(You can now subscribe to our(You can now subscribe to our ETMarkets WhatsApp channelCapital markets regulator Sebi has earlier rolled out a tighter framework for intraday trading in index derivatives , which will take effect from October 1. This allowed certain entities to build speculative positions, especially during the final hours of contract expiry, creating volatility and concerns around market integrity.Sebi's new rules introduce strict intraday checks. Breaches will be scrutinised, and traders may be asked to justify their positions.The changes are especially critical for expiry sessions, where wild swings are seen. This step is intended to discourage reckless position-building that distorts prices and increases systemic risk.The regulator noted several instances of entities creating outsized intraday bets in index options, exposing the system to potential instability. Large players can no longer stretch intraday exposures unchecked, especially during expiry-day strategies like "option writing" or volatility plays.