I've had a few people ask how they should shift their 401K mix to avoid the AI bubble. I honestly don't know what to tell them (aside from the fact I am not in any way a financial advisor). Everything seems exposed.
I personally just keep investing in cheap total world market funds and let the market do its thing.
Berkshire Hathaway last time was an anti bubble stock - it hit a low on the day the NASDAQ peaked in the dot com bubble.