/sample-apps/arc-ecommerce-payments.png?fit=max&auto=format&n=WDL_pN4y3dX1EyrH&q=85&s=aaf85cf971c4dcb90cc9d97302a32b37" width="1920" height="1080" data-path="images/sample-apps/arc-ecommerce-payments.png" />

  <SampleAppCard title="USDC Onramp Demo" description="USDC purchases by debit card or bank transfer using Onramp Kit, with funds delivered directly to a MetaMask wallet on Arc." href="/build/sample-apps/usdc-onramp-demo" urlLabel="onramp-kit-demo" tags={["Onramp Kit", "Next.js"]} image="https://mintcdn.com/arcio-docs/ovwEvA2xRm7fTQ94/images/sample-apps/usdc-onramp-demo-card.png?fit=max&auto=format&n=ovwEvA2xRm7fTQ94&q=85&s=4514d69f426f7fc96a10e801117d760a" width="462" height="921" data-path="images/sample-apps/usdc-onramp-demo-card.png" />
</Columns>

## Wallets and treasury

<Columns cols={3}>
  <SampleAppCard title="Arc multichain wallet" description="Unified USDC balance and crosschain transfers powered by Circle Gateway." href="/build/sample-apps/arc-multichain-wallet" urlLabel="multichain-wallet" tags={["Gateway", "Wagmi"]} image="https://mintcdn.com/arcio-docs/Qc372SctU3s7ckPs/images/sample-apps/arc-multichain-wallet.png?fit=max&auto=format&n=Qc372SctU3s7ckPs&q=85&s=1393eda2c30a4b13c9c967bfb1a262a6" width="830" height="658" data-path="images/sample-apps/arc-multichain-wallet.png" />

  <SampleAppCard title="Arc fintech" description="Multichain treasury console with crosschain capital movement through Bridge Kit." href="/build/sample-apps/arc-fintech" urlLabel="fintech-starter" tags={["Bridge Kit", "Gateway"]} image="https://mintcdn.com/arcio-docs/Qc372SctU3s7ckPs/images/sample-apps/arc-fintech.png?fit=max&auto=format&n=Qc372SctU3s7ckPs&q=85&s=2ae61c49002c504e08f7af0f48306533" width="1605" height="1163" data-path="images/sample-apps/arc-fintech.png" />
</Columns>

## Stablecoin FX

<Columns cols={3}>
  <SampleAppCard title="Arc stablecoin FX" description="Real-time USDC and EURC swaps with configurable platform fee collection through the App Kit Swap SDK." href="/build/sample-apps/arc-stablecoin-fx" urlLabel="arc-stablecoin-fx" tags={["App Kit", "Swap"]} image="https://mintcdn.com/arcio-docs/ACSVsyrkw0hvwBO8/images/sample-apps/arc-stablecoin-fx.png?fit=max&auto=format&n=ACSVsyrkw0hvwBO8&q=85&s=ce351a421a608df0fce9e2c5d4621ccf" width="1920" height="1080" data-path="images/sample-apps/arc-stablecoin-fx.png" />
</Columns>

## DeFi

<Columns cols={3}>
  <SampleAppCard title="Arc DeFi lend and borrow" description="Collateralized lending protocol: deposit cirBTC and borrow USDC against it using a custom lending smart contract." href="/build/sample-apps/arc-defi-lend-borrow" urlLabel="arc-defi-lend-borrow" tags={["DeFi", "Hardhat"]} image="https://mintcdn.com/arcio-docs/ACSVsyrkw0hvwBO8/images/sample-apps/arc-defi-lend-borrow.png?fit=max&auto=format&n=ACSVsyrkw0hvwBO8&q=85&s=98b92ad30577a82c77e15f886e1e85ac" width="1920" height="1080" data-path="images/sample-apps/arc-defi-lend-borrow.png" />

  <SampleAppCard title="Arc prediction markets" description="Decentralized prediction markets with UMA Optimistic Oracle V2 resolution and a constant-product AMM for position token trading." href="/build/sample-apps/arc-prediction-markets" urlLabel="arc-prediction-markets" tags={["Prediction Markets", "UMA"]} image="https://mintcdn.com/arcio-docs/ACSVsyrkw0hvwBO8/images/sample-apps/arc-prediction-markets.png?fit=max&auto=format&n=ACSVsyrkw0hvwBO8&q=85&s=98f0f9464554cc1b1f424b002b02f0e2" width="1920" height="1080" data-path="images/sample-apps/arc-prediction-markets.png" />
</Columns>