SED fitting to the PRISM spectrum of GS-z9-0. The left-hand panel shows the fit performed with BEAGLE, while the right-hand panel shows the fit adopting BAGPIPES with a non-parametric star formation history. In both cases the upper panel shows the best-fit (minimum chi-square) model spectrum superimposed on the observed spectrum (in grey) and the FORCEPHO photometry (red points). The shaded areas mark the wavelength intervals masked during the fit (in particular the region around the Lyα break). The inferred non-parametric star formation history is depicted in the inset for the BAGPIPES fit. The lower panels report (from left to right) the marginalised posterior PDFs from the two fits for stellar mass, stellar age, ionisation parameter, and metallicity (relative to solar).