> ## 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. # Arc Network > A purpose-built Layer-1 blockchain for stablecoin-native financial applications with USDC as gas, sub-second deterministic finality, and full EVM compatibility. Arc is a purpose-built Layer-1 blockchain for stablecoin-native financial applications, with USDC as gas, sub-second deterministic finality, and full EVM compatibility. It supports payments, lending, FX, treasury management, and agentic commerce at scale. Beyond the network, Arc provides [App Kits](/app-kit) for crosschain payment workflows, [AI tooling](/ai/mcp) for agent-based development, and a growing [ecosystem of infrastructure partners](/build#developer-tools). ## Key features USDC is the native gas token. EURC and USYC are natively supported. No volatile token required. Transaction fees are denominated in USDC, so costs stay predictable regardless of market volatility. Transactions finalize in under one second with no risk of chain reorganization. Deploy existing Solidity contracts and use standard Ethereum tooling like Hardhat, Foundry, and Viem. Run Solidity contracts confidentially in Arc Privacy Sector (APS), an opt-in execution environment that finalizes alongside the public EVM. `SLH-DSA-SHA2-128s` wallet signatures protect accounts against future quantum threats. ## Stablecoins on Arc Arc is designed from the ground up around stablecoins. USDC serves as the native [gas token](/arc/references/gas-and-fees), EURC enables euro-denominated transfers, and USYC provides onchain yield. There is no volatile native token. For details on the dual-interface model, native representations, and supported assets, see [stablecoin native model](/arc/concepts/stablecoin-native-model). ## Network architecture Arc separates consensus from execution so each layer can optimize independently while maintaining full compatibility with the Ethereum ecosystem. * **[Consensus layer](/arc/concepts/consensus-layer):** Built on Malachite BFT, delivering sub-second finality and high throughput across a permissioned validator set. * **[Execution layer](/arc/concepts/execution-layer):** Powered by Reth, a Rust Ethereum client that runs the EVM so Solidity contracts, development tools, and wallet infrastructure work without modification. For a complete view of how the layers interact, see the [system overview](/arc/concepts/system-overview). ## Network details | **Property** | **Value** | | - | - | | Consensus | Malachite BFT | | Execution environment | EVM (Osaka hard fork) | | Gas token | USDC | | Block time | \~0.48 s (testnet) | | Chain ID | 5042002 | | Finality | Deterministic, sub-second | | Validator participation | Permissioned | | Developer access | Permissionless | For RPC endpoints and connection details, see [RPC endpoints](/arc/references/rpc-endpoints). For deployed contract addresses, see [contract addresses](/arc/references/contract-addresses). For how Arc validators are selected and how the network is operated, see [consensus layer](/arc/concepts/consensus-layer). ## Start building Ready to build on Arc? Head to the [Build](/build) section for quickstarts and tutorials covering smart contract deployment, crosschain bridging, App Kits workflows, and AI agent integration.