Temporal evolution of broad-band SED of GRB 230812B from Fermi/GBM (Table 1) and Fermi/LAT (Table 2) analysis. Panels (a)–(c): Prompt emission phase (bins 1–3). Panel (d): Prompt-to-afterglow transition (bin 4). Panels (e)–(f): Afterglow phase (bins 5–6). Forward-folded flux data points from the NaI and BGO detectors, as well as from LAT, are shown as filled circles. The green band depicts the best-fit model in keV-MeV band resultant from Fermi/GBM analysis (extended up to 100 GeV in bins 1–4). The blue butterflies show the power-law model fit on Fermi/LAT spectra in 0.1 − E_max. Overall SED evolution shows the emergence and evolution of the spectral components.