x402-rs

Gasless multi-chain payment facilitator with ERC-8004 reputation

 _  _  _  _  ___  ____      ____  ____
( \/ )/ )( \(__ \(  _ \ ___(  _ \/ ___)
 )  ( ) __ ( / _/ )   /(___))   /\___ \
(_/\_)\_)(_/(____)(__\_)   (__\_)(____/

What is this?

A payment settlement service implementing the HTTP 402 protocol. Users sign payment authorizations off-chain, the facilitator submits them on-chain and pays gas fees.

Includes ERC-8004 on-chain reputation for AI agents across 20 networks (11 mainnets + 9 testnets).

No custody. No trust. Just payments.

Supported Networks

Note: Network counts may be outdated. Verify with: curl -s https://facilitator.ultravioletadao.xyz/supported | jq '[.kinds[].network] | unique | map(select(contains("testnet") or contains("sepolia") or contains("devnet") or contains("fuji") or contains("amoy") or contains("alfajores") | not)) | length'

Mainnets (20)

Network	Chain ID	Token	Explorer
Ethereum	1	USDC	etherscan.io
Base	8453	USDC	basescan.org
Arbitrum	42161	USDC	arbiscan.io
Optimism	10	USDC	optimistic.etherscan.io
Polygon	137	USDC	polygonscan.com
Avalanche	43114	USDC	snowtrace.io
Celo	42220	cUSD	celoscan.io
HyperEVM	999	USDC	hyperliquid.xyz
Unichain	130	USDC	uniscan.xyz
Monad	10143	MON	monad.xyz
BSC	56	USDC	bscscan.com
SKALE Base	1187947933	USDC.e	skale-base-explorer
Scroll	534352	USDC	scrollscan.com
Sui	-	USDC	suiscan.xyz
Solana	-	USDC, AUSD	solscan.io
Fogo	-	USDC	fogoscan.com
NEAR	-	USDC	nearblocks.io
Stellar	-	USDC	stellarchain.io
Algorand	-	USDC	allo.info
XRPL	-	XRP, USDC, RLUSD	livenet.xrpl.org

Testnets (17)

Network	Chain ID	Faucet
Ethereum Sepolia	11155111	faucet.circle.com
Base Sepolia	84532	faucet.circle.com
Arbitrum Sepolia	421614	faucet.circle.com
Optimism Sepolia	11155420	faucet.circle.com
Polygon Amoy	80002	faucet.polygon.technology
Avalanche Fuji	43113	faucet.avax.network
Celo Alfajores	44787	faucet.celo.org
HyperEVM Testnet	333	-
Unichain Sepolia	1301	-
SKALE Base Sepolia	324705682	base-sepolia-faucet.skale.space
Solana Devnet	-	solfaucet.com
Fogo Testnet	-	fogoscan.com
NEAR Testnet	-	near-faucet.io
Stellar Testnet	-	friendbot
Algorand Testnet	-	dispenser.testnet.aws.algodev.network
Sui Testnet	-	suifaucet.com
Monad Testnet	10143	monad.xyz

Supported Stablecoins

Note: Run python scripts/stablecoin_matrix.py for the authoritative stablecoin support matrix.

Token	Networks
USDC	All 20 payment networks
AUSD	Ethereum, Polygon, Arbitrum, Avalanche, Monad, BSC, Solana, Sui
EURC	Ethereum, Base, Avalanche
USDT	Arbitrum, Celo, Optimism, Monad
PYUSD	Ethereum
RLUSD	XRPL
XRP	XRPL (native)

Full Matrix:

Network	USDC	AUSD	EURC	USDT	PYUSD
Ethereum	Y	Y	Y	-	Y
Base	Y	-	Y	-	-
Arbitrum	Y	Y	-	Y	-
Optimism	Y	-	-	Y	-
Polygon	Y	Y	-	-	-
Avalanche	Y	Y	Y	-	-
Celo	Y	-	-	Y	-
BSC	Y	Y	-	-	-
Monad	Y	Y	-	Y	-
HyperEVM	Y	-	-	-	-
Unichain	Y	-	-	-	-
Scroll	Y	-	-	-	-
SKALE Base	Y	-	-	-	-
Solana	Y	Y	-	-	-
Sui	Y	Y	-	-	-
Fogo	Y	-	-	-	-
NEAR	Y	-	-	-	-
Stellar	Y	-	-	-	-
Algorand	Y	-	-	-	-
XRPL	Y	-	-	-	-

XRPL note: In addition to USDC (issued token), XRPL also supports RLUSD (issued token) and native XRP. These are not EIP-3009 tokens, so they are not tracked by scripts/stablecoin_matrix.py (which only enumerates EIP-3009 stablecoins). See docs/plans/xrpl-native-x402-integration-plan.md.

Quick Start

# Clone
git clone https://github.com/UltravioletaDAO/x402-rs.git
cd x402-rs

# Configure
cp .env.example .env
# Add your private keys (use testnet keys for development)

# Run
cargo run --release --features solana,near,stellar,algorand

# Test
curl http://localhost:8080/health
curl http://localhost:8080/supported | jq '.kinds | length'
# => 121 (networks listed across v1 and v2/CAIP-2 formats)

Docker

docker-compose up -d
curl http://localhost:8080/

API

Endpoint	Method	Description
`/`	GET	Landing page
`/health`	GET	Health check
`/version`	GET	Current version
`/supported`	GET	List all networks
`/verify`	POST	Verify payment authorization
`/settle`	POST	Submit payment on-chain (supports escrow with `refund` extension)
`/blacklist`	GET	OFAC sanctioned addresses
`/feedback`	GET/POST	ERC-8004 reputation (query/submit)
`/identity/:network/:agentId`	GET	Agent identity lookup
`/reputation/:network/:agentId`	GET	Agent reputation summary
`/discovery/resources`	GET	List registered paid APIs
`/discovery/register`	POST	Register a paid endpoint

Example: Check supported networks

curl -s https://facilitator.ultravioletadao.xyz/supported | jq '.kinds[].network'

Example: Settle a payment

curl -X POST https://facilitator.ultravioletadao.xyz/settle \
  -H "Content-Type: application/json" \
  -d '{"payload": "...", "network": "base"}'

Chain-Specific Features

EVM Chains (EIP-3009)

Standard transferWithAuthorization for gasless USDC transfers.

Solana (SPL Token + Token2022)

Supports both SPL Token (USDC) and Token2022 (AUSD) programs.

NEAR (NEP-366)

Meta-transactions with delegate actions for gasless payments.

Stellar (Soroban)

Smart contract-based authorization on Stellar's Soroban VM.

Algorand (Atomic Groups)

Fee pooling via atomic transaction groups. Facilitator signs transaction 0 (fee tx), user signs transaction 1 (payment tx). Based on GoPlausible x402-avm spec.

ERC-8004 Trustless Agents (On-Chain Reputation)

The facilitator integrates ERC-8004 for AI agent identity and reputation across 20 networks.

What is ERC-8004?

Three on-chain registries enabling trust in the agentic economy:

Identity Registry - ERC-721 based agent handles with verifiable metadata
Reputation Registry - Standardized feedback posting with proof-of-payment
Validation Registry - Third-party attestation of agent capabilities

Supported ERC-8004 Networks (20)

Network	Type	Identity Registry	Reputation Registry
Ethereum	Mainnet	`0x8004A169...9a432`	`0x8004BAa1...dE9b63`
Base	Mainnet	Same (CREATE2)	Same (CREATE2)
Polygon	Mainnet	Same (CREATE2)	Same (CREATE2)
Arbitrum	Mainnet	Same (CREATE2)	Same (CREATE2)
Optimism	Mainnet	Same (CREATE2)	Same (CREATE2)
Celo	Mainnet	Same (CREATE2)	Same (CREATE2)
BSC	Mainnet	Same (CREATE2)	Same (CREATE2)
Monad	Mainnet	Same (CREATE2)	Same (CREATE2)
Avalanche	Mainnet	Same (CREATE2)	Same (CREATE2)
SKALE Base	Mainnet	Same (CREATE2)	Same (CREATE2)
Solana	Mainnet	Anchor program	Anchor program
Ethereum Sepolia	Testnet	`0x8004A818...4BD9e`	`0x8004B663...8713`
Base Sepolia	Testnet	Same	Same
Polygon Amoy	Testnet	Same	Same
Arbitrum Sepolia	Testnet	Same	Same
Optimism Sepolia	Testnet	Same	Same
Celo Sepolia	Testnet	Same	Same
Avalanche Fuji	Testnet	Same	Same
SKALE Base Sepolia	Testnet	Same	Same
Solana Devnet	Testnet	Anchor program	Anchor program

All EVM mainnet contracts use CREATE2 deterministic deployment (same addresses on every chain). Solana uses a dedicated Anchor program.

