> ## 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.

# Stablecoin payin and payout lifecycle

> How Managed Payments stablecoin payins and payouts progress through the Circle APIs, from payment intents and deposit addresses to address book recipients and payout completion

Managed Payments stablecoin payins receive USDC from customers at a deposit
address that Circle assigns, and payouts send USDC to recipients that you
register first. Both flows are asynchronous, so your integration tracks each
resource's status with webhooks or polling.

For how these flows map to fiat in your bank account, see
[Settlement flows](/cpn/managed-payments/concepts/settlement-flows).

## Payins

A payin starts with a
[payment intent](/api-reference/cpn/managed-payments/payment-intents/create-payment-intent),
your request to receive funds onchain. A **continuous** payment intent sets the
settlement currency and blockchain but no amount, so an account gets a stable
address that accepts any number of transfers. A **transient** payment intent
sets a fixed amount and an expiry time, which suits a one-time checkout.

The following diagram shows a continuous payin from checkout to confirmation:

```mermaid theme={null}
sequenceDiagram
    participant Customer
    participant Site as Your website
    participant Server as Your server
    participant CAPI as Circle APIs
    Customer->>Site: Select pay with<br/>stablecoin onchain
    Site->>Server: Create deposit intent<br/>settlement and chain
    Server->>CAPI: POST /v1/paymentIntents
    CAPI-->>Server: Payment intent created
    CAPI-->>Server: Webhook payment intent<br/>address ready
    Server-->>CAPI: Ack
    Server->>Site: Deposit address
    Site->>Customer: Present deposit address
    Customer->>Customer: Send payment from wallet<br/>to deposit address
    CAPI-->>Server: Webhook payment paid
    Server-->>CAPI: Ack
    Server->>Site: Stablecoin payment<br/>completed
    Site->>Customer: Payment confirmed
```

Each transfer to the deposit address creates a payment that starts as `pending`
and moves to `paid` when the funds settle, or to `failed` if it can't be
processed. For all intent, payment, and refund states, see
[Stablecoin payin states](/cpn/managed-payments/references/payment-intent-states).
To build this flow, follow
[Quickstart: Receive stablecoin payins](/cpn/managed-payments/quickstarts/receive-stablecoin-payins).

## Payouts

Payouts only go to recipients in your
[address book](/api-reference/cpn/managed-payments/address-book/create-address-book-recipient).
Circle screens each new recipient, and you can't pay a recipient until its
status is `active`.

The following diagram shows the API calls and status changes in a payout:

```mermaid theme={null}
sequenceDiagram
    participant Server as Your server
    participant CAPI as Circle APIs
    Server->>CAPI: POST /v1/addressBook/recipients
    CAPI-->>Server: Recipient pending or inactive
    CAPI-->>Server: Webhook or poll recipient active
    Server->>CAPI: POST /v1/payouts
    CAPI-->>Server: Payout pending
    CAPI-->>Server: Webhook or poll payout complete
```

For how subaccounts and the main wallet fund payouts, see
[Subaccount architecture](/cpn/managed-payments/concepts/sub-account-architecture).
To build this flow, follow
[Quickstart: Send stablecoin payouts](/cpn/managed-payments/quickstarts/send-stablecoin-payouts).