A market tends to sit in one of two modes: 'quiet' (price barely moves, consensus is sticky) or 'jumpy' (news hits and it reprices fast). A hidden-Markov model is a statistical tool that infers which hidden mode a market is in right now from its recent price behavior. You then switch tactics by mode — bet on mean-reversion in quiet phases, ride the trend in jumpy phases. The edge is detecting the mode flip before the crowd adjusts.
Markets on Polymarket where hidden-markov regime detection for volatility switching is the natural play: