facilitator 0.5.3

X402 Facilitator
facilitator-0.5.3 is not a library.

Facilitator

CI Crates.io Docker License Rust

Production-ready x402 payment protocol facilitator — verifies payment signatures and settles transactions on-chain over HTTP 402.

The facilitator is a trusted third party that acts on behalf of resource servers. It does not hold funds — it only validates payment payloads and broadcasts settlement transactions to the blockchain.

Built on r402, the modular Rust SDK for x402. See Security before using in production.

Quick Start

# Install from crates.io
cargo install facilitator

# Generate a commented config template
facilitator init

# Edit config.toml with your RPC URLs and signer keys, then start
facilitator serve

Docker

# Using pre-built image
docker run -p 8080:8080 -v ./config.toml:/app/config.toml ghcr.io/qntx/facilitator

# Or build from source
docker build -t facilitator .
docker build -t facilitator --build-arg FEATURES=chain-eip155 .   # EVM only
docker run -p 8080:8080 -v ./config.toml:/app/config.toml facilitator

API

Method Path Description
GET /supported List supported payment kinds (version / scheme / network)
POST /verify Verify a payment payload against requirements
POST /settle Settle an accepted payment on-chain
GET /health Health check

CLI

facilitator <COMMAND>

Commands:
  init   Generate a default TOML configuration file
  serve  Start the facilitator HTTP server

Options:
  -h, --help     Print help
  -V, --version  Print version

init

facilitator init [OPTIONS]

Options:
  -o, --output <PATH>  Output path [default: config.toml]
      --force          Overwrite existing file

serve

facilitator serve [OPTIONS]

Options:
  -c, --config <PATH>  Path to TOML config file [default: config.toml]

Configuration

The server loads configuration from a TOML file (default: config.toml). Run facilitator init to generate a fully commented template.

host = "0.0.0.0"
port = 8080

# Global signers — shared across all chains of the same type.
# Env-var references ("$VAR" or "${VAR}") are resolved at startup.
[signers]
evm    = ["$EVM_SIGNER_PRIVATE_KEY"]       # hex, 0x-prefixed
solana = "$SOLANA_SIGNER_PRIVATE_KEY"       # base58, 64-byte keypair

# EVM chains (CAIP-2 key format: "eip155:<chain_id>")
[chains."eip155:8453"]
rpc = [{ http = "https://mainnet.base.org" }]

[chains."eip155:84532"]
rpc = [{ http = "https://sepolia.base.org" }]

# Solana chains
[chains."solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"]
rpc = "https://api.mainnet-beta.solana.com"

# Scheme registrations (optional — auto-generated from configured chains)
# [[schemes]]
# id = "v2-eip155-exact"
# chains = "eip155:{8453,84532}"

Environment Variables

Variable Default Description
HOST 0.0.0.0 Bind address
PORT 8080 Listen port
CONFIG config.toml Config file path (for serve)
OTEL_* — OpenTelemetry configuration

Supported Chains

Family Networks
EVM (EIP-155) Ethereum, Base, Optimism, Arbitrum, Polygon, Avalanche, Celo, Monad, and testnets
Solana (SVM) Mainnet, Devnet, and custom clusters

Feature Flags

Feature Default Description
chain-eip155 ✓ EVM chain support via r402-evm
chain-solana ✓ Solana chain support via r402-svm
telemetry ✓ OpenTelemetry tracing and metrics

Disable unused chains to reduce binary size and compile time:

cargo install facilitator --no-default-features --features chain-eip155

Security

See SECURITY.md for disclaimers, supported versions, and vulnerability reporting.

Acknowledgments

License

Licensed under the Functional Source License, Version 1.1, Apache-2.0 Future License (FSL-1.1-ALv2).

  • You can use, modify, and redistribute for any purpose except competing use.
  • Each version automatically converts to the Apache License, Version 2.0 two years after release.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project shall be licensed as above, without any additional terms or conditions.

A QNTX open-source project.

Code is law. We write both.