Implements USDC x402 payments via PayAI (EIP-3009) and DHM x402 payments via EVVM native (signed pay). Use when adding x402 payment flows, PayAI Echo integration, EVVM pay() for DHM, agent-to-agent payments with Privy, or when the user asks how to do USDC/DHM x402 in the ClawHub/NHS EVVM app.
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This skill documents the two x402 payment flows in the NHS EVVM / ClawHub app: USDC via PayAI Echo and DHM via EVVM native. Reference implementation lives in this repo.
| Flow | Client UI | Server / config |
|---|---|---|
| USDC (PayAI) | frontend/src/components/sections/USDCX402TestSection.tsx |
Config: frontend/src/config/contracts.ts (X402_USDC_ECHO_URL, USDC_BASE_SEPOLIA) |
| DHM (EVVM) | frontend/src/components/sections/X402TestSection.tsx |
server/src/index.ts (GET 402, POST /payments/evvm/dhm) |
| EVVM sign | frontend/src/lib/evvmSign.ts |
— |
Chain: Base Sepolia (chainId 84532).
PayAI returns 402 with an accepts array (not options). Client picks a USDC option, builds EIP-3009 TransferWithAuthorization, signs EIP-712, sends signature in PAYMENT-SIGNATURE header, retries the same URL; server returns 200 and may set PAYMENT-RESPONSE header with result (e.g. transaction hash).
Request resource
GET <Echo URL> (e.g. https://x402.payai.network/api/base-sepolia/paid-content).
Parse 402
PAYMENT-REQUIRED response header (base64-encoded JSON).accepts array.{ x402Version?, error?, resource?, accepts: Array<{ scheme, network, amount, asset, payTo, maxTimeoutSeconds?, extra? }> }.Pick USDC option
accepts, choose entry where asset matches USDC on Base Sepolia or extra.name === "USDC".amount, asset, payTo, extra.name / extra.version for EIP-712.Build EIP-3009 authorization
name = extra?.name ?? "USDC", version = extra?.version ?? "2", chainId = 84532, verifyingContract = asset.TransferWithAuthorization: from, to, value, validAfter (0), validBefore (e.g. now...These signals come from indexed source analysis and may lag behind changes. Check the current source files.
# ClawHub x402 Payments (USDC via PayAI + DHM via EVVM)
This skill documents the two x402 payment flows in the NHS EVVM / ClawHub app: **USDC via PayAI Echo** and **DHM via EVVM native**. Reference implementation lives in this repo.
## Reference paths
| Flow | Client UI | Server / config |
|------|-----------|------------------|
| USDC (PayAI) | `frontend/src/components/sections/USDCX402TestSection.tsx` | Config: `frontend/src/config/contracts.ts` (X402_USDC_ECHO_URL, USDC_BASE_SEPOLIA) |
| DHM (EVVM) | `frontend/src/components/sections/X402TestSection.tsx` | `server/src/index.ts` (GET 402, POST /payments/evvm/dhm) |
| EVVM sign | `frontend/src/lib/evvmSign.ts` | — |
Chain: **Base Sepolia** (chainId 84532).
---
## Flow 1: USDC x402 via PayAI Echo
PayAI returns **402** with an `accepts` array (not `options`). Client picks a USDC option, builds EIP-3009 `TransferWithAuthorization`, signs EIP-712, sends signature in `PAYMENT-SIGNATURE` header, retries the same URL; server returns 200 and may set `PAYMENT-RESPONSE` header with result (e.g. `transaction` hash).
### Client steps
1. **Request resource**
`GET <Echo URL>` (e.g. `https://x402.payai.network/api/base-sepolia/paid-content`).
2. **Parse 402**
- Prefer `PAYMENT-REQUIRED` response header (base64-encoded JSON).
- Fallback: response body may be JSON with `accepts` array.
- Type: `{ x402Version?, error?, resource?, accepts: Array<{ scheme, network, amount, asset, payTo, maxTimeoutSeconds?, extra? }> }`.
3. **Pick USDC option**
- From `accepts`, choose entry where `asset` matches USDC on Base Sepolia or `extra.name === "USDC"`.
- Use `amount`, `asset`, `payTo`, `extra.name` / `extra.version` for EIP-712.
4. **Build EIP-3009 authorization**
- Domain: `name` = `extra?.name ?? "USDC"`, `version` = `extra?.version ?? "2"`, `chainId` = 84532, `verifyingContract` = `asset`.
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