LAMOST time-series spectra and TESS light curve during the stellar flare. Panel A: TESS normalised flux light curve of the flare. The blue shaded interval marks the first LAMOST exposure (sp1), the light orange interval the second (sp2), and the light brown interval the third (sp3). Panel B: time-series Hα line profiles obtained with LAMOST, with the same color scheme as in Panel (A). Panel C: temporal evolution of the excess EW of the Hα line (∆Hα EW). Panel D: dynamic evolution of the Hα line asymmetry, quantified as the difference between the EW of the blue and red wings.