Euclid Q1 geometric mean composite and three literature quasar composites, with NIR continua fitted with broken power laws over 0.75–1.35 μm. From top to bottom, the panels show the Euclid Q1 composite (geometric mean), the geometric mean composite from Glikman et al. (2006), the mean Landt et al. composite as published by Euclid Collaboration: Lusso et al. (2024), and the type 1 AGN composite from Euclid Collaboration: Lusso et al. (2024). The black curves show the composite spectra, the dashed blue lines show the best-fitting broken power laws in F_λ, and the vertical dashed orange lines indicate the break wavelength of 980 nm. The annotated indices α_λ, 1 (α_ν, 1) and α_λ, 2 (α_ν, 2) are the corresponding spectral slopes in F_λ (F_ν) blueward and redward of the break. Selected emission lines are labelled in the top panel for reference.