ADR 0002 — WhatsApp: Baileys in-process, pairing code, mention-required groups

Status: accepted 2026-09-13; implemented 2026-09-17 (angelia pair), running groups daily since. Historical in part: QR became the default pairing once WhatsApp began rejecting pairing codes from third-party clients; the code is still an option (pairing: code). The code now lives in src/adapters/whatsapp/.

Library @whiskeysockets/baileys 7.0.0-rc14 (MIT), one socket per daemon, auth dir ~/.angelia/wa, pidfile lock. Pairing by code (QR fallback), printed to daemon stdout only. Groups default mention: required (@mention of our jid in mentionedJid, or a reply to our message). Sender ids resolved via participantAlt/remoteJidAlt and signalRepository.lidMapping, with the auth dir's lid-mapping-*.json as fallback. Link an established number, not a fresh one: fresh numbers are reported banned within hours. Outbound ceiling 10/min, 1.5-4 s randomised gap between chunks, presence composing while a turn runs, never a proactive send. Disconnect: 401 stop+notify, 515 reconnect now, 440 backoff + one notice per 6 h, else backoff ≤30 s. Media inbound to <cwd>/.inbox/; voice = file, no STT; outbound files v1.1. Rejected: whatsapp-web.js (Chromium), whatsmeow (Go), Evolution API (server product), Cloud API (business number, no personal groups).