If you're building Ethereum tooling in JavaScript or TypeScript, you've probably already shipped this bug. Node's `crypto.createHash('sha3-256')` implements NIST SHA3, not the Keccak-256 variant Ethereum actually uses, and the outputs are silently different. This skill teaches Claude to catch the distinction and use the right helpers from ethers, viem, or web3.js when computing function selectors, event topics, storage slots, or deriving addresses from public keys. It includes grep commands to audit your codebase and side-by-side examples showing why `nistSha3 === keccak` returns false. Small footgun, massive consequences if you get it wrong.
npx skills add https://github.com/affaan-m/everything-claude-code --skill nodejs-keccak256