Premon

Premon is a pre-sign transaction security firewall for EVM wallets. Instead of asking you to sign first and find out what happened after, it decodes and simulates every transaction before it reaches your signature — showing exactly what will change (balances, approvals, contract calls) and checking it against a policy that's actually yours to define, not a fixed preset picked by someone else. Under the hood, GuardPolicy gives you ~20 independently toggleable rules: unlimited-approval blocks, setApprovalForAll blocks, risky/unknown contract exposure, minimum post-tx balance, gas ceilings, and more — tunable visually or as raw JSON. Nothing gets signed until it clears your rules, and every block comes with a plain-language reason. Premon also solves a problem unique to the agentic era: x402 lets an AI agent hit an HTTP 402 paywall and auto-pay to get past it, which by default means blind-signing whatever amount and address the server demands. Premon's extension intercepts the 402 response itself, decodes the real payment requirements, and enforces merchant/asset/facilitator allowlists plus spending caps — so agents keep paying autonomously, but never blind. PaymentGuard.sol, deployed live on Monad testnet, is the on-chain half of that same idea: a spending-limit vault where an agent can settle payments with no human signature at all — the on-chain caps are the firewall. Built and running end-to-end on Monad: browser extension wallet, analyze backend, and three live demo dApps showing the firewall stopping real drainer patterns in the wild.