# Arc Docs

> ## 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](https://docs.arc.io/arc-chain.md): A purpose-built Layer-1 blockchain for stablecoin-native financial applications with USDC as gas, sub-second deterministic finality, and full EVM compatibility.
- [Connect to Arc](https://docs.arc.io/arc/references/connect-to-arc.md): Set up your wallet and configure your development environment for Arc.
- [Deploy on Arc](https://docs.arc.io/arc/tutorials/deploy-on-arc.md): Deploy and interact with a Solidity smart contract on Arc Testnet using Arc Foundry.
- [EVM differences](https://docs.arc.io/arc/references/evm-differences.md): Arc's protocol-level differences from Ethereum: USDC as native gas, value transfer rules, SELFDESTRUCT semantics, EIP-7708 Transfer events, the fee market, and opcode behavior.
- [Stablecoin native model](https://docs.arc.io/arc/concepts/stablecoin-native-model.md): Arc is built around stablecoins as first-class assets, with USDC as the native gas token, EURC for euro-denominated transfers, and USYC for yield-bearing use cases.
- [Stable fee design](https://docs.arc.io/arc/concepts/stable-fee-design.md): Arc's fee market uses EWMA-smoothed base fees denominated in USDC and minimal priority fees, keeping transaction costs predictable and resistant to short-term demand spikes.
- [Deterministic finality and settlement](https://docs.arc.io/arc/concepts/deterministic-finality.md): Arc's deterministic finality delivers irreversible transaction settlement in under one second.
- [Opt-in privacy](https://docs.arc.io/arc/concepts/opt-in-privacy.md): Arc Privacy Sector (APS) is Arc's confidential execution environment for Solidity contracts, running alongside the public EVM with synchronous composability and default-deny contract isolation.
- [Post-quantum security](https://docs.arc.io/arc/concepts/post-quantum-security.md): Arc's post-quantum roadmap covers wallet signatures, validator authentication, private state, and supporting infrastructure against quantum-era attacks.
- [System overview](https://docs.arc.io/arc/concepts/system-overview.md): Arc separates consensus from execution across two layers: Malachite orders and finalizes blocks, Reth processes transactions and maintains state.
- [Consensus layer](https://docs.arc.io/arc/concepts/consensus-layer.md): Arc's Malachite consensus layer orders, validates, and finalizes blocks using a Tendermint-based Proof-of-Authority model.
- [Execution layer](https://docs.arc.io/arc/concepts/execution-layer.md): Arc's execution layer runs Reth, a Rust Ethereum client that maintains blockchain state, executes EVM transactions, and extends the pipeline with stablecoin-native modules including a USDC-denominated Fee Manager and the CallFrom precompile.
- [Gas and fees](https://docs.arc.io/arc/references/gas-and-fees.md): Runtime parameters for Arc gas pricing, including base fee bounds, EWMA smoothing, and best practices for submitting transactions.
- [Contract addresses](https://docs.arc.io/arc/references/contract-addresses.md): Arc mainnet and testnet contract addresses for stablecoins, CCTP, Gateway, StableFX, ERC-8004, and more. Includes the ERC-8183 testnet address.
- [Transaction memos](https://docs.arc.io/arc/concepts/transaction-memos.md): How the Memo contract attaches metadata to a contract call on Arc while preserving the original sender.
- [Batched transactions](https://docs.arc.io/arc/concepts/batched-transactions.md): How Multicall3From batches contract calls on Arc while preserving the original sender.
- [USDC system events](https://docs.arc.io/arc/references/usdc-system-events.md): Reference for how Arc emits USDC balance-change events: the native system Transfer log (EIP-7708) and the ERC-20 USDC contract events, with emitter addresses, signatures, and decimals for indexers.
- [RPC endpoints](https://docs.arc.io/arc/references/rpc-endpoints.md): RPC endpoints, network parameters, and node provider options for connecting to Arc mainnet and testnet.
- [Integrate with Arc](https://docs.arc.io/integrate.md): Connect wallets, exchanges, and infrastructure to the Arc network.
- [Connect to Arc](https://docs.arc.io/integrate/connect-to-arc.md): Set up your wallet and configure your development environment for Arc.
