How does Kaspa handle difficulty adjustment when its block speed changes?

When Kaspa upgrades to a new block speed, it discards the old difficulty window and rebuilds it using only blocks mined after the upgrade activates. Mining difficulty is the measure of how hard it is to find a new block — Kaspa normally tracks a rolling window of recent blocks to keep that difficulty calibrated. At a speed upgrade, the old window contains blocks mined under the previous rules, so using it would give misleading data. Resetting the window ensures the difficulty algorithm is working with accurate information from the start, keeping Kaspa's block rate stable immediately after a major protocol change.