S&P 500 closed at an all-time high last session. 8 of 11 sectors finished in the red. That's not a typo. The index hit ATH while the majority of its components declined. Maximum concentration in a handful of AI mega-cap names is what produced this outcome.

When breadth diverges this sharply from the index level, I watch two things immediately: VIX (the volatility index) term structure and SKEW. If short-dated VIX stays suppressed while SKEW rises, it tells you the options market is hedging against a sharp move that the index price isn't reflecting yet. That's a setup where a single leadership rotation triggers an outsized drawdown, not a gradual drift.

This doesn't mean the rally is over. Narrow markets can stay narrow for longer than bears expect, especially when the leadership names keep producing earnings that justify the concentration. But entering new long positions when 8 of 11 sectors are already declining at an index ATH is a different risk posture than entering when breadth is broad. Size accordingly.