Most stable coin I know are actually tokens and under the ethereum, tron or binance protocol. So they can't on their own go through halving. Maybe there are other stable coin that are new in the market, but I know the most popular stable coin is tether and its under ethereum protocol majorly. Halving can only be experienced when the coin has its own blockchain, just like bitcoin and when it's been programmed to undergo halving periodically, like bitcoin halving is every 4 years and lastly when it uses the proof of work (POW) Algorithm. I don't think halving can be effected on Proof of stake (POS).