- [How-to: Install Arc Foundry](https://docs.arc.io/arc/tutorials/install-arc-foundry.md): Set up Arc Foundry to build and deploy contracts on Arc.
- [Deploy on Arc](https://docs.arc.io/integrate/deploy-on-arc.md): Deploy and interact with a Solidity smart contract on Arc Testnet using Arc Foundry.
- [EVM differences](https://docs.arc.io/integrate/evm-differences.md): Arc's protocol-level differences from Ethereum: USDC as native gas, value transfer rules, SELFDESTRUCT semantics, EIP-7708 Transfer events, the fee market, and opcode behavior.
- [Exchange Integration](https://docs.arc.io/integrate/exchanges.md): Integrate Arc deposits, withdrawals, and USDC liquidity management into your exchange.
- [How-to: Detect and process deposits](https://docs.arc.io/integrate/exchanges/deposits.md): Implement deposit detection on Arc by monitoring native USDC Transfer events from the system emitter, confirming with deterministic finality, and sweeping funds.
- [How to: Process Withdrawals](https://docs.arc.io/integrate/exchanges/withdrawals.md): Build, sign, and broadcast USDC withdrawal transactions from your exchange hot wallet on Arc.
- [How-to: Bridge USDC and EURC with CCTP](https://docs.arc.io/integrate/exchanges/cctp-bridging.md): Move USDC and EURC to and from Arc using Cross-Chain Transfer Protocol for exchange hot wallet funding and liquidity rebalancing.
- [Custody Platform Integration](https://docs.arc.io/integrate/exchanges/custody.md): Reference for adding Arc to a custody platform: register Arc as a custom EVM chain, configure signing policies, and handle the differences that matter—USDC as native gas, deterministic finality, and unified balance management.
- [On/off-ramp integration](https://docs.arc.io/integrate/on-off-ramps.md): Add Arc as a supported network in your fiat-to-crypto and crypto-to-fiat ramp service.
- [How-to: Add Arc to your on/off-ramp platform](https://docs.arc.io/integrate/on-off-ramps/add-arc-to-your-platform.md): Register Arc as a supported network in your fiat-to-crypto and crypto-to-fiat ramp service, including chain configuration, deposit detection, withdrawal processing, and UI display guidance.
- [Wallet integration](https://docs.arc.io/integrate/wallets.md): Add Arc as a supported network in your wallet application.
- [How-to: Add Arc to a wallet](https://docs.arc.io/integrate/wallets/add-arc-to-a-wallet.md): Integrate Arc as a supported network in your wallet, including chain configuration, balance display, transaction history, and fee handling.
- [Transaction Lifecycle](https://docs.arc.io/integrate/wallets/transaction-lifecycle.md): Understand Arc's two-state transaction model, where transactions are either pending or final with no intermediate confirmation states.
- [How to: Display Transaction Fees](https://docs.arc.io/integrate/wallets/fee-display.md): Fetch, calculate, and display transaction fees as USD amounts in your wallet UI.
- [DeFi integration](https://docs.arc.io/integrate/defi.md): Port AMMs, liquidity pools, and DeFi protocols to Arc using USDC as the canonical pool token and native gas asset.
- [How-to: Port an AMM or liquidity pool to Arc](https://docs.arc.io/integrate/defi/amm-and-pools.md): Migrate an AMM, liquidity pool, or DEX router to Arc by applying the correct USDC token address, decimal conversion factor, and Arc-specific EVM behaviors.
- [Relayers and paymasters](https://docs.arc.io/integrate/relayers-and-paymasters.md): Submit gasless transfers and sponsor UserOperations on Arc using USDC for gas.
- [How-to: Operate an EIP-3009 relayer on Arc](https://docs.arc.io/integrate/relayers-and-paymasters/eip-3009-relayer.md): Submit gasless USDC transfers on Arc by collecting a user's transferWithAuthorization signature and broadcasting the transaction from a funded relayer EOA.
- [How-to: Deploy an ERC-4337 paymaster on Arc](https://docs.arc.io/integrate/relayers-and-paymasters/deploy-a-paymaster.md): Deploy and fund an ERC-4337 paymaster on Arc. Arc's native gas token is USDC — fund your paymaster's EntryPoint deposit in native USDC (18-decimal units).
