> ## 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.
# Integrate with Arc
> Connect wallets, exchanges, and infrastructure to the Arc network.
Arc is [EVM-compatible](/arc/references/evm-differences)—it supports the same
bytecode, RPC methods, and tooling as Ethereum. Three key differences drive most
integration work:
* **USDC as gas**: fees are paid in USDC. Any relayer, paymaster, or funded
wallet account must hold USDC. This affects gas estimation, fee display, and
balance APIs.
* **Deterministic finality**—transactions finalize in under one second with no
risk of reorganization. A single confirmation is sufficient.
* **Dual USDC interface**—native balance uses 18 decimals while the ERC-20
interface uses 6 decimals. Both share the same underlying balance.
See [EVM compatibility](/arc/references/evm-differences) for a full list of
differences from Ethereum.
## Exchanges
Integrate Arc deposits, withdrawals, and USDC liquidity management into your
exchange.
Overview of deposit, withdrawal, and bridging workflows for exchanges.
Subscribe to blocks and detect incoming USDC transfers with one-confirmation
finality.
Build, sign, and broadcast withdrawal transactions with USDC gas.
Move USDC liquidity to and from Arc using Cross-Chain Transfer Protocol.
Configure Fireblocks, BitGo, SAFE, and other custody platforms for Arc.
## On/off-ramps
Add Arc as a supported network in your fiat-to-crypto ramp service.
Chain registration, deposit detection, withdrawal processing, and UI display
for ramp providers.
## Wallets
Add Arc as a supported network in your wallet application.
Overview of Arc wallet integration for embedded wallets, smart wallets, and
browser wallet extensions.
Chain configuration, balance display, transaction history, and fee handling
for wallet providers.
Arc's two-state transaction model: pending or final, with no intermediate
confirmation states.
Fetch, estimate, and display transaction fees in USDC.
## Infrastructure
Add Arc support to node services, data indexers, oracle networks, block
explorers, and compliance tools.
Key differences from standard EVM chains and chain metadata for
infrastructure providers.
Unified transfer events, no-reorg indexing, and block streaming guidance.
Finality configuration, CCTP routing, and relay infrastructure for bridge
protocols.
Blocklist enforcement, Memo contract monitoring, and compliance tool
integrations.
## Essentials
RPC endpoints, chain ID, WebSocket URLs, and explorer links.
Deploy, test, and interact with a Solidity smart contract on Arc.
Full EVM differences table, dual USDC interface, and integration pitfalls.
Operate your own Arc node for independent verification or direct RPC access.