> ## 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.

# Transfer USDC on testnet between Aptos and Base using CCTP V1

> Explore this tutorial for transferring USDC between Aptos testnet and Base Sepolia Testnet via CCTP V1

<Warning>
  **This is CCTP V1 version. For the latest version, see [CCTP](/cctp)**.
</Warning>

To get started with CCTP V1 on Aptos testnet, follow the example scripts
provided
[on GitHub](https://github.com/circlefin/aptos-cctp/tree/master/typescript/example).
The examples use the
[Aptos SDK](https://www.npmjs.com/package/@aptos-labs/ts-sdk), to transfer USDC
to and from an address on Aptos testnet and an address on an external
blockchain.

<Warning>
  **Do not reuse keys** As a security measure, these scripts should only be used
  on a testnet for testing purposes. It is not recommended to reuse private keys
  across mainnet and testnet.
</Warning>

Summary of calling `deposit_for_burn()` (full runnable script can be found in
the aptos-cctp repository):

```ts theme={null}
// Aptos Testnet Stablecoin object
const BURN_TOKEN =
  "0x69091fbab5f7d635ee7ac5098cf0c1efbe31d68fec0f2cd565e8d168daf52832";

const aptosClient = new Aptos(new AptosConfig({ network: Network.TESTNET }));
const userAccount = Account.fromPrivateKey({
  privateKey: new Ed25519PrivateKey(APTOS_PRIVATE_KEY),
});

// Create a transaction with deposit for burn script
const buffer = readFileSync(
  "typescript/example/precompiled-move-scripts/testnet/deposit_for_burn.mv",
);
const bytecode = Uint8Array.from(buffer);
const amount = new U64(1);
const destinationDomain = new U32(6);
const burnToken = AccountAddress.from(BURN_TOKEN);
const mintRecipient = AccountAddress.from(evmSigner.address);
const functionArguments: Array<any> = [
  amount,
  destinationDomain,
  mintRecipient,
  burnToken,
];
const transaction = await aptosClient.transaction.build.simple({
  sender: userAccount.accountAddress,
  data: {
    bytecode,
    functionArguments,
  },
});
const pendingTxn = await aptosClient.signAndSubmitTransaction({
  signer: userAccount,
  transaction,
});
const depositForBurnTx = await aptosClient.waitForTransaction({
  transactionHash: pendingTxn.hash,
});
console.log(
  `Deposit for burn transaction completed successfully: https://explorer.aptoslabs.com/txn/${depositForBurnTx.hash}`,
);

// Fetch the event data from the transaction
const messageSentEvent = (
  depositForBurnTx as UserTransactionResponse
).events.find(
  (e: any) =>
    e.type ===
    `${MESSAGE_TRANSMITTER_PACKAGE_ID}::message_transmitter::MessageSent`,
);
```

Summary of calling `receive_message()` (full runnable script can be found in the
aptos-cctp repository):

```ts theme={null}
const bytecode = Uint8Array.from(
  fs.readFileSync(
    "typescript/example/precompiled-move-scripts/testnet/handle_receive_message.mv",
  ),
);
const functionArguments: Array<any> = [
  MoveVector.U8(messageBytes as Buffer),
  MoveVector.U8(attestationSignature),
];
const transaction = await aptosClient.transaction.build.simple({
  sender: userAccount.accountAddress,
  data: {
    bytecode,
    functionArguments,
  },
});
const pendingTxn = await aptosClient.signAndSubmitTransaction({
  signer: userAccount,
  transaction,
});
const receiveMessageTx = await aptosClient.waitForTransaction({
  transactionHash: pendingTxn.hash,
});
console.log(
  `Receive message transaction completed successfully: https://explorer.aptoslabs.com/txn/${receiveMessageTx.hash}`,
);
```