> ## 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.
# Release notes - Gateway - 2026
> 2026 release notes for Gateway
## September 2026
### Blockchain expansion
Added Arc mainnet as a supported blockchain for Gateway.
Updated topics:
* [Contract addresses](/gateway/references/contract-addresses)
* [Supported blockchains](/gateway/references/supported-blockchains)
* [Fees](/gateway/references/fees)
## August 2026
As of August 26, 2026, filtering Gateway x402 transfers by `status` requires a
narrowing filter. Supply at least one of `from`, `to`, or `nonce` in the same
request. This is a breaking change for callers that filter by `status` alone, or
that combine it only with `network`, `token`, or a date range: those requests
return `400`.
Searching every transfer in a given status isn't supported because the query
takes longer than the request timeout allows. To find the transfers for one
account, filter by `from` or `to`. To look up a single transfer you already have
an identifier for, filter by `nonce` or use
[`GET /v1/x402/transfers/{id}`](/api-reference/gateway-nanopayments/get-x402transfer-by-id).
### API updates
The following endpoint was updated on August 26, 2026:
* [`GET /v1/x402/transfers`](/api-reference/gateway-nanopayments/search-x402transfers):
the `status` query parameter requires `from`, `to`, or `nonce`.
### New features
Added ERC-1271 support to Gateway. Smart contracts and smart contract accounts
(SCAs) can now authorize burn intents directly with their own signature
validation logic, so multisigs, passkey-based accounts, and policy-driven
contracts can access a unified USDC balance without adding a delegate.
### Documentation additions
* [ERC-1271 programmable authorization](/gateway/references/erc-1271)
* [How-to: Transfer with ERC-1271](/gateway/howtos/transfer-with-erc-1271)
## July 2026
Added `nonce` support to the Gateway x402 transfer APIs. You can now filter
transfers by nonce, and transfer responses include the `nonce` field along with
a nullable `txHash` field.
### API updates
The following endpoints were updated:
* [`GET /v1/x402/transfers`](/api-reference/gateway-nanopayments/search-x402transfers)—added
optional `nonce` query parameter.
* [`GET /v1/x402/transfers/{id}`](/api-reference/gateway-nanopayments/get-x402transfer-by-id)—response
now includes `nonce` and `txHash`.
## May 2026
Updated the Gateway unified balance Solana quickstart to simplify the
script-based flow and add Direct Mint and Forwarding Service branches.
### Documentation updates
The following documentation was updated:
* [Quickstart: Create and transfer a unified USDC balance on Solana](/gateway/quickstarts/unified-balance-solana)
Updated the Gateway unified balance EVM quickstart to simplify the script-based
flow and add Forwarding Service coverage.
### Documentation updates
The following documentation was updated:
* [Quickstart: Create and transfer a unified USDC balance on EVM](/gateway/quickstarts/unified-balance-evm)
Added Gateway webhook documentation and subscription management API references.
### Documentation additions
The following documentation was created:
* [Gateway webhooks](/gateway/webhooks)
* [Gateway webhook events](/gateway/references/webhook-events)
### API additions
Added the following endpoints to support Gateway webhook subscriptions:
* [`POST /v2/notifications/subscriptions/permissionless`](/api-reference/gateway/all/create-permissionless-subscription)
* [`GET /v2/notifications/subscriptions/permissionless`](/api-reference/gateway/all/get-permissionless-subscriptions)
* [`GET /v2/notifications/subscriptions/permissionless/{id}`](/api-reference/gateway/all/get-permissionless-subscription)
* [`PUT /v2/notifications/subscriptions/permissionless/{id}`](/api-reference/gateway/all/update-permissionless-subscription)
* [`DELETE /v2/notifications/subscriptions/permissionless/{id}`](/api-reference/gateway/all/delete-permissionless-subscription)
* [`POST /v2/notifications/subscriptions/permissionless/{id}/test`](/api-reference/gateway/all/test-permissionless-subscription-connection)
* [`POST /v2/notifications/subscriptions/permissionless/{id}/test-notification`](/api-reference/gateway/all/send-permissionless-subscription-test-notification)
* [`GET /v2/notifications/signatures/{notificationId}`](/api-reference/gateway/all/get-permissionless-notification-signature)
## April 2026
Updated nanopayments documentation to reflect mainnet launch support.
