@harpd/observe

The x402 V2 observability + budget-control extension for Harpd — the neutral observability & control layer for agent payments, sitting above any Facilitator.

Zero runtime dependencies. Runs in Node and the browser.

What it does

Registers the 4 x402 V2 lifecycle hooks and forwards every payment event to a Harpd collector. Harpd never touches funds or signing keys; it only observes and, when budgetControl is on, makes a pre-payment allow/deny decision.

Hook	Purpose
before-payment	Records intent; if budgetControl, returns the collector's atomic budget decision
after-payment	Records the payment event (amount, endpoint, agent, txHash, facilitator)
before-settlement	Records settlement intent
after-settlement	Records settlement result + triggers read-only on-chain verification

Usage

import { harpdPlugin, simulatePayment } from '@harpd/observe'

const plugin = harpdPlugin({
  apiKey: 'harpd_live_xxx',
  endpoint: 'https://collector.harpd.workers.dev',
  budgetControl: true, // Phase 1 — block at the pre-payment hook
})

// In a real x402 V2 client, register `plugin` with your SDK:
//   const client = new x402.Client({ facilitator: 'coinbase', plugins: [plugin] })
//   await client.fetch('https://api.example.com/premium-data')

// Without a live Facilitator, drive the hooks in payment order:
await simulatePayment(plugin, {
  agentId: 'agent-1',
  url: 'https://api.example.com/premium-data',
  amount: 1_000_000, // USDC 6dp → $1.00
  asset: 'eip155:8453/erc20:0xusdc',
  chain: 'eip155:8453',
  txHash: '0xconfirmed_abc',
  facilitator: 'coinbase',
  settlementStatus: 'confirmed',
})

Server side

import { harpdServerPlugin } from '@harpd/observe'

const serverPlugin = harpdServerPlugin({
  apiKey: 'harpd_live_xxx',
  endpoint: 'https://collector.harpd.workers.dev',
})
// Register with your x402 V2 server middleware (e.g. @x402/paywall plugins).

Strict control-plane settlement

Use settlePayment when every settlement must pass through Harpd policy, budget, idempotency, facilitator verification and the commercial ledger:

import { settlePayment } from '@harpd/observe'

await settlePayment({ apiKey: 'harpd_live_xxx', endpoint: 'https://api.harpd.com' }, {
  agentId: 'agent-1', url: 'https://api.example.com/premium-data',
  amount: 1_000_000, asset: 'eip155:8453/erc20:0xusdc', chain: 'eip155:8453',
  idempotencyKey: 'order-123',
})

Direct after-settlement ingest is rejected in production; use this method or POST /v1/gateway/settle instead.

Contract

• Events POST to {endpoint}/v1/events as a JSON array, authenticated by the X-Harpd-Key header.
• The pre-payment budget decision comes from GET {endpoint}/v1/budget/check.
• After settlement, POST {endpoint}/v1/verify-onchain triggers read-only eth_getTransactionReceipt verification + reconciliation.

See harpd/v2 for the collector (Cloudflare Worker + D1 + Drizzle).

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About Harpd

Harpd is the AI Cost Intelligence platform for the agent era — measure, optimize and control production AI spend, from cost per successful task to agent-payment budgets (x402 / USDC).

• Website: https://harpd.com
• GitHub org: https://github.com/harpd-dev
• Contact: mailto:harpdsupport@gmail.com