In a move that will likely be filed under historic, alarming, and probably not sustainable, the S&P 500 closed above 6,400 for the first time, prompting everyone with a ticker tape to issue a caution like it was a pizza coupon.

Reason for caution #1: Valuation gymnastics. If you squint at the P/E ratios, you’ll see a fireworks show that looks more like a magician’s flourish than a map of corporate health.

Reason for caution #2: The buyback ballet. Many companies have spent the year shoveling stock to investors, lifting prices while earnings quietly work from home.

Reason for caution #3: The Fed’s mood ring. The path forward is a rotating color chart that keeps changing colors just when traders think they’ve memorized it.

Reason for caution #4: Concentration anxiety. The index is increasingly a trophy case for a handful of megacaps; remove them and the standings resemble a very expensive hot potato.

Reason for caution #5: The data vs. vibes mismatch. Jobs, inflation, and consumer demand tell a different story than the price ladder on screen, but the ladder keeps climbing anyway.

Reason for caution #6: Seasonality and option expiry. End-of-month portfolios tend to look heroic and then go dark the moment the calendar flips.

Reason for caution #7: The VIX is napping. So is risk management, apparently, which means the snooze button is very popular these days.

Reason for caution #8: Retail investor cosplay. The online chorus promises moonshots, but popcorn is easier to swallow than margin calls.

Reason for caution #9: Global risk appetite. A few headlines from overseas can turn a sunny day into a spreadsheet of could-be headlines.

Reason for caution #10: The bubble’s perfume is inertia. If no one sells, prices drift higher on a breeze that smells suspiciously like ‘this time it’s different’.

Reason for caution #11: Rebalancing season. Funds adjust weights with the seriousness of a DJ lowering the bass, nudging every stock to appear marginally more exciting than it actually is.

Reason for caution #12: The old chorus, ‘This time is different,’ wearing a shiny vest and a better pitch deck.

Bottom line: Celebrate if you must, but wear a helmet and a skeptic’s spine. 6,400 is a milestone, not a magic wand, so keep one eye on the chart and one on your snack budget.