Gamma-ray spectra for the flaring states with TS_hardening ≥ 12. The Fermi-LAT data (black dots), with the best-fit BPL model and its uncertainties (red). The PKS 2155−304 flare identified by the Flip method (top right) partially overlaps with that selected by the Baseline method (lower left) but spans twice the duration, resulting in a more significant SED for the Flip detection. Low-energy data are more uncertain, though we minimized systematics by using PSF event types and by identifying spectral hardening through likelihood ratios rather than individual flux bins.