@cra-agent/router

The buyer rail. It answers a 402 for you: reads the price, asks the spending policy before anything is signed, pays in USDC on Arc through Circle Gateway, and writes what happened to a ledger.

npm i @cra-agent/router @cra-agent/identity @cra-agent/policy @cra-agent/ledger

import { createRail } from "@cra-agent/router";
import { createSigner } from "@cra-agent/identity";
import { parsePolicyString } from "@cra-agent/policy";
import { MemoryLedger } from "@cra-agent/ledger";

const signer = createSigner({ scheme: "secp256k1", privateKey });
const rail = createRail({
  network: "arc",
  signer,
  policy: parsePolicyString("daily=5,per_seller=0.5,per_payment=0.05"),
  ledger: new MemoryLedger(),
  identity: null,
  agentId: signer.address,
  rpcUrl: "https://rpc.blockdaemon.mainnet.arc.io",
});

const quote = await rail.quote(url);      // price and policy verdict, nothing paid
const { response, receipt } = await rail.fetch(url); // pays; receipt is null when the URL was free
const proofs = await rail.resolveSettlements(); // receipts matched to on-chain transfers

Every receipt carries budget (the caps in force, what had been spent, what is left) and attestation, the same facts signed with the agent's key. Anyone can check one offline:

import { verifySpendReceipt } from "@cra-agent/router";
const { valid, signer, withinStatedLimits } = await verifySpendReceipt(receipt.attestation, expectedAgent);

The signature proves the agent's key issued the statement and that nothing was changed since. It is the rail vouching for itself; the settlement on chain is the independent part.

A policy rejection never reaches the signer: it is recorded in the ledger with the rule that stopped it. A seller whose handler fails is recorded as quoted, not charged. chooseRail() is pure and decides between a nanopayment and ERC-8183 escrow by amount and kind.

The buyer needs a Gateway balance first: await rail.deposit("1").

Part of CRA AGENT

Payments for AI agents on Arc, Circle's USDC-native L1. Site: cra-agent.tech · Source: github.com/giupy997/arcagentx402 · MIT