- [Infrastructure Integration](https://docs.arc.io/integrate/infrastructure.md): Add Arc support to node services, data indexers, oracle networks, block explorers, and compliance tools.
- [How to: Index Arc Events](https://docs.arc.io/integrate/infrastructure/indexing-events.md): Configure your data indexer or block explorer to process Arc events, including unified USDC transfers, Memo events, blocklist changes, and CCTP messages.
- [How-to: Add Arc to your bridge protocol](https://docs.arc.io/integrate/infrastructure/bridges.md): Register Arc as a supported chain in your bridge or interoperability protocol, configure confirmation requirements, and deploy relay contracts.
- [How to: Monitor Blocklist Compliance](https://docs.arc.io/integrate/infrastructure/compliance.md): Handle Arc's USDC blocklist enforcement in your compliance monitoring, including Memo and Multicall3From contract attribution.
- [Running a node](https://docs.arc.io/arc/concepts/running-a-node.md): Arc node architecture and the role of full nodes in independently verifying the blockchain.
- [Node requirements](https://docs.arc.io/arc/references/node-requirements.md): System requirements, software, network endpoints, and ports for running an Arc node.
- [Run an Arc node](https://docs.arc.io/arc/tutorials/run-an-arc-node.md): Set up and run an Arc node to independently verify the blockchain and serve a local RPC endpoint. Choose between pre-built binaries, building from source, or Docker Compose.
- [Deploying a node as a service](https://docs.arc.io/arc/tutorials/deploy-node-as-service.md): Configure your Arc node to run as systemd services that auto-restart and survive reboots.
- [Monitor a node](https://docs.arc.io/arc/tutorials/monitor-a-node.md): Verify your Arc node is syncing, view logs, and confirm Prometheus metrics endpoints are reachable.
- [Set up Prometheus and Grafana for an Arc node](https://docs.arc.io/arc/tutorials/set-up-node-monitoring.md): Deploy a local Prometheus and Grafana stack on the same host as your Arc node to scrape metrics and view the pre-built dashboards.
- [Build on Arc](https://docs.arc.io/build.md): Quickstarts, tutorials, and SDKs for building onchain finance applications on Arc.
- [Connect to Arc](https://docs.arc.io/arc/references/connect-to-arc.md): Set up your wallet and configure your development environment for Arc.
- [How-to: Install Arc Foundry](https://docs.arc.io/arc/tutorials/install-arc-foundry.md): Set up Arc Foundry to build and deploy contracts on Arc.
- [Deploy on Arc](https://docs.arc.io/build/deploy-on-arc.md): Deploy and interact with a Solidity smart contract on Arc Testnet using Arc Foundry.
- [Troubleshoot with Arc Foundry](https://docs.arc.io/arc/tutorials/troubleshoot-with-arc-foundry.md): Arc Foundry tools for replaying failed transactions, forking testnet state, and testing USDC interactions locally.
- [EVM differences](https://docs.arc.io/build/evm-differences.md): Arc's protocol-level differences from Ethereum: USDC as native gas, value transfer rules, SELFDESTRUCT semantics, EIP-7708 Transfer events, the fee market, and opcode behavior.
- [Sample apps](https://docs.arc.io/arc/references/sample-applications.md): Open-source reference applications for building on Arc with Circle developer tools, including payment flows, stablecoin FX, DeFi protocols, multichain wallets, and treasury management.
- [Arc Studio](https://docs.arc.io/ai/arc-studio.md): Idea to app in minutes.
- [Arc Studio CLI](https://docs.arc.io/ai/arc-studio-cli.md): Use Arc Studio from your terminal, or let an AI coding agent drive it to write, audit, and deploy onchain code for you.
- [AI skills for building on Arc](https://docs.arc.io/ai/skills.md): Use Circle's open source AI skills to accelerate development on Arc with AI-assisted IDEs.
- [Arc MCP server](https://docs.arc.io/ai/mcp.md): Connect your AI coding tools to Arc documentation using the Model Context Protocol (MCP) server for search and full-page retrieval.
- [Deploy contracts](https://docs.arc.io/arc/tutorials/deploy-contracts.md): Deploy pre-audited smart contract templates on Arc with Circle Contracts.
