A source-critical guide that decomposes “first” claims in mainland China’s transgender medical history into procedure scope, geography, institution, publicity, administrative effect, event time, and source role, comparing the 1983 Zhang Kesha surgery, regional surgery histories of the 1990s, marriage registration in 2003, Geng Zi’s public identity in 2005–2006, and national technical rules from 2009 to 2022.