GOAT Flow

This repository contains the public SDKs, examples, and supporting components for integrating GOAT Flow x402 payments and its current MPP adapter on GOAT Network.

Current Public Product

The current public merchant path is DIRECT:

• the payer transfers an ERC-20 token to the merchant's configured receiving address;
• GOAT Flow software creates and tracks the order record; and
• the merchant confirms fulfillment from server-side order status or webhooks.

For the smallest integration, use a merchant-configured QuickPay product with the hosted checkout. For a custom wallet and order UI, combine the browser SDK with a server SDK so API credentials remain on the backend.

Need	Start here
Hosted DIRECT checkout	docs/goat-flow-checkout.md and goatflow-checkout
Custom wallet/order UI	goatflow-sdk plus goatflow-sdk-server or the Go server SDK
Agent or CLI payment	goatflow-quickpay
Merchant onboarding	docs/goat-flow-onboarding-guide.md
Merchant operations	docs/merchant-guide.md

Hosted checkout and QuickPay identify a product by merchant and product key. Price, accepted tokens, receiving addresses, and other payment configuration remain server-authoritative.

Optional And Internal Components

The repository also contains components that are not required for the public DIRECT merchant flow:

• MerchantCallback.sol is a reference UUPS receiver for an optional, operator-provisioned callback transfer flow. Its withCalldata self-call has no selector allowlist; review the security model.
• TopupCallback.sol is dedicated to the internal topup-service; it is not a general merchant contract.
• USDC.sol and USDT.sol are configurable test tokens, not production token deployments.
• MPP is an independent open protocol, not a GOAT Flow protocol. The MPP clients and middleware in this repository implement GOAT Flow's current JSON-endpoint and signed-receipt profile, require an enabled Core environment, and have no checked-in interoperability test with official MPP SDKs.
• The demo contains config-gated advanced and MPP examples in addition to its default DIRECT checkout path.

Do not deploy a callback contract merely to use DIRECT checkout.

Repository Map

Module	Purpose	Distribution status
goatflow-checkout	Framework-free hosted-checkout browser SDK	Release-managed npm package
goatflow-sdk	EVM buyer-wallet transfer and GOAT Flow MPP-profile client primitives	Release-managed npm package
goatflow-sdk-server	HMAC-authenticated TypeScript server SDK	Release-managed npm package
github.com/goatnetwork/goatflow-sdk-server	HMAC-authenticated Go server SDK	Go module source
goatflow-quickpay	Manifest-driven payer/agent library and CLI	Release-managed npm package
@goatnetwork/mpp-middleware	Express/Fastify verification for the GOAT Flow MPP receipt extension	Source package; not in the npm release runbook
github.com/goatnetwork/goatflow-mpp-middleware-go	Go HTTP verification for the GOAT Flow MPP receipt extension	Go module source
goatx402-contract	Optional/internal callbacks and local test tokens	Foundry project
goatx402-demo	DIRECT checkout plus optional advanced and MPP examples	Private local demo

The npm release procedure covers exactly the four packages marked "Release-managed npm package"; see RELEASING.md.

Chain And Token Configuration

Runtime chain and token availability is configuration-driven. A merchant should use the chains and tokens returned by the merchant API or shown in the Merchant Portal rather than relying on a hard-coded repository list.

Supported Mainnet Chains

The operator-supplied mainnet documentation baseline, reviewed July 23, 2026, is listed below. It is not encoded as one authoritative matrix in this repository; runtime API and portal configuration remain controlling.

The separate GOAT Network x402 overview may also list Polygon (137) and Avalanche (43114). They are intentionally excluded from this GOAT Flow operator baseline until enabled by the active deployment. Do not infer GOAT Flow availability from the protocol overview alone.

Chain	Chain ID	Explorer
GOAT Network	2345	explorer.goat.network
Ethereum	1	etherscan.io
BSC	56	bscscan.com
Arbitrum	42161	arbiscan.io
Optimism	10	optimistic.etherscan.io
Base	8453	basescan.org
Berachain	80094	berascan.com
X Layer	196	X Layer Explorer
Metis	1088	andromeda-explorer.metis.io
Tempo	4217	explore.tempo.xyz

This table is a documentation baseline, not a per-merchant entitlement. Confirm the enabled chain/token pairs and receiving addresses in the target environment before integration or launch.

For DIRECT, each enabled (chain, token) needs a valid merchant receiving address and the deployment's associated service-fee/token configuration. Testnet aliases inside goatx402-contract/foundry.toml are development conveniences and do not describe the public production matrix.

Development Documentation

Use docs/README.md as the documentation hub.

Quick references:

• Developer Quick Start - concise integration path.
• API Reference - Core API and HMAC authentication.
• docs/goat-flow-checkout.md - hosted checkout.
• goatx402-demo/README.md - runnable demo modes.
• goatx402-contract/README.md - contract scope, tests, and deployment tooling.

The complete Mainnet and Testnet3 service-origin map is maintained in docs/README.md. The production API base URL is https://flow-api.goat.network.

License

No single repository-wide license has been declared. The four release-managed npm packages each include their own MIT LICENSE file. Other directories may carry package-level license metadata; review the relevant module before reuse or redistribution.