- [Interact with contracts](https://docs.arc.io/arc/tutorials/interact-with-contracts.md): Execute contract functions on Arc Testnet to mint tokens, transfer assets, and perform contract operations.
- [Monitor contract events](https://docs.arc.io/arc/tutorials/monitor-contract-events.md): Track onchain activity by monitoring contract events.
- [Port a contract to Arc](https://docs.arc.io/arc/tutorials/porting-contracts-to-arc.md): How to adapt an existing EVM contract for Arc, where USDC is the native gas token, and verify it against Arc's value transfer rules before you deploy.
- [Send USDC with a transaction memo](https://docs.arc.io/arc/tutorials/send-usdc-with-transaction-memo.md): Attach memo metadata to a USDC transfer on Arc Testnet and query the emitted Memo events.
- [Send batch USDC transfers](https://docs.arc.io/arc/tutorials/batch-usdc-transfers.md): Send multiple USDC transfers in one Arc transaction with Multicall3From and sender-preserving subcalls.
- [Register your first AI agent](https://docs.arc.io/arc/tutorials/register-your-first-ai-agent.md): Register AI agents with onchain identity, build reputation, and verify credentials using ERC-8004 on Arc Testnet.
- [Create your first ERC-8183 job](https://docs.arc.io/arc/tutorials/create-your-first-erc-8183-job.md): Create an ERC-8183 job, fund escrow with USDC, submit a deliverable hash, and complete settlement on Arc Testnet.
- [P2P Payments](https://docs.arc.io/build/payments.md): Build instant, low-cost peer-to-peer payment flows with stablecoin-native transfers and deterministic finality on Arc.
- [eCommerce Checkout](https://docs.arc.io/build/ecommerce.md): Accept stablecoin payments in your online store with fast settlement, low fees, and built-in compliance on Arc.
- [Stablecoin FX](https://docs.arc.io/build/stablecoin-fx.md): Build real-time, onchain stablecoin FX products with transparent pricing, instant settlement, and predictable fees on Arc.
- [Agentic Economy](https://docs.arc.io/build/agentic-economy.md): Enable autonomous AI agents to coordinate, contract, and settle value in real time on Arc.
- [Prediction markets](https://docs.arc.io/build/prediction-markets.md): Prediction markets on Arc use trustless oracle resolution, position token trading, and USDC settlement to let participants stake on future outcomes.
- [Borrow and lend](https://docs.arc.io/build/borrow-and-lend.md): Build collateralized lending protocols on Arc with instant settlement, native USDC borrowing, and programmable liquidation.
- [Account abstraction](https://docs.arc.io/arc/tools/account-abstraction.md): Account abstraction providers on Arc, offering SDKs, paymasters, and smart wallet infrastructure for building flexible AA flows.
- [Compliance](https://docs.arc.io/arc/tools/compliance-vendors.md): Compliance providers offering analytics, wallet screening, and monitoring tools for Arc applications.
- [Data indexers](https://docs.arc.io/arc/tools/data-indexers.md): Data indexers for querying Arc blockchain data through APIs, sub-graphs, and real-time streams.
- [Node providers](https://docs.arc.io/arc/tools/node-providers.md): Node providers for reliable RPC access, transaction submission, and data queries on Arc.
- [Oracles](https://docs.arc.io/arc/tools/oracles.md): Oracle providers for bringing external market data and offchain signals into Arc smart contracts.
