Expiry-day closing shock / CAS

Today was the first monthly derivatives expiry under the new closing-auction mechanism, and the closing period produced an extraordinary move. The Sensex reportedly moved from roughly 77,200 around 3:17 PM to about 74,983 around 3:23 PM — more than 2,000 points in only a few minutes — before ultimately closing at 76,933.59. Nifty finished at 24,090.85, down 116.90 points (-0.48%). This has immediately raised questions about how the closing-auction mechanism behaved during heavy expiry