Host-subtracted and dereddened light curves of AT 2023clx. The peak epoch is constrained to MJD 59997.2 from fits to the g-band. The short black vertical bars denote the epochs when spectra were taken (Table 1). Non-detections are shown as small downward-facing arrows. The blue shaded region denotes the epochs during which the sharp, narrow emission feature at ∼6353 Å is present in the spectra. Power-law fits to the data over the first 20 days post-peak are shown for the UVW2, UVM2, UVW1, and g bands. For the latter, we also show a power-law fit to the rising part of the light curve. The red dashed vertical line denotes the end of the rapid cooling phase (see Fig. 3 and Sect. 5.3).