- [App Kits](https://docs.arc.io/app-kit.md): Build payment and liquidity workflows across blockchains with App Kits
- [Install the App Kit SDK](https://docs.arc.io/app-kit/tutorials/installation.md): Install the App Kit SDK and your preferred adapter to start building apps
- [App Kits supported blockchains and tokens](https://docs.arc.io/app-kit/references/supported-blockchains.md): Review supported blockchains, tokens, and token aliases available for App Kits
- [Adapter setups](https://docs.arc.io/app-kit/tutorials/adapter-setups.md): Configure Viem, Ethers, Solana, or Circle Wallets adapters for the App Kit SDK
- [App Kit SDK: Send](https://docs.arc.io/app-kit/send.md): Send tokens between wallets on the same blockchain with the App Kit SDK's Send capability
- [Quickstart: Send tokens across wallets on the same blockchain](https://docs.arc.io/app-kit/quickstarts/send-tokens-same-chain.md): Use the App Kit SDK to send tokens from one wallet to another on the same blockchain
- [App Kit SDK: Bridge](https://docs.arc.io/app-kit/bridge.md): Transfer USDC and EURC across blockchains with the App Kit SDK's Bridge capability
- [Quickstart: Bridge tokens across blockchains](https://docs.arc.io/app-kit/quickstarts/bridge-tokens-across-blockchains.md): Use the App Kit SDK to bridge tokens between blockchains with a browser wallet or Circle Wallets adapter
- [How bridge fees work](https://docs.arc.io/app-kit/concepts/bridge-fees.md): How custom fees, CCTP protocol fees, Forwarding Service fees, and source-paid (upfront) fees apply when bridging USDC with the App Kit SDK
- [How-to: Collect custom bridge fees](https://docs.arc.io/app-kit/tutorials/bridge/collect-bridge-fee.md): Configure custom fees to collect on bridge transfers
- [How-to: Estimate costs before bridging](https://docs.arc.io/app-kit/tutorials/bridge/estimate-costs.md): Estimate gas and provider fees before making bridge transfers
- [How-to: Use Forwarding Service](https://docs.arc.io/app-kit/tutorials/bridge/use-forwarding-service.md): Use Forwarding Service on bridge transfers
- [How-to: Pay fees on the source chain](https://docs.arc.io/app-kit/tutorials/bridge/pay-fees-on-source.md): Pay CCTP fees on the source chain so the recipient receives the exact bridge amount
- [How-to: Configure transfer speed and maximum cost](https://docs.arc.io/app-kit/tutorials/bridge/configure-transfer-speed.md): Set a transfer speed and maximum fee to balance performance and cost
- [How-to: Specify a recipient address](https://docs.arc.io/app-kit/tutorials/bridge/specify-recipient-address.md): Send bridged USDC to a different address on the destination chain
- [Error recovery and troubleshooting for bridges](https://docs.arc.io/app-kit/references/bridge-error-recovery.md): Identify bridge transfer failures, recover partial bridge transfers, and implement error handling for App Kit SDK bridge transfers
- [App Kit SDK: Swap](https://docs.arc.io/app-kit/swap.md): Swap stablecoins and native tokens with the App Kit SDK's Swap capability
- [Quickstart: Swap tokens on a blockchain](https://docs.arc.io/app-kit/quickstarts/swap-tokens-same-chain.md): Use the App Kit SDK to swap one token for another on the same blockchain
- [Quickstart: Swap tokens across blockchains](https://docs.arc.io/app-kit/quickstarts/swap-tokens-crosschain.md): Use the App Kit SDK to swap one token on the source blockchain and receive a different token on a destination blockchain in a single call
- [How swap fees work](https://docs.arc.io/app-kit/concepts/swap-fees.md): How custom fees and provider fees apply when swapping tokens with the App Kit SDK
- [How-to: Collect custom swap fees](https://docs.arc.io/app-kit/tutorials/swap/collect-swap-fee.md): Configure custom fees to collect on token swaps
- [How-to: Estimate swap rate](https://docs.arc.io/app-kit/tutorials/swap/estimate-swap-rate.md): Get a pre-swap estimate of the amount to receive before swapping
- [How-to: Set slippage tolerance or stop limit on swaps](https://docs.arc.io/app-kit/tutorials/swap/set-slippage-tolerance-or-stop-limit.md): Set a slippage or stop limit to protect against rate changes
- [How-to: Specify a recipient address](https://docs.arc.io/app-kit/tutorials/swap/specify-recipient-address.md): Send swapped tokens to a different address on the same chain
- [How-to: Get token rates](https://docs.arc.io/app-kit/tutorials/swap/get-token-rates.md): Query cached USD prices for swap-supported tokens before quoting a swap
- [App Kit SDK: Unified Balance](https://docs.arc.io/app-kit/unified-balance.md): Create a chain-agnostic USDC balance and spend it instantly on any blockchain with the App Kit SDK's Unified Balance capability.
