The S&P 500 Index (SPX) has been exhibiting notable activity around the 6400 strike level, which is identified as a significant resistance point due to a large concentration of 0DTE (zero days to expiration) call options. Market participants have observed a strong wall of calls at 6400, making it a key level for potential rally momentum. Recent trading has seen the SPX hovering just above 0DTE put support at 6370 and encountering call resistance near 6380, with the index price around 6372 to 6375. Dealer positioning is under pressure with net gamma and net delta both deeply negative, indicating a high-convexity expansion regime and acute dealer risk. Implied volatility (IV) on SPY options stands at 13.14%, higher than historical volatility (HV) at 8.11%, with IV rising by 2.21%, suggesting a positive volatility regime but also the potential for sharp price swings. The gamma exposure (GEX) profile shows heavy positive gamma at 6300 but a flip from positive to negative gamma exposure at 6385. Overall, the SPX is near its recent highs with strong momentum, trading within a range of approximately 9.7 points, and market participants are closely watching the 6400 strike as a potential breakout or resistance level as the market approaches the end of the trading day.