ERC-8004 API Endpoints

Endpoint	Method	Description
`/feedback`	GET	List ERC-8004 supported networks
`/feedback`	POST	Submit on-chain reputation feedback
`/identity/:network/:agentId`	GET	Query agent identity
`/reputation/:network/:agentId`	GET	Query reputation summary

Example: Submit Feedback

curl -X POST https://facilitator.ultravioletadao.xyz/feedback \
  -H "Content-Type: application/json" \
  -d '{
    "network": "base-mainnet",
    "agentId": "0x...",
    "rating": 5,
    "tags": ["uptime", "quality"],
    "proofOfPayment": "0x..."
  }'

x402r Escrow Extension (Trustless Refunds)

The facilitator supports the x402r extension for trustless refunds via escrow contracts.

Architecture Overview

                           STANDARD PAYMENT FLOW
  ┌──────────┐    ┌───────────────┐    ┌────────────┐    ┌──────────┐
  │  Buyer   │───>│  Facilitator  │───>│   USDC     │───>│ Merchant │
  │ (signs)  │    │  (pays gas)   │    │ (on-chain) │    │(receives)│
  └──────────┘    └───────────────┘    └────────────┘    └──────────┘
       │                 │
       │  EIP-3009       │  transferWithAuthorization()
       │  signature      │

                           ESCROW PAYMENT FLOW (x402r)
  ┌──────────┐    ┌───────────────┐    ┌──────────────┐    ┌──────────┐
  │  Buyer   │───>│  Facilitator  │───>│ DepositRelay │───>│  Escrow  │
  │ (signs)  │    │  (pays gas)   │    │   (proxy)    │    │ (holds)  │
  └──────────┘    └───────────────┘    └──────────────┘    └──────────┘
       │                 │                    │                  │
       │  EIP-3009       │  executeDeposit()  │  deposit()       │
       │  to PROXY       │                    │                  │
       │                 │                    │                  ▼
       │                 │                    │            ┌──────────┐
       │                 │                    │            │ Merchant │
       │                 │                    └───────────>│(after    │
       │                 │                      release()  │ window)  │
       │                 │                                 └──────────┘
       │                 │
       └─────────────────┴───── Buyer can request refund within window

Supported Networks

Network	Chain ID	Factory	Escrow	Status
Base	8453	`0x41Cc...A814`	`0xC409...f6bC`	Production
Base Sepolia	84532	`0xf981...BaC2`	`0xF7F2...0E58`	Testnet

Documentation

Technical Deep-Dive: docs/X402R_ESCROW.md
Testing Guide: docs/X402R_ESCROW_TESTING.md
x402r Proposal: https://github.com/coinbase/x402/issues/864
x402r Contracts: https://github.com/BackTrackCo/x402r-contracts

Configuration

# Wallet keys (leave empty for AWS Secrets Manager)
EVM_PRIVATE_KEY_MAINNET=
EVM_PRIVATE_KEY_TESTNET=
SOLANA_PRIVATE_KEY_MAINNET=
SOLANA_PRIVATE_KEY_TESTNET=
NEAR_PRIVATE_KEY_MAINNET=
NEAR_ACCOUNT_ID_MAINNET=
STELLAR_SECRET_KEY_MAINNET=
STELLAR_SECRET_KEY_TESTNET=
ALGORAND_MNEMONIC_MAINNET=
ALGORAND_MNEMONIC_TESTNET=

# RPC URLs (premium recommended for production)
RPC_URL_BASE=https://mainnet.base.org
RPC_URL_NEAR_MAINNET=https://rpc.mainnet.near.org
RPC_URL_ALGORAND_MAINNET=https://mainnet-api.algonode.cloud
# ... see .env.example for all networks

Architecture

┌─────────────┐     ┌─────────────────┐     ┌──────────────┐
│   Client    │────▶│   Facilitator   │────▶│  Blockchain  │
│  (signs)    │     │  (pays gas)     │     │  (settles)   │
└─────────────┘     └─────────────────┘     └──────────────┘

Payment Flow:

User signs EIP-3009 (EVM), NEP-366 (NEAR), or atomic group (Algorand)
User sends signed payload to facilitator
Facilitator verifies signature and submits on-chain
Facilitator pays gas, user pays nothing

Deployment

AWS ECS (Production)

# Build & push
docker build -t facilitator:v1.46.0 .
docker push 518898403364.dkr.ecr.us-east-2.amazonaws.com/facilitator:v1.46.0