- [Quickstart: Deposit and spend a Unified Balance](https://docs.arc.io/app-kit/quickstarts/unified-balance-deposit-and-spend.md): Deposit USDC from multiple source blockchains into a Unified Balance, then spend from the combined pool on another blockchain
- [Quickstart: Use a delegate to deposit and spend a Unified Balance](https://docs.arc.io/app-kit/quickstarts/unified-balance-delegate-deposit-and-spend.md): Let a backend delegate wallet fund and spend from an owner's Unified Balance while the owner keeps custody
- [How Unified Balance fees work](https://docs.arc.io/app-kit/concepts/unified-balance-fees.md): How fees apply when spending from a Unified Balance and how funds move through a spend transaction
- [How-to: Check Unified Balance total](https://docs.arc.io/app-kit/tutorials/unified-balance/check-unified-balance.md): Check your Unified Balance total and how much USDC sits on each source blockchain
- [How-to: Use fast deposits](https://docs.arc.io/app-kit/tutorials/unified-balance/use-fast-deposits.md): Deposit USDC into a Unified Balance from a source blockchain onto a fast finality destination without waiting for source chain finality
- [How-to: Select source blockchains for a Unified Balance spend](https://docs.arc.io/app-kit/tutorials/unified-balance/select-source-blockchains.md): Control how USDC is drawn from your Unified Balance across blockchains when you spend, using automatic routing or explicit amounts
- [How-to: Estimate spend fees](https://docs.arc.io/app-kit/tutorials/unified-balance/estimate-spend-fees.md): Estimate fees before spending from a Unified Balance
- [How-to: Collect custom spend fees](https://docs.arc.io/app-kit/tutorials/unified-balance/collect-custom-spend-fees.md): Configure custom fees to collect when spending from a Unified Balance
- [How-to: Manage delegates](https://docs.arc.io/app-kit/tutorials/unified-balance/manage-delegates.md): Check, add, and remove delegates for a Unified Balance
- [How-to: Use Forwarding Service](https://docs.arc.io/app-kit/tutorials/unified-balance/use-forwarding-service.md): Use Forwarding Service when spending from a Unified Balance
- [How-to: Remove funds trustlessly](https://docs.arc.io/app-kit/tutorials/unified-balance/remove-funds-trustlessly.md): Initiate and complete a trustless withdrawal from a Unified Balance
- [Troubleshoot Unified Balance deposits](https://docs.arc.io/app-kit/references/unified-balance-error-recovery.md): Identify deposit failures, retry quote errors safely, and recover fast deposits without submitting duplicate source transactions
- [App Kit SDK: Onramp](https://docs.arc.io/app-kit/onramp.md): Embed the Onramp widget so users can buy USDC or EURC on Arc with fiat.
- [Quickstart: Embed the Onramp widget](https://docs.arc.io/app-kit/quickstarts/onramp-embed-widget.md): Mint a session on your server and mount the Onramp widget inline in your app so users can buy stablecoins on Arc.
- [Onramp hosting requirements](https://docs.arc.io/app-kit/references/onramp-hosting-requirements.md): Page-level constraints, Content Security Policy directives, container sizing rules, and webhook obligations for hosting the Onramp widget.
- [Customize session minting](https://docs.arc.io/app-kit/tutorials/onramp/customize-session-minting.md): Add authentication, customize error handling, or mint sessions from a host that does not use the Fetch API standard, such as Express or Fastify.
- [Choose iframe or popup mode](https://docs.arc.io/app-kit/tutorials/onramp/iframe-vs-popup.md): Decide between mounting the Onramp widget inline as an iframe or launching it in a popup window, and handle the cases where popups are blocked.
- [Handle lifecycle events](https://docs.arc.io/app-kit/tutorials/onramp/handle-lifecycle-events.md): Subscribe to Onramp widget lifecycle events to drive your UI, handle session expiry, and tear down cleanly.
- [Onramp error handling](https://docs.arc.io/app-kit/references/onramp-error-handling.md): Catch and classify Onramp errors using KitError fields, see common error codes, and understand how the session route handler maps errors to HTTP status codes.
