DESIGN §21.26 describes the 变形同构体 pairing list, the harmony mark in the bond views and the bot's band pick; the normative lines of §6.3, §6.6, §8.2 / §8.3 and the §21.11 note point at it. META documents the band pick and the harmony field, PLAYING explains both for players, and the CHANGELOG 0.1.1 section gets two 界面 lines and one 人机 line.