LEASH Backend

Onchain policy vault for agent spend allowances on Monad testnet.

Layout

backend/
  src/                 # Solidity (Foundry)
    LeashVault.sol     # personal allowance vault
    LeashFactory.sol   # one vault per owner
    interfaces/
    mocks/             # test ERC20 only
  test/                # forge tests (10 passing)
  script/
    Deploy.s.sol
    deploy.sh          # deploy via monskills keystore
  abi/                 # exported ABIs for frontend/API
  deployments/         # chainId.json after deploy
  api/                 # thin read API (Express + viem)
  .env                 # local secrets / addresses

Contracts

Contract	Role
LeashFactory	createVault() / createVaultFor(owner)
LeashVault	deposit → createSession → spend / revoke

Session policy: total cap, optional period cap, expiry, ERC-8004 agentId, optional recipient allowlist.

Commands

# tests
forge test -vv

# build
forge build

# deploy (agent keystore must have testnet MON)
./script/deploy.sh

# API
cd api && npm install && npm run dev

Env

See .env.example. Public constants match Monad docs / x402 guide:

• Chain ID 10143
• RPC https://testnet-rpc.monad.xyz
• USDC 0x534b2f3A21130d7a60830c2Df862319e593943A3
• Facilitator https://x402-facilitator.molandak.org

Deploy notes

Monskills flow: agent wallet at ~/.monskills/keystore deploys contracts.
Fund AGENT_WALLET_ADDRESS with testnet MON first (your faucet wallet already has funds).

API (after deploy)

Method	Path	Purpose
GET	/health	RPC + factory status
GET	/config	chain + addresses
GET	/abis	factory + vault ABI
GET	/vault/:owner	resolve vault + USDC balance
GET	/vault/:vault/session/:id	session + remaining caps
POST	/vault/:vault/session/:id/can-spend	preflight policy check
GET	/x402/demo/price	payment requirement shape
GET	/x402/demo/resource	402 unless payment header