ArcCast — Arc Prediction Market

A stablecoin-native prediction market and financial dashboard for Arc Testnet. The monorepo contains:

• contracts: factory-deployed, escrowed pari-mutuel markets
• backend: Express API, on-chain reads, metadata and webhook endpoints
• frontend: Vite/React app with Wagmi, Viem and Circle App Kit

Setup

Requires Node.js 22+.

npm install
cp contracts/.env.example contracts/.env # if deploying
cp backend/.env.example backend/.env
cp frontend/.env.example frontend/.env
npm run build

Deploy the factory:

npm run deploy:arc --workspace contracts

Copy the deployed address to PREDICTION_MARKET_ADDRESS and VITE_PREDICTION_MARKET_ADDRESS, then run:

npm run dev

Frontend: http://localhost:5173 · API: http://localhost:4000

Manual administration

Open /admin and connect the wallet that deployed the factory. The admin panel creates markets directly through MarketFactory, saves protected off-chain metadata, and resolves expired markets through their resolver wallet.

To seed the three starter markets, configure contracts/.env, then run:

npm run seed:arc --workspace contracts

Without a deployer key and factory address, the seed command prints a dry-run payload and does not submit transactions.

Security and money semantics

Stakes use the USDC ERC-20 at 0x3600…0000; the client reads decimals() before parsing amounts. Arc's native gas currency is also USDC but has 18 native decimals—these are separate representations. Market resolution is restricted to each market's creator. The backend admin resolution route intentionally does not sign until an oracle policy and production secret management are configured.