The S&P 500 advanced to just below 6,400 on Thursday before reversing course, sliding to an intraday low of 6,334.62 and threatening a bearish outside-day pattern. The pullback erased earlier gains that had taken the benchmark within sight of fresh records. Derivatives positioning pointed to fading bullish conviction. A composite Option Score that had hovered near four to five in recent sessions fell to roughly three as the index approached the 6,400 strike, suggesting diminished demand for upside exposure. Volatility indicators sent mixed signals. Implied volatility on the Nasdaq-100 stood at 15.69% compared with historical volatility of 9.34%, keeping option premiums elevated even though implied-volatility rank was only 5.3%. The put-to-call open-interest ratio on the tech-heavy gauge ticked up to 1.09, and the skew steepened sharply, both hinting at a more defensive stance among traders. Heavy open interest at the 6,400 S&P 500 strike, coupled with positive dealer gamma, is expected to amplify price swings around that level. Strategists said the loss of momentum may encourage short-term sellers unless volatility remains contained.