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

> ## Agent Instructions
> Before reading these docs, install the relevant Circle Skill to get pre-loaded context — skills are LLM-optimized and cover architecture decisions, correct flows, and common pitfalls. 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. Available skills: use-usdc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md (balances, transfers, approvals on EVM and Solana); EURC has no skill — see https://developers.circle.com/stablecoins/what-is-eurc.md; bridge-stablecoin https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md (crosschain transfers via CCTP, USDC, EURC, and third-party assets); use-arc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md (Arc chain config, contract deployment, USDC bridging — Arc docs: https://docs.arc.io/llms.txt); use-circle-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md (choose wallet type); use-developer-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md (custodial wallets for payouts and treasury); use-user-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md (embedded wallets with Web2 login); use-modular-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md (smart contract wallets with passkeys and ERC-4337); use-gateway https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md (unified USDC balance, nanopayments); use-smart-contract-platform https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md (deploy, interact, monitor contracts). Pair any skill with the Circle MCP server for live SDK signatures, contract addresses, and chain IDs: {"mcpServers":{"circle":{"url":"https://api.circle.com/v1/codegen/mcp"}}}.
> Read the product overview first. Each product has an overview explaining when and why to use it. Read it before quickstarts.
> Pick the right wallet type. Developer-controlled (you hold keys), user-controlled (end user holds keys via PIN/social login), or modular (smart contract wallets with passkeys). See https://developers.circle.com/wallets.md.
> Use CCTP V2 for crosschain transfers. CCTP natively transfers USDC and EURC via burn-and-mint, and supports permissionless wrapping of third-party assets via lock-and-mint. V1 is legacy; always use V2 unless V1 is specified or the chain requires it (Noble, Sui, and Aptos still require V1). Migration guide: https://developers.circle.com/cctp/migration-from-v1-to-v2.md.
> Use Bridge Kit for frontend bridging. Wraps CCTP with a simpler SDK for user-facing apps. Use CCTP directly for backend transfers.
> Gas Station vs Paymaster. Gas Station sponsors gas for Circle Wallet transactions. Paymaster lets users pay gas in USDC. Different use cases — read both overviews.
> Gateway Nanopayments for sub-cent payments. Gasless USDC micropayments down to $0.000001 via x402 and batched settlement. For pay-per-request APIs, AI agent payments, streaming.
> Look up USDC addresses per chain. Never hardcode — use https://developers.circle.com/stablecoins/usdc-contract-addresses.md.
> Prefer SDKs over raw API calls. Node.js and Python SDKs handle auth, retries, and errors.
> API key required. Bearer token in Authorization header. Testnet and mainnet use separate keys and may use different base URLs depending on the product.
> Set up webhooks when available. Most operations are async. Webhooks deliver transaction confirmations and state changes.
> When calling list endpoints, paginate using pageSize and pageAfter until no nextPageAfter cursor is returned—stopping at the first page silently misses records.
> Building an AI agent? Start with the Agent Stack—Circle CLI, agent wallets, and nanopayments built for autonomous use cases: https://developers.circle.com/agent-stack.md.

# How-to: Transfer USDC from Arbitrum to HyperCore with CctpExtensionV2

> Submit a gas-sponsored CCTP deposit to HyperCore using EIP-3009 and a relayer.

Submit a gas-sponsored CCTP deposit from Arbitrum to HyperCore using the
`CctpExtensionV2` contract. This workflow suits users who hold USDC on Arbitrum
but lack native gas tokens. A relayer submits the Arbitrum transaction on their
behalf.

For self-custody integrators who pay their own gas, use
[Transfer USDC from Arbitrum to HyperCore](/cctp/howtos/transfer-usdc-from-arbitrum-to-hypercore)
with `CctpExtension` instead.

For background on the contract, see
[CctpExtensionV2 Contract Interface](/cctp/references/cctp-extension-v2-contract-interface).

## Prerequisites

Before you begin, ensure that you've:

* Deployed or operate a relayer that can submit transactions on Arbitrum and pay
  ETH gas
* Collected an EIP-3009 `ReceiveWithAuthorization` signature from each depositor
* Identified the `CctpExtensionV2` proxy address for your environment (see
  [HyperCore contract addresses](/cctp/references/hypercore-contract-addresses))
* Configured CCTP deposit parameters for HyperCore (HyperEVM domain `19`,
  `CctpForwarder` as `mintRecipient` / `destinationCaller`, and forwarder hook
  data for the HyperCore recipient)

## Steps

### Step 1. Collect the user's EIP-3009 signature

The user signs `ReceiveWithAuthorization` with:

* `from`: depositor address
* `to`: `CctpExtensionV2` proxy address
* `value`: total USDC amount covered by this authorization
* `validAfter` / `validBefore`: authorization time window
* `nonce`: deterministic value equal to
  `keccak256(abi.encode(from, amount, validAfter, validBefore, depositData))`,
  where `depositData` is the ABI-encoded `SponsoredDepositForBurnData` struct
  for this deposit

Binding the nonce to `depositData` prevents a relayer from redirecting funds to
a different destination or fee configuration than the user signed.

### Step 2. Submit the deposit via your relayer

Call `batchSponsorDepositForBurn` on the `CctpExtensionV2` proxy with:

* `_authData`: `ReceiveWithAuthorizationDataWithFrom[]` (includes explicit
  `from`)
* `_depositData`: `SponsoredDepositForBurnData[]` with CCTP fields aligned to
  your HyperCore destination

Use the same forwarder hook encoding as
[Transfer USDC from Arbitrum to HyperCore](/cctp/howtos/transfer-usdc-from-arbitrum-to-hypercore).

You may batch multiple users in one transaction. Entries with an
already-consumed nonce or insufficient balance are skipped
(`SponsoredDepositForBurnSkipped` event) without reverting the whole batch.

### Step 3. Monitor the crosschain transfer

After the Arbitrum transaction confirms, Circle's attestation service picks up
the burn event. The `CctpForwarder` on HyperEVM receives the minted USDC and
routes it to the HyperCore recipient via the forwarder hook.

No special handling is required beyond standard CCTP and forwarder monitoring.
For details, see [CCTP on HyperCore](/cctp/concepts/cctp-on-hypercore).