402 Coffee

Non-custodial x402 tip jars for the agentic web. Claim a handle with your wallet, get a live payment endpoint (/t/@you) and an embeddable button. Humans tip from a browser wallet with a signature (no gas); agents tip over HTTP or MCP; every tip settles as USDC straight to the creator's wallet. No custodian, no fee.

Live: https://402coffee.com · MIT · built on x402 v2, Base USDC.

Why non-custodial

payTo is the creator's own wallet. The service composes the payment challenge and asks a facilitator to verify + settle; it never holds keys or funds. Structurally cannot rug anyone, and stays out of money-transmitter territory.

Two front doors, one rail

• Humans — an embeddable widget runs the full x402 flow in-browser: the payer signs an EIP-3009 transferWithAuthorization with MetaMask/Coinbase/Rabby and pays zero gas.
• Agents — every jar is a real x402 endpoint and an MCP tool: tip("@handle", 1.00, "great post").

Embed (any site)

<script src="https://402coffee.com/widget.js" data-handle="tim" async></script>

README badge: [![Tip in USDC](https://402coffee.com/tim/badge.svg)](https://402coffee.com/tim)

Routes

Path	What
GET/POST /t/:handle	The x402 tip endpoint (dynamic payTo, ?amount= / ?tier=)
GET /:handle	Warm creator page (SSR, wall, tiers, embed, OG image)
GET /:handle/dashboard	SIWE-gated dashboard: ledger, per-post analytics, CSV, moderation
GET /:handle/badge.svg	README tip badge
POST /api/creators	SIWE signup / update
GET /api/creators/:handle	Public profile JSON
GET /api/creators/:handle/tips	SIWE-gated ledger (?format=csv) + POST to hide a tip
GET /api/wall/:handle	Public supporter wall
GET /api/search?q= · GET /api/leaderboard	Discovery
GET /api/nonce	SIWE nonce
POST /mcp	Hosted MCP server (get_creator, search_creators, tip)
GET /.well-known/x402 · GET /llms.txt	Machine-readable discovery
GET /api/cron/reconcile	Nightly ledger↔onchain reconciliation (cron)

Protocol (verified onchain, x402 v2)

Built on @x402/[email protected] (protocol v2). All facts re-verified against the live SDK / facilitator / chain — never from memory:

Item	Value
Headers	PAYMENT-REQUIRED / PAYMENT-SIGNATURE / PAYMENT-RESPONSE
Networks	CAIP-2 eip155:8453 (Base) · eip155:84532 (Base Sepolia)
USDC (Base)	0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, 6 decimals
Scheme	exact (EIP-3009 TransferWithAuthorization, payer pays no gas)
Amount / tx	PaymentRequirements.amount (atomic) · SettleResponse.transaction

Architecture

• lib/x402.mjs — thin x402 v2 core: build a challenge; verify + settle (the churn-exposed part)
• lib/tipflow.mjs — the shared settle-and-record core used by both /t/:handle and MCP
• lib/creators.mjs · lib/tips.mjs — Postgres store (creators, idempotent tip ledger)
• lib/siwe.mjs — stateless-nonce Sign-In-With-Ethereum
• lib/notify.mjs — HMAC-signed webhook + optional email
• lib/reconcile.mjs — data-quality gate: ledger vs onchain USDC transfers
• app/ — Next.js App Router (routes above); public/widget.js — the zero-dep widget

Develop

npm install
# local Postgres (Docker):
docker run -d --name pg402 -e POSTGRES_PASSWORD=dev -e POSTGRES_USER=dev -e POSTGRES_DB=coffee402 -p 5433:5432 postgres:16-alpine
cp .env.example .env.local     # set SIWE_SECRET + DATABASE_URL (see below)
npm run migrate                # create schema
npm run dev                    # http://localhost:3000

npm test                       # x402 v2 protocol/codec tests (vs real SDK + live facilitator)
npm run test:db                # DB + SIWE + notify + moderation integration tests
node scripts/e2e-local.mjs     # live HTTP: signup, challenge, ledger
node scripts/e2e-widget.mjs    # simulate the browser widget tip flow
node scripts/e2e-mcp.mjs       # drive the MCP server end to end

Environment

See .env.example. Production (Vercel) needs: DATABASE_URL (Neon), SIWE_SECRET, CDP_API_KEY_ID / CDP_API_KEY_SECRET (mainnet facilitator), X402_NETWORK=mainnet. Optional: CRON_SECRET, RESEND_API_KEY, BASE_RPC_URL.

License

MIT.