Wager is a parimutuel prediction market for USDC on Arc Testnet. Bets pool by side, odds are the live pool ratio, and winners split the losing pool with a 50 bps fee charged only on the winnings share — never on refunds. Settlement runs through OptimisticPredictionMarket.sol, published as its own forkable repo: anyone proposes an outcome, anyone can challenge it within the dispute window by locking a USDC disputeBond, disputed markets go to arbitration, and if no ruling ever lands, forceFinalizeDisputeTimeout returns every stake and the bond in a neutral refund so funds can never be stranded. The contract ships with a mocha test suite and ReentrancyGuard-protected claims. The Next.js app in web/ adds market discovery, odds-over-time charts, profiles, notifications, and full interfaces in ten languages under web/messages/.