@reinconsole/sdk

The demand-side guard of Rein — the control plane for AI agent payments. Wrap your agent's fetch once and every x402 payment is policy-checked, receipted, and observable before a cent moves. Non-custodial: Rein governs the authority to spend, never the funds.

Status: v0.1 — early open-source infrastructure, live on testnet. APIs may change before 1.0. See it running: Rein console.

Install

npm install @reinconsole/sdk
# and something to point it at:
npx -p @reinconsole/policy-engine rein-policy-engine   # the rule engine on :8787

Quickstart

import { createGuard } from '@reinconsole/sdk';

const guard = createGuard({
  engineUrl: 'http://localhost:8787', // @reinconsole/policy-engine (or the durable variant)
  agentId,                            // registered with the engine
});

const fetch = guard.wrap();

// Use it exactly like fetch. When a vendor answers 402:
//  - the guard turns the x402 requirement into a PaymentIntent,
//  - the policy engine evaluates it (budgets, tx caps, allow/deny lists, kill switch),
//  - a signed decision comes back — deny blocks BEFORE any payment exists,
//  - either way you get a Receipt.
const res = await fetch('https://api.vendor.example/answer');

How it behaves

• 402 intercept. The guard wraps the base fetch, underneath any x402 payment library. A blocked paywall never reaches the payment layer; an allowed one flows through, and the payment layer's X-PAYMENT retry is attached to the same receipt.
• Or let it pay. Pass a payer (e.g. the EIP-3009 payer from @reinconsole/x402-rails) and the guard settles allowed payments itself — evaluate → pay → retry, one call.
• Blocked, your way. onBlocked: 'throw' (default) raises PaymentBlockedError; 'respond' returns a synthetic 402 JSON response for agent loops that inspect instead of catch.
• Task context. Attach taskContext (or scope it per call with withTask()) so every decision and receipt says why the agent was spending.
• Receipts either way. Every paywall encounter — allowed, denied, settled — becomes a Receipt; stream them out with onReceipt.
• x402 v1 wire + CAIP-2 ids. Speaks the hosted-facilitator dialect that x402.org still fully supports; network ids accept CAIP-2 forms.

SDK-mode is advisory + observability: an agent that holds its own key can bypass it — and the indexer flags that as shadow spend. The session-key signer tier (keys the agent never holds) is the GA enforcement architecture and lives in the monorepo.

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