Nexus

AI agent payment clearance. Agents lock USDC in escrow, humans approve or reject, funds move on-chain.

Live demo: nexus-clearance.vercel.app

The gap

x402 owns micropayments. Stripe owns consumer commerce. The $10–$10K range for agent services — where trust matters and delivery is uncertain — has no dominant escrow primitive.

When an AI agent books a contractor, commissions research, or pays for a service on your behalf, what's the mechanism? Right now there isn't one. Nexus is a proof of concept for what that primitive could look like.

How it works

AI Agent (Claude MCP)
    ↓  create_escrow("Build me a landing page", $500 USDC)
NexusEscrow.sol  ←— funds locked on-chain
    ↓  getPendingIds()
Approval UI  ←— human reviews work, approves or rejects
    ↓  approveRelease() or refund()
NexusEscrow.sol  →  USDC released to recipient

The agent proposes. The human decides. The contract enforces.

Deployed (Base Sepolia)

What could be built on this

This is a minimal proof of concept. The interesting work is ahead. Some directions worth exploring:

Protocol extensions

• Multi-approver escrow — require M-of-N humans to approve before release
• Time-locked auto-release — funds release automatically after N days unless rejected
• Milestone-based escrow — split a payment across multiple approval checkpoints
• Dispute resolution — third-party arbitration when agent and human disagree
• Reputation layer — on-chain history of agent payment reliability

Integrations

• Any MCP-compatible agent (not just Claude) — the MCP server is the thin layer
• Webhook notifications — ping a URL when an escrow is created or actioned
• Multi-token support — ETH, any ERC-20 beyond USDC
• Mainnet deployment — Base, Optimism, Arbitrum

UX

• Mobile approval UI — approve agent payments from your phone
• Batch approvals — review and action multiple escrows at once
• Email/SMS alerts — get notified when an agent creates an escrow
• Slack/Discord bot — approve directly from where you work

Setup

1. Deploy the contract

cd contracts
forge install
cp .env.example .env  # fill in PRIVATE_KEY, BASE_SEPOLIA_RPC
forge test
forge script script/Deploy.s.sol --rpc-url $BASE_SEPOLIA_RPC --broadcast

Get testnet USDC: https://faucet.circle.com

2. Configure the MCP server

Add to Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "nexus": {
      "command": "node",
      "args": ["/path/to/nexus-protocol/mcp/dist/index.js"],
      "env": {
        "PRIVATE_KEY": "0x...",
        "BASE_SEPOLIA_RPC": "https://sepolia.base.org",
        "CONTRACT_ADDRESS": "0x..."
      }
    }
  }
}

cd mcp && npm install && npm run build

3. Run the approval UI

cd ui && npm install
cp .env.example .env  # set VITE_CONTRACT_ADDRESS
npm run dev

Connect the contract owner wallet to approve/reject pending escrows.

MCP tools

Contract

NexusEscrow.sol is ~115 lines. Ownable, no upgradability, no fees. Read it before you trust it.

• Owner-only approveRelease and refund
• 30-day self-refund window — depositor reclaims if owner is unresponsive
• Emits events for all state changes

Contributing

Fork it, extend it, break it. If you build something interesting on top of this, open a PR or tag @jordanlyall.

License

MIT