- [App Kit SDK: Earn](https://docs.arc.io/app-kit/earn.md): Integrate Earn opportunities for USDC and EURC into your app using the App Kit SDK
- [Quickstart: Deposit into an Earn vault](https://docs.arc.io/app-kit/quickstarts/earn-deposit.md): Discover available vaults and deposit USDC into one on Arc Testnet
- [Quickstart: Withdraw from an Earn vault](https://docs.arc.io/app-kit/quickstarts/earn-withdraw.md): Withdraw USDC from an Earn vault to recover your deposit and any returns generated by the underlying lending protocol
- [How-to: Preview Earn operations](https://docs.arc.io/app-kit/tutorials/earn/preview-operations.md): Inspect the expected outcome of a deposit or withdrawal before submitting a transaction
- [How-to: Check your Earn position](https://docs.arc.io/app-kit/tutorials/earn/check-position.md): Query your current balance and accrued returns in an Earn vault
- [How-to: Deposit crosschain into an Earn vault](https://docs.arc.io/app-kit/tutorials/earn/crosschain-deposit.md): Deposit USDC from a wallet on one blockchain into an Earn vault on another blockchain in a single call
- [How Earn fees work](https://docs.arc.io/app-kit/concepts/earn-fees.md): Vault, deposit, and withdrawal fees that apply when using Earn with the App Kit SDK
- [Earn error handling](https://docs.arc.io/app-kit/references/earn-error-handling.md): Handle errors, retries, and rate limits when calling Earn
- [App Kit SDK: Borrow](https://docs.arc.io/app-kit/borrow.md): Originate and manage cirBTC-collateralized USDC loans on Arc with the App Kit SDK's Borrow capability
- [Quickstart: Originate a loan](https://docs.arc.io/app-kit/quickstarts/originate-a-loan.md): Use the App Kit SDK to borrow USDC against cirBTC collateral on Arc
- [How loan health works](https://docs.arc.io/app-kit/concepts/borrow-loan-health.md): How loan-to-value, health factor, health bands, and liquidation work for Borrow loans
- [How borrow fees work](https://docs.arc.io/app-kit/concepts/borrow-fees.md): How Circle and integrator fees apply when originating a loan with the App Kit SDK
- [How-to: Configure your integrator fee](https://docs.arc.io/app-kit/howtos/borrow/configure-integrator-fee.md): Set the integrator fee rate and recipient address that apply to every loan origination
- [How-to: Preview Borrow operations](https://docs.arc.io/app-kit/howtos/borrow/preview-a-loan-operation.md): Inspect the expected outcome and health impact of a Borrow operation before submitting a transaction
- [Borrow quote methods](https://docs.arc.io/app-kit/references/borrow-quote-methods.md): Quote methods paired with each Borrow operation and their return shapes
- [How-to: Track operation progress](https://docs.arc.io/app-kit/howtos/borrow/track-operation-progress.md): Subscribe to phase events on a loan operation to drive a progress UI or log where an operation stopped
- [Borrow phase events](https://docs.arc.io/app-kit/references/borrow-phase-events.md): Phase names, semantics, and firing rules for Borrow loan operations
- [How-to: Use idempotency keys](https://docs.arc.io/app-kit/howtos/borrow/use-idempotency-keys.md): Attach an idempotency key to a loan operation so the same user intent lands onchain at most once
- [How-to: Add collateral or borrow more against a loan](https://docs.arc.io/app-kit/howtos/borrow/add-collateral-or-borrow-more.md): Post more cirBTC to strengthen an open loan, or borrow more USDC against the same loan
- [How-to: Pay down a loan](https://docs.arc.io/app-kit/howtos/borrow/pay-down-a-loan.md): Repay USDC debt, close a loan in full, and withdraw cirBTC collateral from a Borrow loan
- [How-to: Monitor a loan](https://docs.arc.io/app-kit/howtos/borrow/monitor-a-loan.md): Read a wallet's loans and register webhooks for asynchronous health updates
- [Error handling for Borrow](https://docs.arc.io/app-kit/references/borrow-error-handling.md): Borrow error codes, their categories, and how to respond to them
- [App Kit SDK Reference](https://docs.arc.io/app-kit/references/sdk-reference.md): API reference for App Kit's public interfaces, methods, and types