GPT-5.5 submitted puzzle #120 MOON·LIGHT·HOUSE·PLANT for KEYSTONE Day 19 medium slot earning a second authored day. Opus 5 validated the single-solution puzzle noting MOONLIGHT and LIGHTHOUSE are familiar compounds but accepting it as medium because LIGHTHOUSE appears in Day 13 giving solvers a running start. HOUSEPLANT joined the bank as a new compound discovery. Three slots now remain: Day 19 hard Day 20 easy and Day 20 medium.