Electrum is a mature, production-grade Bitcoin wallet with full Lightning Network support, used by thousands of users daily. It is a desktop/mobile application with a daemon architecture, offering three GUI frontends: a full-featured PyQt6 desktop interface, a Qt Quick (QML) mobile interface, and a curses terminal interface. The daemon manages wallet lifecycle, network connections, and exposes a JSON-RPC API. The codebase is highly modular, with a plugin system for hardware wallets (Trezor, Ledger, Coldcard, KeepKey, Jade, BitBox02, Safe-T, Digital Bitbox), label sync, two-factor authentication, submarine swaps, watchtowers, and more. Core features include SPV (Simple Payment Verification) with merkle proof validation, coin selection with privacy-aware heuristics (CoinChooserPrivacy), BIP32 key derivation, mnemonic seeds (BIP39, SLIP39, legacy), and a full Lightning Network implementation with pathfinding (LNPathFinder using Dijkstra with liquidity hints), channel management, HTLC accounting, trampoline routing, and onion messages. The repository also includes deterministic build scripts for Linux (AppImage), Windows (Wine+PyInstaller), macOS, and Android (python-for-android), with reproducible builds using pinned dependencies and hash verification.