### Documentation updates
The following documentation was updated:
* [Supported networks](/gateway-nanopayments/supported-networks)
* [Gateway supported blockchains](/gateway/references/supported-blockchains)
Expanded the nanopayments documentation with additional buyer, seller,
facilitator, and x402 integration guidance.
### Documentation updates
The following documentation was updated:
* [Quickstart: Pay for resources with nanopayments](/gateway-nanopayments/quickstarts/buyer)
* [Quickstart: Accept payments with nanopayments](/gateway-nanopayments/quickstarts/seller)
* [How-to: Integrate nanopayments into your existing facilitator](/gateway-nanopayments/howtos/facilitator-integration)
* [How-to: Add nanopayments to an x402 buyer](/gateway-nanopayments/howtos/x402-buyer)
* [How-to: Add nanopayments to an x402 seller](/gateway-nanopayments/howtos/x402-seller)
* [How-to: Use nanopayments with x402](/gateway-nanopayments/howtos/x402-integration)
* [How-to: Sign EIP-3009 payment authorizations](/gateway-nanopayments/howtos/eip-3009-signing)
Updated Gateway on Solana documentation to support transfers with the Forwarding
Service and automatic ATA creation.
### Documentation updates
The following documentation was updated:
* [How-to: Transfer with the Forwarding Service](/gateway/howtos/forwarding-service)
* [Quickstart: Create and transfer a unified USDC balance on Solana](/gateway/quickstarts/unified-balance-solana)
* [Gateway fees](/gateway/references/fees)
* [Circle Forwarding Service for Gateway](/gateway/references/forwarding-service)
* [Technical guide for Gateway on Solana](/gateway/references/solana)
## March 2026
Updated the Gateway unified balance quickstarts to support both Circle Wallets
and permissionless implementations on the same page.
### Documentation updates
The following documentation was updated:
* [Quickstart: Create and transfer a unified USDC balance on EVM](/gateway/quickstarts/unified-balance-evm#circle-wallets)
* [Quickstart: Create and transfer a unified USDC balance on Solana](/gateway/quickstarts/unified-balance-solana#circle-wallets)
## February 2026
Added Forwarding Service support for Gateway. The following new topic was
created:
* [Gateway Forwarding Service](/gateway/references/forwarding-service)
Added support for managing delegates for Smart Contract Account (SCA) wallets.
### Documentation additions
The following documentation was created:
* [How-to: Manage delegates for smart contract wallets](/gateway/howtos/manage-delegates)
Updated Gateway quickstart guides and how-tos to use consistent script structure
and console output patterns.
### Documentation updates
The following documentation were updated:
* [Quickstart: Create and Transfer a Unified USDC Balance (EVM)](/gateway/quickstarts/unified-balance-evm)
* [Quickstart: Create and Transfer a Unified USDC Balance (Solana)](/gateway/quickstarts/unified-balance-solana)
* [How-to: Create a unified USDC balance](/gateway/howtos/create-unified-usdc-balance)
* [How-to: Transfer a unified USDC balance instantly](/gateway/howtos/transfer-unified-usdc-balance)
## January 2026
### API additions
Added the following endpoints to support Circle Gateway:
* [`POST /v1/deposits`](/api-reference/gateway/all/get-deposits)
Added support for Gateway on Solana. The following new topics were created:
* [Gateway technical guide](/gateway/references/solana)
* [Gateway Solana Programs and Interfaces](/gateway/references/solana-programs)
* [Gateway Solana Quickstart](/gateway/quickstarts/unified-balance-solana)