The yen soared after Washington and Tokyo jointly intervened to strengthen the currency, making trips to Japan more expensive. Meanwhile, oil prices tumbled on renewed diplomatic efforts with Iran. After a turbulent July, both stocks and bonds are poised for a strong start to August.

If you've browsed YouTube for investing content lately, you've likely encountered alarmist thumbnails featuring illustrated flames and downward arrows—many invoking the name of the world's greatest investor. Warren Buffett isn't predicting a stock-market collapse, but a market gauge he once endorsed just hit a record high.

The Buffett Indicator—which the Oracle of Omaha called "probably the best single measure of where valuations stand at any given moment" a quarter-century ago, when he was a sprightly 71-year-old—has reached unprecedented levels. The metric compares total stock market capitalization to GDP.

While the indicator is flashing red, it could use an update for today's market structure. Buffett himself isn't sounding the alarm, but the reading warrants attention from investors navigating elevated valuations.