> ## 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.

# Borrow and lend

> Build collateralized lending protocols on Arc with instant settlement, native USDC borrowing, and programmable liquidation.

Onchain lending on Arc uses a collateral-backed borrowing model: users lock
crypto assets in a smart contract and borrow USDC against them. Arc's
[deterministic finality](/arc/concepts/deterministic-finality) settles
collateral deposits and repayments in under a second, and its USDC-denominated
gas gives liquidators and borrowers predictable, stable transaction
costs—removing volatile fee overhead from interest rate and liquidation
threshold calculations.

For decentralized trading and speculative position markets, see
[Prediction markets](/build/prediction-markets). For stablecoin exchange
infrastructure, see [Stablecoin FX](/build/stablecoin-fx).

## Sample apps

Open-source examples on GitHub you can fork and customize.

<Columns cols={1}>
  <Card title="Arc DeFi lend and borrow" icon="building-columns" href="https://github.com/circlefin/arc-defi-lend-borrow">
    Lending against collateral on Arc: deposit cirBTC and borrow USDC against it
    using a custom lending smart contract, Circle Modular Wallets, and Supabase.
  </Card>
</Columns>

## Quickstarts

Get up and running with lending contracts in minutes.

<Columns cols={2}>
  <Card title="Deploy on Arc" icon="rocket" href="/arc/tutorials/deploy-on-arc">
    **Beginner**. Deploy, test, and interact with a Solidity smart contract on
    Arc using Foundry.
  </Card>

  <Card title="Batch USDC transfers" icon="layer-group" href="/arc/tutorials/batch-usdc-transfers">
    **Intermediate**. Execute multiple USDC transfers in a single
    transaction—useful for pool distributions and bulk repayments.
  </Card>
</Columns>

## Why build lending on Arc

Arc is purpose-built for stablecoin finance. These capabilities directly support
lending and borrowing applications.

<AccordionGroup>
  <Accordion title="Instant collateral confirmation">
    [Deterministic finality](/arc/concepts/deterministic-finality) confirms
    collateral deposits and repayments in under a second, reducing the window
    during which positions can become eligible for liquidation.
  </Accordion>

  <Accordion title="Native USDC borrowing">
    USDC is Arc's native settlement currency—no wrapping, synthetic pools, or
    bridging overhead. See [contract
    addresses](/arc/references/contract-addresses) for USDC token details.
  </Accordion>

  <Accordion title="Stable, predictable gas">
    USDC-denominated gas removes fee volatility from liquidation calculations.
    Liquidators can model profitability precisely. See [gas and
    fees](/arc/references/gas-and-fees) for current rates.
  </Accordion>

  <Accordion title="Batched liquidations">
    [Batched transactions](/arc/concepts/batched-transactions) let liquidators
    bundle collateral seizure and repayment into a single atomic transaction,
    reducing gas overhead and liquidation complexity.
  </Accordion>

  <Accordion title="Oracle price feeds">
    Integrate Chronicle, Chainlink, or other providers from the
    [oracles](/arc/tools/oracles) page to price collateral accurately for
    loan-to-value enforcement.
  </Accordion>

  <Accordion title="Standard EVM tooling">
    Solidity lending contracts deploy unchanged on Arc. See [EVM
    compatibility](/arc/references/evm-differences) for differences to check
    before deploying.
  </Accordion>
</AccordionGroup>