# Deploy
aws ecs update-service --cluster facilitator-production \
  --service facilitator-production --force-new-deployment

Infrastructure: Terraform configs in terraform/environments/production/

Cost: ~$45/month (Fargate 1vCPU/2GB + ALB)

Development

# Format
cargo fmt

# Lint
cargo clippy --features solana,near,stellar,algorand

# Test
cd tests/integration && python test_facilitator.py

Claude Code Skills

This project includes Claude Code skills for automated development workflows:

Skill	Command	Description
add-network	`/add-network scroll`	Add new blockchain network with automated research, EIP-3009 verification, and deployment
add-erc8004-network	`/add-erc8004-network polygon`	Add ERC-8004 reputation support to a network
stablecoin-addition	`/stablecoin-addition`	Add new EIP-3009 compatible stablecoins (USDT, EURC, AUSD, etc.)
ship	`/ship`	Full automated deployment: commit → build → ECR push → ECS deploy → verify
deploy-prod	`/deploy-prod`	Build and deploy Docker image to production ECS
test-prod	`/test-prod`	Test production facilitator endpoints

Example: Add a new network

> add facilitator scroll

Claude will:
1. Research chain IDs, RPCs, USDC contracts
2. Verify EIP-3009 support
3. Check wallet balances and logo
4. Request any missing prerequisites
5. Implement all code changes
6. Deploy if all prerequisites met

Adding New Networks

See guides/ADDING_NEW_CHAINS.md for the complete manual checklist.

Quick automated path: Use /add-network {network-name} skill.

Version & Docs Maintenance Checklist

When bumping the version, adding endpoints, or adding networks, update all of these:

File	What to update
`Cargo.toml`	`version` field
`src/openapi.rs`	`version` in `#[openapi(info(...))]`, endpoint docs, network lists
`README.md`	Version badge, network tables, API endpoint table, ERC-8004 network count
`static/index.html`	Network cards, stats, ERC-8004 showcase badges, i18n strings (EN/ES)
`docs/CHANGELOG.md`	New version entry
`src/erc8004/mod.rs`	`supported_networks()` when adding ERC-8004 networks

Swagger UI: https://facilitator.ultravioletadao.xyz/docs/ (auto-generated from src/openapi.rs)

Acknowledgments

Special thanks to:

GoPlausible - For the x402-avm specification and documentation that made Algorand integration possible
x402-rs - The upstream project this facilitator is forked from

Links

Live: https://facilitator.ultravioletadao.xyz
Upstream: https://github.com/x402-rs/x402-rs
x402 Protocol: https://www.x402.org

License

Apache 2.0

Built by Ultravioleta DAO

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.cargo		.cargo
.claude		.claude
.github/workflows		.github/workflows
abi		abi
conductor		conductor
config		config
crates		crates
docker		docker
docs		docs
examples		examples
grafana		grafana
guides		guides
lambda/balances		lambda/balances
scripts		scripts
src		src
static		static
terraform		terraform
tests		tests
.cargoignore		.cargoignore
.dockerignore		.dockerignore
.editorconfig		.editorconfig
.env.example		.env.example
.gitignore		.gitignore
CLAUDE.md		CLAUDE.md
Cargo.lock		Cargo.lock
Cargo.toml		Cargo.toml
Dockerfile		Dockerfile
LICENSE		LICENSE
README.md		README.md
docker-compose.observability.yml		docker-compose.observability.yml
docker-compose.yml		docker-compose.yml
justfile		justfile
rust-toolchain.toml		rust-toolchain.toml

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x402-rs

What is this?

Supported Networks

Mainnets (20)

Testnets (17)

Supported Stablecoins

Quick Start

Docker

API

Example: Check supported networks

Example: Settle a payment

Chain-Specific Features

EVM Chains (EIP-3009)

Solana (SPL Token + Token2022)

NEAR (NEP-366)

Stellar (Soroban)

Algorand (Atomic Groups)

ERC-8004 Trustless Agents (On-Chain Reputation)

What is ERC-8004?

Supported ERC-8004 Networks (20)

ERC-8004 API Endpoints

Example: Submit Feedback

x402r Escrow Extension (Trustless Refunds)

Architecture Overview

Supported Networks

Documentation

Configuration

Architecture

Deployment

AWS ECS (Production)

Development

Claude Code Skills

Adding New Networks

Version & Docs Maintenance Checklist

Acknowledgments

Links

License

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