Market participants are flagging roughly $15 billion in Bitcoin short positions that would be forcibly closed if the cryptocurrency climbs to about $125,000, according to aggregated derivatives data circulated on Thursday. Traders say the concentration of stop-loss and margin-call thresholds around that level could amplify price swings, potentially triggering a short squeeze that drives Bitcoin higher. The discussion comes days before the next Bitcoin “halving,” a pre-programmed event that will cut the daily issuance of new coins by 50 percent, further tightening supply.