@reinconsole/policy-engine

The rule engine of Rein — the control plane for AI agent payments. A sandboxed, declarative policy engine that judges every payment intent (deny > escalate > allow > default), with every decision ed25519-signed and sha256 hash-chained into a tamper-evident audit log.

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

Install & run

npm install @reinconsole/policy-engine
# or just run it:
npx -p @reinconsole/policy-engine rein-policy-engine   # HTTP API on :8787 (PORT/HOST env)

Point @reinconsole/sdk's guard at it (engineUrl) and every x402 paywall your agent hits is evaluated here first.

In-process

import { PolicyEngine, buildServer } from '@reinconsole/policy-engine';

const engine = new PolicyEngine();      // in-memory stores by default
const app = buildServer(engine);        // Fastify instance (not yet listening)
await app.listen({ port: 8787 });

What it does

• Declarative policies — budgets over rolling windows, per-tx caps, vendor allow/deny lists by glob, escalation, and reputation rules (vendorReputationLt, fed by @reinconsole/graph). Precedence is deny > escalate > allow > default.
• Kill switch — freeze an agent and there is no allow; the check happens before evaluation.
• Signed decisions — each decision commits to the exact intent it judged (intentHash), is ed25519-signed, and links to the previous decision's hash. verifyDecisionChain validates the whole history offline; the {intent, decision} pair is a self-contained spend voucher downstream tiers verify without calling back.
• Store ports — agents, policies, rolling spend, and the decision log sit behind injectable ports (SpendStorePort, PolicyStorePort, AgentRegistryPort). In-memory implementations ship here; the durable Postgres-backed variant lives in the monorepo (@reinconsole/store) and keeps the hash chain continuous across restarts.
• HTTP API — POST /v1/evaluate, agent + policy CRUD, decision reads. Zod-validated 400s, not 500s.

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