Documentation
Introduction
rail0 is a single immutable smart contract for stablecoin payments. It gives a payment the
card-rail lifecycle (authorize → capture → refund, plus void, release and a dispute
signal) with no owner, no fee and no operator in between. The buyer signs once, off-chain;
the merchant submits and pays gas; every captured token reaches the merchant in full.
Two paths
Section titled “Two paths”The contract is all you need: it is permissionless, and anyone can call it. The gateway is a convenience layer, not a gatekeeper. It holds no funds and no keys, and every operation is still signed by the party the contract allows; it just does the chain work a checkout would otherwise carry itself.
Client libraries
Section titled “Client libraries”The API reference shows every call as plain HTTP. To skip the plumbing, two SDKs wrap the gateway’s REST API; both sign locally, so keys never leave your process, and check what they are asked to sign before signing it.
| Install | Source | |
|---|---|---|
| TypeScript (Node 22+) | npm install @commercelayer/rail0-sdk | commercelayer/rail0-ts |
| Ruby (3.0+) | gem install rail0-sdk, then require "rail0" | commercelayer/rail0-ruby |
Building with an AI agent? The rail0 skill
teaches Claude and other agents the payment flows: npx skills add commercelayer/rail0-skill.
Where it runs
Section titled “Where it runs”rail0 runs on any EVM chain that supports the Cancun fork, with any stablecoin that implements EIP-3009. Live deployments, planned mainnets and their stablecoins are listed under Chains in the protocol docs.
Source
Section titled “Source”The contract, its tests and the deployment scripts are at github.com/commercelayer/rail0. No external audit has been completed yet; see the security model for what the contract guarantees and the trade-offs it accepts.
rail0 is a peer-to-peer protocol: buyer and merchant transact directly, with no processor, gateway, or operator in between. The contract custodies nothing outside the active escrow window, takes no fee, and routes every captured token to the merchant in full. It is immutable and permissionless — no owner, no admin, no upgrade path, no privileged roles, and no arbitration layer; recourse is purely time-based (capture, void, release, refund). No external audit has been completed yet — formal audits are underway and their reports will be published here once available. Until then, review the contract and assess your own risk before use.
