Production-grade reference for building bulletproof crypto wallets: BIP32/39/44/84 key derivation, transaction building & validation, fee estimation, multi-chain support (BTC/EVM/Solana/Cosmos/Tron/XRP), React Native/Expo patterns, and a non-negotiable fund-loss prevention ruleset. Distilled from production wallets (OneKey, MetaMask, BlueWallet). Inject when writing or reviewing wallet code so every key/address/amount/transaction path is verified before touching real funds.